Effects of demineralizing tetracycline-stained human dentine

Summary In view of the belief that tetracycline is removed from bone when it is demineralized, it was decided to investigate the effect of demineralizing agents on human dentine. Teeth which had been stained in vivo with tetracycline were fixed in formalin and demineralized using mineral and organic acids and EDTA at neutral pH. When examined microscopically under ultraviolet light, the tetracycline lines in dentine, although reduced in intensity, were all still present. This indicates that formalin fixation does not appreciably alter the fluorescent effect of tetracycline in teeth and that it is not removed by demineralization. It seems likely therefore that tetracycline is incorporated in both the mineral and organic phases of human dentine.     

大黄提取液对脱矿釉质中钙溶出量的影响

目的 观察大黄提取液对脱矿釉质中钙溶出量的影响.方法 用不同浓度的大黄提取液和去离子水处理牙面后进行脱矿,ASCA生化分析仪对釉质脱矿后的脱矿液进行钙离子浓度的检测.结果 2 mg/ml和4 mg/ml大黄提取液处理后釉质钙溶出量<去离了水(P<0.01)、<1 mg/ml大黄提取液组(P<0.05),>2%氟化钠组但差异无统计学意义(P>0.05).1 mg/ml大黄提取液处理后釉质钙溶出量>2%氟化钠组(P<0.01),<去离子水组但差异无统计学意义(P>0.05).结论 2mg/ ml和4 mg/ml大黄提取液具有抑制脱矿釉质中钙溶出作用:2mg/ml大黄提取液为抑制钙溶出的起始有效浓度.     

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.     

Effect of fluoride toothpaste with nano-sized trimetaphosphate on enamel demineralization: An in vitro study

ObjectiveThis study evaluated the effect of toothpastes containing 1100 ppm F associated or not with micrometric or nano-sized sodium trimetaphosphate (TMP) on enamel demineralization in vitro, using a pH cycling model.DesignBovine enamel blocks (4 mm × 4 mm, n = 96) were randomly allocated into eight groups (n = 12), according to the test toothpastes: Placebo (without fluoride or TMP); 1100 ppm F (1100F); 1100F plus micrometric TMP at concentrations of 1%, 3% or 6%; and 1100F plus nanosized TMP at 1%, 3% or 6%. Blocks were treated 2×/day with slurries of toothpastes and submitted to a pH cycling regimen for five days. Next, final surface hardness (SHf), integrated hardness loss (IHL), differential profile of integrated hardness loss (ΔIHL) and enamel fluoride (F) concentrations were determined. Data were analyzed by ANOVA and Student-Newman-Keuls’ test (p < 0.05).ResultsThe use of 1100F/3%TMPnano led to SHf 30% higher (p < 0.001) and IHL ∼ 80% lower (p < 0.001) when compared to 1100F. This toothpaste also resulted in ∼64% reduction of mineral loss (ΔIHL) when compared to 1100F. Moreover, the addition of nano-sized TMP promoted increases in enamel F uptake of 90%, 160% and 100%, respectively for the concentrations of 1%, 3% and 6%, when compared to 1100F (p < 0.001).ConclusionThe addition of nano-sized TMP at 3% to a conventional toothpaste significantly decreased enamel demineralization when compared to its counterparts without TMP or supplemented with micrometric TMP.     

Scanning Electron Microscope Characterization of Erosive Enamel in Human Teeth

This study aimed to examine the surface characteristics of erosive enamel in extracted human teeth by scanning electron microscopy. Morphologic changes in naturally eroded enamel depend on the stages of dental erosion. In its early stages, the enamel surfaces show a honeycomb appearance due to the dissolution of enamel rod ends. In its advanced stages, the erosive process involves the underlying dentin and the eroded dentin shows exposed dentinal tubules and the dentinal matrix may be exposed due to the dissolution of the peri- and intertubular dentin. Evidence of remineralization is seen at the early stage of natural dental erosion.     

Effect of tricalcium silicate (Ca3SiO5) bioactive material on reducing enamel demineralization: An in vitro pH-cycling study

Objectives

The aim of this study was to investigate the effect of Ca₃SiO₅ on reducing enamel demineralization under pH-cycling conditions.

Methods

Forty bovine enamel samples were treated under four conditions: group 1, double distilled water (negative control); group 2, 1000 ppm F (as NaF, positive control); group 3, Ca₃SiO₅ slurry; and group 4, Ca₃SiO₅–F slurry (Ca₃SiO₅ with 1000 ppm F aq.). All the specimens were treated with treatment materials 4 times each day. Samples in groups 1 and 2 were soaked in test solutions for 2 min and samples in groups 3 and 4 were painted in treatment slurry for 2 min. At times between treatments, they were immersed in citric acid solution 3 times a day and 15 s each time. All the procedures were repeated for 7 days. Knoop microhardness, scanning electron microscopy (SEM), X-ray diffraction (XRD) and atom force microscopy (AFM) were used to examine samples.

Results

After treatment for 7 days, enamels in all the groups were significantly softened. The extents of microhardness reduction were 52.3%, 28.5%, 28.5% and 20.2% for groups 1, 2, 3 and 4, respectively. Samples in the negative control group showed a typical acid etched pattern while enamels in other groups were relatively compact. There was no significant difference between samples treated with Ca₃SiO₅ and F. The combination of Ca₃SiO₅ with F showed the best effect on reducing enamel demineralization.

Conclusions

Ca₃SiO₅ is an effective material against enamel demineralization alone but in combination with F a better anti-demineralization effect may be obtained.     

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。     

饮食调控或牙面清洁预防正畸患者牙釉质脱矿的临床研究

目的探讨调控饮食结构和定期牙面清洁预防正畸患者牙釉质脱矿的效果。方法选择接受固定矫治的患者247例,分为3组,饮食调控组81例,由家长监督患者每天的食物种类,尽量不吃或少吃含糖食物;牙面清洁组83例,每次复诊对牙面进行专业清洗、抛光;对照组83例,仅接受正常的口腔卫生健康宣教、指导。观察正畸患者治疗前后上下颌前牙釉质脱矿情况,计算各组前牙釉质脱矿程度(以釉质脱矿指数表示)和釉质脱矿发生率。结果矫治前3组患者上下颌前牙釉质脱矿的发生率和脱矿程度差异无统计学意义(P>0.05)。矫治后分别对饮食调控组和专业清洁组与对照组患者上下颌前牙牙釉质脱矿的发生率进行比较,差异均有统计学意义(P<0.05);矫治后饮食调控组、牙面清洁组和对照组前牙平均釉质脱矿指数分别为0.078、0.109和0.178,饮食调控组和牙面清洁组分别与对照组比较,差异均有统计学意义(P<0.05)。结论调控饮食结构和定期牙面清洁预防正畸牙釉质脱矿是有效和可行的。     

EFFECT OF IRON SUPPLEMENTATION ON THE EROSIVE POTENTIAL OF CARBONATED OR DECARBONATED BEVERAGE

This study evaluated, in vitro, the effect of iron (previously exposed with enamel powder or added directly to the beverage) on the erosive potential of carbonated or decarbonated beverage. Four sets of experiments were done. For groups E1 and E3, a solution containing 30 mmol/L FeSO₄ was added to bovine enamel powder (particles between 75-106 mm) before exposure to the carbonated or decarbonated beverage (Sprite Zero^®), respectively. For groups E2 and E4, 15 mmol/L FeSO₄ was added directly to the carbonated or decarbonated beverage, respectively. Control groups were included for comparison. In controls C1 and C3, the experiments E1 and E3 were repeated, but the iron solution was replaced by deionized water. For controls C2 and C4, the carbonated and decarbonated beverage, respectively, was used, without addition of iron. After addition of the beverage to the powdered enamel (40 mg enamel powder/400 µL of final volume), the sample was vortexed for 30 s and immediately centrifuged for 30 s (11,000 rpm). The supernatant was removed after 1 min 40 s. This procedure was repeated in quintuplicate and the phosphate released was analyzed spectrophotometrically. The results were analyzed by Student’s t-test (p<0.05). E2 presented the best results with a significant inhibition (around 36%) of phosphate released. For E3 and E4 a non-significant inhibition (around 4 and 12%, respectively), was observed. For E1 an increase in phosphate loss was detected. Thus, the protective effect of iron seems to be better when this ion is directly added to the carbonated beverage.