Fatigue methods for evaluating translucent dental zirconia.

OBJECTIVE: To investigate fatigue methods for the evaluation of translucent zirconia and to associate in vitro failures with clinically reported ones. DATA: Studies published in English that used fatigue tests on dental translucent zirconia. SOURCES: Two databases (MEDLINE/PubMed and Scopus) were electronically searched without any restriction on year of publication. STUDY SELECTION: A total of 4555 studies were identified. After removal of duplicates (78) and irrelevant articles (4316) that did not meet the inclusion criteria, 161 articles were considered eligible based on their titles and abstracts. These articles were fully read, leading to the inclusion of 41 studies in the review. RESULTS: The most widely used fatigue method for evaluation of translucent zirconia was step-stress (18 articles), followed by staircase (seven articles), and step-wise (two articles). Most studies had been conducted in a wet environment with the use of a stainless steel piston to apply load to cemented structures on a dentin-like substrate. Most fracture analyses indicated the fracture originated on the cementation or contact surface where the load was applied. Moreover, studies that utilized anatomical structures (dental crowns) reported fractures starting at the cervical margin of the crowns. CONCLUSION: Most studies used the step-stress method. Only three studies reported failures similar to those found in clinical trials that used translucent zirconia restorations. CLINICAL SIGNIFICANCE: The study findings can assist on correlating clinical failures to the ones observed in vitro.

Biomechanical properties of a 3D printing polymer for provisional restorations and artificial teeth.

OBJECTIVES: To characterize a resin-based polymer used for 3D printing (3D) provisional restorations and artificial teeth by evaluating relevant material's properties (flexural strength (σf), elastic modulus (E), water sorption (Wsp) and solubility (Wsl)) and biocompatibility, and comparing to a bis-acryl composite resin (BA) and a heat-cured acrylic resin (AR). METHODS: Structures were fabricated from 3D, BA and AR. Bar-shaped specimens (n = 30) were submitted to three-point flexure (in 37ºC water and constant displacement rate: 1 ± 0.3 mm/min) until fracture to calculate σf and E. Additional specimens (n = 30) were aged in 37ºC distilled water for six months before testing for σf. Disc-shaped specimens (n = 5) were dried in desiccators and oven until weight stability was reached, then they were immersed in distilled water for seven days, weighed and submitted to the drying process to obtain Wsp and Wsl. SRB and MTT assays were used to evaluate biocompatibility. Data were statistically analyzed using Kruskal Wallis, Student-Newman-Keuls (α = .05), and Weibull distribution. ANOVA and Tukey (α = .05) were used to evaluate the biocompatibility data. RESULTS: 3D structures showed higher σf than AR after aging. The BA showed the lowest values for σf and E, at baseline and after aging. All materials showed Wsp and Wsl values within the recommended standard values. AR structures showed lower cell viability (71.9%) than 3D (92.9%) and BA (90.8%) when using the SRB test. No difference was found when using MTT (p > .05). SIGNIFICANCE: The evaluated polymer-based 3D printing material showed adequate biomechanical behavior for using as a provisional restoration and artificial teeth.