Toshiaki Sekita

Measuring system for lip movements using two video trackers

Movements of soft tissues surrounding the oral cavity, especially lips and cheeks, have a strong influence on mastication and phonetics. They also influence the relationship between a denture and its oral environment. The purpose of this study was to develop a three-dimensional measuring system for soft tissue movement. This system consisted of two video trackers placed stereographically and a computer. In addition, one video tracker was connected for measuring mandibular movements. The accuracy of this system was evaluated using computerized XYZ pulse stage. The resolution of this system was 0.10 x 0.10 x 0.10 mm, when the measurement was carried out in the area of the 24.0 (X) x 20.0 (Y) x 20.0 (Z) mm with a working distance of 500 mm and a frequency of 120 Hz. In the present study, the lip movements of a dentulous subject with mandibular movements during chewing peanuts were analysed using this system. The new system demonstrated its value for analysing soft tissue movement.

Mouthguard biosensor integrated with wireless module for monitoring human oral information

We have developed “Cavitas sensors” into human cavitas sites of oral cavity for non-invasive monitoring of saliva glucose. A salivary biosensor based on the integration of working electrode with an enzyme membrane on a mouthguard was fabricated and demonstrated. This mouthguard biosensor was integrated with a glucose sensor and wireless measurement system. In the investigation of in-vitro characterization, the biosensor showed excellent relationship between the output current and the glucose concentration. In artificial saliva consisting of salts and proteins, the glucose sensor exhibits highsensitive detection in a range of 5–1000 μmol/L. We demonstrated the capability of the sensor and wireless communication module to characterize an inclusion in oral phantom that imitative structure of human oral cavity. The mouthguard biosensor would be useful for real-time and non-invasive method as a novel health care management.

The Movement of the Chin during Mastication.

The purpose of this study was to evaluate suitability of the soft tissue on the chin as a reference point in measuring masticatory movements. The movements of the chin and a lower incisor during mastication were measured simultaneously using a real-time measuring system for three-dimensional movements of soft tissues (3-D Auto Tracking System).The results were as follows1. Computer-based analysis was developed to divide the whole-chewing period into single stroke and determine the beginning of the opening, closing, occluding phase.2. The chin movements were 1/60 sec slower than lower incisor movements at the beginning of the opening phase.3. The chin movements were 1/60 sec faster than lower incisor movements at the beginning of the occluding phase.The results obtained in this study indicate that the soft tissue on the chin was suitable as a reference point in measuring masticatory movements.

[Measurement of facial form using stereo-photogrammetry system].

We have been developing a three dimensional measurement system by 35mm non-metric SLR camera and have been applying this system to the measurement of complete denture base surface area and edentulous cast model surface. The purpose of this study was to apply this system to the measurement of the facial form. The subjects head was fixed and 15 control points were arranged around his face. In order to make the process of stereo-matching easier, we projected mesh on the subjects face and took stereoscopic photographs. These photographs were measured by the digitizer and the 3-D coordinates of about 5000 measuring points were calculated by a personal computer. The geometric model of the face was displayed in three dimensional computer graphics. And the model of the face was carved out from the acrylic resin by the NC milling machine from these data.