Does relative bracket base area affect the accuracy of reconstructed buccal surface in the virtual bracket removal technique?

Background: Virtual bracket removal (VBR) facilitates efficient retainer fabrication for fixed orthodontics in a digital workflow. This study is aimed at assessing the influence of the relative bracket base area (RBA), representing the proportion of the labial/buccal surface area intended for removal, on the surface reconstruction accuracy in the VBR technique.

Methods: 196 teeth from seven resin dental models were included. The maximal bracket base surface area (MBA) was determined by the rectangular area extending to the lateral edges of the tooth labial/buccal surface. On each tooth, diverse RBA percentages (20-100% in 10% increments) of the MBA was removed, respectively. Following removal, the buccal surfaces of the teeth were digitally reconstructed. Subsequently, the root mean square (RMS) values, which represent the surface deviations between the reconstructed and original dentitions was calculated for each tooth. The obtained RMS values were compared within and among groups of different RBAs and compared with the clinically acceptable limit (CAL) of 0.05 mm.

Results: As the RBA increased, there was a discernible trend of elevated RMS values, both for the overall dentition and each specific tooth type. Among the lower teeth, the molars consistently displayed the highest RMS values in almost all groups, with significantly higher mean/median RMS values compared to the lower incisors (P < 0.05), excluding the 0.2MBA group. Specifically, across all tooth types, the mean/median RMS values in groups with 20-80% MBA were significantly lower than CAL of 0.5 mm (P < 0.05). This trend persisted for all tooth types in the 0.9MBA group except the lower canines and molars.

Conclusion: The mean/median RMS values elevated as the RBA increased. VBR technique remains sufficiently accurate for retainer fabrication, provided that the RBA remains below 80% of the MBA for lower canines and molars and 90% for all the other tooth types. Notably, residual bonding materials should be considered in clinical use because they are also removed in VBR and thereby constitute a portion of RBA.