Retention of Pediatric BioFlx Crowns Versus Stainless Steel Crowns Using Different Types of Luting Cements: An In Vitro Study

BioFlx crowns (BFCs) have been introduced in the dental market, combining the flexibility of stainless steel crowns (SSCs) with the esthetic appeal of preformed zirconia crowns. However, the existing literature does not provide adequate insights regarding the retentive strength of various types of luting cement with these newly developed BFCs. Therefore, this study aimed to evaluate and compare the retentive strength of BFCs and SSCs with different types of luting cement (glass ionomer cement [GIC], resin-modified glass ionomer cement [RMGIC], self-adhesive resin cement [SARC], and polycarboxylate cement [PXC]). A total of 160 standardized resin dies were fabricated and divided into two groups based on the type of crown (BFCs or SSCs). Each group was further subdivided into four subgroups (20/group) based on the luting cement used for cementing the crown on the die. A pullout test was performed using a universal testing machine to measure the retentive strength required for crown dislodgement. The residual cement in the crown was scored to determine the cement failure pattern. Data were analyzed using two-way analyses of variance (ANOVAs) to evaluate the interaction between the cement and the type of crown on retentive strength, followed by an independent <i>t</i>-test. Furthermore, Welch's ANOVA and Dunnett's T3 test were used to assess the impact of various types of luting cement on the retentive strength of each crown. The CFP was assessed by comparing the scores using descriptive statistics. Statistical significance was set at <i>p</i> < 0.05. The mean retentive strength of SSCs and BFCs was the highest with SARC (560.29 ± 8.74 N; 657.72 ± 20.60 N), followed by RMGIC (534.20 ± 22.84 N; 454.90 ± 7.95 N) and GIC (435.14 ± 8.66 N; 237.68 ± 9.37 N), while the lowest was with PXC (365.67 ± 19.11 N; 131.26 ± 5.37 N). A significant difference in retention was observed between the crowns (<i>p</i> < 0.05). Cement failure primarily manifested as adhesive failures in the SARC and RMGIC groups; however, both adhesive and cohesive failures occurred in the GIC and PXC groups. Thus, SSCs demonstrate significantly higher retention than BFCs across all types of luting cements, except when using SARC. Within the limitations of this in vitro study, SSCs emerge as the preferred choice for full-coverage restorations that require optimal retention and durability. Nevertheless, BFCs with SARC provide a viable alternative when esthetic considerations are prioritized.