title: Does gum chewing increase the prevalence of temporomandibular disorders in individuals with gum chewing habits?
abstract: OBJECTIVE
  The effect of habitual gum chewing on temporomandibular joint function is controversial. This study evaluated the prevalence of temporomandibular disorder (TMD) in adolescents with and without gum chewing habits and the affiliation of TMD signs with gum chewing.
  
  
  METHODS
  This is a cross-sectional study. Subjects were studied in 2 groups. Subjects in the study group chewed gum for 30, 60, or 120 minutes in a 24-hour day. Subjects in the control group did not have a gum chewing habit. TMD signs of clicking, crepitus, and pain were documented for every subject. Age, gender, duration of gum chewing, and occlusal relationships were variable factors, and TMD signs (clicking, crepitus, and pain) were outcomes of the study. The chi-square test was used to compare TMD signs and gender in the 2 groups, and to evaluate the relationship between TMD signs and duration of gum chewing in the study group. An independent t test was applied to compare the ages of the 2 groups.
  
  
  RESULTS
  Two hundred subjects participated in the study and were divided into 2 groups (100 subjects per group). An evaluation of the data showed no significant differences between the 2 groups in sex, age, and occlusion. The incidence of clicking and pain was statistically higher in the study group than in the control group (P < 0.05). Analysis of the data demonstrated considerable differences in clicking and pain among subjects with various gum chewing times in the study group (P < 0.05). The incidence of pain was higher in subjects with a class II skeletal pattern than others in the study group (P < 0.001). Nevertheless, no significant difference was noticed for clicking among subjects with various occlusions (P > 0.05).
  
  
  CONCLUSIONS
  Considering that intensive gum chewing may affect TMD signs in individuals with a gum chewing habit. It seems a longer duration of gum chewing may increase the prevalence of TMD. Individuals with a class II skeletal pattern may be affected more than others.
authors.affiliation: From the *Oral and Dental Health Care Research Center, Department of Oral and Maxillofacial Surgery, Shiraz University of Medical Sciences, Shiraz; and †Shiraz University of Medical Sciences, Shiraz, Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Tabrizi
authors.forename: Touba
authors.initials: T
authors.lastname: Karagah
authors.forename: Ehsan
authors.initials: E
authors.lastname: Aliabadi
authors.forename: Seyed Ali
authors.initials: SA
authors.lastname: Hoseini
mesh_terms: D000328:Adult; D000367:Age Factors; D016022:Case-Control Studies; D002638:Chewing Gum / Q000009:adverse effects*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007492:Iran / Q000453:epidemiology; D008297:Male; D008409:Mastication / Q000502:physiology; D010146:Pain / Q000209:etiology; D015995:Prevalence; D012737:Sex Factors; D013705:Temporomandibular Joint Disorders / Q000453:epidemiology / Q000209:etiology* / Q000503:physiopathology; D013997:Time Factors; D055815:Young Adult
chemical_list: D002638:Chewing Gum