Clonality of bacterial consortia in root canals and subjacent gingival crevices.

AIM: No oral niche can be considered to be segregated from the subjacent milieu because of the complex community behavior and nature of the oral biofilms. The aim of this study was to address the paucity of information on how these species are clonally related to the subjacent gingival crevice bacteria. METHODS: We utilized a metagenomic approach of amplifying 16S rDNA from genomic DNA, cloning, sequencing and analysis using LIBSHUFF software to assess the genetic homogeneity of the bacterial species from two infected root canals and subjacent gingival crevices. RESULTS: The four niches studied yielded 186 clones representing 54 phylotypes. Clone library comparisons using LIBSHUFF software indicated that each niche was inhabited by a unique flora. Further, 42% of the clones were of hitherto unknown phylotypes indicating the extent of bacterial diversity, especially in infected root canals and subjacent gingival crevices. CONCLUSIONS: We believe data generated through this novel analytical tool shed new light on understanding oral microbial ecosystems.

Diagnostic performance of mandibular bone density measurements in assessing osteoporotic status.

PURPOSE: The study evaluated the diagnostic performance of computed tomography (CT) bone density measurements (in Hounsfield units [HU]) in assessing the osteoporotic status of edentulous subjects (21 men, 40 women) scheduled to receive mandibular implant-supported overdentures. MATERIALS AND METHODS: Density (in HU) of 61 left and 61 right mandibular canine sites was measured. Each subject was also subject to body bone mineral density measurements (dual-energy x-ray absorptiometry). Bone density T-score values of total hip, femoral neck, spine (L1 to L4), and total body were assessed. Pearson correlations were conducted between HU of each mandibular bone site and the subject's T-score values. Sensitivity/specificity and receiver operating characteristic curve analyses were used to assess the diagnostic performance of HU in detecting subjects who were, based on each of the four T-scores: (1) "not osteonormal", ie, with a T-score at or below -1.0; or (2) osteoporotic, ie, with a T-score at or below -2.5. RESULTS: HU measurements of mandibular bone sites were found to have modest but significant correlations with each bone density T-score value (total hip, femoral neck, spine, total body). CT mandibular site HU measurement has diagnostic value in detecting a "not osteonormal" condition when total hip, spine, or total body T-scores were used, but not when femoral neck T-score was used. CONCLUSIONS: Based on the limited sample size, optimal HU cutoff values of ~530, ~600, and ~640 HU for total hip, spine, or total body T-scores, respectively, were proposed. CT mandibular site HU measurement had diagnostic value in detecting osteoporosis when spine T-score was used but not when total hip, femoral neck, and total body T-scores were used. An optimal HU cutoff value of ~460 HU for spine T-score was proposed.

Correlation between dental implant insertion torque and mandibular alveolar bone density in osteopenic and osteoporotic subjects.

PURPOSE: Osteoporotic patients require particular attention during implant placement, and insertion torque (IT) has been established as a simple and noninvasive method to assess local bone quality and primary implant stability. This study aimed to test the hypothesis that IT was not significantly correlated with bone density, as assessed with computed tomography, in a group of osteopenic and osteoporotic patients. In addition, the hypothesis that IT was not significantly correlated with implant length was tested. MATERIALS AND METHODS: Fifty-three completely edentulous patients with compromised bone mineral density (osteoporotic or osteopenic) who required treatment with complete maxillary dentures and complete mandibular implantsupported overdentures participated in the study. Each patient received two screw-shaped self-tapping implants (Branemark Mark III TiUnite) at the mandibular canine regions. The IT of each implant during placement was recorded. The Pearson correlation between IT and implant site bone density (Hounsfield unit) obtained from presurgical computed tomographic scans was analyzed. The relationship between IT and implant length was also studied. RESULTS: IT was significantly correlated to implant site bone density but not to implant length. CONCLUSION: IT can be a viable and practical means to assess mandibular bone quality in patients with compromised general bone density.

Effect of surface treatment on shear bond strength of zirconia to human dentin.

PURPOSE: The effect of surface treatment using tribochemical silica coating/silane coupling on the shear bond strengths of (1) a glass-infiltrated, zirconia-reinforced alumina (In-Ceram Zirconia) and (2) a yttria-stabilized zirconia ceramic (YZ Zirconia) to human dentin was studied. MATERIALS AND METHODS: Twelve specimens of each ceramic were randomly assigned to one of three surface treatments: (1) no surface treatment (control group); (2) a chairside tribochemical silica coating/silane coupling system (CoJet group); and (3) a laboratory tribochemical silica coating/silane coupling system (Rocatac group). The mode of failure of each specimen was determined under magnification. RESULTS: The shear bond strengths (mean ± SD) of In-Ceram Zirconia of the control, CoJet and Rocatec groups were 5.7 ± 4.3 MPa, 11.4 ± 5.4 MPa, and 6.5 ± 4.8 MPa, respectively. The corresponding figures for YZ Zirconia were 8.2 ± 5.4 MPa, 9.8 ± 5.4 MPa, and 7.8 ± 4.7 MPa. Two-way ANOVA revealed significant differences in bond strength due to the difference in surface treatment (p= 0.02), but the bond strengths between the two ceramics were not significantly different (p= 0.56). Post hoc tests showed that In-Ceram Zirconia treated with CoJet had significantly higher shear bond strengths than those untreated (p < 0.05) or treated with Rocatec (p < 0.05). Surface treatment did not affect the shear bond strength of YZ Zirconia significantly (p > 0.05). CONCLUSION: The bonding of In-Ceram Zirconia can be improved by the chairside surface treatment system.

Clinical considerations in managing severe tooth discoloration with porcelain veneers.

BACKGROUND: Although porcelain veneer has been proposed as the treatment of choice in cases of severe tooth discoloration, clinicians should consider a multidisciplinary approach when treating complex cases. Clinicians also need to understand the masking ability of veneer restorations. CASE DESCRIPTION: A 20-year-old woman had severe tooth discoloration, enamel hypoplasia and malocclusion. The patient first underwent orthodontic treatment to correct the dental alignment after the author extracted her hypoplastic first molars. The author then placed porcelain veneers with high-density alumina cores on the patient's maxillary and mandibular anterior teeth. The restorations were in service for seven years without complications. CONCLUSIONS: and CLINICAL IMPLICATIONS: Managing severe tooth discoloration requires thorough consideration of all patient factors, treatment provided in a logical sequence and the use of porcelain veneers with adequate masking ability.

Shear bond strength between nickel-chromium and human dentine using a dual-cure, self-adhesive universal resin luting agent.

The adhesive property of a dual-cure, self-adhesive universal resin luting agent (Rely X Unicem, 3M ESPE) between nickel-chromium (Ni-Cr) and human dentine was compared with three conventional resin luting agents (Calibra, Dentsply; Panavia-F, Kuraray; All-bond 2 C & B cement, Bisco). Ten Ni-Cr rods were bonded to human dentine with each of the four luting agents, and were subjected to shear bond test. Results showed that there was no significant difference in shear bond strengths among the luting agents. A dual-cure, self-adhesive universal resin luting agent was shown to have comparable adhesive property between Ni-Cr and human dentine as three other conventional resin luting agents. Given the simplicity of use of the dual-cure, self-adhesive universal resin luting agent, it appears to be promising in clinical applications.

Oral health status of low-income, middle-aged to elderly Hong Kong Chinese with type 2 diabetes mellitus.

PURPOSE: To study oral health conditions, diabetic medical complications and their association in type 2 diabetes mellitus (DM). MATERIALS AND METHODS: Cross-sectional survey of 364 type 2 DM patients (63.6 +/- 10.1 years, 54% female) and 161 controls (64.1 +/- 10.6 years, 53% female) with or without essential hypertension, predominantly low-income, attending a hospital were recruited. Periodontal disease (Community Periodontal Index [CPI]) and dental status (decayed, missing and filled teeth [DMFT]) were recorded. Fasting plasma glucose and, for DM patients, HbA1C and DM complications were recorded on enrolment and follow up, respectively. RESULTS: Many DM subjects had fair diabetic control. Both groups (control/DM) had poor oral health: DMFT = 14.5/16.8, CPI 4 = 36%/50%, (P < 0.02) while DM subjects had less DT(adjusted) = 2.1/1.4 (P < 0.01). Of the follow-up DM individuals, 294 (81%) had medical complication(s). Regression analyses showed association between advanced periodontal attachment loss (ALoss) and age, male gender, smoking and DM; MT and DMFT were associated with age, female gender, smoking, DM and hypertension. ALoss and DMFT were not associated with DM complications. CONCLUSIONS: The oral health of the surveyed Chinese subjects was poor. Type 2 DM subjects were affected more by ALoss and MT but less DT. Subjects with hypertension had higher odds for MT.

Chemical solubility and flexural strength of zirconia-based ceramics.

PURPOSE: This study was undertaken to investigate the chemical solubility and flexural strengths of 3 zirconia-based dental ceramics: In-Ceram Zirconia (IZ), In-Ceram 2000 YZ CUBES (YZ Zirconia) (Vita Zahnfabrik), and Cercon (Dentsply). A pressable lithium disilicate-reinforced glass ceramic (IPS Empress 2, Ivoclar Vivadent) was used as a control. MATERIALS AND METHODS: Ten block specimens (12 x 6 x 4 mm) of each ceramic material were prepared for chemical solubility testing. Each specimen was refluxed in 4% acetic acid solution for 16 hours. The percentage loss of mass and the loss of mass per unit of surface area for each specimen were calculated. Ten bar-shaped (21 x 5 x 2 mm) and 10 disk-shaped (16 mm diameter, 1.2 mm thickness) specimens of each ceramic material were prepared and tested for uniaxial flexural strength (UFS) and biaxial flexural strength (BFS). X-ray diffraction analyses were conducted to determine the relative amount of the monoclinic phase of the as-sintered and fractured surfaces of the zirconia ceramics. RESULTS: There were no significant differences among the ceramics in chemical solubility by percentage mass or mass/surface area. For UFS, YZ Zirconia (899 +/- 109 MPa) > Cercon (458 +/- 95 MPa) IZ (409 +/- 60 MPa) > Empress 2 (252 +/- 36 MPa). For BFS, YZ Zirconia (1,107 +/- 116 MPa) > Cercon (927 +/- 146 MPa) > IZ (523 +/- 51 MPa) > Empress 2 (359 +/- 43 MPa). The fractured YZ Zirconia surface contained approximately 5 times as much monoclinic phase compared to that of its intact surface. The fractured IZ and Cercon surfaces contained approximately twice as much monoclinic phase compared to those of intact surfaces. CONCLUSION: The ceramics tested all satisfied the chemical solubility allowance required of core ceramic material (type I, Class 1 or type II, Class 1) according to the International Organization for Standardization 6872:1995(E) specifications on dental ceramic. The zirconia-based ceramics possessed significantly higher flexural strengths than the control lithium disilicate ceramic. Their clinical application appears sufficiently promising for long-term clinical studies to be undertaken.

The use of immediate implant placement for the replacement of a periodontally involved malaligned lateral incisor: a clinical report.

Localized severe chronic periodontitis is often seen in middle-aged patients, particularly when plaque control for malaligned teeth is not satisfactory. While orthodontic treatment can realign such teeth with reduced periodontal support, esthetics may be compromised by gingival recession due to preexisting bone loss and resolution of inflammation after periodontal treatment. This clinical report describes how a malaligned maxillary lateral incisor with severe periodontitis was replaced by an immediately placed implant and implant-supported crown with a good esthetic outcome.

Contrast ratios and masking ability of three types of ceramic veneers.

STATEMENT OF PROBLEM: Although ceramic veneers have been proven to be clinically successful in longevity studies, there is little information on the contrast ratios and masking ability of the available ceramic systems because dental laboratory technology and expensive experimental equipment are required for the investigation. Moreover, the complexity in understanding how to evaluate translucent ceramic materials may also explain why information in this area is limited. PURPOSE: The purpose of this study was to determine the contrast ratios and masking abilities of 3 types of all-ceramic veneers by measuring their luminance and color difference over white and black backgrounds. MATERIAL AND METHODS: Disk-shaped specimens (8-mm diameter x 0.7-mm thickness) of Shade A2 (Vita Lumin) of 3 types of all-ceramic systems: Procera (n=8), Empress 2 (n=8), and Vitadur Alpha (n=10) were fabricated. The luminance (as Y) and color (as CIE L*a*b*) of the specimens were measured with a colorimeter. The contrast ratio (CR=Yb/Yw), defined as the ratio of illuminance (Y) of the test material when it is placed on the black background (Yb) to the illuminance of the same material when it is placed over a white background (Yw), was determined. The masking ability of a specimen was evaluated by calculating the color difference (DeltaE) of the veneers over white and black backgrounds. Both CR and DeltaE* data were analyzed with 1-way ANOVA and the Tukey HSD test (alpha=.05). RESULTS: The mean contrast ratios (SD) of Procera, Empress 2, and Vitadur Alpha specimens were 0.50 (0.02), 0.46 (0.05), and 0.39 (0.02), respectively. CR values were significantly different among the 3 materials (P<.001). Procera veneers had a significantly higher CR compared to Empress 2 (P=.01) or Vitadur Alpha (P=.01), whereas the CR of Empress 2 was significantly higher than that of Vitadur Alpha (P=.046). Color difference (DeltaE*) (SD) of Procera, Empress 2, and Vitadur Alpha specimens over black and white backgrounds were 24.46 (1.03), 25.80 (1.03), and 31.08 (1.19), respectively. DeltaE* values were statistically different among the 3 materials (P<.001). Vitadur Alpha specimens had significantly higher DeltaE* when compared with Procera (P<.001) or Empress 2 (P<.001), whereas DeltaE* values between Procera and Empress 2 were not significantly different (P=.331). CONCLUSIONS: Vitadur Alpha had significantly lower contrast ratio and poorer masking ability compared to Procera or Empress 2. The clinical application of Vitadur Alpha as a veneer material over discolored teeth is cautioned. Although the contrast ratio of Procera was significantly higher than that of Empress 2, the masking abilities of these materials were not significantly different. The clinical application of these 2 ceramics as a veneer material may still be limited when applied over intense tooth discoloration because neither can fully mask the color of a black background.

Comparison of the retentive characteristics of cobalt-chromium and commercially pure titanium clasps using a novel method.

This study aimed to compare the retentive forces of cast cobalt-chromium (Co-Cr) and commercially pure titanium (cpTi) clasps. A clasp assembly comprising a pair of symmetrical clasps was made to fit the opposite halves of a hardened stainless-steel sphere. This twin clasp was designed to counterbalance the tipping forces when the clasp assembly was drawn from the sphere. A total of 120 clasp assemblies were fabricated in cast Co-Cr and cpTi and placed at undercut depths of 0.25 mm, 0.50 mm, and 0.75 mm (n = 20 for each). For Co-Cr clasps, the retentive forces at these undercuts depths were 2.34 +/- 0.23 N, 4.65 +/- 0.35 N, and 7.56 +/- 0.50 N, respectively. The corresponding retentive forces for cpTi clasps were 1.24 +/- 0.13 N, 2.34 +/- 0.23 N, and 3.70 +/- 0.27 N. The retentive force of cpTi clasps was approximately half that of Co-Cr clasps for the same undercut depth.

Influence of dental status on nutritional status of geriatric patients in a convalescent and rehabilitation hospital.

PURPOSE: To investigate 6 dental statuses as risk factors for malnutrition in geriatric patients admitted to a convalescent and rehabilitation hospital. MATERIALS AND METHODS: One hundred twenty (59 men and 61 women) geriatric patients admitted to a convalescent and rehabilitation hospital were recruited. Three biochemical and hematologic parameters (albumin, hemoglobin, and lymphocyte count) were used for analysis. Malnutrition was defined as Body Mass Index (BMI) below 18.5 and albumin level under 35 g/L. The number of natural or prosthetic teeth in the dentate patients, and the presence of one or both dentures in the edentate patients, were recorded. Risk factors associated with malnutrition were investigated, namely: (1) edentulism among all patients, (2) edentulism without a set of complete dentures among all patients, (3) edentulism without a set of complete dentures among the edentate patients, (4) decreased number (< 6) of occluding pairs of natural or prosthetic teeth among the dentate patients, (5) decreased number (< 5) of posterior occluding pairs of natural or prosthetic teeth among the dentate patients, and (6) absence of posterior occluding pairs of natural or prosthetic teeth among the dentate patients. One-way ANOVA and Bonferroni multiple comparisons were used to determine if significant differences in the anthropometric, biochemical, and hematologic parameters existed between the patients with different dental statuses. The odds ratio and significance of 6 dental statuses as risk factors of malnutrition were calculated (P = .05). RESULTS: BMI, albumin, and hemoglobin levels of the malnourished patients were significantly lower than those of nourished patients (P < .05). Lymphocyte count was not significantly different between the 2 patient groups (P > .05). The status of edentate patients without a set of complete dentures compared with other edentate and dentate patients was the only independent risk factor (P < .05) in the 6 statuses studied. CONCLUSION: Primary healthcare workers caring for hospitalized geriatric patients should identify edentate patients without a set of complete dentures for the possibility of malnutrition.

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.

Effect of original water content in acrylic resin on processing shrinkage.

PURPOSE: The aim of this study was to determine the original water content of a supplied acrylic resin powder and a monomer and of dry heat-processed acrylic bars. The effect of the original water content of acrylic resin on processing shrinkage was also investigated. MATERIALS AND METHODS: Ten bar specimens were fabricated using dried and as-supplied (control) acrylic resins. The resins were polymerized and cooled, then weighed and measured to determine the amount of shrinkage. The initial water content of the specimens was determined by thorough drying, and results were compared with the Student ttest. RESULTS: The initial water content and processing shrinkage of the dried acrylic resin bars were both significantly lower (P < .0001) than those of the as-supplied acrylic resin bars. CONCLUSION: The processing shrinkage of acrylic resin made from dried constituents was significantly less than that of resin made from products as supplied by the manufacturer. However, it is not known if this change is of clinical significance.

Identification of cultivable microorganisms from primary endodontic infections with exposed and unexposed pulp space.

This study was aimed at comparing the cultivable microorganisms in canals with periapical radiolucencies with exposed and unexposed pulp space. Microbiological samples were taken and analyzed from 45 canals with exposed pulp space, and 43 canals with unexposed pulp space. The canal contents were analyzed by aerobic/anaerobic culture, and conventional identification techniques. There were 211 isolates of bacteria belonging to 28 genera and 55 species recovered from exposed canals. In the unexposed group, 185 isolates of bacteria were recovered, of which 54 species of 28 genera were identified. Among the four most common genera, Prevotella was significantly more common in the exposed group (51/211 in the exposed group versus 30/185 in the unexposed group) (p = 0.049), while there were no differences in prevalence of Actinomyces, Peptostreptococcus, and Campylobacter between two groups of canals. In addition, Fusobacterium nucleatum and Propionibacterium acne were significantly more common in the unexposed canals (p = 0.047 and p = 0.0051, respectively). Similarity in bacterial species in these two groups suggests that pulp space exposure may not be a significant factor in determining the type of bacteria present in infected canals.

Color stability of provisional prosthodontic materials.

STATEMENT OF PROBLEM: Discoloration of provisional prosthodontic materials may result in patient dissatisfaction and additional expense for replacement. PURPOSE: The purpose of this study was to determine the color stability of 5 provisional prosthodontic materials before and after immersion in distilled water or coffee for 20 days or exposure to ultraviolet (UV) light for 24 hours. MATERIAL AND METHODS: A total of 105 disc-shaped specimens (20+/-0.1 mm by 1+/-0.05 mm) were fabricated with 5 provisional prosthodontic materials: polyethyl methacrylate resins (Trim II), polymethyl methacrylate resins (Duralay; Alike), and bis-acryl methacrylate resin (Luxatemp; Integrity), according to manufacturers' instructions (n=21). Seven specimens of each material were randomly selected and immersed individually in distilled water (60 degrees C) or coffee (37 degrees C) for 20 days or exposed to UV irradiation for 24 hours, respectively. Color was measured as CIE L*a*b* with a colorimeter before and after the immersion or UV exposure. Color change (Delta E) was calculated and data were analyzed with 1-way ANOVA and the Tukey multiple comparisons test (alpha=.05). RESULTS: For specimens immersed in water, the color change of bis-acryl-methacrylate-based provisional materials (Integrity and Luxatemp) was significantly less than that of 3 methyl/ethyl methacrylate-based provisional materials (Trim II, Alike, and Duralay) (P<.002). After immersion in coffee, the 3 methyl/ethyl methacrylate-based provisional materials exhibited significantly less color change compared to the 2 bis-acryl methacrylate-based provisional materials (P<.0001). After ultraviolet irradiation, 2 bis-acryl methacrylate-based provisional materials showed significantly less color change than any of the 3 methyl/ethyl methacrylate-based provisional materials (P<.0001). CONCLUSION: Luxatemp and Integrity (bis-acryl-methacrylate-based resins) demonstrated acceptable color stability and were the most color-stable provisional prosthodontic materials tested compared to the methyl/ethyl methacrylate-based resins.

Implant-tissue supported, magnet-retained mandibular overdenture for an edentulous patient with Parkinson's disease: a clinical report.

Degenerative neurologic disorders such as Parkinson's disease are becoming more prevalent as life expectancy is improved. Although the use of an implant-supported overdenture is an acceptable treatment modality, the clinician should recognize the indications and maintenance requirements of different attachment systems for individual patients. The use of a magnetic attachment system in an implant-supported mandibular overdenture for an edentulous patient with Parkinson's disease is presented.

Threshold contrast ratio and masking ability of porcelain veneers with high-density alumina cores.

PURPOSE: The purposes of this study were to: (1) investigate the correlation between the color difference of bilayer porcelain veneers over white and black backgrounds (deltaE1) and their opacity (contrast ratios); (2) determine whether there is a recommendable threshold contrast ratio above which the color difference is clinically acceptable (when deltaE < or = 5); and (3) compare the ability of porcelain veneers to mask a color change from white to black backgrounds (deltaE1) and their ability to mask a color change from white to clinically discolored teeth (deltaE2). MATERIALS AND METHODS: Forty-four maxillary anterior teeth of eight patients with severe tetracycline discoloration were prepared for bilayer porcelain veneers in shade A2 porcelain. The cores were 0.25 mm thick. The color (CIE L*a*b*) and reflectance (Y) of the midbuccal region of each veneer were measured over white and black backgrounds using a colorimeter under artificial daylight. The veneers were bonded to discolored teeth, and their color was measured after 1 week. RESULTS: The mean color difference deltaE1 was 10.6 (SD 2.6). The mean contrast ratio was 0.75 (SD 0.1). There was a close and statistically significant correlation between deltaE1 and contrast ratio. The determined threshold contrast ratio was 0.91. The mean color difference deltaE2 was 11.6 (SD 5.5). A paired t test showed no difference between deltaE1 and deltaE2. CONCLUSION: There was a significant correlation between the masking ability of veneers (deltaE1) and their opacity (contrast ratio). There was no significant difference in the ability of the porcelain veneers in masking a color change from white to black backgrounds compared to their ability to mask the color change from white to the discolored teeth.

Direct detection of Actinomyces spp. from infected root canals in a Chinese population: a study using PCR-based, oligonucleotide-DNA hybridization technique.

OBJECTIVES: The poor sensitivity of phenotypic identification techniques has hampered the taxonomic differentiation of Actinomyces. Hence we developed a sensitive and specific, PCR-based oligonucleotide-DNA hybridization technique to detect Actinomyces spp. and, used this method to detect these organisms in samples directly obtained from infected root canals. METHODS: A total of 32 samples from 28 Chinese patients, with primary root canal infections, aseptically exposed at the first patient visit, were studied. Whole bacterial genomic DNA was isolated directly from paper point samples. The variable regions of 16S ribosomal DNA of bacteria were amplified and labeled with digoxigenin for further hybridization and detection. A total of seven oligonucleotide probes specific for A. bovis, A. gerencseriae, A. israelii, A. meyeri, catalase-negative A. naeslundii (genospecies 1 and 2), catalase-positive A. naeslundii genospecies 2 and A. odontolyticus were used. RESULTS: 16 of the 32 teeth were infected with one or more Actinomyces species. The prevalence rates of the examined species were: A. odontolyticus 31.3%, A. meyeri 9.4%, A. naeslundii 9.4%, A. israelii 6.3% and A. gerencseriae 3.1%; no A. bovis was detected in any of the canals. Furthermore, A. odontolyticus was isolated more frequently from root canals with caries or a history of caries (Fisher's exact test: P=0.0496; Odds ratio=9.00, 95% confidence interval: 0.97-83.63), and A. naeslundii was significantly associated with traumatized teeth (Fisher's exact test: P=0.0121; Odds ratio=57.00, 95% confidence interval: 2.10-1546.90). However, no significant correlation was found between Actinomyces spp. and clinical symptoms and signs, such as pain, swelling, percussion to tenderness, sinus and periapical radiolucency. CONCLUSION: Actinomyces spp. may be important pathogens of root canal infections. A. naeslundii in particular may be related with traumatized teeth. A. odontolyticus appears to be involved in infections related to caries, exposure of dentinal tubules during cavity preparation and/or leaking restoration, but further clarification with large samples is necessary.