Orthodontically induced external apical root resorption (OIEARR) has been classified as surface resorption caused by loss of cementum.  Usually this is superficial and unidentifiable radiographically but if this occurs apically it can be seen as shortening of the tooth.  Typically OIEARR is less than 2mm and clinically insignificant. OIEARR greater than 4mm is severe and occurs in approximately 1–5 per cent of anterior teeth following orthodontic treatment. The aim of this review is to assess the evidence comparing OIEARR in human in vivo root- filled and vital teeth, and to determine if root-filled teeth are more susceptible to OIEARR.

Searches were conducted in Medline, PubMed, Embase, Scopus, Web of Science, CINHAL and the Cochrane Database of Systematic Reviews for randomized or non-randomized clinical trials, cohort studies or case control studies. Study selection and data extraction were conducted independently by two reviewers.

• 4 studies (involving 175 patients) met the inclusion criteria.
• All 4 studies were retrospective cohorts with moderate to high risk of bias
• All included studies found that root-filled teeth did not exhibit significantly more OIEARR than vital analogous teeth

The authors concluded

Based on available evidence, root-filled teeth do not appear to be more susceptible to OIEARR than their analogous vital teeth.

Comment

The availability of evidence to answer the question posed is limited as the reviewers were only able to identify 4 small retrospective cohort studies. The authors note that methodologies to OIEARR are not standardised and point out that a number of potential confounding variables that have been suggested in the literature to affect OIEARR  (history of tooth trauma or injury, extent of previous trauma, presence of external root resorption prior to orthodontic treatment start and variation of orthodontic treatment mechanics) were not examined or accounted for.

Links

Walker SL, Tieu LD, Flores-Mir C. Radiographic comparison of the extent of orthodontically induced external apical root resorption in vital and root-filled  teeth: a systematic review. Eur J Orthod. 2013 Dec;35(6):796-802. doi: 10.1093/ejo/cjs101. Epub 2013 Jan 14. PubMed PMID: 23321851.