Objectives

To measure the effect of placement of glass fibre mesh on the flexural strength and load bearing capacity of repaired polymethylmethacrylate (PMMA) denture base resin.

Materials and methods

A total of 150 heat-polymerised acrylic resin specimens were fabricated with dimensions of 5 × 30 × 50 mm for flexural strength testing. Specimens were divided into 5 groups according to repair width and placement of the fibre mesh. Three groups (n = 90) had a repair width of 20 mm (including the control group), and two groups (n = 60) had a narrower repair width of 16 mm. Fibre mesh was either embedded at the neutral (bottom of the repair area) or tension (top of the repair area) zone of the specimen when subjected to flexural strength testing. Half of the specimens from each group were subjected to artificial ageing by thermocycling (5 °C and 55 °C, 30s dwell time) for 10,000 cycles to stimulate 12 months in vivo. All the specimens were stored in distilled water at 37 °C for 24 h prior to testing. The flexural strength of the specimen was obtained by three-point bend testing, and data were statistically analysed using ANOVA and post-hoc analysis (SPSS; significance level p < 0.05). Probability of failure was calculated using Weibull analysis. Scanning electron microscopy analysis was used to identify the mode of failure.

Results

Specimens repaired with the 20 mm fibre mesh placed in the tension zone showed the highest mean flexural strength (101.33 ± 12.66 MPa) with statistical significance (p = 0.05) to the other groups except for the specimens repaired with the 16 mm fibre mesh placed in the tension zone (p = 0.072). The highest Weibull modulus was found in the thermal cycling group of the specimens with 20 mm repair width repaired with the fibre mesh embedded at the neutral zone (10.01). The lowest Weibull modulus was found in the non-thermal cycling group of the control group (3.15).

Conclusion

Placing fibre mesh in the tension zone of a PMMA specimen significantly improved the flexural strength of the repair. Placing the fibre mesh in the neutral zone or the fibre mesh width was short of the lower support rollers resulted in no significant increase in flexural strength compared to the non-reinforced control group. Ageing via thermal cycling resulted in a decrease in flexural strength across all sample groups. This study highlights the importance of recognising the valid repair region and to have the mesh embedded in certain dimensions, otherwise it will have no significant contribution towards the repair and increase of flexural strength of the denture.

中文翻译：

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纤维增强和修复的 PMMA 义齿基托树脂：放置对弯曲强度和承载能力的影响

目标

测量玻璃纤维网的放置对修复后的聚甲基丙烯酸甲酯 (PMMA) 义齿基托树脂的弯曲强度和承载能力的影响。

材料和方法

总共制造了 150 个热聚合丙烯酸树脂样品，尺寸为 5 × 30 × 50 mm，用于弯曲强度测试。根据修复宽度和纤维网的位置将标本分为5组。三组（n  =90）的修复宽度为20mm（包括对照组），两组（n  =60）的修复宽度较窄，为16mm。当进行弯曲强度测试时，纤维网被嵌入在试样的中性（修复区域的底部）或拉伸（修复区域的顶部）区域。每组一半标本通过热循环（5°C和55°C，30s停留时间）10,000个循环进行人工老化，在体内刺激12个月. 试验前将所有样品在 37 ℃的蒸馏水中储存 24 小时。试样的弯曲强度通过三点弯曲试验获得，数据采用方差分析和事后分析（SPSS；显着性水平p  < 0.05）进行统计分析。使用威布尔分析计算失效概率。使用扫描电子显微镜分析来确定失效模式。

结果

将 20 mm 纤维网置于受拉区修复的试样显示出最高的平均抗弯强度 (101.33 ± 12.66 MPa)，与 其他组相比具有统计学显着性 ( p = 0.05)，除了将 16 mm 纤维网置于受拉区修复的试样外张力区 ( p  = 0.072)。在修复宽度为 20 mm 的试样的热循环组中发现了最高的威布尔模量，其中纤维网嵌入中性区 (10.01)。在对照组的非热循环组中发现最低的威布尔模量 (3.15)。

结论

在 PMMA 试样的受拉区放置纤维网可显着提高修复的抗弯强度。与非增强对照组相比，将纤维网置于中性区或纤维网宽度小于下支撑辊导致抗弯强度没有显着增加。通过热循环老化导致所有样品组的弯曲强度降低。本研究强调了识别有效修复区域并将网格嵌入特定尺寸的重要性，否则对修复和增加义齿的抗弯强度没有显着贡献。