Satish Kumar DDS, MDSc
There is no significant difference in survival (greater than or equal to one year) between short (less than or equal to 8 or
Good evidence provides no support for a difference between short RSDIs and conventional length RSDI in totally or partially edentulous patients in terms of survival.
Is there a significant difference in survival (greater than or equal to 1 year) between short (less than or equal to 8 or
The authors searched two databases for English-language studies published up to August 2007. They considered only prospective studies with a minimum of one year follow-up. The primary outcome measure/variable was the percentage of implants surviving out of the total number placed. An implant was considered to have survived if it was not lost. Implant loss was defined as implant mobility of previously clinically osseointegrated implants and removal of non-mobile implants due to progressive peri-implant marginal bone loss and infection. No secondary outcome measures/variables were used. The primary outcome measure was implant survival risk and not implant survival rate. The associations of the survival of implants with their lengths (short versus conventional) were expressed as a risk ratio (RR). Risk ratios of greater than one indicated a higher percentage of survival with short implants than with conventional implants. The pooled RRs from combinations of studies were obtained through meta-analyses performed separately for totally and partially edentulous patients. The authors assessed publication bias and heterogeneity among the selected studies.
The authors selected 37 articles that reported on 22 patient cohorts.
(a) In totally edentulous patients, six studies qualified for meta-analysis of comparison between implant length less than or equal to 8 mm (surviving/placed implants [percent]: 155/162 [95.68 percent]) versus greater than or equal to 10 mm (572/603 [94.86 percent]). The pooled RR was 1.01 (weighted mean, 95 percent confidence interval [CI] 0.97 to 1.04, P = 0.978). The same six studies also qualified for meta-analysis of comparison between implant length < 10mm (160/172 [93.02 percent]) versus greater than or equal to 10mm (572/603 [94.86 percent]). The pooled RR was 0.99 (95 percent CI 0.94 to 1.06, P = 0.978).
(b) In partially edentulous patients, 12 studies qualified for meta-analysis of comparison between implant length less than or equal to 8mm (594/612 [97.06 percent]) versus greater than or equal to 10mm (1,884/1,916 [98.33 percent]). The pooled RR was 0.99 (95 percent CI 0.98 to 1.00, P = 0.145). The above 12 studies and an additional study reporting only on < 10mm length implants (total of 13 studies) qualified for meta-analysis of comparison between implant length < 10mm (715/736 [97.15 percent]) versus greater than or equal to 10mm (2,016/2,050 [98.34 percent]). The pooled RR was 0.99 (95 percent CI 0.98 to 1.00, P = 0.173.
Hence, there was no statistically significant difference in survival between short and conventional RSDI placed in totally and partially edentulous patients (P > 0.05). Also, there was no statistically significant heterogeneity among studies (P > 0.10) and no evidence of publication bias (P > 0.05).
There is no significant difference in survival (greater than or equal to 1 year) between short and conventional RSDI in totally or partially edentulous patients.
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Importance and Context:
The effect of implant length on their survival has been a controversial issue. Surface roughness has been shown to compensate for shorter implant length. Previous systematic reviews have reported comparable survival rates for short and conventional length RSDI (1, 2). However, a meta-analysis on the effect of implant length on the survival of RSDI has not been performed.
Strengths and Weaknesses of the Systematic Review:
The authors used standard methods to conduct this meta-analysis. A major weakness is that the authors did not include a detailed assessment of design of the included studies, their scientific quality and risk of bias (inherent with observational studies). Hence, the results of this meta-analysis may include unreported bias from the included studies. The authors did not include non-English language literature. The authors excluded studies of patients with systemic disease such as uncontrolled diabetes, untreated periodontal disease and smoking (> 10 cigarettes per day) that may contribute to implant failure. As a result, the findings of this meta-analysis should not be extrapolated to patients that practitioners commonly see in general practice.
Strengths and Weaknesses of the Evidence:
The evidence adequately substantiates the conclusion, and corroborates previous reviews (1-3). Among the weaknesses of the evidence is that the included studies lacked clinically relevant patient related survival data, as well as objective measurements to determine implant prognosis such as clinical and radiographic marginal bone level. Also, the authors could not assess the actual survival rate because the selected studies did not provide the total exposure time of implants. In addition, most of the studies were missing significant amounts of data; to obtain them for their meta-analyses, the authors had to contact the respective study authors.
Implications for Dental Practice:
Good evidence suggests that, in an otherwise healthy population without known systemic or local risk factors for implant failure, clinicians can choose short RSDI to replace missing teeth in totally and partially edentulous patients, especially when the placement of conventional RSDI requires higher cost and morbidity related advanced surgical procedures.
(1) das Neves FD, et al. Short implants–An analysis of longitudinal studies. Int J Oral Maxillofac Implants 2006; 21:86-93.
(2) Renouard F, et al. Impact of implant length and diameter on survival rates. Clin Oral Implants Res
2006; 17(Suppl. 2):35-51.
(3) Hagi D, Deporter DA, Pilliar RM, Arenovich T. A targeted review of study outcomes with short (= 7 mm) endosseous dental implants placed in partially edentulous patients. J Periodontol 2004; 75:798-804.