Fracture Resistante Of Endodontically Treated Mandibular Premolars With Proximal-occlusal Defects Related To Diferent Restorations

Objective:To compare the fracture resistance of endodontically treated premolars with proximal-occlusal defects with different restorations and to discuss the best restoration to provide certain theoretical basis for the clinical doctors.Methods:Fifty recently extracted intact human mandibular premolars for orthodontic reason were collected and randomly divided into five groups (n=10). Group A:intact teeth without any treatments. The other groups were prepared of proximal-occlusal cavities under the same standard following perfect root canal treatments. Every group was restored with different methods. Group B:filled with a light-curing composite resin. Group C:restored with cast metal full crowns following a light-curing composite resin. Group D:restored with cast post-cores and full crowns after teeth preparations. Group E:restored with fiber posts and resin cores and cast full crowns after teeth preparations. Group C、D、E were restored with metal full crowns. All specimens were embeded in self-curing plastic and tested by universal material test machine at a speed of1.00mm/min. The loads were applied at an angle of30degrees to the long angle of the teeth. Fracture loads and models were recorded and analyzed statistically. Results:1. Mean fracture loads of five groups were as follows, respectively. Group A:952.93±102.03N, group B:383.97±46.31N, groupC:733.51±54.94N, group D:604.76±123.73N, group E:893.44±87.08N. There was no significant difference between group A and group E among the five groups.2. The number of unrepairable fracture in group B, C, D, E were2,1,9,3, respectively. The differences were statistically significant between group D and the other groups. There was no significant difference among B, C, E groups.Conclusion:The results in this study suggest that different restorations have influence on the fracture resistance of endodontically treated premolar with proximal-occlusal cavities, and non-metal post-core and full crown can be used as the first choice to restore premolar with proximal-occlusal cavities. Pay attention to protect root canal as far as possible to decrease grinding teeth tissue.