EFFECTS OF AMOUNT OF RESIDUAL TOOTH ON THE ANTIFRACTURE PROPERTY AFTER THE REPAIR OF CAST POST

Objective To evaluate the fracture resistance of endodontically treated mandibular premolars restored with cast posts when different types of ferrule designs were incorporated.Methods Forty-eight mandibular premolars were divided into six groups according to ferrule.In Group 1(control),the teeth with root canal treatments had a full crown prosthesis.In Group 2,the teeth had 1mm circumferential ferrule.In Group 3,the teeth had a 1mm ferrule only in the buccal region.In Group 4,the teeth had 1mm ferrule only in the lingual region.In Group 5,the teeth had 1mm ferrule in the buccal and lingual region.In Group 6,the teeth had no ferrule.All extracted teeth were restored with cast post and cores and porcelain fused to metal crowns.All experimental teeth were subjected to an increasing compressive force with a crosshead speed of 1mm/min,until fracture occurred.Results The loading force value in the second group was 1383.3±187.6N,which is significantly higher than other groups(P0.01).The Group One of(1067.6±234.3)N and the Group Six of(718.8±176.3)N showed significant differences(P0.05).The differences in other groups were not statistically significant.Conclusion Cast post and core can be used to restore the ferrule premolar residual roots.