Interest in international programmes - a survey of Japanese dental hygiene students and educators.

PURPOSE: Globalization of Japanese dental hygienists is important to match the demands in the present society. The purpose of this study was to gauge opinions on international programmes of Japanese dental hygiene students and educators. METHOD: Data were collected using a survey that was sent to all eight Japanese universities of oral hygiene in December 2014. Participants were composed of 466 university students majoring in oral hygiene (463 women; three men; mean age: 21 years) and 45 educators teaching dental hygiene education (mean age: 50 years). The response rates were 83.81% and 46.88%, respectively. RESULTS: 48.06% of 464 students would like to study abroad, and 76.04% of 330 students would like to interact with foreign students frequently. 97.54% of 455 students answered that learning English is important for dental hygienists, but 72.39% of 460 students are not comfortable interacting with foreigners in English. Those who knew more dental English terms had higher interest in studying abroad (odds ratio: 1.136). 75% of 44 educators think that dental hygiene students need to or sometimes need to study abroad. 68.89% of 45 educators think that teaching international programmes is costly. CONCLUSION: We found that Japanese dental hygiene students and educators have positive interest in international programmes. However, they have concerns about their English skills and about the cost of studying it. Therefore, English classes need to be improved, and new approaches are required for lowering the cost of teaching international programmes, while stimulating foreign students' and educators' interest in studying abroad in Japan.

DNA methylation of the BMAL1 promoter.

We previously analyzed transcriptional regulation of the BMAL1 gene, a critical component of the mammalian clock system and found that the BMAL1 gene is expressed with circadian oscillation and that its regulatory region is located in hypomethylated CpG islands with an open chromatin structure. Here, we found that the BMAL1 gene is not expressed with circadian oscillation in CPT-K cells because the CpG islands located in the BMAL1 promoter are hypermethylated and that 5-aza-2'-deoxycytidine (aza-dC) recovered BMAL1 expression. In contrast, CpG islands in the PER2 promoter were hypomethylated, the PER2 gene was expressed and aza-dC enhanced PER2 gene expression in CPT-K cells. Reporter gene assays showed that intracellular transcriptional machinery for the BMAL1 gene is active, suggesting that BMAL1 inactivation is caused by DNA methylation and not by malfunctional promoter activity. Incubating CPT-K cells with aza-dC also increased CRY1 expression, whereas CLOCK expression was not altered and the CRY1 promoter was unmethylated. These results suggest that aza-dC induces BMAL1 expression via DNA demethylation in the BMAL1 promoter and enhances PER2 and CRY1 transcription. Finally, aza-dC recovered the circadian oscillation of BMAL1 transcription. These results suggest that DNA methylation of the BMAL1 gene is critical for interfering with circadian rhythms.

Gender difference in tooth autotransplantation with complete root formation: a retrospective survey.

Gender-related risk factors in the survival of transplanted teeth with complete root formation have not yet been identified. The purpose of this study was to investigate gender differences in tooth autotransplantation at dental clinics. We asked participating dentists to provide information on transplantations they had undertaken from 1 January 1990 to 1931 December 2010. The data were screened to exclude patients who underwent more than one transplantation, smokers or those whose smoking habits were unknown, patients under 30 or who were 70 years old and over, cases where the transplanted teeth had incomplete root formation or multiple roots and those with fewer than 20 present teeth post-operation. We analysed 73 teeth of 73 males (mean age, 47.2 years) and 106 teeth of 106 females (mean age, 45.3 years) in this study. The cumulative survival rate and mean survival time were calculated using the Kaplan-Meier method. The cumulative survival rate for males was 88.3% at the 5-year mark, 64.8% at 10 years and 48.6% at 15 years; for females, it was 97.2% at the 5-year mark, 85.9% at 10 years and 85.9% at 15 years. A log-rank test indicated the difference between males and females to be significant (P = 0.011). There was also a significant difference in the main causes for the loss of transplanted teeth: males lost more transplanted teeth due to attachment loss than females (P < 0.05). These results indicate that males require more attention during the autotransplantation process, particularly at the stage of pre-operation evaluation and that of follow-up maintenance.

Influence of age on tooth autotransplantation with complete root formation.

The aim of this study was to investigate risk factors with age in the long-term prognosis of autotransplantation of teeth with complete root formation at dental clinics. Participating dentists were asked to provide information on transplantations they had undertaken from 1 January 1990 to 31 December 2010. Data on a total of 708 teeth from 637 patients were collected. The data were screened to exclude patients who were under 25 or 70 years of age and over, those who were smokers or whose smoking habits were unknown, those whose transplanted teeth had incomplete root formation or multiple roots and those with fewer than 25 present teeth post-operation. The participants in this study were 71 men (74 teeth) and 100 women (107 teeth) ranging from 25 to 69 years of age. Third molars were used as donor teeth in 89·0% of the cases. The participants were divided into three age groups of 25-39, 40-54 and 55-69. Survival analysis was conducted using the Kaplan-Meier method, and a log-rank test revealed that there were no significant differences in age groups for men or women. Cox regression analysis indicated that the survival of transplanted teeth was not influenced by age. However, although not statistically significant, the clinical success rate was lower in the 55-69-year-old group than that in the younger groups. These results indicate that if suitable donor teeth are available and the conditions are right, autotransplantation is a viable treatment for missing teeth regardless of the age of the patient.

Comparison of prognosis of separated and non-separated tooth autotransplantation.

The aim of this study was to compare the prognosis of separated and non-separated tooth autotransplantation of the upper first and second molars with complete root formation undertaken at dental clinics. The participating dentists were requested to provide information on transplantations they had undertaken from 1 January 1990 to 31 December 2010. Data on a total of 708 teeth from 637 patients were collected. This study analysed 35 separated teeth and 22 non-separated teeth of 47 participants ranging from 27 to 76 years of age (mean age: 55·0 years) after data screening and elimination. The cumulative post-transplantation survival rate at 10 years was 77·1% for separated teeth and 63·6% for non-separated teeth as calculated with the Kaplan-Meier method. There were no significant differences between separated teeth and non-separated teeth in a log rank test (P = 0·687). Separated-tooth autotransplantation can help fill narrow recipient sites and increase occlusal supporting zones, but the clinical success rate was only 48·6%. Although transplantation of teeth with complete root formation has limited prognosis, transplantation of upper first and second molars, whether separated or non-separated, is a viable option to replace missing teeth.

Risk factors affecting third molar autotransplantation in males: a retrospective survey in dental clinics.

The aim of this study was to investigate the risk factors affecting long-term prognosis of autotransplantation of third molars with complete root formation in males at dental clinics. Participating dentists were requested to provide information on transplantations they had undertaken from 1 January 1990 to 31 December 2010. Data on a total of 708 teeth from 637 patients were collected. After data screening and elimination, participants of this study consisted of 183 teeth of 171 males ranging from 20 to 72 years of age (mean age, 44·8 years). The cumulative survival rate was 86·0% at the 5-year mark, 59·1% at 10 years and 28·0% at 15 years. The mean survival time was 134·5 months, as calculated by the Kaplan-Meier method. Single factor analysis using the log-rank test showed that the following factors had significant influence (P < 0·05) on survival of transplanted teeth: periodontal disease as the reason for recipient site tooth extraction, fewer than 25 present teeth and Eichner index Groups B1 to C. Cox regression analysis examined five factors: age, smoking habit, recipient site extraction caused by periodontal disease, fewer than 25 present teeth and Eichner index. This analysis showed that two of these factors were significant: fewer than 25 present teeth was 2·63 (95% CI, 1·03-6·69) and recipient site extraction caused by periodontal disease was 3·80 (95% CI, 1·61-9·01). The results of this study suggest that long-term survival of transplanted teeth in males is influenced not only by oral bacterium but also by occlusal status.

A retrospective survey of autotransplantation of teeth in dental clinics.

The aim of this study was to investigate the usage of tooth autotransplantation in dental clinics which offer the treatment and evaluate its practicality. Participating dentists were requested to provide information on transplantations they had undertaken from 1 January 1990 to 31 December 2010. A total of 614 teeth from 552 patients (37 dentists) ranging in age from 17 to 79 (mean age: 44·1) were examined. Cumulative survival rate and mean survival time were calculated using the Kaplan-Meier method, and log rank test was used for analysis of factors. The mean number of autotransplantation patients per clinic per year was 1·4. Upper third molars constituted 36·8% of donor teeth, while 37·1% were lower third molars. The lower first molar region was the most common recipient site at 32·6%, followed by the lower second molar region (28·0%). Prosthodontic treatment of transplanted teeth involved coverage with a single crown (72·5%) and abutment of bridge (18·9%). A total of 102 transplanted teeth were lost owing to complications such as attachment loss (54·9%) and root resorption (25·7%). The cumulative survival rate in cases where donor teeth had complete root formation was 90·1% at 5 years, 70·5% at 10 years and 55·6% at 15 years. The mean survival time was 165·6 months. Older age was a significant risk factor (P < 0·05) for survival. In cases where suitable donor teeth are available, autotransplantation of teeth may be a plausible treatment option for dealing with missing teeth in dental clinics.

Saliva-promoted adhesion of Streptococcus mutans MT8148 associates with dental plaque and caries experience.

Colonization of enamel surfaces by Streptococcus mutans is thought to be initiated by the attachment of bacteria to a saliva-derived conditioning film (acquired pellicle). However, the clinical relevance of the contribution of saliva-promoted S. mutans adhesion in biofilm formation has not yet been fully elucidated. The aim of this study was to correlate saliva-promoted S. mutans adhesion with biofilm formation in humans. We correlated all measurements of salivary factors and dental plaque formation in 70 healthy subjects. Dental plaque development after thorough professional teeth cleaning correlated positively with S. mutans adhesion onto saliva-coated hydroxyapatite pellets and the glycoprotein content of either parotid or whole saliva. Saliva-promoted S. mutans adhesion and glycoprotein content were also positively correlated with each other in parotid and whole saliva. By contrast, neither salivary mutans streptococci, Lactobacillus nor Candida correlated with biofilm formation. Parotid saliva-mediated S. mutans adhesion was significantly higher in 12 caries-experienced (CE) subjects than in 9 caries-inexperienced (CI) subjects. Salivary S. mutans adhesion was significantly less (p < 0.01) in the CI group than in the CE group. In conclusion, the present findings suggest the initial S. mutans adhesion, modulated by salivary protein adsorption onto the enamel surface, as a possible correlate of susceptibility to dental plaque and caries.

Statherin and histatin 1 reduce parotid saliva-promoted Streptococcus mutans strain MT8148 adhesion to hydroxyapatite surfaces.

Small salivary phosphoproteins--statherin (ST) and histatin 1 (HT1) - are found in the acquired enamel pellicle which modulates Streptococcus mutans adhesion onto dental enamel. However, their roles in S. mutans adhesion onto enamel surfaces are still undefined. The aim of this study was to investigate whether and how ST and HT1 affect (i) S. mutans adhesion and (ii) the adsorption of S. mutans adhesion-promoting salivary proteins onto hydroxyapatite (HA) in vitro. We fractionated human parotid saliva by adsorption to HA and further by gel filtration chromatography. Adhesion of [3H]-labeled S. mutans strain MT8148 onto sintered HA plates was promoted significantly (>10-fold) by high-molecular weight glycoprotein fraction (HMWGP), but not by purified ST or HT1. More interestingly, promotion of S. mutans adhesion onto HA by HMWGP was significantly reduced by adding purified ST or HT1 to HMWGP. [3H]-labeled S. mutans adhesion on HA was positively correlated to the [14C]-labeled HMWGP adsorption onto HA, which was also reduced by the addition of purified ST and HT1. Synthetic peptides corresponding to ST and HT1 reduced the parotid saliva-promoted S. mutans adhesion. However, removal of the negative charges in the N-terminal domains of ST and HT1 diminished their inhibitory effects on S. mutans adhesion promoted by parotid saliva. We conclude that ST and HT1 competitively inhibit the adsorption of salivary HMWGP, and thereby reduce S. mutans adhesion onto HA surfaces.

Reduction of saliva-promoted adhesion of Streptococcus mutans MT8148 and dental biofilm development by tragacanth gum and yeast-derived phosphomannan.

The aim of this study was to investigate materials which reduce saliva-promoted adhesion of Streptococcus mutans onto enamel surfaces, and their potential in preventing dental biofilm development. The effects of hydroxyapatite (HA) surface pretreatment with hydrophilic polysaccharides on saliva-promoted S. mutans adhesion in vitro and de novo dental biofilm deposition in vivo were examined. Saliva-promoted adhesion of S. mutans MT8148 was significantly reduced by pretreatment of the HA surface with tragacanth gum (TG) and yeast-derived phosphoglycans. Extracellular phosphomannan (PM) from Pichia capsulata NRRL Y-1842 and TG reduced biofilm development on lower incisors in plaque-susceptible rats when administered via drinking water at concentrations of 0.5% and 0.01%, respectively. The inhibitory effect of TG on de novo dental biofilm formation was also demonstrated when administered via mouthwash in humans. It is concluded that TG and yeast-derived PM have the potential for use as anti-adherent agents and are effective in reducing de novo dental biofilm formation.

Salivary flow and its relationship to oral signs and symptoms in patients with dry eyes.

OBJECTIVES: The aim of this study was to investigate oral symptoms and clinical parameters in dry eye patients. Subjective reports of the sensation of a dry mouth, salivary flow rates, and clinical parameters of oral disease related to three different types of dry eye patients were examined. SUBJECTS AND METHODS: There were 224 individuals, including dry eye patients and control subjects. The dry eye patients were classified into three types: patients with Sjögren's syndrome (SS-DE), patients without SS-DE (non-SS-DE), and patients with Stevens-Johnson syndrome (SJS-DE). Salivary flow rates were measured using two kinds of sialometry. Subjective and objective oral symptoms and signs were also examined. RESULTS AND CONCLUSION: Over half of the dry eye patients complained of a dry mouth. The flow rates of their stimulated whole saliva and parotid saliva were significantly lower than those of the control groups (P < 0.05, P < 0.01). The sensation of a dry mouth and changes in oral soft tissues, dental caries, and oral Candida frequently occurred in dry eye patients.

Comparison of the activity of four chitosan derivatives in reducing initial adherence of oral bacteria onto tooth surfaces.

We examined the effects of four kinds of chitosan derivatives on initial adherence of oral bacteria onto human anterior teeth surfaces. The buccal surfaces of anterior teeth were used as the experimental surfaces. They were divided into five rectangle areas with outer dimensions of about 2 mm x 4 mm. After applying two ml of a sample solution onto the tooth surfaces, an examiner wiped each rectangle area with a sterilized plastic swab one, three and six hours later. Then we measured bacterial counts in sterilized swabs with mitis salivarius agar. We found that the order of magnitude of the inhibitory effect on the adherence of oral bacteria was low molecular chitosan > phosphorylated chitosan > amorphous chitosan > carboxymethyl chitosan. The solution containing 0.5% low molecular chitosan depressed the bacterial adherence to the same extent as a 50 ppm chlorhexidine digluconate solution for three hours, and 0.1% phosphorylated chitosan also exhibited an inhibitory effect in bacterial adherence for one hour. Amorphous chitosan had a moderate inhibitory effect, but no clear inhibitory activity was found with 0.1% carboxymethyl chitosan. These results suggest that low molecular chitosan and phosphorylated chitosan have the potential to effectively inhibit the initial adherence of oral bacteria onto human tooth surfaces.

Effect of rinsing with phosphorylated chitosan on four-day plaque regrowth.

This clinical investigation examined the effect of phosphorylated chitosan rinsing on plaque development and on the buffering capacity of plaque suspension. Three male adult subjects participated in the trial that was designed as a single blind study. Participants refrained from mechanical oral hygiene procedures during a four-day study and rinsed three times a day with 20 ml of test solutions. A wash-out period of three days was instituted between the placebo and phosphorylated chitosan rinsing period. Clinical evaluation and plaque sampling were performed at the end of each test period. We disclosed plaque accumulations on the buccal upper front teeth with a two-tone disclosing agent to distinguish between newly formed plaque and old plaque. After taking color slides, we then used a computerized image analysis. Tooth areas covered by plaque on the color slides were digitized and expressed as percentages of the tooth area. The buffering capacity of the collected plaque fluid was determined by using a beta-titrator. A mouth rinse containing 0.5% phosphorylated chitosan significantly reduced both newly formed plaque areas (red disclosed; p < 0.001) and old plaque areas (blue disclosed; p < 0.01) compared to a placebo rinsing. However there was no significant difference in the plaque buffering capacity (p > 0.05) between the mouth rinse containing 0.5% phosphorylated chitosan and placebo. These findings might suggest that mouth rinse containing phosphorylated chitosan would be effective in reducing plaque formation and have a slight ability to enhance plaque buffering capacity.

Caries-inducing activity of the hydrogenated derivative of an isomaltooligosaccharide mixture in rats.

The caries-inducing activity of the hydrogenated derivative of an isomaltooligosaccharide mixture (IMO-H) was evaluated in vitro for its acidogenicity and in vivo an experimental caries system with specific-pathogen-free (SPF) rats. Streptococcus sobrinus 6715 (serotype g) did not produce a significant amount of acid from IMO-H, whereas Streptococcus mutans MT8148 (serotype c) gradually produced a small amount of acid, although the degree was less than that of sucrose. In vivo experiments were conducted on rats which were provided with the test sugars at two different times: at the time of organism inoculation, and after the organisms had become completely established. IMO-H did not induce significant dental caries in rats infected with the S. sobrinus 6715 or S. mutans MT8148R strain.

Effects of a hydrogenated isomaltooligosaccharide mixture on glucan synthesis and on caries development in rats.

The caries inhibitory effect of the hydrogenated derivative of an isomaltooligosaccharides mixture (IMO-H) was examined in vitro and in vivo experiments. IMO-H could not be used as a substrate for the crude glucosyltransferases (GTases) of Streptococcus sobrinus 6715 to synthesize water-insoluble glucan. Moreover, it not only significantly inhibited the synthesis of water-insoluble glucan from sucrose, but also the sucrose-dependent adherence of these growing cells the glass surfaces. In the in vivo experiment, the addition of IMO-H to a sucrose-containing diet resulted in significant reduction of caries development in specific-pathogen-free (SPF) rats infected with S. sobrinus 6715.

Evaluation of acidogenicity of commercial isomaltooligosaccharides mixture and its hydrogenated derivative by measurement of pH response under human dental plaque.

The acidogenicity of commercially available isomaltooligosaccharides mixture (IMO) and its hydrogenated derivative (IMO-H) were evaluated by the in vivo pH response under dental plaque of six subjects (aged 25-28) using intraoral apparatus. The apparatus, an indwelling pH sensor of a hydrogen ion-sensitive field effect transducer (ISFET), was placed on the buccal site of the mandibular first molar, and the plaque was accumulated for four days. The test sugars were applied with three methods-dropping the solution directly on the plaque, rinsing the oral cavity with the solution, and sucking a candy made of the test sugar (weight 3-4 g). IMO could not be evaluated as a type of sugar with low acidogenicity, especially by the candy method, but IMO-H could be evaluated as a type of sugar with very low acidogenicity in a similar manner as maltitol or sorbitol in all type of applications. The acidogenic response of dental plaque should be assumed to be closely related to salivary parameters such as the secretion rate or to mutans streptococci level of subjects and types of application.

pH response of human dental plaque to chewing gum supplemented with low molecular chitosan.

The effects of low molecular chitosan (LMCS) on pH responses of human dental plaque following exposure to fermentable carbohydrates were investigated by an ion-sensitive field-effect transistor electrode system. After the plaque pH values were minimized by direct application of 5% glucose solution or consumption of sugared caramel, the subjects started chewing the test gums containing 0 (control), 1 or 3% (w/w) LMCS for three minutes. The pH response was monitored until it recovered to over pH5.5. In the case of the glucose solution, chewing 3% LMCS gum caused significantly more rapid pH recovery toward the resting level than did the control gum. Initial pH rising rate during gum chewing was faster with either of the two LMCS gums than with the control gum. In the case of caramel, additional effects of LMCS were observed numerically as LMCS content increased. The findings indicated that LMCS had a potential to promote recovery of plaque pH after acidogenic challenge and to maintain the plaque pH around neutrality.

The influences of the buffer capacity of various substances on pH changes in dental plaque.

This study clarified the suitable pKa value for buffering substances against plaque pH fall in vitro and simultaneously estimated the effect of low molecular chitosan (LMCS) on plaque pH lowered by metabolized acids in vitro and in vivo. Five buffering substances with different pKa, aspartame (pKa: 7.8), phosphate buffer (7.1), LMCS (6.4), maleate buffer (6.2), and monofluorophosphate (4.8), were tested in this study. In the method using S. mutans cells, phosphate inhibited the pH fall from an initial pH of over 7.0, but phosphate exhibited no effect when the initial pH was 6.0. By the addition with lactic acid, LMCS and maleate exhibited more effective inhibition of the pH-fall than the others. These observations imply that pKa value is an important indicator of the ability of a buffering substance to reduce pH fall in dental plaque and that the optimum pKa value may be around pH 6.3. In the plaque pH measurement using ISFET electrode, LMCS showed an additional effect in inhibiting plaque pH fall following direct application of the glucose solution. The findings indicate that LMCS may be useful as a food additive to decrease the cariogenicity of foods.

Effects of low molecular chitosan on pH changes in human dental plaque.

Effects of six kinds of low molecular chitosan (LMCS) on pH changes in dental plaque were compared in vitro and in vivo in order to clarify the relationship between their characteristics and effectiveness. Six LMCS with different molecular weights (MW) (500-3,000) and degrees of deacetylation (DAC) (50-95%) were prepared for this study. Evaluations using S. mutans cell suspensions in vitro showed that all samples had almost equal abilities to reduce pH fall in dental plaque. They were found to have no influence on the glycolytic activity of S. mutans. However, clinical evaluations of pH fall in dental plaque using an ion-sensitive field-effect transistor (ISFET) electrode showed unexpected results as follows; The most reduction in pH fall was obtained with the LMCS with a MW of 3,000 and a DAC of 50%, which had been presumed to be the most ineffective sample. The second ranked LMCS in this experiment had a MW of 500 and a DAC of 95%; it had been expected to be the most effective one. The findings indicated that LMCS has a high ability to inhibit pH fall in dental plaque and suggested that such properties as molecular weight and degree of deacetylation can have great influences upon its activity in clinical application.

Decline in caries prevalence in 6-14-year-old schoolchildren during 1975-85 in Shizuoka, Japan.

The purpose of this study was to examine changes in caries prevalence during 1975-85 in Japanese schoolchildren who did not have an apparent change in fluoride exposure. A total of 2872 schoolchildren aged 6-14 yr in two primary schools and one junior high school in Shizuoka city, Japan, were examined in 1985. The caries prevalence in 1985 was then compared with data which had been collected in a longitudinal survey on schoolchildren in the same primary and junior high schools by Katayama in 1970-75. The results indicated that DMFT and DMFS indices in 1985 were significantly lower than those in 1970-75 in all the examined ages (P < 0.01). The DMFT indices at age 12 were 3.60 in 1985 and 5.47 in 1970-75. Remarkable decreases in DMFT at age 12 were observed in maxillary incisors (50%), followed by maxillary molars (24%) and mandibular molars (22%). The decline in caries prevalence in the examined area may be mainly attributed to several factors other than use of fluoride, such as changes in dietary pattern, an increasing dental awareness and promotion of dental health care. But the percentage decrease per annum of DMFT index at age of 12 in the examined population was relatively low (-4.1%) in comparison with other industrial countries. Comparing the results with data from national dental surveys, it can be considered that rural areas in Japan do not exhibit a similar decline of caries prevalence as in Shizuoka city, but there will be a lot of districts exhibiting significant reduction in caries prevalence in the near future.