Dental tissue effects of fluoride

It is now well-established that a linear relationship exists between fluoride dose and enamel fluorosis in human populations. With increasing severity, the subsurface enamel all along the tooth becomes increasingly porous (hypomineralized), and the lesion extends toward the inner enamel. In dentin, hypomineralization results in an enhancement of the incremental lines. After eruption, the more severe forms are subject to extensive mechanical breakdown of the surface. The continuum of fluoride-induced changes can best be classified by the TF index, which reflects, on an ordinal scale, the histopathological features and increases in enamel fluoride concentrations. Human and animal studies have shown that it is possible to develop dental fluorosis by exposure during enamel maturation alone. It is less apparent whether an effect of fluoride on the stage of enamel matrix secretion, alone, is able to produce changes in enamel similar to those described as dental fluorosis in man. The clinical concept of post-eruptive maturation of erupting sound human enamel, resulting in fluoride uptake, most likely reflects subclinical caries. Incorporation of fluoride into enamel is principally possible only as a result of concomitant enamel dissolution (caries lesion development). At higher fluoride concentrations, calcium-fluoride-like material may form, although the formation, identification, and dissolution of this compound are far from resolved. It is concluded that dental fluorosis is a sensitive way of recording past fluoride exposure because, so far, no other agent or condition in man is known to create changes within the dentition similar to those induced by fluoride. Since the predominant cariostatic effect of fluoride is not due to its uptake by the enamel during tooth development, it is possible to obtain extensive caries reductions without a concomitant risk of dental fluorosis.     

The neurotropic activity of peptide immunomodulators

Ultrastructure of dental enamel was examined under electron microscope after exposure to hydroxyethylene diphosphonic (HEDP) acid and prophilometry of enamel surface was carried out after its exposure to acid salts; clinical studies in 105 patients aged 18-50 years with different diseases of hard dental tissues were carried out in order to assess the duration of filling preservation after dental enamel treatment with HEDP salts. Clinical results were assessed from subjective sensations of patients and data of examination. The criteria of assessing the results were presence of a filling in a filled carious cavity, marginal adhesion of the filling, alteration of color along the external interface of the filling, caries relapses, status of dental pulp and periapical tissues. Clinical and laboratory studies showed that treatment with HEDP acid creates favorable conditions for tooth filling.     

Estimation of the caries-related risk associated with infant formulas

PURPOSE: Baby bottle tooth decay (BBTD) affects 6% of children under three years of age and is associated with inappropriate bottle use. The objective of this study was to estimate the caries-related risk associated with 26 infant formulas and whole milk. METHODS: First, the plaque pH of adult volunteers was monitored before and after an oral rinse with infant formula to determine the minimum pH obtained in response to each formula. Second, Streptococcus sobrinus 6715 was cultured in each infant formula, and the increase in the number of colony forming units was measured. Third, each infant formula was incubated with powdered enamel and the solubility of enamel mineral was calculated in the absence of bacteria. Fourth, each formula was mixed with standardized concentrations of acid to determine the buffering capabilities. Finally, enamel windows were created on extracted permanent molars and exfoliated primary incisor crowns that were then colonized with mutans streptococci and incubated with infant formula. Caries was assessed visually and radiographically for 18 weeks. The length of time required for the development of enamel caries, dentinal caries and pulpal involvement was recorded. RESULTS: One-way or two-way ANOVA of these five assays demonstrated that 1. Plaque pH varied in response to oral rinsing with infant formula and most formulas did have the ability to reduce the pH significantly below the pH obtained after rinsing with water 2. Some infant formulas supported significant bacterial growth 3. Enamel mineral was dissolved by incubation with certain infant formula 4. The buffer capacity varied among the infant formulas tested 5. The length of time required for caries to reach dentin or pulp differed for the formulas, with some formulas causing dentinal caries by 3.4 weeks and pulpal involvement by 7.2 weeks.     

Oral hygiene as a risk indicator of enamel and dentin caries

Dental researchers have postulated that the risk factors for enamel and dentin caries may not be the same. A review of the literature ascertained that data to support this theory are lacking. OBJECTIVES: To evaluate the risk indicators of enamel and dentin caries of the permanent dentition in a study group who had limited access to fluorides and made limited use of dental services. METHODS: The study was conducted in Goa, India. Data came from a cross-sectional survey of 1189 seventh grade children, which consisted of a clinical dental examination and a self-administered questionnaire to their parents. The cavitated and non-cavitated criteria were used to score for caries, and the Silness-Loe index for plaque. RESULTS: The mean age of the children was 12.2 years. The percentage of children caries free in the permanent dentition was 22.2%, the mean+/-s for dmfs, enamel and dentin lesions were 4.20+/-5.10, 2.59+/-2.89 and 1.61+/-3.30 respectively, and the mean plaque score was 1.00+/-0.48. Results of regression analyses showed that the risk indicators of prevalence and severity of caries differed depending on lesion type. The only variable that was consistently a risk indicator of presence and severity of both dentin and enamel caries was poor oral hygiene. Mother's highest level of education and presence of fluorosis were also risk indicators of enamel and dentin caries. The presence of decayed primary teeth was a risk indicator of enamel caries; and fluorosis severity, use of fluoride toothpaste at the time of the survey, and toothbrushing frequency were risk indicators of dentin caries. The observed caries-oral hygiene association seen is explored further.     

Recognition of a non-standard base pair by thermostable DNA polymerases

Fluoride is a potent preventive agent of caries. It acts at two levels: local and systemic. At the local level it prevents the surface demineralisation of enamel by strengthening the superficial layers, and inhibiting the local bacterial activity. At the systemic level it improves the resistance of the enamel by forming with calcium, fluorapatite which is stronger than hydroxyapatite. Main sources are naturally fluorinated water, artificially enriched water, fluorinated salt, and fluoride medication. Recommended mean daily intake is 0.05 mg/kg, the risk of dental fluorosis occurring when daily intake exceeds 1 mg/kg. The large benefits of regular fluoride supplementation on children dental health must not live down the risk of dental fluorosis resulting from over administration. Therefore when prescribing fluoride to a child, the practitioner must carefully examine his/her possible other fluoride sources.     

The effect of carbon dioxide laser on acid resistance of human tooth enamel: an evaluation by wet chemical analysis and scanning electron microscopy

The use of the laser in improving acid resistance of tooth enamel has captured the imagination of most researchers. Man's susceptibility to dental caries presents itself as one of the most complicated problems to solve. The carbon dioxide laser at a wavelength of 10.6 microns is highly efficient for dental purposes as this wavelength is close to optimum absorption of dental enamel. A study was carried out using a pulsed carbon dioxide laser to find the effects of laser beam on human tooth enamel in an energy range of 2-20 J/cm2 at a pulse rate of 5 Hz. The effective resistance to acid was determined by wet chemical analysis whereas superficial changes seen on the surface were determined using the scanning electron microscope.     

Social facilitation of eating among friends and strangers

In a series of studies to investigate the basic structural features and characteristics of the biological apatite crystals using a transmission electron microscope, we examined the ultrastructure of the human enamel, dentin, and bone crystals through the cross and longitudinal sections at near atomic resolution. Subsequently, using the same approach, we have been able to directly examine the images of the lattice imperfections in the crystal lattices of the human tooth and bone crystals, and the images of the fusion of the crystals. In this research, furthermore, using transmission and scanning electron microscopes, we examined the dissolution of the enamel crystals caused by the carious enamel from the same viewpoint. The material used for the observation of the dissolution of the enamel crystals was obtained from the region which corresponds to the middle layer of the enamel at the portion near the wall of a carious cavity caused by the fissure caries on the occlusal surface of the lower first molars. Small cubes of the materials used for the observation by transmission electron electron microscope were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine methods. The ultrathin sections were cut with a diamond knife without decalcification. The sections were examined with the HITACHI H-800H type transmission electron microscope operated at 200 kV. Each crystal was observed at an initial magnification of 300,000 times and at a final magnification of 10,000,000 times and over. The material used for the observation by the scanning electron microscope was the fractured surface obtained from the carious enamel. The fractured carious enamel surfaces were coated with carbon and gold and observed with the HITACHI HHS-2R type scanning electron microscope operated at 25 kV. The crystals were observed at a final magnification of 50,000 times. As a result, we have confirmed that the dissolution of the enamel crystals caused by a caries occurs in the units of "hexagonal cell". We sincerely believe that the electron micrographs shown in this report are the first to show the images of the dissolution of the enamel crystals caused by a caries at near atomic resolution.     

Prevalence of developmental enamel defects and dental caries in rural pre-school Thai children

The prevalence of developmental enamel defects and dental caries was assessed in 344 Karen children aged 1-4 years who were chronically (70 per cent) and acutely malnourished (9.3 per cent) The teeth were cleaned with gauze to facilitate detection of hypoplastic lesions on labial surfaces of maxillary incisors. At least one tooth with defective enamel was seen in 31.9 per cent of children, while enamel hypoplasia was present in 22.7 per cent of children. Enamel defects were found in 21.2 per cent of teeth, with hypoplasia and opacities occurring in 14.6 and 6.6 per cent of teeth, respectively. Gender did not alter the prevalence of defects. The upper central incisors were affected more than lateral incisors. The prevalence of dental caries was 31.9 per cent with a mean dt of 1.1. The prevalence of caries associated with enamel hypoplasia was significantly greater than that associated with opacities and sound enamel (P < 0.0005).     

Root-surface caries in rats and humans: inhibition by a non-antimicrobial property of tetracyclines

The incidence of root caries has been found to increase as the population ages and as edentulism becomes less prevalent due to improved dental awareness and care, and as exposure of roots due to gingival recession has also increased in the elderly. The mechanism of root caries is thought to be mediated by both bacterial and mammalian proteases produced by plaque and the periodontal tissues, respectively. In the current study, a rat model of periodontal disease was used in which gnotobiotic rats were infected intra-orally with a periodontal pathogen (P. gingivalis). Infecting the rats with P. gingivalis increased the collagenase activity in the gingival tissue in association with severe alveolar bone loss. Treating P. gingivalis-infected rats with doxycycline or CMT-1 prevented the destruction of the periodontium by MMPs, thus preventing exposure of roots to subgingival bacterial plaque and host tissue collagenases and the subsequent development of root caries. In addition, a low-dose doxycycline (LDD, 20 mg bid, non-antimicrobial dose) for 3 months was used in humans predisposed to increased root caries as the result of heavy use of smokeless (chewing) tobacco, causing gingival recession, subgingival plaque accumulation with Gram-negative bacteria, increased gingival crevicular fluid flow (GCF), and elevated GCF collagenase. Daily administration of LDD in smokeless tobacco patients reduced the GCF collagenase and prevented the further development of root caries.     

Transmission electron microscopy of cementum crystals correlated with Ca and F distribution in normal and carious human root surfaces

Root-surface caries, like enamel caries, develops as a subsurface type of mineral loss. Very little is known about the composition of the surface zone covering the body of the lesion, and the ultrastructure and composition of carious cementum are not known. The aim of this study was to correlate the ultrastructure and arrangement of the cementum crystals with the distribution of fluoride and calcium in root cementum from human teeth with sound, unexposed, or exposed root surfaces as well as in early stages of root-surface caries. Microradiographically, unexposed specimens showed a relatively homogeneous mineral distribution contrasting with the formation of an apparently highly mineralized surface layer in exposed and, in particular, in carious cementum. The electron-probe findings showed a substantial fluoride peak corresponding to the surface layers in carious tissues in particular, whereas the calcium profile in the surface did not reflect the apparent increase in mineralization. A substantial increase in size of the cementum crystals was found in specimens with formation of the fluoride-rich, well-mineralized surface zone. The crystal lattice intervals when observed along the (001) plane showed a hydroxyapatite spacing. The findings indicated that a significant crystal growth can be achieved in human cementum concomitant with fluoride accumulation.     

The diabetic heart is more sensitive to ischemic injury

A review of the literature on the impact of dental care on the incidence of dental caries in children and adults suggests that the effect is small. Dental services were relatively unimportant in explaining the recent decline in caries in 5- and 12-year-olds. An important contribution of the dental services to the decline in caries was a change in the diagnostic and treatment criteria. The role of dentistry in reducing dental caries may lie mainly in the non-personal health services. Knowledge of the life history and patterns of caries attack rates within populations and individuals could be used as a benchmark against which interventions can be assessed. Different teeth and tooth sites are affected differentially at different levels of dental caries. This truism may appear obvious but it is not used to evaluate the effectiveness and quality of dental treatment. A working rule is that "As caries prevalence falls, the least susceptible sites (proximal and smooth surfaces) reduce by the greatest proportion, while the most susceptible sites (occlusal) reduce by the smallest proportion." There is a specific relationship between the mean DMFT and mean DMFS, and the percentage of caries-free subjects and the frequency distribution of subjects with different levels of caries. Further more, the best predictor of caries at older ages is DMFT at a younger age. Caries levels follow trend lines for each level of caries. As the mean DMFT declines so post-eruptive time increases for initiation of caries and the progression rates of caries through enamel decreases. This is true regardless of the presence of fluoride.     

Edgard C. Moreno, PhD: a tribute to his major contributions to oral biology research

The seminal contributions of Dr. Edgard C. Moreno to physical chemical aspects of oral biology research are reviewed, with personal insights provided by the author. Dr. Moreno has made major contributions to our understanding of fundamental processes which occur within the oral cavity and which control the formation of mineralized tissues. These contributions include extensive research in the areas of: the chemistry of synthetic calcium phosphates and biominerals, the interaction of salivary proteins and other molecules of biological interest with calcium phosphate surfaces, the mechanism of dental caries formation and the effects of fluoride on this process, the mechanism of dental calculus formation and prevention, and the mechanism of dental enamel formation.     

Ethics summit I: assembling the ethical community

Microhardness of dental tissues was assessed. Hard tissue specimens from 65 teeth removed for medical indications were examined. The enamel microhardness is 30-40% decreased in caries, whereas dentine is virtually intact. Depulpation decreases the enamel microhardness by 23-26%, while the microhardness of dentine is changed negligibly (by 1-1.5%).     

Temporal and site-specific expression of transforming growth factor-beta4 in human endometrium

Orthodontic treatment with fixed appliances increases the caries risk in young persons. The aim of this study was to apply a new caries diagnostic method, quantitative laser fluorescence, for longitudinal in vivo quantification of changes in incipient enamel lesions related to fixed orthodontic appliances. Seven young patients with active caries lesions disclosed at removal of the orthodontic brackets and bands were enrolled in the study. Caries preventive measures were intensified, including dietary advice, oral hygiene instructions, and the regular use of a fluoride dentifrice. The caries lesions were monitored with the quantitative laser fluorescence method after removal of the brackets and once a month thereafter. For each lesion, three quantities were measured: lesion area (mm2), mean fluorescence loss (%) over the lesion, and maximum loss of fluorescence (%) in the lesion. During a 1-year follow-up period, the areas of the lesions decreased and the enamel fluorescence lost was partly regained indicating that a remineralization process had occurred. It was concluded that quantitative laser fluorescence seems suitable for in vivo monitoring of mineral changes in incipient enamel lesions, and useful for the evaluation of preventive measures in caries prone persons, such as orthodontic patients.     

Teeth, vomiting and diet: a study of the dental characteristics of seventeen anorexia nervosa patients

Seventeen anorexia nervosa patients were examined dentally and their dietary histories and eating habits studied. Analysis of the data confirmed earlier observations dental deterioration associated with anorexia nervosa. The deterioration included a pattern of enamel dissolution in cases of vomiting, regurgitation, and/or the consumption of large amounts of citrus fruits; and an altered caries response due to abnormal carbohydrate consumption. Despite the patient's probably insistent denial of 'anorectic' eating habits, the general practitioner should consider the existence of anorexia nervosa in the presence of such abnormal features, especially in young women. The relationship of these findings to larger populations with similar eating habits is discussed.     

In vitro toothbrush-dentifrice abrasion of resin-modified glass ionomers

OBJECTIVES: The three purposes of this study are to: (1) describe the relationship between the prevalence of coronal caries and root caries; (2) describe the relationship between the three-year incidence of coronal caries and root caries; and (3) if the two conditions are associated, develop a multiple regression model that identifies characteristics distinguishing people who had increments of both root caries and coronal caries from people who had increments of either coronal caries or root caries, or who had no new caries. METHODS: Dental examinations and interviews were conducted in the homes of a randomly selected, stratified sample of people over the age of 65 years in five North Carolina counties. The relationships between coronal and root D and DF were analyzed through contingency table analyses, and ordinal logistic regression was used to identify characteristics that differentiated people who had both coronal and root D over the three years from people who had either coronal or root D and people who had no new disease. RESULTS: Evidence of root and coronal caries in whites was much more likely to be in the form of fillings, while for blacks, it was more likely to be in the form of untreated decay. Prevalence rates of coronal and root D and DF were significantly associated for both blacks and whites. Incidence rates based on DF indicated that root and coronal caries were not associated in whites, but were associated in blacks. People more likely to experience both types of caries had more gingival recession at baseline, greater average attachment loss over the three years, and lactobacilli at baseline. In addition, the presence of Porphymonas gingivalis at three years was important for whites. CONCLUSIONS: It appears that coronal and root caries do tend to appear together in the same individuals, but fillings attenuate that relationship. The impact of dental treatment on the epidemiology of dental caries appears to be considerable and calls into question whether the F component of the caries index is related to disease as defined by epidemiologic criteria.     

Nutrient intake and dental health in school children

Diet refers to the customary allowance of food and drink taken by a person from day to day. The diet may affect dental caries by reacting with the enamel surface and by serving as a substrate for cariogenic microorganisms. This study examined the role of specific nutrients in the caries experience of elementary school children. 120 children aged between 6-11, who attended the Pedodontics Department of Marmara University, Faculty of Dentistry for routine dental treatment received a dental examination, parent interview, and a 3-day diet diary. The diary was completed adequately for 100 children (83%). The average daily intake of nutrients were computed and total sugar consumption and Ca/P ratio were calculated. Each child's gender, age, fluoride history, socio-economic state of the family, previous dental experience, brushing habit, and nutrient intake were examined as independent variables. No association was apparent between dental caries and the intake of specific nutrients or Ca/P ratio, except with total sugar consumption.     

Dental disease in the late Medieval population from Nova Raca, Croatia

Male and female dental disease frequencies were compared to test the hypothesis of differential stress levels between the sexes in the late Medieval population from Nova Raca, Croatia. The following categories of dental disease were compared: alveolar bone pathology defined by the presence of periodontal or periapical abscesses or antemortem tooth loss, caries, hypoplastic defects in the enamel and occlusal surface wear. The results show clear gender differences in the frequencies of alveolar bone pathology, carious lesions and occlusal surface wear. In all cases males exhibited significantly greater frequencies. Further analyses indicated that these differences were related to younger (15-29 years) adults and to the upper jaw. Together with paleodemographic data and the fact that females exhibited higher frequencies of enamel defects, this dichotomy in dental disease frequencies is interpreted as the result of a culturally imposed defensive mechanism which selectively buffered young males from malnutrition, exposing them at the same time to higher levels of cariogenic food and thus to higher frequencies of carious lesions and alveolar bone disease.     

Biosynthetic retrovectoring systems for gene therapy

The 5-year incidence of caries was studied in a random sample of 60-, 70- and 80-year-old inhabitants of G?teborg, with 69, 51 and 28 individuals in the different age groups. One aim of the study was to introduce a root caries index (DMFRS%) in which the missing root surfaces are taken into account. This study, as well as other recent studies, has shown that dental caries is the main reason for tooth extraction. The study also revealed that coronal and root caries occurred more frequently in elderly than younger people and the incidence of root caries was positively correlated with coronal caries (r = 0.3, p < 0.001) and negatively correlated with the number of remaining teeth (r = 0.4, p < 0.0001). The 5-year DMFRS% increment values increased with advancing age from 2.7 involved root surfaces per 100 susceptible ones in the 60-year-olds to 4.8 in the 70-year-olds and 10.7 in the 80-year-olds. It should be mentioned, however, that only people able to come to the clinic were enrolled in the study and an analysis of the attrition bias indicated that oral health may be worse in those who are too ill to participate. The frequent utilization of dental care among the participants was reflected in the finding of several new fillings and prosthetic crowns. Most of the very elderly people with carious lesions at baseline, however, had developed new lesions at the margins of the newly made restorations.