New Study Evaluates Effectiveness of 3D Printed Titanium Implants on Bone Growth

A group of researchers from Korean hospitals conducted a retrospective study to verify the efficacy and safety of patient-specific 3D-printed titanium implants on maxillofacial bones.

A total of 16 patients were observed during the study, each undergoing reconstructive surgery for various maxillofacial defects. Patients were fitted with custom titanium implants and received long-term follow-ups over the course of several months.

Of the 28 implants placed, only one failed to unite with the bone while the others showed “satisfactory” results for the treatment of various oral and maxillofacial defects.

Titanium reconstruction of tumor-induced mandibular defects. Image via nature.

3D printed maxillofacial implants

3D printing has been used for some time to produce guides that improve patient outcomes and has recently begun to be used experimentally to create facial grafts that can be implanted into patients’ skulls. For example, scientists at Texas A&M University have developed a new 3D-printed scaffold that directly facilitates bone cell growth after surgery.

As for more end-use applications, the Industrial Research Center of Quebec (CRIQ) has deployed a GE Additive Arcam Q10 3D printer to accelerate its production of custom-made lower jaw implants, while researchers from Paulista University 3D printed a facial prosthesis for a Brazilian cancer survivor, which included her entire right eye.

More recently, Health Canada approved its first Canadian-made 3D printed medical implant, a customizable mandibular plate intended for use in facial reconstruction surgery primarily for patients with oral problems.

Dental implant on a titanium mandible.  Image via nature.
Dental implant on a titanium mandible. Image via nature.

The retrospective study

Autogenous bone grafting or implant placement is the primary method used to treat oral and maxillofacial defects, and although they are largely biocompatible, there can be issues regarding donor site morbidity, failure surgery and the difficulty of reoperation.

Rapid advances in digital technology have opened up new avenues in the field of oral and maxillofacial surgery, with 3D printing enabling faster and more accurate surgeries, especially when it comes to titanium materials whose biocompatibility has improved. already been verified as dental implants.

The titanium maxillofacial implants used in the surgeries recorded by the study were 3D printed via electron beam melting (EBM) and selective laser sintering (SLS) processes. A total of 28 implants were 3D printed and then inserted into the maxilla (dominant part of the face), mandible (lower jaw) or zygoma (cheek/temple) of 16 different patients.

The patients in question, including seven women and nine men, ranged in age from nine to 78 years old. A total of 28 defective areas were operated on, including five mandibular segments, nine zygomes, ten mandibular bodies, angles or chins and four maxillary areas.

A long-term follow-up process was then conducted, varying in duration per patient from eight to 79 months. The study primarily analyzed bone fusion of the titanium implant body, but also recorded postoperative infection, implant malunion, functional outcomes, patient satisfaction, subsidence, osteolysis around the implants and any complications that have occurred.

The study revealed that of the 28 implants, only one failed to bond to the bone. CBCT analysis showed that bone fusion six months after surgery was 96.5%. The study also observed no osteolysis – a progressive condition where bone tissue is destroyed – or subsidence around the titanium implants.

According to the study, patients who participated in the trial were overall aesthetically and functionally satisfied with the results of their surgery. However, two of the five patients who underwent cheekbone reconstruction underwent revision surgery due to dissatisfaction with the appearance of the implant.

Photographs of patients with Treacher-Collins syndrome.  Image via nature.
Photographs of patients with Treacher-Collins syndrome. Image via nature.

Implant examination

The design of the bone-implant interface of the 3D printed implants was either a mesh or a solid, depending on whether stability was required or not. As the rough surface of the titanium mesh implant was found to be more likely to embed into the patient’s bone, this was preferred.

SLS allows additive manufacturing with metals such as titanium at high sintering temperature, however, due to limited dimensional accuracy and poor surface roughness, process improvements are made to improve its properties. EBM uses an electron beam instead of a laser beam to sinter or fuse materials. EBM can be used to fabricate complex geometries by selectively scanning each cross-sectional layer, unlike SLS.

Implants 3D printed via EBM were more expensive than those 3D printed using SLS, but there was no difference in clinical outcomes regarding implant interface type or 3D printing method .

Follow-up appointments revealed that three of the 16 patients experienced complications such as screw fractures and cosmetic dissatisfaction, but all were eventually resolved and postoperative recovery was satisfactory in all patients.

Based on patient experiences, the study offered guidelines for the use of patient-specific 3D-printed titanium implants. In brief, the study recommends that such implants be used for facial bone continuity defects limited to hard tissues for which reconstruction has already been performed and there is no reconstruction option, and for cases where there is a mild or moderate bone defect due to anterior excessive bone preparation in a patient who has undergone facial osteoplasty.

Additionally, the guidelines indicate that 3D printed titanium implants should also be used in cases with high aesthetic requirements such as the correction of skeletal asymmetry, for areas that require functional loading such as the mandible and when simultaneous reconstruction with dental implants is necessary.

Further information on the study can be found in the document entitled: “Reconstruction of Maxillofacial Bone Defects Using Patient-Specific Durable Titanium Implants,” published in the journal Nature. The study was co-authored by H. Lim, Y. Choi, W. Choi, I. Song and U. Lee.

One of the reconstructive surgery case studies.  Image via nature.
One of the reconstructive surgery case studies. Image via nature.

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Featured image shows titanium reconstruction of tumor-induced mandibular defects. Image via nature.

Sara H. Byrd