Change in Trigeminal Mesencephalic Neurons after Teeth Extraction in Guinea Pig.

Abstract

Trigeminal mesencephalic (Mes V) neurons innervating the periodontal mechanoreceptor ( PMR) are known to play an important role in controlling the bite force and jaw-movements during mastication.After teeth loss, the PMR disappears due to loss of the periodontal membrane. The present work is a study on whether cell death is induced in the Mes V neurons in association with teeth loss. The upper and lower incisors were extracted on the right side in 5 guinea pigs (extraction group) and the other 5 guinea pigs were kept intact (control group) . In the extraction group, the animals were kept alive for 58-119 days after teeth extraction. Serial coronal sections (50pm thick) were made of the midbrain and pons and stained with cresyl violet. The Mes V neurons were counted on every other section. In the caudal half of the Mes V nucleus, where the neurons innervating the PMR are reported to be located, the number of neurons was less on the right side than on the left side (P (0.01) in the extraction group, while there was no difference between the right and left sides in the control group. We conclude that teeth extraction can induce cell death in the Mes V neurons innervating the PMR and produce a significant change in the brainstem mechanisms controlling mastication.

Hippocampal Glutamate Release on Learning and Memory in Teeth-loss Rats

“…20 Aoki et al 21 reported that feeding a soft diet inhibited cell proliferation in the dentate gyrus of the rat hippocampus. Kimoto et al 22 conducted a morphological study in rats and proved that tooth loss caused not only receptor loss but also neuro-nal death in the mesencephalic nucleus of the trigeminal nerve. In the present study, molars were extracted from relatively young rats in the EXT group; the rats in this group must have received reduced sensory input from the periodontal membrane to the central nervous system.…”

“…24,25 In addition, reduced information input has been shown to induce neuronal death, 26 suggesting a reduced population of hippocampal pyramidal cells. Tooth loss appeared to not only cause the death of the neurons in the mesencephalic nucleus of the trigeminus 22 but also induce hippocampal dysfunction, thus impeding learning and memory.…”