title: Association between orthodontic treatment need and masticatory performance.
abstract: OBJECTIVE
  This retrospective cohort study assessed the differences between the masticatory performance of individuals with and without orthodontic treatment need.
  
  
  METHODS
  Masticatory performances of 120 participants with equal numbers of males and females (n = 60 each) with and without treatment need (n = 60 each, determined using the index of the complexity, outcome, and need [ICON]) matched by age and sex were assessed. Participants chewed on test foods at sequences of 20, 30, 40, 40, 30, and 20 masticatory cycles. After sieving the chewed particles, the masticatory parameters (median particle size [MPS], masticatory frequency [MF], and broadness of particle distribution [BPD]) were calculated. The associations between treatment need and the MPS with age, weight, and stature, as well as the relationship between sex and MPS and MF, were assessed.
  
  
  RESULTS
  According to the independent samples t test, MPS of subjects with and without treatment need differed significantly (P < .05) while MF did not. The differences between BPD values reached the level of significance only after 40 cycles of mastication (P < .05). Females showed significantly greater MPS values. Only at the 40-cycle sequence did females in need of treatment chew significantly slower. According to the repeated-measures ANOVA, no significant differences existed (P > .05) between each of the MPS, MF, and BPD values measured at different sequences. No significant correlations were found between MPS and age, sex, or stature (P > .05 [Spearman correlation coefficient]).
  
  
  CONCLUSIONS
  The masticatory performance of individuals with and without treatment need differed for MPS and BPD (at the 40-cycle sequence). Age, weight, and stature did not affect the treatment need and MPS. Females showed poorer results regarding MPS--only at the 40-cycle sequence did females with malocclusion chew significantly slower.
authors.affiliation: Department of Orthodontics, Dental Branch, Islamic Azad University, Tehran, Iran.
authors.forename: Behnam
authors.initials: B
authors.lastname: Khosravanifard
authors.forename: Sepideh
authors.initials: S
authors.lastname: Ghanbari-Azarnir
authors.forename: Hamid
authors.initials: H
authors.lastname: Rakhshan
authors.forename: Seyed Hadi
authors.initials: SH
authors.lastname: Sajjadi
authors.forename: Annahita M
authors.initials: AM
authors.lastname: Ehsan
authors.forename: Vahid
authors.initials: V
authors.lastname: Rakhshan
mesh_terms: D015331:Cohort Studies; D006801:Humans; D008310:Malocclusion / Q000628:therapy; D008409:Mastication; D010316:Particle Size; D012189:Retrospective Studies