Retention of Zirconia Crowns Bonded with Five Adhesive Cements

Self adhesive cements are becoming popular due to the direct bonding ability to dentin and enamel without use of an etchant or a primer.

OBJECTIVE: To measure and compare retention rates of Zirconia crowns cemented with three commercially available and one new adhesive cements.

METHODS: Extracted teeth were retained in cylinders using acrylic resin and occlusal surfaces were ground flat, placed into a lathe with diamond cutting tools to produce a uniform crown preparation with exact taper, diameter and fit. After the preparation, Zirconia crowns were waxed and milled and a hole was prepared on the crown. Finished crowns individually fit on the tooth, margins checked for opening and fit (explorer does not catch) and the crowns cemented with Experimental/L.D. Caulk, Maxcem/Kerr, Unicem-Clicker/3M-ESPE, Unicem-Aplicap/3M-ESPE, Biscem/BISCO, GCem/GC, following the manufacturer's directions. A 2kg weight was placed on the cemented crown until the cement has set. Excess cement was removed and the crowns were allowed to set in tap water for 24h before testing. A metal rod was placed through the hole on the crown and through the loops of a wire. Specimens were attached to the hook of the testing machine using the wire (INSTRON Model no: 5565) and loaded in tension at a cross-head speed of 0.5mm/min until debonding occurred. The force (N) of debonding was recorded. The results were analyzed with ANOVA followed by Tukey/Kramer (p=0.05)

RESULTS: Mean ±SD in N

Materials	Experimental	Maxcem	Unicem-Clicker	Unicem-Aplicap	Biscem
Failure Load	282.7±51	103.3±70	431.5±114	493.4±161	155.9±80

CONCLUSIONS: Retention of Zirconia was significantly higher when cemented with Unicem-Aplicap than other tested cements except for Unicem-Clicker. Experimental cement has shown higher results than Biscem (no significance) and Maxcem (significance). Further development of adhesive cements should continue. Supported in part by L.D. Caulk.