Paolo Cardelli

Pilot evaluation of four experimental conditioning treatments to improve the bond strength between resin cement and Y-TZP ceramic.

PURPOSE This study evaluated the bond strength between resin cement and Y-TZP ceramic (Yttrium-stabilized Tetragonal Zirconia Polycrystalline) submitted to different surface conditionings. MATERIALS AND METHODS Fifty Y-TZP ceramic discs (Ø= 10 mm) were allocated into five groups: Gr1 (control)-no conditioning; Gr2-tribochemical silica coating (30-μm SiO(2)) before sintering; Gr3-air abrasion with 50-μm Al(2)O(3) before sintering; Gr4-air abrasion with 110-μ Al(2)O(3) before sintering; Gr5 - air abrasion with 50-μm Al(2)O(3) after sintering. After specimen preparation, cylinders of composite resin were prepared and immediately cemented onto the ceramic. A shear test was performed. RESULTS One-way ANOVA indicated a statistically significant difference among the groups (p= 0.0019). The mean shear bond strengths (MPa) were: Gr1 = 4.7 ± 0.8,(b) Gr2 = 4.6 ± 0.9,(b) Gr3 = 6.4 ± 1.0,(a) Gr4 = 6.5 ± 1.8,(a) Gr5 = 6 ± 1.3(ab) (same superscript letter indicates statistical similarity). Adhesive fracture between the ceramic and resin cement was the most common failure. No complete cohesive fracture at the ceramic or composite cylinders was noted. CONCLUSION Within the limitations of this study, additional surface treatment with air abrasion before and after sintering provided a significant increase in bond strength. Tribochemical silica coating before sintering was not effective as a surface treatment.

Reliability Analysis of Lithium Disilicate Crowns: Effect of Veneering and Milling Production Workflow

Purpose To evaluate the reliability of lithium disilicate crowns produced using either CAD/CAM milling or thermopress workflow, for monolithic or veneered framework design for crowns. Materials and Methods Lithium disilicate crowns (N = 40) were produced using one of four different workflows, namely (a) MTP: monolithic thermopressed crowns, (b) MCM: monolithic CAD/CAM milled, (c) VTP: thermopressed frameworks veneered, or (d) VCM: CAD/CAM milled crowns veneered. The specimens were adhesively luted to resin composite abutments and then tested until fracture in a universal testing machine (1 mm/min). Failure types were classified and further evaluated under stereomicroscope and SEM. The data (N) were analyzed using one-way ANOVA. Weibull distribution values including the Weibull modulus (m), characteristic strength (0), and probability of failure at 5% (0.05) were calculated. Results Fabrication method did not significantly influence the mean fracture strength (N) of lithium disilicate crowns (MTP: 3626 ± 283; MCM: 3719 ± 483; VTP: 3754 ± 485; VCM: 3302 ± 604) (p = 0.154). Weibull distribution presented lower shape value (m) of VCM (m = 5.81) followed by VTP (m = 8.83), MCM (m = 8.84) compared to MTP (m = 12.9). Type V failures (severe fracture of the crown and/or tooth) were experienced explicitly in all groups. The monolithic specimens showed a homogeneous structure without porosities. Wake hackles were observed at the fracture surface, with a radial path directed to the cervical area. The veneered crowns presented twist and wake hackles propagated perpendicularly from the cement-ceramic interface. Conclusion Monolithic or veneered lithium disilicate crowns presented similar fracture strength when frameworks or entire crowns were milled or thermopressed but distribution with Weibull characteristics was more favorable for monolithic pressed crowns and the least reliable for the milled and veneered crowns. Clinical Significance Lithium disilicate ceramic crowns could be produced either by thermopressing or CAD/CAM milling workflow without sacrificing their reliability.

Immediate postextraction implant with simultaneous buccal plate augmentation, restored with lithium disilicate abutment and veneer: a clinical report.

OBJECTIVE To describe the successful use of biphasic calcium sulfate for improving the buccal plate thickness in an immediate postextraction implant, and its fi nal restoration with custom lithium disilicate abutment and veneer. SUMMARY A hopeless lateral incisor was replaced with an immediate postextraction implant in conjunction with a buccal plate augmentation based on biphasic calcium sulfate. Satisfactory soft tissue height and quality were maintained following healing. The fi nal restoration managed the severely reduced prosthetic space due to deep bite, and allowed an adhesive luting procedure.