Although MF was higher in DS individuals than in non-DS individuals, MC, MR, and C-AUL were found to be low. This situation can be explained by the insufficient growth and development and the different morphological features of the MC in DS patients compared to non-DS patients. Although the C-AUL score was found to be lower in individuals with DS than in non-DS individuals, no significant difference was found in terms of gender. This may be explained by the fact that periodontal diseases are more common in DS individuals than in non-DS individuals and cause alveolar bone loss regardless of gender. No significant difference was found between DS and non-DS individuals in terms of C-MLB score. All measurements included in the study were significantly higher in the ≥15 group than in the < 15 group. In addition, C-MLB, MR, and MC scores were higher in males. These results can be explained by the natural effect of growth and development and gender on anatomical features.
Shalini et al. [19] measured the width of MF at 4.19 and 4.37 mm on the right and the left side, respectively, on dry human mandibles. Ikeda et al. [20] reported that the width of the MC was 4.1 mm in the area near the MF in their study, which was performed using multiplanar magnetic resonance (MRI). In this study, MF width was calculated as 4.1 mm on the right and 4.2 mm on the left side. Although the findings of this study are consistent with past reports, the possibility of differences in the imaging/measurement techniques used and the selected guide points in the foramen measurement may have caused variations in the data.
Despite the reduction in the growth rate in some periods observed in DS individuals in a Turkish study, the study demonstrated that the growth curve was similar to that of non-DS individuals. It has also been reported that the head circumference of DS individuals is lower than that of non-DS individuals, and the head circumference of DS girls is lower than that of DS boys. The low MR and MC scores in DS individuals compared to non-DS individuals and DS females compared to DS males are consistent with the literature [3].
The MC enlarges as it approaches the MF, as shown in the study by Chrcanovic et al. [21]. In this study, the MF was always higher than the MC. The MC was found to be low in individuals with DS, although the MF was higher than that in the control group. This suggests that DS individuals may differ from non-DS individuals in terms of mandibular anatomic features. The fact that the MF and MC were not measured in the horizontal when measured in the vertical may have prevented finding the correct diameter.
DS individuals are typically considered to be skeletal class III [4]. Although C-MLB score was significantly higher in males and the ≥15 group, no significant difference was found between DS and non-DS individuals. This can be explained by the effect of growth and development and gender on anatomical features in accordance with the C-MLB score. However, there was no evidence in this study to support the idea that mandibular prognathism is more common in DS individuals.
Abeleira et al. [22] tried to define the morphology of hard palate in DS with performing some measurements with cone beam computed tomography (CBCT) in axial, sagittal and coronal plane. They showed that the hard palate is narrower in DS than in control group, but the anteroposterior measurements are similar in both groups. Hard palate is narrower in the DS group compared to the control group can be explained by growth deficiency. From this point; in the present study, the lower MR, MC and C-AUL scores in DS compared controls were consistent with the literature. Also Abeleira et al. [22] found no statistically significant differences between males and females with DS for any measurements. In the present study, C-AUL and MF score are showed no significant difference in terms of gender only.
Rodríguez et al. [23] reassessed the dental asymmetry and dental morphologic features in DS in their study. They did not find greater dental crown asymmetry in DS individuals than in the controls contrast past reports which was reported greater dental asymmetry. In current study, there is no significant differences between left and the right side in all measurements and this results is not specified in the statistical results because it is considered normal. Also, almost all dental morphometric measurement scores such as root length and mesio-distal diameter of teeth were significantly lower in the individuals with DS compared controls in the study of Rodríguez et al. [23] These results consistent with the current study in terms of lower MR, MC and C-AUL scores in DS than controls.
Sakellari et al. [6] showed that periodontal inflammation was more common in DS individuals than in cerebral palsy patients and in healthy subjects under 30 years of age [5]. In addition, Amano et al. [24] found that the level of Porphyromonas gingivalis in people with DS over 5 years of age was higher than in non-DS individuals. Corcuera-Flores et al. [13] used panoramic radiographs in their study and showed that DS individuals have a higher risk of marginal bone loss around the implants. The C-AUL score was lower in DS individuals than in non-DS individuals, regardless of gender. This result is consistent with the literature with regard to demonstrating marginal bone loss. Because panoramic radiographs were used in this study, only the height of the alveolar bone was measured. There are no data on clinical periodontal measurements or periodontal soft tissues. Therefore, based on the findings of this study, the low C-AUL score in DS individuals compared to non-DS individuals cannot be explained by only marginal bone loss related to periodontal disease. Growth and development retardation in DS individuals or changes/errors in reference measurement points may also be among the reasons for low bone height.
It is mentioned in the literature that there may be an enlarged MC and MF in patients with neurofibromatosis [25]. In this study, the canal width of patients with DS was significantly lower than that in the control group, while the foramen width was found to be greater (Fig. 3). The fact that the MF of each patient had to be measured at the midpoint of the vertical length of the ramus led to the failure to determine the correct MF width.
The average age of individuals with DS has increased over the years. According to research conducted in different societies, the average age of 9 in 1929 increased to 12 in 1949 and to 50–60 in the 2000s [2]. In addition, some studies have reported the social status of DS individuals [26]. Also, although implant applications in patients with DS are usually performed under general anesthesia [8], local anesthesia procedures have also been reported [9, 10]. When the increase in average life span and social adaptation are considered, it is indicative that there will be a patient profile of DS individuals who will attend clinics in the coming years, and this has increased even more than the expectation of complicated treatment has in the past. Implant-supported prostheses may also be included in complicated treatments. Thus, more detailed information about alveolar bone morphology may be needed in DS patients.
Limitations
Due to the two-dimensional imaging technique, which caused erroneous results in the study measurements, and the small number of patients included, the study should be repeated in order to confirm the results. It would be useful to create a larger study group and to use a three-dimensional imaging method such as CBCT and MRI, which produce more reliable measurements.
Only the mandible was included in the study because the superposition of anatomical landmarks such as the palatine bone, zygomatic arch, and maxillary sinus in the maxillary region prevented the correct measurement in panoramic radiographs.