Estimating Molar Root Volume from Panoramic Radiographs Using a Geometric Approach—An Experimental Method Comparison

TL;DR

This study shows how panoramic X-rays can estimate tooth root volume safely, reducing the need for higher-radiation 3D scans.

Contribution

A geometric method is introduced to estimate molar root volume from 2D panoramic radiographs with accuracy comparable to 3D CT scans.

Findings

A correlation factor 'r' of 8.04 was calculated to estimate root volume from panoramic radiographs.

Estimated volumes using the geometric model matched closely with true volumes from CBCT scans.

The method reduces radiation exposure while maintaining accuracy in volume estimation.

Abstract

Background and Objectives: Evaluating jaw augmentation procedures usually necessitates pre- and postoperative tomographic imaging. Ethical considerations emphasize minimizing radiation exposure. Given that panoramic radiographs (PR, 2D) offer a lower radiation dose compared to cone-beam CT (CBCT, 3D), this study explores the feasibility of estimating tooth root volume from PR, potentially allowing safer clinical assessments with reduced radiation exposure. Materials and Methods: To develop a mathematical approximation method, the 2D tooth root surface in PR was defined as an elliptical model and a cuboid (3D). The true root volume (mm3) was gathered from CBCTs. The missing link for tooth root volume assessment in 2D radiographs is the depth of the root (vestibulo-oral dimension). It was hypothesized that the tooth root surface and its volume are related. A correlation factor “r” corresponding to the tooth roots’ depths was then calculated. Descriptive and inferential statistics were computed (p < 0.05). Results: The mathematical model was performed on 27 molars with an average volume of 472.83 mm3 (±130.25–CBCT). The factor “r” (obtained by dividing the true root volume from CBCT by the total root surface from PR) was computed as 8.04 (±1.90). Using “r” for the volume calculation in the cuboid model, an average volume of 472.37 (±152.92) for the 27 molars was computed. These volumes did not differ significantly. Conclusions: This study demonstrates that a mathematical model using elliptical projections from panoramic radiographs reliably estimates molar root volume, yielding comparable results to CBCT while reducing radiation exposure.

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