Meeting Abstract

S2.8  Tuesday, Jan. 4  The ontogeny and physiology of daily oral behaviors LANGENBACH, Geerling EJ*; VAN WESSEL, Tim; ACTA, Amsterdam; University of Twente, Enschede g.langenbach@acta.nl

In the masticatory system, muscle activities are the main source of force. The daily jaw muscle activity is a measure for the total daily loading of the tissues involved. The growth of the masticatory system is characterized by large anatomical changes, accompanied by large modifications in existing oral behaviors. Is the daily activity of the jaw muscles crucial for the adaptive responses of bones and muscles during development? In humans long-term recordings showed irregular activity periods of low jaw muscle activity during sleep, while during the day generally longer and higher level activities were found. Children showed a higher number of activities with longer duration than adults. Using radio-telemetry in rabbits, it was revealed that the daily muscle activities characteristics (total activity duration, burst numbers and burst lengths) were not altered during the transition from suckling to chewing and remained largely unaffected during further postnatal development. During low-level activations muscle groups are presumably activated with a relative large degree of independence, while during high-level activations a more common degree of activation exists. Experimental decrease of the food hardness in rats and rabbits showed a significant decrease in the number of daily bursts. These changes in daily muscle activity were accompanied by changes in fiber type composition and to a lesser extent bone properties. These results suggests that, despite the large anatomical and functional changes, the average daily load of the masticatory system by the jaw muscles appears to be established before chewing develops and remains largely unchanged all the way through development. Whenever the daily muscle activity will change, this seems to have a significant effect on the properties of the tissues involved.