A peculiarity of this study was that panoramic radiographs were analyzed for all kinds of incidental findings not related to dentistry. Both the single prevalence of each of them and the overall prevalence were thus obtained.
Also, MacDonald et al. [6] analyzed consecutive PRs of symptom-free patients, but these ones attended a Canadian general dental practice and solely for dental examination or hygiene. Therefore, this sample was not representative of the general population.
Carotid artery calcification
Cerebral vascular accidents represent the third cause of death in industrialized countries [2]. They are one of the major public health problems, because of their high incidence and the rehabilitation cost of patients [3].
This study showed that panoramic radiography could help to diagnose carotid artery calcifications.
An accurate analysis of PRs for carotid calcifications could be a useful tool in assessing individuals at risk for stroke, although it requires training to detect calcifications on panoramic radiographs Figs. 4, 5, 6, 7, 8, 9 and 10.
Tonsilloliths are superimposed in the right mandibular ramus
A sialolith under right mandibular border
a, b Bilateral carotid artery calcifications at the level of the third cervical vertebra. Superior horn of thyroid cartilage and triticeous cartilage observable at the level of the fourth cervical vertebra
a, b Well defined, bilateral nodular radiopacities were seen at the level of the lower margin of the third and the fourth cervical vertebra (C3 & C4). Based on the radiographic location and appearance of the lesion on the radiograph, a provisional diagnosis of the coronary artery calcification was made
CAC location relating to sex
Percentage of the incidental findings
In literature, we can find some variance in the prevalence of CAC visible on the PRs.
This study found a prevalence of 8.28% of the presence of carotid artery calcifications on the panoramic radiographs, while Monsour [7] found calcifications in 4% of a total of 2628 non-digital panoramic radiographs. However, our study, unlike the study by Monsour [7], uses digital panoramic radiographs, which enables low-density calcifications to be identified, also because the image contrast can be modified.
Dorado et al. [8] found a prevalence of 15.5%, while Bryam et al. [9] obtained a result of 2.1%.
Monteiro et al. [10] found a prevalence of 9.5%, which is similar to the one found in the present study.
We detected CACs through panoramic radiography in 8.28% of the subjects (with an average age of 65.33 years), and most of them were women (62.87%).
The result of women having a significantly higher prevalence of CAC (9.82% vs a prevalence of 6.54% in men), may suggest a relationship between the decline of estrogen levels in the blood of postmenopausal women and CAC, as proposed by Friedlander and Altoman [11]. In fact, they reported that estrogen decreases low-density lipoprotein (LDL) catabolism in blood and that increased LDL cholesterol levels in blood were associated with the risk of cardiovascular pathologies. Although some studies have suggested an increased prevalence in women, this statistical significance has been contested (Levy and Mandel, [12]).
The recognition of CAC on PR has some limitations, such as quantifying the degree of stenosis. Consequently, Doppler ultrasound is still the main diagnostic test of this pathology, being accurate and non-invasive [13, 14].
Elongated stylohyoid process
The measurement of the stylohyoid process on a panoramic radiograph was challenged. In fact, a 12 pattern classification, which displayed significant difference between prevalences of different patterns varied between East Asian and Western communities [15].
In our study, the prevalence of ESP was 12.64%. This value is lower than that found by Rizzatti-Barbosa et al. [16].
Several studies have concluded that there is a large variation in the length of the styloid ligament complex, and this varies from individual to individual. In general, styloid processes > 25 mm are considered to be of abnormal length.
The results from the present study indicated that the length of 28.72% of the calcified stylohyoid processes that were found, was shorter than 25 mm, while the remaining 71.28% was longer than 25 mm.
In the panoramic radiographs with pathological ESP length (> 25 mm), the highest prevalence was found in over 40 years old and male patients.
Concerning the spatial distribution of ESPs, our study, just like that of Rizzatti-Barbosa et al. [16], has shown that it could tend to their bilateral position.
Ultimately, the prevalence of the non-segmented ESPs was significantly higher than the segmented ones and the prevalence of bilateral ESPs was significantly higher than the ones present on the right and the left side.
In conclusion, as proposed by Steinmann [17], there are 3 theories to explain ossification of the stylohyoid process: the theory of reactive hyperplasia, the theory of reactive metaplasia, the theory of anatomic variation.
The latter involves the stylohyoid ligament or the styloid process as ossified structures that develop in the early formative years after birth. This theory may fit in radiographic findings of ossification in children and young adolescents [18]. However, our study showed that just 2 out of the 255 panoramic radiographs presenting ESP, were found in patients younger than 20 years old. Hence, this finding may demonstrate that the theory of anatomic variation proposed by Steinman [17] is not valid in our study.
Maxillary sinus pathologies
Although panoramic radiography is not considered the gold standard for the diagnosis of maxillary sinus pathologies and cannot be used to entirely exclude their presence, it can help to detect some of them. Being frequently used, it may help to identify particularly the asymptomatic ones or the most insidious ones. This may be crucial in the case of malignancies, because early identification can be very important for the prognosis. As reported in literature, early detection can result in at least 80% treatment success rate as determined by the 5-year survival [19, 20]. It has also been found that at the time of diagnosis of antral malignancies, these can be seen on panoramic radiographs in 90% of the cases [21].
Halstead et al. [22], reported that sinus pathologies detected with PR had a prevalence of about 2%. Our study found a similar result, since 1.78% of the radiographs reviewed displayed maxillary sinus pathologies, indicating that PR may be a useful additional tool to detect maxillary sinus diseases. The mean age of these patients was 49, 64 years and they were mostly men (61.11%).
Concerning the spatial distribution, 91.67% of these pathological findings were unilateral, indicating that maxillary sinus diseases are most frequently present on a single side. In particular, the right side showed a higher incidence.
Lastly, antral pseudocyst and maxillary sinusitis showed the highest prevalence, respectively, representing 36.11% and 30.56% of the maxillary sinus pathologies.
The literature reports that the prevalence of mucosal thickening from an inflammatory origin (such as antral pseudocyst and true sinus mucocele), averages around 38.89%, but varies considerably from report to report, perhaps as a function of population, geography and season [22, 23].
Our study included panoramic radiographs performed between December 2013 and June 2016. Hence, all the seasons were included, allowing us to collect a more homogeneous data set.
Compatibly with the literature [22,23,24], our study found a similar prevalence of maxillary sinus inflammatory diseases, since 38.78% of the sinus pathologies found, were assessed as antral pseudocysts, while the remaining cases appeared as maxillary sinusitis.
Other incidental findings
The other incidental findings encountered included: sialoliths, tonsilloliths, residual cysts, radiolucent cyst-like lesions, radiopaque lesions, mixed radiopaque-radiolucent lesions, hyperostosis and foreign bodies of endodontic origin.
The prevalence of these occasional findings was 3.52% and the most frequently seen ones were sialoliths and tonsilloliths, with a prevalence of 0.89% and 0.74%, respectively.
According to Mandel [25], tonsilloliths affect male and female patients equally, while Suarez-Cunqueiro et al. [26] described a greater occurrence in adult males (1.6:1).
Our study, congruently to Suarez-Cunqueiro et al. [26], found a higher prevalence in male patients (ratio = 1.25:1).
