X-ray beam angulation can compromise 2-dimensional diagnosis of interradicular space for mini-implants

Abstract

The aim of this research was to evaluate the influence of x-ray projection geometry on interradicular space of the posterior maxillary arch. Cone-beam computed tomography (CBCT) scans of 32 patients (16.85±4.93years) who met the selection criteria were enrolled. One hundred ninety-two interradicular sites of the posterior maxillary arch were evaluated. Before measurements, each side of the maxillary arch was orientated in all 3 planes of space to obtain CBCT synthesized periapical radiographs with 0° projection geometry (orthogonal x-ray beam-orthogonal X-ray angulation [OX]). Standardized CBCT axial rotations (10°, 20°, -10°, and -20°) were used to simulate periapical radiographs taken with mesial and distal angulation of the x-ray beam (mesial x-ray angulation [MX] and distal x-ray angulation [DX]). Interradicular space widths were measured on OX, MX, and DX CBCT synthesized periapical radiographs. Measurements were performed parallel to the occlusal plane at 3mm and 6mm apical to the midpoint of the alveolar crest. Interradicular distances were statistically compared (P<0.05). Interradicular distances measured on MX and DX CBCT synthesized periapical radiographs were significantly smaller than those measured on OX. Interradicular distance was significantly correlated with the horizontal angulation of the x-ray beam. X-ray projection angle was the most influential variable on interradicular distance. About 30% reduction in interradicular space was observed for every 10° of deviation from orthogonal x-ray. Two-dimensional radiographs obtained away from the 0° projection geometry can reduce the actual interradicular space for mini-implants, inducing misdiagnosis.