Effect of venting and seating techniques on the cementation of complete coverage restorations

The incomplete seating of crowns resulting from cementation phenomena is a universal problem for clinicians. This seating error may lead to disturbances in the occlusion, proximal contacts, reduced retention and open margins. Various cementation protocols are practiced, with no established standard that maximizes crown seating and marginal fit.

This study investigated the effect of various combinations of venting and cementation seating techniques with the routine use of die relief on the seating of complete gold crowns.

Fifty human molars were prepared with a mounted handpiece for complete coverage crowns with a featheredge finish line and six degrees of taper, according to Tylman. Impressions were made, stone dies fabricated, die spacer was applied and the crowns were waxed and cast in type III gold. The respective crowns were placed on the teeth and preloaded. The distance between reference marks on the tooth and crown were measured at four points around each tooth. Zinc phosphate cement was mixed and the crowns were cemented in the following groups: (1) vented, tapping the crown into place with a mallet, (2) non-vented, tapping the crown into place, (3) vented static seating with a 25 kg load, (4) non-vented dynamic seating, (5) non-vented static loading with a 25 kg load. A 25 kg load was then maintained on the crowns during the cement setting time. Distances between reference marks were then measured and the change in post-cementation distances calculated.

ANOVA (F = 14.995, p < .0001) and multiple range tests revealed significant differences between the groups. The mean increased post-cementation distances for the seating groups were (microm): 1) 132 +/- 20, 2) 372 +/- 26, 3) 367 +/- 59, 4) 239 +/- 35, 5) 537 +/- 45.

The vented tapping technique produced the best seating. The non-vented tapping seating group produced seating not significantly different from the vented static method. The non-vented static group had the worst seating, with a gap four times greater than the vented tapping group.