Clinical procedures
tooth
Forty-eight first permanent molars with extensive tissue loss were included in the study. At least two affected first permanent molars from the same child were randomly assigned to one of the following groups (n = 24/group): group 1; SSC (3 M ESPE, St. Paul, MN), and group 2; ZC (NuSmile Zirconia Pediatric Crowns, Houston, TX).Local anesthesia was applied and a suitable crown size was determined prior to preparation by measuring the mesiodistal width of the tooth by a caliper. Then the teeth were cleaned with a slow-speed rotary bristle brush.In the SSC group, the following preparation protocol was used [For ZC, the standard preparation protocol was: occlusal reduction and supragingival circumferential reduction, followed by the preparation of a knife-edge subgingival (1-1.5 mm) finishing line with a tapered bur. A pink try-in crown (NuSmile) was used to check the size, passive fit, and occlusion. Then a white crown of the same size was filled with light-cured resin-modified glass ionomer cement (BioCem; NuSmile), and the crown was cemented in place under cotton roll isolation. The crown was tack-cured from buccal and lingual aspects for 5 s to facilitate easy removal of excess cement from the zirconia surface. Then, the final photopolymerization of 40 s was employed from both buccal and lingual aspects. A new LED light-curing unit (Elipar Deep Cure, 3MESPE, MN) was used.