The aim of this systematic review and meta-analysis was to compare the survival rate of the implants and the peri-implant tissue changes associated with implants inserted in fresh extraction sockets and those inserted in healed sockets. This review has been registered at PROSPERO under the number CRD42016043309. A systematic search was conducted by two reviewers independently in the databases PubMed/MEDLINE, Embase, and the Cochrane Library using different search terms; articles published until November 2016 were searched for. The searches identified 30 eligible studies. A total of 3,049 implants were installed in a total of 1,435 patients with a mean age of 46.68 years and a minimum of 6 months of follow-up. The survival rate of delayed implants (98.38%) was significantly greater than immediate implants (95.21%) ( p = .001). For the marginal bone loss ( p = .32), implant stability quotients values ( p = .44), and pocket probing depth ( p = .94) there was no significant difference between the analysed groups. The immediate implants placed in fresh sockets should be performed with caution because of the significantly lower survival rates than delayed implants inserted in healed sockets.
New designs and surface treatments have made it possible to insert dental implants immediately after tooth extraction. This is a variation of the conventional protocol for osseointegration established by Branemark . Immediate insertion reduces the time required for osseointegration , which takes 3–6 months using the conventional protocol. The novel method also minimizes bone resorption by maintaining the periodontal architecture, and it leads to better aesthetic results, particularly when the front teeth are lost.
Thus, immediate implant placement has been a focus of clinical practice for implantodontists. The technique preserves the alveolar ridge, and it decreases the morbidity and rehabilitation time associated with tooth replacement; furthermore, it increases patient satisfaction with treatment . However, the literature presents no consensus regarding the advantages of immediate implant placement. On the contrary, the following disadvantages have been reported: (1) lower implant survival rates than delayed implants placed into the alveolar ridge after a healing time, (2) marginal bone loss, and (3) changes affecting the peri-implant soft tissues .
To standardize the nomenclature used to classify the time of implant installation, Hammerle et al. published a classification based on morphologic, dimensional, and histologic changes that follow tooth extraction and on common practice derived from clinical experience. This systematic review and meta-analysis was performed according to this classification in which post-extraction implant placement in this context refers to immediate placement (type 1), early placement with soft tissue healing (type 2), early placement with partial bone healing (type 3), and late placement (type 4) .
Therefore, the aim of this study was to compare the implant survival rates and peri-implant tissue changes between implants inserted immediately after tooth extraction (fresh extraction sockets) and those inserted after a conventional healing period (healed sockets). The null hypotheses were as follows: (1) survival rates do not differ between implants inserted into fresh extraction sockets (immediate implants) and those inserted into healed sockets (delayed implants); (2) implants inserted into fresh extraction sockets do not differ significantly from those inserted into healed sockets in terms of the associated marginal bone loss or soft tissue changes.
Materials and methods
This systematic review was structured according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist described by Moher et al. and in accordance with models proposed in the literature . The methods for this systematic review were registered with PROSPERO (CRD42016043309).
Research strategy and information sources
Two researchers (C.M.M. and C.A.A.L.) independently selected the articles to be included in this review according to the inclusion and exclusion criteria described below. The PubMed/Medline, Embase, and Cochrane databases were searched for articles published until November 2016. The following search terms were entered using Boolean operators: “dental implants and immediate implant OR dental implants and immediate dental implant OR dental implants and immediately placed OR dental implants and immediate placement OR dental implants and installed immediately OR dental implants and immediately install”.
The searches attempted to identify studies that compared immediate implant insertion after tooth extraction with implant insertion after a conventional healing period (2–4 months). This systematic review and meta-analysis are based on the classification of Hammerle et al. that defines post-extraction implant placement according to installation time as the following: immediate placement (type 1), early placement with soft tissue healing (type 2), early placement with partial bone healing (type 3), and late placement (type 4) .
Disagreement between examiners regarding which articles should be included was resolved by discussion, and a consensus was reached among all of the study authors. When necessary, careful analysis was performed by a third examiner (E.P.P.) and discussion continued until a consensus was reached.
As a complement to the above database searches, a search of grey literature and a manual search of journals dedicated to a specific area were performed. Specifically, the following journals were searched manually: Clinical Implant Dentistry and Related Research, Clinical Oral Implants Research, International Journal of Oral and Maxillofacial Implants, International Journal of Oral and Maxillofacial Surgery, Journal of Oral and Maxillofacial Surgery, Journal of Clinical Periodontology, Journal of Dental Research, Journal of Oral Implantology, Journal of Oral Rehabilitation, Journal of Periodontology, and Periodontology 2000 .
Studies were initially selected through a reading of the titles and abstracts, and final study selection was performed through a reading of the full texts applying the inclusion and exclusion criteria.
The PICO approach (population, intervention, comparison, and outcome) was used to address the following question: “Do immediately inserted implants perform similarly to implants that are inserted into a healed socket?” Patients (P) that had undergone osseointegrated implant insertion into fresh extraction sockets (I) or healed sockets (C) were evaluated. The primary outcome (O) evaluated was implant survival rate. Marginal bone loss, primary implant stability, and soft tissue changes were considered secondary outcomes.
To qualify for inclusion, studies were required to (1) be randomized controlled trials, (2) be prospective studies, (3) have been published in English, (4) have more than five implants in each group, and (5) involve a follow-up period of at least 6 months.
Studies were excluded from the present review if they were (1) duplicates, (2) retrospective, (3) case series, (4) carried out in vitro , or (5) using animals, (6) systematic reviews, (7) analyses of implant loading protocols (immediate load), or (8) simple evaluations of either delayed or immediate implants—without a comparison group.
The data obtained from the selected studies were evaluated both qualitatively and quantitatively. The total number of immediate implants placed was calculated, as were the survival rate, marginal bone loss, and soft tissue changes associated with the implants. These values were compared with those obtained for implants inserted in healed sockets.
Quality analysis of the studies included
Two investigators (C.C.M. and C.A.A.L) assessed the methodological quality of the studies according to the Jadad scale . The scale ranges from 0 to 5 with scores of 3 or more considered high quality. The Cochrane Collaboration’s tool for assessing risk of bias was used to assess the quality of the studies included in this review.
The kappa coefficient was used to measure inter-rater agreement during article selection. Any disagreements were resolved by discussion and a consensus was reached among all of the authors.
Reviewer Manager 5.3 software (Nordic Cochrane Centre, Copenhagen, Denmark) was used to perform the meta-analysis; p < .05% were considered significant. Marginal bone loss, implant stability quotients (ISQs), and probing pocket depth were assessed as continuous outcome variables using the inverse variance (IV) method; they were recorded as mean differences (MDs) with a 95% confidence interval (CI). Implant survival rates were assessed as a dichotomous outcome using the Mantel–Haenszel method; they were recorded as risk ratios (RRs) with a 95% CI and the weight contribution of each study. The I 2 statistic was used to express the percentage of the total variation across studies due to heterogeneity, with 25% corresponding to low heterogeneity, 50% to moderate, and 75% to high. A funnel plot (plot of effect size versus standard error) was drawn. Asymmetry of the funnel plot may indicate publication bias and other biases related to sample size, although the asymmetry may also represent a true relationship between trial size and effect size .