Surgical techniques: computer-guided surgery
The general principle is to create a virtual image of the jaws through a CT imaging technique (CT scan or CBCT), and a computer 3D reconstruction software. Radiopaque landmarks, included in the images through a radiographic template, allow the simulation of a prosthetic-driven virtual surgery.
A surgical tool (solid guide or live navigation images) is produced and used during actual surgery, so that the clinician is guided to comply with the virtual planning.
The folllowing definitions have been proposed (Hammerle et al., 2009): Computer-assisted surgery consists of the use of 3D imaging software, to combine prosthetic planning with the anatomical structures.
Computer-guided surgery is the use of a static surgical template that reproduces the virtual implant position directly from computed tomographic data and does not allow for intraoperative modification of the implant position.
Computer-navigated surgery is the use of a surgical navigation system that reproduces the virtual implant position directly from computed tomographic data and allows for intraoperative changes in implant position. Also called real-time navigation.
Products and Devices
The CT scan or CBCT data are processed with specific software, allowing the production of a precise 3D reconstruction of the jaw, including prosthetic information of the radiographic template. After virtual surgery, planned implant positions are transferred to a precise surgical template by a stereolithographic process. The template includes fixation devices and drill guides. It can be used by the laboratory before surgery to elaborate a provisional implant-supported FPD, that will be placed at the end of the surgery.
Special devices are securely attached:
- to the patient (during CT radiographic examination and during surgery)
- to the handpiece of the clinician.
During implant surgery, the system records the position of the handpiece and the position of the patient (by infra-red camera, laser or tactile device) and reproduces a 3D real-time image of the situation in progress.
Accuracy is a critical factor which may limit the technique. Accuracy is evaluated by comparing the planned position of the implants with the result after actual implant placement (Table 35.1). Some deviation can occur between the two positions for the entry point, the apex, the axis, and the vertical position of the implant.