Aims and objectives: This study was conducted to evaluate the effect of venting on marginal adaptation of the complete cast crown.

Methodology: Twenty complete cast crowns were fabricated from a 8mm wide and 6mm high stainless steel die with shoulder preparation approximating the volume of a molar crown preparation. Twenty direct dies were fabricated by vibrating autopolymerising resin into complete cast crowns (McCune’s direct die fabrication technique). Ten crowns were vented and ten left unvented. The vented and non-vented crowns were cemented onto the Duralay dies. The Duralay dies with cemented crowns were sectioned with diamond discs. Reflecting microscope was used to measure the mid margin cement space thickness.

Results: The mean of the marginal opening of unvented complete cast crowns is 0.124mm with standard deviation of 0.055 while as the mean of the marginal opening of vented complete cast crowns is 0.067mm with standard deviation of 0.033. The students paired t- test was used to compare the marginal adaptation of vented versus non vented complete crowns at p value of 0.01.