Rehabilitation of the severely resorbed maxilla by using quad zygomatic implant-supported prostheses: a systematic review and meta-analysis (2023)

Stresses applied to zygomatic implants have been determined to be transferred mainly to the zygomatic bone; however, consensus regarding the stress distribution pattern in the bone surrounding zygomatic implants has not yet been reached.

The purpose of this 3-dimensional (3D) finite element analysis (FEA) study was to visually compare the stress distribution pattern in 2 different zygomatic implant treatment modalities and evaluate the effect of masseter musculature involvement.

A 3D FEA craniofacial model was constructed from the computed tomography (CT) data of a selected patient with a severely atrophic edentulous maxilla. Modeled zygomatic and conventional implants were inserted into the craniofacial model supporting a prosthesis superstructure. Two types of treatment were considered in the study: 2 zygomatic implants placed bilaterally or 2 zygomatic implants placed in conjunction with at least 2 conventional implants at the anterior maxilla. The models were loaded with a vertical force of 150 N, a lateral force of 50 N, and a distributed occlusal force of 300 N applied to the insertion area of the masseter muscle. The stresses on and deformations of the bones and implants were then observed and compared with and without the involvement of the musculature component.

The stresses were distributed efficiently along the vertical and horizontal facial buttresses, as in the dentate skull; however, a difference in distribution pattern was observed when the models were loaded without applying the muscle component. The maximum deformation of bones surrounding the implants occurred in the abutment connection of the conventional anterior implant in the model with an additional conventional anterior implant.

The FEA revealed the stresses were distributed efficiently along the vertical and horizontal facial buttresses, as in the dentate skull. However, the stresses in both models were concentrated in the zygomatic bone when incorporating the muscle component. Therefore, incorporating muscular force into FEA studies could affect the analysis result.

Citation Excerpt :

In addition to articles selected for detailed review, a sizable number of excellent general reviews, systematic reviews, meta-analyses, and helpful clinical descriptive articles were also published addressing issues important to prosthodontics. Although it is impractical to provide detailed analysis on all these publications, they are listed here, by the topic area, for the reader’s convenience and include the following: general prosthodontic considerations,5-7 conventional fixed prosthodontics,8-14 conventional removable prosthodontics,15-30 general implant considerations,31-59 implant-fixed prosthodontics,60-76 implant removable prosthodontics,77-79 implant complications,80-84 implant integration,85-93 preprosthetic and implant surgery,94-115 peri-implant tissues and disease,116-131 dental occlusion,132-146 dental impressions,147 digital dentistry,148-150 materials science,151-166 endodontic-prosthodontic topics,167-171 periodontal-prosthodontic topics,172-178 operative dentistry,179 geriatric dentistry,180-193 pathology and oral medicine (OM),194-214 dental radiology and imaging,215-231 adolescent and growing patients,232-243 bruxism,244 mastication,245 dental caries,246-250 therapeutic outcomes,251-261 patient management,262-267 research methods,268-270 COVID-19–related topics,271-276 dental education,277 sleep and sleep disordered breathing,278-280 and the temporomandibular joint (TMJ), temporomandibular disorder (TMD), and orofacial pain (OFP).281-299 Peri-implant bone loss coincident with occlusal loading is thought to be related to poorly controlled stress concentration.

Computer-aided treatment technology has extended its applications to oral implantology. This report describes the authors' initial clinical experience on the application of a commercially available navigation system (VectorVision) in zygomatic implant (ZI) insertion in the severely atrophic maxilla.

This was a retrospective longitudinal study. Eligible patients with maxillary edentulism who were treated with ZI placement were enrolled. Treatment planning was performed on the computer based on previously obtained 3-dimensional imaging data. The surgical procedure was carried out under the guidance of a surgical navigation system. The outcome variable was safety and additional variables were ZI survival rate and radiologic bone-to-implant contact (rBIC) area in the zygoma. Statistical analysis was performed with SPSS 16.0 for Windows (SPSS, Inc, Chicago, IL).

Fifteen patients (8 men, 7 women; age range, 30 to 69yr; average age, 43±3.5yr) were eligible for the study and were enrolled from May 2015 through September 2016. Of the included patients, each of 4 patients received 1 ZI on each side of the zygomatic bone and 2 to 4 standard implants in the edentulous anterior maxilla; the other 11 received a ZI “quad approach” without standard implant insertion. All ZIs were anchored in the site of the maxillary alveolar process and zygomatic bone, and no critical anatomic structure injuries occurred during insertion and postoperative radiographic examination. All ZIs achieved osseointegration, for an overall survival rate of 100% after early healing. The overall rBIC area of ZIs in the study was 4.1 to 24.7mm (average, 14.5±4.6mm).

For the limited clinical cases treated in this study, the procedure for ZI placement was feasible and reliable with the guidance of the surgical navigation system. In addition, the potential risk of complications was minimized and ZIs were placed to make the best possible use of the available bone volume.