Haruyuki Kawahara

Biological evaluation on glass ionomer cement.

Biological properties of a new dental cement of glass ionomer cement were compared with other types of conventional cement. The biological test was carried out by tissue culture method and animal examination. The culture cells showed weaker reaction to the glass ionomer cement than zinc oxide-eugenol or polycarboxylate cement. Pulp tissue reaction showed no significant difference between glass ionomer and zinc oxide-eugenol cement from in vivo experiments using monkeys.

Osseointegration under immediate loading: biomechanical stress-strain and bone formation--resorption.

During the past 10 years, clinicians have used two-piece implants as a one-piece system for immediate loading to accomplish early recovery for function and esthetics. The statistical analysis by the Institute of Clinical Materials demonstrates high survival rates of 92.3 ± 8.3%. Animal experiments of beagle dogs have been carried out to analyze successful conditions of immediate loading according to the dependency of bone formation–resorption upon the biomechanical stress–strain of bone. Histometric investigations clarified that the micromotion of less than 30 &mgr;m at the implant–bone interface did not interfere with the osteogenesis and new bone growth at the implant–bone interface. Bone formation and resorption are discussed from the standpoint of minimum effective strain on living bone.

Cellular Responses to the Dispersion Amalgams in vitro

Three dispersion amalgams were tested in vitro. Spherical-D and Dialloy showed very similar effects on the cells as did the Spherical and fine cut amalgams. The other dispersion amalgam, Dispersalloy, had intense and persistent cytotoxicity even 24 hours after trituration. Difference of the results was presumed to result from different alloy composition.

Electron Microscopic Study of the Cytotoxicity of Cadmium and Mercury In Vitro

The cells treated with cadmium chloride showed severe changes: ribosomes disappeared, mitochondria showed various degrees of destruction, and the endoplasmic reticulum had a swollen and beadlike appearance. In cells treated with mercuric chloride, ribosomes increased in their density and rosette-like polysomes were predominantly observed. The effects of these two metallic ions were discussed.

In Vitro Studies of Cellular Responses to Heat and Vibration in Cavity Preparation

Fibroblasts in tissue culture responded to heat and vibration induced by dental drilling at varying speeds. The in vitro findings suggest that pulpal responses are more likely caused by severance of odontoblastic processes than by the factors studied.

Studies on the tissue adhesive capability to titanium by dynamic wettability test and cell attachment, in vitro

Abstract To investigate better methods of surface treatment of cleaning and sterilization for a titanium implant, measurements of contact angles to water and the critical surface tension were made and the iniial cell attachment on the treated surfaces of cp titanium was also observed. The results showed that cleaning using acetone, or acetone with 4% hydrofluoric acid treatment, yielded smaller contact angles and high critical surface tension values. On the other hand, treatment of detergent cleaning represented a large contact angle and a low critical surface tension. However, the initial cell attachment did not differ, regardless of these surface treatments and/or sterilization.

New Titanium Alloy of Ti-Fe-O-N for Dental Implant

Ti-6Al-4V alloy (Ti-Al-V) is used in dental implants and artificial hip joints to take advantage of its higher mechanical strength compared to cp Ti. However, the toxicity of vanadium and aluminum in the titanium alloy has been reported by several investigators since 1965. This study was carried out to compare the mechanical properties and the biocompatibility of Ti-Fe alloy (TiX®) to those of conventional metallic implant materials. The mechanical properties of TiX® were measured and compared with cp Ti, Ti-Al-V, SUS316, SUS304, Co-Cr-Mo, and Ag-Sn. The tensile strength of TiX® and Ti-Al-V were greater than those of Co-Cr-Mo, SUS316, and SUS304. The yield point of TiX® was slightly lower than that of Ti-Al-V, but higher than that of cp Ti. These results suggested the mechanical properties of TiX® were superior to those of Co-Cr-Mo, SUS316, and SUS304. To evaluate the biocompatibility, cell culture technique with L929 cells was used to investigate the cell multiplication, and SEM to investigate the morphological change of adhered cells onto TiX®. The cell growth rate of TiX® was slightly higher than those of Ti-Al-V and SUS316. Severe cytotoxicity was observed in Ag-Sn, and mild cytotoxicity in Ti-Al-V, SUS316, SUS304 using gyratory culture method. These results revealed that TiX® is a useful metallic material for wire, plate, porous, and mesh in dental and medical use, because of the favorable biocompatibility and easy fabrication.

Histometric Investigation on Bone Contact and Bone Occupancy around Sapphire Implant

Two-piece implants have became to be mainstream because osteogenesis and osseointegration were disturbed by micromotion at the implant bone interface under the biting stress of mastication [1, 2]. In recent year, two-piece implants have been used as a one-piece implant of single stage for immediate placement and immediate loading to accomplish early recovery of function and esthetics, and the survival rates demonstrated 80 to 100% [3, 4]. Statistical analysis of Institute of Clinical Materials, ICM on 55 immediate loading implants demonstrated high survival rate of 92.3±7.3% for 10 years or more [5]. These high survival rates were performed with recent progress in diagnosis of accurate predictability on bone quantity (morphology) and quality (density). As a inevitable result, one-piece implants of single stage might be revived as a latest implant procedure. Clinical investigations on sapphire screw implants of single stage demonstrated high survival rates of 92.65±8.40% [6, 7]. In this study, histometric measurement on bone contact and bone occupancy to/around the implant surface were carried out for the purpose of analyzing the successful condition of the sapphire screw implant under functional load.

Histometric Analysis on Crestal Bone Loss around Implant Neck

Statistical investigations on single stage implants have clarified high survival rates of 80% or more for 10 years over [1]. Clinical investigations on sapphire screw implants of single stage demonstrated high survival rates of 92.65±8.40% [2, 3]. This study was carried out to clarify causes of crestal bone loss around implants neck by histometric investigation using sapphire screw implants of single stage [4] implanted into monkey’s mandibles and maxillae and compare the crestal bone losses between the both implants loaded and unloaded..

Initial Implant Stability: Clinical Testing Methods and its Evaluation

Introduction Since immediate placement and/or loading procedure was introduced for dental implant, quantitative primary fixture stability measurement has become essential examination to achieve its predictability. Quantitative mobility measurement using PeriotestTM or resonance frequency analysis (RFA) immediately after fixture install, or maximum torque during fixture install surgery have been reported to ensure clinical predictability. However inter-relationships of quantitative values by means of these instruments is still unknown very well. The objective of this study is confirm these parameters interrelationships.