Effect of glass infiltration on the retentive force of prefabricated pediatric zirconia crowns: an in vitro study

Background Prefabricated zirconia crowns are increasingly used in pediatric dentistry, but reliable cement retention remains challenging. Glass infiltration may create an etchable, silica-containing internal surface when combined with appropriate conditioning procedures; however, its effect on crown retention remains unclear. This study compared the pull-out retentive force of three pediatric zirconia crown and surface-treatment protocols. Methods Twenty-four specimens were allocated equally into three groups ( n = 8 per group) according to crown type and internal surface protocol: Kids Zirconia Crown (Shinhung, Seoul, South Korea) with no additional surface pretreatment (KZC), KKU KidCrown (Khon Kaen University, Khon Kaen, Thailand) without glass infiltration and treated with 50 μm Al₂O₃ airborne-particle abrasion (KKC-NG), and glass-infiltrated KKU KidCrown treated with 9.5% hydrofluoric acid etching for 60 s followed by ceramic primer application (KKC-GI). Standardized 3D-printed resin abutments simulating primary maxillary right central incisors were used for cementation. All crowns were cemented with self-adhesive resin cement, stored for 24 h, and tested using a universal testing machine at a crosshead speed of 1.0 mm/min until crown dislodgement. Pull-out retentive force was recorded in newtons and analyzed using one-way ANOVA followed by Tukey’s post-hoc test (α = 0.05). After pull-out testing, one specimen from each group was examined stereomicroscopically to qualitatively assess the failure mode. Results Mean retentive force differed among protocols (F(2, 21) = 6.95, p = 0.005). KKC-GI showed the highest value (216.51 ± 40.84 N) and was significantly higher than KKC-NG (136.91 ± 66.52 N; p = 0.012) and KZC (134.44 ± 37.81 N; p = 0.010); KKC-NG and KZC did not differ ( p = 0.995). Stereomicroscopic examination of the specimen from each group showed mixed adhesive and cohesive failure features. Conclusions Within the limitations of this in vitro study, the KKC-GI protocol, which incorporated glass infiltration followed by hydrofluoric acid etching and ceramic primer application, demonstrated the highest immediate pull-out retentive force among the tested protocols. These findings suggest that, under controlled laboratory conditions, this combined surface-treatment protocol may enhance the initial retention of pediatric zirconia crowns and provide a rationale for further clinical validation.