In vitro cytotoxicity of self-curing acrylic resins of different colors

OBJECTIVE: The aim of this study was to assess the in vitro cytotoxicity of acrylic resins of different colors over time. METHODS: Specimens were divided into 4 groups (n = 6) according to the color of the acrylic resin (Orto Class, Clássico, Campinas, São Paulo, Brazil): Group 1: clear acrylic resin; group 2: pink acrylic resin; group 3: blue acrylic resin and group 4: green acrylic resin. All specimens were fabricated according to the mass manipulation technique and submitted to mechanical polishing protocol. The control was performed with an amalgam specimen (C+), a glass specimen (C-) and cell control (CC). Specimens were immersed in Minimum Eagle's Medium (MEM) and incubated for 24 h at 37o C. The extracts from the experimental material were filtered and mixed with L929 fibroblast. Cytotoxicity was evaluated at 4 different times, 24, 48, 72 and 168 h. After contact, cells were incubated for 24 h and added to 100 µ of 0.01% neutral red dye. The cells were incubated for 3 h for pigment incorporation and fixed. Cells viability was determined by a spectroscopic (BioTek, Winooski, Vermont, USA) with a 492-nm wavelength λ=492 nm). RESULTS: There were no statistical differences between the experimental groups and the CC and C- groups. CONCLUSION: Clear, pink, blue and green self-curing acrylic resins fabricated by means of the mass manipulation technique and mechanically polished are not cytotoxic. Neither the pigment added to the self-curing acrylic resin nor the factor of time influenced the cytotoxicity of the material.

### 研究目的
本研究旨在评估不同颜色丙烯酸树脂随时间推移的体外细胞毒性。

### 实验方法
本实验的标本根据所用丙烯酸树脂的颜色分为4组（每组n=6），所用丙烯酸树脂产自巴西圣保罗州坎皮纳斯的Orto Class与Clássico品牌：第1组为透明丙烯酸树脂，第2组为粉色丙烯酸树脂，第3组为蓝色丙烯酸树脂，第4组为绿色丙烯酸树脂。所有标本均采用料团操作（mass manipulation）技术制作，并按照标准化机械抛光流程处理。本实验设置三类对照：银汞合金标本（C+）、玻璃标本（C-）以及细胞对照（CC）。将标本置于伊格尔最低必需培养基（Minimum Eagle's Medium, MEM）中，于37℃条件下孵育24小时。收集实验材料的浸提液并过滤，随后与L929成纤维细胞共培养。分别在24、48、72及168小时四个时间点评估细胞毒性：细胞与浸提液接触后孵育24小时，加入100 μL 0.01%中性红染液，继续孵育3小时使细胞摄取染料，之后固定细胞。采用分光光度仪（BioTek，美国佛蒙特州温诺斯基）在波长λ=492 nm处检测细胞活力。

### 研究结果
各实验组与细胞对照（CC）、阴性对照C-组间均未检测到统计学差异。

### 结论
采用料团操作技术制作并经机械抛光的透明、粉色、蓝色及绿色自凝丙烯酸树脂均无细胞毒性。无论是添加至自凝丙烯酸树脂中的色素，还是时间因素，均未对该材料的细胞毒性造成影响。