The relationship between lip-closing force and dental arch morphology in patient with Angle Class I malocclusion.

Dental arch morphology and tooth position are affected by lip-closing force (LCF). This study aimed to quantitatively evaluate the relationships between the horizontal or vertical balance of the LCF generated during maximum voluntary pursing-like movements and dental arch length (DAL) or width (DAW) or the lingual inclination of the upper or lower 1st molars (LIUM, LILM) in patients with Angle Class I malocclusion. Sixteen subjects with Angle Class I malocclusion (median age: 23·4 ± 5·9 years) who had never undergone orthodontic treatment were randomly selected. LCF was measured in eight directions during maximum voluntary pursing-like lip-closing movements. Dental arch models were scanned and analysed to obtain DAW, DAL, LIUM and LILM measurements. Mandibular deviation was measured on posteroanterior cephalograms. A significant negative correlation was detected between maxillary DAL and upper LCF. Maxillary DAL, DAW and the DAL/DAW ratio displayed significant negative correlations with total LCF and upper LCF. However, no significant correlations were detected between any mandibular dental arch morphological parameter and LCF. The difference in the LIUM between the deviation and non-deviation sides exhibited a significant positive correlation with the difference in upper LCF between the deviation and non-deviation sides and was significantly negatively correlated with the difference in lower LCF between the deviation and non-deviation sides. These results suggest that upper LCF is related to maxillary DAL, and the horizontal balance of the LCF of the upper and lower lips is related to the LIUM during pursing-like lip-closing movements in patients with Angle Class I malocclusion.

Relationship between frontal craniofacial morphology and horizontal balance of lip-closing forces during lip pursing.

The objectives of this study were to quantitatively evaluate the relationship between frontal craniofacial morphology and the horizontal balance of the lip-closing forces (LCF) generated during maximum voluntary pursing-like movements in patients with mandibular deviation. Thirty-one subjects (median age 25·4 ± 8·9 years) without a history of orthodontic treatment were randomly selected from among the orthodontic patients who visited our hospital. Lip-closing forces was recorded in eight directions during maximum voluntary pursing-like lip-closing movements. The subjects were divided into the deviation (two males and 11 females) and non-deviation groups (four males and 14 females). There was no significant difference in the total LCF between the deviation and non-deviation groups. In the deviation group, the mean LCF value on the deviation side of the upper lip was significantly lower than that detected on the non-deviation side of the upper lip, while the mean LCF value for the deviation side of the lower lip was significantly higher than that for the non-deviation side of the lower lip. In contrast, no significant difference in upper or lower lip LCF was detected between the deviation and non-deviation sides in the non-deviation group. The difference in the LCF generated in the lower lip between the deviation and non-deviation sides was significantly positively correlated with mandibular menton deviation and significantly negatively correlated with the difference in maxillary height between the deviation and non-deviation sides. These results suggest that the horizontal balance of the upper and lower lip LCF produced during pursing-like lip-closing movements in patients with mandibular deviation is related to frontal craniofacial morphology.

Impact of the Comprehensive Awareness Modification of Mouth, Chewing and Meal (CAMCAM) Program on the Attitude and Behavior Towards Oral Health and Eating Habits as Well as the Condition of Oral Frailty: A Pilot Study.

OBJECTIVES: Preserving sufficient oral function and maintaining aadequate nutrition are essential for preventing physical frailty and the following long-term care. We recently developed the 6-month Comprehensive Awareness Modification of Mouth, Chewing And Meal (CAMCAM) program, in which participants gather monthly to learn about oral health and nutrition while eating a textured lunch together. This study examined whether the CAMCAM program could improve attitude and behavior towards oral health, mastication, and diet as well as ameliorate oral frailty in community-dwelling older adults. DESIGN: Single-arm pre-post comparison study. SETTING AND PARTICIPANTS: A total of 271 community-dwelling adults (72.3 ± 5.7 years of age; 159 women [58.7%]) in 4 Japanese municipalities were recruited, of which 249 participants (92%) were assessed at the final evaluation. INTERVENTION: Participants gathered once a month at community centers to learn about oral health and nutrition while eating a "munchy" textured lunch containing proper nutrition. MEASUREMENTS: Oral frailty, frailty, and eating behavior were evaluated with the Oral Frailty Index-8 (OFI-8), Kihon checklist (KCL), and CAMCAM checklist, respectively. Participants were divided into Oral frailty (OF) and Robust groups according to OFI-8 scores. The differences in KCL and CAMCAM checklist results between the OF and Robust groups were statistically tested along with changes in scores after the program. RESULTS: KCL and CAMCAM checklist scores were significantly lower in the OF group at the initial assessment. OFI-8 and KCL findings were significantly improved in the OF group after completing the program (all P <0.05). Regarding the CAMCAM checklist, awareness of chewing improved significantly in the Robust group (P=0.009), with a similar tendency in the OF group (P=0.080). CONCLUSION: The findings of this pilot study suggest that the CAMCAM program may improve both oral and systemic frailty in addition to attitudes towards chewing, oral health, and meals, especially in individuals with oral frailty. The CAMCAM program merits expansion as a community-based frailty prevention program.

Masseter EMG activity during sleep and sleep bruxism.

The masseter muscle is involved in the complex and coordinated oromotor behaviors such as mastication during wakefulness. The masseter electromyographic (EMG) activity decreases but does not disappear completely during sleep: the EMG activity is generally of low level and inhomogeneous for the duration, amplitude and intervals. The decreased excitability of the masseter motoneurons can be determined by neural substrates for NREM and REM sleep. The masseter EMG activity is increased in association with the level of arousal fluctuations within either sleep state. In addition, there are some motor events such as REM twitches, swallowing and rhythmic masticatory muscle activity (RMMA), whose generation might involve the additional activation of specific neural circuits. Sleep bruxism (SB) is characterized by exaggerated occurrence of RMMA. In SB, the rhythmic activation of the masseter muscle can reflect the rhythmic motor inputs to motoneurons through, at least in part, common neural circuits for generating masticatory rhythm under the facilitatory influences of transient arousals. However, it remains elusive as to which neural circuits determine the genesis of sleep bruxism. Based on the available knowledge on the masseter EMG activity during sleep, this review presents that the variety of the masseter EMG phenotypes during sleep can result from the combinations of the quantitative, spatial and temporal neural factors eventually sending net facilitatory inputs to trigeminal motoneurons under sleep regulatory systems.

Specific increase in non-functional masseter bursts in subjects aware of tooth-clenching during wakefulness.

Previous studies have reported that subjective awareness of a tooth-clenching habit is associated with increased jaw motor activity (Rao SM, Glaros AG, J Dent Res. 1979;58:1872). The aim of this study was to test the hypothesis that subjects with clenching awareness exhibit different motor expressions specific to non-functional oromotor activity under laboratory conditions without psychological or sensory effects. Polygraphic and audio-video recordings were made for a 30-min period of silent reading by 33 subjects without oro-facial pain. Oro-facial behaviours (e.g. swallowing, lip movements) were scored according to the polygraphic and audio-video records and masseter bursts were quantitatively analysed. Subjective psychological/sensory measures were also recorded before and/or after the polygraphic recording using a visual analogue scale. The subjects were classified into two groups one with 15 subjects who were aware of having a tooth-clenching habit and another with 18 who were not aware of any such habit. There were no differences between the groups with respect to the number of functional oro-facial behaviours or subjective psychological/sensory measures. Masseter bursts unrelated to functional oro-facial behaviours occurred more frequently in subjects with awareness [median (range) = 23 (2-187) bursts] than in those without [9.0 (0-36); P = 0.01], while neither burst activity [12.3 (1.8-34.5) % of maximum voluntary clenching and 10.1 (6.5-25.1) %, respectively] nor duration [1.17 (0.2-2.2) s and 1.28 (0.3-4.1) s, respectively] differed between the groups. The occurrence of functional oro-facial behaviours or other body behaviours (e.g. limb and body movements) did not differ between the two groups. These findings suggest that the increased masseter activity in subjects with tooth-clenching awareness is characterized by a specific increase in non-functional masseter bursts.

Positive Effects of "Textured Lunches" Gatherings and Oral Exercises Combined with Physical Exercises on Oral and Physical Function in Older Individuals: A Cluster Randomized Controlled Trial.

OBJECTIVES: Proper nutrition and physical exercises are essential to prevent frailty in older adults. Proper masticatory performance and oral function may influence on physical activities as well since the mouth is the entrance of nutrition and digestion. Thus, the present study aimed to test the combined program of specially devised lunch gatherings containing textured foods with oral and physical exercises on the improvement of oral and physical function in community-dwelling older adults. DESIGN: A Cluster randomized controlled trial; Setting and Participants: Eighty-six community-dwelling older adults in Daito city, Japan, were randomly assigned into control (n = 43) or intervention (n = 43) groups. INTERVENTION: The control group performed the physical exercise regimen only. The intervention group participated in a 12-week physical and oral exercise program and ate a so-called "munchy lunch" that introduced textured foods with proper nutrients together after performing the physical exercise twice a week following brief dietary instruction at the intervention onset. Physical training and lunch gatherings were held at local public centers. MEASUREMENTS: The differences in measured variables for physical and oral function between baseline and 12 weeks of intervention were statistically tested. RESULTS: Oral function as measured by tongue pressure increased significantly in the intervention group (p=0.031), but not in the control group. Physical properties and activities, including body fat percentage and results of the timed up and go test, decreased more significantly in the intervention group than in controls (p<0.05). CONCLUSIONS: Our findings suggest that a combined program of textured lunch gatherings with oral and physical exercises may improve physical and oral function as a preventative approach for frailty in community-dwelling older adults.

Patterns of masseter muscle activities during sleep in guinea pigs.

Basic neurophysiological mechanisms for sleep bruxism remain unknown. Analyses of masseter muscle activity during sleep in guinea pigs have shown that the duration and activity of masseter bursts differ between non-rapid eye movement (NREM) and rapid eye movement (REM) sleep and that some repetitive burst episodes do occur. Furthermore, masseter bursts occurred in association with a transient heart rate increase. These results suggest that various patterns of masseter bursts occur in association with transient arousal activity during sleep in guinea pigs.

Enhancing effect of 2,3,4,7,8-pentachlorodibenzofuran and 1,2,3,4,7,8-hexachlorodibenzofuran on diethylnitrosamine hepatocarcinogenesis in rats.

Enhancement of diethylnitrosamine(DENA)-induced hepatic tumor production in rats was observed by sequential exposure to 2,3,4,7,8-pentachlorodibenzofuran (PenCDF) or 1,2,3,4,7,8-hexachlorodibenzofuran (HCDF). This effect was more evident in the group of rats treated with 2,3,4,7,8-PenCDF (80 micrograms/rat), in which approximately 43% of this compound administered was accumulated in the liver at 8 weeks after the last treatment.

Neuronal activity in the putamen and the globus pallidus of rabbit during mastication.

The pattern of jaw movements is changed during a masticatory sequence from ingestion of food to its deglutition. The masticatory sequence is divided into three distinct stages in the rabbit. However, the neural mechanism involved in the alteration of the masticatory stages is still unknown. This study was designed to determine whether neuronal activity in the putamen and globus pallidus is related to the alteration of the masticatory stages. Fifty-three percent of the recorded neurons showed significant alterations of activity during mastication. Of these neurons, 16% changed their firing frequency throughout the masticatory sequence (sequence-related neurons) and 84% changed their firing frequency with the transition of the masticatory stages (stage-related neurons). The stage-related neurons were classified into two groups based on their neuronal activity patterns observed during mastication, i.e. simple type and complex type. The former are the neurons that were either facilitated or inhibited once during mastication, and the latter are those showing the facilitation or inhibition twice or more during mastication. Complex-type neurons were observed more frequently in the globus pallidus than in the putamen. These results suggest that the basal ganglia is involved in mastication and may related to the transition between the masticatory stages.

Influence of food thickness and hardness on possible feed-forward control of the masseteric muscle activity in the anesthetized rabbit.

The facilitatory masseteric muscle response (FMR) elicited by polyurethane foam strip application between the opposing molars during cortically-induced rhythmic jaw movements (CRJMs) was induced earlier than masticatory force onset. The occurrence of this early response of the FMR (e-FMR) could not be explained by a simple reflex mechanism. One possible mechanism of the e-FMR is the involvement of a feed-forward control mechanism of the masticatory jaw movement. In the present study, experimentally designed polyurethane foam strips with various thickness and hardness were applied during CRJMs and analyzed in terms of how the e-FMR was modulated by the food hardness and thickness. The FMR onset was not related to the strip thickness or the strip hardness. However, the magnitude of the e-FMR increased in a thickness and a hardness-dependent manner. The sensory information of the food properties in the masticatory cycle may make the FMR adequate to chewing of the food in the following cycle, and such modulation may help chewing rhythms remain stable.

Reversal of multidrug resistance by a liposome-MDR1 ribozyme complex.

PURPOSE: Multidrug resistance (MDR) is a major obstacle in cancer chemotherapy. We examined whether cationic liposome-mediated transfer of a ribozyme could reverse MDR. METHODS: A ribozyme which cleaved codon 196 of MDR1 mRNA was constructed from synthetic oligonucleotides. The MDR1 ribozyme was mixed with N-(1-(2,3-dileoyloxy)propyl)-N,N,N-trimethylammonium methyl sulfate (DOTAP) to form a liposomal complex. The complex was used to treat two P-glycoprotein-producing MDR cell lines: MCF-7/R human breast cancer cells resistant to doxorubicin and MOLT-3/TMQ800 human ALL cells resistant to trimetrexate (TMQ). In order to investigate the differential sensitivity of these two cell lines to the liposome-ribozyme complex, cellular pharmacological studies including phase-contrast and confocal microscopic studies were performed. RESULTS: Treatment with the liposome-ribozyme complex resulted in reversal of vincristine (VCR) resistance in MCF-7/R cells, but not in MOLT-3/TMQ800 cells. In MCF-7/R cells the treatment resulted in decreases in MDR1 mRNA expression and P-glycoprotein production, whereas no changes in these parameters were seen in MOLT-3/TMQ800 cells. Phase-contrast microscopy revealed that in MCF-7/R cells treatment with DOTAP led to the formation of cytoplasmic vacuoles, and treatment with latex beads resulted in the development of a shiny material in the cytoplasm. In contrast, in MOLT-3/TMQ800 cells hardly any morphological changes occurred. Confocal microscopic imaging showed cytoplasmic fluorescence in MCF-7/R cells after treatment with DOTAP/FITC-dextran or FITC-conjugated latex beads. In MOLT-3/TMQ800 cells no fluorescence was detected. Treatment with cytochalasin B abolished fluorescence in MCF-7/R cells after treatment with DOTAP/FITC-dextran or FITC-conjugated latex beads. These studies show that MCF-7/R cells have high endocytotic activity whereas MOLT-3/TMQ800 cells have little activity. CONCLUSIONS: Endocytotic activity was correlated with the success of cationic liposome-mediated transfer of MDR1 ribozyme. Determination of endocytotic activity of target tumor cells may be predictive of efficacy of liposome-mediated gene transfer.

Neostriatal stimulation activates tongue-protruder muscle, but not tongue-retractor or facial muscles: an electrical and chemical microstimulation study in rats.

Whether electrical microstimulation of a rat's striatal jaw region (SJR) in fact induced tongue or facial muscle activity in addition to jaw muscle activity was tested. Microstimulation of SJR-evoked EMG activity in a jaw-opener (anterior digastricus) and tongue-protruder (genioglossus). No activity was evoked in jaw-closers (temporalis or masseter), tongue-retractor (hyoglossus) or in facial muscles. In addition, the EMG effect could still be induced after extensive ablation of the neocortex; it was reproduced by microinjection of 50 mM kainic acid into SJR. The effective sites were histologically localized to a small central striatal region adjoining the anterior commissure. These findings may be of considerable value in understanding the striatal mechanism of orolingual dyskinesia involving involuntary jaw and tongue movements.

Neural activity of chorda tympani mechanosensitive fibers during licking behavior in rats.

The chorda tympani nerve, supplying the anterior two-thirds of the tongue, contains gustatory and mechanosensitive afferent fibers. We have analyzed discharge patterns in rats of various fibers recorded from dissected nerve filaments during licking behavior of which 4 were taste-sensitive and 12 mechanosensitive. The incidence of these two types were estimated electrophysiologically under anesthesia and their conduction velocity measured. Recordings in freely moving animals showed that the mechanosensitive fibers innervating the dorsal part of the tongue gave two burst discharges per lick, suggesting that contact of the tongue with the upper incisors and/or lip occurred during tongue protrusion and retraction. The fibers from the tip of the tongue showed one burst discharge per lick, which was the response to contact with a drinking spout. No rhythmical discharges synchronized with lick signals were observed in the fibers from the lateral part of the tongue or the taste-sensitive fibers. Such mechanoreceptor discharges were difficult to detect in recordings from the whole chorda tympani nerve. This masking of responses was due mainly to activation of a small number of mechanosensitive fibers by licking-induced mechanical stimulation. The lubricating action of saliva also decreased mechanoreceptor sensitivity. Despite their small number, the mechanosensitive fibers had axons with faster conduction velocities (larger diameter) than the taste-sensitive fibers. This was probably the reason why dissected nerve bundles more frequently showed mechanical than taste responses in conscious rats.

Adjustment of the occlusal vertical dimension in the bite-raised guinea pig.

In humans, the inappropriate occlusal vertical dimension (OVD) causes several orofacial disorders, such as bruxism and pain in the masticatory muscles and temporomandibular joint. However, it is still unclear how strictly the OVD is adjusted. To answer this question, we studied the temporal change of the OVD in bite-raised young guinea pigs. The OVD was raised by fixation of a bite-raising appliance to the lower incisors, and increased by either 3 or 1.5 mm at the first molars. After the space produced between the upper and lower molars was filled within 10 days due to eruption of the molars, the appliance was removed. In the bite-raised animals, the raised OVD was reduced until it attained that observed in the control animals, after which the OVD increased according to cranial growth. These results show that the OVD is developmentally changed and strictly controlled.

An involvement of trigeminal mesencephalic neurons in regulation of occlusal vertical dimension in the guinea pig.

Although the occlusal vertical dimension (OVD) is strictly controlled, the neuronal mechanism of its regulation is still unclear. We hypothesize that neurons in the trigeminal mesencephalic nucleus (MesV) play an important role in the regulation of the OVD, because the MesV receives the projection from jaw-closing muscle spindles and periodontal mechanoreceptors. We measured the temporal OVD change in the guinea pig to study the effects of MesV lesions on the OVD. OVD-raised animals without MesV lesions showed a rapid OVD decrease to the same level as that in naïve controls, followed by an OVD increase after the OVD-raising appliance was removed. In contrast, OVD-raised animals with MesV lesions showed only a slight decrease in the OVD for 15 days after removal of the appliance, and then the OVD increased. The time-course of OVD development in normal-bite animals with MesV lesions was similar to that of naïve controls. These results suggest that MesV neurons are involved in OVD regulation.

Characteristics of mastication in the anodontic mouse.

Teeth and periodontal mechanoreceptors play important roles in regulating jaw movements during mastication. However, little is known concerning how jaw movements develop without tooth eruption. To answer this question, we studied masticatory behavior in the osteopetrotic mouse, where tooth eruption does not occur and periodontal mechanoreceptors are missing. A masticatory sequence of the osteopetrotic mouse was divided into two stages: incision and chewing. Incision is characterized by small amplitude and rapid (7 Hz) open-close jaw movements, while slow (5 Hz) and large amplitude open-close jaw movements characterize chewing. The frequency and properties of jaw movements were comparable with those in the normal mouse, though the osteopetrotic mouse had a higher cycle number during incision than did the normal mouse. These results indicate that conversion from sucking to mastication occurs in the anodontic mouse, and the central pattern generator producing the masticatory rhythm develops almost normally without tooth eruption.

Cytologic diagnosis of the maxillary sinus reevaluated.

Preoperative cytologic diagnosis of the maxillary sinus was performed on 57 patients by examining of solutions obtained by local washing following sinus puncture. There were 6 cases of cancer (5 squamous cell carcinomas and 1 adenoid cystic carcinoma), 1 malignant melanoma, 1 odontoma, 8 aspergillosis, 1 inflammatory pseudotumor, 9 odontogenic maxillary sinusitis and conventional chronic sinusitis in residual cases. There were 2 false-negative cytologies in the 7 cases of malignant tumor (i.e., 1 adenoid cystic carcinoma and 1 squamous cell carcinoma). The significance and usefulness of the cytologic approach to preoperative diagnosis of malignancies, including malignant melanoma and fungal infection were discussed.

Effects of short-term (2 weeks) streptozotocin-induced diabetes on acetylcholine and noradrenaline in the salivary glands and secretory responses to cholinergic and adrenergic sialogogues in mice.

Acetylcholine and noradrenaline concentrations in the submandibular, parotid and sublingual glands, and pilocarpine-, isoproterenol- and phenylephrine-induced salivation, were estimated in streptozotocin (STZ)-induced diabetic mice. Diabetic mice showed significant increases in acetylcholine and noradrenaline (expressed as nmol/gland) in sublingual and submandibular glands, respectively. The total volume of crude whole saliva in diabetic mice in response to pilocarpine and isoproterenol but not to phenylephrine was significantly reduced. These results suggest that alterations in the neurotransmitter levels and secretory function in the salivary glands occur rapidly after the induction of STZ diabetes, and that the secretory function appears to be more susceptible to effects of diabetes in the early stages than the autonomic nervous system. Since the alterations in neurotransmitter concentrations in diabetic salivary glands were slight and partial, it seems that they are unrelated to the markedly reduced salivation in response to pilocarpine and isoproterenol observed in these short-term diabetic mice.

Formation of triazene from sulphonamide and nitrite in acidic solution.

Formation of triazene derivatives from sodium nitrite and sulphanilamide, sulphamethizole or sulphamethoxazole in acidic solution containing saliva or canned vegetable juice was studied using reverse-phase high-performance liquid chromatography with ultraviolet light detection at 365 nm. At the optimal pH of 3.2-3.7, the mean yield of the triazene formed by reaction of sulphanilamide and nitrite in saliva was 28.8%, calculated on the nitrite content, and there was a high positive correlation (r = 0.993) between the nitrite concentration in the saliva and the triazene yield. In contrast, at the optimal pH values for triazene formation from sulphamethizole and sulphamethoxazole (3.0-3.5 and 2.5-2.9 respectively), triazene yields were much lower, accounting for only 0.9 and 1.0%, respectively, of the nitrite present. Triazene formation was partly inhibited in the presence of vegetable juice.

Approach to risk assessment of chlorinated dioxins from Yusho PCB poisoning.

A Japanese was estimated to ingest 3 and 11 pg/kg/day of TEQ from PCDD/PCDFs and coplanar PCBs respectively through foods. A Japanese baby was calculated to consume 100-530 pg/kg/day level of TEQ through breast milk feeding, more than 60% being attributed to TEQ of coplanar PCBs. These intakes of TEQ were compared to the average (154 ng/kg/day) and minimum (28 ng/kg/day) intakes of Yusho, a PCB posioning occurred in Japan in 1968. There are three or four orders of magnitude difference between the daily TEQ intakes of general population and Yusho patients. However, the TEQ intakes by breast milk-fed babies of general population are at least 53 times less than the minimum intake of Yusho patients.