The Effect Of Micro/nanorough-surface Implants By Hydrofluoric Acid Etching And Anodizing On Early Osseointegration

Replacing a tooth with a dental implant is the most reliable and effectivetherapy for the patients lacking of tooth, and between the implant and the bonewith perfect osseointegration is necessary to succeed. Howover，the traditionalimplant of osseointegration has a treatment duration of3-6months, whichgreatly affect the work and life of the patients. Therefore how to promoteearly osseointegration of dental implants and increase the earlyweight-bearing capacity of dental implants, so as to shorten the treatmentperiod have become more and more popular in oral implantology clinicalresearch, the treatment of surface in implant dentistry have become animportant issue. In this study, micro/nanorough surface was builted byhydrofluoric acid etching and anodizing at first, which combined both theadvantages of the micro and nano surface. Then early osseointegration wereobserved by micro-CT, histologically and biomechanical test, in order to providea new treatment of implant surface and scientific basis for time-shorttening ofosseointegration in clinical research.Objective：1The aim of the study is to detect the properties of the films, includingsurface morphology, elemental composition and bone biological activity.2Evaluate the effect of micro/nanorough surface by hydrofluoric acidetching and anodizing on osseointegration in early stage of dental implants invivo.Methods：1Micro/nanorough surface construction and testing：the titanium surfacewas polished by sandpaper of silicon carbide, using ultrasonic vibration torinse20minutes in turn of acetone and deionized water. Machined-surfacetitanium with no treatment as the control group; micro/nanorough surface titanium as the experimental group, which was treated by0.5wt%hydrofluoricacid etching for30minutes and later combined with anodisation to formnanotubes. At the end, all the samples were rinsed with acetone, ethanol,deionized water and then drying, plastic package.The titanium surface morphology was observed by field-emissionscanning electron microscope (SEM) and atomic force microscope (AFM).The elemental composition was analyzed by energy dispersive spectrometer(EDS). The bone biological activity was analyzed by X-ray photoelectronspectroscopy after the titanium was immersed in simulated body fluid.2Animal experiments about implant early osseointegration： fortycylindrical screwed titanium implants were randomly divided into twogroups： machined-surface implants as the control group; implants withhydrofluoric acid etched and anodized micro/nanorough surface as theexperimental group (n=20in each group). Twenty Sprague-Dawley rats (3months’old) were included in this study and the operation was done undergeneral anaesthesia with sodium pentobarbital (40mg/kg) given byintraperitoneal injection. After the routine skin preparation, disinfection anddraping, all implants were inserted into the distal femurs of20SD ratsrandomly. Postoperatively penicillin4WU/kg was given for3days toprevention and control of infection.Ten rats were anaesthetised for microcomputed tomography (micro-CT)scanning in vivo at week0and week2after implantation to assessmicro-architectural changes in the bone around, including bone volumefraction (BV/TV，%), trabecular thickness (Tb.Th，μm), trabecular number(Tb.N， mm-1), and trabecular spacing (Tb.Sp， μm). Two weeks afterimplantation，all the rats were then killed and the femurs with implants wereharvested;20samples were examined by histologically. Earlyosseointegration was observed by the light micro-scope and analyze thebone implant contact (BIC%).Twenty femurs with implants were used for the biomechanical test using auniversal material testing system and with the compression speed of2mm/min. Displacement and force were recorded for calculating the maximal pull-outforce (Fmax).Results:1The SEM patterns showed that there was no hole shape or dimple-likestructure in the machined-surface and the machined streaks was clear. Afterhydrofluoric acid etching andanodization, the sharp edge structure ofmicro/nanorough surface was smoothed, and there were a lot number ofcircular or elliptical nanotubes which closed to the size for15to80nm indiameters.2Under AFM observation, the machined-surface was smoothed with nodimple-like structure. The micro/nanorough surface was rough and uniformedsize of the nanotubes. In quantitative roughness analysis showed theroughness of the micro/nanorough surface (31.25±2.45%increased by3.07-fold compared with the machined-surface(7.66±2.18%)(P<0.05).3EDS analysis showed that compared to the machined-surface, there wasF ion in micro/nanorough surface except for O、Ti.4XPS analysis showed that both the characteristics of machined-surfaceand micro/nanorough surface with a bone biological activity because of thedeposition of Ca ion and P ion.5Micro-CT analysis showed that BV:TV, Tb.Th and Tb.N all increasedsignificantly in the micro/nanorough surface compared with themachined-surface(P<0.05), while Tb.Sp decreased significantly in themicro/nanorough surface(P<0.05).6Histological examination: The implants and the surrounding bone wereshown with Ponceau trichrome staining and calcified bone in the stainedslides was distinguished from other tissue by the characteristic colour, for redor brown calcified bone, yellow bone marrow and black implant. There wasmore calcified bone in the micro/nanorough surface compared with themachined-surface. The bone-implant-contact (BIC%) were38.94±9.48%,51.49±12.49%in the machined-surface and the micro/nanorough surface，respectively. There was significant difference between the two groups (P< 0.05).6Biomechanics test indicated that the maximum pull-out forces ofmachined-surface and micro/nanorough surface were64.95±6.11N and81.90±13.10N, respectively. There was significant difference between the twogroups (P<0.05).Conclusions：1Micro/nanorough surface by hydrofluoric acid etching and anodizingshowed good biological compatibility and osteoconductivity, hence a prospectof application of implant surface treatment.2Modification with micro/nanorough surface has a role to stimulate newbone formation could promote dental implants osseointegration in early stageof implantation.