Researcher, Department of Medicine, Surgery and Health Sciences, University of Trieste, Trieste, Italy.
PhD student in Nanotechnology, Department of Medicine, Surgery and Health Sciences, University of Trieste, Trieste, Italy.
J Prosthet Dent. 2021 Jan;125(1):189.e1-189.e7. doi: 10.1016/j.prosdent.2020.06.022. Epub 2020 Oct 29.
The dimensional stability of alginate dental impressions is a key factor for the reliability of delayed gypsum pouring and digital scanning. However, studies of the dimensional stability of alginates with conventional methods that consider the dimensional variations of large impressions are lacking.
The purpose of this in vitro study was to investigate and compare 2 digital methods for the analysis of dimensional stability of large impressions made with 5 different extended-pour alginates and to assess dimensional stability up to 5 days.
Impressions of a simplified master maxillary model were made with Alginoplast, Blueprint, Hydrogum 5, Orthoprint, and Phase Plus and then analyzed at different time points. Digital scans of the alginate impression surfaces were obtained with a desktop scanner and analyzed by evaluating the linear measurements between reference points and by using a novel method that consists of the analysis of the entire scanned surface to evaluate the expansion and contraction of the impressions.
The first method revealed that the dimensional changes did not exceed 0.5%, with the exception of Phase Plus at day 3 (-0.6 ±0.7%), and the average dimensional variation was always lower than or equal to 0.2 mm. Blueprint was the most stable material (-0.2 ±0.6%). The second method revealed dimensional variations always lower than 0.03 mm and confirmed Blueprint as the best performing material (0.001 ±0.006 mm) and Phase Plus the worst (-0.019 ±0.006 mm).
Both the methods used to evaluate alginate stability showed that the analyzed materials remain stable over time; the dimensional variations showed a similar trend, with differences in the absolute values depending on the applied method. Linear measurements are affected by the operator and choice of reference points; however, by evaluating the average variations of the entire structure surfaces, local variations should be minimized. The evaluation of the average variations with the second method offers the advantage of a rapid visual representation of these variations.
藻酸盐牙科印模的尺寸稳定性是延迟石膏浇注和数字扫描可靠性的关键因素。然而，缺乏使用传统方法研究藻酸盐尺寸稳定性的研究，这些传统方法考虑了大印模的尺寸变化。
本体外研究的目的是调查和比较 5 种不同扩展浇铸用藻酸盐制作的大印模的两种数字方法的尺寸稳定性，并评估长达 5 天的尺寸稳定性。
使用 Alginoplast、Blueprint、Hydrogum 5、Orthoprint 和 Phase Plus 对简化的上颌模型进行印模，然后在不同时间点进行分析。使用台式扫描仪获取藻酸盐印模表面的数字扫描，并通过评估参考点之间的线性测量值以及使用包括分析整个扫描表面以评估印模膨胀和收缩的新方法来进行分析。
第一种方法表明，除了第 3 天的 Phase Plus（-0.6±0.7%）外，尺寸变化均不超过 0.5%，平均尺寸变化始终低于或等于 0.2mm。Blueprint 是最稳定的材料（-0.2±0.6%）。第二种方法显示尺寸变化始终低于 0.03mm，并证实 Blueprint 是表现最好的材料（0.001±0.006mm），而 Phase Plus 是最差的（-0.019±0.006mm）。
用于评估藻酸盐稳定性的两种方法均表明，分析材料随时间保持稳定；尺寸变化呈现出相似的趋势，绝对值的差异取决于所应用的方法。线性测量受操作员和参考点选择的影响；然而，通过评估整个结构表面的平均变化，可以最小化局部变化。第二种方法评估平均变化具有快速视觉表示这些变化的优势。
