title: Relationship between upper and lower molars during mastication.
abstract: 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.
authors.affiliation: 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.
authors.forename: Haruo
authors.initials: H
authors.lastname: Okayasu
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Miura
authors.forename: Daizo
authors.initials: D
authors.lastname: Okada
authors.forename: Chiharu
authors.initials: C
authors.lastname: Shin
mesh_terms: 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
chemical_list: D002638:Chewing Gum