Stability and wear of zirconia crowns with micro-layering

Objectives: To investigate stability and wear of tooth-supported zirconia single crowns with micro-layering in -vitro. Materials and methods: Molar crowns and specimens were fabricated from 5Y-TZP zirconia (Gen-X, Amann-Girrbach). Three groups were investigated: ML I: 0.1 mm cutback/painted/glazed (MiYO, Jensen); ML II: occlusal 0.3 mm cutback/painted/veneered/glazed (MiYO), and a monolithic control group (polished). After thermal cycling and mechanical loading (TCML), crowns were loaded to failure in a universal testing machine. Two-body wear test was performed. Wear (mean, maximum, antagonist) and roughness (Ra, Rz) were deter-mined with a 3D laser-scanning-microscope.Results: All crowns survived TCML. In the control (2501.5 N) and ML II group (1775.3 N) significantly lower fracture forces were observed than in ML I (3636.4 N) (p & LE; 0.003). Significant wear differences were found (p & LE; 0.001) but not for antagonist wear (p & GE; 0.202). Lowest wear was observed in the control group 10.2 & PLUSMN; 1.5 & mu;m/ 28.8 & PLUSMN; 6.4 & mu;m, ML I 112.8 & PLUSMN; 37.3 & mu;m/152.9 & PLUSMN; 42.8 & mu;m, and ML II 192.4 & PLUSMN; 49.1 & mu;m/340.7 & PLUSMN; 54.2 & mu;m. Roughness was characterized by a Ra from 1.6 & mu;m (control) to 3.0 & mu;m (ML II), and a Rz from 11.8 & mu;m (Control) to 24.0 & mu;m (ML II). Roughness significantly differed between control group and ML I (p = 0.002) as well as ML I and ML II (p = 0.020).Conclusions: Good in-vitro performance and fracture stability without chipping or fracture were found for all systems. Wear and roughness were comparable to conventional ceramic veneering systems. Clinical Relevance: The micro-layering of zirconia restorations can be recommended, yet the micro-layering could be worn during clinical application.

Automated summary

This study investigated the stability and wear of tooth-supported zirconia single crowns with micro-layering in vitro. The results showed that the micro-layering technique provided good stability and wear performance, comparable to conventional ceramic veneering systems.