The influence of different cement spaces on the marginal gap of lithium disilicate crowns constructed by two scanner and milling unit combinations

BACKGROUND

This study compared the marginal gaps of CAD/CAM lithium disilicate (LDS) crowns constructed using a contemporary and older scanner/milling unit combination at three different cement spaces.

METHODS

Twenty-four undergraduate students prepared a Columbia model lower left first molar for an LDS crown in a simulated environment. From each crown preparation, one LDS crown was constructed using an E4D scanner/E4D milling unit (E4DS/E4DM) and TRIOS 3 scanner/Sirona inLab MC X5 milling unit (TRIO/MCX5) at cement space settings of 50, 100 and 200 μm. Each LDS crown was positioned onto the original crown preparation, and then a stereomicroscope was used to make three vertical marginal gap measurements at four locations (mid-buccal, mid-lingual, mid-mesial and mid-distal). The mean marginal gap (MMG) was calculated for each crown and each individual tooth surface.

RESULTS

The MMGs of CAD/CAM LDS crowns constructed by TRIO/MCX5 were 72.31 at 50, 63.73 at 100 μm and 46.23 μm at 200 μm, which were smaller than E4DS/E4DM at each cement space.

CONCLUSIONS

Increasing the cement space decreased the MMG in both scanner/milling unit combinations. The smallest MMG was found using the newer scanner/milling unit at the 200 μm cement space. © 2024 Australian Dental Association.

The marginal gaps of sequentially milled lithium disilicate crowns using two different milling units

BACKGROUND

The purpose of this study was to compare the marginal gaps of sequentially milled lithium disilicate (LDS) crowns using two different milling units.

METHODS

One lower left first molar typodont tooth prepared for an LDS crown by an undergraduate student in a simulation clinic was selected. The crown preparation was scanned by a TRIOS 3 scanner and twelve LDS crowns milled by an E4D (E4DM) and a Sirona inLab MC X5 (MCX5) milling unit using identical settings. The crowns were seated onto the original crown preparation and three vertical marginal gap measurements were taken at four locations (mid-buccal, mid-lingual, mid-mesial and mid-distal) using a stereomicroscope. The mean marginal gap (MMG) was calculated for each individual tooth surface and each crown.

RESULTS

The MMG for the E4DM (100.40 μm) was not significantly different to the MCX5 (101.08 μm) milling unit (P = 0.8809). In both units, there was a statistically significant trend of increasing MMG with sequentially milled crowns using the same burs (E4DM P = 0.0133; MCX5 P = 0.0240).

CONCLUSIONS

The E4DM and MCX5 milling units produced LDS crowns with similar MMG's and within a clinically acceptable range but with a trend of increasing MMG when analysed sequentially. © 2022 Australian Dental Association.

The marginal gaps of lithium disilicate crowns constructed by different scanner and milling unit combinations

BACKGROUND

The purpose of this study was to compare the marginal gaps of CAD/CAM lithium disilicate (LDS) crowns constructed using three different scanner and milling unit combinations.

METHODS

Twenty-four Columbia model lower left molars were prepared for LDS crowns by undergraduate students in a simulated environment. One LDS crown was constructed for each crown preparation using each of the following intraoral scanner/milling unit combinations: TRIOS 3 scanner/E4D milling unit (TRIO/E4DM); TRIOS 3 scanner/Sirona inLab MC X5 milling unit (TRIO/MCX5); E4D scanner/E4D milling unit (E4DS/E4DM). The crowns were seated onto the original crown preparations and three vertical marginal gap measurements taken at four locations (mid-buccal, mid-lingual, mid-mesial and mid-distal) using a stereomicroscope. The mean marginal gap (MMG) was calculated for each crown and each individual tooth surface.

RESULTS

The TRIO/MCX5 scanner/milling unit combination produced the smallest MMG of 63.73 ± 47.38 μm followed by E4DS/E4DM (88.64 ± 106.51 μm) and TRIO/E4DM (107.41 ± 76.47 μm). There was a significant effect of milling unit (p < 0.0001) on MMG but no significant effect of scanner (p = 0.070) or location (p = 0.182).

CONCLUSIONS

The newer scanner/milling unit combination produced LDS crowns with the smallest MMG. All scanner/milling unit combinations produced LDS crowns within a clinically acceptable MMG.