Review articleShort dental implants versus standard dental implants placed in the posterior jaws: A systematic review and meta-analysis
Introduction
Implants are often used as a treatment option for partially or totally edentulous patients [1]. The success is directly related to the osseointegration process [2], and the use of standard implants allows a larger contact area with the bone tissue, which supports the osseointegration process [3], [4]. Tooth loss in the posterior jaws favors the resorption process of bone tissue [5], causing greater proximity to the inferior alveolar nerve and maxillary sinus, limiting the use of longer implants [3], [6].
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 [5], [7]. Thus, short implants are used, which are considered to be simpler and more effective for rehabilitating atrophic ridges later [8].
As there is no consensus about the definition of short implants, with some authors considering them to be <10 mm [9], [10], while others consider short implants ≤8 mm [4], [11]. Current clinical tendencies consider implants with 7 mm length or less as short or extra-short implants [12]. 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 [13].
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 [14]. However, there is no consensus on the survival rate of short implants in the posterior maxilla and mandible [15]. Some authors have shown low success rates [6], [16], while others have found high success rates for short implants [17], [18], [19].
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.
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Registry protocol
This systematic review was structured following the PRISMA checklist [20] and in accordance with models proposed in the literature [14], [21], [22], [23]. 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
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 [6], [25], [26], [27], [28], [29], [30],
Discussion
Recently, some revisions have verified that short implants are a predictable alternative treatment for the edentulous in the posterior region [10], [54]. However, the present systematic review only included studies with direct comparisons between short and standard implants, in order to reduce bias.
Short implants are considered an alternative for rehabilitation that reduces the complexity of the treatment, mainly in the posterior jaws. This is due to bone resorption maintaining proximity to
Conclusion
Short implants showed marginal bone loss, prosthesis failures and complication rates similar to standard implants, being considered a predictable treatment for posterior jaws, especially in cases that require complementary surgical procedures. However, short implants with length less than 8 mm (4–7 mm) should be used with caution because they present greater risks for implant failures when compared to standard implants.
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