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.