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.


Peri-implantitis: lack of high quality studies for surgical regenerative treatment

implant astra

Implant treatment has a well-established body of evidence supporting its long-term success and efficacy. Following in the shadow of this success however we now have the problem of peri-implantitis, characterised by inflammation and degeneration of the hard and soft tissues surrounding the implant and eventually leading to its loss from the jaw bone. Various techniques have been advocated to treat this infection taking its origins from periodontal treatment such as non-surgical, surgical and regenerative procedures.

The purpose this study was to systematically review the literature on the surgical regenerative treatment of the peri-implantitis and to determine an effective therapeutic predictable option for its clinical management.


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 carried by two independent researchers using Ovid MEDLINE, PubMed, Embase, and Dentistry and Oral Sciences Source. Databases were searched from January 2006 to March 2016 and restricted to English, manual searches were also carried out in the relevant major journals. Inclusion criteria were: Human prospective and retrospective observational studies involving at least one surgical regenerative treatment method for peri-implantitis. Minimum sample size was 10 implants with no less than 12 months follow-up. Excluded studies included animal and in vitro studies, patients with uncontrolled systemic disease that put the implant at risk and ceramic or coated implants. Quality appraisal was carried out by two independent reviewers using the Cochrane Collaboration tool for assessing risk of bias in randomised trials (Higgins JPT et al. 2011)


  • From 883 records only 18 fulfilled the inclusion criteria. This included 8 prospective clinical studies, seven case series and three randomised clinical trials (RCT’s). A total of 528 patients with 713 implants were treated.
  • 2 studies were at low risk of bias, 1 moderate, and 3 high. The remainder were classified as unclear.
Total mean radiological bone level change +2.97 mm (95% CI 1.58 to 2.35)
·       Mean radiological bone level + membrane +1.86 mm (95% CI 1.36 to 2.36)
·       Mean radiological bone level – membrane +2.12 mm (95% CI 1.46 to 2.78)
·       Mean radiological bone level submerged +2.17 mm (95% CI 1.87 to 2.47)
·       Mean radiological bone level non-submerged +1.91 mm (95% CI 1.44 to 2.39)
Total mean probing depth change -2.78 mm (95% CI 2.31 to 3.25)
·       Mean probing depth change + membrane -2.88 mm (95% CI 2.31 to 3.45)
·       Mean probing depth change – membrane -2.60 mm (95% CI 1.90 to 3.30)
·       Mean probing depth change submerged -2.68 mm (95% CI 1.71 to 3.64)
·       Mean probing depth change non-submerged -2.77 mm (95% CI 2.23 to 3.30)
Total mean bleeding on probing change -55% (95% CI 45.2 to 64.4)



The authors concluded: –

Within the limits of this systematic review, surgical regenerative treatment is a predictable option in managing peri-implantitis and improving clinical parameters of peri-implant tissues. There is no fundamental advantage of membrane use for bone graft coverage or submergence of the healing site on the final outcome of peri-implant defect regeneration. Due to the limited number of randomised clinical trials, at the time there is a lack of scientific evidence in the literature regarding the superiority of the regenerative versus non-regenerative surgical treatment


There are a few points to mention in relation to this well conducted review. Firstly, there is a lack of high quality studies with only 2 out of the 18 fulfilling the criteria and how this might influence the overall meta-analysis (this is commonly missed out in dental related systematic reviews, even though it is one of the PRISMA criteria the authors mention they adhere to). PRISMA has since been updated (Moher et al. 2015).   Secondly, the risk of bias tool is designed for RCT’s (3/18) and there was no mention of using one of the tools specifically designed for non-randomised observational studies (Sterne et al. 2016; Wells 2013).

Finally, the author concludes that surgical regenerative treatment is a predictable option for the treatment of peri-implantitis but fails to mention how well or poorly this performs against standard non-regenerative debridement of the lesion. The reason I mention this is that a second paper was published by members of the same team, in the same institution, in the same month that could have shed some light on clinical effectiveness (Ramanauskaite et al. 2016).

First Posted on the National Elf Service


Primary paper

Daugela P, Cicciù M, Saulacic N. Surgical Regenerative Treatments for Peri-Implantitis: Meta-analysis of Recent Findings in a Systematic Literature Review. J Oral Maxillofac Res. 2016 Sep 9;7(3):e15. eCollection 2016 Jul-Sep. Review. PubMed PMID: 27833740; PubMed Central PMCID: PMC5100640.

Other references

Original review protocol on PROSPERO

Higgins JP, Altman DG, Gøtzsche PC, Jüni P, Moher D, Oxman AD, Savovic J, Schulz KF, Weeks L, Sterne JA; Cochrane Bias Methods Group; Cochrane Statistical Methods Group. The Cochrane Collaboration’s tool for assessing risk of bias in randomised trials. BMJ. 2011 Oct 18;343:d5928.

Sterne JA, Hernán MA, Reeves BC, et al. ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interventions. BMJ. 2016 Oct 12;355:i4919. doi: 10.1136/bmj.i4919. PubMed PMID: 27733354; PubMed Central PMCID: PMC5062054.

Wells, G.A., 2013. Newcastle Ottawa scale Coding Manual for Case-Control Studies. The Ottawa Hospital Research Institute.

Ramanauskaite A, Daugela P, Faria de Almeida R, Saulacic N. Surgical Non-Regenerative Treatments for Peri-Implantitis: a Systematic Review. J Oral Maxillofac Res. 2016 Sep 9;7(3):e14. eCollection 2016 Jul-Sep. Review. PubMed PMID: 27833739; PubMed Central PMCID: PMC5100639.




Complete overdentures retained by mini implants.

Posted Dental Elf 10/03/2017

Complete DenturesWith the advances in preventative dentistry one consequence has been patients becoming edentulous later in life. Accepting and adapting to conventional complete denture can be extremely challenging both physically and psychologically. There is now good evidence to support implant supported mandibular overdentures (Feine et al., 2002) using standard implants.
The aim of this review was to evaluate the use of mini-implants (diameter <3mm) to retain complete over-dentures in terms of survival, marginal bone loss, satisfaction and quality of life (Lemos et al, 2016).


The review followed the PRISMA statement (Moher et al., 2009) and was registered with PROSPERO.  Searches were conducted in PubMed/Medline, Embase and the Cochrane Library database checking articles published up to September 2016. In addition, they conducted a hand search of high impact journals in the field of implant retained prosthodontics. The eligibility criteria were, randomised controlled trials (RCTS) or prospective studies published in English. Two reviewers independently selected studies for inclusion, abstracted data and assessed risk of bias using the Newcastle-Ottawa Scale. The primary outcome was the survival rates of the mini implants; and the secondary outcomes included marginal bone loss, satisfaction and quality of life with the mini implants when they were used for retaining overdenture prosthesis.


  • 24 studies (4 RCTs, 20 prospective observational studies).
  • Risk of bias scores were 6 papers scored 9/9, 2 scored 8/9, 2 scored 7/9, 13 scored 6/9 and one paper scored 5/9
  • A total of 2492 mini implants and 386 standard implants were placed in 896 patients.
  • Mean age 65.93
  • No formal meta-analysis was carried out
  • Primary outcomes
    • Mini implant survival rate of 92.32% over 1-7 years
    • Maxillary arch implants had a higher failure rate at 31.17%
  • Secondary outcomes
    • Marginal bone loss below 1.5mm
    • Overdenture prosthesis retained by mini implants exhibited a significant increase in retention, stability chewing, speaking, comfort, aesthetics and improvements in satisfaction/quality of life.
    • Overdenture survival 90.58%


The authors concluded

Within the limitations of this study, the present systematic review indicates that the use of mini implants for retaining overdenture prosthesis may be considered an alternative treatment, since it presents high survival rates of mini implants, acceptable marginal bone loss, and improvements in variables related to satisfaction and quality of life of patients.


This systematic review adopted elements of the PRISMA protocol and identified a good number of prospective studies. A risk of bias analysis was undertaken with the authors scoring 10 papers as low risk of bias and 14 at a high risk of bias. Their outcome measurements were a combination of quantitative and qualitative data. Unfortunately, there was no meta-analysis undertaken and the survival rates given were missing both confidence intervals and a time frame. A quick review of the quantitative data provided by the review authors in table 2 revealed the mode for patients per study was 30 and the mode for follow-up was I year. The two comparison systematic reviews (Dantas et al, 2014; Raghoebar et al, 2014) which the authors concurred with reference high survival rates had similar extremely short follow-up periods and small sample sizes. The results from this systematic review therefore need to be interpreted with extreme caution due to problems with the external validity of the primary research and the synthesis of that data within the review.


Primary Paper

Lemos CA, Verri FR, Batista VE, Júnior JF, Mello CC, Pellizzer EP. Complete overdentures retained by mini implants: A systematic review. J Dent. 2017 Feb;57:4-13. doi: 10.1016/j.jdent.2016.11.009. Review. PubMed PMID: 27888049.

Other references

Dantas Ide S, Souza MB, Morais MH, Carreiro Ada F, Barbosa GA. Success and survival rates of mandibular overdentures supported by two or four implants: a systematic review. Braz Oral Res. 2014;28:74-80. doi: 10.1590/S1806-83242013000600012. Review. PubMed PMID: 24402059.

Feine JS, Carlsson GE, Awad MA, Chehade A, Duncan WJ, Gizani S, Head T, Lund JP, MacEntee M, Mericske-Stern R, Mojon P, Morais J, Naert I, Payne AG, Penrod J,Stoker GT, Tawse-Smith A, Taylor TD, Thomason JM, Thomson WM, Wismeijer D. The McGill consensus statement on overdentures. Mandibular two-implant overdentures as first choice standard of care for edentulous patients. Montreal, Quebec, May 24-25, 2002. Int J Oral Maxillofac Implants. 2002 Jul-Aug;17(4):601-2. Review. PubMed PMID: 12182304.

Moher D, Liberati A, Tetzlaff J, Altman DG; PRISMA Group.. Preferred reportingitems for systematic reviews and meta-analyses: the PRISMA statement. PLoS Med.2009 Jul 21;6(7):e1000097. doi:10.1371/journal.pmed.1000097. PubMed PMID:19621072; PubMed Central PMCID: PMC2707599.

Raghoebar GM, Meijer HJ, Slot W, Slater JJ, Vissink A. A systematic review of implant-supported overdentures in the edentulous maxilla, compared to the mandible: how many implants? Eur J Oral Implantol. 2014 Summer;7 Suppl 2:S191-201. Review. PubMed PMID: 24977255.

Raghoebar, G. M., Meijer, H. J. A., Slot, W., Slater, J. J. R. and Vissink, A. (2014) ‘A systematic review of implant-supported overdentures in the edentulous maxilla, compared to the mandible: how many implants?’, European journal of oral implantology, 7 Suppl 2(November 2016), pp. S191-201.