Pinto José Renato Ribeiro, Mesquita Marcelo Ferraz, Henriques Guilherme Elias Pessanha, de Arruda Nóbilo Mauro Antôonio
School of Dentistry, Paulista University, São Paulo, Brazil.
J Prosthet Dent. 2002 Nov;88(5):516-21. doi: 10.1067/mpr.2002.128953.
Two problems found in prostheses with soft liners are bond failure to the acrylic resin base and loss of elasticity due to material aging.
This in vitro study evaluated the effect of thermocycling on the bond strength and elasticity of 4 long-term soft denture liners to acrylic resin bases.
Four soft lining materials (Molloplast-B, Flexor, Permasoft, and Pro Tech) and 2 acrylic resins (Classico and Lucitone 199) were processed for testing according to manufacturers' instructions. Twenty rectangular specimens (10 x 10-mm(2) cross-sectional area) and twenty cylinder specimens (12.7-mm diameter x 19.0-mm height) for each liner/resin combination were used for the tensile and deformation tests, respectively. Specimen shape and liner thickness were standardized. Samples were divided into a test group that was thermocycled 3000 times and a control group that was stored for 24 hours in water at 37 degrees C. Mean bond strength, expressed in megapascals (MPa), was determined in the tensile test with the use of a universal testing machine at a crosshead speed of 5 mm/min. Elasticity, expressed as percent of permanent deformation, was calculated with an instrument for measuring permanent deformation described in ADA/ANSI specification 18. Data from both tests were examined with 1-way analysis of variance and a Tukey test, with calculation of a Scheffé interval at a 95% confidence level.
In the tensile test under control conditions, Molloplast-B (1.51 +/- 0.28 MPa [mean +/- SD]) and Pro Tech (1.44 +/- 0.27 MPa) liners had higher bond strength values than the others (P <.05). With regard to the permanent deformation test, the lowest values were observed for Molloplast-B (0.48% +/- 0.19%) and Flexor (0.44% +/- 0.14%) (P <.05). Under thermocycling conditions, the highest bond strength occurred with Molloplast-B (1.37 +/- 0.24 MPa) (P <.05). With regard to the deformation test, Flexor (0.46% +/- 0.13%) and Molloplast-B (0.44% +/- 0.17%) liners had lower deformation values than the others (P <.05).
The results of this in vitro study indicated that bond strength and permanent deformity values of the 4 soft denture liners tested varied according to their chemical composition. These tests are not completely valid for application to dental restorations because the forces they encounter are more closely related to shear and tear. However, the above protocol serves as a good method of investigation to evaluate differences between thermocycled and control groups.
带有软衬里的假体存在两个问题，即与丙烯酸树脂基托的粘结失败以及由于材料老化导致的弹性丧失。
本体外研究评估了热循环对4种长期使用的软质义齿衬里材料与丙烯酸树脂基托之间粘结强度和弹性的影响。
根据制造商的说明，对4种软衬里材料（Molloplast - B、Flexor、Permasoft和Pro Tech）和2种丙烯酸树脂（Classico和Lucitone 199）进行处理以进行测试。每种衬里/树脂组合分别制备20个矩形试件（横截面积为10×10 - mm²）和20个圆柱试件（直径12.7 - mm×高度19.0 - mm）用于拉伸和变形测试。试件形状和衬里厚度进行了标准化。样本分为热循环3000次的测试组和在37℃水中储存24小时的对照组。在拉伸测试中，使用万能测试机以5 mm/min的十字头速度测定以兆帕（MPa）表示的平均粘结强度。弹性以永久变形百分比表示，使用ADA/ANSI规范18中描述的测量永久变形的仪器进行计算。两项测试的数据均采用单因素方差分析和Tukey检验进行分析，并计算95%置信水平下的Scheffé区间。
在对照条件下的拉伸测试中，Molloplast - B（1.51±0.28 MPa [平均值±标准差]）和Pro Tech（1.44±0.27 MPa）衬里的粘结强度值高于其他材料（P <.05）。关于永久变形测试，Molloplast - B（0.48%±0.19%）和Flexor（0.44%±0.14%）的数值最低（P <.05）。在热循环条件下，Molloplast - B的粘结强度最高（1.37±0.24 MPa）（P <.05）。关于变形测试，Flexor（0.46%±0.13%）和Molloplast - B（0.44%±0.17%）衬里的变形值低于其他材料（P <.05）。
本体外研究结果表明，所测试的4种软质义齿衬里材料的粘结强度和永久变形值因其化学成分而异。这些测试对于应用于牙科修复并不完全有效，因为它们所承受的力与剪切力和撕裂力更为相关。然而，上述方案是评估热循环组和对照组之间差异的一种良好研究方法。
