Year : 2021 Month : September Volume : 10 Issue : 38 Page : 3333-3337

Analysis of Genial Tubercle Anatomy Using Cone Beam Computed Tomography – A Retrospective Study from Chennai, India

Abarna Jawahar1, Maragathavalli Gopal2

1, 2 Department of Oral Medicine and Radiology, Saveetha University, Saveetha Institute of Medical and Technical Sciences, Maharashtra, India

CORRESPONDING AUTHOR

Dr. Maragathavalli Gopal, Dept. of Oral Medicine and Radiology, Saveetha University, Saveetha Institute of Medical and Technical Sciences, Maharashtra, India.
Email : drgopalvalli@gmail.com

ABSTRACT

BACKGROUND

Analysis of genial tubercle anatomy using three-dimensional (3D) imaging can be valuable in preparation for genioglossus advancement in the treatment of obstructive sleep apnoea, estimation of the safe zone prior to implant surgery and evaluation of mandibular asymmetry. Hence the intention of the study was to analyse the morphological pattern, dimensions of genial tubercles and their position in the mandible using cone beam computed tomography (CBCT).

 

METHODS

A retrospective study was conducted on 100 patients scanned using Sirona Orthophos XG device in the Radiology department, Saveetha dental college and hospital. The genial tubercles were identified, morphological pattern of the genial tubercles was classified into four patterns and linear measurements of the genial tubercle height, width, position of genial tubercles on the mandible in the images were done. The collected data was tabulated and analysed using SPSS software. A paired t - test was used for intra examiner calibration and a chi-square test was used for comparison between genial tubercle patterns in both the sex.

 

RESULTS

On analysing the genial tubercle patterns, type I (44) was the most commonly seen followed by type II (24). Genial tubercles were not evident (type IV) in 20 patients. Type III (12) was least commonly seen among the pattern types.

 

CONCLUSIONS

The anatomy of genial tubercles is highly variable. The mean height of genial tubercles (GTH) measured was 5.36 mm and mean width of genial tubercles (GTW) measured was 5.24 mm.

 

KEY WORDS

Genial Tubercles, Anatomy, Cone Beam Computed Tomography, Mandible

BACKGROUND

Genial tubercles also known as mental spines, spinae mentalis or genial apophysis are tiny bony projections seen on the lingual surface of the mandible. They are a group of four bony projections surrounding the lingual foramen, located between the superior and inferior border of mandible. These bony projections give attachment to genioglossus muscle superiorly and geniohyoid muscle inferiorly.1,2 These muscle actions are associated with mobility of the tongue and deglutition which are essential for speech and mastication of food.3 Traditionally genial tubercles are outlined as 2 pairs of bony projections situated one above the other in the lingual region of mandibular symphysis, but several variations in their anatomy can also be observed. Sometimes excessive movements of the tongue can result in elevated bony projections making it vulnerable to the site of alveolar fracture.

Cone beam computed tomography (CBCT) is an advanced imaging modality, which allows three-dimensional visualization of hard tissue structures. It has been proved to be a successful investigative modality by providing accurate three-dimensional volumetric data in axial, sagittal and coronal planes which can be useful in diagnosing and treating several pathologies in oral and maxillofacial region. CBCT has several applications in dentistry which includes implantology, oral medicine and surgery, endodontics, orthodontics, and periodontics. It has also been expanded in various fields of medical sciences. Radiation exposure from CBCT is comparatively ten folds lower than exposure from conventional CT scans.4 The main advantages of CBCT include easy accessibility, easy handling, in office imaging and offer a real time data set with multiplanar cross-sectional and 3- dimensional reconstruction based on a single scan.5-7

Analysis of genial tubercle anatomy using cone beam computed tomography for its examination can be helpful in preparation for the surgical advancement of genioglossus for correction of sleep apnoea disorder8,9 , for planning implant surgery in the interforaminal zone of mandible10 and assessing the symmetry of mandible.11 Severe atrophy can be seen in the edentulous mandibles of old patients. If the genial tubercles prevail as sharp projections in the mandible of these patients, they can cause significant difficulty to prosthodontists.12-14

Hence it is essential to study the different morphological patterns observed in genial tubercles and their relative position in the mandibular region. The purpose of the study was to analyse the patterns of the genial tubercles, their anatomy and position in the mandible with respect to the mandibular anterior teeth and borders using cone beam computed tomography.

METHODS

A retrospective study was conducted on 100 patients scanned using Sirona Orthophos XG device in the Department of Oral Medicine and Radiology, Saveetha dental college and hospital taken for the purpose of implant placement between September 2020 and February 2021. A sample size of 100 was obtained by using G power with a power of 80. The inclusion criteria included good quality CBCT images and patients aged between 20 and 60 years. The exclusion criteria included any congenital or developmental deformities, traumatic injury or pathologic changes in the mandible, any crown or implant placed in the mandibular anterior region and blurred or distorted CBCT images.

Using Galileo's software, the genial tubercles were identified, the pattern of the GT was assessed, and linear measurements of the images were done in each included CBCT volume. To standardize the measurements CBCT scans were oriented, so that the zygomatic structures bilaterally were at the same level in the axial view. In the coronal view the infra orbital foramina of the right and left sides were parallel to the horizontal line. The Frankfort plane represented the true horizontal axis in the sagittal view. To reduce measurement error, all measurements were repeated on 2 separate occasions in 1 - week interval and the average values were recorded. Differences between the 2 readings for intra examiner variation were tested by using paired t tests.

 

 

Genial Tubercle Pattern Assessment

The morphological patterns of the genial tubercles were analysed and grouped into four patterns as follows - a rough impression of two superior genial tubercles (Type I), two superior genial tubercles and a median ridge representing fusion of inferior genial tubercles below them (Type II), a single median ridge (Type III) and no prominent genial tubercles (Type IV). The morphological patterns of the genial tubercles were analysed in the tangential view along with the axial view (Figure 1).

 

 

Genial Tubercle Size & Position Assessment

Genial tubercle height (GTH) and Genial tubercle width (GTW) were measured in millimetres. Genial tubercle height (GTH) was measured in the cross-sectional view as the vertical distance between the level of the most superior and most inferior border of the genial tubercles (Figure 2a). Genial tubercle width (GTW) was measured in the axial view as the horizontal distance at the widest level between the genial tubercles (Figure 2b). Distance from the apex of the lower central incisors to the superior border of the genial tubercles (I - SGT) and distance from the inferior border of the genial tubercles to the inferior border of the mandible (IGT - IBM) were measured in millimetres. I - SGT and IGT - M were measured in the cross- sectional view by drawing tangent lines from the apex of the lower central incisors to the superior border of the GTs and from the inferior border of the GTs to the inferior border of the mandible (menton), respectively (Figure 2c & 2d).

 

 

Statistical Analysis

The collected data was tabulated and analysed using SPSS software 23.0 for windows. A paired t - test was used for intra examiner calibration and a chi-square test was used for comparison between genial tubercle patterns in both the sex. A statistically significant test was inferred when the P value was < 0.005.

 

 

RESULTS

Data extraction was done from 100 patients in the age group of 20 - 60 years including both the sexes who underwent CBCT imaging for implant planning in the Radiology department of Saveetha Dental College and Hospital who fulfilled the inclusion and exclusion criteria. Paired t - test used to assess the intra-examiner reliability showed statistically no significant difference between the values measured in the two images (P > 0.05). There was nearly perfect agreement P = 0.94 for the measurements and P = 0.92 for the pattern distribution.

 

 

The sex distribution among the study population was 62 males and 38 females. On analysing the genial tubercle patterns (Figure 3) type I (44) was the most commonly seen followed by type II (24). Genial tubercles were not evident (type IV) in 20 patients. Type III (12) was least commonly seen among the pattern types. On analysing the correlation of the pattern of the GTs with sex, there was no statistically significant difference between sexes at P ≤ 0.005 using the chi - square test (Figure 4).