Management of Complications in Oral and Maxillofacial Surgery. Группа авторов

as nerve injury and maxillary sinus perforation. A split mouth randomized case series of 12 subjects in 2019 [8] concluded that angular deviation of the implants placed by guided virtual surgery was lower as compared to implants placed by conventional freehand surgery. However, it is important to understand that despite the advances in technology, errors can occur with the use of VSP and guided surgery, leading to poor implant positioning, making prosthodontic rehabilitation challenging and ultimately compromising functional and esthetic results. Inaccuracies can be incurred at every step in the VSP process, from data gathering (CBCT [cone‐beam CT] acquisition) to dental implant placement. For example, poor CBCT resolution, patient movement during the CBCT, and scanning of an ill‐fitting barium‐impregnated prosthesis (if used) will result in a faulty preoperative database and inaccurate planning and fabrication of an imprecise surgical guide. Another source of error includes the potential for drill deviation during sequential implant osteotomies, due to an inherent tolerance of the sleeve inserts that allow a certain degree of malalignment [9, 10]. Lastly, failure to seat and stabilize the surgical guide appropriately during the surgery can lead to several complications, such as injury to vital structures and poor anatomical placement of implants. As such, it is important to recognize that tooth‐supported surgical guides are more stable than bone‐borne guides, and least stable are the mucosa‐borne guides. Guide pins can be used to stabilize the guides during implant placement to prevent iatrogenic movement. The surgeon should perform periodic verification of the sequential osteotomies during the placement of dental implants, especially in the areas of vital structures. For a minimal deviation during implant placement with a surgical guide, it is crucial to place the drill in the center of the guide, and parallel to the sleeve/cylinder [9, 10]. Additionally, the use of more restrictive longer drill keys and sleeves may improve accuracy and provide more optimal outcomes [9, 10]. In view of concerns associated with the use of surgical guides, dynamic navigation systems have gained acceptance in implant surgical therapy in an attempt to improve precision and accuracy. Table 3.4 delineates the differences between static implant surgical guides/stents and dynamic implant navigation systems [11, 12].

       Prosthodontic and Surgical Treatment Planning

Treatment planning for dental implant reconstruction is a team concept. The restorative dentist and surgeon must both provide input to ensure optimal patient outcomes using a prosthetically driven treatment planning process. Failure to include the restorative dentist in the initial treatment planning phase could lead to prosthodontic failures as a result of a lack of restorability of the implant due to incorrect location, angulation problems, or compromised esthetic issues. Both clinicians (surgeon and restorative dentist) should communicate their preferences and be in agreement with respect to implant number and location. Oftentimes, it is helpful when the restorative dentist provides a surgical guide to assist with implant location and angulation. This prosthetic surgical guide differs from a CT‐generated surgical guide in that the restorative dentist may use a duplicate denture with a window trimmed away to indicate to the surgeon the range of area that should be used for implant placement. Surgical guides are not always necessary depending upon the location of the implants, and the experience and skill of the surgeon, but can be very helpful for complex cases and esthetic zone cases, especially those involving multiple implants. Recently, there has been greater attention paid to computer‐assisted treatment planning, surgical guide fabrication, computer‐guided surgery, and the use of navigation techniques. Currently, no multicenter prospective clinical trials exist that indicate a statistically significant superiority of the use of such computer‐assisted and navigation techniques over conventional freehand implant placement techniques. Although pre‐implant CT or CBCT imaging is performed commonly, it is most beneficial when the treatment planning sites may have significant anatomical limitations (e.g., proximity to nerve or sinus), or following augmentation procedures (e.g., sinus lift, ridge augmentation).

Table 3.4. Differences between static implant guides and dynamic implant navigation

      Sources: Based on Block and Emery [11]; Block et al. [12].

	Static guides	Dynamic navigation
Protocol	Surgeon uses the CT‐generated surgical stent to make sequential osteotomies, with direct visualization	Surgeon uses the navigation screen to make sequential osteotomies, with minimal direct visualization of the drills in patient's mouth
Use of stent or a clip	CT‐generated surgical stent with metal sleeve	CBCT scan obtained with the clip that contains three metallic fiducial markers, placed on the patient's teeth in an area that is not indicated for surgery
Implant positioning	Implants placed in the predetermined position. Intraoperative change in position is not permitted	Real‐time visualization of the implant placement. Ability to make corrections as needed
Implant system	A surgical setup specific to the implant system is required. Unable to change implant system once the CT surgical stent has been fabricated	Compatible with any implant system. Also allows for change in the implant size during its placement
Irrigation of the drills	Difficult to irrigate the drills during the procedure due to limited access to the bone, may increase heat production	Continuous irrigation of the drills during the procedure is possible
Difficult access	Use of surgical stents can be challenging in patients with limited mouth opening, especially when placing an implant in the second molar site	Allows for placement of implants in patients with difficult access
Learning curve	Likely use of a third party to plan the case	Variable learning curve to gain proficiency

Treatment planning addresses not only the location of implants, but also the ideal time interval between extraction and implant placement, immediate extraction and implant placement, time to implant loading, or immediate loading protocols, and time interval to final prosthetic restoration. All of these factors may play a role in the initial implant integration and primary and secondary implant stability. The alveolar ridge undergoes hard and soft tissue dimensional changes after tooth extraction. Several studies have evaluated the amount of bone loss that occurs over time after extraction. These studies show a loss of horizontal width between 30% and 50% at 3–12 months after extraction [13–15]. Immediate and early implant placement has become an accepted technique to attempt to offset the impact of these anatomical changes. However, a study [16] assessed 21 immediate implants in 18 patients, and, upon re‐entry at 4 months, found bone resorption around the implants: approximately 50% bone loss on the buccal surface and 30% on the lingual surface. Another study [17] found similar outcomes and concluded that immediate implant placement does not prevent alveolar ridge resorption. Although these studies suggest that bony resorption continues to take place regardless of when the implant is placed after extraction, there is no evidence to suggest that early or immediate implant placement techniques have a significantly lower (or higher) rate of osseointegration success than those placed in a more delayed fashion. However, prospective randomized clinical studies are needed with clearly defined long‐term outcome measures in order to help guide the choice of appropriate implant treatment protocols.

      The time interval to loading of dental implants is also debated in the literature, and presumably has an effect on the overall success of implant osseointegration. One systematic review [18] examined the time to