Assessment of Orthodontically-induced Root Resorption in Human Premolars by Micro-CT

Objective: To establish a protocol for assessing orthodontically-induced tooth root resorption (OITRR) in human premolars using high resolution micro-CT.

Methods: Ten periotome-extracted maxillary first premolars were obtained from healthy adolescent patients of average age 14 years 9 months ± 20 months – five extracted prior to any orthodontic treatment; five extracted after 1 year of dental arch expansion treatment utilizing progressive sequences of nitinol archwires. Air dried samples were scanned using high resolution SkyScan 1076 Micro-CT imager with vendor-supplied software (V2.6.0), and raw image data was reconstructed using NRecon software (V1.4.4). Reconstructed images were analyzed using CT Analyzer software (V1.6.1.0), and used to assess resorption lacunae characteristics – quantity, depth, volume, location and corono-apical extension along the root surface. Non-parametric statistical analysis was conducted with SPSS software using the Mann-Whitney test, Friedman test, and Wilcoxon signed-rank test with p<0.05.

Results: Orthodontic treatment resulted in significantly greater OITRR as evidenced by greater quantity of lacunae in treated teeth (p = 0.005-0.015 depending on tooth surface), greater maximum depth (p = 0.009), greater corono-apical extension along the root surface (p = 0.047), and greater resorption volume (p = 0.009). Zones of dentin demineralization in resorption lacunae periphery were observed only in orthodontically treated teeth.

Conclusions: We established a protocol to evaluate OITRR quantitatively. Using this protocol, we were able to assess and quantify the type and extent of OITRR. Dentin demineralization zones were also observed subjacent to the resorption lacunae of orthodontically treated teeth. This was a novel observation, indicating possible regions of active resorption or remineralization.