Relationship between upper and lower molars during mastication.
OBJECTIVE
This study investigated the relationship between upper and lower molars in the early stage of mastication.


METHODS
We measured the occlusal contact areas during chewing test foods using the three-dimensional shape measurement system and the six-degree-of-freedom mandibular tracking device. The reference points corresponding to "A" and "B" occlusal contacts were selected from the surface of upper dental cast (UA, UB) and lower dental cast (LA, LB). The distance between reference point UA and LA, UB and LB were calculated (/A/, /B/). For evaluation of relationship between upper and lower molars during chewing gum, the ratios of /A/ / /B/ (AB ratio) were calculated. First 10 consecutive cycles of chewing gum were divided into two phase, early five strokes group (Ge) and last five strokes group (GI). Paired t-test for AB ratios of Ge and GI was performed.


RESULTS
Paired t-test showed a significant difference between AB ratios of Ge and that of GI at 0.5 mm away from the terminal position of masticatory movements (p < 0.05).


CONCLUSIONS
This result suggests the possibility that the path of mastication is influenced by the change of texture of foods with the progress of mastication in early stage of mastication.
Okayasu
Haruo
H
Department of Restorative Sciences, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
Miura
Hiroyuki
H
Okada
Daizo
D
Shin
Chiharu
C
D000328:Adult; D001732:Bite Force; D002638:Chewing Gum; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D007574:Jaw Relation Record; D008297:Male; D008334:Mandible; D008409:Mastication / Q000502:physiology*; D008437:Maxilla; D003765:Models, Dental; D008963:Molar / Q000033:anatomy & histology* / Q000502:physiology; D009068:Movement
D002638:Chewing Gum