Fracture Resistance of Simulated Immature Teeth Reinforced with Different Mineral Aggregate-Based Materials

Abstract This study assessed the fracture resistance of simulated immature teeth reinforced with calcium aluminate cement (CAC) or mineral trioxide aggregate (MTA) containing calcium carbonate nanoparticles (nano-CaCO3). The microstructural arrangement of the cements and their chemical constitution were also evaluated. Forty-eight canines simulating immature teeth were distributed into 6 groups (n=8): Negative control - no apical plug or root canal filling; CAC - apical plug with CAC; CAC/nano-CaCO3 - apical plug with CAC+5% nano-CaCO3; MTA - apical plug with MTA; MTA/nano-CaCO3 - apical plug with MTA+5% nano-CaCO3; and Positive control - root canal filling with MTA. The fracture resistance was evaluated in a universal testing machine. Samples of the cements were analyzed under Scanning Electron Microscope (SEM) to determine their microstructural arrangement. Chemical analysis of the cements was performed by Energy Dispersive X-ray Spectroscopy (EDS). The fracture resistance of CAC/nano-CaCO3 was significantly higher than the negative control (p<0.05). There was no significant difference among the other groups (p>0.05). Both cements had a more regular microstructure with the addition of nano-CaCO3. MTA samples had more calcium available in soluble forms than CAC. The addition of nano-CaCO3 to CAC increased the fracture resistance of teeth in comparison with the non-reinforced teeth. The microstructure of both cements containing nano-CaCO3 was similar, with a more homogeneous distribution of lamellar- and prismatic-shaped crystals. MTA had more calcium available in soluble forms than CAC.

摘要 本研究旨在评估经添加碳酸钙纳米颗粒（nano-CaCO₃）的铝酸钙水泥（calcium aluminate cement, CAC）或三氧化矿物凝聚体（mineral trioxide aggregate, MTA）加固的模拟未成熟恒牙的抗折性能，同时分析两种水泥的微观结构与化学组成。本研究选取48颗模拟未成熟恒牙的犬齿，随机分为6组（每组n=8）：阴性对照组（未行根尖封堵或根管充填）、CAC组（采用CAC实施根尖封堵）、CAC/nano-CaCO₃组（采用添加5%碳酸钙纳米颗粒的CAC实施根尖封堵）、MTA组（采用MTA实施根尖封堵）、MTA/nano-CaCO₃组（采用添加5%碳酸钙纳米颗粒的MTA实施根尖封堵）、阳性对照组（采用MTA实施根管充填）。采用万能试验机测试各组样本的抗折性能；通过扫描电子显微镜（Scanning Electron Microscope, SEM）观察水泥样本的微观结构；采用能量色散X射线光谱（Energy Dispersive X-ray Spectroscopy, EDS）对水泥的化学组成进行分析。结果显示，CAC/nano-CaCO₃组的抗折性能显著高于阴性对照组（p<0.05），其余各组间无显著性差异（p>0.05）。添加碳酸钙纳米颗粒后，两种水泥的微观结构均更为规整。MTA样本中可溶性钙的含量高于CAC组。向CAC中添加碳酸钙纳米颗粒可提升牙齿的抗折性能，优于未加固的样本。添加碳酸钙纳米颗粒的两种水泥的微观结构相似，其层状与棱柱状晶体的分布更为均匀。MTA样本中可溶性钙的含量高于CAC组。