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Table 3 Results of risk of bias assessment by AMSTAR tool

From: Zygomatic implants placed in atrophic maxilla: an overview of current systematic reviews and meta-analysis

Author (year), country of origin, funding(Y/N/?)-Conflict of interest(Y/N/?)
Research question or objectives Primary outcome(s) Number and designs of included studies (number of patients and implants) Control group SR/SR and M Databases searched (search date) Follow-up Quality assessment tools Implant loading (immediate/late) Type of edentulism (total/partial) Main findings Main conclusion
Wang et al. (2015) [49], China and Spain, (Y-N) [Q1; 1,96] To assess the predictability of oral rehabilitation by four zygomatic implants with no anterior support in regard to implant survival, technical and biologic complications The survival rate of the zygomatic implants 3 human clinical trials (2 prospective and 1 retrospective) (49 patients, 196 ZIs) None SR and M (from September 2000 to November 2013) 30–363 (mo) None Immediate loading Fully edentulous - Zygomatic implant survival rate weighted mean (WM) was 96.7% (range, 95.8 to 99.9%), with a 95% confidence interval (CI) of 92.5 to 98.5%.
- Limited number of surgical complications and prosthetic complications
Maxillary rehabilitation by four zygomatic implants with no anterior support is a reliable approach
Tuminelli et al. (2017) [44], USA, (NR-NR) [2.39] To systematically review the outcome of immediate loaded zygomatic implants Immediate load survival, complications 38 articles None SR PubMed (from 1990 until June 2016) At least 12 months follow-up (according to text follow-ups ranged between 1 and 10 (y)) None Immediate loading Both totally or partially edentulous maxilla - The success of implants and prostheses ranged from 96 to 100%.
- The complication rates are relatively few, rarely catastrophic, and easily managed
Immediately loading zygomatic implants for the restoration of the severely atrophic maxilla presents a viable alternative for treatment of the atrophic maxilla and is recommended for the restoration of the severely atrophic maxilla with or without anterior conventional implants
Molinero-Mourel et al. (2016) [47], Spain, (NR-N) [1.07] To analyze and describe the most frequent surgical complications associated with the use of zygomatic implants Complications 13 articles (1 SR, 5 pros, 5 retros, 1 pros and retros, 1 cohort) (3240 ZIs) None SR PubMed (up to December 2015) 1–12 (y) None All studies were immediate loading Both totally or partially edentulous maxilla - Out of the most frequent surgical complications, sinusitis (3.9%) and failure in osseointegration (2.44%) are highlighted Rehabilitation using zygomatic implants is a consolidated therapeutic option although it does not lack in possible complications; therefore, it should be reserved only to professional clinicians with vast surgical experience
Goiato et al. (2014) [46], Brazil (N-N) [1.52] To evaluate clinical studies on the follow-up survival of implants inserted in the zygomatic bone for maxillary rehabilitation. Survival of implants 25 articles (design NR) (748 ZIs) None SR PubMed/MEDLINE, Embase, and Cochrane Library databases (from 2000 to July 2012) Mean follow-up: 42.2 (mo) (range 0–144) None Fifteen studies conducted late loading (prosthesis insertion at 4–6 months after initial implant loading), whereas 10 studies reported immediate loading Both totally or partially edentulous maxilla - These studies reported the insertion of a total of 1541 zygomatic implants and 33 implant failures
-After a 36-month follow-up, the survival rate was 97.86%
- The survival of osseointegrated implants may also be related to the use of suitable presurgical examinations and the parameters used during the surgical procedures
- Zygomatic implants appear to be an effective alternative for the treatment of an atrophic maxilla.
Chrcanovic et al. (2013) [45], Sweden (NR,N) [1.66] “What is the survival rate of zygomatic implants (ZIs)?” and “What are the most common complications related to surgery of zygomatic implants?” Survival rate, complication 42 article, 1145 patients and 2402 ZIs None SR PubMed (Up to March 2012) Range: 6–120 (mo) None Between 42 studies, 12 evaluated the use of ZIs applied with immediate function protocols Both totally or partially edentulous maxilla - 12 evaluated the use of ZIs applied immediate protocol and 3 after maxillary resections for tumor ablations (showed lower success.).
- Of 2402 ZIs, 56 ZIs were reported as failures
- The CSR over a 12-year period was 96.7%.
- ZI placement needs very experienced surgeons since delicate anatomic structures such as the orbita and brain may be involved
- Despite the high survival rate observed, there is an impending need for further investigations
Chrcanovic et al. (2016) [15], Sweden (NR-N) [1.66] To assess the survival rate of zygomatic implants (ZIs) and the prevalence of complications based on previously published studies Complications Sixty-eight studies were included one randomized clinical trial,16 prospective studies, and 51 retrospective analyses, comprising 4556 ZIs in 2161 Conventional implants SR PubMed/Medline, Web of Science, and the Cochrane Oral Health Group Trials Register (up to December 2015) Range: 1–144 (mo) None 26 studies immediate loading and studies 34 studies evaluating delayed loading protocols Both totally or partially edentulous maxilla Immediate loading showed a statistically lower ZI failure rate than other studies (P = .003).
- Studies evaluating ZIs for the rehabilitation of patients after maxillary resections presented lower survival rates.
- Postoperative complications: sinusitis, 2.4% soft tissue infection, 2.0%, paresthesia, 1.0% and oroantral fistulas, 0.4%
- ZIs present a high 12-year CSR, with most failures occurring at the early stages postoperatively.
- Main complication was sinusitis, which can appear several years after placement
Aboul-Hosn Centenero et al. (2018) [48], Spain (Y-N) [1.15] To compare the survival rates (SRs) of oral rehabilitations performed with 2 zygomatic implants (ZIs) combined with regular implants (RIs) versus 4 ZIs Survival rates 6 articles (4 prospective and 2 retrospective case series)
A total of 130 ZIs and 186 conventional implants were placed in 64 patients.
4 ZIs (case) versus2 ZIs combined with regular implants RIs (control) SR and M MEDLINE/PubMed, Cochrane Central register of Controlled trials
Cochrane Oral Health group Trials Register, and EMBASE between 2007, and June 30, 2015
Range: 12–82 (mo) The criteria were modified according to the PRISMA 2009 checklist statement [17] Immediate loading Fully edentulous - ZIs SR weighted mean was 98.0%, CI [96.7 to 99.8%]. For the control group (2 ZIs + 2 RIs) and the test group (4 ZIs), the implant SR was 98.6% and 97.4%, respectively
- No statistically significant differences in terms of SRs were obtained between both groups, P = 0.286.
- No statistical differences in 2 groups in terms of survival and failure rates. The reduction on treatment time and morbidity related to regenerative approaches may be its main advantage.
- The zygoma quad seems to be the treatment of choice for the severely atrophic maxilla.
  1. Legends: Y yes, N no, ZIs zygomatic implants, SR systematic review, M meta-analysis, Mo month(s), Yr year(s)