Lindquist Terry J, Stanford Clark M, Knox Eric
Department of Prosthodontics, College of Dentistry, University of Iowa, Iowa City 52242, USA.
J Prosthet Dent. 2003 Nov;90(5):441-6. doi: 10.1016/s0022-3913(03)00544-4.
Abrasion is a major concern when gypsum products are used for dies, leading to the frequent recommendation that surface hardeners should be used before waxing or scanning.
This study evaluated abrasion resistance and water sorption with 4 commonly used gypsum die materials with and without the application of surface die hardeners.
Three ADA Type IV (Vel-Mix, ResinRock, and Silky-Rock) and 1 Type V die material (Die-Keen) were evaluated for abrasion resistance after application of 2 surface hardeners (Permabond 910 cyanoacrylate and Clear Coat). Thirty specimens of each material were fabricated using an impression of a standard brass die machined with 1-mm high ridges, sloped 45 degrees. Gypsum materials were mixed according to manufacturers' recommendations and allowed to set 1 hour before separating. All replicated dies were allowed to bench set for 14 days before testing. One hour before testing, specimens were arbitrarily assigned to 1 of 3 treatment subgroups (n=10/group): no treatment (control), coated with Permabond 910, or coated with Clear Coat. In the coated groups, die hardener was painted over the grooves and air dried. Abrasion resistance (measured by weight loss) was evaluated using a reciprocal abrasion device in which a stylus applied a 50-g mass perpendicular to the ridges. Mass loss was determined using an analytical balance before and after each test cycle. Five sets of 20 unidirectional passes were made on each specimen. A scanning electron microscope was used to evaluate the surface of specimens in each treatment subgroup. Water sorption was also evaluated using 2 Type IV (Silky-Rock, ResinRock) and 1 Type III (Microstone) gypsum materials. Specimen dies were separated 1 hour after pouring the impression and allowed to bench set 1 week before testing. Five specimens from each material group received a coating of a surface hardener 1 hour before testing. Specimens were placed in distilled water for 15 minutes and differences in mass were determined using an analytical balance before and after each test. A 2-way analysis of variance was completed followed by a Tukey post hoc test (alpha=.05).
The 2-way analysis of variance revealed an interaction between product and surface coating (P=.0459). Given this interaction, the 12 combinations determined by surface treatment and material type were considered individually using the Tukey method. Vel-Mix, control (2.62 +/- 2.64 mg) had the most material loss and Vel-Mix, Clear Coat (0.48 +/- 0.29 mg) had the least material loss. Water sorption results indicated an interaction between the gypsum material and the surface treatment (P<.0001). The control groups of Microstone (299.2 +/- 49.6 mg) and Silky-Rock (159.0 +/- 8.5 mg) showed the most water sorption compared with the other treatment groups.
This study demonstrated that a significant improvement in abrasion resistance occurred only with specific gypsum/surface hardener material combinations. Also, water sorption decreased significantly for Microstone and Silky-Rock gypsum materials when a surface hardener was used.
当使用石膏产品制作模型时，磨损是一个主要问题，这导致人们经常建议在涂蜡或扫描之前使用表面硬化剂。
本研究评估了4种常用石膏模型材料在使用和不使用表面模型硬化剂的情况下的耐磨性和吸水性。
对3种ADA IV型（Vel-Mix、ResinRock和Silky-Rock）和1种V型模型材料（Die-Keen）在使用2种表面硬化剂（Permabond 910氰基丙烯酸酯和透明涂层）后进行耐磨性评估。使用加工有1毫米高棱边、倾斜45度的标准黄铜模型的印模制作每种材料的30个样本。按照制造商的建议混合石膏材料，并在分离前放置1小时凝固。所有复制的模型在测试前在工作台上放置14天。在测试前1小时，将样本随机分配到3个处理亚组之一（每组n = 10）：不处理（对照）、涂有Permabond 910或涂有透明涂层。在涂覆组中，将模型硬化剂涂覆在凹槽上并风干。使用往复式磨损装置评估耐磨性（通过重量损失测量），其中探针垂直于棱边施加50克质量。在每个测试周期前后使用分析天平确定质量损失。对每个样本进行5组每组20次单向通过。使用扫描电子显微镜评估每个处理亚组中样本的表面。还使用2种IV型（Silky-Rock、ResinRock）和1种III型（Microstone）石膏材料评估吸水性。在灌注印模1小时后分离样本模型，并在测试前在工作台上放置1周。每个材料组的5个样本在测试前1小时接受表面硬化剂涂层。将样本置于蒸馏水中15分钟，并在每次测试前后使用分析天平确定质量差异。完成双向方差分析，随后进行Tukey事后检验（α = 0.05）。
双向方差分析显示产品与表面涂层之间存在相互作用（P = 0.0459）。鉴于这种相互作用，使用Tukey方法单独考虑由表面处理和材料类型确定的12种组合。Vel-Mix对照组（2.62 +/- 2.64毫克）的材料损失最大，Vel-Mix透明涂层组（0.48 +/- 0.29毫克）的材料损失最小。吸水性结果表明石膏材料与表面处理之间存在相互作用（P < 0.0001）。与其他处理组相比，Microstone（299.2 +/- 49.6毫克）和Silky-Rock（159.0 +/- 8.5毫克）的对照组显示出最大的吸水性。
本研究表明，仅特定的石膏/表面硬化剂材料组合才能显著提高耐磨性。此外，当使用表面硬化剂时，Microstone和Silky-Rock石膏材料的吸水性显著降低。
