Gingival recession in tooth types in high fluoride and low fluoride areas

The prevalence of gingival recession in individual teeth in 1,884 dentate adults, aged 15–65 years, continuously resident in the natural fluoride area of Hartlepool (1·5–2·0 ppm F) was compared with that found in 2,015 dentate adults from the low fluoride town of York (0.15–0.28 ppm F). In each tooth type, gingival recession increased steadily with age. A distinctive pattern of gingival recession was observed in each community. Mandibular incisors showed the highest prevalence of gingival recession, followed by maxillary first molars, mandibular first molars, premolars, maxillary second molars, mandibular second molars and canines. Maxillary incisors showed the lowest prevalence of gingival recession. There was an extremely high correlation between Hartlepool and York data, for each group of teeth. It was therefore concluded that fluoride in drinking water, at least up to 2 ppm F, has no effect on the pattern of gingival recession in adults.     

氟对牙发育影响作用的研究进展

氟是人体必需的微量元素,在机体和牙的发育过程中有着重要的作用。牙在发育过程中摄入过量的氟,将导致氟斑牙的发生。氟通过对矿化相关的基质、基质蛋白、蛋白酶、相关细胞以及离子跨膜转运等多种途径影响正常的牙矿化模式,造成牙的矿化异常。下面就氟对牙发育、釉基质、基质蛋白酶、成釉细胞、牙本质基质蛋白和蛋白聚糖的影响作用的研究进展作一综述。     

The fluoride content of human tooth enamel in relation to environmental exposure to fluoride

A bstract — Double-layer superimposed biopsies were used for sampling sound labial enamel of upper permanent central incisor teeth of 189 children (mean age 8.4 years, SD = 0.36), comprising five groups, representing life-long exposure to contrasting concentrations of F in the water (range ≤0.12 ppm to 2.8 ppm) and to supplements of 200 or 350 mg F/kg domestic salt. The mean F concentrations of enamel ranged through the groups from 924 ppm to 2401 ppm in the surface layer (average central depth = 0.49 um) and from 450 ppm to 1428 ppm in the subsurface layer (average central depth = 2.62 um). The differences between the mean F concentrations of the groups were significant in each instance and the values consistently reflected the extent of F exposure. It was concluded that the F content of enamel is a reliable indicator of environmental exposure to F for populations, but not for every individual.     

The effect of fluoride on the developing tooth

This review aims to outline the effects of fluoride on the biological processes involved in the formation of tooth tissues, particularly dental enamel. Attention has been focused on mechanisms which, if compromised, could give rise to dental fluorosis. The literature is extensive and often confusing but a much clearer picture is emerging based on recent more detailed knowledge of odontogenesis. Opacity, characteristic of fluorotic enamel, results from incomplete apatite crystal growth. How this occurs is suggested by other changes brought about by fluoride. Matrix proteins, associated with the mineral phase, normally degraded and removed to permit final crystal growth, are to some extent retained in fluorotic tissue. Fluoride and magnesium concentrations increase while carbonate is reduced. Crystal surface morphology at the nano-scale is altered and functional ameloblast morphology at the maturation stage also changes. Fluoride incorporation into enamel apatite produces more stable crystals. Local supersaturation levels with regard to the fluoridated mineral will also be elevated facilitating crystal growth. Such changes in crystal chemistry and morphology, involving stronger ionic and hydrogen bonds, also lead to greater binding of modulating matrix proteins and proteolytic enzymes. This results in reduced degradation and enhanced retention of protein components in mature tissue. This is most likely responsible for porous fluorotic tissue, since matrix protein removal is necessary for unimpaired crystal growth. To resolve the outstanding problems of the role of cell changes and the precise reasons for protein retention more detailed studies will be required of alterations to cell function, effect on specific protein species and the nano-chemistry of the apatite crystal surfaces.     

氟化物对实验家兔牙胚及牙齿氟含量的影响

为进一步探明氟斑牙的发病机理，通过建立氟斑牙动物模型，在组织学及超微结构方面观察高氟对动物牙胚的影响。结果发现氟中毒时造釉器在形态、合成釉基质功能上的改变主要表现在造釉细胞出现空泡性变性，釉基质上出现蜂窝状改变。与此同时，造牙本质细胞以及牙本质也一并受到损伤，造牙本质细胞伯分化必须依靠内釉细胞的诱导，同样釉基质一定要在牙本质形成的基础上才能完成，两者互相依存的密切关系决定了一旦二者出现病理改变时，相互功能必然受到影响，氟中毒时即可在牙齿表面出现氟斑牙的体征     

A study in vitro of the combined effects of soft drinks and tooth brushing with fluoride toothpaste on the wear of dentine

The aim of this study was to measure loss of dentine produced by soft drinks alone and combined with tooth brushing with and without toothpastes. Groups of flat human dentine specimens were exposed for 10 min and then 30 min to orange juice (OJ), carbonated cola (CC) or modified blackcurrant (MB) drinks alone or after the exposures brushed with a fluoride toothpaste for 10 s. Further groups were exposed to OJ as before but brushed with water or non-fluoride toothpaste or placed in slurries of fluoride paste. Five cycles of each regimen were carried out. Tissue loss was determined by profilometry. Water immersion/brushing and brushing controls were included. OJ and CC produced similar erosion and significantly more than MB. Compared with drinks alone, dentine loss was reduced by fluoride toothpaste brushing but increased by water and non-fluoride toothpaste brushing. Fluoride toothpaste slurry had no significant effect on soft drink erosion. Very little abrasion with brushing alone was recorded over the time frame of these experiments. It is concluded that fluoride toothpaste could provide protection, albeit small, against erosion. The data again support the concept of brushing before meals.     

Assessment of loosely-bound and firmly-bound fluoride uptake by tooth enamel from topically applied fluoride treatments

The amounts of loosely-bound fluoride (F) deposited on human enamel by two topical F treatments were measured with use of a constant-composition F washing method. Enamel biopsies conducted before treatment and after the washing were used for determination of the firmly-bound F uptake. The results showed that (1) the washing system did not remove F from untreated enamel surface, (2) a four-minute application of an acidulated phosphate fluoride (APF) gel deposited 27.2 (2.4) (mean, S.E.) micrograms of loosely-bound F per cm2 of enamel surface and 186 (111) ppm of firmly-bound F in the outer 10 microns of enamel, and (3) a four-minute application of a pH-2.1 dicalcium phosphate dihydrate (DCPD)-forming solution followed by APF produced 44.9 (3.1) micrograms/cm2 of loosely-bound F and 1280 (354) ppm of firmly-bound F in the outer 10 microns of enamel. The results showed that the DCPD pre-treatment effectively enhanced the enamel reactivity with F, so that the DCPD-APF treated enamel acquired greater amounts of both loosely-bound F and firmly-bound F than did samples treated with APF alone.     

氟化物对牙本质漂白深度影响的实验研究

目的通过实验观察氟化物对过氧化脲类漂白剂渗透性及漂白效果的影响。方法 36颗离体牙样本使用标准茶溶液染色、VITA比色板比色后,12颗样本使用35%过氧化脲漂白,12颗样本NaF处理后再行漂白,12颗样本放入去离子水中作为空白对照。治疗时间均为30 min。比色后分别从近远中向和唇舌向剖开,使用图像分析软件测量、比较其剩余染色面积。结果两组离体牙漂白后牙齿色阶改变无显著性差异;对比NaF漂白组和漂白组之间的近远中向剖面染色面积和唇舌向两剖面剩余染色面积,漂白组和NaF漂白组对牙本质的漂白深度无显著性差异。结论着色牙漂白术前局部应用氟化物并不影响漂白效果和漂白深度。