Restorative Treatment and Marginal Integrity in Patients with NonCarious Cervical Lesions: Analysis of a Randomized Clinical Trial

Background: Non-carious cervical lesions are difficult to restore because enamel and dentin margins provide different bonding substrates and may deteriorate differently over time. This secondary analysis evaluated whether Er,Cr:YSGG laser preparation, with or without phosphoric-acid conditioning, influenced marginal integrity compared with conventional bur preparation followed by etching. Methods: Aggregate data from a randomized clinical trial of 75 Class V resin-composite restorations were analyzed at baseline and 6, 12, and 24 months. Marginal integrity was evaluated separately at enamel-composite and dentin-composite interfaces using ordinal C-criteria. Post-baseline distributions were compared using Fisher-Freeman-Halton exact tests. Perfect margins (code 0) were additionally summarized with Wilson 95% confidence intervals, risk ratios, and absolute risk differences. Anatomical form, marginal ledge, and marginal discoloration were exploratory outcomes. Results: Treatment-group differences were concentrated at the enamel interface. Perfect enamel margins at 12 months occurred in 73.3% of laser-plus-etch, 62.5% of laser-without-etch, and 20.8% of bur-plus-etch restorations (global p = .007); at 24 months, the corresponding values were 57.1%, 46.7%, and 14.3% (global p = .016). At 12 months, laser plus etching yielded a risk ratio of 3.52 (95% CI 1.60-8.35) for preserving a perfect enamel margin versus conventional treatment. Dentin-margin distributions did not differ significantly at any follow-up. Enamel marginal ledge and discoloration findings were directionally consistent with the primary result. Conclusion: Laser-based preparation was associated with better preservation of enamel-composite marginal integrity over 24 months, whereas no comparable dentin-margin advantage was demonstrated. Additional acid conditioning may support enamel performance, but the small aggregate dataset warrants cautious interpretation.