Fracture Resistance of Prefabricated Esthetic Crowns for Primary Molars

Purpose: To assess the fracture resistance of prefabricated esthetic crowns for primary molars. Methods: Seventy-two human mandibular second primary molars were divided into three groups: preveneered stainless steel crowns (VSS), prefabricated zirconia crowns (PZ) and BioFlx crowns (BF). Crowns were cemented with glass ionomer cement; for each group, 12 samples were tested for fracture resistance and 12 samples underwent 5,000 thermocycles before testing. The fracture mode was assessed for all the samples. Differences in the fracture resistance values between the groups were tested using analysis of variance (ANOVA), followed by Tukey's post hoc test, while the distribution of fracture modes was tested using Fisher's exact test. Statistical significance was set at P =0.05 and analyses were conducted using SPSS version 25.0 software. Results: ANOVA tests indicated a significant difference in fracture resistance among the test groups (P <0.001). The groups were ranked as follows: before thermocycling- (1) PZ group (3,327±1497), (2) BF group (1,694±163) and (3) VSS group (536±12); and after thermocycling-(1) PZ group (3,308±162), (2) BF group (1,579±77) and (3) VSS group (413±16). Tukey's post hoc analysis indicated that the PZ group exhibited a significantly higher fracture resistance than the BF and VSS groups (P <0.001). The VSS group showed a predominance of minimal cracks (5.6 percent) and loss of less than half of the crown (11.1 percent). Conclusions: PZ yielded the highest resistance, followed by BF crowns. VSS may require caution in high-stress areas due to their susceptibility to esthetic component failure, although the underlying crown remains functional.