Review Force encoding by human periodontal mechanoreceptors during mastication Mats Trulsson * Institute of Odontology, Karolinska Institutet, Box 4064, S-141 04 Huddinge, Sweden 1. Introduction To control masticatory movements and forces the brain use sensory signals from a variety of sense organs in the orofacial structures. One important source of information is the period- ontal mechanoreceptors. 1–3 These nerve endings are often described as Ruffini-like and are located close to the collagen fibres in the periodontal ligament. 4,5 When a force is applied to the tooth, the tooth moves slightly in its socket. This movement induces stresses and strains in the periodontal ligament and the receptors have been shown to respond maximally when the ligament in which they reside is in tension. 6 a r c h i v e s o f o r a l b i o l o g y 5 2 ( 2 0 0 7 ) 3 5 7 – 3 6 0 a r t i c l e i n f o Article history: Accepted 12 September 2006 Keywords: Afferent Microneurography Sensory-motor control Tooth Chewing a b s t r a c t This overview summarises current knowledge on the force-encoding properties of period- ontal mechanoreceptors supplying the human postcanine teeth and describe their signalling during chewing. Microneurographic experiments reveal that these receptors adapt slowly to maintained tooth loads. Similar to periodontal receptors at anterior teeth, about half respond to forces applied to more than one tooth and their receptive fields are broadly tuned to direction of force application. However, population analyses demonstrate that periodontal receptors supplying anterior and posterior teeth differ in their capacity to signal horizontal and vertical forces, respectively. Most periodontal receptors exhibit a strongly curved relationship between discharge rate and force amplitude, featuring the highest sensitivity to changes in force at forces below 1 N for anterior teeth and 4 N for posterior teeth. Also the dynamic sensitivity is markedly reduced at high forces. According to a quantitative model of responses in periodontal receptors based on these data, most receptors efficiently encode food contact during chewing, but due to the marked saturation tendencies at higher forces these receptors poorly encode the magnitude of the strong chewing forces and the force changes occurring at these high loads. Information provided by periodontal receptors is critical for the specification of manip- ulative forces used when food is positioned between the teeth and prepared for chewing. When the strong chewing forces are applied to crush the food, the receptors signal functionally important information about the mechanical properties of food as well as the spatial contact patterns between the food and the dentition. # 2006 Elsevier Ltd. All rights reserved. * Tel.: +46 8 5248 80 36; fax: +46 8 746 79 15. E-mail address: mats.trulsson@ki.se. a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / a r o b 0003–9969/$ – see front matter # 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.archoralbio.2006.09.011