In vivo evaluation of the enamel wear of primary molar against four types of crowns using the intra-oral scanner.

Background: Primary tooth wear is a common phenomenon that affects chewing ability, dental sensitivity, aesthetics, and occlusion. This study was conducted to compare the antagonistic enamel wear of primary molars opposed to four different crown materials.

Methods: Forty lower second primary molars of children aged 4-8 years were allocated into 4 groups: Group 1 (n = 10): received stainless steel crowns; Group 2 (n = 10): received prefabricated commercially available zirconia crowns (NuSmile); Group 3 (n = 10): received locally manufactured zirconia crowns created via the CAD/CAM system; and Group 4 (n = 10): received locally manufactured hybrid ceramic (Vita Enamic) crowns created via the CAD/CAM system. All the crowns were cemented with resin-modified glass ionomer cement. The upper arch was scanned with a 3D intraoral scanner immediately (baseline), 6 months, and 1 year after crown cementation to evaluate the wear of the natural enamel of the antagonistic primary molar. The resultant scans were compared via Exocad software to measure the amount of linear wear of the mesiopalatal cusp of the primary upper second molar.

Results: The analysed data revealed statistically significant differences between the studied groups. The highest mean wear was detected in the CAD/CAM zirconia crown group, followed by the NuSmile zirconia crown group and then the CAD/CAM hybrid crown group, and the lowest mean wear was detected for the stainless-steel crown group.

Conclusion: Compared with stainless steel crowns, aesthetic crowns cause more wear in the antagonistic primary molar enamel. CAD/CAM zirconia crowns induce the greatest amount of wear, followed by NuSmile zirconia crowns. The CAD/CAM hybrid crown is an aesthetic tooth-coloured crown that causes less wear of the opposing enamel than zirconia crowns do.

Trial Registration: The ClinicalTrials.gov Protocol Registration and Results System (PRS) has this RCT registered as (NCT06456879) on 07/06/2024.