Periodontal Masseteric Reflex is Changed by Periodontal Sensory Modification during Occlusal Hypofunction in Rats

The purpose of this study was to investigatechanges in the periodontal masseteric reflex(PMR) after experimentally induced occlusalhypofunction. Wistar rats were divided into controlgroups (CGs) and hypofunction groups (HGs).Rats in the HGs had their lower incisors cut downevery other day for 6 weeks. Electrical stimulationwas given to the periodontal ligaments of anupper incisor or the left trigeminal mesencephalicnucleus (MeV) in the CGs and HGs. Recordings ofmasseter motor unit responses were performed at0, 1, 2, 4 and 6 weeks after hypofunction.Compared with the CGs, significant longer latenciesin the PMR were found in the 4w- and 6w- HGs.After MeV stimulation, no significant difference inlatency was found between HGs and CGs. Afterperiodontal stimulation, the threshold value ofmasseteric motor-unit responses was higher inHGs than in CGs in 4and 6 weeks respectively.These results suggest that the PMR can bechanged by periodontal sensory modification duringocclusal hypofunction.