The Effect Of Different Impression Modes On The Single Crown Preparation And Dentition Accuracy

Objective:The objective of the present study is to propose some evidence-based treatment guidelines.In this study,the difference among the direct digital impression,indirect digitalisation of gypsum model and silicon rubber impression is discussed by analysing their accuracy in three dimension.Method:Two types of designated dental study models were used in this study as follows: 1)standard mandibular model;2)prepared right first molar on the lower arch.The study scope is limited by using the impression and scanning guide plate.Each dental study model was scanned to obtain the direct digital impression using intraoral digital scanner,and the data was converted by CEREC matching software saving as STL file;Silicone rubber impression and plaster models were made from both models,scanned by laboratory scanner,and the obtained data was saved as STL files.There are two groups of direct digital printing modules,20 copies;the molds of the silicone rubber and plaster model were scanned in four groups,40 copies.Three-dimensional differences between the control group and experimental group were measured to evaluate the accuracy of each group.Results:1.The digital impression of silicone rubber and gypsum model of the standard full crown preparation model is relatively direct digital impression,except that the difference of the center point of the tooth preparation surface,the fossae of adjacent tooth and the contact areas are statistically significant(p < 0.05),and the accuracy difference of the remaining observation points is not statistically significant.2.The average deviation in the group of the direct digital impression,siliconerubber mold and gypsum model is 1.684 mm,0.379 mm and 0.176 mm respectively.Conclusion:1.The accuracy of the indirect digital impression of the single crown preparation can be comparable to that of the direct digital impression,but in the occlusal and adjacent contact areas of the restoration,the corresponding adjustments need to be made clinically.2.The full dentition precision of digital gypsum impression is better than that of silicone rubber,and the precision of direct digital impression is the worst.