Bone Regeneration Performance Of Trabecular-like 3D Porous Titanium Implants Fabricated By Additive Manufacturing:An In Vivo Study

Three-dimensional laser printing greatly improved the development of materials.As is known,there exist two concerns about titanium,one is that the Young's modulus of it(110GPa)is much higher than that of natural cortical(17~20GPa)and cancellous bone(about 4GPa).The other one is its bone bonding ability.To improve the mechanical and biological properties of titanium implants,According to the biomimetic concept in bone tissue engineering,some researchers proposed trabecular-like 3D porous structure.And many researches in vivo and vitro have been conducted to vertify the bone regeneration performance of this kind of materials.However,for trabecular-like 3D porous structure biomaterial,some important issues are still unresolved.First,it is well known that the porous structure can promote the bone growth into the implant,but bonding strength of bone-implant interface that can be improved has not been evaluated quantitatively,compared to bulk implants.Second,the porosity of natural trabecular bone varies between 50% and 90%,hence the optimal pore characteristics should be confirmed for the design of porous implant.Third,although previous study suggested that the introducing porous structure appears to improve implant stability,whether the porous implant can achieve the enough biological stability with bone tissue in a short time is still unclear.Therefore,the aim of this study is to investigate the bone regeneration performance of trabecular-like 3D porous titanium implants.In order to solve the problems above-mentioned,trabecular-like Ti implants with three porosities(65%,75%,85%,with pore size of 200,350,and 500?m respectively)and one bulk implant were manufactured by AM,and an in vivo experiment was conducted in a rabbit model.To characterize these implants,3D structural analysis using micro-focus X-ray computed tomography(micro-CT)and scanning electron microscopy(SEM)were conducted.Also the mechanical properties were assessed.At last,the biomechanical testing and Non-decalcified histological observation were conducted to evaluate fixation ability and bone formation of each implant.The porous structural analysis showed that porous implants used in this study were similar to natural trabecular bone,and results of mechanical testing were that the Young's modulus(about 5 GPa)of this kind of porous material was closed to natural trabecular bone.The results of both histological analysis and biomechanical tests showed that three porous implants had more bone ingrowth and higher fixation compared with bulk implants at each experimental time-point,among them 75% and 85% groups showed largest bone area and strongest push-out force.With the limitation of this research,we answered three problems mentioned in introduction section and drew conclusions as below: 1)Porous titanium implants showed significantly more new bone ingrowth and higher fixation ability than bulk implants.2)For the trabecular-like porous structure,porosity of 75% and 85%(pore size of 350 and 500?m)is optimal for new bone ingrowth.3)The porous implant can achieve enough biological stability with bone tissue in a short time.