title: Association of masticatory performance with age, gender, number of teeth, occlusal force and salivary flow in Japanese older adults: is ageing a risk factor for masticatory dysfunction?
abstract: OBJECTIVE
  In general, ageing is a risk factor for sensory and motor deterioration, with the rate of decline varying amongst individuals. Concerning masticatory function, missing teeth along with oral disease seem to accelerate the dysfunction. Here, we aimed to confirm whether masticatory dysfunction by ageing is inevitable. This study investigated the effect of age, gender, number of natural teeth, occlusal force and salivary flow on the masticatory performance in a large sample of elderly adults.
  
  
  METHODS
  The study sample consisted of 1288 independently living people aged 60-84 years. Masticatory performance was determined by the comminuted particles of test food. Bilateral maximal occlusal force in the intercuspal position was measured with pressure sensitive sheets. Stimulated whole saliva was collected.
  
  
  RESULTS
  Masticatory performance was significantly correlated to age, number of residual teeth, occlusal force and stimulated salivary flow rate by Pearson's correlation test. The multiple linear regression analysis showed that, with other variables controlled, masticatory performance was significantly associated with the number of residual teeth (β=0.456, P<0.001), occlusal force (β=0.244, P<0.001) and stimulated salivary flow rate (β=0.069, P=0.003). Age was not related to masticatory performance (β=-0.007, P=0.753).
  
  
  CONCLUSIONS
  Declines in the number of residual teeth, occlusal force and salivary flow were associated with a reduction of masticatory performance in older adults. If tooth loss is not considered as an attribute of physiological ageing, then ageing by itself may not be a risk factor for masticatory dysfunction.
authors.affiliation: Department of Prosthodontics and Oral Rehabilitation, Osaka University Graduate School of Dentistry, 1-8 Yamadaoka Suita, Osaka 565-0871, Japan. ikebe@dent.osaka-u.ac.jp
authors.forename: Kazunori
authors.initials: K
authors.lastname: Ikebe
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Matsuda
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Kagawa
authors.forename: Kaori
authors.initials: K
authors.lastname: Enoki
authors.forename: Minoru
authors.initials: M
authors.lastname: Yoshida
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Maeda
authors.forename: Takashi
authors.initials: T
authors.lastname: Nokubi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001732:Bite Force; D003430:Cross-Sectional Studies; D003817:Dentition; D005260:Female; D006801:Humans; D057187:Independent Living; D007564:Japan; D007576:Jaw, Edentulous, Partially / Q000503:physiopathology; D008297:Male; D008409:Mastication / Q000502:physiology*; D008875:Middle Aged; D012307:Risk Factors; D012463:Saliva / Q000378:metabolism*; D012636:Secretory Rate / Q000502:physiology; D012737:Sex Factors; D016388:Tooth Loss / Q000503:physiopathology; D014987:Xerostomia / Q000503:physiopathology