Interplay between fluoride and abrasivity of dentifrices on dental erosion–abrasion

Objectives

Eroded teeth are more susceptible to toothbrushing wear than sound teeth. We tested the hypothesis that fluoride and abrasivity of dentifrices can interact, modulating the development of erosive–abrasive lesions.

Methods

Human enamel and root dentin specimens were submitted to cycles of demineralization, remineralization and toothbrushing using six dentifrices formulated with three different abrasivity levels: low (L), medium (M) and high (H); with (+F) and without (−F) fluoride. Surface loss was quantified by optical profilometry and compared among groups (α = 0.05).

Results

In dentin, it was ranked: L < M < H, for both +F and −F dentifrices. In enamel, +F dentifrices had similar results; however for −F formulations, M and H did not differ. Fluoride reduced surface loss in enamel, at all abrasive levels. In dentin, the same fluoride effect was observed but only for the low abrasive formulation.

Conclusions

Both fluoride and abrasivity were important modulators of enamel surface loss, while abrasivity had a higher impact than fluoride on dentin.     

TiF4 and NaF at pH 1.2 but not at pH 3.5 are able to reduce dentin erosion

Objective

This study aimed to analyse and compare the protective effect of buffered (pH 3.5) and native (pH 1.2) TiF₄ in comparison to NaF solutions of same pH on dentin erosion.

Design

Bovine samples were pretreated with 1.50% TiF₄ or 2.02% NaF (both 0.48 M F) solutions, each with a pH of 1.2 and 3.5. The control group received no fluoride pretreatment. Ten samples in each group were eroded with HCl (pH 2.6) for 10 × 60 s. Erosion was analysed by determination of calcium release into the acid. Additionally, the surface and the elemental surface composition were examined by scanning electron microscopy (two samples in each group) and X-ray energy-dispersive spectroscopy in fluoridated but not eroded samples (six samples in each group). Cumulative calcium release (nmol/mm²) was statistically analysed by repeated measures ANOVA and one-way ANOVA at t = 10 min.

Results

TiF₄ and NaF at pH 1.2 decreased calcium release significantly, while TiF₄ and NaF at pH 3.5 were not effective. Samples treated with TiF₄ at pH 1.2 showed a significant increase of Ti, while NaF pretreatment increased F concentration significantly. TiF₄ at pH 1.2 led to the formation of globular precipitates occluding dentinal tubules, which could not be observed on samples treated with TiF₄ at pH 3.5. NaF at pH 1.2 but not at pH 3.5 induced the formation of surface precipitates covering dentinal tubules.

Conclusion

Dentin erosion can be significantly reduced by TiF₄ and NaF at pH 1.2, but not at pH 3.5.     

Protection of short-time enamel erosion by different tetrafluoride compounds

OBJECTIVE: This in vitro study aimed to analyse the protective effect of differently concentrated titanium (TiF(4)), zirconium (ZrF(4)) and hafnium (HfF(4)) tetrafluoride on enamel erosion. METHODS: Polished enamel surfaces of 36 bovine crowns were covered with tape leaving 4 enamel windows each 3mm in diameter exposed. The crowns were randomly assigned to six groups (each n=6) and pretreated with 4% TiF(4), 10% TiF(4), 4% ZrF(4), 10% ZrF(4), 4% HfF(4) or 10% HfF(4) for 4 min (first window), 10 min (second window) or 15 min (third window). The fourth window of each crown was not pretreated and served as control. Erosion was performed stepwise with 1% HCl (pH 2) in five consecutive intervals of each 15 s (total 75 s). Enamel dissolution was quantified by colorimetric determination of phosphate release into the acid. For each tooth, cumulative phosphate loss of enamel pretreated with one of the tetrafluoride compounds was calculated as percentage of the respective control and statistically analysed using two-way ANOVA. RESULTS: Enamel erosion was significantly reduced by TiF(4), ZrF(4) and HfF(4) application. Cumulative phosphate loss (mean % of control, 75s erosion) after 4-15 min application was significantly lower for 4% ZrF(4) (7-11%), 10% ZrF(4) (2-6%), 4% HfF(4) (11-9%) and 10% HfF(4) (12-16%) compared to 4% TiF(4) (42-27%) and 10% TiF(4) (54-33%). Only for 4% and 10% TiF(4), phosphate loss decreased with increasing duration of application, but also increased with increasing acid intervals. CONCLUSION: TiF(4), ZrF(4) and HfF(4) might protect enamel against short-time erosion, but protection was more enhanced by ZrF(4) and HfF(4) compared to TiF(4) application overtime.     

黑龙江省12岁儿童患龋状况与饮水氟浓度关系的抽样调查

目的:研究黑龙江省不同地区12岁儿童龋齿和氟斑牙的发病情况与当地饮水氟浓度的关系。方法:按照WHO《口腔健康调查基本方法》的要求,采用多阶段分层等容量随机抽样方法,抽取全省城乡6个地区的12岁年龄组792例儿童进行龋齿和氟牙症调查。采用SPSS12.0软件包进行统计学分析。结果:6个地区饮水氟浓度分别为0.29、0.40、0.68、0.77、0.80和1.14mg/L;相应的患龋率为44.7%、43.2%、41.7%、37.1%、28.0%和40.5%。除饮水氟浓度1.14mg/L组外,随着饮水氟浓度的增高,患龋率有下降趋势,两者呈负相关关系(r=-0.81)。社区氟牙症指数(CFI)与饮水氟浓度呈正相关关系(r=0.78)。结论:适当的饮水氟浓度可有效降低龋齿的发病率,在水氟过高的情况下,可能会引起龋病和氟牙症的高发。     

Effects of different fluoride recharging protocols on fluoride ion release from various orthodontic adhesives

Objective

The purpose of this study was to find the most effective fluoride recharging protocol for orthodontic adhesives.

Methods

Five orthodontic adhesives were used: a non-fluoride-releasing composite, a fluoride-releasing composite, a polyacid-modified composite (compomer), and two resin-modified glass-ionomer cements (RMGICs). Each specimen was placed into deionized water (DW) and the initial fluoride ion release was measured for 2 months. Each specimen was then subjected to four different treatments to simulate a fluoride recharge: 1000 ppm NaF solution, acidulated phosphate fluoride gel (APF), fluoride-containing dentifrice and DW (control). After topical fluoride treatment, each specimen was submitted to fluoride re-release tests.

Results

Fluoride-containing adhesives initially showed higher rates of fluoride ion release, but significantly declined to lower levels. The overall cumulative fluoride ion release during the initial period was RMGICs > compomer > fluoride-containing composite > non-fluoride-releasing composite. After topical fluoride treatment, the amount of fluoride ion re-released was proportional to the amount of fluoride ion previously released from the adhesives. However, the amount of fluoride ions released only lasted for 2 days and then returned to the levels before fluoride application. The overall cumulative fluoride ion re-release according to the fluoride treatments was APF and NaF solution > dentifrice.

Conclusion

This study suggests that using the combination of RMGICs and a fluoride-containing mouth rinse solution is the most effective protocol for long-term fluoride re-release from orthodontic adhesives, given the difficulty of routine use of APF at home, although all topical fluoride treatments can recharge fluoride ion in adhesives.     

The effect of increasing sodium fluoride concentrations on erosion and attrition of enamel and dentine in vitro

Objectives

To investigate the effect of an aqueous sodium fluoride solution of increasing concentration on erosion and attrition of enamel and dentine in vitro.

Methods

Enamel and dentine sections from caries-free human third molars were polished flat and taped (exposing a 3 mm × 3 mm area) before being randomly allocated to 1 of 5 groups per substrate (n = 10/gp): G1 (distilled water control); G2 (225 ppm NaF); G3 (1450 ppm NaF); G4 (5000 ppm NaF); G5 (19,000 ppm NaF). All specimens were subjected to 5, 10 and 15 cycles of experimental wear [1 cycle = artificial saliva (2 h, pH 7.0) + erosion (0.3% citric acid, pH 3.2, 5 min) + fluoride/control (5 min) + attrition (60 linear strokes in artificial saliva from enamel antagonists loaded to 300 g)]. Following tape removal, step height (SH) in μm was measured using optical profilometry.

Results

When the number of cycles increased the amount of tooth surface loss increased significantly in enamel and dentine after attrition and erosion and for dentine after attrition. Attrition and erosion resulted in greater surface loss than attrition alone after 15 cycles of experimental wear of enamel. 5000 ppm and 19,000 ppm sodium fluoride solutions had a protective effect on erosive and attritional enamel tooth wear in vitro, however no other groups showed significant differences.

Conclusions

The more intensive the fluoride regime the more protection was afforded to enamel from attrition and erosion. However, in this study no such protective effect was demonstrated for dentine.     

氟离子缓释正畸粘接剂缓释性能的研究

目的全面了解树脂型氟离子缓释正畸粘接剂(fluoride releasing adhesive，FRA)缓释氟离子的性能，建立一套评价FRA氟离子缓释性能的测试方法及指标。方法测定并计算FRA在一定时间中累计氟离子释放量，绘制出时间—氟离子累计释放量趋势线，并计算每单位质量FRA有效氟离子释放量。结果时间—氟离子累计释放量趋势线显示，FRA在90d内能持续、稳定地释放氟离子，每单位质量FRA在90d内有效氟离子释放量为449μg/g。结论本实验FRA试样具有稳定缓释氟离子的能力。     

Artificial enamel dental caries treated with different topical fluoride regimes: an in situ study

OBJECTIVES: To evaluate whether the topical fluoride application (acidulated phosphate fluoride, APF) at high concentration has an additional effect on the control of enamel lesions compared to fluoride dentifrice (FD; low concentration). The frequency of APF treatment on the arrestment of caries lesions and the amount of fluoride deposited on enamel after application of high and low fluoride concentrations were also evaluated. METHODS: Five subjects wore partial dentures with in vitro demineralized blocks during 35 days. All specimens (5p/subject) were brushed three times daily for 1 min with FD (1100 ppmF). Besides the FD treatment, four specimens were submitted to APF gel topical applications (12,300 ppmF) on weekly intervals (one to four applications). The enamel blocks were analyzed at baseline, after demineralization and after intraoral procedures regarding: surface roughness (SR), clinical aspects (brightness and texture), surface microhardness (SMH) and enamel fluoride content. Friedman's test was used to compare SMH and SR among the treatments. Analysis of variance, followed by Tukey's studentized range test, was used to evaluate fluoride content and SR among the groups. The significance level used was 5%. RESULTS: Changes in surface brightness, texture and SR were not detected. FD+3 APF and FD+4 APF were the only treatments capable of increasing SMH values and fluoride content compared to demineralized blocks (p < 0.001), although no differences could be observed within the treatments. CONCLUSIONS: This study showed that > or = 3 APF in addition to FD enhance enamel rehardening and produce a larger reservoir of fluoride.     

含氟牙釉质粘接剂释氟的实验研究

目的：研究国产含氟牙釉质粘接剂的释氟性能。方法：制备含氟牙釉质粘接剂I型和Ⅱ型的测试标本，以ORION720型离子选择性氟电极、参比电极测试氟离子浓度。结果：I型及Ⅱ型含氟牙釉质粘接剂均有氟离子释放，且在第一个24h后氟离子浓度下降显著，可维持21d左右；Ⅱ型含氟牙釉质粘接剂初始状态释放氟离子水平较高。结论：I型及Ⅱ型含氟牙釉质粘接剂均有释氟性能,而以Ⅱ型含氟牙质粘接剂较佳。