Permalink : http://hdl.handle.net/2115/52445

KEYWORDS : microvasculature;dental pulp;occlusal;hypofunction;blood vessel

In clinical orthodontics, hypofunctional teeth are a common problem as it is necessary to move these teeth to be able to restore the occlusal function. Previous studies reported that hypofunctional occlusion could lead to atrophic changes in the microvasculature of the periodontal ligament. However, there is a lack of empirical research on the relationship between hypofunctional occlusion and microvasculature of dental pulp. The purpose of this study is to elucidate details of changes in pulpal microvasculature in the occlusal hypofunctional condition. Twenty-four 7-week-old male Wistar rats were divided into 4 groups: 1 week, 1 month, 3 months, and 6 months after extraction of opposing teeth. To establish an occlusal hypofunctional condition, maxillary left first and second molars were extracted. The mandibular left molar region was used as the experimental group and the opposite sides of the mandible in the same animals were used as the control group. Paraffin cross-sections of the mandibular first molars were stained with hematoxylin-eosin for light microscopic observations. In this study, the terms “Pulpal vascular area” and “Pulp cell nuclear area” refer to the total blood vessel crosssectional area of the dental pulp and the total nuclear area of the dental pulp cells, respectively. The pulpal vascular area and the pulp cell nuclear area in the mesial half of the mandibular first molars were examined at 3 places: 1） in the pulp horn zone, 2） the middle zone, and 3） the root apex zone. All data were expressed as percentages of the measured area. Comparisons of the data in the two groups were performed. The percentages of the vascular area and pulp cell nuclear area in the pulp horn zone were statistically significantly smaller in the experimental group than in the control group at 1 month, 3 months and 6 months, while there were no statistically significant differences between the two groups was observed in the middle and root apex areas. The results suggest that occlusal stimulation affects the microvasculature and the cellular density of the dental pulp in the coronal area of teeth.