Guides used in dental implant surgery add accuracy and an overall predictability. Successful guided implant workflow depends on 3-dimensional image acquisition and precise medical model fabrication. The contemporary process blends acquired images to existing dentition to create implant-specific precise guides. We discuss the overall process, types of guides, and complications to expect during surgery.
Key points
- •
Indications of guided implant surgery include avoiding vital anatomic structures, minimized flap, accurate implant placement, placement in limited access, and maintaining esthetic needs.
- •
Implant surgical techniques: free-handed, static-guided (tooth-, mucosa-, or bone-supported guides), or dynamic guided surgery.
- •
The workflow of guided implant surgery: Conventional compared with modern simplified.
- •
Selection and fabrication of implant surgical guide: 3D printed, dental laboratory, or manufacturer.
Introduction
Guided implant surgery has advanced to become nearly routine for implant placement alongside the availability and widespread use of in-office technology. Technology like cone-beam computed tomography (CBCT) has readily become more common for in-office use. CT-guided surgery has become even more accessible with the increased availability of virtual implant planning software. Adjunctive technology like intraoral scanners and 3-dimensional (3D) printers have both helped streamline the implant planning and surgical guide fabrication while decreasing patient chair time. Dental laboratories and manufacturers have also become fully capable of fabricating guides specific to the wide range of implant systems available, so it is not required to have a full in-office setup of CBCT and 3D printer.
Guided implant surgery
Plain film radiographs (periapical and panoramic) have been mainstays in the preoperative planning of free-handed implant surgery. Two-dimensional images have clear limitations in the planning of dental implants. Although free-handed implant surgery requires less planning and lead time to insertion, results are highly variable. Guided surgery, on the other hand, is a dependable, reproducible, and safe method of doing implant surgery. , The surgeon commonly uses guided surgery when operating in the proximity of vital anatomic structures. Many types of guides will provide vertical stops to avoid excessive osteotomy, whereas others will even allow insertion of the implants through the guides. Those practitioners in favor of minimally invasive surgery will use guides to provide smaller flaps or eliminate them in favor of flapless surgery. Using surgical guides will require less effort to ensure implant parallelism and angulation, which will save significant intraoperative time.
As the technology for guide fabrication is advanced and digital software is improved, the cost of doing guided surgery decreases. This treatment modality is now broadly available, with significantly decreased planning and wait times. Dental implant guides can be classified broadly into static and dynamic, as shown in Table 1 . , Static guides are fabricated ahead of time and provide no surgical feedback during the surgery. So, if the guide does not fit during the surgery, for example, the surgeon has very few options in continuing the surgery guided. Dynamic guide, on the other hand, is a “navigation” type setup that uses the patient’s skeletal structure superimposed on CT and provides the surgeon with real-time feedback. Dynamic guided surgery is developing technology and requires substantial investment and has an increased learning curve.
| Implant Surgical Technique | Advantages | Disadvantages | Indications | Accuracy , |
|---|---|---|---|---|
| Free-handed surgery: | Surgeon-dependent accuracy, most cost-effective | Least accurate when compared with guided surgery with similar surgeon experience | For less-complex implant cases (adequate access, low esthetic demands, sufficient bony dimensions) | Least accurate 2.7 mm deviation (at entry), 2.9 mm (at apex), 9.9 degrees angulation |
| Static-guided surgery: tooth-, mucosa-, bone-supported | 0.6–1.15 mm (at entry) 0.6–1.22 mm (at apex) 2.5–5 degrees angulation | |||
| Tooth-supported | More accurate less invasive flap compared with bone-supported | Requires adjacent dentition | Simple to complex cases | Tooth-supported Slightly more accurate than mucosa- and bone-supported |
| Mucosa-supported | Least-invasive flap and hence less morbidity to patient | Least stable; can be combined with tooth-borne or bone-bore as initial pilot drill followed by bone-supported | Complex partial or full-edentulous cases | |
| Bone-supported | Stable with adequate bone, good accuracy | Most invasive flap (can be minimized with initial pilot drill guide with mucosa-supported) | Required for full edentulous, recommended for long-spanning partial-edentulous patients | |
| Dynamic guided surgery | Perioperative real-time adjustment Higher accuracy than static and free-hand |
High equipment cost Training required Difficulty in the edentulous mandible due to mobility of mandible |
Complex cases Limited access due to limited opening or positioning of second molar |
Most accurate, but less data than static-guided surgery, 0.4-mm deviation at entry, 4 degrees of angulation. |
Dynamic guided surgery systems use optical technologies to track the patient and the handpiece with real-time image display on the monitors. The optical technology uses active or passive tracking arrays. The passive system uses a light source that reflect light emitted (from an overhead source) back to the cameras. While the active system emits light that is tracked by the cameras. Navigation is achieved with the triangulation of the extraoral overhead array, intraoral markers, and handpiece arrays. The intraoral markers consist of a clip that contains metallic markers that fit onto the patient’s teeth. The intraoral clip must be in place during CBCT scan and saved for use again during surgery.
Static guides have a long history of evolution in dentistry. In contemporary dentistry, when one refers to guides, it is usually understood that this is a radiographic type of static guide. It is not uncommon, however, to encounter suck down stents as a communication method between the general dentist and the surgeon. From the surgical point of view, these guides are of minimal use and are quite often used for the first few minutes of the surgery to mark the osteotomy and are rapidly discarded afterward ( Fig. 1 ). Furthermore, these guides did not account for local anatomy or bone resorption and provided no vertical control for the fixture. Occasionally, the general dentist places radiopaque material within the proposed path of the osteotomy. When combined with cone-beam, these guides would confirm the position of alveolar bone along the osteotomy path. The most significant limitation of these guides is the lack of flexibility. Mainly the guide has limited value if the alveolar bone is not within the marked path, as modifications to the surgical protocols are not possible.
Currently, the most popular types of guides combine dentition scans (obtained either conventionally or by scanning the dentition with an intraoral scanner) with the 3-D imaging. These guides usually have an opening to accept manufacturer-specific metal cylinders to control precise width ( Fig. 2 ). It is also possible to obtain the pilot only guide to accommodate the pilot drill only. Regardless of which of these options was chosen, these guides provide information gathered from a patient-specific 3D radiograph. Currently, many dental implant companies have guided surgical kits that allow different sizes of cylinders to be inserted into the surgical guide with a specific goal of controlling the width and direction from the very first drill until the placement of the implant. Furthermore, the guided surgical kits also provide control of the vertical position as well as the depth of implant placement. The control of vertical depth and angulation of the implant are critical. Both factors are critical for successful implant-retained prosthesis, and also if any temporization is intended.
Cases requiring multiple dental implants with extractions and immediate temporization are the most complex implant procedures. The success of the immediate temporary is directly dependent on precise dental implant placement in the vertical and horizontal planes and the quality of the initial impression. Although it is possible to free-hand these surgeries and then use trial and error to find appropriate multiunit abutments, the predictability of such an approach is quite limited.
Workflow of guided implant surgery
The contemporary workflow for guided implant surgery ( Fig. 3 ) incorporates new technology such as optical intraoral scanners, in-office CBCT, virtual implant planning software, and in-office 3D printers. Which of these advanced modalities the practitioner chooses to use will depend on the availability of equipment and experience level. At the time of the first consultation, the dentist should review pertinent medical history, indication, and risks of implant surgery. For complex cases, the practitioner should obtain impressions and CBCT of the patient in the desired occlusion. For straightforward cases with stable posterior occlusion, this can be achieved with patient registration material. Although not required, the dentist may choose to use radiopaque material in the missing tooth area to easier visualize future implant’s relationship to the existing dentition. For situations when the patient has no posterior stable occlusion or is completely edentulous occlusal bite rims or duplicated complete denture is needed. This appliance should have radiographic markers embedded at the time of 3D CBCT and sent to the laboratory for mounting on an articulator. If the duplicated denture is not available, many simple prosthodontic techniques will allow fabrication of acceptable copy. On completion of the 3D CBCT, the dentist may choose to either fabricate the guide in-office using 3D printing technology or to outsource the entire process. We have earlier described a protocol for surgical guide manufacturing. The author prefers to obtain 3-D CBCT, impression, and plan the case virtually in the office. The fabrication of the guide is then outsourced to the outside laboratory. The second visit then is usually a surgical appointment using the fabricated guide. As discussed earlier, outsourcing the guide fabrication increases the lead time significantly but requires a less overall initial investment.
