loupes or microscopic magnification, a solution of chlorhexidine gluconate can be used as irrigation and lubrication to loosen the fractured screw. Any manipulation of the screw should be in a counterclockwise fashion in order to promote backing out of the screw. In certain circumstances, a fine ultrasonic tip on a Cavitron device can help to rotate out the fractured implant component. Careful inspection of all fractured pieces should be done to ensure that all pieces are accounted for and removed. Once removed, an appropriately sized healing abutment should be placed, and imaging should confirm full seating of the newly replaced components. Prior to utilizing the previously placed crown, all efforts should be made to diagnose the etiology of the previous fracture of the restoration. Abutment screws in general are made to tolerate significant forces, but excessive angulation errors (>20°) or poor occlusal planning may lead to screw fracture [41]. These factors should be addressed and corrected in treatment planning for the new restoration.
Table 3.6. Biomechanical complications of implant dentistry
| Acrylic resin veneer fracture (22%) |
| Overdenture attachment fracture (17%) |
| Early implant failure (16% in soft bone or short implants) |
| Porcelain fracture (7%) |
| Prosthetic screw loosening (7%) |
| Acrylic base fracture of overdentures (7%) |
| Abutment screw loosening (6%) |
| Prosthetic framework fracture (3%) |
| Abutment screw fracture (2%) |
| Implant body fracture (1%) |
| Marginal bone loss around implant (1%) |
Fig. 3.18. Implant restorative materials fractures.
Fig. 3.19. Fractured implant.
Fracture of the actual surgical implant fixture itself usually necessitates removal since the implant becomes nonrestorable (Figures 3.20 and 3.21). In most instances, the fracture can once again be related to excessive masticatory forces and occlusal loads, parafunctional habits, or poor occlusal schemes. These should be addressed and plans made to avoid similar circumstances that will almost certainly lead to the same poor outcome. Depending on the location of fracture, and whether or not the internal channel of the implant is intact, there are several methods by which a fractured implant can be removed. Initial attempts should be made at “simply” reversing the implant out of the bone. This may not be simple or straightforward, but maintaining the alveolar bone can be of great benefit when considering possible repeat implant placement. Under ideal circumstances, this implant can be replaced immediately at the time of removal of the fractured implant. A reverse torque wrench may be used, but if the implant internal channel has become compromised, a reverse torque wrench may not seat appropriately for use. In these cases, the implant will require removal with a surgical trephine bur [42]. The narrowest possible trephine that will fit around the implant should be selected in order to maintain as much native bone as possible. These burs are generally run at slower speeds and should be used in unison with hand instrumentation in order to mobilize the fractured implant, similar to an ankylosed tooth. Once removed, the fractured implant should be inspected to confirm complete removal and the surgical site reconstructed in a suitable manner, possibly with bone grafting or GBR. A replacement implant of a wider diameter may be considered for immediate replacement. The removal of multiple implants can create a large bony defect that may compromise the integrity of the jaw. In these instances, the surgeon and patient must have a preoperative discussion involving the possible need for additional fixation in order to treat and/or prevent possible mandible fracture. On rare occasions, the implant fracture may occur at such a level or in such a manner that the implant may remain restorable. Although this is far from ideal, the implant surgeon, restorative dentist, and patient must have a frank discussion about the option of retaining the compromised fixture versus removal and replacement. In the frail patient with minimal bone stock, it may be preferable to retain a restorable fractured implant and closely monitor to ensure no development of infection or component failure. In conclusion, no two clinical situations are exactly the same, and all factors must be considered when determining a final treatment plan (Algorithm 3.8).
Fig. 3.20. Radiograph of fracture of the actual implant fixture.
Fig. 3.21. Clinical view of fracture of the actual implant fixture.
Algorithm 3.8: Fractured Implants and Components
ZYGOMATIC IMPLANT COMPLICATIONS
The use of zygomatic implants is becoming increasingly popular among surgeons for maxillary reconstruction in patients with pneumatization of the maxillary sinus and severe maxillary atrophy, and also for patients who have a significant maxillary defect following tumor removal or trauma. Zygomatic implants utilize the existing native bone of the posterior maxilla and zygomatic buttress and zygoma to stabilize long (>30 mm) implants without the need for bone grafting. There are several advantages to the use of zygomatic implants, including substantial reduction in overall treatment time, reduced costs, and decreased morbidity without the need for bone harvesting from a second surgical site. However, the use of zygomatic implants is not without possible complications. In a systematic review [43], the following complications were noted: sinusitis, non‐osseointegrated implants, infection, oroantral fistula, paresthesia of infraorbital and zygomaticofacial nerves, penetration of the orbital cavity, and labial laceration. Sinusitis and failure of osseointegration of the zygomatic implant are found to be more frequent than the other complications. According to the literature, the incidence of maxillary sinusitis after placement of zygomatic implants is 0–26.6% (Figure 3.22). It has been documented that the varied range results from different criteria used to classify the signs and symptoms of rhinosinusitis. A retrospective cohort study [44] was done to assess the relationship between zygomatic implants and maxillary sinusitis and showed a statistical increase in postoperative radiographic evidence of rhinosinusitis compared with the preoperative status of the sinus. Further analysis revealed increased signs of radiographic alterations of the maxillary sinus in patients who underwent zygomatic placement by an “intrasinus” versus “extrasinus”