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Neuromuscular disorders cause damage to the motor nerves. Arm-hand function can severely be impaired. The needs of and limitations of patients with neuromuscular disorders and the role of their carers in providing oral hygiene were studied. To this end, an online survey was sent to 706 patients with a neuromuscular disorder (amyotrophic lateral sclerosis, spinal muscular atrophy, primary lateral sclerosis and progressive bulbar palsy). The survey questions concerned, among other things, self-reliance, the oral situation and oral hygiene. Oral health-related quality of life and subjective well-being were also measured. A total of 259 patients (36.7%) responded, of whom 71.9% declared themselves not to have been informed about the importance of maintaining good oral health. Moreover, 40.4% wished to receive help from an oral care professional regarding their oral hygiene; 19.8% was not satisfied with the oral care they provided for themselves or as provided by their carers. It was concluded that attention to oral hygiene for patients with neuromuscular disorders by both multidisciplinary treatment teams and oral care professionals is required.Bij neuromusculaire aandoeningen worden de motorische zenuwen aangetast. Hierdoor kan de arm-handfunctie sterk achteruitgaan. De behoeften en barrières van patiënten met neuromusculaire aandoeningen en de rol van hun mantelzorgers of zorgverleners bij het uitvoeren van mondzorg werd onderzocht. Hiertoe werd een online vragenlijst gestuurd naar 706 patiënten met een neuromusculaire aandoening (amyotrofische laterale sclerose, progressieve spinale musculaire atrofie, primaire laterale sclerose en progressieve bulbaire parese). De vragen betroffen onder meer zelfredzaamheid, mondsituatie en mondhygiëne. De mondgezondheid gerelateerde kwaliteit van leven en het subjectieve welzijn werden ook gemeten. In totaal reageerden 259 patiënten (36,7%), van wie 71,9% aangaf niet geïnformeerd te zijn over het belang van een goede mondgezondheid. Bovendien wilde 40,4% graag hulp van een professionele mondzorgverlener ontvangen op het gebied van mondhygiëne, 19,8% was niet tevreden over de mondzorg zoals die door henzelf of hun verzorgers werd uitgevoerd. Geconcludeerd werd dat mondzorg bij patiënten met neuromusculaire aandoeningen aandacht nodig heeft van zowel multidisciplinaire behandelteams als mondzorgverleners.

Dental health care workers are in close contact to their patients and are therefore at higher risk for contracting airborne infectious diseases. The transmission rates of airborne pathogens from patient to dental health care workers are unknown. With the outbreaks of infectious diseases, such as seasonal influenza, occasional outbreaks of measles and tuberculosis, and the current pandemic of the coronavirus disease COVID-19, it is important to estimate the risks for dental health care workers. Therefore, the transmission probability of these airborne infectious diseases was estimated via mathematical modeling. The transmission probability was modeled for Mycobacterium tuberculosis, Legionella pneumophila, measles virus, influenza virus, and coronaviruses per a modified version of the Wells-Riley equation. This equation incorporated the indoor air quality by using carbon dioxide as a proxy and added the respiratory protection rate from medical face masks and N95 respirators. Scenario-specific analyses, uncertainty analyses, and sensitivity analyses were run to produce probability rates. A high transmission probability was characterized by high patient infectiousness, the absence of respiratory protection, and poor indoor air quality. The highest transmission probabilities were estimated for measles virus (100%), coronaviruses (99.4%), influenza virus (89.4%), and M. tuberculosis (84.0%). The low-risk scenario leads to transmission probabilities of 4.5% for measles virus and 0% for the other pathogens. From the sensitivity analysis, it shows that the transmission probability is strongly driven by indoor air quality, followed by patient infectiousness, and the least by respiratory protection from medical face mask use. Airborne infection transmission of pathogens such as measles virus and coronaviruses is likely to occur in the dental practice. The risk magnitude, however, is highly dependent on specific conditions in each dental clinic. Improved indoor air quality by ventilation, which reduces carbon dioxide, is the most important factor that will either strongly increase or decrease the probability of the transmission of a pathogen.

Previous studies have shown that Streptococcus oligofermentans inhibits the growth of cariogenic Streptococcus mutans in biofilms in vitro and is considered a probiotic candidate for caries prevention. This study aimed to examine the effects of various environmental factors on the competition between S. oligofermentans and S. mutans in a dual-species biofilm model. Single or dual S. oligofermentans and S. mutans biofilms were grown in a 96-well active attachment model for 48 h. Several growth conditions were examined in the model, namely: S. oligofermentans was inoculated 24 h before S. mutans or vice versa; the growth medium was supplemented with 0.2% sucrose or 0.4% glucose; biofilms were grown under a constantly neutral pH or pH-cycling condition, which included 8 h of neutral pH and 16 h of pH 5.5. The 48-h biofilms were examined for viable cell counts and lactic acid and hydrogen peroxide production ability. When S. oligofermentans was inoculated first, it clearly inhibited the growth of S. mutans and reduced the biofilm lactic acid production by up to 8-fold through hydrogen peroxide production, independently of sugar supply and pH conditions. When S. mutans was inoculated first, the level of inhibition by S. oligofermentans varied depending on the sugar supply and pH conditions. Thus, the inhibition efficacy of S. oligofermentans against S. mutans in dual-species biofilms is influenced by environmental factors. This study provides practical information on how to maximize the efficacy of S. oligofermentans.

Aim: To describe the application of a newly-developed in vitro model in which the diffusion of antimicrobials in oral biofilms can be studied. Methodology: In a flow chamber consisting of three parallel feeding channels connected with each other by eight perpendicular side channels, multispecies biofilms were grown from saliva of a single donor for 48 h. The dimensions of the side channels were 100 μm × 100 μm × 5130 μm (H × W × L). When one or more side channels were filled with biofilm, the biofilms were stained with fluorescent stains. Then, one side-channel biofilm was selected and treated with phosphate buffered saline, 2% sodium hypochlorite (NaOCl), 17% ethylenediaminetetra-acetic acid (EDTA) or modified salt solution (MSS). Diffusion of the irrigants was observed by acquiring fluorescence images at 10× objective every 15 s for 30 min. Results: It was possible to culture biofilms in the narrow (100 μm) channels. The biofilms varied in phenotype. In this model, no diffusion of NaOCl into the biofilms was seen after its application. Seventeen-percentage EDTA only diffused into the biofilm up to 200 μm in 30 min. MSS did diffuse in the biofilm over a distance of 450 μm within 2 min after a single application. Conclusions: This new model enables the investigation of the diffusion of antimicrobials in biofilms. Other applications to improve our understanding of the characteristics of biofilms are now possible.

AimTo investigate the cytotoxicity of a modified salt solution (MSS) and evaluate the antimicrobial properties of MSS on in vitro biofilm models.MethodologyIn a metabolic assay, fibroblasts derived from periodontal ligaments (PDL) of human extracted teeth were cultured and challenged with MSS or controls. Then, in active attachment biofilm models, the efficacy of MSS in the presence of dentine powder and in eliminating mature biofilms was investigated. In the dentine assay, a biofilm of Enterococcus faecalis was employed. For the final assay, microorganisms were retrieved from infected root canals and cultured to produce biofilms. After the treatments with MSS or the controls, the biofilms were collected, serially diluted and plated. The colony-forming units were counted. One-way anova was used to analyse the differences between the groups. A P < 0.05 was considered significant.ResultsThe PDL fibroblasts remained metabolically active after challenges with MSS. Dentine powder did not alter the efficacy of MSS (P > 0.05). In endodontic biofilms, the culturable bacteria were equally reduced by MSS, 2% chlorhexidine (CHX) or 2% sodium hypochlorite (NaOCl) (P > 0.05).ConclusionsModified salt solution is noncytotoxic in vitro and has good antimicrobial properties equal to CHX and NaOCl. Although the results are promising, ex vivo and in vivo studies are needed before its use as an interappointment root canal dressing can be considered.

AimTo evaluate the fate of Enterococcus faecalis in dual‐species and multispecies biofilms after treatment with calcium hydroxide (Ca(OH)2). MethodologyBiofilms were cultured from laboratory strains of E. faecalis and Pseudomonas aeruginosa, or from microbiota retrieved from primary root canal infections. The biofilms were then treated with Ca(OH)2. The proportion of E. faecalis and P. aeruginosa and their susceptibility to disinfection were evaluated in a viability assay. In the mixed‐species assay, the presence and proportions of E. faecalis before and after Ca(OH)2 treatment were evaluated with a quantitative polymerase chain reaction assay. Groups were compared using Mann–Whitney U‐test and Student's t‐tests. An α ResultsAfter Ca(OH)2 treatment in dual‐species biofilms, the proportion of E. faecalis had increased (P < 0.001), whereas the total number of CFUs per biofilm was equal. Enterococcus faecalis was equally susceptible to disinfection by sodium hypochlorite (NaOCl) or by chlorhexidine. Pseudomonas aeruginosa had become more susceptible to NaOCl disinfection. The root canal isolates contained no detectable amounts of E. faecalis. After biofilm culturing or Ca(OH)2 treatment, it appeared that E. faecalis must have been present in 5 of 6 (83%) root canal samples. ConclusionsCalcium hydroxide favours the population of E. faecalis in a dual‐species biofilm. Culturing multispecies root canal isolates makes E. faecalis detectable. E. faecalis was often present in primary endodontic infections, albeit in low numbers.

The shift in microbial diversity from young to mature plaque, related to caries activity on sound and restored surfaces, was studied using denaturing gradient gel electrophoresis. During a 20-week in situ study on caries progression 8 subjects wearing restored and unrestored dentin and enamel sections, biofilm was sampled after 1 and 20 weeks (young or mature plaque). A higher microbial diversity (mature plaque) was seen in caries-active compared to caries-free subjects. Rothia dentocariosa and Scardovia inopinata were absent from all caries-free sites, but appeared in 50% of the caries-active sites.

van der Waal SV, van der Sluis LWM, Ozok AR, Exterkate RAM, van Marle J, Wesselink PR, de Soet JJ. The effects of hyperosmosis or high pH on a dual-species biofilm of Enterococcus faecalis and Pseudomonas aeruginosa: an in vitro study. International Endodontic Journal, 44, 11101117, 2011. Aim To investigate the effect of hyperosmotic hyperosmosis or alkaline stress on a dual-species biofilm of Enterococcus faecalis and Pseudomonas aeruginosa. Methodology Biofilms were grown on glass cover slips suspended in bacterial inoculate for 96 h, after which the cover slips with attached biofilms were immersed in brain heart infusion broth (BHI-broth) with 6 mol L(-1) sodium chloride (NaCl) representing the hyperosmotic group or Ca(OH)2, pH 12.1, representing the alkaline group. Two per cent sodium hypochlorite and BHI- broth served as positive and negative controls, respectively. After treatment, the biofilms were washed, harvested and plated on blood-agar plates after serial dilution. The bactericidal effect was assessed by determining the colony-forming units (CFU). The effect on the biofilm mass was imaged with confocal laser scanning microscopy (CLSM). Results Hyperosmosis reduced the CFU of both species significantly after 72 h (P < 0.0001). After 168 h, P.aeruginosa was eradicated and the E.faecalis reduction was more than 99%. High pH could not induce a significant bacterial reduction. CLSM revealed dense flocculation of the biofilms incubated in alkaline broth. Conclusion Hyperosmosis effectively reduced a dual-species biofilm of E.faecalis and P.aeruginosa, whilst high pH had limited bactericidal effect in this model

Apical periodontitis is an inflammatory response around the root tip of a tooth to microbial infection of the root canal system. Therefore, disinfection of the root canal system is the most important aim of root canal treatment. There are various mechanical and chemical ways to clean and disinfect. Most methods, however, cannot be relied upon to fully decontaminate in all cases. There are problems, for example, with the proper concentrations of disinfectant agents, like sodium hypochlorite. But the more recent agents, like ethylenediaminetetraacetic acid, calcium hydroxide or antibiotic pastes also have disadvantages, which are mostly a result of poor access of the irrigant to the biofilm bacteria in the affected root canals. Currently, a new strategy with a modified salt solution is under investigation that offers the prospect of being used as a root canal irrigant. At this moment the preferred treatment still seems to be to remove infected tissue as much as possible and to create access for irrigation procedures. The best results are achieved with 1-2% sodium hypochlorite as a disinfectant, possibly alternating with ethylenediaminetetraacetic acid as a cleansing agent. There is no scientific evidence for the successful use of calcium hydroxide.Parodontitis apicalis is een ontstekingsreactie rond de wortelpunt van een gebitselement en wordt vrijwel altijd veroorzaakt door een microbiële infectie van het wortelkanaalstelsel. Daarom is desinfectie van het wortelkanaalstelsel een hoofddoel van de wortel­kanaalbehandeling. Er zijn verschillende mechanische en chemische wijzen om te reinigen en te desinfecteren. Echter, de meeste methoden leiden niet altijd tot volledige decontaminatie. Zo zijn er problemen met de juiste concentratie desinfectiemiddelen, zoals hypochloriet. Maar ook de nieuwere middelen, zoals ethyleendiaminetetra-azijnzuur, calciumhydroxide en antibioticapasta hebben nadelen, die veelal worden veroorzaakt door de slechte bereikbaarheid van de biofilm in de geïnfecteerde kanalen. Op dit moment wordt er een middel onderzocht dat veel perspectief biedt om te gebruiken als wortelkanaalirrigatiemiddel. Vooralsnog lijkt de beste behandeling om het geïnfecteerde weefsel zoveel mogelijk te verwijderen en om toegang te creëren voor het te gebruiken desinfectiemiddel. De beste resultaten worden verkregen met 1-2% natriumhypochloriet als desinfectans, eventueel afgewisseld met ethyleendiaminetetra-azijnzuur als reinigingsmiddel. Voor het succesvol toepassen van calciumhydroxide is nog onvoldoende wetenschappelijk bewijs.

During the past 25 years, oral microbiology has developed from researching a limited number of pathogenic microorganisms to a field in which the entire oral micro flora is studied. While 25 years ago, a limited number of species were studied, now the thousands of species that can be found in the mouth are the subject of research. We can now study the effects of bacteria and fungi on each other, but also make small steps in terms of features that microorganisms occupy in the network of the complex biofilm. The biofilm can be seen as a complex ecosystem, which may be unique to each individual and certainly should not always be treated antimicrobially. It is better to stimulate the healthy biofilm and to prevent transmission of pathogens by targeted infection prevention measures. These measures may only be applied if appropriate microbiological knowledge is present.De orale microbiologie heeft zich in 25 jaar ontwikkeld van het onderzoeken van een beperkt aantal pathogene micro-organismen tot een vakgebied waarin de hele orale microflora wordt bestudeerd. Toentertijd konden beperkte soorten worden bestudeerd, nu zijn de duizenden soorten die zich bevinden in de mond onderwerp van onderzoek. Inmiddels worden de effecten van bacteriën en schimmels op elkaar onderzocht, maar worden ook schoorvoetend stappen gezet op het gebied van functies die micro-organismen innemen in het netwerk van de complexe biofilm. De biofilm blijkt een complex ecosysteem, dat persoonsgebonden is en zeker niet altijd antimicrobieel moet worden behandeld. Het is beter de gezonde biofilm te stimuleren en overdracht van pathogenen te voorkomen door gerichte infectiepreventie maatregelen. Deze maatregelen kunnen alleen worden toegepast als adequate microbiologische kennis aanwezig is.

The heterogeneous bacterial group known as oral streptococci was screened for the presence of cellular polyglycerolphosphate-containing lipoteichoic acid. This compound was detected in phenol extracts of lyophilized cells by an immunoassay in which polyglycerolphosphate-specific monoclonal antibody was used. Polyglycerolphosphate-containing lipoteichoic acid occurred in all 86 strains of oral streptococci examined except the Streptococcus mitis and Streptococcus oralis strains. This confirms the findings of Rosan (B. Rosan, Science 201:918-920, 1978) and Hamada et al. (S. Hamada, J. Mizuno, S. Kotani, and M. Torii, FEMS Microbiol. Lett. 8:93-96, 1980), is consistent with the results of the taxonomic study of oral streptococci performed by Kilian et al. (M. Kilian, L. Mikkelsen, and J. Henrichsen, Int. J. Syst. Bacteriol. 39:471-484, 1989), who emended the descriptions of Streptococcus sanguis, S. oralis, and S. mitis, and reflects the phylogenetic relationship among S. mitis, S. oralis, and Streptococcus pneumoniae.

To investigate the effect of hyperosmotic hyperosmosis or alkaline stress on a dual-species biofilm of Enterococcus faecalis and Pseudomonas aeruginosa.Biofilms were grown on glass cover slips suspended in bacterial inoculate for 96 h, after which the cover slips with attached biofilms were immersed in brain heart infusion broth (BHI-broth) with 6 mol L(-1) sodium chloride (NaCl) representing the hyperosmotic group or Ca(OH)(2), pH 12.1, representing the alkaline group. Two per cent sodium hypochlorite and BHI- broth served as positive and negative controls, respectively. After treatment, the biofilms were washed, harvested and plated on blood-agar plates after serial dilution. The bactericidal effect was assessed by determining the colony-forming units (CFU). The effect on the biofilm mass was imaged with confocal laser scanning microscopy (CLSM).Hyperosmosis reduced the CFU of both species significantly after 72 h (P0.0001). After 168 h, P. aeruginosa was eradicated and the E. faecalis reduction was more than 99%. High pH could not induce a significant bacterial reduction. CLSM revealed dense flocculation of the biofilms incubated in alkaline broth.Hyperosmosis effectively reduced a dual-species biofilm of E. faecalis and P. aeruginosa, whilst high pH had limited bactericidal effect in this model.

An important initial step in biofilm development and subsequent establishment of fungal infections by the human pathogen Candida glabrata is adherence to a surface. Adherence is mediated through a large number of differentially regulated cell wall-bound adhesins. The fungus can modify the incorporation of adhesins in the cell wall allowing crucial adaptations to new environments. In this study, expression and cell wall incorporation of C. glabrata adhesins were evaluated in biofilms cultured in two different media: YPD and a semi-defined medium SdmYg. Tandem mass spectrometry of isolated C. glabrata cell walls identified 22 proteins including six adhesins: the novel adhesins Awp5 and Awp6, Epa3 and the previously identified adhesins Epa6, Awp2 and Awp4. Regulation of expression of these and other relevant adhesin genes was investigated using real-time qPCR analysis. For most adhesin genes, significant up-regulation was observed in biofilms in at least one of the culturing media. However, this was not the case for EPA6 and AWP2, which is consistent with their gene products already being abundantly present in planktonic cultures grown in YPD medium. Furthermore, most of the adhesin genes tested also show medium-dependent differential regulation. These results underline the idea that many adhesins in C. glabrata are involved in biofilm formation and that their expression is tightly regulated and dependent on environmental conditions and growth phase. This may contribute to its potential to form resilient biofilms and cause infection in various host tissues.

Both Candida albicans and lactobacilli are common colonizers of carious lesions in children and adolescents. The purpose of this study is to compare the velocity of acid production between C. albicans and several Lactobacillus species at different pH levels and concentrations of glucose. Washed, pure resting-cell suspensions were obtained by culturing a total of 28 oral isolates comprising the species C. albicans, Lactobacillus rhamnosus, Lactobacillus paracasei paracasei, Lactobacillus paracasei tolerans and Lactobacillus delbrueckii lactis. Acid production from glucose was determined at a constant pH of 7.0, 5.5, 5.0 and 4.0 by repeated titrations with NaOH in an automated pH-stat system. Acid formation rates of yeast and lactobacilli proved to be similar at both neutral and low pH, while in a moderately acidic environment C. albicans produced less acid than the lactobacilli. Ion chromatographic analysis of the cell-free medium after titration revealed pyruvate to be the predominant organic acid anion secreted by C. albicans. The proportion of organic acids to overall acid production by the yeast was below 10% at neutral conditions, in contrast to 42-66% at pH 4.0. Compared to lactobacilli, yeast required a concentration of glucose that was about 50 times higher to allow acid production at half the maximum speed. Considering the clinical data in the literature about the frequency and proportions of microorganisms present in early childhood caries lesions, the contribution of oral lactobacilli as well as C. albicans to overall microbial acid formation appears to be important.

Caries is a multi-factorial disease, primarily caused by acids. Acids are produced by bacteria which ferment sugar. The aetiology and progress of caries are influenced by life-style and environmental factors, as well as congenital components. Based on, among other things, research concerning twins, the literature suggests that there are hereditary components of caries and life-style and environmental components. With the unravelling of the human genome, it is more easy to study individual genes in relation to the caries process. Because of its multifactorial nature, one has to realise that there is only a beginning of understanding the caries processes at molecular level.

Secondary caries has been suggested as the main reason for restoration replacement. We hypothesized that more caries-associated bacteria are found on composite resin restoration material, compared to sound tooth tissue.Both restored and unrestored dentin and enamel samples were placed in a full denture of eight subjects for 20 weeks. The microbiological composition of approximal plaque and the association between caries-associated bacteria and red autofluorescence of dental plaque was studied. Every 4 weeks the specimens were microradiographed using transversal wavelength independent microradiography (T-WIM). After 1 and 20 weeks red fluorescence pictures and plaque samples were taken. Samples were cultured for total anaerobic counts, mutans streptococci, lactobacilli, candida and Actinomyces odontolyticus.Lesion depth in the dentin and enamel was positively associated with lactobacilli, and lesion depth in dentin was positively associated with A. odontolyticus, whereas no association was found between mutans streptococci and lesion depth. The red-fluorescent bacteria A. odontolyticus and lactobacilli did not correlate with red-fluorescent plaque, indicating that red fluorescence is probably not caused by a single species of these bacteria. After 20 weeks, a higher proportion of combined mutans streptococci and lactobacilli was found on restored tissue compared to non-restored tissue (P = 0.04).The higher proportion of caries-associated bacteria on restored tissue indicates that the ecology on the surface of primary lesions differs from that on lesions next to composite, and that secondary caries next to composite may differ from the primary caries process.

This study was aimed at determining whether dental caries is associated with induction of the systemic immune system or cytokine response. For this purpose, 85 children from Den Pasar, Bali, Indonesia, aged 6-7 years, were examined clinically and blood plasma was obtained via finger puncture. The concentrations of the acute-phase protein alpha(1)-acid glycoprotein (AGP), total IgG and the specific IgG and IgM immunoglobulins against Streptococcus mutans were determined. Immunoelectrophoresis was used for the determination of the AGP concentration and ELISA for IgG and IgM detection. The mean dmft of the whole group was 8.8 +/- 2.9, the mean number of infected pulps was 3.9 +/- 2.2 and the mean number of abscesses was 0.5 +/- 0.8. The plasma concentration of AGP ranged between 0.13 and 1.6 mg/ml serum (mean 0.86 +/- 0.26 mg/ml). Stepwise regression analysis revealed that the concentration of IgG against S. mutans (log-transformed) was significantly correlated with dmft (adjusted r(2) = 0.083, standardized beta coefficient = 0.31, p = 0.008). When the concentration AGP was included in the model the correlation improved significantly (for IgG: adjusted r(2) = 0.157, standardised beta coefficient = 0.36, p = 0.002; for AGP: beta coefficient = -0.30, p = 0.009). The results suggest a relationship between caries and systemic parameters of inflammation. On the basis of this, severe caries might have consequences on the general health of the subject.

The relation between oral microbes of mother and child encompasses several aspects. It has been shown that a bad periodontal condition is a risk factor for low birth weight. The bacterium that is most specifically associated with dental caries, Streptococcus mutans, can be transmitted between mother and child; it has been suggested that the age of colonization with this bacterium is a risk factor for caries in the child. Also periodontal bacteria can be transmitted between mother and child. It remains to be elucidated whether this is an additional risk factor for the development of periodontal disease.

The etiology of root caries is thought to be identical to coronal caries, though root caries seem to be more complicated because of the higher susceptibility of exposed roots (dentin) by periodontal therapy to demineralization than intact enamel. This implies that mutans streptococci are the most likely pathogens in the development of root caries. Although it is known that both the numbers of mutans streptococci and the frequency of isolation in root caries lesions are negatively correlated with the distance from the gingival margin, the subgingival sulcus has not been considered a possible habitat for mutans streptococci. However, subgingival occurrence of mutans streptococci in both untreated and treated periodontal patients has not been documented well in the literature.To investigate the presence and levels of mutans streptococci in the subgingival plaque of patients (n=154) in different stages of periodontal therapy. The subgingival sulcus may be a possible habitat for mutans streptococci. This localisation of mutans streptococci may be of importance in the development of root caries after periodontal surgery.In this cross-sectional study, subgingival plaque samples from 154 consecutive adult periodontitis patients were tested for presence and levels of mutans streptococci and putative periodontal pathogens by anaerobic cultures. These patients were divided into 4 groups based on their stage of periodontal treatment: (1) untreated patients; (2) patients after initial periodontal therapy only; (3) patients in the maintenance phase who not underwent periodontal surgery; (4) patients after periodontal surgery.The prevalence of mutans streptococci in the 4 study groups varied from 82% in untreated patients to 94% in maintenance patients. The mean proportion of mutans streptococci was 6.65% in maintenance patients versus 1.86% in untreated patients (p=0.005) and 2.51% in patients after scaling and root planing (p=0.041).The subgingival area is a microbial habitat for mutans streptococci that may be of importance in the development of root caries in periodontitis patients.

The bacterial composition of the dentine of thirty molars with sealed occlusal surfaces (Delton tinted) was examined. Undiagnosed hidden caries was present at the time of treatment. Although clinically assessed as good (age 3.4 years, s.d. 2.1), 47 percent of the sealants had a marginal defect, when assessed with SEM. The dentine of the treated teeth was of a soft consistency. The median of the number of microorganisms was 400 (range 0-3.10(5)) cfu per sample. Mutans streptococci and lactobacilli were found in 53 percent of the samples. No relationship was found between the number of microorganisms and the marginal adaptation of the sealant, when examined under SEM; neither was a relationship found between the age of the sealant and the number of microorganisms (Kendall's Tau-C = 0.17, n.s. and -0.01, n.s., respectively). At present, there are insufficient grounds for treating nonvisible lesions (with a radiolucency on the bitewing) with a resin sealant.

Dentine samples of teeth from patients with occlusal lesions beneath an apparently intact enamel surface were bacteriologically examined. For this purpose two dentine samples, one from the dentinoenamel junction (A) and one just before all caries appeared to be removed clinically (B), were taken under aseptic conditions. In most cases the A and B samples contained considerable numbers of mutans streptococci and lactobacilli, while the dentine after opening was soft with a light colour. These results suggest that one is dealing with active caries lesions, which should be treated as such. Comparison of the saliva data from the patients group with the saliva data of a control group showed no significant differences concerning the numbers of mutans streptococci, secretion rate and buffer capacity.

Eleven teeth from nine patients with occlusal caries lesions beneath an apparently intact enamel surface were treated. Two dentine samples, one from the dentinoenamel junction (Sample A) and one just before all the caries appeared to be removed clinically (Sample B), were taken under aseptic conditions and examined for bacteria. In all cases, the A samples and in ten cases the B samples contained mutans streptococci, lactobacilli or both, while in ten cases the dentine after opening was soft with a light color. This suggests that we are dealing with active caries lesions, which should be treated as such. The salivary data of the patients group were compared with the salivary data of the control group. Although the buffer capacity of the groups were not significantly different (chi-square), further analysis revealed that a significant relationship could be found between the group and the buffer capacity (Kendall's Tau C). While the other salivary components (numbers of mutants streptococci per ml saliva and the secretion rate) showed no significant differences. Unfortunately these occlusal caries lesions are not detected with the present criteria used in epidemiological surveys.

The aim of this study was to investigate the presence of S. sobrinus and S. mutans in specimens of dental plaque and saliva of children five years of age in Reykjavik, Iceland (study 1) and in samples of dental plaque from children nine years of age in Amsterdam, The Netherlands (study 2). The immuneblotting technique (IBT) was a suitable method to evaluate the presence and numbers of S. mutans and S. sobrinus in human dental plaque and saliva. In study 1, eighty-four children were evaluated bacteriologically; of these, 73 percent harbored mutans streptococci in their plaque or saliva. S. sobrinus similarly was present in 29 percent of the children. In study 2 (seventy-two children), the corresponding percentages were 81 percent for S. mutans, and 35 percent for S. sobrinus. The latter was detected in 6 percent of the plaque samples exclusive of S. mutans.