Comparison of direct and indirect occlusal contact examinations with different clenching intensities.

The aims of this study were to examine the change of occlusal contact area following the increment of clenching intensity using silicone materials and electromyography (EMG) in normal subjects and to compare direct intra-oral examination with indirect examination using dental casts mounted by means of two impression methods. Participants were 7 men and 5 women with no more than one missing tooth per quadrant and no pain in the head and neck region. During the task, intercuspal position was maintained with minimal force, 20% maximum voluntary contraction (MVC) and 40% MVC using electromyography visual feedback. Three types of occlusal contact examinations were performed with the aid of blue silicone material in randomised order: (i) intra-oral direct occlusal contact examination (DE), (ii) indirect occlusal contact examination with dental casts using conventional impression method (IEC) and (iii) using occlusal impression method (IEO). Total occlusal contact area during DE and IEO significantly increased from baseline to 20% MVC and from baseline to 40% MVC, but not during IEC. Total occlusal contact area during DE in all tooth clenching conditions was significantly larger compared to IEO and IEC (P < 0·05). At 40% MVC, total occlusal contact area during IEO was significantly larger than during IEC (P < 0·05). These findings suggest that indirect occlusal contact examinations may not accurately reflect the intra-oral occlusal condition. If the intra-oral condition is reproduced using dental casts, these findings also suggest the occlusal impression method was more accurate compared to the conventional method (240 words).

Systematic review and recommendations for nonodontogenic toothache.

Nonodontogenic toothache is a painful condition that occurs in the absence of a clinically evident cause in the teeth or periodontal tissues. The purpose of this review is to improve the accuracy of diagnosis and the quality of dental treatment regarding nonodontogenic toothache. Electronic databases were searched to gather scientific evidence regarding related primary disorders and the management of nonodontogenic toothache. We evaluated the level of available evidence in scientific literature. There are a number of possible causes of nonodontogenic toothache and they should be treated. Nonodontogenic toothache can be categorised into eight groups according to primary disorders as follows: 1) myofascial pain referred to tooth/teeth, 2) neuropathic toothache, 3) idiopathic toothache, 4) neurovascular toothache, 5) sinus pain referred to tooth/teeth, 6) cardiac pain referred to tooth/teeth, 7) psychogenic toothache or toothache of psychosocial origin and 8) toothache caused by various other disorders. We concluded that unnecessary dental treatment should be avoided.

Tactile sensory and pain thresholds in the face and tongue of subjects asymptomatic for oro-facial pain and headache.

The aim of this study was to examine the tactile sensory and pain thresholds in the face, tongue, hand and finger of subjects asymptomatic for pain. Sixteen healthy volunteers (eight men and eight women, mean age 35·7 years, range 27-41) participated. Using Semmes-Weinstein monofilaments, the tactile detection threshold (TDT) and the filament-prick pain detection threshold (FPT) were measured at five sites: on the cheek skin (CS), tongue tip (TT), palm side of the thenar skin (TS), dorsum of the hand (DH) and the finger tip (FT). The difference between the tactile sensory and pain threshold (FPT-TDT) was also calculated. Both for the TDT and FPT, TT and DH had the lowest and highest values, respectively. As for the FPT-TDT, there were no significant differences among the measurement sites. As the difference between FPT and TDT (FPT-TDT) is known to be an important consideration in interpreting QST (quantitative sensory testing) data and can be altered by neuropathology, taking the FPT-TDT as a new parameter in addition to the TDT and FPT separately would be useful for case-control studies on oro-facial pain patients with trigeminal neuralgia, atypical facial pain/atypical odontalgia and burning mouth syndrome/glossodynia.

Influence of different narrative instructions to record the occlusal contact with silicone registration materials.

This study examined the influence of narrative instructions on the occlusal contact area, occlusal contact point and masticatory muscle activities in normal subjects. Twelve healthy men and 12 healthy women with no more than one missing tooth per quadrant participated. Surface EMG was recorded from the masseter and temporal muscle. As a control measurement, intercuspal position was maintained to produce a habitual clenching record (NCR) while the occlusal contact area and occlusal contact point was recorded by means of silicone material. Subsequently, the occlusal contact area was recorded with the narrative instruction for minimum clenching record (MCR), light clenching record (LCR) and strong clenching record (HCR). While the EMG activity (%MVC) increased modestly from MCR to LCR (from 9·3 ± 2·0% to 11·5 ± 1·5%), the occlusal contact area increased rapidly (from 17·2 ± 11·3 mm(2) to 26·8 ± 15·6 mm(2) ) (P < 0·05). Both EMG activity and occlusal contact area increased gradually from LCR to NCR (to 17·7 ± 2·0% and to 31·4 ± 14·2 mm(2) , respectively). Finally, EMG activity still increased from NCR to HCR (to 44·5 ± 3·7%) (P < 0·05), but the occlusal contact area remained stable (to 36·8 ± 16·6 mm(2) ). Occlusal contact points at left posterior, right posterior, anterior and total area were not significantly different between each task. This study showed that narrative instructions while recording the bite can result in largely stable occlusal contact area. An adequate narrative instruction may therefore contribute to taking a stable occlusal recording in natural dentition.

Analysis of brain and muscle activity during low-level tooth clenching--a feasibility study with a novel biting device.

In electromyographic (EMG) and functional magnetic resonance imaging (fMRI) studies, muscle and brain activity was compared during low levels of tooth clenching using a novel biting device to control bite force. A total of 21 healthy subjects performed motor tasks, comprising tooth clenching at 5, 10 and 20 N. During all measurements, subjects kept the novel bite device between the anterior teeth during tooth clenching. The EMG study (n = 15) characterised jaw muscle activity for the three motor tasks and demonstrated significant differences in root mean square (RMS) EMG amplitude between 5-, 10- and 20-N tooth clenching (F = 46.21, P < 0.001). There were no differences in variability of muscle activity between the three tooth-clenching levels. In an fMRI pilot study (n = 6), statistical comparisons were used to identify brain regions with significant activation in the subtraction of baseline from 5- or 20-N tooth-clenching activity. 5- and 20-N tooth clenching significantly and bilaterally activated the sensorimotor cortex, supplementary motor area, cerebellum and basal ganglia (P < 0.05, corrected for multiple comparisons). However, activation of each brain region did not differ significantly between two tooth-clenching tasks. Based on these preliminary findings, we propose that the novel biting device may be useful in further fMRI studies on controlled jaw muscle activation patterns in different craniofacial pain conditions. In addition, our fMRI result suggests that there are no significant differences in brain activity within low levels of tooth clenching with controlled force.

Influence of the thickness of silicone registration material as a means for occlusal contact examination--an explorative study with different tooth clenching intensities.

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.

Interaction of IL-1ß and P2X(3) receptor in pathologic masseter muscle pain.

The exact mechanism underlying chronic masseter muscle pain, a conspicuous symptom in temporomandibular disorder, remains unclear. We investigated whether expression of P2X3 receptor (P2X3R) is involved in mechanical hyperalgesia after contraction of masseter muscle (CMM). As compared with sham rats, the head-withdrawal threshold (HWT) to mechanical pressure stimulation of masseter muscle (MM) (but not after similar stimulation of facial skin) was significantly lower, and IL-1ß level was significantly higher, in CMM rats on day 7 after CMM. The mean percentage of FG-labeled P2X3R-positive neurons was significantly increased in TG following successive IL-1ß injections into the MM for 7 days. Successive administration of an IL-1ß receptor-antagonist into the MM attenuated the increase of P2X3-IR cells in the TG. ATP release from MM after 300-g pressure stimulation of MM was also significantly enhanced after CMM. Administration into MM of the selective P2X3,2/3 receptor antagonist A-317491 attenuated the decrement of HWT in CMM rats. A significant increase in HWT was also observed at 30 min after A-317491 (60 µg) injection in IL-1ß-injected rats. These findings suggest that P2X3R expression associated with enhanced IL-1ß expression and ATP release in MM has a possible important role in MM mechanical hyperalgesia after excessive muscular contraction.

Comparison of cerebral activity during teeth clenching and fist clenching: a functional magnetic resonance imaging study.

Using functional magnetic resonance imaging (fMRI), we compared the cerebral activity during bilateral light fist-clenching and light-teeth clenching to provide more information on the central processing mechanisms underlying awake bruxism. Fourteen subjects participated in our study. Statistical comparisons were used to identify brain regions with significant activation in the subtraction of light fist clenching and light teeth clenching activity minus baseline. Participants also evaluated the perceived effort of clenching for each task, using a visual analogue scale of 0-100, after fMRI was performed. Bilateral light fist-clenching significantly activated the bilateral sensorimotor cortex, while light teeth-clenching was significantly associated with activation of the bilateral sensorimotor cortex, supplementary motor area, dorsolateral prefrontal cortex, and posterior parietal cortex. The VAS scores for fist clenching and teeth clenching were not significantly different. As light teeth-clenching activates a more extensive cortical network compared with light fist-clenching, we suggest that the teeth clenching may induce a more complex cerebral activity compared with the performance of a hand motor task. The clinical significance of these findings remains unknown but could perhaps be related to the propensity to trigger awake bruxism.

Reproducibility of the masseteric exteroceptive suppression period using stimulus-response curves.

The present study evaluated the reproducibility of the late exteroceptive suppression period (ES2) and of pain perception. The surface electro-myogram (EMG) was recorded from the left masseter muscle in 12 males and 12 females (22-31 year). Thirteen fixed stimulus intensities from 5 to 25 mA with 2.5 mA intervals were applied at random to the left mental area, and stimulus-response (S-R) curves were built for each subject. The first stimulation intensity at which the ES2 appeared was defined the reflex threshold, while the lowest stimulus intensity the subjects scored as painful, was called the pain threshold. Using the S-R curves, the other reflex parameters (appearance level, saturation level, slope from appearance to saturation, maximum duration of ES2, and maximum suppression degree) were also determined. Two measurement sessions were scheduled. Both the reflex and the pain sensation appeared at significantly lower stimulus intensity in females than males (P < 0.05). The reflex threshold, the reflex appearance and saturation level showed a significant decrease from the first to second session (P < 0.05), while the pain threshold was significantly higher during the second session (P < 0.01). By contrast, a good reproducibility was found for the maximum duration and suppression degree of ES2. Consequently, if S-R curves would be used to study the relation between the ES2 parameters and stimulus intensity in normal subjects for their applicability in clinical conditions, maximum duration and maximum suppression degree should be focused upon, in order to avoid session and gender effects as confounding factors.

Coronary risk factors in Kawasaki disease treated with additional gammaglobulin.

AIMS: To assess the hypothesis that an additional intravenous gammaglobulin (IVGG) infusion, if administered early, may prevent coronary artery lesions (CAL) in patients with Kawasaki disease (KD) who do not respond to initial IVGG therapy. METHODS: Forty four KD patients (17 with CAL and 27 without CAL), treated with additional IVGG because of persistent or recrudescent fever after initial IVGG therapy, were studied. Main outcome measures were the presence of CAL by echocardiography and the number of febrile days before and after start of additional IVGG infusion (pre- and post-additional IVGG). RESULTS: In univariate analyses, risk factors for CAL were the number of febrile days pre-additional IVGG, the number of febrile days post-additional IVGG, the number of days that initial IVGG was divided over, the white blood cell count pre- and post-additional IVGG, and the C reactive protein concentration pre-additional IVGG. In a multivariate analysis, the only independent risk factor was the number of febrile days pre-additional IVGG (> or =10 days; odds ratio 7.86; 95% CI 1.44 to 42.8; p = 0.02). CONCLUSIONS: Among KD patients with persistent or recrudescent fever after initial IVGG therapy, administration of additional IVGG before the first 10 febrile days was associated with a decreased prevalence of CAL, when compared with the prevalence in those who were retreated later. An additional IVGG infusion, if administered early, may prevent CAL in initial IVGG non-responders.

Reduction of shrinkage on heat-activated acrylic denture base resin obtaining gradual cooling after processing.

Heat-activated acrylic denture base resin is widely used for its many good attributes, although it does show polymerization shrinkage. Although several processing methods have been developed for the purpose of minimizing polymerization shrinkage, some warping after processing is inevitable. The purpose of this study was to examine the development of residual stress relaxation in resin denture base samples in the region where shrinkage was restricted, in order to clarify how cooling variations in the stone mould influenced the shrinkage. Flat, dumbbell-shaped specimens were used. Thermocouples and strain gauges were embedded in the resin for measuring temperature and strain during the dough-stage of resin packing. To clarify stress relaxation in the stone mould, specimens were removed from the stone mould by de-flasking 4 h after the start of cooling at room temperature (control), and 12 and 24 h from the start of gradual cooling in a water bath. The strain differences between before and after removing from the stone mould for the control, and 12- and 24-h experimental groups were 1793, 1354 and 1093 mu epsilon, respectively. Our results suggest that a gradual cooling course for 12 h or more after processing a heat-activated acrylic denture base is effective for lessening deformation of the prosthesis.

Influence of occlusal contact on cervical muscle activity during submaximal clenching.

The aim of this study was to clarify the relationship between changes in the occlusal contact area and cervical muscle activity. A decreases in the occlusal contact area using bite planes (stage 1: full contact bite plane, stage 2: bilateral molar removed from contact, and stage 3: bilateral molar and premolar removed from contact) was experimentally simulated in seven subjects (aged 23-25 years) with normal dentition, and muscle activity of the sternocleidomastoid muscle (SCM) and trapezius muscle (TRM) during 50 and 10% of maximum voluntary contraction (MVC) was measured by surface electromyography. The SCM activity during 50% MVC was stage 1: 31.2 +/- 9.4 microV and stage 3: 35.3 +/- 12.3 microV. The TRM activity during 50% MVC was stage 1: 15.2 +/- 0.7 microV and stage 3: 18.3 +/- 2.9 microV. At the 50% MVC, stage 3 showed significant differences in comparison with stage 1 (P < 0.05, anova). These findings suggested that the sternocleidomastoid and TRM play roles in the exertion of occlusal force, and decreases in the occlusal contact area influence the amount of SCM and TRM activity.

Mandibular condyle movement during mastication of foods.

This study evaluated the mandibular condyle displacement on the working side while masticating certain foods with different textures. For referencing the mandibular condyle movement, the range of voluntary border movement of the mandibular condyle was determined based on the analysis of the sagittal, left lateral and right lateral border motion using Posselt's figure. The test foods consisted of cheese, peanuts, and beef jerky. During mastication of cheese and peanuts, the amount of displacement of the mandibular condyle in all directions was within the range of border movement. Significant posterior and superior shifts of the mandibular condyle were observed during mastication of beef jerky, compared with the findings obtained during border movement. Accordingly, it is suggested that prolonged mastication of hard fibrous foods, may stimulate the temporomandibular joint structure and mandibular dysfunction patients should limit their intake of such foods.

[Clinical evaluation of an immunochromatography test for rapid diagnosis of influenza].

We evaluated a rapid diagnostic kit that detects influenza type A and B viral antigens by immunochromatography, Quick Vue Influenza Test (Quidel Corp., San Diego, CA, USA), with 425 specimens collected from patients with influenza-like symptoms at three hospitals between January and March 2001. The specimens included 184 nasal aspirates, 140 nasal swabs, and 101 throat swabs. The test correctly identified 179 of the 204 culture positive specimens and 203 of the 221 culture negative specimens; the sensitivity and specificity compared with the culture were 87.7% and 91.9%, respectively. The sensitivity of the test was 92.6% (112/121) for nasal aspirates, 83.7% (41/49) for nasal swabs, and 76.5% (26/34) for throat swabs, which is similar to the results for conventional rapid enzyme immunoassay kits for influenza virus infection. The sensitivity and specificity of the QuickVue Influenza Test were equivalent to those of Flu OIA (BioStar, Inc., Boulder, CO, USA), with the agreement of 84.2%. Although the QuickVue Influenza Test does not differentiate between influenza A and B viruses, the easy-to-use kit detects both types in the physician's office, allowing physicians to make a decision on prescription of neuraminidase inhibitor therapy during the initial visit.

[Serum concentration of amantadine in the treatment of children with influenza type A infection].

Fifteen children with influenza type A (H3N2) virus infection (mean age, 38 months) were treated with amantadine. Amantadine was prescribed as 5 mg/kg/day and the serum concentration was measured in 5-7 days. As a result, the mean serum concentration of amantadine was 164.6 +/- 92.5 ng/ml (range, 67.4-446.9 ng/ml). Adverse reactions were not associated to them. Amantadine therapy against influenza type A infection is probably safe in children because of the low serum concentration shown in this study.

[Statistical insight to improve reliability of pharmacological studies].

When pharmaceutical scientists describe characteristics of a drug or when they decide whether it is appropriate to initiate clinical trials to determine the drug's effects in humans, their inferences are frequently grounded in information drawn from non-clinical studies. Therefore, certain and highly objective information is required. By introducing the concept of design of experiments to control some nuisance factors and performing confirmatory studies based on sample size estimation, trustworthy information can be efficiently obtained. This paper does not demand that researchers conduct an additional confirmatory study in a series of studies conducted so far. This is a reconsideration how a series of studies should be carried forward. Statistics ought to contribute much more not only to estimation or hypothetical tests after data are collected, but also to methodology of preliminary experiments and planning of studies. Cooperation with statisticians from an early stage of the studies is all the more helpful in non-clinical studies, in which, in a sense, "perfect" experiments can be conducted more than in clinical studies.

[Clinical evaluation of rapid diagnostic kit detecting separately influenza A and B viruses].

The Directigen Flu A + B kit, a rapid diagnostic device for influenza virus A and B was evaluated. The nasopharyngeal aspirates were obtained from 239 patients who visited our hospital, between January and March, 2000, presenting flu-like symptoms. Influenza virus AH1: 77 and AH3: 51 were isolated from 128 specimens and none from 111 specimens. Directigen Flu A + B showed 115 specimens positive and 106 specimens negative. The sensitivity and specificity of this kit were 89.8% (115/128) and 95.5% (106/111) compared with viral isolation. Agreement on positive and negative interpretations between Direction Flu A and this kit was 97.9% (234/239). In the evaluation of this kit for influenza B virus, 60 frozen nasopharyngeal aspirates collected from February to April, 1999 were used. The sensitivity and specificity of this kit were 88.9% (16/18) and 88.1% (37/42) compared with viral isolation. Agreement on positive and negative interpretations between FLU OIA and this kit was 91.7% (55/60). The Directigen A + B demonstrated sensitivity and specificity equivalent to the conventional kits in nasopharingeal aspirates. This kit can also differentiate influenza A and B viruses, a feature which is useful for treatment using anti-viral agents such as amantadine and neuraminidase inhibitor. To date, the kit is the most effective tool for the rapid diagnosis of influenza.

[Use of a rapid detection assay for influenza virus, on nasal aspirate specimens].

We investigated the usefulness of a rapid antigen detection kit using optical immunoassay for influenza virus (FLU OIA, BioStar, USA). Nasal aspirates were taken from 92 influenza suspected outpatients between March to April of 1999. Compared with virus isolation and PCR, the sensitivity of FLU OIA was 88.5% and 81.6%, and the specificity was 65.2% and 72.2%. All isolated viruses were influenza type B virus. It was difficult to differentiate the weak-positive and negative cases, leading to the rather low specificity, although the assay procedure was easy and quick. FLU OIA may be a useful rapid diagnosis kit for influenza in pediatric outpatient clinics and wards, because it can detect both influenza type A and type B viruses.

Posture correction as part of behavioural therapy in treatment of myofascial pain with limited opening.

In this study, we applied cognitive behavioural intervention to subjects who had painful limited mouth opening, with or without posture correction in daily life. The efficacy of non-intervention control was then compared with it in order to study the effectiveness of posture correction as part of a biobehavioural therapy. The visual analogue scale (VAS) value of pain intensity at maximum mouth opening and disturbance in daily life sharply declined in the group which received only cognitive behavioural intervention and those who received it together with posture correction in daily life compared to the non-intervention control group although there was little difference between the intervention groups. Moreover, pain-free unassisted mouth opening was restored earlier in the group which had added posture correction. This suggests that posture correction in daily life has a positive effect in alleviating myofascial pain with limited mouth opening.

Distortion behavior of heat-activated acrylic denture-base resin in conventional and long, low-temperature processing methods.

There have been many reports on fatal distortion of heat-activated acrylic denture-base resin which is still widely used in the field of removable prosthodontics. However, these reports have failed to report quantitatively on polymerization and thermal shrinkage factors. In the present study, we attempted to verify that the shrinkage of heat-activated acrylic denture-base resin was caused mainly by thermal contraction after processing. Furthermore, we examined the degree of distortion resulting from long, low-temperature processing, and compared the results with that of the conventional method. The strain gauge and thermo-couple were embedded in a specimen at the time of resin packing. The measurement started from the beginning of processing and continued until the specimen was bench-cooled and immediately before and after it was de-flasked, as well as during seven-day immersion in water at 37 degrees C. The resin expanded when processed by the conventional method. Meanwhile, mild shrinkage, possibly polymerization shrinkage, was observed when the resin was processed by the low-temperature method. This suggested that polymerization shrinkage was compensated for by thermal expansion during processing by the conventional method. Moreover, the shrinkage strains in the period from the completion of processing to immediately after de-flasking, in both the conventional and low-temperature methods, were identical to the theoretical value of thermal shrinkage which we obtained by multiplying the linear coefficients of thermal expansion by temperature differences. The shrinkage strain in the specimen processed by the low-temperature method, measured from the end of processing to immediately after de-flasking, averaged 64% of that in the specimen processed by the conventional method. The results revealed quantitatively that the shrinkage of heat-activated acrylic denture-base resin was mainly thermal shrinkage, and demonstrated the advantage of the low-temperature method in reducing thermal shrinkage.