Influence of preparation height on the retention of complete crown

Objective:The retention of complete crown was measured with different height to probe into the ideal preparation height of molar.Method:The 36 extracted molar was produced with 5°crown taper and 7mm diameter.6 groups were divided with the different height:1 mm、2 mm、3 mm、4 mm、5 mm、6 mm, and each group had 6 teeth.Crowns were made on each model.Each group was measured about the retention of crowns by Autograph Force Meter. Result:The retention of crowns on the models with 5° crown taper and 1 mm、2 mm、3 mm、4 mm、5 mm、6 mm height were 84.2500 N,116.6667 N,183.0000 N,268.5833 N,360.9167 N,448.2500 N respectively.The retention of crowns between models increased significantly with the increase of crown height.Conclusion:The retention of complete Crown was relevant to the crown height.When the preparation taper was 5° and the preparation height was more than 2 mm,The retention of complete crown increased obviously.