Lopes Guilherme Carpena, Vieira Luiz Clovis Cardoso, Monteiro Sylvio, Caldeira de Andrada Mauro Amaral, Baratieri Carolina Mascarenhas
Department of Operative Dentistry, Universidade do Sul de Santa Catarina, Tubarão, Brazil.
Oper Dent. 2003 Jul-Aug;28(4):429-39.
This in vitro study verifies whether there are differences between bonding to hypermineralized dentin and normal dentin and if longer acid etching can improve the bond strength to this modified substrate without damaging the bond to normal dentin. Forty-two extracted human molars with chronic occlusal caries were transversally cut with a diamond saw under refrigeration. The occlusal surfaces were ground until the carious lesion was removed, exposing the sclerotic dentin in the center and polished to 600/grid. A 35% phosphoric acid (3M) was applied for 15 seconds in 15 specimens. SingleBond (3M) adhesive system was applied and a hybrid resin composite (Filtek Z250, 3M) was inserted in four 1-mm increments and light-cured. The remaining 15 molars were prepared in the same manner, but with an acid etching time of 30 seconds. After 24 hours in water, the specimens were cut in two perpendicular directions to obtain a cross section of approximately 0.7 mm2 (n=25). A visual examination was conducted to select sticks between the two groups: sclerotic dentin (G15S or G30S) and normal dentin (G15N or G30N). Sticks without 100% sclerotic dentin (translucent area) or those with normal areas were not tested. Two-way ANOVA computed the mu-TBS data taking into consideration dentin type and acid etching time. The dentin Knoop hardness number (KHN) of the sticks was verified. A t-test compared the KHN data between sclerotic and normal dentin. Twelve additional molars (n=6) were prepared to observe the interface under a SEM. The mean (+/- SD) microtensile bond strengths (mu-TBS) were: G15S=56.4(+/- 14.9), G15N=69.7(+/- 17.2), G30S=63.2(+/- 15.6) and G30N=67.7(+/- 13.3). Two-way ANOVA showed higher mu-TBS to normal dentin than sclerotic dentin. Duncan's Post Hoc showed G15N had higher mean mu-TBS than G15S. Other comparisons were not significantly different. The t-test showed statistically higher microhardness in sclerotic dentin than in normal dentin (p<0.0001). The hybrid layer (HL) formation was observed in all specimens without gap formation in any region. In sclerotic dentin (G15S), the HL was very thin, with minimal resin tags in the dentinal tubules and, when present, they were shorter. Doubling the etching time (G30S) resulted in more resin tags with an HL formation on peritubular dentin. The HL on normal dentin was thicker when it was acid etched for 30 seconds (G30N). Numerous resin tags were present with both etching times. The results suggest that the higher mineral amount in sclerotic dentin makes it difficult to bond to this substrate, resulting in a lower mu-TBS. However, doubling the etching time resulted in mu-TBS similar to normal dentin.
这项体外研究验证了与过度矿化牙本质和正常牙本质粘结之间是否存在差异,以及延长酸蚀时间是否能提高与这种改性底物的粘结强度,同时又不损害与正常牙本质的粘结。42颗患有慢性咬合龋的拔除人类磨牙在冷藏条件下用金刚石锯横向切割。磨除咬合面直至去除龋损,暴露中央的硬化牙本质,并抛光至600目/网格。15个样本用35%磷酸(3M)酸蚀15秒。应用SingleBond(3M)粘结系统,并以4个1毫米增量填入混合树脂复合材料(Filtek Z250,3M)并光固化。其余15颗磨牙以相同方式制备,但酸蚀时间为30秒。在水中浸泡24小时后,将样本沿两个垂直方向切割以获得约0.7平方毫米的横截面(n = 25)。进行视觉检查以在两组之间选择粘结样本:硬化牙本质(G15S或G30S)和正常牙本质(G15N或G30N)。没有100%硬化牙本质(半透明区域)或有正常区域的样本不进行测试。双向方差分析计算微拉伸粘结强度(mu-TBS)数据,同时考虑牙本质类型和酸蚀时间。验证样本的牙本质努氏硬度值(KHN)。t检验比较硬化牙本质和正常牙本质之间的KHN数据。另外制备12颗磨牙(n = 6)以在扫描电子显微镜下观察界面。平均(±标准差)微拉伸粘结强度(mu-TBS)为:G15S = 56.4(±14.9),G15N = 69.7(±17.2),G