Identification and adjustment of experimental occlusal interference using functional magnetic resonance imaging.

BACKGROUND: The purpose of this study was to use functional magnetic resonance imaging (fMRI) to quantify changes in brain activity during experimental occlusal interference. METHODS: Fourteen healthy volunteers performed a rhythmical tapping occlusion task with experimental occlusal interference of the right molar tooth at 0 mm (no occlusion), 0.5 mm, and 0.75 mm. The blood-oxygen-level dependent (BOLD) signal was quantified using statistical parametric mapping and compared between rest periods and task periods. RESULTS: In tapping tasks with experimental occlusal interference of 0.75 mm or 0.5 mm, there was clear activation of the contralateral teeth-related primary sensory cortex and Brodmann's area 46. At 0 and 30 minutes after removal of the experimental occlusal interference, the activation clearly appeared in the bilateral teeth-related primary sensory cortices and Brodmann's area 46. At 60 minutes after the removal of the experimental occlusal interference, the activation of Brodmann's area 46 had disappeared, and only the bilateral teeth-related primary sensory cortices were active. CONCLUSIONS: The present results suggest that adjustments for experimental occlusal interference can be objectively evaluated using fMRI. We expect that this method of evaluating adjustments in occlusal interference, combined with fMRI and the tapping task, could be applied clinically in the future.

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.

Effectiveness of denture space recording method in the prosthetic treatment of edentulous patients.

PURPOSE: To present a clinical rationale for the effectiveness of denture space recording methods for the prosthetic treatment of edentulous patients through a review of the literature. STUDY SELECTION: A total of 3167 studies were extracted from a search of four terms, namely denture space, neutral zone technique, flange technique, and piezography using PubMed and J-STAGE databases. A total of 57 documents that matched the inclusion and exclusion criteria were selected. RESULTS: From the extracted articles, the clinical application of denture space recording methods was found to be effective in edentulous patients with severe ridge resorption. The relationship between the labiolingual and buccolingual pressure in patients with neuromuscular problems or with mandibular or lingual defects differs from those without it, so a stable prosthesis can be easily fabricated by locating the neutral zone using denture space recording methods. CONCLUSION: The literature on denture space recording methods suggests that its application on challenging cases of edentulous patients is useful in providing prostheses with improved retention and stability.

The comparison of two different mandibular positions for oral appliance therapy in patients with obstructive sleep apnea.

BACKGROUND: An oral appliance (OA) can alleviate upper airway obstruction by pulling the mandible forward during sleep. While a large mandibular advancement with an OA decreases the number of apnea and hypopnea events, long-term use may cause side effects, such as toothache, stiffness, and pain in the temporomandibular joint. OBJETIVES: This study aimed to evaluate the effectiveness of different mandibular positions for obstructive sleep apnea (OSA) and determine the optimal therapeutic mandibular position. METHODS: Thirty-two patients (17 males and 15 females) with mild to moderate OSA participated in this prospective study. All patients were randomly allocated to receive a 50% mandibular advancement or a 75% mandibular advancement with an OA. The pre- and posttreatment apnea-hypopnea index (AHI), apnea index (AI), and Epworth Sleepiness Scale (ESS) were compared. Treatment effectiveness and treatment success were compared between groups. RESULTS: AHI improved significantly in both groups, and AI improved significantly in the group with 50% mandibular advancement. No significant improvements in the ESS were observed in either group. There was no significant difference in treatment effectiveness between groups. In the proportion of females and males whose treatment was effective in the two groups, females were significantly greater than males. CONCLUSIONS: For patients with mild to moderate OSA, 50% mandibular advancement is recommended as the initial therapeutic mandibular position. It was suggested that gender differences also affect treatment effectiveness.

Evaluation of implant-supported connecting crowns fabricated by optical and conventional impression methods.

Purpose To investigate the accuracy of implant-supported connecting crowns fabricated with digital definitive casts and conventional definitive casts.Methods Using a master model with two implant bodies inserted into the right mandibular molar area, 10 digital definitive casts were fabricated. Additionally, 10 conventional definitive casts were fabricated. The distance and angle between the two abutments of each definitive cast were compared. To compare the amount of lift of the incisal pin, each of the 10 superstructures was fabricated via computer-aided design/computer-aided manufacturing and then returned to the master model.Results No significant difference was observed for either the angle or the distance between the two abutments. The amount of lift of the incisal pin when the superstructure obtained via the optical method was returned to the master model was significantly larger than that when the superstructure obtained via the conventional method was returned to the definitive cast and the master model. No significant difference was observed after occlusal adjustment of the superstructures obtained using the conventional method.Conclusions The precision of definitive casts obtained via the optical method was virtually equal to that of definitive casts obtained via the conventional method. The accuracy of implant-supported connecting crowns fabricated using the optical method was significantly lower than that of implant-supported connecting crowns fabricated using the conventional method. This is attributed to the alignment of the maxillary and mandibular digital definitive casts.

Side effects of boil and bite type oral appliance therapy in sleep apnea patients.

INTRODUCTION: Based on a mail-out questionnaire, this study analyzed compliance and side effects of one commonly used (TheraSnore) boil and bite oral appliance (OA) in patients with obstructive sleep apnea. METHODS: The questionnaire was sent to 84 patients 6 months after the delivery of the OA. RESULTS: Fifty-eight percent (n = 47) of the patients returned the questionnaire. There was no significant difference in baseline data [age, body mass index (BMI), apnea-hypopnea index or the Epworth Sleepiness Scale (ESS)] between the returned and nonreturned questionnaires. Of the responding patients, 74.5% (n = 35) continued to use the appliance. Nonusers had a higher BMI and higher baseline ESS when compared with users. The majority (74.3%) of the users and 50.0% of the nonusers previously used a nasal continuous positive airway pressure machine. Some 82.9% of the users wore their OA more than 3 days a week. Of the nonusers, 77.8% stopped using the OA in the first 3 months, and the most frequent reason given was "uncomfortable." Many users complained about a dry mouth and/or excessive salivation and nonusers significantly complained more about ill-fitting appliances. Over 80% of the users experienced improvement in their snoring, daytime sleepiness, and apnea. More than 60% of the users were satisfied with OA therapy. CONCLUSION: While this study demonstrated similar self-reported compliance as previous reports, there were different side effects from those reported for custom-made appliances. Difficulty in optimal fit is considered to be the main cause of the subsequent stopping of the use of the boil and bite appliance.

Blood flow changes of a superficial temporal artery before and after low-level laser irradiation applied to the temporomandibular joint area.

PURPOSE: The aim of this study was to evaluate the blood flow changes of a superficial temporal artery before and after low-level laser irradiation was applied to the TMJ area of healthy subjects. METHODS: Right TMJ areas of six healthy subjects were irradiated with a CO2 laser. Variation of diameter, blood flow rate, and blood flow volume of the vessel, on both the irradiated side and opposite side, before and after irradiation on the TMJ were evaluated by using a Doppler flowmeter. RESULTS: The diameter and blood flow volume of the vessel after irradiation increased significantly compared to that before irradiation. CONCLUSION: Low-level laser irradiation applied to the right TMJ area caused an expansion of blood vessels and an increase in blood flow volume. The same result on the contralateral side may be caused by the vasodilator reflex via the hypothalamic thermostat.

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.

[Effects of wearing palatal plate on swallowing and its habituation].

PURPOSE: The aim of this study was to evaluate the effects of wearing a palatal plate on swallowing and its habituation. METHODS: Nine healthy dentate subjects participated in this study. They wore palatal plates of 1.5 mm thickness. While they were eating agar jelly, jaw movements and surface EMGs were recorded and the changes of duration of mastication, number of times of mastication, duration from the end of mastication to the beginning of pharyngeal stage, and duration of pharyngeal stage immediately after insertion of the palatal plate from the control were evaluated. We also investigated habituation from the daily changes of duration from the end of mastication to the beginning of the pharyngeal stage. RESULTS: Although no difference was found in duration of mastication, number of times of mastication or duration of pharyngeal stage, a significant prolongation in duration from the end of mastication to the beginning of the pharyngeal stage was found. This prolongation decreased by one day after wearing the plate to the same level as the control. Although a significant decrease was found in the duration one day after wearing from immediately after wearing the plate, no difference was found two days after, and a significant decrease was found again from three days after. No difference was found in the change within subjects. CONCLUSION: These results suggested that the duration from the end of mastication to the beginning of the pharyngeal stage was affected by wearing the palatal plate, but habituation was obtained about 3 days after wearing and its effect disappeared.

Assessment of oral appliance for obstructive sleep apnea patients.

Although oral appliances (OAs) have become widely used for the management of obstructive sleep apnea (OSA), side effects of OAs are generally related to poor utilization. The purpose of the present study was to evaluate relationship between utilization and treatment efficacy of a boil-and-bite appliance for OSA patients. A total of 135 patients with OSA who had used an OAs were mailed a questionnaire to determine whether they were currently using the OA. If so, they were asked about OA use, improvement of signs and subjective symptoms, and utilization. Otherwise, they were asked to indicate why and when they quit using the OA. Results of overnight polysomnography (PSG) before and after treatment were reviewed. Of the 48 responding patients, 33 patients were currently using the OA. The most common complication was excessive salivation (n = 11). All indices from PSG excluding arousal index were significantly improved after treatment (p < 0.05). Thirty patients showed improved signs and subjective symptoms. Eight out of 12 subjects (66.7%) were successfully treated, achieving an apnea-hypopnea index (AHI) < 10/h and >50% reduction in apnea-hypopnea index. Of the 15 patients no longer using the OA, the primary reason for quitting was "no treatment effect" (n = 5). No indices from PSG recording differed between before and after treatment in the not-using group. These results suggest that both subjective and objective signs and symptoms improved with use of the OA in the using group. However, no signs and subjective symptoms or indices of sleep quality differed between before and after treatment in the not-using group. Device improvements are needed to achieve better treatment efficacy, and thus improve compliance. The present study evaluated relationship between utilization and treatment efficacy of a boil -and bite appliance for OSA patients. Device improvements are needed to achieve better treatment efficacy, thus improve compliance.

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.

Evaluation of facial thermographic changes before and after low-level laser irradiation.

OBJECTIVE: The aim of the present study was to evaluate the facial thermographic changes before and after low-level laser irradiation applied to the temporomandibular joint in normal subjects. BACKGROUND DATA: Although this therapy has been reported to be effective in the pain management of patients with rheumatoid arthritis and degenerative joint disease, several researchers have stated that this therapy has no effect on pain of myogeneous origin. MATERIALS AND METHODS: Nine healthy subjects underwent irradiation using the continuous wave setting of a CO2 laser with a power output of 1.0 W. The laser tip was positioned 10 cm above the skin over the right TMJ area for 10 min. The actual fluence on the facial surface was 7.64 J/cm2. Variation of the facial temperature was evaluated by using thermography. RESULTS: The facial temperature 10 min after stopping irradiation was higher than that after 10 min of irradiation applied to the opposite side. The warmer area was found not only over the TMJ area but also over the temporal area, forehead area, and eyelid area on both sides. CONCLUSION: These results suggested that low-level laser irradiation had a long-lasting effect on facial cutaneous tissues.

[Evaluation of effective jaw position and body posture for oral appliance of patients with obstructive sleep apnea syndrome].

PURPOSE: The aim of this study was to evaluate whether substantial airflow changes occur by changing both jaw position and body posture in normal subjects and patients with obstructive sleep apnea syndrome (OSAS). METHODS: Fifteen normal controls (9 males and 6 females) and 15 male OSAS patients participated in this study. For all subjects their maximum forced inspiratory flow (FIF(25-75)) curve was measured in seven positions as follows: a) 0% jaw forward-upright position, b) 0% jaw forward-supine position, c) 50% jaw forward-supine position, d) 75% jaw forward-supine position, e) 0% jaw forward-lateral position, f) 50% jaw forward-lateral position, and g) 75% jaw forward-lateral position. RESULTS: Although FIF(25-75) was increased by changing the body posture from supine to lateral in normal subjects, it was not increased by increasing the jaw forward position of them. On the other hand, the more forward the jaw position, the more FIF(25-75) increased in OSAS patients. However, it was not increased by changing the body posture of them. There were no significant differences between the 50% forward and 75% forward jaw positions in both groups. CONCLUSIONS: In normal subjects, change of jaw position was more effective than that of body posture for FIF(25-75). However, in OSAS patients, change of body posture was more effective than that of jaw position for FIF(25-75). It was suggested that the treatment effect in the 50% forward position was similar to that in the 75% forward position.

Personal exposure to particulate matter and inflammation among patients with periodontal disease.

The association between particulate air pollution and high-sensitivity C-reactive protein (hs-CRP) has been well documented in epidemiological studies. Periodontitis has been linked to elevated hs-CRP levels in recent studies. It is still unknown whether patients with periodontal infections are more susceptible to particulate air pollution. The aim of this study was to investigate whether particles with aerodynamic diameters of less than 2.5 µm (PM2.5) had greater effects on increasing hs-CRP among patients with periodontal infections compared to periodontally healthy individuals. We conducted a cross-sectional study on two panels of adult subjects, 100 adult patients with chronic periodontitis and 100 periodontally healthy adults, in order to evaluate the association between particulate matter (PM) and hs-CRP. We collected blood samples from each subject, measured hs-CRP and monitored average exposure to PM2.5 over 24h four times during 2010 to 2012. We used mixed-effects models to estimate the association between PM2.5 and hs-CRP and adjusted for cardiovascular risk factors. We found that a 10 µg/m(3) increase in PM2.5 was associated with a 3.22% (95% confidence interval, CI: 1.21, 5.23; p<0.01) increase in hs-CRP among all adult subjects. The effect of PM2.5 in patients was significantly higher than the effect in healthy participants. In the healthy adult panel, a 10 µg/m(3) increase in PM2.5 was associated with a 1.17% (95% CI: 0.54, 1.80; p<0.01) increase in hs-CRP. For adults in the patient group, a 10 µg/m(3) increase in PM2.5 was associated with a 9.62% (95% CI: 7.05, 12.19; p<0.01) increase in hs-CRP. We concluded that personal exposure to PM2.5 was associated with increases in hs-CRP among adult subjects. The presence of periodontal disease led to a considerably increased effect magnitude by more than eight fold.

Diagnostic image analyses of activator treated temporomandibular joint in growth and maturing stages.

This study evaluates the condylar response to activator in growth and in maturing patients using radiographs and magnetic resonance images (MRI). Seven patients (four in growth and three in maturing stages) treated for mandibular distal occlusion were studied. In all seven patients, lateral roentgen cephalograms, panoramic radiograms, and MRIs were made before and following functional treatment. All patients' mandibles advanced during treatment. Downward and forward mandibular growth was observed by superimposition of lateral cephalograms. On the condylar posterosuperior regions for both groups, double contours were sometimes observed on the panoramic radiograms following therapy. These double contours coincided with an area of high intensity in the MRIs for both groups. In the mature adult group, the double contours were more clearly observed when compared with those in the growth group. There were differences in the condylar adaptation types between the growth and mature development stages. Condylar adaptation to the newly created mandibular position was nevertheless found even in adult patients.

Significance of frequency-selective fat saturation T2-weighted MR images for the detection of bone marrow edema in the mandibular condyle.

The objective of this study was to evaluate the utility of frequency-selective fat saturation (FS) T2-weighted images (T2WI) for the detection of bone marrow edema in the mandibular condyle. MR evidence of bone marrow abnormalities was examined on the set of FS T2WI and conventional T1WI or of conventional T2WI and T1WI in 200 patients with temporomandibular joint (TMJ) related pain. Other parameters studied were TMJ effusion, disk displacement categories, and cortical bone abnormalities. The detection rate and area of bone marrow edema by FS T2WI and T1WI were significantly greater than those assessed by conventional T2WI and T1WI. The correlation between bone marrow abnormalities on FS T2WI and T1WI and pain was significantly stronger than with conventional T2WI and T1WI. This study confirms that FS T2WI is useful for the detection of the "edema pattern" in the mandibular condylar associated with TMJ-related pain.

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.

Alterations of the Temporomandibular Joint on Magnetic Resonance Imaging according to Growth and Development in Schoolchildren.

The paper explains the alterations of the temporomandibular joint (TMJ) visualized by magnetic resonance imaging (MRI) according to the growth and development of schoolchildren. Appearance and disappearance of a "double contour-like structure" (DCLS) of the mandibular condyle on MRI according to the growth and development of schoolchildren were demonstrated. In addition, possible constituents of DCLS and the significance of detection of DCLS on MRI were also speculated. The relationship between red marrow and yellow marrow in the articular eminence of temporal bone, the disappearance of DCLS, and alterations of the mandibular condyle have been elucidated.

Effects of head and body positions on 2- and 3-dimensional configuration of the oropharynx with jaw protruded: a magnetic resonance imaging study.

OBJECTIVE: The aim of this study was to evaluate the effect of altering changing head and body positions on the 2- and 3-dimensional (3D) configuration of the oropharynx with jaw protrusion. STUDY DESIGN: Twelve healthy individuals (8 male, 4 female) with no history of sleep disturbances were invited to participate. For each subject, an acrylic splint was made with the mandible in protruded position. Subjects were imaged using magnetic resonance imaging in 4 different jaw, head, and body positions: 1) supine without protrusion; 2) supine with jaw protrusion; 3) supine with head rotation and jaw protrusion; and 4) laterally recumbent position with jaw protrusion. The 2- and 3D images of the upper airway in different positions were reconstructed by using a free DICOM reconstruction software. The dimension changes (anteroposterior and lateral dimensions, cross-sectional area, and volume) of the oropharynx (divided into retropalatal region and retroglossal region) were calculated and analyzed. Statistical analyses were performed using the Bartlett test and 1-way analysis of variance with α = .05. RESULTS: Compared with nonprotruded position, dimensions of the oropharynx for both retropalatal region and retroglossal regions were found to be greater than with jaw protrusion. Head and body positions had little effect on configuration of the oropharynx with jaw protrusion in either 2- or 3D. The only change noted was a greater anteroposterior dimension of retropalatal region with head rotation and lateral supine position compared with the supine position. CONCLUSIONS: Head and body positions have little effect on 2- and 3D airway dimensions on supine patients with jaw protrusion.