Ld mini implants by dr vp abhishek open access

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Mini Implants
CHHATTISGARH DENTAL COLLEGE & RESEARCH INSTITUTE
RAJNANDGAON, CHHATTISGARH
2011
MINI -
IMPLANTS
Dr. V.P Abhishek Sahu
Ayush And Health Sciences University of Chhattisgarh
L I B R A R Y D I S S E R TA T I O N

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Contents
1 INTRODUCTION.........................................................................................................4
2 HISTORY OF MINI IMPLANTS ...............................................................................8
3 THE DESIGN OF ORTHODONTIC MINI-IMPLANTS. ....................................18
3.1 Classifications of miniscrew Implants...............................................................18
3.2 Elements of Implant Design: ..............................................................................22
4 ANATOMICAL CONSIDERATIONS .....................................................................33
5 BIOMECHANICAL CONSIDERATIONS .............................................................40
5.1 Maxillary anterior en masse retraction mechanics in extraction cases..........40
5.2 Mandibular anterior en masse retraction mechanics in extraction cases.......42
5.3 Anterior Intrusion Mechanics in the Maxillary Arch.......................................43
5.4 Anterior Intrusion Mechanics in the Mandibular Arch ...................................43
5.5 Anterior en masse Retraction with Anterior Intrusion.....................................44
5.6 Molar Intrusion Mechanics for Open bite Cases..............................................44
5.7 Maxillary Anterior Lingual Root Torque Mechanics.......................................44
5.8 Molar Distalization Mechanics for Non-Extraction Cases .............................45
5.9 Protraction Mechanics in Extraction Cases ......................................................46
5.10 Minor Tooth Movements Using Mini Implant Anchorage..........................47
5.11 Buccal Cross bite (Scissors Bite) Correction................................................48
6 INDICATIONS & CONTRAINDICATIONS .........................................................50
6.1 Indications .............................................................................................................50
6.2 Contraindications..................................................................................................51

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6.3 Relative Contraindications ..................................................................................52
7 CLINICAL APPLICATIONS ....................................................................................54
8 BIOLOGY OF ORTHODONTIC IMPLANTS.......................................................59
9 COMPLICATIONS WITH MINI IMPLANTS & THEIR MANAGEMENT ....65
9.1 Complications During Insertion .........................................................................66
9.2 Complications Under Orthodontic Loading......................................................71
9.3 Soft-Tissue Complications ..................................................................................74
9.4 Complications During Removal .........................................................................76
10 ADVANTAGES OF MINI IMPLANTS...............................................................79
11 BIBLIOGRAPHY....................................................................................................80
12 APPENDIX I.......................................................................................................86
13 APPENDIX II.....................................................................................................88

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INTRODUCTION
“Truth is neither objectivity nor the balanced view; truth is a selfless subjectivity.”
-Knut Hamsun

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1 INTRODUCTION
The goal of Orthodontic practice is to achieve the desired results with minimum
undesired consequences, which is largely dependent on the availability of anchorage.
One such effect is the loss of anchorage. Anchorage, the degree of resistance to
displacement, is a critical component to successful orthodontic treatment. Anchorage
control is a fundamental problem in the treatment of malocclusions1.
In orthodontics, malpositioned teeth are corrected and proper alignment is achieved
by inducing strategically planned tooth movements through application of force. This
force originates from wires, elastics and other appliances attached to the teeth. To make
this force work in the planned direction, with the planned magnitude and for the
planned time, it is necessary to reduce or completely eliminate unwanted reciprocal
effects by using a reliable anchorage and to respect the principles of orthodontic
biomechanics at the same time.
Often, teeth that are in proper alignment are used to provide the force to move those
that are not, and are referred to as anchorage teeth. In accordance with Newton’s Third
Law of motion, outlined in 1687, which states that an applied force comprises of an
‘Action’ component & an equal & opposite ‘Reaction’ component; There is a reactive
or “equal and opposite force” for every applied force. Unfortunately, these reactive
orthodontic forces often result in undesirable movements of the teeth serving as
anchorage. As a result, orthodontists have historically used a variety of appliances and
strategies to enhance anchorage; particularly when minimal movement of the teeth
providing the anchorage is desired. This allows the movement of malaligned teeth
while leaving teeth that do not need to be moved relatively undisturbed.
However, with dental anchorage dependant on the number and quality of the teeth, if
anchorage is lost during the planned correction of the malocclusion anomaly will not
be achieved. Anchorage enhancing appliances, such as headgear, are highly dependent

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upon patient compliance for success. All manner of anchorage control concepts have
come and gone in the ensuing years, including Baker anchorage, headgear, lip
bumpers, Nance holding arches, Tip-back bends, lingual arches, uprighting springs,
sectional mechanics, dual arch mechanics and elaborate methods to set anchorage. But
in reality, absolute anchorage did not practically exist.
In an effort to establish anchorage without significant reliance on patient
cooperation, other forms of anchorage have been investigated2.
Restorative dental implants, despite their stability in bone, have limited use in
orthodontics due to cost, an extensive healing period after surgical placement, and
anatomic placement limitations. Still, the use of these titanium dental implants as a
form of anchorage has provided the potential for absolute, compliance independent,
orthodontic anchorage. The use of prosthetic implants as orthodontic anchorage made a
great advance. In osseointegrated implants, the relationship between the implant and
bone can be defined as a functional ankylosis.
Orthodontic miniscrew implants (read mini-implants) have been designed to
circumvent the limitations posed by restorative dental implants. These smaller bone
screws are significantly less expensive, are easily placed and removed, and can be
placed in almost any intra-oral region, including between the roots of the teeth.
Starting with the use of vitalium screws3 and progressing to conventional
osseointegrated implants which have been used as orthodontic anchorage, orthodontic
therapy seems to be essentially facilitated.

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1.1 List of common terms used for mini-screw implants :
• Microimplants
• Micro-implant anchors
• Mini implants
• Mini implants for orthodontic anchorage
• Mini screws
• Ortho implants
• Ortho TAD
• TAD – Temporary Anchorage Devices
• Titanium screw Anchorage
As described by Ludwig 4
In 2005 by Carano and Melsen5 , it was agreed that the word Mini-Implant should
be applied to all these terms. In 2005 Mah and Bergstrand agreed to this aspect and
they pointed out that mini-implant is more appropriate than micro-implant or screw6,
because the word “micro” is defined as a magnitude of 10-6.
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History of Mini Implants
“I am the owner of the sphere, the seven stars and of the solar year of Caeser’s
hand, and Plato’s brain, of Lord Christ’s heart, and Shakespeare’s strain, I am
History.”
- Ralph Waldo Emmerson

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2 HISTORY OF MINI IMPLANTS
In the 19th century, concepts were designed to anchor teeth to structures other than
teeth. This led to the development of Extra-oral anchorage systems. These appliances,
although mechanically efficient, imposed enough discomfort to the patients to deter
them from continuing their use and created practical compliance issues, affecting the
overall therapy negatively.
The era of skeletal anchorage began later, in 1945, with the failed experiments of
Gainsforth and Higley3 to anchor screws in the jaws of mongrel dogs. Using a 2.4-mm
pilot hole, a 3.4-mm-diameter X 13-mm-long Vitallium screw was placed in the
ascending ramus of 6 dogs. A rubber band delivering between 140 and 200 g of force
was attached from the screw head to a 0.040-inch wire that slid through a tube on the
upper molar band and was soldered to the upper canine band. The system was designed
to distally tip/retract the canine by immediately loading the screws with the rubber
bands. However, all the screws were lost in 16-31 days. The experiment, although
unsuccessful, the authors concluded that “anchorage may be obtained for orthodontic
movements in the future.”
There were no more published reports of attempts to use endosseous implants to
move teeth until the clinical case reports of Leonard Linkow in 19697. He used
mandibular blade-vent implants in a patient to apply Class ll elastics for retraction of
maxillary incisors.

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Figure 1 A- Spiral-shaft
implants (Chercheve). B- Various
sizes ofearly designed vent-plant
implants. C - a tripod implant,
assembled. D- Various early
designed blade implants. 8
In the 1970s, after Branemark and co-workers reported the successful
osseointegration of implants in bone
9, many orthodontists began taking
an interest in using implants for
orthodontic anchorage. Sherman
placed six vitreous carbon dental
implants into the extraction sites of
mandibular third premolars of dogs
and applied orthodontic forces in
1978. Two of the implants were firm
and were considered to be successful 10.
1979, Smith won the Milo Hellman Research Award of the American Association of
Orthodontists by studying the effects of loading bioglass-coated aluminum oxide
implants in monkeys and reported no significant movement of the implants during
force application. He described the interface between the bioglass implants and the

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surrounding tissue as fusion or ankylosis, despite the observation that intervening areas
of connective tissue were present 11.
After other similar efforts did not show much success, it was revisited by Creekmore
and Eklund in 1983. They inserted vitallium surgical bone screws below spina nasalis
to anchor upper incisor intrusion 12; the result was 6 mm of intrusion. Later, in similar
experiments, by Turley et al13 , the in-depth clinical and animal experimental
investigations established the base for today’s use of skeletal anchorage techniques.
The most important studies published between 1970 and 2000 were systematically
reviewed and, related to implants for orthodontic anchorage by Favero and Bressan in
their published article Orthodontic anchorage with specific fixtures: related study
analysis. The literature analysis was divided in specifics topics as materials, size and
screws shape, biomechanics, loading and healing time, used strength, surgery and
reasons to evaluate the success. One of very important aspects is that biocompatible
material had to be used.

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In Favero et al’s literature review there are different studies by different authors,
done with different materials 14.
EXPERIMENTS WITH TITANIUM
Experiments on animals Experiments on humans
Roberts 1984
Garetto1985
Turley 1988
Roberts 1989
Linder-Aronson 1990
Wehrbein 1993
Block 1995
Southard 1995
Miotti 1996
Wehrbein 1997
Parr 1997
Akin -Nergiz 1998
Van Roekel 1989
Roberts 1990
Haanaes 1991
Higuchi 1991
Odman 1994
Roberts 1994
Wehrbein 1996
Kanomi 1997
Wehrbein 1998
Umemori 1999
Wehrbein 1999

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Experiments With Other Materials
Ceramics Biodegradable
materials
(Polyactide)
Vitallium Ticonium
Sherman 1978
Smith JR 1979
Mendez C 1980
Paige S 1980
Turley PK 1980
Gray 1983
Glatzmaier 1995
Glatzmaier 1996
Turley PK 1983
Gray JB 1983
Creekmore TD 1983
Douglass 1987
It took 60 years to progress from vitallium to the current standard, titanium.
Although, it ranks ninth among the earth’s most abundant elements, titanium was
not discovered until 1791 and was not mass produced before 1948 15. Three times
stronger than stainless steel, it exhibits little response to heat, electricity or magnetic
forces. It is highly biocompatible; and is inert. Type v titanium has the highest
tensile strength, hence most suitable for bone screws.
In 1988, Shapiro and Kokich described the possibility of using dental implants
for anchorage during orthodontic treatment prior to being used for prosthodontic

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purposes 16. They emphasized the importance of the position of the implants as well
as the proper case selection and implant requirements during diagnosis and
treatment planning.
1994, Roberts and co-workers reported on the clinical application of 3.75 mm x
7.0 mm standard Branemark ﬁxture as anchorage in the retromolar area for closing
a mandibular ﬁrst molar extraction site17. An anchorage wire attached to the implant
was extended to the vertical tube of the premolar bracket. Stabilizing the premolar
anterior to the extraction site allowed mesial movement of the molars without distal
movement of the more anterior teeth.
The osseointegration is analogous to the situation in which ankylosed tooth that
can be orthodontically loaded without moving, working as a stable anchorage unit,
keeping in mind that the absence of the periodontal membrane does not allow the
cell alterations which result in movements18. Nevertheless conventional dental
implants can be placed only in limited areas such as in the retromolar region or in
edentulous areas. 19, 20. Another limitation has been the direction of force
application such as when a dental implant is placed on the alveolar ridge and is too
large for horizontal orthodontic traction. Furthermore, dental implants are
troublesome for patients because of the severity of surgery, the discomfort of the
initial healing, and the difficulty of oral hygiene.

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In 1997, Kanomi described a mini-
implant specifically made for orthodontic
use21. He reported that 1.2 mm diameter
titanium mini-implants provided sufficient
anchorage for intruding the lower anterior
teeth. After four months, the mandibular incisors
were intruded 6 mm. Neither root resorption nor
periodontal pathology was evident. Kanomi applied an orthodontic force on the
mini-implant Figure 3 several months after implantation, anticipating
osseointegration between the mini-implant and the bone.
Figure 3 Intrusion achieved by mini implants in studies by Kanomi 21
He also mentioned the possibility of mini-implants being used for horizontal
traction, for molar intrusion, and as an anchor for molar distalization and distraction
osteogenesis.
1998 Costa et al presented a screw with a bracket-like head, using 2mm titanium
miniscrews for orthodontic anchorage22. The screws were inserted manually with a
screw driver directly through the mucosa without making a ﬂap and were loaded
immediately. Of the 16 miniscrews used during the clinical trial, two became loose
Figure 2 Placement of mini-implant

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and subsequently were lost before treatment was ﬁnished. They suggested that
miniscrews could be placed into
 Inferior surface of the anterior nasal spine,
 Midpalatal suture,
 Infrazygomatic crest,
 Retromolar area,
 Mandibular symphysis area, and
 Between the premolar and molar regions.
Majzoub and colleagues, in 1999, investigated the bone response of endosseous
implants to orthodontic loading23. Twenty-four short-threaded titanium implants
were inserted into the calvarial midpalattal suture of 10 rabbits. Two weeks
following insertion, a continuous distalizing force of 150 gm was applied for a
period of eight weeks. All but one test implant remained stable, exhibiting no
mobility or displacement throughout the experimental loading period.
The clinical applications with different micro-implants shapes and the micro-
implants with bracket head advantages were described in a research24. The micro-
implants with bracket head have two fins and a slot as a bracket making it easy for
the wire and ligature placement. There are two different threads for micro-implants:
clockwise and anticlockwise (must be anticlockwise clamped). This new technique
allows a simplified treatment, letting many possibilities of confection without the
necessity of complete appliances. This way, the treatment is faster, without the
patient’s cooperation. Different head types and shapes available in the market were
presented.

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The self-puncturing titanium orthodontic micro-screws have changed the
concepts as in regard to surgical orthodontic treatments which use the skeletal
anchorage through a simplified and safe surgical approach. The installation of this
new device requires specific knowledge on surgical techniques, clinical application
and judgment for selecting the micro-screws, as well as the orthodontic activation
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The design of Orthodontic
mini-implants.
“Simple is good”
-Jim Henson

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3 THE DESIGN OF ORTHODONTIC MINI-IMPLANTS.
3.1 Classifications of miniscrew Implants.
Labanauskaite et al in 2005 classified Orthodontic implants. 25
I. According to the shape and size
II. According to the implant bone contact.
Conical
(cylindrical)
Micro
implants
Palatal
implants
Prosthodontic
implants.
Miniplate
implants
Disc implants
(onplants);
Osseointegrated. Nonosseointegrated.

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III. According to the application
- Used only for orthodontic purposes (orthodontic implants)
- Used for prosthodontic and orthodontic purposes
(prosthodontic implants).
Cope 26 classified Temporary anchorage devices as –
 Biocompatible TADs.
 Biologic TADs.

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Biocompatible TADs are further classified as follows-
Figure 4. Classification of Biocompatible TADs.
Biocompatible TADs
Osseointegration
Dental Implant
Palatal Implant
Retromolar
Implant
Palatal
Onplant
Mechanical Retention
Fixation
Screws
FixationScrews
withPlates
Mini Implants
Fixation
Wires

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Biologic Temporary Anchorage devices are classsified as -
Figure 5 Classification of Biologic TAD.
Currently, there are a number of commercially available miniscrew
implant systems for orthodontic use (Table I);
Biological TADs
Osseointegration
Ankylosedteeth
Mechanical
Dilaceratedteeth

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3.2 Elements of Implant Design:
The main differences between the currently available miniscrew implants relate to
their composition, size, and design and include:
1. The alloy or metal used for their fabrication
2. Biocompatibilty
3. The design of the head portion
4. The design and diameter of threaded portion,
5. The length of the implant
3.2.1 Implant alloy or metal used -
The material must be nontoxic and biocompatible, possess excellent mechanical
properties, and provide resistance to stress, strain, and corrosion.
The materials commonly used for implants can be divided into 3 categories 14:
1. Biotolerant (stainless steel, chromium-cobalt alloy),
2. Bioinert (titanium, carbon), and
3. Bioactive (vetroceramic apatite hydroxide, ceramic oxidized
aluminum).
Commercially pure titanium is the material most often used in implantology. It
consists of 99.5% titanium, and the remaining 0.5% is other elements, such as
carbon, oxygen, nitrogen, and hydrogen. Most studies in the literature report on the
use of traditional titanium for prostheses, sometimes modified in the abutments to
adapt to orthodontic requirements. However, pure titanium has less fatigue strength

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than titanium alloys. A titanium alloy—titanium + aluminum+ vanadium
(Ti6Al4Va)—is used to overcome this disadvantage. Its mechanical characteristics,
moreover, are well suited to implant requirements: it is very lightweight, and it has
excellent resistance to traction and breaking, enabling it to withstand both
masticatory loads and the stresses of orthodontic forces.
The Orthodontic Mini Implant (OMI) [Leone, Italy] is made from implant steel
1.4441, which is still used in traumatology.
3.2.2 Biocompatibility:
With the exception of the Orthodontic Mini Implant, which is fabricated from
stainless steel, all other aforementioned systems are made of medical type IV or type
V titanium alloy. Because of its particular characteristics, titanium is considered an
excellent material: no correlation has been shown between titanium and the
development of neoplasm, and no allergic or
immunological reactions have been noted
that could be traced to the use of pure
titanium. Bone grows along the titanium
oxide surface, which is formed after contact
with air or tissue fluid. 27
Figure 6

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3.2.3 Head design:
Most miniscrew implant systems are available in different designs to
accommodate both direct and indirect anchorage and avoid tissue irritation. The
most frequent is the button-like design with a sphere or a double sphere-like shape
or a hexagonal shape.
Figure 7 Various miniscrew implants. A, The Aarhus Anchorage System. B, The AbsoAnchor. C,
The Spider Screw Anchorage System . D, The IMTEC Mini Ortho Implant
Miniscrew implants available with this design include the Aarhus Anchorage
System, the AbsoAnchor System, the Dual-Top Anchor System, the IMTEC Mini
Ortho Implant, the Lin/Liou Orthodontic Mini Anchorage Screw, the Miniscrew
Anchorage System, the Orthoanchor Kl System, and the Spider Screw Anchorage

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System. 28With a hole through the head or the neck of the screw, usually 0.8 mm in
diameter, this design is mostly used for direct anchorage.
A bracket like design is also available, which can be used for either direct or
indirect anchorage as provided by the Aarhus Anchorage System, the AbsoAnchor
System, the Dual-Top Anchor System, the Spider Screw Anchorage System, and the
Temporary Mini Orthodontic Anchorage System. 29.
Finally, a further hook
design is used by the LOMAS
miniscrew implant.
Dalstra 28 found that as
Bone density increases, the
resistance created by the stress
surrounding the screw be-
comes more important in
removal than in insertion of
the screw. At removal, the
stress is concentrated in the
neck of the screw. If an Allen
wrench is used for insertion and
removal, the hole in the center
of the screw will weaken the neck, which may lead to fracture. A hollow neck
facilitates the insertion of a ligature, but also weakens the neck. The strength of the
screw is optimized by using a slightly tapered cortical shape and a solid head with a
screwdriver slot.
Figure 8 From left to right: 1.5 mm cylindrical mini-implant
with a slot at the screw head; 1.6 mm tapered mini-implant with
a slot at the screw head; and 2.0 mm cylindrical mini-implant
with threads at the screw head

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3.2.4 Thread design:
3.2.4.1 Self-drilling versus self-tapping –
The miniscrew implant can have self tapping or self drilling thread design. A
prerequisite for self tapping placement is pilot drilling to prepare a hole for the
implant. Particularly for interradicular microimplants, pilot drilling has potential
dangers, such as damage to tooth roots, drill-bit breakage, overdrilling, and thermal
necrosis of bone. While self drilling screws doesn’t need pilot drilling for placement
and can be placed conveniently in narrow interdental areas.
Yan Chen 30 in 2008, compared the influences of Self-drilling versus self-tapping
orthodontic microimplants on the surrounding tissues biomechanically and
histologically in dogs. Fifty-six titanium alloy microimplants were placed on the
buccal side of the maxillae and the mandibles in 2 dogs were divided into 2 groups
of 28; one group of microimplants was self-drilling, and the other was self-tapping.
Approximately 200 g of continuous and constant forces were applied immediately
between 2 microimplants by stretching closed nickel-titanium coil springs for 9
weeks. Peak insertion torque and removal torque were recorded immediately after
the implants were placed and when the dogs were killed, respectively.
They found that success rates were higher in the self-drilling group (93%) than in
self-tapping group (86%). Higher peak insertion torque and peak removal torque
values were seen in the self-drilling group in both the maxilla and the mandible. The
mean Peak Insertion Torque (PIT) values of the Self Drilling Implants (SDIs) in the
maxilla and the mandible were 5.6 and 8.7 Ncm, respectively. In the Self Tapping
Implants (STI) group, PIT values were 3.5 Ncm for the maxilla and 7.4 Ncm for the
mandible. A tendency to fracture was found in self-drilling group. The percentage
of bone-to-implant contact values was greater in the self-drilling group. They
further found that microimplants with high PIT might have closer initial contact
with bone and might be good for bone remodeling. SDIs cause less damage to bone

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during placement; therefore, osseointegration might happen earlier and be better
than with STIs. From an anchorage perspective, the greater the contact between the
surface of the microimplant threads and the cortical bone, the higher the initial grip
of microimplants would be.
They concluded that Self-drilling microimplants can provide better anchorage
and can be recommended for use in the maxilla and in thin cortical bone areas of the
mandible.
It should be noted that even though SDIs have many advantages, if the bone is
dense, they should not to be chosen. STIs should be considered instead. In the
maxilla and areas with thin cortical bone in the mandible, microimplants would
penetrate easily. Failure due to stripping of bone was infrequent, so pilot drilling
was not necessary.
3.2.4.2 Conical Versus Cylindrical Designs –
Wilmes et al in 2008 found that conical mini-implants achieved higher primary
stabilities than cylindrical designs 31. Shinya Yano in 2006 suggested that tapered
orthodontic miniscrews induce bone-screw cohesion following immediate loading
hence advocated use of tapered rather than cylindrical designs. 32
Many other authors advocated the use of conical, rather than cylindrical designs,
of the implant body.
Another concern of using conical design is
a significant increase of MIT was observed
mainly in the taper type miniscrew which
leads to higher bone to implant contact surface
along with higher initial stability of the
implants.
Although the conical group required high

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removal torque, which means good initial stability, it also showed high insertion
torque which could affect adjacent tissue healing. The success rates and
histomorphometric analysis showed no significant difference between the
cylindrical and conical groups.
The conical shape may need modification of the thread structure and insertion
technique to reduce the excessive insertion torque while maintaining the high
resistance to removal.
3.2.5 Length and diameter of the miniscrew implant -
Miniscrew implants are available in different lengths and diameters to
accommodate placement at different sites in both jaws. Most miniscrew implants
have a thread diameter ranging from 1.2 to 2.0 mm and a length from 4.0 to 12.0
mm, although some of them are also available at lengths of 14.17 or even 21 mm.
The advantage of thin screw is the ease of insertion between the roots without the
risk of root contact.
Seong-A Lim in 2008 suggested that that the maximum insertion torque
increased with increasing diameter and length of the orthodontic miniscrews as well
as increasing cortical bone thickness 33. An increase in screw diameter can
efficiently reinforce the initial stability of miniscrews, but the proximity of the root
at the implanted site should be considered. Miyawaki et al in 2003 reported that a
diameter of 1.0 mm or less were associated with mobility and failure of the screw 34.
While Lin et al in 2003 and Dalstra in 2004 showed that there increased chances
of fracture with miniscrews of diameters less than 1.2 mm 35.
Miyawaki in 2003 34 suggested use of miniscrew implant longer than 5 mm and
diameter more than 1mm. Costa et al in 2005 reported that miniscrew implants of 4
to 6 mm in length and diameter more than 1.2 mm are safe. Deguchi et al 36 after

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evaluating the cortical bone thickness with the help of three-dimensional computed
tomographic suggested use of miniscrew implant of length 6 - 8 mm and 1.2- to 1.5-
mm maximum diameter. In addition, for lingual orthodontics, the recommended
location is mesial to the first molar at 30°, and 8 to 10 mm in length.
Overall recent studies unanimously agree using miniscrew implant of length 6 -
8 mm and 1.2- to 1.5-mm in diameter is safe.
3.2.6 Osseointegration:
Because complete osseointegration of screws used in orthodontic applications is
a disadvantage that complicates the removal process, most of these devices are
manufactured with a smooth surface, thereby minimizing the development of bone
in growth and promoting soft tissue attachment at ordinary conditions and in the
absence of special surface treatment regimens. Till now only one study has been
done by Chaddad 37 in 2008 who have tried to modify miniscrew-implant surface
sandblasted, large grit, acid-etched (SLA).
Chaddad evaluated the clinical performance and the survival rate of machined
titanium versus sandblasted, large grit, acid-etched (SLA) mini-implants under
immediate orthodontic loading. Seventeen machined titanium (MT) mini-implants
and 15 sandblasted, large grit, acid-etched (SLA) mini-implants were placed in 10
patients. The mini-implants were immediately loaded and the patients seen at 7, 14,
30, 60, and 150 days. Clinical parameters such as anatomical location, character of
the soft tissue at the screw head emergence, type of mini-implant system, diameter,
and length were analyzed. In addition, the insertion torque recorded at the time of
insertion was also assessed.
Although the survival rate of the SLA mini-implants in this investigation was
higher compared with the MT group (93.5% to 82.5%), the correlation between the
implant surface characteristics and the rate of success was not statistically

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significant 37. These findings suggest that altering an implant surface to create more
surface area and increase bone contact may not be the primary consideration when
using mini-implants as orthodontic anchors. The SLA mini-implants presented a
higher level of osseointegration at the time of removal. This clinical observation
was based on the higher torque necessary for removal of SLA mini-implants when
compared with smooth machined titanium implants. Authors clinical experience
indicates that surface treated (SLA) implants could be advantageous in areas of poor
bone quality, and loading should be delayed for 6 to 8 weeks when initial
osseointegration has occurred.
In the failure group, all the fixtures had their screw emergence at the oral mucosa
and recorded a torque range of less than 15 Ncm. The insertion torque statistically
influenced the survival rate of the mini-implants (P <.05). Surface treatment,
anatomical location, as well as soft tissue emergence were not statistically
significant.
Authors concluded that surface characteristics did not appear to influence
survival rates of immediately loaded mini-implant. A torque value of more than 15
Ncm recorded at the time of insertion appears to be one of the critical variables for
mini-implant survival under immediate loading.
3.2.7 Insertion torque -
The initial stability of a miniscrew is important because most incidences of
orthodontic miniscrew failure occur at the early stage. Miyawaki in 2003 reported
that the insertion torque is commonly used to evaluate the mechanical stability of
implants including miniscrews.
Studies have shown that a certain level of insertion torque is necessary in order to
achieve the initial anchorage at the screw and the bone interface, and that the
insertion torque of mini screws is an important factor in determining the appropriate
initial stability of a screw. Furthermore, it was suggested that excessive insertion

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Mini Implants
torque, heat at the border between the screw and bone, and mechanical injury can
cause degeneration of the bone at the implant-tissue interface.
Motoyoshi determined an adequate implant placement torque (IPT) for obtaining
a better success rate of 124 miniscrew-implants that were screwed into the buccal
alveolar bone of the posterior region in 41 orthodontic subjects 38. The peak value of
IPT was measured using a torque screwdriver. The success rate of the mini-implant
anchor for 124 implants was 85.5%. The mean IPT ranged from 7.2 to 13.5Ncm,
depending on the location of the implants. There was a significant difference in the
IPT between maxilla and mandible. The IPT in the mandible was, unexpectedly,
significantly higher in the failure group than in the success group. Therefore, a large
IPT should not be used always. According to author’s calculations of the risk ratio
for failure, to raise the success rate of 1.6-mm diameter miniimplants, the
recommended IPT is within the range from 5 to 10Ncm.
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Mini Implants
Anatomical Considerations

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Mini Implants
4 Anatomical Considerations
Miniscrews, mini implants, and miniplates are relatively easy clinical
alternatives. Orthodontic fixation screws can be placed either with or without flap
raising. When screws are placed without a flap, either drilling with a slow-speed
handpiece or self-tapping with a screwdriver (or a combination of them) can be
used. Screws pass through the soft tissue, and therefore the thickness of the soft
tissue and cortical bone at the surgical site are critical factors for success. Therefore,
the use of endosseous implants for absolute orthodontic anchorage has been the
focus of many studies and clinical trials. When the intraoral anchorage is stable,
biocompatible, and free from site specificity, it can be used effectively without
patient compliance . Systems that can satisfy these criteria include miniplates, and
mini implants. These implants can be placed in the inferior ridge of the pyriform
aperture, maxillary alveolar bone, the infrazygomatic crest, palatal alveolar bone, a
maxillary tuberosity, the hard palate, and the midpalatal suture area. To obtain
sufficient screw fixation, understandings of the bone density, screw shape and
length as well as soft tissue and cortical bone thickness are essential. This is
probably responsible for the high prevalence of complications such as
hypersensitivity of the root, root fracture, and alveolar bone fracture resulting from
miniscrew insertion.
Here, the anatomical aspect on the maxilla and mandible, with the special
reference on the alveolar bone of the jaws will be introduced and described.

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Mini Implants
4.1 Possible sites for placement of Miniscrew Implants in Maxilla –
Figure 9 Maxillary mini-implant locations. A. Below nasal spine. B. In the palate. C.
Infrazygomatic crest 39
Maxilla is the largest among the facial bones and forms the main part of the mid-
face region. Anatomically, the maxillary sinus is occupying as an air-filled space
within the maxilla. In this reason, the cortical plate surrounding the maxillary sinus
is very thin compared with the mandibular cortical plate. Furthermore, the facial
aspect of the maxilla above the level of the root apices is mainly composed of the
cortical plate with little spongy bone. The principal advantage of the miniscrewing
on the buccal interdental alveolar region is the ease in access. Even though the
cortical plate is very thin in this region, the initial anchorage can be provided in the
adult patients. However, care should be taken not to injure the dental roots and
maxillary sinus when performing the miniscrewing.
i. Area below the nasal spine the palate median or the paramedian area,
ii. Infrazygomatic crest,
iii. Maxillary tuberosities, and
iv. Alveolar process (both buccally and palatally) between the roots of the teeth.

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Mini Implants
4.2 Possible sites for placement of Miniscrew Implants in Mandible –
The mandible is the largest, strongest and lowest bone in
the face. It has a horizontally curved body that is convex
forwards, and two broad rami, that ascend posteriorly. The
body of the mandible supports the mandibular teeth within
the alveolar process. The rami bear the coronoid and
condylar processes, and the condyle articulates with the
temporal bones at the temporomandibular
joints.
i. Symphysis or Parasymphysis,
ii. Alveolar process (between the roots of the teeth), and
iii. Retromolar area.
Deguchi et al quantitatively evaluated cortical bone thickness in various
locations in the maxilla and the mandible with the help of three-dimensional
computed tomographic images reconstructed for 10 patients 36. The distances from
intercortical bone surface to root surface, and distances between the roots of
premolars and molars were measured to determine the acceptable length and
diameter of the miniscrew for anchorage during orthodontic treatment.
They found that significantly less cortical bone thickness at the buccal region
distal to the second molar compared with other areas in the maxilla. Significantly
more cortical bone was observed on the lingual side of the second molar compared
with the buccal side. In the mandible, mesial and distal to the second molar,
significantly more cortical bone was observed compared with the maxilla.
Furthermore, significantly more cortical bone was observed at the anterior nasal
spine level than at Point A in the premaxillary region. Cortical bone thickness
Figure 10 Mandibular mini-implant locations.
A. Retromolar area and molar region. B. Alveolar
process. C. Symphysis

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Mini Implants
resulted in approximately 1.5 times as much at 30° compared with 90°.
Significantly more distance from the intercortical bone surface to the root surface
was observed at the lingual region than at the buccal
region mesial to the first molar. At the distal of the
first mandibular molar, significantly more distance
was observed compared to that in the mesial, and also
compared with both distal and mesial in the maxillary
first molar. There was significantly more distance in
root proximity in the mesial area than in distal area at
the first molar, and significantly more distance was
observed at the occlusal level than at the apical level.
They suggested that suggests that the best available location for a miniscrew is
mesial or distal to the first molar, and the best angulation is 30° from the long axis
of the tooth. From findings of the distance from the intercortical bone surface to the
root surface and the root proximity, the safest length is 6 mm with a diameter of 1.3
mm. In addition, for lingual orthodontics, the recommended location is mesial to the
first molar at 30°, and 8 to 10 mm in length.
Maria Poggio40 provided an anatomical map to assist the clinician in miniscrew
placement in a safe location between dental roots using volumetric tomographic
images of 25 maxillae and 25 mandibles.
They suggest the order of the safer sites available in the interradicular spaces of
the posterior maxilla is as follows:
a. On the palatal side, the interradicular space between the maxillary first
molar and second premolar, from 2-8 mm from the alveolar crest.

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Mini Implants
b. On the palatal side, the interradicular space between the maxillary
second and first molars, from 2-5 mm from the alveolar crest.
c. Both on buccal or palatal side between the second and first premolar,
between five and 11 mm from the alveolar crest.
d. Both on buccal or palatal side between the first premolar and canine,
between five and 11 mm from the alveolar crest.
e. On the buccal side, in the interradicular space between the first molar
and second premolar, from five to eight mm from the alveolar crest.
f. In the maxilla, the more anterior and the more apical, the safer the
location becomes.
g. The least amount of bone was in the tuberosity
The following is the order of the safer sites available in the interradicular spaces
of the posterior mandible:
a. Interradicular spaces between the second and first molar.
b. Interradicular spaces between the second and first premolar.
c. Interradicular spaces between the first molar and second premolar at 11
mm from alveolar crest.
d. Interradicular spaces between the first premolar and canine at 11 mm
from the alveolar crest.
e. The least amount of bone was between the first premolar and the canine.

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Mini Implants
They suggested that the features of the ideal titanium miniscrew for orthodontic
skeletal anchorage in the interradicular spaces should be 1.2- to 1.5-mm maximum
diameter, with 6–8 mm cutting thread and a conic shape.
4.3 Safety Distance -
Huang suggested a method to evaluate the possibility of damaging the
periodontal ligament (PDL) is to calculate the safety distance41.
Safety distance: Diameter of the implant + PDL space (normal range 0.25 mm ±
50%) minimal distance between implant and tooth (1.5 mm) Example: Safety
distance (mm) of mini-implants when inserted between roots 1.2+(0.25 +
50%)+(1.5 +1.5) = 4.575. Therefore, the distance between roots needs to be at least
4.6 mm to reduce the risk.
4.4 Safety Distance Modified
Gautam P and Valiathan A in 2006 42.
Safety distance = Diameter of the implant + 2 × [PDL space (normal range 0.25
mm ± 50%)] minimal distance between implant and tooth (1.5 mm)
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Biomechanical Considerations
in Mini Implant Use

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Mini Implants
5 BIOMECHANICAL CONSIDERATIONS
The type of tooth movement that can be produced with Mini Implant anchorage
is determined by the same biomechanical principles and considerations that operate
during conventional orthodontic treatment, e.g. force, moment, center of resistance,
center of rotation. A Mini Implant can be placed in many different areas of the
mouth and at different heights on the gingiva relative to the occlusal plane, creating
several biomechanical orientations, e.g., low, medium and high. Thus, various types
of tooth movement can be produced depending on the position of the Mini Implant,
the height of the elastomer attachment, and the magnitude of the force applied. The
following are various clinical protocols that can be used routinely for effective tooth
movement using Mini Implant anchorage.
5.1 Maxillary anterior en masse retraction mechanics in extraction cases
For maxillary anterior en masse retraction, the line of action and the moment
created will vary depending on the location of the Mini Implant relative to the
occlusal plane. En masse retraction mechanics in extraction cases can be classiﬁed
into three categories much like the descriptors used traditionally for headgear
traction: low, medium, and high-pull mechanics.
Figure 11

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Mini Implants
5.1.1 Medium—Pull Mechanics for the MaxillaryArch
Maxillary Mini Implants usually can be placed buccally between the second
premolar and first molar roots for anterior en masse retraction. When a maxillary
Mini Implant is placed about 8 to 10 mm above the main archwire, the term
medium-pull en masse retraction mechanics is used. If force is applied from a
medium-pull Mini Implant to a hook located between the lateral incisor and canine
that extends 6 to 7 mm vertically, the maxillary occlusal plane ordinarily can be
maintained. Thus, medium-pull mechanics are useful in treating patients who have
normal overbite relationships.
5.1.2 Low-Pull Mechanics for the MaxillaryArch
When a Mini Implant is placed buccally between the roots of the maxillary
second premolar and first molar and is less than 8 mm away from the main
archwire, the term low-pull en masse retraction mechanics is used. If force is
applied from a low-pull Mini Implant to an anterior hook extending 6 to 7mm above
the main archwire, the maxillary Occlusal plane usually can be rotated in a
clockwise direction. Therefore, low-pull mechanics are useful in treating patients
who have an open bite or an open-bite tendency.
5.1.3 High-Pull Mechanics for the MaxillaryArch
When a Mini Implant is placed buccally between the maxillary second premolar
and the first molar roots, and is more than l0 mm away from the main archwire, the
term high-pull en masse retraction mechanics is used. If force is applied from a
high-pull Mini Implant to an anterior hook extending 6 to 7 mm above the main
archwire, the maxillary occlusal plane usually will rotate in a counterclockwise
direction. Thus, high-pull mechanics are useful in treating patients who have a deep
bite or deep bite tendency.

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Mini Implants
5.2 Mandibular anterior en masse retraction mechanics in extraction cases
5.2.1 Medium-Pull Mechanics for the Mandibular Arch
Mandibular Mini Implants usually are placed buccally between the second
premolar and first molar roots for anterior en masse retraction. When a mandibular
Mini Implant is placed 6 to 8 mm away from the main archwire, the term medium-
pull en masse retraction mechanics is used. If force is directed from a medium-pull
Mini Implant to a hook located between the lateral incisor and canine that extends 4
to 6 mm below the main archwire, the mandibular occlusal plane usually can be
maintained. Therefore, medium-pull mechanics are useful in treating patients who
have normal overbite relationships.
5.2.2 Low-Pull Mechanics for the Mandibular Arch
When a Mini Implant is placed buccally between the roots of the mandibular
second premolar and first molar and is less than 6 mm away from the main
archwire, the term low-pull en masse retraction mechanics is used. If force is
applied from a mini implant in a low-pull location to an anterior hook extending 4
to 6 mm below the main archwire, a counterclockwise rotation of the mandibular
occlusal plane typically can be achieved. Low-pull mechanics are useful in treating
patients who have an open bite or open bite tendency.
5.2.3 High-Pull Mechanics for the Mandibular Arch
High-pull en masse retraction mechanics result when a Mini Implant is placed
buccally between the mandibular second premolar and first molar roots and more
than 8 mm away from the main archwire. If force is applied from a high-pull Mini

P a g e | 43
Mini Implants
Implant to an anterior hook extending 4 to 6 mm below the main archwire, the
mandibular occlusal plane usually can be rotated in a clockwise direction.
Therefore, high-pull mechanics are useful in treating patients with a deep bite or
deep bite tendency.
5.3 Anterior Intrusion Mechanics in the MaxillaryArch
For intrusion of the maxillary anterior teeth, Mini Implants can be placed
between the roots of the upper incisors. Force can be applied from the mini implant
directly to the main archwire. Usually a force originating from a single Mini
Implant placed between the maxillary central incisor roots is adequate to intrude the
anterior dentition. However, if there is a transverse cant to the occlusal plane. Two
mini implants can be placed bilaterally between the central and lateral incisor roots.
Forces of differing magnitudes then can be applied on each side for improvement of
the canted occlusal plane during intrusion.
5.4 Anterior Intrusion Mechanics in the Mandibular Arch
For intrusion of the mandibular anterior teeth, Mini Implants can be placed
between the roots of the lower incisors. Again, force can be applied from the Mini
Implant directly to the main archwire. One mini implant placed between the lower
central incisor roots usually is sufficient to allow for intrusion of the entire
mandibular anterior segment. However, if the occlusal plane is canted transversely,
two mini implants can be inserted between the central and lateral incisor roots
bilaterally. Differential forces then can be applied for improvement of the canted
occlusal plane during intrusion.

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Mini Implants
5.5 Anterior en masse Retraction withAnterior Intrusion
In deep bite extraction cases, high-pull mechanics are recommended in the
maxillary arch for intrusion of the anterior teeth during en masse retraction. In
reality, it is difficult to place Mini Implants higher in the buccal vestibule. In
addition, high-pull mechanics do not produce much of a horizontal force compared
to low-pull or medium-pull mechanics. Thus, we recommend using two posterior
Mini-Implants in low or medium-pull orientation combined with one or two anterior
Mini Implants. Posterior Mini Implants usually will be more effective in retracting
the anterior teeth, whereas anterior Mini Implants will be more effective in their
intrusion. Furthermore, anterior intrusion Mini Implants will counteract the
tendency for incisors to tip lingually during their retraction
5.6 Molar Intrusion Mechanics for Open bite Cases
‘In that it is possible to intrude molar teeth using Mini Implants, open bites can
be corrected relatively easily, especially skeletal open bites. If 1mm of absolute
molar intrusion is achieved posteriorly, an anterior open bite of 2 to 3 mm will be
closed anteriorly. A Mini Implant can be placed between the roots of the maxillary
second premolar and first molar and/or the ﬁrst molar and second molar buccally
and/or palatally, for the intrusion of maxillary molar teeth. A transpalatal arch (TPA)
is used for palatal support in the absence of palatally-placed Mini Implants. In the
mandibular arch, however, it is not advisable to insert mini implants lingual to the
molar roots: a lingual holding arch can be used for support instead.
5.7 MaxillaryAnterior Lingual Root Torque Mechanics
After anterior en masse retraction in an extraction case, severe lingual tipping of
the maxillary anterior teeth sometimes is observed. Whenever lingual root torque
then is applied, labial crown tipping usually is observed instead. To prevent this

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Mini Implants
kind of labial crown tipping, Class II elastics are required. Moreover, to prevent the
side effects of Class II elastics, up-and-down vertical elastics and high-pull
headgear are used. Mini Implants in the maxillary buccal area, however, also can
prevent labial crown tipping during lingual root torque application; ligature wires
are connected from the Mini Implants to the anterior portion of the main archwire.
5.8 Molar Distalization Mechanics for Non-Extraction Cases
To correct Class II or Class III molar relationships, sometimes it is necessary to
distalize molar.
Mini Implants can be placed between the roots of the second premolar and ﬁrst
molar, and nickel titanium coil springs can be used. After molar distalization, the
anterior teeth will need to be retracted. The ﬁrst Mini Implant can be removed if it
interferes with this
retraction, & a second mini
implant is placed just distal
to the first one or between
the first molar & second molar roots
5.8.1 Retraction of the Entire Maxillary or Mandibular Dentition
Two buccally placed mini implants can provide
sufficient anchorage to move the entire maxillary or
mandibular dentition posteriorly. Usually mini implants
are inserted between the roots of second premolar and
first molar.
Retraction of the entire dentition is more positive in patients who have mesially
tipped posterior teeth. Thus, Mini Implants function nicely in combination with the
Figure 12

P a g e | 46
Mini Implants
multiloop edgewise archwire (MEAW) technique of Kim (Kim, 1999a,b, 141_.;
Chang and Moon, 1999) for retraction of the entire dentition.
5.8.2 Midpalatal Mini Implant Placement For Molar Distalization
The midpalatal area also is a good site for mini implant placement because the
palate is covered with relatively thin keratinized mucosa and has adequate bone
volume. Additionally, there is no concern about a Mini Implant touching the roots of
adjacent teeth during implantation. However, if the patient has a broad unossiﬁed
suture, sufficient mechanical stability is not possible. In this situation it is better to
place the Mini Implants parasagittally. For molar distalization, orthodontic forces
can be applied from a Mini Implant to the center point of a transpalatal arch.
Furthermore, a mid-palatal mini implant can be used to anchor orthodontic force,
which is applied from a level high above the center of rotation of the molars. Thus,
distalization traction or distal tipping of roots can be achieved rather easily with
midpalatal implants than with buccally placed Mini implants.
If a bracket head type of Mini Implant is placed in the midpalatal area, a
transpalatal arch can be inserted directly into the bracket slots. Force can be applied
directly to the teeth from the transpalatal arch, much in the same manner as with a
pendulum appliance (Hilgem 1992;)_ The incorporation of a midpalatal mini
implant into a transpalatal arch can be technically challenging, however, because of
the level of precision required. In addition the application of elastomers for tooth
movement can be difficult especially in patients who have high and narrow palates
5.9 Protraction Mechanics in Extraction Cases
Sometimes molar protraction is needed in minimum or moderate anchorage cases
or unusual extraction cases. However, molar protraction is one of the most difficult
tooth movement to accomplish, especially in patients with a low mandibular plane,
Class 2 & a deep bite. If mini implants are incorporated into the treatment protocol,
molars can be moved forward more effectively and without disturbing the anterior

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Mini Implants
teeth. Mini implants, for this purpose can be placed between the roots of the
mandibular canine and first premolar or first premolar and 2nd premolar.
5.10 Minor Tooth Movements Using Mini Implant Anchorage
5.10.1 Retromolar Mini Implants for Single Molar Uprighting -
A single retromolar Mini Implant is useful in uprighting
a mesially tipped molar. Elastic chain or ligature wire can
be connected from a retromolar Mini Implant to an
attachment on the tipped molar (Fig.5-31). These
mechanics produce an intrusive force during molar
uprighting and prevent the occlusal trauma that normally
would occur with conventional uprighting techniques.
However, this type of simple retromolar Mini Implant
mechanics cannot control the movement of a tooth precisely.
5.10.2 Molar Distalizatien Using a Single Mini Implant in an Edentulous Area
For distalization of a molar tooth (or teeth) that is (are)
adjacent to an edentulous area, an open coil spring can be
used on the main archwire in the edentulous region. To
prevent tipping, the anterior teeth labially, a Mini
Implant can be placed in the edentulous area and
connected by a ligature wire to a sliding hook on the
main archwire as shown in Figure 14. The open coil NiTi
spring is compressed by tying the ligature to the sliding
hook and moving the hook posteriorly along the
Figure 14
Figure 13

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Mini Implants
archwire.
5.10.3 Molar Uprighting and/or Protraction or Distalization Mechanics Using
Two Mini Implants in an Edentulous Area
A single Mini implant cannot resist rotational or torquing forces. To resist
rotational and torquing forces, two Mini Implants can
be placed side-by-side in an edentulous area and then
joined together using light-cured resin. Subsequently, a
bracket can be bonded to the resin of the Mini Implant-
supported structure. A rectangular wire inserted into
this bracket will facilitate three-dimensional
movement of the involved tooth (Figure 12)
5.11 Buccal Cross bite (Scissors Bite) Correction
Correcting a scissors bite with conventional orthodontic mechanics requires the
use of through-the bite elastics (Graber, I972; Moyers, 1988;) However, if these
elastics are used, undesirable extrusion of the posterior teeth may occur. To correct a
scissors bite without causing molar extrusion, intra-arch mechanics, rather than
interarch mechanics, must be used. Transpalatal and lingual arches can be used to
reinforce anchorage in conventional intra-arch methods. If mini implants are used,
the same type of uprighting and intrusion is observed
during buccal cross bite correction. With only one
Mini Implant, however, it is difficult to apply
orthodontic force in the proper direction; if a bracket
head type of Mini Implant is selected, a wire can be
extended from the slot of the bracket to allow the
force to be applied more effectively. Different handed screws, i.e., right and left-
handed, are inserted depending upon the moment and force to be applied
Figure 15
Figure 16

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Mini Implants
Indications &
Contraindications
“That, which does not kill us, makes us stronger.”
– Freidrich Nietzsche

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Mini Implants
6 Indications & Contraindications
Indications, Contraindication & Relative Contraindications
Absolute anchorage represents new orthodontic paradigm and it is maybe the
most important advancement in recent times, because it offers the orthodontics of "
action without reaction", practically eliminating the third principle of Newton.
Indications for miniimplants can be for achieving the absolute anchorage or forces
directions which would be very difficult to achieve using the traditional mechanics.
There are two basic forms of absolute anchorage: -
Direct anchorage:
When active segment is pulled directly from min implant
.
Indirect anchorage:
When active segment is pulled from the reactive segment and this segment is
fixed to miniimplant to increase anchorage.
6.1 INDICATIONS
The most frequent indications are:
1. Molar intrusion.
2. Molar uprighting by crown distalizing or by root mesializing.
3. Anterior open bite treatment with molar intrusion (with or without
extractions).

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Mini Implants
4. Anterior deep bite treatment with incisal intrusion (with or without
extractions) .
5. Leveling of transverse tipping of occlusal plane.
6. Extraction cases.
7. Distalizing or anchorage after distal movement with other kinds of
appliances, such as Pendulum.
8. Forced eruption of included or non-included teeth.
9. Asymmetric expansion.
10. Bodily movement of teeth or a group of teeth.
11. As surgical fixation with lingual brackets.
12. Absolute anchorage in lingual orthodontics.
13. They can be used in a growing patient.
14. Edentulous spaces closure.
6.2 CONTRAINDICATIONS
1. Systemic diseases such as diabetes, osteoporosis, osteomyelitis, blood
dyscrasias, metabolism disorders,etc.
2. Patient undergoing the radiotherapy in arches.
3. Psychological disorders.

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Mini Implants
4. Presence of active oral infections.
5. Uncontrolled periodontal disease.
6. Presence of pathological formations in the zone, such as tumors or
cysts.
7. Insufficient space for insertion of miniimplant.
8. Thin cortical bone and insufficient retention.
9. Deficient quality of the bone.
10. Soft tissue lesions, such as lichen planus, leucoplakia, etc.
11. Patient who does not accept miniimplant treatment.
6.3 RELATIVE CONTRAINDICATIONS
1. Tobacco, alcohol and drugs abuse.
2. Mouth breather.
3. Absence of 'ability to maintain the correct oral hygiene’.
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Mini Implants
Clinical Applications

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Mini Implants
7 CLINICAL APPLICATIONS
Guire reported potential uses of TADs for Orthodontic Purposes 43:
Three Dimensions and Three Tissue Considerations (3D/3T).
3D/3T Anterior-Posterior Vertical Transverse
Skeletal Possibly as anchors to
prevent unwanted dental
movement during
conventional orthopedic
corrections such as Herbst.
Possibly eliminate
compensatory
eruption of teeth occurring as
a result of natural growth to
yield a more anterior rather
than vertical growth.
Intrusion of upper
and/or lower facial
height in cases of excess
vertical growth through
counterclockwise
rotation of the mandible.
Possibly intrusion of
entire upper and/or
lower dental arch to
eliminate excess alveolar
display ("gummy
smile")
in cases of maxillary
alveolar hyperplasia.
Possibly true
orthopedic
maxillary
expansion, without
the undesirable
tipping of posterior
teeth that occurs in
traditional
expansion.

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Mini Implants
Soft tissue Close spaces completely
from the posterior to maintain
the incisor position for
optimal lip support.
Close spaces completely
from the anterior to reduce
excessive lip protrusion.
In selectedcases,
eliminate lip
incompetency through
decreasing lower-face
height.
Dental Close spaces completely
from anterior or posterior
congenitally missing teeth,
thus eliminating the need for
bridge or implant.
Close spaces in cases of
previously extracted or lost
teeth, thus possibly
eliminating a bridge or
implant.
Retract maxillary and/or
mandibular anterior segments
completely without unwanted
anterior molar movement,
i.e., loss of posterior
anchorage.
Uprighting tipped molars
without extruding.
Intrusion of over-
erupted Upper and/or
lower Anterior teeth in
cases of Deep bite.
Intrusion of
overerupted single or
multiple posterior teeth.
Extrusion of impacted
teeth without unwanted
reciprocal effects on
anchor teeth
True unilateral
movement of
buccal segments to
eliminate true
unilateral cross-
bites

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Mini Implants
Maintain torque control of
incisors during retraction by
directing forces through the
center of resistance.
En masse movement of
arches mesially or distally to
correct Class II or III molar
and canine relations.
Asymmetric correctionof
Class II or III dental relation.
Correctionof a canted
occlusal plane.
3D/3T Anterior-Posterior Vertical Transverse
Other factors:
1. Oral health May decrease orthodontic treatment time, thereby
minimizing deleterious effect of orthodontic appliances
on oral hygiene procedures.
2. Perimeter In cases requiring the extraction of permanent teeth,
the orthodontist has the ability to choose a malformed,
previously restored, or otherwise compromised tooth

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Mini Implants
rather than a virgin tooth that might normally be needed
in planning for anchorage requirements.
In Class I cases having a non-extraction lower arch
and congenitally missing one or two maxillary lateral
incisors, there is the possibility of unilateral or bilateral
space closure from the posterior, thus giving patient the
option of substituting a canine for the lateral incisor
instead of a bridge or implant.
Ability to distalize molars through translation (i.e.,
bodily movement) rather than tipping
3. Interactions Eliminate the need for patient compliance in headgear
or elastic wear thus reducing treatment time.
----------------------------Ω-------------------------------

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Biological aspects of
Orthodontic Mini-implants

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8 Biology of orthodontic implants
Biologic aspects of orthodontic implantation, the healing process, and the
formation of the tissue-implant interface.
8.1 Bone-to-Implant interface:
Anabolic modeling on bone surfaces is the first osseous healing reaction
following implantation of a biocompatible device into cortical bone. Similar to
fracture healing, a bridging callus forms at the periosteal and endosteal surfaces.
Under optimal conditions (minimal trauma and vascular compromise) the callus
originates within a few millimeters from the margin of the implantation site. In
rabbits, the lattice of woven bone reaches the implant surface in about 2 weeks and
is sufficiently compacted and remodeled by 6 weeks to provide adequate resistance
to loading. There is no quantitative data for the early healing process in humans.
Extrapolating from relative durations of the remodeling cycles (6 weeks vs. 4
months), timing for the primary callus (woven bone) may be similar to rabbits but
the remodeling-dependent maturation process probably requires 3 times longer (up
to 18 weeks).
If periosteum is stripped, the callus must originate in the nearest untraumatized
osteogenic tissue. Since healing reactions are self limiting, extensive loss of the
osteogenic (inner) layer may preclude periosteal bridging altogether.
Reapproximating retracted periosteum when the wound is closed positions the
nonosteogenic fibrous (outer) layer near the implant. A compromised osteogenic
reaction, associated with a defect in the periosteal margin of bone, may favor
invasion of fibrous connective tissue. Extensive stripping of periosteum
substantially inhibits the initial healing response. Even though stimulating cytokines
and growth factors are released from the blood clot at the surgical site, essentially
no competent osteoprogenitor cells survive periosteal stripping. These cells must be
reintroduced by ingrowth of new vascular tissue. Therefore the surgeon should

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minimize periosteal trauma consistent with adequate access and appropriate soft
tissue management.
Efficient reduction of an osseous defect by a bridging callus requires relative
stability of the approximating segments. An unloaded healing phase (two-stage
implantation procedure) is widely used to prevent extensive functional movement
during healing. However, there are other important biomechanical considerations:
 Mechanical retention of the implant within the wound
 Approximation of the periosteal margin of the cortex to the implant surface
and
 Functional flexure of the implanted bone.
Healing implants in functioning bones are never really "unloaded." The initial
callus reaction near the implant is primarily driven by local cytokines and growth
factors; however, the overall size and extent of the periosteal callus is mechanically
dependent.
A surgical defect weakens the bone and, as a result, may increase peak strains at a
distance from the surgical site. Focal areas of new bone formation (additional
regions of woven or lamellar bone) are often noted around the bone. Remodeling of
the callus begins early in the healing period. According to the principle of adequate
strength with minimal mass, the callus reduces in size and reorients as internal
maturation and strength are attained. 18
Interface remodeling is essential in establishing a viable interface between the
implant and original bone. About a millimeter of compacta adjacent to the osseous
wound dies postoperatively despite optimal surgical technique. This is probably
because of inflammation and the relatively poor collateral circulation within cortical
bone. Dead bone is not useless tissue; it provides important structural support
during the initial healing phase. However, it must be replaced with vital bone (via

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remodeling) to strengthen the interface and provide adaptable tissue for long-term
maintenance.
Remodeling of the nonvital interface is achieved by cutting/filling cones
emanating from the endosteal surface. The mechanism is similar to typical cortical
remodeling except that many of the cutting/filling cones are oriented perpendicular
to the usual pathway (long axis of the bone). In longitudinal sections, cutting/filling
cones occasionally deviate from the plane of the interface, turn 90 degrees, and
form a secondary osteon perpendicular to the interface. At the/same time the
interface is remodeled, the adjacent nonvital cortex (viewed in cross-section) is
penetrated by typical cutting/filling cones.
Maturation of the interface and supporting bone has been suggested to require an
elapsed time after implant placement of about 3 sigma (12 months) 44. The first 4
months (1 sigma) is the initial "unloaded" healing process. During maturation the
callus volume is decreased and interface remodeling continues. The bone
maturation phase requires an additional 2 sigma (8 months).
It was previously believed that maturation involved two physiologic transients:
 The regional acceleratory phenomenon (RAP) and
 Secondary mineralization of newly formed bone.
Extensive remodeling (RAP) in cortical bone is a well-known healing reaction to
surgical wounds and is certainly evident in bone surrounding implants. In general,
the remodeling sites decrease with increasing distance from the wound 27. It is also
well accepted that stiffness and strength of lamellar bone are directly related to
mineral content. Because of this, it was previously suggested that full strength of
bone supporting an implant would not be achieved until about 12 months (54
weeks) after the bone is formed, that is, after completion of the secondary
mineralization process. However, recent evidence has shown that elevated
remodeling is an ongoing response of bone adjacent (<1 mm) to an implant 45.

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Because of rapid remodeling at the interface, it is likely that the secondary
mineralization process is not completed and the mineral content of bone supporting
an implant remains lower than that of the surrounding bone.
Long-term maintenance of the rigid osseous fixation involves continuous
remodeling of the interface and supporting bone. Bone, like other relatively
rigid materials, is subject to fatigue. Repetitive loading results in microscopic cracks
(microdamage). If allowed to accumulate, these small defects can lead to structural
failure. Because osteoclasts preferentially resorb more highly mineralized tissue,
cutting cones tend to remodel the oldest and presumably most weakened bone. This
physiologic mechanism helps to maintain structural integrity indefinitely. Human
cortical bone from long-bone midshaft diaphysis and rib remodels at a rate of about
2% to 10% per year 27. No human data is available for mandibular cortical bone.
However, based on recent studies in dogs (which have diaphyseal and rib
remodeling rates similar to humans), cortical bone supporting the teeth may have a
substantially higher remodeling rate (30% to 40% per year). The interaction of
mechanical and metabolic factors in controlling adult bone remodeling is not well
understood. Cortical bone around an endosseous implant continues to remodel.
Long-term maintenance of rigid osseous fixation involves a remodeling rate of as
much as approximately 500% per year in bone immediately adjacent (within 1 mm)
to an implant 27. Although the precise reason for the sustained remodeling response
is unclear, its physiologic control appears strongly related to the mechanical stress
distribution concentrated in bone adjacent to the interface. Data from four animal
species (including humans) indicate that the elevated remodeling response is a
universal mechanism necessary for the long-term retention of rigidly integrated
implants.

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8.2 Support and load transfer /mechanisms:
The three basic means of retention of an endosteal dental implant in function are
i. Fibroosseous retention,
ii. Biointegration and
iii. Osseointegration.
According to the American Academy of Implant Dentistry (AAID) Glossary of
Terms (1986) 46
Fibrosseous retention is defined as tissue-to-implant contact; interposition of
healthy, dense collagenous tissue between the implant and bone.
Osseointegration is defined as contact established between normal and remolded
bone and an implant surface without the interposition of non-bone or connective
tissue.
Bioactive retention is achieved with bioactive materials such as hydroxyapatite
(HA), which bond directly to bone, similar to ankylosis of natural teeth. Bone
matrix is deposited on the HA layer as a result of some type of physiochemical
interaction between the collagen of bone and HA crystals of implant.
To a certain extent, it appears to be within the hands of the clinician to control
which method of load bearing will he established by the host. Relative movement
during healing has been shown to be the determining factor 47. If the implant is
loaded so that the implant moves relative to its surrounding bone during the healing
phase, then a tendon or ligament will occur around a plate or subperiosteal implant.
If the implant is allowed to heal without relative movement, then ankylosis can be
expected to occur.

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Complications with Mini
Implants & their
management

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9 Complications with use of Mini Implants & their
management
Risks, Complications of Orthodontic miniscrews and Measures to prevent it.
Complications can arise during miniscrew placement and after orthodontic
loading that affect stability and patient safety 48 .
COMPLICATIONS DURING INSERTION
i. Trauma to the periodontal ligament or the dental root.
ii. Miniscrew slippage.
iii. Nerve involvement.
iv. Air subcutaneous emphysema.
v. Nasal and maxillary sinus perforation.
vi. Miniscrew bending, fracture, and torsional stress.
COMPLICATIONS UNDER ORTHODONTIC LOADING
i. Stationary anchorage failure.
ii. Miniscrew migration.
SOFT-TISSUE COMPLICATIONS
i. Aphthous ulceration.
ii. Soft-tissue coverage of the miniscrew head and auxiliary.
iii. Soft tissue inflammation, infection, and peri-implantitis.

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COMPLICATIONS DURING REMOVAL
i. Miniscrew fracture.
ii. Partial osseointegration.
9.1 COMPLICATIONS DURING INSERTION
9.1.1 Trauma to the periodontal ligament or the dental root.
Interradicular placement of orthodontic miniscrews risks trauma to the
periodontal ligament or the dental root. Potential complications of root injury
include loss of tooth vitality, osteosclerosis, and dentoalveolar ankylosis. Trauma to
the outer dental root without pulpal involvement will most likely not influence the
tooth's prognosis 49. Dental roots damaged by orthodontic miniscrews have
demonstrated complete repair of tooth and periodontium in 12 to 18 weeks after
removal of the miniscrew. 50
Interradicular placement requires proper radiographic planning, including
surgical guide with panoramic and periapical radiographs to determine the safest
site for miniscrew placement.
During inter-radicular placement in the posterior region, there is a tendency for
the clinician to change the angle of insertion by inadvertently pulling the hand-driv-
er toward their body, increasing the risk of root contact. 48 To avoid this, the
clinician may consider using a finger-wrench or work the hand-driver slightly away
from their body with each turn. If the miniscrew begins to approximate the
periodontal ligament, the patient will experience increased sensation under topical
anesthesia. If root contact occurs, the miniscrew may either stop or begin to require

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greater insertion strength 51. If trauma is suspected, the clinician should unscrew the
miniscrew 2 or 3 turns and evaluate it radiographically.
9.1.2 Miniscrew slippage
The clinician might fail to fully engage cortical bone during placement and
inadvertently slide the miniscrew under the mucosal tissue along the periosteum.
High-risk regions for miniscrew slippage include sloped bony planes in alveolar
mucosa such as the zygomatic buttress, the retromolar pad, the buccal cortical shelf,
and the maxillary buccal exostosis if present. Slippage in the retromolar pad can
lead to the greatest risk of iatrogenic harm if the miniscrew moves lingually in the
submandibular or lateral pharyngeal space near the lingual and inferior alveolar
branch nerves. In the retromolar region, serious consideration should be given to
flap exposure for direct visualization and a predrilled pilot hole, even for self-
drilling miniscrews. If the alveolar tissue is thin and taut, some clinicians advocate
placing the pilot hole with a transmucosal method, using a slow-speed bur to
perforate both tissue and cortical bone without making a flap 52.
Miniscrew slippage can occur in dentoalveolar regions of attached gingiva if the
angle of insertion is too steep. Placement of miniscrews less than 30° from the
occlusal plane, typically to avoid root contact in the maxilla or to gain cortical
anchorage in the mandible, can increase the risk of slippage. To avoid this, the clini-
cian can initially engage bone with the miniscrew at a more obtuse angle before
reducing the angle of insertion after the second or third turn. Miniscrews should
engage cortical bone after 1 or 2 turns with the hand-driver. Only minimal force
should be used with the hand-driver, regardless of bone density. Greater forces
increase the risk of miniscrew slippage.
9.1.3 Nerve involvement:
Nerve injury can occur during placement of miniscrews in the maxillary palatal
slope, the mandibular buccal dentoalveolus, and the retromolar region. Most minor

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nerve injuries not involving complete tears are transient, with full correction in 6
months. Long-standing sensory aberrations might require pharmacotherapy
(corticosteroids), microneurosurgery, grafting, or laser therapy 48.
Placement of miniscrews in the maxillary palatal slope risks injury to the greater
palatine nerve exiting the greater palatine foramen. The greater palatine foramen is
located laterally to the third molar or between the second and third molars.
Location, size, and shape of the foramen can vary with ethnicity. 53 The greater
palatine nerve exits the foramen and runs anteriorly, 5 to 15 mm from the gingival
border, to the incisive foramen. Miniscrews inserted in the palatal slope should be
placed medial to the nerve and mesial to the second molar. Placement of the
miniscrew above the nerve could increase the risk of palatal root contact and reduce
biomechanical control.
Placement of the miniscrews in the mandibular buccal dentoalveolus risks injury
to the inferior alveolar nerve in the mandibular canal. The mandibular canal travels
forward in an S-shaped curve moving from buccal to lingual to buccal. The inferior
alveolar nerve occupies its most buccal position within the body of the mandible at
the distal root of the second molar and the apex of the second premolar, before exit-
ing from the mental foramen. Miniscrews inserted near the mandibular second
molar and the second premolars are at greatest risk for accidental damage to the
inferior alveolar nerve. 54 The soft-tissue appearance of the dentoalveolus can be
deceptive, and a panoramic radiograph should be taken to determine the vertical
position of mandibular canal and the location of the mental foramina. Greater
caution is needed in adult patients who might have a more occlusal position of the
mandibular canal due to resorption of the alveolar ridge.
Placement of miniscrews in the retromolar pad risks injury to the long buccal
nerve and the lingual nerve. The long buccal nerve branches off the mandibular
nerve trunk and crosses high on the retromolar pad supplying the mucosa of the
cheek. The lingual nerve runs immediately under the floor of the mouth and

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supplies general sensory innervation to the anterior two thirds of the tongue. To
avoid nerve involvement and slippage, the retromolar miniscrews should be no
longer than 8 mm and placed in the buccal retromolar region below the anterior
ramus is been recommended.
9.1.4 Air subcutaneous emphysema:
Air subcutaneous emphysema is the condition in which air penetrates the skin or
submucosa, resulting in soft-tissue distention. Subcutaneous emphysema can occur
during routine operative dental procedures if air from the high-speed or air-water
syringe travels under the gingival tissues. The main symptom of air subcutaneous
emphysema is immediate mucosal swelling with or without crepitus (crackling).
Additional sequelae include cervicofacial swelling, orbital swelling, otalgia, hearing
loss, mild discomfort, airway obstruction, and possibly interseptal and interproximal
alveolar necrosis. Clinically visible swelling of the skin and mucosa occurs within
seconds to minutes after air has penetrated the submucosal space and typically
spreads to the neck (in 95% of cases) or the orbital area (in 45% of cases).
The clinician should be alert for subcutaneous emphysema during miniscrew
placement through the loose alveolar tissue of the retromolar, mandibular posterior
buccal, and the maxillary zygomatic regions. If a purchase point or pilot hole is to
be drilled through the mucosa, the clinician should use slow speed under low rotary
pressure. If either a pilot hole or a mucosal punch is placed, an air-water syringe
should never be used. Air from the syringe can enter the submucosal space through
the small tissue opening, even in attached tissue. Bleeding and saliva should be
controlled with suction, cotton, and gauze, rather than an air-water syringe. 48 In
case of subcutaneous emphysema, the clinician should immediately discontinue the
procedure and take periapical and panoramic radiographs to determine the extent of
the condition. The patient should not be dismissed until the swelling begins to
regress and an infection can be ruled out. Upon dismissal, the patient should be

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instructed to apply light pressure with an ice pack for the first 24 hours. The
clinician could prescribe a mild analgesic, an antibacterial rinse, such as
chlorhexidine, and an antibiotic prophylaxis for a week. In most cases of
subcutaneous emphysema, careful observation for further problems or infection is
adequate, and swelling and symptoms generally subside in 3 to 10 days.
9.1.5 Nasal and maxillary sinus perforation:
Perforation of the nasal sinus and the maxillary sinuses can occur during
miniscrew placement in the maxillary incisal, maxillary posterior dentoalveolar, and
zygomatic regions. A posterior atrophic maxilla is a major risk factor for sinus
perforation. The sinus floor is deepest in the first molar region and can extend to fill
a large part of the alveolar process in posterior edentulous spaces. Penetration of the
Schneiderian membrane is a well-documented phenomenon that often occurs when
the thin, lateral wall of the sinus is infractured from the buccal side. Small (<2 mm)
perforations of the maxillary sinus heal by themselves without complications. 55
Ardekian et al and Branemark et al 56 reported that immediately loaded dental
implants that perforated the nasal and maxillary sinuses showed no differences in
implant stability.
If the maxillary sinus has been perforated, the small diameter of the miniscrew
does not warrant its immediate removal. Orthodontic therapy should continue, and
the patient should be monitored for potential development of sinusitis and
mucocele. For miniscrews placed in pneumatized, edentulous regions of the
maxilla, or placed higher in the posterior maxilla when intrusive forces are desired,
the clinician should consider angulating the miniscrew perpendicular to the alveolar
ridge to avoid damage to the sinus.
9.1.6 Miniscrew bending, fracture, and torsional stress:
Increased torsional stress during placement can lead to implant bending or
fracture, or produce small cracks in the peri-implant bone, that affect miniscrew

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stability. 39 Self-drilling miniscrews should be inserted slowly, with minimal
pressure, to assure maximum miniscrew-bone contact. A purchase point or a pilot
hole is recommended in regions of dense cortical bone, even for self-drilling
miniscrews. During miniscrew placement in dense cortical bone, the clinician
should consider periodically derotating the miniscrew 1 or 2 turns to reduce the
stresses on the miniscrew and the bone. The clinician should stop inserting the
miniscrew as soon as the smooth neck of its shaft has reached the periosteum. Over
insertion can add torsional stress to the miniscrew neck, leading to screw loosening
and soft-tissue overgrowth. Once the miniscrew has been inserted, torsional stress
from wiggling the hand-driver off the miniscrew head can weaken stability. When
removing the hand-driver from the miniscrew head, the clinician should gently
separate the hand-driver handle from its shaft and then gently remove the shaft from
the miniscrew head.
9.2 COMPLICATIONS UNDER ORTHODONTIC LOADING
9.2.1 Stationary anchorage failure:
According to the literature, the rates of stationary anchorage failure of
miniscrews under orthodontic loading vary between 11% and 30%. If a miniscrew
loosens, it will not regain stability and will probably need to be removed and
replaced. 57 Stability of the orthodontic miniscrew throughout treatment depends on
bone density, peri-implant soft tissues, miniscrew design, surgical technique, and
force load. 58
The key determinant for stationary anchorage is bone density. 59 Stationary
anchorage failure is often a result of low bone density due to inadequate cortical
thickness 49. Bone density is classified into 4 groups (Dl, D2, D3, and D4) based on
Hounsfield units (HU)—an x-ray attenuation unit used in computed tomography
scan interpretation to characterize the density of a substance.132

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a) D1 (>1250 HU) is dense cortical bone primarily found in the anterior
mandible and the maxillary midpalatal area.
b) D2 (850-1250 HU) is thick (2 mm), porous cortical bone with coarse
trabeculae primarily found in the anterior maxilla and the posterior mandible.
c) D3 (350-850 HU) is thin (1 mm), porous cortical bone with fine trabeculae
primarily found in the posterior maxilla with some in the posterior mandible.
d) D4 (150-350 HU) is fine trabecular bone primarily found in the posterior
maxilla and the tuberosity region.
Figure 17 Areas according to Bone density

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Sevimay et al 60 reported that osseointegrated dental implants placed in Dl and
D2 bone showed lower stresses at the implant-bone interface. D1-D3 bone is
optimal for self-drilling miniscrews. Placement of miniscrews in Dl and D2 bone
might provide greater stationary anchorage under orthodontic loading. Placement of
miniscrews in D4 bone is not recommended due to the reported high failure rate. In
general, stationary anchorage failure is greater in the maxilla, with the exception of
the midpalatal region, due to the greater trabeculae and lower bone density. 61 Loss
of mid-palatal miniscrews is likely a result of tongue pressure.
Peri-implant soft-tissue type, health, and thickness can affect stationary
anchorage of the miniscrew. Miniscrews placed in nonkeratinized alveolar tissues
have greater failure rates than those in attached tissues. 62 The movable,
nonkeratinized alveolar mucosa is easily irritated; soft-tissue inflammation around
the miniscrew is directly associated with increased mobility 34. Additionally,
miniscrews placed in regions of thick keratinized tissue, such as the palatal slope,
are less likely to obtain adequate bony stability. Thin, keratinized tissue, seen in the
dentoalveolar or midpalatal region, is ideal for miniscrew placement.
Miniscrew geometry and surgical technique directly influence the stress
distribution of peri-implant bone. Most miniscrew losses occur as a result of
excessive stress at the screw-bone interface. Self-drilling miniscrews can have
greater screw-bone contacts (mechanical grip) and holding strengths compared with
self-tapping screws. 33 Heidemann et al 63 reported greater residual bone between
screw threads of self-drilling miniscrews compared with self-tapping miniscrews.
Self-tapping miniscrews, like self-drilling screws, can be placed without a predrilled
pilot hole in the dentoalveolar region if the cortical bone is thin. If a pilot hole is to
be used, for either self-drilling or self-tapping miniscrews, the pilot hole size should
be no greater than 85% of the diameter of the miniscrew shaft for optimal stability.
It is still not clear the maximum force-load a miniscrew can withstand in regard
to stationary anchorage. Dalstra et al 35reported that miniscrews inserted into thin

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cortical bone and fine trabeculae should be limited to 50 g of immediate loaded
force. Buchter et al 58 reported that miniscrews placed in dense mandibular bone re-
mained clinically stable with up to 900 g of force. Many articles reported miniscrew
stability with loading forces of 300 g or less. In regions of poor bone density,
simply placing a longer miniscrew under smaller orthodontic force does not ensure
stationary anchorage. 64
9.2.2 Miniscrew migration:
Orthodontic miniscrews can remain clinically stable but not absolutely stationary
under orthodontic loading.64 Unlike an endosseous dental implant, that
osseointegrates, orthodontic miniscrews achieve stability primarily through
mechanical retention, and can be displaced within the bone. Liou et al reported that
orthodontic miniscrews loaded with 400 g of force for 9 months extruded and tipped
-1.0 to 1.5 mm in 7 of 16 patients. To account for potential migration, the clinician
should allow a 2-mm safety clearance between the miniscrew and any anatomical
structures.
9.3 SOFT-TISSUE COMPLICATIONS
9.3.1 Aphthous ulceration:
Minor aphthous ulcerations, or canker sores, can develop around the miniscrew
shaft or on the adjacent buccal mucosa in contact with the miniscrew head. Aphthi
are characterized as mildly painful ulcers affecting nonkeratinized mucosa. Minor
aphthous ulcerations are typically caused by soft-tissue trauma but might occur as a
result of genetic predisposition, bacterial infection, allergy, hormonal imbalance,
vitamin imbalance, and immunologic and psychologic factors. Minor aphthous
ulcerations are self-limiting and resolve within 7 to 10 days without scarring. 65
Placement of a healing abutment, a wax pellet, or a large elastic separator over the
miniscrew head, with daily use of chlorhexidine (0.12%, 10 mL), typically prevents

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ulceration and improves patient comfort. The occurrence of aphthous ulceration
does not appear to be a direct risk factor for miniscrew stability, but its presence
might forewarn of greater soft-tissue inflammation.
9.3.2 Soft-tissue coverage of the miniscrew head and auxiliary:
Miniscrews placed in alveolar mucosa, particularly in the mandible, might
become covered by soft tissue. The bunching and rubbing of loose alveolar tissue
can lead to coverage of both the miniscrew head and its attachments (ie, coil spring,
elastic chain) within a day after placement. Soft-tissue coverage might be a risk
factor for miniscrew stability, as well as a clinical concern for the patient, who
might think that the miniscrew has fallen out. Miniscrew attachments (elastic chain,
coil spring) that rest on tissues will likely become covered by tissue. The soft-tissue
overlaying the miniscrew is relatively thin and can be exposed with light finger
pressure, typically without an incision or local anesthetic. Soft-tissue overgrowth
can be minimized by placement of a healing abutment cap, a wax pellet, or an
elastic separator. In addition to its antibacterial properties that minimize tissue
inflammation, chlorhexidine slows down epithelialization and might reduce the
likelihood of soft-tissue overgrowth. The authors suggest partial insertion with a
longer miniscrew (10 mm) in regions of loose alveolar mucosa, leaving 2 or 3
threads of the shaft exposed to minimize the possibility of soft-tissue coverage.
9.3.3 Soft tissue inflammation, infection, and peri-implantitis:
Healthy peri-implant tissue plays an important role as a biologic barrier to
bacteria. Tissue inflammation, minor infection, and peri-implantitis can occur after
miniscrew placement. 66 Inflammation of the peri-implant soft tissue has been
associated with a 30% increase in failure rate. Peri-implantitis is inflammation of
the surrounding implant mucosa with clinically and radiographically evident loss of
bony support, bleeding on probing, suppuration, epithelia infiltrations, and pro-
gressive mobility. The clinician should be forewarned of soft-tissue irritation if the

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soft tissues begin twisting around the miniscrew shaft during placement. Some cli-
nicians advocate a 2-week soft-tissue healing period for miniscrews placed in the
alveolar mucosa before orthodontic loading.135
9.4 COMPLICATIONS DURING REMOVAL
9.4.1 Miniscrew fracture:
The miniscrew head could fracture from the neck of the shaft during removal.
The authors recommend a minimum diameter of 1.6 mm for self-drilling mini-
screws that are 8 mm or longer placed in dense cortical bone. The proper placement
technique can minimize the risk of miniscrew fracture during its removal. If the
miniscrew fractures flush with the bone, the shaft might need to be removed with a
trephine. 49
9.4.2 Partial osseointegration:
Although orthodontic miniscrews achieve stationary anchorage primarily through
mechanical retention, they can achieve partial osseointegration after 3 weeks,
increasing the difficulty of their removal 19. The miniscrew typically can be
removed without complications a few days after the first attempt of removal.111
9.4.3 Ingestion of the mini-implant :
Byung-Ho Choi et al evaluated 10 dogs that each ingested 1 screw and 1 reamer.
All screws were passed spontaneously within 1 day, suggesting that spontaneous
evacuation usually occurs for orthodontic anchorage screw ingestion. Patients who
swallow these screws should be carefully observed before resorting to early surgical
removal of the screws 67. Eight of the 10 reamers ingested passed by the fourth day,
but 2 became lodged.
Patients who swallow reamers should be carefully observed to determine whether
surgical removal is necessary. 68

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Advantages of Mini-
implant use

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10 Advantages of Mini Implants
• Absolute anchorage.
• New directions of forces.
• Major effectiveness of "en masse" dental movements.
• Reduction of treatment time.
• Less necessity for patient cooperation, especially if we compare microimplants
with intermaxillary elastics or headgear.
• Even though the failure index of microimplants is still high, it shouldn't be the
reason for worries if we take into account the following:
- Headgear and intermaxillary elastics also have a high percentage of failure due
to the absence of patient cooperation.
- Anchorage with auxiliary appliances such as Nance appliance also have a high
index of failure: Anchorage loss of approximately 2mm, lesions due to
pressure against palatine mucosa, infections (for example, candida albicans),
debondings and fractures of appliances, etc.
- Consequences of failures of a microimplant are nothing else but mobility or loss
of microimplant, which can be reinserted in the same site (another
microimplant with the larger diameter if the space permits it and if there is no
inflammation in the zone), or in different zone.

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11 BIBLIOGRAPHY
1. Nanda, R., Biomechanics in clinical orthodontics. 1997: WB Saunders Co.
2. Feldmann, I. and L. Bondemark, Orthodontic anchorage: a systematic review. The Angle
orthodontist, 2006. 76(3): p. 493-501.
3. Gainsforth, B.L. and L.B. Higley, A study of orthodontic anchorage possibilities in basal
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