Fracture Resistance of Endodontically Treated Upper Premolars with Different Cavity Designs

Abstract

This study was conducted to evaluate the effect of the type of the restoration technique (direct or indirect), the cavity design (no cusp reduction, palatal cusp reduction and palatal-buccal cusp reduction) and the reinforcement with resin-impregnated glass fibres on fracture resistance, outward cuspal deflection and adaptation of the restoration of endodontically treated maxillary premolars with MOD cavities restored with a highly filled resin composite. A total of 325 sound upper premolars were used in this study. They were divided randomly into three sets; 120 were used for fracture resistance testing (n=10), 120 for outward cuspal deflection examination (n=10) and 60 for examining the internal adaptation of the restorations (n=5). The remaining 25premolars served as a control. For each test, the premolars were divided into two equal groups according to the technique of restoration, either direct or indirect. Each group was further divided into three subgroups according to the cavity design: Mesio-Occluso-Distal (MOD) cavity, MOD cavity with palatal cusp reduction and MOD cavity with palatal-buccal cusp reduction. Each subgroup was divided into two divisions according to the restoration reinforcement, one reinforced with resin-impregnated glass fibers and the other unreinforced. The control group had MOD cavity prepared to be restored directly with a resin composite of a regular filler loading.