Effect of fluoride gels with nano-sized sodium trimetaphosphate on the in vitro remineralization of caries lesions

Abstract Objective To evaluate the effects of fluoride (F) gels supplemented with micrometric or nano-sized sodium trimetaphosphate (TMPmicro and TMPnano, respectively) on the in vitro remineralization of caries-like lesions. Methodology Bovine enamel subsurface lesions (n=168) were selected according to their surface hardness (SH) and randomly divided into seven groups (n=24/group): Placebo (without F/TMP), 4,500 ppm F (4500F), 4500F + 2.5% TMPnano (2.5% Nano), 4500F + 5% TMPnano (5% Nano), 4500F + 5% TMPmicro (5% Micro), 9,000 ppm F (9000F), and 12,300 ppm F (Acid gel). The gels were applied in a thin layer for one minute. Half of the blocks were subjected to pH cycling for six days, whereas the remaining specimens were used for loosely- (calcium fluoride; CaF2) and firmly-bound (fluorapatite; FA) fluoride analysis. The percentage of surface hardness recovery (%SHR), area of subsurface lesion (ΔKHN), CaF2, FA, calcium (Ca), and phosphorus (P) on/in enamel were determined. Data (log10-transformed) were subjected to ANOVA and the Student-Newman-Keuls’ test (p<0.05). Results We observed a dose-response relation between F concentrations in the gels without TMP for %SHR and ΔKHN. The 2.5% Nano and 5% Micro reached similar %SHR when compared with 9000F and Acid gels. For ΔKHN, Placebo and 5% Nano gels had the highest values, and 5% Micro, 2.5% Nano, 9000F, and Acid gels, the lowest. All groups had similar retained CaF2 values, except for Placebo and Acid gel. We verified observed an increase in Ca concentrations in nano-sized TMP groups. Regarding P, TMP groups showed similar formation and retention to 9000F and Acid. Conclusion Adding 2.5% nano-sized or 5% micrometric TMP to low-fluoride gels lead to enhanced in vitro remineralization of artificial caries lesions.

摘要 目的：评估添加微米级或纳米级三偏磷酸钠（sodium trimetaphosphate, TMP，分别记为TMPmicro与TMPnano）的氟化物（fluoride, F）凝胶对龋样病损（caries-like lesions）体外再矿化（in vitro remineralization）的影响。方法：选取168个牛牙釉质亚表层龋损样本，根据其表面硬度（surface hardness, SH）进行筛选，随后随机分为7组（每组24个样本）：安慰剂组（不含氟与TMP）、4500ppm氟组（4500F）、4500F+2.5%纳米级TMP组（2.5% Nano）、4500F+5%纳米级TMP组（5% Nano）、4500F+5%微米级TMP组（5% Micro）、9000ppm氟组（9000F）以及12300ppm氟酸性凝胶组（Acid gel）。将各组凝胶以薄层形式涂布1分钟。将半数样本进行6天的pH循环处理，剩余样本则用于检测釉质内/表面的松散结合态[氟化钙（calcium fluoride, CaF₂）]与紧密结合态[氟磷灰石（fluorapatite, FA）]氟含量。检测指标包括表面硬度恢复率（percentage of surface hardness recovery, %SHR）、亚表层病损面积（ΔKHN）、釉质内/表面的CaF₂、FA、钙（calcium, Ca）与磷（phosphorus, P）含量。对经log10转换的数据采用方差分析（analysis of variance, ANOVA）与Student-Newman-Keuls检验进行统计分析（p<0.05）。结果：不含TMP的氟凝胶中，氟浓度与%SHR及ΔKHN呈剂量效应关系。2.5% Nano组与5% Micro组的%SHR分别与9000F组及酸性凝胶组相当。ΔKHN方面，安慰剂组与5% Nano组数值最高，而5% Micro、2.5% Nano、9000F及酸性凝胶组数值最低。除安慰剂组与酸性凝胶组外，其余各组的CaF₂留存量无显著差异。我们观察到纳米级TMP组的钙浓度有所升高。磷方面，含TMP组的磷形成与留存量与9000F组及酸性凝胶组相当。结论：向低浓度氟凝胶中添加2.5%纳米级或5%微米级TMP，可增强人工龋损的体外再矿化效果。