Cone beam computed tomography for assessment of root length and marginal bone level during orthodontic treatment

Abstract

Objective: To evaluate the accuracy and precision of cone beam computed tomography (CBCT) with regard to measurements of root length and marginal bone level in vitro and in vivo during the course of orthodontic treatment.

Materials and methods: Thirteen patients (aged 12-18 years) from an ongoing study and a dry skull were examined with CBCT using multiplanar reformatting for measurements of root length and marginal bone level. For in vivo evaluation of changes in root length, an index according to Malmgren et al was used, along with a modification of this method.

Results: The in vitro mean difference between physical and radiographic measurements was 0.05 mm (SD 0.75) for root length and -0.04 mm (SD 0.54) for marginal bone level. In vivo the error was <0.35 mm for root length determinations and <0.40 mm for marginal bone level assessments.

Conclusion: Despite changes in tooth positions, the CBCT technique yields a high level of reproducibility, enhancing its usefulness in orthodontic research.

Figures

Figure 1

Measurement procedure for assessment of root length and marginal bone level by means of reformatted images in axial, sagittal, and coronal planes. (a) Root length—measurement from a reference line between buccal and palatal cemento-enamel junction (CEJ) to apex. The levels of CEJ and root apex were assessed using a combination of axial, sagittal, and coronal images. (b) Buccal and palatal/lingual bone levels—measurement in frontal and/or axial views from a reference line at CEJ, according to Figure 1a, to the buccal and palatal/lingual marginal bone crest, respectively. (c) Mesial and distal bone levels—measurement from a reference line at CEJ to the mesial and distal marginal bone crest, respectively. An adjusted axial view was used to determine the level of the reference line between the mesial and distal CEJ.

Figure 2

Index according to Malmgren et al. 1 indicates irregular root contour; 2, minor resorption; 3, severe resorption; and 4, extreme resorption.

Figure 3

Modified index for describing slanted surface resorptions at buccal, palatal/lingual, and mesial and distal surfaces at the root apex.

Figure 4

Mean values and standard deviations of in vitro root length measures obtained by direct physical and radiographic means. * indicates a significant difference at P

Figure 5

Mean differences and standard deviations between physical and radiographic in vitro bone level measurements. * indicates a significant difference at P

Figure 6

Precision of radiographic in vivo assessments of root length and bone level at baseline, 6-month, and end-point examinations.

Figure 7

Intraobserver agreement between readings 1 and 2 at 6-month and end-point examinations using an index by Malmgren et al.

Figure 8

Intraobserver agreement between readings 1 and 2 at 6-month and end-point examinations using a modified index for description of slanted surface resorption.