Discussion
extensive multi-surface caries, tooth
Full coverage restoration of permanent molars with SSCs has been recommended for the treatment of extensive multi-surface caries, developmental enamel and dentinal defects, carious partially erupted molars and after endodontic treatment [Despite those advantages, however, the use of SSCs in primary molars appears to be more common than in permanent molars [More recently, preformed zirconia crowns for permanent molars have been introduced as an esthetic alternative to permanent molar SSCs. Although many studies are present comparing the SSCs and ZCs on primary molars, to the best of our knowledge, no clinical trial has been published on the clinical performance of permanent molar ZCs. Permanent molar ZCs can be utilized in partially erupted molars and can be installed in a single session without the requirement for analog or digital impressions, in addition to the inherent benefits of primary molar ZCs [In the present study, the crowns were placed and assessed during the COVID-19 pandemic. Even though this circumstance had an impact on the study’s intended sample size, the achieved sample size was still adequate based on the estimation with 80% power. Restorative treatments have dramatically decreased during the pandemic [The results of the present study should be assessed along with a number of limitations. First, the examiners could not be blinded due to the color difference of the crowns. Second, Covid-19 pandemic caused challenges in recruiting additional patients who met the inclusion criteria and accepted participating in the study, likewise other clinical trials. Another limitation was that the indications for SSCs and ZCs might be different since tooth preparation is more extensive for zirconium crowns which required more patient compliance. Neither crown type led to visible, clinically-detectable wear on antagonist tooth, but measuring the quantification of enamel wear with three dimensional (3D) techniques [