The effect of root canal preparation tapers on planktonic bacteria and biofilm reduction in the apical third: A correlative microtomography and microbiological laboratory study

AIM

To evaluate the influence of different preparation tapers on the reduction in planktonic bacteria and biofilms of Enterococcus faecalis and Candida albicans in the apical third (4 mm) of the mesial roots of mandibular molars, correlating decontamination with canal shape.

METHODOLOGY

After microtomography analysis for morphological standardization of the canals, 48 mandibular molar roots, each containing two canals (96 canals), were contaminated with E. faecalis and C. albicans and divided into four groups (n = 11) for canal instrumentation using ProDesign Logic 2 files with different tapers G (.03): # 25.03; G (.04): # 25.04; G (.05): # 25.05; and G (.06): # 25.06 and irrigation with 2.5% sodium hypochlorite. Four roots were examined under a scanning electron microscope (SEM) to qualitatively assess biofilm formation. Eight roots were used as the negative control group (samples were not contaminated). Bacteriological samples were taken exclusively from the apical third of the roots before and after chemical-mechanical preparation and bacterial counts were determined (CFU/mL). The final micro-CT scan was used to quantify the volume variation and unprepared canal area in the apical third. Statistical analysis was performed using the Kruskal-Wallis, Student-Newman-Keuls and Wilcoxon tests for analysis of microbiological data. anova and the Tukey or Games-Howell test were used for analysis of micro-CT data and Spearman's test for correlations (α = 5%).

RESULTS

All groups showed a significant reduction in bacteria (p < .05), with no statistically significant difference between groups. There was no significant difference in per cent volume increase between groups. The unprepared area (Δ%) was affected by the file used (p = .026) and was significantly lower for G (.06) compared to G (.03). There was no statistically significant correlation among bacterial reduction, volume and unprepared area (p > .05).

CONCLUSION

The different preparation tapers influenced root canal shaping in the apical third but did not improve decontamination in this region.

Elimination of E. faecalis with NaOCl versus chlorhexidine gluconate from primary molar root canal systems: an ex vivo model study

OBJECTIVES

This ex vivo human study aimed to evaluate the efficacy of NaOCl and chlorhexidine gluconate (CHG) irrigations in eliminating Enterococcus faecalis from the RCS of primary molars.

MATERIALS AND METHODS

Disinfected extracted primary molars were inoculated with E. faecalis for 24 h. Then, the RCS samples were then irrigated with either 2.5% NaOCl, 0.2% and 2% CHG, or sham saline. The samples were collected immediately after irrigation; and 24 h later, the bacterial viability and counts were measured using blood agar and qRT-PCR, respectively. Histological sections were used to measure E. faecalis penetration and viability in dentin tubules using fluorescence microscopy.

RESULTS

The recovery of viable E. faecalis after the irrigation of the primary molars showed more significant bactericidal effects of NaOCl and 0.2% and 2% CHG than of saline. Immediately after the irrigation, the NaOCl group showed the greatest reduction in E. faecalis; and 24 h later, all the groups had lower viable E. faecalis than the saline control. The bacterial penetration was also lowest in the NaOCl group, although there was no difference in bacterial viability in the tubules between the groups.

CONCLUSION

In primary teeth, NaOCl and CHG showed similar degrees of bacterial elimination efficacy in terms of E.faecalis.

CLINICAL RELEVANCE

Within the limitations of this study, NaOCl and CHG have the similar ability to perform endodontic irrigation of primary ex vivo teeth regarding the elimination of E.faecalis, but NaOCl penetrates dentin tubules better.

Polyacrylic Acid with Methylene Blue Dye as a Sensitizing Agent for Photodynamic Therapy to Reduce Streptococcus mutans in Dentinal Caries

Objective: To evaluate 11.5% polyacrylic acid (PA) containing 0.3% methylene blue (MB) dye as a photosensitizer for photodynamic therapy (PDT) of carious dentin. Methods: One hundred twenty molars were selected and the dentin was exposed for cariogenic challenge, where the molars were placed in brain heart infusion medium containing a standard strain of Streptococcus mutans (ATCC). Samples were randomly divided into eight groups (n = 15): S: saline, PA, MB: MB 0.3%, PA+MB: PA containing 0.3% MB + LLL: irradiation with low-level laser, PDT (MB): MB 0.3% + laser, PDT (PA): PA + laser, and PDT (PA+MB): PA containing 0.3% MB + laser. Carious dentin was collected before and after exposure to S. mutans. All samples of carious dentin were homogenized, diluted, and seeded in mitis salivarius bacitracin medium, and the cultures were incubated at 37°C for 15 days in anaerobic jars. The Wilcoxon test was used for analysis. Results: The percent microbial reduction achieved with each treatment was as follows: PDT (MB), 53.62%; PDT (PA+MB), 50.47%; PDT (PA), 46.73%; PA, 38.51%; MB, 19.75%; PA+MB, 17.18%; LLL, 12.83%; S, 5.99%. The greatest reductions in S. mutans growth occurred with PDT (MB), PDT (PA+MB), and PDT (PA) when compared to the S group (p = 0.0002, 0.0023, and 0.0232, respectively). Conclusions: PA containing 0.3% MB can be used as a photosensitizer for PDT to reduce S. mutans burden in carious dentin.

[Effect of molar ligation and local Porphyromonas gingivalis inoculation on alveolar bone loss in the mouse]

OBJECTIVE

To compare the extent and time course of alveolar bone loss and osteoclast activation in two murine models of periodontal disease: molar ligation and Porphyromonas gingivalis (P. gingivalis) oral inoculation.

METHODS

A split-mouth design was applied to two groups of mice (C57BL6, 6-8 weeks old, n=24 in both groups), resulting in four treatment groups: (1) Control group: unligated upper right 2nd molars receiving CMC only, (2)Ligature group: ligation of a 9-0 suture around the upper left 2nd molar, (3) P. gingivalis group: unligated upper right 2nd molar receiving P. gingivalis challenge only, (4)Ligature+P.gingivalis group: ligation of the upper left 2nd molar in combination with oral inoculation with 109 colony-forming units(CFU) P. gingivalis. Alveolar bone loss was measured as the cementoenamel junction and alveolar bone crest (CEJ-ABC) distance. In the study, 48 C57BL6 mice were designed and treated as described above, and osteoclasts were counted on histological sections following tartrate-resistant acid phosphatase (TRAP) staining and counts were normalized to alveolar bone surface distance. Then 36 C57BL6 mice were investigated, of which 30 were ligated a 9-0 silk ligature around the 2nd molar in the left maxillary quadrant and 6 were not ligated. After ligation for 1 week, the ligatures in 12 mice were taken off for either 1 week or 2 weeks. The CEJ-ABC distance of the 6 mice without ligation was baseline. The CEJ-ABC distances were measured and analyzed. The data were analyzed with one-way ANOVA.

RESULTS

Molar ligation induced marked alveolar bone loss after 3, 6, 9 and 12 weeks [(0.16±0.04) mm, (0.16±0.02) mm, (0.18±0.03) mm, (0.17±0.02) mm], vs. corresponding controls [(0.09±0.03)mm,(0.10±0.01)mm,(0.12±0.04)mm,(0.12±0.01)mm] and P. gingivalis group [(0.09±0.03)mm, (0.12±0.01)mm,(0.12±0.02)mm,(0.10±0.01)mm], P<0.05. Combined treatment with molar ligation and P. gingivalis did not further increase the CEJ-ABC distance. Evidence for osteoclast activation was found one day after molar ligation, and TRAP-positive cell numbers peaked on day 3 (12±4 vs. control 2±2, P<0.01). After taking off ligature following ligation for 2 weeks, it showed significantly regrowth of alveolar bone compared with that before removal of the ligature on day 7 [(0.07±0.02)mm vs. (0.13±0.01)mm, P<0.01].

CONCLUSION

Molar ligation is a rapid and effective way to induce periodontal bone loss in mice. Osteoclast activation occurs within 24 hours of ligature placement, and the extent of bone loss well exceeds that of the P.gingivalis-induced bone loss. Removing ligature after periodontal disease might help bone regeneration by regrowth of the alveolar bone.

[Observation of oral Streptococcus oligofermentans colonization in rats]

OBJECTIVE

To study the colonization ability of Streptococcus oligofermentans (S. oligofermentan) in the condition of high sucrose in oral cavity of rats.

METHODS

In this study, 48 SPF-SD rats aged 21 days were selected. From 24th to 27th days, the rats were fed with water of antibiotic and fed with high glucose diet continuously. On the 28th day, the rats were divided into four groups randomly, 12 rats per group. From the 28th day to 30th day, the first group (SM group) was inoculated with S. mutans, the second group (SO group) with S. oligofermentan, the third group (SO+SM group) with mixture of S. mutans and S. oligofermentan, the control group not with any bacteria. On the next day and the 10th day after inoculation of bacteria, the samples of dental plaque of the rats were acquired by scrubbing occlusal, buccal and lingual surfaces of bilateral mandibular molars with sterile swabs. The samples of SM group were inoculated on MSB and BHIS, of SO group on MSAE, of SO+SM group on MSB, MSAE and BHIS,of the control group on MSB and MSAE. S. mutans were screened and calculated on MSB, the suspected colonies of S. oligofermentan were screened and identified by the analysis of 16S rDNA.

RESULTS

On the next day, the detection rate of S. oligofermentan was 33.3% (4/12) in the group of SO; in the group of SO+SM, the detection rate of S. oligofermentan was 0, the detection rate of S. mutans 100.00%, and the proportion of S. mutans 14.70%±4.53%; in the group of SM, the detection rate of S. mutans was 100.00%, the proportion of S. mutans 12.42%±4.27%. On the 10th day, in the group of SO, the detection rate of S. oligofermentan was 0; in the group of SO+SM, the detection rate of S. oligofermentan was 0, the detection rate of S. mutans 100.00%, and the proportion of S. mutans 15.78%±5.10%; in the group of SM, the detection rate of S. mutans was 100.00%,and the proportion of S. mutans 17.08%±5.75%.

CONCLUSION

In the condition of the experiment where high glucose was maintained in the oral cavity in rats, S. oligofermentan appeared transiently and couldn't colonize in the rats.

Assessment of Periodontopathogens in Subgingival Biofilm of Banded and Bonded Molars in Early Phase of Fixed Orthodontic Treatment

To assess the prevalence and occurrence of eleven periodontopathogens in subgingival biofilm of banded and bonded molars during the first period of fixed orthodontic treatment. Subjects were selected from patients referred to orthodontic treatment and were divided in two groups: group A comprised fifteen patients (14.4±2.45 years of age) who received orthodontic bands on first permanent molars and group B of ten patients (15.7±1.87 years of age) with directly bonded tubes on the labial surface of the same teeth. Subgingival sample collection was performed before bands and tubes application and 4-7 weeks after attachment placement. DNA-strip tehnique was used to assess the presence of eleven putative periodontopathogens at each time point. Fusobacterium nucleatum, Eikenella corrodens and Capnocytophaga spp. were found in a large number of samples, other periodontopathogens were present in a smaller rate. The 4-7 weeks after attachment placement a slight increase of putative species was observed in both groups. The presence of orthodontic tubes and bands influence the accumulation and composition of subgingival microbiota. Higher level of oral hygiene should be achieved before and during orthodontic treatment in order to prevent any side effects on periodontal tissues.

Supragingival Microbial Profiles of Permanent and Deciduous Teeth in Children with Mixed Dentition

Objectives

The present study was designed to investigate the microbial profiles of teeth in different locations in mixed-dentition-stage children, and to compare the microbiomes of permanent and deciduous teeth in the same healthy oral cavity.

Methods

Supragingival plaque samples of teeth in various locations—the first permanent molars, deciduous molars, deciduous canines and incisors and permanent incisors—were collected from 20 healthy mixed-dentition-stage children with 10–12 permanent teeth erupted. Plaque DNA was extracted, and the V3–V4 hypervariable region of the bacterial 16S rRNA gene was amplified and subjected to sequencing.

Results

On average, 18,051 high-quality sequences per sample were generated. Permanent tooth sites tended to host more diverse bacterial communities than those of deciduous tooth sites. A total of 12 phyla, 21 classes, 38 orders, 66 families, 74 genera were detected ultimately. Five predominant phyla (Proteobacteria, Firmicutes, Bacteroidetes, Fusobacteria and Actinobacteria) were highly variable among sites. Of 26 genera with a mean relative abundance of >0.1%, 16 showed significant differences in relative abundance among the groups. More than 20% of the total operational taxonomical units were detected only in permanent or deciduous teeth. The variation in the microbial community composition was due mainly to permanent teeth being enriched in Actinomyces and deciduous teeth in Treponema. The core microbiome of supragingival plaque in mixed dentition comprised 19 genera with complex correlationships.

Conclusion

Our results suggest differences in microbial diversity and composition between permanent and deciduous teeth sites in mixed dentition. Moreover, the core microbiome of these sites was determined. These findings enhance our understanding of the development of the native oral microbiota with age.

The effect of a chlorhexidine-fluoride varnish on mutans streptococci counts and laser fluorescence readings in occlusal fissures of permanent teeth: A split-mouth study

OBJECTIVE

To evaluate the effect of a new chlorhexidine-fluoride varnish on mutans streptococci (MS) counts and laser fluorescence (LF) readings in fissures of permanent molars.

METHOD AND MATERIALS

The study group consisted of 57 healthy schoolchildren (7 to 14 yrs) that volunteered after informed consent. A double-blind split-mouth design was employed and 87 pairs of non-cavitated permanent molars were randomly assigned to treatments with either chlorhexidine-fluoride varnish (CHX-F) or chlorhexidine-thymol varnish (CHX-T, Cervitec Plus) as active control. The varnishes were topically applied at baseline and every sixth week throughout the 24-week study period. Endpoints were MS counts (CRT test) and occlusal LF readings (DIAGNOdent pen) registered regularly during follow-up.

RESULTS

At baseline, > 50% of the occlusal fissures harbored high MS counts (≥ 105 CFU), but a significant decrease (P < .05) was found after treatment with both varnishes. After 24 weeks, less than 5% exhibited high counts. There were no significant differences between the varnishes at any time point. The mean LF values were similar in both treatment groups at baseline, but a significant reduction (P < .05) was scored in the CHX-F group after 12 and 24 weeks. A similar reduction was found also in the CHX-T group after 24 weeks. No adverse events were reported.

CONCLUSION

There were no significant differences between the CHX-F and CHX-T varnishes in terms of MS suppression after four applications over 24 weeks. Both varnishes also reduced the LF readings significantly compared with baseline, but further long-term studies are needed to confirm a caries-preventive effect.

Correlation Between Bacterial Endotoxin Levels in Root Canals of Primary Teeth and the Periapical Lesion Area

PURPOSE

The purposes of this study were (1) to assess the endotoxin levels in root canals of primary teeth with necrotic pulps and periapical lesions; and (2) to evaluate the correlation of endotoxin levels with the periapical lesion size.

METHODS

Twenty primary molars with necrotic pulps and periapical lesions were selected. Standardized radiographs were obtained and the lesions were measured. Material from each root canal was collected to quantify the bacterial endotoxin. The results were analyzed using Pearson's correlation, student's t test, and Fisher's exact test (α equals five percent).

RESULTS

The initial amount of bacterial endotoxin in the root canals ranged from 0.089 to greater than 50.00 endotoxin units (EU)/mL and was detected in 100 percent of the samples. A positive but not significant correlation was observed between the amount of endotoxin and periapical lesion size in primary molars.

CONCLUSION

Endotoxin was observed in 100 percent of root canals of primary teeth with a periapical lesion. However, there was no statistical significance between bacterial endotoxin levels and the periapical lesion area.

Probiotics and their effect on oral bacteria count in children: a pilot study

AIM

To assess the effect of the daily ingestion of a mixture of probiotics on the amount of Streptococcus mutans in the oral cavity of preschool-age patients with a high risk of caries.

MATERIALS AND METHODS

Forty patients, aged between 4 and 6 years, with a high risk of dental caries were included in this pilot study. Patients were randomly assigned to two study groups: the Experimental Group (A) included patients who brushed their teeth and used fluoridated toothpaste in addition to consuming probiotics daily, and the Control Group (B) inclused patients who brushed their teeth and used fluoridated toothpaste but did not consume probiotics. Using the CariScreen, the microorganism count was determined at different times: baseline, 7, 14, 21 and 30 days. To identify the differences between both groups, a Mann-Whitney U test was performed, with a significance level of 0.05.

RESULTS

It was observed that both groups showed similar microbial counts at the beginning of the trial (p>0.05), and a significant decrease in the count at the end of the study was found in the experimental group (p<0.05) 15 days after suspending ingestion.

CONCLUSION

We found a significant reduction of RLU values in preschool children who ingested the tested probiotics in relation to the baseline values and 15 days after ceasing consumption.

The Incidence of Furcation Region Patency in Molars Before and After Simulated Periodontal Therapy

PURPOSE

To determine if there is increased bacterial communication through the furcation region in molar teeth after simulated periodontal therapy.

METHODS

Sixty-five extracted first and second molars were accessed and the roots were sectioned 4 mm apical to the furcation. The canals and external suface of the root were sealed except the furcation region. In Phase I, the teeth were sterilized and then suspended in Rogosa SL broth. A broth containing Lactobacillus casei was placed in the pulp chamber. The Rogosa SL broth in the bottom chamber was monitored daily for 30 days for turbidity, and once turbidly was noted, the broth was plated to confirm the presence of L. casei. In Phase II, the furcation regions were scaled and cementum removed, the teeth were sterilized, and the microbial leakage was repeated.

RESULTS

The Phase I and Phase II median times to turbidity were 9.5 days and 4 days, respectively, and the difference was statistically significant (p = 0.0035). Phase I turbidity rate was 86.5%, and Phase II was 92.3%, which was not statistically significant (p = 0.25).

CONCLUSIONS

The root canal system communicated with the furcation region an average of 86.5% and 92.5% after scaling and root planing during the 30 days of the experiment. The time of leakage between the two groups decreased from 9.5 to 4 days (p = 0.0035).

CLINICAL SIGNIFICANCE

Periodontal instrumentation of the furcation region in molar teeth can increase the risk of bacterial contamination by 39% while shortening the time for bacterial penetration in teeth with exposed dentin or furcation canals. accessory canals, scaling, and root planing.

Bacterial removal promoted by 2 single-file systems: Wave One and One Shape

INTRODUCTION

Different single-file systems are available for endodontic treatment; however, comparative studies are scarce. Thus, the present study evaluated bacterial reduction promoted by 2 single-file systems: Wave One (Dentsply Maillefer, Ballaigues, Switzerland) and One Shape (Micromega, Besancon, France).

METHODS

Forty-five distobuccal root canals of upper molars sterilized with ethylene oxide were infected with Enterococcus faecalis for 21 days, and then root canal initial bacterial sample was collected with paper cones and plated on M-enterococcus agar. The specimens were randomly divided into 3 groups according to instrumentation (n = 15): Wave One, One Shape, and the crown-down manual technique (control group). The other 6 specimens without contamination were control asepsis. After instrumentation, samples were collected with the use of scraping and paper cones. The bacterial reduction was calculated, and then intragroup analysis was performed using the paired t test and intergroup analysis using analysis of variance (both at 5% significance).

RESULTS

All techniques significantly reduced the number of bacteria in the root canal (P < .05), with no significant difference between them (P > .05). The aseptic control group did not show any bacterial growth.

CONCLUSIONS

It can be concluded that the single-file systems Wave One and One Shape significantly reduce the bacterial number in the root canal and that there is no significant difference in their bacterial reduction abilities.

Incomplete caries removal and indirect pulp capping in primary molars: a randomized controlled trial

PURPOSE

To compare the effect of incomplete caries removal (ICR) and indirect pulp capping (IPC) with calcium hydroxide (CH) or an inert material (wax) on color, consistency and contamination of the remaining dentin of primary molars.

METHODS

This double-blind, parallel-design, randomized controlled trial included 30 children presenting one primary molar with deep caries lesion. Children were randomly assigned after ICR to receive IPC with CH or wax. All teeth were then restored with resin composite. Baseline dentin color and consistency were evaluated after ICR, and dentin samples were collected for contamination analyses using scanning electron microscopy. After 3 months, restorations were removed and the three parameters were re-evaluated. In both groups, dentin became significantly darker after 3 months.

RESULTS

No cases of yellow dentin were observed after 3 months with CH compared to 33.3% of the wax cases (P < 0.05). A statistically significant difference over time was observed only for CH regarding consistency. CH stimulated a dentin hardening process in a statistically higher number of cases than wax (86.7% vs. 33.3%; P = 0.008). Contamination changed significantly over time in CH and wax without significant difference between groups. It was concluded that CH and wax arrested the carious process of the remaining carious dentin after indirect pulp capping, but CH showed superior dentin color and consistency after 3 months.

The efficacy of gaseous ozone on some cariogenic bacteria

The aim of this study is to analyze ozone impact on some cariogenic bacteria in ex vivo and in vitro conditions. The in vitro part of study inoculated dentine with strains of Streptococcus mutans ATCC 33402 and Lactobacillus paracasei ATCC 11974 bacteria. Samples of dentine before and after 40s ozone treatment were collected and anaerobically incubated. Samples of cariogenic dentine (N = 24) were collected from permanent molars within the ex vivo segment of the study, prior and after 40s ozone treatment and a number of colonies were counted after incubation. For the in vitro part of study, results have shown a statistically significant average value of reduction of Streptococcus mutans ATCC 33402 and Lactobacillus paracasei ATCC 11974 prior and after ozone treatment (p < 0.001). The ex vivo segment of the study has also demonstrated a statistically significant difference in the number of bacteria prior and after ozone implementation (p < 0.001). Gaseous ozone demonstrated a strong antimicrobial effect on cariogenic bacteria in both in vitro and ex vivo conditions and it can be used as an adjuvant in caries therapy.

Microbiologic findings 1 year after partial- and full-mouth scaling in the treatment of moderate chronic periodontitis

OBJECTIVE

To investigate the impact on microbiologic variables of full-mouth scaling (FMS) and conventional scaling and root planing (cSRP) after 12 months.

METHOD AND MATERIALS

In a prospective randomized controlled clinical study, 37 volunteers with moderate chronic periodontitis were treated by FMS or by cSRP in two sessions at 4-week intervals. Clinical attachment level, probing depth, and bleeding on probing were recorded at baseline as well as at 6 and 12 months. Four subgingival plaque samples were taken from the deepest sites in premolars and molars at baseline and after 12 months. Pooled sample analysis was performed using real-time polymerase chain reaction for the identification of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola.

RESULTS

At baseline, the bacterial load of A actinomycetemcomitans was significantly higher in the cSRP group compared to the FMS group (P = .042). In the cSRP group, this load decreased significantly (P = .011), leading to similar quantities of A actinomycetemcomitans in both groups. Further, significant reductions in frequency were found in the FMS group for T forsythia and P gingivalis and in the cSRP group for A actinomycetemcomitans and T denticola.

CONCLUSION

The data suggest that both therapy modalities lead to similar effects on target periodontal pathogen species. FMS compared to cSRP was not favorable in reduction of periodontopathogens.

[Colonization of Tannerella forsythus and Prevotella intermedia in dental plaque samples from children of Changchun Ziqiang primary school]

OBJECTIVE

To detect the presence of Tannerella forsythus (Tf) and Prevotella intermedia (Pi) using polymerase chain reaction (PCR) in the oral plaque samples from children and investigate the relationship between bacteria and clinical parameters.

METHODS

A total of 151 children aged 7 to 12 years were selected from Changchun primary school. The supragingival plaque sample was collected from the mesiobuccal and labial surfaces of the right maxillary central incisor (FDI1) and the right maxillary first molar (FDI6). Extracted DNA from plaque samples was used for PCR analysis. Intraoral examination, probing depth (PD) and bleeding on probing (BOP) were performed and recorded.

RESULTS

The detection rate for Tf was 40.3% (118/293) and Pi was 46.4% (136/293) in supragingival plaque. The detection rates for Tf and Pi in molars were much higher than those in incisors (P < 0.01). The detection rate of Tf and Pi was positively related to BOP+ and PD. The detection rate for Pi decreased gradually with age, and the detection rate for Tf was highest in the group aged 7 to 8 and the detection rates for Tf and Pi were higher in the gingiva with BOP+ than that with BOP- (P > 0.05). The detection rates for Tf increased remarkably with BOP+ and especially when PD was greater than 4 mm.

CONCLUSIONS

Detection rates of putative periodontal pathogens from healthy children of 7 to 12 years of age were high. The detection rates for Tf and Pi in molars were much higher than those in incisors, and the presence of Tf and Pi in supragingival plaque was related to periodontal parameters.

Prevalence of sealants in relation to dental caries on the permanent molars of 12 and 15-year-old Greek adolescents. A national pathfinder survey

BACKGROUND

The use of sealants as an effective measure for the prevention of pit and fissure caries in children has been well documented by several studies; either they are used on an individual or on a public health basis. In order to plan and establish a national preventive program with sealants in a community, it is mandatory to know the epidemiological pattern of caries along with other variables influencing their use and effectiveness.

AIMS

To assess the utilization and distribution pattern of pit and fissure sealants on the first and second permanent molars of Greek adolescents and to evaluate whether the existing usage of sealants and some socio-demographic factors are correlated to caries prevalence on the population examined

METHODS

A stratified cluster sample of 2481 Greek adolescents was selected according to WHO guidelines (1224 twelve and 1,257 fifteen-year-old), living in urban and rural areas in 11 districts within the country. Five calibrated examiners carried out clinical examinations, recording caries experience at the dentine threshold (BASCD criteria) and presence or absence of sealants along with Socio-demographic indicators associated with oral health. Mann Whitney and Pearson's chi-square non parametric tests were utilized for assessing the data. The level of significance was p < 0.05.

RESULTS

Sealants utilization varied considerably within the different districts, with 8,3% of the 12 and 8,0% of the 15-year-old adolescents having at least one sealed molar. Sealants reduced DMFS scores by 11% in the 12-year-olds and by 24% in the 15-year-olds, while 15-year-old adolescents from rural areas had a statistically significant (p = 0.002) less chance of having sealants (71%) compared to children from urban areas. Girls had higher chance to receive sealants in both age groups (26% for the 12 and 19% for the 15-year-old) as well as patients that visited the dentist for prevention compared to those visiting the dentist because they thought they needed a restoration or because they were in pain.

CONCLUSIONS

The finding that sealants reduced DMFS scores despite their very low utilization, along with the high prevalence of dental caries found on the occlusal surfaces of the posterior teeth of Greek adolescents, is calling for a national preventive program with sealants which could eliminate caries to a larger extent.

Molar incisor hypomineralization. Morphological and chemical aspects, onset and possible etiological factors

OVERALL AIM: The general objective of this thesis was to enhance the understanding of Molar Incisor Hypomineralization (MIH) in areas of the histological, chemical and mechanical properties of the hypomineralized enamel, objective and subjective clinical symptoms in relation to bacteria findings. Further, to estimate a time for onset of the disturbance and investigate possible etiological factors.

MATERIAL & METHODS

22 teeth diagnosed with MIH were used in the histological and chemical studies. A number of analytical methods were used; Light microscopy, Polarized light microscopy, Scanning electron microscopy, X-ray microanalysis, Vickers hardness test and X-ray Micro Computed Tomography. Decalcified sections were stained with bacterial staining. An ozone device was tested for the ability to kill strains of oral bacteria. In collaboration with the prospective ABIS study, 17.000 individuals were examined and possible etiological causes of severe demarcated opacities were tested.

RESULTS & CONCLUSIONS

The hypomineralized enamel was mainly located in the buccal enamel of the teeth and had a high degree of porosity extending from enamel-dentin-junction with a distinct border to the normal cervical enamel. Teeth diagnosed MIH had lower hardness values in hypomineralized enamel and differences in the chemical composition. Bacteria were observed in the enamel and deep into the dentin. Ozone treatment for 20 seconds or more was effective to kill oral microorganisms. Significant relations were found between MIH in first molars and breast feeding more than 6 months, late introduction to gruel and infant formula (later than 6 months). The onset for the hypomineralized enamel was estimated to around 200 days from start of the enamel mineralization.

A microbiological assessment of polymer and conventional carbide burs in caries removal

PURPOSE

The purpose of this study was to compare the caries removal efficiency of polymer burs (Smartburs) and conventional carbide burs microbiologically.

METHODS

Twenty-four patients participated, each presenting 2 active carious lesions on the occlusal surfaces of primary molars. Sample-taking and caries-removal were done in the following order: (1) first sample (from the carious dentin); (2) caries removal (with a Smartbur or carbide bur); and (3) second sample (from the caries-free dentin), respectively. The samples were processed in a laboratory and spread on various media. The colonies on the agar plates were counted, and then numbers of CFU/ml were calculated.

RESULTS

There were no statistically significant differences between the numbers of CFU/ml in the carious dentin before preparation, comparing the Smartbur group and carbide bur group for all the media used (P>.05). There were statistically significant differences in the numbers of CFU/ml before and after preparation comparing both types of burs for all the media used (P<.05). There were no statistically significant differences in the reductions of the numbers of CFU/ml, comparing the 2 preparation instruments (P>.05).

CONCLUSION

The polymer burs were found as effective as the conventional carbide burs microbiologically in caries removal.

Etiopathogenesis of mandibulofacial and maxillofacial abscesses in mice

The etiologic agent of mandibulofacial and maxillofacial abscesses in mice is reportedly coagulase-positive Staphylococcus aureus. Although suggested to be through the oral cavity, the exact route of entry has not been documented. Among the clinical cases of mandibulofacial and maxillofacial abscess we report here, each case that was cultured yielded coagulase-positive S. aureus. Histologically, all of the abscesses examined were directly associated with intralesional hair shafts, both vibrissae and pelage, that were introduced into the submucosa via the maxillary or mandibular molar gingival sulci. Grossly, a variable amount of hair was imbedded in the lingual, buccal, or mesial gingival sulci of the maxillary or mandibular molars or both. Computed tomography revealed that the presence of the hair resulted in inflammation and resorption of alveolar bone. With these findings, we propose that mandibulofacial and maxillofacial abscesses are induced by the mastication and fragmentation of hair ingested during the barbering process. From the resulting foreign body periodontitis, abscess formation originates at the maxillary lingual, buccal, or mesial gingival sulci, resulting in infection of the maxillary molar tooth roots with swelling or rupture through the skin inferior to the eye, or at the mandibular lingual, buccal, and or mesial gingival sulci, resulting in infection of the mandibular molar tooth roots and osteomyelitis with drainage through the skin of the ventral mandible.

A histologic investigation of direct pulp capping in rodents with dentin adhesives and calcium hydroxide

OBJECTIVE

To investigate reactions of pulp tissue when in contact with the dentin adhesives Resulcin AquaPrime + MonoBond (RAPMB, Merz Dental), Scotchbond 1 (SB1, 3M ESPE), and Gluma Comfort Bond (GCB, Heraeus Kulzer) in comparison with calcium hydroxide after 1 to 70 days.

METHOD AND MATERIALS

An occlusal cavity was prepared in 152 molars of 76 Wistar rats. The pulps were exposed and dentin adhesives placed on the pulp tissue of 10 molars for each dentin adhesive group and time period. Eight molars per time period served as controls and were capped with calcium hydroxide. All cavities were restored with composite resin. The animals were sacrificed 1, 3, 7, and 70 days after pulp capping. Pulp tissue was histologically evaluated for the following criteria: bacterial infection, inflammatory cells, necrosis, and reparative dentin. The data were statistically evaluated using the Kruskal-Wallis test (P < .05).

RESULTS

Overall, significantly more bacterial infections were detected 1, 3, 7, and 70 days after pulp capping with dentin adhesive (P < .05). In all dentin adhesive groups, 1 day after direct pulp capping, significantly more inflammatory cells were found, whereas after 7 days, this was only the case for the SB1 group (P < .05). After 70 days, capping with calcium hydroxide resulted in significantly less necrosis than with RAPMB and SB1 (P < .05). Regarding necrosis, SB1 showed the worst results: Pulp necrosis occurred significantly more often than with calcium hydroxide and GCB (P < .05). After the application of calcium hydroxide, significantly more reparative dentin formation occurred (P < .05).

CONCLUSION

Direct pulp capping with calcium hydroxide seems to produce remarkably better results than with dentin adhesive.

[Distribution of periodontal pathogens in dental plaque samples from 7 to 12-years-old children of Changchun Ziqiang primary school]

OBJECTIVE

To detect the presence of Porphyromonas gingivalis (Pg) and Actinobacillus actinomycetemcomitans (Aa) using polymerase chain reaction (PCR) in the oral plaque samples from children and investigate the relationship between bacteria and clinical parameters.

METHODS

A total of 151 children aged 7 to 12 years were selected from Changchun Ziqiang primary school. The supragingival plaque sample was collected from the mesiobuccal and labial surfaces of the right maxillary central incisor and the right maxillary first molar. Extracted DNA from plaque samples was used for PCR analysis. Intraoral examination, probing depth (PD) and bleeding on probing (BOP) were performed and recorded.

RESULTS

The detection rate for Pg was 27.6% and Aa 54.3% in supragingival plaque. The detection rates for Pg in molars were much higher than those in incisors (P < 0.01). The detection rate of Pg was positively related to BOP+ and PD. The detection rate for Pg increased gradually with aging, and the detection rate for Aa was highest in the group aged 11 to 12 and the detection rates for Pg and Aa were higher in the gingiva with BOP+ than that with BOP- (P < 0.05). The detection rates for Pg increased remarkably with BOP+ and especially when PD was greater than 4 mm.

CONCLUSIONS

Detection rates of putative periodontal pathogens from healthy children of 7 to 12 years of age were high. The detection rates for Pg in molars were much higher than those in incisors,and the presence of Pg and Aa in supragingival plaque was related to periodontal parameters.

The antimicrobial effect of iodine-potassium iodide after cleaning and shaping procedures in mesial root canals of mandibular molars

The aim of this study was to evaluate the antibacterial activity of 2% iodine potassium iodide (IKI) used as a final rinse after the cleaning and shaping procedures in mesial root canals of mandibular molars infected with Enterococcus faecalis. Seventy two mandibular first molars were used. The root canals were infected with Enterococcus faecalisfor 30 days. After the infection procedures, the root canals were cleaned and shaped by using the Pro Taper rotary system and manual files. The teeth were randomly assigned to four experimental groups (N = 18). In group 1, the root canals were irrigated with sterile distilled water (control). In group 2, the root canals were irrigated with 1% Sodium hypochlorite (NaOCl) during instrumentation. In group 3, root canals were irrigated with 1% NaOCl during instrumentation and a five minute final irrigation using 2% IKI. In group 4, the root canals were irrigated with 1% NaOCl during instrumentation and a 15 minutes final irrigation with 2% IKI. Bacteria colony-forming units (CFU) from root canals were semi-quantified and the presence of negative cultures among the groups was compared using Fisher's test (p < 0.05). The order of effectiveness was: 1% NaOCI plus 2% IKl for 15 minutes (95%), 1% NaOCl plus 2% IKl for 5 minutes (44%), 1% NaOCl (17%) and sterile distilled water (0%). Fisher's exact test showed a significant difference among the groups (p < 0.05). It was concluded that under in vitro conditions, IKI was able to eliminate the Enterococcus faecalis from infected dentin significantly in a 15-minute time frame after the cleaning and shaping procedures.

Regional differences within the dentition for plaque, gingivitis, and anaerobic bacteria

OBJECTIVE

This investigation assessed regional differences in dental plaque and gingivitis within the human dentition in conjunction with microbiological analyses of dental plaque.

METHODS

Forty-one adults (23 males and 18 females; age range 19-44 years) were enrolled, and a calibrated dental examiner completed whole mouth examinations for dental plaque (PI) and gingivitis (GI) using the Turesky modification of the Quigley-Hein Index (TMQH) and the L6e-Silness (LS) Index, respectively. Dental plaque samples were collected from the anterior surfaces and posterior teeth to determine viable anaerobic bacteria. During this visit, subjects underwent a whole mouth dental prophylaxis and were provided a marketed fluoride dentifrice for twice-daily oral hygiene. Subjects were recalled on day 15 and day 30 for whole mouth assessments of PI and GI, followed by the collection of dental plaque from the anterior and posterior teeth for microbiological analyses during these visits.

RESULTS

Low plaque and gingival scores were common on anterior surfaces, in contrast to greater frequencies of higher PI and GI scores on the posterior regions or the entire dentition. Correspondingly, mean scores for PI and GI were significantly lower among the anterior surfaces in comparison to all other regions of the mouth (posterior, Ramfjord surfaces, or the entire dentition) over each phase of the study (p < 0.0001). While prophylaxis resulted in lower clinical scores from baseline to the day-15 recall visit (p < 0.05), anterior surfaces demonstrated lower scores than posterior regions during this recall visit (p < 0.05). Although dental plaque scores increased from the day-15 to the day-30 evaluations, gingival scores maintained broad reductions, with anterior scores consistently lower than the corresponding posterior regions (p <0.05). Microbiological analyses indicated significantly lower numbers of viable bacteria from the anterior surfaces in comparison to posterior regions at both recall visits (p < 0.05).

CONCLUSION

Anterior surfaces routinely demonstrated lower levels of dental plaque scores than the other regions of the dentition. Higher gingival inflammation levels were also correlated with increased plaque deposits associated with posterior teeth. Microbiological analyses confirm clinical observations with significantly higher numbers of viable bacteria in the dental plaque collected from the posterior regions. The human dentition demonstrates significant regional differences in the prevalence of dental plaque, gingivitis, and corresponding anaerobic bacteria, with posterior surfaces consistently reporting higher scores than the anterior regions. These consistent differences should be taken into account in performing plaque and gingivitis studies when assessing the efficacy of oral health products for controlling dental health.

Effect of topical applications of a novel chlorhexidine-thymol varnish formula on mutans streptococci and caries development in occlusal fissures of permanent molars

OBJECTIVE

To evaluate the effect of a new formula of a chlorhexidine-thymol varnish on mutans streptococci (MS) colonization and fissure caries development.

METHODS

The study group consisted of 58 healthy adolescents (12-17 years old) undergoing orthodontic treatment with fixed appliances. A double-blind split-mouth design was applied, and 116 pairs of molar teeth were randomly assigned to topical varnish applications with either the new Cervitec Plus or its predecessor Cervitec. Both varnishes contained 1% CHX and 1% thymol (CHX/T) as active ingredients, but differed with respect to adhesive properties. The varnishes were applied in the fissures at baseline, and then every sixth week throughout the 48-week study period. Endpoints were MS colonization (CRT test) and occlusal laser fluorescence (LF, DIAGNOdent) recordings carried out regularly during follow-up.

RESULTS

A significant reduction in the levels of MS in the fissures after the initial treatment was displayed with both varnishes (p < 0.05), and the levels remained consistently suppressed throughout the follow-up period. A non-significant but clear tendency was noted in favor of the new formula after six and 12 weeks, with fewer teeth harboring high counts (> or = 10(5) CFU) of MS (6w:12% vs. 24%, 12w:16% vs. 26%). No new lesions were registered in any subject, and the mean LF recordings did not change significantly over time in the groups.

CONCLUSION

There were no statistically significant differences between the CHX/T varnishes in terms of bacterial growth and caries prevention. For MS suppression, a tendency towards an initially superior effect was displayed with the new formula.

A new in vitro model to study the relationship of gap size and secondary caries

OBJECTIVES

To investigate the relationship of gap size and secondary caries in a newly developed secondary caries microbial model that permits adjustment of the gap between the tooth and a restoration.

METHODS

Tooth-resin-matrix composite specimens were mounted on gap-model stages with a gap size of 50 or 500 microm in experiment 1, and 0, 25, 250, or 1,000 microm in experiment 2. They were attached to plastic Petri plates, gas-sterilized and then incubated in a microbial caries model (with Streptococcus mutans TH16 in 1% sucrose tryptic soy broth for 1 h, 4 times/day, and with a buffer solution for the rest of the day). After 8 days of incubation, tooth specimens were sectioned and stained overnight with a rhodamine B solution. Digital images taken under a confocal microscope were analyzed for lesion size at the outer surface lesion and wall lesion (WL).

RESULTS

Gap size was found to affect the development of dentin WL area in experiment 1 and enamel and dentin WL areas in experiment 2, with bigger lesions being observed in the wider gap group (p < 0.05).

CONCLUSION

The findings of this study suggest that the size of the gap between tooth and restoration affects the development of secondary caries along the cavity wall.

Mutans streptococci colonization and longitudinal caries detection with laser fluorescence in fissures of newly erupted 1st permanent molars

OBJECTIVE

To longitudinally apply a laser fluorescence (LF) device (DIAGNOdent) in newly erupted 1st permanent molars over a 3-year period and to relate the findings to mutans streptococci (MS) colonization, fissure morphology, and caries development.

MATERIAL AND METHODS

The material consisted of 101 consecutive 5 to 6-year-old children attending a Public Dental Clinic and who volunteered after ethical approval and informed consent had been given. Only fully erupted molars with clinically sound fissures were included. At baseline, the fissures were subjectively categorized as "shallow" or "deep", and, prior to the LF readings, a plaque sample was collected and cultivated for MS using a chair-side kit. The registrations were repeated annually and the microbial samplings after 2 years. The total drop-out rate was 12%.

RESULTS

The mean LF values increased significantly (p<0.05) with increasing age from 8.2 to 12.4 in the teeth that remained sound. Thirty-five teeth were decayed or filled during the follow-up and their mean LF values increased from 13.4 to 40.7. The LF readings were significantly higher in molars with "deep" fissures (p<0.05) at all visits. MS colonization at baseline was associated with an increased risk for caries (OR = 11.6, p<0.05) and significantly elevated LF readings. Baseline LF readings > or =12 were not diagnostic for dentin caries or fillings over the study period (sensitivity 0.57; specificity 0.86).

CONCLUSION

LF readings could be used to some extent to monitor fissure morphology and caries development in fissures of newly permanent molars over time, but elevated initial values were not predictive for caries development.

The In Vivo Evaluation of Hand/Rotary/Ultrasound Instrumentation in Necrotic, Human Mandibular Molars

This in vivo, prospective, randomized, single-blinded study histologically compared biofilm/necrotic debridement efficiency of a hand/rotary technique versus a hand/rotary/1 min ultrasound technique in the mesial roots of necrotic, human mandibular molars. The hand/rotary group consisted of 20 mesial roots. The hand/rotary/ultrasound group consisted of 20 mesial roots prepared with the same hand/rotary technique followed by 1 min of ultrasonic irrigation, per canal, utilizing an ultrasonic needle in a MiniEndo unit. Following extraction, histologic preparation and staining, 0.2 mum cross-sections from the 1- to 3-mm apical levels were evaluated for percentage of biofilm/necrotic debris removal. Cleanliness results at the 1-, 2- and 3-mm levels for the hand/rotary and hand/rotary/ultrasound techniques, respectively, were: Canals, 80% versus 95%, 92% versus 99%, and 95% versus 100%; Isthmuses, 33% versus 83%, 31% versus 86%, 45% versus 91%. Statistical analysis revealed mean percent canal and isthmus cleanliness values to be significantly higher for hand/rotary/ultrasound technique at all levels evaluated.

Effect of 40% chlorhexidine varnish on mutans streptococci counts in pits and fissures of permanent first molars

OBJECTIVES

This study aimed to test the following hypotheses: (1) a carry-over effect of EC40 does not occur in a split-mouth model, (2) two consecutive applications of EC40 varnish with an interval of 3 months per year has a better inhibiting effect on mutans streptococci in pit and fissure plaque of permanent first molars of 6-7-year olds than a repeated application at each 6 months and (3) EC40 exerts an inhibiting effect on mutans streptococci for at least a 6-month duration.

METHODS

Using a split-mouth design, test molars received EC40 on fissures and pits and control molars remained without treatment. One group of test molars received EC40 at baseline, 6, 12 and 18 months and another group at baseline, 3, 12 and 15 months. Plaque samples were taken from pits and fissures of test and control molars at baseline, 6, 9, 12 and 24 months. A mixed ANOVA model was used to analyze the data.

RESULTS

The first hypothesis was accepted, the second rejected and the third accepted.

CONCLUSIONS

Twice a year EC40 application on pits and fissures of permanent first molars of 6-7-year-old children can significantly reduce mutans streptococci numbers for a 6-month period, but the reductions were small.

Leakage of food-borne Enterococcus faecalis through temporary fillings in a simulated oral environment

AIM

To evaluate the hypothesis that food-borne viable Enterococcus faecalis cells could enter the root canal space via coronal leakage.

METHODOLOGY

In a simulated oral environment under mastication the capacity of a calcium sulphate-based temporary filling material (Cavit W) to prevent leakage of E. faecalis from a cheese through the endodontic access cavity into the pulp chamber was assessed. Standardized class I access cavities were prepared in human maxillary molars. These were filled with Cavit of either 2 or 4 mm thickness (n=16, each). Empty access cavities served as positive, teeth filled with a light-curing composite material acted as negative controls (n=8, each). A cheese containing viable E. faecalis cells was placed on the occlusal aspects of test and control teeth, which were subsequently subjected to 680 mastication loads per day for 1 week in a masticator device perfused with artificial saliva at 37 degrees C. Leakage of E. faecalis from the cheese into the pulp chamber was assessed by culture on a kanamycin aesculin azide agar and compared between groups using Fisher's exact test.

RESULTS

All of the positive controls showed pure growth of E. faecalis. In addition, one of the negative control teeth leaked. The 4 mm application of Cavit prevented leakage of E. faecalis significantly better than the corresponding 2 mm application: 1 of 16 specimens compared with 6 of 16 specimens had leakage, respectively (P<0.05).

CONCLUSIONS

The current results substantiate the suspicion that food-derived microbiota could enter the necrotic root canal system via microleakage.

Ultrastructural and microbiological analysis of the dentin layers affected by caries lesions in primary molars treated by minimal intervention

PURPOSE

The purpose of this in vivo study of primary teeth was to analyze the ultrastructure and microbiology of dentin layers affected by caries lesions before and after restorations with resin-modified glass ionomer.

METHODS

Samples of carious dentin from primary teeth removed prior to restoration placement (baseline-0 day) were compared with samples taken after 30 and 60 days. Dentin from 8 primary molars was analyzed by scanning electron microscopy (SEM) and dentin from 22 primary molars was examined microbiologically to compare bacteria (total of viable counts, Streptococcus spp, Streptococcus mutans, Lactobacillus spp, and Actinomyces spp) before and after treatment (30 and 60 days).

RESULTS

Baseline caries samples had enlarged dentinal tubules with bacteriol invasion. SEM samples after treatment suggest better tissue organization, with more compact collagen fibers arrangement and narrower dentinal tubules. The number of bacteria decreased in all samples at both 30 (98%) and 60 (96%) days, with all bacteria species showing similar trends.

CONCLUSIONS

The minimal intervention approach is very effective to promote beneficial changes in the lesion environment and favorable conditions for the healing process in primary teeth.

Chlorhexidine-releasing methacrylate dental composite materials

Light curable antibacterial, dental composite restoration materials, consisting of 80 wt% of a strontium fluoroaluminosilicate glass dispersed in methacrylate monomers have been produced. The monomers contained 40-100 wt% of a 10 wt% chlorhexidine diacetate (CHXA) in hydroxyethylmethacrylate (HEMA) solution and 60-0 wt% of a 50/50 mix of urethane dimethacrylate (UDMA) and triethyleneglycol dimethacrylate (TEGDMA). On raising HEMA content, light cure polymerisation rates decreased. Conversely, water sorption induced swelling and rates of diffusion controlled CHXA release from the set materials increased. Experimental composites with 50 and 90 wt% of the CHXA in HEMA solution in the monomer were shown, within a constant depth film fermentor (CDFF), to have slower rates of biofilm growth on their surfaces between 1 and 7 days than the commercial dental composite Z250 or fluoride-releasing dental cements, Fuji II LC and Fuji IX. When an excavated bovine dentine cylinder re-filled with Z250 was placed for 10 weeks in the CDFF, both bacteria and polymers from the artificial saliva penetrated between the material and dentine. With the 50 wt% experimental HEMA/CHXA formulation, this bacterial microleakage was substantially reduced. Polymer leakage, however, still occurred. Both polymer and bacterial microleakage were prevented with a 90 wt% HEMA/CHXA restoration in the bovine dentine due to swelling compensation for polymerisation shrinkage in combination with antibacterial release.

Microbial status of apical root canal system of human mandibular first molars with primary apical periodontitis after “one-visit” endodontic treatment

OBJECTIVE

To assess the in vivo intracanal microbial status of apical root canal system of mesial roots of human mandibular first molars with primary apical periodontitis immediately after one-visit endodontic treatment. The residual intracanal infection was confirmed by correlative light and transmission electron microscopy.

STUDY DESIGN

Sixteen diseased mesial roots of mandibular first molars were treated endodontically, each in one visit. Mesio-buccal canals were instrumented using stainless steel hand files and mesio-lingual canals with a nickel-titanium rotary system. The canals were irrigated with 5.25% sodium hypochlorite (NaOCl) during the instrumentation procedures, rinsed with 10 mL of 17% ethylenediamine tetraacetic acid (EDTA), and obturated with gutta-percha and zinc oxide eugenol cement. Thereafter, the apical portion of the root of each tooth was removed by flap-surgery. The specimens were fixed, decalcified, subdivided in horizontal plane, embedded in plastic, processed, and evaluated by correlative light and transmission electron microscopy.

RESULTS

Fourteen of the 16 endodontically treated teeth revealed residual intracanal infection after instrumentation, antimicrobial irrigation, and obturation. The microbes were located in inaccessible recesses and diverticula of instrumented main canals, the intercanal isthmus, and accessory canals, mostly as biofilms.

CONCLUSIONS

The results show (1) the anatomical complexity of the root canal system of mandibular first molar roots and (2) the organization of the flora as biofilms in inaccessible areas of the canal system that cannot be removed by contemporary instruments and irrigation alone in one-visit treatment. These findings demonstrate the importance of stringent application of all nonantibiotic chemo-mechanical measures to treat teeth with infected and necrotic root canals so as to disrupt the biofilms and reduce the intraradicular microbial load to the lowest possible level so as to expect a highly favorable long-term prognosis of the root canal treatment.

The microflora of the erupting first permanent molar

The relationship between microflora, eruption status and caries status in the first permanent molar of young children was investigated in 177 children aged 6-7 years. A significantly greater proportion of fully erupted teeth were classified as sound and plaque-free compared to partially erupted teeth. Fully erupted teeth yielded greater numbers and proportions of mutans streptococci compared with significantly greater numbers and proportions of Actinomyces israelii in partially erupted teeth. Logistical regression analysis showed significant associations between white spot lesions in partially erupted teeth and increased numbers of Streptococcus oralis, mutans streptococci and Streptococcus salivarius whereas the presence of Actinomyces naeslundii was associated with health. Significantly greater numbers and proportions of S. oralis and S. salivarius were isolated from partially erupted teeth with white spot lesions whereas Streptococcus mutans was isolated in significantly greater numbers and proportions from fully erupted molars with white spots. This study suggests that organisms other than mutans streptococci are associated with caries development in erupting permanent molar teeth.

Bartonella quintana in a 4000-year-old human tooth

Bacteria of the genus Bartonella are transmitted by ectoparasites (lice, fleas, ticks) and have mammalian reservoirs in which they cause chronic, asymptomatic bacteremia. Humans are the reservoir of B. quintana, the louse-borne agent of trench fever. We detected DNA of B. quintana in the dental pulp of a person who died 4000 years ago.

Chlorhexidine-containing glass ionomer cement. A clinical investigation on the fissure caries inhibiting effect in first permanent molars

Glass ionomer cement with addition of chlorhexidine used as a varnish on tooth surfaces has been shown to reduce the number of interproximal mutans streptococci (ms). The effect of a single application of such a varnish containing 2.5% chlorhexidine on occlusal caries development of the first permanent molars on 6-year-old children in a high caries incidence area was investigated. The children were examined according to WHO criteria and 262 children with 2 caries free contra-lateral molars were selected for treatment. Salivary ms samples were collected using the Strip-mutans (SM) method. After brushing the occlusal surfaces with a toothbrush and pumice in water slurry, rinsing and drying with a cotton roll, glass ionomer cement containing chlorhexidine (GI-CHX) and glass ionomer (GI) were applied randomly with a micro brush and the varnish was covered with occlusal wax. At baseline, the mean defs was 18.18 and DMFS was 0.25 and after one year 18.24 and 0.83 respectively. The salivary ms scores were high or very high (SM 2 and 3) in 85.6% at baseline. At the one-year follow up, the GI-CHX and GI materials could not be detected in the fissures. Also, a large number of fissure sealants had been placed in the molars outside the study protocol; thus 4% of the GI-CHX and GI, and 70% of the untreated were sealed at year one. Overall, there was no significant difference between the caries-reducing effect of GI-CHX and GI, but a trend towards a higher effect was seen for GI-CHX. Excluding the sealed molars the reduction was 74% in the GI-CHX-group, and 71% in the GI-group.

CONCLUSION

Addition of 2.5% chlorhexidine to glass ionomer did not seem to increase the caries-reducing effect of the varnish in this high caries incidence population.

Molecular detection of Bartonella spp. in the dental pulp of stray cats buried for a year

Bartonella henselae causes chronic bacteremia in cats. To test if B. henselae DNA can be recovered from the dental pulp of cats buried a year previously, we used PCR with primers for a sequence of the conserved groEL to test 104 teeth from 11 cats. Seven of the cats were found positive; canine teeth were more frequently positive than molar teeth. Where PCR sequences could be determined, they were identical to those of B. henselae Marseille (four cats), B. henselae Houston (one cat) or similar to those of B. grahamii (one cat). Our study indicates that dental pulp from the teeth of cats, especially the canine teeth, may be used for the PCR detection of Bartonella in animals buried for a year.

In vitro growth, acidogenicity and cariogenicity of predominant human root caries flora

Streptococcus mutans (Sm), Lactobacillus acidophilus (La) and Actinomyces israelii (Ai) have been associated with root surface caries, which is an increasing problem in elderly Chinese. The aim of this study therefore, was to evaluate in vitro, the growth, acidogenicity and cariogenicity of these organisms, both in mono- and co-cultures using an in vitro model. Forty-eight root specimens were prepared using intact extracted human molars. Fresh, wild-type bacteria obtained from root caries lesions were assembled into seven experimental groups as either mono- or co-cultures and incubated with the root specimens. Appropriate controls were included. Growth curve of each experimental group was monitored for 24h, aerobically, at 37 degrees C using a microplate reader. The pH of the medium was recorded after 24-h incubation using a pH meter. Mean depths of artificial root lesions produced in each cultural group were measured using polarized light microscopy in specimens cut into thin sections (100+/-20 microm). Compared with mono-cultures, synergistic growth was observed in co-cultures of 'La+Sm', 'Ai+La' and 'Ai+La+Sm'. Mean lesion depth produced in La group was significantly shallower than other mono- or co-culture groups (p<0.01). The pH values of all culture media were similar after 24-h incubation. The current data elucidate the complex interactions of three predominant bacterial species considered prime agents of human root surface caries.

A Method for Mapping the Distribution Pattern of Cariogenic Streptococci within Dental Plaque in vivo

This study was carried out to develop a method for mapping the distribution of cariogenic oral streptococci, Streptococcus mutans and Streptococcus sobrinus, from the outermost to the innermost plaque. Ten consenting subjects were asked to form plaque by abstaining from tooth brushing over 3 days within in situ plaque-generating devices, which were placed on the upper molars. The plaque formed in the devices was separated into 8-10 layered fractions (100 microm thick). Genomic DNA was extracted from each plaque fraction by a commercial DNA purification kit and used for the amplification of the 16S ribosomal RNA gene sequences by polymerase chain reaction (PCR) with universal primers. The products were then amplified by PCR with S. mutans- or S. sobrinus-specific nested primers. The final products were separated on agarose gels, stained and photographed to confirm the existence of S. mutans and S. sobrinus. The results showed that S. mutans was detected in the plaque obtained from all of the 10 subjects and S. sobrinus in the plaque of 7 subjects. However, the distribution patterns of fractions positive for S. mutans and S. sobrinus varied among the subjects, with a tendency for frequent detection of both species in the outer to middle layers of dental plaque. There were no plaque fractions in which only S. sobrinus was found. This method could be useful to map the distribution of cariogenic microorganisms and to estimate the bacterial ecology for oral biofilm.

Human salivary function in relation to the prevalence of Tannerella forsythensis and other periodontal pathogens in early supragingival biofilm

OBJECTIVE

Previously, we screened 149 subjects and established four groups high or low for salivary killing of oral bacteria, and for aggregation and live and dead adherence of oral bacteria (as a combined factor). Caries scores were significantly lower in both High Aggregation-Adherence groups. Subsequently, we found that supragingival total biofilm DNA, total streptococci and two major streptococcal rRNA variants also were significantly lower in the High Aggregation-Adherence groups. In this study, we looked at the effects of those differences in salivary function on three periodontal pathogens.

DESIGN

Quantitative PCR was used to determine levels of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis and Tannerella forsythensis (formerly Bacteroides forsythus) in stored DNA extracts of overnight supragingival biofilm collected from buccal upper central incisors (UC), lingual lower central incisors (LC) and buccal upper and lower first molars (BM) and lingual upper and lower first molars (LM) of subjects in the four groups.

RESULTS

A. actinomycetemcomitans and P. gingivalis were almost completely absent from these samples. T. forsythensis was found in 11 of 35 persons at the buccal molar site. Only two of those subjects were in the High Aggregation-Adherence groups, and that difference was statistically significant. The mean quantity of T. forsythensis also was significantly lower in the High Aggregation-Adherence groups.

CONCLUSIONS

The difference between the Low and High Aggregation-Adherence groups might reflect direct interactions of salivary proteins with T. forsythensis. Alternatively, the higher levels of total biofilm and total streptococci seen in the Low Aggregation-Adherence groups might create a favourable environment for early secondary colonization of T. forsythensis.

Validation and inter-examiner agreement of mutans streptococci levels in plaque and saliva of 10-year-old children using simple chair-side tests

Since there are few validation studies of chair-side tests of oral mutans streptococci, we compared a commercially available strip test with the conventional laboratory assay. Two plaque samples obtained from the mesial surfaces of the upper right and lower left permanent molars of sixty-five 10-year-old children (boys = 38, girls = 27) were cultured and incubated using chair-side site strip tests (Dentocult SM, Orion Diagnostica). Two plaque sampling tools, namely dental floss and micro-brush, were compared, and inter-examiner agreement between recordings of three examiners was assessed. Paraffin-stimulated saliva was then collected for laboratory and chair-side assays. The plaque and saliva chair-side tests correlated well with each other (Spearman rho, r = 0.72) and with the laboratory method, showing coefficients of 0.76 and 0.80 for saliva and plaque, respectively. Compared to the laboratory method, the sensitivity (Sn), specificity (Sp), accuracy (A), and kappa (K) values of the salivary and plaque chair-side tests were 0.63, 0.75 (Sn), 0.93, 0.90 (Sp), 0.82, 0.85 (A), and 0.58, 0.66 (K), respectively. Agreement between the two plaque sampling techniques was good (0.91). Inter-examiner agreement of plaque scores ranged between 0.65 and 0.86 when all density categories were analysed separately; when dichotomized into low and high categories, complete agreement was found. Agreement between the plaque and saliva chair-side tests and the laboratory salivary assay was good, and in terms of sensitivity, accuracy, and kappa values, the site strip plaque test surpassed the salivary chair-side test.

Colonization of Streptococcus mutans and Streptococcus sobrinus Genotypes and Caries Development in Children to Mothers Harboring Both Species

The major route of early acquisition of mutans streptococci in humans is a vertical transmission from mother to child. The purpose of this longitudinal study was to examine the acquisition, distribution and persistence of Streptococcus mutans and Streptococcus sobrinus in children whose mothers harbored both species and to study the caries incidence in relation to colonization of these bacteria. Fifteen mother-child pairs were followed during the child's first 7 years. Stimulated salivary samples were taken from the mothers and the children. Plaque samples were also collected from the teeth and the tongue of the children. The samples were analyzed by cultivating techniques together with genomic fingerprinting and hybridizing. The caries experience was evaluated on the sampling occasions and retrospectively using the records of caries registrations from the community clinics. During the 7-year period 10 of the 15 children acquired mutans streptococci. Only 4 of them were colonized by both S. mutans and S. sobrinus despite the fact that their mothers harbored both species. In 2 of the children S. sobrinus was found later than S. mutans. A total of 26 genotypes were found in the children and 9 of them were identical to their mothers. New genotypes and a gain-loss pattern were noted especially in the children but also in their mothers. The groups of teeth first positive for the two species were the deciduous molars. The caries experience was low during the study period with 8 children showing no caries.

A new in vivo interdental sampling method comparing a daily flossing regime versus a manual brush control

OBJECTIVE

The impact of flossing the interdental space is typically assessed by visual methods of questionable reliability, such as clinician observations and evaluations for scoring of plaque on visual tooth surfaces. The objective of this study was to develop and validate a method to measure interproximal quantities of dental plaque, thereby permitting quantitative evaluations of between-teeth cleaning and biofilm removal.

METHODOLOGY

Laboratory studies were performed correlating the quantity of bacteria to the amount of measured protein in a sample using a standardized protein assay (Bio-Rad Protein Assay) and samples containing single bacterial species and saliva/bacterial pellets. Analysis of the plaque was standardized against a bovine serum albumin (BSA) control. Pilot studies helped develop a technique for hygienist-applied interproximal flossing, reducing contamination from saliva and other possible sources of indeterminate error. Repeated sampling experiments were carried out to optimize the technique needed to remove the majority of quantifiable plaque, the best choice of flossing material, and establish the technique for collection. A pilot clinical trial assessed the benefits of daily flossing in reducing measurable quantities of interproximal plaque using the developed method. Thirty-nine subjects had six interdental sites (distributed across all four quadrants, pre-molar and molar boundaries) sampled on either side, over a three-week treatment period, in two balanced and equally sized treatment groups, with twice-daily manual brushing with or without daily flossing.

RESULTS

Laboratory studies confirmed the accuracy of the protein detection kit in assaying bacterial plaque loads from single species or complex biofilms. In pilot developmental screens, single flossing sweeps with appropriate dental floss were sufficient to remove the majority of quantifiable biomass from interproximal sites. The clinical study demonstrated that after three weeks, interdental plaque in floss users was significantly reduced versus baseline scores. Non-floss users showed no significant reduction. In direct comparison, less interdental plaque was recovered from subjects who had followed a daily flossing regime compared to subjects who had used a manual toothbrush alone (p = 0.0866).

CONCLUSION

The sampling method quantified the cleaning effects of daily flossing on interproximal plaque levels. Daily flossing significantly reduced the amount of plaque found between the teeth compared to a manual brushing regimen alone. This new method should be useful in future studies on the evaluation of mechanical or chemical means of interproximal plaque control.

Detection of Streptococcus mutans and Streptococcus sobrinus on the permanent first molars of the Mosuo people in China

Streptococcus mutans and Streptococcus sobrinus are associated with the development of dental caries. The purpose of this study was to differentiate these bacteria by morphology, biochemical characteristics and PCR, and to compare their occurrence with the prevalence of dental caries in the Mosuo people. Plaque samples were collected from the permanent first molar in 126 Mosuo people (83 females, 43 males, aged 25-55 years, average age 36.1 +/- 7.73). Dental status was recorded as DMFT by WHO caries diagnostic criteria. Males had a significantly lower prevalence of caries and DMFT than females: 11.4 vs. 86.9% and 1.65 vs. 6.95, respectively (p<0.001). Morphological and biochemical tests gave unreliable results. The prevalence of S. mutans and S. sobrinus was 75.4 and 57.1%, respectively. 26.5% of females and 53.5% of males were positive for S. mutans alone, 18.1% of females and 16.3% of males were positive for S. sobrinus alone, while 50.6% of females and 18.6% of males were positive for both S. mutans and S. sobrinus and 4.8% of females and 11.6% of males were negative for both species. The DMFT scores of subjects positive for both S. mutans and S. sobrinus were significantly higher than of those positive for either S. mutans or S. sobrinus alone. These results indicate that subjects harboring both S. mutans and S. sobrinus have a significantly higher prevalence of dental caries than those with S. mutans or S. sobrinus alone.

[Bacteriological findings for endodontical and apical molar dental diseases in the horse]

In most cases the diagnosis of any molar dental disease in horses is made at an advanced stage, so that permanent restoration of the diseased teeth is not feasible. Complications such as bacteraemia and septicaemia due to infections as a result of dentogenous sinusitis and following dentosurgical procedures have been described in human medicine and in veterinary medicine. Twenty patients were available for examination from the Clinic for Horses of the School of Veterinary Medicine Hannover with molar dental disease in upper or lower jaw. As a result of this disease the infected tooth had to be removed surgically. The aim of this study was to determine the presence of and to identify microbes in 20 patients. Swab samples were taken from infected pulpa, from dental abscesses and from involved nasal sinuses. The samples were examined microbiologically and tested for aerobes and anaerobes at the same time. Infectious agents were found in 19 of 20 horses. In all, 27 different species of infectious agents were isolated, including both aerobic and anaerobic microbes. Fifteen patients (75%) showed a mixed flora. Further differentiation indicated a preponderance of the group of gram-negative obligatory anaerobic agents isolated from a total of 17 horses. In all these samples there was a high concentration of infectious agents of these genera, the most common of which were Prevotella spp (n = 16) and Fusobacterium spp. (n = 15). Pre-surgical antibacterial therapy is recommended to reduce the risk of intra- and/or post-surgical bacteraemia and its serious consequences. In light of these microbiological results and considering the high degree of resistance among all anaerobic microbes, all patients in this study were treated with Amoxicillin.

Clinical, histological and microbiological study of hand-excavated carious dentine in extracted permanent teeth

Changes in cultivable flora in dentine samples collected before and after hand excavation were examined in association with clinical status of the cavity surface, light microscopy and scanning electron microscopy (SEM). Thirty-five extracted permanent molar teeth with an occlusal caries lesion were excavated with hand instruments according to the atraumatic restorative treatment (ART) approach. Excavation pressure, dentine colour and consistency were recorded at the dentine-enamel junction (DEJ) prior to carious dentine removal and at the cavity floor after the final excavation; a microbiological sample of dentine was taken at both stages. Twelve restored teeth; six with positive and six with negative bacterial growth on the second sample, were selected for light microscopy and SEM. The hand-excavation removed tooth structure was soft, irreversibly damaged, dark and highly infected. Hand excavation reached dentine of increased hardness with a more normal colour to provide a sound structural base for restoration. Light and SEM examination of the cavity floor showed infected dentinal tubules in all 12 teeth examined. Linear logistic analysis showed a statistical association between light-yellow dentine on the cavity floor and an absence of bacterial growth (P = 0.006). This short-term in vitro study showed that caries-producing bacteria remained in dentine close to the cavity floor in 26/35 teeth despite clinical observations that indicated a suitably prepared cavity floor.

Evaluation of mutans streptococci in plaque and saliva: correlation with caries development in preschool children

OBJECTIVES

To test the ability of a site-specific method of evaluating mutans streptococci (MS) present in plaque in order to predict caries risk in children and to compare the results with those obtained from estimating the levels of MS present in saliva.

METHODS

Caries prevalence was examined twice, 6 months apart, in 129 preschool children ranging in age from 1.5 to 5. A commercial strip method was used to evaluate the MS score (0-3) in plaque collected from four selected tooth surfaces at two interdental spaces and in saliva.

RESULTS

The screening criteria of the MS score for caries incidence between scores 1 and 2, and scores 0 and 1 were the most valid for evaluating plaque (accuracy of prediction, 80%) and saliva (accuracy of prediction, 71%), respectively. Based on these screening criteria, the evaluation of saliva MS was invalid when the plaque MS score was considered. Screening plaque MS was effective, regardless of caries experience at baseline, according to the chi-square test (p<0.01), but screening saliva MS was ineffective when caries experience was present at baseline. A multivariate logistic regression analysis including six variables showed that the plaque MS score and caries experience at baseline were significantly correlated with caries incidence: caries experience at baseline (OR=5.02, 95%CI: 1.81-14.59) and high plaque MS score (2 or 3) (OR=12.59, 95%CI: 3.18-67.08).

CONCLUSIONS

These results suggest that the semi-quantitative evaluation of plaque MS sampled from only two proximal sites on the molars is more effective for screening preschool children at a high risk of developing caries in their primary dentition than other important caries risk indicators.

In vivo killing of Porphyromonas gingivalis by toluidine blue-mediated photosensitization in an animal model

Porphyromonas gingivalis is one of the major causative organisms of periodontitis and has been shown to be susceptible to toluidine blue-mediated photosensitization in vitro. The aims of the present study were to determine whether this technique could be used to kill the organism in the oral cavities of rats and whether this would result in a reduction in the alveolar bone loss characteristic of periodontitis. The maxillary molars of rats were inoculated with P. gingivalis and exposed to up to 48 J of 630-nm laser light in the presence of toluidine blue. The number of surviving bacteria was then determined, and the periodontal structures were examined for evidence of any damage. When toluidine blue was used together with laser light there was a significant reduction in the number of viable P. gingivalis organisms. No viable bacteria could be detected when 1 mg of toluidine blue per ml was used in conjunction with all light doses used. On histological examination, no adverse effect of photosensitization on the adjacent tissues was observed. In a further group of animals, after time was allowed for the disease to develop in controls, the rats were killed and the level of maxillary molar alveolar bone was assessed. The bone loss in the animals treated with light and toluidine blue was found to be significantly less than that in the control groups. The results of this study show that toluidine blue-mediated lethal photosensitization of P. gingivalis is possible in vivo and that this results in decreased bone loss. These findings suggest that photodynamic therapy may be useful as an alternative approach for the antimicrobial treatment of periodontitis.

Determination of eight selected periodontal pathogens in the subgingival plaque of maxillary first molars in Japanese school children aged 8-11 years

To prevent the onset or progression of periodontitis, we must understand when periodontal pathogens are first harbored and how they develop the biofilm that causes periodontal disease. The purpose of this study was to determine the relationship between clinical status and selected periodontal pathogens in subgingival plaque in school children. This study was conducted with 95 school children, 8-11 years old. The presence and distribution of eight selected periodontal pathogens sampled from the maxillary right first molar were determined by an indirect immunofluorescent technique and compared with clinical parameters. Of the 95 sites sampled, only one site had all eight pathogens and five sites did not have any of the eight pathogens. The mean number of positive pathogens per site was 3.5 +/- 1.8 and mean percentage of positive pathogens was 3.82 +/- 4.22%. The number and total percentage of positive pathogens were strongly correlated with the Plaque Index (PI). In addition, the number of positive pathogens was correlated to the presence of subgingival calculus. The most frequently found pathogens were Campylobacter rectus (84.2%) and Eikenella corrodens (83.2%), and the least, Actinobacillus actinomycetemcomitans serotype c (7.4%). Of the eight pathogens, the frequency and distribution of Porphyromonas gingivalis were significantly correlated with PI and the presence of calculus. In addition, seven sites with both P. gingivalis and Bacteroides forsythus showed a correlation with gingival inflammation. In conclusion, the presence of P. gingivalis or P. gingivalis and B. forsythus may be a risk marker to be sought in screening for the onset of periodontal disease.