# 2D vs. 3D Radiological Methods for Dental Age Determination around 18 Years: A Systematic Review
## 3 Results
In the last two decades, various types of detectors have been developed: image intensifiers coupled to a charge-coupled device (CCD), amorphous silicon (\(\alpha\)-Si) flat panels (FP), and complementary metal-oxide semiconductor (CMOS) FP. Amorphous silicon and CMOS flat panels are used in many of the CBCT machines available today. CMOS has several useful characteristics: it requires low power to operate, has high-speed readout, is capable of on-chip integration of electronic circuitry, and produces digital signals without external converters. Compared with \(\alpha\)-Si flat panels, it has the advantage of a smaller pixel size, resulting in higher resolution, and it does not suffer from image lag, a residual charge left behind in the sensor that degrades overall image quality. A disadvantage of CMOS flat panel sensors is the size of the active detection area, which makes it difficult to produce a single CMOS chip in a large size, unlike \(\alpha\)-Si flat panels: a common technique to overcome this issue is tiling multiple CMOS chips to form a larger mosaic [35; 36]. Several studies focused on the comparison between CBCT and OPG, and also between CBCT and MSCT, in the diagnostic process of a wide range of different pathologies [37; 38]. From a therapeutic point of view, the recent digitalization of dental lab procedures, coupled with the guided surgical protocol based on the patient bones 3D reconstruction obtained from CBCT images, gave the last push to the diffusion of this radiologic technology also in small practices. Small practices are finally able to \"close the circle,\" exploiting the availability of in-office Computer Aided Design--Computer Aided Manufacturing (CAD-CAM) systems conceived for delivering chair-side restorations to the dental patient [39]. The MSCT scanners would also make this theoretically possible, but because of the anisotropic nature of their voxel, the accuracy of the re-formatted bone reconstructions was not as reliable as with the isotropic voxel that characterize CBCT scanners. Furthermore, the higher X-rays dose administered to the patient by MSCT compared to CBCT scanners limited the utilization of this technique only to more severe cases; the biological cost-benefit ratio was in favor of this more invasive radiologic technique. The over-prescription of MSCT would contrast the public health mission to protect population health avoiding unjustified radiologic exposures, and would lead to inappropriate expenses. [PERSON] et al. [40] compared the effective dose levels, according to the ICRP 103 (2007) guidelines, of three CBCT scanners for maxillofacial applications with those of three MSCT scanners. They measured values ranging from 13 to 82 \(\upmu\)Sv for CBCT and from 474 to 1160 \(\upmu\)Sv for MSCT. Despite dose levels for CBCT imaging remained far below those of clinical MSCT protocols, they concluded recommending that--considering the wide dose span even using the same type of scanner--it is of outmost importance to buy the appropriate equipment needed for a specific practice, to justify the selection of each of these imaging protocols, and to optimize the radiation dose while achieving a sufficient image quality. [PERSON] et al. [41], combining a literature review with the expert opinion of senior members of the European Academy of Dento-maxillo-facial radiology (EADMFR) and of the Dental X-ray Protection Services of the UK Health Protection Agency (HPA), tried to give specific indications regarding remedial and suspension levels in different dental CBCT equipment. The analysis of these two valuesis useful when selecting the CBCT scanner to be installed in a specific dental primary care facility. Remedial levels, i.e., when the margin of deviation from the standard requires action to rectify it, were available for operating potential accuracy and precision, tube output consistency, Half-value layer (HVL), and Hounsfield value (CT number) uniformity.