UMKC School of Dentistry, Kansas City, MO 64108, USA.
J Prosthodont. 2013 Jul;22(5):362-6. doi: 10.1111/jopr.12011. Epub 2013 Feb 6.
Difficult impression removal has been linked to high rigidity and hardness of elastomeric impression materials. In response to this concern, manufacturers have reformulated their materials to reduce rigidity and hardness to decrease removal difficulty; however, the relationship between impression removal and rigidity or hardness has not been evaluated. The purpose of this study was to determine if there is a positive correlation between impression removal difficulty and rigidity or hardness of current elastomeric impression materials.
Light- and medium-body polyether (PE), vinylpolysiloxane (VPS), and hybrid vinyl polyether siloxane (VPES) impression materials were tested (n = 5 for each material/consistency/test method). Rigidity (elastic modulus) was measured via tensile testing of dumbbell-shaped specimens (Die C, ASTM D412). Shore A hardness was measured using disc specimens according to ASTM D2240-05 test specifications. Impressions were also made of a custom stainless steel model using a custom metal tray that could be attached to a universal tester to measure associated removal force. Within each impression material consistency, one-factor ANOVA and Tukey's post hoc analyses (α = 0.05) were used to compare rigidity, hardness, and removal force of the three types of impression materials. A Pearson's correlation (α = 0.05) was used to evaluate the association between impression removal force and rigidity or hardness.
With medium-body materials, VPS exhibited significantly higher (p ≤ 0.05) rigidity and hardness than VPES or PE, while PE impressions required significantly higher (p ≤ 0.05) removal force than VPS or VPES impressions. With light-body materials, VPS again demonstrated significantly higher (p ≤ 0.05) hardness than VPES or PE, while the rigidity of the light-body materials did not significantly differ between materials (p > 0.05); however, just as with the medium-body materials, light-body PE impressions required significantly higher (p ≤ 0.05) removal force than VPS or VPES. Moreover, there was no positive correlation (p > 0.05) between impression removal force and rigidity or hardness with either medium- or light-body materials.
The evidence suggests that high impression material rigidity and hardness are not predictors of impression removal difficulty.
弹性印模材料的高刚性和硬度与难以脱模有关。为了解决这一问题，制造商对材料进行了重新配方，以降低刚性和硬度，从而降低脱模难度；然而，脱模与刚性或硬度之间的关系尚未得到评估。本研究的目的是确定当前弹性印模材料的脱模难度与刚性或硬度之间是否存在正相关关系。
对轻体和中体聚醚（PE）、乙烯基聚硅氧烷（VPS）和混合乙烯基聚醚硅氧烷（VPES）印模材料进行了测试（每种材料/稠度/测试方法各 5 个样本）。通过对哑铃形试样（ASTM D412 中的模具 C）进行拉伸试验来测量刚性（弹性模量）。根据 ASTM D2240-05 测试规范，使用圆盘试样测量肖氏 A 硬度。还使用定制的金属托盘对定制不锈钢模型进行了印模，该托盘可以连接到通用试验机上以测量相关的脱模力。在每种印模材料稠度中，使用单因素方差分析和 Tukey 的事后分析（α=0.05）来比较三种印模材料的刚性、硬度和脱模力。使用 Pearson 相关性（α=0.05）来评估脱模力与刚性或硬度之间的关系。
对于中体材料，VPS 的刚性和硬度显著高于 VPES 或 PE（p≤0.05），而 PE 印模所需的脱模力显著高于 VPS 或 VPES 印模（p≤0.05）。对于轻体材料，VPS 的硬度再次显著高于 VPES 或 PE（p≤0.05），而轻体材料的刚性在材料之间没有显著差异（p>0.05）；然而，就像中体材料一样，轻体 PE 印模所需的脱模力也显著高于 VPS 或 VPES（p≤0.05）。此外，无论是中体还是轻体材料，脱模力与刚性或硬度之间均无正相关关系（p>0.05）。
证据表明，高印模材料刚性和硬度不是脱模难度的预测指标。
