Effect of internal relief, vibration, and venting on the vertical seating of cemented crowns.

The presence of a vent hole in the occlusal surface, vibration during seating, and internal relief inside cast crowns were investigated individually and in all combinations for their effect on vertical seating on metal dies, using zinc phosphate cement. It was found that: 1. Vibration, applied horizontally, had no effect by itself or any interaction with venting or internal crown relief. 2. Venting and internal relief alone effectively achieved good seating. 3. Venting and internal relief together were the most effective combinations. 4. When crowns were seated well, they tended to tilt less.