Nikolaos Pandis DDS, MS, dr. med. dent
Palatal implants and miniplates have higher survival probabilities (= 90 percent) than miniscrews and onplants (83 percent) after a minimum follow-up period of 12 weeks.
In adolescent and adult orthodontic patients, what are the survival probabilities of temporary anchorage devices under active loading for at least 12 weeks?
The authors searched only one database (1966 to January 2009), and hand searched both the reference lists of all full-text articles and eight relevant journals (2004 to January 2009). English-only publications were searched. They did not search for grey literature. Two independent reviewers performed study selection, data abstraction and quality assessment. Any disagreement was resolved by discussion. The number of failures was analyzed. Adverse events such as premature removal due to healing or stability failures were recorded. All failures were treated as independent events. The authors assessed statistical heterogeneity. Although they reported using the Poisson regression model with random effects (if P value < 0.05 for the heterogeneity test), they only reported pooled probabilities/risks and not pooled estimates. They did not perform any sensitivity analyses.
Twenty seven studies met the inclusion criteria (study participants ranged in number from 3 to 209, number of anchorage devices per study ranged from 10 to 480, and participant ages ranged from14 to 30 years). One RCT that examined onplants showed a failure risk of 17.2 percent. For miniscrews, 17 studies (six prospective cohorts, 10 retrospective cohorts, one RCT) contributed data whose pooled risk of failure of 16.4 percent. Additionally, miniscrews with a diameter less than 1.2 mm had a two-fold increase in failure risk over that of miniscrews with a diameter greater than 2 mm. For palatal implants, six studies (two RCTs, three prospective cohorts, one retrospective cohort) provided data with a pooled risk of failure of 10.5 percent. For miniplates, five studies (two prospective cohorts and five retrospective cohorts) provided data with a pooled risk of failure of 7.3 percent. Subgroup comparisons indicated that miniplates and palatal implants combined showed almost a two-fold decrease in risk of failure as compared with miniscrews and onplants.
Temporary anchorage devices show relatively low risk of failure with consistency (except for onplants). Palatal implants and miniplates are more reliable options than miniscrews and onplants.
Source of Funding:
Clinical Research Foundation for the Promotion of Oral Health, Brienz, Switzerland
Importance and Context:
The decision to use orthodontic anchorage depends greatly on patient cooperation, which can limit treatment options. Temporary anchorage devices (TADs) have expanded orthodontic anchorage options, and their use has been reported to improve patient outcomes with minimal or no patient cooperation.
Strengths and Weaknesses of the Systematic Review:
The authors conducted a relatively weak systematic review with unclear inclusion and exclusion criteria. Because their search was not thorough, there may be study selection bias. The authors did not discuss quality assessment. They failed both to clarify if the reviewers were blinded and discuss possible publication bias. The heterogeneity among the included studies, in terms of design and interventions, weakens the validity of the rationale and appropriateness of meta-analysis. Inconsistencies between intended and reported data synthesis were identified. The authors did not closely follow PRIMSA guidelines for systematic reviews.
Strengths and Weaknesses of the Evidence:
The mix of studies and the use of lower levels studies provides limited evidence, however the consistency among all of the studies increases one’s confidence in the evidence. Appropriate quality assessment of included studies was not reported and therefore the risk of bias of the included studies and its effect on the evidence is difficult to be assessed. Unclear reporting or lack of reporting on quality assessment raises doubts about the strength of the evidence.
Implications for Dental Practice:
Evidence suggests that temporary anchorage devices are reliable options for orthodontic anchorage. Although the methodological quality of the available studies is low, the relatively consistent low risk of failure rate among them strengthens the authors' conclusions. There is some evidence that miniplates and palatal implants are more reliable than onplants and miniscrews. Other factors such as the cost of the insertion of miniplates and palatal implants could that other factors should also be considered when considering these implants.