Ameloblastoma is a rare, benign, slowly-growing odontogenic neoplasm associated with aggressive potential for local invasion and a high recurrence rate. The aim of this study was to investigate the long-term treatment outcomes of ameloblastoma and to evaluate the recurrence rate and risk factors for recurrence at a single institution over a 23-year period. The study used data from the Second Department of Oral and Maxillofacial Surgery in Osaka Dental University Hospital from January 1995 to December 2017. We recorded demographic data of patients, tumor sites, radiographic patterns and findings, histological type, treatment modality, duration of follow-up, and timing of recurrence. We also statically analyzed several possible factors associated with the recurrences. Fifty-five of the patients were initially treated by a conservative surgical approach and 15 by a radical surgical approach. Recurrence occurred in 11 cases among the 55 conservative surgery group. In contrast, no recurrences were observed among the 15 in the radical surgical group. The total recurrence rate was 16% (11/70) for all cases. Eleven of the recurrences occurred during the follow-up period of 12 to 284 months after the primary surgery. The required period from primary surgery to recurrence was 12 to 88 months (median: 29 months). No factor showed a statistically significant relationship with recurrence (p<0.05). The 1-, 2-, 3- and 5-year recurrence rates according to Kaplan-Meier analysis were 1.4%, 7.1%, 12.0% and 12.0%, respectively. (J Osaka Dent Univ 2020; 54: 177-181)

Surveillance systems for vancomycin-resistant enterococci (VRE) are indispensable for medical and health care facilities. Appropriate examination methods should be selected according to the circumstances of the individual facilities. Loop-mediated isothermal amplification (LAMP) assays were developed for simple and rapid detection of vancomycin-resistant genes (vanA and vanB). With the LAMP, both vanA and vanB were amplified under isothermal conditions at 64°C within 40 min. Detection limits were identical to the conventional polymerase chain reaction (PCR) method (10 cells per reaction tube), and naked eye inspection was possible with the same detection limit by addition of SYBR-Green I. The LAMP and conventional PCR methods concordantly detected vanA and vanB (B1 and B2 subtypes) in 73 of 74 VRE isolates and 20 reference strains. Only one mismatch was observed in the detection of vanB in an isolate. For further simplification, intact cells were subjected to the LAMP assay, and vanA and vanB were detected with a limit of less than 100 cells. The LAMP has the potential as an alternative method for genotyping VRE (vanA, vanB) and has the advantage of being rapid and simple. (J Osaka Dent Univ 2020; 54: 183-191)

Bimaxillary protrusion, which causes facial disharmony due to protrusion and incomplete closure of the lips, has many psychological effects on the patient. We investigated whether changes in soft tissue morphology could be predicted by using the revised analysis method proposed by Arnett to determine the relationship between changes in hard tissue morphology and changes in the soft tissue profile before and after orthodontic treatment of adult patients with bimaxillary protrusion. The subjects were 17 patients who were diagnosed as having bimaxillary protrusion. We measured each item of the TVL Projections with Arnett analysis to determine the amount of change in soft tissue using cephalograms before and after treatment, and examined the correlation between changes in the hard and soft tissues. We found correlations between the Nasal Tip and U1 to SN; A' and SNA; the Upper Lip Anterior and OJ, U1 to SN; Maxillary 1 and OJ, U1 to SN; and Mandibular 1 and L1 to MP. These results suggest that it is necessary to understand the relationship between changes in the hard and soft tissues before and after orthodontic treatment. (J Osaka Dent Univ 2020; 54: 193-198)

Osaka Dental University started a basic life support (BLS) course for healthcare providers and clerical employees of affiliated hospitals, dental students, and those from dental hygiene schools based on a new concept in August 2004. The new curriculum was adopted to: incorporate automated external defibrillator (AED) training, to include training to relieve an obstructed airway, to make sure that each instructor teaches 5 or fewer students using one manikin and one AED training device, to start skills testing, to use textbooks, to specify requirements for instructors, to use DVD media, and to use pocket face masks. The participants included 4,154 (49.5%) students of our dental school, 1,914 (22.8%) dental hygiene school students in clinical training, 396 (4.7%) dental residents trained at affiliated hospitals, 582 (6.9%) faculty members of our school, and 1,353 (16.1%) dental professionals from outside the school. The number of participants each year was between 350 and 700, except in 2004 and 2020, when the duration of the course was shorter than 12 months. The importance of BLS education will continue to increase as society ages. (J Osaka Dent Univ 2020; 54: 199-203)

The tongue microbiome has been linked to oral health and disease. A variety of methods for removing the tongue coating, such as tongue brushing and tongue scraping, have been developed aiming to reduce bad breath and prevent pneumonia. We investigated the effect of tongue brushing on tongue microbial diversity. A controlled study was performed to measure how the tongue and saliva microbiota of 10 healthy participants changes following tongue brushing. Tongue brushing did not alter either the α- or β-diversity of the tongue microbiota. However, it significantly increased the abundance of Prevotella melaninogenica, Prevotella nanceiensis, Veillonella parvula and Veillonella parvula in the tongue microbiota, while decreasing the abundance of Prevotella histicola. Tongue brushing may be useful to improve oral health without influencing the microbiome diversity. (J Osaka Dent Univ 2020; 54: 205-212)

Masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) is a new disease entity that is characterized by hard, severe limited mouth opening due to contracture of the masticatory muscles. This study examined the usefulness of surgical treatment for MMTAH through the outcomes of patients who underwent surgery. The duration of follow-up was one year. Thirty-eight patients who attended the study hospital and were given a diagnosis of MMTAH were included. Nineteen of them underwent surgery, while the others did not. Maximum mouth opening, mandibular movement and occlusal force were investigated before and after surgery. EMG activity of the masseter muscles and anterior temporalis muscles were significantly decreased after surgery. Further, the maximal opening increased markedly and occlusal force decreased significantly after surgery. Following mouth opening training after surgery, the mean increase in opening after one year was 16.2 mm. It is important to carefully evaluate the general condition and personality of each individual to determine whether he can withstand the pain associated with mouth opening training after surgery. The results of this study suggest that surgical treatment is useful for the management of MMTAH. (J Osaka Dent Univ 2020; 54: 213-218)

We conducted a clinical analysis of 46 cases involving patients who visited our department in the past 15 years from 2004 to 2018 who were histopathologically diagnosed with salivary gland tumors. We recorded demographic data for the patients, tumor sites, histological type, and treatment modality. The cases comprised 24 males and 22 females, representing a male to female ratio of 1.1:1. The age of the patients at diagnosis ranged from 11 to 84 years with a mean of 47 years. 28 cases were benign tumors(61%), while 18 were malignant (39%). The incidence of benign tumors was greater in males (61%, 17/28) while malignant tumors were more common in females (61%, 17/28). Of the 44 cases, 90% occurred in minor salivary glands. Among them, both benign (20/28) and malignant (9/18) tumors were most common in the palatal glands. Histopathologically, the most frequent type of benign tumor was pleomorphic adenoma (75%, 21 cases), followed by myoepitherioma (18%, 5 cases). On the other hand, the most frequent type of malignant tumor was mucoepidermoid carcinoma (44%, 8 cases), followed by adenoid cystic carcinoma (22%, 4 cases). Both the benign and malignant tumors were treated surgically. Recurrence occurred in 1 case among the 18 patients in the malignant group, while no recurrences were observed among the 28 patients in the benign group. (J Osaka Dent Univ 2020; 54: 219-224)

We evaluated the sterilization efficacy of a commercial denture cleaner compared with the combined use of the denture cleaner and ultrasonic cleaning on dentures used by patients. After cleaning the dentures with a denture brush, bacteria were collected from one half of the mucosal surface with a sterile cotton swab. Complete and partial dentures were cleaned by immersion in a dedicated commercial denture cleaning solution for 30 min. We also examined the effect of 5 min of cleaning with a commercial ultrasonic cleaner and a denture cleaner after mechanical cleaning. The dentures with a viable bacteria count greater than 4.54×109 CFU/mL before rinsing at 40°C showed a high sterilization rate greater than 95%. The sterilization rate of dentures with a low bacterial count before immersion was low. Similar results were obtained for anaerobic bacteria. Regarding the ultrasonic cleaner, debris was visually removed from all 30 dentures. These results suggest that it is important to evaluate denture cleansers to the extent that they can reduce bacterial counts rather than sterilization rates. (J Osaka Dent Univ 2020; 54: 225-238)

Active participation of students is paramount not only for their learning experience, but also for their academic performance. However, several shortcomings in the methods developed to promote active learning have increased students' sense of burden and discomfort. This study attempted to determine the efficiency of a low-load web-based review quiz built to enhance students' reviewing habits and facilitate active class participation. The participants were 53 first-year dental hygiene students in a 10-session microbiology course. After each class, all students were given a web-based quiz to prepare them for a paper-based review test that assessed the learning of the content covered in the previous classes. We then analyzed the correlation between frequency of participation in the web-based quiz and the average score of the weekly review tests or the final examination score. The average scores on the review test correlated positively with the final examination. Consequently, voluntary participation in the web-based quiz correlated positively with both the short-term and long-term learning outcomes of the students. The blended learning including this web-based quiz enabled students to develop the "self-learning attitude" needed to pass the National Dental Hygiene Examination. We concluded that a method for increasing student participation in such a quiz would encourage students to achieve active learning. (J Osaka Dent Univ 2020; 54: 239-244)

We compared the fracture strength of telescopic Ce-TZP/A secondary crowns of different taper and thickness. Both primary and secondary crowns were made of Ce-TZP/A. The half taper angles of the primary crowns were 2° and 4°. The thicknesses of the secondary crowns were 0.5 and 1.0 mm. After the secondary crowns were placed on the primary crowns, a load was applied with a stainless steel ball of 10 mm diameter on the occlusal surface of the secondary crowns to measure the force required to break the secondary crowns. We performed a two-way analysis of variance with the taper angle and secondary crown thickness as the factors. We found that only the secondary crown thickness was a significant factor in resisting the load (p<0.01). The mean fracture strength was 524 N for the secondary crowns with a thickness of 0.5 and 1,814 N for those with a thickness of 1.0 mm. This finding implies that while secondary crowns with a thickness of 1.0 mm can provide adequate resistance clinically, those with a thickness of less than 0.5 mm have a risk of breaking because of insufficient strength. We found that a minimum thickness of 0.6 mm was required for Ce-TZP/A secondary crowns to resist the maximum occlusal force. (J Osaka Dent Univ 2020; 54: 245-249)

The combined use of epigallocatechin gallate (EGCG) and gelatin is a promising method to prepare usable gelatin-based materials for various industries. Nevertheless, the mechanisms of the molecular interaction between these substances have not been fully elucidated. This study aims to investigate the effect of EGCG on the gelation of gelatin using two different catechins, sol-gel transition analysis, and quartz crystal microbalance (QCM). First, 0-0.7 mg EGCG, having galloyl moiety, or epigallocatechin (EGC), lacking galloyl moiety, was dissolved in a 10 mg/mL gelatin solution. The sol-gel transition of each solution was evaluated at -20, 4, and 37°C. A high dose of EGCG hindered gelation at 4°C, whereas EGC did not. The QCM analysis demonstrated that a larger amount of EGCG was adsorbed onto gelatin than EGC. The results suggest that galloyl moiety contributes to the adsorption of EGCG to gelatin, leading to the impaired gelation of gelatin. These results provide a basis for the development of functional catechin-gelatin-based materials. (J Osaka Dent Univ 2020; 54: 251-255)

The dental hygienist training course at our university was a three-year vocational school course until fiscal year 2016. However, in 2017 it was newly positioned as a university department and the curriculum was expanded to four years. As a background to this, the role of dental hygienists has gone beyond preventative measures for patients with dental disease and assisting with dental treatment that they have traditionally been expected to perform. Dental hygienists now have a wide-ranging role that includes putting into practice dental and oral health measures from an overall health promotion perspective, and proactive participation in comprehensive community care based on multidisciplinary cooperation. The purpose of the present study was to evaluate and verify what results might be obtained when recently-matriculated students intending to become dental hygienists or dental technicians, with almost no specialized knowledge or skill, carried out hands-on training in dental treatment settings shortly after matriculation. Following the early hands-on clinical training, the proportion of subjects who responded that they had increased interest in training, and the proportion who responded that they were prepared to become health professionals, was over 60% in both cases. In addition, many subjects responded that they learned about "clinical and university hospital dental practice," "details of treatment at different departments," and "conduct and response of dental professionals to patients," suggesting that the experience of dental healthcare settings served as motivation for pursuing dental healthcare professions. The subjects of the present study were first-year students intending to become dental hygienists or dental technicians who had matriculated at a university with a four-year course. However, their number was small because the Faculty of Health Sciences at which the subjects studied had only been established in 2017. Detailed analysis and study of the effects of early hands-on clinical training on these students will require ongoing analysis in the future. The results of this study suggest that effective hands-on learning in dental healthcare settings early after matriculation will stimulate interest and curiosity toward their studies in first-year students wanting to become dental hygienists or dental technicians, and can give them motivation to aim for a career as a dental healthcare professional. (J Osaka Dent Univ 2020; 54: 257-262)

To assess the use of an intraoral scanner (IOS) for basic periodontal treatment and dental health guidance, we evaluated the data of periodontal tissue records and the range in which changes in periodontal tissues could be observed. An IOS was used to record the three-dimensional shape of complete dentures and wax dentures. Measurement points on cross sections were made with a design knife at 32 points on the model gingiva. The shapes of the upper and lower complete dentures and wax dentures were then recorded six and five times, respectively, using the IOS. Then, seven gingival regions of both the upper and lower wax dentures were slightly reduced and rerecorded five times, and the records before and after the reductions were compared. The results indicated that it is possible to detect changes in periodontal tissue with high precision. By superimposing the records, changes in the gingiva could be compared. In addition, the amount of change could be displayed quantitatively based on changes in the cross sections. (J Osaka Dent Univ 2020; 54: 263-272)

The bacterial composition of oral samples has traditionally been determined by PCR amplicon sequencing of 16S rRNA genes. Recent amplicon sequence variant (ASV)-based analyses of 16S rRNA genes differ from that based on operational taxonomic unit (OTU) clustering in the way it deals with sequences having potential errors. However, little information is available on its application in oral microbiome studies. Here, we conducted ASV-based analysis of oral microbiome samples using QIIME 2. We investigated the optimal parameters for sequence denoising, using DADA2, and found the trimming of first 20 nucleotides from 5′-end of both paired reads avoided excessive sequence loss during chimera removal. Truncating reads at positions 240-245 allowed the removal of low-quality sequences while maintaining sufficient length to merge matching paired ends. Taxonomic assignment, using the naïve Bayes classifier trained with the V3-V4 region of reference 16S rRNA sequences in the extended human oral microbiome database (eHOMD), resulted in bacterial compositions similar to those of OTU-based analyses. Contrary to OTU-based clustering, ASV-based analysis showed taxonomic abundance at the genus or species level to not differ significantly in tongue microbiomes, regardless of brushing. QIIME 2 can, therefore, be a standard pipeline for ASV-based analysis of oral microbiomes. (J Osaka Dent Univ 2020; 54: 273-281)

The number of patients with impacted teeth is increasing. We investigated the relationship between impacted canines and jawbone growth and development. Panoramic and lateral cephalometric radiographs of 80 patients with malocclusion involving impacted maxillary canines were analysed and classified using sector and McSherry and Pitt et al.'s classifications. Sella turcica bridging and ponticulus posticus formation were studied to assess the relationship of growth and development with impacted maxillary canines. Bone age was assessed by Baccetti's cervical vertebral maturation stages. Classes I, II and III sella turcica bridging occurred in 48.7%, 47.5%, and 3.8% of the cases, while ponticulus posticus classifications occurred in 82.5%, 12.5%, and 5% of cases, respectively. Cervical vertebral maturation stages were one stage lower than chronological age. Although the chronological age and the positional assessment of the impacted canines were correlated positively with the sector classification and McSherry and Pitt et al.'s classification for Classes 1 and 3, they correlated negatively for Class 2. The trend in bone growth delay correlated negatively with the distribution in McSherry and Pitt et al.'s Class 2. Assessing cervical vertebral maturation stage, sella turcica bridging, and the ponticulus posticus formation may facilitate early diagnosis of impacted canines, and could facilitate future orthodontic treatment. (J Osaka Dent Univ 2020; 54: 283-292)