Evaluation of the effect of demineralizations developed around orthodontic brackets bonded with different types of adhesive agents on shear bond strength: In-vitro study

Aim: The objective of this study was to evaluate, under laboratory conditions, effect of demineralization on shear bond strength of orthodontic brackets bonded with different adhesive agents. Methods: Sixty extracted human maxillary premolars with bonded Gemini metal brackets were divided into three groups of 20 samples each. Demineralized and bracketed teeth bonded with Transbond™XT (acid+primer+adhesive) in Group 1, GC Ortho Connect®(acid+one-step adhesive) in Group 2, and Transbond™Plus(primer+adhesive) in Group 3. Samples with mean demineralization values determined at baseline (T0) and after 28 days in artificial cariogenic solution (T1) were tested under cyclic loading using low-cycle, closed-loop fatigue machine (10N capacity, 300mm/min), and shear bond strength was compared based on number of strokes to failure. Results: No significant differences were found among the groups in demineralization values at T0 and T1 (p>0,05). At T1, compared with T0, all groups showed significant increase in demineralization (p<0,05). The number of shear strokes in Group 2(GC Ortho Connect®) was significantly higher than in Group 1(Transbond™XT) and Group 3(Transbond™Plus) (p<0,05), while no significant difference was observed between Group 1 and Group 3 (p>0,05). A significant negative correlation was found between demineralization and shear strokes (p<0,05). Hard tissue damage was observed in 9 samples in Group 1 and Group 3, and 7 samples in Group 2. Conclusions: Increased demineralization around brackets reduced bond strength regardless of adhesive type or bonding technique. The GC Ortho Connect® agent, applied as acid+adhesive, showing acceptable demineralization with relatively low hard tissue damage and superior shear strength, may offer clinical advantages in long-term orthodontic treatments.