The dimensional accuracy of CBCT as a measuring instrument was determined by comparing the RLM of C1 with the PLM (C0) in the transverse, sagittal, and vertical planes. The observed p-values after the paired t-test were statistically non-significant (p > 0.05) in all three planes.
In the transverse plane, the PLM (C0) was 9.23 mm, 10.77 mm, and 10.63 mm for A-a, B-b, and C–c in the superior plane, while the minimum and maximum RLM for test groups observed were 9.37 mm (TG1) and 9.63 mm (TG7), 10.57 mm (TG1) and 10.93 mm (TG6), and 9.37 mm (TG4 and TG5) and 10.73 mm (TG6) for A-a, B-b, and C-c, respectively. Similarly, PLM(C0) for D-d, E-e, and F-f in the inferior plane was 8.30 mm, 8.12 mm, and 7.19 mm, respectively, as compared to the observed minimum and maximum RLM values of 9.37 mm (TG1, TG4, and TG5) and 8.37 mm (TG7), 7.83 mm (TG5) and 8.03 mm (TG1 and TG7), 6.83 mm (TG7) and 7.13 mm (TG4 and TG5) for D-d, E-e, F-f thus, showing statistically significant results in the superior axial plane (Table 1).
The sagittal plane PLM for A-B, B-C, D-E, and E-F was 15.47 mm, 12.25 mm, 15.72 mm, and 10.83 mm, respectively, with minimum and maximum test group RLM values of 15.53 mm (TG4, TG6, and TG7) and 15.93 mm (TG5), 12.13 mm (TG4) and 12.27 mm (TG2), 16.03 mm (TG6) and 16.27 mm (TG3), 10.83 mm (TG6 and TG7) and10.97 mm (TG1) for A-B, B-C, D-E, E-F. PLM and test RLM at A-B, B-C, and D-E in the sagittal plane were statistically significant (p < 0.01) (Table 2).
The vertical plane PLM (C0) for A-D, B-E, and C-F was 15.43 mm, 14.36 mm, and 15.35 mm, respectively, with a minimum and maximum value of test group RLM observed of 15.23 mm (TG1) and 15.63 mm (TG4, TG5, and TG7), 13.37 mm (TG6) and 14.33 mm (TG2, TG4, and TG5), 14.93 mm (TG4 and TG5), and 15.47 mm (TG1), respectively, for A-D, B-E, and C-F. There was a statistically significant difference between PLM and RLM at A-D, B-E, and C-F (p < 0.01) (Table 3). An intra-group analysis of test CBCT also revealed statistically significant differences across groups.
Quantification of artifacts of CBCT in the presence of implants or prostheses showed that with an increase in the number of implants or prostheses, the mean grayscale values increased. The highest mean grayscale value was seen in full-arch prostheses (170 ± 90.90), while the lowest grayscale value was seen in the single implant with prosthesis (98.03 ± 84.47) (Table 4). The mean grayscale change was greatest in the vicinity of the implant and implant prosthesis, with the greatest (64.64 78.097) at 3 mm and the least (8.63 81.269) at 10 mm (Table 5).
The canine and molar implant artifacts followed geometric distribution patterns. The grayscale changes at a 3 mm distance from the center of the canine implant (1 mm from the surface) had the highest values at 90° (94.33 ± 38.43) (lingual) and 270° (98.62 ± 41.722) buccally. Similarly, the highest grayscale values were observed around the molar implant at 90° (87.33 ± 49.808) and 270° (122.19 ± 74.682). In the region between canine and molar, reduced grayscale values were observed, i.e., at canine 180° (− 17.14 ± 62.041) and molar 0° (− 26.10 ± 61.173) due to the influence of implant or prosthesis (Table 6).
The grayscale changes at a 5 mm distance from the center of the canine implant had the highest values at 90° and 270°. The highest grayscale values were observed around the molar implant at 115° and 270° (Table 7).
The grayscale changes at a 7.5 mm distance from the center of the canine implant had the highest values at 115° and 270°. The highest grayscale values were observed around the molar implant at 90° and 270° (Table 8).
The grayscale changes at a 10 mm distance from the center of the canine implant had the highest values at 90° and 270°. The highest grayscale values were observed around the molar implant at 90° and 270° (Table 9).
In the region between canine and molar, reduced grayscale values were observed, i.e., at canine 180° and molar 0° due to the influence of implant or prosthesis (Tables 6, 7, 8, 9).
Grayscale and change in grayscale(∆G) were evaluated at 0.25 mm,10 mm, and 20 mm Voxel integration scale (VIS). The grayscale value increased at a VIS (10 mm and 20 mm), and statistically significant (p < 0.01) results were observed in mean grayscale and grayscale change (∆G) at different VIS (Tables 10 and 11).
