Endosseous Craniofacial Implants

Armamentarium

  • #9 Periosteal elevator

  • #15 Scalpel blade

  • Appropriate sutures

  • Extraoral implant

  • Extraoral profile drill for implant 2.8 mm

  • Extraoral stop drill for implant (2.8 mm)

  • Handpiece and motor unit

  • Healing cap

  • Implant inserting device

  • Local anesthetic with vasoconstrictor

  • Mayo scissors

  • Needle electrocautery

  • Parallel gauge

  • Ratchet with torque control device

  • Round bur (2.3 mm)

  • SCS screw driver

  • Skin retractors

  • Tweezers with and without titanium plasma-coated tips

History of the Procedure

Traditionally, craniofacial prostheses have been used to cover facial defects in cases when surgical reconstruction is not an option. As early as 1965, subperiosteal implants were suggested for the use of fixation of extraoral prostheses. Due to local inflammation and loosening, the clinical application of these devices was unpredictable and largely unsuccessful.

In 1969, Dr. Per-Ingvar Branemark and colleagues were the first to report the long-lasting direct contact of bone with a metallic implant under functional loading. In the years following, endosseous implants in the oral cavity revolutionized the treatment of the edentulous jaw. Based on this work, the first clinical trials with skin-penetrating implants in the mastoid process began in 1977. Five years later, favorable results and a low complication rate for percutaneous endosseous implants as retention elements for facial prostheses were reported. Since then, multiple publications and case reports have demonstrated the successful craniofacial rehabilitation of patients who are often not only confronted with a deadly disease but also have to cope with a potentially disfiguring treatment.

History of the Procedure

Traditionally, craniofacial prostheses have been used to cover facial defects in cases when surgical reconstruction is not an option. As early as 1965, subperiosteal implants were suggested for the use of fixation of extraoral prostheses. Due to local inflammation and loosening, the clinical application of these devices was unpredictable and largely unsuccessful.

In 1969, Dr. Per-Ingvar Branemark and colleagues were the first to report the long-lasting direct contact of bone with a metallic implant under functional loading. In the years following, endosseous implants in the oral cavity revolutionized the treatment of the edentulous jaw. Based on this work, the first clinical trials with skin-penetrating implants in the mastoid process began in 1977. Five years later, favorable results and a low complication rate for percutaneous endosseous implants as retention elements for facial prostheses were reported. Since then, multiple publications and case reports have demonstrated the successful craniofacial rehabilitation of patients who are often not only confronted with a deadly disease but also have to cope with a potentially disfiguring treatment.

Indications for the Use of the Procedure

Microsurgical techniques have overcome many of the traditional problems in craniofacial reconstructive surgery, and, whenever possible, surgical reconstruction is the treatment of choice. However, in some cases, primary reconstruction of soft tissue and bone defects is likely to fail or not be desirable or feasible. Generally, older age in connection with age-related health problems is a limiting factor for extensive surgical reconstructions, as the risks associated with anesthesia increase and postoperative immobilization and rehabilitation become a problem. In these cases, secondary reconstruction, including endosseous craniofacial implants, becomes the preferred option. In some cases, such as in ablation of the auricle or in certain orbital defects in which the upper and lower lid are missing, implant-supported prostheses may be the only option or can provide simpler, safer, and aesthetically superior results than plastic reconstructive surgery.

The successful rehabilitation of patients with craniofacial defects depends on the motivation of the patient, careful preoperative planning, interdisciplinary cooperation, and adequate surgical and prosthodontic techniques. Ideally, the surgeon, the prosthodontist, and the anaplastologist should discuss all therapeutic options, including surgical and implant-based reconstruction, before any surgery. If craniofacial endosseous implants and rehabilitation with a prosthesis are considered (e.g., before removal of an auricle), an impression of the auricle can be taken and used to model the prosthesis. Furthermore, the tissue bed can be prepared for extraoral implants during ablative surgery. When possible, bone can be preserved or reconstructed in areas crucial for later placement of endosseous implants; in some cases, immediate implantation can be considered. The soft tissue can also be prepared for implantation; for example, split-thickness skin grafts can be transplanted to create an area of thin and hairless skin at the intended implantation site.

For each individual case, the repair of craniofacial defects using endosseous implants should be uniquely planned, with implants being placed wherever bone is available. In general, the temporal bone, the supraorbital rim, the zygoma, the piriform aperture, and the pterygoid process provide sufficient bone for the anchorage of implants.

Preoperative Planning

Functional and aesthetic reconstruction of craniofacial defects requires thorough preoperative planning and preparation, with careful evaluation of the unique clinical situation. The thickness and mobility of the soft tissue at the margins of the defect are especially important for the aesthetic result, as the appearance of an extraoral prosthesis is usually limited in areas where the surrounding tissue is mobile due to muscle movements in the face (e.g., in the cheeks). Therefore, ideal indications are for the replacement of the ear, the eye, and the nose. At the implantation sites, the thickness and mobility of the skin are even more important. An area of thin and hairless skin should be created around the implants to avoid inflammatory reactions and loss of the implants.

Assessment of the bone available for implantation is essential during preoperative planning. The introduction of improved imaging such as computed tomography (CT) allows for the visualization of the precise anatomic extent of craniofacial hard and soft tissue defects and the structure and thickness of the bone available prior to implant placement. Surgical navigation has been introduced into dental implantology. A substantial advantage of navigation is precise preoperative planning, which is optimized by taking into consideration anatomic and prosthetic aspects. Using this technology, a plastic template of the ideal position of the implants is made using radiopaque markers, and the patient is scanned with the template. The available bone can then be assessed, and implant placement can be planned such that damage to critical anatomic structures is avoided, improving intraoperative safety ( Figure 23-1 ). For example, in cases in which the external ear, the mastoid process, and its air-cell system are replaced, the position of the sigmoid sinus and the level of the middle cranial fossa can be determined to avoid penetration during implantation.

Figure 23-1
A, Preoperative planning CT for surgical navigation. B, Multiplanar views allow the assessment of bone available for implantation. The position of plastic ear models with radiopaque markers is visible in all views.

If no bone has been removed during surgery, a CT scan of the temporal bone is not required. However, if an orbital, nasal, or midface prosthesis is planned, a CT scan is necessary to select the ideal implantation site with respect to the amount and quality of bone available. Furthermore, implants in the orbital rim are difficult to position, as they need to point internally into the orbit and sufficient bone needs to be available. CT scans and surgical navigation allow for the precise planning of the implantation site and the angulation of the implants necessary for camouflage by the prosthesis later on.

Prosthodontic Methods in Endosseous Craniofacial Implants

The prosthetic requirements of treatment with extraoral or complex combination devices differ greatly from those for intraoral prostheses. In all cases of craniofacial defects following tumor surgery, the surgical and prosthodontic team should discuss the approach to rehabilitation. General guidelines comparable to intraoral rehabilitation are difficult to establish because of the great interindividual differences in defect size and location, the amount of bone available and bone quality, and the thickness and mobility of the soft tissue. Accordingly, the number and site of implants to be placed vary greatly and largely depend on the individual situation. For example, for the retention of an auricular prosthesis, two implants may be sufficient, whereas in extended midface defects, as many implants as possible should be placed to distribute the load. If necessary, craniofacial defects secondary to malignant tumor surgery can be minimized by plastic surgery techniques without obstruction of potential implantation sites ( Figure 23-2 ).

Figure 23-2
A, For an auricular prosthesis, two to three implants are inserted into the temporal bone, approximately 1 cm dorsal of the external meatus. Ideally, the implants should be placed in a semilunar fashion. Placement of implants into the frontal bone ( B ) and the orbital rim ( C ). D, Areas suitable for implantation of implants in combined intra-/extraoral defects.

Prosthodontic assessment of the implantation sites should take a number of fundamental principles into account. First, the retention and support for the prosthesis should fall within the peripheral extension of the device. Preferably, the margins of the prosthesis should extend in areas of limited mobility of the bordering tissue bed. Overextension of a prosthesis, especially in the midface, is therefore limited.

Only gold members can continue reading. Log In or Register to continue

Jun 3, 2016 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Endosseous Craniofacial Implants
Premium Wordpress Themes by UFO Themes