Narayana Vanamala, Ashwathanarayana Srirekha, Nadig Gururaj, Rudraswamy Sushma, Doggalli Nagabhushana, Vijai S
Senior Lecturer, Department of Conservative Dentistry and Endodontics, DAPMRV Dental College and Hospital, Bangalore, Karnataka, India.
Head, Department of Conservative Dentistry and Endodontics, The Oxford Dental College Hospital and Research Center, Bangalore, Karnataka, India.
J Int Oral Health. 2014 Jul;6(4):35-41.
Dental composites are one of the most desired restorative materials today. Composite materials can be bonded successfully to human tooth enamel; however, developing the same degree of adhesion to dentin or cementum is a more challenging task. Polymerization contraction stress of dental composites is often associated with marginal and interfacial failures of bonded restorations. The magnitude of stress depends on composite composition and its ability to flow before gelation, which is related to the cavity configuration and curing characteristics of the composite.
This study was carried out on 24 extracted human molars and divided into three groups. Class II (slot) cavities were prepared on the mesial and distal surfaces of the teeth with the gingival wall in dentin/cementum, and the microleakage was observed. After preparation the teeth were randomly assigned into three groups of eight specimens each. The cavities were restored with: Group 1: Packable composite (Surefil, Dentsply); Group 2: Hybrid composite (Filtek Z250, 3M Dental Products); Group 3: Nanocomposite (Filtek Z350, 3M Dental Products). Sixteen samples of each group were subjected to 500 cycles of thermocycling between 5°C and 55°C. All the teeth were immersed in methylene blue for 8 h and then left in tap water for 12 h. The teeth were sectioned mesiodistally with a diamond disc, and examined under a stereomicroscope.
The analysis indicated that packable composite showed more microleakage than all the other groups. Hybrid composite showed less microleakage than packable composite, but more leakage than nanocomposite.
All composites under the study exhibited a certain amount of microleakage in the dentin/cementum margin. Packable composite showed the most microleakage and nanocomposite showed least microleakage. Since these results were obtained in vitro, long-term clinical trials are needed to fully understand the performance of these materials.
牙科复合材料是当今最受欢迎的修复材料之一。复合材料能够成功粘结到人体牙釉质上；然而，要实现与牙本质或牙骨质相同程度的粘结则是一项更具挑战性的任务。牙科复合材料的聚合收缩应力通常与粘结修复体的边缘和界面失效有关。应力的大小取决于复合材料的组成及其在凝胶化前的流动能力，这与窝洞形态以及复合材料的固化特性有关。
本研究选取24颗拔除的人类磨牙并分为三组。在牙齿的近中面和远中面制备Ⅱ类（槽形）窝洞，龈壁位于牙本质/牙骨质内，观察微渗漏情况。窝洞制备后，将牙齿随机分为三组，每组8个样本。分别用以下材料修复窝洞：第1组：可压实复合材料（Surefil，登士柏公司）；第2组：混合复合材料（Filtek Z250，3M牙科产品公司）；第3组：纳米复合材料（Filtek Z350，3M牙科产品公司）。每组16个样本在5℃至55℃之间进行500次热循环。所有牙齿在亚甲蓝中浸泡8小时，然后在自来水中放置12小时。用金刚石盘将牙齿沿近远中方向切片，并在体视显微镜下检查。
分析表明，可压实复合材料的微渗漏比其他所有组都多。混合复合材料的微渗漏比可压实复合材料少，但比纳米复合材料多。
本研究中的所有复合材料在牙本质/牙骨质边缘均表现出一定程度的微渗漏。可压实复合材料的微渗漏最多，纳米复合材料的微渗漏最少。由于这些结果是在体外获得的，因此需要进行长期临床试验以全面了解这些材料的性能。
