Whitening and laminate veneer techniques are often used for esthetic dental treatment. However, these treatments do not prevent stains from sticking to the surface of teeth. We developed a novel prevention of staining by chemical modification of the tooth surface. We investigated whether a perfluoro fatty acid (PFFA) could prevent tea stains from binding to a hydroxyapatite (HAp) disc used as a model of the tooth surface by coating the disc with a PFFA. The coated samples were prepared by modifying the saliva-precoated HAp disc with a 10,000 ppm PFFA ethanol solution. The PFFA-coated samples and non-coated controls were immersed in tea at 37°C. The color space values (L*, a*, b*) of the discs were recorded using a spectrophotometer before and after the tea-immersion and the color difference ΔE* was calculated from these values. ΔE values of the non-coated group increased significantly in a short time. On the other hand, ΔE values of the PFFA-coated group increased only moderately. These results suggest that tea-induced discoloration of saliva-precoated HAp discs can be inhibited by modifying the pellicle surface with PFFA molecules. (J Osaka Dent Univ 2020; 54: 1-6)

We evaluated the effect of hydroxyapatite (HAp) incorporated into resin-modified glass ionomer cement (RMGIC). Commercial RMGIC (Fuji II LC; GC, Tokyo, Japan) was used as a control (GIC-LC) and the base material of the AIC group (AIC-LC). The AIC-LC powder contained 88 wt% Fuji II LC glass powder and 12 wt% spherical-shaped hydroxyapatite powder with an average particle size of 20μm. The AIC-LC specimens were created by mixing the AIC-LC powder and Fuji II LC liquid with the same powder to liquid ratio as that of the GIC-LC specimens. The flexural strength and flexural modulus as well as the dose releases of fluoride and other mineral ions were evaluated in this study. No significant differences in the flexural strength or modulus were noted between GIC-LC and AIC-LC. The dose of fluoride ion released from the AIC-LC specimens was significantly greater than that from the GIC-LC. In addition, the doses of Al, Si, Ca, and Sr released from AIC-LC were also significantly greater than those from GIC-LC. We concluded that adding porous spherical-shaped HAp to RMGIC is effective for improving the function of RMGIC in the prevention and remineralization of dental caries. (J Osaka Dent Univ 2020; 54: 7-13)

To clarify the effects of orthognathic surgery and mandibular setback on morphological changes in the airway, we assessed the safety of this operation and the methods by which stable treatment results can be obtained and displacement can be determined. Airway width before and after surgery was measured and evaluated using cephalometric radiographs of patients without functional problems post-surgery. The results suggested that there was long-term stability in the orthognathic surgery patients. No patients were found with functional abnormality changes. This study demonstrated safe displacement that did not trigger major morphological changes or functional disorders in the jawbone or soft tissue post-surgery. (J Osaka Dent Univ 2020; 54: 15-28)

The purpose of this study was to observe the dynamics of tongue movement during eating in real time via ultrasonography. We determined the anatomical organs that could be observed, and assessed the inter-rater reliability of the measurements. The participants were eight healthy men who were examined by three dentists. The tongue was observed using an ultrasound diagnostic device. Tongue movements during chewing and swallowing in a sitting position were observed via ultrasound with a coronal view. The test food was a chew-swallow management food. The examination targets were the distance from the skin surface below the chin to the dorsum of the tongue, the distance between the dorsum of the tongue and the lower edge of the genioglossus muscle, and the thickness of the geniohyoid muscle during chewing and swallowing. We calculated the internal correlation coefficients of ICC (2, 1) and ICC (2, 3). We found that when observing the tongue in real time using ultrasonography, we could clearly observe movement in not only the dorsum of the tongue, but also the genioglossus and geniohyoid muscles. In addition, our measurements had high inter-rater reliability. (J Osaka Dent Univ 2020; 54: 29-34)

During cardiopulmonary resuscitation (CPR) training, trainees practice artificial respiration using expiration. At this time, the manikins may become contaminated by saliva, which is well-known to contain blood. Therefore, we examined manikins for blood stains after training the use of the luminol reaction for evaluating contamination by body fluids. Although we found no body fluid stains, such as blood, blood was detected on the face 10% of the time, in the airway 30% of the time, and in the manikin lungs 35% of the time. The origin of this blood is exposure to airborne droplets of saliva or expired air from the trainees during resuscitation practice. The detection of blood on the face, in the airway, and in the lungs suggests that the respiratory system, including the face, was contaminated. Although we use a pocket face mask with a one-way valve for resuscitation training to prevent the transmission of saliva (i.e., blood) among students via manikins, this study revealed that more thorough preventive measures, including disinfection of manikins after use, should be implemented. (J Osaka Dent Univ 2020; 54: 35-38)

Japan is rushing headlong into an unprecedented new era with a declining birthrate, a growing proportion of older people, and a decline in the overall population. To ensure that the population is provided with appropriate oral healthcare in the future, and that a supply structure capable of meeting the demand for dental care is maintained, we examined the factors related to the supply and demand for dental services. We obtained basic data for examining potential problems in the future supply and demand for dentistry, with a focus on employment trends among female dentists, which is likely to affect future supply and demand. This study was carried out using data from official statistical surveys conducted by the Ministry of Health, Labour and Welfare of Japan from 1996 to 2017. These data were used to clarify the numbers and trends of dental clinics, the numbers and proportions of people passing the National Examination for Dentists, and the actual situation regarding dentists working at dental clinics, and to investigate how these phenomena relate to trends among female dentists in Japan.

The results showed that the increase in the number of dental clinics has been slowing since 2008. Due to a decreasing trend in the number of newly-opened clinics, combined with an increase in the number of temporarily or permanently closed clinics, the overall number of clinics in 2017 decreased by 331 compared with the previous year. At the same time, the proportion of women among those passing the National Examination for Dentists has shown gradual annual increases, and has steadily been over 40% since the 2012 examination. Although approximately 78% of female dentists in the 25-29-year age group were working at a dental clinic, a steady decline in this proportion, with no transfer to other occupational categories, was seen among the female dentists aged 40 years and older who left clinics. Only a few female dentists who left their job after the age of 40 went on to establish or become the head of a new clinic, which suggests that most no longer had occupations that utilized their qualifications as a dentist.

Considering the recent increase of women going into dentistry among the younger generation, we think that observing employment trends among female dentists closely is essential for understanding issues related to the supply and demand for dental services, including the number of dental clinics. (J Osaka Dent Univ 2020; 54: 39-44)

We investigated the level of exposure of dental anesthesiologists to sevoflurane during induction of general anesthesia, designed countermeasures against this exposure, and evaluated their usefulness. We first measured the sevoflurane level in samples collected in vacuum bottles using a gas chromatograph, and then evaluated countermeasures against sevoflurane exposure for four conditions. Sevoflurane was detected in 5 of 40 cases of general anesthesia for which samples were collected. However, it was not detected with the double method group in our second experiment. This method minimized exposure, clarifying its usefulness as a countermeasure against sevoflurane exposure. (J Osaka Dent Univ 2020; 54: 45-50)

We clarified the coefficient of static friction for two types of zirconia with different surface roughness that are used for telescopic crowns. We examined the effect on retention that alumina blasting had on the primary and secondary crowns. The two surface categories were smooth and rough. We used two types of zirconia, Y-TZP and Ce-TZP/A. The coefficient of static friction for Y-TZP and Ce-TZP/A were 0.18 and 0.17 when both surfaces were smooth, 0.18 and 0.17 when one surface was smooth and the other was rough, and 0.31 and 0.38 when both surfaces were rough, respectively. The retentive force of telescopic Ce-TZP/A crowns on the primary and secondary crowns was increased by alumina blasting. (J Osaka Dent Univ 2020; 54: 51-60)

The purpose of this study was to determine reference ranges for the periodontal mechanosensitive thresholds in molars stimulated from the buccal and occlusal directions in healthy subjects with natural dentition. In addition, we compared the periodontal mechanosensitive threshold (PMT) of molars in middle-aged healthy subjects with natural dentition to the reference range for the PMT stimulated from both directions. We selected 50 healthy adults with no history of orthodontic treatment, no abnormalities in the occlusal contacts, and no occlusal discomfort as the subjects for setting the reference range for the PMT. For the middle-aged healthy group, we selected 12 subjects who were 40 years of age or older, had natural dentition with no abnormalities in stomatognathic function, and normal occlusion. The Semmes-Weinstein (SW) monofilament (Touch Test^Ⓡ; North Coast Medical, Morgan Hill, CA, USA) and the modified SW monofilament were used for measurement of the PMT. We set a reference range of the PMT from each stimulated direction. We found that all subjects were within this range. (J Osaka Dent Univ 2020; 54: 61-72)

Large-scale cohort studies using saliva samples have been performed to elucidate the relationship between oral and systemic health and oral resident microbiota. Although standardization of the sampling and processing procedures for saliva that is used in next-generation sequencing (NGS) analysis is underway, the storage conditions after collecting saliva have not been studied in detail. In this study, we monitored changes in the salivary microbiota during short-term storage at room temperature. Saliva samples were collected from 11 subjects and stored at room temperature (23°C) for 3 h. When the V3-V4 region of the 16S rRNA gene was analyzed using NGS, although there was no change in the β-diversity of salivary bacterial microbiota, a significant decrease in α-diversity was observed. Additionally, a significant decrease was observed in four operational taxonomic units (OTUs). These results suggest that even short-term storage of saliva samples at room temperature may affect the diversity of salivary microbiota and the relative abundance of specific OTUs. (J Osaka Dent Univ 2020; 54: 73-81)

CAD/CAM crowns are generally fabricated by laboratory optical scanning of the definitive cast to obtain the morphology of the dentition and abutment tooth. This method requires skilled operations for making the stone cast and mounting it on an articulator. Laboratory scanners using the blue light-emitting diode (LED) have been developed that can measure both the stone cast and dental impression with high speed and precision. They can measure dental impressions even with deep and narrow shapes quickly and reliably. When fabricating CAD/CAM crowns based on the direct measurements of triple impressions using these laboratory scanners, there is no need to produce a definitive cast and mount it on an articulator. Consequently, errors caused by stone expansion and cast mounting are eliminated. However, there are no reports on the fitting accuracy of CAD/CAM crowns fabricated using direct triple impression measurements. The purpose of this study was to evaluate the fitting accuracy of composite resin CAD/CAM crowns fabricated from the laboratory scanning of silicone impressions (SI). Twelve CAD/CAM crowns each were fabricated for a maxillary left central incisor and a mandibular right first molar from SI and conventional definitive casts (DC). The fitting gaps of the incisal edge or occlusal surface, axial surface, and marginal regions were measured. The paired t-test was used for statistical comparison. No significant differences were observed in the fitting accuracy between the crowns fabricated using CAD/CAM from DC and those from SI in any part of the abutment teeth (p>0.05). These results indicate that there are no issues concerning the clinical application of CAD/CAM crowns fabricated from SI scans. (J Osaka Dent Univ 2020; 54: 83-90)

Lipocalin-type prostaglandin D2 Synthase (LPGDS), a major cerebrospinal fluid (CSF) protein known as β-trace, reportedly scavenges biliverdin in the CSF of patients with subarachnoid hemorrhage and functions as a major amyloid β-chaperone, suggesting a clearance role in the central nervous system. However, the source of LPGDS in the cerebral cortex following stroke has not been elucidated. We examined changes in the cellular localization of LPGDS in post-stroke cerebral cortices of mice. Immunofluorescence staining were performed to determine the localization of LPGDS. Immunoelectron microscopy for LPGDS was also performed. In normal cerebral cortices, immunoreactive LPGDS structures were rarely observed. However, higher LPGDS expression levels were observed on PDGFRβ+ pericytes and nestin+ stem cells. Immunoelectron microscopy confirmed that pericytes in association with the endothelial cells expressed LPGDS. It is strongly expressed in brain pericytes following ischemic insult, suggesting that the ischemic pericytes are the major site of LPGDS expression following stroke. Knowledge of these expression profiles may be useful for future PC-based stem cell therapies. (J Osaka Dent Univ 2020; 54: 91-99)

We investigated the effects of low-temperature atmospheric pressure plasma treatment (PS) on the bond strength of adhesive resin cement with enamel, crown dentin, and root dentin. Extracted virgin teeth were prepared and three types of surface treatments were done for the enamel, crown dentin and root dentin after phosphoric acid treatment: primer treatment (Pm), PS treatment (Ps) and primer treatment after PS treatment (PsPm). Shear bond tests were then conducted, and the adhesion cross-section of the resin cement was observed by SEM for each treatment. Based on the shear bond test, PsPm had greater adhesion values than Pm or Ps in enamel, crown dentin and root dentin. SEM observation showed that the enamel surface structure following PsPm was coarser and more complex than that for Pm or Ps. In crown dentin and root dentin, the resin tags with PsPm were longer and thicker than those with Ps or Pm. The combination of primer and PS treatments was found to be effective in improving the bond strength between teeth and adhesive resin cement. (J Osaka Dent Univ 2020; 54: 101-108)

We analyzed changes in airway patency at varying angles of head flexion and extension by evaluating changes in airway pressure and mucosal contact pressure using high-resolution manometry (HRM). Propofol (2 mg/kg) was administered to 24 adult patients to induce sleep, followed by a dose of rocuronium (0.6 mg/kg). Mechanical ventilation was performed with the use of 5% sevoflurane. Using HRM with a diameter of 8 Fr (2.64 mm), the larynx was expanded, followed by the fixation of sensor 1 at the soft palate, sensors 2 and 3 at the tongue root mucosa, and sensor 4 below the epiglottis. Measurement was conducted during mask ventilation using a volume-controlled respirator with the tidal volume set at 7 mL/kg and the ventilation frequency set at 10 times/min. The patient's head was bent or extended at eight levels of flexion or extension. The mask pressure measurement and manometric measurement of airway pressure and mucosal contact pressure were conducted at intervals of 30 s. The highest mucosal contact pressure was recorded at the tongue root, indicating that the earliest obstruction of the airway occurred at this point among the four sites examined. During extension of greater than 5°, the mucosal contact pressure decreased, and the airway began to become patent. The airway patency was optimal during extension of greater than 20°, suggesting that ventilation was possible at these head positions. HRM was considered to be a useful method to assess changes in airway patency. (J Osaka Dent Univ 2020; 54: 109-115)

This study was designed to explore potential messenger RNA (mRNA)-based biomarkers for detecting vascular senescence that can be applicable to the diagnosis of atherosclerosis-related diseases. The study was performed in two parts, an in silico search for candidate genes utilizing multiple public databases, and wet-experiments to validate the utility of candidate mRNAs as biomarkers. The relationship between the candidate mRNAs and the clinical parameters was evaluated using real-time qPCR, brachial ankle pulse wave velocity (baPWV), ankle-brachial index (ABI) and carotid ultrasound. Five candidate genes (CCNA1, HSD17B2, ADRB1, CMPK2 and RNF213) were selected based on the in silico experiments. Only CMPK2 and RNF213 were detectable in the saliva of both the young (20-30 year old) and senior (over 65 years old) groups. The salivary CMPK2 expression in the senior group was 3.8-fold greater than that in the young group (p=0.0371). When appropriate expression levels of CMPK2 were used as the cut-off values for detecting arterial stiffness in the young group and plaque formation in the senior group, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were in the range of 66.7%-100%. These results suggest that salivary CMPK2 may be a promising biomarker for chronological aging, arterial stiffness, and atherosclerosis. (J Osaka Dent Univ 2020; 54: 117-125)

Hydroxyapatite (HA) has high biocompatibility. Because, it is non-absorbable and remains in the bone, its influence on the surrounding tissue must be considered. We placed dental implants in the lower right first premolar region and then packed HA around the fixtures and investigated the stress on the surrounding bone during load application using the three-dimensional finite element method. Three-dimensional image data of the edentulous mandible and implant were imported into analysis software. A three-wall bone defect model was fabricated where HA was filled on the distal of the implant, and the stress on the mesial surface adjacent to the implant body where the load was applied was measured using nonlinear analysis with a friction coefficient of 0.33, and using linear analysis. In the HA filling group, equivalent stress, compressive stress, and tensile stress increased with nonlinear analysis compared with linear analysis. There was no difference in stress in the models without bone defects. Compressive stress was greater than tensile stress in all models. When HA is used as bone filling material during dental implant placement, osseointegration is the key to success. (J Osaka Dent Univ 2020; 54: 127-134)

Oral squamous cell carcinoma (OSCC) is characterized by highly invasive tumor cells. Hepatocyte growth factor (HGF) signaling plays an important role in the induction of epithelial-mesenchymal transition (EMT), a process that converts immotile epithelial cells into motile mesenchymal cells and is involved in cancer metastasis by promoting tumor cell scattering. The c-Met, which is a transmembrane tyrosine kinase receptor that may be activated by HGF, regulates the associated downstream gene expression. This process is important to cell migration in normal and cancerous conditions. This study explored the potential effects of c-Met on HGF-induced EMT in an OSCC cell line.

We investigated the function of c-Met in the process of EMT, and its molecular mechanism in oral cancer. OSCC cell line, HSC3 cells, were treated with HGF for varying durations. EMT-associated proteins, including E-cadherin and vimentin, were examined by western blot analysis. The role of c-Met in the mediation of EMT-like changes was investigated using western blot analysis and knockdown by c-Met inhibitor. Moreover, we carried out investigations using immunohistochemical and immunofluorescence staining.

We found that treatment with HGF induced EMT-like changes and enhanced the migrative potential of HSC3 cells. Furthermore, HGF-mediated EMT-like changes were associated with c-Met activation, and these changes could be blocked by c-Met knockdown. In particular, immunohistochemical and immunofluorescence staining of c-Met strongry expressed in the invasion front of the tumor cells. This study clearly demonstrated a crucial function for c-Met in EMT development in oral cancer. c-Met-targeted treatment may be an effective therapy for oral cancer. We believe that our data demonstrated that c-Met inhibitor could reduce HGF-induced EMT and cell motility via c-Met blockade and down-regulation of the pro-survival extracellular signal-regulated kinases pathway. (J Osaka Dent Univ 2020; 54: 135-144)

Ameloblastoma is one of the most common benign odontogenic tumors in the oral cavity, and may recur because it grows in a locally invasive manner. Although many studies have been performed on ameloblastoma, its bioactive characteristics remain unclear. Retinoic acid, a metabolite of fat-soluble vitamin A, which is used as a leukemia drug, has been demonstrated to have antitumor effects on some tumor types. We examined whether retinoic acid has potential as a new remedy for ameloblastoma. We found that retinoic acid inhibited the proliferation of cells derived from ameloblastoma and induced differentiation. However, its intracellular signaling and regulatory mechanisms remain unclear. In this study, we primarily cultured cells from ameloblastoma to elucidate signal transduction, and examined the differences in gene expression levels due to retinoic acid action by microarray analysis. Surgically removed specimens were obtained with consent of the patients from the Second Department of Oral and Maxillofacial Surgery, Osaka Dental University Hospital. Primary culture was started with medium for the epithelium, followed by cloning to be used as ameloblastoma cells. Subsequently, retinoic acid was added at a final concentration of 10-6 to 10-7 M and incubated for 6 hours to prepare an experimental group. A control group was also prepared without addition of retinoic acid. After culturing, the cells were collected to extract RNA from each group for microarray analysis.

In the experimental group, increase in the expression of the EDF1 gene was most pronounced, whereas that of the TM4SF10 gene was most markedly suppressed. Furthermore, the expression levels of the MMP3 and FGF2 genes were suppressed by 0.37- and 0.48-fold, respectively. The regulation of cell growth and differentiation comprises comprehensive regulatory mechanisms, such as protein synthesis, degradation, complex formation, and phosphorylation, in addition to gene expression. Our study suggested that changes in the expression of FGF2 and MMP3 genes are partly involved in the inhibition of growth and promotion of differentiation by retinoic acid in ameloblastoma-derived cells. (J Osaka Dent Univ 2020; 54: 145-151)

To treat facial deformation, we must start with an accurate analysis of the deformation. Orthodontists need to understand facial balance and perform treatment, accordingly. The face is roughly divided into forehead, eyes, nose, lips and chin. It is necessary to fully consider the balance of these components before starting orthodontic treatment. The participants in this study were 72 males and 50 females with normal occlusion, who met the inclusion criteria from 647 fifth-year degree students at Osaka Dental University. The mean and standard deviation of each measured value of the aesthetic triangle obtained from the cephalograms were calculated. In males, the mean (standard deviation) of NFr, NFa, NM, MC and NL were 129.97° (1.95°), 32.67° (0.90°), 132.14° (1.09°), 111.17° (2.50°) and 89.81° (2.46°), respectively. The ANB angle, interincisal angle and FMA for females were 2.48° (0.19°), 124.24° (1.41°) and 28.04° (1.41°), respectively. In females, NFr, NFa, NM, MC and NL were 136.78° (1.90°), 32.14° (0.91°), 131.32° (1.81°), 104.53° (2.66°) and 89.44° (2.51°), respectively. We concluded that these values were useful for orthodontic analysis of Japanese. (J Osaka Dent Univ 2020; 54: 153-157)

Impacted maxillary canines are a common dental eruption abnormality that occurs in between 1% to 13% of the population. We conducted a study of 70 patients between 7 to 14 years of age who visited the Orthodontic Department of Osaka Dental University Hospital between 2009 and 2018. They had Hellman dental developmental stage IIIB and impacted maxillary canines based on the Sector classification according to Lindauer et al.,¹ the classification of McSherry,² and Pitt et al.³ Among them 42.9%, 13.3%, 9.5% and 34.3% had a Sector classification of I, II, III and IV, respectively. By the classification of McSherry and Pitt et al., in division ①, ①-1 was the most common, in division ②, ②-2 was the most common, in division ③, ③-2 was the most common, and in division ④, ④-2 was the most common. Determining the correlation between the Sector classification, the classification of McSherry and Pitt et al., as well as the growth and development of the maxillofacial complex and bone age (cervical vertebral maturation), should aid in the early diagnosis of impacted maxillary canines and aid in the treatment of impacted teeth during orthodontic treatment. (J Osaka Dent Univ 2020; 54: 159-163)

To provide feedback to the instructors and achieve a formative evaluation of students in education through basic training, we introduced practical training tests in the Objective Structured Clinical Examination (OSCE) style 10 years ago at our university. In this study, we examined the contents of the basic practical training tests in operative dentistry and reviewed the past 10 years since its introduction. The period for carrying out each theme used to consist of 30 seconds to present the theme, 4 minutes to carry out the theme, and 30 seconds for the students to move. However, now it consists of 30 seconds to present the theme, 6 minutes to carry out the theme, 1 minute for feedback, and 30 seconds for the students to move. While we introduced the OSCE style in order to give feedback on practical training to the instructors, we thought considered that introducing feedback to the students immediately after the test would improve their understanding. The faculy must continually receive feedback on the practical training of students. These tests in the OSCE style are necessary to meet the demands of new clinical treatment methods and changes in questions for the Japanese National Board Dental Examination. (J Osaka Dent Univ 2020; 54: 165-173)