Purpose: To assess whether the amount of residual coronal dentin and the placement of a prefabricated (DT Light Post) (LP) or a customized fiber post (Ever Stick Post) (ES) have a significant influence on the 3-year survival of endodontically treated premolars.
Methods: A sample of 345 patients provided six groups of 60 premolars in need of endodontic treatment. Groups were defined based on the amount of dentin left at the coronal level after endodontic treatment and before abutment build-up. Within each group teeth were randomly divided into three subgroups (n = 20). In Subgroup A, no root canal retention was provided for the coronal restoration. In Subgroups B and C, LP and ES, respectively, were placed inside the root canal. All the teeth were finally restored with a single unit metal-ceramic crown.
Results: Data were not affected by any loss to follow-up. The overall 36-month survival rate of crowned endodontically treated premolars was 76.7%. The lowest survival rate was recorded for teeth restored without any root canal retention (62.5%). Teeth restored with LP had a survival rate higher (90.9%) than those restored with ES (76.7%). The Cox regression analysis showed that the presence of root canal retention was a significant factor for survival (P < 0.05). The decrease in failure risk was higher in teeth restored with LP (HR = 0.1; 95% CI for HR = 0.09 to 0.34; P < 0.001) than when using ES (HR = 0.5; 95% CI for HR = 0.3 to 0.7; P = 0.003). Teeth retaining one (HR = 0.3; 95% CI for HR = 0.2 to 0.7; P = 0.003), two (HR = 0.2; 95% CI for HR = 0.1 to 0.5; P < 0.001), or three coronal walls (HR = 0.1; 95% CI for HR = 0.05 to 0.3; P < 0.001) had a significantly lower failure risk than teeth deprived even of the ferrule effect. Similar failure risks existed for teeth missing all the coronal walls regardless of the presence or absence of a ferrule effect (P > 0.05). Interaction terms were not significant (P > 0.05). Post placement and the amount of residual coronal dentin affected the 3-year survival of endodontically treated premolars.