Compare The Accuracy Of Impression Of Two Shapes Tray

Experiment One: Two shape tray impression crown cervical margin accuracyObjective：To compare impression crown cervical margin accuracy between thestainless steel tray without holes and stainless steel perforated trayMethod: Using tray without holes and perforated tray to prepare the same experimentalmaster model separately by one-step impression and two-step impression methods,analyze two trays accuracy difference by using one-step impression and two-stepimpression at NO.21position of full ceramic crown abutment preparation, then analyzethe data statistically.Results:(1)By one-step impression, tray without holes is better than perforated tray withstatistically significant(2) By two-step impression, excellent rate of tray without holes is better than perforatedtray with no statistically significantExperiment Two: Comparison of impression linear change rate between two traysObjective：To compare impression linear change rate between the stainless steel traywithout holes and stainless steel perforated trayMethod: Using tray without holes and perforated tray to prepare the same experimentalmaster model separately by one-step impression and two-step impression methods,measure the distance between each mark point of the main model and plaster model,analyze change of the linear change rate of two trays on different impressions.Results: Comparison on linear change rate, change rate of perforated tray is larger thantray without holes by two methods impression with no statistically significant.Conclusion: There is not obvious size difference between original model and modulussilicone rubber mold filling model on tray without holes and perforated tray, impression deformation is within clinically acceptable scope. But tray without hole is better thanperforated tray on crown cervical margin copy.