Khosravanifard Behnam, Rakhshan Vahid, Araghi Solmaz, Parhiz Hadi
Associate Professor, Department of Orthodontics, Dental Branch, Islamic Azad University, Tehran, Iran.
J Dent Res Dent Clin Dent Prospects. 2012 Spring;6(2):59-64. doi: 10.5681/joddd.2012.013. Epub 2012 Jun 6.
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.
漂白会显著降低用复合粘结剂粘结的正畸托槽的剪切粘结强度（SBS）。应用抗氧化剂是一种逆转漂白对复合材料与牙釉质粘结负面影响的方法。然而，抗氧化剂对使用树脂改性玻璃离子水门汀（RMGIC）粘结的托槽增加SBS的效果尚未得到研究，这是本研究的目的。
用35%过氧化氢（Pola Office Bleaching，SDI）对50颗新鲜拔除的人类上颌第一前磨牙进行漂白。将10%的抗坏血酸钠应用于实验组标本（n = 25）。所有标本均用37%磷酸（Ivoclar/Vivadent）蚀刻，并用RMGIC（Fuji Ortho LC，GC）粘结。标本进行孵育（37°C，24小时）和热循环（1000次循环，5 - 55°C，停留时间 = 1分钟）。在0.5毫米/分钟的脱粘十字头速度下测量SBS。在×10放大倍数下对粘结剂残留指数（ARI）进行评分。使用曼 - 惠特尼U检验、单样本和独立样本t检验以及费舍尔精确检验（α = 0.05）对数据进行分析。
实验组和对照组的平均SBS分别为11.97±4.49和7.7±3.19兆帕。差异具有统计学意义（t检验P = 0.000）。根据单样本t检验，对照组（P = 0.014）和实验组（P = 0.000）的SBS均显著高于最低可接受的6兆帕的SBS。
当使用RMGIC时，应用抗坏血酸可以保证牢固的粘结。然而，RMGIC可能在最少的SA处理（或者可能无需处理）情况下耐受漂白的负面影响，这值得进一步研究。
