| Biomechanical compatibility and histocompatibility of the dental implants are the basisfor their success and long-term stability. During the dental implant designing procedure, themachinability and other properties of materials such as the shape, length and diameter of thedental implant and abutment, as well as the connection type between them should beconsidered. Meanwhile, attention should be paid to build biomimetic structure on the surfaceof the implant and to systematically research the interaction mechanism between the relatedcells and materials. This research would emphasize on constructing a Titanium-based dentalimplant with calcium phosphate coatings, which is rational in structure, excellent inmechanical properties, and also possess the mimic micro/nano-topological structure of thebone extracellular matrix skeleton as well as the good osseointegration ability. In vitrobiomimetic mineralization test, protein adsorption test and animal experiment were carriedout to determine the osteogenic property of the surface treated implants. And then prospectivehuman trial was done to evaluate the safety and fuction of the plasma sprayed calciumphosphate coating implants. This research could provide vital information for the design andpreparation of the new type of surface modified titanium alloy dental implants with long-termstability so as to meet the requirement of clinical application.According to the mechanics, biomechanics principles, combining with the Chinesehuman teeth and the anatomical characteristics of jaw, we designed a dental implant systemfor clinical use. This dental implant system has two forms: cylinder and threaded cylinderwith five different diameters and five lengths. Their abutment and implant were connected bythe7degree Morse taper, with360degree rotation positioning and platform switchingstructure. When4,5,6,7and8degree tapered abutments are under the preload force of35N·cm, the cold welding appears between the abutment and implant, therefore, the dislocationtorque is5%-10%greater than the preload torque, and no significant difference was foundbetween the different tapered ones. If the preload torque is more than40N·cm, the coldwelding interface will be destroyed. Through the3D-FEA test, we discovered that the stressdistribution was similar among the different degree of the tapered abutments (4-8degree)under vertical and horizontal load, and the stress concentration area was in the neck of theimplant and abutment. With the increase of the taper degree, the stress decreased linearly.Horizontal loaded stress and strain displacement were significantly higher than the verticalloaded one, indicating that the horizontal force had more damaging effects on the structure ofthe implant.3D-FEA test also showed that when implants with0,15,45degree shoulder slope design connected with7degree tapered abutment were similar under the vertical andhorizontal loaded stress, the stress distribution between the implants and the surrounding jawhad no evident differences, and there were also no significant differences in the maximumstress value of cortical bone between the horizontal and vertical loaded stress. Although thestress within the cancellous bone caused by the horizontal loaded stress was increased about1.5times compared with vertical loaded one, the stress position clearly moved to the root ofthe implant, showing that platform switching could effectively reduce the stress concentrationof the bone around the implant neck, therefore, the absorption of bone around implant couldbe reduced, which would be beneficial to the long-term success of implant restoration.In this research, acid etching and sand blasting were carried out to rebuild the surfacetopography on titanium alloy implant. Acid etching was carried out in different types of acidand different HCl/H2SO4treated times. The HCl/H2SO4treated sample surface formedmorphologies with micro and nanoscale topography, which included large pits with diameterof10-20μm constituted by1-2μm diameter pits. Surface examinations were taken to analyzethe influence of the type of acid and the acid etching time on the surface property. Thetopographies were formed by the combination of intercrystal crack and corrosive pitting.These multiscale structures would be able to simulate the produce of the physical signalingfrom the excellular matrix so as to promote the behavior of the bone integrating related cellssuch as the adhesion, proliferation and the differentiation, and eventually, accelerate the boneintegration process.The bone integrating ability of the implants is very important for their stabilization at theearly stage. Plasma spraying technology was also applied in this research to fabricatefunctional calcium phosphate coatings on titanium alloy surface. The parameters, includingthe power, powder diameter and spraying distance were examined to detect their effects onthe properties of the coating, which included the surface morphology, the phase compositionin the coating and density of the coating.Results showed that the parameters of30kw power,110mm spraying distance and20-50μm HA powder diameter would be beneficial to thecoating properties. The acid etched samples and the plasma sprayed samples were immersedinto simulated body fluid to examine their apatite formation ability. After6days of immersion,amphorous ball-like apatite was formed on acid etched sample, while thicker and highercrystalline apatite was formed on the sprayed sample. The mechanism of apatite depositionwas then discussed. Furthermore, the qualitative and quantitative analysis of proteinadsorption on the sandblasting etching and plasma sprayed Ca/P coating surfaces showed thatthere was significant promotion of protein adsorption on the surfaces. The result verified that the newly prepared surfaces were conducive to cell adhesion and proliferation.In vivo implanting experiment of the two kinds of surface treatment of titanium alloyimplant was carried out on rabbit legs. The results showed that two kinds of implants could betightly bound with bone tissue to osseous union, which could significantly improve thebonding strength between the implant and bone tissue, thus accelerate the growth of bonetissue. Further clinical study showed that no liver and kidney damages or complications werefound in the patients. A total of117implant were tested during the3years clinical trials andthe survival rate of the implants was99.2%. An average vertical bone loss of0.07mm wasfound during the first and second stage after surgery implanting. After the restoration of1~3years, panoramic X-ray measurement of bone resorption showed an average value of0.14mm.The index of the implant surrounding and gingival had no obvious changes, which suggestedthat the soft tissue around the implant was healthy and stable. Clinical studies have shown thatdental implant can form effective bone integration, and the structure design of the implantingsystem and surface modification are beneficial to reducing the absorption of bone tissue aswell as maintaining the health and quantities of the soft tissue.This paper systematically described the development of dental implant systems and itsapplication in clinic. Implant surface treatment and the design of implant structure and shapeare the key factors in the clinical application, which were deeply investigated in this research.The clinical studies have also been done for years to prove the safety and efficiency of theprepared biological functional dental implants. |
PDF Full Text Request