Modeling and measurement of root canal using stereo digital radiography

Determining root canal length is a crucial step in success of root canal treatment. Root canal length is commonly estimated based on pre-operation intraoral radiography. 2-D depiction of a 3-D object is the primary source of error in this approach. Techniques based on impedance measurement are more accurate than radiographic approaches, but do not offer a method for depicting the shape of canal. In this study, we investigated a stereotactic approach for modeling and measurement of root canal of human dentition. A weakly perspective model approximated the projectional geometry. A series of computer-simulated objects was used to test accuracy of this model as the first step. Then, to assess the clinical viability of such an approach, endodontic files inserted in the root canal phantoms were fixed on an adjustable platform between a radiographic cone and an image receptor. Parameters of projection matrix were computed based on the relative positions of image receptors, focal spot, and test objects. Rotating the specimen platform from 0 to 90 degrees at 5-degree intervals set relative angulations for stereo images. Root canal is defined as the intersection of two surfaces defined by each projection. Computation of error for length measurement indicates that for angulations greater than 40 degrees the error is within clinically acceptable range.