Influence of mechanical surface treatments on the indentation fracture toughness of glass infiltrated zirconia toughened alumina "GI-ZTA" disks

Flavio T Da Silva,Helio Salim De Amorim,Marcio A.N Zacché

doi:10.1590/s1517-70762007000200020

Abstract

The main objective of this study was to evaluate the influence of mechanical surface treatments for excess glass removal on the fracture toughness of a glass infiltrated zirconia toughened alumina "GI-ZTA" disks (In-Ceram® Zirconia). The GI-ZTA disks were submitted to three different mechanical surface treatments after glass infiltration (grinding, sandblasting and grinding/sandblasting/annealing). Fracture toughness was evaluated through indentation fracture (IF) test. Reliability of tests results was accessed through Weibull statistics. Results: Indentation fracture tests (IF) of GI-ZTA disks have shown that grinding was the surface treatment that presented the lowest K Ic and reliability. An annealing treatment after grinding and sandblasting promoted an increase in K Ic, mainly due to monoclinic-tetragonal reverse transformation recovering the tetragonal zirconia lost during the different mechanical surface treatments. The highest K Ic values were observed after sandblasting and grinding/sandblasting/annealing. Significance: The proposed mechanical surface treatments played an important role on the metastability of tetragonal zirconia and strongly influenced the mechanical performance of GI-ZTA. Kruskhall-Wallis test indicated that K Ic values of the three mechanical surface treatments were statistically distinct.

Highlights

IntroductionAll ceramic restorations were indicated only for single crowns and partial coverage restorations due to their low flexural strength and fracture toughness
The loss or destruction of teeth due to periodontal disease, caries or trauma, have lead dentistry and engineering professionals to develop new materials and search for prosthetic treatments for the replacement of those missing teeth.Until recently, all ceramic restorations were indicated only for single crowns and partial coverage restorations due to their low flexural strength and fracture toughness
The In-Ceram® Zirconia (Vita Zahnfabrik) is composed of α-alumina with 33wt% partially stabilized zirconia partially sintered in two steps at low temperatures (1120 and 11800C) to avoid shrinkage followed by glass infiltration at 11400C, resulting in a dense and high strength ceramic core, mainly used for replacing posterior teeth with all-ceramic restorations

Summary

Introduction

All ceramic restorations were indicated only for single crowns and partial coverage restorations due to their low flexural strength and fracture toughness. The relationship between mechanical properties and their clinical performance are influenced by many factors, some of those properties have been used as initial parameters to determine the clinical potential and limitations of these materials [1]. There is a straight relationship between strength and fracture toughness in brittle materials, where the critical crack size to initiate failure is determined by the inherent flaw population introduced during material processing and component manufacture [2,3,4,5].

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Conclusion