Dysphagia is a mechanical or functional difficulty in one or more phases of the swallowing process from food ingestion in the oral cavity to a bolus passing through the esophagus. Recent studies have shown that the cause of dysphagia is in the oral phase of swallowing; Therefore there is increasing importance in evaluations of the relationship between oral function and swallowing. Oral functions of oral organs, tongue, jaw, teeth, and cheek, have been studied from the viewpoint of prosthetic dentistry for rehabilitation of the oral structure and function. However, such studies focused on mastication rather than swallowing. In this report, we review recent literature on (1) senescence changes in swallowing of the elderly, (2) dysphagia and oral function, (3) oral prosthesis and swallowing; especially our past studies on the relationship between complete dentures and swallowing in the elderly. In the near future, with the rapid increase of an aged Japanese population, prosthetic dentistry will need more information to be available with respect to oral prostheses for oral feeding functions that include not only mastication but also swallowing data. Furthermore, prosthetic dentistry should research relevancies among oral prostheses, reconstruction of the oral feeding function, and preservation of deconditioning. From this some indications might be found for how to prevent disuse syndrome and aspiration pneumonia. This will be one of the responsibilities of prosthetic dentistry in its contribution to oral rehabilitation for health and long life of the elderly.

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Two child patients who have congenital heart disease were treated under general anesthesia for severe dental caries in order to prevent infectious endocarditis after the heart operation. Although both the caries treatment and the subsequent heart operation of these two cases were satisfactorily completed, the necessity of early and periodical oral management for these kinds of patients was strongly suggested. The pediatric dentistry department of a general hospital should play a role in building a close cooperation system between pediatricians and the local dental practitioners for the dental welfare of child patients who are susceptible to infectious disease.

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This report describes two cases of gingival overgrowth which occurred around the anterior teeth. Two adult patients visited the Department of Periodontics for investigation and treatment of their gingival overgrowth. Case 1 : A 73-year-old female was receiving amlodipine for treatment of hypertension. A remarkable inflammation and overgrowth in the periodontal tissues was observed around the upper and lower anterior teeth. Histochemically, the epithelium was elongated and inflammatory cells were ubiquitously infiltrated in the connective tissue. An increase of collagen fibers was observed with the accumulation of fibroblasts. The initial treatment was successfully carried out, followed by flap operation with osteoplasty. After completing all the treatments, no gingival overgrowth was seen. Case 2 : A 34-year-old female with no systemic disease had an esthetical problem in the gingival tissues around the upper left central incisor. The gingival overgrowth was seen in the gingiva ranging from distal to mesial interdental papilla. Histochemical findings showed its cell-rich fibrous connective tissue, but no inflammatory changes were seen in either epithelial or subepithelial tissues. The gingivectomy was performed and the overgrowth vanished. Fortunately, both patients recovered healthy periodontal tissues without gingival overgrowth. It should be noted that dentists are expected to understand and solve true worries behind the chief complaint from each patient.

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Oral mucosal Merkel cells are known to show polymorphism, but the biological significance of the polymorphism is not clear. To determine the biological significance, we analyzed effects of inflammation on numerical density, external figure and innervation of Merkel cells in human gingival mucosae from patients with chronic periodontitis by means of immunohistochemistry and electron microscopy. It was found that mildly inflamed gingival areas usually contained abundant Merkel cells and peripheral nerve fibers in their epithelia, whereas severely inflamed areas contained only small numbers of cells and nerve fibers. Merkel cells in mildly inflamed areas showed a high degree of polymorphism, and only oval- and round-shaped Merkel cells were in contact with nerve terminals. There were a number of Merkel cells atypically located in the prickle to granular cell layers in the mildly inflamed area. These results suggest that Merkel cells transiently disappear from gingival epithelia as a result of nerve fiber atrophy caused by severe inflammation but that these structures are regenerated as the inflammation abates. Electron microscopy revealed that some Merkel cells in the mildly inflamed epithelium make contact with lymphocytes and Langerhans cells. From these findings, it was speculated that some Merkel cells play a role in initiation or termination of gingival inflammation via the modulation of these cells.

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In humans, infusion of water to the pharyngolaryngeal region elicits swallowing. Thus, it has been thought that water receptors reside in the pharyngolaryngeal region. In the present study, we investigated how water receptors are involved in the initiation of swallowing in humans. Ten healthy subjects were studied. Each subject was instructed to repeat swallowing as fast as possible. Water (distilled water) or 0.05-0.3 M NaCl solution was delivered to the pharyngolaryngeal region through a fine tube at slow rates of 0.2, 2.0 and 5.0ml/min. The intervals between two consecutive swallowings in a test were measured. Swallowing intervals increased with increasing concentration of NaCl, suggesting that excitation of water receptors was inhibited by the presence of NaCl. The effect of water on swallowing was determined by subtracting the mean swallowing interval using water from that using 0.3 M NaCl in each subject. Under the same stimulating condition, swallowing intervals varied with subjects. There was a linear relationship between the effect of water on swallowing for eliciting a swallow and the swallowing interval in 10 subjects such that the longer swallowing intervals, the stronger the effect of water on swallowing. Current findings were discussed with respect to the interplay between volition and sensory stimulation in the timing of initiation of swallowings. The present results indicate that the inhibition of water receptors by NaCl is due to Clions. Since saliva secreted in a resting state contains relatively low concentrations of Clions, accumulated secretions of saliva from the pharynx may excite water receptors continuously, thereby shortening the interval between spontaneous swallowings that operate to clear the mouth of saliva.

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Expressions of genes and proteins of human salivary gland cells (HSG cells) were investigated on three-dimensional culture comprised in collagen sponge in order to understand the response of simple epithelial cells at the molecular level. HSG cells were seeded in collagen sponges (COL-S)(three-dimensional culture) with an agitated seeding method, and cultured for various times. As a control, HSG cells were cultured on a polystyrene dish (PS) or a collagen coated dish (COL-C)(monolayer culture). The morphological features indicate that HSG cells cultured with COL-S presented a globular shape compared with monolayer culture such as with PS or COL-C. We focused on cytokeratins (CK) that are used as the marker proteins for epithelia to characterize the cultured cells. In HSG cells, CK7, CK8, CK17 and CK18 are expressed, but CK13 which is expressed specifically in mucosal epithelia is not expressed. The expression levels of CK genes were investigated by RT-PCR. The results were that the level of CK8 and CK18 were downregulated. The level of CK13 was upregulated. On the other hand, no alternation of the expression levels of CK7 and CK17 was observed. Western Blotting was carried out to investigate the expression of protein. The bands of CK8 and CK18 were detected. The expression level of CK8 and CK18 protein was reduced as well as the mRNA level. CK13 protein was not detected in this way. The expression level of the Nm23-H1 gene, which is one of tumor suppressor genes and concerned with ERK/MAPK signal transduction, was downregulated. These results suggest that HSG cells were altered by three-dimensional culture for different expression patterns of CKs which were not contained in the simple epithelium.

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In order to establish an even and patient-oriented relationship between patients and dentists, the importance of smooth, bi-directional communication should be increasingly recognized. Dentists should make efforts to explain the treatment contents and instruct oral health care using clear and understandable words. The dental terminology sometimes can be a barrier to better mutual understanding between patients and dentists. In this study, the recognition rate for dental terms in guardians of child patients was investigated using a questionnaire method. Also, the recognition rate of the guardians for dental terminology was speculated by pediatric dentists, dentists under first year residency and dental students of 1st, 4th, 5th and 6th year using the same questionnaire. Prior to asking them to complete the questionnaire, the purpose and content of this study was explained to the subjects and consent was obtained. Among the 33 dental terms, "gingiva", "wisdom tooth" and "milk teeth" were 100% recognized by the guardians and nine other terms showed a recognition rate of more than 90%. As for speculation by dentists and dental students, they estimated the recognition rate lower than the actual rates in many cases, which means that the possibility is low for them to make explanations using dental terminology that is unfamiliar to the guardians. There existed a certain amount of gap between the recognition rate of dental terminology in the guardians of child patients and the estimation by the dentists and dental students. These results indicated that the explanations by dentists to the guardians of child patients should be conducted confirming carefully that they understand it.

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