Читать книгу Management of Complications in Oral and Maxillofacial Surgery - Группа авторов - Страница 84

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 loading of dental implants, and identified only 22 papers for inclusion, and, due to the study design heterogeneity, different clinical applications, variable outcomes, and lack of high‐level evidence, the authors could not make a definitive conclusion regarding time to loading of dental implants. The trend was in favor of delayed loading, but there are no indications that immediate or early loading cannot be performed safely. With many variables to consider (e.g., bone quantity and quality, type of implant, timing of implant placement relative to extraction, patient local and systemic factors, prosthetic plan, stability of implant at time of placement, etc.), it is not possible at this time to support the superiority for any one dental implant loading strategy over another one.

Another factor to consider with respect to timing of implant placement and loading includes augmentation of the alveolar ridge or maxillary sinus. One systematic review [19] sought to determine which hard tissue augmentation procedures are most successful in providing ideal bony foundational support for implant placement. The study included 90 articles that were acceptable for data extraction and analysis, and found that sinus augmentation with allogeneic or non‐autogenous composite grafts had the best long‐term retention for implants (93%); autogenous bone grafts were second at 92%, followed by alloplastic materials at 82%. When assessing alveolar ridge augmentation, the most success for implant survival was in sites augmented with guided bone regeneration (GBR), onlay veneer grafting, and distraction osteogenesis. The systematic review did acknowledge the limited number of acceptable studies, and the variation in those studies that prevented the establishment of a definitive conclusion regarding the most ideal hard tissue augmentation to support long‐term implant survival.