Electrotactile Augmentation for Carving Guidance.

In this study, we presented an efficient and unobtrusive tactile feedback system, which is used to train dental technicians in carving tasks using a wax stick and knife. First, we developed a method for generating performance metrics using a model-based estimation of clearance angles between an object's surface and the carving blade. The calculated clearance angles are compared with desired angles obtained from expert operators. Then, angular errors are presented as tactile cues to the user's finger pads through electrical stimuli at the middle phalanx of the index finger and the thumb. Subsequently, we conducted a feasibility test with novice dental technicians, who showed improvement in initial clearance angles of carving strokes. Moreover, the results showed significant reduction in the occurrence rate of poor-carving when using the proposed system. From these results, we concluded that electrotactile augmentation can provide effective guidance for carving tasks.

The effect of wearing custom-made mouthguards on the aeroacoustic properties of Japanese sibilant /s/.

BACKGROUND/AIM: There have been many reports on the discomfort of speech when wearing oral appliances. Fricatives articulated in an oral cavity can be difficult to pronounce when oral appliances are worn, because the oral cavity is partially changed by their installation. Sibilant /s/, one fricative, is especially difficult to pronounce when wearing oral appliances. This study investigates the effect of the difference in the setting positions of the palatal margin of custom-made mouthguards on the aeroacoustic characteristics of sibilant /s/. MATERIALS AND METHODS: Eighteen subjects (11 women and seven men) participated. The palatal margin of mouthguards was set at the gingival line for nine subjects and 4 mm from the line for another nine subjects. Acoustical analyses examined the difference of the palatal margins of the mouthguards on the autocorrelation coefficient, the zero crossing count, and the spectral peaks of sibilant /s/. RESULTS: The results showed that the zero crossing count of the waveforms and the spectral peaks of sibilant /s/ were significantly broadened and shifted toward the low-frequency range with the mouthguard whose palatal margin extended 4 mm from the gingival line than the mouthguard whose palatal margin was set at the gingival line. CONCLUSION: We believe that a more appropriate palatal mouthguard design for custom-made mouthguards can be made by considering the aeroacoustical effects. Our study supported the mouthguard whose palatal margin was set at the gingival line by considering the influence on pronouncing sibilant /s/. We believe that a more appropriate palatal mouthguard design for custom-made mouthguards can be made based on the balance of aeroacoustical effects and mechanical requirements.