Computer-Assisted Dental Implant Placement Following Free Flap Reconstruction: Virtual Planning, CAD/CAM Templates, Dynamic Navigation and Augmented Reality

Abstract

Image-guided surgery, prosthetic-based virtual planning, 3D printing, and CAD/CAM technology are changing head and neck ablative and reconstructive surgical oncology. Due to quality-of-life improvement, dental implant rehabilitation could be considered in every patient treated with curative intent. Accurate implant placement is mandatory for prosthesis long-term stability and success in oncologic patients. We present a prospective study, with a novel workflow, comprising 11 patients reconstructed with free flaps and 56 osseointegrated implants placed in bone flaps or remnant jaws (iliac crest, fibula, radial forearm, anterolateral thigh). Starting from CT data and jaw plaster model scanning, virtual dental prosthesis was designed. Then prosthetically driven dental implacement was also virtually planned and transferred to the patient by means of intraoperative infrared optical navigation (first four patients), and a combination of conventional static teeth supported 3D-printed acrylic guide stent, intraoperative dynamic navigation, and augmented reality for final intraoperative verification (last 7 patients). Coronal, apical, and angular deviation between virtual surgical planning and final guided intraoperative position was measured on each implant. There is a clear learning curve for surgeons when applying guided methods. Initial only-navigated cases achieved low accuracy but were comparable to non-guided freehand positioning due to jig registration instability. Subsequent dynamic navigation cases combining highly stable acrylic static guides as reference and registration markers result in the highest accuracy with a 1-1.5-mm deviation at the insertion point. Smartphone-based augmented reality visualization is a valuable tool for intraoperative visualization and final verification, although it is still a difficult technique for guiding surgery. A fixed screw-retained ideal dental prosthesis was achieved in every case as virtually planned. Implant placement, the final step in free flap oncological reconstruction, could be accurately planned and placed with image-guided surgery, 3D printing, and CAD/CAM technology. The learning curve could be overcome with preclinical laboratory training, but virtually designed and 3D-printed tracer registration stability is crucial for accurate and predictable results. Applying these concepts to our difficult oncologic patient subgroup with deep anatomic alterations ended in comparable results as those reported in non-oncologic patients.

Keywords: 3D printing; augmented reality; computer-aided surgery; dental implants; dynamic navigation; free flaps; static navigation; virtual surgical planning.

Figure 1

(A) Double barrel fibula flap CBCT 16 months after irradiation with 70 Gy. A basal reconstructive plate and a crestal miniplate. (B) Scanned lower jaw plaster model merged with the CBCT and virtual tooth design. (C) Prosthetically driven implant planning and in blue the teeth supported rigid splint designed with windows for insertion verification. (D) Lingual view seen from the floor of the mouth of the crestal fibula segment and the prosthetically driven implant placement. (E) VSP, preoperative implant planned position superimposed in the CBCT (F) Postoperative orthopantomogram.

Figure 2

Initial protocol example, from the ablative surgery to the final orthopantomogram (A) Right segmental mandibulectomy. (B) Double-barrel fibula flap in place. (C) Postoperative orthopantomography. (D) Redundant fibula skin paddle. (E) Implant placement virtual surgical planning with Nobel Clinician-DivX software. (F) Teeth supported silicone jig holding the 3D-printed dynamic reference frame. (G) Intraoperative screen view of the navigated handpiece and the real-time drilling trajectory. (H) Handpiece and patient’s optical markers ready for dynamic navigation. (I) Still redundant skin paddle after implant surgery. (J) Intraoral view after vestibuloplasty and implant second phase. (K) Screw retained porcelain fused to metal fixed prosthesis lingual view. (L) Final occlusion. (M) Final panorex with the prosthesis in place.

Figure 3

(A) Virtual model of the surgical guide with four pinholes (red) for intraoperative registration and a socket for the attachment of the dynamic reference frame. (B) 3D-printed biocompatible teeth-supported resin guide holding the dynamic reference frame during computer-assisted surgery in a right hemotingue epidermoid carcinoma reconstructed by means of an ALT with vastus lateralis free flap.

Figure 4

Calibration of handpiece tool prior to dynamic navigation. (A) Surgeons recording reference points in the tool calibration platform. (B) 3D model of the calibration platform.

Figure 5

Visualization layout during dynamic navigation. (A) 3D view of the handpiece position during drilling with respect to the virtual surgical plan. (B) 2D target view to control linear deviation of the handpiece tip at the entry crestal point. (C) 2D target view to control angular deviation of the drilling trajectory.

Figure 6

Verification of implant position using augmented reality visualization. (A) Surgeon using a smartphone inserted into a sterile cover. (B) Augmented reality visualization of the virtual surgical plan overlaid on the patient’s anatomy.

Figure 7

Metrics used to compare the final position of implants with the preoperative virtual surgical plan.

Figure 8

Virtual surgical planning in yellow comparison with final intraoperative position. Excellent accuracy in implants 1,2,4,5, mismatch error in implant 2. Implant 2 while inserting into an extremely narrow alveolar bone developed a vestibular complete fenestration. We intraoperatively corrected the position freehand seeking adequate bone volume. Since this implant is not guided, we withdrew the final result from our study.

Figure 9

(A) Mismatch between the initial 2-mm drilled holes suggested by the static splint (see white arrows) and the final intraoperative implant position achieved with dynamic navigation guidance. (B) Static splint-based dynamic navigation accuracy is higher than static navigation alone in this double-barrel fibula case. Postoperative implant position analysis, the achieved position in red, the virtual surgical planned position in green.