Association of Root Biofilm Bacteriome with Root Caries Lesion Severity and Activity.

INTRODUCTION: This research aimed to assess the association of root biofilm bacteriome with root caries lesion severity and activity in institutionalised Colombian elderlies and was conducted to gather data on the root caries bacteriome in this population. METHODS: A bacteriome evaluation of biofilm samples from sound and carious root surfaces was performed. Root caries was categorised (ICDAS Root criteria) based on severity (sound surfaces, initial: non-cavitated, moderate/extensive combined: cavitated) and activity status (active and inactive). DNA was extracted and the V4 region of the 16S rRNA gene was sequenced; afterwards the classification of features was conducted employing amplicon sequence variants and taxonomic assignment via the Human Oral Microbiome Database (HOMD). Bacterial richness, diversity (Simpson's and Shannon's indices), and relative abundance estimation were assessed and compared based on root caries severity and activity status (including Sound surfaces). RESULTS: A total of 130 biofilm samples were examined: sound (n = 45) and with root caries lesions (n = 85; by severity: initial: n = 41; moderate/extensive: n = 44; by activity: active: n = 60; inactive: n = 25). Species richness was significantly lower in biofilms from moderate/extensive and active groups compared to sound sites. There was a higher relative abundance of species like Lechtotricia wadei, Capnocytophaga granulosa, Cardiobacterium valvarum, Porphyromonas pasteri - in sound sites; Dialister invisus, Streptococcus mutans, Pseudoramibacter alactolyticus and Bacteroidetes (G-5) bacterium 511 - in moderate/extensive lesions, and Fusobacterium nucleatum subsp. animalis, Prevotella denticola, Lactobacillus fermentum, Saccharibacteria (TM7) (G-5)bacterium HMT 356 - in active lesions. CONCLUSION: Root caries bacteriome exhibited differences in species proportions between the compared groups. Specifically, cavitated caries lesions and active caries lesions showed higher relative abundance of acidogenic bacteria.

Salivary levels of five microorganisms of root caries in nursing home elderly: a preliminary investigation.

BACKGROUND: Streptococcus, Bifidobacteria, Lactobacillus and Actinomyces are acidogenic aciduria that may be associated with root caries (RC). The aim of the study was to analyze Streptococcus mutans (S. mutans), Streptococcus sobrinus (S. sobrinus), Bifidobacterium spp., Lactobacillus spp. and Actinomyces naeslundii (A. naeslundii) in the saliva of nursing home elderly, to assess the correlation between bacterial composition and RC for five putative catiogenic organisms. METHODS: In this study, we collected 43 saliva samples and divided into two groups: the root caries group (RCG, n = 21) and the caries-free group (CFG, n = 22). Bacterial DNA was extracted from the saliva samples. The presence and abundance of the five microorganisms were detected by Quantitative real-time PCR (qPCR). Spearman correlation test was performed to evaluate the relationship between the numbers of root decayed filled surfaces (RDFS) and root caries index (RCI) and salivary levels of the bacteria. RESULTS: The salivary levels of S. mutans, S. sobrinus, Bifidobacterium spp. and Lactobacillus spp. were significantly higher in RCG than in CFG (p < 0.05). RDFS and RCI (RDFS/RCI) were positively associated with salivary levels of S. mutans, S. sobrinus and Bifidobacterium spp. (r = 0.658/0.635, r = 0.465/0.420 and r = 0.407/0.406, respectively). No significant differences in presence and amounts of A. naeslundii was observed between the two groups (p > 0.05). CONCLUSION: S. mutans, S. sobrinus and Bifidobacterium spp. in saliva appear to be associated with RC in the elderly. Taken together, the findings indicate that specific salivary bacteria may be involved in the progression of RC.

A Co-Association of Streptococcus mutans and Veillonella parvula/dispar in Root Caries Patients and In Vitro Biofilms.

Root caries in geriatric patients is a growing problem as more people are maintaining their natural teeth into advanced age. We determined the levels of various bacterial species previously implicated in root caries disease or health using quantitative real-time PCR in a pilot study of 7 patients with 1 to 4 root caries lesions per person. Levels of 12 different species on diseased roots compared to healthy (contralateral control) roots were measured. Four species were found at significantly higher levels on diseased roots (Streptococcus mutans, Veillonella parvula/dispar, Actinomyces naeslundii/viscosus, and Capnocytophaga granulosa) compared across all plaque samples. The level of colonization by these species varied dramatically (up to 1,000-fold) between patients, indicating different patients have different bacteria contributing to root caries disease. Neither of the two species previously reported to correlate with healthy roots (C. granulosa and Delftia acidovorans) showed statistically significant protective roles in our population, although D. acidovorans showed a trend toward higher levels on healthy teeth (P = 0.08). There was a significant positive correlation between higher levels of S. mutans and V. parvula/dispar on the same diseased teeth. In vitro mixed biofilm studies demonstrated that co-culturing S. mutans and V. parvula leads to a 50 to 150% increase in sucrose-dependent biofilm mass compared to S. mutans alone, depending on the growth conditions, while V. parvula alone did not form in vitro biofilms. The presence of V. parvula also decreased the acidification of S. mutans biofilms when grown in artificial saliva and enhanced the health of mixed biofilms.

Studies on antimicrobial peptide-loaded nanomaterial for root caries restorations to inhibit periodontitis related pathogens in periodontitis care.

AIMS: To prepare a novel antimicrobial peptide Nal-P-113 loaded poly (ethylene glycol) combined chitosan nanoparticles (Nal-P-113-PEG-CSNPs) for root caries restorations to control the periodontitis related pathogens in periodontitis care. METHODS: Nanoparticles were prepared by simple polymerisation method and characterised using effective analytical methods (TEM, UV, etc.). The antimicrobial activity and biofilm formation of Nal-P-113-PEG-CSNPs was tested against periodontal bacterial pathogens by different in vitro methods. RESULTS: The size of Nal-P-113 loaded PEG-Chitosn nanoparticles was 216.2 ± 1.6 nm. The drug encapsulation efficiency (%EE (w/w) of Nal-P-113-PEG-CSNPs was found to be 89.33 ± 1.67% (w/w). The antimicrobial examination showed that prepared NPs have effectively inhibited the growth of Fusobacterium nucleatum, Streptococcus gordonii, and Porphyromonas gingivalis with the MIC of 23 µg/mL, 6 µg/mL and 31 µg/mL, respectively. CONCLUSIONS: The prepared antimicrobial peptide-loaded PEG-CSNPs provide excellent in vitro efficiency but, further studies are necessary to confirm its therapeutic efficacy on periodontitis care.

Bacterial analysis of biofilms from tooth root surfaces presenting different caries activity / Análise bacteriológica de biofilmes de superfícies dentárias radiculares apresentando diferentes estágios de atividade de cárie

This study evaluated the numbers and determined the proportion of mutans streptococci and Lactobacillus spp., which are possible relevant cariogenic organisms, in biofilms recovered from lesions at root surfaces with active caries lesions (ARC), inactive caries lesions, and sound root surfaces (SRS). Samples were cultured in MSB agar for mutans streptococci counts, Rogosa agar for Lactobacillus spp. counts, and brain-heart infusion agar for total viable anaerobic counts. After incubation, the number of colony-forming units (CFUs) was determined and compared between groups by the Mann-Whitney U test with a significance level set at 95%. The proportion of counts of mutans streptococci and Lactobacillus spp. in the total viable microorganisms was also analyzed by Chi-square test. Ninety samples (30 from each surface) from 37 patients were cultured and analyzed. The CFU was similar between mutans streptococci and Lactobacillus spp.These species were present in at least half of the samples and no difference was found in the frequency of isolation of these species. Only 6 samples showed a proportion of more than 10% of mutans streptococci; 4 of the samples were from ARC. Most (93%) SRS samples did not contain viable Lactobacillus spp. The data indicate the low counts of mutans streptococci and Lactobacillus spp. in root sur-faces, regardless of the activity of caries lesions.

O estudo analisou contagens e proporções de mutans strep-tococci e Lactobacillus spp., que podem ser microorganismos importantes em lesões de cárie radicular com diferentes atividades. Biofilmes foram coletados em três locais: ARC ­ superfície radicular com lesão ativa de cárie; IRC ­ superfícies radiculares com lesão inativa de cárie; SRS ­ superfícies de raizes hígidas. As amostras foram cultivadas em agar MSB para contagens de mutans streptococci; agar Rogosa para Lactobacillus spp., e agar BHI para contagens de microrganis-mos viáveis anaeróbicos totais. Após a incubação, o número de unidades formadoras de colônias (UFCs) foi determinado e comparado entre os grupos pelo teste de Mann-Whitney U test. O nível de significância foi estabelecido em 95%. A pro-porção de contagem de mutans streptococci e Lactobacillusspp. no total de microrganismos viáveis também foi analisado através do teste de qui-quadrado. Um total de 90 amostras de 37 pacientes foram cultivadas e analisadas: 30 amostras de ARC, 30 de IRC e 30 de SRS. Números de UFC foram seme-lhantes entre os grupos para ambos, mutans streptococci e Lactobacillus spp. Estas espécies estavam presentes em pelo menos metade de todas as amostras e nenhuma diferença foi encontrada na frequência de isolamento dessas espécies dentro dos grupos. Apenas 6 amostras apresentaram mais de 10% de mutans streptococci e 4 foram de ARC. Em relação aos Lactobacillus spp., 93% das amostras não apresentaram proporção dessas bactérias nas SRS. Mutans streptococci e Lactobacillus spp. estão presentes em baixa proporção nas superfícies radiculares, independentemente da atividade das lesões de cárie.

Gene expression profile of Scardovia spp. in the metatranscriptome of root caries.

A few investigations of caries biofilms have identified Scardovia spp.; however, little is known about its involvement in caries pathogenesis. The purpose of this study was to assess the gene expression profile of Scardovia spp. in root caries, and compare it with other microorganisms. Clinical samples from active root caries lesions were collected. Microbial mRNA was isolated and cDNA sequenced. The function and composition of the Scardovia were investigated using two methods: a) de novo assembly of the read data and mapping to contigs, and b) reads mapping to reference genomes. Pearson correlation was performed (p < 0.05). Proportion of Scardovia inopinata and Scardovia wiggsiae sequences ranged from 0-6% in the root caries metatranscriptome. There was a positive correlation between the transcriptome of Lactobacillus spp. and Scardovia spp. (r = 0.70; p = 0.03), as well as with other Bifidobacteriaceae (r = 0.91; p = 0.0006). Genes that code for fructose 6-phosphate phosphoketolase (the key enzyme for "Bifid shunt"), as well as ABC transporters and glycosyl-hydrolases were highly expressed. In conclusion, "Bifid shunt" and starch metabolism are involved in carbohydrate metabolism of S. inopinata and S. wiggsiae in root caries. There is a positive correlation between the metabolism abundance of Lactobacillus spp., Bifidobacteriaceae members, and Scardovia in root caries.

The role of Candida albicans in root caries biofilms: an RNA-seq analysis.

Objective This study sought to analyze the gene expression of Candida albicans in sound root surface and root caries lesions, exploring its role in root caries pathogenesis. Methodology The differential gene expression of C. albicans and the specific genes related to cariogenic traits were studied in association with samples of biofilm collected from exposed sound root surface (SRS, n=10) and from biofilm and carious dentin of active root carious lesions (RC, n=9). The total microbial RNA was extracted, and the cDNA libraries were prepared and sequenced on the Illumina Hi-Seq2500. Unique reads were mapped to 163 oral microbial reference genomes including two chromosomes of C. albicans SC5314 (14,217 genes). The putative presence of C. albicans was estimated (sum of reads/total number of genes≥1) in each sample. Count data were normalized (using the DESeq method package) to analyze differential gene expression (using the DESeq2R package) applying the Benjamini-Hochberg correction (FDR<0.05). Results Two genes (CaO19.610, FDR=0.009; CaO19.2506, FDR=0.018) were up-regulated on SRS, and their functions are related to biofilm formation. Seven genes ( UTP20 , FDR=0.018; ITR1 , FDR=0.036; DHN6 , FDR=0.046; CaO19.7197 , FDR=0.046; CaO19.7838 , FDR=0.046; STT4 , FDR=0.046; GUT1 , FDR=0.046) were up-regulated on RC and their functions are related to metabolic activity, sugar transport, stress tolerance, invasion and pH regulation. The use of alternative carbon sources, including lactate, and the ability to form hypha may be a unique trait of C. albicans influencing biofilm virulence. Conclusions C. albicans is metabolically active in SRS and RC biofilm, with different roles in health and disease.

The role of Candida albicans in root caries biofilms: an RNA-seq analysis

Abstract Objective This study sought to analyze the gene expression of Candida albicans in sound root surface and root caries lesions, exploring its role in root caries pathogenesis. Methodology The differential gene expression of C. albicans and the specific genes related to cariogenic traits were studied in association with samples of biofilm collected from exposed sound root surface (SRS, n=10) and from biofilm and carious dentin of active root carious lesions (RC, n=9). The total microbial RNA was extracted, and the cDNA libraries were prepared and sequenced on the Illumina Hi-Seq2500. Unique reads were mapped to 163 oral microbial reference genomes including two chromosomes of C. albicans SC5314 (14,217 genes). The putative presence of C. albicans was estimated (sum of reads/total number of genes≥1) in each sample. Count data were normalized (using the DESeq method package) to analyze differential gene expression (using the DESeq2R package) applying the Benjamini-Hochberg correction (FDR<0.05). Results Two genes (CaO19.610, FDR=0.009; CaO19.2506, FDR=0.018) were up-regulated on SRS, and their functions are related to biofilm formation. Seven genes ( UTP20 , FDR=0.018; ITR1 , FDR=0.036; DHN6 , FDR=0.046; CaO19.7197 , FDR=0.046; CaO19.7838 , FDR=0.046; STT4 , FDR=0.046; GUT1 , FDR=0.046) were up-regulated on RC and their functions are related to metabolic activity, sugar transport, stress tolerance, invasion and pH regulation. The use of alternative carbon sources, including lactate, and the ability to form hypha may be a unique trait of C. albicans influencing biofilm virulence. Conclusions C. albicans is metabolically active in SRS and RC biofilm, with different roles in health and disease.

Gene expression profile of Scardovia spp. in the metatranscriptome of root caries

Abstract A few investigations of caries biofilms have identified Scardovia spp.; however, little is known about its involvement in caries pathogenesis. The purpose of this study was to assess the gene expression profile of Scardovia spp. in root caries, and compare it with other microorganisms. Clinical samples from active root caries lesions were collected. Microbial mRNA was isolated and cDNA sequenced. The function and composition of the Scardovia were investigated using two methods: a) de novo assembly of the read data and mapping to contigs, and b) reads mapping to reference genomes. Pearson correlation was performed (p < 0.05). Proportion of Scardovia inopinata and Scardovia wiggsiae sequences ranged from 0-6% in the root caries metatranscriptome. There was a positive correlation between the transcriptome of Lactobacillus spp. and Scardovia spp. (r = 0.70; p = 0.03), as well as with other Bifidobacteriaceae (r = 0.91; p = 0.0006). Genes that code for fructose 6-phosphate phosphoketolase (the key enzyme for "Bifid shunt"), as well as ABC transporters and glycosyl-hydrolases were highly expressed. In conclusion, "Bifid shunt" and starch metabolism are involved in carbohydrate metabolism of S. inopinata and S. wiggsiae in root caries. There is a positive correlation between the metabolism abundance of Lactobacillus spp., Bifidobacteriaceae members, and Scardovia in root caries.

Effect of Silver Diamine Fluoride Treatment on Microbial Profiles of Plaque Biofilms from Root/Cervical Caries Lesions.

PURPOSE: To assess the effect of silver diamine fluoride (SDF) on microbial profiles present in plaque from root/cervical carious lesions, and its association with caries lesion arrest. MATERIALS AND METHODS: Twenty patients with at least one soft cavitated root/cervical carious lesion were included. One lesion/patient was randomly selected and treated with 38% SDF. Supragingival plaque samples were harvested at preintervention and 1 month postintervention. Using an MiSeq platform, 16S rDNA sequencing of the V3-V4 regions was used to determine bacterial profiles. Clinical evaluation of lesion hardness was used to evaluate arrest. t tests, principal component analysis (PCA), multidimensional scaling (MDS), and generalized linear models (GLMs) tests were used for statistical comparisons. RESULTS: From a total of 40 plaque samples, 468 probe targets were observed. Although 60% of lesions became hard postintervention, PCA and MDS tests showed no distinct pre- and postintervention groups. In addition, pre- and postintervention differences in diversity (Shannon index) of microbial profiles between patients with and without lesion arrest were not statistically different. A likelihood ratio test for pre- versus postintervention differences within patients, i.e., adjusting for differences between patients using negative binomial GLMs, showed 17 bacterial taxa with significant differences (FDR <0.05). CONCLUSION: Although 60% of lesions hardened after SDF treatment, this was not directly due to either overall statistically significant differences in microbial profiles or differences in microbial diversity. Nevertheless, there was a trend with some acid-producing species in that their relative abundance was reduced postintervention. The negative binomial GLMs showed 17 bacterial taxa that were significantly different after SDF treatment.

Root caries prevention via sodium fluoride, chlorhexidine and silver diamine fluoride in vitro.

Uncertainty exists as to how to best prevent root caries development. The aim of the present study was to compare sodium fluoride (NaF), chlorhexidine (CHX) and silver diamine fluoride (SDF) varnishes (V) and rinses (R) regarding their caries preventive effect in an artificial caries biofilm model. 140 bovine root dentin samples were cut, polished and embedded. Samples were allocated to seven treatment groups (n = 20/group): Four varnishes (applied once prior biofilm challenge): 38% SDF (SDFV), 35% CHX-varnish (CHXV), 22,600 ppm NaF-varnish (NaFV), placebo-varnish (PV); two rinses (applied once daily during biofilm challenge): 500 ppm NaF solution (NaFR), 0.1% CHX solution (CHXR); one untreated group. Caries was induced in a multi-station, continuous-culture Lactobacillus rhamnosus GG (LGG) biofilm model. Bacteria were inoculated 1 × daily, while 2% sucrose was supplied 8 ×/day followed by artificial saliva for 10 min. After 12 days, mineral loss (ΔZ) was measured in the effect area and adjacent to the varnished areas. Bacterial counts were assessed on de-Man-Rogosa-Sharpe agar. ΔZ was significantly lower in the NaFR group compared with all other groups. Varnishes did not significantly prevent mineral loss in adjacent areas. None of the agents had a significant antimicrobial effect on LGG. Regular fluoride rinses showed highest root caries-preventive effect.

Starch Combined with Sucrose Provokes Greater Root Dentine Demineralization than Sucrose Alone.

Since there is no consensus about whether starch increases the cariogenic potential of sucrose, we used a validated 3-species biofilm model to evaluate if starch combined with sucrose provokes higher root dentine demineralization than sucrose alone. Biofilms (n = 18) composed by Streptococcus mutans (the most cariogenic bacteria), Actinomces naeslundii (which has amylolytic activity), and Streptococcus gordonii (which binds salivary amylase) were formed on root dentine slabs under exposure 8 ×/day to one of the following treatments: 0.9% NaCl, 1% starch, 10% sucrose, or a combination of 1% starch and 10% sucrose. Before each treatment, biofilms were pretreated with human whole saliva for 1 min. The pH of the culture medium was measured daily as an indicator of biofilm acidogenicity. After 96 h of growth, the biofilms were collected, and the biomass, bacteria viability, and polysaccharides were analyzed. Dentine demineralization was assessed by surface hardness loss (% SHL). Biofilm bioarchitecture was analyzed using confocal laser scanning microscopy. Treatment with a starch and sucrose combination provoked higher (p = 0.01) dentine demineralization than sucrose alone (% SHL = 53.2 ± 7.0 vs. 43.2 ± 8.7). This was supported by lower pH values (p = 0.007) of the culture medium after daily exposure to the starch and sucrose combination compared with sucrose (4.89 ± 0.29 vs. 5.19 ± 0.32). Microbiological and biochemical findings did not differ between biofilms treated with the combination of starch and sucrose and sucrose alone (p > 0.05). Our findings give support to the hypothesis that a starch and sucrose combination is more cariogenic for root dentine than sucrose alone.

Novel bioactive root canal sealer to inhibit endodontic multispecies biofilms with remineralizing calcium phosphate ions.

OBJECTIVE: The objectives of this study were to: (1) develop a bioactive endodontic sealer via dimethylaminohexadecyl methacrylate (DMAHDM), 2-methacryloyloxyethyl phosphorylcholine (MPC) and nanoparticles of amorphous calcium phosphate (NACP) for the first time; and (2) evaluate inhibition of early-stage and mature multispecies endodontic biofilm, bond strength to root canal dentine, and calcium (Ca) and phosphate (P) ion release. METHODS: A series of bioactive endodontic sealers were formulated with DMAHDM, MPC, and NACP. Root dentine bond strength was measured via a push-out test. Three endodontic strains, Enterococcus faecalis, Actinomyces naeslundii, and Fusobacterium nucleatum, were grown on endodontic sealer disks to form multispecies biofilms. Biofilms were grown for 3 days (early) and 14 days (mature). Colony-forming units (CFU), live/dead assay, metabolic activity and polysaccharide were determined. Ca and P ion release from endodontic sealer was measured. RESULTS: Incorporating DMAHDM, MPC and NACP did not decrease the push-out bond strength (p>0.1). Adding DMAHDM and MPC reduced endodontic biofilm CFU by 3 log. DMAHDM or MPC each greatly decreased the biofilm CFU (p<0.05). Endodontic sealer with DMAHDM+MPC had much greater killing efficacy than DMAHDM or MPC alone (p<0.05). Endodontic sealer with DMAHDM+MPC had slightly lower, but not significantly lower, Ca and P ion release compared to that without DMAHDM+MPC (p>0.1). CONCLUSIONS: A novel bioactive endodontic sealer was developed with potent inhibition of multispecies endodontic biofilms, reducing biofilm CFU by 3 log, while containing NACP for remineralization and possessing good bond strength to root canal dentine walls. CLINICAL SIGNIFICANCE: The new bioactive endodontic sealer is promising for endodontic applications to eradicate endodontic biofilms and strengthen root structures. The combination of DMAHDM, MPC and NACP may be applicable to other preventive and restoration resins.

Ecological hypothesis of dentin and root caries.

'...questionable whether bacteria play a role in the initial stages of the degradation of the organic components of teeth.'

Understanding Caries From the Oral Microbiome Perspective.

Dental caries is a major disease of the oral cavity with profound clinical significance. Caries results from a transition of a healthy oral microbiome into an acidogenic community of decreased microbial diversity in response to excessive dietary sugar intake. Microbiological cultivation, molecular identification, gene expression and metabolomic analyses show the importance of the entire microbial community in understanding the role of the microbiome in the pathology of caries.

Ecological Hypothesis of Dentin and Root Caries.

Recent advances regarding the caries process indicate that ecological phenomena induced by bacterial acid production tilt the de- and remineralization balance of the dental hard tissues towards demineralization through bacterial acid-induced adaptation and selection within the microbiota - from the dynamic stability stage to the aciduric stage via the acidogenic stage [Takahashi and Nyvad, 2008]. Dentin and root caries can also be partly explained by this hypothesis; however, the fact that these tissues contain a considerable amount of organic material suggests that protein degradation is involved in caries formation. In this review, we compiled relevant histological, biochemical, and microbiological information about dentin/root caries and refined the hypothesis by adding degradation of the organic matrix (the proteolytic stage) to the abovementioned stages. Bacterial acidification not only induces demineralization and exposure of the organic matrix in dentin/root surfaces but also activation of dentin-embedded and salivary matrix metalloproteinases and cathepsins. These phenomena initiate degradation of the demineralized organic matrix in dentin/root surfaces. While a bacterial involvement has never been confirmed in the initial degradation of organic material, the detection of proteolytic/amino acid-degrading bacteria and bacterial metabolites in dentin and root caries suggests a bacterial digestion and metabolism of partly degraded matrix. Moreover, bacterial metabolites might induce pulpitis as an inflammatory/immunomodulatory factor. Root and dentin surfaces are always at risk of becoming demineralized in the oral cavity, and exposed organic materials can be degraded by host-derived proteases contained in saliva and dentin itself. New approaches to the prevention and treatment of root/dentin caries are required.

Bactericidal effect of Er:YAG laser combined with sodium hypochlorite irrigation against Enterococcus faecalis deep inside dentinal tubules in experimentally infected root canals.

This study evaluated the bactericidal effect of Er:YAG laser radiation combined with sodium hypochlorite (NaOCl) irrigation in the treatment of Enterococcus faecalis deep inside dentinal tubules. The Er:YAG laser was activated, respectively, at 0.3, 0.5 and 1.0 W for either 20 or 30 s; 52.5 g l(-1) NaOCl and normal saline were used for the control groups. Root canals before and after treatments were examined using scanning electron microscopy (SEM). Bacterial reductions both on the root canal walls and at 100, 200, 300, 400 and 500 µm inside the dentinal tubules were analysed using a one-way analysis of variance. SEM results showed that the Er:YAG laser combined with NaOCl disinfected the dentinal tubules from 200 to over 500 µm depth as irradiation power and time increased. This combination killed significantly more bacteria than both the negative control group at each level tested and the positive control group at 300, 400 and 500 µm inside the dentinal tubules. It reached 100% in all experimental groups, both on the root canal walls and at 100 and 200 µm inside the dentinal tubules. However, at 300, 400 and 500 µm inside the dentinal tubules, only the groups treated with 0.5 and 1.0 W for 30s exhibited no bacterial growth. Of the two groups in which no bacteria were detected at all tested depths, Er:YAG laser irradiation at 0.5 W for 30 s combined with NaOCl irrigation was preferable because of the lower emission power and shorter irradiation time, and may serve as a new option for effective root canal disinfection.

Effect of over-the-counter fluoridated products regimens on root caries inhibition.

OBJECTIVE: This study aimed to evaluate the effect of fluoridated dentifrice (FD) and mouthwash (FM) under different treatment regimens on root caries (RC) inhibition. METHODS: Dual-species biofilms formed by Streptococcus mutans and Lactobacillus casei were grown on the surface of bovine root dentine slabs which were exposed during 3 consecutive days to one of the following treatments: T1-distilled and deionized water 3×/day; T2-FD (1450ppmF) 2×/day; T3-FD 2×/day+FM (226ppmF) 1×/day; T4-FD 3×/day. Viable microorganisms counts were performed after 4 days of biofilm formation. Percentage of surface microhardness change (%SMC), lesion depth (LD; µm), integrated mineral loss (IML; vol%×µm) and the percentages of change (Δ%) in the ratio of fluorapatite (FAp/amide) and hydroxiapatite (HAp/amide) were calculated. RESULTS: Minor changes were found on microbial counts in response to different treatments (p<0.05). %SMC in T4 was statistically lower compared with T2, but with no significant difference compared with T3. LD of slabs treated with T4 was statistically lower compared with T2 and T3, which were not significantly different between them. No significant differences were found for IML, FAp and HAp among the fluoridated treatments (p>0.05). CONCLUSION: The use of FD 3×/day may be more effective than the use of FD 2×/day or the tested association between FD and FM on RC inhibition.

Development of a multifunctional adhesive system for prevention of root caries and secondary caries.

OBJECTIVES: The objectives of this study were to: (1) develop a novel adhesive for prevention of tooth root caries and secondary caries by possessing a combination of protein-repellent, antibacterial, and remineralization capabilities for the first time; and (2) investigate the effects of 2-methacryloyloxyethyl phosphorylcholine (MPC), dimethylaminohexadecyl methacrylate (DMAHDM), and nanoparticles of amorphous calcium phosphate (NACP) on dentin bond strength, protein-repellent properties, and dental plaque microcosm biofilm response. METHODS: MPC, DMAHDM and NACP were added into Scotchbond Multi-Purpose primer and adhesive. Dentin shear bond strengths were measured. Adhesive coating thickness, surface texture and dentin-adhesive interfacial structure were examined. Protein adsorption onto adhesive resin surface was determined by the micro bicinchoninic acid method. A human saliva microcosm biofilm model was used to investigate biofilm metabolic activity, colony-forming unit (CFU) counts, and lactic acid production. RESULTS: The resin with 7.5% MPC+5% DMAHDM+30% NACP did not adversely affect dentin shear bond strength (p>0.1). The resin with 7.5% MPC+5% DMAHDM+30% NACP produced a coating on root dentin with a thickness of approximately 70µm and completely sealed all the dentinal tubules. The resin with 7.5% MPC+5% DMAHDM+30% NACP had 95% reduction in protein adsorption, compared to SBMP control (p<0.05). The resin with 7.5% MPC+5% DMAHDM+30% NACP was strongly antibacterial, with biofilm CFU being four orders of magnitude lower than that of SBMP control. Significance The novel multifunctional adhesive with strong protein-repellent, antibacterial and remineralization properties is promising to coat tooth roots to prevent root caries and secondary caries. The combined use of MPC, DMAHDM and NACP may have wide applicability to bonding agents, cements, sealants and composites to inhibit caries.

Extensive description and comparison of human supra-gingival microbiome in root caries and health.

Knowledge of the polymicrobial etiology of root caries is limited. To conduct a comprehensive research study on root caries, we utilized 454-pyrosequencing of 16S rRNA gene libraries and quantitative PCR to compare supra-gingival bacterial communities from healthy sites and carious sites of 21 patients with root caries (Patient-controls and Patient-cases) and the sites of 21 healthy individuals (Healthy-controls) from two nursing homes. Healthy-controls and Patient-cases showed no significant differences in terms of biomass, species richness, and species diversity. However, as for beta diversity based on either community membership metric (unweighted UniFrac) or community structure metric (weighted UniFrac), Healthy-controls and Patient-cases were clearly distinguished from each other, appearing more variable in the community membership and structure in root caries microbiome but relatively conserved in the health microbiome. The Patient-controls group was at an intermediate stage between Healthy-controls and Patient-cases, but was more inclined to the former. Demonstrated in both relative abundance and prevalence of species in health and root caries, Propionibacterium acidifaciens, Streptococcus mutans, Olsenella profusa, Prevotella multisaccharivorax, and Lactobacillus crispatus were found to be most associated with root caries, whereas Delftia acidovorans, Bacteroidetes[G-2] sp., Lachnospiraceae[G-3] sp., and Prevotella intermedia are most associated with health. Our study provides a basis for further elucidating the microbial etiology of root caries in the elderly.