Pontics in Fixed Partial Dentures

Editor's Notes

1. The restorations of edentulous areas with fixed partial dentures (FPDs) present a particular challenge for the clinician. Because of their ease of use and favorable long term results, conventional FPDs represent the most popular treatment measure today. In these restorations, the pontic must fulfill the complex roles of replacing the function of the lost tooth, achieving an In addition the pontic must meet certain structural requirements to ensure the mechanical stability of the restorations.
2. When orthodontic repositioning is not possible, increasing the proximal contours of adjacent teeth may be better than making an FDP with undersized pontics If there is no functional or esthetic deficit, the space can be maintained without prosthodontic intervention.
3. soft tissue from the lingual side of the edentulous site is used. The epithelium is removed, and the tissue is thinned and rolled back upon itself, thereby thickening the facial aspect of the residual ridge
4. Pouches may also be prepared in the facial aspect of the residual ridge into which subepithelial or submucosal grafts harvested from the palate or tuberosity may be inserted
5. a wedge-shaped connective tissue graft is inserted into a pouch preparation on the facial aspect of the residual ridge. The epithelial portion of the wedge may be positioned coronally to the surrounding epithelium if an increase of ridge height is desired
6. Useful for treating Class III ridge defects. It is a thick “free gingival graft” harvested from partial or full-thickness palatal donor sites.
7. Class 3 ridge defect. Donor site. Graft sutured in place.. Augmented ridge
8. Preservation of the alveolar process can be achieved through immediate restorative and periodontal intervention at the time of tooth removal. Because socket preservation is dependent on underlying bone contour, the extraction of the tooth to be replaced should be atraumatic and aimed at preserving the facial plate of bone. The scalloped architecture of interproximal bone forming the extraction site is essential for proper papilla form, as are facial bone levels in the prevention of alveolar collapse.
9. Immediately after preparation of the extraction site, a carefully shaped interim FDP is placed
10. Pontic selection depends primarily on esthetics and oral hygiene. In the anterior region, where esthetics is a concern, the pontic should be well adapted to the tissue to make it appear that it emerges from the gingiva. Conversely, in the posterior regions (mandibular premolar and molar areas), esthetics can be compromised in the interest of designs that are more amenable to oral hygiene
11. Hyperbolic paraboloid
12. Morton L Perel in 1972 described a modified sanitary pontic which has a free archway design and is concave mesiodistally. Proximally the solder joints of the pontic are elongated. This addition increases the strength of what is considered to be the weakest part of any posterior fixed prosthesis.
13. It is called ridge lap because it overlaps the facial lingual aspects of the ridge.
14. There could be a faciolingual concavity on the facial side of the ridge, cleaned and well tolerated as long as the tissue contact is narrow M-D and F-L
15. To enable optimal plaque control, the gingival surface must have no depression or hollow. Rather, it should be as convex as possible from mesial to distal (the greater the convexity, the easier the oral hygiene)
16. easy for the patient to keep clean.
17. a knife-edged residual ridge will necessitate flatter contours with a narrow tissue contact area. This type of design may be unsuitable for broad residual ridges, because the emergence profile associated with the small tissue contact point may create areas of food entrapment The sanitary or hygienic pontic is the design of choice in these clinical situations.
18. before 1930 the root tipped pontic. Careful treatment planning is necessary for successful results
19. The ovate pontic’s advantages include it’s pleasing appearance and it’s strength, when used successfully with ridge augmentation, it’s emergence from the ridge appears identical to that of a natural tooth. This type of pontic design, however, requires an adequate amount of soft tissue, which has to be sculpted accordingly.13 Various techniques are available for this purpose, ranging from controlled regeneration directly after the extraction of the tooth (immediate pontic technique) to plastic surgery (gingival grafting), which is accompanied by tissue conditioning in the course of the subsequent prosthodontic treatment.
20. its recessed form is not susceptible to food impaction. The broad convex geometry is stronger than that of the modified ridge lap pontic Because the tissue surface of the pontic is convex in all dimensions, it is accessible to dental floss
21. The apical opening of the pulp canal was cleaned, enlarged slightly, and sealed with composite resin. A modified ridge-lap pontic was designed-The pontic was stabilized in the extraction socket with a resin-wire splint as a provisional restoration. After 1 month recall the tooth was stablised on the cast. A retention lock was also prepared on the palatal aspect of the natural tooth pontic (4-mm high, 3.5-mm wide, and 2- mm deep;
22. the pressure area should be identified with a disclosing medium (i.e, pressure indicating paste) and the pontic recontoured until tissue contact is entirely passive. This passive contact should occur exclusively on keratinized attached tissue.
23. Unlike removable partial dentures, FPDs cannot be taken out of the mouth for daily cleaning. Patients must be taught efficient oral hygiene techniques, with particular emphasis on cleaning the gingival surface of the pontic. The shape of the gingival surface, its relation to the ridge, and the materials used in its fabrication will influence ultimate success.
24. Unlike removable partial dentures, FPDs cannot be taken out of the mouth for daily cleaning. Patients must be taught efficient oral hygiene techniques, with particular emphasis on cleaning the gingival surface of the pontic.
25. abricate the pontic should provide good esthetic results where needed; biocompatibility, rigidity, and strength to withstand occlusal forces; and longevity. FPDs should be made as rigid as possible, because any flexure during mastication or parafunction may cause pressure on the gingiva and cause fractures of the veneering material. Occlusal contacts should not fall on the junction between metal and porcelain during centric or eccentric tooth contracts, nor should a metal ceramic junction occur in contact with the residual ridge on the gingival surface of the pontic.
26. Placing ceramic on the tissue side of the pontic may weaken the design of the metal substructure, particularly with porcelain occlusal surface
27. Reducing the buccolingual width of the pontic by as much as 30% has been suggested as a way to lessen occlusal forces on, abutment teeth. forces are lessened only when chewing food of uniform consistency and that a mere 12% increase in chewing efficiency can be expected from a one third reduction of pontic width. In fact, narrowing the occlusal table may actually impede or even preclude development of a harmonious and stable occlusal relationship. Like a malposed tooth, it may cause difficulties in plaque control and may not provide proper cheek support. For these reasons, pontics with normal occlusal widths (at least on the occlusal third) are generally recommended. One exception is if the residual alveolar ridge has collapsed buccolingually. Reducing pontic width may then be desired, thereby lessening the lingual contour and facilitating plaque control measures. Potentially harmful forces are more likely to be encountered if an FPD is loaded by the accidental bitting on a hard object or by parafunctional activities like bruxism rather than by chewing foods of uniform consistency. These forces are not reduced by narrowing the occlusal table.
28. These factors can lead to fracture of the prosthesis or displacement of the retainers. Long span posterior FPDs are particularly susceptible to mechanical problems. significant flexing from high occlusal forces and because The deflection of a fixed dental prosthesis is proportional to the cube of the length of its span
29. However, mechanical failure can occur and often is attributable to inadequate frame work design. A reliable technique for ensuring uniform thickness of porcelain is to wax the fixed prosthesis to complete anatomic contour and then accurately cut back the wax to a predetermined depth The metal surfaces to be veneered must be smooth and free of pits. Surface irregularities will cause incomplete wetting by the porcelain slurry, leading to voids at the porcelain metal interface the reduce bond strength and increase the possibility of mechanical failure . Sharp angles on the veneering area should be rounded. They produce increased stress concentrations that can cause mechanical failure.
30. Their resistance to abrasion was lower then enamel or porcelain, and noticeable wear occurred with normal tooth-brushing. Furthermore, the relatively high surface area/volume ratio of a thin resin veneer made dimensional change from water absorption and thermal fluctuations (thermo cycling) a problem. Because no chemical bond existed between the resin and the metal framework, the resin was retained by mechanical means (eg., undercuts). They are easy to manipulate and repair and do not require the high–melting range alloys needed for metal ceramic techniques.
31. The physical properties of this system, combined with its excellent marginal adaptation and esthetics, make it a possible metal free alternative for FPDs, although long term clinical performance is not yet known.
32. Many esthetic considerations that pertain to single crowns also apply to the pontic. Several problems unique to the pontic may be encountered when attempting to achieve a natural appearance.
33. The greatest challenge here is to compensate for anatomic changes that occur after extraction.
34. To achieve the illusion of a natural tooth, an esthetic pontic must deceive observers into believing they are seeing a natural tooth.
35. in normal situations, light falls from above and an object’s shadow is below it. Unexpected lighting or unexpectedly placed shadows can be confusing to the brain. Because of past experience, the brain “knows” that a tooth grows out of the gingiva, and it therefore “sees” a pontic as a tooth unless telltale shadows suggest otherwise.
36. Obtaining a correctly sized pontic simply by duplicating the original tooth is not possible. The height of a tooth is immediately obvious when the patient smiles and shows the gingival margins. This fact can be used to produce a pontic of good appearance by recontouring the gingival half of the labial surface. The observer sees a normal tooth length but is unaware of the abnormal labial contour. The illusion is successful.
37. However, such pontics then have considerably increased tissue contact and require scrupulous plaque control for long term success. Ridge augmentation procedures have been successful in correcting areas of limited resorption. When bone loss is severe, the esthetic result obtained with an RPD is often better than with an FPD.
38. If augmentative measures are contraindicated or undesirable, small alveolar deficiencies and missing papillae can be reconstructed by restorative measures. First, the exact shade of the gingiva has to be established. This can be accomplished with special gingival shade guides that are supplied with the different commercially available pink veneering materials. The basal surface must demonstrate a convex shape similar to the ovate pontic designs for the dental floss to establish tight contact with all the surface areas.
39. an impression is taken of the labial surface of tbe restoration using a customized tray and a medium-viscosity polyether materialThe masks are bonded to the existing restoration with a light-curing, low-viscosity resin composite, This solution, however, increases the risk of plaque accumulation. Because the material ages quickly, the prosthesis has to be replaced on a regular basis
40. In the same way that the brain can be confused into misinterpreting the relative sizes of shapes or lines because of an erroneous interpretation of perspective, a pontic of abnormal size may be designed to give the illusion of being more natural size. This is usually due to uncontrolled tooth movement that occurred when a tooth was removed and not replaced.
41. The width of an anterior tooth is usually identified by the relative positions of the mesiofacial and distofacial line angles, and the over all shape by the detailed pattern of surface contour and light reflection between these line angels.
42. A 52-year-old woman. The areas of the pencil marks represented the region where the patient would have the deepest point of tissue adaptation and was scored to a depth of 1 mm and trim the alveolar crest to 0.5 mm. the pontic was convex in the buccal and lingual regions and concave in the middle of the pontic
43. Slowly screwing prosthesis into place for 15 minutes allows tissue to contour after complete seating. 1 week, 2 weeks, 1 month, 3, 6, and 10 months to evaluate the the tissue beneath the pontic. An oral hygiene evaluation, especially of the tissue under the pontics, was performed at each visit. The provisional implant fixed partial denture was worn for 10 months before the definitive prosthesis was inserted.
44. Compression of the pontic site in the mid-lingual portion, along with deeper sculpting depth at the facial gingival margin and interproximal line angles, is enough to ensure complete seating of the pontic and abutment crowns
45. The pontic design is said to determine the success or failure of a bridge. Designs that allow easy plaque control are especially important to a pontic’s long term success. Minimizing tissue contact by maximizing the convexity of the pontic’s gingival surface is essential. Special consideration is also needed to create a design that combines easy maintenance with natural appearance and adequate mechanical strength. Based on classic clinical studies, a number of authors have advocated the use of modified ridge lap pontics with a well polished and smooth, convex surface that results in pressure free or mild contact with the alveolar ridge over a very small area for a better preservation of the soft tissue health. However, the modified ridge lap pontic design has certain limitations, depending on the pattern of alveolar ridge resorption, and cannot always be used without compromising esthetics and functions. Because the aforementioned factors are decisive in restoring anterior teeth, new alternatives in pontic design were developed, giving the illusion that the replaced tooth emerges from the gingiva like a natural tooth. This ovate pontic design requires the preparation of a suitable recipient site, which can be achieved by the application of modern ridge preservation techniques, including an atraumatic extraction and the direct support of the extraction socket by the use of the immediate pontic technique. Metal ceramic pontic fabrication is straightforward and practical. However, it requires careful execution for maximum strength, appearance, and effective plaque control. Alternatively procedures may some times be helpful, particularly when gold alloys are used for the retainers. Resin veneered pontics should be restricted to use as longer term provisional restorations, and all metal pontics may be the restoration of choice in non-esthetics situations, particularly where forces are high. Thus the design of the pontic is probably the most important factor in determining the success of the restoration of the patient. If the patient is unable to clean effectively and maintain the pontic the restoration will be unsuccessful.