Proportions of Streptococcus mutans, lactobacilli and Actinomyces spp in root surface plaque

Abstract – The incidence of Streptococcus mutans, lactobacilli and Actinomyces was examined in root surface dental plaque from 24 subjects with root surface caries and in 24 subjects with exposed root surfaces as a consequence of periodontitis but without root surface caries. Plaque was collected from the most posterior teeth in each quadrant: in the caries group from carious lesions and in the periodontitis group from buccal root surfaces. There were significantly higher proportions of S. mutans and lactobacilli in dental plaque samples taken from subjects suffering from root surface caries than in samples from subjects without root surface caries. The level of the group A. viscosus/naeslundii in the periodontitis group was higher than that found in the root surface caries group, but the difference was not statistically significant.     

Proportions of Streptococcus mutans, lactobacilli and Actinomyces spp in root surface plaque

The incidence of Streptococcus mutans, lactobacilli and Actinomyces was examined in root surface dental plaque from 24 subjects with root surface caries and in 24 subjects with exposed root surfaces as a consequence of periodontitis but without root surface caries. Plaque was collected from the most posterior teeth in each quadrant: in the caries group from carious lesions and in the periodontitis group from buccal root surfaces. There were significantly higher proportions of S. mutans and lactobacilli in dental plaque samples taken from subjects suffering from root surface caries than in samples from subjects without root surface caries. The level of the group A. viscosus/naeslundii in the periodontitis group was higher than that found in the root surface caries group, but the difference was not statistically significant.     

Actinomyces spp. in supragingival plaque of ethnic Chinese preschool children with and without active dental caries

Very limited molecular epidemiological data are available on the role of Actinomyces spp. in the pathogenesis of caries in the primary dentition. Therefore, we investigated their distribution in supragingival plaque of ethnic Chinese preschool children from Singapore and Hong Kong, either with or without active caries. Plaque samples were taken from intact interproximal enamel areas using dental floss. Bacterial genomic DNA of each sample was extracted and variable regions of 16S ribosomal DNA amplified and labelled with digoxigenin. Oligonucleotide probes specific for Actinomyces bovis, Actinomyces gerencseriae, Actinomyces israelii, Actinomyces meyeri, Actinomyces odontolyticus, catalase-negative Actinomyces naeslundii (genospecies 1 and 2) and catalase-positive Actinomyces naeslundii genospecies 2 (previously Actinomyces viscosus serotype II) were used to detect these species using Southern hybridization with a Minislot and Miniblotter system. A. odontolyticus, A. gerencseriae and A. meyeri were detected with similar frequency in both Singapore and Hong Kong samples or in those with and without active caries. However, the prevalence of A. naeslundii was significantly different in the two locales (p<0.05). A. odontolyticus (88.7%), A. gerencseriae (56.6%) and A. naeslundii (50.9%) were detected in a majority of the samples and the positive hybridization signals of A. gerencseriae in the caries-active group were stronger than from the caries-free group. A. bovis and A. israelii were undetectable in any of the samples. These data imply that A. odontolyticus, A. naeslundii and A. gerencseriae may play an important role in supragingival plaque formation on primary teeth in ethnic Chinese, with others such as A. meyeri contributing.     

Of human dental plaque bacteria, Actinomyces viscosus accelerates immunoglobulin A protease secretion in Streptococcus sanguis

Streptococcus sanguis and A. viscosus were co-cultured in a dialysis system containing tryptic soy broth. Strep. sanguis grown in the presence of A. viscosus produced 2–3 times the extracellular immunoglobulin A (IgA) protease during logarithmic growth compared to control cultures dialysing against sterile medium or an identical Strep. sanguis culture. In stationary phase the reverse was observed; IgA protease activity in Strep. sanguis/A. viscosus co-culture dropped within 2 h to about one half its peak value while the activity of the controls remained constant.     

Inhibition of Actinomyces viscosus by bacteriocin-producing strains of Streptococcus mutans in the dental plaque of gnotobiotic rats.

Gnotobiotic rats were infected with both Actinomyces viscosus Ny 1 and various strains of Streptococcus mutans. The simultaneous inoculation of Strep. mutans. OMZ 1766, a strain devoid of bacteriocin activity against A. viscosus Ny 1 in vitro, did not prevent the establishment of strain Ny 1 in the plaque. In contrast, Strep. mutans C 67-1, which is bacteriocinogenic against A. viscosus Ny 1, prevented the establishment of strain Ny 1 when it was introduced up to two days before the Strep. mutans C 67-1. A. viscosus Ny 1 could only be established if it was inoculated 13 days before infection with Strep. mutans C 67-1. Electron microscopic examination of these plaques supported this antagonistic relationship. The same phenomenon was observed with Strep. mutans T2, a strain that also shows in-vitro bacteriocin activity against A. viscosus Ny 1. In contrast, strain Ny 1 was successfully established in the presence of mutagen-induced non-bacteriocinogenic isolates of Strep. mutans C 67-1 and T2. These findings suggest that although bacteriocins may be important in the regulation of the flora in plaque, at least on a micro-ecological scale, they do not necessarily completely eliminate the sensitive species.     

荧光原位杂交观察口腔原位菌斑中链球菌和具核梭杆菌的动态变化的研究

[摘要] 目的 观察口腔原位菌斑形成过程中链球菌和具核梭杆菌的动态变化。方法 专业洁治后,7个志愿者佩戴可形成口内菌斑生物膜以供原位菌斑研究的上颌装置,分别佩戴12 h、1 d、2 d、3 d、5 d后,取下样本,与链球菌和具核梭杆菌的特异性寡核苷酸探针进行荧光原位杂交,于激光共聚焦显微镜下观察菌斑生物膜的形成过程及2种细菌在菌斑形成发育中的分布及比例。结果菌斑生物膜厚度由5.26μm逐渐发育增加为46.93μm。12 h细菌仅形成平铺片状,链球菌占绝大多数,未见具核梭杆菌;此后细菌排列趋于密集,菌斑厚度逐渐增加,最后形成团块状菌斑。链球菌在2、3 d菌斑中比例下降;具核梭杆菌在5 d菌斑中比例比3 d上升107%。结论 链球菌在早期菌斑中为优势菌,具核梭杆菌在菌斑发育中期数量逐渐增加。2种细菌在菌斑形成中起到重要作用。     

Transient acid-impairment of growth ability of oral Streptococcus, Actinomyces, and Lactobacillus: a possible ecological determinant in dental plaque

Introduction:  Dental plaque pH decreases to about 4 through bacterial fermentation of carbohydrates and this low pH is maintained for from several minutes to about an hour. Repeated acidification causes demineralization of the tooth surface, resulting in caries formation. The acidification also influences plaque bacteria. Severe acidification kills bacteria efficiently, while physiological acidification, the condition occurring in plaque, kills bacteria partially and may impair growth ability. We, therefore, investigated the effects of physiological acidification on representative caries-related bacteria.
Methods:  Streptococcus mutans , Streptococcus sobrinus , Streptococcus sanguinis , Streptococcus oralis , Lactobacillus paracasei , and Actinomyces naeslundii were used. Effects of physiological acidification at pH 4.0 on cell viability and growth ability, as well as the growth rate of these bacteria at pH 4.0–7.0, were investigated.
Results:  Mutans streptococci and Lactobacillus grew at pH 4.0 but the growth of S. sanguinis and S. oralis ceased below pH 4.2 and pH 4.2–4.4, respectively. Acidification at pH 4.0 for 1 h killed 43–89%, 45% and 35–76% of S. sanguinis , S. oralis , and Actinomyces , respectively. Furthermore, assessment of bacterial growth curves revealed that the growth ability of the surviving cells of S. sanguinis , S. oralis and Actinomyces was impaired, but it was recovered within 2–5 h after the environmental pH had returned to 7.0. The acidification neither killed nor impaired the growth of mutans streptococci and Lactobacillus .
Conclusions:  These results indicate that physiological and transient acidification is not sufficient to kill bacteria, but it causes a temporary acid-impairment of their growth ability, which may function as an ecological determinant for microbial composition in dental plaque.     

Competition between fluoride-resistant and fluoride-sensitive Streptococcus mutans in rat dental plaque.

The experiments were designed to study the effects of fluoride on the competition between a fluoride-sensitive strain of Streptococcus mutans (C180-2) and a fluoride-resistant mutant (S. mutans C180-2FR) in rat dental plaque. Competition was induced either by superinfecting rats or by co-caging rats infected with either strain with non-infected rats. Sodium fluoride was applied in diet and drinking water (60 ppm F), as daily brushings with a 1% F solution, or as a combination of both administrations. The fluoride applications favoured S. mutans C180-2FR, but not enough to outcompete the parent strain successfully under all conditions. Fluoride protected rat dental plaque harbouring S. mutans C180-2FR against colonization by the parent strain. In rats not previously infected with S. mutans, the fluoride in diet and drinking water in combination with the fluoride brushings favoured S. mutans C180-2FR in colonizing rat dental plaque. However, the fluoride applications did not benefit S. mutans C180-2FR in colonizing plaque in which the parent strain was already present. Human dental plaque may be colonized by fluoride-resistant S. mutans strains after spontaneous mutation in response to a fluoride pressure. Our data suggest that this pressure may also provide an ecological advantage to this mutant to colonize the dental plaque.     

建立口内菌斑模型研究菌斑超微结构

目的:系统了解菌斑形成的超微结构。方法:建立一种口内的菌斑模型,并将1、5、9d形成的菌斑标本制成电镜切片后用透射电镜观察。结果:显示初期菌斑的细菌较少,主要为球状菌。随着时间的延长,细菌的数量和种类开始增加,出现丝状菌和杆状菌。成熟菌斑结构是两侧为丝状菌中间为球状菌的栅栏状结构,其中部分细菌会出现坏死的现象。结论:所建立的菌斑模型较接近天然菌斑结构,具有一定的参考价值。     

Carbohydrate metabolism of Streptococcus mutans in dental plaque in gnotobiotic rats.

The fermentation products of Streptococcus mutans C67-1 were investigated in fissure plaque of rats, that were mono-associated with this strain. In addition to lactic acid, acetic acid and ethanol were present. The finding that a mixed acid fermentation occurred and that ethanol was produced suggests that the carbohydrate source rather than the nitrogen source was the growth-limiting substrate for Strep. mutans in plaque.     

Immuno-electron microscopic study of antigenic surface components of Actinomyces naeslundii in human dental plaque.

Rabbit antiserum to formalin-killed Actinomyces naeslundii I was used to investigate the ultrastructural location and distribution of the antigenic sites of A. naeslundii. Antigenic sites were identified by an indirect technique using goat anti-rabbit IgG coupled to horseradish peroxidase, also used to identify individual cells of A. naeslundii in a mixed bacterial population and in freshly isolated dental plaque. The bound antibody and associated reaction product were visible in ultrathin sections as an electron-dense amorphous material (100–150 nm thick) in juxtaposition to the bacterial cell wall. The location of the immuno-reactants suggested that the antigens are distributed superficially and evenly over the entire bacterial cell surface. Bridge-like extensions of the immuno-reactants connected adjacent cells, suggesting that a limited amount of antigenic material might extend out from the cell wall to provide structural continuity with similar material on adjacent cells.     

Effects of phenytoin on dental caries and plaque in Streptococcus sobrinus-infected rats.

Effects of phenytoin (PHT) administration on dental caries in rats infected with Streptococcus sobrinus 6715 were investigated. Twenty-day-old specific pathogen-free Fischer male rats were infected with S. sobrinus 6715 and fed diet 2000 containing 56% sucrose with or without PHT for 52 days. Antibody responses against anti-S. sobrinus in serum and saliva failed to show a statistical difference between PHT-treated and nontreated rats. These results indicate that PHT treatment increased plaque deposition and dental caries in the rats infected with S. sobrinus 6715 and fed diet 2000 containing PHT (1-2 mg/g), as compared with those similarly infected and fed diet without PHT (P < 0.001).     

Genotypes of Streptococcus mutans in saliva versus dental plaque

OBJECTIVE: The aim of this study was to investigate whether genotypes of Streptococcus mutans strain can be detected as effectively in saliva samples as in plaque samples from buccal surfaces and occlusal surface fissures of permanent first molars. DESIGN: The study included 20 school children aged 6-7 years who were positive for mutans streptococci. Samples of stimulated saliva and of dental plaque on buccal surfaces and occlusal surface fissures of permanent first molars were collected. Samples were cultivated in MSB agar. Up to nine isolates compatible with mutans streptococci were obtained and identified by means of biochemical tests. All isolates identified as S. mutans were genotyped by arbitrarily primed polymerase chain reaction. RESULTS: A total of 28 genotypes of S. mutans were isolated: 23 in saliva samples, 23 in buccal surface plaque samples, and 16 in plaque samples from occlusal surface fissures. CONCLUSIONS: Although, saliva sampling did not reveal all genotypes isolated, it was equally as effective as plaque sampling from the buccal surfaces of permanent first molars, and more effective than plaque sampling from fissures on their occlusal surfaces.     

The effect of oral health education on dental plaque development and the level of caries-related Streptococcus mutans and Lactobacillus spp

The aim of this study was to determine the influence of oral hygiene instruction (OHI) on oral hygiene status and on the reduction of inducing bacteria (Streptococcus mutans and Lactobacillus spp.) in 30 subjects (12 males and 18 females) with an age range from 10 to 14 years. The patients were instructed on how to carry out effective oral hygiene close to brackets and ligatures, and in the use of dental floss for cleaning spaces around brackets, between the teeth and under archwires. The plaque index (PI) was used to measure oral hygiene status, and the level of S. mutans and Lactobacillus spp. was determined using the colour reaction time test before and after 1 month of OHI. Statistical analysis included a Student's t-test and chi-square test. The results showed that OHI significantly improved oral hygiene. The percentage of patients with a PI exceeding 1 decreased from 23.3 to 10 per cent and for those with a PI below 0.1 it increased from 20 to 60 per cent. The level of S. mutans and Lactobacillus spp. was not reduced. The percentage of subjects with excessive levels of S. mutans (above 10(6) bacteria in 1 ml of saliva) decreased after OHI but only from 73.3 to 70 per cent. For Lactobacillus spp., a level above 10(5) of bacteria in 1 ml of saliva was found for all subjects at both time points. Patients with fixed appliances, trained in scrupulous tooth cleaning, remain at risk of developing caries and should be carefully monitored.     

A proposed human needs conceptual model for dental hygiene: part I.

To date, research and theory development in dental hygiene have been largely sporadic and lacking in focus. Dental hygiene has begun to develop its body of knowledge by adopting a definition of the discipline and a structural hierarchy of knowledge that includes a global paradigm, conceptual model(s), and theory. By identifying major concepts and linking theory to an expanding knowledge base, dental hygiene can begin to evolve as a scientific discipline. Conceptual models and theories will characterize the uniqueness of dental hygiene and move it into collegiality with other professional disciplines. In the future, practitioners, educators, and researchers may adopt an organizational framework for dental hygiene. Doing so will enhance dental hygiene research, teaching, and client care. Most importantly, it will enhance dental hygiene's view of itself. This in turn will facilitate dental hygiene's continuing evolution toward professionalization.