Retention of Bioflx crowns, Zirconia Crowns Compared to Stainless Steel Crowns: In Vitro

Abstract

Aim The aim of this study was to conduct an in vitro comparison of the retention of Nusmile BioFLX crowns, EZ Sprig zirconia crowns, and the standard-of-care stainless steel crowns on extracted primary mandibular second molars. Materials and Methods A total of 54 extracted primary mandibular second molars were randomly assigned to one of three experimental groups: BioFLX crowns (BFCs), stainless steel crowns (SSCs), or EZ Sprig crowns (EZCs), with 18 teeth in each group (N = 18). All teeth were mounted in self curing acrylic molds and prepared for crown cementation. The crowns were cemented using Ketac-Cem Maxicap, and periphery blue wax was applied around the crown margins. The coronal sections were subsequently mounted in acrylic. Retention testing was performed using an Instron 68TM- 10 machine, with pull-out tests conducted at a rate of 0.5 mm per minute until failure occurred. The force at the point of failure was recorded in Newtons (N). Differences in retention among the groups were analyzed using the Kruskal-Wallis test, and post-hoc comparisons were performed using Dunn’s test with Bonferroni correction. Results The Kruskal-Wallis H test revealed a significant difference among the three groups (P = 0.03). The highest mean force in Newtons was observed in the SSC group, with a mean force of 180.38 (standard deviation = 1.96). In contrast, the EZ Sprig group exhibited the lowest mean force of 133.65 (standard deviation = 37.41), while the BioFLX crowns group fell in between, with a mean force of 168.62 (standard deviation = 37.81). Post-hoc pairwise comparisons using Dunn’s test with Bonferroni correction indicated that the difference between the SSC and EZ Sprig groups was statistically significant (P = 0.04). However, comparisons between the BioFLX group and the other groups were not statistically significant (BioFLX vs. SSC, P = 1.00; BioFLX vs. EZ Sprig, P = 0.09). Conclusion There was no statistically significant difference in retentive strength when Bioflx crowns were compared to zirconia crowns and stainless-steel crowns. However, stainless steel crowns demonstrated significantly higher retention than zirconia crowns while exhibiting comparable retention to Bioflx crowns.