Oral parafunctions as temporomandibular disorder risk factors in children.

Oral parafunctions are generally considered to be important factors in the etiology of temporomandibular disorders (TMDs) and many reports have been published about their prevalence in adults and schoolchildren. However, few have included significant numbers of children below the age of 7. The aim of this study was to examine the association between parafunctions and oral/facial TMD-related pain in preschool children. Bruxism, nail biting, and thumb sucking were found to be significantly associated with important oral/facial pain symptoms of clinical interest in the diagnoses of TMD indicating that those parafunctions are risk factors. The study included 525 4- to 6-year-old African-American and Caucasian children, mean age 5.1 +/- 0.65 (SD). An alpha level of 5% was chosen for comparison with a Pearson Chi-Square test. Bonferroni correction was made and a p-value of < 0.005 was accepted as significance level. Only 28% of the children had no history of any parafunction. More girls (82%) than boys (63%) in the Caucasian subgroup had at least one parafunction (p approximately 0.00017). No such difference was found in the African-American subgroup where the corresponding figures were 71% for girls and 73% for boys. Thumb sucking was reported by 57% of the children, more often by Caucasian girls (69%) than by Caucasian boys (43%) (p < 0.00001). Thirty percent still had the habit. Forty-one percent had a history of nail biting. Bruxism was noted in 20% of the children, but occurred mostly in combination with other parafunctions and was seldom (in 3.4%) the only parafunction. Of the 10 pain variables, bruxism was significantly associated with eight, thumb sucking with three, and nail biting with two. Analysis with logistic regression confirmed the results. Association does not, however, tell if a parafunction is the cause or the consequence of pain, or if a third factor is causing both pain and increased prevalence of oral parafunctions. Further prospective longitudinal studies including higher age groups are needed to clarify those relations and to determine if there are long-term effects of childhood parafunctions.