A retrospective diagnostic study of prevalence of orofacial calcifications using panoramic radiograph: To insinuate the unseen

Background The prevalence of calcifications in the head and neck region has long been observed and has a strong value of presaging systemic illness. The observations of such calcifications in routine panoramic radiographs (PR) demands keen follow-up and health check-up of patients. In developing countries, the use of routine panoramic radiographs is a common one owing to its cost effectiveness and feasibility. Thus, knowledge of prevalent calcifications and the ability to diagnose it while correlating with possible systemic condition is mandatory. This article is primarily about the prevalence of soft tissue calcifications in head and neck region while emphasising the clinical importance. Material and Methods A total of 22,000 panoramic radiographs were included after adapting the inclusion and exclusion criteria. All the included radiographs were examined using Dentsply Sirona Sidexis 4 Dental imaging software in full screens. Results A total of 22,000 PRs were analyzed, of which 7,832 were male and 14,168 were female. The age range of patients included were from 6 to 88 years with a mean of 41 years ± 11.4 years standard deviation. Of the analyzed PR’s, a total of 1228 calcifications were found in 1041 (4.731%) patients which comprised of 497(6.34%%) calcifications in male and 731 calcifications in female (5.159%). From which, 16 different soft tissue calcifications were reported while stylomandibular ligament calcification being the most reported one. Conclusions Panoramic radiographs is yet an essential diagnostic tool, as a dentist our role in diagnosing systemic conditions is inevitable. A high prevalence of calcifications demands thorough examination of radiographs on routine. Early detection od calcifications ensures prevention of further progression of disease. Key words:Orofacial calcification, panoramic radiography, atherosclerosis, dystrophic calcification.


Introduction
The deposition of calcium salts in tissues such as calcium phosphate, in sites other than osteoid/bone or hard tissues of teeth structure such as soft tissues in an unordered fashion is called Heterotopic or Pathologic calcification (1,2). Such Soft Tissue Calcifications (STC) are usually undiagnosed unless incidentally found during routine radiologic examination. There are three major types of STC, namely dystrophic, metastatic and idiopathic. They are classified mainly based on the serum calcium levels and the site where they get deposited. Dystrophic calcification occurs when the serum calcium levels are normal and seen mostly in dead and degenerated tissues. Metastatic calcification occurs when serum calcium and phosphate levels are elevated i.e.) deranged metabolism and hypercalcemia (1)(2)(3)(4). Finally, idiopathic calcification also referred as calcinosis occurs in normal tissues in presence of normal calcium levels. STC in the head and neck region are uncommon and are mostly asymptomatic. However, the presence of some calcification indicates presence of serious underlying systemic disease which warrants definitive treatment. They are identified mostly based on their anatomic location, number, distribution, calcification pattern, size and shape (5). The listing and classification for STC was drafted by White and Pharoah initially. It ranges from the most common stylohyoid ligament calcification, sialolith, lymph node calcification, myositis ossificans, Carotid artery calcification, antrolith and phlebolith. Epidemiologically, people above 40 years of age have high chances of developing pathologic calcifications and also there is a reported female predilection. Panoramic radiographs (PR) play a vital role in dental diagnostic procedures. They are 2-Dimensional radiograph which provides detailed visualisation of oral and para oral structures. During routine radiographic examination, STC may be detected as an incidental finding. Detection of such STC in PR is of greater significance and importance as they are early indicators of undiagnosed underlying systemic disease or an impending risk. Thus, this study is mainly aimed to detect the STC during routine clinical examination by analysing Panoramic Radiographs (PR). Furthermore, this is the first kind of study to be done in South Indian population to include 16 different types of head and neck calcifications with added advantage of using a large sample size.

Material and Methods
-Patient Assortment: This population based retrospective descriptive study was designed to evaluate the incidental findings of STC in PR of patients attending Oral Medicine and Radiology department between March 2017 to March 2022. A total of 22,000 PRs were assessed and evaluated. PR of all patients irrespective of age and gender were included in this study.
-Exclusion criteria: • Faulty radiographs which include processing errors, imaging errors and patient positioning errors were not included.
• Images which didn't extend up to styloid process above and hyoid bone below were excluded.
-Image acqusition: The PRs were taken using orthopantomographic device. The images were taken by specially trained radiograph technicians following proper guidelines and under ALARA (As Low As Reasonably Achievable) principle. Standard principles such as 66 kV, 5-10 mA for an exposure time of 17.6 seconds were followed while recording the radiographs.
-Image analysis: The acquired PR were assessed on full screen in a Dentsply Sirona Sidexis 4 Dental imaging software in full screens, the exposure of image was adjusted as needed to get a clear observation over the necessary areas. The radiopacities found in radiographs were assessed further for its size, shape, borders, number and location, either unilateral or bilateral. This be used further for risk assessment and to determine the prognosis of patients. Then PR divided into 12 sections by using one horizontal line across occlusal plane and 5 vertical lines along angle of mandible on both sides, through distal aspect of first molars on both sides and through midline as shown below were used as a guide for locating the position and for better recording (Fig. 1).
-Objectives: • Prevalence of soft tissue calcification seen in PR.
• Estimate and compare the prevalence of soft tissue calcifications seen in male and females • Estimate the most common age group affected • Evaluate and compare the incidence of each calcification included • Evaluation of most common location of occurrence of each calcification. Find the relation between various factors associated with soft tissue calcification. -Statistical analysis: IBM SPSS (Statistical Package for Social Sciences) was used. Spearman's rank correlation was used to find the association between STC and various associated factors. Multinomial analysis is used to figure out the most commonly affected age group in each type of STC.
-Soft tissue calcification assessed: The STC included in this study is listed in Table 1

Results
A total of 22,000 PRs were analyzed, of which 7,832 were male and 14,168 were female. The age range of patients included were from 6 to 88 years with a mean of 41 years ± 11.4 years standard deviation. Of the analyzed PR's, a total of 1228 calcifications were found in 1041 (4.731%) patients which comprised of 497(6.34%%) e291 Fig. 1: OPG segmenting.

Calcification
Location Shape, perihery and number Radiographic features

Calcified stylohyoid ligament
Located between cervical spine and posterior border of ramus, below and mesial from the angle. May be unilateral or bilateral.
It is slender, tapering, linear, regular in shape, approximately more than 3 cm in length.
Has a more radiopaque outline when compared to inner structure, may be segmented.

Calcified atherosclerotic plaque
Along the course of main arteries supplying face.
Irregular nodular mass, curvy or oval or rectangular or roughly verticolinear with irregular margin. May be single or multiple in one or more sites Almost fully radiopaque structure

Tonsilolith
In middle portion of ramus where the dorsal surface of tongue passes ramus and angle. Mostly below the mandibular canal.
Round to oval, small and multiple, single and large, well-defined structure.

Triticeous cartilage calcification
Within the thyrohyoid ligament, at the level of C3 and C4 vertebrae.
Usually oval, surrounded by a smooth well-defined border. May be unilateral or bilateral.
Almost fully radiopaque

Rhinolith
Above floor of nose, embedded or between nasal conchae Single, small to large, may have uniform borders, round to oval or irregular shape Almost fully radiopaque, laminated 6. Antrolith Above the floor of maxillary sinus, unilateral or bilateral Well defined, smooth or irregular. May be small or large. Almost fully radiopaque

Phlebolith
Located along the course of veins in face.
Small, single or multiple, usually has regular borders, circular to oval in shape. Radiopaque.

TMJ calcifications
Synovial osteochondromatosis, CPDD-In soft tissues around TMJ, as amass of calcification surrounding mandibular condyle Large, globular, irregular or smooth borders. Almost fully radiopaque

Sialolith
Submandibular sialolith: below or on the body and mesial to the angle of mandible, usually above hyoid bone Parotid sialolith: on upper third of ramus of mandible. May be anterior or posterior to it. Sublingual sialolith: in the floor of mouth may be above or below to it.
May be regular, irregular depending on location of sialolith. Round or oval in shape May be single or multiple.

Radiopaque mass and may have different degrees of calcifications
if multiple stones are present. May have stippled appearance.

Myositis ossificans
Along the regions of muscles of mastication, in single or multiple locations. Small cluster of radiopaque structures Almost fully radiopaque, laminated

Stylomandibular ligament calcification
Located between styloid process and angle of mandible Difference Slender, linear calcified structure, present on either side.
Usually have a radiopaque outline with radiolucent body. Usually appears as partially calcified structure which follows the pattern of pinna    bilateral occurrence (p=.011), similarly rhinolith, antrolith, sialolith, calcified lymph nodes, Monkeberg atherosclerosis and calcinosis cutis occurs significantly unilaterally. Petrified ear showed a significant female predilection (p-.023). When considering the level of calcification, tonsilolith, rhinolith, sialolith, calcified lymph nodes show a statistically significant completely calcified structure. Almost 90% of the incident sialolith were found in submandibular region, followed by sublingual and parotid region. Most of the encountered lymph node calcifications were of submandibular lymph nodes, only one case showed cervical node calcification. When looking into calcified atherosclerotic plaque, maximum was of carotid artery calcifications, few were superficial temporal artery calcification.
The most common region of occurrence of STC was L (164), followed by G (119) in cases when STC occurs unilaterally. When STC occurs bilaterally, the most common region of occurrence was L, G combined (326) and A, F combined (203) ( Table 3).
A spearman's rank correlation test was carried out to find the correlation of STC and its associated factors such as sex, age, level of correlation. This resulted in a significant correlation between age, calcification level and the side of occurrence of calcification (Table 4).
Here, no further assessment was made to correlate the systemic conditions of included patients with STC, rather this correlation was justified using literature evidences while highlighting the insinuation of STC in patients health.

Discussion
Panoramic radiography is one of the common extra-oral diagnostic tools in dentistry, advised when there is a need to examine the oral cavity with extraoral structures. This study is mainly pertained to the evaluation and analysis of the STC encountered accidentally during routine radiographic examination. The sample size of 22,000 PR makes this study to more valuable and serves as a chance to gain additional information which might help to orient imminent investigations in this field.  (7). The presence of calcifications in artery implies impending risk of developing complications. Patients with carotid artery calcifications are more prone to develop ischemic heart disease which is also linked to high risk or morbidity and mortality (8). When calcifications are in higher region as in superficial temporal artery, they are prone to develop intracranial ischemic disease (9) and more related to patients with chronic kidney disease. Additionally, it has been reported that patients with carotid plaque are in increased risk of developing peripheral vestibular disorder (PVD) (10). Masaoki Wada et al. in their study concluded that the hazard ratio of developing PVD is about 3.25 to 4.41.
Monckeberg arteriosclerosis is a disease characterized by dystrophic calcification of tunica media and internal elastic lamina ultimately leading to reduced arterial compliance. It has been associated with increased mortality and morbidity (11). This disease is usually of unknown etiology, sometimes maybe associated with hyperparathyroidism, coronary artery disease. In our study, a total of 5 cases were identified with a mean age of 45 years, male predilection was noted, this finding is in accordance with that of Kroger et al. findings. Middle aged male patients were most commonly affected. Radiographically, multiple tortuous vascular calcifications in the region adjacent to posterior border of mandibular ramus were noted. Few cases showed presence of a dense tram track appearance mostly of the maxillary and facial artery. A single case showed presence of carotid atherosclerotic plaque. 14 cases of petrified ears were also noted in this study. The mean age of reported patients were 55.5 years with a female predilection. Middle aged women were mostly affected. There was a significant bilateral involvement and most of the reported cases were partially calcified. Petrified ears are an uncommon finding which is nothing but hardening of articular cartilage as a result of calcification. Various endocrinopathies such as Addison's disease, diabetes, hypothyroidism may cause this calcification of ears (12). Usually, the presence of ear calcification is a useful sign as it may precede the development of endocrinopathies by many years. Further, mechanical trauma and frost bite are other two major causes.
The second most common incident STC is triticeous cartilage calcification. These are tiny oval shaped cartilage located at the lateral border of thyrohyoid membrane just below hyoid bone in C3-C4 region. Though triticeous cartilage doesn't pose a significant and specific function, calcification of it is a usual thing and said to occur in same pattern as thyroid cartilage (13). In our study, significant bilateral calcification was noted with a female predilection. Calcification usually begins in the second decade of life and terminated at the elderly age. In our study, most of the calcifications were partially calcified irrespective of the age group. This denoted triticeous cartilage calcification is independent of aging, in accordance with findings of Hatley et al. (14). Though triticeous cartilage calcification is of less clinical significance being asymptomatic and the cartilage having no known functions, it should be investigated for the presence of dysphagia, odynophagia (15) and any endocrinopathies.
Another noteworthy STC sialolith, they are calcific deposits in the gland formed around a central nidus.
In this study about 90% of sialolith were encountered in submandibular gland. This finding is in accordance with findings of Lustman et al. (16). Radiographically, they had a homogenous calcification with a laminated appearance. Though sialolith are of less clinical significance when they are of small size, they have potential to be the basis of various salivary gland pathologies such as sialadenitis which may result in total excision of the gland. Further about 20% of submandibular gland stones and 40% of parotid gland stones are unseen on routine plain films (17). Thus, an additional sialogram should be performed followingly to rule out presence of additional sialolith.
Tonsilolith showed significant completely calcified structures with male predilection and unilateral involvement. Most of the calcified structures were spherical (68%) in shape followed by oval and a significant multiple calcifications (p=.009) were found to the highest of 8 calcifications per side. A mean size of 1*1 cm was observed. Tonsilolith was observed in a broad age range while adult and middle-aged persons were most commonly affected. Presence of tonsil stones may indicate the presence of long standing or chronic tonsilitis which warrants definitive treatment. Most prevalent STC is the stylohyoid ligament calcification. Bilateral stylohyoid ligament calcifications were common with a mean size of 2.5 ± 0.5 cm, with comparatively more partial calcifications and female predilection. When looking into region, occurrence in L, G region was most commonly noted followed by A, G regions in bilateral cases. Region L was most commonly involved in unilateral cases. In most of the instances this condition is asymptomatic, only 28% of cases show symptoms (18). The symptoms vary from a simple foreign body sensation in throat to Eagle's syndrome. Severe calcification of the ligament can be an indicator for underlying disturbance in calcium homeostasis resulting from endocrinopathies. The longest of the observed stylohyoid ligament calcification was 8 cm long with a width of 1.5 cm extending all the way from the styloid process to hyoid bone bilaterally (48 years, male). Likewise, calcification of the stylomandibular ligament was also noted which mostly occurred unilaterally with female predilection. An interesting case of cervical lymph node calcification of size 2.5*3 cm was observed in our study in a patient of age 17 years. When checking the medical background of the patient, previous tuberculous infection was identified. Tuberculous lymphadenitis-scrofula is one of the primary causes for dystrophic lymph node calcification (19). Other possible causes include cancer metastasis, chronic infection. In our analysis, most of the lymph node calcifications in oral and maxillofacial region were submandibular of size 1.5*1 cm, having irregular completely calcified features. The mean age of incidence was 51 years with a female predilection. Usually, they are asymptomatic and no treatment is needed. Whereas in patients with cancer, resection of the lymph nodes is necessary to prevent further spread and recurrence (20).
Other STC identified in this study include antrolith, rhinolith, calcinosis cutis, TMJ calcifications and myositis ossificans. These calcifications had a strong unilateral involvement with a female predilection. They were mostly partially calcified structures of size 1*1 cm.
Antrolith and Rhinolith are calcified masses present in the maxillary sinus and nasal cavity respectively. Radiographically they appeared round to ovoid shape and antrolith was accompanied with the features of maxillary sinusitis, which includes mucosal thickening. Patients with antrolith and rhinolith may be asymptomatic until incidental radiographic identification. Some of the symptoms associated include difficulty breathing, purulent discharge, anosmia and oroantral fistula with palatal or nasal septal perforation (21). TMJ calcifications are comparatively rare and when identified proper care should be taken as they have high chances to progress into severe joint deformities. Two possible causes for TMJ calcifications include synovial chondromatosis and calcium pyrophosphate dihydrate deposition (22). In our examination, they appeared as small multiple partially calcified structures in the region between mandibular coronoid process and articular eminence. Mean size was 0.5*0.5 cm.

Conclusions
PR is an essential diagnostic tool used in routine dental procedures which also has an added advantage of early diagnosis of diseases with the help of STC present. Soft tissue calcifications in the oral and maxillofacial regions are relatively common and are also of great importance.
Majority of the calcifications reported in this study were stylohyoid ligament calcification followed by calcified atherosclerotic plaque, sialolith, triticeous cartilage calcification. As dentists we play an important role in early identification of undiagnosed systemic disease with incidental detection of STC present in routine PR. The early detection is also important to prevent further progression of disease thus reducing mortality and morbidity of patients. In order to achieve this a thorough interpretation of all routine radiographs extending beyond the area of interest is decisive. Few crucial STC reported in this study include calcified atherosclerotic plaque of carotid and superficial temporal artery, petrified ear, oro-pharyngeal calcification, monckeberg atherosclerosis.