Accuracy of the preparation depth in mixed targeted restorative space type veneers assisted by different guides: An in vitro study.

PURPOSE

Most veneers are mixed targeted restorative space (MTRS)-type restorations that are partially within the original tooth and require inconsistent preparation depths. This study aimed to evaluate the accuracy of the preparation depth for MTRS veneer preparation.

METHODS

MTRS veneer preparation models were developed using the twisted maxillary central incisor (MCI) as the original tooth and the standard MCI as the waxing. Veneer preparations were performed using freehand (MF), silicone (MS), thermoplastic (MT), 3D-printed uniform (MD), and auto-stop (MA) guides. The prepared and original MCI were scanned and superimposed using a custom-made base. The mean absolute differences (MADs) were measured to evaluate the accuracy of the preparation depth. Statistical analysis was performed using the multivariate analysis of variance (MANOVA) test (α=0.05).

RESULTS

The accuracy of the preparation depth was 0.237±0.090, 0.191±0.099, 0.149±0.078, 0.093±0.050, and 0.059±0.040 mm in MF, MS, MT, MD, and MA, respectively. The MADs between the groups were significant (P<0.05). The accuracy of the trial restoration was 0.140±0.081 mm in the MS, and the accuracy of the guiding tube was 0.055±0.033, 0.036±0.011, and 0.033±0.010 mm in the MT, MD, and MA, respectively.

CONCLUSIONS

In MTRS veneer preparation for MCI, tooth preparation guides improved the accuracy of the preparation depth by visualizing the TRS profile and providing clear measurement points. The accuracy of the guide is influenced by its flexibility, and the accuracy of the preparation depth is affected by the accuracy of the measurement points.