3D Evaluation of the Relationship between Different Vertical Growth Patterns and Cranial Base Angulations

Abstract

Objective  This study aimed to compare cranial base angulations in subjects with high-angle, low-angle, and normal-angle vertical growth patterns using cone beam computed tomography (CBCT).

Design  This study is a retrospective clinical research.

Settings  This study was carried out at the Dentistry Faculty of Eskisehir Osmangazi University.

Participants  According to skeletal vertical face growth patterns, 78 subjects (48 females and 30 males, average age: 13.19 ± 1.73 years) were divided equally into three groups: high angle, low angle, and normal angle groups.

Main Outcome Measures  Cephalometric images were derived from CBCT, and patients were classified according to the SN-GoGn angle (sella-nasion, gonion gnathion angle). Sagittal, axial, and coronal cranial base angulations were measured in three-dimensional (3D) CBCT images. Data were analyzed using the Kolmogorov–Smirnov normality, Kruskal–Wallis, and Mann-Whitney U statistical tests.

Results  There were statistically significant differences between the low-angle and high-angle groups according to sagittal cranial base angulation parameters ( p  = 0.01). Conversely, there were no statistically significant differences between vertical facial growth patterns according to coronal and axial cranial angle variables ( p  > 0.05).

Conclusion  According to the study results, there were no effects of cranial base angulations in two planes (coronal and axial) on different vertical skeletal growth patterns. In the sagittal cranial base angulation parameter, the high-angle group showed greater angulation values than the low-angle group. CBCT may be helpful for evaluating, diagnosing, and predicting 3D cranial base differences.

Introduction

Growth and development of craniofacial structures play a very crucial role for diagnosis, treatment, finishing, and retention periods in orthodontic practice. It is known that approximately 86% of the growth of the anterior cranial base is complete by the age of 4.5 years. In addition to this, 98% of cranial base growth is totally completed by the age of 15 years. ^{1 2} Several studies have shown that the anteroposterior dimensions of the presphenoid part and cribriform plate can be considered stable after the age of 7. ³ The front region of the cranial base has long been described as a stable morphological cephalometric landmark for diagnosing skeletal disharmony between the upper face and lower jaw. The upper skeleton–facial complex is placed under the anterior cranial base and the lower jaw is associated with the middle cranial fossa in the neighborhood of the temporomandibular joint. Therefore, different growth modifications and angulations of the cranial base may lead to variable jaw relationships. The relationship of the upper and lower jaw in the sagittal plane is evaluated according to the angle (ANB angle) value formed between point N, point A, and point B. ANB angles from 0 to 4 degrees were classified as the Class I group, >4 degrees were classified as skeletal Class II, < 0 were classified as Class III. ⁴ Dibbets remarked that the cranial base angle (nasion-sella-basion [N-S-Ba]) was decreased and both the anterior and posterior lines (S-N and S-Ba) were shortened from Class II, then Class I, and Class III malocclusion, respectively. Another study revealed that the glenoid fossa was placed anteriorly more often in skeletal Class III than Class II subjects. ^{5 6}

In orthodontic literature, although the relationship between the cranial base and sagittal malocclusion has been substantively compared in several studies, ^{7 8} there has not been any three-dimensional (3D) comparison study between cranial base angulations and different vertical growth patterns performed. The classification of vertical skeletal development pattern stems from the need to evaluate diagnosis, treatment, and prognosis with different approaches in patients with different vertical dimensions. Understanding of vertical pattern of facial growth will be meaningful to prevent skeletal and dental abnormality.

The vast majority of the literature on cranial base angulations is associated with sagittal malocclusion by using two-dimensional (2D) radiographs. Cephalometric 2D images have distortion and inaccuracy in diagnosis and treatment planning of orthodontic treatment. ⁹ Cone beam computed tomography (CBCT) is more beneficial than conventional 2D cephalometric radiographs in that it provides 3D multiplanar images, models, and knowledge of craniofacial structures. ^{10 11} There is a lack of other 2D and CBCT-induced cephalogram studies which only investigated the cranial base angulation in a single plane. Because of this situation, our study was designed to investigate the relationship between the vertical growth pattern of the dentofacial skeletal structures and cranial base morphology using CBCT with the real 3D multiplanar model.

Materials and Methods

This retrospective study was sourced from the pretreatment 3D CBCT archive records of patients from the Orthodontic Department of the Eskişehir Osmangazi University Dentistry Faculty and approved by the Human Research Ethical Committee at the Eskişehir Osmangazi University (2019–2089). The study sample consisted of 78 subjects (48 females, 30 males, average age: 13.19 ± 1.73 years) diagnosed as high-angle, low-angle, and normal-angle groups according to skeletal vertical face growth patterns. ¹² CBCT-derived cephalometric images were used, and the cephalometric angular parameter SN-GoGn (angle drawing between the gonion-gnathion line and the sella-nasion line) was traced for the classification of vertical skeletal growth pattern determination with the Dolphin 9.0 (Dolphin Imaging & Management Solutions, Chatsworth, California, United States) cephalometric tracing program. None of the subjects had any bad oral habits, craniofacial malformations, and syndromes, previous fixed orthodontic treatments, or orthognathic surgery.

Patients were divided into groups according to the following criteria: ( Table 1 , Fig. 1 )

Table 1. Descriptive statistics of study groups.

Groups	Mean age ± standard deviation	Male ( n )	Female ( n )	Total
Low angle	13.59 ± 1.66	12	14	26
Normal angle	12.83 ± 1.65	10	16	26
High angle	13.16 ± 1.86	8	18	26
Total	13.19 ± 1.73	30	48	78

Fig. 1.

The classification of different growth patterns. ( A ) Low-angle group: Sn-GoGn angle was less than 26 degrees. ( B ) Normal-angle group: Sn-GoGn angle was between 26 and 38 degrees. ( C ). High-angle group: Sn-GoGn angle was more than 38 degrees. Sn-GoGn, sella-nasion, gonion gnathion angle.

• Low-angle group : Sn-GoGn angle was less than 26 degrees ( n  = 26).

• Normal-angle group : Sn-GoGn angle was between 26 and 38 degrees ( n  = 26).

• High-angle group : Sn-GoGn angle was more than 38 degrees.

CBCT images were procured in a standing position with a CBCT machine (Planmeca Promax 3D mid, Helsinki, Finland) and taken under the following exposure parameters: 94 kVp tube voltage, 14 mA tube current, and 27 second time. Simplant O&O (Materialise, Leuven, Belgium) tracing software was used to define the sagittal, axial, and coronal cranial base angulations in 3D images. ¹⁰ Measurements were performed by a single orthodontist who was skilled in 3D tracing (F.K.). Cephalometric landmarks used in both cephalometric radiographs and multiplanar 3D images are described in Table 2 . 3D cephalometric angular variables are specified in Table 3 . All 3D cephalometric tracings are shown in Fig. 1 ( Tables 2 and 3 ; Figs. 2 3 4 5 )

Table 2. Cephalometric landmarks used in the three-dimensional images.

Sella (S)	3D center of the pituitary fossa
A point	Deepest point of the upper alveolar process between anterior nasal spine and the supradentale.
B point	Deepest point in the profile mandibula between pogonion and infradentale.
Nasion (N)	Located on the bony surface at the junction of the frontal and nasal skeleton.
Gonion (Go)	Constructed intersection point formation of the mandibular plane and posterior border line of the ramus mandibula.
Gnathion (Gn)	Constructed intersection point formation of the mandibular plane and facial plane.
Basion (Ba)	Most posteroinferior point of the clivus in the midsagittal plane.
Orbitale (Or)	The most inferior point on the orbital inferior margin.
SAC point	Sella at midpoint of the anterior clinoid processes.
Right pterygoid notch	Most superior furcation point of right medial and right lateral sphenoid plate.
Left pterygoid notch	Most superior furcation point of medial and left lateral sphenoid plate.
Right spheno-orbital	Most anterior and upper point between right greater wing of the sphenoid bone and right zygomatic bone.
Left spheno-orbital	Most anterior and upper point between left greater wing of the sphenoid bone and left zygomatic bone.

Abbreviation: 3D, three dimensional.

Table 3. Three-dimensional cephalometric angular parameters used in the study.

Sagittal cranial angle	Angle between the nasion—SAC—basion points.
Axial cranial angle	Angle between right spheno-orbital to SAC to left spheno-orbital points.
Coronal cranial angle	Angle between right pterygoid notch to SAC to left pterygoid notch points.
Sn-GoGn angle	Angle between sella-nasion line and gonion-gnathion line.

Abbreviations: SAC, sella at midpoint of the anterior clinoid processes; Sn-GoGn, sella-nasion, gonion gnathion angle.

Fig. 2.

All three-dimensional cephalometric landmarks for tracings. ( A ) Nasion (N), SAC point, and Basion (Ba) on sagittal CBCT slice. ( B ) Right and left spheno-orbital points on axial CBCT slice. ( C ) Right and left pterygoid notch points on coronal CBCT slice. ( D ) 3D appearance of cephalometric landmarks on CBCT. 3D, three-dimensional; CBCT, cone beam computed tomography.

Fig. 3.

Frontal view of all three-dimensional cephalometric tracings.

Fig. 4.

Right view of all three-dimensional cephalometric tracings.

Fig. 5.

Left view of all three-dimensional cephalometric tracings.

Statistical Analysis

Descriptive statistics of the study groups were performed using Excel software (Microsoft Corp., Redmond, Washington, United States). The MedCalc Software for Windows (Version 17.5, Broekstraat, Mariakerke, Belgium) program was used for all statistical analyses. To define the normality, the Kolmogorov–Smirnov statistical test was used, which showed that the data were non-normally distributed. The nonparametric Kruskal–Wallis and Mann-Whitney U tests were used for statistical analyses. A significance level of p  < 0.05 was used for all statistical analyses.

Results

According to the nonparametric Kruskal–Wallis and Mann-Whitney U tests, the mean values for the 3D sagittal cranial base angulation for the low-angle, normal-angle, and high-angle groups were 126.27 ± 5.65 degree, 128.01 ± 6.29 degree, and 130.76 ± 7.70 degree, respectively. After applying the Kruskal–Wallis statistical test, a statistically significant difference was found between the groups for the sagittal cranial base angulation ( p  = 0.04). The high-angle group showed significantly greater 3D sagittal cranial base angulation values than the low-angle group ( p  = 0.01). In the evaluation of the coronal cranial angle, the average values found for the low-angle and high-angle groups were 56.17 degrees with a standard deviation of 5.54 degrees and 56.01 degrees with a standard deviation of 5.40 degrees, respectively. Although there was no statistically significant difference between the three vertical facial growth groups ( p  = 0.38), the average value of the coronal cranial angle for the normal-angle group was slightly lower than the other groups, with a value of 54.76 degrees and a standard deviation of 5.55 degrees.

Also, there were no significant differences between the vertical growth groups according to axial cranial angle measurement ( p  = 0.78). The high-angle group had a larger axial cranial angle than the low-angle and normal-angle vertical growth groups ( Table 4 ).

Table 4. Three dimensional cranial base angular measurements of low-angle, normal-angle, and high-angle groups.

Variables	Low angle	Normal angle	High angle	Kruskal-Wallis p -value	Low and normal	Low and high	Normal and high
Sagittal cranial angle	126.27 ± 5.65	128.01 ± 6.29	130.76 ± 7.70	0.04 a	NS	S a ( p  = 0.01)	NS
Coronal cranial angle	56.17 ± 5.54	54.76 ± 5.55	56.01 ± 5.40	0.38	NS	NS	NS
Axial cranial angle	107.74 ± 3.55	107.94 ± 5.43	108.80 ± 6.64	0.78	NS	NS	NS

^a Statistically significance set at p  < 0.05.

Discussion

In this study, the sample consisted of the CBCT images of 78 subjects selected retrospectively on the basis of the vertical growth patterns. According to the different vertical facial pattern (high-angle, low-angle, and normal-angle) groups, sagittal, axial, and coronal cranial angles were identified and measured in 3D CBCT images.

The important role of cranial base angulations in sagittal jaw relationships has been clearly determined. ¹³ The straightening of the cranial base angle leads to clockwise rotation of the lower jaw. ¹⁴ It is known that the mandibular plane (Go-Gn or Go-Me) and gonial angle used in vertical face growth prediction and dimension measurements can be affected by clockwise rotation of the mandible. In addition to this, maxillary growth is also subject to the impact of cranial base development. ⁷ For these reasons, the vertical growth pattern of the subjects may be influenced by the cranial base growth direction and angulation. No previous 3D research has studied the relationship between skeletal vertical face growth and cranial base angulations for prediction of the patient's growth direction.

According to the results, 3D coronal and axial cranial base angulations did not show any statistically significant differences between the low-angle, normal-angle, and high-angle subjects. Also, there were no statistically significant differences between the vertical growth groups according to axial cranial angle measurement. The high-angle group had a larger axial cranial angle than the low and normal vertical growth groups.

It may be considered that the 3D cranial base angulations are not the only factors evaluating vertical growth patterns. Some bad oral habits and differences between vertical ramal growth and dentoalveolar growth are other factors that influence the vertical face growth pattern.

Gong et al remarked that sagittal cranial base angulations were significantly smaller in skeletal Class III malocclusion and larger in Class II malocclusion. ¹⁵ In the present study, for the 3D sagittal cranial base angulation for the low-angle, normal-angle, and high-angle groups, there were statistically significant differences between the groups. The high-angle group showed significantly greater 3D sagittal cranial base angulation values than the low-angle group. When the results of this study are supported by other studies investigating the effect of anteroposterior malocclusions on cranial base angulation, it can be said that there is a sagittal cranial angle increase in skeletal Class II and high-angle individuals. Bhattacharya et al ¹⁶ studied the relationship between cranial base angle and maxillofacial morphology. ¹⁶ Similar to the results of the present study, they revealed that the cranial base angle nasion-sella-articulare (NSAr) was correlated with vertical pattern angles, such as Y-axis (angle formed between the sella-gnathion line and Frankfort horizontal plane) and SN-GoGn. According to the cranial base angle, the larger cranial base angulation (NSAr >125 degrees) group showed a statistically significantly greater SN-GoGn value than the smaller cranial base angulation (120 degrees <NSAr) group. In addition to this, they did not find any statistically significant difference in the Y-axis parameter between the cranial base angulation groups. In light of this information in the literature, it can be thought that the increase in cranial base angle can cause a clockwise rotation of the mandible. As opposed to the findings of the present study, Klocke et al ¹⁴ described that there was no statistically significant difference between the large cranial base angle group and the small cranial base angle group according to the sella-nasion mandibular plane angle angle parameter at both 5 years and 12 years of age. In addition to this, they revealed that there were no statistically significant differences between the large and small cranial base angle groups according to the upper vertical facial measurement, i.e. palatal plane to mandibular plane. ¹⁴ This contradictory situation may be due to certain reasons, such as the fact that the other studies are 2D cephalometric studies and also that the present study used SAC (sella at midpoint of the anterior clinoid processes) point as an alternative to sella point (pituitary cavity), which is a point in the gap that is not clearly a certain landmark.

Within the limitations of this study, the following conclusions can be drawn:

• Axial and coronal cranial base angle measurements did not show statistically significant differences between the high-angle, low-angle, and normal-angle groups.

• The high-angle group showed significantly greater 3D sagittal cranial base angulation values than the low-angle group. The results of this study may be useful to predict the vertical growth patterns of individuals before the time for active orthodontic treatment.

• The use of 3D CBCT images and analysis might play a crucial role in detection and evaluation of 3D cranial base morphology and multiplanar angulations.

Conclusion

Only a small number of diagnostic tools are available for early identification of a vertical pattern of facial growth that will be useful to prevent abnormal and improper skeletal and dental relationships. In orthodontic treatments, early prediction is crucial for the intervention and prevention of more serious vertical and sagittal malocclusions. Due to the early growth completion of the cranial base structures, such as cribriform palate and presphenoid region, cranial base angulations in three planes may be useful for the early prediction of orthodontic disorders. Further studies with larger sample sizes are needed to determine the exact effects of cranial base angulations on vertical growth patterns on CBCT images.

Funding Statement

Funding None.