Fig. 3.2. A closer CBCT view of an implant causing IAN transection.
Fig. 3.3. Implant violation of the superior aspect of the IAC.
Damage to Adjacent Teeth
Poor dental implant placement with respect to the adjacent dentition can lead to a variety of potential problems (Figure 3.5). An erroneous location of an implant may cause an esthetic issue with the need to alter the shape or emergence of the crown, as well as potential compromise of the periodontal health of the tooth and adjacent tooth. The etiological factors involved include poor surgical planning, incorrect placement and/or improper angulation, direct damage to the adjacent tooth due to placement of an implant with an excessively wide diameter into a narrow interdental space, and indirect tooth damage due to the generation of excessive heat in proximity to the teeth (similar to thermal injury from proximity to the IAC as discussed previously) [21]. As a consequence of violation of the periodontal ligament space, devitalization of adjacent teeth may occur, as well as external root resorption, resulting in the need for additional treatments such as endodontic therapy, apicoectomy, tooth bleaching, crowns and bridges, and/or tooth extraction. To avoid damage to adjacent teeth, a preoperative clinical and radiographic evaluation is of utmost importance. Radiographic analysis should include measurements between the natural teeth, and determination of the presence of root dilacerations and inclinations of the teeth adjacent to the planned implant site(s). The minimum recommended implant to tooth distance is 1.5 mm, and the minimum interimplant distance is 3.0 mm in order to respect the periodontal ligament spaces as well as biological width. Implants placed too close together may lead to a compromised periodontium and interimplant bone loss (Figures 3.6 and 3.7).
Fig. 3.4. A closer CBCT view of an implant violating the IAC.
Algorithm 3.1: Nerve Injury
Fig. 3.5. Damage to the adjacent tooth and bone loss due to poor implant position.
Fig. 3.6. Implants placed too close together compromising gingival esthetics and periodontal health.
In order to prevent excessive tilting and improper angulation during implant placement, some form of paralleling technique should be utilized by the clinician, if the implants are being placed in a freehand fashion. The use of intraoperative periapical radiographs with a guide pin or implant pilot drill after the initial osteotomy is useful to guide the need for redirection of the implant osteotomy as it is prepared further for implant placement (Algorithm 3.2). Of course, the use of a CT‐generated surgical guide or dynamic navigation techniques may also be beneficial in reducing the possibility of iatrogenic injury to adjacent teeth. Furthermore, based on a landmark study [22], in order to minimize heat‐induced hard tissue injury and indirect damage to adjacent teeth, copious irrigation at a temperature <47 °C per minute must be maintained. However, as mentioned, it is not possible to irrigate the tip of the drill within the bone (note: internally irrigated drills had been used in the past, but became clogged with bone debris and were not very functional), so sharp, new drills should be used at the correct drill speed to avoid excessive heat generation.
Fig. 3.7. Periapical radiograph showing implants placed too close together resulting in bone loss.
Algorithm 3.2: Damage to Adjacent Teeth
Implant Displacement and Migration
Since iatrogenic displacement of implants may occur during the surgical procedure, it is prudent to include this risk in the informed consent discussion. Due to its location and size, proximity to the posterior maxillary teeth, and poor quality bone in the posterior maxilla, the maxillary sinus is a target site for displaced objects (Figures 3.8 and 3.9). Teeth and tooth roots, root canal filling materials, and dental implants are common objects that are displaced into the maxillary sinus, and case reports in the literature cite these occurrences. Displacement, or migration, of dental implants into the maxillary sinus can be an acute or a delayed event. The causes for an acute displacement include insufficient vertical maxillary bone (<4.0 mm) below the sinus floor, leading to poor primary implant stability, and either immediate or delayed migration of the implant into the sinus. An incorrect surgical plan could be responsible if that plan should have considered the use of sinus floor elevation prior to implant placement to augment bone height for implant stability. Also, the use of improper surgical techniques that violate the Schneiderian membrane or unsuccessful bone regeneration after prior sinus lifting results, again, in insufficient bone to ensure implant stability [23]. More commonly, an implant is displaced at the time of placement, although several reports describe implants that have migrated into the maxillary sinus several weeks, months, or years after initial placement or even after osseointegration and prosthetic restoration has occurred. It is unclear what causes the migration of such implants, but the most accepted reasons are osteopenia/osteoporosis alone, or in combination with excessive occlusal forces, and inflammatory reactions around the implants leading to constant bone destruction and implant mobility [23]. On occasion, the displacement of an implant into the maxillary sinus is found at the middle meatus, or displaced from the nose, due to the action of the mucociliary elevator of the sinus membrane in an attempt to clear the foreign body from the sinus. The treatment of such an incident, whether acute or delayed, includes implant retrieval via a Caldwell–Luc lateral maxillary wall antrostomy, or transnasal endoscopy or transoral endoscopy, and the surgeon may