Masanobu Horiuchi

Use of interimplant displacement to measure mandibular distortion during jaw movements in humans.

It has been reported that the mandibular body and the dental arch distort during jaw movements because of contraction of the jaw muscles. In the present study the relative position between two biointegrated implants approx. 10 mm apart was measured during maximum opening and protrusive movements of the jaw using a magnetic sensor system. Mandibular distortion was evaluated as the change in the sensor signal. In all participants the distal implant deviated to the lingual side relative to the mesial implant and the deviation with jaw protrusion was larger than that with opening movement. The linear displacement of the two implants ranged from 8 to 25 microns during maximum opening and from 10 to 37 microns during jaw protrusion. Further investigation is required to establish the mechanism of this mandibular distortion, which may be of relevance to implant therapy.

Three‐dimensional examination of bone structure around hydroxyapatite implants using digital image processing

This study introduced a new method for three-dimensional (3D) examination of the bone structure around an implant and presented 3D bone-implant contact rates. A block of nondecalcified implant tissue was ground gradually at an interval of 80 micrograms for the collection of serial two-dimensional (2D) images. An image of the stained block surface was instantly recorded by a charge-couple device (CCD) camera and computer-aided system. A 3D model was reconstructed from 60-70 sheets of serial 2D images. The 3D bone structure around the implant was shown in perspective and displayed all sides of the implant. The bone-implant contact rate depended on the cutting position and direction in the specimen. The 3D model will be necessary and valuable for the biomechanical study of dynamic bone changes around implants.

Trial production and application of an optical system for measuring the movements of organs composed of soft tissue

A new optical system to measure movements of less accessible organs composed of soft tissue is proposed. The sensor unit is composed of a phototransistor and two light-emitting diodes (LEDs). The LEDs act as light sources and are driven by two phase signals with a phase shift of 90 degrees. The distance between the sensor and the measuring object can be obtained as a function of the phase angle of reflected light detected by the phototransistor. This system can be easily constructed and simultaneously records data from multiple points in real time. The relative precision was 0.5 mm and the resolution was 0.05 mm. Output characteristics of this system were not significantly affected by the reflection factor of the object. Tongue movements in speech production were observed by use of this system.

Influence of Palatal Form of Molar Region on Tongue Movement for Pronunciation of /s/ Sound.

The purpose of this study was to investigate the influence of palatal form changing with the position of upper posterior artificial teeth on tongue movement for pronunciation of /s/sound. Subjects were seven males and speech material was /asa/. Two experimental palatal plates were made for each subject: a normal 1.5-mm-thick plate and the plate augmented by a 4-mm-thick lateral seal of palatal surface. Tongue-palatal contacts were measured by a dynamic palatography when wearing either of the two plates. The influence of the palatal form was estimated using the following parameters: the onset of the tongue-palate contact, maximum contact speed, the timing of the constriction for /s/, and palatogram pattern at the constriction and consonant duration for /s/.The speech behavior when wearing the augmented plate was divided into 4 groups comparing to normal plate:Group 1: Tongue-palate contact started earlier, maximum contact speed decreased and the timing of the constriction was constant.Group 2: The onset of tongue-palate contact and maximum contact speed were constant. Butthe timing of the constriction was delayed.Group 3: Tongue-palate contact started earlier, maximum contact speed decreased and thetiming of the constriction was delayed.Group 4: Temporal aspect of tongue-palate contact was constant. But the consonant durationwas shorter and abnormal palatogram pattern was observed.

Development and application of an optical system to measure the movements of organs with soft tissue

We proposed a new optical system to measure the movements of less accessible organs with soft tissue. The sensor unit is composed of a phototransistor and two LEDs. Two LEDs of light sources are driven by two phase signals with phase shift of 90 degrees. The distance between the sensor and the measuring object can be obtained as the function of the phase angle of reflex light signal detected by the phototransistor. The system can be easily constructed and provides simultaneous recordings of multiple points with the fast response in real time. The Relative precision is 0.5 mm and the resolution is 0.05 mm. Output characteristic of the system was less affected by the reflection factor of the object. We conducted to observe the tongue movements in speech production.