Coronavirus infectious disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was declared a pandemic in March 2020 by the World Health Organization. Periodontitis, one of the most prevalent diseases worldwide, leads to alveolar bone destruction and subsequent tooth loss, and develops due to pro-inflammatory cytokine production induced by periodontopathic bacteria. Periodontopathic bacteria are involved in respiratory diseases, including aspiration pneumonia and chronic obstructive pulmonary disease (COPD), and other systemic diseases, such as diabetes and cardiovascular disease. Patients with these diseases have an increased COVID-19 aggravation rate and mortality. Because aspiration of periodontopathic bacteria induces the expression of angiotensin-converting enzyme 2, a receptor for SARS-CoV-2, and production of inflammatory cytokines in the lower respiratory tract, poor oral hygiene can lead to COVID-19 aggravation. Conversely, oral care, including periodontal treatment, prevents the onset of pneumonia and influenza and the exacerbation of COPD. The reduced chance of receiving professional oral care owing to long-term hospitalization of patients with COVID-19 may increase the aggravation risk of infection in the lower respiratory tract. It can be hypothesized that periodontopathic bacteria are involved in the COVID-19 aggravation and therefore, the management of good oral hygiene potentially contributes to its prevention.

Numerous studies have confirmed the effectiveness of cognitive behavioral therapy (CBT) for chronic pain, and it is generally regarded as an appropriate intervention. However, it may not be effective for some pain sites, and the duration of the effect may be limited. In addition, some studies of CBT lacked a comparison group. This review summarizes evidence for the effectiveness of CBT for orofacial pain and assists in the development of guidelines for orofacial pain management. A literature search in PubMed was performed for studies published from April 1990 through March 2020. The search keywords were “burning mouth syndrome,” “temporomandibular disorders,” “myofascial pain syndrome,”“chronic orofacial pain conditions,” “cognitive behavioral therapy,” and “non-pharmacological therapy.” The results indicate that CBT alone or in combination with other treatments, such as intraoral appliance, stress management, or biofeedback, is effective for the vast majority of orofacial pain cases. Therefore, dentists should consider using CBT to manage orofacial pain in their patients.

WaveOne Gold, ProTaper Gold, Reciproc Blue, ProTaper Next, WaveOne and ProTaper files were selected to compare the phase transformation behaviors and mechanical properties of nickel-titanium (NiTi) rotary files after gold heat and blue heat treatments. The reverse transformation finishing point temperatures of WaveOne Gold, ProTaper Gold, ProTaper Next and WaveOne were higher than those of the other two instruments investigated. At a deflection of 0.5 mm, the loads were significantly varied except for ProTaper Next and ProTaper Gold. At a deflection of 3.0 mm, the loads of Reciproc Blue and WaveOne Gold were significantly varied compared to WaveOne and ProTaper. Cycles to failure were reduced in the order of WaveOne Gold, Reciproc Blue, ProTaper Gold, ProTaper Next, WaveOne and ProTaper. NiTi instruments after gold heat and blue heat treatments exhibited significantly higher bending properties and cyclic fatigue resistances, representing an improved performance over traditional and M-wire instruments.

This study aims to evaluate the impact of adding a novel tricyclodecane dimethanol diacrylate comonomer on the flexural strength (FS) and impact strength (IS) of heat-cure denture base resin at 10% and 20% (v/v) concentrations. To test the FS and IS, a sum total of 150 bar-shaped specimens were prepared according to standard specifications. For the FS, the specimens were subjected to the three-point bend test with a span length of 50 mm. For the IS, Charpy’s test was executed with a span length of 60 mm. The FS was measured in MPa, and the IS was measured in kJ/m². There was a statistically significant difference (P < 0.001) between the control and experimental groups in that both the FS and IS were increased in the experimental groups relative to the control group.

This in vitro study was performed to evaluate the surface roughness (Ra) and morphology by scanning electron microscopy (SEM) of composite resins that had been stored in acidic solutions typical of those present in the diet. Three composite resins (4 Seasons, Z250, and P90) were selected and divided into three groups (n = 7) according to the solutions tested: G1: distilled water; G2, Coca-cola, and G3: orange juice. The Ra test was repeated after immersion periods of 15, 90, and 180 days. The mean Ra values were subjected to LS means analysis and the Tukey-Kramer (P < 0.05). One test specimen of each composite resin was selected for SEM analysis after each period. The Ra data indicated that P90 had the lowest Ra values. 4 Seasons and Z250 had statistically similar roughness values for all the solutions and evaluation periods. With the exception of 180-day immersion in Coca-cola, 4 Seasons showed significantly higher values than Z250. SEM analysis showed that P90 was the composite resin most resistant to the actions of all acid solutions for the periods analyzed. Interaction between components of the solutions and the active components of other dietary items, as well as oral hygiene, may affect the chemical degradation of composite resins.

Purpose: To investigate inter- and intra-individual variation in the levels and outputs (concentration multiplied by salivary flow rate) of salivary metabolites in patients with primary Sjögren’s syndrome (pSS).

Methods: A total of 56 samples of stimulated saliva were collected from 14 female pSS patients during four laboratory visits within 20 weeks and analyzed using proton nuclear magnetic resonance spectroscopy. Single saliva samples from each of 15 controls were also analyzed.

Results: Among 21 quantified metabolites, choline was significantly elevated in the pSS patients at each time point (P ≤ 0.015), taurine at the last three time points (P ≤ 0.013), alanine at the last two time points (P ≤ 0.007) and glycine at the last time point (P = 0.005). Inter-individual variation in metabolite concentrations was generally larger among the patients than among the controls, and significantly large variations were observed for glycine (P ≤ 0.007, all time points), choline (P ≤ 0.033, three last time points) and alanine (P = 0.028, baseline). Metabolite output analysis showed that choline had the lowest intra-patient variation.

Conclusion: In spite of considerable intra- and inter-individual variation, levels and outputs of specific metabolites in patients with pSS differ from those in controls, and may be potentially applicable as new biological markers for monitoring of the response to treatment.

Minimal intervention is generally achieved by using direct composite resin (CR) restorations. However, deep caries lesions may lead to pulpal complications. This study evaluated the risk of endodontic complications after CR restoration in relation to depth of caries lesions. Data on 507 teeth from 316 adults treated with CR were analyzed. Caries depth was expressed as a percentage of the distance between the outer edge of the dental enamel and the pulp base on preoperative radiographs. The interval between CR restoration and follow-up root canal treatment was obtained from electronic treatment records for a period of 24 months. A Cox proportional hazards model was used to investigate the association between risk of endodontic complications and caries depth. Sixteen teeth (3.2%) required root canal treatment within 24 months. No root canal treatment was required after CR treatment for caries affecting <50% of the outer edge of enamel and pulp. As compared with CR treatment of caries lesions with a size of <80%, there was a significantly higher risk of root canal treatment for caries lesions with a size of 80% to 89% (hazard ratio, [95% CI]: 34.68 [4.23-284.11]) and ≥90% (92.01 [10.36-817.41], respectively).

Purpose: This study evaluated the flexural strength of bulk-fills after immersion in food-simulating solvents.

Methods: Four overlapping segments along both sides of bar-shaped specimens (25 × 2 × 2 mm) made from bulk-fill composite were irradiated with an Elipar LED light-curing (1,200 mW/cm² for 20 s) device. The specimens were then divided into four groups (n = 20), according to storage media—namely, distilled water, 99% ethanol, heptane, and methyl ethyl ketone—at 37^oC for 4 weeks. Flexural testing was done with a universal testing machine at a crosshead speed of 1 mm/min.

Results: Data were analyzed with the two-way and one-way ANOVA and post-hoc Tukey (HSD) tests (P < 0.05), along with the Weibull statistic. Flexural properties significantly differed in relation to the bulk-fill and solvent used. The flexural properties of bulk-fills decreased in solvents. SonicFill in distilled water had the highest values for flexural properties (σ_f = 165.77 MPa; E_f = 10.3 GPa), followed by the values for SonicFill in ethanol and those for X-tra base and everX Posterior in water. Venus Bulk Fill in methyl ethyl ketone yielded the lowest values (σ_f = 74.11 MPa; E_f = 3.06 GPa).

Conclusion: The flexural properties of bulk-fills are affected by the food-simulating solvent used and by the filler content, type, and resin component.

Purpose: This study assessed the effectiveness of incobotulinum toxin type A (IBTx) for chronic myofascial pain affecting the masseter and temporal muscles.

Methods: Twenty two patients who received a diagnosis of chronic masseter and temporalis myofascial pain were evaluated by using a visual analog pain scale (VAS), digital pressure algometry, and the SF-36 Health Survey at baseline (T0), before IBTx injection. Patients were again evaluated at 2 months (T1) and 7 months (T2) after IBTx injection.

Results: VAS scores for pain significantly differed (P = 0.029, Friedman test). Post-hoc tests showed a significant reduction in pain at 2 months (T0–T1) and 7 months (T0–T2) (P = 0.011 and P = 0.028, respectively; Wilcoxon test) but not between 2 and 7 months (P = 0.676; Wilcoxon test). There was no significant difference in pressure algometry values (P = 0.385, Friedman test). Quality of life (QOL) assessment showed a significant difference (P = 0.002, Friedman test). Post-hoc tests showed a significant improvement in QOLat 2 months, but no significant difference at 7 months (P = 0.004 and P = 0.260, Wilcoxon test).

Conclusion: IBTx injection resulted in safe, effective short-term pain relief for patients with chronic facial pain affecting the masseter and temporalis muscles.

Purpose: Whether it is possible to prevent mechanical stress on teeth via an occlusal splint remains to be clarified. This study aimed to assess the same by simultaneously recording the occlusal pressure and strain on the teeth in humans.

Methods: Eleven participants (five women and six men; mean age 25.7 years) were enrolled in this study. Hard and soft oral appliances were fabricated for the maxillary arch of each participant. The strain on the four target teeth (right maxillary and mandibular first premolars, and first molars) and occlusal pressure were concurrently measured, while the participants performed maximum voluntary teeth clenching under each condition (hard, soft, or no occlusal splint).

Results: Compared to the absence of an occlusal splint, hard occlusal splints generated less strain on molar teeth but more strain on premolar teeth, while soft occlusal splints did not lower the strain on all target teeth significantly.

Conclusion: Considering the limitations of this study, hard occlusal splints should be used for the protection of molar teeth but for premolar teeth caution is required and depends on the case. On the other hand, soft occlusal splints may not have any benefit for the protection of either type of teeth for patients exhibiting excessive occlusal pressure.

Purpose: The present study was conducted to determine oxidative stress and cell viability after contact with resin composites polymerized for different times.

Methods: Disk-shaped specimens of Admira Fusion, Ceram X One Universal, Solare x and Filtek Z550 (n = 12) were prepared, and two subgroups with polymerization times of 20 and 40 s were employed. The specimens were incubated with mouse fibroblast cells for 48 and 72 h, and changes in reactive oxygen species (ROS) production and cellular viability were determined by an assay with a cell-permeable fluorescent dye, 2’,7’-dichlorodihydrofluorescein diacetate (H₂DCF-DA), and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, respectively.

Results: At 72 h, ROS production in the presence of Admira Fusion polymerized for 40 s was reduced relative to that in the presence of Admira Fusion polymerized for 20 s (P < 0.05). Cell viability was maximal in the Admira Fusion and Solare x groups and there was no difference relative to the control group at 48 h. Cell viability was higher in the Admira Fusion and Solare x groups polymerized for 40 s than for the same materials polymerized for 20 s at 72 h (P < 0.05).

Conclusion: Extension of the polymerizaton time has a material-specific effect and may be used as a strategy to increase the biocompability of resin composites.

Purpose: Ni-Ti alloy has been increasingly applied to dental and medical devices, however, it contains nickel, which is known to have adverse effects on the human body. The purpose of this study was to form a nickel-free surface oxide layer on Ni-Ti alloy by electrolytic treatment for better biocompatibility.

Methods: Ni-49.15Ti (mol%) alloy was used, and the electrolytic treatment was performed in the electrolytes under 50 V for 30 minutes. The electrolytes were composed of lactic acid, water, and glycerol with different compositions. Surface analysis and characterization of Ni-Ti alloy were carried out by means of X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).

Results: Results indicated that the outmost surface oxide layer was nickel-free when using an electrolyte comprising 7.1% lactic acid, 57.2% water, and 35.7% glycerol by volume. The composition of this nickel-free surface oxide layer was determined as TiO_1.92(OH)_1.35 ∙ 0.43H₂O by XPS, similar to that of unalloyed titanium. The thickness of this nickel-free layer was estimated at 6.4 nm by AES.

Conclusion: The nickel-free surface oxide layer produced on Ni-Ti alloy is considered to improve the biocompatibility of medical and dental devices having shape memory effect and/or super-elasticity.

Age estimation of unidentified bodies is important in forensic medicine and crime scenes. There is accumulating evidence that DNA methylation in the human genome isolated from body fluids changes with age. Most of the data have been obtained by pyrosequencing. In the forensic field, a simple, quick, and economical method is required to evaluate the age of various types of samples. In this study, an age estimation method based on methylation levels of DNA extracted from teeth using real-time methylation-specific PCR (MSP) was developed. The CpG island in the upstream region of ELOVL2, which is known as a validated biomarker in blood samples, was selected as a target site. The CpG methylation levels highly correlated with age (r = 0.843, n = 29). Age-related increase in DNA methylation levels was not affected by sex differences. In addition, the simple regression model based on methylation status of the CpG island exhibited moderate accuracy with a mean absolute deviation between chronological age and predicted age of 8.94 years. The results imply that real-time MSP can be a new tool to perform age prediction of unidentified bodies in forensic scenes.

Purpose: To establish a digital assessment method for changes in gingiva morphology following initial periodontal therapy.

Methods: Ten periodontal-healthy participants were selected, and digital models obtained by intraoral scanning and digitizing conventional impressions. Using dentition as a reference, best fit alignment between digital models was carried out. Root mean square (RMS) was calculated to evaluate differences in models, and gingival volume discrepancy (GVD) was calculated after combining separated models. Trueness of intraoral scanning used on the gingiva was evaluated using RMS and GVD between intraoral and conventional models with conventional models as references; precision was evaluated among different intraoral models of one participant. Twenty-three periodontitis-affected participants underwent intraoral scanning immediately after supragingival scaling and two weeks after initial periodontal therapy. The GVD of gingiva between two digital models was calculated to assess gingival changes and related factors after therapy.

Results: Trueness of intraoral scanning used on the entire gingiva was 83.65 ± 14.43 μm; precision was 70.71 ± 25.58 μm; GVD error measured by digital models was 15.28 ± 10.00 mm³. Gingival volume in periodontitis-affected participants decreased 104.04-1155.09 mm³ after therapy. Probing depth, bleeding index, and keratinized gingival width positively correlated with changes in gingival volume.

Conclusion: Intraoral scanning can be recommended as a method of evaluating morphological changes in gingiva.

The purpose of this study was to examine the effect of heating on the physical properties of four types of premixed calcium silicate-based root canal sealers. Endoseal MTA, Well-Root ST, EndoSequence BC Sealer, EndoSequence BC Sealer HiFlow, and AH Plus (epoxy resin root canal sealer) were heated at 100°C for 1 min, and changes in setting time, flow, and film thickness were evaluated in accordance with ISO 6876:2012 standards. In addition, pH measurement and scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses of the set materials were performed. All root canal sealers heated at 100°C showed significant decreases in setting time and flow, particularly Endoseal MTA. In addition, the film thickness of Endoseal MTA increased significantly after heating at 100°C. The pH and SEM/EDS results were not affected by heating. Heating calcium silicate-based root canal sealers accelerated setting time, decreased flow, and increased film thickness. However, the degree of these changes varied among the products. The present findings indicate that heat-induced changes in the physical properties of calcium silicate-based root canal sealers could adversely affect the quality of warm vertical condensation technique.

Purpose: The aim of this study was to compare the influence of the number of coronal walls and post-endodontic restorations on the mechanical strength of 165 recently extracted endodontically treated maxillary premolars.

Methods: The teeth were divided into 3 control (no post) and 3 test groups according to the number of residual walls. Each test group was divided into subgroups according to the type of post-endodontic restoration (single, oval, and multi-post techniques). Samples were prepared conforming to the assigned subgroup. A universal loading machine applied a load parallel to the longitudinal axis of the teeth, thus simulating physiological occlusion. ANOVA and the Kruskal Wallis test were used for comparisons (P ≤ 0.05), and Tukey’s test for multiple comparisons.

Results: For intact teeth, significant differences were found among all 3 subgroups, with single post showing the highest values. For 3 residual walls, oval post resulted in significantly lower values than single and multi-post systems. For 2 residual walls, the multi-post technique showed almost twice the resistance of oval post restorations.

Conclusion: In oval canals the use of a single or multi-post technique increased post-and-core resistance even in intact teeth, whereas oval fiber posts showed no improvements. Multi-post design improved fracture resistance mostly in maxillary premolars lacking both marginal ridges.

The purpose of this study was to explore the effects of nicotine on the activity of Streptococcus mutans (S. mutans) in soft drinks. Regular soft drinks contain large proportions of high-fructose corn syrup (HFCS), which increases the activity of S. mutans resulting in high-caries risk compared with sugar-free soft drinks. Nicotine use exhibits a strong correlation with increased S. mutans biofilm formation. The soft drinks chosen were (Coca-Cola Classic, Diet Coke, Coca-Cola Zero Sugar, Caffeine-Free Coca-Cola, Caffeine-Free Diet Coke, Caffeine-Free Coca-Cola Zero Sugar). S. mutans was grown overnight in tryptic soy broth; nicotine was diluted in tryptic soy broth supplemented with 1.0% sucrose followed by soft drinks in dilution of 1:3. Total growth absorbance and biofilm growth were determined by spectrophotometry, absorbance measured to determine biofilm formation, and metabolic activity quantified. One-way ANOVA showed a considerable effect for HFCS and caffeine in the presence of nicotine and their interaction in all measures. Results showed sugar-free caffeinated colas demonstrated significant effect in inhibiting S. mutans biofilm formation and metabolic activity with nicotine. Nicotine-induced S. mutans increased biofilm formation and metabolic activity in the presence of HFCS and caffeine in soft drinks. In conclusion, smokers should consider sugar-free caffeinated versions to minimize the chance of developing dental caries dut to the reduction of biofilm formation.

Purpose: To examine the relationship between oral intake function and oral health status in convalescent inpatients.

Methods: Subjects were 222 patients admitted to a convalescent hospital between 1 January and 30 June 2018. Investigation items were age, sex, causative disease, body mass index, functional oral intake scale (FOIS), functional independence measure, occlusal contact, assistance with oral cleaning, and oral health assessment tool (OHAT) scores. Multiple regression analysis was performed with FOIS as the dependent variable, and investigation items were related to FOIS as independent variables.

Results: Results of multiple regression analysis for all patients suggested that saliva and denture scores were significantly associated with FOIS. However, analysis excluding non-oral feeding patients did not show a significant association between FOIS and OHAT scores.

Conclusion: The results of this study suggest that oral health status is associated with oral intake function. In addition, the oral health status of inpatients may be strongly related to whether or not they are eating orally. Therefore, it is necessary to take good care of oral health in non-oral feeding patients in the convalescent ward.

Purpose: Circadian rhythm is associated with the pathogenesis of systemic disease and bone mineral metabolism. This study aimed to radiographically evaluate morphological characteristics of the interalveolar septum in circadian rhythm deficient animals.

Methods: Heads of 10 brain and muscle arnt-like protein-1 (BMAL1)-knockout (KO) mice and 10 wild-type mice sacrificed at 36 weeks were imaged using micro-computed tomography. The mean depth from the cementoenamel junction to the alveolar ridge (virtual bone sounding: VBS) of the interalveolar septum between the first and second molars, and the bone mineral density (BMD) of the interalveolar septum and the mandibular inferior cortex region were calculated. Tooth diameter was also measured.

Results: The VBS of the interalveolar septum in the BMAL1-KO mice was significantly deeper than that in wild-type mice. The BMD in the BMAL1-KO mice was significantly lower than in the wild-type mice in both regions. No significant difference was observed in tooth diameter between BMAL1-KO and wild-type mice.

Conclusion: These results suggest that low BMD in the interalveolar septum accelerates bone resorption in the interalveolar septum in BMAL1-KO mice.

Purpose: The spatial resolution of cone-beam computed tomography (CBCT) in small fields of view (FOVs) is important for clinical applications. However, it is difficult to measure spatial resolution reliably due to error factors such as noise. The aim of this study was to obtain a modulation transfer function (MTF) more accurately.

Methods: A CBCT apparatus was used with small FOV. An aluminum pipe slightly tilted at an inclination ratio of 77/3 (25.7) was used as the measurement phantom. The MTF was calculated from the edge image of the phantom. The actual oversampling ratio was determined by regression analysis. The experiment was repeated 16 times and the edge-spread function (ESF) was approximated by the least-square method. Furthermore, a low-pass filter (LPF) was applied to eliminate the component at frequencies above the Nyquist frequency. Finally, the MTF was calculated from the pre-processed ESF.

Results: Results showed that pre-processing reduced the noise of the ESF. The MTFs at frequencies of 1.0 and 2.0 LP/mm were 0.59 and 0.18, respectively, in air and 0.52 and 0.16, respectively, in water.

Conclusion: The repeating-edge oversampling method combined with ESF pre-processing improved the accuracy of the MTF under clinically relevant conditions with a phantom.

Purpose: Implant component fractures are one of the most serious complications in implant treatment. With a better understanding of the risk factors for fracture in the preoperative, surgery, superstructure, and post-loading phases of implant treatment, low-risk treatment could reduce implant component fractures, leading to a better prognosis. The aim of this study was to clarify the risk factors for abutment and implant fractures that occur after loading, and to perform a retrospective, approximately 10-year follow-up study to explore the risk factors in each treatment phase.

Methods: Subjects were fitted with an implant prosthesis between January 2008 and December 2009. In total, 1,126 Ankylos implants in 430 patients were included for analysis. Binary logistic regression analysis was performed to extract factors related to non-fracture and fracture of the abutment or implant as a dependent variable.

Results: Gender (OR = 3.466, 95% CI 1.296-9.268, P = 0.013), gonial angle (OR = 3.420, 95% CI 1.308-8.945, P = 0.012), and splinting status of the superstructure (OR = 4.456, 95% CI 1.861-10.669, P = 0.001) were identified as significant risk factors.

Conclusion: The risk of fracture is increased in males, especially those with a mandibular angle of less than 120° on panoramic radiographs, and those with a non-splinted superstructure.

The purpose of this study was to clarify the usage and understanding of denture adhesives among 1,825 denture wearers, aged 40 years and older in Japan, using a web-based survey. The NTTCom Online survey (a closed investigation) was conducted over a period of 4 days using a 13-item questionnaire about denture adhesives. Results showed that 67.1% of the respondents were satisfied with their dentures; 81.5% of respondents knew about denture adhesive, but only 347 (19.0%) had used the product. Products used by the 347 denture wearers included cream type (79.7%), cushion type (16.2%), and powder type (3.2%). The most common reason for the selection of a particular type was “Saw the product” (59.9%), followed by “Saw an advertisement” (19.3%), and “Explanation at a dental clinic” (8.4%). The response of “Ill-fitting denture” significantly affected the response of “Use of denture adhesives” (chi-square test; P < 0.001). Moreover, the sensitivity (0.56) was lower than the specificity (0.75). These findings show that denture adhesives were not always necessary for those with ill-fitting dentures.

A simple sandwich technique using buttons to compress grafted tissue combined with a tie-over technique for intraoral split-thickness skin grafts (STSGs) is introduced. This technique yielded an excellent engraftment rate (90.5%) and no instances of total graft failure were recorded. This simple sandwich technique for STSGs is readily applicable and inexpensive, and the present results show that it would be potentially useful for repair of defects in the oral cavity.

Congenital insensitivity to pain with anhidrosis (CIPA) is a rare disease caused by a mutation in the nerve growth factor (NGF) receptor, which results in an absence of Aδ and C fibers. It can be considered that this defect may also lead to deterioration of oral sensations. The aim of the present study was to clarify the ability of CIPA patients to perceive pungent, gustatory, and olfactory stimuli, which is essential for eating function, and the impact of the defect on dietary habits. Sensitivities to capsaicin and the five basic tastes were evaluated by measuring their threshold values, and dietary habits were examined using a questionnaire. Additionally, odor identification ability was evaluated using the odor stick method. The detection threshold for capsaicin and the recognition threshold for sour taste were significantly higher in the patients than in healthy volunteers. The questionnaire responses showed that the patients consumed spicy food more often. All patients were able to identify the tested odors, except those to which they had not been well accustomed. Since the abilities of CIPA patients to perceive taste and smell were not basically impaired, despite their lower sensitivity to capsaicin, it was suggested that their dietary habits were only minimally affected, except for intake of pungent foods.

During the current coronavirus disease 2019 (COVID-19) pandemic, dental education and training requiring face-to-face interaction must prioritize infection prevention and the safety of students, staff, and patients. In July 2020, the Association for Dental Education, Asia Pacific (ADEAP) published safety guidelines for safe dental education during the COVID-19 pandemic. These guidelines summarize ADEAP recommendations for classroom-based courses, reopening of simulated training courses and dental clinics, and provision of clinical skills training courses in dentistry during the COIVID-19 pandemic. They have been formulated to ensure the safety of students and teaching staff, dental auxiliary staff, and patients. However, the present guidelines are considered appropriate only when the number of COVID-19 epidemic cases has been significantly reduced, i.e. when the epidemiological curve has flattened in the area concerned. The criteria for lifting restrictions on activities should be consistent with relevant jurisdictional guidelines.

A study was conducted to evaluate the basic mechanical properties of a pure cellulose nanofiber (CNF) material in comparison with a commercial denture base material (polymethylmethacrylate [PMMA] acrylic resin). The working hypothesis was that CNFs have potential for use as denture base materials. Pure CNF specimens fabricated under various conditions were examined. The flexural strength (FS) and flexural modulus (FM) of the specimens were measured using the three-point bending test, and the morphologies of the fractured surfaces were examined using scanning electron microscopy. Addition of tricalcium phosphate to dehydrate the CNFs did not improve their FS or FM. Conversely, substitution with methanol effectively improved the dehydration process and significantly affected the mechanical properties of the CNFs. As the degree of CNF defibration increased, the physical properties of the specimens improved significantly. However, addition of CNFs to PMMA liquid to create CNF-reinforced PMMA did not improve the mechanical properties. Pure CNF specimens fabricated under particular conditions had higher FS and FM values than the control, suggesting that CNFs have potential as a “petroleum-free” alternative to acrylic resin denture base materials. Pure CNF would be potentially useful as a denture base material, and presumably applicable to computer-aided design/manufacture (CAD/CAM).

Few prospective studies have reported the effects of periodontal therapy on patients who attempted to quit smoking. This study aimed to assess how smoking cessation affects periodontal therapy. Twenty-five smokers with periodontitis were investigated by dividing them into two groups, a smoking cessation support group and a continued smoking group. Those in the support group received counseling and nicotine replacement therapy, followed by periodontal treatment conducted by dentists who had completed an e-learning course on smoking cessation. Clinical parameters were measured at baseline, 3, and 6 months. Most clinical parameters improved for those in the smoking cessation support group. There were no significant improvements in bleeding on probing (BOP) or the number of severe periodontal disease sites in the continued smoking group. Probing pocket depth (PPD) and clinical attachment levels (CAL) at sites that received scaling and root planing (SRP) significantly improved in all subjects. BOP did not improve at reevaluation in the smoking relapse subgroup. Patients in the smoking cessation support program led by dental professionals showed more improvement in BOP than those in the continued smoking group.

Cast titanium restoration for molars has high biocompatibility and is covered by the Japanese national health insurance. Titanium casting requires specific investment material and casting apparatus. A cast restoration for the mandibular left second molar was fabricated using titanium in this study. A wax pattern fabricated on a definitive cast was invested in calcium aluminate-bonded magnesia investment material. Titanium was cast using an argon gas pressure one-chamber casting apparatus. No defects were observed on the surface and the hole was clearly reproduced. A smooth surface on the restoration was obtained by polishing at low speed. Reproductivity and polishing properties of the titanium restoration fabricated in this study were comparable to those of conventional dental metal restorations.

This report discusses a case of a 75-year-old female patient with metachronous multicentric carcinomas in the oral cavity at 4 different sites. In this patient, there were no generally associated characteristics, such as drinking alcohol, chewing betel quid or smoking cigarettes. However, her elder sister died due to oral carcinoma. Although well-known risk factors for oral carcinoma were not detected, a previous family history was found. These findings suggest the potential for an unknown genetic anomaly associated with oral carcinoma. This is the first report to describe a female patient with oral multicentric carcinoma arising from four different sites.