Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, United States.
Dent Mater. 2010 Nov;26(11):e227-35. doi: 10.1016/j.dental.2010.07.004. Epub 2010 Aug 12.
Secondary caries and restorative fracture are the two main reasons for restoration failures. Fluoride ion (F) release can help inhibit caries. Plaque pH after a sucrose rinse can decrease to a cariogenic pH of 4-4.5. The objective of this study was to investigate the effects of solution pH and immersion time on the mechanical properties and F release of restorative materials.
Three resin-modified glass ionomers (Viremer, Fuji II LC, Ketac Nano), one compomer (Dyract Flow), and one composite (Heliomolar), were tested. Flexural strength and elastic modulus were measured before and after 84d of immersion in solutions of pH 4, 5.5, and 7. F release was measured as a function of pH and immersion time.
Immersion and material type had significant effects on mechanical properties. Vitremer had a flexural strength (mean±sd; n=6) of 99±25MPa before immersion; it decreased to 32±9MPa after 84d of immersion (p<0.05). In comparison, Heliomolar had a smaller strength loss, decreasing from 99±9MPa to 65±7MPa (p<0.05). Solution pH had little effect on mechanical properties. For example, Fuji II LC had a strength of 63±15MPa at pH 4, similar to 61±30MPa at pH 5.5, and 56±22MPa at pH 7 (p>0.1). In contrast, solution pH had a significant effect on F release. F release at 84d for Fuji was 609±25μg/cm(2) at pH 4, much higher than 258±36μg/cm(2) at pH 5.5, and 188±9μg/cm(2) at pH 7.
The restoratives tested were able to greatly increase the F release at acidic, cariogenic pH, when these ions are most needed to inhibit caries. However, mechanical properties of these F-releasing restoratives degraded significantly in immersion. Efforts are needed to develop F-releasing restoratives with high levels of sustained F release, as well as improved durability of mechanical properties for large stress-bearing restorations.
继发龋和修复体折裂是修复失败的两个主要原因。氟离子（F）的释放有助于抑制龋坏。蔗糖漱口后菌斑 pH 值可降至致龋的 4-4.5。本研究的目的是探讨溶液 pH 值和浸泡时间对修复材料机械性能和 F 释放的影响。
测试了 3 种树脂改性玻璃离子体（Viremer、富士 II LC、Ketac Nano）、1 种复合体（Dyract Flow）和 1 种复合树脂（Heliomolar）。在 pH 值为 4、5.5 和 7 的溶液中浸泡 84d 前后测量弯曲强度和弹性模量。F 释放作为 pH 值和浸泡时间的函数进行测量。
浸泡和材料类型对机械性能有显著影响。Viremer 浸泡前的弯曲强度（均值±标准差；n=6）为 99±25MPa，浸泡 84d 后降至 32±9MPa（p<0.05）。相比之下，Heliomolar 的强度损失较小，从 99±9MPa 降至 65±7MPa（p<0.05）。溶液 pH 值对机械性能影响较小。例如，富士 II LC 在 pH 值为 4 时的强度为 63±15MPa，与 pH 值为 5.5 时的 61±30MPa 相似，与 pH 值为 7 时的 56±22MPa 相似（p>0.1）。相比之下，溶液 pH 值对 F 释放有显著影响。富士在 pH 值为 4 时的 84d F 释放量为 609±25μg/cm²，明显高于 pH 值为 5.5 时的 258±36μg/cm²，以及 pH 值为 7 时的 188±9μg/cm²。
测试的修复体在酸性、致龋 pH 值下能够大大增加 F 的释放，此时这些离子最需要抑制龋坏。然而，这些释放 F 的修复体的机械性能在浸泡后显著下降。需要努力开发具有高持续 F 释放水平以及改善大承载修复体机械性能耐久性的释放 F 的修复体。
