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Estimation of single-root surface area from true thickness data and from thickness derived from digital dental radiography

¹ Graduate Institute of Clinical Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan; ² Division of Oral and Maxillofacial Imaging, School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan; ³ Graduate Institute of Civil Engineering, College of Engineering, National Taiwan University, Taipei, Taiwan; ⁴ Department of Civil Engineering, College of Engineering, National Taiwan University, Taipei, Taiwan; ⁵ Institute of Biomedical Engineering, National Taiwan University, Taiwan; ⁶ Department of Mechanical Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan

*Correspondence to: Ssu-Kuang Chen, No. 1 Chang-Te Street, Dentistry, National Taiwan University Hospital, Taipei, Taiwan; Email: cskchen{at}ntu.edu.tw

Received 26 March 2004; revised 20 July 2004; accepted 9 August 2004

Objectives: The prognosis of a tooth affected by periodontitis may depend on the amount of bone remaining around the root surface. The aim of this study was to find how the surface area of a single root is related to the true thickness data and the calculated thickness data from digital dental radiographs.

Methods: Eight extracted single-root teeth were digitized three-dimensionally for direct surface area measurement. Meanwhile, they were also exposed to a digital dental X-ray system. The true thickness of the tooth root was measured. The estimated circumference data were calculated from both the measured thickness and the thickness estimated from the digital image and then measured and estimated circumferences were compared.

Results: (1) The largest circumference difference mean for measured thickness and for estimated thickness was –4.94% (±0.07%) and 23.02% (±1.12%) respectively. (2) The largest 95% confidence interval for difference means for measured thickness and for estimated thickness was (–2.82%, –1.87%) and (–5.42%, 2.22%), respectively.

Conclusions: When the thickness data are available, the surface area of a single-root tooth can be estimated to an error of less than 5%. Theoretically, the root thickness can be derived from the projected radiological image of the tooth. However, the error of estimated circumference from digital dental radiography may be over 20%. This error can be minimized if the estimated thickness from digital dental radiography can be made more accurate.

Keywords: root surface area, X-ray projection, digital radiology, simulation