Fusobacterium nucleatum enters normal human oral fibroblasts in vitro.

BACKGROUND: Fusobacterium nucleatum, a commensal opportunistic oral bacterium, is capable of invading gingival epithelial cells, but the entrance into human primary oral fibroblast cells has not been documented. This study evaluated the ability of three strains of F. nucleatum (F. nucleatum ssp. nucleatum, F. nucleatum ssp. polymorphum, and F. nucleatum ssp. vincentii) to enter gingival fibroblasts (GFs) and periodontal ligament fibroblasts (PLFs). METHODS: GFs and PLFs were cocultured for various periods of time with different strains of F. nucleatum. Scanning and transmission electron microscopy, together with confocal laser scanning microscopy, were used to visualize the entrance and presence of bacteria in host cells. Flow cytometry was performed to compare the load of internalized bacteria in GFs and PLFs exposed for 3 and 5 hours to live F. nucleatum labeled with fluorescein isothiocyanate. RESULTS: All three strains of F. nucleatum were found entering and located in the cytoplasm of GFs and PLFs after 1 hour of exposure. Flow cytometry tests revealed a significant increase in the fluorescent signal, compared to baseline, derived from bacteria internalized in fibroblasts exposed for 3 hours (P <0.001); a further increase was found at 5 hours. The greatest bacterial mass in exposed fibroblasts of both types was of F. nucleatum ssp. polymorphum; the smallest was of F. nucleatum ssp. vincentii. Although not statistically significant, PLFs had a higher bacterial load than corresponding GFs. CONCLUSION: F. nucleatum was capable of entering GFs and PLFs in a manner that is dependent on the cell type and the bacterial strain.

Dental caries prevalence and risk factors among 12-year old schoolchildren from Baghdad, Iraq: a post-war survey.

AIM: To examine the prevalence of dental caries in 12-year-old schoolchildren from Baghdad after the end of the United Nations' economic sanctions and to investigate related dental caries risk factors including gender, socio-demographic factors, oral hygiene and sugar intake. DESIGN: A cross-sectional dental caries examination and questionnaire survey was conducted in 10 schools from west Baghdad. METHODS: Dental examinations based on WHO criteria and questionnaire surveys were performed on 392 children. Water samples were collected and fluoride concentration assessed. RESULTS: The mean DMFT and DF were 1.7 and 1.3. The rate of caries experience (DMFT > 0) was 62%. DMFT increased significantly with higher education of the mother, not being embarrassed to smile, missing school due to dental pain and between-meals mode of drinking. Increased sugar consumption was associated with being a boy, having mothers with low education, living in a low socio-economic area and brushing at least once-a-day. Positive oral hygiene practices were higher for girls. Western sweet snacks were preferred and sweet tea was frequently consumed. The fluoride content in drinking water was too low for caries prevention. CONCLUSION: It is important to maintain the low prevalence of caries among children by increasing awareness and promoting oral health care strategies.

In vitro antimicrobial and resistance-modifying activities of aqueous crude khat extracts against oral microorganisms.

OBJECTIVES: To assess antimicrobial activities of aqueous crude khat (Catha edulis) extracts against a panel of oral microorganisms and to test their ability to modify bacterial resistance to tetracycline and penicillin in vitro. DESIGN: Lyophilized aqueous extracts were prepared from three khat cultivars. The agar dilution method of the NCCLS was used to test the extracts, at concentrations of 20-1.25 mg/ml, against 33 oral strains. MIC was defined as the lowest concentration at which there was no visible growth. Slight growth was defined as marked growth reduction (MGR). The E-test was used to determine the MICs of tetracycline and penicillin-G for three resistant strains in absence and presence of a sub-MIC of the khat extracts (5mg/ml). RESULTS: Eighteen strains (55%) were sensitive to the extracts (MICs 5-20 mg/ml). Most of these were periodontal pathogens with Porphyromonas gingivalis and Tannerella forsythensis being the most susceptible (MIC 5-10mg/ml). Veillonella parvula, Actinomyces israelii and some streptococci were not sensitive. Except for Lactobacillus acidophilus that showed MGR at 1mg/ml, cariogenic species were neither sensitive. The extracts were active against Streptococcus pyogenes (MIC 10-20 mg/ml) but not against Candida albicans and Staphylococcus aureus. The presence of the khat extracts at a sub-MIC resulted in a 2-4-fold potentiation of the tested antibiotics against the resistant strains. CONCLUSIONS: Khat has water-soluble constituents possessing selective antibacterial activity against oral bacteria. There is preliminary evidence for presence of an antibiotic resistance-modifying component. Further investigation is needed to identify the active components and assess their clinical relevance.

Knowledge and behaviour related to oral health among secondary school students in Khartoum Province, Sudan.

OBJECTIVE: This study explores secondary school students in the Khartoum Province, Sudan, with respect to frequency and quality of use and the socio-demographic distribution of oral health knowledge and behaviour. METHODS: Six secondary schools were selected at random and 10% of the students enrolled in each class (3 grades) were randomly selected to participate. A total of 400 students (207 boys) (mean age 15.3 years) were selected, of which 396 completed questionnaires at school. RESULTS: 44.3% boys and 42.5% girls scored highly on knowledge of caries. The corresponding rates regarding knowledge of gingivitis were 39.2% and 47.0%, respectively. Tooth brushing and use of miswak > or = 2 times a day was confirmed by 67.2% boys and 75.5% girls and by 64.3% boys and 52% girls, respectively. Living in a town, having received oral health information and having a mother of medium education were associated with higher odds for being knowledgeable about tooth decay. CONCLUSION: There is gender equality in knowledge and practise of oral hygiene among secondary school students in Khartoum Province. Awareness of oral health issues is high, but specific misconceptions exist. Mother's education might be used as a social marker in oral health risk group evaluations.

The knowledge and practices of oral hygiene methods and attendance pattern among school teachers in Riyadh, Saudi Arabia.

OBJECTIVE: The aim of this study was to find out the knowledge and practices of oral hygiene methods among primary and secondary school teachers in Riyadh, Kingdom of Saudi Arabia (KSA). METHODS: The study was carried out using a self-administered questionnaire. Four hundred and seventy teachers, male 236 (50.2%) and female 234 (48.8%) responded with a response rate of 85.5%. The study was conducted during October to December 2001 at primary and secondary schools in Riyadh City, KSA. RESULTS: Almost 86% of male and 90% of female teachers felt that dental caries is due to the wrong method of tooth brushing, while sugar and sugary drinks were considered the main factor by 90% of male and 98% of female teachers. Seventy-five percent of male and 72% of female teachers considered irregular tooth brushing a cause of gums disease with 32% of male and 39% of female teachers not knowing details with regards to microbial relationship of gum disease. Tooth brushing preference was common among 45% male and 49% female teachers due to perceived effect of better cleaning, while almost an equal percentage of male and females (62%) used miswak due to Sunnah. Thirty-three point five percent of female teachers brushed 3 times a day as compared to 19% male teachers. On daily basis brushing 3 times, a day was common among >5000 SR monthly income group. Male teachers preferred horizontal tooth brushing (40%) while female teachers preferred circular tooth brushing (45%). Miswak was more commonly used by male teachers as compared to female teachers. Female school teachers had a higher income as compared to male schoolteachers. Thirty-two percent of females and 28% of male teachers were regular attendees to the dentist. Males were more satisfied by their oral health as compared to female teachers and 56% of male and 63% of female teachers visited the dentist only on having pain (toothache). CONCLUSION: It is concluded that there is much resemblance in knowledge and practice of oral hygiene habits among male and female schoolteachers and there is a need to enhance their knowledge regarding oral health and disease. Both need more awareness regarding oral health promotion to have a positive role in school oral health education for their students in collaboration with oral health care workers.

Ethnic disparities in the prevalence of periodontitis among high school students in Sudan.

BACKGROUND: There are limited data on the epidemiology and risk factors of periodontitis in young populations in developing nations. This study assesses the prevalence of periodontal attachment loss and aggressive periodontitis and the association with ethnicity among high school students in Sudan. METHODS: The study sample consisted of 1,200 students, 13 to 19 years old, selected from 38 public and private high schools using a multistage, stratified sampling design. The subjects were interviewed and examined clinically. Periodontal parameters were assessed at six sites per tooth. Subjects with aggressive periodontitis were identified. RESULTS: A total of 3.4% of the subjects had aggressive periodontitis, and 16.3% and 8.2% of the subjects had at least one tooth with > or = 4 and > or = 5 mm attachment loss, respectively. A significantly higher percentage of subjects of African tribal ethnicity had attachment loss > or = 4 and > or = 5 mm compared to Afro-Arab tribes (19.8% versus 14.7%, P = 0.02; and 12% versus 6.4%, P = 0.004, respectively), and had a higher prevalence of aggressive periodontitis (6% versus 2.3%; P = 0.01) and higher risk of being diagnosed with this disease (odds ratio = 2.7; P <0.0001). African ethnicity was also associated with a significantly higher number of teeth with attachment loss than in Afro-Arabs (P <0.01). Comparison by gender showed a significantly higher percentage of males with aggressive periodontitis (4.9% versus 2%; P <0.01) and a higher risk for this disease (odds ratio = 2.5; P = 0.01) than in females. However, the prevalence of subjects with attachment loss > or = 4 and > or = 5 mm was comparable in the two gender groups. CONCLUSIONS: Our results show that aggressive periodontitis is highly prevalent in this population. African ethnicity (versus Afro-Arab) and male gender were risk factors for aggressive periodontitis.

Primary chronic osteomyelitis of the jaw--a microbial investigation using cultivation and DNA analysis: a pilot study.

OBJECTIVES: The aims of this study were to investigate the infectious etiology of primary chronic osteomyelitis (PCO) of the jaw using an extraoral sampling approach and molecular methods. STUDY DESIGN: In this pilot study, bone biopsies from the mandibles of 5 patients with PCO were sampled with an extraoral sterile approach. Cultivation and polymerase chain reaction (PCR) were performed. RESULTS: Two of the biopsies yielded growth of Propionebacterium acnes. One biopsy also demonstrated Staphylococcus capitis. The biopsies with bacterial growth were also positive for the same bacteria by PCR analysis. CONCLUSION: No specific bacterial etiology was demonstrated. However, the results of bacterial cultivation and PCR analysis were in agreement. Based on these findings, the molecular procedure used in this study can be considered to be suitable for identification of bacterial specimens in mandibular biopsies. Further studies are needed with larger patient populations to confirm these findings.

Incidence of antibiotic prescribing in dental practice in Norway and its contribution to national consumption.

OBJECTIVES: To assess dentistry-based utilization of the 11 antibiotics prescribed by dentists in Norway and its relative contribution to national outpatient consumption and to determine the relationship between numbers of prescriptions and the consumption of these antibiotics. METHODS: Data on national antibiotic prescriptions by dentists in 2004 and 2005 were used. Consumption of the antibiotics was expressed using WHO defined daily doses (DDDs), DDDs per 1000 inhabitants per day (DIDs) and numbers of prescriptions per 1000 inhabitants (PIDs). RESULTS: Analysis of 268,834 prescriptions issued by 4765 dentists showed that the dentists' prescriptions contributed 8% of the total national consumption of the 11 antibiotics and 13.5%, 2.8% and 1.2% of the national beta-lactam penicillins, macrolides and lincosamides and tetracyclines utilization, respectively. The dentists' contributions to the national phenoxymethylpenicillin, spiramycin and metronidazole consumptions were considerably higher (> or =13.2%) than for the other prescribed antibiotics (< or =8.6%). There was a strong positive correlation between numbers of DDDs and numbers of prescriptions and between DIDs and numbers of PIDs. CONCLUSIONS: Reliance of Norwegian dentists on phenoxymethylpenicillin as their first choice suggests a low prevalence of antibiotic resistance among oral bacteria in Norway. Norwegian dentists prefer to prescribe narrow-spectrum antibiotics; their prescribing is conservative and relatively low compared with that of physicians.

Efficacy of high-level microwave disinfection of dental gypsum casts: the effects of number and weight of casts.

The aim of this study was to determine if the bactericidal effect of microwaving gypsum casts is maintained at maximum capacity of the oven (16 casts). Batches of 8 and 16 gypsum casts made from in vivo impressions were divided in half. One half of each cast was microwaved at 900 W for 5 minutes. The remaining halves were left untreated. When assessed for bacteriological growth, the median cfu/mL of the untreated casts was between 10(5) and 10(6) [corrected] while the microwaved casts showed a cfu/mL of 0, indicating that microwaving as described will disinfect gypsum casts even at maximum capacity of the oven.

Knowledge of prescribing antimicrobials among Yemeni general dentists.

OBJECTIVE: Overuse of antimicrobial agents is closely related to an increase in bacterial resistance. A sound knowledge of appropriate prescribing of antimicrobials among health professionals is thus critical in combating the resistance. The objectives of this study were to assess the rationale for and patterns of antimicrobial prescriptions by general dental practitioners in Yemen. MATERIAL AND METHODS: A questionnaire containing 65 closed questions was used for this cross-sectional study and distributed to 280 dentists in the three major governorates in Yemen. The anonymously completed questionnaires sought answers to demographic questions and to questions on the therapeutic and prophylactic use of antimicrobial agents in dentistry. Correct and incorrect answers were defined according to information available in the current authoritative literature. Each correct answer was given a score of 1 while an incorrect answer scored 0. Thus, the total score had an attainable range from 0 to 65. Frequencies, means, and associations were assessed statistically. RESULTS: Out of 181 collected forms (response rate 64.6%), 150 were appropriately completed and used for data analyses. Penicillins were the most frequently prescribed drugs (72%), followed by spiramycin (10%). It was found that up to 84% of practitioners were likely to prescribe an antimicrobial agent when there was no clinical indication for such a medication. Many respondents (70%) would consider antibiotics for at least one of the given non-clinical factors. CONCLUSIONS: The results suggest that dental practitioners in Yemen lack uniformity in the rationale for appropriate prescribing of antimicrobials to their patients. Consequently, to reduce overuse, there is an urgent need for the dental community in the country to be informed about evidence-based guidelines and the appropriate use of antimicrobial agents in clinical dental practice.

High-level microwave disinfection of dental gypsum casts.

PURPOSE: To test whether microwave oven irradiation can disinfect gypsum casts in compliance with current disinfection requirements, and to determine whether this procedure would be as effective as a validated method of chemical disinfection of impressions. MATERIALS AND METHODS: In 2 in vitro experiments, samples of 5 irreversible hydrocolloid impressions of a disinfected acrylic resin model were contaminated with suspensions of recommended test organisms Staphylococcus aureus and Pseudomonas aeruginosa, respectively. In 1 in vivo experiment, 10 impressions were made of 10 subjects. All impressions were poured and the resulting casts cut in 2 halves. One half of each cast was exposed to 5 minutes of irradiation in a microwave oven at 2,450 MHz and 900 W. The other halves were left untreated as controls. In a second in vivo experiment, 10 impressions were disinfected by immersion in a 0.07% solution of NaOCl at pH of about 10 for 3 minutes, and then poured. All casts were incubated aerobically in Bacto tryptic soy broth at 37 degrees C for 6 hours and assessed for bacterial growth by counting colony-forming units per milliliter (cfu/mL) of the culture. The results were analyzed using the Wilcoxon signed-rank test. RESULTS: Untreated gypsum casts showed cfu/mL counts with a median log value of 6, while microwave-irradiated ones had median cfu/mL counts of 0. Casts poured from chemically disinfected impressions demonstrated cfu/mL counts with a median log value of 4. CONCLUSION: Under the described conditions, microwave-irradiated gypsum casts satisfy current disinfection requirements, but gypsum casts poured from chemically disinfected impressions do not.

Khat (Catha edulis)-an updated review.

The habit of chewing fresh leaves and twigs of khat (Catha edulis) for their stimulating amphetamine-like effects is highly prevalent in East Africa and southwest on the Arabic peninsula. There is an extensive literature on khat providing information about its history, botany, production, geographical distribution, chemistry and pharmacology, and exploring the social, economic, medical, psychological and oral aspects related to its use. Some of this literature dates as early as the 11th century; however, most of it appeared after the first scientific description of khat by Peter Forskal in 1775. This review provides a panorama of khat and the various aspects of its use. A non-technical description of the plant chemistry and pharmacology is included. The medical, psychological and oral aspects are emphasized, and the current knowledge about the microbiological effects of khat is also presented.

In vitro effects of crude khat extracts on the growth, colonization, and glucosyltransferases of Streptococcus mutans.

Millions of Yemenites, East Africans, and immigrants to Western countries chew khat daily for its amphetamine-like effects. There is little information in the literature concerning the possible effects of the habit on oral microbiota. Our objective was to study in vitro crude khat extract effects on Streptococcus mutans growth and sucrose-dependent colonization, and on its glucosyltransferase (GTF) activity and production. Three khat cultivars were used. Lyophilized crude aqueous khat extracts were applied to the different assays at concentrations of 0-1% (w/v). Sucrose-dependent colonization was assessed as the ability of Streptococcus mutans UA159 to form adherent biofilms in glass culture tubes. Colony forming units (CFUs) in the planktonic phase served as a measure of bacterial growth, while CFUs in the biofilm phase were used to quantify viability in the biofilms. GTFs activity was tested by incubating a crude GTFs preparation with sucrose and determining the amount of water-soluble and water-insoluble glucans formed. GTFs production was assayed by comparing intensities of GTF bands in Western blots of extracts from control and khat-containing cultures. The khat extracts effectively inhibited biofilm formation. The minimum biofilm inhibitory concentration (MBIC) varied among the cultivars (0.25-1%). The extracts also inhibited synthesis of both glucan types, particularly insoluble glucans (average 85% inhibition at 1%), with significant differences among the cultivars. However, khat increased bacterial growth and at sub-MBIC also viability within biofilms; there were no inter-cultivar differences. It is shown that khat leaves contain water-soluble constituents that inhibit some cariogenic properties of S. mutans in vitro.

Respiratory pathogens in dental plaque of hospitalized patients with chronic lung diseases.

Bacterial cultivation studies have shown that dental plaque is a reservoir for respiratory pathogens in intensive care unit patients and in elderly who are debilitated, hospitalized or in a nursing home, placing them at risk of bacterial pneumonia. No information is available, however, concerning dental plaque as a reservoir of putative respiratory pathogens in hospitalized patients with chronic lung diseases. Supragingival plaque colonization of 34 hospitalized chronic lung-diseased Romanian citizens, excluding those with tuberculosis and less than 20 teeth, was therefore assessed by checkerboard DNA-DNA hybridization using a selected panel of whole genomic DNA probes produced from eight respiratory pathogens and eight oral pathogens. Thirty-one lung-healthy dental outpatients served as reference population. Respiratory pathogens were detected in plaque from 29 of the 34 (85.3%) hospitalized patients and 12 of the 31 (38.7%) reference population subjects. Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacter cloacae occurred significantly (p<0.05) more frequent among the hospitalized patients. Hospitalized chronic lung-diseased patients harbored in their supragingival plaque samples bacteria known to cause nosocomial pneumonia significantly (p<0.001) more frequent than lung-healthy dental outpatients. Our results indicate that dental plaque in patients with chronic lung diseases often serves as a reservoir of bacteria known to cause nosocomial pneumonia in susceptible individuals.

The coinitiator DMABEE induces death by apoptosis and necrosis in human monoblastoid cells.

4-N,N-Dimethyl amino benzoic acid ethylester (DMABEE), a leachable lipophilic component of polymer-based dental-filling materials, has been shown to interact with cell membrane phospholipids, such as phosphatidylcholine and phosphatidylserine (PS). One marker of cellular death by apoptosis is the change in architecture of the plasma membrane involving the translocation of the negatively charged PS from the inner to the outer leaflet of the cell membrane. We therefore hypothesized that DMABEE has the potential to induce apoptosis. The necrosis inducing potential was also investigated. To test our hypothesis human monoblastoid U-937 cells were exposed to 10, 20, 40, 80, 120, 160, and 200 microM of DMABEE for 24, 48, and 72 h. At the culture end-points apoptotic and necrotic cells were detected by flow cytometry. DMABEE enhanced cell death by apoptosis and necrosis in U-937 cells in a dose-dependent fashion. The data support our hypothesis that DMABEE triggers death-signaling pathways.

Subgingival microbiota levels and their associations with periodontal status at the sampled sites in an adult Sudanese population using miswak or toothbrush regularly.

Little information is available on the effect of miswak use on gingival microbiota. We assessed levels of 28 oral bacteria in subgingival plaque of adult Sudanese miswak (n = 38) and toothbrush users (n = 36) age range 20-53 years (mean 34.6 years) to study associations between these bacteria, oral hygiene method, and periodontal status at the sampled sites. A pooled subgingival plaque sample from 6 probing sites of 1 selected tooth in each jaw was obtained from each subject. Whole genomic DNA probes and the checkerboard DNA-DNA hybridization were used in assessing 74 pooled samples. Using 10(5) bacterial cells threshold, between 2.6% and 47.4% of miswak users and between 2.8% and 36.1% of toothbrush users harbored the investigated species. The percentages of subjects with the investigated species at 10(6) bacterial cells varied between 2.6% and 39.5% in miswak and between 2.8% and 36.1% in toothbrush users. Miswak users harbored significantly higher Streptococcus intermedius, Actinobacillus actinomycetemcomitans, Veillonella parvula, Actinomyces israelii, and Capnocytophaga gingivalis, and significantly lower Selenomonas sputigena, Streptococcus salivarius, Actinomyces naeslundii, and Streptococcus oralis than did toothbrush users. Probing pocket depth > or = 6 mm showed significantly (P < 0.05) higher levels of Porphyromonas gingivalis, Treponema denticola, Bacteroides forsythus, Fusobacterium nucleatum, and V. parvula than those 4-5 mm. Our results indicate that the type of oral hygiene had a significant effect on levels of 11 out of 28 bacterial species, and that the type of effect was also dependent on type of bacteria and probing pocket depth.

Correlations between bacterial levels in autologous subgingival plaque and saliva of adult Sudanese.

The aim of this study was to assess levels of oral bacteria and their correlations in paired samples of saliva and subgingival plaque in a population of adult Sudanese. Whole saliva and pooled subgingival plaque samples from six probing sites of one tooth in each jaw were obtained from 56 Sudanese adults (mean age 35.2+/-8.9 years). Levels of 24 oral bacteria in the autologous saliva and pooled plaque sample of each subject were assessed by DNA probes and checkerboard DNA-DNA hybridization. There were significantly ( P< or =0.01) higher percentages of subjects with > or =10(5) bacterial cells of Prevotella intermedia, Campylobacter rectus, Veillonella parvula, Streptococcus mutans, Lactobacillus acidophilus, Streptococcus anginosus, Streptococcus salivarius, and Leptotrichia buccalis and significantly ( P< or =0.01) lower percentages with Treponema denticola in saliva than in subgingival plaque. The detection frequencies at > or =10(6) bacterial cells were significantly higher for Selenomonas sputigena, S. anginosus, Streptococcus sanguis, and S. salivarius and significantly lower for Porphyromonas gingivalis in saliva than in subgingival plaque ( P< or =0.01). Porphyromonas gingivalis, Fusobacterium nucleatum, S. sputigena, S. sanguis, and Streptococcus mitis demonstrated significant ( P< or =0.05) positive correlations between their levels in plaque and saliva. This study indicates that the levels of P. gingivalis, F. nucleatum, S. sputigena, S. sanguis, and S. mitis correlate significantly in saliva and subgingival plaque and that higher accuracy of detection and assessment of the levels of these bacteria in the oral cavity may be achieved by concurrent sampling of saliva and subgingival plaque.

Salivary microbiota levels in relation to periodontal status, experience of caries and miswak use in Sudanese adults.

OBJECTIVES: The purpose of the present investigation was to assess the salivary levels of 25 oral bacteria in relation to periodontal status and experience of caries, and to compare the levels of these bacteria between habitual miswak and toothbrush users in adult Sudanese subjects. MATERIAL AND METHODS: The study subjects consisted of 56 individuals with age range 19-53 years (mean 35.2 years) and included 30 miswak and 26 toothbrush users. The periodontal status and presence of dental caries were assessed clinically. Whole saliva was collected from all subjects, and the levels of 25 selected bacterial species in saliva were assessed by the checkerboard DNA-DNA hybridization method using whole genomic DNA probes. RESULTS: A high percentage of the subjects had detectable levels (> or = 105 bacterial cells) of several bacterial species in saliva. Between 12% and 16% of the subjects showed high (> or = 106 cells) salivary levels of the periodontitis-associated bacteria A. actinomycetemcomitans, P. melaninogenica, P. intermedia, C. rectus and E. corrodens, whereas only two (3.6%) and four (7.1%) subjects had high levels of P. gingivalis and F. nucleatum, respectively. There were no significant differences in the levels of all or most bacterial species by age group, gender or periodontal status. Presence of > or = 105 L. acidophilus bacterial cells in saliva was associated with high caries scores (p = 0.02). There were significantly higher levels of A. actinomycetemcomitans, P. melaninogenica, C. rectus, P. micros, V. parvula, S. mutans, S. anginosus, A. israelii, C. sputigena, and C. gingivalis, and significantly lower levels of P. intermedia, F. nucleatum, S. sputigena, E. corrodens, L. acidophilus, S. sanguis, S. salivarius, S. oralis, and S. mitis in the miswak than in the toothbrush group. CONCLUSIONS: : The findings suggest that miswak may have a selective inhibitory effect on the level of certain bacteria in saliva, particularly several oral streptococci species. This is the first report that the checkerboard DNA-DNA hybridization method can be useful for assessing the levels of a wide range of bacterial taxa in saliva.