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Since Veillonella species obtain the energy for their growth by fermenting organic acids, e.g., lactate, this metabolism has the potential to remove a potent, dental-caries producing acid. Therefore, the presence of Veillonella in plaque biofilm may reduce the caries-producing potential of plaque biofilm. Quantification of genera Veillonella and Streptococcus in healthy supragingival plaque biofilm microflora of children was performed in the present study. Total bacteria and the target genera ( Veillonella and Streptococcus ) were quantified by real-time PCR using universal and genus-specific primers, respectively, and the proportion of each genus was calculated. The proportion of genera Veillonella and Streptococcus was 2.1 ± 4.1% and 19.4 ± 16.7%, respectively. The results of the present study showed that Veillonella and Streptococcus normally inhabit the human mouths of both deciduous and permanent dentition.

Maltotriitol is known to inhibit α-glucosidase and maltose metabolism of Streptococcus mutans . In this study, we evaluated inhibitory effects of maltotriitol on the growth and adhesion of mutans streptococci. Bacterial adherence to glass surfaces and bacterial culture pH in the presence or absence of maltotriitol were determined. In the presence of maltotriitol, the growth of Streptococcus sobrinus with glucose, maltose, and sucrose was decreased, while the adhesion was not inhibited. On the other hand, maltotriitol did not decrease the growth of S. mutans except the cell growth with glucose, while maltotriitol inhibited the bacterial adhesion. The culture pH was less acidic when the growth was inhibited by maltotriitol. These results suggest that inhibitory effects of maltotriitol on mutans streptococci are different among species: maltotriitol inhibits the growth of S. sobrinus , while it inhibits the adhesion of S. mutans .

Placebo-controlled trial demonstrated that consuming yogurt with Lactobacillus reuteri could not significantly reduce the habitat for mutans streptococci within plaque in vivo.

This study aimed to examine effects of α-amylase and its inhibitors on acid production from starch by streptococci. Glucose-grown streptococci were anaerobically incubated with various carbohydrates, including starch in the presence or absence of α-amylase pH fall and acid production rate were measured. α-amylase inhibitors were added to the reaction mixture and the effects were evaluated. In the absence of α-amylase, both pH fall and acid production rate from starch were small. In the presence of α-amylase, pH fall and acid production rate from starch by Streptococcus mutans and Streptococcus sanguinis were similar to those from maltose. The pH fall from starch by S. mutans was similar to that by S. sanguinis . The addition of α-amylase inhibitors decreased the acid production rates from starch in the presence of α-amylase. These results suggest that starch is acidogenic similarly to maltose in the presence of α-amylase, and that the acidogenic potential of starch by S. sanguinis was comparable to that by S. mutans .

This study aimed to evaluate inhibitory effects of glass-ionomer cement (GIC) on the acid production of caries-related oral streptococci, and to identify the components responsible for the inhibition. GIC eluate contained silicon, fluoride, and aluminum, and inhibited the pH fall and the rate of acid production by oral streptococci at acidic pH, with a concomitant decrease in lactic acid production. These inhibitions were comparable to those of a potassium fluoride solution containing the same concentration of fluoride as the eluate. This study indicates that the GIC eluate inhibits the acid production of the caries-related oral streptococci, and suggests that the effect is attributed to the fluoride derived from GIC. Thus, adjacent to GIC fillings, bacterial acid production and the subsequent bacterial growth may decrease, establishing a cariostatic environment.

This study aimed to profile microflora of root canals before and after root canal treatments, using real-time PCR and cloning-sequence analyses based on 16S rRNA genes. Six infected root canals of single-rooted teeth with periapical lesions were included. The quantification of total bacteria was performed by realtime PCR using universal primers based on 16S rRNA genes. PCR products were cloned and partially sequenced, and bacterial identification to the species level was performed by comparative analysis with the GenBank database. The concentrations of bacterial DNA after root canal treatments were less than those before root canal treatments. The cloning-sequence analysis suggested that the root canal microflora in cases of after root canal treatments was clearly distinct from that of before root canal treatments.

A nested polymerase chain reaction (PCR) method was developed for rapid and sensitive detection of periodontopathic bacteria in subgingival plaque samples. Species-specific nested PCR amplification of 16S ribosomal RNA genes was used to detect Aggregatibacter actinomycetemcomitans, Eubacterium saphenum, Mogibacterium timidum, Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Tannerella forsythia, Treponema denticola, Treponema medium, Treponema socranskii, Treponema vincentii , and Slackia exigua . A universal set of PCR primers for bacterial 16S rRNA gene was introduced for the first PCR, and then species-specific primers for the 16S rRNA gene sequences of the respective species were used for the second PCR.

The aim of this study was to evaluate whether the oral administration of lactobacilli could change the periodontal condition and microflora compared with placebo. Sixty-six healthy volunteers were randomized into two groups to receive lactobacilli or placebo for 8 weeks. The mean Plaque Index, Gingival Index, and bleeding on probing were significantly improved at 4 and 8 weeks in both groups, but showed the biggest change on smokers in the test group. Occurrence of Porphyromonas gingivalis and Treponema denticola in the subgingival plaque sample significantly decreased in the test group at 8 weeks. Oral administration of probiotic lactobacilli successfully reduced the prevalence of periodontopathic bacteria from the subgingival plaque, and possibly contributed to the beneficial effects on periodontal conditions.

Porphyromonas gingivalis is the most common organism linked to adult forms of periodontal disease. The proteome analysis of P. gingivalis cells that were placed in a mouse subcutaneous chamber revealed that ten proteins were upregulated in host tissues, whereas four proteins were downregulated. Among them, three upregulated proteins, PG1089 (DNA-binding response regulator RprY), PG1385 (TPR domain protein), and PG2102 (immunoreactive 61 kDa antigen) were chosen for further analysis. Mouse abscess model experiments revealed that the mutant strains defective in PG1089 and PG1385 were clearly less virulent, whereas the mutant defective in PG2102 was as virulent as the wild type parent strain. These results indicate that PG1089 and PG1385 proteins are involved in virulence of P. gingivalis . Using the yeast two hybrid system, PG1385 was associated with 40 proteins including four periplasmic proteins; lack of PG1385 may result in loss of physiological function of these proteins.

Oral lichen planus is a refractory and chronic inflammatory disease with bilateral white reticular lesions on oral mucosa. Identification of Candida species including non- Candida albicans from buccal mucosa, tongue surfaces, and tooth surfaces of oral lichen planus patients by molecular biological method was performed in the present study. The Candida isolates were identified at species level by polymerase chain reaction (PCR) for genes of 18S, 5.8S, and 25/28S ribosomal RNAs and the sequence analyses of these PCR products. The isolation frequency of Candida species was higher from oral lichen planus than from healthy subjects. Non- C. albicans species ( Candida glabrata, Candida fukuyamaensis , and Candida parapsilosis ) were isolated only from oral lichen planus patients. In addition, Candida fukuyamaensis and Candida parapsilosis were genetically close to C. albicans , while C. glabrata was genetically distinguished from these species. These results support that Candida species are related with oral lichen planus, and suggest that C. glabrata may have a unique pathogenicity to oral lichen planus.