Load fatigue of compromised teeth: A comparison of 3 luting cements

Purpose: This study compared the number of cycles to failure of central inc isors restored with full cast crowns and then cemented with 3 different lut ing cements. Materials and Methods: Fifteen human maxillary central incisor s received cast post-and-core restorations. These were cemented with zinc p hosphate. The teeth were then divided into 3 groups of 5 samples each. Each tooth had a ferrule length of 1.0 mm and was prepared for a full crown. A waxing jig was used to standardize the load application point on all waxed crowns. Complete cast crowns were cemented to the compromised teeth using 3 different luring cements: a zinc phosphate cement (control group), a resin -modified glass-ionomer cement, and a resin cement with a dentin bonding ag ent. A fatigue load of 1.5 kg was applied at a rate of 72 cycles per minute until failure of the cement layer occurred between the crown and the tooth (preliminary failure). The independent variable was the number of load cyc les required to create preliminary failure. An electrical resistance strain gauge was used to provide evidence of preliminary failure. Results and Con clusion: The resin cement samples had a significantly higher number of load cycles to preliminary failure than both the zinc phosphate and the resin-m odified glass ionomer (P less than or equal to 0.05). There was no signific ant difference between the zinc phosphate and the resin-modified glass-iono mer cements.