Laboratory evaluation of fracture strength of endodontically composite restored molars

Endodontically treated molars have the risk of fracture. The purpose of this study was to determine the fracture strength of endodontically treated molars after treatment with various types of cavity preparations and time of load cycling intervals. Methods & Materials: In this conventional and parallel study, one hundred and seventeen extracted human molars were selected and randomly divided into 3 groups (n=39) based on cavity preparations of MOD, MOD accompanying with lingual cusp reduction (CCL) and MOD with lingual and buccal cusp reduction (CCLB). The control group consisted of thirteen intact molars. All of the teeth were filled with a packable composite (Tetric Ceram HB). Each group was divided into three subgroups (n=13) based on the load cycling: 1) without any load cycles, 2) 1000,000 and 3) 2000000 load cycles. Then the specimens were fractured in Instron testing machine by a crosshead speed of 5 mm/min. The statistical analysis (ANOVA and Duncan’s test) was performed for analysis of data (α =0.05). 1) There was statistically interaction between two variables of cavity preparation and time interval (P<0.05). 2) In MOD group the most fracture strength was observed at the base line (P<0.05) and there was no significant difference between four and eight year groups. 3) The least fracture strength was related to CCBL group at the base line (P<0.05). 4) The most fracture strength was related to CCL group in four and eight year groups (P<0.05). The most fracture strength was observed in control group (intact teeth). The adhesive packable composite restorations in molars after lingual cusp capping could create a fracture strength similar to intact teeth until four years.J Dent Sch 2006 24(3): 12 Keywords: Fracture strength, Endodontically, Molar, Composite