Key points
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Zygoma implants with or without traditional dental implants are a safe and predictable first line of treatment in lieu of more time-consuming and financially burdensome traditional bone grafting approaches.
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When adequate maxillary alveolar bone is present, the placement of regular dental implants should always be considered with zygoma implants, becoming an adjuvant to the dental implant reconstruction.
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The goal of the combination of traditional and zygoma implants is to improve the distribution of biting forces, allowing an increase of the support of the final prosthesis.
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The single most important factor for success is the establishment of a prosthetically driven treatment plan between the surgeon and the restorative dentist.
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The selection of the proper combination of traditional and zygoma implants is based on the amount of residual maxillary alveolar bone, the biomechanical requirements of the final prosthesis, necessary hygiene considerations, finances as well as surgeon and restorative dentist preferences and experience.
Patient evaluation
The complexity of implant reconstruction of the atrophic maxilla calls for a prosthetically driven treatment plan. Therefore, the single most important factor for treatment success is a team approach between the surgeon and the restorative dentist. The treatment goals and potential limitations are similar to those of traditional dental implant patients, with an assessment of the patient’s chief complaint, perceptions, expectations, cooperation, and past surgical and medical history. The financial burdens of the surgical and prosthetic treatment plan should not be underestimated. Unique to zygoma implant candidates, a preoperative discussion should also include any history of failed implant/bone regeneration procedures, previous history of sinusitis, and any previous sinus surgeries.
The physical and radiographic examination is focused on the identification of residual areas where sufficient bone is present for traditional dental implant placement. The physical examination for zygoma implant patients is not unlike the examination used for traditional dental implant patients. In zygoma implant candidates, a focused examination also evaluates the availability of maxillary keratinized gingiva, examines the transition zone, which is generally placed higher than the smile line, making esthetic considerations less critical, and assesses the ability of the patient to adequately open their mouth to accommodate surgical instrumentation. Panorex imaging was previously sufficient for the preoperative radiographic evaluation of the severely atrophic maxilla. Since the advent of office-based computer tomographic (CT) imaging with 3-dimensional (3D) reconstruction, CT imaging has become the gold standard for preoperative implant evaluation and planning. CT imaging can also be used for computer-assisted planning, custom drill guide fabrication, and computer-aided surgical navigation systems. In addition, more complex cases may require a haptic approach, and 3D stereolithographic model fabrication is most useful.
Planning
The preoperative planning starts with a critical analysis of the bone anatomy of the maxilla. The process is facilitated by dividing the maxilla into 3 zones: zone 1, premaxilla; zone 2, bicuspids; zone 3, molars. This division is performed with the idea to identify residual maxillary alveolar bone where regular dental implants can be placed. Several distinct clinical scenarios can be described when combining traditional and zygoma implants ( Fig. 1 ). These scenarios include the following:
Two zygoma implants and two anterior regular dental implants
Patients with adequate bone stock in zone 1, but bone deficits in zones 2 and 3, are included in this scenario. These patients demonstrate available bone to only accommodate 2 regular implants in the premaxilla and 1 zygoma implant posteriorly on each side. Normally, the 2 dental implants are placed around the area of the canines, and 2 zygomas are placed in the second premolar/first molar region. A potential third traditional implant can be placed in the middle of the maxilla to decrease the span between the dental implants and to increase the anteroposterior spread, thus improving the distribution of forces.
Two zygoma implants and four anterior regular dental implants
Patients with adequate bone stock in zones 1 and 2, but deficient in zone 3, are included in this scenario ( Fig. 2 ). These patients may be managed with the placement of 4 regular implants within zones 1 and 2, and 1 posterior zygoma implant bilaterally. Usually, 2 of the dental implants are placed in the sites of the central incisors; the other 2 are placed around the area of the canines, and 2 zygomas in the second premolar/first molar region. Some practitioners will choose to place only 3 traditional implants to increase the space between them with the purpose of facilitating the hygiene of the final prosthesis. Although most of these cases can be managed with more traditional techniques, such as an all-on-four, this approach normally represents a reaction to an increase in biomechanical demands of the final maxillary dental rehabilitation. For example, the combination of regular and zygoma implants will better distribute the biting forces generated by patients with a full set of natural opposing dentition or patients with parafunctional habits. Another example is when zygoma implants are considered to help protect regular implants in cases in which there is a compromised amount of premaxillary alveolar bone that can only house dental implants that are either thin, short, or a combination of both.
Four zygoma implants and two anterior regular dental implants
Patients with adequate bone stock in zone 1, but bone deficits in zones 2 and 3, are included in this scenario ( Fig. 3 ). These patients demonstrate available bone to accommodate 2 regular implants anteriorly and 2 zygoma implants bilaterally. Typically, the 2 dental implants are placed in the sites of the central incisors, the anterior zygomas around the area of the canines and the 2 posterior zygomas in the second premolar/first molar region. This type of cases could potentially be managed by using a quad-zygoma approach, but the addition of 2 dental implants anteriorly allows the decrease of anteroposterior cantilevers in cases whereby the final dental rehabilitation needs to withstand increased biomechanical demands as described above.
Four zygoma implants and two posterior regular dental implants
Patients with adequate bone stock posterior in zone 3, with deficits in zones 1 and 2, are included in this scenario ( Fig. 4 ). The anterior zygoma implant is placed around the area of the lateral incisors/canines with the 2 posterior zygoma implants located in the second premolar/first molar region, and a regular dental implant placed posterior to the first molar. Although most of these patients will do well with a quad-zygoma approach, cases with increased biomechanical demands will benefit from the placement of 1 implant in available bone of the molar area, tuberosity, or pterygoid plate bilaterally.
