| BackgrondThe pure titanium is widely used in the field of dental implantology due to its good physical and mechanical properties and highly biocompatibility. Implant denture as human the third vice teeth is widely accepted in recent years for its beauty, comfort and can be a very good recovery on chewing function.There are two different modes of bone healing:contact osteogenesis and distance osteogenesis. Contact osteogenesis is that osteoblasts secrete bone matrix to implant surface directly and then form the bone. The growth direction is from the surface of the implant to the base bone surround the implant. On the contrary, distance osteogenesis is that new bone form in the surface of base bone.The growth direction is from the surface of the base bone surrounding to the surface of implant. The woven bone directly form by contact osteogenesis in the surface of the implant is beneficial to increase the mechanical stability of the implant in the early stage. Establish the conditions of contact osteogenesis as soon as possible would promote bone formation.The rate and degree of bone healing depends on the extent of the implant surface contact osteogenesis.There are two influence factor of contact osteogenesis:1.The biological characteristics of the implantation sites;2. The surface character of the implant.The biological characteristics of the implantation sites is the bone metabolism and bone physiology, including bone density, blood, etc. Different bone structure leads to the different bone biomechanics and different ability of bone healing and bone rebuilding.Studies have proven that when different animal implant the same materal in the same part of body, the results were different. The bone colonization appeared statistically higher in the femur of rabbits (48.5%) than in the tibia (12.6%) and calvaria (22.9%) sites. This slightly higher degree of bone healing was related to differences in the bone architecture of the implantation sites. These different types of bone architecture may lead to different types of biomechanical stress and thus different rates of bone healing and remodeling. Rong implant three implant in three part of rabbit tibial metaphysis. the different implantation sites demonstrated different early osseointegration. However, in the different parts of the jaw, is there any different on the surface of the implant? In which areas of the jaw, contact osteogenesis effect best? There is no more positive results.The surface character of the implant are surface topography, elementary composition, molecular structure, electrical charge, surface free energy, wettability, etc. After treatment, implant can change its surface properties, thus promotes contact osteogenesis, shorten the time needed for bone integration, improve the success rate of planting. In order to shorten the time of implant-tissue intergration effectively, a series of surface treatment technologies have emerged in the past two decades. such as titanium plasma sprayed, hydroxyapatite coating, sandblasting with large grit and acid-etching, double etching,electron beamheat treatmentlaser treatment, anodic oxidation, micro-arc oxidation. Changes insurface topography of the implant surface, elemental composition, molecular structure,charge state,surface free energy, hydrophobic and hydrophilic characteristics, thus changing the biological characteristics of the implant surface. Sandblasting with large grit and acid-etching (SLA) treatment is one of the most common methods to improve implant surfaces in clinic. The holes with diameter10-30μm in the implant surface can be obtained by the large particles blasting, these holes were good for the bone formation. Meanwhile, a large number of pores (size at about1-3μm) were formed by the acid-etched method.It could be said that, the primary roughness was helpful to the osteoblasts adhesion, and proliferation and differentiation of osteoblasts could be stimulate by secondly roughness. There are many research reports about its surface morphology, surface roughness, biocompatibility and osteoconductive properties. SLA suface is most widely used in the world currently.The SLA surface with multi-level pores has been demonstrated enhancement of bone deposition in histomorphometric studies and higher removal torque values in biomechanical testing.However, titanium surface is time-dependent degradation. When the titanium placed in the dark for4weeks would due to aging and reduces protein adsorption compared to a fresh surface.The experimental prove that when the titanium stored in the dark at different times due to the Hydrocarbons increases, protein adhesion reduction, cell adhesion decrease.Ultraviolet (UV) irradiation would prevent titanium surface from time-dependent degradation. Fuminori had found that UV has been applied in surface treatment of implant to obtain super-hydrophilic property, as well as the attachment of osteoblast. Aita found that titanium specimen treated additionally with UV show ssuper-hydrophilic property, and better promote attachment, proliferation, differentiation and mineralization of osteoblast. Studies have shown that the implant which used in clinical exist hydrocarbons contamination. There are statistically significant correlation between the decrease in biological activity and the increase in carbon atoms. Uetsuka and Henderson show that UV radiation can remove hydrocarbons in the titanium surface, and then Ti4+sites exposed. This site promotes the protein and cell-surface interactions, promotes protein adsorption and osteoblast attachment. There are also studies indicate that the static electricity stimulate by UV promote protein adsorption which exceed the effect of surface hydrophilicity in protein adsorption.However, the study about UV focus on physicochemical properties and cytological experiments in the world at present. There are lack of animal experiments.The first purpose of the present study was to establish an animal model of beagle dogs and implant the titanium implant with SLA surface, Observe the contact osteogenesis in different parts of the jaw bone. The second purpose of the present study was to establish an animal model of beagle dogs and implant the titanium implant with SLA surface and SLA+UV surface. Then compare the contact osteogenenisis between the two surface.Materials and Methods:1. Experimental animal:Four one-year-old male beagle dogs (approximate weight14-15kg) were Included in the experiment2. Tooth extraction:After adaptive feeding for one week, the mandibular second, third, and fourth premolar and first molar was extract bilaterally.3. Dental implant:WEGO implant,3.8x9mm, surface treatment is SLA.4. UV radiation:Some of the SLA implant were irradiated by15W UVC germicidal lamp in a sterile environment,10cm close to the material surface, and irradiated48h.5. Grouping:4healthy adult male Beagle dogs were randomly divided into two and four weeks group. A split-mouth study was designed. One side of the mandibular was experiment group, the other side of the mandibular was control group. Every Beagle dog had10implant,5were experiment group and5were control group.6. Implant surgery:After three months of healing, surgical implantation of implant was performed. After general anesthesia which was induced by the injection of Sumian Xin and pentobarbital sodium intramuscularly, the skin and oral mucosa was disinfected. And then a flap was elevated to expose the mandibular bone. With the drill, the planting holes were prepared and10implants were place for every beagle dogs. Each implant received a cover-screw and the mucoperiosteal flaps were sutured to submerge the implants.7. Fluorochrome bone labels:Fluorochrome bone labels were given as single injections subcutaneously oxytetracycline for25mg/kg body weight13days before sacrifice and calcein for5mg/kg body weight3days before sacrifice.8.The animals were sacrificed after2and4weeks. The jaws were dissected, and blocks containing the implant specimens were obtained. All specimens were fixed in10%neutral buffered formalin solution for48h.9.Micro CT examination:The mandibular specimens were fixed in10%formalin,and then move to70%alcohol. X-ray tube voltage:90KV, Electricity:45μA, Projection:720perspectives, Integral time:0.5s, Image resolution:15μm. Take the area around implant coarse thread45μm to300μm and300μm to600μm for3D reconstruction and then calculate the bone volume fraction.10. The preparation of bone biopsy:The specimens were dehydrated,infiltrated and embedded for nondecalcified sectioning. Blocks were serial sectioned parallel with the long axis of the implant in a buccolingual direction and ground to a final thickness of approximately30μm. Upon completion of the fluorescent light examination, all sections were stained with methylene blue-fuchsin acid for histopathologic and histomorphometric analysis using light microscopy.11.Observe osteogenesis differences from different parts of the implant in the jaw. The first part is300μm distance from the bottom of the implant to Cortical bone, the second part is300-600μm distance from the bottom of the implant to Cortical bone, the third part is exceed600μm distance from the bottom of the implant to Cortical bone.12.Evaluation of new bone area around implant and calculate the BIC in group SLA and SLA+UV.13.Statistical analyses:The experimental data are expressed as mean±standard deviation (SD). Statistical analysis was carried out by SPSS(?) v13.0software (SPSS Inc., Chicago, USA). For the single factor data, when meet the normal distribution and homogeneity of variance, using factorial classification ANOVA, then one way ANOVA was using. The LSD multiple comparison test was used for post-hoc analysis to determine which groups were significantly different, and the Levene statistic was used to test homogeneity of variances. If did not pass the Levene test, The Dunnett’s T3multiple comparison test was used. A p<0.05was considered statistically significant.Results:1.During the experiment, all animals showed uneventful healing of the surgical area. Finally, postoperative infections were not observed.2.The sample general observation:the histological sections revealed that none of the titanium implants were dislocated from their original position.3.Micro CT observation:From adjusted by section, every facial of the implant can be observed. Target can be the overall division measurement, slice in any direction, get more complete data. Three-dimensional reconstructed45-300μm,300-600μm around implant coarse thread. Many slender bone trabeculae grew into the thread. Because of the influence of the metal artifacts,0-45μm is not clear. Hard tissue section can only take one direction of cross section, but of the implant surface0-45microns region shows clear. It is a good way to observe the direction of the implant surface osteogenesis, contact osteogenesis phenomenon can be seen clearly.4.Magenta acidic methylene blue staining:Different distances between implant and cortical bone, different amounts of new bone in the thread. In two weeks, when the distance between the bottom of implant and cortical bone was about300μm, many new bone grew into the thread; when the distance between the bottom of implant and cortical bone was about300-600μm, some new bone grew into the thread; when the distance between the bottom of implant and cortical bone was exceed600μm, few new bone grew into the thread. In four weeks, when the distance between the bottom of implant and cortical bone was about300μm, many new bone grew into the thread; when the distance between the bottom of implant and cortical bone was about300-600μm, some new bone grew into the thread; when the distance between the bottom of implant and cortical bone was exceed600μm, few new bone grew into the thread.Bone histomorphometry:Test BIC and new bone area of the different distance between implant and cortical bone. The BIC and new bone area of the area under300μm between implant and cortical bone>the area300-600μm between implant and cortical bone> the area more than600μm between implant and cortical bone in two weeks and four weeks. The closer between the bottom of the thread and cortical bone, the better results of implant-bone contact.5.The early osteogenenisis of Ultraviolet Irradiation on Sandblasted and Acid-etched Titanium implant Surfaces.(1) Fluorescence analysis。In two weeks, fluorescence are scattered around the implant and thread, mainly focus on implant thread. More fluorescence distribute at cortical bone than bone marrow cavity. In groups SLA, fluorescence are mainly focus on the skew wall of the thread and the arounding of implant. In groups SLA+UV, except the skew wall of the thread and the arounding of the implant, many fluorescence focus on the bottom of implant thread. In four weeks, except the inside of the thread and the arounding of the implant, new bone was found in the area of bone marrow cavity. There are more fluorescence scattered in group SLA than group SLA+UV.(2)Methylene blue-acid fuchsin staining:At two weeks, New bone trabecular number comes from the surrounding bone,crawling along the implant thread in group SLA. In gorup SLA+UV, new bone not only grew along the inclined wall of the thread, but also in the bottom of the thread. At four weeks, new bone grew among the thread, haversian system was not seen obvious among the thread in group SLA, in group SLA+UV, many new bone was not only found in the inclined wall of the thread but also at the bottom of the thread. Contact osteogenesis is very obvious. Haversian system was seen among the thread.(3)Bone tissue metrology analysis:In two weeks and four weeks, the BIC of group SLA+UV> the BIC ofgroup SLA. The difference was statistically significant.But the difference of the new bone area with two groups were not statistically significant. Conclusion:l.This beagle dog mandible model simulated the clinical situation and can be used to investigate bone formation around implant. The new planting model can be more clearly observed the effects of different surface treatments on osteogenesis.2.Micro CT can be used to measure the bone with three-dimensional structure,and it has the advantage of continuity and integrity. But because of the existence of the metal artifacts, the implant-bone interface of osteogenesis reflect poor condition. Hard tissue sliciing is a single-layer tissue section and the production process is complicated, and will destroy the integrity of the specimen. But the subtle changes of implant surface osteogenesis reflect clearly.3.The closer from bottom of thread to cortical bone, the better implant-bone contact.4. Group SLA+UV have better contact osteogenesis, and the BIC%is higher in group SLA+UV than in group SLA. |
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