Effect of Different Cusp Coverage Patterns on Fracture Resistance of Maxillary Premolar Teeth in MOD Composite Restorations

Received: 6 Sept 2012 Accepted: 21 May 2013 Abstract Background and Aim: Tooth fracture is a common complication following MOD restorations.This study sought to assess the effect of different cusp coverage patterns on fracture resistance of maxillary premolar teeth in MOD composite restorations. Materials and Methods: In this invitro experimental study, 40human maxillary sound premolar teeth were chosen and stored in Chloramine solution. Usingbleaching shield, an over impression was made from each tooth and then wide MOD cavities were prepared. The teeth were randomly divided into 4groups of 10each: Group A, without cusp coverage; Group B, with 1.5 mm palatal cusp coverage; Group C, with 1.5 mm buccal cusp coverage; and group D, with 1.5 mm both buccal and palatal cusp coverage. The cavities were restored using Z100 composite resin and the prepared over impressions (in order to restore the normal anatomyof teeth). The teeth were then stored in water at 37°C for 24h and their fracture resistance was assessed using Universal Testing Machine. The load at fracture was recorded in N. Data were analyzed using one-way ANOVA and Tukey’s test with 95% CI. Results: The mean fracture strength was 873.11±243.5 N in group A, 750.53±270.7 N in group B, 824.22±330.2 N in group C and 1499.25±305 N in group D. The results showed that the fracture resistanceof MOD restorations with the coverage of both cusps was significantly more than that of other groups (P<0.05). Conclusion: MOD restorationswith cusp coverage in maxillary premolar teeth increased the fracture strength of teeth against compressive forces.However, covering only one cusp had no significant effect on fracturestrength.