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American Society for Testing and Materials

Microtensile bond strength of different components of core veneered all-ceramic restorations.

Microtensile bond strength of different components of core veneered all-ceramic restorations Part II: Zirconia veneering ceramics

Statement of problem After the development of a variety of ceramic restorative systems over the past 20 years, the fabrication of fixed dental prostheses has undergone considerable change. Esthetics and resistance to fracture are two of the main determinants of the success of a restoration; the third is marginal adaptation. Therefore, a systematic review of the literature dedicated to the marginal accuracy of ceramic systems is indicated. Purpose This study reviewed the current scientific literature that pertains to the marginal fit of ceramic crowns fabricated with different systems and investigated the factors that influence marginal adaptation. Material and methods An electronic search was completed by using the PubMed and Scopus databases with the following combination of key words: (discrepancy or fit or gaps or adaptation) and (disilicate or ceramic) and (copings or crowns). The search was limited to English-language peer-reviewed articles published before April 15, 2012. Titles and abstracts were read to identify articles that fulfilled the inclusion criteria designed for this review. Results Of 469 studies identified, 54 satisfied the selection criteria and were included in this review. All were published between 1994 and 2012. A total of 17 ceramic systems were tested in 48 in vitro and 6 in vivo studies. Of all the marginal gaps measured, 94.9% were in the range of clinical acceptability. Study heterogeneity made it impossible to conduct a proper meta-analysis of research findings and to compare and rank the various systems in terms of marginal fit. Four parameters were found to influence marginal adaptation: finish line configuration, value of the predefined cementing space, veneering process, and cementation. Conclusions The systems evaluated in the selected articles generally provide a clinically acceptable marginal fit. The current state of research does not allow for a proper comparison of the various systems in terms of marginal fit. The use of computer x-ray microtomography is recommended for further research on marginal adaptation.

Marginal adaptation of ceramic crowns: A systematic review

Shear bond strengths between different zirconia cores and veneering ceramics and their susceptibility to thermocycling

Statement of problem The strength of all-ceramic restorations can be adversely affected by surface defects, leading to restoration failures. Additionally, when a 2-layer all-ceramic restoration is required for esthetic purposes, part of the stronger ceramic core material is replaced by veneering porcelain. Purpose This study evaluated the effect of different surface treatments on the strength of a ceramic core material and veneering porcelain, as well as the influence of veneering porcelain on the strength of a 2-layer ceramic structure. Material and methods Fifty heat-pressed ceramic cores and 30 veneering porcelain discs (17 mm diameter × 2 mm) were made. From the ceramic core group, 20 discs were selected and reduced to a thickness of 1 mm and veneered with 1 mm of porcelain. These specimens were divided into 2 groups of 10 each. The remaining 30 ceramic core and the 30 veneering porcelain discs were divided into 2 sets of 3 equal sized groups (n=10). Ceramic core groups were prepared for testing having the following surfaces: airborne-particle abrasion, ground, and overglazed. Veneering porcelain groups were tested: as fired (no additional treatment), ground, and overglazed. Biaxial flexural strength was measured using the ball-on-ring test method. All specimens were loaded to fracture. One and 2-way analysis of variance were used to analyze the data (α=.05). Results The ceramic core discs were significantly ( P =.001) stronger than the veneering porcelain discs for the airborne-particle abrasion, as-fired, and ground surface treatments (82 ± 11 MPa vs 51 ± 8 MPa and 93 ± 14 MPa vs 60 ± 6 MPa, respectively). For the overglazed treatment, there was not a significant difference between the core (115 ± 1 4 MPa) and the veneer materials (107 ± 14 MPa). The ground 1-layer core was significantly ( P =.015) stronger (93 ± 14 MPa) than the 2-layer with the core tested in tension (72 ± 19 MPa). There was no significant difference between 1-layer veneer overglazed (107 ± 14 MPa) and 2-layer discs when tested with the veneer in tension (105 ± 16 MPa). Conclusion The overglazed surface treatment significantly improved the strength of the materials tested, as well as the strength of 2-layer discs with the veneer in tension. The veneering porcelain influenced the strength of 2-layer specimens only when tested with the ground ceramic core surface in tension.

Giuseppe Isgrò

Papers

The influence of the veneering porcelain and different surface treatments on the biaxial flexural strength of a heat pressed ceramic

The effects of thermal mismatch and fabrication procedures on the deflection of layered all-ceramic discs

The influence of multiple firing on thermal contraction of ceramic materials used for the fabrication of layered all-ceramic dental restorations.

Thermal dimensional behavior of dental ceramics

Fracture toughness comparison of three test methods with four dental porcelains