Abstract: Navigation-guided surgery has recently been introduced into
various surgical disciplines, including oral and maxillofacial surgery.
Since the advent of dental implants, dental computed tomography (CT)
scans have been used as a diagnostic tool for preoperative planning, but
not as part of the surgical phase. This article explains the principles of
computer-assisted surgery and describes the use of a computer-guided
navigation system in dental implantology. The system uses preoperative
dental CT scans for planning and as an integral part of the surgical procedure. This system allows continuous intraoperative coordination of the
implantation phase with the preoperative plan, optimizing the accuracy
of implant surgery. Deviations from the planned location of the implants
are minimal. Several cases are discussed.
I
mage-guided surgery (IGS), also called computer-assisted surgery, was
recently introduced in many surgical specialties.1 These systems are similar in principle to the Global Positioning System; they combine tracking technology with a highly accurate road map of a patient’s anatomy, so
that the surgeon can navigate within the surgical field. The high-speed processing unit can track the movement of the surgical instruments, calculate
their position within the surgical field, and display the instruments in relation to the patient’s anatomy detailed from the imaging data. During the surgical procedure, the surgeon can view an image of the surgical instruments
superimposed on the detailed image of the patient’s anatomy (Figure 1).
History
Image-guided surgery was first introduced into neurosurgery,
2 f o llowed by other surgical fields, including oral and maxillofacial surgery.
3
H o w e v e r, the implementation of this technology to the field of dental
implantology was delayed because of 2 obstacles. The first obstacle was
related to the fact that conventional IGS had to be performed under full
anesthesia with a completely fixed surgical field. Early attempts to use
this technology with dental implants were limited to the fixed upper
j a w.
4 The second obstacle was related to the accuracy of the available
systems. Accuracy was reported to be in the range of 2 mm to 5 mm.
3
Although this level of accuracy is beneficial in some surgical proced u r e s ,5 – 1 0 it is unacceptable for dental implant surgery.
Tracking Technologies
Two elements require tracking during IGS: the real-time position of the
patient and the position of the surgeon-operated handpiece. Currently,
there are 4 types of tracking technologies: electromechanical, sonic, electromagnetic, and optical.11,12 Electromechanical tracking relies on detectors
located within the joints of a mechanical arm system. It is cumbersome and
doesn’t achieve the required accuracy because of
imprecise registration and elasticity of the arms
and joints.
Sonic tracking determines position by measuring the time needed for the sound from an
emitter to travel to a microphone array of known
g e o m e t r y. This technique is influenced by temperature changes, which may lead to inaccurac i e s .
Electromagnetic tracking superimposes a
magnetic field around the area of interest. The
position can be determined by using a probe that
can detect gradients in the magnetic field.
Ferromagnetic substances, aluminum, and electromagnetic radiation may distort the magnetic
fields and impair the accuracy of localization.
Optical tracking is the most commonly used
t e c h n o l o g y. This technique is based on arranging
infrared light-emitting diodes(LEDs) in a known
geometric pattern, attaching them to the patient
in proximity to the surgical field, and installing
them on the surgical instruments. The infrared
emission is detected by a camera and transferred
to a processing unit that reconstructs the position
of the patient and the surgical instruments.
Image-Guided Implantology System
The Image-Guided Implantologya (IGI) is a
newly developed, optically based navigational
system that is specifically designed to facilitate
planning and execution of dental implant placement (Figure 2). Because the system uses a special appliance to track the patient’s head and jaw
movements, immobilization is not required. The
s y s t e m ’s mean spatial navigation error was established to be 0.35 mm.
1 3 In a controlled environment it allows the transfer of the preoperative
plan with a deviation of less than 1 mm,
1 4 w h i c h
is acceptable for dental implants.
The surgeon uses the software to plan the
implants’ positions based on the reconstructed
dental computed tomography (CT) image. The
surgeon assesses the alveolar bone and then identifies and marks critical anatomical structures to
be avoided. With a simulation of the future
restoration, the surgeon can correlate the
implants’ position with the patient’s occlusion,
establishing optimal implant placement for bone
morphology and prosthetic needs. The system
then guides the surgeon in placing the implants
