# A Literature Review on the Uncommon Use of Extraoral Periapical Radiography
###### Abstract  
Periapical radiography is a regular radiographic procedure performed by dentists. However, at times, it may not be possible to position the image receptor into a patient's mouth in an optimized or practical way. For these cases, some dentists advocated the use of extraoral periapical radiography (EOPA). This literature review aimed to review the dental literature on the use of EOPA. In October 2023, PubMed, Web of Science, and Scopus were searched to identify papers that reported on the use of EOPA, supplemented by manual reference tracing and Google Scholar searches. After screening, 18 papers published between 2003 and 2022 were identified, including 14 original articles and 4 reviews. From very limited and conflicting evidence, it was found that root length/working length measurements between EOPA and IOPA did not significantly differ or EOPA showed inferiority. No data were available to compare EOPA with other extraoral modalities such as panoramic radiography. The technique used in EOPA to visualize posterior teeth in the maxilla and mandible varied across studies, such as the vertical angulation of the primary beam, whether mouth should be opened or closed, and whether a holder should be used or not. At the current time, EOPA probably should not be advocated for regular use. dental medicine; diagnostic value; endodontics; periapical radiograph; radiology +
Footnote †: journal: Medical  
also helps in the detection of secondary caries beneath existing restorations, which can be challenging to diagnose otherwise [9]. The versatility and high resolution of IOTA make it an indispensable tool across various dental specialties, contributing significantly to comprehensive care of dental patients. However, IOTA requires a dentist to place an image receptor directly into the oral cavity of a patient, which a patient may not tolerate well. For instance, a recent study suggested that the Asian population may not tolerate an image receptor of a standard size because of anatomical constraints or a lack of space in the oral cavity [10]. It was found that patients generally felt that the lower posterior regions were most uncomfortable during IOTA [11], and the retake risk of IOTA of the lower third molar was significantly higher if patients felt very uncomfortable during the first take [12]. Moreover, pediatric patients often find it challenging to tolerate the placement of image receptors due to their smaller oral cavities and heightened gag reflexes. This can lead to increased anxiety and discomfort [13], which may necessitate the use of alternative imaging techniques or sedation in some cases. Similarly, patients with special needs or those suffering from temporomandibular joint disorders may experience significant discomfort or pain when opening their mouths wide enough to accommodate the image receptor. Several material types of image receptors are available for IOTA. In terms of digital imaging, a phosphor plate closely resembles the traditional analogue film in terms of its physical dimensions, whereas an intraoral sensor made of a charge-coupled device (CCD) or complementary metal-oxide semiconductor (CMOS) is usually much thicker than a traditional film. A previous study has shown that a phosphor plate is a more comfortable image receptor compared to CCD or CMOS intraoral sensors among adults [11]. However, another study reported that the use of intraoral sensors was more comfortable than the use of a phosphor plate or traditional film among adults [12]. Moreover, another study reported no significant difference in adult patient comfort level between the use of intraoral sensors and phosphor plates [14]. In pediatric patients, it was reported that the use of phosphor plate and traditional film was much more comfortable than the use of intraoral sensors [15]. This was reasonable as the mouth of a child is much smaller than that of an adult, and hence intraoral sensors children may complain that they are \"too thick\" very easily.