Comparison of patient satisfaction with mini-implant versus standard diameter implant overdentures: a systematic review and meta-analysis of randomized controlled trials

Implants have been considered to improve treatment outcomes of completely edentulous patients with anatomical challenges compromising the retention and stability. The root form dental implants which are 3–5 mm in diameter are considered standard diameter implants while less than 3 mm diameter implants are termed mini-implants [1]. Initially, mini-implants were used as a temporary measure, with an objective to replace it with standard diameter implants at a later date. However, they provided good stability and healing [2]. In 1997, they were approved for long-term use by the FDA. They are recently being used for complete and partial denture stabilization and also for fixed bridges [2, 3]. They are primarily indicated when there is lack of space or insufficient bone to support a standard diameter implant [3]. The survival rate of mini-implants has been reported to be 94.2% [4]. They are commonly used with ball attachment, O-rings, or a soft reline material and are usually placed using a flapless surgical procedure. Although the utility of mini-implants for implant-supported overdentures has been tested in various randomized controlled trials and case reports, a comparison between standard diameter implants and mini-implants in terms of patient satisfaction and other clinical parameters is of prime importance. Hence, the aim of this systematic review and meta-analysis is to identify patient satisfaction with mini-implant-retained overdentures compared to standard diameter implant-retained overdentures.

The protocol for this review was registered with International prospective register of systematic reviews (PROSPERO) with the registration number CRD42016043075. The review protocol can be accessed at https://​www.​crd.​york.​ac.​uk/​PROSPERO/​display_​record.​asp?​ID=​CRD42016043075. A through literature search was conducted and was completed on 9 July 2016. The primary database used was MEDLINE (via PubMed), Cochrane Central Register of Clinical Trials (CENTRAL), and Database of Abstracts of Reviews of Effects (DARE). The search strategy was ((((((implant overdenture [tiab] OR dentur* [tiab] OR full dentur* [tiab])) AND (implan* [tiab] OR mini-implan* [tiab] OR mini implan* [tiab] OR narrow implan* [tiab] OR diameter reduced implan* [tiab])) AND Humans[Mesh])) AND ((randomized [tiab] OR randomised [tiab] OR RCT [tiab] OR clinical trial [tiab]) AND Humans[Mesh])) NOT ((review [pt] OR review [ti] OR meta-analysis [tiab] OR metaanalysis [tiab]) AND Humans[Mesh]). This search was further supplemented by hand searching of relevant references from review articles and other eligible studies. No limits were applied to the year of study but studies published only in English language were included for the present review.

Only those studies with randomized controlled design with the following requirements were included in the present study:

Both the authors of this study independently screened the abovementioned databases for studies and independently reviewed abstracts for suitability. Full-text articles were obtained for those found to be eligible to be included in the review and those that were inconclusive on the abstract screening. A pre-tested data extraction form was created, and both the authors independently extracted the following data from each eligible study: trial site, year, trial methods, participants, intervention, and outcomes. Disagreement between the authors was resolved through discussion. The extracted data were analyzed using non-Cochrane mode in RevMan 5.0 software. The methodological quality of eligible trials was independently assessed by both the authors using the Cochrane collaboration’s tool for assessing the risk of bias. We followed the guidance to assess whether trials took adequate steps to reduce the risk of bias across six domains: sequence generation, allocation concealment, blinding (of participants, personnel, and outcome assessors), incomplete outcome data, selective outcome reporting, and other sources of bias. The judgment was categorized into low, high, or unclear risk of bias [5]. Percent difference between the mini-implant group (experimental) and standard diameter implant (control) was assessed from each of the eligible studies, and the mean difference in the percent and percent standard error was considered for final assessment. The heterogeneity between the studies were assessed using the Forest plot visually, I ² statistics wherein more than 50% was considered to have moderate to severe heterogeneity, and chi-square test with a statistical P value of less than 0.10 to indicate statistical significance. Random-effect models were used in case of moderate heterogeneity. Considering the presence of very few trials that can be included in the review, publication bias could not be assessed. The present meta-analysis was conducted and presented in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [6]. The grading of quality of included studies was carried out as per Cochrane’s grading of recommendations assessment, development and evaluation tool (GRADE) [7].

A total of 183 articles were identified using the search strategy. Screening of these papers yielded four studies comparing mini-implant-retained overdentures and standard diameter implant overdentures and were found eligible to be included in the systematic review [8‐11]. Two studies [8, 11] comparing patient satisfaction between the groups were included for the meta-analysis. The PRISMA flow diagram is depicted in Fig. 1. The key characteristics of the included studies are mentioned in Table 1 [8‐11]. Risk of bias of the included studies is depicted in Fig. 2.