Slots vs pins: a comparison of retention under simulated chewing stresses

The specimens of composite resin retained by pins exhibited significantly lower cycle life than did all other groups. At low loads, the pins and slots are comparable (when composite resin is used), but there is a dramatic decrease in the life of restorations retained with pins as the load is increased. At the 30-micrometer end point, the composite restorations retained with pins failed at a mean of 250 cycles, whereas the composite restorations retained with a slot failed at 250,000 cycles - a 1000X increase in cycle life. In general, cycle life of composite resin retained with a slot is comparable to or greater than that of amalgam retained with a slot or pins. Whether the life difference between the pin- and slot- retained amalgam restoration is clinically significant is not known; however, the baseline for a clinical study of the two types of retention for definitive amalgam restorations has been completed and will be reported in the future.