Fracture strength of teeth restored with ceramic inlays and overlays

This study evaluated the fracture strength of teeth restored with bonded ceramic inlays and overlays compared to sound teeth. Thirty sound human maxillary premolars were assigned to 3 groups: 1- sound/unprepared (control); 2- inlays and 3- overlays. The inlay cavity design was Class II MOD preparation with an occlusal width of 1/2 of the intercuspal distance. The overlay cavity design was similar to that of the inlay group, except for buccal and palatal cusp coverage The inlay and overlay groups were restored with feldspathic porcelain bonded with adhesive cement. The specimens were subjected to a compressive load until fracture. Data were analyzed statistically by the Kruskal-Wallis test at 5% significance level. The fracture strength means (KN) were: Sound/unprepared group = 1.17, Inlay group= 1.17, and Overlay group = 1.14. There were no statistically significant differences (p>0.05) among the groups. For inlays and overlays, the predominant fracture mode involved fragments of one cusp (70% of simple fractures). The fracture strength of teeth restored with inlay and overlay ceramics with cusp coverage was similar to that of intact teeth.

Effect of ion-exchange temperature on mechanical properties of a dental porcelain

The objective of this study was to determine the influence of different ion-exchange temperatures on the biaxial flexural strength (sigma(f)), hardness (HV) and indentation fracture resistance (K(IF)) of a dental porcelain. Disk-shaped specimens were divided into five groups (n = 10) and submitted to an ion-exchange procedure using KNO(3) paste for 15 min in the following temperatures (degrees C); (I) 430; (II) 450; (III) 470; (IV) 490; (V) 510; and control (no ion exchange). The value of sigma(f) was determined in artificial saliva at 37 degrees C. The values of HV and K(IF) were obtained using 3 Vickers indentations in each specimen (19.6 N). Results showed that ion exchange increases significantly the properties of the material as compared to the control and no significant differences were found among the temperatures tested for any of the properties studied. (C) 2010 Elsevier Ltd and Techna Group S.r.l. All rights reserved.