Initiation Of Caries Research Articles

Proposed methods for improving the efficiency of the DMFS index in assessing initiation and progression of dental caries

Recent changes in the epidemiology of dental caries and advances in the development of new diagnostic measurement techniques have stimulated interest in improved methods of assessing changes in dental caries status. Traditional methods for assessing change focus primarily on the development of new lesions at the cavitation level and incorporate incomplete information on the progression of existing cavitated lesions. A methodology to expand the clinical recording of dental caries in clinical studies to include 1) both non-cavitated and cavitated lesions and 2) the surface area affected for restorations is suggested. New indices are proposed to estimate changes in the number of new lesions, the progression of existing carious lesions, and the total change in caries status for a subject. It is anticipated that the new indices will produce more efficient methods of assessing change in caries status in longitudinal clinical studies. The degree of improvement can be estimated directly. Improvements in efficiency may reduce the duration or number of subjects required in caries clinical trials.

Impact of dental treatment on the incidence of dental caries in children and adults.

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.

Caries prevention: Current Strategies, New Directions

Despite major advances in caries prevention, a large subset of the U.S. population still needs additional control measures. In numerous other countries, needs are escalating as caries rates continue to rise. Building on current strategies and new insights into the specific mechanisms of caries initiation, researchers are creatively using a variety of new technologies, especially in molecular biology, to fashion a new generation of preventive measures.

Cariogenicity of Streptococcus mutans strains with defects in fructan metabolism assessed in a program-fed specific-pathogen-free rat model.

To define the role of dental plaque fructans and the enzymes involved in their metabolism in the initiation and progression of dental caries, we constructed otherwise-isogenic mutants of Streptococcus mutans defective in the ability to synthesize fructans, to degrade fructans, or to do both. The cariogenic potential of these organisms was evaluated in a specific-pathogen-free rat model in which the feeding patterns of the animals were controlled by means of a König-Hofer programed feeder. Specifically, rats were infected with wild-type S. mutans UA159 or derivatives of this strain which contained an insertionally-inactivated fructanase (fruA) gene, fructosyltransferase (ftf) gene, or which had both genes inactivated. The animals were fed 17 meals per day of Diet 2000 containing 56% sucrose at 70-minute intervals for five weeks, and caries experience was evaluated. Animals infected with S. mutans with a mutated fruA gene only had statistically significant decreases in sulcal caries severity. Such a decrease was not observed in previous studies with ad libitum-fed animals (Wexler et al., 1992). The manifestation of diminished virulence in the programmed feeding model, but not in ad libitum-fed animals, supports the concept that the primary contribution of FruA to virulence is through the utilization of fructans storage polysaccharides. Animals infected with strains carrying the ftf mutation or simultaneous mutations in ftf and fruA did not display decreased virulence, perhaps indicating that sucrose utilization pathways may compete for substrate in vivo, or that accumulation of fructans may affect the ecology or the physicochemical characteristics of dental plaque in such a way as to reduce its cariogenic potential. The results of this study also emphasize that the contribution of a particular virulence determinant to the caries process may be highly dependent on the experimental design, feeding regimen and diet, and the presence or absence of other enzymatic activities.

Detection of dental decay and its extent using a.c. impedance spectroscopy.

Dental caries (decay), the most prevalent of diseases, represents a health problem of immense proportions. It principally affects posterior (back) teeth on occlusal (biting) and approximal (adjacent contacting) surfaces. Caries starts as a subsurface demineralization of enamel, may progress to the underlying dentine and, eventually, to cavitation of the surface. Accurate diagnosis before cavitation would permit targeted preventive treatment, thereby significantly improving dental health and reducing the need for expensive drilling and filling. Inaccessibility of caries initiation sites and recent changes in lesion morphology contribute to the relatively poor accuracy of conventional diagnostic methods. Among alternative techniques, measurements of electrical resistance have shown the most promise. Here we describe a new experimental technique that demonstrates an outstanding 100% correlation between a.c. impedance measurements of whole teeth and the actual extent of approximal caries in vitro. Only relatively minor modifications should be required to transfer the technique to in vivo applications.

Caries experience in deciduous dentition of rural Chinese children 3-5 years old in relation to the presence or absence of enamel hypoplasia.

The association of enamel hypoplasia (EHP) with dental caries of the deciduous dentition was determined in 1,344 rural Chinese children aged 3-5 years. The degree of EHP was determined using a modified DDE Index. Number of decayed, missing, and filled teeth and tooth surfaces were determined for all subjects. Anthropometric assessment of body weight and height was done as an indirect measure of the nutritional status of the children. Results from the study showed that the prevalence of EHP was 22.3% in the total study population. The prevalence of dental caries was 82.3%. There was no difference in the caries experience between males and females. Significantly greater caries experience was observed among the children living in a low socioeconomic county and children with low height for age. Children with low birth weight showed a slightly higher percentage of caries than those born with normal birth weight. Children with enamel hypoplasia demonstrated a significantly higher caries experience than those who did not have such defects. The results of this study consistently support previous studies that found nutritional deficiency to have an important impact on tooth development and susceptibility to dental diseases. This study also indicates that the presence of enamel hypoplasia may be a predisposing factor for initiation and progression of dental caries, and a predictor of high caries susceptibility in a community, particularly if fluoride programs are not implemented.

What is Known About Caries in Relation to Restorations as a Reason for Replacement? a Review

In the past 20 years, a great many studies have identified secondary caries to be the most common reason for the replacement of restorations. This review raises the question whether clinicians use 'secondary caries' as a catch-all into which they put a variety of reasons for replacement, or whether they do have professionally based reasons for focusing on caries adjacent to restorations. There is no consensus among researchers concerning the nature of secondary caries, but it is possible to identify two major-and conflicting-trends : One adheres to a critical approach concerning the frequency of replacements and recommends a much more conservative evaluation of existing fillings. In contrast, the other trend focuses on the clinical undetectable microleakage as the major risk factor for the initiation and uncontrolled dentinal spread of secondary caries. Since the latter trend offers a reasonable explanation for the clinicians' concern about invisible 'secondary caries', and hence reinforces the tendency to replacement, it is relevant to reconsider the conventional concept that microleakage leads to the initiation of secondary caries. Available data indicate that visible gaps and marginal discrepancies are poorly related to secondary caries, and that secondary caries is a localized phenomenon caused by localized conditions for the evolution of cariogenic plaque. Consequently, secondary caries is not a universal attack along the entire interface between tooth and restoration, but rather a new lesion or a re-beginning of caries on the surface due to local conditions for plaque formation with cariogenic potential. It is concluded that reinforcement of a new and more appropriate professional behavior should be based on diffusion of existing knowledge of dental caries as a disease rather than on simplified criteria for the placement and replacement of dental restorations.

Microbial induction of dentinal caries in human teeth in vitro

The ability of Lactobacillus casei, Streptococcus sobrinus, Actinomyces viscosus, and Streptococcus salivarius to induce dental caries was determined in vitro. A class I cavity (depth: 2mm) was prepared in extracted human caries-free premolars to make dentin blocks. The blocks were inoculated with these four bacterial strains in a monoinfective fashion and were incubated under anaerobic conditions. In addition to the monoinfection groups, mixed-infection groups of L. Casei with S. sobrinus or A. viscosus were also prepared. Half of the culture medium was renewed every 3 days, and the pH of the medium was measured. After 4 or 12 wk, these dentin blocks were prepared by Brown-Brenn staining and by contact microradiography for light microscopic observation and for immunohistochemical staining. The final pH of the S. salivarius group was the highest among the experimental groups, at approximately 5.1; that of the others was approximately 4.3. Bacterial invasion into the dentinal tubules was observed in all but the S. salivarius group. Among the monoinfection groups, the S. sobrinus group showed the highest invasion rate, followed by the A. Viscosus group and the L. casei group. The invasion rate was also high in the mixed-infection groups. Immunohistochemical staining revealed invasion only by L. casei, and not by S. sobrinus and A. viscosus. The invasion rate by L. casei was higher in the mixed-infection group with either S. sobrinus or A. viscosus than in the monoinfection groups. These findings suggest that lactobacillus might play an important role in the initiation and progress of dentinal caries, and that this bacterial species might exhibit a cooperative cariogenicity when it coexists with other bacterial species that surpasses its individual cariogenicity.

Role of Models in Assessing New Agents for Caries Prevention-Non-Fluoride Systems: Reaction Paper

Several important issues have been raised concerning the need for consideration of alternatives to fluoride. The principle reason to do so has been the lack of comprehensive effectiveness of fluoride, which in turn reveals incomplete understanding of the caries process. Included among the topics required for clarification of caries initiation would be quantitative methods for relating plaque pH values to the formation of caries. Thus, methods for assessing the activity of anticaries agents over time would be of considerable assistance in monitoring the effects of these test compounds on bacteria. The use of recombinant oral micro-organisms containing genetic fusions, to provide information on the effects of agents on bacteria growing in model systems, is discussed as a possible means of obtaining relevant data in situ.

Effect of sucrose and xylitol diets on dentin formation and caries in rat molars

To investigate the effects of a high sucrose diet and xylitol on secondary dentinogenesis and dentinal caries, a part of the sucrose in a high-cariogenic diet was replaced by xylitol. Fifty-four 3-wk-old Wistar rats were labeled with tetracycline and divided into groups. One group received a high sucrose diet (43% sucrose). In two other groups 5% and 20% of the sucrose was replaced by xylitol. A control group received non-cariogenic food. Six weeks later the mandibles were sectioned sagittally. Schiff staining was used to classify the caries, and the areas of dentin formed during the experiment and dentinal caries in first and second molars were measured planimetrically. The high sucrose diet reduced dentin formation of the molars, and this reduction was further increased by xylitol. Caries initiation and dentinal caries progression were significantly reduced by 20% xylitol, whereas only a slight reduction in caries progression was observed with 5% xylitol. Also, a negative correlation between the dentin formation and dentinal caries progression was observed in the high sucrose and 5% xylitol groups. In conclusion, xylitol together with high sucrose reduced dentin formation and dentinal caries progression, and the effect was dose-dependent.

Human Root Caries: Microbiota in Plaque Covering Sound, Carious and Arrested Carious Root Surfaces

The plaque microbiota covering sound or carious root surfaces were studied and compared with that covering arrested root caries lesions. From each of these categories five extracted teeth were examined. The experimental design of the study allowed us to relate the qualitative and quantitative microbial composition to the degree of integrity of the root surface. Plaque was sampled by a newly developed 'mowing' technique. Plaque samples were cultured anaerobically on nonselective Columbia blood agar plates supplemented with 5% hemolyzed human blood and on media selective for Lactobacillus spp. and streptococci of the mutans group. The cultivable microbiota were quantitatively speciated using Rapid ID 32A, Rapid ID 32 Strep, API 20 Strep, API ZYM, and API 50 CH tests and SDS-PAG electrophoresis. Regardless of the state of mineralization, the microbiota on all surfaces resembled marginal plaque associated with gingivitis. In addition to the gram-positive predominant facultative anaerobic genera Streptococcus, Staphylococcus, Lactobacillus and Actinomyces, gram-negative anaerobes, predominantly Bacteroides, Prevotella, Selenomonas, Fusobacterium, Leptotrichia, and Capnocytophaga, showed the highest isolation frequencies. On all surfaces Actinomyces spp. predominated, with streptococci and lactobacilli forming a minor part of the microbiota. With respect to the detected proportions of anaerobes, microaerophiles, Actinomyces naeslundii, Prevotella buccae and Selenomonas dianae, significant differences were observed between the three categories of root surfaces. The total CFU's on both caries-free and caries-active surfaces were significantly higher than on arrested lesions. In general, the results support a polymicrobial etiology for caries initiation on root surfaces, with A. naeslundii, Capnocytophaga spp., and Prevotella spp. making specific contributions to the processes of cementum and dentin breakdown.

Acid Profiles and pH of Carious Dentin in Active and Arrested Lesions

Organic acids in caries lesions play important roles in initiation and progress of dental caries. We investigated relationships between clinical types of dentin caries and acid profile or pH in the lesions. Caries lesions in dentin from 76 permanent teeth were classified into active, arrested, situated beneath a restoration, and unclassified types. The pH of carious dentin was distinctly lower than that of sound dentin (p < 0.001). Carious dentin with a high percentage of lactate had a lower pH than that with a high percentage of acetate and propionate (p < 0.001). Dentin from active lesions showed a mean pH of 4.9, and the dominant acid was lactate (mean percentage, 88.2). In contrast, carious dentin from arrested lesions showed a higher pH, 5.7, with acetate and propionate as the dominant acids (mean percentages of acetate and propionate, 64.0 and 18.2, respectively). The acid profile (mean percentages of acetate and propionate, 54.0 and 27.7, respectively) and pH (mean 5.8) of carious dentin sampled from lesions beneath a restoration were similar to those of dentin from arrested lesions. This study showed a clear relationship between clinical classification of dentin caries and acid profile and pH, suggesting that both factors are important in dentin caries etiology.

Human experimental caries models: intra-oral environmental variability.

In situ caries models serve purposes other than just being a simpler way to obtain data than running a clinical trial. However, variation in information obtained not only among individuals but also, in particular, depending on different locations of the models within the oral cavity have so far been given little attention. In the present review, the aim has been to characterize the different designs of in situ caries models and to describe some important factors which may vary within the oral cavity and thus influence the outcome of the way the different in situ models are used. Advantages and disadvantages of in vivo models vs. in situ models are discussed. In the latter case, the distinction is made between dental appliance models and so-called "single tooth" models. The review concludes that in situ models differ distinctly with regard to their "biological potential". Because of regional differences in salivary film velocity, pH, and composition of the microflora, results obtained by the various models are not likely to be immediately comparable. Moreover, local factors in relation to specimen environment, such as degree of "protection" and plaque thickness, may further add to the differences. It is suggested that these observations are important in considerations of the relevance of substituting clinical trials with in situ studies. Because of the pronounced intra-oral variation in certain parameters thought to be important for caries lesion development, we conclude that no in situ model can, by itself, fulfill the role as the "model of choice". Finally, although in situ models are useful adjuncts in attempts to estimate the relative effects of new anticaries methods or compounds on caries initiation, the selection of in situ study model design will strongly depend on the aim and purpose of the study.

In Vivo Caries Models-Mechanisms for Caries Initiation and Arrestment

The effects of intra-oral mechanical forces on caries initiation, progression, and arrestment are evaluated by examination of different in vivo caries models. The models are grouped in four categories: (1) a population study, (2) short-term clinical trials, (3) clinical experiments, and (4) controlled clinical observations. Taken together, these in vivo studies convincingly demonstrate that partial or total elimination of the intra-oral mechanical forces operating during mastication or toothbrushing leads to evolution of cariogenic plaque, resulting in localized carious enamel dissolution. In addition, they show that re-exposure to the partly or totally eliminated mechanical forces not only arrests further lesion progression, but also results in partial lesion regression. The data from in vivo caries studies also show that the clinical and structural changes associated with lesion arrestment or partial regression are not related to any salivary repair mechanism, but are solely the result of mechanical removal of the cariogenic biomass which is physically interrelated with the eroded surface of the active, dull-whitish enamel lesion. No indications of superficial mineral deposition or "blocking" of the external intercrystalline spaces are seen in the surface layer of lesions arrested in vivo. For this reason, the conventional usage of the terminology 'remineralization' is considered absolutely misleading when used to describe the mechanisms responsible for the arrest of lesion progression in vivo.

Streptococcus sobrinusandStreptococcus mutansin a Longitudinal Study of Dental Caries

Mutans streptococci have been correlated with human dental caries. Much is known about the role of Streptococcus mutans in the caries process, but the role of S. sobrinus is less clear. This bacterium has been reported to be very acidogenic and aciduric in vitro and cariogenic in rats and should, therefore, have at least some cariogenic potential in humans. This study was aimed at determining the possible relationship between S. sobrinus, S. mutans and dental caries in a longitudinal study by using a non-selective culturing method and species-specific monoclonal antibodies. At the beginning of this study, 158 children aged 4 yr were examined clinically and salivary mutans streptococci were counted on MSB agar. At 5 and 6 yr of age, the children were examined and mutans streptococci were detected by using species-specific monoclonal antibodies and MSB agar. The carriage rate of S. sobrinus increased between 5 and 6 yr from 25 to 48 per cent. The presence of this microorganism was significantly associated with caries incidence ( P =0.03). Relationships between the presence of S. sobrinus and salivary pH, buffer capacity or flow rate were not found. The presence of S. sobrinus or S. mutans was not significantly correlated with dmft when using the species-specific monoclonal antibodies. However, this correlation was highly significant (P< 0.001) when the mutans streptococci were detected by using the selective medium MSB. This suggests that differences in cariogenic potential occur within the species S. mutans or S. sobrinus . The present longitudinal study indicates that S. sobrinus is correlated with caries incidence, but its role in the initiation of caries could not be ascertained. Keywords - Streptococcus mutans , S. sobrinus , Mutans streptococci, Mitis salivarius agar, Immunoblotting, Monoclonal antibodies, Dental caries

Streptococcus sobrinus and Streptococcus mutans in a Longitudinal Study of Dental Caries

Mutans streptococci have been correlated with human dental caries. Much is known about the role of Streptococcus mutans in the caries process, but the role of S. sobrinus is less clear. This bacterium has been reported to be very acidogenic and aciduric in vitro and cariogenic in rats and should, therefore, have at least some cariogenic potential in humans. This study was aimed at determining the possible relationship between S. sobrinus, S. mutans and dental caries in a longitudinal study by using a non-selective culturing method and species-specific monoclonal antibodies. At the beginning of this study, 158 children aged 4 yr were examined clinically and salivary mutans streptococci were counted on MSB agar. At 5 and 6 yr of age, the children were examined and mutans streptococci were detected by using species-specific monoclonal antibodies and MSB agar. The carriage rate of S. sobrinus increased between 5 and 6 yr from 25 to 48 per cent. The presence of this microorganism was significantly associated with caries incidence (P=0-03). Relationships between the presence of S. sobrinus and salivary pH, buffer capacity or flow rate were not found. The presence of S. sobrinus or S. mutans was not significantly correlated with dmft when using the species-specific monoclonal antibodies. However, this correlation was highly significant (P< 0-001) when the mutans streptococci were detected by using the selective medium MSB. This suggests that differences in cariogenic potential occur within the species S. mutans or S. sobrinus. The present longitudinal study indicates that S. sobrinus is correlated with caries incidence, but its role in the initiation of caries could not be ascertained.

Characteristics and cariogenicity of a fructanase-defective Streptococcus mutants strain.

Polymers of D-fructose produced by a variety of oral bacteria are believed to function as extracellular carbohydrate reserves. Degradation of these polysaccharides in plaque following exhaustion of dietary carbohydrates is thought to contribute to the extent and duration of the acid challenge to the tooth surface and thus to the initiation and progression of dental caries. Streptococcus mutans produces a fructanase, the product of the fruA gene, which is capable of degrading beta(2,6)- and beta(2,1)-linked fructans that are commonly synthesized by dental plaque microorganisms. To evaluate the role of the FruA protein in exopolysaccharide metabolism and to assess the contribution of this enzyme to the pathogenic potential of S. mutans, a fructanase-deficient strain of S. mutans was constructed. Inactivation of a cloned fruA gene was accomplished in Escherichia coli by using a mini-Mu dE transposon, and then an isogenic mutant of S. mutans UA159 was constructed by allelic exchange. Successful inactivation of fruA was confirmed through the use of biochemical assays, Western blotting (immunoblotting) with anti-recombinant FruA antisera, and Southern hybridization. The data indicated that FruA was the only fructan hydrolase produced by S. mutans UA159. Inactivation of fruA had no significant effects on glucosyltransferase or fructosyltransferase activity. In the rat caries model using animals fed a high-sucrose diet and ad libitum, there were no significant differences in the number or severity of smooth surface, sulcal, or root caries elicited by the fruA mutant and the wild-type organism.

Humoral IgG antibodies to oral microbiota in a population at risk for root-surface caries.

Mutans streptococci have been strongly implicated in the initiation of dental caries on coronal surfaces. Their role in development of root-surface caries is less clear. The etiologic agents of both types of dental caries are likely to elicit systemic immune responses. The objective of the present study, therefore, was to study the association of clinical variables of disease with humoral IgG antibodies to nine oral micro-organisms in 314 adult subjects, aged 45-65 years, who were at risk for root-surface caries. Antibody activity to Streptococcus mutans strain Ingbritt, S. mutans/S. sobrinus GTFs, S. faecalis strain 19433, Actinomyces viscosus strain WVU 626, Actinomyces naeslundii strain 12, Lactobacillus casei, Actinobacillus actinomycetemcomitans strain Y4, Porphyromonas gingivalis strain 381, Eikenella corrodens strain 1073, and Wolinella recta strain 371 was measured by ELISA. Pearson correlation coefficients among log10 antibody levels within subjects revealed marked positive correlations among subgingival bacteria, generally weak positive correlations among supragingival micro-organisms, and no correlations between elements of the supragingival battery with the subgingival battery. IgG antibody levels to mutans streptococcal antigens were significantly correlated with subject DMF scores (r = 0.23; p less than 0.0001). No significant correlation was seen between DMF scores and antibody to any other supragingival micro-organism tested. Further relationships between levels of S. mutans antibody and individual clinical variables were analyzed by step-wise multiple linear regression, resulting in a model that was highly significant (p = 0.0001), with an r2 = 0.14. Numbers of missing teeth, coronal caries, root-surface caries, and root-surface restorations were each positively associated with antibody levels to mutans streptococci.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of phenytoin medication on dentin apposition, root length, and caries progression in rat molars.

To determine the effect of phenytoin (PHT) on dentin apposition and the rate of caries progression in dentin, 40 Wistar rats were treated daily for 35 days with intraperitoneal injections of 5,5-diphenylhydantoin. Twenty-eight controls received saline with pH adjusted to that of PHT. One PHT and one control group were fed a 43% sucrose diet, and the others a non-cariogenic pellet diet. Streptococcus sobrinus was inoculated to induce caries. Schiff staining was used to determine caries. The areas of dentin apposition and dentinal caries lesions were quantified after tetracycline staining. The root lengths were measured. PHT reduced slightly the dentin apposition and activated significantly the progression of the dentinal carious lesions. No difference in caries initiation was found. The high-sucrose diet reduced dentin apposition and increased the rate of progression of existing caries greatly. Our study suggests that both the high-sucrose diet and PHT have an effect on secreting odontoblasts, which can be seen as an alteration in dentin apposition and caries progression rates in dentin.

Caries prevalence and salivary mutans streptococci in 0–2‐year‐old children of Japan

The prevalence of caries and the number and species distribution of salivary mutans streptococci in 356 children (aged 0-2 yr old) in Japan were examined twice at an interval of 1 yr. No mutans streptococci were isolated from the predentate children. The detection rate of mutans streptococci and the prevalence of caries increased with age. Mutans streptococci were isolated from 39.9% of the subjects. The majority of isolates were identified as Streptococcus mutans. The concentration of mutans streptococci correlated with the number of erupted teeth (r = 0.339). In addition, the concentration of mutans streptococci was more closely correlated to the caries prevalence of the next year (r = 0.465) than that of the year when the salivary concentration of mutans streptococci was first evaluated (r = 0.368). The children who had no caries but harbored mutans streptococci in the first year showed significantly higher caries prevalence in the next year than did the children with neither caries nor mutans streptococci. These results indicate that the establishment of mutans streptococci is associated with caries initiation in early childhood.