不同种类饮料对青少年牙釉质钙浓度的影响

目的：探讨三种不同的碳酸饮料对我国14岁以下青少年的牙釉质中钙浓度的影响。方法：收集在我院进行减数拔牙的14岁以下青少年的第一前磨牙30颗进行研究。从超市购买同批次的雪碧,百事可乐和冰茶进行试验。首先,使用全自动生化分析仪（Olympus AU5400）对购买的三种饮料进行检测,确定其钙离子的浓度。使用购买的同批次的各种碳酸饮料对标本进行浸泡,浸泡时间为1周,取出,对浸泡后的牙齿使用显微硬度仪进行牙釉质硬度的检测,对浸泡后的溶液,使用全自动生化分析仪进行钙浓度的检测,比较浸泡后的牙釉质和浸泡前牙釉质的硬度变化和饮料中钙离子浓度的变化。结果：购买的饮料中雪碧的钙浓度为0．57mmol／L,百事可乐的钙离子浓度为0．93mmol／L,冰茶的钙离子浓度为0．18mmol／L。三种饮料均能导致牙釉质中钙离子的溶出。不同种类饮料导致牙釉质中钙离子溶出的量不同,差异具有统计学意义（P〈0．05）。显微硬度仪的检测,发现经过三种饮料处理的牙齿硬度均下降,差异具有统计学意义（P〈0．05）。结论：三种饮料都能导致牙釉质脱矿,其中可乐的脱矿作用最强。     

Demineralization effects of 10 percent carbamide peroxide

Objectives: The purpose of this in vitro study was to measure the amount of calcium lost from enamel exposed to a 10% carbamide peroxide solution.

Methods: Nine teeth (3 incisors, 2 premolars, 4 molars) were sectioned to serve as paired test and control specimens. Each tooth half was coated with wax, leaving a uniform 3 mm × 4 mm window of exposed enamel. Test specimens were placed in culture tubes with 1.00 ml of deionized water and 0.02 ml of 10% carbamide peroxide for 6 h; controls were exposed to water alone. Calcium concentrations in the solutions were measured using a Perkin-Elmer 5100 atomic absorption spectrophotometer.

Results: Teeth exposed to carbamide peroxide lost an average of 1.06 μg/mm² of calcium. This amount of loss was significantly greater than controls (p < 0.001), according to ANOVA. For comparison, teeth were exposed to a cola beverage for 2.5 min, the time equivalent of drinking a 16 oz. beverage. The amount of calcium lost from these teeth was also about 1 μg/mm².

Conclusions: Teeth exposed to 10% carbamide peroxide lost calcium. However, the amount of loss was small, and may not be clinically significant.     

Fluor Protector对饮料所致牙釉质脱矿的抑制作用

目的　研究 Fluor Protector对饮料导致牙釉质脱矿的抑制作用。方法　将牛牙齿标本分成实验组和对照组 ,实验组在 Fluor Protector预处理釉质后用不同种类饮料处理 ,对照组不经 Fluor Protector处理而直接用饮料处理。饮料的处理为 5分钟 /次 ,10次 /天 ,处理 7天以后 ,分别用肉眼和扫描电镜观察牙釉质表面发生的改变。结果　肉眼观察发现无论是实验组还是对照组 ,有色饮料均能导致牙釉质表面颜色发生改变 ,均能使牙釉质脱矿 ,表现为釉质呈不同程度的白垩色改变。扫描电镜观察发现 ,对照组除去离子水外 ,牙釉质的超微结构均发生改变 ,表现为牙釉柱中心晶体、釉柱间隔有不同程度的溶解 ,而实验组则表现出较明显的抑制作用。结论　 FluorProtector具有明显的抑制饮料脱矿的作用     

Dolomite as a possible magnesium-containing phase in human tooth enamel

Summary A solid-state chemical model is derived to estimate the solubility of dolomites having different degrees of cation ordering. It is shown that the solubility of dolomites formed by precipitation at ordinary temperatures is such that it allows for the formation of dolomite in tooth enamel duringin vivo mineralization.     

Demineralization of bone matrix: Observations from electron microscope and electron-probe analysis

Displacement or removal of mineral during the processing of calcified tissues for electron microscopy is a recognized phenomenon. An electron microscope analysis has been made of artefactual mineral loss during ultramicrotomy of osteogenic tissue. It is concluded from morphological investigation and the use of electron diffraction that this loss of crystalline mineral during sectioning can considerably change the morphology of calcified tissues and may lead to inaccurate interpretation of cell and matrix morphology. Electron probe X-ray microanalysis has been used to demonstrate in a semi-quantitative manner, the artefactual loss of calcium and phosphorus. Problems of specimen preparation for such analytical work are discussed.     

Ultrasound Characterization of Bone Demineralization

Quantitative ultrasound (QUS) assessment of bone may permit an assessment of bone properties currently not available by bone densitometry techniques. To explore the effects of the quantity of bone mineral on acoustic parameters, we carried out an in vitro study of the impact of demineralization on attenuation of ultrasound in trabecular bone. Ten fresh cubes of trabecular bone obtained from bovine distal femurs were progressively demineralized using formic acid solution. The progression of demineralization was controlled by monitoring the specimen bone mineral density (BMD) using dual x-ray absorptiometry (DXA). At five stages of demineralization—0% (baseline), 25%, 50%, 75%, and 100% (all mineral removed)—the US properties of the specimens were assessed (Walker Sonix UBA 575+). The US parameters investigated were broadband ultrasound attenuation (BUA) and ultrasound attenuation in bone (UAB). Both DXA and QUS measurements were made along the three orthogonal axes of each cube. Our results demonstrated significant variability in both BUA and UAB along the three principle axes of the cubes whereas BMD did not differ in the different directions. A strong but nonlinear correlation was found between BMD and US attenuation. A reduction in BMD to 50% of the baseline values resulted in BUA (UAB) reduction to 25% and 19%, respectively. A random effect model analysis supported a multiplicative relationship between BMD and the US parameters. US attenuation is a sensitive indicator of bone mineral changes with nonlinear dependence on bone mineral loss. Bone collagen structure reinforced by hydroxyapatite crystal accounts for fundamental US characteristics. Ultrasound attenuation associated with trabecular orientation is basically dominated by the mineral spread in a collagen framework. Received: 3 February 1997 / Accepted: 2 July 1997     

电化学人工釉质龋和早期光滑面釉质龋组织病理学比较

为进一步研究电化学人工龋模型和龋病的关系，我们采用生物显微镜和扫描电子显微镜等手段，对体外形成的电化学人工釉和早期光滑面釉质龄的组织病理学进行了对比观察。结果表明电化学人工釉质龋在生物显微镜下和早期光滑面釉质龋一样形成以表层下脱矿为主要特征的病理改变，电化学人工釉质龋在扫描电子显微镜下主要表现为釉柱的釉柱的核心脱矿溶解，这亦和早期光滑面釉质龋相似。因此本研究结果提示二者有着十分相似的病理特点和病变     

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.     

Effect of ethylene oxide sterilization on enamel and dentin demineralization in vitro

For in situ studies into caries prevention, sterilization of tooth samples is essential. However, sterilization may influence the caries process itself. The aim of this study was to assess the effect of sterilising sound human enamel and dentin with ethylene oxide on lesion depth and mineral loss before and after in vitro demineralization. Lesion depth and mineral loss were measured using transversal microradiography (TMR). The experiment was carried out with 32 enamel and 32 dentin samples. We found a significant reduction of lesion depth due to sterilization in demineralized enamel (-9.8microm; 95% CI: -15.1 to -4.4microm). The small effect of sterilization on demineralized enamel is considered to be irrelevant for in situ studies of de- and remineralization.     

Rehardening of acid-softened enamel and prevention of enamel softening through CO2 laser irradiation

Objectives

The aims of the present study were to investigate whether irradiation with a CO₂ laser could prevent surface softening (i) in sound and (ii) in already softened enamel in vitro.

Methods

130 human enamel samples were obtained and polished with silicon carbide papers. They were divided into 10 groups (n = 13) receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C); and submitted to 2 different procedures: half of the groups was acid-softened before surface treatment and the other half after. Immersion in 1% citric acid was the acid challenge. Surface microhardness (SMH) was measured at baseline, after softening and after treatment. Additionally, fluoride uptake in the enamel was quantified. The data were statistically analysed by two-way repeated measurements ANOVA and post hoc comparisons at 5% significance level.

Results

When softening was performed either before or after laser treatment, the L group presented at the end of the experiments SMH means that were not significantly different from baseline (p = 0.8432, p = 0.4620). Treatment after softening resulted for all laser groups in statistically significant increase in SMH means as compared to values after softening (p < 0.0001). Enamel fluoride uptake was significantly higher for combined laser-fluoride treatment than in control (p < 0.0001).

Conclusion

Irradiation of dental enamel with a CO₂ laser at 0.3 J/cm² (5 μs, 226 Hz) not only significantly decreased erosive mineral loss (97%) but also rehardened previously softened enamel in vitro.