Understanding occlusal balance in complete dentures requires conceptualizing mandibular movement and denture dynamics, which many dental students find difficult. This study introduced and evaluated an instructional digital model designed to facilitate accurate 3-dimensional and dynamic representation of these phenomena. This model allowed 360° visualization of mandibular movement and denture dynamics. Its effectiveness was evaluated when used in conjunction with small-group discussions (SGDs) for teaching occlusal balance to undergraduate dental students. Fifth-year students (n=128) at Tokyo Dental College completed both an SGD session and a digital-model learning session, with the order randomized at the small-group level (SGD-first group, n=67; digital model-first group, n=61). Comprehension was assessed using a pre-test and two posttests administered after each session (post-test 1 and post-test 2), each scored on a 10-point scale. Inter- and intra-group comparisons were performed using the Mann-Whitney U and Wilcoxon signed-rank tests, respectively. There were no significant differences between the SGD-first and digital model-first groups in pre-test (4.01±1.90 vs. 4.20±2.00) or post-test 1 scores (5.12±1.91 vs. 4.54±2.20). After completing both sessions, post-test 2 scores were higher in students who completed SGD followed by digital model learning (6.12±2.09) than in those who completed digital model learning followed by SGD (5.59±2.10), with a statistically significant difference between instructional sequences (p=0.046). Intra-group analyses also showed a statistically significant difference between post-test 1 and post-test 2 in both groups, with higher scores at post-test 2 (p<0.05). These results suggest that combining SGDs with the digital model enhances student comprehension of occlusal schemes and balance as it allows these phenomena to be confirmed visually.

As a population ages, the need for complete dentures and other large, removable prostheses remains high in edentulous adults. Appropriate denture fabrication requires comprehension of the anatomical structures of the edentulous mucosa and submucosa. This study aimed to clarify the educational challenges of teaching these structures. Dental student level of comprehension and instructor perception of teaching difficulty when using edentulous models were evaluated. Participants comprised 137 third-year dental students at Tokyo Dental College. Before a lecture on anatomical landmarks and the structure of the edentulous mucosa and submucosa, they were required to complete a pre-test to assess identification of 10 mucosal and 10 submucosal structures in the maxillary and mandibular edentulous ridges. Following the lecture, they participated in a practical session using a commercially available soft-tissue edentulous model under guidance from 19 instructors. A post-test followed this practical session. Correct answer rates were determined and total mucosal and submucosal scores compared. Instructors also completed a questionnaire regarding the difficulty of teaching each structure. The mean mucosal score increased from 60.7% (pre) to 83.8% (post), and the submucosal score increased from 39.3% to 72.3%. Both changes were statistically significant (p<0.0001). However, pre-test scores for submucosal structures were markedly lower than those for mucosal structures. Seven of the 10 mucosal structures were reported by 10% or fewer of the instructors as difficult to teach, whereas 9 of the 10 submucosal structures were reported by over 50% of the instructors as difficult to teach. Despite lectures and currently available models, comprehension of submucosal structures remains challenging for students. Moreover, these structures are perceived to be difficult to teach. Improved educational tools that reproduce the 3-dimensional relationships between mucosa and underlying bone are needed to enhance education regarding complete denture fabrication.

Agenesis of 5 or more permanent teeth is infrequent, and orthodontic treatment for asymmetric or multiple consecutive missing teeth is challenging. Collaboration among dental specialists to develop individualized treatment plans is critical to achieving optimal outcomes and ensuring patient satisfaction. A 15-year-old non-syndromic girl presented with skeletal Class I malocclusion. She had agenesis of 5 asymmetric permanent teeth, comprising 3 consecutive teeth (the maxillary left canine and first and second premolars), the maxillary right second premolar, and the mandibular right first premolar, and 5 persistent deciduous teeth. Miniscrews were placed distal to the mandibular right first deciduous molar and first molar. The mandibular right molars were uprighted and the space left by first premolar agenesis closed by miniscrew-assisted mesial movement of the molars. The bilateral maxillary deciduous second premolars were preserved. After extracting the maxillary left deciduous canine and the first deciduous molar, 2 miniscrew-supported pontics were placed perpendicular to the alveolus to control the adjacent teeth and maintain space. Active treatment lasted 36 months. Prosthetic treatment for the maxillary left canine and first premolar was completed 3 years after dental implant placement. Occlusion remained stable, even after 5 years of retention. This report highlights the finding that excellent occlusion and esthetics can be achieved by collaborative management involving orthodontists, oral surgeons, and prosthodontists in cases of hypodontia.

The aim of this study was to identify which factors influenced the perceived brushing sensation of different manual toothbrushes. A total of 23 dental hygiene students from a vocational school in the Kanto region of Japan evaluated five commercially available toothbrushes through paired comparisons across 16 sensory and functional attributes. An exploratory factor analysis was conducted to determine the underlying structure of the 16 items measuring perceived brushing sensation. Two distinct factors were identified: one reflecting tactile and functional characteristics, such as firmness and plaque removal, and another associated with usability and post-brushing sensation, including head size and feelings of freshness. The findings of this study suggest that the perceived brushing sensation of manual toothbrushes is influenced primarily by bristle hardness and brush head dimensions.

This observational study employed dental cone-beam computed tomography (CBCT) to evaluate the incidence and anatomical features of neurovascular structures within the lateral incisive canal (LIC). Images obtained from 221 patients were evaluated to determine the presence, diameter, and length of the LIC. Lateral incisive canals were identified in 24.4% of the CBCT images examined (bilaterally in 61.1% and unilaterally in 38.9%). One LIC was observed in 57.4% of cases, 2 in 16.7%, and 3 in 14.8%, with only a minority of cases displaying 4 to 6 LICs. The mean diameter of the LIC was 0.7±0.3 mm (0.3-1.8 mm) while that of the foramen was 0.8±0.4 mm (0.3-2.3 mm). Moreover, the mean length of the LIC was 8.9±4.1 mm (2.1-32.3 mm). The incidence of LICs (24.4%) was lower than that reported in previous CBCT studies of Asian populations. However, there may be regional differences in the incidence of anatomical structures, even among individuals of the same ethnic group. These results show that using CBCT to identify LICs can provide valuable information in the planning of surgical procedures involving the anterior maxilla.

This report describes a case in which a removable partial mandibular denture made of polycarbonate resin was fabricated using a computer-aided design and manufacturing (CAD/CAM) system for a patient with microstomia and trismus caused by scar contracture in the maxillofacial region after multiple tumor resections and reconstructive surgeries. The patient was an 82-year-old woman with a history of multiple oral cancer surgeries and radiotherapy. She presented with a markedly narrow oral aperture circumference (145 mm) and had no prior experience with dentures. Given the difficulty of applying conventional impression techniques in this case, impressions were obtained using unilateral stock trays and split custom trays. The denture base and artificial teeth were milled from a polycarbonate disk into a single-piece structure to create a denture with no microgaps. One month after insertion, the patient's Oral Health Impact Profile-54 score improved from 36 to 6, masticatory efficiency increased from 84 mg/dL to 131 mg/dL, and the facial scale score improved from 13/20 to 7/20. Furthermore, the smooth denture surface minimized denture plaque adhesion, aiding oral hygiene maintenance. In addition to the low water absorption and high smoothness of polycarbonate resin, integrated design achieved using CAD/CAM contributes to the prevention of denture stomatitis and oral candidiasis.

2q37 deletion syndrome is an extremely rare chromosomal disorder, with approximately 150 cases reported worldwide. Affected individuals are known to have multisystem involvement, though dental findings associated with this syndrome remain poorly documented. This report describes the long-term dental management and oral characteristics of a pediatric patient with 2q37 deletion syndrome. The patient was an 11-year 2-monthold boy who presented with the chief complaints of dental caries and maxillary anterior crowding. Similarly to in previous reports regarding this syndrome, a clinical examination revealed short stature (120 cm, approximately 3 standard deviations below the mean), intellectual disability, tetralogy of Fallot, and habitual vomiting. Intraoral findings included 6 carious teeth, a high-arched palate, a constricted maxillary arch, and severe anterior crowding. Mild dental erosion associated with habitual vomiting was also noted. The initial dental treatment addressed the caries in the maxillary first molars and anterior teeth. Due to limited cooperation from the patient, orthodontic treatment was deferred, though regular follow-up examinations were conducted over a period of 7 years. Caregiver motivation remained high and patient cooperation improved, and sectional orthodontic treatment was initiated when he reached the age of 18 years 2 months. Throughout the approximately 10-year period of dental care, the mother of the patient, serving as caregiver, has remained consistently engaged, allowing for routine dental management to be maintained. No new carious lesions have developed during this period and notable improvement in anterior alignment has been achieved. Long-term follow-up will be continued.

When teeth or odontogenic structures are present in excess of the normal number in the dental arch they are referred to as supernumerary. This paper describes a rare case of a maxillary right distomolar and left paramolar in an otherwise non-syndromic individual. The patient was a 23-year-old Japanese man who presented at our clinic seeking periodontal treatment. Intraoral examination revealed supernumerary teeth in the maxilla, and an extraction plan including the wisdom teeth was developed.

The purpose of this study was to investigate the impacts of diabetes and smoking on the risk of tooth loss in adults and the elderly. Dental receipts and specific health checkup data were used to assess increase in tooth extraction among people with a high blood glucose level or a smoking habit. The data were obtained from a database maintained by DeSC Healthcare Corporation, which supports the integrity of data held by health insurers. Dental receipts and specific health checkup data from 2018 to 2021 were used to obtain information on fasting blood glucose levels, smoking habits, and tooth extraction in 12,219 individuals aged 45-69 years. The results showed that the proportion of tooth extractions between 2018 and 2021 (32.3%) was higher in those with hyperglycemia. The proportion of tooth extractions in smokers (34.0%) was also significantly higher than that in non-smokers (21.6%). These results suggest that measures must be taken to promote dental and oral health care in those with hyperglycemia and in those with a smoking habit.

Remimazolam (Re) is an ultra-short-acting benzodiazepine used for intravenous sedation, general anesthesia, and intensive care unit sedation. Although benzodiazepines, including midazolam, possess anti-inflammatory properties and suppress macrophage activity, the impact of Re on macrophage-mediated immune responses remains uncertain. The purpose of this study was to investigate the effects of Re on lipopolysaccharide (LPS)-stimulated macrophage activation using thioglycolate-induced mouse peritoneal macrophages (TGC-macrophages). The findings demonstrated that Re significantly attenuated the production of proinflammatory cytokines, tumor necrosis factor α, and interleukin-6 by LPS-stimulated TGC-macrophages. Notably, this inhibitory effect on cytokine production remained unaffected by flumazenil, a specific antagonist of the γ-aminobutyric acid type A (GABAA), indicating that Re exerts its anti-inflammatory effects on macrophages through a mechanism independent of GABAA receptor signaling. In Re-treated macrophages, the expression levels of antigen presentation-related molecules, including CD86, a costimulatory molecule, and major histocompatibility complex class II, were significantly reduced following LPS stimulation. Conversely, Re did not affect the phagocytic capacity of TGC-macrophages, as evaluated by fluorescein isothiocyanate-labeled dextran, even at concentrations that inhibited inflammatory cytokine production and costimulatory molecule expression in LPS-activated TGC-macrophages. These findings suggest that Re exerts anti-inflammatory effects without suppressing essential innate immune functions, such as phagocytosis by macrophages.

More than 700 types of bacteria coexist in the human oral cavity, including motile and non-motile taxa. Fusobacterium nucleatum plays an important role in this environment as a bridge between early- and late-colonizing bacteria. We hypothesized that Treponema denticola, a motile bacterium, receives a non-contact benefit from coexisting F. nucleatum. To evaluate this hypothesis, the growth and gene expression of T. denticola were investigated in an environment where F. nucleatum was present but not in contact with it. The results showed that proliferation of T. denticola increased in this environment, and that this was attenuated by autoinducer-2 (AI-2) inhibitor D-ribose. The results of RNA-seq and qRT-PCR showed that the presence of F. nucleatum increased the gene expression levels of TDE_0039 and TDE_0040. These findings revealed that proliferation of T. denticola increased via a substance produced by F. nucleatum. Importantly, this phenomenon occurs even without direct contact between the two species. In other words, T. denticola may gain a survival advantage by moving through the oral environment, and F. nucleatum may play a crucial role in facilitating this.

Porphyromonas gingivalis, a key periodontal pathogen, employs extra-cytoplasmic function (ECF) sigma factors to adapt to the dynamic oral environment and establish chronic infection. Among these, PGN_1740 (SigH) has been implicated in oxidative stress response and iron acquisition, yet its transcriptional regulatory mechanisms remain poorly understood. The aim of this study was to elucidate the functional role of SigH using sigH-deficient mutants. Quantitative reverse transcription-polymerase chain reaction was performed to assess the transcriptional profiles of sigH and its putative target genes, sod and ltp1, throughout the growth of P. gingivalis. Electrophoretic mobility shift assay (EMSA) was conducted to evaluate the direct binding of recombinant SigH to the sod and ltp1 promoter regions. Oxygen sensitivity was also assessed using hydrogen peroxide susceptibility and cell invasion assays. The results of these experiments revealed that sigH transcription peaked during the mid-log and early stationary phases, followed by a significant decline in the late stationary phase. The EMSA analysis demonstrated that rSigH directly binds to the ltp1 promoter, but not to the sod promoter. Notably, the sigH-deficient mutant exhibited increased oxidative stress sensitivity in the hydrogen peroxide susceptibility assay. Furthermore, unlike the wild type, the sigH-deficient mutant was unable to invade telomerase-immortalized gingival keratinocytes. These findings suggest that the ECF sigma factor SigH regulates oxidative stress tolerance via sod, and iron metabolism via ltp1, in P. gingivalis.

This study explored the association between tooth extraction, dental visit frequency, and blood glucose levels over a 3-year period in middle-aged and older adults using a large health insurance claims database (DeSC, Tokyo, Japan). Data from 31,373 individuals aged 45-70 years who participated in Specified Medical Checkups and Health Guidance between April 2018 and March 2022 were analyzed. Participants were categorized based on the frequency of their annual dental visits and tooth extractions. The primary outcome was high blood glucose level, defined as HbA1c≥6.5%, or fasting plasma glucose level, at ≥126 mg/dl. Individuals who underwent tooth extractions at baseline had lower odds of high blood glucose levels after 3 years, regardless of their baseline glycemic status. Participants with three or more yearly dental visits had lower odds of a high blood glucose level, particularly those with a high baseline blood glucose level and a body mass index ≥25.0 kg/m2. These findings suggest an association between regular dental care and improved glycemic control, particularly in individuals with obesity. However, causal relationships cannot be inferred from this study, and further research is required to examine the impact of periodontal treatment and other dental interventions on diabetes management.

The WHO Classification of Head and Neck Tumors (2024) defines solitary neurofibromas as benign peripheral nerve sheath tumors comprising a mixture of Schwann cells, perineuronal cells, fibroblasts, and axons. In the orofacial region, such tumors usually occur on the tongue, and only rarely in the lip. This report describes a case of a solitary neurofibroma arising in the lower lip. The patient was a 59-year-old man who was referred to our hospital with a mass on the lower lip. Palpation revealed that it was elastic, hard, painless, and mobile. Magnetic resonance imaging confirmed the presence of a mass. It was identified as a suspected benign tumor and surgical excision conducted under general anesthesia. A diagnosis of solitary neurofibroma was made based on histopathological findings. One and a half years have passed since the surgery, and no recurrence has been noted. Long-term follow-up has been planned.

Deterioration of oral function can impair articulation, making it essential to evaluate tongue movement during articulation training. Previous reports have indicated an improvement in motor speech disorders, such as glossectomy-related glide issues, through rapid speech exercises, suggesting the potential benefits of non-invasive training. This study aimed to investigate the effect of tongue training on oral function using tongue twisters in healthy Japanese-speaking women. The participants performed tongue twisters designed to engage both the tongue tip and root, with data collected at baseline, 1 month, and 7 months. Participants were required to complete sentences involving the repeated use of /ta/ and /ka/ sounds. This training was conducted 5 times per week for 1 month. Oral diadochokinesis (ODK) was used to measure the number of repetitions per second of each sound, while ultrasound imaging captured the vertical motion of the tongue during pronunciation. The ODK test was used to evaluate speed and regularity of articulatory movement, and ultrasound measurement to assess vertical motion dynamics of the tongue during pronunciation of /ta/ and /ka/. The results indicated a significant improvement in the number of repetitions per second for both /ta/ and /ka/ after 1 month of training. This increase in repetition frequency was maintained for /ta/ even after 7 months, whereas /ka/ showed no further increase in repetition frequency beyond the 1-month mark. Despite this, vertical distance of tongue movement decreased significantly for both syllables after 1 and 7 months. This suggests that /ta/ benefited from both increased efficiency and speed, whereas /ka/ prioritized refined motor control over frequency. The complexity of posterior tongue elevation in /ka/ may require greater precision, limiting increase in repetition despite improved efficiency. This study demonstrates that regular tongue-twister training effectively refines oral function in young women, with sustained benefits over time. The simplicity and accessibility of this method make it a promising approach to maintaining and enhancing oral and articulatory function.