Akiko Nomura

Effects of low-energy electron beam irradiation on flexural properties of self-curing acrylic resin.

PURPOSE The purpose of this study was to confirm the effectiveness of LEB irradiation onto the polymer powder for improving the mechanical properties of self-curing acrylic resin. METHODS The polymer powder of self-curing acrylic resin was irradiated with total LEB doses of 25, 50, 75 or 100kGy. Non-irradiated powder was used as a control. After LEB irradiation, ESR measurement, weight-average molecular weight measurement and three-point bending test were performed. RESULTS ESR spectrum of control had no peaks. After LEB irradiation, nine peaks were observed in each ESR spectrum, which indicates the presence of free radicals from main polymer chain. The quantity of free radicals increased linearly up to 100kGy. Calibrated weight-average molecular weights were as follows: control, 960,000; 25kGy, 500,000; 50kGy, 440,000; 75kGy, 410,000; and 100kGy, 390,000. Molecular weight decreased with increasing LEB irradiation dose. The mean values of flexural strength (MPa) were as follows: control, 61.5±3.0; 25kGy, 68.1±4.0; 50kGy, 73.0±1.9; 75kGy, 70.4±3.6; and 100kGy, 67.7±2.3. The flexural strength of the specimens cured with the LEB-irradiated powder was significantly higher than that of control (p<0.01). These results indicate that flexural strength of polymer materials cured with the LEB-irradiated powder increases because of increase in cross-linking structure. CONCLUSION It is confirmed that LEB irradiation onto the polymer powder of self-curing acrylic resin improves the flexural strength.

Evaluation of newly developed devices for denture placement and removal in the dependent elderly

OBJECTIVE The purpose of this study was to subjectively evaluate the utility of newly developed denture placement and removal devices. Objective observations were also made to support the evidence. MATERIALS AND METHOD Twenty-one subjects were instructed to place and remove their dentures with and without the devices. We evaluated the device based on a questionnaire. Objective observations were based on a 2-D image analysis. We analysed three factors: the time, the area and the circumference required to insert and remove the dentures. RESULTS Image analysis showed that the effectiveness and ease with which the subject used the device significantly improved with practice. The questionnaire data showed that a majority of the subjects appreciated the device after the first and second time. While there was no significant decrease in time required to place and remove dentures even with the device, the area and circumference of the movement on 2-D images were significantly reduced. CONCLUSION In this study, the utility of denture placement and removal devices was evaluated both subjectively and objectively. Our data reveal that the device is effective in the elderly. Further minor improvement in the device might be required to increase its effectiveness.

Prosthetic Management for a Patient with Microstomia.

This paper describes the treatment of a partially edentulous patient with microstomia. A 65-year-old patients face was severely burned when he was 2 years old. His mouth circumference was about 120 mm and perioral burn scar contraction strictly limited access to the oral cavity. Upper and lower preliminary impressions were obtained by using a sectioned stock tray for an edentulous patient. A sectional custom tray was made for a maxillary final impression. A larger section encompassed an area of the denture base and retainers. A small section encompassed a remaining dental arch. This technique minimized the influence of errors resulting from sectional impression. Two halves could be assembled and disassembled in the mouth and reassembled outside the mouth by LEGO plastic building blocks.An outline of the deture base was simplified by partial overdeture, which an isolated and mobile tooth was served as an abutment. An arm tip of the farthest clasp from the denture base travelled mesially so as not to injure the angle of the mouth. Upper and lower partial dentures could be carefully inserted and twisted into place. Upon reexamination 1 year later, the dentures were in good condition.

A Study on the Prosthodontic Treatment for Cleft Lip and Palate Patients.

Cleft lip and palate patients show several characteristic clinical and functional findings, such as:a. Cross bite, open bite and unstable occlusion in ICP.b. Tight upper lip, midface retrusion and scar contracted vestibular sulcus.c. Malposition of teeth, oronasal fistula and velopharyngeal incompetence.d. Relapse of teeth and segment.To consider a prosthodontic therapy to be successful, two factors must be satisfied:1. Reconstruction for optimum occlusion: stable occlusion in ICP and anterior guidanceproviding harmonious jaw movement.2. Prosthesis must satisfy requests of esthetics, comfort, simplicity and durability.In this study, the clinical and prosthetic findings of 10 patients before and after prosthetictreatment were compared.Results:1. All patients were satisfied with the given prosthodontic treatment.2. In 2 patients, both factors were established.In 4 patients who had anterior malocclusion, stable occlusion in ICP was established, butoptimum anterior guidance was not.In 4 patients who had severe malocclusion, optimum occlusion was not established with oralreconstruction.3. Many patients who had upper malpositioned teeth, oronasal fistula, relapse of teeth andsegment showed that their prostheses were more complicated and larger.Therefore, we reconfirm that prosthodontists, oral surgeons and orthodontists must coordinate and discuss how to accomplish a successful rehabilitation of cleft lip and palate patients.