Cheryl Straub-Morarend DDS
Although the failure rate of short dental implants may appear similar to standard length implants, with the majority of failures attributed to poor bone quality and a smooth implant surface, better evidence is needed for confirmation.
Due to the limited quality of both the evidence and the systematic review, the implication that there are similar failure rates between short and standard length dental implants is not clear.
In adult patients, what are the failure rates and factors that influence failure of short dental implants (
The authors searched two databases for publications in English between the years 1980 and 2009 and also examined citations in the retrieved publications. They screened titles and abstracts independently and in duplicate, and similarly screened full texts, resolving differences by discussion. They limited included studies to those with a therapeutic group with an implant length of <= 10 mm having data on implant length, failure rates, and well-defined criteria for implant failure. Exclusion criteria involved studies with bone augmentation or inferior alveolar nerve repositioning. They excluded review articles. The authors employed single-factor analysis to evaluate the potential predictors for the prognosis of implants as well as multivariate logistic regression to control various factors associated with failure of short dental implants.
The initial search identified 558 articles of which 35 met the inclusion criteria. Their analysis included 14,722 implants, of which 659 of these implants failed. The overall mean failure rate for dental implants (all lengths combined) is 4.5%. The authors did not identify any randomized controlled trials, and they were unable to complete a meta-analysis due to the low quality and heterogeneous nature of the identified studies. Nineteen of the included articles described the failure time of dental implants, with 66 failures occurring before loading and 48 after loading. The mean follow-up period was 5.91 years (range of 1 to 10 years). The cumulative survival rates reported ranged from 89.6% to 100%.
The authors noted statistically significantly higher failure rates between short dental implants placed in the maxilla compared to the mandible. In addition, they reported a higher failure rate of short dental implants with a smooth surface versus a roughened surface. They did not identify any significant differences in survival rates of short dental implants placed in a single stage versus a two-stage surgical approach.
Source of Funding:
No sources of funding were reported.
Importance and Context:
Anatomical limitations such as reduced alveolar bone height or location of the inferior alveolar nerve can restrict placement of standard-length dental implants. In these cases, the traditional approach includes invasive surgical interventions. Short dental implants may offer an alternative option in these cases. A recently published systematic review assessing short dental implant therapy in the management of atrophic alveolar ridges concluded that prostheses supported by short dental implants are a valid treatment option.1 In addition, a meta-analysis concluded the use of short dental implants may reduce the need for invasive bone augmentation procedures in areas of reduced alveolar bone height.2 These systematic reviews serve to outline existing knowledge related to short dental implant therapy as well as identify inconsistencies in the research of short dental implants. High-quality controlled clinical trials are warranted to determine the influence of various factors on dental implants with a shorter length and whether failure rates are truly comparable to conventional standard-length dental implants.
Strengths and Weaknesses of the Systematic Review:
This systematic review was weakened by the lack of a focused research question, a limited search strategy to identify studies, and publication bias that was not discussed or assessed. A summary table of included studies provided limited characteristics; however, no information was provided regarding excluded studies. Although the review stated that included studies were of low quality, it did not report or provide discussion of quality assessment. This systematic review defined standard length implants as 10 mm and did not include any studies of implants greater than 10 mm in length. The authors based their conclusions on limited heterogeneous data without appropriate assessment of the data. Furthermore, they were not transparent regarding which articles were included in different analyses. The authors attempted to analyze the influence of different factors on implant failure without sufficient quantity and quality of data.
Strengths and Weaknesses of the Evidence:
Of the 35 studies identified, no randomized controlled trials were found. The authors noted the following weaknesses: a lack of complete baseline information for most patients in the included studies; discrepancies related to lengths of implants classified as "short"; a concern regarding standard reporting of implant length that may not represent the actual length of the implant that is embedded in bone; discrepancies in reporting type and timing of abutment connections, which may result in changes in alveolar bone height; inconsistency in findings related to failures prior to or after prosthesis connection; as well as a non-uniform bone classification criteria. They identified only three articles that outlined bone quality with respect to failure rates.
Implications for Dental Practice:
The limited quality and quantity of evidence presented in this systematic review regarding short dental implants should be cautiously considered when planning the use of short dental implants in a patient’s rehabilitation. Utilization of dental implants with a shorter implant length may allow for greater rehabilitative options without invasive surgical procedures; however, treatment recommendations cannot be made based on the limited evidence provided in this systematic review. The utilization of short dental implants continues to show great promise for rehabilitation.
1. Annibali S, Cristalli MP, Dell'Aquila D, et al. Short dental implants: a systematic review. J Dent Res 2012;91(1):25-32. 2. Pommer B, Frantal S, Willer J, et al. Impact of dental implant length on early failure rates: a meta-analysis of observational studies. J Clin Periodontol 2011;38(9):856-63.