Influence of Masticatory Functional Loss on the Remodeling of Alveolar Bone in Rats

Kei Ogawa,Takamichi Yamada,Yurie Okada,Norimitsu Hirai,Takehiko Shimizu,Wataru Morita,Seiko Yamamoto-Nemoto

doi:10.4236/ojst.2020.1012032

Abstract

There is plenty of literature on masticatory function and its impact on maxillofacial development. However, the influence of masticatory hypofunction on bone turnover in the alveolar bone has hardly been studied. This study aimed to clarify the influence of tooth loss and soft diet on the alveolar bone turnover during the growth period. Three-week-old Wistar rats were randomly divided into the following three groups: Hard diet group (rats raised on solid standard diet), Powder diet group (rats raised on powdered standard feed diet), and Extraction group (rats raised on powdered standard diet with maxillary molars extraction). BV, BMC, and BMD in the cancellous bone of M1 were measured using micro-CT analysis. To analyze the histological bone turnover, we prepared non-decalcified thin sections of alveolar cancellous bone when rats were 20 weeks old. On three-dimensional constructed images, the experimental groups (the Powder diet and Extraction groups) showed expansion of the medullary cavity of the interradicular septum of the first molar compared to controls (the Hard diet group). BV, BMC, and BMD were significantly lower in the experimental groups, with the difference from controls being greater in the Extraction group. On histomorphometric analysis, the bone mass parameters, bone formation parameters, and bone mineralization parameters were significantly lower in the experimental groups compared to controls. The bone resorption parameters were significantly higher in the experimental groups. From this study, we found that soft diet and tooth loss might worsen the bone microstructure, reduce osteogenesis, and promote bone resorption in alveolar bone.

Highlights

Amid the growing popularity of processed food and soft food diets, children increasingly prefer softer foods that require fewer mastication iterations and less time for mastication
In the three-dimensional constructed images, both the Extraction group and the Powder diet group showed expansion of the bone medullary cavity of the interradicular septum of the first molar compared to the Hard diet group
In the Extraction group, we reduced masticatory stimulation to the mandibular alveolar bone even further by extraction of molars, simulating a case of congenital hypodontia or premature tooth loss caused by dental trauma or dental caries

Summary

Introduction

Amid the growing popularity of processed food and soft food diets, children increasingly prefer softer foods that require fewer mastication iterations and less time for mastication This preference for softer foods may affect the child’s maxillofacial development, narrowing the jaw and tooth rows and resulting in malocclusion. There are many experiments on reduced chewing stimulation with a soft diet These experiments showed a reduction in maxillary width, mandibular height and mandibular condyle thickness, and expansion of the size of the mandibular angle [2] [3] [4] [5] [6]. Our previous research showed masticatory hypofunction in rats, due to extraction of maxillary molars and a diet of powdered feed, was associated with reduced mandibular volume, bone density, mandibular height, and mandibular condyle thickness [7] [8]. It is reported that new bone was added at the outer layer of the alveolar bone, with an atrophic change in the periodontal ligament fibers [17]

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