Roberts Howard W, Berzins David W, Charlton David G
Dental Biomaterials Evaluations, USAF Dental Evaluation and Consultation Service, Great Lakes, IL, USA.
J Esthet Restor Dent. 2009;21(4):262-72. doi: 10.1111/j.1708-8240.2009.00273.x.
The polymerization of bulk-placed resin-modified glass-ionomer (RMGI) restoratives is compromised when penetration of the curing light is limited because of the materials' thickness. It is unknown if additional post light-curing resin polymerization and/or glass-ionomer setting occurs over time to ensure adequate polymerization.
The primary objective was to evaluate the depth of cure of various thicknesses of RMGI restorative products over 1 year using Knoop hardness (KH) testing.
The materials were placed in Delrin molds having an internal diameter of 5.0 mm and heights of 2, 3, 4, and 5 mm and were photopolymerized with a halogen light-curing unit. Five specimens of each depth were prepared for each time period evaluated. Specimens were stored in darkness at 37 +/- 2 degrees C and 98 +/- 2% humidity until being tested at 24 hours, 1 week, and 1, 3, 6, 9, and 12 months after fabrication. Mean KH values were calculated for the bottom and top surfaces of each thickness group and used to determine bottom/top hardness ratios. Data were compared using two-way analysis of variance (factors of time, thickness) at a 0.05 significance level with Scheffé's post hoc analysis, where required.
The materials had relatively stable top surface KH, which permitted valid assessment of changes in bottom surface KH over time. The bottom surface KH of some RMGIs changed significantly over time (p < 0.001), but degrees of change were material dependent. Certain RMGIs demonstrated a potential for statistically significant post light-activation hardening; however, that too was material dependent. As compared with top surface KH, deeper layers of the thicker RMGI specimens consistently failed to achieve an adequate degree of polymerization.
Although certain RMGI materials demonstrate a potential for post light-activation chemically initiated resin polymerization and/or polyalkenoate acid/base reaction, these reactions may not be sufficient to ensure that the material is adequately polymerized for long-term success. This is particularly true when RMGI materials are placed in thicker layers where curing light penetration may be compromised.
RMGI materials should not be placed in bulk but photopolymerized in layers to ensure adequate light activation. The results of this study suggest that Photac-Fil Quick be placed in layers no thicker than 2 mm while Fuji II LC and Vitremer may be placed in layers up to 3 mm in thickness.
当由于材料厚度导致固化光穿透受限，整体放置的树脂改性玻璃离子（RMGI）修复材料的聚合反应会受到影响。随着时间推移，是否会发生额外的光固化后树脂聚合和/或玻璃离子固化以确保充分聚合尚不清楚。
主要目的是使用努氏硬度（KH）测试评估1年内不同厚度的RMGI修复产品的固化深度。
将材料置于内径5.0 mm、高度分别为2、3、4和5 mm的聚甲醛模具中，并用卤素光固化单元进行光聚合。对每个评估时间段，每种深度制备5个样本。样本在37±2℃、湿度98±2%的黑暗环境中储存，直至在制作后24小时、1周以及1、3、6、9和12个月进行测试。计算每个厚度组底面和顶面的平均KH值，用于确定底面/顶面硬度比。在需要时，使用双因素方差分析（时间、厚度因素）在0.05显著性水平下进行数据比较，并进行谢费尔事后分析。
材料顶面的KH相对稳定，这使得能够有效评估底面KH随时间的变化。一些RMGI材料的底面KH随时间有显著变化（p < 0.001），但变化程度因材料而异。某些RMGI材料显示出光激活后有统计学显著硬化的潜力；然而，这同样因材料而异。与顶面KH相比，较厚RMGI样本的更深层始终未能达到足够的聚合程度。
尽管某些RMGI材料显示出光激活后化学引发树脂聚合和/或聚烯酸酸碱反应的潜力，但这些反应可能不足以确保材料为长期成功而充分聚合。当RMGI材料放置在较厚层中，固化光穿透可能受影响时尤其如此。
RMGI材料不应整体放置，而应分层光聚合以确保充分的光激活。本研究结果表明，Photac - Fil Quick应分层放置，每层厚度不超过2 mm；而Fuji II LC和Vitremer每层厚度可达3 mm。
