Measurement of cement thickness under lithium disilicate crowns using an impression material technique
- نوع فایل : کتاب
- زبان : انگلیسی
- مؤلف : Sven Reich ,Sophia Uhlen ,Stephan Gozdowski ,Ulrich Lohbauer
- چاپ و سال / کشور: 2010
Description
According to the literature, marginal gaps below 120 ƒتm are recommended for conventionally cemented crown restorations. Therefore, the null hypothesis tested was as follows: the upper bound of the 95% confidence interval of the marginal accuracy of chair-side generated lithium disilicate crowns lies below 120 ƒتm. Prior to definite insertion, the accuracy of 20 lithium disilicate crowns (e.max CAD LT) was evaluated by a replica technique. A light-body silicone was used to document the gap between crown and abutment. The thickness of the light-body silicone layer was examined under microscope (MM40, Nikon Corp., Tokyo, Japan; magnification, پ~50) at four different landmarks (LM): LM1 = marginal discrepancy, LM2 = mid-axial discrepancy of the inner crown surface, LM3 = axio-occlusal discrepancy, and LM4 = midocclusal discrepancy. At LM1, the mean marginal discrepancy revealed 100 ƒتm (SD, پ}61 ƒتm); the median was 81 ƒتm. The lower bound of the 95% confidence interval was 90 ƒتm, and the upper bound was 110 ƒتm. The means of internal gaps at LM2, LM3, and LM4 showed 148 ƒتm (SD, پ}61 ƒتm), 227 ƒتm (SD, پ}83 ƒتm), and 284 ƒتm (SD, پ}95 ƒتm), respectively. The lower bounds of the 95% confidence interval revealed values between 137 ƒتm (LM2) and 269 ƒتm (LM4). The upper bounds were between 158 ƒتm (LM2) and 300 ƒتm (LM4). The null hypothesis was not rejected. Within the limits of the study, the chairside generated lithium disilicate crowns exhibited a sufficient clinical accuracy.
Clin Oral Invest (2011) 15:521–526 DOI 10.1007/s00784-010-0414-x Received: 14 April 2009 / Accepted: 13 April 2010 / Published online: 12 May 2010
