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Stabilisation splint therapy has long been thought to be effective for the management of temporomandibular disorders (TMD). However, the superiority of stabilisation splint therapy compared to other TMD treatments remains controversial. The aim of this study was to determine the efficacy of stabilisation splint therapy combined with non-splint multimodal therapy for TMD. A total of 181 TMD participants were randomly allocated to a non-splint multimodal therapy (NS) group (n = 85) or a nonsplint multimodal therapy plus stabilisation splint (NS+S) group (n = 96). Non-splint multimodal therapy included self-exercise of the jaw, cognitive--behavioural therapy, self-management education and additional jaw manipulation. Three outcome measurements were used to assess treatment efficacy: mouth-opening limitation, oro-facial pain and temporomandibular joint sounds. A two-factor repeated-measures analysis of variance (ANOVA) was used to evaluate the efficacy of the two treatment modalities (NS vs. NS+S), and Scheffe's multiple comparison test was used to compare the treatment periods. Subgroup analyses were performed to disclose the splint effects for each TMD diagnostic group. All three parameters significantly decreased over time in both groups. However, there were no significant differences between the two treatment groups in the total comparison or subgroup analyses; an exception was the group with degenerative joint disease. No significant difference between the NS and NS+S treatment approaches was revealed in this study. Therefore, we conclude that the additional effects of stabilisation splint are not supported for patients with TMD during the application of multimodal therapy. [ABSTRACT FROM AUTHOR]

A posterior cross-bite is defined as an abnormal bucco-lingual relationship between opposing molars, pre-molars or both in centric occlusion. Although it has been reported that patients with unilateral posterior cross-bite often show unique chewing patterns, the relationship between the form of cross-bite and masticatory jaw movement remains unclear in adult patients. The objective of this study was to investigate masticatory jaw movement among different forms of cross-bite. One hundred and one adults were recruited in this study: 27 had unilateral first molar cross-bite ( MC group); 28, unilateral pre-molar cross-bite ( PC group); 23, anterior cross-bite ( AC group); and 23, normal occlusion (control group). Masticatory jaw movement of the lower incisor point was recorded with six degrees of freedom jaw-tracking system during unilateral mastication. Our results showed that the reverse chewing ratio during deliberate unilateral mastication was significantly larger in the MC group than in the PA ( P < 0·001), AC ( P < 0·001) and control ( P < 0·001) groups. These findings suggest that compared to the anterior or pre-molar cross-bite, the first molar cross-bite is more closely associated with a higher prevalence of a reverse chewing cycle. [ABSTRACT FROM AUTHOR]

This study explored the influence of the thickness of silicone registration material on evaluation of the occlusal contact area and number of occlusal contact points, during increasing tooth clenching conditions in normal subjects. Twenty-four subjects with no more than one missing tooth per quadrant participated. Surface electro-myography was recorded from the masseter muscle. As a baseline measurement, intercuspal position was maintained with minimal force, and occlusal contact was recorded using blue silicone material. Occlusal contact was also recorded at 20% maximum voluntary contraction ( MVC) and 40% MVC using visual feedback. The occlusal contact area and number of occlusal contact points were analysed using five levels of thickness of silicone registration material: Level 1 (0-149 μm); Level 2 (0-89 μm); Level 3 (0-49 μm); Level 4 (0-29 μm); and Level 5 (0-4 μm). The anterior part and the left and right posterior regions of the dental arch were analysed separately. At all detection levels, the occlusal contact area significantly increased from baseline to 20% MVC and to 40% MVC in the molar area ( P < 0·05). In the anterior part, the occlusal contact area significantly increased from baseline to 20% MVC and to 40% MVC only when using Level 5. The number of occlusal contact points significantly increased from baseline to 20% MVC and to 40% MVC only when using Level 5 in the molar area ( P < 0·05). It suggested that occlusal contacts may be different at low tooth clenching intensity with potential effects on the teeth or periodontal tissues. [ABSTRACT FROM AUTHOR]

Serum albumin levels are a practical marker of general health status in the elderly and have been used to determine the severity of underlying diseases and the risk for death. This longitudinal study evaluated the relationship between serum albumin concentrations and tooth loss over 10 years in elderly subjects, after controlling for confounding factors. A sample of 554 dentate subjects among enrolled subjects ( n = 600) was involved in this planned longitudinal study with follow-up examinations after 5 and 10 years. At the 5-year follow-up, 373 (67·3%), subjects were available for re-examination. In addition, 331 (59·7%) were available at the 10-year follow-up. Multiple Poisson regression analysis was conducted to evaluate the relationship between the number of missing teeth over 5 or 10 years and serum albumin levels at baseline after adjusting for 10 variables: gender, serum markers levels at baseline, dental status, smoking habits and educational years and oral health behaviour. The number of missing teeth over 5 or 10 years was significantly negatively associated with serum albumin levels at baseline [incidence rate ratios ( IRR) = 0·373, P < 0·0001 for 5 years; IRR = 0·570, P < 0·0001 for 10 years]. We conclude that elderly subjects with hypoalbuminemia are at high risk for 5- and 10-year tooth loss. [ABSTRACT FROM AUTHOR]

Efficient mastication of different types and size of food depends on fast integration of sensory information from mechanoreceptors and central control mechanisms of jaw movements and applied bite force. The neural basis underlying mastication has been studied for decades but little progress in understanding the dynamics of bite force has been made mainly due to technical limitations of bite force recorders. The aims of this study were to develop a new intraoral bite force recorder which would allow the study of natural mastication without an increase in the occlusal vertical dimension and subsequently to analyze the relation between electromyographic (EMG) activity of jaw-closing muscles, jaw movements and bite force during mastication of five different types of food. Customized force recorders based on strain gauge sensors were fitted to the upper and lower molar teeth on the preferred chewing side in fourteen healthy and dentate subjects (21-39 years), and recordings were carried out during voluntary mastication of five different kinds of food. Intraoral force recordings were successively obtained from all subjects. anova showed that impulse of bite force as well as integrated EMG was significantly influenced by food ( P < 0·05), while time-related parameters were significantly affected by chewing cycles ( P < 0·001). This study demonstrates that intraoral force recordings are feasible and can provide new information on the dynamics of human mastication with direct implications for oral rehabilitation. We also propose that the control of bite force during mastication is achieved by anticipatory adjustment and encoding of bolus characteristics. [ABSTRACT FROM AUTHOR]

Summary The aim of this study was to investigate the influence of chewing force on salivary stress markers (alpha-amylase activity, salivary cortisol level and secretory immunoglobulin A secretion rate) as indicators of mental stress. Participants comprised 20 healthy men. The first set of saliva specimens (S1) was collected at immediately after a 20-min rest to evaluate stress markers. As stress loading, the participants were required to perform arithmetic calculations for 20 min, after which the second set of saliva specimens (S2) was collected. Each participant was then required to chew a piece of tasteless gum for 10 min, after which the third set of saliva specimens (S3) was collected. After a 20-min rest, the fourth set of saliva specimens (S4) was collected. Weak, habitual and strong chewing forces were assigned. Change rates of stress markers between S2 and S3, and S2 and S4 were calculated. A significant difference was observed in the change rate of cortisol levels between S2 and S3. Cortisol level decreased more under strong chewing than under weak chewing. No significant differences were observed in the change rate of amylase activity or s-IgA secretion rate among the three chewing forces. The results suggest that differences in chewing force influence the salivary cortisol level of the three stress markers, and that a strong chewing force induces a greater reduction in mental stress than a weak one. [ABSTRACT FROM AUTHOR]

Summary A large tongue is recognised as a factor that increases the collapsibility of the upper airway in obstructive sleep apnoea (OSA) patients. We hypothesised that the propensity to develop severe OSA could be minimised if the dental arches were enlarged in obese OSA people who are thought to have a large tongue. We therefore compared the size of the dental arches in obese and non-obese OSA patients. Using a lateral cephalogram and study models, we compared the sizes of the tongue and dental arches in 23 obese and 23 non-obese Japanese male OSA patients, who were matched for age, apnoea hypopnea index (AHI) and maxillomandibular size. The median age (years) and AHI (events per hour) for the obese and non-obese groups were 36·5 and 39·0, and 13·4 and 14·3, respectively. The maxillomandibular size was matched with regard to SNA, SNB and lower face cage obtained from cephalometric measurements. The parameters that were measured for the study model included dental arch width, dental arch length, overjet and overbite. Tongue size ( P < 0·05) and both upper ( P < 0·01) and lower ( P < 0·05) dental arch widths were significantly larger in obese than in non-obese OSA patients, and there was no difference in the severity of OSA between the two groups. These findings suggest that the tongue was larger and dental arches were enlarged in obese patients compared with non-obese patients under the same disease severity. Wider dental arches in obese OSA patients may help to offset the impact of the enlarged tongue on upper airway patency. [ABSTRACT FROM AUTHOR]

Summary The purpose of this study was to compare the tongue pressure against the hard palate during the articulation of a monosyllable with that during swallowing. The participants were 20 healthy adults without swallowing or articulation disorder (10 men and 10 women, mean age ± standard deviation: 22·5 ± 0·9 years). Tongue pressure during articulation of [ki] (articulatory pressure) and during dry swallowing (swallowing pressure) was recorded by a 0·1-mm-thick sensor sheet with five measuring points attached to the hard palate. Biomechanical parameters such as maximal magnitude, duration, integrated value and slope gradient were compared between articulatory pressure and swallowing pressure at each measuring point. Although swallowing pressure was produced at each measuring point, articulatory pressure was found only in the posterior circumferential parts of the hard palate and was smaller in magnitude (14·9-16·7% of swallowing pressure) and integrated value, which meant the amount of work by tongue pressing (7·0-7·9%), shorter in duration (26·6-31·8%) and shallower in slope gradient, which meant the speed of tongue pressing (26·9-27·4%). Maximal magnitude was closely correlated with duration ( R2 = 0·386) and slope gradient ( R2 = 0·843) for articulatory pressure. These results first show the biomechanical differences between articulation and swallowing in terms of tongue contact with the hard palate. The findings suggest that tongue pressure measurement might be a useful investigation for patients with tongue motor disorder. [ABSTRACT FROM AUTHOR]

Summary The purposes of this study were to determine whether a response shift was observable after partial denture treatment and to identify the predictors that influenced the response shift magnitude and direction. A total of 173 consecutive patients with no more than eight missing teeth who received implant-supported, fixed or removable partial dentures at Okayama University Dental Hospital were asked to complete a full-version Oral Health-Related Quality of Life (OHRQoL) questionnaire before (pre-test) and after treatment (post-test). Additionally, a short form (then-test) consisting of seven questions selected from the full version had its reliability verified and was utilised to retrospectively assess the pre-treatment OHRQoL status. The difference between the summary scores of the then-test and the pre-test determined the response shift magnitude and direction. The then-test mean score (22·9 ± 6·6) was significantly lower (worse OHRQoL) than that of the pre-test (26·4 ± 5·2). The response shift effect size was of moderate magnitude and negative direction ( d = −0·78). A multiple regression analysis showed that age (younger patients) ( P < 0·01), number of replaced teeth (fewer) ( P < 0·01) and pre-test scores (lower) ( P < 0·01) were the significant predictors for response shift. In conclusion, a response shift phenomenon with negative and moderate effect size was observed after partial denture treatment. The significant predictor variables were young age, fewer numbers of replaced teeth and lower pre-test scores [ABSTRACT FROM AUTHOR]

Summary The aim of this study was to investigate the impact of missing occlusal units (MOUs) on objective masticatory function with respect to food comminuting and mixing ability. Sixty partially dentate patients (mean age, 64·1 years) with shortened dental arches participated in the study. Food comminuting ability was assessed using a masticatory performance test with peanuts as a test food. Food mixing ability was assessed using a mixing ability test with a two-coloured wax cube. Maximum bite force (MBF) was measured using a pressure-sensitive film as a mediator for food comminuting and mixing ability. A structural equation model was constructed based on a hypothesis that MOUs would be associated with reduced MBF and impairment of food comminuting and mixing ability. Structural equation modelling analysis found significant direct effects of MOU on median particle size and mixing ability index (MAI) ( P < 0·001). In addition, MOU had significant indirect effects on median particle size and MAI with MBF as a mediator ( P < 0·05). These results suggest that decrease in occlusal platform area and reduced MBF because of MOUs are associated with the impairment of food comminution and mixing in patients with shortened dental arches. [ABSTRACT FROM AUTHOR]

Summary Tongue pressure measured with a disposable hand-held balloon probe has been used for assessing tongue function; however, no diagnostic standard for assessing other oral functions exists currently. In this study, to develop a method for multifactorial manometric evaluation of oral functions, 20 men and 20 women (21-32 years of age) were instructed to apply 7-s maximal voluntary muscular effort on a hand-held balloon probe placed against the anterior and lateral parts of the palate, buccal surface of the molars on the habitual chewing side and labial surface of the anterior teeth for measuring anterior and posterior tongue, cheek and lip pressures (LPs), respectively. Intra-session reproducibility was determined by three repeated measurements, and associations between the obtained and the conventional data on oral diadochokinesis were tested. The men exhibited higher values of all the pressure types. Further, both genders showed a positive correlation between anterior and posterior tongue pressures (PTPs) ( P < 0·05), but only the women exhibited positive correlations between anterior tongue and cheek pressures, cheek and PTPs, anterior tongue and LPs, and cheek and LPs ( P < 0·05). No statistically significant correlation was found between the pressures and the number of syllabic articulations, except between LP and the number of /pa/ articulations in the women ( r = 0·524, P < 0·05). In conclusion, the balloon probe method enables objective manometric evaluation of oral functions and could be an effective tool for clinical epidemiological studies and evidence-based decision-making in nursing care. [ABSTRACT FROM AUTHOR]

Summary The aim of the present study was to elucidate whether self-assessed masticatory ability (masticatory ability) is significantly related to muscle strength of the body evaluated as handgrip strength and skeletal muscle mass of the whole body (kg) (SMM) after adjusting for confounding variables, including, age, gender, height, weight, employment status, type of household, educational background, social interaction, chronic medical conditions, smoking habit, drinking habits and dentition status among the elderly. A total of 381 persons aged 67-74 years were enrolled. Masticatory ability was classified into one of three categories: ability to chew all kinds of food, ability to chew only slightly hard food or ability to chew only soft or pureed food. Handgrip strength was measured, and bioimpedance analysis was used to estimate SMM. One-way analysis of variance and Bonferroni methods were used to examine differences in handgrip strength and SMM among the three groups of masticatory ability. An ordinal regression model was conducted with masticatory ability as the dependent variable and handgrip strength as the principal independent variable. Handgrip strength was significantly lower in those individuals who could chew only soft or pureed food than in those individuals who could chew all kinds of food. No significant difference in SMM was found among the three groups of masticatory ability. Masticatory ability was significantly related to handgrip strength after adjusting for SMM, dentition status and background factors. Chewing ability may be related to muscle strength of the body evaluated as handgrip strength, but not evaluated as SMM. [ABSTRACT FROM AUTHOR]

The aims of this study were to examine the incidence of temporomandibular disorders (TMDs) over a 3-year period and to evaluate the risk of self-reported TMDs among university students in Japan. The study population comprised 2374 university students examined at the start of their undergraduate course and 492 students re-examined after 3 years using questionnaires on symptoms of TMD and experiences of jaw injury, stress, orthodontic treatment and parafunctional habits. Cumulative incidence (%) and relative risks were calculated overall. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to determine the degree of risks of these variables for symptoms of TMDs using logistic regression. Results of logistic regression analysis showed that male subjects with experience of jaw injury had a 3·54 (CI = 1·45-8·68, P < 0·01)-fold higher risk of temporomandibular joint (TMJ) pain than that for those who did not. Female subjects who reported experiencing stress and bruxism had 10·56 (CI = 1·28-87·54, P < 0·05)- and 5·00 (CI = 1·21-20·71, P < 0·05)-fold higher risks of TMJ sound, respectively, than the risk for female subjects who had not experienced stress or bruxism. The results indicated that experiences of jaw injury, stress and bruxism were significantly associated with increased risks of development of TMJ disorders in a 3-year cohort. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the relationships between objective masticatory function with respect to masticatory performance and food mixing ability, patients' perception of chewing ability and oral health-related quality of life (OHRQoL). Partially dentate patients with removable partial dentures ( n = 131, mean age 67·1 year) participated in the study. Four tests were performed to evaluate objective and subjective masticatory function and OHRQoL. Masticatory performance and food mixing ability were assessed using peanuts or a two-coloured wax cube as test items. Patients' perception of chewing ability was rated using a food intake questionnaire. OHRQoL was measured using the Japanese version of the oral health impact profile. A structural equation model was constructed based on hypothesis in which objective masticatory function would be related to OHRQoL via perceived chewing ability as a mediator. Structural equation modelling analysis found a statistically significant medium effect of perceived chewing ability on OHRQoL and statistically significant medium or small effects of masticatory performance on perceived chewing ability and OHRQoL ( P < 0·05); however, the effect of food mixing ability on perceived chewing ability or OHRQoL was not statistically significant ( P > 0·05). A fit index indicated that the model fitted well to the data (Goodness-of-fit index = 0·99). These results suggest that perceived chewing ability is a critical factor for OHRQoL and that masticatory performance rather than food mixing ability is important for perceived chewing ability and OHRQoL in patients with removable partial dentures. [ABSTRACT FROM AUTHOR]

The purpose of this study was to reveal the relationship between chewing-side preference and anterior disc displacement (ADD) of the TMJ. Thirty-two healthy subjects with ages ranging from 26 to 34 years were selected from volunteer students at the Okayama University Dental School. Subjects were asked to chew freely with two kinds of test foods, beef jerky (hard food) and chiffon cake (soft food), thus expecting different amounts of mechanical loading on the TMJ. One, 4, and 7 s after starting the mastication, subjects were asked to open their mouth momentarily to have a digital image of their mouth taken. The bolus placement area was measured by processing the digital images, calculated as the number of pixel of bolus area. Area asymmetry index was used for the determination of preferred chewing side (PCS). Oblique sagittal MRI scanning in the closed mouth position was taken to evaluate the articular disc position. In asymptomatic subjects with ADD, a significant predominance of the PCS on the ipsilateral side of ADD was observed during the mastication of hard food. On the contrary, no correlation was found between unilateral ADD and PCS for the soft food. From the results of this study, it is suggested that ADD is the associating factor of PCS for hard food. Therefore, it would be necessary to break down the concept of PCS into at least two categories, one for hard food and one for soft food, considering the mechanical loading on the TMJ. [ABSTRACT FROM AUTHOR]

Fibroptic endoscopic evaluation of swallowing (FEES) is a useful way for dentists to evaluate oropharyngeal dysfunction. However, no study has paid attention to inter- and intra-rater reliability of FEES evaluation about oropharyngeal dysfunction. The purpose of this study is to verify whether dentist who trained and experienced for evaluation of dysphagia could diagnose oropharyngeal function with FEES. Nine dentists independently evaluated FEES images of 10 cases four times each. At first, evaluators performed the first evaluation without consulting the evaluative criteria. Subsequently, evaluators independently re-evaluated at 1-week intervals for three consecutive weeks, consulting the evaluative criteria. And then, inter- and intra-rater reliability was calculated. Cohen's Kappa was used to assess reliability. The results found that overall inter-rater reliability was 0·35 ± 0·04 (first evaluation), 0·45 ± 0·05 (s), 0·44±0·05 (third) and 0·46 ± 0·04 (fourth). Most of inter-rater reliability related to aspiration was moderate to high, but lower for categories that evaluated timing of swallowing and mastication. In contrast, intra-rater reliability was moderate to high for overall categories, at 0·53 ± 0·04 (first vs. second evaluation), 0·55 ± 0·04 (first vs. third), 0·53 ± 0·04 (first vs. fourth), 0·55 ± 0·03 (second vs. third), 0·60 ± 0·03 (second vs. fourth) and 0·78 ± 0·03 (third vs. fourth). FEES is reliable for experienced dentists to diagnose oropharyngeal function. Moreover, repeated evaluation with the aids of evaluative criteria is useful to improve the reliability of FEES. [ABSTRACT FROM AUTHOR]