Brosky M E, Major R J, DeLong R, Hodges J S
Department of Restorative Sciences, School of Dentistry, University of Minnesota, Minneapolis 55455, USA.
J Prosthet Dent. 2003 Nov;90(5):434-40. doi: 10.1016/j.prosdent.2003.08.021.
Numerous investigations have been done to determine the most accurate method to reproduce a dental arch. Investigations have used different definitive cast configurations, materials, and measuring techniques to evaluate dimensional change, leaving clinicians undecided as to the most accurate method to reproduce a dental arch.
The purpose of this investigation was to evaluate the effect of impression tray selection on accuracy of reproductions of a dental arch using a 3-dimensional optical digitizer.
Impressions were made of a stone cast of a dental arch using vinyl polysiloxane impression material in custom and stock impression trays (n=12). Custom trays, designed with full palatal coverage, were fabricated on a separate standard stone cast using 2 layers of pink baseplate wax as the spacer and tissue stops on 1 anterior tooth and both first molar teeth. Impressions were poured with type IV gypsum and allowed to set with the tray inverted (n=5) or not inverted (n=5). The standard cast and resulting casts were digitized using an optical digitizer. Custom software was used to align and process the 3-dimensional images created by the digitizer. Each image was superimposed onto the standard cast image, curves were created of the percent of points less than a defined distance between the 2 superimposed images, and the area under the curve was calculated. A weighted average area was calculated for each cast, and these values were analyzed using a 2-way ANOVA (alpha=.05).
The main effect of tray type, laboratory setting technique, and the interaction between these 2 characteristics was analyzed. None of these effects was significant.
The differences in accuracy of reproductions of a dental arch, regardless of the impression and laboratory techniques, were not significant when evaluated using a 3-dimensional optical digitizer.
已经进行了大量研究以确定复制牙弓的最准确方法。这些研究使用了不同的最终模型配置、材料和测量技术来评估尺寸变化，这使得临床医生对于复制牙弓的最准确方法仍无法确定。
本研究的目的是使用三维光学数字化仪评估印模托盘选择对牙弓复制准确性的影响。
使用乙烯基聚硅氧烷印模材料在定制和成品印模托盘中对牙弓的石膏模型制取印模（n = 12）。定制托盘设计为覆盖整个腭部，在单独的标准石膏模型上制作，使用两层粉色基板蜡作为间隔物，并在一颗前牙和两颗第一磨牙上设置组织阻挡。印模用IV型石膏灌注，并在托盘倒置（n = 5）或不倒置（n = 5）的情况下凝固。使用光学数字化仪对标准模型和所得模型进行数字化处理。使用定制软件对齐和处理数字化仪创建的三维图像。将每个图像叠加到标准模型图像上，绘制出两个叠加图像之间小于定义距离的点的百分比曲线，并计算曲线下面积。计算每个模型的加权平均面积，并使用双向方差分析（α = 0.05）对这些值进行分析。
分析了托盘类型、实验室凝固技术的主要影响以及这两个特征之间的相互作用。这些影响均不显著。
当使用三维光学数字化仪进行评估时，无论印模和实验室技术如何，牙弓复制准确性的差异均不显著。
