Abstract
Objective
The purpose of the present systematic review and meta-analysis was to compare short implants (equal or less than 8 mm) versus standard implants (larger than 8 mm) placed in posterior regions of maxilla and mandible, evaluating survival rates of implants, marginal bone loss, complications and prosthesis failures.
Data
This review has been registered at PROSPERO under the number CRD42015016588. Main search terms were used in combination: dental implant, short implant, short dental implants, short dental implants posterior, short dental implants maxilla, and short dental implants mandible.
Source
An electronic search for data published up until September/2015 was undertaken using the PubMed/Medline, Embase and The Cochrane Library databases.
Study selection
Eligibility criteria included clinical human studies, randomized controlled trials and/or prospective studies, which evaluated short implants in comparison to standard implants in the same study.
Conclusion
The search identified 1460 references, after inclusion criteria 13 studies were assessed for eligibility. A total of 1269 patients, who had received a total of 2631 dental implants. The results showed that there was no significant difference of implants survival ( P = .24; RR:1.35; CI: 0.82–2.22), marginal bone loss ( P = .06; MD: −0.20; CI: −0.41 to 0.00), complications ( P = .08; RR:0.54; CI: 0.27–1.09) and prosthesis failures ( P = .92; RR:0.96; CI: 0.44–2.09). Short implants are considered a predictable treatment for posterior jaws. However, short implants with length less than 8 mm (4–7 mm) should be used with caution because they present greater risks to failures compared to standard implants.
Clinical significance
Short implants are frequently placed in the posterior area in order to avoid complementary surgical procedures. However, clinicians need to be aware that short implants with length less than 8 mm present greater risk of failures.
1
Introduction
Implants are often used as a treatment option for partially or totally edentulous patients . The success is directly related to the osseointegration process , and the use of standard implants allows a larger contact area with the bone tissue, which supports the osseointegration process . Tooth loss in the posterior jaws favors the resorption process of bone tissue , causing greater proximity to the inferior alveolar nerve and maxillary sinus, limiting the use of longer implants .
To overcome these problems, bone grafts or maxillary sinus lifting have been indicated to reestablish the height of restored bone tissue and allow for placement of standard implants. However, these techniques are associated with increased postoperative morbidity, higher costs, and higher risks of complications during patient rehabilitation . Thus, short implants are used, which are considered to be simpler and more effective for rehabilitating atrophic ridges later .
As there is no consensus about the definition of short implants, with some authors considering them to be <10 mm , while others consider short implants ≤8 mm . Current clinical tendencies consider implants with 7 mm length or less as short or extra-short implants . The discrepancy in the crown-to-implant ratio can increase the risk of mechanical problems, but it did not increase the risk of peri-implant marginal bone loss .
Another important aspect to consider is the implants installation area, because the chances of failure are higher when the implants are installed in low-density bone, such as in the posterior maxilla . However, there is no consensus on the survival rate of short implants in the posterior maxilla and mandible . Some authors have shown low success rates , while others have found high success rates for short implants .
The aim of this study was to evaluate the survival rate of short implants (equal or less than 8 mm) compared to standard implants (larger than 8 mm) in the posterior jaws. The null hypotheses are: (1) there are no differences between short implants and standard implants with regard to survival rates of implants and (2) there are no differences in marginal bone loss, complications, and prosthesis failures between short implants and standard implants.
2
Materials and methods
2.1
Registry protocol
This systematic review was structured following the PRISMA checklist and in accordance with models proposed in the literature . Moreover, the methods for this systematic review were registered with PROSPERO (CRD42015016588).
2.2
Eligibility criteria
The eligible studies should present the following characteristics: (1) randomized controlled trials, (2) prospective studies, (3) with at least ten patients, (4) studies published within last 10 years, (5) comparisons between short implants and standard implants in the same study, (6) published in english.
The exclusion criteria used were: (1) in vitro studies, (2) animal studies, (3) case series or case reports, (4) retrospective studies, (5) computer simulations, (6) patients or data repeated in other included articles, and (7) studies that showed only short implants without comparison group, (8) studies that considered short implants larger than 8 mm.
The PICO approach (population, intervention, comparison, outcomes) was used to address the question: do short implants have similar survival rates compared to standard implants. In this process, the population was patients rehabilitated with dental implants in the posterior jaws (maxilla and mandible). Intervention was short implants in the posterior jaw, and the comparison was made with patients who received standard implants in posterior jaws. The primary outcome evaluated was the survival rates of implants in the posterior jaws. The marginal bone loss, complications, and prosthesis failures were the secondary outcomes.
2.3
Search strategy and information sources
The selection of articles was done individually by two of the authors (C.A.A.L. and M.L.F.A.) being selected studies that evaluated the survival of short implants (equal or less than 8 mm) installed in maxilla and mandible posterior compared to standard implants (larger than 8 mm). Electronic searches were conducted at the selected databases PubMed/Medline, Embase, and Cochrane Library for articles published until 10 September 2015, according to the eligibility criteria. The keywords used in this study were: “short implant AND dental implant OR short dental implants OR short dental implants posterior OR short dental implants maxilla OR short dental implants mandible”.
To complement this review, a search in grey literature and manual search in journals specific area was carried out: 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 Clinical Periodontology, Journal of Dentistry, Journal of Oral and Maxillofacial Surgery, Journal of Oral Implantology, Journal of Oral Rehabilitation, Journal of Periodontology, Periodontology 2000 .
2.4
Data analysis
One of the authors (C.A.A.L.) collected relevant information from the articles, and a second author (R.O.) checked all of the collected information. A careful analysis was performed to check for disagreements among authors, and a third author (E.P.P.) settled all of the disagreements between the investigators through discussion until a consensus was obtained.
2.5
Risk of bias
Two investigators (C.A.A.L. and M.L.F.A.) assessed the methodological quality of studies according to the Jadad scale , which ranges from 0 to 5, with scores of ≥3 considered high quality. The cochrane collaboration criteria for judging risk of bias was used to assess the quality of the studies included for review.
2.6
Summary measures
The meta-analysis was based on the Mantel–Haenzel (MH) and Inverse Variance (IV) methods. Survival rates of implants, complications and prostheses failures were the outcome measures evaluated by risk ratio (RR) and marginal bone loss, the continuous outcome were evaluated by mean difference (MD) and the corresponding 95% confidence intervals (CI). The RR and MD values were considered significant when P < 0.05. The software reviewer manager 5 (Cochrane Group) was used for meta-analysis.
2.7
Additional analysis
The Kappa score was used to calculate the inter-reader agreement during the inclusion process for publication-evaluated databases. Any disagreements were resolved by discussion and consensus of all authors.
2
Materials and methods
2.1
Registry protocol
This systematic review was structured following the PRISMA checklist and in accordance with models proposed in the literature . Moreover, the methods for this systematic review were registered with PROSPERO (CRD42015016588).
2.2
Eligibility criteria
The eligible studies should present the following characteristics: (1) randomized controlled trials, (2) prospective studies, (3) with at least ten patients, (4) studies published within last 10 years, (5) comparisons between short implants and standard implants in the same study, (6) published in english.
The exclusion criteria used were: (1) in vitro studies, (2) animal studies, (3) case series or case reports, (4) retrospective studies, (5) computer simulations, (6) patients or data repeated in other included articles, and (7) studies that showed only short implants without comparison group, (8) studies that considered short implants larger than 8 mm.
The PICO approach (population, intervention, comparison, outcomes) was used to address the question: do short implants have similar survival rates compared to standard implants. In this process, the population was patients rehabilitated with dental implants in the posterior jaws (maxilla and mandible). Intervention was short implants in the posterior jaw, and the comparison was made with patients who received standard implants in posterior jaws. The primary outcome evaluated was the survival rates of implants in the posterior jaws. The marginal bone loss, complications, and prosthesis failures were the secondary outcomes.
2.3
Search strategy and information sources
The selection of articles was done individually by two of the authors (C.A.A.L. and M.L.F.A.) being selected studies that evaluated the survival of short implants (equal or less than 8 mm) installed in maxilla and mandible posterior compared to standard implants (larger than 8 mm). Electronic searches were conducted at the selected databases PubMed/Medline, Embase, and Cochrane Library for articles published until 10 September 2015, according to the eligibility criteria. The keywords used in this study were: “short implant AND dental implant OR short dental implants OR short dental implants posterior OR short dental implants maxilla OR short dental implants mandible”.
To complement this review, a search in grey literature and manual search in journals specific area was carried out: 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 Clinical Periodontology, Journal of Dentistry, Journal of Oral and Maxillofacial Surgery, Journal of Oral Implantology, Journal of Oral Rehabilitation, Journal of Periodontology, Periodontology 2000 .
2.4
Data analysis
One of the authors (C.A.A.L.) collected relevant information from the articles, and a second author (R.O.) checked all of the collected information. A careful analysis was performed to check for disagreements among authors, and a third author (E.P.P.) settled all of the disagreements between the investigators through discussion until a consensus was obtained.
2.5
Risk of bias
Two investigators (C.A.A.L. and M.L.F.A.) assessed the methodological quality of studies according to the Jadad scale , which ranges from 0 to 5, with scores of ≥3 considered high quality. The cochrane collaboration criteria for judging risk of bias was used to assess the quality of the studies included for review.
2.6
Summary measures
The meta-analysis was based on the Mantel–Haenzel (MH) and Inverse Variance (IV) methods. Survival rates of implants, complications and prostheses failures were the outcome measures evaluated by risk ratio (RR) and marginal bone loss, the continuous outcome were evaluated by mean difference (MD) and the corresponding 95% confidence intervals (CI). The RR and MD values were considered significant when P < 0.05. The software reviewer manager 5 (Cochrane Group) was used for meta-analysis.
2.7
Additional analysis
The Kappa score was used to calculate the inter-reader agreement during the inclusion process for publication-evaluated databases. Any disagreements were resolved by discussion and consensus of all authors.
3
Results
3.1
Literature search
The search in the databases retrieved 1460 references, including 1171 from PubMed/MEDLINE, 272 from Embase and 17 from The Cochrane Library. After duplicate references were removed, a detailed review was done on the titles and abstracts of the selected comparative studies, and after applying the inclusion/exclusion criteria, 30 full papers were selected for the eligibility assessment ( Fig. 1 ). After reading the full texts of these articles, 13 studies were included in the final review. The reasons why studies were excluded are detailed in Table 1 .
| Reason | References |
|---|---|
| Patients or data repeated in other included articles | |
| Absence of comparison group | |
| Retrospective study | |
| Not report which group failed | |
| Considered larger than 8 mm short implants |
3.2
Description of the studies
Detailed data of the 13 included studies are listed in Table 2 . The 13 selected studies, 10 were RCTs and 3 were prospective, 2631 implants were installed, including 1650 standard implants and 981 short implants installed in 1269 patients with a mean age of 53.43 within the period of January 2004 to 10 September 2015. Ten of the selected studies evaluated the survival rates in the maxillary posterior, whereas nine studies evaluated survival rates in the mandibular posterior. One study did not report the region that was rehabilitated.
| Author/ Year |
Study Design | Length standard implants and number of implants and | Length short implants and number of implants | Diameter (ø mm) |
Implant systems | No. of patients | Mean age | Arch | Follow-up | Outcomes measures | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Standard implants | Short implants | ||||||||||
| Esposito et al. | RCT | ≥8.5 mm 69 maxilla 47 mandible |
4 mm 46 maxilla 78 mandible |
Standard 4.0 mm Short: 4.0 mm |
TwinKon Universal SA2-(Global D) | 150 | 55 | Maxilla and Mandible | 4 months | Implants survival: 2 lost (1 maxilla and 1 mandible) MBL → 0.43 (±0.25) Prosthesis survival: 2 lost Complications: 2 |
Implants survival: 3 lost (1 maxilla and 2 mandible) MBL → 0.39 (±0.30) Prosthesis survival: 2 lost Complications: 3 |
| Rossi et al. | RCT | 10 mm 15 maxilla 15 mandible |
6 mm 12 maxilla 18 mandible |
Standard 4.1 mm Short 4.1 mm |
Straumann implants | 45 | 48.05 | Maxilla and Mandible | 5 years | Implants survival: 1 lost (1 maxilla) MBL → 2.64 (±0.56) |
Implants survival: 4 lost (3 maxilla and 1 mandible) MBL → 2.30 (±0.52) |
| Thoma et al. | RCT | 11–15 mm 70 implants |
6 mm 67 implants |
Standard 4 mm Short: 4 mm |
OsseoSpeed 4.0S (Astra Tech) |
101 | 50.5 | Maxilla | 1 year | Implants survival: 1 lost | Implants survival: 2 lost |
| Esposito et al. | RCT | ≥10 mm 38 maxilla 30 mandible |
5 mm 34 maxilla 26 mandible |
Standard6 and 4 mm Short 6 mm |
Rescue and EZ Plus (MegaGen) | 30 | 56 | Maxilla and Mandible | 3 years | Implants survival: 2 lost (1 maxilla and 1 mandible) Prosthesis survival: 0 lost MBL → Mandible: 1.97 (±0.57) Maxilla: 1.74 (±0.57) Complications: 12 mandibular and 1 maxillary |
Implants survival: 5 lost (3 maxilla and 2 mandible) Prosthesis survival: 3 lost MBL → Mandible: 1.79 (±0.51) Maxilla: 1.36 (±0.57) Complications: 9 mandibular and 4 maxillary |
| Felice et al. | RCT | ≥10 mm 61 implants |
6.6 mm 60 implants |
Standard 4 mm Short: 4 mm |
Nanotite parallel walled (Biomet 3i) |
60 | 55.5 | Mandible | 5 years | Implants survival: 3 lost Prosthesis survival: 5 lost MBL → 3.01 (±0.74) Complications: 25 |
Implants survival: 5 lost Prosthesis survival: 5 lost MBL → 2.24 (±0.47) Complications: 6 |
| Romeo et al. | RCT | 10 mm 19 implants |
6 mm 21 implants |
Standard 4 mm Short 4 mm |
Straumann implants | 18 | 53 | Maxilla and Mandible | 5 years | Implants survival: 0 lost Prosthesis survival: 0 lost MBL → 2.99 (±0.90) Complications: 3 |
Implants survival: 1 lost Prosthesis survival: 1 lost MBL → 2.97 (±0.47) Complications: 5 |
| Queiroz et al. | Non-RCT | 10/11.5 mm42 implants | 5.5 and 7 mm 48 implants | Standard 4 mm Short 5 mm | Master Porous (Conexão) | 23 | 53.35 | Mandible | 3 months | Implants survival: 0 lost | Implants survival: 6 lost |
| Pistili et al. (A) | RCT | ≥10 mm 37 maxilla 32 mandible |
5 mm 36 maxilla 31mandible |
Standard 5 mm Short 5 mm |
ExFeel (MegaGen) | 80 | 57.75 | Maxilla and Mandible | 1 year | Implant survival: 1 lost (mandibular) Failure prosthesis: 2 mandibular MBL → Mandible: 1.53 (±0.29) Maxilla: 1.09 (±0.05) Complications: 17 mandibular and 5 maxillary |
Implant survival: 1 lost (maxilla) Failure prosthesis: 1 maxillary MBL → Mandible: 1.15 (±0.12) Maxilla: 0.87 (±0.07) Complications: 8 mandibular |
| Canizzaro et al. | RCT | ≥10 mm 44 implants |
8 mm 38 implants |
Standard 3.7 and 4.7 mm Short 4.7 and 6 mm |
TS Vent MP-1HA Dual Transition (Zimmer Dental) |
40 | 50.4 | Maxilla | 5 years | Implants survival: 5 lost Prosthesis failure: 2 MBL: 0.72 (±0.41) Complications: 8 |
Implants survival: 1 lost Prosthesis Failure: 1 MBL: 0.41 (±0.42) Complications: 4 |
| Pistili et al. (B) | RCT | ≥10 mm 44 maxilla 47 mandible |
6 mm 39 maxilla 41 mandible |
Standard 4 mm Short 4 mm |
Southern Implants | 40 | 55.85 | Maxilla and Mandible | 1 year | Implant survival: 3 lost (mandible) Prosthesis failure: 2 mandibular MBL → Mandible: 1.03 (±0.07) Maxilla: 0.94 (±0.05) Complications: 10 mandibular e 4 maxillary |
Implant survival: 0 lost Failure prosthesis: 0 lost MBL → Mandible: 1.41 (±0.31) Maxilla: 1.02 (±0.06) Complications: 0 |
| Guljé et al. | RCT | 11 mm 101 implants |
6 mm 107 implants |
Standard 4 mm Short 4 mm |
OsseoSpeed 4.0S (Astra Tech) |
95 | 54.5 | Maxilla and Mandible | 1 year | Implants survival: 1 lost MBL → 0.02 (±0.60) |
Implants survival: 3 lost MBL → 0.06 (±0.27) |
| Arlin | Non-RCT | 10–16 mm 454 implants |
6 and 8 mm 176 implants |
3.3; 3.5; 4.1 and 4.8 mm | Straumann Implants | 264 | – | – | 5 years | 12 implants lost | 3 implants lost |
| Ferrigno et al. | Non-RCT | 10 and 12 mm 485 implants |
8 mm 103 implants |
4.1 and 4.8 mm |
Straumann Implants | 323 | 51.2 | Maxilla | 12 years | 14 implants lost | 4 implants lost |
3.3
Inter-investigator agreement
The inter-investigator agreement (Kappa) was calculated by evaluating the selected titles and abstracts, and then obtaining a value for selected articles on PubMed/MEDLINE (kappa = 0.79), Embase (kappa = 0.86) and Cochrane Library (kappa = 1.00) presenting a high level of agreement between the reviewers under the Kappa criteria .
3.4
Assessment of study quality
The Jadad scale was used to check the level of evidence, and indicated that all studies except for three were of high quality ( Table 3 ). The Cochrane criteria indicated low risk of bias for the randomization and allocation of the studies. However, there was high risk of bias concerning the blinding of participants and personnel. This could be justified by the difficulty of blinding the surgeon and patients, especially in the studies that performed bone augmentation procedures. All studies were adequate for addressing incomplete outcome data and were free of selective outcome reporting and other sources of bias ( Fig. 2 ).
| Studies | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Quality criteria | Esposito et al. | Rossi et al. | Thoma et al. | Esposito et al. | Felice et al. | Romeo et al. | Queiroz et al. | Pistili et al. (A) | Cannizzaro et al. | Pistili et al. (B) | Guljé et al. | Arlin | Ferrigno et al. |
| 1. Was the study described as random? | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | No | No |
| 2. Was the randomization scheme described and appropriate? | Yes | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | No | No |
| 3. Was the study described as double-blind? | No | No | No | No | No | No | No | No | No | No | No | No | No |
| 4. Was the method of double blinding appropriate? | No | No | No | No | No | No | No | No | No | No | No | No | No |
| 5. Was there a description of dropouts and withdrawals? | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Jadad score | 3 | 3 | 3 | 3 | 3 | 3 | 1 | 3 | 3 | 3 | 3 | 1 | 1 |
| Quality of study | High | High | High | High | High | High | Low | High | High | High | High | Low | Low |
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