Effect of surface treatments and adhesive materials on the shear bond strength of PET-G aligner material.

PURPOSE: To evaluate the effects of surface treatments and adhesive materials on the shear bond strength to a polyethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate (PET-G) clear aligner material. METHODS: PET-G specimens were randomly assigned to eight non-factorial groups (n = 11 per group). Transbond XT, LC Orthomite, and Super-Bond were evaluated without pretreatment and after alumina abrasion; Transbond XT was additionally tested with primer alone and with alumina abrasion plus primer. Shear bond strength was measured at 0.5 mm/min. Failure modes and debonded surfaces were examined by stereomicroscopy and field-emission scanning electron microscopy (FE-SEM). Data were analyzed using the Kruskal-Wallis and Steel-Dwass tests (α = 0.05). RESULTS: Super-Bond showed significantly higher bond strength (25.1-27.0 MPa) than Transbond XT and LC Orthomite under untreated and alumina-abraded conditions. For Transbond XT, alumina abrasion, primer, and their combination significantly increased bond strength. Alumina abrasion also significantly increased LC Orthomite bond strength. Adhesive failure predominated in low-strength groups, whereas cohesive failure within PET-G or mixed failure was frequent in high-strength groups. CONCLUSION: Under the present conditions, Super-Bond showed high initial bond strength without pretreatment. Primer application and alumina abrasion improved Transbond XT bond strength, whereas alumina abrasion improved LC Orthomite bond strength.