Influence of cementum on the demineralization and remineralization processes of root surface caries in vitro

The influence of the nature of the root surface on the demineralization and remineralization processes within artificial fluoride-treated caries lesions was investigated using microscopic and X-ray microanalytical methods. Traces of fluoride were detected in the outer parts (about 25 micrometers) of the lesions after the application of fluorides, and a high mineral content was proved for the same region by means of microanalytical calcium estimation. The location of this mineral-rich band in relation to the root surface was deeper into the root depending on the existence and thickness of a cementum layer. However, within the dentine the location and intensity of the mineral content were unaffected by the cementum. Investigation of artificial caries lesions without fluoride treatment showed the following: The degree of mineralization was kept at a higher level near the root surface in the presence of cementum. Consequently, a cementum layer gives some initial caries resistance of the root surface.     

Effect of a CPP-ACP agent on the demineralization and remineralization of dentine in vitro

OBJECTIVES: The aim of this study was to determine in vitro the effect of a commercial paste based on CPP-ACP complex on the demineralization of sound human dentine and on remineralization potential of artificial caries-like lesions formed on dentine surfaces. METHODS: Forty dentine specimens were prepared with hard tissue microtome. The specimens were divided in four groups the A, B, C and D (n=10). The specimen surfaces were subjected to surface analysis by Fourier transformance micro multiple internal reflectance infrared spectroscopy (micro MIR-FTIR). Tooth mousse was applied on surface specimens of A group, while no agent were applied on the specimens of B group. Afterwards, groups A, B, C and D were immersed in demineralization solution for 7 days. Afterwards, the surfaces were subjected to micro MIR-FTIR analysis and the mineral to matrix ratio was used to assess the extent of dentin demineralization (DM). Tooth mousse was applied on specimens of group C, while no agent was applied on specimens of group D. The groups C and D immersed in artificial saliva for 7 days and were subjected to analysis by micro MIR-FTIR and the mineral to matrix ratio was used to assess the extent of dentin remineralization (RM). RESULTS: Group A showed significant lower %DM in comparison to group B. Group C resulted in a significant higher %RM compared to group D. CONCLUSIONS: The presence of agent CPP-ACP on dentine surfaces provoked lower demineralization and higher remineralization in comparison with the dentine surfaces without agent.     

Incipient caries lesions on cementum by mono- and co-culture oral bacteria

Objectives

There is increasing prevalence of root caries. We hypothesized different biofilms will cause varying demineralization in cementum. This study investigated the extent of demineralization of cementum by oral biofilm formed from three major cariogenic microorganisms: Streptococcus mutans, Lactobacillus acidophilus, and Actinomyces israelii. Sound cementum tooth blocks were incubated with mono-, bi-, and tri-species combinations of the bacteria under investigation.

Materials and methods

The matrix (amide I) and phosphate content of the lesions was analyzed by Fourier-transform infrared spectroscopy (FTIR), and calcium and phosphorus levels were analyzed by scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDX).

Results

The log[amide I:HPO₄²⁻ absorbance] values showed that A. israelii mono-culture caused significantly more demineralization than the other bacterial cultures. log[Ca:P] showed that all carious lesions were confined to the cementum.

Conclusions

Oral biofilm arising from bacterial species A. israelii alone was the most cariogenic of those tested and produced the most demineralization in incipient carious lesions in cementum.     

The efficacy of techniques for the disinfection of artificial sub-surface dentinal caries lesions and their effect on demineralization and remineralization in vitro

OBJECTIVES: The efficacy of three techniques for the disinfection of artificial sub-surface root caries lesions and their response to subsequent episodes of de- and remineralization was investigated quantitatively in vitro. METHODS: Sub-surface dentinal lesions (n=20), cut into four experimental blocks and deliberately contaminated with Streptococcus mutans, were subject to either steam autoclaving (121 degrees C, 5min), gamma irradiation (4100Gy), immersion in 0.1% (w/v) thymol-distilled water solution (24h) or reserved as a control. Next, the lesions were incubated aerobically in sterile nutrient broth for 24h at 37 degrees C and resultant cultures plated onto blood agar and neutralisation agar. Ten blocks from each experimental group were then immersed in an acidic buffer solution or exposed to artificial saliva for 5 days. Baseline changes in the mineral content and distribution of the lesions were assessed by transverse microradiography (TMR). RESULTS: Micro-organisms were recovered from each control block and one block treated by gamma irradiation. Steam autoclaving and immersion in a thymol solution significantly decreased (p<0.05) the amount of mineral lost from the body of lesions subject to a further acid challenge. Mineral ion uptake by lesions exposed to artificial saliva was significantly increased (p<0.05) through disinfection by steam autoclaving. CONCLUSIONS: Gamma irradiation proved the most acceptable method for the disinfection of sub-surface root dentine lesions having the least adverse effect on demineralization and remineralization.     

釉质脱矿与再矿化的实验室及临床评估方法

釉质再矿化的研究是近年研究的热点,对釉质再矿化前后的评估方法多种多样,目前国际尚无统一的标准。作者就评估脱矿与再矿化的实验室及临床研究方法及其应用范围、优缺点进行综述。     

The effect of xylitol and fluoride on remineralization for primary tooth enamel caries in vitro

The effect of fluoride and xylitol on remineralization at the early stage of the enamel caries in primary tooth was studied. The samples were divided into four groups (control, 10% xylitol, 950 ppm NaF and 10% xylitol+950 ppm NaF) and analyzed by the using single thin section method and pHcycling model in vitro. The remineralizing ratio were control –8.9%, xylitol –0.4%, NaF 8.3% and xylitol + NaF 32.4%, respectively. Xylitol+NaF group particularly showed significantly smaller ΔZ value compared with 0 days (P<0.05). Therefore we assume that the effect of xylitol and fluoride are additive. We concluded that xylitol and fluoride treatment to the tooth enamel may be an effective caries-preventive measure in both primary and permanent tooth enamel.     

Effect of three fluoride agents on remineralization and fluoride uptake on enamel lesion

This study is to compare the fluoride uptake of three fluoride agents and the effect of remineralization on artificial enamel lesions. Eight human third molars were all divided into four slabs. The slabs were randomly assigned to the following four groups: group A (9,040 ppm F, APF gel), group B (968 ppm F, SnF₂ home gel), group C (22,600 ppm F, fluoride varnish, FV) and a control group. After 72-hour demineralizing and 10-day pH-cycling period with the application of corresponding fluorides. The distribution of fluoride and mineral change was analyzed with EPMA and CMR respectively. There was a significant increase in the amount of F uptake after the application of the three fluoride agents compared to the control group. Group A showed an extremely greater F uptake compared to group C and B. The amount of F uptake from group C was greater than that of group B. The three tested groups showed signs of significantly greater amounts of remineralization as compared to the control group. Remineralization of group C was detected to be the greatest, followed by group A and group B, but there was no significant difference in them under statistical analysis. It can be concluded that all of the tested agents were effective in regaining mineral loss. FV may be recommended as a professional topical fluoride. It is as effective, if not more so, as traditionally used APF gel. Also 0.4% SnF₂ home gel is an efficient self-applied topical fluoride for daily use.     

Effects of a self-etching resin coating system to prevent demineralization of root surfaces

OBJECTIVES: The purpose of this study was to evaluate the ability of an experimental self-etching resin coating system to protect against demineralization of the root surface in vitro, comparing its effectiveness with two commercial one-step self-etching adhesives. METHODS: The experimental resin coating system (EC), consisting of a self-etching primer and an acrylate-based resin, or the two commercial self-etching adhesives, Adper Prompt-L Pop (AD) and Clearfil Tri-S Bond (S3), was applied to the cementum of a human extracted tooth root. The specimens were immersed in acetate buffer at pH 5.5 for 4 weeks, and the degree of demineralization underneath the materials was evaluated by microscopic observation and contact microradiography. Each material's sealing and interfacial ultrastructure on the cementum was morphologically examined by scanning electron microscopy, and their bonding ability to cementum was determined by microtensile bond strength (MTBS) tests. RESULTS: Application of AD and S3 showed limited effects to protect against demineralization, but no demineralization was observed for EC. EC showed greater coating thickness than the other two materials, with formation of integral hybridized layers with cementum. Although the MTBS values for EC were significantly lower than those for AD and S3, cohesive failure in resins was the prevalent fracture mode for EC, showing no possible disadvantages in bonding ability. SIGNIFICANCE: The experimental resin coating system effectively prevented acid demineralization on root surfaces due to its ability to produce an appropriately thick coating and an integral hybridized layer.     

Effect of low level fluoride on demineralization kinetics of human dental enamel

The purpose of this study was to examine the effect of fluoride levels similar to those reported for saliva from low fluoridated and high fluoridated water areas on the demineralization of human permanent enamel. An adaptation of the method described by Robinson et al. was used. Sections of sound enamel were immersed in a vial containing demineralizing solution [2.0 mM Ca(NO₃)₂, 1.2 mM KHPO₄ in 50 mM acetic acid, pH 4.8] for 1 hour. The demineralizing solution contained 0, 0.02 or 0.05 ppm fluoride, added as NaF was prepared. Twenty microliters aliquots were taken from the demineralizing solution at the time point up to 1 hour, with a sampling frequency bias towards the early time point. The phosphate content of the removed sample was determined by colorimetry. When the mineral loss curves for fluoridated and non-fluoridated demineralizing solutions were compared, there were significant differences between both groups. There was a decrease in the net mineral loss when fluoride was used. This result suggested that salivary fluoride levels of 0.02 ppm and 0.05 ppm had a protective effect against demineralization.     

三种氟素制剂对离体乳牙牙釉质抗酸性影响的比较研究

目的 比较三种常用氟素制剂对离体乳牙牙釉质抗酸性的影响。方法 40个离体乳前牙，随机分为4组。开窗，酸蚀，1、2、3组分别涂布10%（NH4）2MoO2F4溶液，38%Ag(NH3)2F溶液，APF-LaCl3溶液联用3min,第4组涂去离子水3min，将经上述处理的牙齿标本分别浸泡于8ml0.1mol/L乳酸中，开始记时，于1、3、6、12、24、48、72、144h各取出1ml液体，检测其Ca^2 浓度的A值，计算各处理组各时间点釉4质钙溶出总量，统计分析。结果 同对照组相比，3种氟素制剂处理组牙釉质脱矿总量显著降低。其中APF-LaCl3溶液联用处理组最低，10%（NH4）2MoO2F4溶液与38%Ag(NH3)2F溶液处理组牙釉质脱矿总量无差别。结论 3种氟素制剂均可有效地抑制牙釉质脱矿。其中APF-LaCl3溶液联用作用最强，10%（NH4）2M煤F4溶液与38%Ag(NH3)2F溶液抑制牙釉质脱矿作用的能力相当。     

Promotion of enamel caries remineralization by an amelogenin-derived peptide in a rat model

ObjectiveAn amelogenin-derived peptide has been shown to promote remineralization of demineralized enamel in an in vitro model of initial caries induced by pH cycling. The present study examines whether the peptide exerts similar effects within the complex oral environment in vivo.DesignSpecific pathogen-free Sprague-Dawley rats (n = 36) were infected with Streptococcus mutans, given ad libitum access to Diet 2000 and drinking water supplemented with sucrose (10%, w/v), and then randomly divided into three groups treated with 25 μM peptide solution, 1 g/L NaF or deionized water. Molar teeth were swabbed twice daily with the respective solutions for 24 days. Then animals were killed, their jaws were removed and caries lesions were analyzed using the quantitative light-induced fluorescence-digital (QLF-D) technique to measure changes in mineral content. To verify QLF-D results, caries were scored for lesion depth and size using the Keyes method, and analyzed using polarized light microscopy (PLM).ResultsMineral gain was significantly higher in teeth treated with peptide or NaF than in teeth treated with water (p < 0.05), based on the QLF-D results (ΔF and ΔQ). Incidence of smooth-surface and sulcal caries based on Keyes scores was similar in rats treated with peptide or NaF, and significantly lower in these groups than in rats treated with water (p < 0.05). Lesions on teeth treated with peptide or NaF were shallower, based on PLM. No significant differences were observed between molar enamel caries treated with peptide or NaF.ConclusionsThis amelogenin-derived peptide can promote remineralization in a rat caries model, indicating strong potential for clinical use.     

氟化牛奶再矿化及抗龋作用的体内观察

目的：探索氟化牛奶在口腔局部的防龋作用机制。方法：利用口内装置,采用交叉对照的试验方法,观察氟化牛奶在口腔局部的再矿化作用和搞龋作用,结果：氟化牛奶有明显的再矿化作用,本试验条件下未观察到抗龋作用,结论氟化牛奶在口腔局部的作用机制主要是再矿化。     

Studies of dental root surface caries. 2: The role of cementum in root surface caries

Artificial caries lesions were produced in roots of teeth using an acetate buffer system, when the layer of cementum was either normal in thickness, excessively thickened by hypercementosis, of had been removed completely. The rates of lesion progression were measured in each case using polarized light microscopy to measure lesion depth. Analysis of calcium (Ca) and phosphorus (P) loss during the demineralizing process was carried out. The removal of cementum was found to significantly increase the initial rate of penetration of the lesion into the root, although this rate progressively reduced to a level consistent with that found in normal roots after seven days of demineralization. The overall depth remained consistently greater than that observed in normal roots, or when lesions were produced entirely within hyperplastic cementum. Chemical analysis also showed removal of cementum resulted in an initial doubling of the Ca and P lost from the root surface.
Prior direct exposure of segments of normal roots to the oral environment was found not to significantly alter the rate of artificial lesion progression, in comparison with that in the originally protected segment of the root surface.
It was concluded that an intact cementum layer has the intrinsic ability to protect the underlying dentine of exposed tooth roots against acidic demineralization and that prior exposure to the oral environment does not significantly alter this ability.     

Effect of fluoride on artificial caries lesion progression and repair in human enamel: regulation of mineral deposition and dissolution under in vivo-like conditions

OBJECTIVE: This study was carried out to determine in vitro the effect of fluoride on (1) the demineralization of sound human enamel and (2) the progression of artificial caries-like lesions, under relevant oral conditions. METHODS: Thin sections of sound human enamel were exposed to solutions undersaturated with respect to tooth enamel to a degree similar to that found in dental plaque fluid following sucrose exposure in vivo, containing fluoride concentrations (0-0.38ppm) found in plaque fluid. Mineral changes were monitored for 98 days, using quantitative microradiography. The effect of fluoride (1.0-25.0ppm) on the progression of artificial caries-like lesions was similarly studied. RESULTS: Fluoride concentrations of 0.19ppm and greater were found to prevent the demineralization of sound enamel in vitro. However, significantly higher concentrations of fluoride (25.0ppm) were required to prevent further demineralization of artificial caries-like lesions. Demineralizing solutions with intermediate fluoride concentrations (2.1-10.1ppm) induced simultaneously remineralization in the outer portion of the lesion and demineralization in the inner portion. Simultaneous remineralization and demineralization were also observed in hydroxyapatite pellets. CONCLUSIONS: Our results show that the observed effect of fluoride on enamel demineralization is not solely a function of bulk solution properties, but also depends on the caries-status of the enamel surface. A mechanistic model presented indicates that, in comparison to sound enamel surfaces, higher concentrations of fluoride are required to prevent the progression of artificial caries-like lesions under in vivo-like conditions since the diffusion of mineral ions that promote remineralization is rate-limiting.     

Effects of fluoride concentration on enamel demineralization kinetics in vitro

Objectives

The aim of the present study was to measure the effects of fluoride concentration on the real-time in vitro demineralization of enamel during exposure to caries-simulating conditions using Scanning Microradiography (SMR).

Methods

Enamel blocks obtained from non-carious human molars were fixed in SMR environmental cells, through which acidic solutions (0.1 M acetic acid, pH 4.0) were circulated for periods of 48 h. SMR was used to quantitatively measure continuous mineral mass loss. Subsequently, the effects of sequentially increasing fluoride concentration (0.1–4500 mg/L [F⁻]) in the acidic solutions were measured on the rate of enamel demineralization.

Results

The data shows a log-linear relationship between [F⁻] and reduction in demineralization up to 135 mg/L [F⁻]. Above 135 mg/L, no further significant decrease in demineralization occurred.

Conclusion

The optimum range of local fluoride concentration for reducing enamel demineralization was in the range 0.1–135 mg/L [F⁻] under the conditions studied.

Clinical significance

Relatively low [F⁻] can exhibit near-optimum protection. Increasing the fluoride concentrations above 135 mg/L may not necessarily give an increased cariostatic benefit. Improving the means of delivery of relatively low fluoride concentrations to the oral fluids through slow releasing mechanisms, such as the oral fluoride reservoirs, is the more appropriate way forward for sustaining long-term clinical efficacy.     

3种氟制剂对邻面去釉后牙釉质再矿化效果的影响

目的 比较3种氟制剂对邻面去釉后牙釉质再矿化效果的影响,为临床选择预防邻面去釉后牙釉质脱矿的最佳氟制剂提供参考.方法 收集正畸减数拔除的前磨牙60颗,行近远中邻面去釉,牙冠颊舌向劈开后共120个标本,随机分为4组.对照组单纯用人工唾液进行再矿化,A组加用0.1 mol/L氟化钠溶液处理,B组加用6 000 mg/L(6 000 ppm)氟化泡沫处理,C组加用氟含量0.1％(质量分数)的氟保护漆处理.每4周处理1次,共处理3次.应用显微硬度仪测量每个标本再矿化前及再矿化后4周去釉面的显微硬度值,并进行统计学分析.结果 再矿化前、后牙釉质显微硬度差值在对照组为(3.42 ±2.27) kg/mm2,A组为(13.06 ±4.22) kg/mm2,B组为(20.21±4.96)kg/mm2,C组为(16.05 ±5.51) kg/mm2.各组再矿化前、后的显微硬度变化均有统计学意义(P＜0.01).再矿化前、后显微硬度差值在4组间的差异有统计学意义(F =26.168,P=0.000);两两比较,A、B、C3组与对照组的差异均有统计学意义(P＜0.01),B组和A、C组间的差异有统计学意义(P＜0.01),A组和C组间的差异无统计学意义(q=2.142,P=0.139).结论 氟化钠溶液、氟化泡沫、氟保护漆对去釉后的牙釉质再矿化均具有良好的促进作用,其中氟化泡沫的效果优于其他2种制剂.     

In vitro evaluation of fluoride and calcium sodium phosphosilicate toothpastes, on root dentine caries lesions

Objectives

The aim of this in vitro study was to assess the effect of toothpastes containing three different sodium fluoride concentrations and a calcium sodium phosphosilicate system, on root dentine demineralization and remineralization.

Methods

During a fourteen-day pH-cycling protocol, pre-softened bovine root dentine specimens were immersed twice daily, before and after the demineralization periods, for 2 min, in the following toothpaste slurries: (a) non-fluoridated (control), (b) 7.5% calcium sodium phosphosilicate, (c) 1450 ppm F, (d) 2800 ppm F, and (e) 5000 ppm F. Subsequently, the slabs were subjected to a fifty-hour acid resistance test. Knoop microhardness at different lesion depths was assessed in specimen cross-sections and KHN values were converted to vol.% mineral. Comparisons between the groups were performed at each lesion depth through ANOVA-based tests and furthermore, regression analysis of the derived statistic of “integrated vol.% mineral loss” was carried out. Also, lesions were evaluated qualitatively using transmission and polarized light microscopy.

Results

The 5000 ppm F toothpaste group, during pH-cycling, presented significantly less total vol.% mineral loss and subsequently exhibited considerably increased surface acid resistance, compared to all the other tested groups. The calcium sodium phosphosilicate toothpaste, during pH-cycling, inhibited demineralization and/or promoted remineralization of the surface layers significantly more effectively than the control group nevertheless, subsequently, the acid resistance of the calcium sodium phosphosilicate dentifrice group was similar to that of the control group. These observations were confirmed by microscopic examination of the lesions.

Conclusions

Under the present experimental conditions, the 5000 ppm F toothpaste, promoted remineralization and inhibited demineralization more effectively, than the other tested toothpastes.     

根面处置牙周炎患牙根面牙骨质后内毒素水平的变化

目的:观察不同方法处置牙周炎患牙根面牙骨质后内毒素水平的变化.方法:选择临床上因正畸拔除的健康前磨牙6例,重度牙周炎拔除的后牙36例.每颗牙取釉-牙骨质界下2 mm牙根,制成2片4 mm×4 mm×1 mm的牙骨质片,对每个牙周炎患牙进行编号.健康牙作为阴性对照组,36颗牙周炎患牙中,每颗牙的1个牙片不进行根面处理,作为牙周炎组.其余36片牙周炎牙片随机平均分成6组:龈下刮治及根面平整(scaling and root planning,SRP)组、SRP+抗菌肽A组、SRP+抗菌肽B组、SRP+EDTA组、SRP+ Nd:YAG激光组和SRP +Er:YAG激光组.用显色基质鲎试剂检测每个牙片的内毒素浓度.按照编号,记录每颗牙的内毒素浓度,计算每组每个牙周炎患牙治疗前、后内毒素浓度的变化.采用SPSS 17.0软件包对数据进行统计学分析.结果:与牙周炎组相比,各治疗组内毒素浓度有不同程度降低,均有显著差异(P＜0.01).与SRP组相比,SRP+抗菌肽A组、SRP+抗菌肽B组、SRP +Er:YAG激光组内毒素浓度显著下降(P＜0.01),SRP+EDTA组、SRP+ Nd:YAG激光组之间无显著差异(P＞0.05).结论:不同方法处理牙周炎患牙根面均可降低内毒素含量,抗菌肽A+SRP处理牙周炎根面可能更为有效.     

护牙素与多乐氟对放射线照射后牙骨质显微硬度的影响

目的 探讨护牙素与多乐氟对放射线照射后牙骨质显微硬度值的影响.方法 收集因正畸减数拔除的前磨牙40颗,随机分为4组,其中3组在20℃下对牙根表面开窗区进行放射线照射：直接照射组直接采用放射线照射开窗区;护牙素组每次照射前先在开窗区涂上护牙素,再进行放射线照射,照射结束后去离子水冲洗表面;多乐氟组首次照射前在开窗区按照操作步骤涂多乐氟,再次照射前无需再涂;另设空白对照组,只在相同环境中保存,开窗区表面不做任何处理.照射前后分别测量各组的牙骨质表面显微硬度值.结果 照射前直接照射组、护牙素组、多乐氟组、空白对照组的显微硬度值分别为86.8±6.88、90.9±9.34、84.5±7.87、91.2±9.81,各组牙骨质表面显微硬度值差异无统计学意义（P＞0.05）.照射后,直接照射组显微硬度值（30.7±5.62）明显低于护牙素组（113.4±10.15）、多乐氟组（135.9±8.52）、空白对照组（91.2±9.81） （P ＜0.05）,护牙素组显微硬度值明显高于空白对照组（P＜0.05）,而多乐氟组显微硬度值明显高于空白对照组与护牙素组（P＜0.05）.结论 应用护牙素或多乐氟能够有效预防放射线所致的牙骨质脱矿,并能促进其再矿化,但多乐氟的防龋效果优于护牙素.     

含氟涂料和含氟牙膏对釉面再矿化和抗酸作用的实验研究

目的：观察含氟涂料与含氟牙膏对釉质表面再矿化和抗酸作用。方法：取牛恒切牙制备釉质片;统一酸蚀脱矿后随机分为4组（n＝3）;分别为生理盐水（A组对照）、Duraphat含氟涂料（B组）、Fluor Protector含氟涂料（C组）、含氟牙膏规律处理（D组）;处理期间标本置于人工唾液孵育2周;再次酸蚀;各阶段均用显微硬度仪测定釉面显微硬度、扫描电镜观察釉面,图像分析电镜下釉面微孔隙面积差异;统计分析。结果：首次酸蚀后釉面明显脱矿。分组处理2周,A组釉面再矿化不明显;B组和C组釉面形成涂料保护层;D组釉面可见明显再矿化。再次酸蚀后：A组和D组显微硬度下降,B组和C组涂料保护层有明显抗酸作用。再次酸蚀后,A组和D组釉面微孔隙面积增加（P＜0．05）,但D组小于A组（P＜0．05）;B组、C组无显著变化（P＞0．05）。结论：含氟涂料在釉面形成保护层,具有抗酸蚀和促进釉面再矿化作用;含氟牙膏能促进脱矿釉面再矿化,抗酸作用较弱。