Effect of Remodeling Root Surfaces by New Cementum Formation on Orthodontically Induced Tooth Root Resorption in Rats Open Access

[摘要] Background: The etiology of dental root surface resorption associated with orthodontic tooth movement is not fully understood. However, under normal circumstances, the cementum layer covering the dental root surfaces provides a protective barrier against resorption. Objective: To investigate the effect of cementum layer remodeling, induced either by cyclosporine A (CsA) or by low-level laser therapy (LLLT), on the amount of root resorption caused by orthodontic tooth movement. Methods: Two different animal experiments were performed. The first experiment lasted two weeks and used three groups of female Sprague-Dawley (SD) rats as follows: six rats received daily 10mg/kg CsA subcutaneous injections; six rats received daily LLLT treatment delivered by gallium-aluminum-arsenide (GaAlAs) laser at an 830nm wavelength; and six rats received no treatment (control). In vivo micro-computed tomography (micro-CT) was used to analyze volumetric changes in the root hard tissue. The cementum thickness was also evaluated histologically. A follow-up split-mouth study was performed using nine female SD rats. The right side maxillary first molars received daily LLLT treatment using the same laser exposures as in the previous experiment for two weeks. The left side was not treated and served as the control. Immediately after LLLT treatment, orthodontic appliances were placed bilaterally to move the right and left molars mesially over four weeks. Ex vivo micro-CT was used to evaluate the volume of root resorption. The extent and severity of root resorption were then assessed histologically. Results: In the first experiment, the cementum was significantly thicker (P=0.019) over the root surfaces in the LLLT group compared with the control and CsA groups. The follow-up experiment showed significantly less (P=0.028) root resorption volume due to tooth movement on the LLLT side compared with the control side. This protective effect against root resorption was more, on average, on the root surfaces that showed more cementum growth in response to our LLLT treatment. Conclusion: Our LLLT treatment significantly increased the thickness of dental root cementum in rats. Moreover, remodeling of the rats’ dental root surfaces using our LLLT treatment resulted in a significant decrease in the volume of root surface resorption following application of orthodontic force.

[发布机构] University of Alberta

[效力级别] Dental root surface resorption