[Influence of different restorations on the fracture resistance of endodontically treated premolars with minor loss of dental defect].

PURPOSE: To evaluate the influence of 3 different restorations on the fracture resistance of endodontically treated premolars with minor loss of dental defect in order to direct clinical design. METHODS: Seventy-two recently extracted intact and single-rooted human mandibular premolars for orthodontic reason were collected and randomly divided into 3 groups (group A, B, C, n=24). Each group was respectively prepared into 1/3 defect of occlusal surface (group A), 1/2 defect of occlusal surface (group B) and 1/3 defect of proximal-occlusal surface model (group C). Then each group was divided into 3 subgroups with one restored with a light-curing composite resin(group A1, B1, C1), one restored with cast metal full crowns following a light-curing composite resin (group A2, B2, C2), and one restored with fiber posts and resin cores and cast full crowns after teeth preparations (group A3, B3, C3, n=8). Static loading tests were performed on each specimen until cracked.Fracture strength was tested and fracture patterns were examined. The data was analyzed using SPSS17.0 software package. RESULTS: The fracture resistance of subgroup A2 was different when compared with subgroup A1 and subgroup A3. In group B and C, the fracture resistance of teeth in subgroup B2, B3, C2 and C3 were significantly higher than that in subgroup B1 and C1. There was no significant difference in the fracture mode of 3 restorations in group A, B and C. CONCLUSIONS: A composite resin combined with cast metal full crowns can be used as the first choice to restore endodontically treated premolars with proximal-occlusal 1/3 defects and occlusal defects that do not surpass 1/2 dimension of occlusion.