The effect of venting on pulpward pressure transmission and seating on crown cementation: a laboratory study.

Measurable hydraulic forces towards the pulp chamber can occur whilst cementing a crown. This study investigated the effect of crown venting and the use of two different seating forces (100 and 2. 5 N) on pulpward pressure transmission. Forty single-rooted premolar teeth were collected from patients requiring extractions for orthodontic reasons. A standardized crown preparation was made and impressions taken to construct individual base-metal alloy crowns. The teeth were divided into four groups based on the type of crown (vented or non-vented) and force used (100 or 2.5 N). The teeth mounted on a specially constructed stand and connected to a 0-104 kPa pressure transducer. The pulp chamber was perfused with saline driven by nitrogen gas at 83 kPa for up to 2 h until a steady state perfusion rate was achieved. Crowns were cemented to the teeth on a uniaxial seating device using zinc phosphate cement. Simultaneous recordings of both pressure pulse and seating discrepancies were recorded. The 40-fold increase in seating force from 2.5 to 100 N resulted in a significant increase (P<0.001) in pulpward pressure in both vented and non-vented crowns. Seating was also significantly improved for the vented crowns regardless of which force was used. Venting had no significant effect on pulpward pressure transmission. It was concluded that a significant relationship existed between seating force and pulpward pressure transmission. Venting improved crown seating but did not have a demonstrable effect on pulpward pressure transmission.