Contemporary Orthodontic Bonding: A Systematic Review of Surface Preparation for Enamel and Restorative Substrates

Objective: Orthodontic bonding has evolved with the growing number of adult patients presenting with dental restorations. This systematic review synthesizes current evidence from open-access sources on surface preparation protocols for bonding to natural enamel and restorative substrates, including zirconia, composite resin, and glass ceramics. Methods: A systematic search and qualitative synthesis were performed following PRISMA guidelines. Electronic databases (PubMed, Cochrane Library) were searched for open-access publications between January 2013 and February 2026. Scopus was not searched as it requires an institutional subscription, which would compromise the transparency and reproducibility of this review. Inclusion criteria: systematic reviews, randomized controlled trials, and in vitro studies reporting shear bond strength or clinical failure rates for orthodontic bonding to enamel or restorative substrates. Exclusion criteria: non-English publications, case reports, opinion pieces, paywalled articles, and studies without clear outcome measures. Due to heterogeneity in methodologies and outcomes, a qualitative synthesis was performed. The study selection process followed PRISMA guidelines and is illustrated in the PRISMA flow diagram (Supplementary File 2). Results: Three eligible open-access studies met the predefined inclusion criteria and were included in qualitative synthesis. For natural enamel, 37% phosphoric acid etching for 15-60 seconds remains the benchmark, with self-etch primers showing higher clinical failure rates (Peto OR 1.55; 95% CI 1.16-2.07) based on a Cochrane systematic review encompassing 20 randomized controlled trials (n=1,305 participants). For high-translucent zirconia, tribochemical silica coating combined with MDP-containing adhesives yields the highest shear bond strength (17.93 ± 2.88 MPa), whereas hydrofluoric acid is ineffective (4.68 ± 1.75 MPa). Composite restorations require mechanical roughening and phosphoric acid etching; however, very high-strength adhesives may increase the risk of restoration fracture during debonding. Clinical situations such as recent fluoride exposure and MIH require modified protocols including three-week delay or deproteinization with 5% NaOCl. Conclusions: Surface preparation must be substrate-specific. No universal protocol exists; appropriate pretreatment is essential to optimize bond strength, clinical longevity, and prevention of iatrogenic damage during debonding. All conclusions are drawn from publicly available, open-access sources, ensuring global accessibility and verifiability.