The Comparison of Styloid Processes in the Edentulous and the Posterior Dentate Patients Using Panoramic Radiography

The styloid process is a protrusion of the temporal bone, it has a cylindrical shape, which is localized in front of the stylomastoid foramen and is attached to the hyoid bone via styloid ligament (1). The styloid process is located in the anterior-inferior direction between the internal and external carotid arteries towards the apex of the tonsillar fossa and the styloid process. The distal end is attached to three muscles as stylopharyngeus, stylohyoid, and styloglossus and two ligaments as stylohyoid and stylomandibular ligaments (2). Eagle stated in 1937 that the average length of styloid process is between 25 mm and 30 mm, and in case of being longer than 30 mm, he named it an elongated styloid process and stated that this elongation could cause styloid syndrome or eagle syndrome (3). Eagle syndrome may cause earache, throat ache, dysphagia, and foreign body perception in the throat and pain in the mouth, neck, and face area during the mouth opening, swallowing and head movements (4-6). Although there are a large number of theories related to the aetiology of the elongation of the styloid process including reactive hyperplasia, reactive metaplasia, anatomical variation, anomaly due to age, degenerative process, renal transplantation and genetic hypothesis, the exact aetiology is still unknown (7,8).  However, the elongated styloid process is common in the population and generally, it does not cause any symptoms or clinical findings (1). In the Eagle syndrome, the main treatment option is surgical intervention, use of non-steroid anti-inflammatory agents, application of anaesthetics through local infiltration can be used (9).

 Although CT and CBCT make the correct measurement of anatomic structures, digital panoramic radiography application is easy and also gives sufficient correct information about the diagnosis of elongated styloid process (10).

In edentulous patients, occlusal disagreements might be accepted more than dentate patients. According to Scaf et al.(11) elongated styloid process frequency is affected by muscle tension  originated from occlusal disarrangements.  The study planned with this opinion. The aim of this study is to evaluate the length styloid processes of edentulous and posterior dentate patients retrospectively by using panoramic radiography images.

Materials and Methods

Before the study, ethics committee approval was taken from Inonu University Health Sciences Scientific Research and Publication Ethics Committee (2020/1262). The study was conducted by retrospective evaluation of 200 styloid processes (110 female and 90 male) on panoramic radiographs of 121 patients with the age of 51-90 years old referred to Inonu University Faculty of Dentistry Department of Oral and Maxillofacial radiology for various reasons. Of these styloid processes, 100 belonged to posterior dentate patients and 100 belonged to edentulous patients. For this purpose, the files including panoramic radiography and treatment plans of patients were evaluated between 01.01.2019 and 30.10.2020. Digital panoramic radiographic images used in the study were obtained by using PlanmecaProline XC (2009; Helsinki, Finland) device. All panoramic radiographic images were obtained with 66 kVp, 5mA and 18 sec exposure parameters. In case of any systemic disease that can influence bone metabolism, syndrome or drug use, and presence of surgical operation in the study area, the patients were excluded. In addition, if they did not have enough quality for evaluation, the panoramic images were excluded from the study. The styloid process was measured on each panoramic image by a clinician with six years of experience. Planmeca Romexis software program was used for the measurements. In styloid process length measurement, the method by İlgüy et al. (12) was used and the point where the styloid process separated first from the temporal bone and the extreme point were determined as reference points.. The magnification factor was accepted as 1.2 for the measured values and the real size was calculated.  The distance was recorded according to edentulous and posterior dentate groups. Also the measurements longer than 30 mm were accepted as the elongated styloid process (figure 1). The elongated styloid processes were recorded according to edentulous and posterior dentate groups, right and left sides groups and genders.

The Kolmogorov-Smirnov test was used to check the normal distribution in our data for styloid process length and ages. The results indicated that our data do not show normal distribution. Mann Whitney U test was used for the comparison of styloid process length, while the chi-square test for the frequency of elongated styloid processes according to groups. To define intraobserver error rate, measurements were repeated on randomly selected 30% of all images intraclass correlation coefficients (ICC).  Statistical analysis of data was conducted by using Statistical Package for Social Sciences (SPSS) program.  The significance level was set at P <0.05.

Results

ICC scores were 0.85-0.90 for all measurements.  In our study, a total of 121 panoramic radiographs (58 male, 63 female) of edentulous and posterior dentate patients were evaluated. In the edentulous patients, the minimum age was 52, the maximum age was 88, and the average age was found as 70.96 ±7.18. However, in the posterior dentate patients the minimum age was 51, the maximum age was 90, and the average age was found as 70.6 (±7.15). No statistically significant difference was found between age of posterior dentate patients and edentulous patients (P=0.44) (Table I). Of the styloid processes evaluated in edentulous patients, 44 belonged to male patients, 56 belonged to female patients; of the styloid processes in posterior dentate patients, 46 belonged to male patients and 54 belonged to female patients and there were no statistically significant differences ( P=0,77). A total of 200 styloid processes were measured (100 edentulous, 100 posterior dentate). Length measurements of 200 styloid processes according to the dental status shown in Table I. According to this, the mean length of styloid processes was found as 24.9±6.66 mm (9.2-50.5 mm) in edentulous patients and as 25.75±5.64 mm (16.6-48 mm) mm in posterior dentate patients. No statistically significant difference was found between the styloid process length of posterior dentate patients and edentulous patients (P=0.39). Elongated styloid process frequency between posterior dentate patients and edentulous patients were shown in Table I. In the edentulous patients, the frequency of elongated styloid processes was 19 (19%). Nonetheless, the frequency of elongated styloid processes was 14 (14%) in the posterior dentate patients. The frequency of total elongated styloid processes was found as 33 (16.5%). No statistically significant difference was found between posterior dentate and edentulous patients in terms of elongated styloid process frequency (P=0.341). Table II shows the patients’ elongated styloid process in terms of gender. Table III shows the right and left side elongated styloid process distributions.

Table I: Compare of styloid process length and age mean between edentulous and dentate patient groups with mann whitney U test and compare of frequencies of elongated styloid process with chi-square test.

Table II: Compare of elongated styloid process frequent between female and male gender groups with chi-square test.

Table III: Compare of elongated styloid process frequent between right and left side groups with chi-square test.

Figure 1: Measuring the length of the styloid process.