Evaluation of surgical techniques in survival rate and complications of zygomatic implants for the rehabilitation of the atrophic edentulous maxilla: a systematic review

Abstract

Purpose: To assess the outcome [zygomatic implant (ZI) survival] and complications of the original surgical technique (OST) and an Anatomy-Guided approach (AGA) in the placement of ZI in patients with severely atrophic maxillae.

Methods: Two independent reviewers conducted an electronic literature search from January 2000 to August 2022. The inclusion criteria were articles reporting at least five patients with severely atrophic edentulous maxilla undergoing placement OST and/or AGA, with a minimum of 6 months of follow-up. Number of patients, defect characteristics, number of ZI, implant details, surgical technique, survival rate, loading protocol, prosthetic rehabilitation, complications, and follow-up period were compared.

Results: Twenty-four studies comprised 2194 ZI in 918 patients with 41 failures. The ZI survival rate was 90.3-100% in OST and 90.4-100% in AGA. Probability of complications with ZI with OST was as follows: sinusitis, 9.53%; soft tissue infection, 7.50%; paresthesia, 10.78%; oroantral fistulas, 4.58%; and direct surgical complication, 6.91%. With AGA, the presenting complications were as follows: sinusitis, 4.39%; soft tissue infection, 4.35%; paresthesia, 0.55%; oroantral fistulas, 1.71%; and direct surgical complication, 1.60%. The prevalence of immediate loading protocol was 22.3% in OST and 89.6% in the AGA. Due to the heterogeneity of studies, statistical comparison was only possible after the descriptive analysis.

Conclusions: Based on the current systematic review, placing ZI in severely atrophic edentulous maxillae rehabilitation with the OST and AGA is associated with a high implant survival rate and surgical complications within a minimum of 6 months follow-up. Complications, including sinusitis and soft tissue infection around the implant, are the most common. The utilization of immediate loading protocol is more observed in AGA than in OST.

Keywords: Complications; Maxillary atrophy; Maxillary defect; Survival; Technique; Zygomatic implant.

Fig. 1

The original surgical technique described by Branemark (OST) begins with a Le Fort I-type incision. A full-thickness mucoperiosteal flap is elevated to provide direct visualization of the trajectory of the implant from the premolar/molar region of the alveolar bone to the zygoma body. The dissection is continued from the lateral wall of the maxilla towards the zygomatic bone to allow for increased visibility of the zygomatic region and the infraorbital nerve. A lateral window of approximately 10 * 5 mm is then made into the lateral aspect of the maxillary sinus using a round bur (A). Once the membrane has been exposed, it should be carefully elevated medially and superiorly. The entrance of the ZI is marked with a round bur on the palatal side of the crest. The drilling sequence starts at the alveolar ridge, passing through the maxillary sinus, and the drill is advanced to reach the body of the zygoma to the desired emergence level (B) [2] (Figure provided by Yiqun Wu)

Fig. 2

For Anatomy-Guided as an evolution of the extra-sinus approach, the relationship of the zygomatic buttress–alveolar crest area is classified into five different types. In this technique, the path of the ZI body can range from total intra-sinus (ZAGA 0) to the wall of the maxilla (ZAGA 1 & 2) to total extra-maxillary sinus (ZAGA 3 & 4). The curvature of the external wall of the maxillary buttress determines the final relationship between the implant and the anterior maxillary wall. For surgical access, a slightly beveled palatal incision starts from the posterior buccal aspect of the maxillary tuberosity to the midline. According to the prosthodontics aspect, the starting point (implant head emergence) should be at or close to the top of the alveolar ridge crest. When the residual bone at the sinus floor level has adequate thickness and width (minimum: 4 mm height, 6 mm width) in a patient without a history of periodontitis, the position of the entry point should be close to the middle portion of the crest with an intra-sinus starting path of the implant if the maxillary wall is flat or convex. When the crestal bone height or thickness is inadequate, the alveolar entrance point should be shifted to the buccal, regardless of the maxillary wall curvature. Based on the maxillary wall concavity and the height of the new bone, the osteotomy is shaped like a tunnel or canal [16, 22]

Fig. 3

PRISMA flow diagram

Fig. 4

Distribution of the type of ZAGA classification between eligible studies [14, 37, 39, 41, 43] and ZAGA studies [15, 46]. ZAGA-A evaluated the anterior ZI’s distribution in the ZAGA classification, and ZAGA-P evaluated the posterior ZI’s distribution [46]