Doh Re-Mee, Choi Won-Il, Kim Seo Young, Jung Bock-Young
Department of Advanced General Dentistry, College of Dentistry, Dankook University, Cheonan, Korea.
Department of Advanced General Dentistry, College of Dentistry, Yonsei University, Seoul, Korea.
PLoS One. 2025 Jan 30;20(1):e0318217. doi: 10.1371/journal.pone.0318217. eCollection 2025.
Polylactic acid (PLA) has garnered attention for use in interim dental restorations due to its biocompatibility, biodegradability, low cost, ease of fabrication, and moderate strength. However, its performance under intraoral conditions, particularly under heat and moisture, remains underexplored. This study evaluated the mechanical properties of PLA interim crowns compared with those of polymethylmethacrylate (PMMA) and bisphenol crowns under simulated intraoral conditions with thermocycling. Three CAD/CAM polymers-PMMA (milling), PLA (fused deposition), and bisphenol (stereolithography)-were tested for fracture resistance, hardness, and surface roughness. For fracture strength, 25 crowns from each group were cemented onto dies. The Shore D hardness and surface roughness were measured on round discs before and after 10,000 thermocycles (5°C/55°C). The surface topography was assessed via scanning electron microscopy. PMMA exhibited the highest fracture strength (2787.93 N), followed by bisphenol (2165.47 N) and PLA (2088.78 N), with no significant difference between the latter two. PMMA and bisphenol showed vertical fractures and cracks, whereas PLA showed crown tearing or die deformation. Bisphenol had the highest Shore D hardness, followed by PMMA and PLA, with no significant changes after thermocycling. The surface roughness (Ra) was lowest for bisphenol and similar between PMMA and PLA. The roughness (Rz) increased from bisphenol to PMMA to PLA. The roughness of the PMMA remained unchanged after thermocycling, whereas the Ra but not the Rz of the PLA increased. Bisphenol showed a significant increase in both Ra and Rz (p<0.0001). In conclusion, PLA interim crowns demonstrated mechanical properties comparable to those of conventional PMMA and bisphenol crowns after thermocycling.
聚乳酸（PLA）因其生物相容性、生物可降解性、低成本、易于加工和适中的强度，在临时牙修复体中的应用受到关注。然而，其在口腔内条件下的性能，尤其是在热和湿度条件下，仍未得到充分研究。本研究在热循环模拟口腔内条件下，评估了PLA临时冠与聚甲基丙烯酸甲酯（PMMA）和双酚冠的机械性能。测试了三种CAD/CAM聚合物——PMMA（铣削）、PLA（熔融沉积）和双酚（立体光刻）——的抗断裂性、硬度和表面粗糙度。对于断裂强度，每组25个冠被粘固在代型上。在10000次热循环（5°C/55°C）前后，在圆盘上测量肖氏D硬度和表面粗糙度。通过扫描电子显微镜评估表面形貌。PMMA表现出最高的断裂强度（2787.93 N），其次是双酚（2165.47 N）和PLA（2088.78 N），后两者之间无显著差异。PMMA和双酚出现垂直骨折和裂缝，而PLA出现冠撕裂或代型变形。双酚具有最高的肖氏D硬度，其次是PMMA和PLA，热循环后无显著变化。双酚的表面粗糙度（Ra）最低，PMMA和PLA之间相似。粗糙度（Rz）从双酚到PMMA再到PLA增加。热循环后，PMMA的粗糙度保持不变，而PLA的Ra增加但Rz未增加。双酚的Ra和Rz均显著增加（p<0.0001）。总之，热循环后，PLA临时冠的机械性能与传统PMMA和双酚冠相当。
