[Functional model of the middle ear ossicles].

In students' dissection practice, it is very difficult to teach students the structures and functions of the middle ear ossicles. The middle ear ossicles are too small to explain their structures and functions. Models are useful in explaining these points, but there have been no models that accurately explain the movements of the middle ear ossicles and the functions of the muscles in the middle ear. This time, we have made a model of middle ear ossicles. Our ear ossicles are made of paper-mache with metal in it. The incudomalleolar and incudostapedial articulations are made of rubber. The tensor tympani and the stapedius muscles are made of wire and the two wires can be fixed by cord stoppers. Our model explains clearly the following mechanisms of the middle ear ossicles. 1. The mechanism of sound conduction system. When the sound vibrates the tympanic membrane, malleus and incus rotate together. The long process of the incus pushes the head of the stapes. The sound is amplified by leverage. 2. Attenuation of sound by contractions of tensor tympani and stapedius muscles. When a loud sound is transmitted through the ossicular system, the tensor tympani muscle pulls the malleus inward while the stapedius muscle pulls the stapes outward. These two forces oppose each other and increase rigidity of the ossicular system, thus reducing the ossicular conduction. 3. The mechanism of how paralysis of stapedius muscle, caused by an injury to the facial nerve, results in hyperacusis. 4. This model also suggests a possible reason why the pars lucida of the tympanic membrane exists.

[Model for the functional instruction of swallowing].

It is difficult to teach students about the mechanism of swallowing. There are three phases of swallowing; oral phase, pharyngeal phase and esophageal phase. The bolus of food is propelled to back of mouth by the tongue and the swallowing reflex happens. After nasopharynx and mouth closure, the glottal closure occurs, then hyoid and larynx are lifted by the contractions of suprahyoid and thyrohyoid muscles. As for the epiglottis, it is compressed by the tongue and inclines downward. As the larynx is lifted upward and anteriorly, slight vacuum is caused in the lower pharynx and upper esophagus at the same time, and pharyngeal constrictor compress bolus, therefore, the bolus passes the piriform fossa, and is inhaled into the esophagus. This time, we made a model in order to explain this complicated mechanism. The mandible is made of paper clay by using a metallic plate in it. The tongue, the soft palate, and the epiglottis are made by using the EVA (Ethylene Vinyl Acetate) sheet. Styloglossus, suprahyoid, thyrohyoid muscles are made with the wire. Moreover, a movable wooden chip represents the contraction of the pharyngeal constrictor muscles. The spring is put in the trachea in order to lift the larynx. The upper part of esophageal constrictor is made with spring plates.

[Current status of team communication considered from a questionnaire survey on the laboratory prescription card].

Team communication between dentists and dental technicians offers high-quality medical treatment for patients. When dentists and dental technicians understand dental treatments and laboratory procedures and talk to each other from an equal standpoint, good team communication between them can be established. However, undergraduate dental students do not sufficiently understand the content and processes of laboratory procedures because the subjects and hours in laboratory procedures have been reduced at present. Education on team communication between dentists and dental technicians is not sufficiently included in the training content of postgraduate training practice. It seems that at present, it is difficult for good team communication to be established between new graduate dentists and dental technicians. In view of this, the current status of the team communication between dentists and dental technicians in the present clinic was investigated, because a guideline for constructing team communications between dentists and dental technicians is given in the dental education before and after graduation. That is to say, the current status of the team communication of dentists and dental technicians was investigated by considering a questionnaire survey on the laboratory prescription card, which is the most important information means for connecting dentists with dental technicians in the dental clinic. The results were as follows: The entry items were insufficient on the laboratory prescription cards. Therefore, it is necessary to prepare such laboratory prescription cards that required items are entirely indicated as well as to enter them fully by dentists.

Immobilization of octadecyl ammonium chloride on the surface of titanium and its effect on microbial colonization in vitro.

The aim of our study was twofold: to immobilize an organosilicon quaternary ammonium salt (3-(trimethoxysilyl)-propyldimethyl-octadecyl ammonium chloride, Si-QAC) on the surface of pure titanium and to investigate the antimicrobial activity of Si-QAC-immobilized titanium against microbial adherence and biofilm formation. The results of ToF-SIMS analysis of Si-QAC-titanium suggested the possibility of immobilizing Si-QAC on titanium surface through Ti-O-Si coupling, and that Si-QAC treatment significantly reduced both the adherence and colonization of Candida albicans and Streptococcus mutans isolates. The antimicrobial activity was achieved through at least two mechanisms: the first was attributed to the octadecyl alkyl chain which inhibited initial adherence, and the second was attributed to the quaternary ammonium salt which killed initial adherent cells as well as retarded or inhibited subsequent microbial growth. Further, thermocycling did not significantly reduce the antimicrobial activity of Si-QAC-titanium, and no significant cytotoxicity of Si-QAC-titanium was observed in either cell viability test or proinflammatory cytokine production test using human gingival fibroblasts. These results, taken together, favorably suggested that Si-QAC treatment would be a helpful means to inhibit dental plaque or denture plaque formation.