LAUSR

BACKGROUND Though prefabricated zirconia crowns (PZCs) have different properties from stainless steel crowns and different tooth preparation principles for optimal crown adaptation, little is known about how clinicians prepare teeth for PZCs. AIM To investigate prepared tooth forms for PZCs and identify the shared patterns of tooth preparation. DESIGN Twenty participants prepared primary maxillary first molars and mandibular second molars for PZCs. A model with ideally prepared tooth was digitally generated as a reference. The prepared teeth were digitally scanned and superimposed to the reference. A three-dimensional analysis software (Gom Inspect 2018 software) was used to evaluate the discrepancy between ideal and prepared surface for overall surface and subdivided area. RESULTS Half of the surfaces received excessive reduction, and 24 % showed error within 0.2mm (p < 0.001) in maxilla. 41.6 % of surfaces showed error within 0.2mm and 20 % were excessively prepared (p = 0.002) in mandible. The highest discrepancies were at the mesiopalatal line angles (maxillary) and the distobuccal line angles (mandibular). There were significant discrepancies on the occlusal surfaces, especially the cusps. CONCLUSIONS Tooth preparations for PZCs showed wide variations related to depth among the participants.