Biomaterials, titanium or polymers?
A wide range of metal-, plastic- and biomaterials are used to repair and replace damaged bone today. However, no type of implant is currently able to meet all clinical needs, and the question of which material is most suitable for bone reconstruction remains controversial.
Biomaterials allow for natural, degradable implants
Biomaterials ― which may be natural or synthetic ― are often biodegradable, and some are bioabsorbable, meaning that they are gradually degraded or reabsorbed by the body after fulfilling a function. For example, such a function could be to support, enhance or replace damaged tissue or a biological function in the body.
Biomaterials are recognized to have many advantages over non-degradable bone implants in reconstructive- and plastic surgery. Namely, as they possess the desired native qualities of bone, have a lesser risk of migration, infection, and inflammation, accelerate recovery time, and improve aesthetic results. Moreover, discoveries in tissue engineering and regenerative medicine are fuelling demand for biomaterials. (You can read more about how 3D printed biomaterials are used for the creation of lifelike bone research models in the blog post here).
The natural and degradable implant P3D Bone is made from the biomaterial ß-tricalcium phosphate (ß-TCP), belonging to the bioceramic segment which also includes hydroxyapatite, α-TCP, and biphasic calcium phosphates among others.
β-TCP is the major mineral of the intercellular composite of human bones and has been used clinically for reconstructing and filling bony defects in orthopedic surgery and dentistry for 30 years. Now, by 3D printing the bioceramic material, Particle3D creates implants that are far less dense than usual and not only replace damaged bone, but encourage new bone to grow back.
The β-TCP material demonstrates favorable biocompatibility, osteoconduction with a rapid formation of new vascularized bone, and a simultaneous and balanced biodegradability.
As new bone marrow and blood vessels develop inside the implant, it gradually remodels into the patient’s own living bone.
Although bioceramics represent the preferred material type for bone reconstruction ― of which β-TCP is the most commonly used degradable bone graft ― implant manufacturers widely use non-biodegradable materials such as titanium, polymers, or bioceramic-polymer mixes.
Foreign body materials with high loading tolerances
Manufactured implants, particularly those that are patient specific, generally use non-degradable materials such as polymers or titanium. These are foreign body materials that don’t behave like organic matter like biomaterials, and are associated with high complication rates, namely infection. Unlike biomaterial-based implants that support strong bone ingrowth, implants made from plastic or metal are permanent. However, they demonstrate favorable load-bearing properties that are required for some bone implants where the stability of the bone is affected.
One of the most widely used synthetic materials, polyetheretherketone (PEEK), has the favorable properties of being biocompatible, resistant to thermal and ionizing radiation, and resembles cortical bone biomechanically. Additionally, it is suitable for load-bearing implants in reconstructive surgeries. In consequence, PEEK has proved useful in complex reconstructions of maxillofacial and cranial defects.
Meanwhile, titanium is the most widely used material for patient specific bone implants, especially in orthopedic surgery. Titanium provides great mechanical properties with a compressive strength that is required for load-bearing indications; for example in the knee or hip. This adds another level of safety in terms of stability with which biomaterials cannot compete.
Particularly, for bone repair in lower limp orthopedic surgery, the loading tolerance of the material is of vital importance, therefore favoring titanium. If bioceramics were to be used in such indications where the stability of the bone is affected, a titanium plate would likely need to be added. On the other hand, when used in cranial- and facial indications, the compressive strength of bioceramics is satisfactory, and the degradable biomaterials prove to be safer and better than foreign body materials on several parameters.