Development of the jaw sensorimotor control and chewing - a systematic review.

Mastication is a complex sensorimotor interaction between the central nervous system and the peripheral masticatory apparatus. To understand the effect of oro-facial abnormalities on mastication, it is important to first understand the normal development of jaw sensorimotor control and chewing in healthy children. Original studies which investigated four main objective parameters of chewing, i.e. maximum occlusal bite force, electromyography (EMG), jaw kinematics and chewing efficiency in children were systematically searched using three established databases. The targeted sample was healthy children below the age of 18-years. All studies that subjectively assessed mastication, studies of children with abnormalities, or non-English studies were excluded. A total of 6193 papers were identified, 53 met the final inclusion criteria. Results are presented according to the dentition stage. Children below 6-years (primary dentition) had lower biting forces and EMG activity, and the frontal jaw movement pattern was more laterally displaced and less stable than children older than 6-years. EMG activities and bite forces increased in children 6- to 10-year-old (early mixed dentition) with a reduction in lateral jaw displacement and an increase in vertical jaw displacement. Twelve-year-old children were able to chew food into smaller particles compared to 6-year-olds. Gender differences were visible in all parameters except EMG activity in late mixed dentition (10- to 12-years). After 12-years, there was a significant increase in bite forces and EMG activities, and the frontal jaw pattern became similar to adults. Studied chewing parameters gradually improve with the development of the oro-facial structures and were mainly influenced by dental eruption. A significant development of chewing parameters occurs after 12 years of age. A transition to the adult-type of masticatory behavior occurs between 10- to 14-years of age.