氟对大鼠氟斑牙形成和成釉细胞DNA损伤的研究

目的：研究在氟中毒引起氟斑牙时,氟对大鼠切牙成釉细胞DNA损伤的影响。方法：给雄性SD大鼠饮用含10、50、100mg/LNaF的高氟水120d,制备氟斑牙模型,用单细胞凝胶电泳检测DNA的损伤。结果：雄性SD大鼠饮用高氟水后,血清氟含量较对照组显著增高,P〈0.05。饮水氟含量与血清氟含量的相关系数为0.9153（P〈0.05）,具有较好的剂量-效应关系,大鼠切牙呈现典型的氟斑牙改变。在50mg/LNaF的剂量条件下,大鼠切牙成釉细胞彗星长与对照组比较,P〈0.05。在100mg/LNaF的剂量条件下,彗星长、Olive尾距、尾分布距与对照组比较,P〈0.05,而尾长值虽比对照组增加,但P〉0.05。低剂量染氟组（10mg/LNaF）大鼠切牙成釉细胞DNA损伤情况与对照组比较,没有显著性差异（P〉0.05）。结论：在氟中毒引起氟斑牙的过程中,大鼠切牙成釉细胞发生明显的DNA损伤。     

Strategies and dental care in the treatment of patients with myelomeningocele

Myelomeningocele (MMC) is a congenital malformation that occurs in the embryonic period, characterized by failure in closure of the caudal portion of the neural tube during central nervous system formation. Alterations and complications can be associated with this condition, such as hydrocephalus, neurogenic bladder, orthopedic problems, and motor and cognitive impairment. This patients with MMC also have predisposition to develop latex allergy and high caries risk and activity due to deficient oral hygiene, fermentable carbon hydrate‐rich diet and prolonged use of sugar‐containing oral medications. This paper reports the oral findings and dental treatment in a 15‐year‐old female patient diagnosed with MMC and describes the strategies used to improve dental treatment conditions and reduce the impact of associated risks to her health. The measures and precautions adopted in this case could be useful to reduce the barriers for patients with the same condition to access oral health care: regular visits to the dentist, initiating as early as possible; frequent reinforcement of oral homecare instructions and diet counseling; minor adaptions to the dental chair and dental office to improve ease of access due to patients’ mobility problems; prevention of latex‐related allergic reactions; reduction of gag reflex during dental procedures.     

Prevalence of developmental defects of enamel and dental caries in New Zealand children receiving differing fluoride supplementation

A survey of the prevalence of dental caries and developmental enamel defects in 666 New Zealand children aged 9 years and with differing histories of fluoride supplementation was carried out in 1982. In the LF (low fluoride) group 22.8% of children had diffuse white opacities compared with the WF (water fluoridation) group, 36.7%, and the CT (continuous use of fluoride tablets) group 49.4% (P = 0.0018). When the tooth prevalence was determined, the differences were more marked with 4.9% of teeth affected in the LF group and 24.7% in the CT group. Dental caries prevalence in the fluoride history groups displayed an inverse relationship with fluoride supplementation, the LF group had a DMFT of 2.4, the WF group, 1.7 and the CT group, 1.2. The prevalence of both diffuse opacities and of dental caries in the PT group where tablets had been used to 5-6 yr of age was anomalous. The survey confirmed that diffuse opacities occur in children with a low fluoride intake but the prevalence increases in groups of children given fluoride supplements.     

人牙源性上皮细胞的体外培养研究

目的：建立人牙源性上皮细胞的体外培养方法，为牙齿组织工程研究提供可靠的种子细胞来源。方法：采用组织块法原代培养人牙源性上皮细胞，用更换培养液类型、多次差别消化法和反复贴壁法进行纯化，在倒置显微镜下观察细胞形态及生长状况，用免疫荧光法检测细胞表达角蛋白和成釉蛋白的情况。结果：原代培养的人牙源性上皮细胞生长良好，但有少量成纤维细胞混杂，经纯化后明显好转，上皮细胞呈片状生长，表达角蛋白及成釉蛋白。传至第5代后，细胞逐渐变为长梭形，失去上皮细胞形态。结论：体外培养的人牙源性上皮细胞在较长时间内可保持其特性，有望作为牙齿组织工程研究的种子细胞。     

Comparison of dental fluorosis and caries in primary teeth of preschool-children living in arid high and low fluoride villages

Abstract The aim of this study was to determine the degree of fluorosis in the primary dentition and the accompanying caries patterns in groups of preschool-children in high and low fluoride areas. Among 331 coloured children, aged 1 -5 years, living in an area with water F concentrations ranging from 2.2 to 4.1 parts/10⁶, 82% were caries free and the dmft values ranged from 0 to 15 with a mean dmft of 0.8 ± 2.1. Varying degrees of fluorosis in the primary teeth were present in 50.6% of the children. In 177 coloured children of similar ages from an adjacent area with 0.2 parts/10⁶ F in the drinking water the dmft values ranged from 0 to 20 with a mean dmft of 5.4 ± 5.8. Only 28% of the children were caries free. None of the children in this area had fluorosis. The caries prevalence was significantly higher in the low fluoride area than in the high fluoride area. The degree of fluorosis found in the primary dentition in the children from the high fluoride area was higher than had been anticipated and was accompanied by a very low caries prevalence.     

甲状旁腺激素对人牙乳头细胞牙本质基质蛋白1表达的影响

目的：观察甲状旁腺激素(parathyroid hormone，PTH)对体外培养的人牙乳头细胞(human dental papilla cells，HDPC)牙本质基质蛋白1(dental matrix protein，DMP1)合成分泌的影响。方法：原代方法培养出人牙乳头细胞，用不同浓度的甲状旁腺激素刺激培养的第5代人牙乳头细胞，免疫组化观察结果，并采用图像分析的方法，进行半定量分析。结果：PTH可刺激人牙乳头细胞DMP1的表达，诱导的DMP1主要表达于细胞胞浆内，呈一定的浓度依赖性，0．3μg／mL为刺激最佳浓度。结论：PTH能够刺激人牙乳头细胞产生DMP1，对牙乳头细胞向成牙本质细胞分化有一定促进作用，可能是成牙本质细胞分化的重要介质之一。     

Biological mechanisms of dental fluorosis relevant to the use of fluoride supplements

Fluorosis occurs when fluoride interacts with mineralizing tissues, causing alterations in the mineralization process. In dental enamel, fluorosis causes subsurface hypomineralizations or porosity, which extend toward the dentinal-enamel junction as severity increases. This subsurface porosity is most likely caused by a delay in the hydrolysis and removal of enamel proteins, particularly amelogenins, as the enamel matures. This delay could be due to the direct effect of fluoride on the ameloblasts or to an interaction of fluoride with the proteins or proteinases in the mineralizing matrix. The specific mechanisms by which fluoride causes the changes leading to enamel fluorosis are not well defined; though the early-maturation stage of enamel formation appears to be particularly sensitive to fluoride exposure. The development of fluorosis is highly dependent on the dose, duration, and timing of fluoride exposure. The risk of enamel fluorosis is lowest when exposure takes place only during the secretory stage, but highest when exposure occurs in both secretory and maturation stages. The incidence of dental fluorosis is best correlated with the total cumulative fluoride exposure to the developing dentition. Fluoride supplements can contribute to the total fluoride exposure of children, and if the total fluoride exposure to the developing teeth is excessive, fluorosis will result.     

Determination of optimal fluoride concentration in drinking water in an area in India with dental fluorosis

The present study was made to determine the optimal fluoride concentration in drinking water in a fluorotic zone. The area under study was divided in four parts on the basis of fluorides present in drinking water. A sample of 1320 persons was examined, where prevalence of dental fluorosis varied from 3.8% to 65.4% depending on the fluoride concentration in drinking water. Statistically significant increase in the prevalence of dental fluorosis was found (a) with I he rise in fluoride in drinking water, (b) with the rise in age, peak being found at 15-19 years age group and (c) amongst the bona fide residents of the area. A significant positive correlation was found between fluoride in drinking water and Community Fluorosis Index. While determining the optimal level of fluoride in drinking water, values obtained were 1.05 parts/10⁶, 0.8 parts/10⁶and 0.34 part/10⁶, respectively, by different formulae in a fluorotic zone of western India.     

Influence of chlorhexidine on in vitro uptake of fluoride in dental enamel

ABSTRACT – Chlorhexidine gluconate and sodium fluoride were found to be compatible in the concentration range of interest in clinical use. Admixture of chlorhexidine to sodium fluoride solutions did not interfere with the fluoride uptake in clinically intact premolars in vitro .     

F^—对牙髓细胞亚细胞结构的体外影响

目的：观察不同浓度Ｆ－对牙髓细胞亚细胞结构的直接影响。方法：鼠牙髓细胞体外培养，透射电镜观察。结果：１０ｍｇ／Ｌ、２５ｍｇ／ＬＦ－组随Ｆ－浓度增加，细胞内粗面内质网逐渐扩张，游离核蛋白体减少；５０ｍｇ／ＬＦ－组，细胞内部结构变化明显，染色质分布不均，细胞器萎缩，膜结构模糊。结论：高浓度Ｆ－（５０ｍｇ／Ｌ）对牙髓细胞结构、代谢和分裂增殖活动有抑制性影响     

Enzyme activities in the isolated enamel organ from the rat incisor during the two main stages of amelogenesis

abstract – The enamel organ from the rat incisor was dissected out. The amount of connective tissue in the samples was checked by light microscopy. Samples representative of the stage of enamel matrix formation and of enamel maturation were taken and the activities of the following enzymes were estimated: aldolase, pyruvate kinase, lactate dehydrogenase, malate dehydrogenase, glucose-6-phosphate dehydrogenase and alkaline phosphatase. The enzyme activities were related to the amount of tissue protein and the amount of DNA. All the enzymes, except alkaline phosphatase, showed an increase in measured activity during the stage of enamel maturation. The significance of these changes in in vitro activities is discussed.     

Spatial distribution of groundwater fluoride levels and population at risk for dental caries and dental fluorosis in Sri Lanka

Objectives: To investigate the distribution of groundwater fluoride levels in Sri Lanka in relation to its population distribution to determine the population at risk for dental caries or dental fluorosis. Methods: The study used the most upgraded spatial distribution map of groundwater fluoride levels in Sri Lanka, and it was overlaid with a census of population data of the country. Results: The results indicated that 12% of children aged <12 years were at risk for dental fluorosis, while 81.4% of those who lived in low-fluoride zones were vulnerable for development of dental decay. Overall, 82.4% of the country’s population lived in low-fluoride zones and 11.2% were at risk of potential health hazards posed by ingestion of excessive fluoride. Conclusion: The spatial approach provides a useful decision-support tool for developing an oral health strategy of safe fluoride use based on predicted oral health risks in communities.Key words: Groundwater, dental fluorosis, dental caries, spatial distribution     

F^—对牙髓细胞影响的扫描电镜观察

目的：利用扫描电镜、光镜观察不同浓度Ｆ－对鼠牙髓细胞形态和表面结构的直接影响。方法：大鼠牙髓细胞培养，相差显微镜、扫描电镜观察。结果：１０ｍｇ／Ｌ、２５ｍｇ／Ｌ、５０ｍｇ／ＬＦ－使细胞表面嵴和囊泡样结构减少。浓度越高，改变越明显。结论：高浓度Ｆ－对牙髓细胞表面结构有抑制性伤害，局部用氟化物直接作用牙本质－牙髓复合体应控制Ｆ－浓度     

Influence of exposure to various fluoride technologies on the prevalence of dental fluorosis

Abstract An increase in the prevalence of dental fluorosis among children in North America is well documented. Published reports of the relationship between the occurrence of dental fluorosis and early exposure to various fluorides and the use of different types of infant feeding practices have begun to provide insights into possible causes for this increase. This study was designed to investigate this issue for children living in a non-fluoridated and a fluoridated community in British Columbia, Canada. Parents or guardians completed a questionnaire which detailed exposure to different types of fluorides and infant feeding practices during the first 6 yr of life. Completed questionnaires were returned and examinations were performed on 1131 children. 60% of children had dental fluorosis, and only 8% presented with scores of 2 or greater. Logistic regression analyses showed that the use of infant formula and parental educational attainment were significantly associated with the occurrence of dental fluorosis in the range of scores from 2 to 6. Despite these statistically significant findings, these variables actually had little additional predictive value beyond a chance occurrence in determining which children would have dental fluorosis.     

Incorporation of iron in rat incisor enamel

ABSTRACT – The electron microprobe technique was used to study the accumulation of iron in rat incisor ameloblasts as well as the subsequent release of iron from the cells and deposition into the outer layer of the enamel. Starting about 3 mm from the developing end, a gradual accumulation of iron occurred in the ameloblasts. At a stage where the iron content of the cells had reached a maximal level, and the calcium content of the adjacent hard tissue had reached the level of mature enamel, the initial incorporation of iron in the enamel was seen. In the iron incorporation zone the iron content of the enamel increased from less than 0.1 % to about 9 % and the iron content of the ameloblasts was gradually reduced. Concomitant with the increase of iron in the enamel, a decrease of the calcium content was observed in the same region, indicating a withdrawal of calcium from the enamel. Since the incorporation of iron occurs at a stage where the enamel is highly mineralized, the processes involved can hardly be explained as an interaction with the organic matrix. The key to the understanding of these processes should therefore be sought in the adjacent cell layer.     

Morphologic changes in the rat enamel organ following a single intraperitoneal injection of sodium fluoride

abstract — Enamel organs in developing teeth of young rats were studied after single intra peritoneal injections of a high dose of sodium fluoride (60 mg NaF/kg body wt.). The study employed primarily light microscopy, but electron microscopy was used to clarify some of the light microscopic findings. The pathogenesis of the fluoride-induced changes was followed during 72 h. Cellular changes were consistently found in the molars, but were never seen in the incisors. In the maxillary molars, ameloblastic injury was most commonly seen on the mesial surfaces of the cusps. One hour after injection, the most prominent findings were swollen mitochondria in the secretory ameloblasts and cleft formations between the ameloblasts and the enamel matrix. The clefts were filled with a stippled material. Some of the clefts gradually expanded to cystic cavities. The stippled material began to calcify after 24 h and formed small, darkly stained globules. After 72 h dearranged ameloblasts were found as islands intermingled with calcified rounded structures in the stellate reticulum. In stratum intermedium numerous atypic autophagic vacuoles appeared 2 h after injection. No light microscopic changes were observed in the postsecretory ameloblasts.     

Cytochemical demonstration of adenyl cyclase in rat incisor enamel organ

abstract — With adenylyl-imidodiphosphate as a specific substrate, adenyl cyclase has been demonstrated at the plasma membranes of all epithelial cells except the ameloblasts in the enamel organ of rat incisors. Hydrolysis of the substrate was found to be stimulated by 10 mM sodium fluoride in the incubation medium.     

Fluoride-induced developmental changes in enamel and dentine of European roe deer (Capreolus capreolus L.) as a result of environmental pollution

Using macroscopic, microradiographic and scanning electron-microscopic methods, the effects of increased fluoride exposure on enamel and dentine formation were studied in fluorosed mandibular premolars and molars of roe deer from the heavily industrialized Ruhr area, Germany. Macroscopically, fluorosed teeth were characterized by opaque and stained enamel and in more severe cases also by enamel surface lesions, reduction or loss of enamel ridges on their occlusal surfaces and increased wear. Microradiographically, fluorosed enamel exhibited different degrees of subsurface hypomineralization, in part apparently indicating a fluoride effect during enamel maturation. In some specimens, a pronounced but varying enhancement of the pattern of Retzius lines was observed throughout the enamel, denoting strongly intermittent fluoride exposure during enamel matrix secretion. This variation in exposure was also reflected histologically in dentine, by bands of interglobular dentine and marked accentuation of incremental lines. Microradiography of sections through enamel surface hypoplastic lesions showed the enamel forming the bottom and partly also the walls of the lesions to be highly mineralized. Scanning electron microscopy showed that the outer enamel along the more pronounced hypoplastic lesions consisted of stacked, thin layers of ‘aprismatic’ enamel, indicating that the ameloblasts in these areas had lost the distal (rod-forming) regions of their Tomes' processes. These observations demonstrate that the origin of enamel hypoplasias in deer clearly differs from that in rodents, where fluoride induces the formation of subameloblastic cysts. The differences in the degree of fluorotic alteration between the teeth of a single tooth row could be related to the developmental sequence of the dentition in roe deer. The roe deer is thus considered to be a very sensitive and useful bioindicator of environmental pollution by fluorides.