Effect of Bioflex crowns on periodontal health of primary molars indicated by interleukin-1 beta levels in gingival crevicular fluid: a randomized controlled clinical trial

Background Stainless-steel crowns (SSCs) are durable and cost-effective, but do not fulfill aesthetic demands. This randomized controlled clinical trial compared the effects of Bioflex crowns and SSCs on the periodontal health of primary molars by measuring interleukin-1 beta (IL-1β) levels in the gingival crevicular fluid (GCF). Methods A clinical split-mouth RCT was conducted on 20 children (4–8 years) who required full-coverage restorations on bilateral primary molars. In each child, one molar received a Bioflex crown, while the contralateral molar received an SSC. A third sound tooth served as an internal healthy control (total 60 teeth). GCF IL-1β concentration was measured at baseline and 7 and 90 days post-cementation using enzyme-linked immunosorbent assay (ELISA). Plaque Index (PI) and Gingival Index (GI) were recorded at all visits. Data were analyzed using generalized linear mixed models. Results Baseline IL-1β levels were comparable ( p > 0.05). At day 7, IL-1β levels significantly increased in the SSC group compared with the Bioflex and control groups ( p < 0.001). By day 90, IL-1β levels in the SSC group decreased, and both SSC and Bioflex groups showed comparable results. No statistically significant differences in GI or PI scores were observed. Conclusions Bioflex crowns demonstrated a more favorable early inflammatory response, indicated by the lower GCF IL-1β levels at day 7. By day 90, this initial inflammatory difference had resolved, and both crowns showed comparable periodontal health. These findings suggest that Bioflex crowns offer an esthetic full-coverage restorative option for primary molars without adversely affecting periodontal health. Trial registration Pan African Clinical Trial Registry ( www.pactr.samrc.ac.za ; #PACTR202511815030369). Retrospectively registered on 17 November 2025.