Conventional and Self-Etching Adhesive Effects on Retention of Luting Resins

Objectives: To compare the effectiveness of luting resins for orthodontic bracket bonding on enamel treated with H₃PO₄ or a self-etching adhesive. Methods: Advantage (ADV, OrthoOrganizers) and iBond (IBO) with Durafill (DUR, Heraeus Kulzer) were evaluated. Human enamel, ground on SiC paper #600 or cleaned with Prophy Paste, was treated with H₃PO₄ (ADV) or IBO and assessed by SEM. Shear bond strengths (SBS) were evaluated on abraded enamel after specimen storage in 37 C water for 10 min, 1, 7, or 30 days (n = 8). Additionally, SBSs were measured after 24 h storage of IBO/ADV and H₃PO₄/DUR specimens. Fractures were classified as adhesive, cohesive, or mixed failures. Flexural strengths (FLS) and moduli (FLM) of the resins were determined at conditions and time intervals as above (n = 6). Data treatment: ANOVA, Duncan?fs test (p<0.05), and regression analyses. Results: IBO creates shallower etching patterns than H₃PO₄. The morphology on abraded or prophied enamel with H₃PO₄ and IBO, respectively, is very similar. SBSs of H₃PO₄/ADV and IBO/DUR increased from 23 and 12 MPa after 10 min (p<0.05) to averages of 35 and 20 MPa between 1 and 30 days (p>0.05). After 24 h H₃PO₄/ADV showed 38, H₃PO₄/DUR 27 MPa, IBO/ADV and IBO/DUR 28 and 18 MPa. Twenty H₃PO₄/ADV specimens had cohesive and 12 mixed failures, the figures for IBO/DUR were 15 and 17. FLS and FLM of both luting resins increased with prolonged storage (p<0.05). At all testing times the FLS of DUR was 75%, the FLM 25% of ADV, approximately. SBS vs. FLS and FLM were linearly correlated (r>0.9). Conclusion: Although IBO offers lower SBS than H₃PO₄ etched enamel and although the microfilled resin DUR provides less SBS than ADV, IBO/DUR is less invasive, protects enamel better from cracking during bracket debonding, and resin remnants are presumably easier removed from enamel.