A study on restorative effect of strontium-loaded nanotube-based pure titanium implants on alveolar bone defects

HE Jiahuan; SONG Liye; CHENG Bingkun; TIAN Xiaomei; LIU Yingqi

doi:10.3969/j.issn.1674-3806.2025.07.11

Abstract：Objective To explore the restorative effect of strontium-loaded nanotube-based pure titanium(Ti)implants on alveolar bone defects.Methods Thirty 3-month-old Sprague-Dawley(SD)rats were selected for experiment and were randomly divided into blank group,nanotube group and strontium-loaded nanotube group,with 10 rats in each group.Smooth cylindrical implants without screw threads(with a diameter of 4.5 mm and a length of 8 mm)were made of pure Ti.The implants in the three groups were treated differently.For the implants in the blank group,no treatment was given after conventional polishing.The implants of the nanotube group were treated using hydrofluoric acid solution with a mass fraction of 0.5％,with graphite as the cathode and the implants as the anode,and anodic oxidation treatment at a voltage of 20 V for 1 hour.The implants of the strontium-loaded nanotube group were treated with 0.02 mol/L strontium hydroxide solution in a sealed water bath at 200 ℃ for 1 hour on the basis of the treatment of the nanotube group.The incisors of the left mandible of the rats were extracted,and the prepared alveolar sockets were rinsed with normal saline.The implants were placed in the alveolar sockets about 8 mm deep from the edge of the gingiva,approximately at the position of the root of the first molar.Then,the wound was sutured using 5-0 absorbable sutures.Five rats in each group were sacrificed at the 4th and 12th weeks after operation,respectively,and mandibular specimens were taken for detection.The elemental composition of the implant surface was analyzed using an energy spectrum analysis tool of Energy Dispersive Spectrometer built in the electron microscope.The surface roughness of the implants was detected by using atomic force microscopy.Micro-computed tomography,Masson staining and immunohistochemistry staining were used for histological evaluation.Results Compared with those in the blank group,the Ti content detected on the surface of the implants was decreased,while the oxygen(O)content and fluorine(F)content detected on the surface of the implants were increased in the nanotube group and the strontium-loaded nanotube group.The F content detected on the surface of the implants in the strontium-loaded nanotube group was higher than that in the nanotube group.Compared with that in the blank group,the surface roughness of the implants in the nanotube group and the strontium-loaded nanotube group was increased significantly(P＜0.05),and the surface roughness of the strontium-loaded nanotube group was greater than that of the nanotube group(P＜0.05).Compared with those in the blank group,bone volume/total volume(BV/TV),bone surface/bone volume(BS/BV)and trabecular thickness(Tb.Th)in the nanotube group and the strontium-loaded nanotube group were significantly increased at the 4th week after operation(P＜0.05).At the 12th week after operation,compared with those in the blank group and the nanotube group,BV/TV,BS/BV and Tb.Th in the strontium-loaded nanotube group were significantly increased,while there were no statistically significant differences in BV/TV,BS/BV and Tb.Th between the nanotube group and the blank group(P＞0.05).At the 4th and 12th weeks after operation,there were no statistically significant differences in trabecular number(Tb.N)and trabecular spacing(Tb.Sp)among the three groups(P＞0.05).The Masson staining results showed that a large amount of thick mature bone tissues were formed around the bone defect area of the strontium-loaded nanotube group,while the nanotube group and the blank group had less bone mass and lacked integrity in the formation of new bones.At the 12th week after operation,compared with those in the blank group,the positive staining areas of osteopontin(OPN)and bone morphogenetic protein 2(BMP2)in the bone defect site of the rats in the nanotube group and the strontium-loaded nanotube group were increased,and the positive staining areas of OPN and BMP2 in the bone defect site of the rats in the strontium-loaded nanotube group were larger than those in the nanotube group,with statistically significant differences(P＜0.05).Conclusion Strontium-loaded nanotube-based pure Ti implants can promote the restorations in alveolar bone defects.