A Comparison of Computed Tomography Scans and Digital Periapical Radiographs Ridge Height Measurements
To investigate the agreement between computerized tomography scans (CT) and intraoral periapical digital radiographs (PA) alveolar ridge height measurements in maxillary and mandibular posterior regions. We reviewed 100 implant patient radiographic records and identified 27 mandibular sites in 19 patients and 23 maxillary sites in 13 patients with available CT scans and matching PA radiographs. The distance from the crest of the ridge to the floor of the maxillary sinus or to the superior border of the inferior alveolar canal was measured. PAs were measured with Dexis software v. 8.0 and CTs were measured with Simplant software v. 11.02. Two examiners (RJ and MM) recorded the measurements separately; each examiner recorded two readings. The average of the 4 readings was used for data analysis. Absolute agreement: Paired t test comparing ridge-height measurements between the two imaging methods showed no differences for maxillary sites (P > 0.2) and significant differences for the mandibular sites (CT > PA, P = 0.0009). Relative agreement: Kendall rank correlation analysis of ridge-height measurements between the 2 imaging methods showed a high positive correlation for maxillary sites (Kendall's tau = 0.76, P = 0.0001) and moderate correlation for the mandibular sites (Kendall's tau = 0.46, P = 0.001). Maxillary PAs tend to approximate CT ridge-height measurements. By contrast mandibular PAs tend to underestimate the distance from the crest of the ridge to the inferior alveolar canal.
Figure 1. Example images of mandibular radiographic matched sets. (a) Represents a periapical (PA) radiograph showing an edentulous area distal to a mandibular premolar. (b) Represents a computerized tomography (CT) cross-sectional view 4 mm distal to the mandibular premolar. Figure 2. Example images of maxillary radiographic matched sets. (a) Represents a PA radiograph showing an edentulous area distal to a maxillary broken premolar. (b) Represents a CT cross-sectional view 4 mm distal to the maxillary broken premolar. Figure 3. Ridge height measurement diagrams. (a) Illustrates a mandibular CT cross-sectional view of an edentulous area 4 mm distal to an adjacent natural tooth. A straight line perpendicular to a tangent at the crest of the ridge was extended to the superior border of the inferior alveolar canal, with the length of the line measured in mm. (b) Illustrates a mandibular PA image of the same site presented in image (a). Ridge height was recorded at a distance of 4 mm distal to the natural tooth immediately anterior to the edentulous area. A straight line parallel to the vertical axis of the natural tooth was extended from the alveolar crest to the superior border of the inferior alveolar canal, with the length of the line measured in mm. IAC indicates inferior alveolar canal.
Figure 4. Difference against average measurement for all ridge-height data. Maxillary sites represented by black points and mandibular sites by white points. “Mean” line: is the mean difference (d) between computerized tomography (CT) and periapical digital radiograph (PA) measurements. “Mean + 2SD” lines: represent the “limits of agreement” as per Bland and Altman. Figure 5. Difference against average measurement for maxillary ridge-height data. “Mean” line: is the mean difference (d) between CT and PA measurements. “Mean + 2SD” lines: represent the “limits of agreement” as per Bland and Altman. Figure 6. Difference against average measurement for mandibular ridge-height data. “Mean” line: is the mean difference (d) between CT and PA measurements. “Mean + 2SD” lines: represent the “limits of agreement” as per Bland and Altman.
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