Statement of problem

The appropriate postpolymerization of stereolithography (SLA) resins with the least effect on dimensional accuracy and with optimal polymerization is unclear.

Purpose

The purpose of this in vitro study was to investigate the dimensional accuracy and degree of polymerization of a photopolymer resin for SLA with different postpolymerizing times and temperatures.

Material and methods

Sixty 1.5-mm-thick specimens were made from clear photopolymer resin with a 3D printer to simulate a maxillary complete denture. They were postpolymerized for different periods (15 and 30 minutes) at 3 different temperatures (40 °C, 60 °C, and 80 °C). Both prepolymerization and postpolymerization gap sizes for each specimen were measured at 5 different locations under a stereomicroscope. The tissue surface was scanned before and after polymerization, and the images were superimposed. The deviation was analyzed by using computer-aided design (CAD) software; root mean square estimates (RMSE) and color map data were obtained. Fourier transform infrared spectrometry was used to determine the degree of conversion (DC) of all specimens. The Kruskal-Wallis and Mann-Whitney tests were used to calculate the difference value of the gap sizes (α=.05). One-way ANOVA and the Tukey test were used for RMSE and DC (α=.05).

Results

The smallest average change in gap sizes was found at 15 minutes and 40 °C, and the largest change at 30 minutes and 80 °C. The lowest RMSE was obtained at 30 minutes and 40 °C (P<.05). On the color map, a uniform deposited layer was created at 15 minutes and 40 °C and 30 minutes and 40 °C. The highest DC was found at 30 minutes and 60 °C, which differed significantly from 15 minutes and 40 °C (P<.05). The lowest degree of polymerization was found at 30 minutes and 40 °C.

Conclusions

The polymerizing temperature exerted a greater effect than polymerizing time, with lower temperatures leading to improved fit and tissue surface accuracy. The recommended parameters for SLA polymerization are 15 minutes and 40 °C. These conditions offered high dimensional accuracy, favorable surface tissue adaptation, and satisfactory DC.

中文翻译：

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不同后聚合条件下立体光刻光敏树脂尺寸精度和聚合度的评价：体外研究

问题陈述

尚不清楚对尺寸精度影响最小且聚合效果最佳的立体光刻（SLA）树脂的适当后聚合。

目的

这项体外研究的目的是研究具有不同后聚合时间和温度的SLA用光敏聚合物树脂的尺寸精度和聚合度。

材料与方法

用3D打印机用透明的光敏聚合物树脂制成60个1.5毫米厚的样本，以模拟上颌全口义齿。它们在3个不同的温度（40°C，60°C和80°C）下进行不同时间（15和30分钟）的后聚合。在立体显微镜下，在5个不同的位置测量了每个样品的预聚合和聚合后的间隙大小。在聚合之前和之后扫描组织表面，并叠加图像。使用计算机辅助设计（CAD）软件分析偏差；获得了均方根估计值（RMSE）和颜色图数据。使用傅立叶变换红外光谱法确定所有样品的转化度（DC）。使用Kruskal-Wallis和Mann-Whitney检验来计算间隙大小的差异值（α= .05）。

结果

在15分钟和40°C时，发现缝隙尺寸的平均变化最小，而在30分钟和80°C时，变化最大。在30分钟和40°C时获得最低的RMSE（P <.05）。在色图上，在15分钟和40°C以及30分钟和40°C的温度下会形成均匀的沉积层。在30分钟和60°C时发现最高DC，与15分钟和40°C时有显着差异（P <.05）。在30分钟和40℃下发现最低的聚合度。

结论

聚合温度比聚合时间发挥更大的作用，而较低的温度导致改善的贴合性和组织表面准确性。SLA聚合的推荐参数为15分钟和40°C。这些条件提供了较高的尺寸精度，良好的表面组织适应性和令人满意的DC。