Three-dimensional Evaluation of Tooth Preparation Forms in Paediatric Zirconia Crowns: An in Vitro Study

Background: Though prefabricated zirconia crowns (PZCs) differ from stainless steel crowns and have different preparation guidelines for optimal crown adaptation, little is known about how clinicians prepare teeth for PZCs.

Aim: To investigate the 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 on the reference. Three-dimensional analysis 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 0.2 mm (p < .001) in maxilla. 41.6% of surfaces showed error within 0.2 mm, and 20% were excessively prepared (p = .002) in mandible. The highest discrepancies were found at the mesiopalatal line angles (maxillary) and at the distobuccal line angles (mandibular). Significant discrepancies were observed on the occlusal surfaces, especially at the cusps.

Conclusions: Tooth preparations for PZCs showed wide variations related to depth among the participants.