Tetsuji Kusumoto

Effect of nanosheet surface structure of titanium alloys on cell differentiation

Titanium alloys are the most frequently used dental implants partly because of the protective oxide coating that spontaneously forms on their surface. We fabricated titania nanosheet (TNS) structures on titanium surfaces by NaOH treatment to improve bone differentiation on titanium alloy implants. The cellular response to TNSs on Ti6Al4V alloy was investigated, and the ability of the modified surfaces to affect osteogenic differentiation of rat bone marrow cells and increase the success rate of titanium implants was evaluated. The nanoscale network structures formed by alkali etching markedly enhanced the functions of cell adhesion and osteogenesis-related gene expression of rat bone marrow cells. Other cell behaviors, such as proliferation, alkaline phosphatase activity, osteocalcin deposition, and mineralization, were also markedly increased in TNS-modified Ti6Al4V. Our results suggest that titanium implants modified with nanostructures promote osteogenic differentiation, which may improve the biointegration of these implants into the alveolar bone.

Effect of Amelogenin Coating of a Nano-Modified Titanium Surface on Bioactivity

The interactions between implants and host tissues depend on several factors. In particular, a growing body of evidence has demonstrated that the surface texture of an implant influences the response of the surrounding cells. The purpose of this study is to develop new implant materials aiming at the regeneration of periodontal tissues as well as hard tissues by coating nano-modified titanium with amelogenin, which is one of the main proteins contained in Emdogain®. We confirmed by quartz crystal microbalance evaluation that amelogenin is easy to adsorb onto the nano-modified titanium surface as a coating. Scanning electron microscopy, scanning probe microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy analyses confirmed that amelogenin coated the nano-modified titanium surface following alkali-treatment. In vitro evaluation using rat bone marrow and periodontal ligament cells revealed that the initial adhesion of both cell types and the induction of hard tissue differentiation such as cementum were improved by amelogenin coating. Additionally, the formation of new bone in implanted surrounding tissues was observed in in vivo evaluation using rat femurs. Together, these results suggest that this material may serve as a new implant material with the potential to play a major role in the advancement of clinical dentistry.

Functions of the masticatory muscle characterized by muscle-microvibration. 2 Muscle-microvibration during relaxation and contraction of the masseter and anterior temporal muscles.

The purpose of this paper was to investigate microvibration on the masticatory muscle (M-MV), the possibility of its use for studying the functions of masticatory muscle and its usefulness of clinical application.M-MV amplitudes of the masseter muscle (Mm) and the anterior temporal muscle (Ta) were measured in different mandibular positions with and without tooth contact. The signal analysis procedure consisted of observations on analogue waves of Mm and Ta and of assessment of M-MV amplitude (the root mean square, RMS) with AID converter and micro-computer (sampling frequency: 100 Hz, points: 512).The results obtained were as follows:1) It was considered that M-MV of Mm and Ta at the mandibular rest position most probably originated from the system of circulation (Apexcardiographic activity).2) M-MV amplitudes of Mm and Ta upon further opening from the rest position were almost the same as those at the rest position and were synchronized with Apexcardiographic activity, but were larger with various degrees of closing from the rest position and were not synchronized with Apexcardiographic activity.3) With changes of the horizontal mandibular position without tooth contact, M-MV amplitudes of Mm at all the eccentric positions and that of Ta at the retrusive position except the protrusive and lateral positions were increased and not synchronized with Apexcardiographic activity.4) There were marked increases in the relations of activity in the recordings from Mm and Ta during muscle contraction compared with those at the rest position.5) It was shown that the typical pattern of M-MV amplitude for Mm and Ta at centric occlusion was smallest in all horizontal and vertical occlusal positions.6) M-MV amplitudes of Mm and Ta were increased by experimental muscle fatigue.7) It was considered that M-MV during muscle contraction originated from vibrations of the muscle fibers.

Functions of the masticatory muscle characterized by muscle-microvibration. 1 Validity of the measurement system with the improved accelerometer.

An attempt was made to apply microvibration (MV) on the skin surface of the skeletal muscle to investigate some functions of the masticatory muscle.The purpose of this study was to investigate the influences of the weight and the methods used for attaching the improved accelerometer on the acceleration output of the masseter muscle (Mm) and the anterior temporal muscle (Ta).For this purpose, the transmissibility on the skin surface of Mm and Ta of the vibration table driven by the regular continuous sinusoidal vibration was measured by sweeping the vibration frequency from 1 to 60Hz.Furthermore, the validity of this measurement system for MV with the improved accelerometer was checked by the other method using photoelectric principles without the sensing element making contact with the body.The results obtained were as follows:1) From investigations of the weight of the accelerometer (4, 8 and 12g), the accelerometer weighing 4g was considered appropriate.2) A comparison of three methods of attachment (surgical-tape, double-faced tape and adhesive) to Mm and Ta showed there was little difference between them.3) The transmissibility measured by the improved accelerometer corresponded to that measured by the photoelectric method.4) From the transmissibility for Mm and Ta, for a vertical directional vibration, the vibration behaviors of Ta showed a double resonance system and those of Mm showed a triple system, while for a horizontal directional vibration, those of Ta and Mm showed a single resonance system.