Department of Restorative Dentistry and Periodontology, Dental School of the Ludwig-Maximilians-University, Goethestr. 70, D-80336 Munich, Germany.
Dent Mater. 2010 Mar;26(3):223-31. doi: 10.1016/j.dental.2009.09.013. Epub 2009 Nov 13.
The aim of this study was to develop a method to experimentally determine and visualize the direction and amount of polymerization shrinkage.
We modified a composite to include 1.5 wt% traceable glass beads. A cylindrical cavity (6mm diameter, 3mm height) was restored with this traceable composite, with and without dentin adhesive, and digitized with high-resolution micro-computed tomography (microCT). Image segmentation was performed to extract the glass beads from the acquired 3D microCT images (uncured and cured). Afterwards, each glass bead was subjected to local rigid registration. The resulting displacement vectors were used to examine and calculate the changes.
In unbonded restorations, the displacement vectors were oriented inwards to the center of mass, although not perfectly. Bonded restorations exhibited two contraction patterns: either toward one side of the cavity or toward the top-surface of the restoration. The displacement vector length values (mean/SD) for the bonded group (46.8 microm/10.0 microm) was significantly higher (p<0.01) than unbonded group (31.3 microm/8.5 microm), and the histogram curve was flatter (skew/kurtosis: 0.10/-0.56) as compared to the unbonded group (skew/kurtosis: 0.03/-0.26).
The proposed method can visualize real 3D displacement vectors generated by polymerization shrinkage. The bonding quality and cavity geometry are critical for the direction of polymerization contraction. This method has the potential to validate current models concerning the amount and orientation of shrinkage vectors.
本研究旨在开发一种实验方法来确定和可视化聚合收缩的方向和程度。
我们修改了一种复合材料，使其包含 1.5wt%可追踪的玻璃珠。使用这种可追踪的复合材料，在有和没有牙本质粘结剂的情况下，修复一个圆柱形腔（直径 6mm，高度 3mm），并用高分辨率微计算机断层扫描（microCT）进行数字化。通过图像分割从获得的 3D microCT 图像（未固化和固化）中提取玻璃珠。然后，对每个玻璃珠进行局部刚性配准。使用所得的位移向量来检查和计算变化。
在未粘结的修复体中，位移向量向内指向质心，但并不完全如此。粘结修复体表现出两种收缩模式：要么向腔的一侧，要么向修复体的上表面。粘结组的位移向量长度值（平均值/标准差）（46.8μm/10.0μm）明显高于未粘结组（31.3μm/8.5μm）（p<0.01），且直方图曲线更平坦（偏度/峰度：0.10/-0.56）与未粘结组（偏度/峰度：0.03/-0.26）相比。
所提出的方法可以可视化聚合收缩产生的真实 3D 位移向量。粘结质量和腔几何形状对聚合收缩的方向至关重要。这种方法有可能验证当前关于收缩向量的数量和方向的模型。
