Effect of Ascorbic Acid on Shear Bond Strength of Orthodontic Brackets Bonded with Resin-modified Glass-ionomer Cement to Bleached Teeth

• Published in: Journal of dental research, dental clinics, dental prospects dental clinics, dental prospects, 2012-01, Vol.6 (2), p.59-64
• Main Authors: Khosravanifard, Behnam, Rakhshan, Vahid, Araghi, Solmaz, Parhiz, Hadi
• Format: Article
• Language: English
• Subjects: Ascorbic acid; Original; orthodontic brackets; resin-modified glass-ionomer; shear bond strength (SBS); tooth bleaching
• ISSN: 2008-210X; 2008-2118
• DOI: 10.5681/joddd.2012.013

Bleaching can considerably reduce shear bond strength (SBS) of orthodontic brackets bonded with composite adhesives. Application of antioxidants is a method to reverse the negative effect of bleaching on composite-to-enamel bond. However, the efficacy of antioxidants in increasing the SBS of brackets bonded using resin-modified glass-ionomer cement (RMGIC) has not been studied, which was the aim of this study. Fifty freshly extracted human maxillary first premolars were bleached with 35% hydrogen peroxide (Pola Office Bleaching, SDI). Sodium ascorbate 10% was applied to the experimental specimens (n=25). All the specimens were etched with 37% phosphoric acid (Ivoclar/Vivadent) and bonded using RMGIC (Fuji Ortho LC, GC). The specimens were subjected to incubation (37°C, 24h) and thermocycling (1000 cycles, 5-55°C, dwell time = 1 min). The SBS was measured at 0.5 mm/min debonding crosshead speed. The adhesive remnant index (ARI) was scored under ×10 magni-fication. Data were analyzed using Mann-Whitney U test, one- and independent-samples t-test, and Fisher'sexact test (α=0.05). The mean SBS of experimental and control groups were 11.97 ± 4.49 and 7.7 ± 3.19 MPa, respectively. The dif-ference was statistically significant (P=0.000 by t-test). SBS of both control (P=0.014) and experimental (P=0.000) groups were significantly higher than the minimum acceptable SBS of 6 MPa, according to one-sample t-test. Application of ascorbic acid can guarantee a strong bond when RMGIC is to be used. However, RMGIC might tolerate the negative effect of bleaching with minimum SA treatments (or perhaps without treatments), which de-serves further studies.