Periodontium and prosthodontics

PERIODONTIUM AND PROSTHODONTICS
1. Dentistry has progressed from the times when a missing tooth
was replaced by an animal tooth to the present when it is being
replaced with an implant.
2. We have moved into a new era in which dentistry can no longer
be practiced in isolated specialty divisions to meet the overall
needs of the patients. The team approach is replacing the
individual approach resulting in more effective patient care.
3. A prosthesis can be beneficial or detrimental depending on the
forethought given to it. The best environment for the prosthesis is
obtained by a pretreatment consultation between the periodontist
and the prosthodontist. This will prevent needless treatment of
teeth that are of questionable value or the needless extraction of
teeth that could prove vital to long-range goals.
4. This also represents outstanding opportunities for professional
cooperation.
5. It is possible to reconstruct an entire mouth decayed to the root,
but it is almost insurmountable task to maintain the mouth after

advanced periodontal disease. The best way to serve patients for
continued dental health is through early recognition and
prevention.
In the following deliberation I would like to bring about the
various periodontal aspects to be considered in designing a prosthesis
which may be called as “Periodontal Restorative Interrelationship”.
BASIC CONSIDERATIONS
The periodontium is the attachment apparatus of the teeth and
consists of cementum, periodontal ligament, alveolar bone and a portion
of the gingiva.
Gingiva:
It is divided anatomically into marginal, attached and interdental
areas.
- The attached gingiva extends from the mucogingival junction to
the projection on the external surface of the bottom of the
gingival sulcus.
- The width of the attached gingiva on the facial aspect differs in
different areas of the mouth. It is generally greatest in the incisor

region (3.5 to 4.5mm) and less in the posterior segments with the
least width in the first premolar area 1.9mm.
- Mucogingival junction remains stationary throughout the adult
life. Width of the attached gingiva increases with age and in
supraerupted teeth.
- Keratinized gingiva includes both the attached gingiva as well as
the marginal gingiva.
- Clinical gingival sulcus depth normally measures 2-3mm.
Periodontal Ligament
It is composed of collagen fibres arranged in bundles that are
attached from the cementum of the tooth to the alveolar bone. In humans
the width of the periodontal ligament ranges from 0.15 to 0.38mm.
Occlusal loading in function affects the width of the periodontal
ligament. If occlusal forces are within physiologic limits, increased
function leads to increase in the width of the ligament.
- In single rooted teeth, the axis of rotation is located in the area
between the apical third and middle third of the root. In
multirooted teeth, the axis of rotation is located in the bone
between the roots.

The ligament is narrowest in the region of axis of rotation. Due to
physiologic mesial migration, the periodontal ligament is thinner on
the mesial surface than on the distal surface.
Functions of Periodontal Ligament
I. Physical
a) Resistance to impact occlusal forces.
b) Transmission of occlusal forces to bone.
II. Formative and remodeling function.
III. Nutritional and sensory function.
Pathological deepening of gingival sulcus is termed as
periodontal pocket. It is due to the direct extension of gingivitis into the
alveolar bone.
Probing
The thinnest probe is desired that permits probing the depth of the
pocket without patient discomfort. While probing the dentist must pay
attention to the root anatomy.
Local anesthesia is recommended when the bony contours are
probed to establish whether surgery is necessary. This procedure is
called Bone Sounding.

Mobility
It can be determined by holding the tooth between the handles of
two metallic instruments or with one metallic instrument and one finger.
An effort is made to move the tooth in all directions. Mobility is graded
as:
Grade I – Barely distinguishable tooth movement.
Grade II – Any movement upto 1mm (Labiolingual or mesiodistal).
Grade III – Any movement more than 1mm or teeth that can be
depressed or rotated in their sockets.
Trauma from occlusion
When the occlusal forces exceed the adaptive capacity of the
tissues, tissue injury results. The resultant injury is termed trauma from
occlusion.
Trauma from occlusion may be caused by altrations in occlusal
forces or reduced capacity of the periodontium to withstand occlusal
forces. When trauma from occlusion is the result of alterations in
occlusal forces, it is called primary trauma from occlusion. When it
results from reduced ability of the tissues to resist occlusal forces, it is
known as secondary trauma from occlusion.

Trauma from occlusion occurs in the supporting tissues and does
not affect the gingiva.
The changes in TFO consists of a) increased width of periodontal
ligament space, b) thickening of lamina dura along the lateral aspect of
the root, c) vertical rather than horizontal destruction of interdental
septum, d) root resorption, e) radiolucence and condensation of alveolar
bone.
Thus, in the absence of inflammation, the response to TFO is
limited to adaptation to increased forces. In the presence of
inflammation, the changes in the shape of the crest may be conducive to
angular bone loss with infrabony pockets. Most common clinical sign of
TFO is increased tooth mobility.
Radiographs
The radiograph is a valuable aid in the diagnosis, prognosis and
evaluation of the treatment outcome of periodontal disease.
The most useful technique in evaluating the tooth to bone
relationship is the long cone technique. A film positioning holder should
be used. The areas to be reviewed on the radiographs are:
1) Alveolar crest resorption.

2) Integrity and thickness of lamina dura.
3) Evidence of generalized horizontal bone loss.
4) Evidence of vertical bone loss.
5) Widened periodontal ligament space.
6) Density of the trabeculae of both the arches.
7) Size and shape of the roots compared to crown, to determine
crown root ratio.
Occlusion and its effect on periodontium
The effect of occlusal forces on the periodontium is influenced by
their severity, direction, duration and frequency. When severity
increases, the periodontal fibers thicken and increase with the alveolar
bone becoming denser.
Changing the direction of occlusal forces changes the orientation
of periodontal ligament fibres. The principal fibres of the periodontal
ligament best accommodate occlusal forces along the long axis of the
tooth.
Lateral forces initiate bone resorption in areas of pressure and
bone formation in areas of tension.

Rotational forces cause tension and pressure on the periodontium
and are most injurious forces.
Occlusal Therapy as a Part of Periodontal Treatment
Studies indicate that the gain in the attachment level after
periodontal therapy is inversely proportional to the degree of mobility.
Occlusal therapy should be performed as a part of periodontal
treatment-whenever there is a functional indication for it.
a) A diagnosis of TFO fully justifies occlusal therapy.
b) When malocclusion interferes with achievement of stable
intermaxillary relationship. E.g. Migrating teeth, diastemas,
flaring of anterior teeth.
c) Bruxism may require treatment, since it is the basis for every type
of dysfunctional manifestation and often is the first evidence of
lack of adaptation to occlusion.
Occlusal therapy is also indicated when missing teeth need to be
replaced or food impaction needs to be corrected. Occlusal therapy
should not be initiated unless there is evidence to indicate that the
system is no longer adapting to the occlusal scheme of the individual.

Occlusal Adjustment
1. Removing occlusal prematurities in centric relation and centric
occlusion. A ‘long-centric’ or ‘freedom in centric’ when cusp tips
contact horizontal stops in the fossae.
2. Eliminating balancing interferences which will allow the
mandible to move freely laterally and protrusively.
3. Adjusting working contacts in lateral movements and anterior
contacts in protrusion. Depending on the occlusal pattern of the
individual no single tooth should be overloaded during
excursions with either group function or a cuspid protected
occlusion.
When to perform occlusal therapy in the sequence of periodontal
treatment
It is preferable to postpone any procedures related to occlusion
until root preparation has been completed and the patient has been
instructed in oral hygiene procedures. When inflammation has been
controlled, teeth will modify their position within the socket and will be
more stable and less mobile. Thus, after controlling inflammation,
occlusal therapy is performed when indicated.

Occlusal patterns in periodontal therapy
a) Indications for Group function
Group function includes contact of cuspid, bicuspids and perhaps
molars on working side.
1. If the existing occlusion is in group function and there is
no temperomandibular joint or muscular dysfunction or
tooth mobility, group function relation is acceptable.
2. If a cuspid is periodontally weakened or presents mobility
on lateral excursive contacts, a group function is indicated.
Even if a cuspid is periodontally compromised, it should
still be adjusted to remain in contact-during group function
working relationship.
b) Indications for mutual protection
In many mouths with healthy periodontium and minimum wear,
the teeth were arranged so that the overlap of the anterior teeth
prevented the posterior teeth from making any contact on either working
or non working sides, during mandibular excursions. This separation
from occlusion is termed disocclusion. According to this concept of

occlusion, the anterior teeth bear all the load when the posterior teeth are
disoccluded in any excursive position of the mandible.
The position of maximum intercuspation coincides with the
optimal condylar position of the mandible. All posterior teeth are in
contact with the forces being directed along their long axis. The anterior
teeth contact lightly or are very slightly out of contact. As a result of the
anterior teeth protecting the posterior teeth in all mandibular excursions
and the posterior teeth protecting the anterior teeth at the intercuspal
position, this type of occlusion came to be known as mutually protected
occlusion.
To reconstruct a mouth with mutually protected occlusion it is
necessary to have anterior teeth that are periodontally healthy. In the
presence of anterior bone loss or missing canines, the mouth should
probably be restored to group function.
Splinting
Splinting refers to any joining together of two or more teeth for
stabilization.
Occlusal correction and construction of an appliance precede
splinting.

Splinting has 3 purposes:
i) To protect loose teeth from injury during stabilization in a
favourable occlusal relationship.
ii) To Distribute occlusal forces for teeth weakened by loss of
periodontal support.
iii) To prevent a natural tooth from migrating.
The number of teeth required to stabilize a loose tooth depends on:
a) Degree and direction of mobility.
b) The remaining bone.
c) The location of the mobile tooth.
d) Whether the tooth is to be used as an abutment tooth.
Reducing mesiodistal mobility is easier than reducing
buccolingual mobility because of approximating teeth that aid in
support. It is advisable to use more than one firm tooth to stabilize a
mobile tooth.
If the mobile teeth are splinted to adjacent teeth without
correction of the occlusal traumatism or parafunctional habits, the entire
splint can become unstable.
Splinting methods:

It may classified as
1. Temporary or reversible.
2. Provisional.
3. Permanent.
Some methods of reversible splinting are ligature wire,
circumferential wiring, removable appliances and bonding. Removable
appliances include the Hawley’s Retainer and a continuous clasp RPD.
A swing-lock RPD though costly and can be damaging is used for
medically compromised patients.
Splinting by Bonding
Newer materials have made splinting teeth easier. The composite
resins have greater strength and light cured bonding permits better
control of contours. Temporary splinting is accomplished with the
composite material alone or in combination with extracoronal or intra
coronal wires or screen meshes.
Permanent splinting can also be performed with resin bonded
retainers (Maryland bridges) or bars and plates.
Provisional splinting with full coverage acrylics
This method is commonly used with periodontally compromised
patients where there is a commitment to fixed splints after periodontal

therapy. Before periodontal treatment, the teeth are prepared and heat
processed acrylic treatment restorations are constructed and cemented
with sedative cements. When the tissue has healed and matured after
surgery, cast splints are inserted.
Indications for splinting
Splinting is indicated if mobility is increasing after periodontal
and initial occlusal therapy and the teeth are interfering with chewing
ability and comfort.
According to Lindhe, candidates for splinting are:
1. Progressive (increasing) mobility of a tooth as a result of
gradually increasing width of the periodontal ligament in teeth
with a reduced height of alveolar bone.
2. Increased bridge mobility despite splinting.
Progressive mobility in situation 1 can often be controlled by
unilateral splints.
Situation 2 requires cross-arch splinting.

PLACEMENT OF MARGINS OF RESTORATION
Whenever possible margins are prepared supragingivally on the
enamel of the anatomic crown. Any restorative material is a foreign
body in the gingival sulcus and unfortunately they provide an area
favourable for plaque formation.
Advantages of supragingivaly placed margins are:
a) Favourable reaction of the gingiva.
b) Wider shoulder tooth preparations can accommodate an adequate
bulk of porcelain without-pulpal injury.
c) Metal margin finishing techniques are easier.
Intracrevicular Margin Placement
Despite the advantages of supragingival margins there are clinical
situations requiring intracrevicular margin placement. They are:
1. Esthetics.
2. Severe cervical erosion, restorations or caries extending beyond
gingival crest.
3. Adequate crown retention in short or broken down clinical
crowns.
4. Elimination of persistent root sensitivity.

Intracrevicular Depth
Accurate estimate of true gingival crevice is important to ensure
that margins do not impinge on junctional epithelium or connective
tissue attachment (biologic width). This requires the use of an accepted
periodontal probe. Position of the probe and probing force are critical
for accuracy.
In health, the probe is stopped by the junctional epithelium,
whereas gingivitis allows penetration of junctional epithelium and
connective tissue fibres.
Studies have estimated that the ideal intracrevicular depth for
margins is 0.5-1mm beneath gingival crest and not more than 0.5mm
when the crevice is adjacent to root surfaces.
Studies have also demonstrated that a space of 2mm is needed for
supracrestal connective tissue attachment and junctional epithelium to
attach to the tooth. This 2mm band is a physiologic dimension that is
required around every tooth in the mouth. It has been called as biologic
width. If the restoration infringes on this width, there is no place for
attachment apparatus to insert. An inflammatory response results,
attachment loss with apical migration occurs and pocket formation
ensues.

Adequate attached keratinized tissue
To know the width of attached gingiva, one must first
differentiate between attached and unattached gingiva. In the best of
situations, the gingival sulcus will probe atleast 1mm so that this amount
of keratinized tissue will be unattached. Next we encounter a millimeter
of junctional epithelial cells, accounting for another millimeter of
unattached gingiva. Thus inorder to provide atleast 1mm of attached
gingiva in an ideal situation of a very shallow probing depth, atleast
3mm of keratinized tissue must be present. If more than 1mm of gingiva
coincides with the sulcus depth, then an even greater amount of
keratinized tissue is necessary.
Berman has given a method of placing the margins subgingivally
with a collar of metal.
First step is to prepare the tooth to the crest of the gingiva.
Gingival retraction is obtained with a chord or electrosurgery.
A diamond point with an angled tip of calibrated length is
introduced to prepare the bevel. This instrument eliminates the sharp
edge of the shoulder and the undercut which extends apically from the
shoulder.

Gingival Retraction and Impressions
All retraction methods induce transient trauma to the junctional
epithelium and connective tissue of gingival sulcus.
a) Retraction chord: It usually produces limited gingival recession
and can protect the sulcular tissues during preparation. If used
carelessly when inadequate attached gingiva is present, injury to
gingival fibres occurs. This can allow the impression material to
be forced into the gingival connective tissue and bone producing
a foreign body reaction.
b) Electrosurgery : They have certain limitations. But when used
properly the cellular healing is comparable to a scalpel cut.
Controlled depth cutting electrode tips avoid bone trauma but
injure the gingival fibres, if the tip is not angled properly in the
sulcus. Oringer’s solution or surgical pack may enhance healing.
In patients with thin covering of gingiva and alveolar bone over
the root, electrosurgery should not be used as the loss of tissue from the
internal or crevicular surface can result in gingival recession. In these
patients, the gingiva should be retracted with retraction chords.

TEMPORARY AND PROVISIONAL CROWNS
Improperly constructed “interim” restorations may cause
periodontal inflammation and gingival recession. The requirements for
fit, polish and contour in the interim restoration should be the same as
for the final restoration.
Long-term restorations should not be called as temporary but
should be regarded as provisional or treatment restorations. These allow
the dentist to assess the effect of final restoration.
EMBRASURES
When teeth are in proximal contact, the spaces that widen out
from the contact are known as embrasures. Each interdental space has 4
embrasures.
1) An occlusal or incisal embrasure that is coronal to the contact
area.
2) A facial embrasure.
3) A lingual embrasure.
4) A gingival embrasure which is the space between the contact area
and the alveolar bone.

In health, the gingival embrasure is filled with soft tissue, but
periodontal diseases may result in attachment loss creating open
gingival embrasures.
The gingival embrasure: From a periodontal view point, the gingival
embrasure is the most significant.
Periodontal diseases cause tissue destruction, which reduces the
level of alveolar bone, increases the size of the gingival embrasure and
creates an open interdental space. Restorations may be constructed to
preserve the morphologic features of the crown and root and retain the
enlarged embrasure space or when esthetic situations dictate, the teeth
may be reshaped by the restorations so that the gingival embrasures are
relocated close to the new level of the gingiva.
To relocate the gingival embrasure, the dentist changes the
contour of the proximal surfaces and broadens the contact areas more
apically.
Dimensions of gingival embrasure : Height, width, depth.
The proximal surfaces of crowns should taper away from the
contact area facially, lingually and apically. Excessively broad proximal
contacts and bulky contour in the cervical region crowd out the gingival

papillae. This can make oral hygiene difficult resulting in gingival
inflammation and attachment loss.
Restorative dental procedures too often result in the restorative
materials taking up spce that is normally occupied by the interdental
papilla. The problem begins with underpreparation of tooth, so that the
technician is left with no choice except to place an excessive amount of
restorative material into the interproximal space. During the preparation
of dies for cast restorations, the technician first removes all of the
replicated tissue to gain access to the finish lines. Thus it is impossible
for him to visualize the space available for dental restoration in the
interproximal embrasure area. If two models are poured from the same
impression and the second one is used as an indicator of how much
space is currently occupied by gingival tissues, the technician can have a
much better understanding of what the contour of the final restorations
should be.
In fixed prosthesis and / or multiunit fixed splints, the
interproximal contact and / or soldered joint is frequently carried for too
apically so that it invades the embrasure space from its coronal aspect.
This leads to inflammation and destruction of periodontal tissues.
The responsibility of determining the size of the interproximal
contact should rest with the dentist, not the technician.

CROWN CONTOUR
The contours of full and partial coverage restorations play a
supportive role in establishing a favourable periodontal climate. The
theories of crown contouring that have evolved are:
1) Gingival protection.
2) Gingival stimulation.
3) Muscle action.
4) Access for oral hygiene.
1. Gingival Protection Theory:
It advocates that contours of cast restorations be designed to
protect the marginal gingiva from mechanical injury. In 1962 this
concept was challenged by Morris who reported that the response of
gingival tissue around teeth prepared for complete artificial crowns but
which had lost their temporary crowns were similar to the adjacent
unprepared teeth. Schluger stated that the so called protective cervical
bulge protects nothing but the microbial plaque.
2. Gingival stimulation theory:
This concept reasons that as food is masticated, it will pass over
the gingiva stimulating it and causing increased keratinization of the
epithelium. Keratinized epithelium would be more resistant to

periodontal breakdown. Several authors have shown that the gingival
margin is not in the path of masticated food. Even if the food passing
over the teeth were to increase keratinization, this stimulating would
occur at the buccal and lingual surfaces.
3. Muscle action theory:
This theory advocates that the perioral musculature (tongue,
cheeks) are responsible for maintaining a healthy periodontal
environment. They suggest that overcontouring prevents normal
cleansing action by the musculature and allows food to stagnate in the
overprotected sulcus.
4. Theory of access for oral hygiene
This theory is based on the concept that the prime etiologic factor
in caries and gingivitis is plaque. Thus, crown contour should facilitate
plaque removal, not hinder it.
Four guidelines to contouring crowns are:
1) Buccal and lingual contours – flat, not fat

Plaque retention on the buccal and lingual surfaces occurs
primarily at the infrabulge of the tooth. Reduction or elimination of
infrabulge would reduce plaque retention.
2) Open embrasures
Every effort must be made to allow easy access to interproximal
area for plaque control. An overcontoured embrasure will reduce the
space intended for the gingival papilla.
3) Location of contacts
Contacts should be directed incisally or occlusally and buccally
in relation to the central fossa, except between maxillary first and
second molars. This creates a large lingual embrasure space for
optimum health of lingual papilla.
4) Furcation involvement
Furcations that have been exposed owing to loss of periodontal
attachment should be ‘fluted’ or ‘barreled out’. It is based on the concept
of eliminating plaque traps.

Facial and Lingual sulcular contours
In the patient whose gingival margins are apical to the CEJ the
sulcular morphology differs from that of a healthy patients whose
gingival margins are on enamel.
The intracrevicular contours of an artificial crown should be as
close to the original enamel contour as possible. Wagman has estimated
the angle of enamel flare from CEJ to be approximately 22.5 degrees
from the vertical axis of gingival housing.
As the gingival margin progresses more apically, the sulcus
narrows and the intracrevicular contours of the tooth become the flat
contours of the root rather than the convex surface of the anatomic
crown. Intracrevicular contours in such cases depend on the adjacent
gingival morphology.
When the intracrevicular margins are adjacent to thin gingiva on
the root, the sulcular contours of the artificial crown should be flat,
mimicking the shape of the root.
Often the gingiva adjacent to a flat root surface develops a thick
free gingival margin when the underlying bone is thick. In these
situations it may be advisable to create a thicker intracrevicular crown
contour similar to that of a natural crown.

PONTIC DESIGN
A pontic should meet the following requirements.
1. Be esthetically acceptable.
2. Provide occlusal relationships that are favourable to abutment
teeth.
3. Restore the masticatory effectiveness.
4. Be designed to minimize accumulation of irritating dental plaque
and food debris.
5. Provide embrasures for passage of food.
The health of the tissues around the fixed prosthesis depends
primarily on the patients oral hygiene. The material with which pontics
are constructed make little difference and pontic design is important
only to the extent that it enables the patient to keep the area clean.
Plaque accumulates to an equal degree under pontics made of
glazed and unglazed porcelain, polished gold and polished acrylic resin.
The principles of contours of crowns apply equally well to pontics but
with pontics there is an additional concern associated with the contour
of the tissue facing surfaces.

In the mandibular posterior region, esthetics is not a major
consideration, so the spheroidal pontic is the design of choice because of
its contour.
In the maxillary posterior area, the modified ridge lap satisfies
both esthetics and hygiene.
Mandibular anterior area also requires a ridge lap design. When
using a spheroidal design, the pontic contacts without pressure the tip of
the ridge or the buccal surface.
When there is excessive bone loss and the rigidity of the
connector is suitable (non-esthetic posterior areas), the pontic is not
required to touch the ridge. There should be atleast 3mm of space so that
the patient can maintain hygiene.
CEMENTATION
During cementation it is important that the restoration be seated
as close to the tooth preparation as possible. A minimal cement line at
the margin reduces plaque formation. It is extremely important that all
excess cement be removed from the sulcus after cementation. Removal
of cement from the interproximal joints can be facilitated by lightly
coating the exterior surfaces of the prosthesis with petroleum jelly prior
to cementation.

RESTORATION OF MOLAR TEETH WITH FURCATION
INVASIONS
In long-term studies of tooth longevity, molars are the teeth that
are most often lost. This is due to the complex root anatomy and
furcations that make periodontal therapy and plaque control difficult for
the patients.
In the maxillary molars, the distal furcation is usually more apical
on the tooth than the mesial furcation. It is less frequently involved with
periodontal attachment loss than the mesial and buccal furcations. The
concavities and root alignments result in a furcation chamber that is
wider than the entrances.
In the mandibular molars, the root surfaces facing the furcation,
both have a high prevalence of concavities.
Classification of furcation involvement
Grade I – Incipient or early lesion. Radiographic changes not seen.
Grade II – Bone is destroyed on one or more aspects of the furcation,
but a portion of alveolar bone and periodontal ligament
remains intact, permitting only partial penetration of probe
into the furcation.

Grade III – Interradicular bone is completely destroyed, but facial or
lingual orifices of the furcation are occluded by gingival
tissue.
Grade IV – Interradicular bone is completely destroyed and gingival
tissue is also receded apically so that the furcation opening
is clinically visible.
Diagnosis of furcation: Naber’s probe
Probing of mandibular molar furcations is easier because there
are only two entrances.
In maxillary molars, the distal and buccal furcations are also
accessible as they are located midway buccolingually and mesiodistally.
The mesial furcation is however not situated midway buccolingually but
towards the palatal side due to wide buccolingual width of the
mesiobuccal root.
If a full coverage restoration is indicated on a Grade I or early
Grade II furcally involved teeth, the principles are same as that for a
normal tooth except that the preparation has to be fluted or barreled into
anatomic depressions.

RESTORATION OF ROOT RESECTED MOLARS
Root amputation : Removal of a root from a multirooted teeth.
Root resection : Surgical removal of a root after endodontic treatment.
Hemisection : Surgical separation of a multirooted tooth through the
furcation area in such a way that a root or roots may
be surgically removed along with associated portion
of the crown.
Bisection : Splitting and retaining the roots and accompanying
crowns of a mandibular molar or any two roots of
maxillary molar.
Indications for Root resection or Hemisection
1. Vertical bone loss around one root but not others.
Post surgical healing: It is critical when intracrevicular margins have to
be placed on resected or hemisectioned teeth. A minimum of 4 to 6
weeks of healing after surgery is required before the soft tissues can
resist the trauma of tooth preparation.
Root amputation procedures – Digramatic (OHP)

Post and cores
Brittleness of the pulpless root resected tooth is the primary
reason for root fractures over time. Complete coverage of root resected
teeth is recommended especially over resection area.
There is no evidence that post and cores are beneficial in resected
teeth and infact they can be detrimental. If a post and core is required
because of a coronal damage, a custom cast dowel core is preferable to
prefabricated dowel.
Crown Preparation
Intracrevicular margins are usually required to cover portions of
root-resected area. The crown margin should be apical to the pulp
chamber or root canal that was exposed by resection.
To preserve remaining tooth structure and encourage a better
fitting restoration a chamfer finish line is recommended.
The gingival third of the restoration is fabricated with a flat
emergence profile from the gingiva to facilitate oral hygiene.

PRE-PROSTHETIC PERIODONTAL SURGERY
I. Mucogingival surgery
Teeth with subgingival restorations and narrow zones of
keratinized gingiva have higher gingival inflammation scores than teeth
with similar restorations and wide-zones of attached gingiva.
Coverage of denuded roots is also another objective of
mucogingival surgery.
Mucogingival surgery can also create some vestibular depth
when it is lacking.
Techniques for increasing attached gingiva.
i) Free gingival autografts.
ii) Apical displacement flap.
When there is a pocket formation, thick manageable pocket walls
can be used for an apically displaced flap – this flap should be the first
choice.
When the pockets are absent and there is a need for increasing
width of attached gingiva, free gingival graft is the technique of choice.

Root coverage : Two techniques are recommended.
i) Langer’s technique – uses a connective tissue graft under a
partial thickness flap.
ii) Tarnow technique – Semilunar coronally displaced flap.
Langer’s technique is an excellent solution in most of the cases,
but Tarnow’s technique is the first choice in isolated upper teeth.
II. Crown lengthening procedures
In situations in which a tooth has a short clinical crown that is
deemed inadequate for the retention of a required cast restoration, it is
necessary to increase the size of the clinical crown using periodontal
surgical procedures. By definition, the clinical crown is that portion of
the tooth that is coronal to the alveolar crest. Therefore, to lengthen it
bone margin has to be remodeled. This is done with an apically
displaced flap and ostectomy. The removal of bone is usually not
necessary all around the tooth but if undertaken should be done with
great caution. It is essential that there be atleast 2mm of connective
tissue attachment between the most apical extension of the restoration
margin and alveolar bone crest.

III. Ridge Augmentation procedures
Aimed at correcting the excessive loss of alveolar bone that
sometimes occurs in the anterior region as a consequence of advanced
periodontal disease. The excessive bone loss may create a difficult
esthetic problem and complicate prosthetic reconstruction.
Several prosthetic solutions have been proposed:
a) Placement of a thick mucosal autograft obtained from
palate or tuberosity.
b) Placement of non-porous dense hydroxyapatite under a
split thickness flap or a pouch created under a full
thickness flap.
c) A double flap technique used in conjunction with
hydroxyapatite.
REMOVABLE PARTIAL DENTURES AND THE
PERIODONTIUM
From the periodontal viewpoint, fixed prosthesis are the
restorations of choice for replacement of missing teeth, but there are
some clinical situations in which removable partial prosthesis are the
only possible way to restore the lost function of the dentition.

It is unwise consider a removable partial denture in patients
whose oral hygiene is inadequate.
DESIGN
Every effort must be made to retain posterior teeth for the distal
support of edentulous areas. When posterior teeth cannot be retained, the
design for removable partial prosthesis becomes challenging.
Clasps:
Studies have shown that I-bar type of clasps have little or no
detrimental effect of periodontal health. This design utilizes a gingivally
approach clasp, mesially positioned occlusal rest and a proximal plate.
Clasps should be passive and exert no force on teeth when the
partial denture is at rest.
Occlusal rests: They should be designed so that the occlusal forces are
directed along the vertical axis of the tooth. The angle formed by the
occlusal rest and the vertical minor connector should be less than 90°.
Only this way can the occlusal forces be directed along the long axis of
the abutment tooth.

Combined Fixed and Removable prosthesis
Isolated teeth with reduced periodontal support are particularly
vulnerable to periodontal injury and loosening when used as abutments
in removable partial prosthesis. The isolated teeth should be joined to
their nearest neighbours with a fixed prosthesis and then can be used as
abutments for removable prosthesis.
Major connectors: They should not impinge on the free gingival
margins. The major connector should be placed 6mm away from the
gingival margin.
When periodontally compromised mandibular anterior teeth
require stabilization, a special design of major connector should be used
for splinting teeth together. A lingual plate should extend to the middle
third of the surface of the mandibular anterior teeth and the coronal
border should follow the natural curvature of the supracingula surface.
OVERDENTURES
Over dentures have three obvious advantages
1) Increased retention and stability of record base.
2) Proprioception is dramatically improved compared to a patient
with complete dentures.

3) Reduction of stresses to the edentulous ridges resulting in less
bone resorption over time.
It is important that appropriate periodontal considerations be a
part of the treatment planning process.
a) Presence of adequate zone of attached gingiva is of critical
importance around the abutment teeth.
b) Any remaining periodontal defects must be treated in the
same way as they would be around any periodontally
involved tooth prior to fixed restoration.
One great advantage that the overdenture concept has for
periodontally involved teeth is that it is possible to improve the crown
root ratio dramatically. This results in a great diminution of forces
applied to the remaining root.
Implant supported restorations
The main principles that determine success or failure from a
periodontal view point for an implant supported restoration are:
1) Patient selection.
2) Investing tissues.
3) Force distribution

Investing tissues can be defined as including both hard and soft
tissue. Both the bone height and width must be adequate for implant
placement. In partially edentulous patients it has been observed that
keratinized tissue around implants offer the greatest resistance to peri-
implant infection.
Force distribution
a) Crown implant ratio – This is very important in the presence of
lateral forces. Lateral forces result in a moment of the force on
the implant and an increase in horizontal stresses. Implants
placed in the anterior maxilla experience more frequent
complications because of lateral stresses.
The greater the crown-implant ratio, the greater the moment of
force under lateral loads.
b) Bone density:
The density of bone is in direct relationship with the amount of
implant bone contact. The very dense bone of a resorbed anterior
mandible (D-1) or the lateral cortical bone in the anterior mandible has
the highest percentage of lamellar bone in contact with an endosteal
implant. The percentage of bone contact is significantly greater in
cortical bone than in trabecular bone. The initial bone density not only

provides mechanical immobilization during healing, but also permits
better distribution and transmission of stresses from the implant-bone
interface. Open marrow spaces or zones of unorganized fibrous tissue do
not permit force dissipation. The sparse trabeculae of bone often found
in posterior maxilla (D-4) offer less areas of contact with the body of the
implant. Consequently, greater implant surface area is required to obtain
the same amount of implant-bone contact as for a mandibular anterior
implant. Progressive bone-loading changes the amount and density of
implant-bone contact. The body is given time to respond to a gradual
increase in occlusal load. This increases the quantity of bone at the
implant surface, improves bone density and improves the overall support
system mechanism.
Other factors to be considered are:
 Bilateral simultaneous contact is mandatory.
 Occlusal vertical dimension must be in harmony with the
patient’s muscular system.
 All interferences must be eliminated.
 Centric vertical contacts should be aligned with the long axis of
the implant whenever possible.

 Posterior occlusal tables may be narrowed in order to prevent
inadvertent lateral forces.
 Enameloplasty of the cusp tips of the opposing natural teeth is
indicated to help improve to direction of vertical forces.

Periodontium and prosthodontics

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