The purpose of this study was to reveal the structural properties that need to be considered in dental implant treatment by investigating differences between dentulous and edentulous maxillae in the three-dimensional (3D) microstructure of the incisive canals (ICs) and their surrounding bone. A total of 40 maxillary bones comprising 20 dentulous maxillae and 20 edentulous maxillae were imaged by micro-CT for 3D observation and measurement of the IC and alveolar bone in the anterior region of the IC. The Y-morphology canal was most frequently observed at 60% in dentulous maxilla and 55% in edentulous maxilla. There was a significant difference between dentulous and edentulous maxillae in IC diameter and volume, but no significant difference between the two in the major axis of the ICs. The anatomic structure surrounding the IC has limited area for implant placement. Therefore, where esthetic and long-term maintenance requirements are taken into account, careful attention is needed when setting the placement position. Also, due to the resorption of bone, edentulous maxillae have a different IC morphology from dentulous maxillae, and therefore, a cautious approach is required.

Owing to a rapid increase in aging population in recent years, the deterioration of motor function in older adults has become an important social problem, and several studies have aimed to investigate the mechanisms underlying muscle function decline. Furthermore, structural maintenance of the muscle–tendon–bone complexes in the muscle attachment sites is important for motor function, particularly for joints; however, the development and regeneration of these complexes have not been studied thoroughly and require further elucidation. Recent studies have provided insights into the roles of mesenchymal progenitors in the development and regeneration of muscles and myotendinous junctions. In particular, studies on muscles and myotendinous junctions have—through the use of the recently developed scRNA-seq—reported the presence of syncytia, thereby suggesting that fibroblasts may be transformed into myoblasts in a BMP-dependent manner. In addition, the high mobility group box 1—a DNA-binding protein found in nuclei—is reportedly involved in muscle regeneration. Furthermore, studies have identified several factors required for the formation of locomotor apparatuses, e.g., tenomodulin (Tnmd) and mohawk (Mkx), which are essential for tendon maturation.

Jin ZW, et al. Anat Cell Biol. 2019 Aug;52:e14. https://doi.org/10.5115/acb.19.020

A decline in the body’s motor functions has been linked to decreased muscle mass and function in the oral cavity and throat; however, aging of the junctions of the muscles and bones has also been identified as an associated factor. Basic and clinical studies on the muscles, tendons and bones, each considered independently, have been published. In recent years, however, research has focused on muscle attachment as the muscle–tendon–bone complex from various perspectives, and there is a growing body of knowledge on SRY-box9 (Sox9) and Mohawk(Mkx), which has been identified as a common controlling factor and a key element. Myostatin, a factor that inhibits muscle growth, has been identified as a potential key element in the mechanisms of lifetime structural maintenance of the muscle–tendon–bone complex. Findings in recent studies have also uncovered aspects of the mechanisms of motor organ complex morphostasis in the superaged society of today and will lay the groundwork for treatments to prevent motor function decline in older adults.