Kangwankai Kanokrat, Sani Sarah, Panpisut Piyaphong, Xia Wendy, Ashley Paul, Petridis Haralampos, Young Anne Margaret
Department of Restorative Dentistry, Unit of Prosthodontics, UCL Eastman Dental Institute, London, United Kingdom.
Unit of Orthodontics, UCL Eastman Dental Institute, London, United Kingdom.
PLoS One. 2017 Nov 14;12(11):e0187757. doi: 10.1371/journal.pone.0187757. eCollection 2017.
The aim was to assess monomer conversion, dimensional stability, flexural strength / modulus, surface apatite precipitation and wear of mono / tri calcium phosphate (CaP) and polylysine (PLS)-containing dental composites. These were formulated using a new, high molecular weight, fluid monomer phase that requires no polymerisation activator.
Urethane and Polypropylene Glycol Dimethacrylates were combined with low levels of an adhesion promoting monomer and a light activated initiator. This liquid was mixed with a hybrid glass containing either 10 wt% CaP and 1 wt% PLS (F1) or 20 wt% CaP and 2 wt% PLS (F2). Powder to liquid mass ratio was 5:1. Commercial controls included Gradia Direct Posterior (GD) and Filtek Z250 (FZ). Monomer conversion and polymerisation shrinkage were calculated using Fourier Transform Infrared (FTIR). Subsequent volume increases in water over 7 weeks were determined using gravimetric studies. Biaxial flexural strength (BFS) / modulus (BFM) reduction and surface apatite precipitation upon 1 and 4 weeks immersion in water versus simulated body fluid (SBF) were assessed using a mechanical testing frame and scanning electron microscope (SEM). Mass / volume loss and surface roughness (Ra) following 7 weeks water immersion and subsequent accelerated tooth-brush abrasion were examined using gravimetric studies and profilometer.
F1 and F2 exhibited much higher monomer conversion (72%) than FZ (54%) and low calculated polymerization shrinkage (2.2 vol%). Final hygroscopic expansions decreased in the order; F2 (3.5 vol%) > F1 (1.8 vol%) ~ Z250 (1.6 vol%) > Gradia (1.0 vol%). BFS and BFM were unaffected by storage medium type. Average BFS / BFM upon 4 weeks immersion reduced from 144 MPa / 8 GPa to 107 MPa / 5 GPa for F1 and 105 MPa / 6 GPa to 82 MPa / 4 GPa for F2. Much of this change was observed in the first week of immersion when water sorption rate was high. Surface apatite layers were incomplete at 1 week, but around 2 and 15 micron thick for F1 and F2 respectively following 4 weeks in SBF. Mass and volume loss following wear were equal. Average results for F1 (0.5%), F2 (0.7%), and FZ (0.5%) were comparable but lower than that of GD (1%). Ra, however, decreased in the order; F1 (15 μm) > F2 (11 μm) > GD (9 μm) > FZ (5 μm).
High monomer conversion in combination with large monomer size and lack of amine activator should improve cytocompatibility of the new composites. High monomer molecular weight and powder content enables low polymerisation shrinkage despite high conversion. Increasing active filler provides enhanced swelling to balance shrinkage, which, in combination with greater surface apatite precipitation, may help seal gaps and reduce bacterial microleakage. High monomer conversion also ensures competitive mechanical / wear characteristics despite enhanced water sorption. Furthermore, increased active filler could help reduce surface roughness upon wear.
旨在评估含单/磷酸三钙（CaP）和聚赖氨酸（PLS）的牙科复合材料的单体转化率、尺寸稳定性、弯曲强度/模量、表面磷灰石沉淀和磨损情况。这些复合材料采用一种新型的高分子量流体单体相配制而成，无需聚合活化剂。
将聚氨酯和聚丙二醇二甲基丙烯酸酯与低含量的粘合促进单体和光活化引发剂混合。该液体与含有10 wt% CaP和1 wt% PLS（F1）或20 wt% CaP和2 wt% PLS（F2）的混合玻璃混合。粉液质量比为5:1。商业对照包括Gradia Direct Posterior（GD）和Filtek Z250（FZ）。使用傅里叶变换红外光谱（FTIR）计算单体转化率和聚合收缩率。通过重量法研究测定7周内水的后续体积增加情况。使用机械测试框架和扫描电子显微镜（SEM）评估在水中与模拟体液（SBF）中浸泡1周和4周后的双轴弯曲强度（BFS）/模量（BFM）降低以及表面磷灰石沉淀情况。使用重量法研究和轮廓仪检查7周水浸及随后加速牙刷磨损后的质量/体积损失和表面粗糙度（Ra）。
F1和F2的单体转化率（72%）远高于FZ（54%），且计算出的聚合收缩率较低（2.2 vol%）。最终吸湿膨胀率依次降低；F2（3.5 vol%）> F1（1.8 vol%）~ Z250（1.6 vol%）> Gradia（1.0 vol%）。BFS和BFM不受储存介质类型影响。F1在浸泡4周后的平均BFS / BFM从144 MPa / 8 GPa降至107 MPa / 5 GPa，F2从105 MPa / 6 GPa降至82 MPa / 4 GPa。这种变化在浸泡的第一周，即吸水率较高时最为明显。在SBF中浸泡1周时表面磷灰石层不完整，但F1和F2在浸泡4周后分别约为2微米和15微米厚。磨损后的质量和体积损失相等。F1（0.5%）、F2（0.7%）和FZ（0.5%）的平均结果相当，但低于GD（1%）。然而，Ra依次降低；F1（15μm）> F2（11μm）> GD（9μm）> FZ（5μm）。
高单体转化率、大单体尺寸以及缺乏胺活化剂应能改善新型复合材料的细胞相容性。尽管转化率高，但高单体分子量和粉末含量可实现低聚合收缩率。增加活性填料可增强膨胀以平衡收缩，这与更多的表面磷灰石沉淀相结合，可能有助于密封间隙并减少细菌微渗漏。高单体转化率还能确保尽管吸水率增加，但仍具有有竞争力的机械/磨损特性。此外，增加活性填料有助于减少磨损后的表面粗糙度。
