Extra-oral implants: barclips versus magnets


Patients may develop severe facial defects as a consequence of trauma, cancer surgery or congenital disorders. Craniofacial prosthesis to restore tissue loss in the eye, ear, nose and at multiple sites have been developed over the years to improve the individual’s quality of life and disguise the aesthetic problems created post surgery. These craniofacial prostheses can be retained either with skin adhesives or mechanically with extraoral implants.The purpose of this systematic review (Brandao et al. 2016) was to analyze the current data to identify the best retention system for implant-retained craniofacial prostheses.


The review followed the PRISMA statement (Moher et al. 2009), the protocol was also registered on the International Prospective Register of Systematic Reviews (PROSPERO) database. Searches were conducted by two independent reviewers in MEDLINE using PubMed and Web of Science databases. Dates were limited to January 2005 to September 2015 and the English language. Manual searches were also carried out in the relevant major journals. Eligibility criteria were as follows: studies published in English describing at least 10 participants evaluating different types of retention system or presented information on implant survival, peri-implant soft tissue reaction, or prosthetic complications in the aftercare period. Exclusions included case reports and case-series and narrative reviews. Two independent reviewers selected studies for inclusion, abstracted data and assessed risk of bias/quality using the Jadad scale (Jadad et al. 1996). Outcome was defined as implant survival, and peri-implant soft tissue reaction related to the extraoral implants and complications caused by the retention systems.


  • 12 studies fulfilled the inclusion criteria (2 prospective and 10 retrospective).
  • The quality of the evidence was low, 7 scored 0/5 and 5 scored 1/5 on the Jadad scale.
  • 492 participants were included, mean age 48 years. All selected studies for meta-analysis were retrospective.
Primary Outcomes (Implant survival)
Overall implant survival rate was 90.1%
Non-irradiated sites 93.3%
Irradiated sites 82.2%
Auricular 99.1%
Orbital 85.2%
Nasal 89.5%
Secondary outcome (Peri-implant soft tissue reaction)
Grade 0 55.4%
Grade 1 22.4%
Grade 2 15.6%
Grade 3 7.2%
Grade 4 0.2%
Prosthesis types (n), retention system (bar clips/magnets)
Nasal 125,81,22
Auricular 353, 129,18
Orbital 268, Mostly magnets
Large facial 14, 8,6
  • Retention system failure 29 of 159 implants with magnets (18.2), 25 of 79 implants with bars (31.6)


the authors concluded

The limited data collected indicate that the type of retention system appears not to affect the prosthetic treatment outcome or the survival of extraoral implants, and no definitive conclusions as to the best retention system can be drawn. Further well-designed research such as randomized clinical trials (RCTs) comparing both options should be performed considering participant preferences.


The results of this review should be considered with caution as the main limiting factor (which the author does address in the discussion section) was the quality of the primary research. By its very nature, the area for study does not lend itself to large numbers of participants or the undertaking of RCTs. It was interesting to note that the author used the Jadad scale to assess quality even though there were no RCTs and the use of this scale is  explicitly discourages in the Cochrane Handbook of Systematic Reviews of Interventions (Higgins & Green 2009) since it has a strong emphasis on reporting rather than conduct.

The small sample sizes compound the problem of the type of defect, site, duration of study and prosthesis. The author cites survival rates in the results but they contain neither time frame nor confidence intervals, also a definition for the grading scale for peri-implant soft tissue reaction is missing.

An interesting area for discussion is whether the included studies are cohort studies or case-series (Agha et al. 2016; Dekkers et al 2012) as the studies the authors included resemble an amalgamation of multiple case-reports rather than a clearly structured study cohort or RCT. In this review the difficulty in producing any ‘high quality’ survival data figures would add more weight to defining the studies as case-series, since a central feature of a cohort study is that it enables anabsolute risk estimate for the outcome to be calculated.


Dental Elf Summary Review Link

Primary paper

Brandao, T.B. et al., 2016. A systematic comparison of bar-clips versus magnets. Journal of Prosthetic Dentistry, 117(2), p.321–326.e2.

Other references

Agha, R.A. et al., 2016. Systematic review of the methodological and reporting quality of case series in surgery. British Journal of Surgery, 103, pp.1253–1258.

Dekkers OM,et al. Distinguishing case series from cohort studies. Ann Intern Med. 2012;156:37-40.

Higgins, J. & Green, S., 2009. 8.3.3 Quality scales and Cochrane reviews. Cochrane Handbook for Systematic Reviews of Interventions, p.192. Available at: http://handbook.cochrane.org/chapter_8/8_3_3_quality_scales_and_cochrane_reviews.htm [Accessed March 18, 2017].

Jadad, A.R. et al., 1996. Assessing the quality of reports of randomized clinical trials: Is blinding necessary? Controlled Clinical Trials, 17(1), pp.1–12.

Moher, D. et al., 2009. Preferred Reporting Items for Systematic Reviews and Meta-Analyses : The PRISMA Statement. , 6(7).

Short dental implants for the atrophic posterior mandible?


The main aim of this systematic review is to look at implant based restorative options for restoring the atrophic posterior mandible using osseointegrated dental implants. The atrophic posterior mandible is defined here as having a residual ridge height of 8mm from the inferior dental nerve to the crest of the ridge. The two options considered are short dental implants < 8mm in length placed in pristine bone compared to standard long implants >8 mm placed after bone augmentation procedures, in this care either autogenous onlay grafts or non-onlay autogenous and xenogeneic bone grafts


This review followed the PRISMA statement. Searches were screened by two independent researchers using Medline, and Cochrane Oral Health Group databases. Databases were searched from January 1st 2006 to July 30th 2016 and restricted to English, manual searches were also carried out in the relevant major journals.

Inclusion criteria were: Randomised clinical studies (RCT’s) that included clinical or radiological outcomes of the surgical strategies for rehabilitation of atrophic posterior mandibles in partially edentulous patients. This including any dimensional change, survival rate and adverse event and follow-up from 12 to 24 months. Excluded studies included animal studies, repeated reports of the same study, and studies including patients who were heavy smokers, drinkers, or had poor oral hygiene.

Quality appraisal was carried out by each of the authors  using the Cochrane Collaboration tool for assessing risk of bias in randomised trials. The primary outcomes were implant failure and marginal bone loss. Secondary outcomes were biological complications and prosthesis failure.


  • From 138 records only 12 fulfilled the inclusion criteria. A total of 353 patients with 674 implants were treated.
  • None of the papers selected were judged as having a low risk of bias.
  • The authors ranked the studies into three categories:
    • Group A: 5 studies which compared outcomes of standard implants placed in augmented bone (long implants group) vs. outcomes of short implants placed in pristine bone (short implants group).
    • Group B: 4 studies which compared outcomes of standard implants placed in bone augmented with onlay block (onlay blocks group) vs. outcomes of standard implants placed in augmented bone with any of the other augmentation procedures that did not involve onlay blocks (non-onlay blocks group).
    • Group C: 4 studies not included in category A) or B). Meta-analysis could not be performed.
Group A Risk Ratio 95% Confidence Interval P-Value
Short implant v. long implant (Implant failure) 1.59  0.54 to 4.69 0.397
Short implant v. long implant (Prosthesis failure) 1.49  0.0.56 to 3.96 0.426
Short implant v. long implant (biological complications) 2.82  1.81 to 4.4 <0.0001
Mean Diff 95%Confidence Interval P-Value
Short implant v. long implant (marginal bone loss) 0.05 mm 0.026 to 0.079 <0.0001
Group B Risk Ratio 95% Confidence Interval P-Value
Onlay Group v. Non-onlay Group 1.81  0.42 to 7.84 0.43
  Mean Diff 95% Confidence Interval P-Value
Onlay Group v. Non-onlay Group 0.006 mm  -0.19 to 0.177 0.946



The authors concluded:-

Findings from subgroup analyses revealed that

(1) short implants placed in the posterior atrophic areas of partially edentulous mandibles were associated with superior outcomes compared with long implants in augmented bone, such as lower rate of biological complications and of peri-implantbone loss; whereas

(2), there was no evidence that onlay augmentation was inferior to any of theother augmentation techniques employed


Even though the results of this systematic review and meta-analysis favour short implants over standard implants placed in augmented bone the evidence must be interpreted with extreme caution for the following reasons:

  • A wider literature search may have found more relevant papers.
  • There were no studies that were at a low risk of bias.
  • The mean number of implant in the studies were 28/arm of study leading wide confidence intervals
  • The study durations were very short and only one study extended beyond 4 years, 5 out of 12 studies were only 12 months long.

In general, there are issues with statistical v. clinical significance. Even though the risk ratio favours short implants in terms of reduced biological complications there are no other metrics where there is a visible clinical difference; an example would be marginal bone loss of 0.05mm. Some qualitative research would be interesting to explore the patient’s experience of bone augmentation procedures in terms of morbidity against short implant placement into pristine bone.


Primary paper

Toti, P. et al., 2017. Surgical techniques used in the rehabilitation of partially edentulous patients with atrophic posterior mandibles: A systematic review and meta-analysis of randomized controlled clinical trials. Journal of Cranio-Maxillofacial Surgery.

Other references

Dental Elf – 2nd Dec 2015

All-on-4®’ treatment concept: current evidence limited

wordleThe Nobel Biocare websites states  “All-on-4® treatment Concept: A minimally invasive solution with a fixed full-arch restoration for high patient satisfaction. In 1998 Dr Paulo Malo successfully treated the first patient with the All-on-4® treatment concept. Since then hundreds of thousands of patients have been treated with this concept using Nobel Biocare implants. The All-on-4® treatment concept is the best solution for full-arch treatment using tilted implants. But only when Nobel Biocare products are combined. Many have tried to mirror this ground-breaking concept, but only we have the scientifically documented success to back it up.”(NobelBiocare 2016).

The objective of the authors was to systematically review the literature on the All-on-4® (Ao4) treatment concept regarding its indications, surgical procedures, prosthetic protocols, technical and biological complications after at least three years in function.(Soto-Penaloza et al. 2017)


The review followed the PRISMA statement. Searches were conducted by two independent reviewers using MEDLINE (via PubMed), EMBASE, and the Cochrane Library of the Cochrane Collaboration (CENTRAL). This was supplemented with grey literature via Open Grey . The dates were limited to January 2005 – April 2016 with no language restriction. Eligibility criteria were systematic reviews, ran­domized clinical trials, controlled clinical trials, prospec­tive and retrospective cohort studies and case series; only studies involving human individuals, aimed at showing efficacy of the all-on-four treatment concept, including ≥ 10 patients, with a minimum follow-up of three years, and reporting data related to treatment indication, surgical pro­cedures, prosthetic protocols and complications (prosthetic and biological) associated to the all-on-four protocol. Two reviewers independently selected studies for inclusion, abstracted data and assessed risk of bias using a modified version of the Cochrane Collaboration tool for assessing risk of bias (Higgins JPT et al. 2011) for the randomised control trial , and the Newcastle-Ottawa Scale   for the non-randomised studies. The authors cited three outcome criteria:

  1. Treatment indications, surgical procedures, pros­thetic protocols (loading time, prosthetic material, abutment, type of fixation, occlusal control).
  2. Technical complications (prosthesis fracture, abutment fracture, screw fracture or losses).
  3. Biological complications (mucositis, peri-implanti­tis, implant failure).


  • 24 studies fulfilled the inclusion criteria (1 randomised control trial, 9 prospective studies, 14 retrospective studies and 7 case series.
  • According to the authors assessment 13 studies were at high risk of bias and 11 at low risk of bias.
  • A total of 1963 patients received 11,743 implants, no mean follow-up time or number of prosthesis were specified.

Primary outcome

  • This was presented as a narrative review showing the wide variability in inclusion criteria, surgical techniques, and prosthetic protocol while remaining within the Ao4 concept guidance protocol and products.
  • The most common prosthetic complication was fracture of the acrylic prosthesis. 23.2% of patients had a breakage of the definitive prosthesis.
  • An implant survival rate at 24 months of 99.8%.


The author concluded:-

The all-on-four treatment concept offers a predictable way to treat the atrophic jaw in patients that do not prefer regenerative procedures, which increase morbidity and the treatment fees. The results obtained indicate a survival rate for more than 24 months of 99.8%. However, current evidence is limited due the scarcity of infor­mation referred to methodological quality, a lack of adequate follow-up, and sample attrition. Biological complica­tions (e.g., peri-implantitis) are reported in few patients after a mean follow-up of two years. Adequate definition of the success / survival criteria is thus necessary, due the high prevalence of peri-implant diseases.


This comprehensive review looked at large volume of data concerning the Ao4 concept, but as the author points out in the conclusion there is also a lack of reproducible data to make high quality quantitative conclusions with. One concern was that several papers exhibited conflicts of interest with Nobel Biocare which were not disclosed in the literature.  A second concern that needed investigating was the mention of a survival rate for more than 24 months of 99.8%, which seemed too good to be true. I therefore spent a bit of time doing a sensitivity analysis by filtering their reviews. I excluded all the papers that were retrospective, were at high risk of bias and less than 5-years follow-up and I reviewed the full-text primary research papers that remained. This immediately shrank the eligible studies from 24 down to 6  and then eventually to 2 papers (Cavalli et al. 2012; Lopes et al. 2015).

From the 60-month survival data and imputing the missing data results the best-case survival at five years /implant was 97% (95% CI: 94 to 100) and at worst 86% (95% CI: 79 to 93). The authors offered no figures on peri-implantitis incidence or prevalence but the latest paper from the University Hospital Ghent (Browaeys et al. 2015) concluded that after examining 80 implants placed using the A-on-4 concept, after 3 years 49.2% had an unacceptable ongoing bone loss. It is important that researches make use of their quality and risk of bias assessments when undertaking SRs and follow up on missing data.

First posted on The Dental Elf


Primary paper

Soto-Penaloza, D. et al., 2017. The all-on-four treatment concept: Systematic review. Journal of Clinical and Experimental Dentistry, 9(3), pp.0–0.

Other references

Browaeys, H. et al., 2015. Ongoing Crestal Bone Loss around Implants Subjected to Computer-Guided Flapless Surgery and Immediate Loading Using the All-on-4?? Concept. Clinical Implant Dentistry and Related Research, 17(5), pp.831–843.

Cavalli, N. et al., 2012. Tilted implants for full-arch rehabilitations in completely edentulous maxilla: A retrospective study. International Journal of Dentistry, 2012.

Higgins JPT et al., 2011. The Cochrane Collaboration’s tool for assessing risk of bias in randomised trials. British Medical Journal, 343, pp.889–893.

Lopes, A. et al., 2015. The NobelGuide All-on-4 Treatment Concept for Rehabilitation of Edentulous Jaws: A Prospective Report on Medium- and Long-Term Outcomes. Clinical Implant Dentistry and Related Research, pp.e406–e416.

NobelBiocare, 2016. All-on-4. Nobel Biocare Services AG.