Effectiveness of universal adhesives for orthodontic bonding to enamel and restorative materials: A systematic review

Universal adhesives (UAs), introduced in 2011, are well established in restorative dentistry but remain relatively unexplored in orthodontics, where their capacity to bond to enamel and multiple restorative materials could simplify bonding protocols and reduce the need for primers. This systematic review evaluated the bond strength of UA for orthodontic applications - including bracket bonding, fixed retainers, and bonding to restorative surfaces - compared with conventional adhesives.

Searches were conducted in PubMed, Embase, Scopus, Web of Science, and the Cochrane Library, supplemented by Google Scholar and reference lists. The protocol was registered in PROSPERO (ID: CRD420250654277). The search covered 2011 to 1 December 2024. Eligible studies were in vitro, in vivo, or clinical studies in English assessing UA for orthodontic bonding. Exclusion criteria were case reports, reviews, abstracts, theses, and non-orthodontic applications. Risk of bias was assessed with QUIN tool (in vitro) and RoB-2 (clinical).

Of 401 records, 323 remained after removing duplicates; 248 were excluded at title/abstract and 38 at full text, leaving 37 studies (36 in vitro; 1 with an in vitro and clinical component). Seven orthodontic applications were investigated. UA generally provided sufficient bond strength, except on some metal restorations. On enamel, phosphoric-acid etching for 15s improved adhesion. On ceramics, hydrofluoric acid etching (HF) or sandblasting enhanced performance. For polymethyl-methacrylate (PMMA) and composite restorations, bur roughening or sandblasting improved results.

UAs may simplify orthodontic bonding across enamel and restorative surfaces without separate primers, but more clinical studies are needed.