Intraoral radiographs are the most commonly used radiographic images in dentistry; consequently, examiners are generally more experienced in their interpretation.
An advantage of periapical radiography (PAR) lies in its capacity to deliver superior spatial resolution. It continues to be regarded as the modality of choice when maximum resolution is required. Among the factors that determine radiographic image quality, spatial resolution stands out as one of the most decisive—especially in dental applications where the identification of small anatomical structures is fundamental.
Data from the literature show that cone-beam computed tomography (CBCT), even under highly controlled experimental conditions, seldom exceeds a maximum theoretical spatial resolution of 3 lp/mm, with most systems reporting median values close to 2 lp/mm.
In contrast, intraoral radiographic techniques offer a substantially superior resolution—nearly ten times higher—reaching approximately 10 lp/mm at 10% contrast. This level of detail is achievable only in two-dimensional imaging modalities, such as periapical radiographs.
In combination with modern digital sensors, PAR can achieve 12–20 lp/mm, thereby enabling precise visualization of subtle anatomical structures. Moreover, PAR exhibits minimal distortion when properly angled, and the reliability of linear distance measurements with standardized PAR has been well documented.
Gher et al. evaluated the accuracy of implant fixture measurements using PAR and computer-assisted tomography. Their findings showed that 90-degree PAR produced the clearest and most detailed images, as well as the most precise measurements when image distortion was considered. The recorded length deviations after calibration ranged from 0.0 to 0.3 mm compared with the actual dimensions.
Wakoh et al. conducted an experimental study comparing measurement accuracy using PAR, orthopantomography (OP), and computed tomography (CT). The standardized PAR demonstrated the highest precision in linear measurements, with results that matched or even exceeded the accuracy of CT scans. This superior performance is likely attributable to the image clarity and high resolution typical of standardized PAR.
Vandenbergh et al. compared digital PAR and CBCT for bone-level measurements, concluding that there were no significant differences between the two methods. The mean error was 0.56 mm for intraoral radiography and 0.47 mm for CBCT.
Misch et al. found no significant differences in bone-level measurements using PAR (mean error of 0.27 mm) or cross-sectional CBCT slices (mean error of 0.41 mm).
In conclusion, numerous studies have demonstrated the effectiveness of standardized PAR for obtaining linear measurements. However, it should be considered that most of these studies were conducted under controlled laboratory conditions.