Influence of surface treatment and cyclic loading on the durability of repaired all-ceramic crowns

Objective: This study investigated the durability of repaired all- ceramic crowns after cyclic loading. Material and methods: Eighty In- ceram zirconia crowns were fabricated to restore prepared maxillary premolars. Resin cement was used for cementation of crowns. Palatal cusps were removed to simulate fracture of veneering porcelain and divided into 4 groups (n = 20). Fracture site was treated before repair as follows: roughening with diamond bur, (DB); air abrasion using 50 mu m Al2O3, (AA) and silica coating using Cojet system followed by silane application, (SC). Control group (CG) 20 specimens were left without fracture. Palatal cusps were repaired using composite resin. Specimens were stored in water bath at 37 degrees C for one week. Ten specimens of each group were subjected to cyclic loading. Fracture load (N) was recorded for each specimen using a universal testing machine. Two- way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) test (alpha=.05) were used for statistical analysis. Results: There was statistically significant difference between control and tested groups, (p<0.001). Post Hoc analysis with the Tukey HSD test showed that cyclic loading fatigue significantly decreased means fracture load of control and test groups as follows (CG, 950.4 +/- 62.6 / 872.3 +/- 87.4, P = 0.0004), (DB, 624.2 +/- 38 / 425.5 +/- 31.7, P <.001), (AA, 711.5 +/- 15.5 / 490 +/- 25.2, p < 0.001) and (SC, 788.7 +/- 18.1 / 610.2 +/- 25.2, P <.001), while silica coating and silane application significantly increased fracture load of repaired crowns (p<0.05). Conclusions: Repair of fractured Inceram zirconia crowns after chairside treatment of the fracture site by silica coating and silane application could improve longevity of repaired In-ceram zirconia crowns.