Introduction

Radiography is the most commonly recommended modality for measurement of residual dentin thickness. Cone beam computed tomography (CBCT) is an accurate method for most linear measurements, but its measurement accuracy can be influenced by field of view (FOV) and voxel size.

Objectives

This study compared the accuracy of two CBCT scanners with different FOVs for measurement of radicular dentin thickness of maxillary first molars.

Material and methods

In this in vitro study, 50 extracted maxillary first molars were decoronated, embedded in paraffin blocks, and scanned using Carestream CBCT with 4 × 4 cm and 5 × 8 cm FOVs (75 μm) voxel size as well as Cranex 3D with 4 × 6 cm (136 μm) and 6 × 8 cm FOVs (200 μm). Two observers measured radicular dentin thickness of mesiobuccal and palatal roots at furcation, and 2 mm and 4 mm below it, using OnDemand software. Horizontal sections were made at the same levels, and actual dentin thickness was measured with a digi­tal caliper as the gold standard. Paired t-tests were used for comparison (α = 0.05).

Results

The interobserver agreement was acceptable (> 0.780). Carestream with large FOV and Cranex with small FOV showed acceptable accuracy, with a difference of 0.03 mm and 0.08 mm between the two FOVs, respectively (p < 0.05). Cranex had a significantly higher accuracy than Carestream in small FOV (p < 0.05). Small FOV yielded a significantly higher accuracy than large FOV (p < 0.05), except for furcation and 2 mm below the furcation (p > 0.05).

Conclusions

Cranex was more accurate than Carestream in small FOV. Small FOV provided a higher measu­rement accuracy than large FOV. Although it was clinically negligible, small FOV should be preferred for endo­dontics cases diagnosed with CBCT to minimize radiation dose while maintaining accuracy.