Weibull analysis of bond strength of orthodontic buccal tubes bonded to resin composite surface with various techniques

The objective of this study was to analyze the survival probabilities of various surface preparation techniques for bonding buccal tubes on resin composite surface. Resin composite specimens (hybrid), 33 per group were prepared. 8 experimental groups were (1) sandblast 90 μm; (2) sandblast 50 μm; (3) abrasion using diamond bur; (4) hydrofluoric acid etching for 1 min (HF 1 min); (5) HF 2 min; (6) HF 3 min; (7) 37% orthophosphoric etching for 10 min (H₃PO₄ 10 min) and (8) control (unetched surface). Plastic conditioner was applied then buccal tubes were bonded. Shear bond strength was tested with the universal testing machine and the Weibull analysis was performed. The results at a stress level of 7.8 MPa and 10 MPa, revealed the probabilities of survival for sandblast 50 μm (100%, 99.9%), sandblast 90 μm (99.7%, 98.7%), diamond bur (98.3%, 93.4%), HF 2 min (95.9%, 85.3%), HF 1 min (78.3%, 61.4%), HF 3 min (70.6%, 46.3%), H₃PO₄ 10 min (61.4%, 44.5%) and control (26.3%, 6.9%), respectively. Therefore, surface preparation by sandblast (50 μm and 90 μm), or diamond bur followed by plastic conditioner were highly effective for bonding orthodontic buccal tubes on hybrid resin composite surface. HF 2 min was acceptable. However, HF 1 min, 3 min, H₃PO₄ etching and unetched surface could not achieve adequate bond survival.