Department of Restorative Dentistry, School of Dentistry, University of Detroit Mercy, Detroit, MI 48208-2576, USA.
J Prosthodont. 2013 Apr;22(3):179-83. doi: 10.1111/j.1532-849X.2012.00923.x. Epub 2012 Sep 17.
Conventional denture base polymethyl methacrylate (PMMA) is low in strength, soft, and brittle on impact. Improvements in the mechanical properties of denture base materials have been sought by adding different reinforcing phases to the PMMA matrix. The purpose of this work was to study the effects of mica reinforcement on the mechanical properties, flexural strength, and microhardness of PMMA denture base resin.
Wet ground muscovite mica and Lucitone 199 original shade denture base resin were used. Two micas were tested: W200 and P66 with average particle sizes (d50) of 131 μm and 30 μm, respectively. The mica was silane treated in a solution of 3-methacryloxypropyl trimethoxysilane, ethanol, and water, and then dried. The specimens were fabricated using the denture base resin manufacturer's instructions with a powder : liquid ratio of 21 g/10 ml and a mixing time of 30 seconds. Five treatment groups were produced with differing amounts of mica added to the PMMA denture base resin: (A) control group with 0 vol% mica, (B) 10 vol% W200 mica, (C) 20 vol% W200 mica, (D) 10 vol% P66 mica, (E) 20 vol% P66 mica. The mica replaced equal volumes of the PMMA powder component to minimize changes in viscosity. The three-point bending flexural strength specimens were 70 × 11 × 3 mm(3) . Seven specimens were prepared for each treatment group. The hardness specimens were prepared from the ends of the three-point bend specimens after they were broken (N = 7). After deflasking, the specimens were polished with 600 grit silicon carbide paper to achieve smooth surfaces. A standard three-point bending jig with a span length of 50 mm was attached to an Instron universal testing machine. The specimens were placed on the jig, and loading was carried out using a 1 mm/min crosshead speed until failure. Microhardness was measured using a Clark microhardness tester with a Knoop indenter. The load was set to 200 g and the dwell time to 15 seconds. ANOVA and Tukey tests were used for statistical analyses (Alpha = 0.05).
The flexural strength of the control group was between 77% and 94% higher than all the mica-containing groups (p≤ 0.05). No significant differences were found within the four mica groups. Microhardnesses of the 20% mica groups (both fine and coarse) were 33% and 26% higher than the control (p≤ 0.05). The 10% mica groups had higher hardness than the control group, but the increase was not statistically significant (p > 0.05).
Mica additions to denture PMMA reduced flexural strength; however, with the specimens containing highest mica concentrations (20%), microhardness significantly increased.
传统义齿基托聚甲基丙烯酸甲酯（PMMA）强度低、质软且易碎。为了改善义齿基托材料的机械性能，已经向 PMMA 基质中添加了不同的增强相。本研究的目的是研究云母增强对 PMMA 义齿基托树脂的机械性能、弯曲强度和显微硬度的影响。
使用湿磨云母和 Lucitone 199 原色义齿基托树脂。测试了两种云母：W200 和 P66，平均粒径（d50）分别为 131 μm 和 30 μm。云母在 3-丙烯酰氧基丙基三甲氧基硅烷、乙醇和水的溶液中进行硅烷处理，然后干燥。根据义齿基托树脂制造商的说明，用粉末：液体比为 21 g/10 ml 混合 30 秒来制备样品。将不同量的云母添加到 PMMA 义齿基托树脂中，制备了 5 个处理组：（A）对照组，云母体积分数为 0 vol%；（B）W200 云母体积分数为 10 vol%；（C）W200 云母体积分数为 20 vol%；（D）P66 云母体积分数为 10 vol%；（E）P66 云母体积分数为 20 vol%。云母取代了 PMMA 粉末成分的等体积，以最小化粘度变化。三点弯曲弯曲强度试样为 70×11×3mm（3）。每个处理组制备 7 个试样。三点弯曲试样断裂后从其末端制备硬度试样（N=7）。脱模后，用 600 目碳化硅砂纸对试样进行抛光，以获得光滑表面。将带有 50mm 跨度的标准三点弯曲夹具连接到 Instron 万能试验机上。将试样放置在夹具上，以 1mm/min 的十字头速度进行加载，直到试样破坏。使用带有克努普压头的 Clark 显微硬度计测量显微硬度。将负载设置为 200g，停留时间设置为 15 秒。采用方差分析和 Tukey 检验进行统计学分析（Alpha=0.05）。
对照组的弯曲强度比所有含云母组高 77%至 94%（p≤0.05）。在四个云母组中没有发现显著差异。20%云母组（细和粗）的显微硬度比对照组高 33%和 26%（p≤0.05）。10%云母组的硬度高于对照组，但增加不具有统计学意义（p>0.05）。
向义齿 PMMA 中添加云母降低了弯曲强度；然而，随着试样中云母浓度的增加（20%），显微硬度显著增加。
