Gerard J. Chiche

A retrospective survey on long-term survival of posterior zirconia and porcelain-fused-to-metal crowns in private practice

OBJECTIVES This retrospective survey assessed the clinical survival of zirconia-based crowns (PFZ) and conventional porcelain- fused-to-metal (PFM) crowns on posterior teeth in private practice. METHOD AND MATERIALS A print survey of 13 private practitioners was conducted to assess the long-term survival of previously placed full-coverage crowns. The practitioners reported a total of 2,182 premolar (n = 881) and molar (n = 1,301) full-coverage single crowns, 1,102 PFZ and 1,080 PFM, fabricated by one dental laboratory (Cusp, Boston) and followed over 7.4 years. All post-cementation complications (eg, porcelain fractures and chippings) were recorded as failures. In the PFZ group, one veneering porcelain (CZR, Kuraray Noritake) was used in combination with three coping systems (Lava, 3M ESPE; Procera, Nobelbiocare; Katana, Kuraray Noritake). Kaplan-Meier survival analysis was used for statistical analyses. RESULTS The probability of survival of posterior crowns investigated over the period of study (7.4 years) was 99.3% for PFM and 99.2% for PFZ restorations. There was no statistically significant difference (P = .614) between PFZ and PFM groups. In the PFZ group, probability of survival was 97.7% for Lava, 100% for Procera, and 99.5% for Katana. There were no statistically significant differences (P = .34) between the three PFZ systems or the location of the crowns (premolar or molar; P = .454). CONCLUSION PFZ crowns fabricated with CZR and three commercial zirconia coping systems revealed excellent long-term success rates. Survival times and survival probabilities of posterior PFZ crowns did not differ from PFM crowns and were independent of type of coping system and location (molar or premolar teeth).

Comparison of Marginal Fit between All‐Porcelain Margin versus Alumina‐Supported Margin on Procera® Alumina Crowns

PURPOSE Procera Alumina crowns are widely used; however, the effect of crown margin design on marginal fit is unknown. This study measured and compared the precision of fit of Procera Alumina crowns with two crown margin designs: all-porcelain versus alumina-supported margins. MATERIALS AND METHODS Sixteen noncarious extracted human premolars were prepared for Procera((R)) Alumina crowns with an internally rounded shoulder preparation. Impressions were made from all teeth, and master dies were poured with type IV dental stone. The specimens were randomly divided into two groups. Procera Alumina crowns were fabricated: eight crowns with circumferential porcelain-butt (all-porcelain) margins and eight crowns with coping (alumina-supported) margins (control). Precision of fit was measured at six points on each crown with a profilometer (profile projector). The data were statistically analyzed with an independent-samples t-test (alpha < 0.05). RESULTS The mean marginal gap size (microm) of coping margins was 68.07 +/- 16.08 and of porcelain-butt margins was 101.29 +/- 43.71. There was no statistically significant difference (p= 0.065) of the marginal gap size between coping margins and porcelain-butt margins. CONCLUSION The results of this study demonstrate that there was no statistically significant difference in the marginal fit of coping and porcelain-butt margins. Both margin designs are within clinically acceptable ranges. Therefore, clinicians may choose to use a coping margin, as it is less labor intensive and requires less time for fabrication, unless there is a specific high esthetic need for a porcelain-butt margin.

Laminated single impression technique for cast posts and cores

A laminated single impression technique for cast post and core has been described. Its advantages are the ease and versatility with prefabricated or customized post techniques (Fig. 14) and the one-step registration of single or multiple divergent canals. Its disadvantage is the necessity for additional laboratory procedures.

Injectable technique for direct provisional restoration

OBJECTIVE New technique describes an alternative treatment modality of making direct provisional restoration. CLINICAL CONSIDERATIONS A preoperative wax-up should be fabricated, followed by fabrication of a transparent polyvinyl siloxane (VPS) matrix in a clear plastic prefabricated tray with retentive holes. After the tray is separated from the model, two additional holes will be made through the tray and the VPS for injecting and venting of the temporary resin. After the teeth are prepared and the separating medium applied to them, the resin should be injected into the entrance hole using the provided auto-mix cartilage tip. The flow of the resin around the preparation can be observed through the clear mold and once the resin starts to extrude from the exit hole. It is necessary to block the exit hole with a finger while continuing to inject. This will increase the pressure inside the mold and improve marginal adaptation. Before complete polymerization, the matrix is removed. The provisional restorations are removed from the matrix and contoured, adjusted, and polished. CONCLUSION This technique will help the clinicians to enhance the quality of the provisional restorations, to prevent entrapment of bubbles, improve marginal precision and prevent seating error. CLINICAL SIGNIFICANCE This study described a novel technique for constructing a direct provisional restoration by injecting bis-acryl temporary resin into a matrix that is already seated over the prepared tooth.

Effect of different ceramic primers on shear bond strength of resin-modified glass ionomer cement to zirconia

Abstract Purpose: This study evaluated and compared the effect of different ceramic primers on the shear bond strength of RMGIC to zirconia with and without air-particle abrasion. Material and Methods: 120 zirconia square specimens (5 mm × 5 mm × 2 mm) were fabricated. Half of the specimens were air-particle abraded (A) and the other half were left untreated (NA). Both groups were further divided into six subgroups (n = 10). Composite cylinders (2.9 mm × 3.0 mm) were fabricated and bonded to the zirconia samples with RMGIC (RelyX Plus) after different priming methods: no ceramic primer (group NS); Z-Prime (group ZP); Clearfil ceramic primer (group CP); cleaned with Ivoclean then Monobond plus (IV/MS); Monobond plus (group MS); and Rely X ceramic primer (group RX). Specimens were rinsed, stored in distilled water, and thermocycled (TC) for 10,000 cycles between 5 and 60 °C with a dwell time of 15s. Data were analyzed with two-way ANOVA and the Tukey–Kramer method test (a = .05). Results: air-particle abrasion significantly affected bond strength of RMGIC to zirconia regardless of the primer used (p < 0.001 for all primers and the control). After TC, A-ZP (11.1 ± 0.6 MPa), A-CP (11.9 ± 0.6 MPa), and A-MS (11.9 ± 0.5 MPa) revealed the highest shear bond strength values, while NA-NS (2.9 ± 0.3 MPa) and NA-RX (4.7 ± 0.5 MPa) had the lowest. Failure modes were primarily adhesive. Conclusion: air-particle abrasion with aluminum oxide and application of MDP-based ceramic primers provide the highest bond strength of RMGIC to zirconia.

Nonanatomic patterns for full cast gold crowns

lhe combination of anatomic-nonanatomic artificial teeth is a recommended posterior arrangement for complete denture occlusion.‘,’ The advocated advantages over nonanatomic teeth arrangements include improved cusp efficiency, concentration of vertical forces, improved esthetics, and elimination of lateral planes.3-5 In situations in which an upper complete denture is occluded with mandibular cast gold crowns, this occlusal scheme is incorporated through the use of acrylic patterns.