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Pontics Design in fixed prosthodontics


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Pontics Design in fixed prosthodontics

  2. 2. 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 esthetic appearance, enabling adequate oral hygiene, and preventing tissue irritation. In addition the pontic must meet certain structural requirements to ensure the mechanical stability of the restorations. INTRODUCTION
  3. 3. The histories of fixed and of removable partial prosthetic appliances go more or less in hand and it is difficult at times to tell just where to draw the line between these two types from the available data. Since the use of prosthodontics, the most old dental prosthesis is believed to be a fixed type. HISTORY
  4. 4.
  5. 5. Replaced tooth was sewed in place by using ligatures made from gold or silver. Egyptians and Phoeniceans were the pioneers in the field of pontics and were the first to construct dental bridge work. These were mostly made of calf bone or ivory. It is suggested that teeth of ivory and bone secured by copper wire or catgut string were used in China for ages before they were introduced in Europe.
  6. 6. It was Mancy in 1928 who laid the foundation to present day FPD design, however Pierre Fauchard (1923) has often been referred to as the ‘Father of Modern Dental Prosthesis’. In his work in the field of FPD he used what he called ‘tenons’ which were in reality dowels or pivots screwed into the roots to retain some of the bridges and it is possible that he may have been the first to attach dental bridges to tooth roots by this method.
  7. 7. Selberg (1936) pointed out that basic materials had changed but little in the past few years. These materials were gold or porcelain or a combination of the two. He summed up by saying that the restoration must meet the following requirements: Protection, comfort, esthetics, durability and utility.
  8. 8. The Glossary of prosthodontic terms 5 defines Pontics as - An artificial teeth on a fixed partial denture that replaces missing natural teeth, restores it’s function and usually fills the space previously filled by the natural teeth. Tylman 4 defines Pontics as the suspended member of a fixed partial denture which replaces the lost natural tooth, restores function and occupies the space of the missing tooth. DEFINITION
  9. 9. It is not a simple replacement, because placing an exact anatomic replica of the tooth in the space would be hygienically unmanageable. They must be compatible with continued oral health and comfort. The edentulous areas where a fixed prosthesis is to be provided may be overlooked during the treatment-planning phase. Unfortunately, any deficiency or potential problem that may arise during the fabrication of a pontic is often identified only after the teeth have been prepared or even when the master cast is ready to be sent to the laboratory. Proper preparation includes a careful analysis of the critical dimensions of the edentulous areas: mesiodistal width, occlusocervical distance, buccolingual diameter, and location of the residual ridge.
  10. 10. To design a pontic that will meet hygienic requirements and prevent irritation of the residual ridge, particular attention must be given to the form and shape of the gingival surface. Merely replicating the form of the missing tooth or teeth is not enough. The pontic must be carefully designed and fabricated not only to facilitate plaque control of the tissue surface and around the adjacent abutment teeth but also to adjust to the existing occlusal conditions. In addition to these biologic considerations, pontic design must incorporate mechanical principles for strength and longevity as well as esthetic principles for satisfactory appearance of the replacement
  11. 11. According to Shillingburg et al 3 Pontics are classified : 1. Depending on the shape of the pontic contacting the tissues 2. Depending on the materials. 3. Depending upon the manufacturer’s design CLASSIFICATION
  12. 12. 1. On Shape i. Conical or root extension pontics ii. Spheroidal pontic iii. Ridge Lap pontic iv. Modified ridge Lap v. Hygienic or Centric pontic vi. Saddle pontic
  13. 13. i. All metal- Gold, cobalt-chromium, nickel- chromium etc. ii. Non metallic – Porcelain iii. Combination – Metal and porcelain, metal and resin 2. On Materials used
  14. 14. 3. Design by the manufacturer or pre- fabricated pontics a. Trupontic – There is a large bulk of gingival porcelain which can be adapted to the ridge. A horizontal tubular slot in the facing runs from the center to the lingual. This slot in combination with wide proximal bevels provides the retention for the facings. These were used widely in the past. These can be altered by the dentist and reglazed if necessary. These include:
  15. 15. b. Interchangeable facings – Manufactured with vertical slot running down the flat lingual surface, this facing is retained with a lug which engages the retention slot. The tissue contact should be made a part of the backing to ensure a smooth surface.
  16. 16. c. Sanitary pontic – The original pontic bearing this name is a round blunt porcelain blanks. There is a flat surface towards the occlusal with a slot running out to one side towards the lingual during the fabrication of the pontic. After it is ground to fit the edentulous space it is reglazed.
  17. 17. d. Pin facing – A flat back facing with two horizontal pins for retention. This facing has been used where the occluso-gingival space is limited. This tissue contact should be part of the backing to prevent the porcelain-gold finish line from crossing the tissue contact area where it would be a source of irritation.
  18. 18. e. Reverse pin facing – Porcelain denture teeth can be modified to be used as the bridge facing. The pins are ground off. Porcelain is added to the gingival end of the facing. It is adapted to the ridge and multiple precision pin holes are drilled into the lingual surface with a tungsten carbide drill. Nylon bristles are placed in the holes and incorporated into the backing wax pattern. This facing affords a good retention when a deep overbite would force the use of very short pins in a conventional
  19. 19. f. Porcelain fused to metal facing – When maximum aesthetics is required particularly for an anterior tooth, this pontic is indicated. If one of the retainers must be porcelain fused to metal, the pontic should be made in the same way for better esthetics and easier fabrication. This type of pontic can be soldered to a partial veneer or full veneer retainers
  20. 20. g. Harmony facing – This facing is supplied with an uncontoured porcelain gingival surface and usually two retentive pins on the lingual side. The gingival area is adapted to the ridge and then reglazed. This type of facing does not work well in situations where the occlusogingival dimension is short.
  21. 21. According to Rosenstiel et al 1 Pontic designs are classified into two general groups: Those that contact the oral mucosa and those that do not. A. Mucosal contact B. No mucosal contact 1. Ridge lap 1.Sanitary (hygienic) 2. Modified ridge lap 2. Modified sanitary (hygienic) 3. Ovate 4. Conical
  22. 22. 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 gingival. 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 PONTIC SELECTION
  23. 23. As its name implies, the primary design feature of the sanitary pontic allows easy cleaning, because its tissue surface remains clear of the residual ridge. This hygienic design permits easier plaque control by allowing gauze strips and other cleaning devices to be passed under the pontic and seesawed in shoe-shine fashion. It’s disadvantages include entrapment of food particles, which may lead to tongue habits that may annoy the patient. SANITARY OR HYGIENIC PONTIC The hygienic pontic is the least “toothlike” design and is therefore reserved for teeth seldom displayed during function (i.e., the mandibular molars)
  24. 24. A modified version of the sanitary pontic has been developed. Its gingival portion is shaped like an archway between the retainers.15 This geometry permits increased connector size while decreasing the stress concentrated in the pontic and connectors. It is also less susceptible to tissue proliferation that can occur when a pontic is too close to the residual ridge. LITERATURE
  25. 25. The saddle pontic has a concave fitting surface that overlaps the residual ridge buccolingually, simulating the contours and emergence profile of the missing tooth on both sides of the residual ridge. SADDLE OR RIDGE LAP PONTIC
  26. 26. However, saddle or ridge lap designs should be avoided because the concave gingival surface of the pontic is not accessible to cleaning with dental floss, which will lead to plaque accumulation. This design deficiency has been shown to result in tissue inflammation.
  27. 27. The modified ridge lap pontic combines the best features of the hygienic and saddle pontic designs, combining esthetics with easy cleaning. MODIFIED RIDGE LAP PONTIC The modified ridge lap design overlaps the residual ridge on the facial (to achieve the appearance of a tooth emerging from the gingival) but remain clear of the ridge on the lingual.
  28. 28. 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). Tissue contact should resemble a letter T whose vertical arm ends at the crest of the ridge. Facial ridge adaptation is essential for a natural appearance.
  29. 29. Although this design was historically referred to as ridge-lap, the term ridge-lap is now used synonymously with the saddle design.3,17 The modified ridge lap design is the most common pontic form used in areas of the mouth that are visible during function (maxillary and mandibular anterior teeth and maxillary premolars and first molars).
  30. 30. Often called egg-shaped, bullet-shaped, or heart- shaped, the conical pontic is easy for the patient to keep clean. It should be made as convex as possible, with only one point of contact at the center of the residual ridge. This design is recommended for the replacement of mandibular posterior teeth where esthetics is a lesser concern. CONICAL PONTIC
  31. 31. The facial and lingual contours are dependent on the width of the residual ridge; 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.
  32. 32. The ovate pontic is the most esthetically appealing pontic design. Its convex tissue surface resides in a soft tissue depression or hollow in the residual ridge, which makes it appear that a tooth is literally emerging from the gingival. Careful treatment planning is necessary for successful results. OVATE PONTIC
  33. 33. Socket-preservation techniques should be performed at the time of extraction to create the tissue recess from which the ovate pontic form will emerge. For a preexisting residual ridge, soft tissue surgical augmentation is typically required. When an adequate volume of ridge tissue is established, a socket depression is sculpted into the ridge with surgical diamonds
  34. 34. 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.
  35. 35. In addition, 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 unsupported, thin porcelain that porcelain that often exists at the gingivofacial extent of the pontic is eliminated Because the tissue surface of the pontic is convex in all dimensions, it is accessible to dental floss ; however, meticulous oral hygiene is necessary to prevent tissue inflammation resulting from the large area of tissue contact. Other disadvantages include the need for surgical tissue management and the associated cost.
  36. 36. In addition to these other modifications of pontics like soft tissue conditioning 13 , gingival- coloured ceramics, all-ceramic gingival masks and gingival masks have been discussed. 9
  37. 37. The biologic principles of pontic design pertain to the maintenance and preservation of the residual ridge, abutment and opposing teeth, and supporting tissue. Factors of specific influence are pontic ridge contact, amenability to oral hygiene, and the direction of occlusal forces. BIOLOGIC CONSIDERATIONS
  38. 38. Pressure free contact between the pontic and the underlying tissue is indicated to prevented ulceration and inflammation of the soft tissues. If any blanching of the soft tissues is observed in try-in, 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. RIDGE CONTACT
  39. 39. This passive contact should occur exclusively on keratinized attached tissue. When a pontic rests on mucosa, some ulcerations may appear as a result of the normal movement of the mucosa in contact with the pontic.
  40. 40. Positive ridge pressure may be due to excessive scraping the ridge area on the working cast. 7 This was once promoted as a way to improve the appearance of the pontic ridge relationship. However, because of the ulceration that inevitably results when flossing is not meticulously performed, the concept is not recommended, unless done as previously described as an ovate pontic.
  41. 41. The chief cause of ridge irritation is the toxins released from microbial plaque, which accumulate between the gingival surface of the pontic and the residual ridge, causing tissue inflammation and calculus formation. 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. ORAL HYGIENE CONSIDERATIONS
  42. 42. Normally, where tissue contact occurs, the gingival surface of a pontic is inaccessible to the bristles of a tooth brush. Therefore, excellent hygiene habits must be developed by the patient. Gingival embrasures around the pontic should be wide enough to permit oral hygiene aids. However, to prevent food entrapment, they should not be opened excessively. To permit passage of floss over its entire tissue surface, tissue contact between the residual ridge and pontic must be
  43. 43. If the pontic has a depression or concavity in its gingival surface, plaque will accumulate, because the floss cannot clean this area, and tissue irritation will follow. This is usually reversible; when the surface is subsequently modified to eliminate the concavity, inflammation disappears.
  44. 44. Therefore, an accurate description of pontic design should be known to the laboratory, and the prosthesis should be checked and corrected if necessary before cementation. Prevention is the best solution for controlling tissue irritation.
  45. 45. Any material chosen to fabricate 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. PONTIC MATERIAL
  46. 46. Investigations into the biocompatibility of materials used to fabricate pontics have centered on two factors : 1. The effect of the materials and 2. The effects of surface adherence.
  47. 47. Glazed porcelain is generally considered the most biocompatible of the available pontic materials, 11 and clinical data tend to support this opinion 7 , although the critical factor seems to be the material’s ability to resist plaque accumulation (rather than the material itself). Well polished gold is smoother, less prone to corrosion, and less retentive of plaque than an unpolished or porous casting. However, even highly polished surfaces will accumulate plaque if oral hygiene measures are ignored. LITERATURE
  48. 48. Although glazed porcelain looks very smooth, when viewed under a microscope, its surface shows many voids and is rougher than either polished gold or acrylic resin. Nevertheless, highly glazed porcelain is easier to clean than other materials. For easier plaque removal and biocompatibility, the tissue surface of the pontic should be made in glazed porcelain. However, ceramic tissue contact may be contra indicated in edentulous areas where there is minimal distance between the residual ridge and the occlusal table.
  49. 49. In these instances, placing ceramic on the tissue side of the pontic may weaken the design of the metal substructure, particularly with porcelain occlusal surface. If gold is placed in tissue contact, it should be highly polished. Regardless of the choice of pontic material, patients can prevent inflammation around the pontic with meticulous oral
  50. 50. Reducing the buccolingual width of the pontic by as much as 30% has been suggested as a way to lessen occlusal forces on, and thus the loading of, abutment teeth. This practice continues today, although it has little scientific basis. Critical analysis reveals that 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. 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. OCCLUSAL FORCES
  51. 51. 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.
  52. 52. The prognosis of fixed partial denture pontics will be compromised if mechanical principles are not followed closely. Mechanical problems may be caused by improper choice of materials, poor frame work design, poor tooth preparation, or poor occlusion. These factors can lead to fracture of the prosthesis or displacement of the retainers. Long span posterior FPDs are particularly susceptible to mechanical problems. MECHANICAL CONSIDERATIONS
  53. 53. When metal ceramic pontic are chosen, extending porcelain onto the occlusal surfaces to achieve better esthetics should also be carefully evaluated. In addition to its potential for fracture, porcelain may abrade the opposing dentition if the occlusal contacts are on enamel or metal. Therefore, evaluating the likely forces on a pontic and designing accordingly are important. For example, a strong all metal pontic may be needed in high stress situations rather than a metal ceramic pontic which would be more susceptible to fracture.
  54. 54. OCCLUSAL SURFACE The occlusal surface of the pontic should roughly correspond with that of the tooth it replaces. In posterior region it is important that it be confined within the margins of the abutment teeth.18 It is sometimes desirable to decrease the width by 20% to reduce any torque on the retainers and abutments and simplify the provision of an easily cleanable pontic with minimal soft tissue contact. However width of the pontic required will be governed by factors such as esthetics, length of span, the strength of the abutment teeth, the ridge form and last but not the least occlusion.
  55. 55. It has also been advised that the occlusal surface should not be narrowed arbitarily since this may create a food impaction and/or plaque retention situation similar to that of malposed teeth. The cusp tip-to-cusp tip width of a posterior pontic should be the same width as the original missing tooth. 8
  56. 56. Some fixed partial dentures are fabricated entirely of metal, porcelain, or acrylic resin, but most use a combination of metal and porcelain. Acrylic resin veneered pontics have had limited acceptance because of their reduced durability (wear and discoloration). The newer indirect composites, based on high inorganic filled resins and the fiber reinforced materials, have revived interest in composite resin and resin-veneered pontics. AVAILABLE PONTIC MATERIALS
  57. 57. Most pontics are fabricated by the metal ceramic technique. If properly used, this technique is helpful for solving commonly encountered clinical problems. A well fabricated metal ceramic pontic is strong, easy to keep clean, and looks natural. METAL CERAMIC PONTICS However, mechanical failure can occur and often is attributable to inadequate frame work design.
  58. 58. The framework must provide a uniform veneer of porcelain (approximately 1.2mm). Excessive thickness of porcelain contributes to inadequate support and predispose to eventual fracture. This is often true in the cervical portion of an anterior pontic. 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.
  59. 59. 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 that 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.
  60. 60. The location and design of the external metal porcelain junction require particular attention. Any deformation of the metal frame work at the junction can lead to chipping of the porcelain. For this reason, occlusal centric contacts must be placed at least 1.5mm away from the junction. Excursive eccentric contacts that might deform the metal ceramic interface must be watched carefully.
  61. 61. Historically, acrylic resin-veneered restorations had deficiencies that made them acceptable only as longer term provisionals. 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). Continuous dimensional change of the veneers often caused leakage at the metal-resin interface, with subsequent discoloration of the restoration. RESIN-VENEERED PONTICS
  62. 62. Nevertheless, there are certain advantages to using polymeric materials instead of ceramics; they are easy to manipulate and repair and do not require the high melting range alloys needed for metal ceramic techniques. Recently introduced indirect composite resin systems have resolved some of the problems inherent in previous indirect resin veneers. These new generation indirect resins have a higher density of inorganic ceramic filler than traditional direct and indirect composite resins. Most use a post curing process that results in high flexural strength, minimal polymerization shrinkage, and wear rates comparable to those of tooth enamel. In addition, improvements in the bond between the composite resin and metal may lead to a reappraisal of resin veneers.
  63. 63. Composite resins can be used in fixed partial dentures without a metal substructure. A substructure matrix of impregnated glass or polymer fiber provides structural strength. 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. FIBER-REINFORCED COMPOSITE RESIN PONTICS
  64. 64. No matter how well biologic and mechanical principles have been followed during fabrication, the patient will evaluate the result by how it looks, especially when anterior teeth have been replaced. 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. ESTHETIC CONSIDERATIONS
  65. 65. As esthetically successful pontic will replicate the form, contours, incisal edge, gingival and incisal embrasures, and color of adjacent teeth. The pontic’s simulation of a natural tooth is most often betrayed at the tissue pontic interface. The greatest challenge here is to compensate for anatomic changes that occur after extraction. Special attention should be paid to the contour of the labial surface as it approaches the pontic-tissue junction to achieve a “natural” appearance. THE GINGIVAL INTERFACE
  66. 66. This cannot be accomplished by merely duplicating the facial contour of the missing tooth, because after a tooth is removed, the alveolar bone undergoes resorption and/ or remodeling. If the original tooth contour were followed, the pontic would look unnaturally long incisogingivally. To achieve the illusion of a natural tooth, an esthetic pontic must deceive observers into believing they are seeing a natural tooth.
  67. 67. The modified ridge-lap pontic is recommended for most anterior situations; it compensates for lost buccolingual width in the residual ridge by overlapping what remains. Rather than emerging from the crest of the ridge as a natural tooth would, the cervical aspect of the pontic sits in front of the ridge, covering any abnormal ridge morphology resulting from tooth loss. Fortunately, because most teeth are viewed from only two dimensions, this relationship remains undetected. A properly designed, modified ridge lap provides the required convexity on the tissue side, with smooth and open embrasures on the lingual side for ease of cleaning. This is difficult to accomplish.
  68. 68. Clinically, many pontics are seen with less than optimal contour, many pontics are seen with less than optimal contour, resulting in an unnatural appearance. This can be avoided with careful preparation at the diagnostic waxing stage. 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.
  69. 69. Special care must be taken when studying where shadows fall around natural teeth, particularly around the gingival margin. If a pontic is poorly adapted to the residual ridge, there will be an unnatural shadow in the cervical area that looks odd and spoils the illusion of a natural tooth. In additional, recesses occurring at the gingival interface will collect food debris, further betraying the illusion of a natural tooth.
  70. 70. When appearance is of utmost concern, the ovate pontic, used in conjunction with alveolar preservation or soft tissue ridge augmentation, can provide an appearance at the gingival interface that it virtually indistinguishable from a natural tooth. Because it emerges from a soft tissue recess, this pontic is not susceptible to many of the esthetic pitfalls previously described for the modified ridge lap pontic. However, in most cases, the patient must be willing to undergo the additional surgical procedures that an ovate pontic requires.
  71. 71. Obtaining a correctly sized pontic simply by duplicating the original tooth is not possible. Ridge resorption will make such a tooth look too long in the cervical region. The height of a tooth is immediately obvious when the patient smiles and shows the gingival margins. An abnormal labiolingual position or cervical contour, however, is not immediately obvious. 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. INCISOGINGIVAL LENGTH
  72. 72. One solution is to shape the pontic to simulate a normal crown and root with emphasis on the cementoenamel junction. The root can be stained to simulate exposed dentin. Another approach is to use pink porcelain to simulate the gingival tissues. 9 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.
  73. 73. Frequently, the space available for a pontic will be greater or smaller than the width of the contra lateral tooth. This is usually due to uncontrolled tooth movement that occurred when a tooth was removed and not replaced. If possible, such a discrepancy should be corrected by orthodontic treatment. If this is not possible, an acceptable appearance may be obtained by incorporating visual perception principles into the pontic design. MESIODISTAL WIDTH 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.
  74. 74. 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. The features of the contra lateral tooth should be duplicated as precisely as possible in the pontic, and the space discrepancy can be compensated by altering the shape of the proximal areas. The retainers and the pontic can be proportioned to minimize the discrepancy. (This is another situations in which a diagnostic waxing procedure will help solve a challenging restorative problem).
  75. 75. Space discrepancy presents less of a problem when posterior teeth are being replaced because their distal halves are not normally visible from the front. A discrepancy here can be managed by duplicating the visible mesial half of the tooth and adjusting the size of the distal half.
  76. 76. Available materials Over time, several techniques for pontic fabrication evolved. Prefabricated porcelain facings were very popular for use with conventional gold alloys. As use of the metal ceramic technique increased during the 1970s, prefabricated facings lost their popularity and essentially disappeared. Although an acceptable substitute, custom made metal ceramic facings never gained widespread acceptance. PONTIC FABRICATION
  77. 77. Most pontics are now made with a metal ceramic technique, which provides the best solution to the biologic, mechanical, and esthetic challenges encountered in pontic design. Their fabrication, however, differs slightly from the fabrication of individual crowns.
  78. 78. METAL CERAMIC PONTICS A well designed metal ceramic pontic provides easy plaque removal, strength, wear resistance, and esthetics. It fabrication is relatively simple. The metal frame work for the pontic and one or both of its retainers is cast in one piece. This facilitates pontic manipulation during the successive laboratory and clinical phases.
  79. 79. For strength and esthetics, an accurately controlled thickness of porcelain is needed in the finished restoration. To ensure this, a wax pattern is made to the final anatomic contour. This also permits an assessment of connector design adequacy and the relationship between the connectors and the proposed configuration of the ceramic veneer. ANATOMIC CONTOUR WAXING
  80. 80. 1. Wax the internal, proximal, and axial surfaces of the retainers 2. Soften the inlay wax, mold it to the approximate desired pontic shape, and adapt it to the ridge. This is the starting point for subsequent modification. Alternatively an impression may be made of the provisional restoration. Molten wax can then be poured into this to form the initial pontic shape. Prefabricated pontic shapes are also available as a starting point. STEP BY STEP PROCEDURE
  81. 81. 3. If a posterior tooth is being replaced, leave the occlusal surface flat because the occlusion is best developed with the wax addition technique 4. Lute the pontic to the retainer and, for additional stability, connect its cervical aspect directly to the master cast with sticky wax. Then wax the pontic to proper axial and occlusal (or incisal) contour.
  82. 82. 5. Complete the retainers and contour the proximal and tissue surfaces of the pontic for the desired tissue contact. The pontic is now ready for evaluation before cut back.
  83. 83. The form of the wax pattern is evaluated and any deficiencies are corrected. Particular attention is given to the connectors, which should have the correct shape and size. The connectors provide firm attachment for the pontic so it does not separate from the retainers during the subsequent cut back procedure. EVALUATION
  84. 84. Use a sharp explorer to outline the area that will be veneered with porcelain. The porcelain metal junction must be placed sufficiently lingual to ensure good esthetics. Make depth cuts or grooves in the wax pattern. CUT BACK
  85. 85. Complete the cut back as far as access will allow with the units connected and on the master cast. Section one wax connector with a thin ribbon saw (sewing thread is a suitable alternative) and remove the isolated retainer from the master cast.
  86. 86. Finish the cut-back of this retainer, making sure there is a distinct 90-degree porcelain metal junction. Reflow and finalize the margins. The pontic is held in position by the other retainer during this procedure. Refined the pontic cut back where access is improved by removal of the first retainer. Reseat the first retainer, reattach it to the pontic, section the other connector, and repeat the process. Sprue the units and do any final reshaping as needed. Invest and cast
  87. 87. Step by step procedure Recover the castings from the investment and prepare the surfaces to be veneered Finish the gingival surface of the pontic. Do not over-reduce this area. METAL PREPARATION
  88. 88. EVALUATION Less than 1 mm of porcelain thickness is needed on the gingival surface, because once it is cemented, the restoration will be seen from the facial rather than from the gingival. Excessive gingival porcelain is a common fault in pontic frame work design and may lead to fracture and poor appearance. To facilitate plaque control, the metal ceramic junction should be located lingually. Then tissue contact will be on the porcelain and not on metal, which retains plaque more tenaciously.
  89. 89. Prepare the metal and apply opaque Apply cervical porcelain to the gingival surface of the pontic and seat the casting on the master cast. A small piece of tissue paper adapted to the residual ridge on the cast by moistening with a brush will prevent porcelain powder from sticking to the stone. (Cyanoacrylate resin or special separating agents can be used for the same purpose.) PORCELAIN APPLICATION Many of the steps for porcelain application are identical to those in individual crown fabrication.There are some features peculiar to pontic fabrication, however, and these will be emphasized. Step by step procedure
  90. 90. Build up the porcelain with the appropriate distribution of cervical, body, and incisal shades. The tissue paper will act as a matrix for the gingival surface of the pontic.
  91. 91. When the porcelain has been condensed, section between the units with a thin razor blade. This will prevent the porcelain from puling away from the framework as a result of firing shrinkage. A second application of porcelain will be needed to correct any deficiencies caused by firing shrinkage. Such additions usually are needed proximally and gingivally on the pontic. Apply a porcelain separating liquid to the stone ridge so that the additional gingival porcelain can be lifted directly from the cast
  92. 92. Mark the desired tissue contact and contour the gingival surface to provide as convex a surface as possible. The pontic is now ready for clinical evaluation and soldering procedures, characterization, glazing, finishing and polishing.
  93. 93. EVALUATION The porcelain on the tissue surface of the pontic should be as smooth as possible. Pits and defects will make plaque control difficult and promote calculus formation. The metal framework must be highly polished, with special care directed to the gingival embrasures (where access for plaque removal is more difficult.).
  94. 94. Pontics made from metal require fewer laboratory steps and are therefore sometimes used for posterior FPDs. However, they have some disadvantages (e.g. their appearance) In addition, investing and casting must be done carefully because the mass of metal in the pontic is prone to porosity as the bulk increases. A porous pontic will retain plaque and tarnish and corrode rapidly ALL METAL PONTICS
  96. 96. 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.
  97. 97. 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.
  98. 98. 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.
  99. 99. 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.
  100. 100. 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.
  102. 102. Harmon C B: Pontic design. J Prosthet Dent 1958; 8: 496 Carlos B Harmon in 1958 doing a study on the pontic design said that the success of a bridge can be attained only when correct form and materials are combined in a well engineering pontic design capable of meeting the exact factors of durability and the maintenance of health and cleanliness. According to him porcelain, despite certain unfortunate properties, was the standard as a component part of pontic construction. Colour form and texture of natural teeth are readily reproduced in porcelain. Also its remarkable tissue tolerance, when contacting the gingival has played an important part in advanced fixed bridge work. High fusing porcelain when correctly glazed will display surface traits remarkably close to those of a natural tooth.
  103. 103. Stein RS: Pontic- residual ridge relationship: A research report. J Prosthet Dent 1966; 16: 251 Shaldon Stein in 1966 did a study on the pontic residual ridge relationship. The purpose of his study were : To determine the frequency and the nature of tissue reaction of underlying the residual ridge mucosa to specific pontic designs. To compare the frequency and the nature of tissue reactions of the residual ridge mucosa to various materials used in pontic constructions.
  104. 104. This 1966 Stein classic article on pontic design was largely responsible for a change in philosophy from a “sanitary” or bullet shape design to what is now commonly called a “modified ridge lap” design. The modified ridge lap design in the posterior region and the ridge lap design in the anterior region after minimal tissue contact, acceptable cosmetic value, proper check support, and accessibility for adequate oral hygiene.
  105. 105. It has now been established that the design of the pontic may be the most important factor in preventing inflammatory reactions, not the materials used in the pontic. In addition to properly designing the under surface of the pontics. It is imperative to open embrasure spaces adjacent to abutments to allow room for inter dental tissue and access for pontics are healthy and pink even after several year of use of the pontics.
  106. 106. He postulated certain specifications for pontic design Posterior pontic design – a correctly designed pontic should have 1. All surfaces should be convex, smooth and properly finished. 2. Contact with the buccal contiguous slopes should be minimal (pin point) and pressure free (modified ridge lap). 3. Occlusal table must be in functional harmony with the occlusion of all of the teeth. 4. Buccal and lingual shunting mechanism should conform to those of the adjacent teeth. 5. The overall length of buccal surface should be equal to that of the adjacent abutments or pontics.
  107. 107. Anterior pontic design – a correctly placed anterior pontic should have 1. All surfaces should be convex, smooth and properly finished. 2. Contact with the labial mucosa should be minimal (pin point) and pressure free (lap facing). 3. The lingual contour should be in harmony with adjacent teeth or pontics.
  108. 108. Henry P J et al: Tissue changes beneath fixed partial dentures. J Prosthet Dent 1966; 16: 937 P. J. Henry in 1966 in a study placed 14 pontics on human gingival tissue. He reported no clinical or histologic difference in the gingival response to polished gold. Glazed porcelain or unglazed porcelain after the pontics had been in the mouth for six months. He also noted that there were general histologic changes in the tissue under all the materials tested. Some investigators have reported that acrylic resin is not as well tolerated by gingival tissue as other materials for pontic. He also noted that glazed porcelain was the most hygienic material used and it is superior in terms of esthetics and ease of cleaning.
  109. 109. Cavozos E : Tissue response to fixed partial denture pontics. J Prosthet Dent 1968; 20: 143 Cavazos in 1968 did a study to demonstrate that the adaptations of pontic to the ridge or the amount of “relief” (scraping of the cast provided) on the cast is highly significant and directly proportional to the amount of unfavourable tissue change. Absolute minimal (0.0 to 0.25mm of cast scraping) produced no tissue changes. When the cast scraping was increased to 1mm, tissue changes were produced varying from mild inflammation to acute ulceration
  110. 110. 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. Perel M L : A modified sanitary pontic. J Prosthet Dent 1972; 28: 587
  111. 111. D.A. Behrend in 1981 did a study for designing multiple pontics. He said that in multiple pontics, placement of a V-shaped notch between the pontics on their tissue aspect (an inter-pontic embrasure) serves no useful purpose. It acts as a niche to collect plaque and interrupts the smooth passage of dental flows along the tissue surface of the pontics. It also complicates the construction of the prosthesis and reduces the rigidity of a long pontic section. The principle of “fusing” multiple pontics on their tissue aspect to give a smooth, unbroken surface can be applied to fixed partial dentures in the mandibular posterior, mandibular anterior and maxillary posterior segments. Donald A B : The design of multiple pontics. J Prosthet Dent 1981; 46: 634
  112. 112. His design principle should also be used routinely for the maxillary anterior segment, using pink porcelain to fill inter- pontic embrasures which also enhances esthetics. Since the natural papillae have been lost the use of pontic with buccal surfaces of adjacent embrasures.
  113. 113. Antony H L in 1983 described a technique of pontic design for extreme resorption of alveolar ridge. In this the undersurface of the pontic was shaped slightly convex or flat bucco-lingually to aid in complete disruption of dental plaque with dental floss or interproximal toothbrushes. The flat undersurface allowed easy cleaning from either the lingual or buccal aspect. Antony H L: A sanitary “ Arc- fixed partial denture” : Concept and technique of pontic design. J Prosthet Dent 1983; 50: 338
  114. 114. Porter CB: Anterior pontic design; a logical progression. J Prosthet Dent 1984; 51; 774-776. Carles. B. Porter in 1984 carried out a study on the anterior pontic design. He stated that until Stein described his pontic modification in 1966, only limited deviations have been noted on traditional pontic design. With minor exceptions steins pontic design has replaced the “Saddle Type” pontic, but it seems limited when multiple pontics must be used.
  115. 115. Parkinson C.F: Pontic design of posterior fixed partial prosthesis; is it a microbial misadventure? J Prosthet Dent 1984; 51; 51-54 In 1984 Parkinson and Schoberg did a study on the pontic design of posterior fixed partial prosthesis. Present designs are commonly based on tooth replacement without replacement of basic or soft tissue. The designs cause patients dissatisfaction because of “whistling” during speech and cause patient complaints such as, “food always get stuck under the bridge”. Calculus build up on fixed partial denture pontics, which is difficult to remove can be due to poor oral hygiene caused by manipulation difficulties.
  116. 116. By the restriction of pontic embrasures, plaque accumulation and calculus deposition are eliminated.The number of surfaces the patient must clean are reduced and oral hygiene is simplified. In addition, more of the missing natural structures are replaced.
  117. 117. L.B. Jacques et al in this article describes a technique for the improvement of esthetics with conditioning of tissue beneath the pontics by displacing tissue with a treatment restoration. Lateral displacement of tissues under gradual, controlled pressure enhances the interdental papilla which improves esthetics. Jacques L B et al: Tissue sculpturing: An alternative method for improving esthetics of anterior fixed prosthodontics. J Prosthet Dent 1999; 81: 630 BACK
  118. 118. In 2002 Daniel Edelhoff et al did a review of the different clinical and technical options that are available for designing esthetic and functional pontics for anterior region. He mentions the use of Gingiva coloured ceramics, all-ceramic gingival masks and gingival prosthesis to achieve maximum esthetics in the anterior region. Daniel E , H Spiekermann: A review of esthetic pontic design options. Quintessence Int 2002;33:736-746
  119. 119. The conical pontic was used to prevent the extraction site from collapsing after the removal of a tooth and to imitate the natural emergency profile of the tooth. After extended periods of service, however, the adjacent soft tissue tended to become inflamed, and the alveolar bone resorbed. Based on the information available today, these reactions probably occurred because the pontic did not allow adequate oral hygiene.
  120. 120. The hygienic pontic fulfils the prerequisites for maintaining a healthy periodontium, because it does not come in contact with the underlying soft tissue and provides easy access for oral hygiene aids to clear the abutment teeth. The gap between the pontic and the alveolar ridge, however, is large enough to trap food particles and to allow the tongue to enter.
  121. 121. The saddle-shaped pontic achieves highly esthetic results, if the alveolar ridges are free of defects. The emergency profile, which is very similar to that of the natural tooth, ensures that no palatal gap forms, which could cause phonetic problems Trapping of food particles is not expected, because the pontic seamlessly adapts itself to the alveolar ridge. Today, however, it is generally agreed that this technique should not be used, because the large concave contact area with the alveolar ridge prevents the removal of adherent plaque.
  122. 122. A reduction of the surface area (ridge lap pontic) does not significantly improve hygiene underneath the pontic, because the basal contour remains concave, unsuitable to provide a tight contact to the dental floss.
  123. 123. The modified ridge lap pontic is the most popular type of pontic. The convex basal surface, which rests on a small area of the alveolar ridge, fulfils the recommendation made in the dental literature with regard to hygiene procedures and prevention of irritation of the underlying soft tissue.
  124. 124. In contrast to the classic requirements for pontics which suggest the importance of pressure free contact over a small area, the ovate pontic comes in contact with a larger area of the underlying soft tissue an applies light pressure. This design has been found to produce highly esthetic results following suitable pretreatment of the alveolar ridge.
  125. 125. Because this design produces an emergence profile that looks very similar to that of the natural tooth, it fulfills ideally the esthetic and functional requirements of a pontic for the anterior region. This type of pontic design, however, requires an adequate amount of soft tissue, which has to be sculpted accordingly.
  126. 126. 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. GINGIVA-COLORED CERAMICS Daniel E , H Spiekermann: A review of esthetic pontic design options. Quintessence Int 2002;33:736-746
  127. 127. Separately fabricated ceramic gingival masks can be used to make subsequent adjustments in permanently placed restorations. This method is particularly suitable for patients with a local alveolar ridge defect that has not been corrected by augmentation of the soft tissue. For this purpose, an impression is taken of the labial surface of the restoration using a customized tray and a medium viscosity polyether material. The color of the gingiva is determined with an individually fabricated shade guide. ALL-CERAMIC GINGIVAL MASKS
  128. 128. GINGIVAL PROSTHESIS Gingiva-colored removable prosthesis made of soft silicone materials offer an uncomplicated solution for correcting large alveolar ridge defects that are associated with esthetic and phonetic problems. They can be fixed to the restoration with precision attachments.
  129. 129. 1. Rosenstiel S F et al : Contemporary Fixed Prosthodontics, ed 3, Missouri, Mosby Inc, pg 513 2. Shillingburg H T et al : Fundamentals of fixed prosthodontics, ed 3, Chicago , Quintessence Publishing, pg 485 3. Shillingburg H T et al : Fundamentals of fixed prosthodontics, ed 2, Chicago , Quintessence Publishing, pg 387 4. Malone F P et al : Theory and practice of fixed prosthodontics, Eight Edition , Ishiyaku Euro America, Inc 5. The glossary of prosthodontic terms : J Prosthet Dent 1999; 81 6. Antony H L: A sanitary “ Arc- fixed partial denture” : Concept and technique of pontic design. J Prosthet Dent 1983; 50: 338 7. Cavozos E : Tissue response to fixed partial denture pontics. J Prosthet Dent 1968; 20: 143 8. Curtis M B: Current theories of crown contour, margin placement and pontic design. J Prosthet Dent 1981; 45: 268 9. Daniel Edelhoff, H Spiekermann: A review of esthetic pontic design options. Quintessence Int 2002;33:736-746 REFERENCES
  130. 130. 10. Donald A B : The design of multiple pontics. J Prosthet Dent 1981; 46: 634 11. Harmon C B: Pontic design. J Prosthet Dent 1958; 8: 496 12. Henry P J et al: Tissue changes beneath fixed partial dentures. J Prosthet Dent 1966; 16: 937 13. Jacques L B et al: Tissue sculpturing: An alternative method for improving esthetics of anterior fixed prosthodontics. J Prosthet Dent 1999; 81: 630 14. Parkinson C.F: Pontic design of posterior fixed partial prosthesis; is it a microbial misadventure? J Prosthet Dent 1984; 51; 51-54. 15. Perel M L : A modified sanitary pontic. J Prosthet Dent 1972; 28: 587 16. Porter CB: Anterior pontic design; a logical progression. J Prosthet Dent 1984; 51; 774-776. 17. Stein RS: Pontic- residual ridge relationship: A research report. J Prosthet Dent 1966; 16: 251 18. Roberts DH : Fixed Bridge Prostheses ; John Wright and Sons, Bristol 1980, pg 68
  131. 131.