3D Printing with Porous Ti6Al4V for Improved Dental Implants

As implants continue to be a challenge for dental patients, researchers from Taiwan are experimenting with better ways to accommodate bone defects after failed implants must be removed. Results of their study are outlined in ‘3D laser-printed porous Ti₆Al₄V dental implants for compromised bone support.’

Lack of suitable and supporting alveolar bone is a common issue for dental patients with failed implants, and especially those who have developed inflammation with peri-implantitis. Defects may cause less attachment and bone regeneration, along with decreased clinical improvement. With bone tissue engineering via bioprinting (here, Bio-ActiveITRIdental implants were fabricated on the EOSINT M 280 system) the authors foresee a range of new possibilities for patients through the ability to create tissue scaffolds with features like:

• Internal architecture
• Porosity
• Interconnectivity
• Patient-specific dimensions

Procedures of animal experiment. Osteotomy defect (T-shaped; 7.5 mm (D)
7.0 mm (L) on the top and 3.5 mm(D)
3.0 mm (L) at the bottom) was prepared at the lateral aspect of distal femoral condyle of New Zealand white rabbit. Either side was randomly inserted with the NobelActiveäimplants (control group) or the Bio-ActiveITRIdental implants (ITRI group). At 4,8 and 12 weeks after the implant insertion, animals were sacrificed by injection of pentobarbital.

Implants were tested on rabbits, with the specimens available both for X-ray and CT assessment, along with biomechanical analysis. Bone ingrowth was tested at different implant locations, with each area evaluated. Biomechanical testing exhibited the effect the histologic responses on implants, along with ‘progressive increase’ in strength as related to bone growth, along with mineralization and maturation of the engineered tissue. Implants with a rougher surface tended to show better osseointegration, compared to the control group samples with smoother surfaces.

Micro-CT analysis. Radiographs of the distal part of the femur were taken with its orientation both perpendicular andparallel to the long axis of the long axis of implant and then the subjects were positioned in the in micro-CT scanner in a cra-niocaudal orientation with suitable stabilization. Datasets were reconstructed using CTvox 2.4 software. The tissue volume (TV:mm3), bone volume (BV: mm3), percent of bone volume (BV/TV: %), trabecular thickness (Tb.Th: mm), trabecular separation(Tb.Sp: mm), Total porosity [Po(tot): %], ratio of the segmented bone surface to the total volume of the region of interests (bonesurface/tissue volume; i.e., bone surface density), and interface surface were analyzed; while results of bone mineral density(BMD) was expressed in mg/cm3.

“Although fabricating Ti alloy dental implants with defined porous scaffold structure is a promising strategy for improving the osseoinduction of implants, in a study using laser beam melting 3D printing technique to fabricate  porous  Ti6Al4V  dental  implant  with  three controlled pore sizes (200, 350 and 500mm), the 350 and500mm pore-sized implants demonstrate a better biocompatibility in terms of cell growth, migration and adhesion,” concluded the researchers. “The pore size of 350mm provides an optimal provides an optimal potential for improving the mechanical shielding to the surrounding bones and osseoinduction of the implant itself.

“Further study on the effect of different pore size and porosity without sacrificing their mechanical property is mandatory to optimize the clinical outcome.”

Gross morphology analysis. Control sample (three lower pictures of the left panel) showed fibrous tissue proliferationaround the coronal region of the implants with no secure fixation between the implant and the surrounding bony tissue. Experi-mental ITRI sample (two pictures of the left panel and pictures of right two panels) exhibited active bony proliferation andpenetration of new bone into the porous structures of implants. BarZ4.3 mm in control pictures; BarZ8.1 mm in experimentalpictures.

Bone regeneration continues to be a source of challenge for medical researchers, spanning numerous areas of medicine. In 3D printing the hope is that with patient-specific cells, better sustainability is possible. And while dental implants are important for so many patients today, a wide range of 3D printed implants have been created for the sustainability of bone, from the use of nanofibers with tubes to porous metallic biomaterials, and even titanium alloys.

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