Biomedical subjects

R Wigianto

Publications and source records attributed to R Wigianto.

6 recordsLinked to original sources

PubMed2000

Bone changes around hydroxyapatite and titanium implants after abutment placement in rabbits-observations using histological and three-dimensional examinations.

We have previously developed a computer-aided system for examination of the three-dimensional bone structure around implants and observed the bone changes in the healing period after implant placement. This paper describes the bone changes around hydroxyapatite (HA) and titanium (Ti) implants after abutment placement using histological and three-dimensional examinations. Twenty-four HA and Ti implants were embedded in the tibias of adult male New Zealand white rabbits. After 8 weeks, the abutment had passed through periosteum and was placed under the skin. Rabbits were sacrificed 4 and 8 weeks following abutment placement. In conclusion, histological examination showed that, at 4 weeks after abutment placement, bone resorption around the implant neck was seen in both HA and Ti implants, and at 8 weeks, excessive bone formation was seen around the implant neck. Three-dimensional bone examination showed that abutment placement may affect bone formation and cause additional bone hypertrophy in the bone marrow area.

Animals↗

PubMed1999

Three-dimensional bone structure around hydroxyapatite and titanium implants in rabbits.

Long-term support of dental implants requires adequate bone thickness in the area surrounding the implant. A three-dimensional examination, including calculations of percent bone-implant contact and percent bone volume, was conducted to clarify the bone structure around pure titanium (Ti) and dense hydroxyapatite (HA) implants. The implants were installed in the tibiae of rabbits, and the bone structure was examined after 2, 4, 6 and 8 weeks. The bone formation following implantation differed in the cortical bone and cancellous bone areas. In the cortical bone area, the percent bone-implant contact and percent bone volume were comparatively consistent for both Ti and HA implants during the observation period. In the cancellous bone area, both findings were influenced by the implantation period, and the chronological bone structure in the cancellous bone area also differed between Ti and HA implants. The percent bone-implant contact and percent bone volume in the Ti implant increased over 8 weeks, whereas the dense HA implant increased for the first 4 weeks and then decreased. The implant materials, Ti and HA, affected the bone remodeling in the cancellous bone area.

Analysis of Variance↗

PubMed1997

Three-dimensional examination of bone structure around hydroxyapatite implants using digital image processing.

This study introduced a new method for three-dimensional (3D) examination of the bone structure around an implant and presented 3D bone-implant contact rates. A block of nondecalcified implant tissue was ground gradually at an interval of 80 micrograms for the collection of serial two-dimensional (2D) images. An image of the stained block surface was instantly recorded by a charge-couple device (CCD) camera and computer-aided system. A 3D model was reconstructed from 60-70 sheets of serial 2D images. The 3D bone structure around the implant was shown in perspective and displayed all sides of the implant. The bone-implant contact rate depended on the cutting position and direction in the specimen. The 3D model will be necessary and valuable for the biomechanical study of dynamic bone changes around implants.

Animals↗

PubMed1997

Influence of bone quality on the stress distribution. An in vitro experiment.

Adequate bone quality and stress distribution to the bone are of decisive importance for implant success. The purpose of this in vitro study was to investigate the influence of bone quality on the stress distribution using 2 implant-bone mimicking models, simulating compact and cancellous bone quality. The resin model was made of an acrylic resin only simulating compact bone quality. The hybrid model was made of 2 kinds of materials, acrylic resin covered with a 1-mm layer of urethane to simulate cancellous bone quality. An implant was embedded in each model, and the abutment and suprastructures were connected to the implant. A strain gauge was placed perpendicular to the implant on the surface of the model and a small accelerometer was attached to the abutment. When an impact load was applied to the suprastructure, both strain and acceleration were measured. Both abutment acceleration and surface strain in the hybrid model decreased rapidly as time progressed when compared to the resin model. Abutment accelerations in the resin model were significantly lower than those in the hybrid model. In the hybrid model, the strain increased as the loading site was moved closer to the strain gauge. The influence of loading sites on strain in the resin model was greater than in the hybrid model. Therefore, the occlusal stress was distributed more widely in the hybrid model than in the resin model. This may indicate that occlusal stress in compact bone may have a tendency to concentrate in particular regions.

Acrylic Resins↗

PubMed1996

Rapid bone resorption adjacent to hydroxyapatite-coated implants.

This paper describes rapid bone resorption in the peri-implantitis of HA implants based on both our clinical observations of and histological research on extracted dense hydroxyapatite (HA) implants. The surfaces of extracted HA implants were rough, although they were smooth at fixture placement. Plaque formed on the necks of the implants, whereas little plaque was seen on the bottoms. The plaque consisted of cocci and rods, including filamentous bacteria. Few spirochetes were observed. Although surrounding bone was formed rapidly around the HA implant, bone thickness gradually decreased compared with the titanium implant. These facts suggest that the rigid biointegration of HA with the thin surrounding bone--that is, the overstressing of the bone--causes rapid bone resorption rather than plaque accumulation on HA.

Adult↗

PubMedDate not supplied

In vitro study of mandibular implant-retained overdentures: the influence of stud attachments on load transfer to the implant and soft tissue.

This study investigated the occlusal stress distribution to the implant and soft tissue for the implant-retained overdenture. The stress at the molar residual ridge and the strain around the implant were measured on an experimental resin cast using static and dynamic loading. The influence of connecting structures of stud attachments on stress distribution was discussed. The occlusal stress had a tendency to concentrate on the implant, especially in the areas distal to the implant. The modified magnetic attachment system, using a silicone-covered magnet, provided the optimal stress distribution.

Bite Force↗