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Density value means in the evaluation of external apical root resorption: an in vitro study for early detection in orthodontic case simulations

¹ Department of Oral Facial Development, Indiana University School of Dentistry, Indianapolis, IN, USA; ² Department of Oral Pathology, Medicine and Radiology, Indiana University School of Dentistry, Indianapolis, IN, USA; ³ Division of Biostatistics, Indiana University School of Medicine, Indianapolis, IN, USA

*Correspondence to: Dr Francisco Eduardo Eraso, Indiana University School of Dentistry, Department of Oral Facial Development, Indianapolis, IN 46202-5186, USA; Email: feraso{at}iupui.edu

Received 12 July 2005; revised 27 March 2006; accepted 1 April 2006

Objectives: The purpose of this study was to develop an alternative diagnostic tool for the early detection of external apical root resorption (EARR).

Methods: Mandibular incisors (n=36) with and without simulated EARR lesions were used. 18 teeth with facial and proximal windows, each with a range of 2 sizes, were placed in 6 N hydrochloric acid (HCl) baths for 10 min. A sample of the acid solution was analysed for calcium concentration by atomic absorption spectrophotometry. Incisors were imaged at 80°, 90° and 100° under 3 test conditions (bracketed, non-bracketed and with subtraction registration templates (SRTs)). The images were reconstructed and subtracted to determine the accuracy and sensitivity of the method. Quantified histograms for each subtracted image were constructed.

Results: At either an angle of 80° or 100°, the bracketed group had the largest mean standard deviation of the subtraction histograms while the SRT group had the smallest. Density values as a function of total calcium removed were plotted indicating a linear relationship between subtraction density units and calcium loss.

Conclusion: The use of the SRTs was significantly more accurate than the use of the brackets alone for digital subtraction radiography reconstructions. This model shows promise for detecting EARR prior to a noticeable decrease in root length. It may be useful for early detection of resorptive lesions during routine orthodontic treatment.

Keywords: root resorption; digital subtraction radiography; root apex; orthodontics