IT HAS BEEN ONE OF THE ALLURING ASPECTS OF GUIDED SURGERYTO AVOID AN INCISION AND FLAP Digital technology greatly aids this communication, in the initial stages of treatment by allowing three-dimensional (3D) information that details the availability of bone and ideal position of the restoration via cone beam computed tomography (CBCT) with a radiographic guide that can later be converted to a surgical guide. Recent advances in computer aided design and computer aided manufacturing (CAD/CAM) allow the fabrication of highly accu- rate surgical guides that facilitate precise implant positioning. More specifically, the use of CAD technology can be utilized in implant surgery by taking CBCT images and using specialized software to virtually place implants. In turn, the resulting imaging can be shared between the surgeon, restorative den- tist and laboratory (Figure 1). This serves as an excellent communication tool and helps reduce potential discrepancies between the desired and actual implant positioning. The CBCT will show the surgeon where the crown will be from the radiographic guide, the restorative doctor can see where the surgeon plans to place the implant (based on availability of bone), and the laboratory can provide valuable input to the surgeon and restorative doctor. If the position of the implant is acceptable to all parties, the radiographic template can be converted into a manually fabricated surgical guide, or modifications can be made. It is also possible to place virtual restorations on the implant if a radiographic template was not made. In addition, clinicians can super- impose the CBCT on the patient’s 3D scans or stone models (Figures 2A and 2B), with our without wax-ups. Besides virtual treatment planning, providers can implement all-digital workflows — from scanned impressions to surgical placement through a 3D-image-guided template, and, ultimately, milling of the restoration.1 As might be expected, approaches to the fabrication of surgical guides have evolved over the last 15 years. At first, the guides were designed to be placed on bone, then on soft tissue and later on teeth (Figures 3A and 3B). This technology requires great accuracy in order to yield predictable outcomes, and this article will address this issue in detail. Placing 3D-image-guided implants entails two levels of “complete- ness,” which has led to the distinction between fully guided and partially guided. Assuming there is adequate keratinized gingiva, the fully guided approach allows for flapless surgery, full drilling with vertical control of the drills through the guide, and placement of the implant through the guide 12 Decisions IN DENTISTRY • December 2017 with a vertical stop (Figures 4A and 4B, page 14). At this time, however, not all implant products allow the use of the fully guided approach. In a partially guided technique, there may be vertical control on some of the drills, but the implant is not placed through the guide with vertical control. This typically means that it is not flapless surgery. These guides are still use- ful, albeit slower and possibly not as accurate as fully guided systems — although there may be insufficient data to support that statement. SURGICAL ACCURACY Like all developing technologies, CBCT-image-guided implant surgery has evolved through several generations of the imaging and fabrication processes. The first guides were designed to be placed on bone and fabricated using stereolithography (3D) printing technology. An early comprehensive report on this approach by van Steenberghe et al2 eval- uated edentulous patients receiving multiple implants with an imme- diate loading protocol. FIGURE 1. Available from various companies, special implant software — such as this Anatomage Invivo example — aids clinicians in virtual treatment planning. whose team avoided flap and bone exposure by using a computer-guided approach in the edentulous maxilla in a pilot prospective case series involving 13 patients receiving 89 implants. The researchers used Procera software and a NobelGuide approach to place the implants in atrophic fully edentulous patients. The team noted a 94.4% implant success rate, which, for the atrophic edentulous maxilla, Conventional implant surgery has almost always included exposing the implant site with an incision and flap. Yet, with the additional 3D information about the architecture of the underlying bone, it has been one of the alluring aspects of guided surgery to avoid an incision and flap. This means the guide is placed and held on soft tissue, osteotomies are performed and implants placed with a guide that is based on the CBCT plan. One of the first studies of flapless image-guided surgery was by Merli et al,3 ANDERS NATTESTAD, DDS, PhD, is a professor, director and interim cochair of oral and maxillofacial surgery at the Arthur A. Dugoni School of Dentistry, University of the Pacific in San Francisco. He can be reached at [email protected]. The author has no commercial conflicts of interest to disclose. DecisionsInDentistry.com
