Influence of porcelain veneering on the marginal fit of Digident and Lava CAD/CAM zirconia ceramic crowns

Abstract

PURPOSEMarginal fit is a very important factor considering the restoration's long-term success. However, adding porcelain to copings can cause distortion and lead to an inadequate fit which exposes more luting material to the oral environment and causes secondary caries. The purpose of this study was to compare the marginal fit of 2 different all-ceramic crown systems before and after porcelain veneering. This study was also intended to verify the marginal fit of crowns originated from green machining of partially sintered blocks of zirconia (Lava CAD/CAM system) and that of crowns obtained through machining of fully sintered blocks of zirconia (Digident CAD/CAM system).MATERIALS AND METHODS20 crowns were made per each system and the marginal fit was evaluated through a light microscope with image processing (Accura 2000) at 50 points that were randomly selected. Each crown was measured twice: the first measurement was done after obtaining a 0.5 mm coping and the second measurement was done after porcelain veneering. The means and standard deviations were calculated and statistical inferences among the 2 groups were made using independent t-test and within the same group through paired t-test.RESULTSThe means and standard deviations of the marginal fit were 61.52 ± 2.88 µm for the Digident CAD/CAM zirconia ceramic crowns before porcelain veneering and 83.15 ± 3.51 µm after porcelain veneering. Lava CAD/CAM zirconia ceramic crowns showed means and standard deviations of 62.22 ± 1.78 µm before porcelain veneering and 82.03 ± 1.85 µm after porcelain veneering. Both groups showed significant differences when analyzing the marginal gaps before and after porcelain veneering within each group. However, no significant differences were found when comparing the marginal gaps of each group before porcelain veneering and after porcelain veneering as well.CONCLUSIONThe 2 all-ceramic crown systems showed marginal gaps that were within a reported clinically acceptable range of marginal discrepancy.

Multifactorial analysis of the impact of different manufacturing processes on the marginal fit of zirconia copings

“…For the manual adapted copings, the mean marginal gaps varied from 54 to 59.9 μm. This is in accordance with marginal gaps reported for CAD/ CAM-generated zirconia copings in other studies, in which marginal gaps ranged from 24 to 110 μm 6,11,14,15,31) . The large variation in the reported mean values can be explained by a number of infl uencing factors, including CAD/CAM components and differences between presintered and post-sintered milling of the zirconia blank.…”

“…It has been reported that allceramic crowns show a mean marginal discrepancy that ranges from 19-160 μm [7][8][9][10] . The mean marginal gap for CAD/CAM-generated crowns is reported to be 23-110 μm 6,[11][12][13][14][15] . Many authors accept the criterion established by McLean and von Fraunhofer (1971) who proposed after a 5-year examination of 1,000 restorations that 120 μm should be considered the maximum marginal gap 6,[15][16][17] .…”

“…The mean marginal gap for CAD/CAM-generated crowns is reported to be 23-110 μm 6,[11][12][13][14][15] . Many authors accept the criterion established by McLean and von Fraunhofer (1971) who proposed after a 5-year examination of 1,000 restorations that 120 μm should be considered the maximum marginal gap 6,[15][16][17] . To generate the best marginal accuracy of CAD/CAM-based restorations, most manufacturers' recommendations imply convergence angles of 6-8° for the preparation of the abutment.…”

“…This, in turn, can lead to a failure of the restoration 4,5) . There are variable defi nitions regarding what constitutes a clinically acceptable margin 6) , and there is no concrete threshold for the maximum marginal discrepancy that is clinically acceptable. It has been reported that allceramic crowns show a mean marginal discrepancy that ranges from 19-160 μm [7][8][9][10] .…”

The marginal fit of E.max Press and E.max CAD lithium disilicate restorations: A critical review

“…This technique reduces processing errors that may be associated with conventional sintering and has been shown to improve mechanical stability 21,22) . Marginal fit is an important factor in the success of restorations 23,24) . Marginal fit is related to both vertical and horizontal discrepancies.…”