Actual state of the diurnal masseteric electromyogram: Differences between awareness and non-awareness of awake bruxism.

PURPOSE: This study aimed to elucidate the relationship between diurnal masseter muscle activity and awareness of diurnal awake bruxism (d-AB) by conducting a comparative analysis of electromyographic (EMG) data from individuals with and without awareness of diurnal awake bruxism (d-AB), utilizing EMG data gathered from multiple subjects. METHODS: Unilateral masseter electromyography (EMG) recordings were performed during the daytime using an ultraminiature wearable EMG device. A total of 119 participants (59 with awareness of diurnal tooth clenching [d-TC] and 60 without awareness of d-TC) were included. Waveforms longer than 0.25 s with the two amplitude conditions, exceeding twice the baseline and >5% of maximum voluntary clenching, were extracted. In addition, the number of bursts and episodes (groups of bursts), burst duration, and burst peak amplitude were calculated for each participant. RESULTS: There were no significant differences in the EMG parameters between the groups with and without awareness of d-TC. Additionally, the frequency distribution of the number of EMG waveforms exhibited wide ranges and substantial overlap between the two groups. CONCLUSIONS: The variability in the number of bursts and episodes, burst peak amplitude, and burst duration among subjects suggests the need for an objective classification of d-AB severity based on EMG values. The absence of significant differences and large overlap in frequency distributions between the groups with and without awareness of d-TC indicate difficulty in predicting muscle activity solely based on awareness of d-AB.

Influence of Meal Sequence and Number of Teeth Present on Nutrient Intake Status: A Cross-Sectional Study.

Intake of fiber, as well as protein, and lipid preloading help to control postprandial glycemic elevation in people with type 2 diabetes and in healthy individuals. However, there are few studies on the awareness of meal sequence and nutrient intake status that consider oral conditions. This cross-sectional study aimed to determine the effects of meal sequences on nutrient intake status and whether these relationships were related to the number of teeth present. The subjects were recruited from the Medical and Dental Collaboration Center of Kanagawa Dental University Hospital between 2018 and 2021. Medical and dental examinations were performed, and a questionnaire was used to determine whether the diet consisted of vegetables, meat or fish, and carbohydrates in that order. Nutrient intake status was assessed using the brief-type self-administered diet history questionnaire. Data were collected from 238 participants. The group with awareness of meal sequence ingested increased nutrients such as n-3 fatty acids, total dietary fiber, calcium, and vitamin C. Saturated fatty acid intake increased in those with fewer teeth, while it was not significantly related to meal sequence. In conclusion, our results showed that meal sequence was associated with nutrient intake status. In addition, the intake of saturated fatty acids increased when many teeth were lost, regardless of meal sequence.

Prosthodontic treatment can improve the ingestible food profile in Japanese adult outpatients.

PURPOSE: To investigate the effect of prosthodontic treatment on the ingestible food profile in adult Japanese outpatients, and to identify the related risk factors that can deteriorate the profile. METHODS: The participants were 277 outpatients who visited university-based specialty clinics in Japan for prosthodontic treatment. The demographic data, number of present teeth assessed via intraoral examination, and oral health-related quality of life assessed by the total Oral Health Impact Profile (OHIP-J54) scores of all participants were recorded before treatment. Ingestible food profile score (IFS) was recorded using a validated food intake questionnaire. Eligible participants who answered the questionnaire before and after treatment were categorized into five groups based on the prosthodontic treatments they received (i.e., crowns, bridges, removable partial dentures, removable complete dentures, and removable complete and partial dentures). RESULTS: Multivariate analysis of covariance revealed a statistically significant main effect of prosthodontic intervention (time course: before and after treatment) on mean IFS (P=0.035, F=4.526), even after adjusting for covariates (age, number of present teeth, and treatment modality). Multiple linear regression analysis revealed that the low number of present teeth (r=0.427, P<0.001) and a high OHIP-J54 total score (r=-0.519, P<0.001) of the patients at the baseline were significantly associated with their baseline IFSs, even after adjusting for confounding variables. CONCLUSIONS: The findings of this multicenter follow-up study indicate the importance of prosthodontic rehabilitation in improving patients' ingestible food profiles.

Impact of number of functional teeth on independence of Japanese older adults.

AIM: To examine the relationship between the number of present and functional teeth at baseline and future incidence of loss of independence. METHODS: Participants were community-dwelling older individuals who participated in a comprehensive geriatric health examination conducted in Kusatsu town, Japan, between 2009 and 2015. The primary endpoint was the incidence of loss of independence among participants, defined as the first certification of long-term care insurance in Japan. The numbers of present and functional teeth at baseline were determined via an oral examination. Demographics, clinical variables (e.g., history of chronic diseases and psychosocial factors), blood nutritional markers, physical functions, and perceived masticatory function were assessed. RESULTS: This study included 1121 individuals, and 205 individuals suffered from loss of independence during the follow-up period. Kaplan-Meier estimates of loss of independence for participants with smaller numbers of present and functional teeth were significantly greater than for those with larger numbers of teeth. Cox proportional hazard analyses indicated that a smaller number of present teeth was not a significant risk factor after adjusting for demographic characteristics. However, the number of functional teeth was a significant risk factor after the adjustment (hazard ratio: 1.975 [1.168-3.340]). Additionally, higher hazard ratios were observed in other adjusted models, but they were not statistically significant. CONCLUSIONS: The number of functional teeth may be more closely related to the future incidence of loss of independence than the number of present teeth. This novel finding suggests that prosthodontic rehabilitation for tooth loss possibly prevents the future incidence of this life-event. Geriatr Gerontol Int 2022; 22: 1032-1039.

Effectiveness of the socket shield technique in dental implant: A systematic review.

PURPOSE: Dental implant therapy is a common clinical treatment for missing teeth. However, the esthetic result is not as satisfactory as expected in some cases, especially in the anterior maxillary area. Poor esthetic results are caused by inadequate preparation of the hard and soft tissues in this area before treatment. The socket shield technique may be an alternative for a desirable esthetic outcome in dental implant treatments. STUDY SELECTION: In the present systematic review, PubMed-Medline, Google Scholar, and ScienceDirect were searched for clinical studies published from January 2000 to December 2018. RESULTS: Twenty studies were included, comprising one randomized controlled trial, two cohort studies, 14 clinical human case reports, and three retrospective case series. In total, 288 patients treated with the socket shield technique with immediate implant placement and follow-up between 3-60 months after placement were included. A quality assessment showed that 12 of the 20 included studies were of good quality. Twenty-six of the 274 (9.5%) cases developed complications or adverse effects related to the socket shield technique. Most studies reported implant survival without the complications (90.5%); most of the cases that were followed up for more than 12 months after implant placement achieved a good esthetic appearance. The failure rate was low without the complications, although there were some failures due to failed implant osseointegration, socket shield mobility and infection, socket shield exposure, socket shield migration, and apical root resorption. CONCLUSIONS: The socket shield technique can be used in dental implant treatment, but it remains difficult to predict the long-term success of this technique until high-quality evidence becomes available.

Association of Periodontal Status, Number of Teeth, and Obesity: A Cross-Sectional Study in Japan.

Recent reports have shown an association between obesity and periodontitis, but the precise relationship between these conditions has yet to be clarified. The purpose of this study was to compare the status of periodontitis, tooth loss, and obesity. Participants comprised 235 patients at the Center for Medical and Dental Collaboration in Kanagawa Dental University Hospital between 2018 and 2020. Clinical examinations such as blood testing, body composition analysis, periodontal measurement, assessment of chewing ability, salivary testing, and oral malodor analysis were performed. Periodontal inflamed surface area (PISA) was significantly associated with the number of teeth and body mass index (BMI). The number of teeth was negatively associated with age, but positively with chewing ability. Chewing ability was associated negatively with age, and positively with high-sensitivity C-reactive protein (hsCRP). The level of methyl-mercaptan in breath and protein and leukocyte scores from salivary testing were positively associated with PISA. The rate of insufficient chewing ability was increased in subjects with hemoglobin (Hb)A1c ≥ 7%. The high PISA group showed increased hsCRP. BMI as an obesity marker was positively associated with PISA, indicating periodontal inflammation. Chewing ability was related to serum markers such as HbA1c and hsCRP.

A comparison of colorimetric and visual methods for the assessment of masticatory performance with color-changeable chewing gum in older persons.

BACKGROUND/PURPOSE: Color-changeable chewing gum is used for the evaluation of masticatory performance. However, it is currently unclear whether colorimetric and visual assessment methods yield consistent results. This study aimed to clarify the consistency between colorimetric and visual methods used for the evaluation of color changes in color-changeable chewing gum. MATERIALS AND METHODS: The sample comprised 644 older persons (mean age, 75.4 ± 6.4 years). The chewing gum was masticated 60 times at the participant's own chewing rate and then expectorated. The color of the chewing gum was evaluated with the ΔE values and a∗ values, measured using a colorimeter, and the 10 Color Shades (10CSh) and 5 Color Scales (5CSc), using visual evaluation. Spearman's correlation analysis was performed to examine the correlation between the results obtained by the four methods. The significance level was set at α = 0.05. RESULTS: The ΔE values, a∗ values, 10CSh scores, and 5CSc scores were all significantly correlated. The highest correlation coefficient (0.979) was between the ΔE values and a∗ values. The lowest correlation coefficient (0.847) was between the a∗ values and 5CSc scores. Decreased masticatory performance was observed with increased age. CONCLUSION: Significant correlations were found for all four methods used in the assessment of masticatory performance with color-changeable chewing gum. While visually based assessments are valid, colorimetric methods are more sensitive to smaller changes in masticatory performance.

Number of functional teeth more strongly predicts all-cause mortality than number of present teeth in Japanese older adults.

AIM: Previous studies on the association between intraoral conditions and mortality in community-dwelling older individuals reported that fewer present teeth (PT) are significant risk factors for mortality. However, how the number of PT relative to the number of functional teeth (FT), including both present and rehabilitated teeth, influences mortality has not been investigated fully. This study examined the impact of the number of FT on mortality among community-dwelling Japanese older adults. METHODS: This study was a retrospective, observational and population-based follow-up study, which examined 1188 older individuals who participated in an annual geriatric health examination from 2009 to 2015. The average follow-up period was 1697.0 ± 774.5 days. The primary outcome was all-cause mortality at follow-up. The numbers of PT and FT of each participant were counted during an oral examination. In addition, demographics, clinical variables, blood nutrient markers, physical functions and perceived masticatory function were measured. RESULTS: Kaplan-Meier analysis, followed by a log-rank test, revealed that fewer PT (P < 0.001) and FT (P = 0.002) were significantly associated with a reduced survival rate. Cox's proportional hazard analysis indicated that the number of FT, but not the number of PT, was a significant independent mortality risk factor after adjusting for demographics, clinical variables, nutrient markers and physical functioning (P = 0.036, hazard ratio: 2.089). CONCLUSIONS: Current results suggest that the number of FT more strongly predicts all-cause mortality than the number of PT among community-dwelling older adults. Further studies are necessary to consider the confounding of socioeconomic status and disability status. Geriatr Gerontol Int 2020; ••: ••-••.

Microcirculation changes in gingival tissue after ultrasonic tooth preparation in beagle dogs.

OBJECTIVE: Ultrasonic wave technology is widely used during dental treatments. We previously demonstrated that this method protects the gingival tissue. However, the physiological change on the gingival microvasculature caused by this method remains unclear. The aim of this study was to investigate the relationship between the morphological and physiological effects on gingival microcirculation when preparing teeth, using the conventional dental turbine or ultrasonic method. METHODOLOGY: The lower premolar teeth of beagle dogs were prepared along the gingival margin by using a dental turbine or ultrasonic wave instrument. Gingival vasculature changes were investigated using scanning electron microscopy for corrosion resin casts. Gingival blood flow at the preparation site was determined simultaneously by laser Doppler flowmetry. These assessments were performed immediately (Day 0), at 7 days and 30 days after tooth preparation. RESULTS: At day 0, in the turbine group, blood vessels were destroyed and some resin leaked. Furthermore, gingival blood flow at the site was significantly increased. In contrast, the ultrasonic group demonstrated nearly normal vasculature and gingival blood flow similar to the non-prepared group for 30 days after preparation. No significant alterations occurred in gingival circulation 30 days after either preparation; however, the turbine group revealed obvious morphological changes. CONCLUSIONS: Based on multiple approach analyses, this study demonstrated that ultrasonic waves are useful for microvascular protection in tooth preparation. Compared with a dental turbine, ultrasonic wave instruments caused minimal damage to gingival microcirculation. Tooth preparation using ultrasonic wave instruments could be valuable for protecting periodontal tissue.

Microcirculation changes in gingival tissue after ultrasonic tooth preparation in beagle dogs

Abstract Ultrasonic wave technology is widely used during dental treatments. We previously demonstrated that this method protects the gingival tissue. However, the physiological change on the gingival microvasculature caused by this method remains unclear. Objective The aim of this study was to investigate the relationship between the morphological and physiological effects on gingival microcirculation when preparing teeth, using the conventional dental turbine or ultrasonic method. Methodology The lower premolar teeth of beagle dogs were prepared along the gingival margin by using a dental turbine or ultrasonic wave instrument. Gingival vasculature changes were investigated using scanning electron microscopy for corrosion resin casts. Gingival blood flow at the preparation site was determined simultaneously by laser Doppler flowmetry. These assessments were performed immediately (Day 0), at 7 days and 30 days after tooth preparation. Results At day 0, in the turbine group, blood vessels were destroyed and some resin leaked. Furthermore, gingival blood flow at the site was significantly increased. In contrast, the ultrasonic group demonstrated nearly normal vasculature and gingival blood flow similar to the non-prepared group for 30 days after preparation. No significant alterations occurred in gingival circulation 30 days after either preparation; however, the turbine group revealed obvious morphological changes. Conclusions Based on multiple approach analyses, this study demonstrated that ultrasonic waves are useful for microvascular protection in tooth preparation. Compared with a dental turbine, ultrasonic wave instruments caused minimal damage to gingival microcirculation. Tooth preparation using ultrasonic wave instruments could be valuable for protecting periodontal tissue.

A multi-centered epidemiological study evaluating the validity of the treatment difficulty indices developed by the Japan Prosthodontic Society.

PURPOSE: The Japan Prosthodontic Society developed a multi-axis assessment protocol to evaluate the complex variations in patients who need prosthodontic care, and to classify the level of treatment difficulty. A previous report found the protocol to be sufficiently reliable. The purpose of this multi-center cohort study was to evaluate the validity of this multi-axis assessment protocol. METHODS: The treatment difficulty was evaluated using the multi-axis assessment protocol before starting prosthodontic treatment. The time required for active prosthodontic treatment, medical resources such as treatment cost, and changes in the oral health-related QOL before and after treatment, were evaluated after treatment completion. The construct validity of this protocol was assessed by the correlation between the dentist's pre-operative subjective assessment of the treatment difficulty, and the level of difficulty determined by this protocol. The predictive validity was assessed estimating the correlations between a "comprehensive level of treatment difficulty" based on the four axes of this protocol and total treatment cost, total treatment time, and changes in the oral health-related QOL before and after treatment. RESULTS: The construct validity of this protocol was well documented except for psychological assessment. Regarding the predictive validity, the comprehensive level of treatment difficulty assessed before treatment was significantly correlated with the three surrogate endpoints known to be related to the treatment difficulty (total treatment cost, treatment time, and improvement in the oral health-related QOL). To further clarify the validity of the protocol according to patients' oral condition, a subgroup analysis by defects was performed. Analyses revealed that treatment difficulty assessment before treatment was significantly related to one or two surrogate endpoints in the fully edentulous patients and the partially edentulous patients. No significant relationship was observed in the patients with mixture of full/partial edentulism and the patients with teeth problems, possibly due to the small sample size in these groups. CONCLUSION: This study revealed that the multi-axis assessment protocol was sufficiently valid to predict the level of treatment difficulty in prosthodontic care in patients with fully edentulous defects and with partially edentulous defects.

Occlusal Dysesthesia: A Clinical Report on the Psychosomatic Management of a Japanese Patient Cohort.

PURPOSE: A cohort of Japanese patients diagnosed with occlusal dysesthesia (OD) was clinically analyzed for psychosomatic background, management, and treatment outcome. MATERIALS AND METHODS: The study group comprised 61 patients (17 men and 44 women) who met the OD criteria. Treatment outcomes were categorized as improvement, interruption, and transfer to another department. RESULTS: The diagnosed OD was resolved in 25 patients (41%), 20 patients (33%) discontinued treatment, 13 (21%) were referred or transferred to other specialties such as psychiatry, and 3 (5%) continued to receive treatment following an engagement period of 3 months, 2 years, and 5 years, respectively. Among the 20 patients who discontinued treatment, complaints persisted for 10 and they did not comply with treatment, 1 had immodithymia characterized by adherence to symptoms, 3 had depressive states, 2 were suspected to have schizophrenia, and 2 were suspected to have so-called phantom bite syndrome. CONCLUSION: This study suggests that OD treatment should take into account the underlying psychiatric disorder manifesting as physical complaints.

Reliability and validity of the patient disability-oriented diagnostic nomenclature system for prosthetic dentistry.

PURPOSE: The Japan Prosthodontic Society (JPS) has proposed a new diagnostic nomenclature system (DNS), based on pathogenesis and etiology, to facilitate and improve prosthodontic treatment. This system specifies patient disability and the causative factor (i.e. "B (disability) caused by A (causative factor)"). The purpose of this study was to examine the reliability and validity of this DNS. STUDY SELECTION: The JPS Clinical Guideline Committee assessed mock patient charts and formulated disease names using the new DNS. Fifty validators, comprising prosthodontic specialists and dental residents, made diagnoses using the same patient charts. Reliability was evaluated as the consistency of the disease names among the validators, and validity was evaluated using the concordance rate of the disease names with the reference disease names. RESULTS: Krippendorff's α was 0.378 among all validators, 0.370 among prosthodontic specialists, and 0.401 among dental hospital residents. Krippendorff's α for 10 validators (3 specialists and 7 residents) with higher concordance rates was 0.524. Two validators (1 specialist and 1 resident) with the highest concordance rates had a Krippendorff's α of 0.648. Common disease names had higher concordance rates, while uncommon disease names showed lower concordance rates. These rates did not show correlation with clinical experience of the validator or time taken to devise the disease name. CONCLUSIONS: High reliability was not found among all validators; however, validators with higher concordance rates showed better reliability. Furthermore, common disease names had higher concordance rates. These findings indicate that the new DNS for prosthodontic dentistry exhibits clinically acceptable reliability and validity.

A retrospective study to compare improvement of implant maintenance by Medical Treatment Model.

BACKGROUND: Study comparing the improvement of implant maintenance is limited. Clinicians must be aware of implant maintenance to improve long-term success of implant. AIMS: The aim of this retrospective study was to evaluate whether the Medical Treatment Model (MTM), which is a comprehensive treatment, includes initial risk assessment, lifestyle instructions, such as diet and habits, and a customized maintenance program to improve implant prognosis. MATERIALS AND METHODS: Patients who were comprehensively treated were included and divided into two groups, test and control groups. The test group included patients who started treatment with MTM, whereas control group included patients who started treatment without MTM introduction. Moreover, subsequently, compliance with maintenance, occurrence of biological complications, and implant failure were evaluated. RESULTS: About 199 patients with 515 implants were analyzed in the control group and 38 patients with 59 implants in the test group. In the control and test groups, the percentages of patients in the four compliance categories were, respectively, 73.9% and 89.5% for excellent compliance, 7.0% and 7.9% for good compliance, 14.6% and 0% for fair compliance, and 4.5% and 2.6% for poor compliance. There was a statistically significant difference in the compliance with periodontal and implant maintenance between the test and control groups (P = 0.029). CONCLUSIONS: Within the limitation of this study, MTM significantly enhanced the compliance of patients treated with implants.

[Relationship between Occlusal Discomfort Syndrome and Occlusal Threshold].

Occlusal dysesthesia has been defined as persistent uncomfortable feelings of intercuspal position continuing for more than 6 months without evidence of physical occlusal discrepancy. The problem often occurs after occlusal intervention by dental care. Although various dental treatments (e. g. occlusal adjustment, orthodontic treatment and prosthetic reconstruction) are attempted to solve occlusal dysesthesia, they rarely reach a satisfactory result, neither for patients nor dentists. In Japan, these symptoms are defined by the term "Occlusal discomfort syndrome" (ODS). The aim of this study was to investigate the characteristics of ODS with the simple occlusal sensory perceptive and discriminative test. Twenty-one female dental patients with ODS (mean age 55.8 ± 19.2 years) and 21 age- and gender-matched dental patients without ODS (mean age 53.1 ± 16.8 years) participated in the study. Upon grinding occlusal registration foils that were stacked to different thicknesses, participants reported the thicknesses at which they recognized the foils (recognition threshold) and felt discomfort (discomfort threshold). Although there was no significant difference in occlusal recognition thresholds between the two patient groups, the discomfort threshold was significantly smaller in the patients with ODS than in those without ODS. Moreover, the recognition threshold showed an age-dependent increase in patients without ODS, whereas it remained comparable between the younger (< 60 years old) and elderly (60 years old or more) patient subgroups with ODS. These results suggest that occlusal discomfort threshold rather than recognition threshold is an issue in ODS. The foil grinding procedure is a simple and useful method to evaluate occlusal perceptive and discriminative abilities in patients with ODS.

Japan Prosthodontic Society position paper on "occlusal discomfort syndrome".

PURPOSE: Dentists may encounter patients who present with a sense of a malocclusion but in whom no objective findings can be detected. For the patient who insists that there is occlusal discomfort, in the absence of evidence some dentists elect to perform an occlusal adjustment that not only fails to alleviate symptoms, and may, in fact, exacerbate the discomfort. The patient-dentist relationship is then likely compromised because of a lack of trust. STUDY SELECTION: In 2011, the Clinical Practice Guidelines Committee of the Japan Prosthodontic Society formulated guidelines for the management of occlusal discomfort. When formulating clinical practice guidelines, the committee bases their recommendations on information derived from scientific evidence. For "occlusal dysesthesia," however, there are an insufficient number of high-quality papers related to the subject. Therefore, a consensus meeting was convened by the Japan Prosthodontic Society to examine evidence in the Japanese- and English-language literature and generate a multi-center survey to create an appropriate appellation for this condition. RESULTS: As a result of the consensus meeting and survey findings, this condition may be justifiably termed "occlusal discomfort syndrome." CONCLUSIONS: The Japan Prosthodontics Society believes that identification of an umbrella term for occlusal discomfort might serve as a useful guide to formulating clinical practice guidelines in the future. This position paper represents summary findings in the literature combined with the results of a multicenter survey focused on dental occlusal treatment and the condition of patients who present with occlusal discomfort syndrome.

Diagnosis of occlusal dysesthesia utilizing prefrontal hemodynamic activity with slight occlusal interference.

Clinical diagnosis of occlusal dysesthesia (OD), also referred to as phantom bite syndrome, is currently based on the absence of objective occlusal discrepancy despite the persistent complaint of uncomfortable bite sensation. We previously demonstrated that the subjective feeling of occlusal discomfort generated by artificial occlusal interference can be objectively evaluated using prefrontal hemodynamic activity in young healthy individuals. The aim of this study was to investigate whether dental patients with and without OD show distinct prefrontal activity during grinding behavior with an occlusal interference. Six dental patients with OD (OD group) and eight patients without OD (control group) grinded piled occlusal strips placed between their first molars and reported their perception and discomfort thresholds during continuous monitoring of prefrontal hemodynamic activity with a portable functional near-infrared spectroscopy. Although patients without OD showed the typical hemodynamic pattern of increased oxyhemoglobin and reduced deoxyhemoglobin (HHb) concentration, those with OD showed persistent incremental increases of HHb concentration that began at the loading of occlusal strips on their molars before they executed grinding. The intensities of the task-related HHb activities showed statistically significant differences between OD and control groups, particularly at channel 3, arranged over the left frontal pole cortex. When the discrimination criterion was set using the intensity values of channel 3 from both groups, the overall accuracy of the OD discrimination was 92.9%. Although physiological interpretation has yet to be elucidated, the task-related response of an increase in HHb may be a useful neuronal signature to characterize dental patients with OD.

Prefrontal Hemodynamic Changes Associated with Subjective Sense of Occlusal Discomfort.

We used functional near-infrared spectroscopy to measure prefrontal brain activity accompanying the physical sensation of oral discomfort that arose when healthy young-adult volunteers performed a grinding motion with mild occlusal elevation (96 µm). We simultaneously evaluated various forms of occlusal discomfort using the visual analogue scale (VAS) and hemodynamic responses to identify the specific prefrontal activity that occurs with increased occlusal discomfort. The Oxy-Hb responses of selected channels in the bilateral frontopolar and dorsolateral prefrontal cortices increased in participants who reported increased severity of occlusal discomfort, while they decreased in those who reported no change or decreased occlusal discomfort during grinding. Moreover, the cumulative values of Oxy-Hb response in some of these channels were statistically significant predictive factors for the VAS scores. A generalized linear model analysis of Oxy-Hb signals in a group of participants who reported increased discomfort further indicated significant cerebral activation in the right frontopolar and dorsolateral prefrontal cortices that overlapped with the results of correlation analyses. Our results suggest that the increased hemodynamic responses in the prefrontal area reflect the top-down control of attention and/or self-regulation against the uncomfortable somatosensory input, which could be a possible marker to detect the subjective sense of occlusal discomfort.

Clinical application of removable partial dentures using thermoplastic resin. Part II: Material properties and clinical features of non-metal clasp dentures.

This position paper reviews physical and mechanical properties of thermoplastic resin used for non-metal clasp dentures, and describes feature of each thermoplastic resin in clinical application of non-metal clasp dentures and complications based on clinical experience of expert panels. Since products of thermoplastic resin have great variability in physical and mechanical properties, clinicians should utilize them with careful consideration of the specific properties of each product. In general, thermoplastic resin has lower color-stability and higher risk for fracture than polymethyl methacrylate. Additionally, the surface of thermoplastic resin becomes roughened more easily than polymethyl methacrylate. Studies related to material properties of thermoplastic resin, treatment efficacy and follow-up are insufficient to provide definitive conclusions at this time. Therefore, this position paper should be revised based on future studies and a clinical guideline should be provided.

Clinical application of removable partial dentures using thermoplastic resin-part I: definition and indication of non-metal clasp dentures.

This position paper proposes a definition and naming standard for removable partial dentures (RPDs) using thermoplastic resin, and presents a guideline for clinical application. A panel of 14 experts having broad experience with clinical application of RPDs using thermoplastic resin was selected from members of the Japan Prosthodontic Society. At a meeting of the panel, "non-metal clasp denture" was referred as the generic name of RPDs with retentive elements (resin clasps) made of thermoplastic resin. The panel classified non-metal clasp dentures into two types: one with a flexible structure that lacks a metal framework and the other having a rigid structure that includes a metal framework. According to current prosthetic principles, flexible non-metal clasp dentures are not recommended as definitive dentures, except for limited cases such as patients with a metal allergy. Rigid non-metal clasp dentures are recommended in cases where patients will not accept metal clasps for esthetic reasons. Non-metal clasp dentures should follow the same design principles as conventional RPDs using metal clasps.