To analyze the influence of glass fibre post restoration on premolars fracture resistance with different numbers of coronal dentin walls defect.

According to different numbers of coronal dentin walls defect and restoration methods, forty-eight mandibular first premolars were randomly divided into six groups. Group A1: one-wall defect with glass fibre post-composite resin core restoration; Group A2: one-wall defect with composite resin core restoration; Group B1: two-wall defect with glass fibre post-composite resin core restoration; Group B2: two-wall defect with composite resin core restoration; Group C1: three-wall defect with glass fibre post-composite resin core restoration; Group C2: three-wall defect with composite resin core restoration. Every sample was loaded till failure by mechanical testing machine. The maximum loading value and failure mode were recorded. Two independent samples t test was used in statistical analysis.

There is no statistical significance in the maximum loading capacity between Group A1 and Group A2(P > 0.05). Statistical significance was found in the maximum loading capacity between Group B1 and B2, as well as Group C1 and C2(P < 0.05). Irreparable fracture mainly occurs in Group A1, A2 and B2.

There is no effect of glass fibre post-composite core restored on the fracture resistance of teeth with one-wall defect(t_A=1.830, P_A=0.10). When the number of coronal dentin wall defect is two or three, glass fibre post-composite core restoration is better than composite resin core restoration on the fracture resistance of teeth(t_B=4.741, P_B=0.001; t_C=3.491, P_C=0.005).