Short dental implants versus standard dental implants placed in the posterior jaws: A systematic review and meta-analysis

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.

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.

Materials and methods

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).

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.

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 .

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.

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.

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.

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.

Materials and methods

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).

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.

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 .

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.

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.

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.

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.

Results

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 .

Fig. 1
Flow diagram of the search strategy.

Table 1
Reasons for the exclusion of 16 articles.
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

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.

Table 2
Characteristics of studies included ( n = 13).
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
MBL = Marginal bone loss

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 .

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 ).

Table 3
Quality assessment of the selected studies.
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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Jun 19, 2018 | Posted by in General Dentistry | Comments Off on Short dental implants versus standard dental implants placed in the posterior jaws: A systematic review and meta-analysis
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