M. Ai

Influence of nocturnal bruxism on the stomatognathic system. Part I: a new device for measuring mandibular movements during sleep

The purpose of this study was to investigate the influence of bruxism on the stomatognathic system. A new device for measuring nocturnal mandibular movements was developed using a PIN photodiode sensor, integrated with polysomnography including electromyography (EMG), electroencephalography (EEG) and electro oculography (EOG). One bruxing event was defined depending upon EMG activities above 5% maximum voluntary contraction (MVC), and mandibular movement for each event was classified into three patterns (clenching, grinding and mix). Three subjects were selected for this study. Two of these reported a bruxing habit and one subject had some symptoms of temporomandibular dysfunction (TMD). Mandibular movement was analysed for these subjects. Frequency and duration of the bruxism events were 4.5-10.9 and 47.8-174.9 s h(-1) respectively. Clenching type bruxism was most frequently observed for all three subjects and EMG activities during clenching were stronger than grinding.

Influence of protrusive tooth contact on tapping point distribution.

This study investigated the influence of protrusive tooth contacts (tooth contacts during mandibular protrusion) on the tapping point distribution. Nine healthy subjects volunteered for this study and the protrusive tooth contact pattern, as well as the retrusive tooth contact pattern, was altered on four maxillary occlusal splints. The first splint was adjusted to make the sagittal incisal path of protrusion and retrusion equivalent to that of the natural dentition. The second and third splints had partial and complete elimination of the protrusive tooth contact, respectively. The fourth splint had complete elimination of both protrusive and retrusive tooth contacts. The subjects were asked to use each splint continuously for 1 week. The tapping point distribution was measured on the 7th day after insertion of each splint. The four experimental occlusal conditions were found to have a significant effect on the tapping point distribution. The complete elimination of the protrusive tooth contact caused an anterior tapping point location and an increase in the tapping point area. The former tendency was found to be independent of the presence of the retrusive tooth contact. In conclusion, it was suggested that the protrusive tooth contact plays a significant role in maintaining the consistency and stability of the tapping point.

[Autopolymerized resins containing 4-META for prosthetic use. 2. Adhesive strength and physical properties of experimentally produced MB-3 and MB-4].

Adhesive strengths and physical properties of two different new autopolymerized resins have been studied for the prosthetic clinical application. New resins are divided into two types, MB-3 for denture repair resin and MB-4 used for relining of metal based denture. MB-3 and MB-4 are composed of three components, a bonding liner, a liquid and a powder. The bonding liner contains 7wt% 4-META in MMA-solvent. Liquid and powder consist of MMA and Poly-MMA the same as conventional cold-curing resins. Adhesive strength of MB-3 to the Co-Cr alloy was 155±15 kg/cm2 after 90 days immersion in 37°C water, and 106±20 kg/cm2 after 3, 000 thermal cycles. Setting time of MB-3 was 4′30′, slightly slow as compared with Unifast, but other physical properties, brinell hardness, water sorption and color stability were almost the same as the contrast. MB-4 showed physical properties approximately similar to those of Rebaron. MB-3 indicated no acute toxity and no deposit from the boiling water solution of bowl milled specimen. It was concluded from the results that two different new resins were acceptable in a clinical application.