Clinical Success of Short Dental Implants: Systematic Review and Meta-Analysis on Randomized Controlled Trials

Lee, Sung-Ah

Sung-Ah Lee¹, Chun-Teh Lee¹, Martin M. Fu¹, Waeil Elmisalati¹, Sung-Kiang Chuang^1,2

¹Harvard School of Dental Medicine

²Massachusetts General Hospital

In clinical situations where bone height is not adequate, numerous techniques have been proposed to address this issue such as guided bone regeneration, sinus augmentation, and transposition of the inferior alveolar nerve. However, bone augmentations have resulted in complications and patients' morbidity. Therefore, alternative treatments have been proposed such as placement of short dental implants. There have been growing evidences, which demonstrated short dental implants could be successfully used. However, the clinical effectiveness of short implants versus long implants was not thoroughly investigated. Therefore, the aim of our study is to perform systematic review with meta-analyses on randomized controlled trials (RCTs) to compare clinical outcomes of short implants with lengths of 8mm or less to standard implants with lengths more than 9mm, focusing on survival, success, failure, and complications.

An electronic search through PUBMED and MEDLINE databases was conducted to find related articles from January 1998 to September 2012. Only RCTs which mainly investigated clinical outcomes of short implants versus long implants were included. Risk of bias assessments of all the RCTs were performed. Number of implants and patients, implant and patient characteristics, implant locations, surgical techniques, and follow-up periods were extracted from the included studies, and comparative meta-analyses were performed.

Failure rates and standard errors of failure event rates were calculated based on extracted data, cumulative survival rates (CSR) and the associated 95% confidence interval were estimated. I-squared (I²) statistics describing variation in risk ratio was used to assess heterogeneity between studies. Based on presence or absence of heterogeneity between studies, meta-analysis with random-effects or fixed-effects was used using weighting scheme on the study's total exposure time. All statistical analyses were performed using STATA statistical software Version 11.2, 2009 (Stata Corp, College Station, TX, USA), and level of statistical significance was at 0.05.

In total, 804 implants were investigated, which were mostly placed in maxillary or mandibular posterior regions (short implants: 396, long implants: 408). Lengths of short implants ranged from 5 to 8mm; 6 mm length was the most frequent length (44.95%). All implants included in this study had rough surface type. The average follow-up period in all the RCTs was 1.7 years. Short implants had an estimated 1 year CSR of 98.6%, whereas long implants had an estimated 1 year CSR of 97.4%, showing no statistically significant difference in CSRs between both groups. The estimated 5 year CSR was 93.4% for short and 88.5% for long implants. Both groups showed similar prosthetic complication rates with no statistically significance (p=0.834). However, short implant group showed much lower biological complication rate compared to long implant group (risk ratio = 0.209, p=0.014). Much higher biological complications in long implants mainly came from the very technique sensitive surgical procedures, which were required to address limited bone height.

In conclusion, placement of short dental implants could be an alternative treatment plan comparing to standard dental implants to reduce surgical complication rates in the situations where vertical augmentation procedures are necessary. However, to enhance successful clinical outcomes, patient selection could be of paramount importance.

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