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.     

Development of novel oligonucleotide probes for seven Actinomyces species and their utility in supragingival plaque analysis

OBJECTIVE: The traditional, biochemical and enzymatic methods of identifying Actinomyces species are frequently confounded by the similar phenotypic characteristics shared by the different members of this genus. Therefore, we developed novel species-specific oligonucleotide probes to accurately speciate seven pathogenic Actinomyces species, namely, Actinomyces bovis, A. gerencseriae, A. israelii, A. meyeri, A. naeslundii, A. odontolyticus and A. viscosus. METHODS: A pair of universal primers and seven 15- to 19-base oligonucleotide probes with a tail of 20 thymidines on the 5' end were developed. The variable regions of 16S ribosomal DNA of 36 strains of Actinomyces belonging to the above species were amplified and labeled with digoxigenin, and an oligonucleotide-DNA hybridization assay was performed to examine the specificity and sensitivity of these probes. RESULTS: All seven, newly developed probes were specific and sensitive, and accurately detected 36 reference and wild type strains belonging to Actinomyces species, without cross-reactions. The probe for A. naeslundii detected all strains belonging to the genospecies 1 (12 strains) and catalase-negative genospecies 2 (four strains); it failed to detect catalase-positive A. naeslundii genospecies 2 (previous A. viscosus serotype II) (two strains). However, the latter strains of catalase-positive A. naeslundii genospecies 2 were correctly detected by the probe developed for A. viscosus. The new probes were then field tested using supragingival plaque samples from 28 healthy preschool children. Whilst A. odontolyticus was detected in almost all samples (96.4%), A. gerencseriae, A. meyeri, catalase-negative A. naeslundii and catalase-positive A. naeslundii genospecies 2 were detected in < 50% samples. CONCLUSION: We conclude that the developed oligonucleotide probes, complementary to the variable regions of 16S rDNA, would be of potential value for differentiating Actinomyces spp. in clinical samples from the oral cavity and other ecosystems where such species may abound.     

Direct detection of cell surface interactive forces of sessile, fimbriated and non-fimbriated Actinomyces spp. using atomic force microscopy

Actinomyces species are predominant early colonizers of the oral cavity and prime mediators of inter-bacterial adhesion and coaggregation. Previous workers have evaluated the adhesion of Actinomyces spp. by quantitative assessment of sessile, as opposed to planktonic cells attached to substrates, but did not quantify the cell surface interactive forces. Therefore we used atomic force microscopy to directly detect the interactive force between an approaching silicon tip and sessile Actinomyces spp. adhering to a substrate, at nanonewton (nN) range force levels. A total of eight strains each belonging to fimbriated and non-fimbriated Actinomyces species were employed, namely A. bovis, A. gerencseriae, A. israelii, A. meyeri, A. naeslundii genospecies 1 and 2, A. odontolyticus and A. viscosus. The sterile mica discs, used as the adhesion substrate, were immersed in mono-species bacterial suspensions for five days to obtain a thin bacterial biofilm. Interactive forces were measured using a silicon nitride cantilever attached to a Nanoscope IIIA atomic force microscope. The interactive forces between the approaching silicon nitride tip and bacterial biofilm surfaces were randomly quantified at three different locations on each cell; namely, the cell surface proper, the periphery of the cell and the substrate and, the interface between two cells. When the interactive forces at these locations of the same species were compared, significantly higher force levels at the cell-cell interface than the other two locations were noted with A. gerencseriae (P < 0.001), A. viscosus (P < 0.01) and A. israelii (P < 0.05). When the interactive forces of different Actinomyces spp. at an identical location were compared, fimbriated A. naeslundii genospecies 2 showed the greatest interactive force at the cell surface proper (-32.6 +/- 8.7 nN, P < 0.01). A. naeslundii genospecies 1, 2 and A. viscosus demonstrated greater interactive force at the cell-mica periphery than the other five species (P < 0.05); A. viscosus (-34.6 +/- 10.5 nN) displayed greater interactive force at the cell-cell interface than the others (P < 0.01), except for A. gerencseriae (P > 0.05). These data indicate that fimbriated Actinomyces spp., including A. naeslundii genospecies 1, 2 and A. viscosus exert higher cell surface interactive forces than those devoid of fimbriae and, such variable force levels may modulate their adhesion and coaggregation during biofilm formation.     

The predominant Actinomyces spp. isolated from infected dentin of active root caries lesions.

Actinomyces are Gram-positive pleomorphic rods (GPPR) which form a large proportion of the oral microflora of all mammals. They have been implicated in root caries, although their role in dental caries initiation and progression is not well-understood. Many studies have focused on Actinomyces naeslundii, but few reports have documented other members of the GPPR. Therefore, we investigated the GPPRs isolated from infected dentin of active root caries lesions (n = 9) to determine which species were the most frequently isolated. The GPPR were isolated under both aerobic and anaerobic conditions and identified by biochemical and physiological tests to the species level according to the new taxonomy. Of 654 GPPR isolates investigated, 607 were identified as belonging to the genus Actinomyces. Of these, 242 were identified as A. israelii, 225 as A. gerencseriae, 109 as A. naeslundii, 15 as A. odontolyticus, and 13 as A. georgiae. Individual strains of A. israelii (n = 56) and A. gerencseriae (n = 46) were also investigated at the DNA level by means of Repetitive Extragenic Palindromic polymerase chain-reactions (REP-PCR) for the study of clonal diversity. Although only a small number of isolates was investigated, REP-PCR showed that the genotypes of both A. gerencseriae and A. israelii populations were heterogeneous within individual root caries lesions. A. gerencseriae and A. israelii strains from the same lesions did not share the same REP-PCR patterns, showing the robustness of the identification scheme. A significantly greater proportion of A. gerencseriae was isolated from the aerobic plates (p < 0.05), while the proportion of A. israelii was significantly (p < 0.05) greater from anaerobic plates. The role of individual Actinomyces spp. in the root caries process remains unclear, since various populations of GPPRs were isolated from individual active root caries lesions.     

儿童口腔放线菌与儿童龋的关系初探

目的检测儿童牙面龈上菌斑中的放线菌,初步探讨口腔放线菌与儿童龋病发生的关系。方法选择40例3~5岁儿童为研究对象,其中无龋组和龋敏感组各20例。用无菌牙签收集乳牙表面3个不同部位的龈上菌斑。龋敏感组收集完整面、白垩斑和龋洞内（ 牙本质层）的菌斑;无龋组收集唇面、邻面和!面沟裂的菌斑。提取菌斑的细菌DNA,用放线菌特异性引物进行聚合酶链反应,对其电泳条带进行记录分析。结果无龋组放线菌检出率为100%,龋敏感组为95%,二者间无统计学差异（ P>0.05）。内氏放线菌、戈氏放线菌、龋齿放线菌、衣氏放线菌和黏性放线菌在两组儿童的菌斑中均有检出,前3种放线菌在无龋组的检出率高于龋敏感组,二者间有统计学差异（ P<0.05）。2组儿童3个检测部位间的检出率无统计学差异（ P>0.05）。结论放线菌是儿童乳牙龈上菌斑中的主要定植细菌,可能是有益菌;其检出情况与乳牙检测部位的关系不大。     

In vitro activity of amoxicillin, clindamycin, doxycycline, metronidazole, and moxifloxacin against oral Actinomyces

Actinomyces spp have been increasingly associated with endodontic infections. However, the antimicrobial susceptibility of this genus has not been studied extensively. The objective of this study was to determine the susceptibility of oral isolates of Actinomyces naeslundii, Actinomyces gerencseriae, Actinomyces israelii, Actinomyces viscosus, and Actinomyces odontolyticus to amoxicillin, clindamycin, doxycycline, metronidazole, and moxifloxacin using in vitro assays. The minimum inhibitory concentration (MIC) of each bacterial isolate was determined by using E-test strips (AB Biodisk, Solna, Sweden). The MIC(90) was 0.19 microg/mL for amoxicillin, 0.25 microg/mL for doxycycline, 0.50 microg/mL for moxifloxacin, and 1.00 microg/mL for clindamycin. However, metronidazole was not active against any of the Actinomyces spp tested (MIC(90)>256 microg/mL).     

Ribotype diversity of Actinomyces with similar intraoral tropism but different types of N-acetyl-beta-D-galactosamine binding specificity

Sixty-three isolates of Actinomyces naeslundii genospecies 1 and 2 and Actinomyces odontolyticus from three subjects clustered into 22 ribotypes. Unique ribotypes were found in the subjects and within individual tissue sites (bucca, tooth and tongue). A odontolyticus ribotypes shared tongue-specific binding properties, while those of genospecies 1 and 2 from buccal and tooth surfaces shared different types of N-acetyl-beta-D-galactosamine binding specificity.     

Identification of oral Actinomyces species using DNA probes

Oral Actinomyces comprise a major segment of both the supra- and subgingival microbiota; however, little is known about the distribution of individual species in different sites or clinical conditions. The purpose of the present investigation was to develop DNA probes for suggested species and genotypes of oral Actinomyces. Whole genomic DNA probes to 12 human oral species and/or serotypes were labeled with digoxigenin and used to seek cross-reactions among the taxa using the checkerboard DNA-DNA hybridization assay. The Actinomyces formed three distinct groups: 1) Actinomyces georgiae, Actinomyces meyeri and Actinomyces odontolyticus serotypes I and II; 2) Actinomyces viscosus and Actinomyces naeslundii serotypes I, II, III and WVA 963; and 3) Actinomyces gerencseriae and Actinomyces israelii. Cross-reactions among taxa were detected and minimized by increasing the temperature of the post-hybridization high-stringency wash to 80 degrees C. Despite the elevation in high stringency wash temperature, cross-reactions among strains of the A. naeslundii/A. viscosus group persisted. Probes for two of the three currently recognized genospecies in this group were prepared by removing the DNA in common between cross-reacting species using subtraction hybridization and polymerase chain reaction. Nine species and genospecies could be clearly separated by a combination of whole genomic and subtraction hybridization probes and by increasing the high-stringency wash temperature. A total of 195 fresh isolates of Actinomyces were grouped in a blind study using DNA probes and separately by SDS-PAGE protein profiles. Concordance between the two methods was 97.3%. The probes and hybridization conditions were tested for their ability to detect the Actinomyces species and genospecies in samples of supragingival and subgingival plaque from periodontitis subjects using checkerboard DNA-DNA hybridization. The probes detected the species in samples of supragingival and subgingival plaque. We concluded that whole genomic and subtraction hybridization DNA probes facilitate the detection and enumeration of species and genospecies of Actinomyces in plaque samples.     

Identification of cultivable microorganisms from root canals with apical periodontitis following two-visit endodontic treatment with antibiotics/steroid or calcium hydroxide dressings

The study was aimed at comparing the efficacy of disinfection of root canals with periapical radiolucencies when treated with either antibiotics/steroid medicaments (Ledermix or Septomixine) or a calcium hydroxide paste (Calasept). Microbiological samples were taken before and after two-visit endodontic treatment from 88 canals with apical periodontitis. All of the canals but one (87 of 88) had cultivable growth before treatment. After dressing with Ledermix, Septomixine, or Calasept, the percentages of canals remained with positive growth were 48% (13 of 27), 31% (8 of 26), and 31% (11 of 35), respectively. The chi(2) tests showed there were no significant differences in the number of canals with positive growth or mean colony forming units counts after instrumentation, irrigation and dressing. In the Ledermix group, 38 strains of bacteria were recovered. The Septomixine group had 25 strains, and the Calasept group had 25 strains. Gram-positive facultative anaerobic cocci (including staphylococci and streptococci) were more prevalent than the Gram-negative obligate anaerobic rods after treatment in all three groups. Similarities in the reduced number of canals with residual growth, and the prevalence of Gram-positive facultative anaerobic cocci suggest that the use of different inter-appointment dressings produced similar microbiological outcomes. However, factors other than the antimicrobial effectiveness of intracanal medicaments may also be responsible for the results observed.     

Combinations of bacterial species in endodontic infections

AIM: This study was undertaken to investigate combinations of bacteria found in root-canal infections of teeth with periapical bone destruction without clinical signs and symptoms. METHODOLOGY: Endodontic samples from 58 root canals were cultured anaerobically and microorganisms were counted and identified. Eighty-one combinations of microorganisms were found and tested for a symbiotic relationship using the Fisher's exact test and Odds ratio calculation. RESULTS: All samples contained microorganisms with a median CFU mL(-1) of 8x10(4) per sample. Strict anaerobic species accounted for 87% of the microflora. The most prevalent bacteria were Prevotella intermedia, Peptostreptococcus micros and Actinomyces odontolyticus, present in 33, 29 and 19%, respectively, of the cultured canals. A significant relationship (P<0.05) and an Odds ratio >2 were found between P. intermedia and P. micros, P. intermedia and P. oralis, A. odontolyticus and P. micros, Bifidobacterium spp. and Veillonella spp. Conclusions: These results indicate that endodontic pathogens do not occur at random but are found in specific combinations.     

Genotypic diversity of oral Actinomyces naeslundii genospecies 1 and 2 in caries-active preschool children

A total of 991 isolates of Actinomyces naeslundii were obtained from sound approximal tooth sites in either caries-active (n = 35) or caries-free (n = 20) preschool children. From this group of isolates, 101 strains were chosen to study the genotypic diversity of A. naeslundii genospecies 1 (n = 30), catalase-positive (n = 30), and catalase-negative genospecies 2 (n = 41). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), with a pair of primers targeting the 16S ribosome RNA gene (16S rDNA), and MnlI digestion together with randomly amplified polymorphic DNA (RAPD) with eight arbitrary, single 10-mer primers were performed to generate genetic profiles of selected Actinomyces isolates. The hierarchic relationships of genetic profiles were finally analyzed using computerized dendrograms. There was no significant difference in the prevalence rates and proportions of either genospecies 1 or 2 between the caries-free and caries-active groups, although a higher prevalence of genospecies 2 was noted in the total population. Dendrogram analyses of the 16S rDNA PCR-RFLP profiles revealed that all strains belonging to A. naeslundii genospecies 1 could be subgrouped into three genotypes (T7, T18, and T19), with a single predominant genotype, T18 (27/30). Catalase-positive strains for genospecies 2 fell into three subtypes (T4, T7, and T17), whereas the catalase-negative counterparts were distributed amongst 16 subtypes. No specific genotype was significantly associated with caries activity. We conclude that heterogeneous subgroups of A. naeslundii genospecies 1 and 2, particularly the latter, are the constituent flora of dental plaque in children and may contribute to the pathogenesis of childhood caries.     

Occurrence of Actinomyces in infections of endodontic origin

Species of Actinomyces have been associated with endodontic treatment that failed to heal. In this study polymerase chain reaction was used with a pair of universal primers for Actinomyces and species-specific primers to evaluate the contents of infected root canals and aspirates from abscesses or cellulitis for the presence of Actinomyces israelii, A. naeslundii, and A. viscosus. DNA was extracted from 131 clinical samples. DNA from 2 of the original 131 samples was not available for polymerase chain reaction with the universal primer for Actinomyces and A. naeslundii. DNA reacting with the universal primer for Actinomyces was detected in 72 of 129 (55.8%) clinical samples. Of those 41 of 51 (80.4%) were from infected root canals, 22 of 48 (45.8%) were from abscesses, and 9 of 30 (30%) were associated with cellulitis. A. viscosus was detected in 42 of 131 (32.1%) clinical samples. Of those 31 of 52 (59.6%) were from infected root canals, 6 of 43 (14%) were from abscesses, and 5 of 36 (13.9%) were associated with cellulitis. A. israelii was detected in 31 of 131 (23.7%) clinical samples. Of those 14 of 52 (26.9%) were from infected root canals, 11 of 43 (25.6%) were from abscesses, and 6 of 36 (16.7%) were associated with cellulitis. A. naeslundii was detected in 11 of 131 (8.5%) clinical samples. Of those 7 of 51 (13.7%) were from infected root canals, 2 of 48 (4.2%) were from abscesses, and 2 of 30 (6.7%) were associated with cellulitis.     

The effect of antibacterial monomer MDPB on the growth of organisms associated with root caries

MDPB, 12-methacryloyloxydodecylpyridinium bromide, was tested for its ability to inhibit the growth of organisms associated with active root caries lesions and to modify the growth characteristics of these organisms at sub-MICs. MICs and MBCs of MDPB for independent isolates (n=5) of the following taxa: Streptococcus mutans, Streptococcus oralis, Streptococcus salivarius, Actinomyces naeslundii, Actinomyces israelii, Actinomyces gerensceriae, Actinomyces odontolyticus, Lactobacillus spp., and Candida albicans were determined, and the effects at sub-MIC on microbial growth kinetics were assessed. All isolates were sensitive to inhibition by MDPB. The median MICs and MBCs of MDPB for these organisms were in the range of 3.13 to 25.0 microg/ml and 6.25 to 50.0 microg/ml, respectively. As for the influence of pH, inhibition was sensitive to acidic pH. Even at sub-MICs, the growth of all strains, measured as cell yield and doubling time, was significantly reduced. Based on the results of this study, MDPB exhibited the potential to inhibit the growth of microbiota associated with active root caries lesions.     

Oral colonization with Actinomyces species in infants by two years of age

In early childhood, the human mouth is already colonized by actinomycetes. Due to recent taxonomic changes within the genus Actinomyces, up-to-date data are warranted on the time and succession of different Actinomyces species in the oral cavity. By using a longitudinal study design and culture techniques, we examined the age-related occurrence of Actinomyces species in saliva from 39 healthy infants at 2, 6, 12, 18, and 24 months of age. Altogether 428 Actinomyces isolates were available for this study. Identification was based on biochemical tests and gas chromatographic demonstration of metabolic end-products, and when needed, cellular fatty acid profiles were determined. The frequency of the total actinomycetal flora increased from 31% to 97% within 2 years. A. odontolyticus was the most prominent Actinomyces colonizer at all five sampling occasions. A. naeslundii was the second most common Actinomyces sp. but was not detected before the age of 1 year. As a novel observation, we found A. graevenitzii in the oral cavity. The number of A. graevenitzii isolates indicates that this species is not just occasionally present in infants' mouths. We also found A. viscosus, A. gerencseriae, A. israelii, and A. georgiae. Based on the present results, we suggest that A. odontolyticus is the main primary Actinomyces species on oral mucosal surfaces in infants up to 2 years of age.     

ELIMINATION OF INTRACANAL INFECTION IN DOGS' TEETH WITH INDUCED PERIAPICAL LESIONS AFTER ROTARY INSTRUMENTATION: INFLUENCE OF DIFFERENT CALCIUM HYDROXIDE PASTES

The aim of this study was to evaluate the antiseptic efficacy of rotary instrumentation associated with calcium hydroxide-based pastes prepared with different vehicles and antiseptics. Chronic periapical lesions were experimentally induced in 72 premolar root canals of four dogs. Under controlled asepsis, after initial microbiological sampling (A1), the root canals were instrumented using the ProFile system in conjunction with 5.25% sodium hypochlorite and the intracanal medication was placed. Four experimental groups were formed according to the pastes used: group 1- Calen (n=18), group 2- Calen+CPMC (n=20), group 3- Ca(OH)₂ p.a.+ anaesthetic solution (n=16) and group 4- Ca(OH)₂ p.a.+ 2% chlorhexidine digluconate (n=18). After 21 days, the pastes were removed; the canals were emptied and 96 hours later a second microbiological sample was obtained (A2). The incidence of positive microbiological cultures and the number of cfus in stages A1 and A2 were compared statistically by the Wilcoxon test while the influence of the different treatments in intracanal infection was evaluated by Kruskal-Wallis test at 5% significance level (p<0.05). Large numbers of strict and facultative anaerobes, and viridans group streptococci were found in 100% of root canals of A1 samples. Among A2 samples, all treatments showed significant reduction of cfus and positive cultures (p<0.05), but only groups 3 and 4 showed 100% of root canals free of microorganisms. Rotary instrumentation plus NaOCl 5.25% associated with intracanal medication produced a drastic reduction or elimination of intracanal microbiota, whose performance was not influenced by the nature of the vehicle or the antiseptic added to the Ca(OH)₂ p.a.     

Comparison of the distribution of Actinomyces in dental plaque on inserted enamel and natural tooth surfaces in periodontal health and disease

The distribution of Actinomyces naeslundii, Actinomyces viscosus and Actinomyces odontolyticus in healthy and diseased adult populations was studied in 3 different ways. First, supragingival plaque formation at 2 through 72 h was examined in 12 periodontally healthy adults using a removable pre-measured surface of enamel bonded to molars and premolars. Second, a cross-sectional examination of the composition of both supragingival and subgingival plaque of unknown age was conducted in 205 adults exhibiting periodontal health to moderate disease. Third, the effects of oral hygiene instruction and root planing on the subgingival micro-flora of a subset of 19 subjects with moderate periodontitis were examined. The evaluation of 12 adults revealed that the predominant species in early plaque formation (2, 4 and 8 h) was A. odontolyticus, A. viscosus and A. naeslundii were present in developing plaques in almost all subjects in 2-h plaque, but absent in half the subjects when 4-, 8- or 24-h plaque was examined. These two species significantly increased in numbers per mm² enamel surface area in 48- and 72-h plaques. A. odontolyticus was not related to clinical signs of periodontal disease in 205 adults, and its subgingival proportions in plaque did not change following periodontal treatment of 19 individuals. A. naeslundii was found in significantly higher numbers in supragingival than subgingival plaques in the 205 adults examined. The mean proportion of A. naeslundii significantly decreased as the magnitude of probing depth and attachment loss increased. The proportions of A. naeslundii and A. viscosus were found to be significantly increased in subgingival plaques following periodontal treatment.     

Effectiveness of castor oil extract on Escherichia coli and its endotoxins in root canals

This in vitro study sought to evaluate the effectiveness of castor oil extract used as an irrigating solution on Escherichia coli and its endotoxins in root canals. Sixty single-rooted teeth were prepared (using castor oil extract as irrigating solution) and divided into five groups (n = 12): Group 1 samples were treated with calcium hydroxide (Ca(OH)2), Group 2 samples were treated with polymyxin B, Group 3 samples were treated with Ca(OH)2 and 2% chlorhexidine gel (CHX), and Group 4 samples were treated with castor oil extract. A control group used physiological saline solution as an irrigant. Canal content samples were collected at four different times: immediately after instrumentation, seven days after instrumentation, after 14 days of intracanal medication, and seven days after removal of intracanal medication. A plating method was used to assess antimicrobial activity and the quantification of endotoxins was evaluated by the chromogenic Limulus lysate assay. Data were submitted to ANOVA and a Dunn test (a = 5%). Irrigation with castor oil extract decreased E. coli counts but had no effect on the level of endotoxins. Samples taken seven days after removal of medication revealed a significant reduction in endotoxin levels in Groups 3 and 4. Compared to the saline solution irrigation, castor oil extract decreased microorganism counts in root canals immediately after canal preparation. None of the medications used completely eliminated endotoxins in the root canal.     

The comparative cariogenicity and plaque-forming ability in vivo of four species of the bacterium Actinomyces in gnotobiotic rats

Gnotobiotic WAG/RIJ rats on a high sucrose diet were monoinfected with 12 strains of Actinomyces spp. Moderate levels of caries were induced by a single strain of Actinomyces naeslundii and low levels by two strains of Actinomyces viscosus, three strains of A. naeslundii and one strain of Actinomyces israelii. No caries was induced by single strains of A. viscosus and A. israelii or by three Actinomyces odontolyticus strains. Only fissure caries was observed. Scanning electron microscopy showed that all strains colonized the fissures and most colonized the lingual surface of the teeth, but to a limited extent. Production of abundant and dense plaque was not always accompanied by caries.     

Influence of infection at the time of root filling on the outcome of endodontic treatment of teeth with apical periodontitis

This study investigated the role of infection on the prognosis of endodontic therapy by following-up teeth that had had their canals cleaned and obturated during a single appointment. The root canals of 55 single-rooted teeth with apical periodontitis were thoroughly instrumented and irrigated with sodium hypochlorite solution. Using advanced anaerobic bacteriological techniques, post-instrumentation samples were taken and the teeth were then root-filled during the same appointment. All teeth were initially infected; after instrumentation low numbers of bacteria were detected in 22 of 55 root canals. Periapical healing was followed-up for 5 years. Complete periapical healing occurred in 94% of cases that yielded a negative culture. Where the samples were positive prior to root filling, the success rate of treatment was just 68%— a statistically significant difference. Further investigation of three failures revealed the presence of Actinomyces species in each case; no other specific bacteria were implicated in failure cases. These findings emphasize the importance of completely eliminating bacteria from the root canal system before obturation. This objective cannot be reliably achieved in a one-visit treatment because it is not possible to eradicate all infection from the root canal without the support of an inter-appointment antimicrobial dressing.     

The effects of calcium hydroxide removal methods on bond strength of Epiphany SE with two irrigation protocols

Abstract

Objective: The purpose of this study was to compare the effects of five calcium hydroxide removal methods on the bond strength of Epiphany SE sealer after canal irrigation with NaOCl+EDTA or NaOCl+MTAD. Materials and methods: The 120 roots were instrumented by using the ProTaper rotary system under irrigation with 2.5% sodium hypochlorite and randomly divided into two major groups according to the final irrigation: 1.3% NaOCl + MTAD and 5% NaOCl + 17% EDTA. For controls, 10 roots from each of the final irrigations with NaOCl + MTAD and NaOCl + EDTA (20 roots) were not filled with Ca(OH)₂. The intra-canal paste, Ca(OH)₂ was applied to each of the 100 remaining roots and stored at 37°C for 7 days. Each group was sub-divided into five sub-groups (n = 10) according to the removal technique for the intra-canal dressing: Group-1: recapitulation with size 30 K file + 3 ml of saline solution, Group-2: recapitulation with size 30 K file + 3 ml of 5% NaOCl, Group-3: using 5% NaOCl + 17% EDTA, Group-4: using 5%NaOCl + 15% citric acid, and Group-5: using 1.3% NaOCl + 5 ml MTAD. The root canals were filled with Resilon and Epiphany SE sealer. The bond strength was measured. Results: The mean bond strength of Epiphany SE to root dentine irrigated with NaOCl + MTAD was lower than that of NaOCl + EDTA. The highest bond strengths were 3.31 ± 0.057 and 2.60 ± 0.054 in the NaOCl + citric acid group when Ca(OH)₂ was applied to roots treated with NaOCl + EDTA and NaOCl + MTAD, respectively (p < 0.05). Conclusion: For root canals treated with NaOCl + EDTA or NaOCl + MTAD, the use of NaOCl + chelating agent for Ca(OH)₂ removal does not adversely affect the bond strength of Epiphany SE to dentin.