A microbiological study in relation to the presence of caries and calculus

Microbial Relationship of Carious Deciduous Molars and Adjacent First Permanent Molars

(1) Epidemiological studies have shown that deciduous molar caries are related to and more severe than permanent molar caries. This study aimed to investigate whether caries subtypes in deciduous molars were associated with caries in first permanent molars and to explore taxonomic and functional profiles of the microbiota involved in different subtypes. (2) 42 mixed-dentition children were recruited and were divided into DMC (carious deciduous molars but caries-free first permanent molars; n = 14), C (carious deciduous and first permanent molars; n = 13), and control (n = 15) groups. Metagenomic sequencing was performed for supragingival plaque samples obtained separately from deciduous and first permanent molars. (3) The microbiota of deciduous molars in the DMC and C groups differed not only in species-based beta diversity but also in compositional and functional profiles. In the C group-like subtype, 14 caries-related species and potential pathways were identified that could be responsible for the caries relationship between the deciduous and permanent molars. In the DMC group-like subtype, the overall functional structure, the levels of Leptotrichia wadei, Streptococcus anginosus, and Stomatobaculum longum and KOs in sugar transporters and fermentation, quorum sensing, and TCA cycle in their first permanent molars surprisingly resembled those of the C group rather than the control group. This suggested that these clinically sound first permanent molars were at a greater risk for caries. (4) Classification of deciduous molar caries according to the microbiota could serve as a caries risk predictor for adjacent first permanent molars.

A laboratory study to assess the formation of effluent volatile compounds and disinfection by-products during chemomechanical preparation of infected root canals and application of activated carbon for their removal

AIM

To assess in a laboratory setting using extracted teeth the formation of volatile compounds (VOCs) and disinfection by-products (DBPs) in effluent aliquots, during chemomechanical preparation of artificially infected root canal specimens, and determine the role of silver-impregnated activated carbon (Ag-AC) in their removal.

METHODOLOGY

Single-rooted human teeth were decoronated to obtain 15 mm-long root specimens and a nutrient-stressed multispecies biofilm was grown in the root canals. Specimens were randomly assigned into three groups [Group 1; instrumentation with rotary files and irrigation with sterile saline, Groups 2 and 3; instrumentation with rotary files and irrigation with 2.5% NaOCl and 17% EDTA]. A portable medical suction device was used to collect the effluent aliquots during root canal irrigation. In Groups 1 and 2, the reaction products of the collected effluents were analysed by selected ion flow tube mass spectrometry (SIFT-MS). The effluents from Group 3 were treated with Ag-AC prior to SIFT-MS analysis, to assess the removal capacity of Ag-AC against the reaction products. The synthesis of Ag-AC was characterized with scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). Two-way analysis of variance (anova) with post hoc Tukey tests was used for data analysis and determination of a significant difference (P < 0.05).

RESULTS

In Group 1, effluent VOCs and DBPs were detectable at very low levels. In Group 2, the collected effluent aliquots released high concentrations of methanol, propanol, ammonia, chloroform and formaldehyde, which were significantly greater compared to Group 1 (P < 0.001). SEM/EDS analysis confirmed impregnation of Ag within the AC matrix. The treatment of effluent aliquots with Ag-AC (Group 3) resulted in a significant reduction in concentrations of acetone, acetic acid, propanol, acetaldehyde, acetonitrile and chloroform, compared to Group 2 (P < 0.001). The concentration levels of ethanol, methanol, ammonia and formaldehyde remained unaffected (P > 0.05).

CONCLUSIONS

In this laboratory setting using extracted human teeth, the chemomechanical preparation of artificially infected root canals resulted in the formation of toxic VOCs and DBPs as effluent suspensions. Their release during aspiration with dental suction indicates that potential environmental hazards should be investigated. The use of silver-impregnated activated carbon had potential for the point-of-use treatment of post-irrigation effluent aliquots.

Antimicrobial Effectiveness of Calcium Silicate Sealers against a Nutrient-Stressed Multispecies Biofilm

Purpose: This study compared the antimicrobial efficacy of calcium silicate sealers (BioRoot RCS and Total Fill BC) and conventional sealers (AH Plus and Tubli-seal) against planktonic bacteria and a nutrient-stressed multispecies biofilm. Methods: Antimicrobial properties of freshly mixed sealers were investigated using the direct contact test (DCT) and a nutrient-stressed multispecies biofilm comprised of five endodontic strains. Antimicrobial activity was determined using quantitative viable counts and confocal laser scanning microscopy (CLSM) analysis with live/dead staining. The pH of the sealers was analysed over a period of 28 days in Hanks Balanced Salt Solution (HBSS). Analysis of variance (ANOVA) with Tukey tests and the Kruskal–Wallis test were used for data analysis with a significance of 5%. Results: All endodontic sealers exhibited significant antimicrobial activity against planktonic bacteria (p < 0.05). BioRoot RCS caused a significant reduction in viable counts of the biofilms compared to AH Plus and the control (p < 0.05), while no significant difference could be observed compared to TotalFill BC and Tubli-seal (p > 0.05). CLSM analysis showed that BioRoot RCS and TotalFill BC exhibited significant biofilm inhibition compared to Tubli-seal, AH Plus and the control (p < 0.05). BioRoot RCS presented with the highest microbial killing, followed by TotalFill BC and Tubli-seal. Alkalizing activity was seen from the onset by BioRoot RCS, TotalFill BC and AH Plus. After 28 days, BioRoot RCS demonstrated the highest pH in HBSS (pH > 12). Conclusions: Calcium silicate sealers exhibited effective antimicrobial properties. This was demonstrated by superior biofilm inhibition capacity and microbial killing, with strong alkalizing activity compared to epoxy-based and zinc oxide-eugenol-based sealers.

Analysis of Predisposing Factors for Rapid Dental Calculus Formation

Background: Calculus accumulation varies widely between individuals. Dental calculus has been associated with the principal periodontal diseases. The aim of this study was to analyze individual characteristics, and salivary and microbiological parameters among patients considered to be rapid calculus formers and patients who form calculus slowly. Methods: Individual characteristics were recorded in a sample of 74 patients (age, sex, smoking, periodontal diagnosis, and dental crowding), as well as salivary parameters (unstimulated saliva flow, pH, and biochemical analysis of saliva) and microbiological parameters (by means of semi-quantitative polymerase chain reaction (PCR) analysis). Results: A statistically significant association (p = 0.002) was found between the rate of calculus formation and the diagnosis of periodontal disease. A greater presence of dental crowding was observed among the group of rapid calculus formers. Urea and phosphorus levels were higher among rapid calculus formers. Regarding microbiological parameters, differences were found in Streptococcus mutans, this being higher in the group of slow formers. Conclusions: Rapid calculus formation appears to be linked to patients diagnosed with more severe periodontal diseases. Rapid calculus-forming patients present more dental crowding and a lower proportion of S. mutans.

Evaluation of Cadmium Levels in Dental Calculus of Male Oral SCC Patients with Betel-Quid Chewing in Hunan Province of China

Cadmium (Cd) is a widespread trace toxic heavy metal with long biological half-life and may induce higher risk of cancer on multiple organs of human body. Recent studies have confirmed that dental calculus has enormous potential for investigation of exposure to Cd in the human mouth by acting as a time capsule. We aimed to examine relationship between Cd levels in dental calculus due to betel-quid chewing and risk of oral cancer. This study included 85 male oral squamous cell carcinoma (SCC) cases with betel-quid chewing and smoking as observation subjects (group A) and 67 healthy people with smoking but without betel-quid chewing as control subjects (group B) in Hunan province of Mainland China. Cd levels in calcified dental calculus samples from all participants were measured by inductively coupled plasma mass spectrometry (ICP-MS). The results of this study indicated that cadmium levels in dental calculus were significantly higher in male oral SCC patients with betel-quid chewing and smoking than that in healthy individuals without habit of betel-quid chewing and with smoking (p < 0.0001). This study gives some evidence to support that there may be a positive relationship between cadmium in dental calculus due to betel-quid chewing and risk of oral SCC.

The synthesis of nano silver-graphene oxide system and its efficacy against endodontic biofilms using a novel tooth model

OBJECTIVE

The deleterious caustic effects of sodium hypochlorite (NaOCl) as a root canal irrigant makes it imperative that alternative methods are developed for root canal disinfection. The purpose of this study was to examine the antimicrobial efficacy of silver nanoparticles (AgNPs) synthesized on an aqueous graphene oxide (GO) matrix (Ag-GO), with different irrigant delivery methods to enhance the disinfection regimen, using a novel ex vivo infected tooth model.

METHODS

AgNPs were prepared by reducing AgNO₃ with 0.01M NaBH₄ in presence of GO. Elemental analysis was performed with scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) and scanning transmission electron microscopy (STEM) was used for size and morphology analysis of GO and Ag-GO. Nutrient stressed, multi-species biofilms were grown in prepared root canals of single-rooted teeth. The irrigants used were sterile saline, 1% and 2.5% NaOCl, 2% chlorhexidine gluconate (CHX), 17% EDTA and an aqueous suspension of 0.25% Ag-GO. The antimicrobial efficacy of the irrigants were performed with paper point sampling and measurement of microbial counts. The biofilm disruption in dentine tubule surfaces was analysed with confocal laser scanning microscopy (CLSM). The acquisition of total biovolume (μm³/μm²) and biofilm viability was performed using software BioImage_L. Two-way analysis of variance (ANOVA) with post hoc Tukey tests was used for data analysis with level of statistical significance set at P<0.05.

RESULTS

SEM/EDS analysis confirmed impregnation of Ag within the GO matrix. TEM images showed polygonal GO sheets and spherical AgNPs of diameter 20-50nm, forming a network on the surface of GO sheets. The use of ultrasonic activation enhanced the efficacy of Ag-GO compared to 1% NaOCl, 2% CHX, 17% EDTA and sterile saline (P<0.05). The microbial killing efficacy of 2.5% NaOCl was superior compared to the experimental groups. The maximum biofilm disruption, in dentine tubule surfaces, was achieved by 2.5% NaOCl, however Ag-GO caused a significant reduction of total biovolumes compared to the rest of the experimental groups (P<0.05%).

SIGNIFICANCE

The successful documentation of the microbial killing and biofilm disruption capacity of Ag-GO is a promising step forward to explore its unique properties in clinical applications and biomaterials in dentistry.

Presence of Helicobacter pylori and Campylobacter ureolyticus in the oral cavity of a Northern Thailand population that experiences stomach pain

Objective: To investigate oral diseases and microbiological conditions, such as the presence of ureolytic bacteria in dental plaque, in relation to experience of stomach pain in a remote adult Asian population. Methods: Ninety-three adults, 40-60-years old, from the Karen Hill tribe in Northern Thailand with no regular access to dental care were examined. Clinical registrations were performed and interproximal gingival plaque samples were collected and analyzed with the checkerboard (CKB) method for the presence of 14 oral bacterial species. Results: A number of 61 subjects reported daily stomach pain while 32 subjects had no symptoms from the stomach. The subjects with stomach pain had fewer remaining teeth (p < 0.05), higher caries experience (p < 0.05) and less BoP (p < 0.01). Most of the bacterial species were clustered statistically in three factors in a factor analysis, which together explained 65% of the microbiological variance. Factor 1, explaining 43.0% of the variance, was statistically associated with stomach pain (p < 0.001). Conclusions: The interproximal plaque/biofilm in adults of the study population showed a common presence of two gastrointestinal pathogens H. pylori and C. ureolyticus. The study also indicates for the first time a potential association between C. ureolyticus and stomach pain.

Bacteria community study of combined periodontal-endodontic lesions using denaturing gradient gel electrophoresis and sequencing analysis

BACKGROUND

The entire microbial population and predominant microflora of root canals (RCs) and adjacent periodontal pockets (PPs) from teeth with combined periodontal-endodontic lesions were determined and compared.

METHODS

Pooled RC and PP samples were collected from the molars of 20 patients diagnosed with combined periodontal-endodontic lesions. DNA was extracted for polymerase chain reaction-based denaturing gradient gel electrophoresis (PCR-DGGE), cloning, and sequence analysis. A coefficient of similarity (Cs) was used to determine the similarity of the bacterial profiles from RCs and PPs.

RESULTS

Significantly fewer bands were produced by PCR-DGGE from RCs (5.9 ± 1.7) than from PPs (8.0 ± 1.8) (P <0.001). The average Cs of the RC and PP samples was 93.81% ± 10.26%. Overall, 60 genera/species were identified by sequencing. Of these, the predominant genera in RCs were Porphyromonas sp. (13.9%), Filifactor sp. (12.5%), and Parvimonas sp. (11.1%), similar to the genera obtained from PP samples. In total, 43 genera/species were common to the RC and PP samples. The most prevalent bacteria in both the RC and PP samples were (in descending order) Filifactor alocis, Parvimonas micra, Porphyromonas gingivalis, and Tannerella forsythia.

CONCLUSIONS

The high similarity in the sets of organisms present in both RC and PP samples in this study suggests that the pocket could be a source of RC infection. The data also demonstrate that combined periodontal-endodontic lesions consist of a diverse and complex microbial community.

Supragingival plaque microbial analysis in reflection to caries experience

Background

Dental caries develops as a result of the metabolism of carbohydrates by cariogenic bacteria present in a complex biofilm. The present study aimed to examine if bacteria in pooled supragingival plaque samples quantified using a “checkerboard DNA-DNA hybridization” based panel of caries-related bacteria, could reflect the caries experience in a manner similar to saliva samples analysed using a chair-side method in a previous investigation.

Methods

A total of 86 mothers and their children aged 4–6 years and 12–16 years old participated. Caries experience (DMFT/dmft; Decayed, Missing and Filled Teeth for permanent and primary teeth) was registered clinically and radiographically. Caries was recorded at the D₃ level (caries into dentine). The D/d component was divided into three categories. A pooled supragingival plaque sample per participant was obtained from posterior approximal sites. Analyses of 15 bacterial species were performed using the checkerboard DNA-DNA hybridisation technique.

Results

No significant relationships were found between the bacterial scores and DMFT/dmft nor D/d groups.

Conclusions

Unlike the saliva samples and the chair-side method, interproximal pooled plaque samples analysed using the “checkerboard DNA-DNA hybridization technique” did not reveal any significant relations between the bacterial counts and the caries experience.

Filifactor alocis interactions with gingival epithelial cells

An association between the gram-positive anaerobe Filifactor alocis and periodontal disease has recently emerged; however, possible pathogenic mechanisms have not been investigated. In this study we examined the responses of primary cultures of gingival epithelial cells (GECs) to infection with F. alocis. Secretion of the pro-inflammatory cytokines interleukin-1β, interleukin-6 and tumor necrosis factor-α from GECs was stimulated by F. alocis infection. F. alocis also induced apoptosis in GECs through pathways that involved caspase-3 but not caspase-9. Apoptosis was coincident with inhibition of mitogen-activated protein kinase kinase (MEK) activation. These results show that F. alocis has characteristics in common with established periodontal pathogens and has the potential to contribute to periodontal tissue destruction.