Yo Taguchi

Sour taste stimulation facilitates reflex swallowing from the pharynx and larynx in the rat

Chemical stimulation of the pharynx and larynx is effective in eliciting reflex swallowing. A sour taste bolus facilitates the onset of swallowing in patients with neurogenic dysphagia, but the mechanism of the facilitation has not been clarified. We investigated the effect of sour solutions on the elicitation of reflex swallowing in anesthetized rats. The main ducts of salivary glands were ligated to avoid the effect of saliva. A small amount of water, sour solutions, and other taste solutions were applied to the mucosa of the pharyngolaryngeal region. Acetic acid and citric acid, which provide a sour taste, had a stronger effect on evoking reflex swallowing as compared with other taste solutions. The effectiveness of these acids increased with increasing concentrations. We also examined the contribution of the superior laryngeal nerve (SLN) and the pharyngeal branch of the glossopharyngeal nerve (GPNph) to reflex swallowing. Acetic acid was greatly effective in evoking swallowing in both the region innervated by the SLN and the GPNph. On the other hand, water was effective in the SLN region but only slightly effective in the GPNph region. The results indicate that stimulation of the pharyngolaryngeal region with sour solutions facilitates reflex swallowing, suggesting that the facilitation may be due to increases of sensory inputs via the SLN and GPNph.

Role of the pharyngeal branch of the vagus nerve in laryngeal elevation and UES pressure during swallowing in rabbits.

Elevation of the larynx during swallowing plays an important role in protecting the laryngeal inlet and in the opening of the upper esophageal sphincter (UES). The thyrohyoid (TH) muscle is the most important muscle for laryngeal elevation, and it is thought to be innervated by the thyrohyoid branch. However, in preliminary studies we found that laryngeal elevation was severely disturbed after sectioning of the pharyngeal branch of the vagus nerve (X-ph). In the present study, we examined the role of the X-ph in laryngeal elevation and the contribution of this nerve to UES pressure. Ten male rabbits under anesthesia were used. Sectioning of the X-ph not only abolished the electromyographic activities of the TH and cricopharyngeus (CP) muscles, it also greatly reduced the maximal value of laryngeal elevation during swallowing. On the other hand, sectioning of the hypoglossal nerve, which contains the thyrohyoid branch, produced no appreciable change in the electromyographic activity of either muscle and it reduced the maximal value of the elevation only slightly. These results indicate that the X-ph innervates the TH and CP muscles and suggest that the X-ph plays an important role in elevating the larynx and in regulating the UES pressure in rabbits.

Eruption disturbances in Japanese children and adolescents

Abstract The aims of this report were to determine the nature of eruption disturbances and to establish the pattern of management for these teeth in a group of Japanese children and adolescents. Data were collected from the clinical records of patients in the Pediatric Dental Clinic of Niigata University Medical and Dental Hospital. There were 700 patients (364 males and 336 females) and 748 teeth (26 primary teeth and 722 permanent teeth) who were treated for eruption disturbances between 1979 and 2002. During this period, 17,365 new patients visited the clinic, of whom approximately 4% had eruption disturbances. The most frequently affected permanent teeth were the maxillary central incisors (38.6%), followed by the maxillary canines (15.4%). Of the permanent teeth, 52.5% were in males and 47.5% in females. Although there were more cases of maxillary central incisors in males than in females, the number of cases involving maxillary canines was higher in females. Whereas delayed eruption was noted in 76.7% of maxillary central incisors, 18.6% were impacted and 4.7% demonstrated abnormal direction/position which required treatment. In contrast, a higher percentage (64.8%) of maxillary canines that showed abnormal direction/position was treated. Eruption disturbances were found in 40% of the patients during routine examinations. This suggests that regular routine examinations are important for pediatric dentists to detect and treat eruption disturbances early.

Changes in the mouthful weights of familiar foods with age of five years, eight years and adults

Abstract For effective mastication and swallowing, to take optimum mouthful food regularly is necessary. The purpose of this study is to compare the weights and the variance of a mouthful food between children and adults. We studied mouthful weight and the coefficient variation in 5-year-old children (n=10), 8-year-old children (n=10) and adults (n=10) while they were eating rice, bread, sausage and apple on two different days. The test foods were served in random order 2–4 hours after lunch. Each portion was weighed before and after each bite to measure the mouthful weight, and the weight of the last bite of each portion was eliminated from the data. The mean weight and coefficient variation in each subject were calculated. The results showed the mean weight was largest in the adults, intermediate in the 8-year-old children, and smallest in the 5-year-old children for all test foods (ANOVA). Moreover, the mean coefficient variation among the weights of the groups revealed that mouthful weight within an individual varied most widely in the 5-year-old children and most narrowly in the adults, and that 8-year-old children could show the same coefficient variation of mouthful weight as adults in rice and apple (Steel-Dwass test). Our results suggest that mouthful weight becomes larger and more regularly with age.

A diagnostic proposal to support early treatment of ectopically erupting maxillary canines

Although early diagnosis is essential for the correction of ectopically erupting canines, it is difficult to determine whether the condition of a canine is within acceptable normal limits, particularly in children aged 10 years or younger. The purpose of the present study was to ascertain the appropriate time for a preventive procedures, such as extraction of the predecessor, in order to avert impaction of maxillary canines. Orthopantomograms of 225 normal children without dental anomalies were examined to compare the eruption stages of mandibular and maxillary canines. Sixty-four patients with 68 unerupted and/or impacted maxillary canines were examined. In normal children, mandibular canines exhibited earlier movement toward oral emergence than maxillary canines on the same side. This tendency was particularly prominent after exfoliation of the mandibular primary canine. In contrast, nearly half of the patients with anomalies were treated before oral emergence of the mandibular canine through simple procedures such as extraction of the primary canine or exposure of the affected canine. The present findings may provide a useful supplemental rule for early diagnosis and aid in decisions whether to treat ectopically erupting maxillary canines, particularly when the anomaly is obscure.

Leptin modulates the response to oleic acid in the pharynx

Leptin released from the adipose tissues is known to inhibit obesity by regulating food intake. In this study, we investigated the effect of leptin on afferent nerve responses to fats and fatty acid in the pharyngolaryngeal region. The afferent nerve activities were recorded from the whole nerve bundle or pauci-fiber bundles of the pharyngeal branch of the glossopharyngeal nerve (GPN-ph) in Wistar normal and fatty rats. Oleic acid (long-chain fatty acid), mineral oil (nonfat oil) and safflower oil (vegetable oil; middle-chain fatty acid) were applied to the surface of pharyngolaryngeal mucous membrane. Oleic acid elicited vigorous stimulation of the GPN-ph activity in both normal and fatty rats but other oils had no significant effect on the activity. After intravenous administration of leptin (30 ng/kg, 1 ml), the response to oleic acid was significantly decreased in normal rats, whereas such a decrease was not found in fatty rats. These results are the first findings to indicate the existence of a suppressive mechanism of leptin on the response of the GPN-ph to fatty acid in normal rats, but that such a mechanism is lacking in fatty rats.

Anterior crossbite in the primary dentition: proposal for a new analytical method in children.

The aim of this study was to clarify the features of profiles of patients with anterior crossbite in early childhood, using a new method of analysis. Lateral cephalograms of 139 (68 males; 71 females) untreated child patients with anterior crossbite in the primary dentition were assessed. The patients were aged from 3 to 5 years. To evaluate disharmony between the maxilla and the mandible, a proprietary calculating system, the Theoretical Individualized Profile drawing System (TIPS), was applied. Using this system, individualized standard cephalometric values were obtained for normal occlusion. This standard profile, which was harmonized with the cranial base structure of each patient, was compared with the child’s original profile. The sizes of the mandibles in the children with anterior crossbite, subclassified into three age groups (3, 4, and 5 years) were greater, both horizontally and vertically, than those in the mean profiles derived from TIPS. The vertical size of the maxilla was smaller than that derived from TIPS in the patients aged 3 years. In contrast, in the patients aged 5 years, the vertical size of the maxilla was larger than that derived from TIPS. These results suggest that, in children with anterior crossbite, the vertical growth of the maxilla is closely related to the variation of morphological conditions with development.

Unilateral application of an inflammatory irritant to the rat temporomandibular joint region produces bilateral modulation of the jaw-opening reflex

The aim of this study was to determine the effect of unilateral acute inflammation of craniofacial deep tissues on the ipsilateral and contralateral jaw-opening reflex (JOR). The effects of mustard oil (MO), injected into the temporomandibular joint region, were tested on the JOR recorded in the digastric muscle and evoked by low-intensity electrical stimulation of the ipsilateral and contralateral inferior alveolar nerve in anesthetized rats. The MO injection induced a long-lasting suppression of the amplitude of both ipsilaterally and contralaterally evoked JOR, although the latency and duration of the JOR were unaffected. The suppressive effect was more prominent for the contralaterally evoked JOR, and observed even when background activity in the digastric muscle was increased by the MO injection. The results indicate that changes in the JOR amplitude following MO injection do not simply reflect alterations in motoneuronal excitability, and suggest that inflammation of deep craniofacial tissues modulates low-threshold sensory transmission to the motoneurons.

Genesis of the decrement of intraluminal pressure in the UES during swallowing in rabbits.

The intraluminal pressure in the upper esophageal sphincter (UES) briefly decreases during swallowing. This decrement in pressure plays an important role in smooth transport of the ingested bolus from the pharynx to the esophagus. It is known that the decrement is caused by cessation of tonic activity of the cricopharyngeus (CP) muscle and also by elevation of the larynx. On the other hand, it is suspected that the recurrent laryngeal nerve (RLN) also contributes to the decrement, since our preliminary study showed for the first time that the decrement in UES pressure was much reduced after the RLN was sectioned. In the present study, we examined the genesis of the decrement of the UES pressure in anesthetized rabbits. When swallowing was elicited by repetitive electrical stimulation of the superior laryngeal nerve, the UES pressure briefly decreased and then abruptly increased. After bilateral sectioning of the RLN, the decrement of the pressure was significantly reduced, whereas the increment was little altered. Sectioning of the pharyngeal branch of the vagus nerve (X-ph) and the RLN mostly eliminated both the decrement and increment of the pressure, and abolished tonic and burst activities of the CP muscle. Electrical stimulation of peripheral end of the RLN decreased the pressure. These results indicate that the RLN and X-ph are involved in the decrement of the UES pressure during swallowing. The RLN generates the decrement by adducting the arytenoid cartilage and closing the glottis. The X-ph contributes to the decrement both by suppressing the tonic activity of the CP muscle and by regulating the laryngeal elevation.

Regional odontodysplasia: Long-term observation of a case on the mandibular left side

Abstract Regional odontodysplasia is an unusual non-hereditary developmental anomaly of tooth structures in both primary and permanent dentitions. The appropriate treatment differs for each individuals clinical findings. The purpose of this study was to describe the clinical findings and the long-term progress as to the treatment and the management of a male patient who was diagnosed with regional odontodysplasia on the left side of the mandible. The mandibular left primary molars had shown a remarkable “ghost-like” appearance on x-ray, but they had already been extracted by an oral surgeon because of osteomyelitis due to pulpal infection, when the patient was referred to our pediatric dental clinic at 5 years of age. According to x-ray findings, the five permanent teeth (32, 33, 34, 35, 36) on the mandibular left side were delayed in formation. During the 15 years from age 5 to age 20, the patient was treated and managed in our clinic and the prosthodontic clinic of our hospital. Because the patient lost his mandibular left primary teeth early but presented delayed eruption of succedaneous permanent teeth, the patient used a temporary removable space maintainer for a long time. Although the affected first molar was extracted, the second premolar erupted and the other three unerupted teeth were not removed. The edentulous region was rehabilitated with a removable partial acrylic prosthesis when the patient was 19 years and 4 months. It was found that a multidisciplinary approach was essential for the long-term follow-up of typical regional odontodysplasia.