Association between Maxillary Sinus Dimensions and Midface Width: 2-D and 3-D Volumetric Cone-beam Computed Tomography Cross-sectional Study
Corresponding Author: Anwar Alhazmi, Department of Preventive Dental Science, Division of Orthodontics, Jazan University, College of Dentistry, Jazan, Kingdom of Saudi Arabia, Phone: +966 173295000 Ext. 5565, e-mail: firstname.lastname@example.org
How to cite this article Alhazmi A. Association between Maxillary Sinus Dimensions and Midface Width: 2-D and 3-D Volumetric Cone-beam Computed Tomography Cross-sectional Study. J Contemp Dent Pract 2020;21(3):317–321.
Source of support: Nil
Conflict of interest: None
Aim: Evaluating the association of maxillary sinus dimensions and the maxillary arch dimensions may help to understand the interrelationship between the maxillary sinus and the anatomical facial features. The study aimed to investigate the correlation of the 2-D and 3-D maxillary sinus dimensions with the linear measurement of the maxillary arch width (MAW) in adult individuals.
Materials and methods: A cross-sectional observational study was conducted using 54 cone-beam computed tomography scans obtained from patients starting their treatment in dental clinics of dental college, Jazan University. Maximal vertical diameter (maximal height) of the maxillary sinus (MSH), maximal horizontal diameter (maximal width) of the maxillary sinus (MSW), maximal anteroposterior diameter (maximal length) of the maxillary sinus (MSL), MAW, and maxillary sinus volume (MSV) were measured and recorded using 3-D Slicer software. The Spearman’s rank correlation coefficient (rho—ρ) was used to analyze the strength and type of the relationship between variables.
Results: In both males and females, moderate to strong correlation (ρ range between 0.65 and 0.80) was observed between MSV for all linear measurements of the maxillary sinuses on both sides. The maxillary sinus length showed the weakest correlation with MAW in both genders
Conclusion: The relationship of MAW with MSV on both sides shows a stronger correlation than its relationship with all 2-D linear measurements of maxillary sinuses.
Clinical significance: The clinician should take into consideration the structure and function of the maxillary sinus when treating the midfacial structures for trauma or congenital malformations.
Keywords: Cone-beam computed tomography, Maxillary sinus, Midface, Volumetric analysis.
The postnatal growth of the human skull involves dynamic changes in the size and shape of the viscerocranium.1 According to functional matrix theory, structures of head and neck form independent functional units. Each of these units consists of the functional matrix (soft tissues and spaces) and supporting skeletal structures.2,3 The development of the skeletal elements of the human skull is codependent on the development of the functional spaces, i.e., the orbits, nasal cavity, and oral cavity as well as the soft tissues. Also, the interaction between the components of the skull is governed by a multitude of the internal (hormonal and genetic) and external factors (growth of soft tissues, development of teeth, and biomechanical factors).4–7 It was further opined by Enlow and Bang8 that all the individual components of the face have to be analyzed individually to thoroughly understand the growth and development of the viscerocranium size as different components exhibit different growth patterns. Consequently, the analysis of the maxillary sinus morphology, dimensions, and MSV as separate functional structures seems to be justified.
The maxillary sinus is located just behind the anterior bony surface of the midface. The boundaries of the surrounding bony structures determine its structural shape. Thus, shape and size of the maxillary sinus is a reflection of the development of the midfacial bones, thereby, the form of midface.9 The relationship of pneumatization of the maxillary sinus and the craniofacial parameters has been observed even when severe congenital anomalies exist. Decrease in MSV accompanies maxillary hypoplasia and has been documented in the diseases manifested by developmental anomalies within viscerocranium, i.e., Apert syndrome, Goldenhar syndrome, Williams syndrome, Crouzon syndrome, and cleidocranial dysostosis.10 Therefore, evaluating the association of maxillary sinus dimensions and the maxillary arch dimensions may help to understand the interrelationship between the maxillary sinus and the midfacial anatomical features.
Furthermore, the pneumatization pattern and the accurate assessment of sinus anatomy is of great clinical importance for head and neck surgeons, otorhinolaryngologists, pediatricians, and radiologists for diagnosis and treatment planning.11 The anatomical dimensions of many structures including the paranasal sinuses can be measured from computed tomography (CT) images.12 Previous studies have shown that dimensions of maxillary sinus obtained by CT scans correspond with the measurements on human skulls.13 Thus, CT is considered a reliable method for morphometrical evaluation of the maxillary sinus.12 Over the years, the use of CT in clinical practice for diagnosis and treatment planning has raised alarm regarding radiation exposure and its hazards. Therefore, efforts to reduce radiation dosage and exposure, especially for younger patients, have become paramount. With the advent of cone-beam computed tomography (CBCT), lower radiation doses and faster image acquisition times have become possible.14
The study aimed to investigate the correlation of the 2-D and 3-D maxillary sinus dimensions with the linear measurement of the MAW in adult individuals.
MATERIALS AND METHODS
Study Design and Study Population
A cross-sectional observational study was conducted to correlate the maxillary sinus dimensions with the linear measurement of the MAW in adult individuals. The sample consisted of 54 CBCT scans from the initial records needed for diagnosis and treatment planning of patients aged 18–24 years, reporting to dental clinics of Jazan University, Kingdom of Saudi Arabia.
Informed Consent and Ethical Approval
Ethical approval was obtained from the institutional review board of Jazan University. Written informed consent was obtained from the study participants after explaining the study protocol and purpose.
Inclusion Criteria and Exclusion Criteria
- Digital Imaging and Communications in Medicine file,
- No previous orthodontic treatment,
- No other treatment that might interfere with the natural course of maxillomandibular growth and development,
- Optimal health conditions.
- No pathologies within the maxillary sinuses.
All CBCT scans were performed using one device (Accuitomo 3D®; Morita, Kyoto, Japan), according to the manufacturer-recommended protocol necessary for adequate image quality. The scanning parameters were constant for all patients (FOV 170 × 120 mm, 90 kV, 5–8 mA, 17.5 seconds exposure time, and 0.25 mm voxel size). The CBCT scans were made with each subject sitting in a vertical position, with the Frankfort horizontal plane parallel to the ground, and with maximum intercuspation. All the scans were performed by one experienced oral radiologist.
The 3-D Volumetric Analysis
Cone-bean computed tomography image reconstruction and direct measurements selected for the dimensional assessment of the maxillary sinuses were made with 3-D Slicer software (Brigham and Women’s Hospital, Boston, MA). The 3-D volumes of maxillary sinuses were measured with the tool for volume calculation in the 3-D mode of the software at different threshold values. The limits for each portion of interest were defined in the axial slice, and the software automatically completed the anatomical area and calculated the total volume in the selected region (Figs 1 and 2).
Maxillary Sinuses and Maxillary Arch Measurements
To allow reconstruction of volumetric data on an accuracy level of 1 mm, the slice thickness was maintained at 0.25 mm as a standard for further 2-D and 3-D reconstruction. All measurements were triplicated to obtain the maximal accuracy and avoid errors. The linear dimensions of the maxillary sinuses and maxillary arch were preceded by identification of the orientation points on CBCT images, according to definitions found in the literature. The most lateral and inferior point of the maxillozygomatic suture, observed on the frontal image, was designated in every patient (zygomaxillare or zm point). The following measurements were performed: zm–zm (total maxillary width) and zm–mid-palatine (one side maxillary width; Fig. 3). We followed the methods of Przystańska et al.1 for maxillary sinus measurement. Assessment of the maxillary sinus in each patient included the following bilateral measurements in maximum diameter (Figs 4 and 5):
- Maximal vertical diameter (maximal height) of the maxillary sinus (MSH) involves the longest distance from the lowest point of the inferior wall to the highest point of the superior wall as presented in the sagittal image.
- Maximal horizontal diameter (maximal width) of the maxillary sinus (MSW) involves the longest distance perpendicular from the most prominent point of the medial wall to the most prominent point of the lateral wall as presented in the axial image.
- Maximal anteroposterior diameter (maximal length) of the maxillary sinus (MSL) involves the longest distance from the most anterior point of the anterior wall to the most posterior point of the posterior wall on the axial image.
Statistical analysis was performed using R software (R Core Team 2015—R: A language and environment for statistical computing). Descriptive statistics, including means and standard deviations, were calculated for all quantitative variables. The Spearman’s rank correlation coefficient (rho—ρ) was used to analyze the strength and type of relationship between variables.
The study sample consisted of CBCT scans from 54 (27 male and 27 female) patients reporting to dental clinics of dental college, Jazan University, Kingdom of Saudi Arabia. All the participants were of age 18–24 years.
In both males and females, moderate to strong correlation (ρ range between 0.65 and 0.80) was observed for MSV, with all linear measurements of the maxillary sinuses on both sides. Moreover, in males, moderate to strong correlation (ρ range between 0.54 and 0.72) was also seen between MSV and MAW on both sides. However, in females, the correlation between MSV and MAW on both sides was weak to moderate (ρ range between 0.29 and 0.42). In males and females, the correlation between MAW and other linear measurements of maxillary sinuses (MSW, MSH, and MSL) was weaker compared to the correlation between MAW and MSV. The MSL showed the weakest correlation with MAW in both genders (Table 1).
The present study was conducted to investigate the correlation of the 2-D and 3-D maxillary sinus dimensions with the linear measurement of the MAW in adult individuals.
Since its advent, the CT has proven to be extremely advantageous in qualitative and quantitative assessments of postnatal growth and development of the head and neck. Cone-beam computed tomography has several advantages over conventional CT, including reduced cost and space requirement, improved accuracy and speed, lower radiation dose, and fewer imaging artifacts.15 Conventional cephalometric radiography expresses 3-D structures onto a 2-D plane, resulting in the overlapping of anatomical structures that interfere with landmark identification and lead to image magnification and distortion. Alternatively, in CBCT imaging, the anatomical structures are represented in all three viewing planes with the help of a computer software. As a result, the CBCT images are enhanced with more accurate landmark identification.14 It has been reported that the reproducibility of measurements on cephalometric radiographs obtained from CBCT scans was better than that with conventional CT. Multiplanar views are especially advantageous in identifying bilateral landmarks.14
Several authors have documented the importance and practical use of MSV.13,16 The practical use of MSV has been described by Bolger et al.10 who classified maxillary sinus hypoplasia based on the volume estimate ratio. The MSV is the best indicator of its hypoplasia, which is a common symptom in patients with craniofacial abnormalities.
MSV, maxillary sinus volume; MSW, maxillary sinus width; MSH, maxillary sinus height; MSL, maxillary sinus length; MAW, maxillary arch width.
It was observed that MAW exhibited a stronger correlation to maxillary sinus volumetric measurement compared to the 2-D linear measurement of the maxillary sinus in both genders. A review of the literature revealed that no study evaluated the 3-D volumetric maxillary sinus size in relation to the dimensions of the maxillary arch. Similarly, several studies have reported that some measurements of the frontal sinus are closely related to specific facial features.17,18 The changes in individual dimensions of the maxillary sinus, if referred to the appropriate dimensions of the middle face, might assist the clinician in understanding the maxillary sinus growth pattern and its interrelationship with anatomical facial features. Butaric et al. investigated the structural and functional relationships between the sinus, midface, and nasal cavity. They concluded that the maxillary sinus form is related to not only nasal cavity form but multiple aspects of midfacial skeletal morphology.1 This association of sinus and the overall midfacial morphology is consistent with the evolutionary changes as well as the functional structural/architectural hypotheses of maxillary sinus function. It can be suggestive of interdependence of maxillary sinus morphology and the growth and development patterns of the surrounding skeletal structures.19–21
Additionally, the relationship of midfacial structures and the MSV has been established by studies conducted on patients with midfacial hypoplasia.9,22 Midfacial or maxillary hypoplasia is expressed in many craniofacial diseases, such as Treacher-Collins syndrome, Crouzon syndrome, and Apert syndrome. In a study conducted by Song et al. on Crouzon syndrome patients, it was observed that the volume of the maxillary sinus has the highest correlation with the width of the sinus.8 Uchida et al. reported that the height of the maxillary sinus is the primary determinant of the volume of the sinus and depth is the second most important variable.22 However, in the present study, the strongest correlation was observed between MSW and MSV. This variation could be because the former study was conducted on cadaver heads with age ranging from 46 years to 94 years, while in our study the patients belonged to a single age-group.
Furthermore, the results of this study show a moderate to strong association of maxillary sinus volumetric measurement and MAW in males; however, it shows weaker association in females. This sexual dimorphism needs further investigation to evaluate the possibility of using this finding as a tool for gender determination based on the correlation between MSV and MAW.
The present study is cross-sectional; therefore, growth-related changes and their effects on the relationship between MSV and midfacial measurements could not be evaluated. Hence, it is advisable to conduct longitudinal studies that can quantify the aforementioned changes. Also, the study sample consisted of CBCT scans from adult patients only. The power of the study could be improved by considering a larger sample size, with participants from different age-groups to evaluate the growth potentials of the maxillary arch with respect to the growth pattern of maxillary sinuses. Furthermore, the association of maxillary sinus dimensions with the skull base dimensions as well as the dimensions of the other paranasal sinuses can be investigated.
The following conclusions can be drawn from the present study:
- The relationship of MAW with MSV on both sides shows a stronger correlation than its relationship with all 2-D linear measurements of maxillary sinuses.
- The relationship of MSV with linear measurements of the MAW on both sides have stronger Spearman’s correlation in males compared to females.
- There is a possibility of sexual dimorphism, regarding the correlation between MSV and MAW that would need further investigation on bigger and broader samples.
The shape and structure of the maxillary sinus is interdependent on the development of the midfacial structures. Hence, it is paramount for the clinician to consider maxillary sinus when treating the midfacial structures for trauma or congenital malformations.
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