Читать книгу Management of Complications in Oral and Maxillofacial Surgery - Группа авторов - Страница 103

There are a variety of biomechanical and prosthetic complications of implant dentistry (Table 3.6), and fracture of dental implants and fractured implant components are other complications that have become more common with the increased number of implants being placed by dentists and specialists. From a prosthodontic standpoint, porcelain fractures from an implant crown are managed the same as porcelain fractures from a crown on a natural tooth (Figure 3.18). If the crown is screw‐retained, it is removed easily, and repaired or replaced. With regard to fractured components within the body of the dental implant (e.g., abutment screws, cover screws, healing abutments), the process is more complex, since if the fractured components cannot be retrieved the implant will require removal and replacement [40]. Once identified, the loose portions of the fractured implant or components should be removed in order to avoid aspiration or ingestion (Figure 3.19). Ideally, blind attempts at retrieval should be avoided since this may lead to the fractured foreign body becoming permanently lodged in the implant necessitating implant removal, even with integrated implants, since they will not be able to be restored properly. Visualization of the internal channel of the implant can be extremely difficult, especially in the posterior maxilla and mandible, and for this reason magnification is required when attempting to retrieve a broken screw or other part within an implant body. There are several commercially available screw retrieval kits on the market that can assist in removal of fractured implant components. These must be used with caution since they often involve the use of rotary instrumentation within the delicate inner channel of the implant and iatrogenic damage will also require implant removal. In many cases, the fractured screw or implant part can be removed with basic dental hygiene instruments and some patience. Once the fractured screw is visualized using either 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.