Ralph Kent

The Forsyth Institute, Cambridge, Massachusetts, United States

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Publications (36)74.63 Total impact

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    Jacques Izard · Hajime Sasaki · Ralph Kent
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    ABSTRACT: The available passive mode of periodontal infections in mice requires high efficiency of bacterial attachment and invasiveness and is not always suitable to test the pathogenicity of genetically engineered mutant strains. We developed an active mode of oral infection, using microinjection in the marginal gingiva of mice, to test the pathogenicity of a genetically engineered Treponema denticola mutant strain deficient in intermediate-like filaments, compared to the wild-type strain. This targeted mode of infection inoculates the bacterial strain to be tested directly at a lesion site (needle entry point) located at the future periodontal lesion site. The efficiency of T. denticola wild-type strain to elicit bone loss contrasted with the lack of pathogenicity of the intermediate-like filament deficient mutant strain in comparison to the sham infection. The periodontal microinjection oral model in mice can be used for a variety of applications complementary to the passive mode of periodontal infection in context of pathogenicity testing.
    Full-text · Article · Jul 2012 · International Journal of Dentistry
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    ABSTRACT: Severe early childhood caries (ECC) results from bacterial acid production in an acidic environment. The purpose of this study was to determine Streptococcus mutans, Streptococcus sobrinus, and acid-tolerant counts in severe early childhood caries. Two- to 6-year-olds with severe-ECC (N=77) or who were caries-free (N=40) were examined. Plaque samples from teeth and the tongue were cultured anaerobically on blood, acid, and S. mutans selective agars. Severe-ECC children were monitored post-treatment for recurrent caries. Severe-ECC and caries-free children were balanced by household income and education level. Carious lesions were observed in 75% maxillary incisors and >80% molars in severe-ECC. At baseline, S. mutans, and S. sobrinus counts and proportions of S mutans were higher in severe-ECC than caries-free children. Acid and blood counts were elevated only in anterior samples of severe-ECC children. Baseline counts of S. sobrinus, but not S. mutans, were higher in children with recurrent compared with no recurrent caries. S. mutans counts were lower following treatment than pretreatment, particularly for children without caries recurrence. Other counts did not differ between before and after therapy. Severe and recurrent early childhood caries was better explained by mutans streptococci than the aciduric microbiota. Streptococcus mutans did not predict children with recurrent caries.
    Full-text · Article · Mar 2012
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    ABSTRACT: To compare the treatment outcome of scaling and root planing (SRP) in combination with systemic antibiotics, local antibiotic therapy and/or periodontal surgery. One hundred and eighty-seven patients were assigned to eight groups treated by SRP plus none, one, two or three adjunctive treatments and monitored for 24 months in a randomized controlled clinical trial using a 2 × 2 × 2 factorial design. Systemic amoxicillin + metronidazole (SMA), local tetracycline delivery (LTC) and periodontal surgery (SURG) were evaluated as adjuncts. Changes in clinical attachment level (CAL) and probing pocket depth (PPD) were statistically evaluated by ancova of main effects. Effects of adjunctive therapy to SRP were minimal at 3 months. Between 3 and 6 months PPD reduction occurred particularly in patients receiving periodontal surgery. After 6 months, both CAL gain and PPD reduction reached a plateau that was maintained at 24 months in all groups. The 24-month CAL gain was improved by SMA (0.50 mm) while PPD was reduced by SMA (0.51 mm) and SURG (0.36 mm). Smoking reduced CAL gain and PPD reduction. Patients receiving adjunctive therapies generally exhibited improved CAL gain and/or PPD reduction when compared with the outcome of SRP alone. Only additive, not synergistic effects of the various adjunctive therapies were observed.
    No preview · Article · Feb 2012 · Journal Of Clinical Periodontology
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    ABSTRACT: Background: This study compares the changes to the subgingival microbiota of individuals with "refractory" periodontitis (RP) or treatable periodontitis (good responders [GR]) before and after periodontal therapy by using the Human Oral Microbe Identification Microarray (HOMIM) analysis. Methods: Individuals with chronic periodontitis were classified as RP (n = 17) based on mean attachment loss (AL) and/or >3 sites with AL ≥2.5 mm after scaling and root planing, surgery, and systemically administered amoxicillin and metronidazole or as GR (n = 30) based on mean attachment gain and no sites with AL ≥2.5 mm after treatment. Subgingival plaque samples were taken at baseline and 15 months after treatment and analyzed for the presence of 300 species by HOMIM analysis. Significant differences in taxa before and post-therapy were sought using the Wilcoxon test. Results: The majority of species evaluated decreased in prevalence in both groups after treatment; however, only a small subset of organisms was significantly affected. Species that increased or persisted in high frequency in RP but were significantly reduced in GR included Bacteroidetes sp., Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella spp., Tannerella forsythia, Dialister spp., Selenomonas spp., Catonella morbi, Eubacterium spp., Filifactor alocis, Parvimonas micra, Peptostreptococcus sp. OT113, Fusobacterium sp. OT203, Pseudoramibacter alactolyticus, Streptococcus intermedius or Streptococcus constellatus, and Shuttlesworthia satelles. In contrast, Capnocytophaga sputigena, Cardiobacterium hominis, Gemella haemolysans, Haemophilus parainfluenzae, Kingella oralis, Lautropia mirabilis, Neisseria elongata, Rothia dentocariosa, Streptococcus australis, and Veillonella spp. were more associated with therapeutic success. Conclusion: Persistence of putative and novel periodontal pathogens, as well as low prevalence of beneficial species was associated with chronic refractory periodontitis.
    No preview · Article · Feb 2012 · Journal of Periodontology
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    ABSTRACT: Photodynamic therapy (PDT) is increasingly being explored for treatment of oral infections. Here, we investigate the effect of PDT on human dental plaque bacteria in vitro using methylene blue (MB)-loaded poly(lactic-co-glycolic) (PLGA) nanoparticles with a positive or negative charge and red light at 665 nm. Dental plaque samples were obtained from 14 patients with chronic periodontitis. Suspensions of plaque microorganisms from seven patients were sensitized with anionic, cationic PLGA nanoparticles (50 µg/ml equivalent to MB) or free MB (50 µg/ml) for 20 min followed by exposure to red light for 5 min with a power density of 100 mW/cm2 . Polymicrobial oral biofilms, which were developed on blood agar in 96-well plates from dental plaque inocula obtained from seven patients, were also exposed to PDT as above. Following the treatment, survival fractions were calculated by counting the number of colony-forming units. The cationic MB-loaded nanoparticles exhibited greater bacterial phototoxicity in both planktonic and biofilm phase compared to anionic MB-loaded nanoparticles and free MB, but results were not significantly different (P > 0.05). Cationic MB-loaded PLGA nanoparticles have the potential to be used as carriers of MB for PDT systems.
    Full-text · Article · Sep 2011 · Lasers in Surgery and Medicine
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    ABSTRACT: Objectives: Severe early childhood caries (ECC) can devastate the dentition of pre-school children. This study characterized this infection using rapid, comprehensive methods. Methods: Severe-ECC (n=57) and caries-free (n=33) children (2-6 years) had clinical measurements and plaque samples taken. Severe-ECC children were monitored for 12 months post-therapy. Plaque samples were assayed using the HOMIM microarray and by PCR to S. mutans (Sm), Bifidobacteriaceae (bifids) and Scardovia wiggsiae, a new species associated with severe-ECC. Results: By microarray (p<0.01) species detected more frequently in severe-ECC were Slackia exigua, S. parasanguinis and P. melaninogenica, whereas species detected more frequently in caries-free children were C. hominis, C. matruchotii, Leptotrichia hofstadii and S. mitis bv 2. By PCR, S. mutans (p=0.03), bifids (p<0.0001), S. wiggsiae (p=0.002), and combinations of Sm with Bifids (p<0.001) and Sm with S. wiggsiae (p =0.002) were detected more frequently from severe-ECC than caries-free children. Species detected by microarray at baseline more frequently in children with new lesions compared to no recurrence were C. ochracea, C. matruchotii, P. nigrescens, and an unnamed Capnocytophaga. None of the species assayed by PCR at baseline were significantly associated with detection of new carious lesions post-therapy, and there were no differences in the PCR-detected species before and after treatment, except for S. mutans that detection reduced from 51% to 27% in children without new lesions (p=0.032). Species detected more frequently in children with mean GI ≥1 included A. gerensceriae, E. saphenum, S. artemidis, unnamed Leptotrichia and Selenomonas taxa, and a Prevotella cluster. Conclusions: Bifidobacteriaceae, S. wiggsiae and combinations of these species with S. mutans, were associated with severe-ECC indicating the importance of non-mutans bacteria in dental caries. Several species detected in severe-ECC were associated with gingivitis suggesting their presence could be inflammation related. Supported by NIH/NIDCR Grants DE-015847, T32-DE-007327 and the Throne-Holst foundation, Sweden.
    No preview · Conference Paper · Mar 2011
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    ABSTRACT: The objective of this study was to evaluate the antimicrobial effects of photodynamic therapy (PDT) on infected human teeth ex vivo. Fifty-two freshly extracted teeth with pulpal necrosis and associated periradicular radiolucencies were obtained from 34 subjects. Twenty-six teeth with 49 canals received chemomechanical debridement (CMD) with 6% NaOCl, and 26 teeth with 52 canals received CMD plus PDT. For PDT, root canal systems were incubated with methylene blue (MB) at concentration of 50 μg/mL for 5 minutes, followed by exposure to red light at 665 nm with an energy fluence of 30 J/cm(2). The contents of root canals were sampled by flushing the canals at baseline and after CMD alone or CMD+PDT and were serially diluted and cultured on blood agar. Survival fractions were calculated by counting colony-forming units (CFUs). Partial characterization of root canal species at baseline and after CMD alone or CMD+PDT was performed by using DNA probes to a panel of 39 endodontic species in the checkerboard assay. The Mantel-Haenszel χ(2) test for treatment effects demonstrated the better performance of CMD+PDT over CMD (P = .026). CMD+PDT significantly reduced the frequency of positive canals relative to CMD alone (P = .0003). After CMD+PDT, 45 of 52 canals (86.5%) had no CFUs as compared with 24 of 49 canals (49%) treated with CMD (canal flush samples). The CFU reductions were similar when teeth or canals were treated as independent entities. Post-treatment detection levels for all species were markedly lower for canals treated by CMD+PDT than they were for those treated by CMD alone. Bacterial species within dentinal tubules were detected in 17 of 22 (77.3%) and 15 of 29 (51.7%) canals in the CMD and CMD+PDT groups, respectively (P = .034). Data indicate that PDT significantly reduces residual bacteria within the root canal system, and that PDT, if further enhanced by technical improvements, holds substantial promise as an adjunct to CMD.
    Full-text · Article · Feb 2011 · Journal of endodontics
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    ABSTRACT: This report is a further analysis of a study designed to determine clinical and microbial risk indicators for progressing periodontitis. One hundred ninety subjects who were periodontally healthy or had early signs of periodontitis (age range: 20 to 40 years) were monitored clinically at 6-month intervals followed by supragingival cleaning. At each visit, gingival crevicular fluid (GCF) and blood were collected for determination of interleukin (IL)-1β content (in GCF) and IL-1 genotype (in blood). Interproximal sites with a >1.5-mm increase in clinical attachment over 18 months were considered disease active. Characteristics were compared between active and inactive subjects. IL-1β levels in GCF increased with the severity of disease and correlated well with clinical signs of incipient disease. However, the IL-1 genotype did not show any significant associations with disease or the extent of disease. Indicators of inflammation may be important clinical determinants of future periodontal disease progression, but the IL-1 genotype was not a risk indictor for early (slight) periodontitis as defined in this subject population.
    Full-text · Article · Nov 2010 · Journal of Periodontology
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    ABSTRACT: Frequent consumption of cariogenic foods and bacterial infection are risk factors for early childhood caries (ECC). This study hypothesized that a short diet survey focused on frequency of foods, categorized by putative cariogenicity, would differentiate severe ECC (S-ECC) from caries-free children. Children's diets were obtained by survey and plaque bacteria detected by PCR from 72 S-ECC and 38 caries-free children. S-ECC children had higher scores for between-meal juice (p < 0.01), solid-retentive foods (p < 0.001), eating frequency (p < 0.005), and estimated food cariogenicity (p < 0.0001) than caries-free children. S-ECC children with lesion recurrence ate fewer putative caries-protective foods than children without new lesions. Streptococcus mutans (p < 0.005), Streptococcus sobrinus (p < 0.005), and Bifidobacteria (p < 0.0001) were associated with S-ECC, and S. mutans with S. sobrinus was associated with lesion recurrence (p < 0.05). S. mutans-positive children had higher food cariogenicity scores. Food frequency, putative cariogenicity, and S. mutans were associated with S-ECC individually and in combination.
    Full-text · Article · Nov 2010 · Journal of dental research
  • C. A. Palmer · R. Kent · C. Loo · C. Hughes · A. Tanner

    No preview · Article · Sep 2010 · Journal of the American Dietetic Association
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    ABSTRACT: Objectives: We investigated the effect of endodontic treatment alone (ENDO) or ENDO and photodynamic therapy (ENDO+PDT) on root canal microorganisms in 23 (43 canals) and 26 (52 canals) freshly extracted human teeth, respectively, with pulpal necrosis and periapical lesions that were obtained from 32 subjects. Methods: Following instrumentation and irrigation in the ENDO+PDT group, root canals were incubated for 5 min with 50 g/ml methylene blue and then exposed to red light at 665 nm for 5 minutes (100 mW/cm2, 30 J/cm2). Light was delivered from a diode laser via a 250 in diameter optical fiber that uniformly distributed light at 360o. The contents of root canals were sampled at baseline and following ENDO alone or ENDO+PDT. Serial dilutions were prepared, and 100 l aliquots were inoculated onto blood agar and incubated anaerobically for 7 days. Root canal species at baseline and following ENDO alone or ENDO+PDT were characterized using DNA probes to a panel of 39 endodontic species in the checkerboard assay. Results: The ENDO treatment led to <3 log10 CFU reduction compared with baseline, whereas ENDO+PDT led to >5 log10 CFU reduction. Following ENDO+PDT, 17 species were not detected. The frequency of occurrence of the remaining 22 microorganisms was up to 10 times greater in ENDO compared with ENDO+PDT. Conclusions: We conclude that the synergism of standard endodontic treatment and PDT may contribute towards better root canal disinfection. Supported by RO1-DE-16922
    No preview · Conference Paper · Jul 2010
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    ABSTRACT: Objectives: Severe early childhood caries (S-ECC) is an aggressive infection affecting pre-school children. Recent studies have characterized S-ECC using non-cultural molecular methods. This study aimed to determine the cultivable species associated with dental caries by examining S-ECC, a rapidly progressive disease with high clinical significance. Methods: S-ECC and caries-free (CF) children (2-6 years) were recruited, and plaque samples cultured on blood (pH 7), and acid (pH 5) agars. Isolates were identified by comparing partial 16S rRNA sequences with taxa (species) in the Forsyth Human Oral Microbiome Database (HOT taxa). Results: Over 5,000 isolates were sequenced from 42 S-ECC children and 40 CF children. S-ECC children, mean dmft 12.4 0.63, had significantly higher plaque and gingivitis scores than CF children. Isolates were identified to 230 different taxa, many belonging to unnamed, including previously uncultivated, species. Species that were significantly associated with S-ECC children from blood agar included S. mutans (p< 0.001), Scardovia sp. HOT 195 (p<0.01), V. parvula (p<0.05), Porphyromonas catoniae (p<0.05), and S. cristatus (p<0.05). Plaque or gingivitis-associated species included Scardovia sp. HOT 195, P. catoniae, S. mutans, Parascardovia denticolens, and S. sobrinus. No species or clinical features pretreatment differentiated children that did or did not develop new caries after treatment. On blood agar there were higher detection frequencies of most Selenomonas, Capnocytophaga, Prevotella, Porphyromonas, Campylobacter, and Fusobacterium , species whereas mutans streptococci, Lactobacillus, Scardovia, and selected Actinomyces and non-mutans streptococci were preferentially detected on acid agar. Conclusions: In these children with over 50% carious teeth, anaerobic culture detected a wide diversity of species, as reported using clonal analyses. While greater species diversity was detected on blood agar, certain species were only detected on acid agar. We conclude that several non-mutans species may play a role in this aggressive caries infection. Supported by NIH/NIDCR Grant DE-015847.
    No preview · Conference Paper · Mar 2010
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    ABSTRACT: Objectives: Severe early childhood caries (S-ECC) is an aggressive infection affecting preschool children for which diet and bacterial infection are major risk factors. Following treatment, up to 50% children develop recurrent early childhood caries (ECC). This study aimed to compare diet and infection between S-ECC and caries-free (CF) children, and between S-ECC children with and without the risk for recurrent ECC post treatment. Methods: Children ages 2 to 6 years old with S-ECC or were CF were recruited. Children's parents/caregivers completed a diet survey. Caries children were monitored longitudinally to determine whether they experienced recurrent ECC. Food and beverages were assigned to a 5 level cariogenicity score (CS), and a period incidence (PI) score was created for frequency of all food intakes. Dental plaque samples were assayed for S. mutans, S. sobrinus and Bifidobacterium species by PCR. Results: 72 S-ECC children, mean age 3.9 yr, and 39 CF children mean age 3.6 yr were measured. S-ECC children had a mean dmft of13.7 and dmfs of 39.1. At baseline, S-ECC children had more food with higher cariogenicity scores, and higher food intake frequencies, than CF children. S-ECC children had higher detection frequencies of S. mutans (p<0.005), S. sobrinus (p<0.05), and Bifidobacterium species (p<0.0001). Few baseline features differentiated post treatment outcomes although children with recurrent ECC had, at baseline, higher frequencies of cariogenic foods and Bifidobacterium detection frequencies. Children lost to recall had lower family income, and higher baseline between meal juice and Bifidobacterium species. Conclusions: S-ECC and CF children differed in baseline diet and infection, including Bifidobacterium species. Baseline higher frequencies of cariogenic foods and Bifidobacterium species differentiated children who developed recurrent ECC, or were lost to treatment. These findings highlight the importance of cariogenic foods and infection in S-ECC and recurrent ECC. Supported by NIH/NIDCR Grant DE-015847.
    No preview · Conference Paper · Mar 2010
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    ABSTRACT: Objectives: Severe early childhood caries (S-ECC) is an aggressive infection that has a high rate of recurrent caries post therapy. This study aimed to evaluate the association of the aciduric microbiota with S-ECC at baseline, and with subsequent caries post treatment. Methods: Strains from S-ECC and caries-free (CF) children (2-5 years) were isolated on an acid (pH 5) agar and characterized using 16S rRNA partial sequencing to Forsyth Human Oral Microbiome Database Oral Taxons (HOT). S-ECC children were monitored after treatment. The predominant aciduric microbiota was compared between S-ECC and CF children at baseline and between S-ECC children that did or did not show recurrent caries. Species detection frequencies between disease categories were compared by Chi Square analysis. Results: 40 CF children and 42 S-ECC children were sampled. Mean dmft and dmfs for S-ECC children were 12.4 0.63 and 33.4 4.00 respectively. Principal species at increased detection in S-ECC at baseline were: S. mutans 68% (p<0.001), S. sobrinus 15% (p=0.01), L. fermentum 10% (p<0.04), Bifidobacterium dentium 10% (0.04), Scardovia sp. HOT195 41% (p<0.001), and Parascardovia denticolens 17% (p=0.006). There was no difference in baseline caries scores between children with and with out recurrent caries. Post treatment, 35% S-ECC children showed no new caries, 28% had new caries and 33% were lost to follow-up. Baseline species detected more frequently in recurrent caries were S. anginosus 33% (p=0.008), P. denticolens 33% (p= 0.02), but not S. mutans or Scardovia sp. HOT195. Conclusions: While several species showed a strong association with S-ECC, only S. anginosus and P. denticolens were detected more frequently at baseline in children with subsequent caries. Severity of baseline caries did not influence treatment outcomes. Supported by NIH/NIDCR Grant DE-015847.
    No preview · Conference Paper · Mar 2010
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    ABSTRACT: Dental caries in pre-school children has significant public health and health disparity implications. To determine microbial risk markers for this infection, this study aimed to compare the microbiota of children with early childhood caries with that of caries-free children. Plaque samples from incisors, molars, and the tongue from 195 children attending pediatricians' offices were assayed by 74 DNA probes and by PCR to Streptococcus mutans. Caries-associated factors included visible plaque, child age, race, and snacking habits. Species were detected more frequently from tooth than tongue samples. Lactobacillus gasseri (p < 0.01), Lactobacillus fermentum, Lactobacillus vaginalis, and S. mutans with Streptococcus sobrinus (all p < 0.05) were positively associated with caries. By multifactorial analysis, the probiotic Lactobacillus acidophilus was negatively associated with caries. Prevotella nigrescens was the only species (p < 0.05) significantly associated with caries by the 'false discovery' rate. Analysis of the data suggests that selected Lactobacillus species, in addition to mutans streptococci, are risk markers for early childhood caries.
    Full-text · Article · Feb 2010 · Journal of dental research
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    ABSTRACT: To study the in vitro effects of poly(lactic-co-glycolic acid) (PLGA) nanoparticles loaded with the photosensitizer methylene blue (MB) and light against Enterococcus faecalis (ATCC 29212). The uptake and distribution of nanoparticles in E. faecalis in suspension was investigated by transmission electron microscopy (TEM) after incubation with PLGA complexed with colloidal gold particles for 2.5, 5, and 10 minutes. E. faecalis species were sensitized in planktonic phase and in experimentally infected root canals of human extracted teeth with MB-loaded nanoparticles for 10 minutes followed by exposure to red light at 665 nm. The nanoparticles were found to be concentrated mainly on the cell walls of microorganisms at all three time points. The synergism of light and MB-loaded nanoparticles led to approximately 2 and 1 log10 reduction of colony-forming units (CFUs) in planktonic phase and root canals, respectively. In both cases, mean log10 CFU levels were significantly lower than controls and MB-loaded nanoparticles without light. The utilization of PLGA nanoparticles encapsulated with photoactive drugs may be a promising adjunct in antimicrobial endodontic treatment.
    Full-text · Article · Feb 2010 · Journal of endodontics
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    ABSTRACT: The objectives of this study were to measure levels of gingival crevicular fluid (GCF) biomarkers and subgingival bacterial species in periodontally healthy subjects and subjects with periodontitis to explore the relationships among these biomarkers, the subgingival microbiota, and the clinical parameters of periodontal disease. Clinical periodontal parameters were measured at six sites per tooth in 20 subjects with periodontitis and 20 periodontally healthy subjects. GCF and subgingival plaque samples were obtained from the mesio-buccal aspect of every tooth. GCF levels of interleukin (IL)-1beta and IL-8 and matrix metalloproteinase 8 were measured using checkerboard immunoblotting, and the levels of 40 bacterial taxa were quantified using checkerboard DNA-DNA hybridization. A subset of "clinically healthy" sites from each group was analyzed separately. The significance of the differences between groups was determined using the unpaired t test or the Mann-Whitney test. Correlations among immunologic, microbiologic, and clinical data were determined using the Spearman rank correlation coefficient. There were positive correlations among mean clinical parameters, mean levels of the three biomarkers, and the proportions of orange and red complex species (P <0.05). Clinically healthy sites from subjects with periodontitis had higher levels of IL-1beta and IL-8 and higher proportions of orange and red complex species (P <0.05) than clinically healthy sites from periodontally healthy subjects. Red complex species were positively associated with the expression of all biomarkers (P <0.05), whereas purple and yellow complex species had negative correlations with IL-1beta and IL-8 (P <0.05). Clinically healthy sites from subjects with periodontitis have higher levels of GCF biomarkers and periodontal pathogens than clinically healthy sites from periodontally healthy subjects. Different microbial complexes demonstrated distinct associations with specific GCF biomarkers.
    Full-text · Article · Jan 2010 · Journal of Periodontology
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    ABSTRACT: The purpose of this study was to assess the in vitro synergistic effect of methylene blue (MB) and red light on human gingival fibroblasts and osteoblasts with parameters similar to those that may be applied in a clinical setting for endodontic disinfection. Both cell types were sensitized with 50 microg/mL MB followed by exposure to red light at 665 nm for 5 minutes with an irradiance of 10, 20, and 40 mW/cm(2). After photodynamic therapy (PDT), cell viability and mitochondrial activity were evaluated by the neutral red and MTT assay, respectively. The assessment of PDT-induced apoptosis was investigated by western blot analysis using cleaved poly(ADP-ribose) polymerase-specific antibodies. Light at 20 and 40 mW/cm(2) with MB had modest effects at 24 hours on osteoblasts in both assays, whereas sodium hypochlorite completely eliminated cells. Western blot analysis revealed no signs of apoptosis in either cell type. The data suggest that there is a safe therapeutic window whereby PDT can inactivate endodontic pathogens without affecting host cell viability.
    Full-text · Article · Nov 2009 · Journal of endodontics
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    ABSTRACT: This study compared the subgingival microbiota of subjects with refractory periodontitis (RP) to those in subjects with treatable periodontitis (GRs = good responders) or periodontal health (PH) using the Human Oral Microbe Identification Microarray (HOMIM). At baseline, subgingival plaque samples were taken from 47 subjects with periodontitis and 20 individuals with PH and analyzed for the presence of 300 species by HOMIM. The subjects with periodontitis were classified as having RP (n = 17) based on mean attachment loss (AL) and/or more than three sites with AL >or=2.5 mm after scaling and root planing, surgery, and systemically administered amoxicillin and metronidazole or as GRs (n = 30) based on mean attachment gain and no sites with AL >or=2.5 mm after treatment. Significant differences in taxa among the groups were sought using the Kruskal-Wallis and chi(2) tests. More species were detected in patients with disease (GR or RP) than in those without disease (PH). Subjects with RP were distinguished from GRs or those with PH by a significantly higher frequency of putative periodontal pathogens, such as Parvimonas micra (previously Peptostreptococcus micros or Micromonas micros), Campylobacter gracilis, Eubacterium nodatum, Selenomonas noxia, Tannerella forsythia (previously T. forsythensis), Porphyromonas gingivalis, Prevotella spp., Treponema spp., and Eikenella corrodens, as well as unusual species (Pseudoramibacter alactolyticus, TM7 spp. oral taxon [OT] 346/356, Bacteroidetes sp. OT 272/274, Solobacterium moorei, Desulfobulbus sp. OT 041, Brevundimonas diminuta, Sphaerocytophaga sp. OT 337, Shuttleworthia satelles, Filifactor alocis, Dialister invisus/pneumosintes, Granulicatella adiacens, Mogibacterium timidum, Veillonella atypica, Mycoplasma salivarium, Synergistes sp. cluster II, and Acidaminococcaceae [G-1] sp. OT 132/150/155/148/135) (P <0.05). Species that were more prevalent in subjects with PH than in patients with periodontitis included Actinomyces sp. OT 170, Actinomyces spp. cluster I, Capnocytophaga sputigena, Cardiobacterium hominis, Haemophilus parainfluenzae, Lautropia mirabilis, Propionibacterium propionicum, Rothia dentocariosa/mucilaginosa, and Streptococcus sanguinis (P <0.05). As determined by HOMIM, patients with RP presented a distinct microbial profile compared to patients in the GR and PH groups.
    Full-text · Article · Sep 2009 · Journal of Periodontology
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    ABSTRACT: Photodynamic therapy has been advocated as an alternative to antimicrobial agents to suppress subgingival species and to treat periodontitis. Bacteria located within dense biofilms, such as those encountered in dental plaque, have been found to be relatively resistant to antimicrobial therapy. In the present study, we investigated the ability of photodynamic therapy to reduce the number of bacteria in biofilms by comparing the photodynamic effects of methylene blue on human dental plaque microorganisms in the planktonic phase and in biofilms. Dental plaque samples were obtained from 10 subjects with chronic periodontitis. Suspensions of plaque microorganisms from five subjects were sensitized with methylene blue (25 microg/mL) for 5 min then exposed to red light. Multispecies microbial biofilms developed from the same plaque samples were also exposed to methylene blue (25 microg/mL) and the same light conditions as their planktonic counterparts. In a second set of experiments, biofilms were developed with plaque bacteria from five subjects, sensitized with 25 or 50 microg/mL of methylene blue and then exposed to red light. After photodynamic therapy, survival fractions were calculated by counting the number of colony-forming units. Photodynamic therapy killed approximately 63% of bacteria present in suspension. By contrast, in biofilms, photodynamic therapy had much less of an effect on the viability of bacteria (32% maximal killing). Oral bacteria in biofilms are affected less by photodynamic therapy than bacteria in the planktonic phase. The antibacterial effect of photodynamic therapy is reduced in biofilm bacteria but not to the same degree as has been reported for treatment with antibiotics under similar conditions.
    Full-text · Article · Aug 2009 · Journal of Periodontal Research

Publication Stats

1k Citations
74.63 Total Impact Points

Institutions

  • 2000-2012
    • The Forsyth Institute
      • Department of Cytokine Biology
      Cambridge, Massachusetts, United States
  • 2010
    • Harvard University
      • Department of Oral Health Policy and Epidemiology
      Cambridge, Massachusetts, United States
    • Aristotle University of Thessaloniki
      Saloníki, Central Macedonia, Greece