Statement of problem

The addition of ultraviolet (UV) protectives may affect the materials’ mechanical properties, which can limit the service life of facial prostheses.

Purpose

The purpose of this in vitro study was to investigate the effect of UV protectives on the mechanical properties of maxillofacial silicones after artificial aging.

Material and methods

Six color groups (unpigmented, white, yellow, red, blue, and mixed) of addition-type maxillofacial silicone were prepared. Four UV protectives, benzophenone-3 (UV-BP), ethylhexyl methoxycinnamate (UV-EM), titanium dioxide (UV-TD), and ethylhexyl salicylate (UV-ES), at 0.5% and 1% concentrations by weight were incorporated into the silicone before polymerization. The specimens were subjected to accelerated aging in a weathering chamber for 300 and 600 hours and to thermocycling. The tensile strength and percentage elongation, tear strength, and hardness of maxillofacial silicones were evaluated. Data were analyzed by using 4-way ANOVA. The differences were compared by the Tukey honestly significant difference test (α=.05).

Results

Tensile strength decreased after 300 and 600 hours of UV aging in 0.5% and 1% UV-BP protective–added groups and increased in thermocycled groups (P<.05). Aging conditions generally showed no effect on the tensile strength of UV-EM, UV-TD, and UV-ES added groups (P>.05). Aging generated a decrease in percentage elongation values compared with nonaged specimens of groups (P<.05). The addition of UV protectives generally did not significantly affect the tear strength of specimens compared with control in the aged groups (P>.05). The hardness of UV protective–added groups increased when compared with that of nonaged groups after 300 and 600 hours of UV aging (P<.05). Also, thermally aged groups showed increased hardness than nonaged groups (P<.05).

Conclusions

The protective UV-BP addition caused decreased tensile strength, percentage elongation, and tear strength in both concentrations. The UV-EM and UV-ES provided increases in tensile strength and percentage elongation of the silicone in the 0.5% concentration. The addition of UV-BP, UV-EM, and UV-ES did not make significant differences; however, UV-TD significantly decreased the hardness values of the silicone.

中文翻译：

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紫外线防护剂对颌面硅胶弹性体的影响，第2部分：人工老化后的力学性能

问题陈述

添加紫外线 (UV) 防护剂可能会影响材料的机械性能，从而限制面部假体的使用寿命。

目的

这项体外研究的目的是研究紫外线防护剂对人工老化后颌面硅胶机械性能的影响。

材料与方法

制备了六种颜色组（无色素、白色、黄色、红色、蓝色和混合）的添加型颌面硅胶。四种紫外线防护剂，三苯甲酮 (UV-BP)、甲氧基肉桂酸乙基己酯 (UV-EM)、二氧化钛 (UV-TD) 和水杨酸乙基己酯 (UV-ES)，按重量计浓度分别为 0.5% 和 1%。聚合前的硅胶。样品在风化室中加速老化 300 和 600 小时，并进行热循环。评估了颌面硅胶的拉伸强度和伸长率、撕裂强度和硬度。使用 4 向方差分析对数据进行分析。通过 Tukey 真实显着性差异检验 (α=.05) 比较差异。

结果

在 0.5% 和 1% UV-BP 保护添加组中，拉伸强度在 300 和 600 小时紫外线老化后降低，而在热循环组中增加（ P <.05 ）。老化条件通常对 UV-EM、UV-TD 和 UV-ES 添加基团的拉伸强度没有影响 ( P >.05)。与组中未老化的标本相比，老化导致伸长率百分比值降低 ( P <.05)。与老年组的对照组相比，添加紫外线防护剂通常不会显着影响样本的撕裂强度 ( P >.05)。紫外光老化300和600小时后，与未老化组相比，添加紫外保护组的硬度有所增加（P<.05). 此外，热老化组的硬度高于非老化组 ( P <.05)。

结论

添加保护性 UV-BP 会导致两种浓度的拉伸强度、伸长率和撕裂强度降低。0.5% 浓度的 UV-EM 和 UV-ES 提高了有机硅的拉伸强度和伸长率。添加 UV-BP、UV-EM 和 UV-ES 没有显着差异；然而，UV-TD 显着降低了有机硅的硬度值。