Clinical resolution of oral lichenoid lesions after amalgam replacement: A systematic review and meta-analysis of observational studies

Introduction Oral lichenoid lesions (OLLs) can mimic oral lichen planus but are often linked to contact with dental amalgam. Replacement with biocompatible materials has been associated with lesion resolution, yet prior evidence lacked quantitative synthesis. Materials and methods Following PRISMA 2020 (PROSPERO: CRDXXXXXXXXXX2), eight databases (1986–2024) were searched for adult in vivo studies reporting OLL resolution after amalgam replacement. Two reviewers independently screened, extracted data, and assessed bias (ROBINS-I, Newcastle–Ottawa Scale, JBI). Random-effects meta-analysis estimated pooled odds ratios (OR) for clinical resolution; certainty was graded with GRADE. Results Of 2368 records, 35 studies were qualitatively synthesized and 11 entered meta-analysis (N = 365). Amalgam was replaced with glass ionomer, ceramics, composite resin, or gold alloys. Replacement markedly increased odds of lesion resolution (OR = 122.18; 95 % CI: 55.64–268.26; p < 0.001) with moderate heterogeneity (I 2 = 42 %). Risk of bias across observational studies was generally low to moderate. Funnel-plot asymmetry and Egger's test (p < 0.001) suggested publication bias; overall certainty was moderate. Subgroup analyses indicated greater benefit when lesions had direct amalgam contact, when patch testing was positive, and when ceramics or gold were used. Sensitivity analyses supported strength of the primary findings. Conclusion Amalgam replacement was linked with substantially higher odds of OLL resolution. However, between-study heterogeneity and indications of publication bias temper confidence in the pooled effect. Confirmatory, prospective, registered studies with standardized diagnostic criteria, outcome definitions, and material categories are needed to refine effect size estimates and strengthen certainty.