Retentive properties of self-threading pins and cemented pins

Objectives: The purpose of this study was to evaluate the retentive properties of self-threading pins (STP) and cemented dental pins (CP).

Materials and methods: Twenty posterior human teeth were mounted into retaining cylinders and the occlusal dentin was exposed using a circular saw. A pin drill (0.525mm diameter) was used to prepare a 2mm deep channel perpendicular to the dentin surface. A titanium dental pin (0.6mm diameter) was threaded into each tooth specimen. Three additional 2 mm deep pinholes were prepared in each tooth using a pin drill 0.675mm in diameter. Titanium pins (0.6 mm diameter) were cemented into the channels using resin-modified-glass-ionomer cement (RMGIC), self-adhesive resin cement (SRC) or zinc phosphate cement (ZP).

Titanium dental pins (0.6mm diameter) were embedded to a depth of 2mm into three types of dental restorative materials (n=20): resin composite (RC), resin modified glass-ionomer (RMGI) and dental amalgam (DA). Axial loads were applied in the tensile mode using a universal testing machine and the load at failure was recorded. Statistical analysis of the data included an ANOVA followed by Student-Newman-Keuls multiple comparison tests (á < 0.05).

Results: The retention strength of STP group (116.04 Newtons) was significantly higher than all CP groups (p < 0.001). The values of SRC, RMGIC and ZP groups were 49.88, 43.53, and 34.39 Newtons, respectively. The retention SRC was greater than that of ZPC (p = 0.0335). The retention values of pins embedded in DA, RC and RMGI restorative materials were 239.9, 206.5 and 234.48 Newtons, respectively. Pin retention in RC was statistically lower than retention in DA or RMGI. (p=0.001).

Conclusion: The retention strength of dental pins threaded into dentin is significantly higher than pins secured with cements. The retention strength of dental pins in restorative materials is lowest in resin composite.