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Title Meta-Analysis of the Treatment-Related Factors of External Apical Root Resorption
Clinical Question What factors cause root resorption during comprehensive orthodontic treatment?
Clinical Bottom Line The treatment-related causes of root resorption appear to be the total distance the apex of a tooth has moved during treatment and the time in treatment. (See Comments on the CAT below)
Best Evidence (you may view more info by clicking on the PubMed ID link)
PubMed ID Author / Year Patient Group Study type
(level of evidence)
#1) 15180086 Segal/2004 Comprehensive Orthodontic Patients with root resoptionMeta-Analysis
Key resultsMean apical root resorption, in mm, was strongly correlated with total apical displacement in mm(r = 0.822) and treatment duration in years (r = 0.852). Recently, it was reported that variations in theIL-1b allele 1 cytokine is strongly associated with increased risk of EARR. Patients who were homozygous for IL-1b allele 1 had a 95% chance of having root resorption greater than 2 mm. Of all the treatment related variables, treatment duration is most often correlated with apical root loss. Still, several recent publications report no association between treatment duration and EARR. There are several possible explanations for these disparate findings. Prolonged duration of treatment does not necessarily indicate extended periods active treatment. Certain clinicians prefer lengthy periods between appointment intervals. This could increase the likelihood that a patient will experience diminishedforce levels between appointments. Total apical displacement might represent a better marker for overall treatment activation. A tooth that is moved greater distances through bone, is subjected to longer durations of activation. There is no way to move a tooth between two points with fixed appliances, without causing hyalinization. Perhaps, this is why maxillary incisors are most likely to exhibit severe levels of EARR.
Evidence Search ("meta-analysis"[Publication Type] OR "meta-analysis as topic"[MeSH Terms] OR "meta-analysis"[All Fields]) AND Treatment-related[All Fields] AND Factors[All Fields] AND External[All Fields] AND Apical[All Fields] AND ("root resorption"[MeSH Terms] OR ("root"[All Fields] AND "resorption"[All Fields]) OR "root resorption"[All Fields])
Comments on
The Evidence
Of the 150 articles identified, only nine met the initial inclusion/exclusion criteria. Inclusion/exclusion criteria were explicitly stated: papers with a sample size >10, fixed appliances, pre- and post-operative radiographs, and apical displacement recorded were included. History of trauma, prior root resorption and endodontic treatment were excluded. Appropriateness of these selections was tested with a funnel plot analysis. Individual studies were assessed for validity. Meta-analysis was done. Search was detailed and comprehensive and included relevant trials.
Applicability Prior to this study the only conclusive evidence related to root resorption was patient-related factors. We now can suggest a specific treatment-related etiological factor of External Apical Root Resorption: factors that are associated with the duration of active treatment might result in increased levels of apical root resorption in the pre-disposed individual. (Treatment duration, Distance apex of tooth is moved, and genetic factors of IL-1b allele 1 cytokine).
Specialty/Discipline (Endodontics) (Orthodontics) (Restorative Dentistry)
Keywords external root resorption, orthodontic treatment, IL-1b allele 1 cytokine
ID# 735
Date of submission: 11/11/2010spacer
E-mail leejs@livemail.uthscsa.edu
Author Josh Lee
Co-author(s) e-mail
Faculty mentor/Co-author Clarence C. Bryk, DDS, MS
Faculty mentor/Co-author e-mail BRYKC@uthscsa.edu
Basic Science Rationale
(Mechanisms that may account for and/or explain the clinical question, i.e. is the answer to the clinical question consistent with basic biological, physical and/or behavioral science principles, laws and research?)
post a rationale
None available
Comments on the CAT
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by Alessandra Chacon (San Antonio, Texas) on 07/10/2012
Recent studies in 2011 and 2012, such as PMID: 22349547 and PMID: 21811005, continue showing the correlation between duration, amount of tooth movement and the genetic factors associated to the cytokine IL-1b as causes of external root resorption.

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