ADHESIVE FAILURE AT THE ROOT DENTIN-CEMENT-POST INTERFACES

Post retention depends upon the adhesion achieved at the resin cement-dentin and resin cement-post interfaces. The percentage of cement adhered to the surface of a removed post allows determining which is the main adhesive interface responsible for the failure. Aim: To determine the interface where adhesive failure of posts occurs in wide, non-circular root canals. Method: 60 lower bicuspids with a steady length of 15mm were used. Root canal treatment was performed with the ProTaper Universal system, and filled with gutta percha points by lateral condensation and AH Plus resin based sealant (Dentsply, Maillefer). Samples were randomly assigned to 5 groups. Group 1: control – conventional technique with organic post. Group 2: cast post. Group 3: anatomic post. Group 4: dentin reinforcement. Group 5: post and cement. In groups 2 to 5 a wide, standardized preparation of root canals was performed. Multilink self-curing cement and FRC Postec Plus (Ivoclar/Vivadent) were used in all groups. Traction tests were performed with a universal testing machine (Digimess MX5000) with a crosshead speed of 0.5mm/min, until post removal. Post surfaces were measured as well as the cement and resin adhered to the posts. Images were digitalized with morphometric software Image Pro Plus V 4.52. Data were analyzed by ANOVA and Duncan post hoc tests. Results: 50% of cast post samples had less than 20% of their surfaces exhibiting adhered cement, showing a statistically significant difference (p<0.05) compared to the organic post groups (groups 3, 4 and 5 – showing 83.7%) and to group 1 (91.7%). Conclusions: Organic post groups experienced adhesive failure at the cement-post interface, while in cast post group such failure occurred at the cement-dentin interface.