Abstract
The aim of this systematic review was to evaluate the survival and success rates of osseointegrated implants determined in longitudinal studies that conducted a follow-up of at least 10 years. A broad electronic search was conducted in MEDLINE/PubMed and the Cochrane Central Register of Controlled Trials (CENTRAL) for relevant publications in indexed journals, evaluating the clinical performance of dental implants. Using inclusion and exclusion criteria, two reviewers analyzed titles, abstracts, and complete articles, prioritizing studies of the randomized clinical trial type. A total of 23 articles were included in this review. Ten prospective studies, nine retrospective studies, and four randomized clinical trials, which evaluated 7711 implants, were selected. The mean follow-up time of the studies included was 13.4 years. All of the studies reported survival rates and mean marginal bone resorption values, with cumulative mean values of 94.6% and 1.3 mm, respectively. Fourteen studies related success rates. Taking into consideration the disparate outcome measures employed to assess dental implant performance and within the limitations of this systematic review, we may affirm that osseointegrated implants are safe and present high survival rates and minimal marginal bone resorption in the long term.
The first longitudinal studies evaluating osseointegrated implants showed satisfactory results. Today, with over 40 years of scientific evidence, the clinical use of implants has increased by the day. Nevertheless, few studies have conducted follow-up for periods longer than 10 years, which is fundamental to enable us to understand the biological behaviour of implants.
In longitudinal studies on osseointegrated implants, the terms ‘survival’ and ‘success’ are used routinely. However, these terms continue to generate confusion with regard to their real meanings, and are frequently used incorrectly, even in scientific studies. Knowledge and standardization of these terms is necessary to facilitate communication, comparison, and complete understanding among professionals in this field.
Studies on success rates in implant dentistry are complex because of the large number of existing variables, such as surgical techniques, materials used, and duration of follow-up. In addition, various criteria have been proposed for the definition of success, and the absence of international standardization makes comparison between studies difficult.
The aim of this study was to evaluate, by means of a systematic review of the literature, the survival and success rates of osseointegrated implants determined in longitudinal studies with follow-up periods of at least 10 years.
Materials and methods
Focused question and study objective
The focused research question was “What is the survival and success rate of implants in a period of at least 10 years of follow-up?” The objective of this systematic review was to attempt to fill the void in the literature related to the long-term survival and success data of dental implants. This knowledge provides a basis on which the clinician can make decisions in treatment planning.
Development of a protocol
To investigate the survival/success rate of implants, an extensive search was done to identify longitudinal studies in humans, in which follow-up of at least 10 years was conducted. This systematic review was carried out in accordance with the steps of practice based on scientific evidence and the methodology was adapted to the PRISMA statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). The clinical questions of this review were broken down and organized using the PICO strategy (population, intervention, comparison, outcome), as proposed by evidence-based practice.
Search strategy
A broad electronic search was made from January 2012 to November 2013 in the database of the National Library of Medicine, Washington, DC (MEDLINE/PubMed) and the Cochrane Central Register of Controlled Trials (CENTRAL) for relevant publications in indexed journals. The search strategy was implemented using the following key words: ((endos$) OR (dental) OR (osseointegra$)) and ((implant$) OR (fixture$)) and ((prospective) OR (retrospective) OR (comparative) OR (longitudinal)).
The following criteria had to be met for inclusion: (1) human study (partially or completely edentulous); (2) publication in English; (3) randomized controlled clinical trial (RCT), or cohort prospective or retrospective study; (4) minimum period of follow-up of 10 years; (5) study evaluating the survival or success rate and level of marginal bone resorption around osseointegrated implants.
The following were excluded: animal studies, case reports and narrative reviews, and studies involving zygomatic implants, patients undergoing radiotherapy, chemotherapy or those making use of bisphosphonates, implants placed in areas of bone regeneration, bone resorption analyzed by means of panoramic radiographs, patients with systemic diseases including autoimmune diseases, syndromes, and osteoporosis, patients under the age of 18 years, and those with periodontitis without previous treatment. Studies classified as having a high risk of bias according to the specific analysis carried out were also excluded.
The papers were first screened independently by two reviewers (V.M.F. and E.P.B), by title and abstract. Next, as a second step, the full-text papers were read in detail. Those papers that fulfilled all selection criteria were processed for data extraction. Disagreements were resolved by discussion. If disagreement persisted, the judgement of a third reviewer (V.F.F.) was decisive.
Assessment of heterogeneity
To evaluate the heterogeneity of the primary outcome between the selected studies, the following factors were recorded: study design, follow-up time, primary objective of the study, number of participants, gender, number of drop-outs, age range, mean age, number of implants, implant systems, size of implants, type of dental prosthesis, mean probing depth, mean marginal bone loss, success rate, criteria of success, survival rate, and author conclusions.
Quality analysis
With a view to increasing the reliability of the studies included, and to diminish the risk of bias, a careful quality analysis was done. The methodology used for analysis of the studies was that proposed by Nguyen et al. combined with the PRISMA criteria, Needleman guide, and the Cochrane recommendations to evaluate the risk of bias. The methodology of the RCT studies was evaluated in accordance with the RCT checklist available in the CONSORT statements. Table 1 lists the various criteria assessed with their potential scores, which added together generate a maximum possible score of 16 points. Table 2 shows the evaluation of the articles identified for inclusion; the methodological quality of each study was classified according to the potential risk of bias: low (score >12), moderate (score 10–12), or high (score <10).
| Criteria | Maximum score |
|---|---|
| Sample size | 2 |
| Studies with samples <100 participants = 1 | |
| Studies with samples ≥100 participants = 2 | |
| Follow-up time | 2 |
| Studies with a period of follow | |
| Studies with a period of follow | |
| Selection criteria | 2 |
| Selection criteria not mentioned or poorly defined = 1 | |
| Selection criteria well defined = 2 | |
| Description of population | 1 |
| Studies that did not make available the age or gender of patients = 0 | |
| Studies that made available the age and gender of patients = 1 | |
| Available statistical methods | 2 |
| Studies that did not make available the statistical methods used = 0 | |
| Studies that made available the statistical methods used, but did not describe them clearly = 1 | |
| Studies that made available the statistical methods used, and described them clearly = 2 | |
| Criteria of success | 1 |
| Studies that used a scale of success for evaluation of implants and described it = 1 | |
| Description of objectives | 2 |
| Objective of study undefined = 1 | |
| Objective of study clearly defined = 2 | |
| Randomized study | |
| Randomized clinical trials (RCT) | 1 |
| Number of implants evaluated | 2 |
| Studies with samples <100 implants = 1 | |
| Studies with samples ≥100 implants = 2 | |
| Conclusions | 1 |
| If the conclusions are in accordance with the objective of the study |
| Author | Sample size (2) | Follow-up time (2) | Selection criteria (2) | Description of population (1) | Statistical methods described (2) | Criteria of success (1) | Description of objectives (2) | Randomized study (1) | Number of implants evaluated (2) | Conclusions (1) | Total (16) | Potential risk of bias |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Åstrand et al. | 1 | 2 | 1 | 1 | 0 | 0 | 2 | 0 | 2 | 1 | 10 | Moderate |
| Deporter et al. | 1 | 1 | 1 | 1 | 1 | 1 | 2 | 0 | 1 | 1 | 10 | Moderate |
| Deporter et al. | 1 | 2 | 1 | 1 | 1 | 1 | 2 | 0 | 1 | 1 | 11 | Moderate |
| Carlsson et al. | 1 | 2 | 1 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 12 | Moderate |
| Degidi et al. | 1 | 1 | 2 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 12 | Moderate |
| Gotfredsen | 1 | 1 | 2 | 1 | 1 | 1 | 2 | 0 | 1 | 1 | 11 | Moderate |
| Jacobs et al. | 1 | 2 | 2 | 1 | 1 | 0 | 2 | 1 | 1 | 1 | 12 | Moderate |
| Jemt and Johansson | 1 | 2 | 1 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 12 | Moderate |
| Jemt | 1 | 2 | 1 | 1 | 1 | 1 | 2 | 1 | 1 | 1 | 12 | Moderate |
| Ji et al. | 1 | 1 | 1 | 1 | 0 | 1 | 2 | 0 | 1 | 1 | 9 | High |
| Karoussis et al. | 1 | 1 | 1 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 11 | Moderate |
| Kim et al. | 1 | 1 | 1 | 0 | 1 | 1 | 2 | 0 | 1 | 1 | 9 | High |
| Lekholm et al. | 2 | 1 | 1 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 12 | Moderate |
| Leonhardt et al. | 1 | 1 | 2 | 1 | 1 | 1 | 2 | 0 | 1 | 1 | 11 | Moderate |
| Lops et al. | 2 | 2 | 2 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 14 | Low |
| Mangano et al. | 2 | 1 | 2 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 13 | Low |
| Mertens et al. | 1 | 1 | 2 | 1 | 1 | 1 | 2 | 0 | 1 | 1 | 11 | Moderate |
| Misje et al. | 1 | 2 | 1 | 1 | 0 | 0 | 2 | 0 | 1 | 1 | 9 | High |
| Östman et al. | 1 | 1 | 2 | 0 | 0 | 0 | 2 | 0 | 2 | 1 | 9 | High |
| Pikner et al. | 2 | 2 | 1 | 1 | 1 | 0 | 2 | 0 | 2 | 1 | 12 | Moderate |
| Ravald et al. | 1 | 2 | 1 | 1 | 1 | 0 | 2 | 1 | 2 | 1 | 12 | Moderate |
| Rocci et al. | 1 | 1 | 2 | 1 | 1 | 0 | 2 | 0 | 1 | 1 | 10 | Moderate |
| Romeo et al. | 2 | 2 | 2 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 14 | Low |
| Simonis et al. | 1 | 2 | 1 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 12 | Moderate |
| Ma et al. | 2 | 1 | 2 | 1 | 1 | 1 | 2 | 1 | 2 | 1 | 14 | Low |
| Telleman et al. | 1 | 1 | 1 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 11 | Moderate |
| van Steenberghe et al. | 2 | 1 | 2 | 1 | 1 | 1 | 2 | 0 | 2 | 1 | 13 | Low |
Statistical analysis
After a preliminary evaluation of the selected papers, it was found that considerable heterogeneity was present in the study designs, characteristics, outcome variables, and results. It was therefore not possible to perform a valid quantitative analysis of the data and subsequent meta-analysis. Instead, a descriptive type of data presentation was used.
Results
Search results
The initial search resulted in 6958 titles in MEDLINE/PubMed and 89 titles in the Cochrane Central Register of Controlled Trials. The titles that had no abstract available and those that deviated from the subject of this systematic review were excluded. After the first analysis, the abstracts of 135 articles were obtained. Fifty-nine complete articles were chosen for careful reading. After evaluating each article, 23 studies published between the years 1999 and 2014 were selected.
The most frequent reason for exclusion was a follow-up period of less than 10 years. Of the potential studies for inclusion ( n = 59), 36 were excluded after careful analysis. The study screening and selection process, including the frequency and reasons for exclusion, is shown in Fig. 1 .
Quality analysis and assessment of heterogeneity
As a result of the analysis, four studies were classified as having a high risk of bias. Therefore, with a view to including only studies with reliable methodological quality, these articles were excluded from the review. Five studies were considered to have the highest level of evidence with an estimated low risk of bias. Table 2 shows the scores of each article after the quality analysis.
The selected studies showed considerable heterogeneity.
Studies included
A total of 23 studies evaluating the survival/success of implants were included in this review. Details of the studies included are listed in Tables 3 and 4 . The mean follow-up time was 13.4 years. Ten prospective studies, nine retrospective studies, and four randomized clinical trials (RCTs) were included.
| Author | Study design Follow-up time Primary study objective |
Number of participants Gender Dropouts (%) |
Age range Mean age (years) |
Number of implants Implant system Implant size (mm) |
Dental prosthesis |
|---|---|---|---|---|---|
| Lekholm et al. | Prospective 10 years Implant survival |
127 54 M/73 F 30 |
18–70 50 |
461 Brånemark System ∅ 7, 10, 13, 15, 18, 20 × 3.75–4.0 |
FPD |
| Carlsson et al. | Prospective 15 years Bone level alteration |
60 16 M/44 F 5 |
33–64 NR |
348 Brånemark System ∅ 10–NR |
FCDP |
| Van Steenberghe et al. | Retrospective 12 years Bone level alteration |
158 114 M/44 F 2.5 |
32–82 59.2 |
316 Brånemark System ∅ 7, 8, 10, 12, 13, 15, 18, 20 × 3.75, 4.0, 5.0 |
IOD |
| Leonhardt et al. | Prospective 10 years Others |
15 8 M/7 F 21 |
21–71 NR |
57 Brånemark System ∅ NR |
FPD |
| Karoussis et al. | Prospective 12 years Survival and success |
89 34 M/55 F 29.9 |
19–79 49.3 |
179 ITI ∅ NR |
SC/FPD |
| Telleman et al. | Retrospective 10 years Others |
38 8 M/30 F 36.6 |
46–90 64 |
115 ITI ∅ NR |
IOD |
| Jemt and Johansson | Retrospective 15 years Others |
76 48 M/28 F 56.6 |
32–76 61.1 |
450 Brånemark System ∅ 7, 10, 13, 15, 18 × NR |
FCDP |
| Romeo et al. | Retrospective 14 years Others |
129 61 M/68 F 17.8 |
NR 53 |
265 ITI ∅ 8, 10 × 3.75, 4.1, 4.8 |
SC/FPD |
| Åstrand et al. | Retrospective 20 years Implant survival |
21 7 M/14 F 56.2 |
40–74 54.3 |
123 Brånemark System ∅ NR |
FCDP |
| Jemt 32 | RCT 15 years Others |
114 74 M/40 F 44 |
NR 42.7 |
123 Brånemark System ∅ NR |
SC |
| Pikner et al. | Retrospective 20 years Bone level alteration |
640 255 M/385 F NR |
18–83 52.3 |
3462 Brånemark System ∅ NR |
SC/FPD/FCDP |
| Simonis et al. | Retrospective 16 years Survival and success |
55 21 M/34 F 28 |
29–88 68.7 |
131 ITI ∅ 6, 8, 10, 12 × NR |
SC/FPD |
| Jacobs et al. | RCT 16 years Others |
18 6 M/12 F 33.3 |
32–75 55.1 |
95 Brånemark System/Astra Tech ∅ 7, 8, 9, 10, 11, 13, 15, 18, 19 × 3.75, 4.0 |
FPD |
| Ma et al. | RCT 10 years Bone level alteration |
106 40 M/66 F 25.4 |
NR 65.3 |
212 Brånemark System/Southern Implants/Steri-Oss ∅ NR |
IOD |
| Mertens et al. | Prospective 10 years Others |
14 3 M/11 F 14.2 |
37–71 57.9 |
52 Astra Tech ∅ 8, 9 × 3.5, 4.0, 4.5 |
SC/FPD/FCDP |
| Lops et al. | Retrospective 20 years Others |
121 57 M/64 F 24.7 |
22–69 54 |
257 ITI ∅ 8, 10 × 3.75, 4.1, 4.8 |
SC/FPD/FCDP |
| Gotfredsen | Prospective 10 years Others |
20 10 M/10 F 5 |
18–59 33 |
20 Astra Tech ∅ 11, 13, 15 × 4.5 |
SC |
| Degidi et al. | Prospective 10 years Others |
48 21 M/27 F 18.6 |
NR 49.9 |
158 Brånemark System ∅ 10 to 15 × 3.3, 3.75, 4.0 |
SC/FPD/FCDP |
| Deporter et al. | Prospective 10 years Survival and success |
24 8 M/16 F 20.8 |
20–72 NR |
48 Endopore ∅ 7, 9 × 4.1 |
SC/FPD |
| Deporter et al. | Prospective 20 years Others |
52 17 M/35 F 32.7 |
NR 55.3 |
156 Endopore ∅ 7, 8, 9, 10 × NR |
IOD |
| Ravald et al. | RCT 15 years Implant survival |
46 27 M/19 F 25.3 |
51–88 74.4 |
371 Astra Tech/Brånemark System ∅ 9 to 19 × 3.5, 3.75, 4.0 |
FCDP |
| Rocci et al. | Retrospective 10 years Others |
46 26 M/20 F NR |
24–77 51 |
97 Brånemark System ∅ 8.5 to 18 × NR |
SC/FPD |
| Mangano et al. | Prospective 10 years Others |
194 104 M/90 F 25.7 |
24–74 49.1 |
215 Leone Dental Implants ∅ 8 × 3.3, 4.1, 4.8 |
SC |
| Author | MPD (mm) | MMBL (mm) | Success rate (%) Criteria of success |
Survival rate (%) | Author conclusions |
|---|---|---|---|---|---|
| Lekholm et al. | NR | 0.7 | NR Albrektsson et al. (1986) |
92.6 | The Brånemark implant system used to treat partial edentulism presented excellent survival rates during 10 years of follow-up. Good periodontal health and minimal marginal bone resorption were observed. The majority of failures occurred by virtue of mechanical overload, and short implants failed more frequently than long implants. |
| Carlsson et al. | NR | 0.5 | 99 Albrektsson et al. (1986) |
96 | During the period of follow-up there was little marginal bone loss around the implants, which was similar between maxilla and mandible. The results of the study were considered a success. All the implant losses occurred before placement of dentures, leading to the conclusion that there had been failure in the osseointegration process. Smoker patients presented greater bone resorption in comparison with non-smokers. |
| Van Steenberghe et al. | NR | 2.67 | 97.2 Albrektsson et al. (1986) |
98.5 | A high success rate and minimal marginal bone resorption indicated that rehabilitation of the mandibular arch with overdentures is a reliable treatment modality. Only the factor time had a significant influence on bone resorption around the implants in treatments with overdentures. |
| Leonhardt et al. | 1.9 | 1.7 | NR | 94.7 | It is fundamental that patients with periodontal disease be treated before they begin rehabilitation with implants, and after being treated they must take part in a strict maintenance programme. The bacteria that colonize the peri-implant tissues are similar to those found in the periodontal tissues. |
| Karoussis et al. | 2.87 | 0.98 | 85.5 Karoussis et al. (2003) |
92.4 | The ITI HS (Hollow Screw) implants presented a higher survival and success rate and fewer occurrences of biological complications when compared with the ITI HC (Hollow Cylinder) implants. Correct planning of cases is fundamental to increasing success rates. |
| Telleman et al. | 3.3 | 2.2 | 92.2 Albrektsson et al. (1986) |
96.3 | The ITI HS (Hollow Screw) and ITI HC (Hollow Cylinder) implants presented stable results in the long term for supporting mandibular overdentures. Annual follow-up of the marginal bone level and probing depth is important, particularly in patients with a long period of implants in function. |
| Jemt and Johansson | NR | 2.1 | 86.8 Albrektsson et al. (1986) |
90.9 | The implants functioned in a satisfactory manner during the 15 years of follow-up, and the factor time contributed in an insignificant manner to the survival of implants. The results suggest that patients in good health, with a healthy lifestyle, and who cooperate with the treatment maintenance programme obtained a better performance during the 15 years of follow-up. |
| Romeo et al. | 2.2 | 1.65 | NR Zarb and Albrektsson (1998) Roos et al. (1997) |
97.5 | The success and survival of short implants (8 mm) and standard implants (10 mm) showed no statistically significant differences. The prognosis of short implants appears to be related to the bone quality of the region. |
| Åstrand et al. | 3.4 | 2.33 | NR | 99.2 | The treatments with implants in completely edentulous patients revealed excellent results with a low incidence of technical and biological complications over a period of two decades. The fact that the study was conducted with a surgical technique at two time intervals and implants with treated surfaces may have contributed positively to the results. |
| Jemt | NR | 2 | NR Albrektsson and Isidor (1993) |
97.7 | Implants for maxillary central incisors alone presented a higher rate of technical and biological problems compared with fixed partial dentures (control group). Patients at an advanced age and with health problems present lower implant survival rates. |
| Pikner et al. | NR | 2.5 | NR | 98.2 | The study demonstrated a low rate of bone loss during the follow-up period, and that patients at an advanced age, and implants placed in the mandible tend to present greater bone resorption over the course of time. |
| Simonis et al. | 2.73 | 2.25 | 51.9 Simonis et al. (2010) |
83.7 | There are frequent technical and biological complications in implant dentistry, and patients with a history of periodontal disease and smokers have a greater risk of complications. |
| Jacobs et al. | 2.55 | 0.16 | 98.8 NR * |
93.9 | The study showed that there is no statistical difference in the probing depth and marginal bone loss between the two types of implant systems. In addition, the authors suggested that age, cleaning (hygiene), type of prosthetic loading, and the abutment/implant interface may contribute to the probing depth and changes in marginal bone level. |
| Ma et al. | NR | 0.29 | 100 Albrektsson and Isidor (1993) Roos et al. (1997) |
100 | Dentures of the overdenture type supported by two isolated implants presented low marginal bone resorption in the long term. The bone losses that occurred were considered physiological and occurred more noticeably in the first year of prosthetic loading. |
| Mertens et al. | 3.26 | 0.3 | 100 Albrektsson et al. (1986) |
100 | Treatment with short implants is a reliable and stable option in the long term, particularly in areas where there is little bone availability (atrophic ridges). |
| Lops et al. | 2.2 | 1.85 | 79.8 Albrektsson et al. (1986) Roos et al. (1997) |
94.1 | The differences in the success and survival rates of short and standard implants were statistically insignificant. The prognosis of short implants in the posterior region, in the long term, was comparable with that for implants in the anterior region. The results of the study demonstrated good performance of short implants (8 mm) in the long term. |
| Gotfredsen | NR | 0.75 | NR Albrektsson and Isidor (1993) |
100 | The study presented 100% survival of the implants placed. In addition, marginal bone loss was less than 1 mm and there was no difference between the results of immediate and late implants. The most common complications were the presence of biofilm and mucositis. |
| Degidi et al. | 2.54 | 1.95 | 34.9 Misch et al. (2008) |
97.2 | Within the limitations of the study, the results were positive in terms of maintenance of marginal bone around the implants in the period of follow-up. The authors suggest that immediate implants tend to undergo greater bone resorption when compared with implants placed in healed alveoli. |
| Deporter et al. | NR | 1.21 | 95.5 NR * |
95.5 | The SPS short implants offer an effective and predictable solution for partial edentulism in the posterior region of the mandible, provided that there is bone thickness and peri-implant keratinized gingiva. |
| Deporter et al. | NR | 0.67 | 73.4 Albrektsson et al. (1986) |
73.4 | During the 20-year follow-up period, the short SPS implants demonstrated acceptable results for the treatment of complete edentulism, with mandibular overdentures for patients with severe alveolar resorption. |
| Ravald et al. | 3.93 | 0.55 | NR | 95.1 | Treatment with Astra Tech TiOblast and Brånemark implants supporting complete fixed dentures demonstrated good results with a low incidence of marginal bone resorption, indicative of peri-implantitis. No statistically significant differences were found between the two implant systems throughout the 12–15 years of follow-up. |
| Rocci et al. | NR | 0.1 | NR | 91.1 | The high success rate and low rate of bone resorption confirmed the technical success of immediate prosthetic loading in the maxilla, with surgeries without flap elevation, during the 10 years of follow-up. All failures occurred in the first 2 months after placement of the provisional restorations. |
| Mangano et al. | NR | 0.62 | 95.9 Zarb and Albrektsson (1998) |
98.5 | Short implants (8 mm) are a feasible alternative to complex bone regeneration surgeries. In this study, the use of short implants for rehabilitating single posterior crowns was shown to be an alternative with high survival rates in the period of follow-up. |
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