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Periodontium and prosthodontics

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Indian Dental Academy: will be one of the most relevant and exciting training center with best faculty and flexible training programs for dental professionals who wish to advance in their dental practice,Offers certified courses in Dental implants,Orthodontics,Endodontics,Cosmetic Dentistry, Prosthetic Dentistry, Periodontics and General Dentistry.

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  • 1. 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
  • 2. 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
  • 3. 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.
  • 4. 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.
  • 5. 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.
  • 6. 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.
  • 7. 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.
  • 8. 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.
  • 9. 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.
  • 10. 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
  • 11. 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.
  • 12. 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:
  • 13. 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
  • 14. 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.
  • 15. 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.
  • 16. 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.
  • 17. 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.
  • 18. 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.
  • 19. 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.
  • 20. 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
  • 21. 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.
  • 22. 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
  • 23. 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
  • 24. 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.
  • 25. 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.
  • 26. 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.
  • 27. 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.
  • 28. 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.
  • 29. 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.
  • 30. 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)
  • 31. 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.
  • 32. 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.
  • 33. 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.
  • 34. 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.
  • 35. 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.
  • 36. 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.
  • 37. 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
  • 38. 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
  • 39. 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.
  • 40.  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.