It is necessary to remove artifacts caused by metal in the mouth in order to make a living body model from three-dimensional CT images. This has become a problem that cannot be ignored, because in recent years CT scanners have become more efficient and the number of images output has increased greatly. So, to assist this work, we examined a method of automatically detecting of artifacts on the basis of a change of CT value. To catch artifacts, we examined 11,991 CT images of 147 samples taken in the past, and traced changes of range 1 （CT value from －1024 to －961）, range 2 （CT value from －960 to －897） and range 17 （CT value from 0 to 63）.
As a result, we could automatically detect more than 70 % of slice images which had artifacts.

View full abstract

Speech evaluation is important in maxillofacial rehabilitation. The monosyllable speech intelligibility （SI） test is one of the most widely used evaluation methods in Japan.However, the listening part of the test, taking time and effort, makes the test unduly subjective. The aim of the present study was to develop an automatic SI test system that does not require listening procedures. The speech of ten normal adults and seventeen maxillectomy patients with and without prostheses was evaluated using a newly developed automatic SI test system that employs computerized speech recognition techniques. The results from patients were compared with their corresponding Sls obtained using a perceptual method. The new system was used without any problems and enabled the examiner to obtain the results immediately: in normal subjects, there was no significant difference in their scores for the automatic SI test which involved three days. In patients with prostheses, there was no significant correlation between the scores on the automatic SI test and the scores on SI test obtained by the perceptual method, whereas in patients without prostheses, there was a highly significant correlation observable. These results indicate that our system, which involves no listening procedure, may effectively be used in identifying speech disorders in maxillofacial patients.

View full abstract

The purpose of this study was to evaluate subjectively and objectively the masticatory function of patients with implant-supported mandibular dento-maxillary prostheses. Three patients underwent partial resection of the mandible for the treatment of oral carcinomas involving gingiva, floor of the mouth and/or tongue. Occlusal reconstruction was achieved using an overdenture type dento-maxillary prosthesis supported by endosseous implants. Thereafter, masticatory function was assessed by a questionnaire, masticatory efficiency of a gummy jelly and maximal occlusal force. According to the analysis of questionnaires, all patients were satisfied with their prosthesis. The masticatory efficacy and maximal occlusal force were improved in all patients, but the improvement was dependent on the defect of the mandible, the condition of the upper teeth and the morbidity of the tongue.
These results indicate that our methods to measure masticatory function are useful to demonstrate the efficacy of implant-supported mandibular prostheses.

View full abstract

For patients with dentulous maxillary defects, residual teeth are especially significant as the most important retentive sources. Therefore, one of the most important factors is the design of retainers for the preservation of residual teeth. Case 1 was a 42-year-old female with a hemi-maxillary defect, first examined in 1982. Her first maxillary prosthesis had a multiple T-type bar cast clasps fabricated in our Department of Oral and Maxillofacial Surgery, Tsurumi University in 1983, and was used for 18 years. Subsequently, a new maxillary prosthesis was fabricated by the same design after one of her six maxillary teeth was lost. Case 2 was a 26-year-old female with an anterior-maxillary defect, first examined in 1982, and already fitted with a maxillary prosthesis with wire clasps. A new metal-based maxillary prosthesis with three T-type bar cast clasps was fabricated in 1984. This new prosthesis was applied with no tooth loss for over 20 years.
A clinical evaluation of these case reports suggested that the passive retainer of single or multiple Roche bar-clasps for maxillary prostheses are effective means to preserve the residual teeth and to retain the prosthesis.

View full abstract

The patient was a 62-year-old woman with left maxillary defect and who was totally edentulous, who had undergone a left partial maxillectomy 25 years ago. A dento-maxillary prosthesis with open type obturator was fabricated. Elastic polyester material was used for the obturator and light polymerized resin was used for the palatal denture plate. The weight of the prosthesis could be reduced because the thickness of the obturator and the palatal denture plate was controlled.

View full abstract

Ready-to-use applicators and spacers are now available for radiotherapy. However, there are cases in which a more sophisticated device is required to meet highly specific therapeutic needs: cases, as in the maxillofacial region, where radiation is applied in a tightly defined site which is part of a complex structure or cases where a precise distance must be maintained between irradiation source and target. We report two applicators that we have devised in our department for specific purposes. One applicator, equipped with a ¹³⁷Cs small radiation source, was for intracavitary irradiation on an oral cavity tumor, and another for surface irradiation on a penis tumor, both with built-in shield effect to keep healthy tissues surrounding the lesion from accidental exposure to radiation. In the oral tumor case, the applicator itself was made of lead alloy, which has a natural radiation shielding effect, and the possibility of peri-lesion healthy tissues becoming exposed to radiation was minimized. To reduce the radiation dose that the radiologist would be exposed to, the fastening and detaching of the small radiation source was made as easy as possible by an attachment device. In the penis tumor case, a shape-specific applicator was made of acrylic board, fastening of a small radiation source thereon was also made easy, and sufficient shielding was built in to protect the testes from exposure. We have had good results by using these applicators.

View full abstract

A light-polymerized resin for denture base was used for fabricating the obturator part of an immediate post-surgical maxillary prosthesis. A clear MMA resin base and retainers were prefabricated based on the pre-surgical maxillary model. One week after the surgery, the obturator part was molded directly to a patient maxillary defect using the light-polymerized resin. After polymerization of the obturator part, a tissue conditioning material was applied to improve tissue adaptation. Then, another light-polymerized resin for artificial teeth was appended to the prosthesis for recovering esthetic and masticatory function. This method has advantages of not irritating the post-surgical tissue of the patient, ease of handling by dentists, and shorter chair-time compared to the conventional method.

View full abstract

In the field of maxillofacial prosthetics, the pivotal function of which is to enhance the functional rehabilitation of patients, substantial attention has been paid on how to assess the functional rehabilitation in question, as seen in the literature. Assessment criteria, however, seem to differ widely from institution to institution.
Twenty-six papers which appeared in Journal of Maxllofacial Prosthetics （1995-2004） were surveyed from the point of view of functional rehabilitation, and the following results were obtained:
1. The masticatory function was characteristically assessed using a questionnaire asking what foodstuffs the patient could eat.
2. The speech function was characteristically assessed by means of a speech intelligibility test.
3. The swallowing function was characteristically assessed by means of a water drinking test.
4. Half of the papers surveyed seemed to use a reliable criterion, whereas the rest seemed to use a somewhat less reliable criterion.

View full abstract

Various mandibular movements of patients who have undergone mandibulectomy in the past are unique. The closure pathway of mandibular movement is quite different from that of nonsurgical patients. Viewed from the frontal plane, the closure pathway is angular rather than vertical on the terminal occlusal position of mandibular movements. The normal articulator’s movement pathway is vertical. Generally, such a pathway is not suitable for patients suffering from bone defects. We have manufactured a trial version of a new type of articulator. A brief outline of our new type of articulator and a clinical case is reported.

View full abstract