Subgingival microbiota in adult Down syndrome periodontitis.

BACKGROUND AND OBJECTIVE: The subgingival microbiota in Down syndrome and non-Down syndrome adults receiving periodic dental care was examined for 40 bacterial species using checkerboard DNA-DNA hybridization and the results were related to clinical periodontal attachment loss. MATERIAL AND METHODS: A total of 44 Down syndrome, 66 non-Down syndrome mentally retarded and 83 mentally normal adults were clinically evaluated. This involved, for each subject, the removal of subgingival specimens from three interproximal sites on different teeth; all subgingival samples per subject were then pooled and assessed for the presence and levels of 40 bacterial species using species-specific whole-genomic DNA probes and checkerboard DNA-DNA hybridization. Significant group differences in species proportions averaged across subjects were evaluated using the Kruskal-Wallis test, and associations between subgingival species and mean subject attachment loss within Down syndrome and non-Down syndrome subject groups were quantified using Pearson correlation and multiple linear regression analysis. RESULTS: Down syndrome subjects exhibited greater attachment loss than non-Down syndrome subjects (p=0.05). Most microbial species were present in Down syndrome subjects at levels similar to non-Down syndrome subjects, except for higher proportions of Selenomonas noxia, Propionibacterium acnes, Streptococcus gordonii, Streptococcus mitis and Streptococcus oralis in Down syndrome subjects compared with non-Down syndrome study subjects, higher proportions of Treponema socranskii in Down syndrome subjects compared with non-Down syndrome mentally retarded subjects, and higher proportions of Streptococcus constellatus in Down syndrome subjects compared with mentally normal subjects. Down syndrome adults classified with periodontitis revealed higher subgingival levels of T. socranskii than Down syndrome subjects with no periodontitis (p=0.02). Higher subgingival proportions of S. constellatus, Fusobacterium nucleatum ssp. nucleatum, S. noxia and Prevotella nigrescens showed significant positive correlations (r=0.35-0.42) and higher proportions of Actinomyces naeslundii II and Actinomyces odontolyticus showed negative correlations (r=-0.36 to -0.40), with increasing mean subject attachment loss in Down syndrome adults. CONCLUSION: Individuals with Down syndrome show higher levels of some subgingival bacterial species and specific associations between certain subgingival bacterial species and loss of periodontal attachment. These findings are consistent with the notion that certain subgingival bacteria may contribute to the increased level of periodontal disease seen in Down syndrome individuals and raise the question as to the reason for increased colonization in Down syndrome.

Factors affecting human supragingival biofilm composition. II. Tooth position.

BACKGROUND AND OBJECTIVE: Little is known regarding the factors that affect the microbial composition of supragingival biofilms. This study was designed to test the hypothesis that tooth location affects the microbial composition of supragingival plaque beyond the effect due to plaque mass as reflected by total DNA probe count. MATERIAL AND METHODS: Supragingival plaque samples were taken from the mesiobuccal aspect of each tooth in 187 subjects (n = 4745 samples). All samples were individually analyzed for their content of 40 bacterial species using checkerboard DNA-DNA hybridization. Significance of differences in mean species counts and proportions were determined among tooth surfaces and six tooth type categories: molars, bicuspids, incisors/canines in the mandible and maxilla separately using the Kruskal-Wallis test. Stepwise multiple linear regression was employed to examine the relationship between species proportions and total DNA probe count, tooth location, periodontal and smoking status, age and sex. RESULTS: All species differed significantly among tooth types and among the six tooth categories. Higher plaque levels were seen on molars and lower incisors. Some differences observed between tooth types could be partly explained by the level of plaque. Teeth with high plaque mass exhibited high levels of Capnocytophaga gingivalis, Actinomyces naeslundii genospecies 2, Campylobacter rectus and Campylobacter showae. However, certain species, such as Veillonella parvula and Streptococcus sanguinis, differed significantly at different tooth locations despite similarities in plaque mass. Twenty of the test species exhibited a significant association with tooth location after adjusting for total DNA probe count and subject level factors. CONCLUSION: While plaque mass was associated with differences in proportions of many species in supragingival biofilms, tooth location also was strongly associated with species proportions in both univariate and multivariate analyses.

Identification of early microbial colonizers in human dental biofilm.

AIMS: To elucidate the first colonizers within in vivo dental biofilm and to establish potential population shifts that occur during the early phases of biofilm formation. METHODS AND RESULTS: A 'checkerboard' DNA-DNA hybridization assay was employed to identify 40 different bacterial strains. Dental biofilm samples were collected from 15 healthy subjects, 0, 2, 4 and 6 h after tooth cleaning and the composition of these samples was compared with that of whole saliva collected from the same individuals. The bacterial distribution in biofilm samples was distinct from that in saliva, confirming the selectivity of the adhesion process. In the very early stages, the predominant tooth colonizers were found to be Actinomyces species. The relative proportion of streptococci, in particular Streptococcus mitis and S. oralis, increased at the expense of Actinomyces species between 2 and 6 h while the absolute level of Actinomyces remained unaltered. Periodontal pathogens such as Tannerella forsythensis(Bacteroides forsythus), Porphyromonas gingivalis and Treponema denticola as well as Actinobacillus actinomycetemcomitans were present in extremely low levels at all the examined time intervals in this healthy group of subjects. CONCLUSION: The data provide a detailed insight into the bacterial population shifts occurring within the first few hours of biofilm formation and show that the early colonizers of the tooth surface predominantly consist of beneficial micro-organisms. SIGNIFICANCE AND IMPACT OF THE STUDY: The early colonizers of dental plaque are of great importance in the succession stages of biofilm formation and its overall effect on the oral health of the host.

Effectiveness of calcium lactate added to food in reducing intraoral demineralization of enamel.

Following the demonstration that rinses with solutions of soluble calcium salts reduced sucrose-induced demineralization, a study was undertaken to determine whether a similar effect could be obtained by the supplementation of a solid food with calcium lactate (CL). Subjects wore palatal appliances containing blocks of bovine enamel that were coated with Streptococcus mutans IB 1600 and ate 5-gram portions of cookies made with defined levels of CL. Determinations were made of changes in iodide penetrability (delta Ip) of the enamel, as well as the pH, calcium and inorganic phosphate of the streptococcal plaque. CL at 3.2% (w/w) reduced delta Ip from 12.9 +/- 1.7 to 6.1 +/- 0.9 units, i.e. by 52.7%. Plaque pH was not affected. Demineralization was reduced progressively with increasing concentrations of added CL, and CL was most effective with increasingly sweet cookies. Plaque contained 32.4 +/- 6.0 and 17.1 +/- 4.2 mM calcium after 1 and 5 min, respectively. Calculations showed that the plaque was saturated with respect to enamel during the first 5-10 minutes after food ingestion, in spite of the progressive drop in plaque pH. In conclusion, the present study demonstrated the reduction of the cariogenic potential of solid food by relatively low concentrations of CL. The effect appeared to be related to the ability of the food to maintain high levels of calcium in the streptococcal plaque during the period of active acidogenesis.

Effects of a high-bicarbonate dentifrice on intraoral demineralization.

Dentifrices available on the market today contain sodium bicarbonate in a wide range of concentrations. Anticaries efficacy has been demonstrated for these dentifrices in a variety of tests. New insights were gained in the present study in which the effect of a high-bicarbonate dentifrice on the sucrose-induced demineralization of tooth enamel in situ was examined. With the intraoral Delta Ip system it is possible to follow the minute changes in tooth enamel that essentially model the daily episodes of demineralization accompanying the ingestion of various foods. The results revealed a pronounced effect on the pH of the test plaque and a considerable reduction in mineral loss from the enamel. The effect persisted for more than 1 hour and, during that time, appeared to predominate over the effect of fluoride. These findings suggest that bicarbonate may provide additional protection against the loss of tooth enamel. Such effects may be significant for the design of new high-bicarbonate products.

Effects of a high-bicarbonate dentifrice on intraoral demineralization.

Dentifrices available on the market today contain sodium bicarbonate in a wide range of concentrations. Anticaries efficacy has been demonstrated for these dentifrices in a variety of tests. New insights were gained in the present study in which the effect of a high-bicarbonate dentifrice on the sucrose-induced demineralization of tooth enamel in situ was examined. With the intraoral Delta Ip system it is possible to follow the minute changes in tooth enamel that essentially model the daily episodes of demineralization accompanying the ingestion of various foods. The results revealed a pronounced effect on the pH of the test plaque and a considerable reduction in mineral loss from the enamel. The effect persisted from more than 1 hour and, during that time, appeared to predominate over the effect of fluoride. These findings suggest that bicarbonate may provide additional protection against the loss of tooth enamel. Such effects may be significant for the design of new high-bicarbonate products.

Delayed effect of wheat starch in foods on the intraoral demineralization of enamel.

There is considerable evidence for an association between dental caries and food starches. However, the intraoral utilization of starch may be quite complex, giving rise to conflicting results. Demineralization induced by unsweetened cookies was examined in an intraoral model system that utilized palatal appliances containing blocks of bovine enamel. The enamel surfaces were covered with either a filter paper disc to trap sugars or a layer of Streptococcus mutans to metabolize the sugars and bring about enamel demineralization. Demineralization was determined as an increase in porosity with respect to iodide ions (delta Ip). Measurements revealed a rapid elevation and maintenance of high levels of maltose in the plaque space after ingestion of the unsweetened or sweet cookies. Entrapped food particles appeared to serve as a reservoir of maltose. Unsweetened cookies brought about enamel demineralization, but the pH of the streptococcal plaque fell slowly, and the initiation of demineralization was delayed. Thus, delta Ip and plaque pH were -0.3 +/- 1.3 U and 6.1 +/- 0.3, respectively, after 15 min. The delay was shown to be related to the need to induce the acidogenic streptococci to metabolize maltose. Once induced, delta Ip rose rapidly and reached a maximum at 45 min. Sweet cookies released sucrose and maltose and brought about a rapid onset of demineralization. In summary, the data demonstrated (1) that maltose was released rapidly from unsweetened cookie particles and diffused into the plaque space of the model system and (2) that maltose-dependent demineralization of enamel required time for the induction of the streptococcal cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of timing of administered calcium lactate on the sucrose-induced intraoral demineralization of bovine enamel.

A number of soluble calcium salts are known to reduce the demineralization of enamel in the mouth. The present study was undertaken to examine the effects of rinses containing different concentrations of calcium lactate, and the time of giving the rinses with respect to sucrose challenges. Subjects wore palatal appliances containing blocks of bovine enamel whose surfaces were covered with Streptococcus mutans IB 1600, and rinsed with 10% sucrose for 1 min. Changes in iodide penetrability of the enamel, and the pH and extracellular ion concentrations of the streptococcal plaque were determined. When added to the sucrose rinse, 100 or 150 mM calcium lactate reduced demineralization by about 35%, although the plaque pH was not affected. Plaque calcium was elevated but diffused away rapidly so that concentrations after 45 min were close to control values. Plaque inorganic phosphate and lactate were not affected. Ongoing demineralization appeared to be stopped when 100 mM calcium lactate was given 15 min after the sucrose rinse. When the lactate was given 15 min before the sucrose rinse, demineralization was reduced by only about 25%, consistent with the rapid diffusion of plaque calcium. The combination of (i) pretreatment with calcium lactate and (ii) admixture of calcium lactate with sucrose was most effective. Demineralization was reduced about 55% with 100 mM calcium lactate under these conditions, and protective effects were seen with as little as 25 mM. In summary, the findings demonstrate the enamel-protective effect of relatively low concentrations of calcium lactate, and point to the need to sustain a high plaque calcium during periods of maximum acidogenicity.

Limitations in the intraoral demineralization of bovine enamel.

A model system was used to examine the relation between the duration of plaque pH fall and enamel demineralization following the intake of dietary carbohydrate in humans. Subjects wore palatal appliances containing blocks of bovine enamel covered with Streptococcus mutans IB 1600, and rinsed with 5 or 10% sucrose. Changes in iodide penetrability (delta Ip) of the enamel, and the pH and extracellular calcium and inorganic phosphate (Pi) concentrations of the streptococcal plaque were determined. Following rinses with 5% sucrose, delta Ip increased with time and reached a maximum (11.2 +/- 2.2 units) at 45-60 min although the S. mutans plaque remained acidic (pH = 4.8 +/- 0.6). After 10% sucrose, the maximum (14.7 +/- 3.1 units) was reached while the plaque pH was 4.0 +/- 0.3. Second rinses with sucrose increased delta Ip at most by 30%. Thus, demineralization did not persist throughout the period of low plaque pH, but occurred primarily during the early phase of plaque acidogenesis. Enamel demineralization appeared to be limited by factors other than the pH of the streptococcal plaque. Calcium concentrations in the S. mutans plaque rose to a maximum of 10.9 +/- 2.8 mEq/l at 30 min after the 5% sucrose rinses, then fell; Pi reached a stable level of 12.2 +/- 2.3 mEq/l by 60 min. Calculations showed that conditions approached saturation with respect to enamel and dicalcium phosphate dihydrate as demineralization reached a maximum. Demineralization appeared to be limited at low plaque pH, therefore, by the accumulation of high levels of mineral ions in the streptococcal plaque.(ABSTRACT TRUNCATED AT 250 WORDS)

Accumulation of enamel constituents in Streptococcus mutans plaque during intraoral demineralization.

Studies were carried out with an intraoral demineralizing system in order to determine whether calcium and inorganic phosphate (Pi) accumulate in plaque during active demineralization of enamel. Blocks of bovine enamel were coated with Streptococcus mutans and were carried in palatal appliances worn by human volunteers. Demineralization was determined as changes in the iodide penetrability (delta Ip) of the enamel surfaces. Ca and Pi were determined in the extracellular spaces of the synthetic plaque. Delta Ip increased with time after administration of rinses containing 5% (w/v) sucrose, while plaque pH dropped and then returned toward neutrality. Ca increased to 10.9 +/- 2.8 mmol/l at 30 min, while Ca2+ and Pi rose to 3.0 +/- 2.1 and 9.5 +/- 3.1 mmol/l, respectively. The Ca:Pi ratio was 1.15. Rinses with 10% (w/v) sucrose gave similar results. Concentrations of Ca and Pi were considerably higher than those in saliva. Accumulation of the mineral constituents was shown to be dependent on metabolic activity of the S. mutans plaque, and experiments in which enamel blocks were replaced with blocks made of acrylic plastic gave Ca and Pi concentrations of 2.5 +/- 0.6 and 6.6 +/- 2.4 mmol/l, respectively, demonstrating that most of the Ca and about one-third of the Pi were derived from enamel. The data suggested, furthermore, that Ca and Pi were partially bound to complex macromolecules, and that part eventually recrystallized as mineral within the plaque.

Prevention of sucrose-induced demineralization of tooth enamel by chewing sorbitol gum.

Measurements were made of the effect of chewing sorbitol gum on the intra-oral demineralization induced by rinsing with 10% sucrose solutions. Blocks of bovine enamel were covered with a layer of Streptococcus mutans IB1600, and mounted on palatal appliances that were worn by five subjects for defined periods of time. Enamel demineralization was determined by following changes in iodide penetrability (delta Ip) of the enamel surfaces. Delta Ip increased to a maximum of about 15 units between 30 and 45 min, while the pH of the S. mutans plaque dropped to below 4 by 15 min. Plaque pH returned to 4.9 by 60 min. Chewing sorbitol gum after the sucrose rinse minimized further increases in delta Ip and brought about a more rapid return of the S. mutans plaque pH toward neutrality. The effect of chewing gum was greater when chewing was initiated earlier so that, when gum was given at five min after the sucrose rinse, demineralization was only 37% of that obtained without gum. The findings confirm earlier reports on the effect of gum on plaque pH, and directly demonstrate the profound protective effects that chewing sorbitol gum can have on tooth enamel.

Increased permeability of enamel to iodide ions following the ingestion of cookies varying in sucrose or fat content.

Experiments showed that the intraoral iodide permeability (Ip) method can be used in a reproducible and sensitive manner with solid foods. Ingestion of 5-gram portions of cookies made with defined concentrations of sucrose or fat led to an increased Ip (due to demineralization) of Streptococcus mutans-covered bovine enamel blocks in vivo. Demineralization increased with time to a maximum of 45 min, and the pH of the plaque dropped accordingly. Continued exposure in the mouth beyond 45 min led to an elevation of the pH and a decrease in delta Ip consistent with remineralization of the enamel. Control blocks worn without ingestion of cookies exhibited negative delta Ip values. Demineralization increased with increasing sucrose content of the cookies and reached a plateau when cookies containing 1.08 g sucrose per morsel were administered. Cookies prepared without added sucrose gave a high delta Ip. High fat content raised the delta Ip when sucrose was low. These findings are consistent with clinical and other observations, and emphasize the complex relation between foods and enamel demineralization.