Clinical-technological Clinical-technological stages of dental bridges stages of dental bridges making. Factors which making. Factors which

provide fixing of provide fixing of unremovable unremovable

constructions.constructions.

Fig. 3-23. Four pontic designs in descending order of strength based on cross sectional diameter of the metal substructure. When vertical space is minimal, design 4 (porcelain tissue and occlusal coverage) may be contraindicated.

Fig. 3-24. Failure of a long span metal-ceramic FPD subjected to high stress.

Fig. 3-25. Failure resulting from improper laboratory technique.

Fig. 3-26. Failure of unsupported gingival porcelain.

Fig. 3-27. A, Waxing to anatomic contour and con trolled cut-back are the most reliable approaches to fabricat ing a satisfactory metal substructure (B).

Fig. 3-28. Failure caused by occlusal contact across the metal-ceramic junction.

Fig. 3-29. Wear of an acrylic resin-veneered prosthesis.

Fig. 3-30. Correct incisogingival height is critical to es thetic pontic

design. A, Esthetic failure of a four-unit FPD replacing the right central and lateral incisors. The

pontics have been shaped to follow the facial contour of the

miss ing teeth, but because of bone loss they look too long.

B, The replacement FPD. Note that the gingival half of each

pontic has been reduced. Esthetics is much improved.

C, This esthetic failure is the result of excessive reduction.

The central incisor pontics look too short.

Fig. 3-31. Optical illusion. A and B are identical except that one image is upside down. Most people make different three-dimensional interpretations of each photograph, in terpreting one as a negative impression and the other as a positive cast. (Verify the illusion by turning the book.) The interpretation is based on how shadows fall; in normal situ ations, objects are seen illuminated from above.

CORRECT INCORRECT

Fig. 3-32. A pontic should be interpreted as "growing" out of the gingival tissue. The second pre molar pontic in the four-unit FPD (A) is successful because it is well adapted to the ridge; however, the pontic for the first premolar is evident because of its poor adaptation to the ridge, which creates a shadow. B, Shadows around the gingival surface (arrow) spoil the esthetic illusion.

Fig. 3-33. A, A pontic should have the same incisogingival height (H) as the original tooth. B, Correctly contoured pontic. C, Incorrect contour. (The dotted lines in B and C show the original tooth contour.) The shelf at the gingival margin may trap food and create an estheti-cally unacceptable shadow.

It is often necessary to recontour a substantial portion of the facial sur face (B) to minimize a shadow or food trap at the heoriginal too th contou r.)

Fig. 3-34. It is difficult without surgical augmentation to fabricate an esthetic fixed

prosthesis for a patient with exten sive alveolar bone loss. A and B, One approach is to contour the crowns

normally and shape and stain the apical extension to simulate exposed root

surface. Better esthetics is obtainable withanRPD (C).

(A and B redrawn from Blancheri RL: Rev Asoc Dent Mex 8:103, 1950.)

Fig. 3-35. Fixed partial denture replacing maxillary left central and lateral incisors. This patient had lost significant bone from the edentulous ridge. Appearance of the prosthesis was enhanced with the use of pink porcelain between the pontics to simulate gingival tissue. The patient has been able to maintain excellent tissue health through the daily use of SuperFloss.

Fig. 3-36. An abnormally sized anterior pontic space can be restored esthetically by matching the location of the line angles and adjusting the interproximal areas. Large (A) and small (B) pontic spaces. Dimension a should be matched in the replacement. (Redrawnfrom BlancheriRL: Rev Asoc Dent Mex 8:103, 1950.)

Form is compromised in the lesser visible half.

Fig. 3-37. When replacing a posterior tooth (A), dupli cate the dimension of the more visible mesial half of the ad jacent tooth. Narrow (B) and wide (C) pontic spaces. (Redrawnfrom Blancheri RL: Rev Asoc Dent Mex 8:103, 1950.)

Fig. 3-38. A, Eight-unit FPD with porcelain facings. B and C, This three-unit posterior FPD has been fabricated by postceramic soldering of a metal-ceramic facing to conventional gold. D, Metal-ceramic FPD with a modified ridge lap pontic (canine) appears to emerge from the gingiva.

Waxing armamentarium Fig. 3-39

Prefabricated wax pontics. Fig. 3-40

Fig. 3-41. Luting the pontic to the retainers.

Complete contour wax patterns. Fig. 3-42.

Fig. 3-42. Cut-back procedure for a three-unit anterior FPD. A, Delineating the porcelain-metal junction. B, The central incisor has already been cut back, and the pontic has been troughed. The canine is still at anatomic contour. C, A ribbon saw is used to section the connector.

Fig. 3-43. Metal substructure ready for airborne particle abrasion and oxidation.

Fig. 3-44.Failure of unsupported

gingival porcelain.

Fig. 3-45. Armamentarium for porcelain application.

Fig. 3-46.

Porcelain application. A, Substructure ready for opaquing. B, Opaque application. C, Body porcelain application. D, A piece of moistened tissue paper (arrow) on the edentulous ridge. E, The porcelain after the first firing.

Fig. 3-47. Metal-ceramic pontic replacing a lateral incisor.

Fig. 3-48. All-metal, three-unit FPDs.