Influence of incomplete partial ferrule location on fracture resistance of post-and-core crown：an in vitro test

Abstract:

Objective： The purpose of this in vitro test was to investigate the fracture resistance of post and crowned maxillary premolar with various ferrule configurations. Methods：According to the partial ferrule location, thirty two maxillary premolar after endodontical treatment were assigned to four groups：（Group A：with a circumferential ferrule；Group B：with a complete palatal ferrule；Group C：with a complete buccal ferrule；Group D：with a complete proximal ferrule）. All specimens were reconstructed with fiber posts，resin cores，and metal crowns，then specimens were mounted and loaded at 45° to the long axis，at the top 1/3 of the lingual surface of the buccal cusp in a universal testing machine until fracture occurred，the speed set at 1.0 mm/min. Results：The mean fracture load was （826.3±183.1），（587.8±142.4），（406.1±189.7），（486.3±317.4） N respectively. One-way ANOVA analysis showed statisti－cally significant difference（P<0.05） existed between those groups，the anti-fracture ability of Group A was significantly higher than other groups B，C and Group D（P=0.037，0.001，0.004）. No significant differences were found between the other groups（P>0.05）. The predominant fracture mode was an oblique fracture at cervical one-third observed from palatal to buccal side，while only one specimen fracture line was observed at root one-third in Group A. Conclusion： Post and cored crown with a complete ferrule could significantly improve the fracture resistance of the pulpless tooth. When the residual dentinal tissue is not enough，preserve more palatal dentinal tissue may enhance the fracture resistance by protecting the in－tegrity of the adhesive layer between the dentin and resin.