Comparison of Coronal Restorations in Primary Molars After Root Canal Treatment Under General Anesthesia: A 2-Year Follow-up

Abstract

Background: Dental caries in primary teeth often progresses to pulpitis, compromising masticatory function and permanent tooth development. Although root canal treatment (RCT) preserves affected teeth, long-term success depends on durable restorations, which is particularly critical in general anesthesia (GA) settings, where severe caries and poor cooperation necessitate definitive treatment. However, the comparative efficacy of stainless steel crowns (SSCs), SonicFill bulk-fill resin, and conventional layered resin under GA remains unclear. Objectives: This study aimed to evaluate the long-term efficacy of three coronal restorations after RCT in primary molars performed under GA. Methods: This retrospective cohort study included 120 children who underwent primary molar RCT under GA between 2021 and 2022 at a tertiary pediatric hospital in Shanghai, China. Patients were allocated to the SSC, SonicFill, or layered resin groups (n = 40 each) according to parental choice. Follow-up evaluations were conducted at 3, 12, and 24 months. The primary outcome was restoration success at 24 months. Secondary outcomes included restoration integrity, marginal adaptation, and secondary caries, assessed using the American Public Health Association (APHA) criteria at all time points, as well as occlusal function and parental satisfaction at 12 months. The analysis applied the worst-tooth principle, with a tooth-level generalized estimating equation (GEE) sensitivity analysis. Between-group comparisons were performed using Fisher exact test with Bonferroni correction (α = 0.017). Effect estimates included risk difference (RD), relative risk (RR), number needed to treat (NNT), and 95% CIs. Multivariable logistic regression was adjusted for prespecified confounders, including age, sex, caries extent, and tooth arch. Results: At 24 months, SSCs showed higher success rates than SonicFill (97.5% vs 80.0%; RD, 17.5%; P = 0.015) and layered resin (97.5% vs 75.0%; RD, 22.5%). All 120 patients completed follow-up at all three time points (3, 12, and 24 months), resulting in 100% follow-up completeness. Multivariable analysis confirmed an increased risk of failure with SonicFill (adjusted odds ratio [aOR], 6.8; 95% CI, 1.4 - 33.2) and layered resin (aOR, 9.5; 95% CI, 1.9 - 47.6) compared with SSCs. The resin groups showed time-dependent deterioration (P < 0.01), whereas SSCs remained stable (P = 0.368). SSCs also achieved the highest occlusal function scores and parental satisfaction. Conclusions: Stainless steel crowns are the preferred restoration for primary molars after RCT under GA, with advantages attributable to their mechanical properties. SonicFill may serve as a short-term alternative (≤ 1 year). Layered resin should be used with caution in GA settings.