Treatment planning of implants in posterior quadrants /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
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To sum up series number 1…
“rationale for dental implants”

Recap…..


Dental implants are a more conservative
long term option than long span bridges

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Placement of dental implants serves to
preserve bone

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Dental implants can provide long term
posterior support than RPD’s



Dental implants are resistant to disease

Treatment planning of
implants in posterior
quadrants


Introduction
The risk of FPD’s reduced with the
introduction of implants in the posterior
quadrants.
From 1993 till now, single tooth implants
are considered the most successful method of
tooth replacement, which are shown by multiple
studies done by Schmitt (1993), Carlson (1994),
Becker (1995) and Henry (1996)
Dental implants does not depend on the
abutment teeth and allowed segmentation of the
restoration.

The advantages of segmentation includes
 Easier fabrication
 Improved marginal fidelity
 Retrievability
When it comes to the treatment planning of posterior
quadrants, decision must be made on a long term basis &
whether to use conventional treatment procedures or
implants.
Buser (1996) and Volgel (2000) stated that no limits
exists to placement of implants due to advances in the
surgical procedures like bone augmentation procedures,
sinus lift procedures and distraction osteogenesis.

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There are many advantages of implant retained
restorations over RPD’s.
They include:
Improved support
Preservation of bone
More stable occlusion
Simplification of the prostheses
Improvement of the long term oral health
Use of implants in the posterior quadrants is not
entirely dependant on the long term reports but also
on other factors like biomechanical advantages and
availability of prefabricated components.

The success of implants in the posterior
quadrants depends on the following factors:
1. Available space
2. Implant number and position

3. Occlusal considerations
4. Type of prostheses
5. Overall treatment plan


Available space
The space available should be considered in three
directions:
a)
b)
c)

Mesiodistal
Buccolingual
Occlusogingival


Mesiodistal
Although esthetics is not the prime concern while
replacing the posterior teeth, care should be taken with
the implant position such that it develops proper
occlusion and comfort. Mesiodistal space is evaluated
in 2 dimensions.
The required MD space depends on the type and
number of teeth which is being replaced.


The natural maxillary first and second premolar
and molar have an average MD size of 7.1, 6.6 and
10.4mm.
Hebel (1997) and Woelfel (1990) stated
that the dimensions of these teeth at the CEJ are 4.8, 4.7
and 7.9mm and at a distance of 2mm from the CEJ they
measure 4.2, 4.1 & 7.0mm.


Hence while deciding with the implant size, the following
guidelines can be used.
 The implant should be at least 1.5mm away from the
adjacent teeth.
 The implant should be at least 3mm away from the
adjacent implant.
 A wider diameter implant should be selected for a molar
teeth.
Similar guidelines are followed for the mandibular
teeth. When planning for a premolar restoration the
implant is placed 1.5mm away from the adjacent root,
and for a molar its about 2.5mm away from the adjacent
tooth. (as molar teeth are wider mesiodistally)

Buccolingual
If a 4mm diameter implant is used, then 6mm of
bone is required buccolingually. If 5mm diameter
implant is planned, then 7mm of bone is
required.
The fixture must be contained within the crown.
The screw access must be positioned towards the
centre of the occlusal surface.
Mandibular fixture – exit angle – inner inclines of
palatal cusp
Maxillary fixture – exit angle – inner inclines of
buccal cusp

Occlusogingival
It is also considered in 2 dimensions.
The parameters include:


Adequate space for restoration

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Adequate osseous volume for implant placement


Adequate space for restoration:
Sufficient space must be present between the residual
ridge and the opposing occlusal plane. Ideally 7 – 10
mm of space is required.



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Adequate osseous volume for implant placement:

One of the FAQ is “what is the minimal height of the
implant required to support a posterior restoration?”
Initially it was thought that the unfavorable
implant : suprastructure resulted in crestal bone loss.
But studies conducted by Nedir(2001) and Ten
Bruggengate(1998) showed that the unfavorable ratio
did not produce any crestal bone loss.
Ideally, 7.5mm of bone height is required for a 6mm long
fixture and 8.5mm is required for a 7mm long fixture.

Critical structures like maxillary sinus, inferior alveolar
nerve canal, mental foramen should be evaluated by a
CT scan.
There should at least 2mm of bone between the apical
end of the implant and the neurovascular structures.
The diameter of the implant is also important in
Occlusogingival placement.
Studies done by Graves & Jansen(1990) stated that the
wider diameter implants more closely replicate the
emergence profile. Balshi(1990) advocated the
placement of 2 implants in molar positions which had
a poor bone quality.

The advantages of double implants includes:
 It resembles the anatomy of the roots
 It increases anchorage
 Eliminates antero-posterior cantilever
 Reduces the rotational forces
 Reduces screw loosening
The disadvantage includes the maintenance of
daily oral hygiene.


Implant number and position
There is no scientific evidence to decide on the
number of implants required to rehabilitate the
patient with multiple missing posterior teeth. It
can be derived from traditional prosthodontic
experience.
When three posterior teeth are missing , 2 or 3
implants may be required. In the maxilla where
the bone is less dense, placement of one implant
per tooth is preferred.

The choice between using 2 or 3 implants depends on
the how the load is distributed. With 3 implants it is
possible to offset the implant and position them for a
tripod effect.
Rangert & Langer(1995) stated that this arrangement
gives more bone support than linear arrangement.


If the osseous volume is reduced, bone augmentation
procedures can be done. But if the patient is not
willing for sinus lift procedures then implants can be
placed in the tuberosity area. This technique was
described by Bahat(1992).


Occlusal considerations
Carr & Laney(1987) stated that masticatory
forces with an implant supported restoration is
equal to that of a natural dentition.
General assessment of the likely load to be
placed on implants should be made, because
complications with dental implants occurs due
to improper treatment planning.


Occlusion for implants should be that there is an
anterior guidance and disclusion of the posterior teeth
on lateral excursion.

Initial occlusal contact should occur on the natural
dentition.
The cuspal inclinations should be shallower on the implant
supported restorations.
The author also prefers to splint the teeth.

Type of prostheses
Screw retained / cemented:
The author of the present article prefers the use of
screw retained restorations. It has the advantage
of retrievability.
It helps in:
 individual implant evaluation
 soft tissue inspection
 and any necessary prostheses modifications.



Certain practitioners prefer cement retained prostheses, as
it is more esthetic and screw holes can be avoided.
The choice for screw retained or cemented restoration is
dependent on the tooth that is replaced.
For instance, the occlusal surface of a premolar is small
and patients may object to occlusal holes, in such cases
cement retained restoration can be used.


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Splinted (or) non – splinted:
Cibirka & Razoog(1997) stated that stress
distribution can be manipulated by splinting.

Splinting offers the following advantages:
1.
Increases retention
2.
Reduces the risk of screw loosening
3.
Fewer proximal contacts to adjust
4.
Delivery made easy


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Abutment level vs. implant level restoration,
segmented vs. non segmented:

Screw retained abutments are only used when the
implants are placed deeply or soft tissue depth is
excessive.
When cement retained restorations are used the abutments
placed should have proper contours and must be
retentive.
The cement margin should not be placed more than 1mm
sub mucosal to facilitate cement removal. When cement
retained restorations are planned there must be
sufficient inter occlusal space.

Overall treatment plan
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The difficulty with implant treatment essentially
lies in the ability to detect risk patients.

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A risk patient is a patient in which the strict
application of the standard protocol does not give
the expected results.

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The clinician has to decide whether to retain the
compromised tooth versus an implant.

1. Single tooth planning for molar replacements:
(implants in clinical dentistry – Richard N Palmer)

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Two – implant solutions

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Single implant solutions with wide - diameter
implants


The author states that if space and economics allow,
choose the two implant option.
In other cases ensure that the Buccolingual width will
accommodate a wider diameter implant (assuming the
MD space is inadequate).
Advantages:
1.
Better force distribution
2.
Reduction of leverage forces
3.
Implant is stronger and less likely to fracture
4.
The abutments and abutment screws are usually
bigger and stronger
5.
The surface area of the abutment is usually larger and
provides more retention.

2. Treatment sequence & planning protocol:
(Risk factors in implant dentistry – Franck Renouard)
The author states that it is important to distinguish
between available bone volume, necessary bone
volume & useful bone volume.
Available bone volume:
represents the total amount of bone in which it is
theoretically possible to place an implant in a certain
region
Necessary bone volume:
represents the minimum amount of bone required for
placement of an implant that will function in the
given clinical situation

Useful bone volume:
represents the amount of bone that can be utilized in a
given clinical situation, considering the prosthodontic
parameters (esthetic as well as functional).
Summing up:
Available bone volume = surgical evaluation
Necessary bone volume = prosthetic evaluation
Useful bone volume = surgical + prosthetic evaluation
Note:

If only the available bone volume is considered
during the preoperative examination, the prosthetic
result may suffer

Summary

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Based on long term treatment options
implants must be considered for every treatment
plan. The implants are the choice of treatment for
the missing posterior teeth because it:
Improves support
Provides more stable occlusion
Preserves bone
Improves long term oral health

Next article
the next article in this series will focus on

“treatment planning of implants in the
esthetic zone”


Treatment planning of implants in posterior quadrants /certified fixed orthodontic courses by Indian dental academy

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Treatment planning of implants in posterior quadrants /certified fixed orthodontic courses by Indian dental academy