Influence of Pre-treatments on Flexural Strength of Zirconia and Debonding Crack-initiation Strength of Veneered Zirconia

Purpose: The aim of the present study was to assess the influence of pre-treatments of zirconia by sandblasting and/or heat treatment on the flexural strength of zirconia and debonding/crack-initiation strength of porcelain-veneered zirconia ceramic. Materials and Methods: Zirconia ceramic specimens were divided into four groups according to treatment (grinding as controls, sandblasting, heat treatment at 1000°C for 10 min, and heat treatment after sandblasting). The porcelain- veneered zirconia specimens were also prepared. The zirconia specimens were subjected to three-point bending tests, and flexural strength was calculated. The debonding/crack-initiation strength of porcelain-veneered zirconia ceramic was measured according to ISO 9693. X-ray diffractometry (XRD) was used to estimate the relative amount of monoclinic phase. Results: There was no significant difference in flexural strength between the four treatments (p > 0.05). The highest amount of monoclinic phase was found after sandblasting. No monoclinic phase was obtained from heat treatment and heat treatment after sandblasting groups, and these two groups showed significantly higher debonding/crack-initiation strength than other two groups (p 0.05). All specimens failed within the veneering porcelain. No elements of veneering porcelain were detected on the zirconia side at the interface using EPMA (electron probe microanalyzer). Conclusion: The present study suggests that the pre-treatment of zirconia with heat treatment after sandblasting prior to firing porcelain does not affect the debonding/crack-initiation strength of porcelain-veneered zirconia ceramic. Keywords: zirconia, sandblasting, heat treatment, debonding/crack-initiation strength