Dental implant placement into fresh extraction sockets

indexImmediate placement of dental implants into fresh extraction sockets has for some time been an established surgical technique. The theory is that it preserves alveolar ridge, reduces morbidity, and is more acceptable to the patient. However, there may also be disadvantages such as reduced implant survival, unfavourable changes in the hard/soft tissue and extended treatment times. To standardise the type of implant placement they have been classified into four types:


  • Immediate placement (type 1).
  • Early placement with soft tissue healing (type 2).
  • Early placement with partial bone healing (type 3).
  • Late placement (type 4).

The research question for this systematic review and meta-analysis was: ‘‘Do immediately inserted implants perform similarly to implants that are inserted into a healed socket?’’


This review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement and registered with PROSPERO.

The population (P) was patients who had undergone osseointegrated implant insertion into fresh extraction sockets (I) or healed sockets (C). The primary outcome (O) evaluated was implant survival rate. Marginal bone loss, primary implant stability, and soft tissue changes were considered secondary outcomes. The following inclusion criteria were applied: Randomised controlled or prospective studies in English. More than five implants per group with a minimum of six months follow-up. Exclusion criteria were animal and in vitro studies, simple evaluations without comparators or analyses of loading protocols.

Two researchers independently selected and screened articles PubMed/Medline, Embase, and Cochrane databases and manually searched relevant specialist journals. Quality assessment was undertaken using the Jadad scale and Cochrane Collaboration’s tool for assessing risk of bias.


  • The systematic Search found 30 papers out of 3049 which fulfilled the inclusion criteria. On the Jadad risk of bias assessment only 8/30 studies were evaluated as high quality.
  • Meta-analysis results (Primary outcomes)
Relative risk(95% Confidence Interval) Probability
Survival favours healed sockets 2.49, (1.44 – 4.29) p = 0.001
Type 1 compared with type 2 1.45, (0.53 – 3.98). p = 0.47
Type 1 compared with type 3 5.25, (1.67 – 16.49) p = 0.005
Type 1 compared with type 4 2.86, (1.22 – 6.70) p = 0.02
  • There were no statistical differences in the secondary outcomes.


The authors concluded:-

In conclusion, immediate implant insertion should be performed with caution because implant survival rates are significantly lower than with implants inserted into healed sockets.


My intuition tells me that the authors may have the right answer but the evidence they present does not support this for various methodological reasons. The major problem is that the survival data is of relatively short duration and heterogeneous with a mean follow-up being 24 months, median 18 months and a mode  of 12 months.

Clinicians mostly will only be interested in long-term data (60 months plus). Focusing on just these longer-term studies papers in the review just leaves three papers (Cooper et al 2014, Polizzi et al 2000 and Raes et al 2016) , so a second Raes paper (Raes et al 2013)  with a stated 52 months follow up and the 2015 Oxby paper with 55 months follow up were reviewed and meta-analysed.

Looking at these research papers with the longest follow-up is simpler to appraise than the 30 the authors included. Full texts were obtained and the following conclusions made:

  • The Raes paper (Raes et al 2013) states only 52 weeks follow-up not 52 months as in the review, which is quite important if we are meant to be looking a survival studies.
  • In the Polizzi paper (Polizzi et al 2000) there is no randomisation between the healed and fresh extraction sockets.
  • The Oxby paper reads as though it is retrospective review and 25% of the sample was excluded after implant placement as the loading protocol exceeded 60 days (this group could possibly contain the failures?). Not all the implants were reviewed at 60 months (38/182 were reviewed between 36-48 months, 114/182 between 49-60 months and 30/182 between 60-63 months).
  • Lost to follow (LTF) up in the studies varies from 13% – 40%. The authors classified the LFT patients as missing completely at random to optimise the survival data.

The 2013 Raes paper was therefore excluded as the follow-up was too short, and the Oxby paper as a retrospective study (exclusion criteria). The remaining studies were included in a meta-analysis. Group a. is the data as published in the systematic review and Group b. where LTF is considered in the calculations as a failure.

Fig.1 shows the new risk ratio (RR) for the long-term data has reduced from 2.49 to 1.28. If missing data is considered as a failure the RR drops to 1.06 (Fig. 2). An interesting observation is that the risk difference for Group a (Fig. 3) is 0.01.

Fig. 1. Forest plot for the event ‘60-month implants survival rates’ for Group a.


Fig. 2. Forest plot for the event ‘60-month implants survival rates’ for Group b.


Fig. 3. Forest plot for the Risk Difference ‘60 month implants survival rates’ for Group a.


In conclusion from this data there is no difference between techniques, possibly due to the ability to select cases rather than a true randomisation. One interesting point is that long-term survival for fresh v. healed was 94.4 and 96.9; if missing data is considered a failure 5-year survival drops by a further 15%. As usual the truth lies somewhere in between.


Primary paper

Mello CC, Lemos CAA, Verri FR, Dos Santos DM, Goiato MC, Pellizzer EP.Immediate implant placement into fresh extraction sockets versus delayed implants into healed sockets: A systematic review and meta-analysis. Int J Oral Maxillofac Surg. 2017 May 3. pii: S0901-5027(17)31361-9. doi: 10.1016/j.ijom.2017.03.016. [Epub ahead of print] Review. PubMed PMID: 28478869.

Other references

Cooper LF, Reside GJ, Raes F, Garriga JS, Tarrida LG, Wiltfang J, Kern M, De Bruyn H. Immediate provisionalization of dental implants placed in healed alveolar ridges and extraction sockets: a 5-year prospective evaluation. Int J Oral Maxillofac Implants. 2014 May-Jun;29(3):709-17.

Polizzi G, Grunder U, Goené R, Hatano N, Henry P, Jackson WJ, Kawamura K, Renouard F, Rosenberg R, Triplett G, Werbitt M, Lithner B. Immediate and delayed implant placement into extraction sockets: a 5-year report. Clin Implant Dent Relat Res. 2000;2(2):93-9.

Raes S, Raes F, Cooper L, Giner Tarrida L, Vervaeke S, Cosyn J, De Bruyn H. Oral health-related quality of life changes after placement of immediately loaded single implants in healed alveolar ridges or extraction sockets: a 5-year prospective follow-up study. Clin Oral Implants Res. 2017 Jun;28(6):662-667. Epub 2016 May 22.

Oxby G, Oxby F, Oxby J, Saltvik T, Nilsson P. Early Loading of Fluoridated Implants Placed in Fresh Extraction Sockets and Healed Bone: A 3- to 5-Year Clinical and Radiographic Follow-Up Study of 39 Consecutive Patients. Clin Implant Dent Relat Res. 2015 Oct;17(5):898-907.

Raes F, Cosyn J, De Bruyn H. Clinical, aesthetic, and patient-related outcome of immediately loaded single implants in the anterior maxilla: a prospective study in extraction sockets, healed ridges, and grafted sites. Clin Implant Dent Relat Res. 2013 Dec;15(6):819-35.

Dental Elf – 2 August 2017

Dental Elf -12th Dec 2014


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.