From the initial search, 135 citations were found (Fig. ). Based on the evidence categories of articles, 30 articles were finally selected and full texts were obtained.
Flow diagram for the search strategy.
Ten studies were excluded after deep analysis (Table ) (8
). Four studies were excluded owing to an insufficient follow-up period (less than 12 months) (8
). Another one did not report any specific outcome and focused only on patient satisfaction (17
). Two were clinical reports and were not included (9
) and two more were excluded due to insufficient sample size (no more than 10 implants) (10
). One study was excluded because implants were placed following a delayed protocol (16
List of excluded articles after the final selection.
Out of the included articles (Table , , ), 8 did not include a control group (18
). Among the included studies, all of them presented a survival rate over 90%. 1139 Immediate implants placed on 904 patients were carefully analyzed with a follow-up of 12 to 60 months.
The questions proposed in this systematic review were then answered and compared with the included articles:
Are there significant differences in crestal bone resorption between immediate and delayed implants? Where?
In the prospective clinical study using platform switching, immediate implants showed reduced crestal bone loss (mean 0.08mm ± 0.53 mesial 0.09 ± 0.69 distal) (20
). Nevertheless, a similar study found no difference between platform switching and platform matching (on average from 7.71 to 7.51 –0.2mm- vs. 9 to 8.57 -0.4mm-) (26
A randomized clinical trial of 40 implants were placed in 40 patients in the anterior maxilla–20 immediate implants and 20 dela-yed implants. After a 24-month follow-up period, the control group resulted in a mean bone loss of 1.16mm and the test group of 1.02mm. Once again, there were no statistically significant differences (27
The survival rate of early-loaded implants placed in fresh extraction sockets of teeth with endodontic and periodontal lesions in the mandible demonstrated no implants failures; a mean marginal bone loss of 0.7mm was recorded during the follow up period. No signs of infection around the implants were detected at any control visit (25
Differences between delayed-immediate (Im) and the delayed (De) protocols for implant placement were also evaluated. A statis-tically significant radiographic marginal bone resorption had occurred in the Im group (mesial 0.5mm distal 1mm; mean=0.8mm) and in the De group (mesial 0.8mm distal 0.6mm; mean=0.7mm) during the follow-up period. It was demonstrated that probing pocket depths and marginal bone levels after 18 months of loading of the implant-retained crowns were not affected by the pre-sence of peri-implant bone defects immediately after implant placement (28
Botticelli et al. treated 18 patients with 21 immediate implants. The follow-up period was 5 years. The crestal bone loss was mea-sured in the interproximal areas (m-d aspects facing tooth surfaces showed a higher degree of radiographic bone gain 0.39mm ± 0.59 compared to implant sites that faced adjacent implants 0.04mm ± 0.59) showing a stable bone level over time, even a gain in immediate implants (18
According to the literature reviewed, measurements of interproximal bone levels are well recorded but few of them show diffe-rences between immediate and delayed protocols.
Do immediate implants have a significant effect on soft tissue recession outcomes?
A randomized clinical trial comparing delayed and immediate implant placement and concluded that immediate placement had an improved average gingival recession outcome of 1mm. However, crestal bone levels were not better preserved with the delayed protocol, and they concluded there were no statistically significant differences (29
The platform switching study showed an interproximal soft tissue (papillae) of 0.88mm and a 0.45mm buccal recession in plat-form matching and 0.18mm and 0.045mm respectively in platform switching on average; therefore a soft tissue gain was demonstrated (26
Measurements of soft tissue recessions in a 5-year study with an outcome of 5 buccal sites exhibited soft tissue recession; four of them were positioned in the lower jaw showing the metal margin of the restoration. The mean width of the keratinized mucosa decreased 0.3 mm (buccal site) and 0.4mm (lingual site) during the follow up period (18
In a 2-year follow-up study on which 16 patients were treated for single tooth replacement and randomly divided into two groups, the test group patients received immediate implants and the control group received implants in healed sites. The following para-meters were evaluated: marginal bone resorption (IP 0.54mm ± 0.51mm vs. DP 0.46mm± 0.54mm) and the position of the mucosal margin (IP: 0.8mm± 0.7mm; DP: 0.6mm± 0.6mm). No statistically significant differences were found between the test and control groups, as in the study performed by Lindeboom et al. 2006 (<1mm in 7 IP and 4 DP; <2mm in 2 IP and 0 in DP) (30
However, once again, literature of long-term follow-up studies does not show significant differences between both groups.
Does the presence of periapical infection have an effect on the immediate implant success or survival rate?
In most of the studies (19
) analyzed in this review, when a periapical infection was present the implant was not placed immediately, instead a delayed placement protocol was performed or patients were just excluded. In fact, in most texts the presence of periapical infection was an exclusion criteria.
However, the clinical outcome of implants immediately placed into fresh extraction sockets of teeth affected by chronic lesions was examined. 17 Patients with periapical infection and 17 patients without it for immediate placement were chosen in another. When infection was present, granulation tissue was removed previously and antibiotics were given (Amoxicillin 750mg 1h before the treatment and 750mg every 8hours, 5 days post-operation). From the initial 34 patients, 4 test and 1 control were excluded due to the lack of primary stability. The rest of the implants presented a survival rate of 100% after 1 year follow-up period. Periapical pathology did not show an increased rate of failures. There was a statistically significant loss of vertical bone height at the adjacent teeth and the implant site, and of buccal keratinized mucosa between baseline and 12 months in both groups (36
Also, a randomized clinical trial conducted to evaluate clinical outcome when all implants were placed in sockets affected by chronic periapical pathology. 25 Implants were immediately placed (IP) after extraction and 25 after a 3-month healing period (DP, delayed placement). Antibiotic was only given one hour before the surgical procedure (Clyndamicine 600mg). Degranulation of the socket was immediately performed after dental extraction. Gingival recession was more prominent and clinically significant in the IP group (see (Table 5a, 5b, 5c). 2 Implants from the IP group were lost, achieving a survival rate of 92% for IP implants versus 100% for DP implants (23
Does the gap treatment minimize crestal bone loss?
Bovine bone matrix and collagen membrane is the most common grafting material when the distance between the implant and the bone wall needs to be filled in order to preserve crestal bone (19
). Bio-Oss an Bio-Gide were used when the gap exceded 1mm (19
Nonetheless, mineralized bone allograft when needed without specifying the gap size or PRGF and autogenous bone graft to cover deshiscences were also used (22
). Implant macrodesign as an expanded platform was taken in advantage to cover the coronal area of the gap (20
). 150 Immediate implants were also placed and if the marginal defect between the implant surface and the inner wall of the extraction socket exceeded 2mm autogenous bone chips were used (32
A prospective study evaluating healing of marginal defects in immediate transmucosal implants grafted with bovine bone matrix was performed. 30 Implants in the esthetic zone were analyzed of 30 patients that randomly received Bio-Oss (n=10), Bio-Oss and resorbable collagen membrane (n=10) or no graft as a control group (n=10). No significant differences were found regarding vertical defects, although horizontal resorption was significantly greater in the control group (31
50 Implants were placed in fresh extraction sockets in maxillae and posterior mandibles, including defects around the implants in 19 patients. Temporary prostheses were connected immediately after surgery or within 7 days. Thirteen did not require any type of regenerative procedure (no defect), 33 were filled with autogenous bone (closed defect), and 4 were filled with autogenous bone and also had a resorbable membrane (open defect). After 18 months, none of the implants had failed. In the no defect group, the mean resorption was 1.1mm; in the closed defect group, 0.6mm and in the open defect group 2.1mm (37
Are there any significant differences in implant stability between immediate and delayed implants?
An important clinical factor to ensure osseointegration is primary implant stability. There are several methods described to mea-sure this parameter. The most common are: during the implant placement with the insertion torque, and resonance frequency analysis (RFA) with the Ostell Mentor device (20
In Calvo-Guirado et al. study, immediately placed implants were included with an initial primary stability over 60 ISQ as measu-red with the Ostell Mentor. The mean ISQ values (±SD –standard deviation-) were 71.1 ±6.2 at baseline and 75.8 ± 6.9 at 12-month follow-up. The differences in these results were not statistically significant (20
Lang et al. compared primary stability of immediately placed implants of tapered versus cylindrical design using RFA. No statis-tically significant differences were found. However, the authors reported that this “study had not been powered to reveal potential differences between standard cylindrical and tapered devices” (33