| Background and Objection:Titanium has been widely used for orthopedic and reconstructive implants in oral and maxillofacial region due to its excellent mechanical properties and biocompatibility since osseointegration was confirmed by researches. The functional capacity of implant depends mainly on the quality of interface between the implant and bone. Hence, the characteristics of implant surface play an important role on the progression towards osseointegration. Titanium surface with moderate roughness has been considered to be suitable for osteoblast to attach, proliferate and differentiate on in comparison with the smooth one. In order to obtain a relatively rough titanium surface which has an affinity to osteoblast for rapid osseointegration, various surface modification techniques, such as grit blasting, chemical etching, anodic oxidizing and plasma spraying, are employed in optimizing the physical and chemical properties of implant surfaces.Sandblasting with large grit and acid-etching (SLA) treatment is one of the most common methods to improve implant surfaces in clinic. 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, conventional SLA surface is kept dry in the air and made hydrophobic. It has been found that hydrophobic surface would prevent water from spreading on while hydrophilic one which is easier wet by water could enhance the interaction with surrounding biological environment and promote protein adsorption and MC3T3-E1osteoblast response. Hence, modified SLA (modSLA) surface with similar morphology makes the change to be protected in liquid from contamination of hydrocarbons in the air and is proved hydrophilic and beneficial for gene expression, osteoblast behaviors, bone mineralization and early osseointegration.Recently, ultraviolet (UV) irradiation has been applied in surface treatment of implant to obtain super-hydrophilic property. Titanium specimen treated additionally with UV shows better biocompatibility compared with those completed by single modification. In addition, the bioactivity of acid-etched titanium surface has been found to degrade over time due to the accumulated amount of hydrocarbons contamination. Interestingly, the old specimen preserved for a long time could be recovered by UV treatment and showed even better affinity than the fresh one to protein adsorption and attachment, proliferation, differentiation and mineralization of osteoblast, as well as the in vivo capability of osseointegration. However, the biocompatibility of titanium surface treated jointly with SLA and UV irradiation has not yet been studied and, furthermore, comparison among SLA, modSLA and UV-SLA surfaces could contribute to analyzing the different biological functions resulted from different wettability properties and hydrocarbons contents.The purpose of the present study was to establish a comparison model composed of three kinds of rough titanium surfaces with similar morphology and relatively homogeneous chemical composition and to evaluate the influence of different wettability properties and hydrocarbons contents on their biocompatibility. Also, the biological characteristic of UV-SLA surface was accessed.Methods and materials:1. Preparation of experimental specimens:Strictly select and control various parameters of surface treatments to combine sandblasting, acid-etching, preservation in water, UV irradiation and et al techniques to prepare relatively consistent and repeatable SLA, modSLA and UV-SLA surfaces with multi-pores morphology and moderate roughness.2. Detection of physical and chemical properties:measure the morphology, roughness, elemental composition and wettability with scanning electron microscopy, optical profilometer, X-ray photoelectron spectroscopy and contact angle measuring device, respectively, to assess the physical and chemical properties of SLA, modSLA and UV-SLA surfaces.3.1n-vitro assay of bioactivity:measure the morphology, attachment, proliferation, differentiation and mineralization with scanning electron microscopy, confocal laser scanning microscopy and cellular tests, respectively, to assess the in-vitro biocompatibility of SLA, modSLA and UV-SLA surfaces.4. In-vitro detection of ability of mineralization:measure the quality, morphology, composition and crystalline phase of deposited mineralization after lw,2w,3w and4w immersion in SBF to assess the in-vitro induction ability of SLA, modSLA and UV-SLA surfaces.Statistical analyses:The experimental data are expressed as mean (*)±standard deviation (s). Sample size (n) was three. Statistical analysis was carried out by SPSS v13.0software (SPSS Inc., Chicago, USA). After checking for normal distribution and homogeneity of variances, Factorial design variance analysis was used to detect the main effects and interaction of factors. Then, data were analyzed using one-way analysis of variance (ANOVA) followed by Post hoc Bonferroni tests for severe multiple comparisons. When observed values were distributed normally but variances were not homogeneous, Welch test and Dunnet’s T3multiple comparison test were applied to compare data among groups. When observed values were not distributed normally or variances were not homogeneous, non-parameter analysis of Kruskal-Wallis H test and Nemenyi multiple comparison test were applied to compare data among groups. The hypothesis test was a two-sided test and the test level was0.05. Probabilities (P)<0.05was considered to be statistical difference and P＜0.01was considered to be significantly statistical difference.Results:1. Relatively consistent and repeatable SLA, modSLA and UV-SLA surfaces which were consistent with the expected design were achieved by strictly selecting and controlling various parameters of surface treatments.2. Analysis of physical and chemical properties showed SLA, modSLA and UV-SLA surfaces had similar topography with multi-level pores characterized by10-30μm pits and1～3μm micropits and possessed moderate Sa of approximate2.43μm. But there were significant differences of hydrocarbon content, wettability and SFE among groups. Compared with the hydrophobic SLA surface with low SFE (23.16mN/m) and high content of C (32.01%At), both modSLA (25.31%At C) and UV-SLA (14.26%At C) surfaces acquired hydrophilicity and high SFE (74.06mN/m). Meanwhile, UV-SLA surface obtained a large number of hydrophilic groups--OH (60.90%At O).3. In-vitro assay of bioactivity showed that the morphology of MG63osteoblast on different surfaces were fine. Hydrophilic modSLA surface showed better affinity to mineralization of MG63cells than hydrophobic polluted SLA surface at14d (P<0.01). Furthermore, UV-SLA surface with super-hydrophilicity had most greatly promoted the attachment, proliferation, differentiation and mineralization of MG63cells (P＜0.05or P＜0.01).4. In-vitro assay of ability of mineralization showed that the quality of mineralized tissue deposited on UV-SLA surface was much more than those of SLA and modSLA surfaces at3w (P<0.05). At4w, the deposited mineralized tissues with greater Ca-P ratio on UV-SLA (3.23±0.35mg) and modSLA (2.13±0.95mg) surfaces which increased in a large amount to cover the entire surface were, respectively, approximately eight and five times of that on SLA surface (0.43±0.15mg). The difference was considered statistically significant. XRD analysis indicated that the deposited mineralized tissue was composed of apatite.Conclusion:Hydrocarbons were found to be an important influencing factor to compatibility of biomaterials. In addition, preservation in dH2O could effectively maintain the bioactivity of rough surface and UV irradiation was recognized as a trustworthy method for surface cleaning without change of topography and roughness and could ever lead to greater biocompatibility of sandblasted and acid-etched titanium surface. |
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