Panoramic Radiographic Analysis of Age- and Sex-related Variations in Upper Mandibular Morphology: Focus on the Condyle, Sigmoid Notch, and Coronoid Process

Abstract

Background/Aim

This study aimed to investigate age- and sex-related morphological variations of the mandibular condyle, sigmoid notch, and coronoid process in a mid-sized German population using panoramic radiographs.

Patients and Methods

A total of 150 participants (89 males, 61 females) aged between 18 and 80 years were included. Participants were divided by age and sex. Panoramic radiographs were obtained, and the right and left condylar processes, sigmoid notches, and coronoid processes were evaluated for shape variations.

Results

Age-related differences were found in the mandibular condyles, with younger individuals exhibiting round-shaped condyles more frequently, while older participants showed a higher prevalence of flat-shaped condyles (p<0.001). Sex-related differences included females displaying more diamond-shaped condyles (p=0.033) and triangular-shaped coronoid processes (p=0.004), whereas males exhibited more round condylar processes.

Conclusion

This study highlights significant age- and sex-related morphological variations in the mandibular condyles, sigmoid notches, and coronoid processes. These findings have important clinical implications for the diagnosis and treatment of temporomandibular joint disorders and maxillofacial surgery. Understanding these variations can improve diagnostic accuracy and surgical outcomes in patient-specific care.

The human mandible plays a critical role in a variety of functions, such as mastication, speech, and facial structure support (1). Anatomically, it houses essential structures, including the temporomandibular joint (TMJ), the condylar processes, sigmoid notches, and coronoid processes. These anatomical elements not only influence functional aspects of the jaw but also contribute to the overall biomechanics of the TMJ and craniofacial complex (1,2). Their structural integrity is fundamental to oral health, mandibular motion, and the balance of the facial skeleton. Understanding the diversity and variations in these structures is pivotal for clinicians involved in fields, such as maxillofacial surgery, orthodontics, and the diagnosis and treatment of TMJ disorders (1-3).

The condylar process is crucial for mandibular articulation with the skull, forming the TMJ, which facilitates jaw movements including opening, closing, and lateral motions. The shape and size of the condyle, as well as its alignment within the joint, directly influence the biomechanics of the TMJ, impacting occlusion, chewing efficiency, and even speech articulation (1,4). The sigmoid notch, located between the condylar and coronoid processes, serves as a passageway for neurovascular structures, while its shape contributes to mandibular stability. The coronoid process serves as an attachment point for the temporalis muscle, one of the main muscles involved in elevating the mandible during chewing. Variations in the size and shape of these processes can affect the mechanics of mastication and the TMJ, potentially leading to functional disorders, such as TMJ dysfunction or malocclusion (1,3,5).

The morphology of these mandibular structures can vary significantly across individuals. These variations are influenced by a range of factors, including genetic predispositions, environmental influences, age, and sex. While subtle anatomical differences in the mandible may not result in clinical symptoms for most individuals, they can be highly relevant in the context of maxillofacial surgery, dental restoration, or when diagnosing TMJ pathologies (1,4-6). Detailed knowledge of the normal range of morphological variations is crucial for tailoring clinical interventions to the unique anatomy of each patient. For instance, reconstructive surgeries of the jaw or TMJ arthroplasty may require modifications based on the patient’s mandibular structure (6,7).

A growing body of literature suggests that age and sex are significant determinants of mandibular morphology, particularly in relation to the condylar processes, sigmoid notches, and coronoid processes (8-10). Age-related morphological changes are commonly observed in the condylar heads, which often become flattened or deformed over time due to degenerative processes such as osteoarthritis. These changes can result in TMJ dysfunction, contributing to symptoms like pain, reduced mobility, and altered jaw alignment (11). Studies have also noted that the coronoid process may change shape with age, affecting muscle attachment and potentially altering the functional mechanics of the jaw (11,12).

Sex differences in mandibular morphology are also well-documented, with variations attributed to both hormonal influences and developmental patterns (13). For instance, males typically exhibit larger and more robust mandibular structures compared to females, reflecting differences in craniofacial growth that are influenced by factors such as testosterone levels during puberty (13,14). In contrast, females may have more gracile and narrower mandibles, and these differences can extend to specific morphological traits such as the shape of the condyles or coronoid processes. Hormonal fluctuations during a woman’s life, including those associated with estrogen levels, may also affect bone density and joint health, potentially influencing the susceptibility to TMJ disorders (15,16). Understanding these sex-specific differences is critical for clinicians, as they may inform personalized treatment strategies for conditions like TMJ dysfunction or mandibular fractures.

However, currently there remains a lack of literature studying the mandibular morphology regarding age and sex in a German population. The use of panoramic radiography allows for a non-invasive, detailed examination of the mandible, providing an ideal method for assessing variations across a wide range of patients.

Clinicians often rely on a combination of clinical examination and imaging techniques to diagnose and treat mandibular pathologies. A more detailed understanding of normal anatomical variations will improve the ability to differentiate between pathological and non-pathological conditions, minimizing the risk of misdiagnosis.

Therefore, this study aimed to address the literature gaps mentioned above by conducting a panoramic radiographic analysis of the upper mandible, focusing on the morphological variations of the right and left condylar processes, sigmoid notches, and coronoid processes. By evaluating these structures across both age and sex groups, the research aimed to provide a clearer understanding of how these anatomical features vary within a mid-sized German population. By analyzing these variables, the study hopes to enhance diagnostic precision in clinical practice, particularly in the fields of maxillofacial surgery and TMJ disorder management.

Patients and Methods

Study design. This cross-sectional study analyzed panoramic radiographs to investigate morphological variations of the upper mandible, focusing on the right (RPC) and left (LPC) condylar processes, right (RSN) and left (LSN) sigmoid notches, and right (RPCO) and left (LPCO) coronoid processes (RPCO and LPCO). The aim was to evaluate these structures’ variations by age and sex in a sample population.

Sample population. A total of 150 individuals, aged between 18 and 80 years, participated in the study, with a mean age of 46.17±22.48 years. The cohort consisted of 89 males (59.3%) and 61 females (40.7%). Participants were divided into two age groups: younger than 46 years (n=82) and older than 46 years (n=68) as well as by sex.

Inclusion and exclusion criteria. The inclusion criteria for this study were as follows: 1) Individuals aged 18 to 80 years. 2) Availability of clear, recent panoramic radiographs with no significant image distortion. 3) No history of prior surgical interventions affecting the mandible. 4) No known congenital mandibular anomalies or fractures. 5) No clinical signs or history of TMJ dysfunction at the time of radiographic imaging.

Exclusion criteria included individuals with severe dental malformations (i.e., edentulous jaws, multiple missing teeth), previous mandibular trauma, systemic conditions affecting bone morphology (i.e., osteoporosis), or any radiographs showing technical artifacts that compromised the visibility of the mandibular structures. Individuals with incomplete radiographs or those lacking visibility of the RPC, LPC, RPCO or LPCO were also excluded.

Radiographic analysis. Panoramic radiographs were obtained using standardized radiographic techniques in a clinical setting. All images were captured using the same model of panoramic radiographic machine (Planmeca ProMax, Helsinki, Finland), which was calibrated prior to each imaging session to ensure consistent image quality and magnification. Images were obtained with the patient’s head in a natural upright position, ensuring that the Frankfort horizontal plane was parallel to the floor during image capture.

Panoramic radiographs were obtained using standard procedures, and morphological variations of the RPC, LPC, RSN, LSN, RPCO, and LPCO were classified based on shapes—round, flat, diamond, convex, sloping, wide, triangular, or beak (Figure 1, Figure 2, Figure 3). These characteristics were analyzed using standardized criteria, and their relative distributions were compared between the age and sex groups.

Figure 1.

Shapes of the condyle.

Figure 2.

Shapes of the sigmoid notch.

Figure 3.

Shapes of the coronoid process.

Each of these shapes was determined by visual assessment and digital caliper measurements to quantify their dimensions where necessary. All radiographic measurements were obtained by two independent observers (FD, OS), both experienced in panoramic imaging interpretation, to ensure inter-observer reliability. Discrepancies between observers were resolved through joint discussion and review of the images.

Ethics approval and consent to participate. This study was conducted in accordance with the principles of the Declaration of Helsinki. Ethical approval was waived by the clinical Ethics Committee (IRB). All the procedures/diagnostics performed were part of the routine care. Informed consent was waived by the clinical ethical board due to the retrospective nature of the study.

Statistical analysis. Data are presented as means and standard deviations for continuous variables, and as counts and percentages for categorical variables. Comparisons between groups were made using chi-square tests, and p-values were calculated to determine statistical significance. Data were recorded in a structured database and subjected to both descriptive and inferential statistical analyses. Continuous variables, such as age, were reported as means and standard deviations, while categorical variables, such as the shape of the condylar processes, sigmoid notches, and coronoid processes, were presented as counts and percentages.

Comparisons between groups (age <46 years vs. age ≥46 years; male vs. female) were performed using chi-square tests for categorical variables, such as the distribution of morphological shapes, and t-tests for continuous variables where appropriate. For all statistical tests, a p-value of less than 0.05 was considered indicative of statistical significance.

Results

Baseline characteristics. The study included 150 participants with a mean age of 46.17±22.48 years (Table I). The cohort comprised 89 males (59.3%) and 61 females (40.7%) (Table I). Participants were grouped into two age categories: younger than 46 years (n=82) and older than 46 years (n=68), as well as by sex (Table I, Table II, and Table III).

Table I. Baseline characteristics.

Data are presented as mean (SD) and/or absolute values (percentage).

Table II. Analysis by age.

Data are presented as absolute values (percentage). RPC: Right proc. condylaris; LPC: left proc. condylaris; RSN: right sigmoidal notch; LSN: left sigmoidal notch; RPCO: right proc. coronoideus; LPCO: left proc. coronoideus. Statistically significant p-values are shown in bold.

Table III. Analysis by sex.

Data are presented as absolute values (percentage). RPC: Right proc. condylaris; LPC: Left proc. condylaris; RSN: right sigmoidal notch, LSN: left sigmoidal notch; RPCO: right proc. coronoideus; LPCO: left proc. coronoideus. Statistically significant p-values are shown in bold.

Age-specific morphological variations. Analysis of the mandibular structures revealed significant age-related variations, particularly in the RPC and LPC (Table II). Younger participants (<46 years) showed a significantly higher frequency of round-shaped RPC (59.8%) compared to older individuals (41.2%) with a p-value of 0.023 (Table II, Figure 4). The occurrence of flat-shaped RPC was more common in the older age group, with 29.4% of older participants displaying this feature compared to only 3.7% in the younger cohort (p<0.001) (Table II, Figure 4). This trend was also observed in LPC, where round shapes were more frequent in the younger group (63.4%) compared to older participants (36.8%), while flat LPC shapes were predominant in older individuals (36.8%, p<0.001) (Table II, Figure 4).

Figure 4.

Shapes of the right (A) and left (B) Proc. condylaris - Relative distributions (%) by age.

In addition to these differences in the condylar processes, age-related variations were also noted in the sigmoid notches (RSN and LSN) (Table II). The sloping shape of the RSN was more commonly found in younger participants, with 19.5% of the younger group displaying this shape, compared to 10.3% in the older cohort (Table II). Conversely, wide RSN shapes were more frequently observed in the older age group (51.5% vs. 36.6%, p=0.056) (Table II). Similar trends were found in the LSN, where sloping shapes were more common in younger individuals (22.0%), and wide shapes were more prevalent in the older group (55.9%, p=0.067) (Table II).

Sex-specific morphological variations. The study also revealed significant sex-related differences in mandibular morphology (Table III). Females exhibited a higher prevalence of diamond-shaped RPC (19.7%) compared to males (7.9%, p=0.033) (Table III). In contrast, males had a greater occurrence of convex-shaped RPC, although this difference did not reach statistical significance (Table III). The analysis of the sigmoid notches revealed that wide RSN and LSN shapes were more common in females (50.8% and 55.7%, respectively) compared to males (38.2% and 41.6%) (Table III).

The coronoid processes (RPCO and LPCO) also demonstrated sex-specific variations (Table III). Triangular-shaped RPCO was significantly more common in females (62.3%) than in males (38.2%, p=0.004), suggesting that females tend to have more pronounced muscle attachment points at the coronoid process, potentially influencing mandibular movement and function (Table III). Round-shaped RPCO, on the other hand, was more frequently observed in males (51.7% vs. 34.4%, p=0.037), indicating a potential sex-based difference in the mechanical properties of the mandible (Table III).

Discussion

This study examined the morphological variations of key mandibular structures—the RPC, LPC, RSN, LSN, RPCO and LPCO—and explored the influence of age and sex on these variations. The findings reveal significant differences across various anatomical features, offering valuable insights into how these structures change with age and differ between males and females. These observations have important clinical implications, particularly in the fields of TMJ disorders, maxillofacial surgery, and orthodontics.

Age-related differences. The study found that age significantly influenced the shape of the condylar processes and sigmoid notches. Younger individuals (<46 years) had a higher prevalence of round-shaped RPC and LPC, whereas older individuals showed a higher frequency of flat shapes in both the right and left condylar processes. These findings are consistent with previous research that links degenerative changes in the TMJ to aging, leading to flattening of the condylar heads over time (17,18). This may reflect the natural wear and tear associated with aging, which could have clinical implications for the diagnosis and treatment of TMJ disorders in older patients. Similarly, the sigmoid notch exhibited age-related variations, with younger participants more frequently presenting sloping shapes, whereas older individuals had a higher prevalence of wide-shaped sigmoid notches. These changes may be attributed to age-related remodeling of the mandibular notch, which could be influenced by both functional and degenerative factors (2,18). The widening of the sigmoid notch in older individuals may also reflect compensatory changes due to alterations in condylar shape and TMJ mechanics (2,18,19).

Sex-related differences. Sex also played a significant role in the morphological variations observed in this study. Females had a higher prevalence of diamond-shaped RPC and wide sigmoid notches (RSN and LSN) compared to males. These differences may be attributed to variations in hormonal influences and developmental patterns between males and females, which affect craniofacial growth and mandibular development. The higher frequency of diamond-shaped RPC in females suggests that sex-specific factors may influence the condylar morphology, potentially affecting the biomechanics of the TMJ differently in males and females (2,4,18-20).

Furthermore, the study identified that the triangular shape of the coronoid process (RPCO and LPCO) was significantly more common in females. Since the coronoid process plays a crucial role in muscle attachment and mandibular movement, these findings suggest that sex-specific morphological differences may contribute to differences in TMJ function, which could have implications for the diagnosis and management of TMJ disorders in males and females.

Clinical implications. The observed variations in mandibular morphology have important clinical implications. The shape of the condylar processes and coronoid processes is critical for surgical planning in maxillofacial procedures, including TMJ surgeries, mandibular reconstruction, and orthognathic surgery (2,18,21). Understanding the tendency for flat condyles in older individuals can help surgeons anticipate potential challenges in TMJ arthroplasty or repair and may indicate progressive degeneration of the TMH (21,22). Moreover, the sex-specific differences in mandibular morphology underscore the importance of considering patient sex in both diagnosis and treatment planning, particularly in orthodontic and reconstructive procedures.

Recognizing the different variations in mandibular anatomy based on age and sex can help clinicians avoid misinterpretations that could lead to incorrect diagnoses or unnecessary interventions since panoramic radiographs remain a commonly used diagnostic tool in dental and maxillofacial settings.

Limitations and future directions. While this study provides valuable insights into age- and sex-related variations in mandibular morphology, there are several limitations to consider. First, the study relied on a cross-sectional design, which limits the ability to infer longitudinal changes in mandibular morphology. Future studies should consider longitudinal designs to better understand the progressive nature of these variations. Additionally, the sample size, although adequate, could be expanded to include a more diverse population in terms of ethnicity and geographic background, as mandibular morphology may vary across different populations. Future research could also explore the functional implications of these morphological variations, particularly in relation to TMJ mechanics, bite force distribution, and muscle function. Investigating the relationship between morphological variations and clinical outcomes in patients with TMJ disorders could further enhance our understanding of how these anatomical differences contribute to pathology.

Conclusion

This study highlights significant age- and sex-related variations in the morphology of the condylar processes, sigmoid notches, and coronoid processes of the mandible. These findings provide important insights for clinical practice, particularly in the context of diagnosing and treating TMJ disorders, planning maxillofacial surgeries, and understanding the anatomical differences between males and females. Recognizing these variations can enhance the precision of diagnostic imaging and improve outcomes in surgical interventions, ultimately contributing to more personalized and effective patient care.

Funding

The Authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Conflicts of Interest

The Authors have no relevant financial or non-financial interests to disclose in relation to this study.

Authors’ Contributions

OS, MG, and FD treated the patients and revised the article. FD, SD, and CK researched the scientific literature, and provided statistical findings/analysis. FD wrote the article. All Authors gave final approval for publication.