Satheesh Elangovan BDS., ScD., DMSc
Based on included prospective studies with a mean follow-up period of 2.08 years, implants placed into fresh extraction sockets had a high 2-year survival rate of 98.4 percent (95 percent CI: 97.3 percent-99 percent).
Limited evidence suggests that immediate implants have high 2- to 3-year survival rates in select clinical situations. Long-term studies that assess patient-centered and esthetic outcomes are needed.
In humans, what are the survival and clinical success rates of immediate implants and their attached prostheses; the prevalence of their biological, technical and esthetic complications; and the magnitude of soft tissue changes following placement?
The authors searched two electronic databases for articles published between January 1991 and July 2010 and hand searched eight journals published between January 2000 and December 2010. They searched for randomized clinical trials (RCTs), prospective cohort studies and case series (with a minimum of 10 subjects) with a mean follow-up time of 12 months or more following implant placement. They only included studies that reported survival rates of immediate implants. They excluded studies with multiple interventions or those that did not clearly state the timing of restorations or loading. Two reviewers searched and appraised the evidence. Disagreements between reviewers were resolved by discussion. Data extraction included implant survival, biological complications, technical complications, esthetic outcomes and marginal bone levels from included studies. They used Poisson regression to calculate the summary estimated survival rates and assessed the degree of heterogeneity among included studies.
The search process yielded a total of 46 prospective studies, of which 10 were RCTs. The reviewed studies included a total of 2,908 implants in 2,130 patients who had anterior and/or posterior implants placed in the maxilla and/or mandible. Types of bone grafts used ranged from none to a wide array at the time of placement. A majority of studies (93.5 percent) used rough surface implants. In addition, most studies used conventional loading (> 2 months), with single crowns being the most prevalent restoration. The estimated annual failure rate was significantly lower when antibiotics were taken pre- or postoperatively. The reason for extraction, location of implant or the timing of loading had no effect on the estimated annual failure rate. Marginal bone loss occurred predominantly in the first year, and it was less than 1 mm.
The estimated annual failure rate of immediate implants is 0.82 percent (95 percent CI: 0.48 percent - 1.39 percent), which translates to a 2-year survival rate of 98.4 percent (95 percent CI: 97.3 percent - 99 percent). A lack of studies reporting implant complications prevented the determination of true prevalence of biological and technical complications related to immediate implants. Based on included studies with an observation period of 3 years or more, buccal gingival recession seemed to be the most common esthetic complication.
Source of Funding:
This review was supported by Osteology Foundation, Switzerland, and the Clinical Research Foundation for the Promotion of Oral Health, Switzerland.
Importance and Context:
Different techniques and materials are constantly being explored to shorten the overall duration of implant therapy. One such established technique is the placement of the implant at the time of extraction.(1) Therefore, it is extremely important to know the success rate of this technique, which has the potential to reduce treatment time, number of surgical sessions, morbidity and discomfort. This review differs from an earlier systematic review focused on the timing of implant placement (2) by including non-randomized trials and clinical studies that did not have a comparison/control group.
Strengths and Weaknesses of the Systematic Review:
This review addressed an important question using a search strategy that had some limitations. While searching for articles using well-defined inclusion criteria, the authors did not search for grey literature or non-English– language articles. Strengths include: the use of more than one reviewer to perform the article selection and data extraction; adequate quality assessment of the included articles; and adequate evaluation of heterogeneity. However, the authors did not assess the likelihood of publication bias nor adequately describe the study designs of selected studies. There is a discrepancy between the text and the tables in designating study designs for the included articles. In the included RCTs, the data from the control sites were not included in the assessment. The review assumed a constant annual failure rate to calculate summary survival estimates, therefore the rate should not be extrapolated to longer follow-up times.
Strengths and Weaknesses of the Evidence:
Of the included 46 prospective clinical trials, 10 studies were RCTs, of which four were judged to be at a high risk of bias and the remaining six were considered to have unclear risk of bias, making the overall evidence limited. Most of the studies had a mean follow-up time of less than 3 years. The included studies exhibited significant variation in terms of the type of implant system or biomaterials used, antibiotic use, oral location of implant, loading protocol and prosthesis delivered. The authors performed multivariable Poisson regression analysis to determine annual failure rate based on follow-up time, antibiotic use, reason for extraction and oral location of implant; they found low heterogeneity but did not consider other variables such as type of prosthesis delivered. Also, the included studies did not focus on any of the patient-centered outcomes such as morbidity or cost of treatment, but focused only on surrogate end points (soft tissue and hard tissue changes around implants and aesthetic outcomes). Since some of the included studies have small sample size, publication bias can threaten the validity of the results.
Implications for Dental Practice:
This review suggests that immediate implant placement in select clinical situations exhibits a very low short-term annual failure rate (1.6 percent). As the results are based on short-term data, the possibility of long-term biological, technical and esthetic complications associated with implants and the prostheses they support cannot be completely ruled out. Due to the lack of control groups in the assessment, this review does not provide recommendation on the optimal timing of implant placement.
1. Chen ST, Wilson TG Jr, Hämmerle CH. Immediate or early placement of implants following tooth extraction: review of biologic basis, clinical procedures, and out-comes. Int J Oral Maxillofac Implants 2004;19 Suppl:12-25.
2. Esposito M, Grusovin MG, Polyzos IP, et al. Timing of implant placement after tooth extraction: immediate, immediate-delayed or delayed implants? A Cochrane systematic review. European Journal of Oral Implantology. 2010; 3(3):189-205.