A Study on the Association between Skeletal Malocclusion, Upper Airway Cross-Sectional Area, and Upper Airway Volume Using CBCT Scans

Keywords

pharynx - malocclusion - orthodontics - cone beam computed tomography - diagnostic Imaging

Introduction

An important factor to be considered during the process of orthodontic treatment procedure is the status of respiratory function of the patients.[1] The upper part of the airway comprises three regions, namely, nasopharynx, oropharynx, and hypopharynx. These anatomical components play a very important role in respiration, deglutition, and malocclusion.[2]

Researchers have described the upper airway using radiographic landmarks extending superiorly from the posterior nasal spine to inferiorly the third cervical vertebra.[3]

The comparative size and growth of the soft tissues around craniofacial structures influence the pharyngeal space volume. Craniofacial anomalies such as short mandibular body, increased anterior face height, high palatal vault, maxillary or mandibular retrognathism, narrow maxilla, and clockwise rotation of the jaw have been linked with dimensional changes of the pharyngeal airway.[4]

It has been observed that if the upper airway spaces get narrower, the resistance to airflow increases, thereby leading to an increase in the risk of snoring, further leading to obstructive sleep apnea (OSA) in advanced cases.[2] This is characterized by upper airway collapse throughout sleep.[2] When OSA occurs, it results in functional imbalance, which might lead into mouth breathing manner, which, if prolonged, will result in tooth malposition, respiratory dysfunction, maxillofacial deformities, and impaired speech.[5]

In recent years, cone beam computed tomography (CBCT) has been used as a diagnostic instrument in evaluating airway space. The images generated by CBCT are linear and isotropic, and the angular measurements are anatomically accurate,[6] offering rapid scanning time and decreased cost.[7] In addition, the 3D multiplanar eliminates the overlapping of anatomical structures and allows clear visualization of the internal structures and also provides volumetric analysis of the upper airway.[8] Some studies have assessed the correlation between upper airway volume and skeletal malocclusion. However, in these studies the airway cross-sections have been measured along the horizontal plane of the image and not according to the curvature of the airway.[8] To the best our knowledge, there are no reported studies that measure the cross-section of the airway along the curvature and associate it with volumetric changes. In this study, we will be measuring the cross-section of the airway along the curvature. We will also be analyzing the association of the airway cross-sections at different levels and the upper airway volume. The aims of the study were to analyze the pharyngeal airway volume area among different skeletal malocclusion patterns, to evaluate the association between the upper airway volume and upper airway cross-sections among different skeletal malocclusion pattern, and to compare different skeletal patterns in terms of upper airway volume and upper airway cross-sections.

Materials and Methods

Study Population and Sampling Technique

A study of the 90 CBCT scans of patients reporting for dental treatment to University Dental Hospital, Sharjah (UDHS) was conducted. The study protocol was consented by the Research Ethics Committee, University of Sharjah (REC-22–10–27–01-S). Among the 90 CBCT scans, 30 scans belonged to patients with class I malocclusion, 30 belonged to skeletal class II malocclusion, and 30 belonged to skeletal class III malocclusion. To get the required number of samples to each of the groups, 1,500 CBCT scans were analyzed. The scans were acquired using Planmeca Viso7 CBCT unit (Finland) using the following parameters: 18 cm × 20 cm field of view (FOV), voxel size of 450 μm, 100 kVp, and 12.5 mA.

Sample Size Estimation

The sample size estimation was performed based on the method used by Buyukcavus and Kocakara, 2020.[9] Power analysis for the upper airway space was performed with a power of 80% and α error of 0.05 and (G* Power, version 3). The assessment revealed that a minimum number of 21 study subjects were necessary for each of the study groups. To enhance the power of this study, we included more CBCT scans of study subjects (30 in each group).

Inclusion and Exclusion Criteria

The CBCT scans of patients from both genders between the ages of 22 to 60 years from the existing archives of oral radiology department were involved in the study. No new scans were made for the purpose of this study. CBCT scans of patients with previous history of orthodontic therapy and craniofacial abnormalities involving the jaw were not included in the study. CBCT scans with an incomplete view of the region of interest were also eliminated from the study, and scans of patients with loss of posterior teeth were not included in the study.

Allocation of the CBCT scans to the study groups based on the type of malocclusion: The cephalometric analysis was achieved using the virtual cephalometric functionality of Romexis 6.2.1.19 software ([Fig. 1]).

Fig. 1 Explorer view of the Romexis software showing virtual cephalometric functionality (yellow circle).

The anteroposterior skeletal malocclusion was determined by the ANB angle in degrees. The landmark identification was performed by cephalometric guidelines by Steiner.[10] Point “A” was marked as the most posterior point in the concavity of the anterior maxilla, Point “B” was identified as the most posterior point in the concavity of the anterior mandible, and point “N” (nasion) was marked as the most anterior point on the frontonasal suture.[10] According to the ANB angles, each study subject was classified into three groups, which determined the skeletal pattern ([Fig. 2]):

Fig. 2 Classification of malocclusion according to skeletal landmarks on lateral cephalogram.

• 1 degrees < ANB < 4 degrees: class I malocclusion.

• ANB > 4 degrees: class II malocclusion.

• ANB < 0 degrees: class III malocclusion.

Each cephalogram was analyzed independently by two examiners. In case of a conflict between the two examiners, a third examiner was consulted for the cephalometric analysis.

Airway Analysis of the CBCT Scans

The extract airway module of Romexis software 6.2.1 was used for segmentation of the upper airway ([Fig. 3]). Once the airway module is activated, the software provides us with a sagittal section to mark the airway. The first point was marked at the level of the epiglottis. The horizontal yellow line (AB) drawn from this point defined the lower extent of the airway segmentation. The next points were connected in the middle of the airway till the most posterior point of the hard palate was reached. This point defined the upper extent of airway segmentation (line CD in [Fig. 3]).

Fig. 3 The line AB shows the inferior extent of the airway segmentation and line CD shows the superior extent of airway segmentation used in the study. The green lines across the yellow path show the points marked by the operator. The yellow circle shows the activated extract airway module.

The airway extraction module then showed a colored airway area with details of maximum cross-sectional area (MACA), minimum cross-sectional area (MICA), and airway volume ([Fig. 4]).

Fig. 4 The points marked along the airway (yellow vertical line with horizontal and oblique green lines). After completion of the markings Done command given (yellow circle).

In addition to these parameters, the cross-sectional area at the level of the hard palate (PCA), the cross-sectional area at the level of the epiglottis (ECA) of the airway, and volume (Vol) were also obtained. The airway was also viewed in the 3D reformatted setting ([Fig. 5]).

Fig. 5 The lower right window showing the segmented airway in 3D rendering.

Statistical Analysis

The data were evaluated statistically utilizing IBM SPSS (version 22, IBM Corp, Armonk, NY, United States). The MACA, MICA, PCA, ECA, age, and volume were compared using analysis of variance (ANOVA), followed by pairwise comparison. Gender-wise comparison of the parameters among the study groups were done utilizing the independent sample t-test. The airway volume was correlated with study variables using Pearson's correlation. Linear regression was used to find the association between pharyngeal volume and study variables.

Results

The study was conducted using 90 CBCT scans of patients attending the dental clinics of UDHS. Two examiners evaluated the upper airway parameters. The inter- and intra-examiner reliability was assessed using the concordance coefficient correlation. The inter-examiner reliability varied from 0.990 (volume) to 0.996 (ECA; [Table 1]).

Table 1 Inter-examiner reliability for the parameters used in the study

Parameters	MACA (maximum cross-sectional area	MICA (minimum cross-sectional area)	PCA (palatal cross-sectional area), mm2	ECA (epiglottis cross-sectional area)	Volume
Correlation coefficient	0.995	0.991	0.995	0.996	0.990

Each examiner re-examined 10% (n = 12) of the scans after a period of 1 week and measured the parameters. The intra-examiner reliability varied from 0.991 to 0.998 for examiner 1, and for examiner 2, it ranged from 0.992 to 0.997 ([Table 2]).

Table 2 Intra-examiner reliability for the parameters used in the study

Parameters	MACA (maximum cross-sectional area	MICA (minimum cross-sectional area)	PCA (palatal cross-sectional area), mm2	ECA (epiglottis cross-sectional area)	Volume
Examiner 1	0.998	0.992	0.991	0.998	0.994
Examiner 2	0.992	0.997	0.997	0.995	0.993

When the MACA (in mm²) was compared among the three groups: Class II study subjects showed the lowest MACA values. Class I cases showed higher MACA values compared with class III cases. Class I showed higher MICA (in mm²) values, followed by class III and class II cases ([Table 3]).

Table 3 Comparison of variables between the study groups

	Study groups	N	Mean	SD	ANOVA
					F	p -value
Age	Class 1	30	30.77	8.87	0.08	0.92 (NS)
	Class II	30	30.73	8.79
	Class III	30	29.97	7.90
MACA (maximum cross-sectional area), mm2	Class I	30	666.27	75.56	105.30	< 0.001[a]
	Class II	30	438.17	52.10
	Class III	30	671.27	82.04
MICA (minimum cross-sectional area), mm2	Class I	30	289.33	62.91	40.12	< 0.001[a]
	Class II	30	170.90	42.69
	Class III	30	282.63	64.40
PCA (palatal cross-sectional area), mm2	Class I	30	236.20	29.35	2.12	0.13 (NS)
	Class II	30	245.93	31.73
	Class III	30	252.57	31.73
ECA (epiglottis cross-sectional area), mm2	Class I	30	363.43	32.38	166.47	< 0.001[a]
	Class II	30	308.60	27.99
	Class III	30	484.03	50.23
Volume (cm3)	Class I	30	33.24	5.63	33.29	< 0.001[a]
	Class II	30	24.53	5.73
	Class III	30	35.92	5.61

Abbreviations: ANOVA, analysis of variance; NS, not significant; SD, standard deviation.

^a p < 0.05: statistically significant; p > 0.05: nonsignificant.

Class III cases had the highest ECA (in mm²) measurements, followed by class I and II cases. However, the PCA (in mm²) did not show a significant difference (p = 0.13) among the three study groups ([Table 3]).

Class III cases had a higher volume than class I and II cases. There was a significant difference (p < 0.001) in the airway volume of the three study groups ([Table 3]).

Pairwise comparison revealed that age difference was not significant among the three groups ([Table 4]). Class I cases had significantly higher MACA values than class II cases (p < 0.001). However, there was no significant difference in the MACA values between class I and III cases (p = 0.96; [Table 4]).

Table 4 Pairwise comparison of variables between the study groups

Dependent variable	(I) Skeletal malocclusion	(J) Skeletal malocclusion	Mean difference (I-J)	Standard error	p -value	95% confidence interval
						Lower bound	Upper bound
Age	Class 1	Class II	0.03	2.20	1.00	–5.22	5.29
		Class III	0.80	2.20	0.93	–4.45	6.05
	Class II	Class III	0.77	2.20	0.94	–4.49	6.02
MACA (maximum cross-sectional area), mm2	Class I	Class II	228.10	18.35	< 0.001[a]	184.34	271.86
		Class III	–5.00	18.35	0.96	–48.76	38.76
	Class II	Class III	–233.10	18.35	< 0.001[a]	–276.86	–189.34
MICA (minimum cross-sectional area), mm2	Class I	Class II	118.43	14.85	< 0.001[a]	83.02	153.85
		Class III	6.70	14.85	0.89	–28.72	42.12
	Class II	Class III	–111.73	14.85	< 0.001[a]	–147.15	–76.32
PCA (palatal cross-sectional area), mm2	Class I	Class II	–9.73	7.99	0.45	–28.79	9.33
		Class III	–16.37	7.99	0.11	–35.43	2.69
	Class II	Class III	–6.63	7.99	0.69	–25.69	12.43
ECA (epiglottis cross-sectional area), mm2	Class I	Class II	54.83	9.84	< 0.001[a]	31.38	78.29
		Class III	–120.60	9.84	< 0.001[a]	–144.06	–97.14
	Class II	Class III	–175.43	9.84	< 0.001[a]	–198.89	–151.98
Volume (cm3)	Class I	Class II	8.71	1.46	< 0.001[a]	5.23	12.19
		Class III	–2.68	1.46	0.16	–6.17	0.80
	Class II	Class III	–11.40	1.46	< 0.001[a]	–14.88	–7.91

^a p < 0.05: statistically significant; p > 0.05: nonsignificant.

Class II patients had significantly lower MICA values than those of class I and III patients (p < 0.001). However, class I patients had higher MICA values than class III patients, but this difference was not statistically significant (p = 0.89; [Table 4]).

Pairwise comparison of the PCA revealed no significant differences among the three study groups ([Table 4]). By contrast, class II patients showed lower ECA values than class I and III patients (p < 0.001). Class I patients showed significantly lower ECA values compared with class III patients (p < 0.001; [Table 4]).

Pairwise comparison of the airway volume among the three groups revealed that class II patients had significantly lower volumes than those of class I and III patients (p < 0.001). However, there was no significant difference between the airway volumes of class I and III patients (p = 0.16; [Table 4]).

When the study variables of age, ANB angle, MACA, MICA, PCA, ECA, and airway volume were compared between both genders of study patients in each group, there was no significant difference ([Table 5]).

Table 5 Comparison of variables between gender in each study groups

Skeletal malocclusion		Gender	N	Mean	SD	Mean Difference	95% confidence interval of the difference		t	df	p -value
							Lower	Upper
1	Age	Male	21	30.33	7.64	–1.44	–8.79	5.90	–0.40	28	0.69 (NS)
		Female	9	31.78	11.75
	ANB	Male	21	2.41	0.64	0.10	–0.45	0.64	0.36	28	0.72 (NS)
		Female	9	2.31	0.75
	MACA	Male	21	668.86	63.34	8.64	–54.04	71.31	0.28	28	0.78 (NS)
		Female	9	660.22	103.00
	MICA	Male	21	294.19	64.51	16.19	–35.68	68.06	0.64	28	0.53 (NS)
		Female	9	278.00	61.13
	PCA	Male	21	231.14	27.72	–16.86	–40.35	6.63	–1.47	28	0.15 (NS)
		Female	9	248.00	31.28
	ECA	Male	21	369.52	28.75	20.30	–5.42	46.02	1.62	28	0.12 (NS)
		Female	9	349.22	37.55
	Volume	Male	21	33.08	5.69	–0.54	–5.21	4.13	–0.24	28	0.81 (NS)
		Female	9	33.62	5.81
2	Age	Male	21	32.10	9.32	4.54	–2.55	11.63	1.31	28	0.2 (NS)
		Female	9	27.56	6.86
	ANB	Male	21	6.87	1.32	0.71	–0.26	1.69	1.50	28	0.15 (NS)
		Female	9	6.16	0.80
	MACA	Male	21	441.14	53.64	9.92	–33.18	53.02	0.47	28	0.64 (NS)
		Female	9	431.22	50.67
	MICA	Male	21	171.81	41.88	3.03	–32.41	38.47	0.18	28	0.86 (NS)
		Female	9	168.78	47.07
	PCA	Male	21	244.00	34.38	–6.44	–32.68	19.79	–0.50	28	0.62 (NS)
		Female	9	250.44	25.74
	ECA	Male	21	308.76	22.13	0.54	–22.70	23.78	0.05	28	0.96 (NS)
		Female	9	308.22	40.19
	Volume	Male	21	25.49	6.40	3.21	–1.38	7.80	1.43	28	0.16 (NS)
		Female	9	22.28	2.87
3	Age	Male	23	28.74	7.25	–5.26	–12.07	1.55	–1.58	28	0.13 (NS)
		Female	7	34.00	9.18
	ANB	Male	23	–2.71	2.67	–0.25	–2.68	2.19	–0.21	28	0.84 (NS)
		Female	7	–2.47	3.03
	MACA	Male	23	673.70	88.69	10.41	–63.31	84.13	0.29	28	0.78 (NS)
		Female	7	663.29	59.96
	MICA	Male	23	284.65	62.81	8.65	–49.20	66.51	0.31	28	0.76 (NS)
		Female	7	276.00	74.24
	PCA	Male	23	250.17	29.19	–10.26	–38.53	18.02	–0.74	28	0.46 (NS)
		Female	7	260.43	40.60
	ECA	Male	23	477.35	48.47	–28.65	–72.47	15.16	–1.34	28	0.19 (NS)
		Female	7	506.00	53.35
	Volume	Male	23	36.40	6.02	2.03	–2.96	7.02	0.83	28	0.41(NS)
		Female	7	34.37	3.95

Abbreviations: ECA, epiglottis cross-sectional area; MACA, maximum cross-sectional area; MICA, minimum cross-sectional area; NS, nonsignificant; PCA, palatal cross-sectional area; SD, standard deviation.

Note: Independent sample t-test.

*p < 0.05: statistically significant; p > 0.05: nonsignificant, NS.

When the study variables of age, ANB angle, MACA, MICA, PCA, and ECA were correlated with their corresponding volume in all three study groups, no significant correlation was observed. However, there was a moderate correlation between airway volume and MICA values in class I and II study groups ([Table 6]).

Table 6 Correlation between volume and study variables in each study groups

		Volume
		Class 1	Class II	Class III
Age	R	0.26	0.05	–0.08
	p-value	0.17 (NS)	0.81 (NS)	0.67 (NS)
ANB	R	0.27	0.09	0.03
	p-value	0.15 (NS)	0.65 (NS)	0.88 (NS)
MACA	R	0.01	–0.003	–0.02
	p-value	0.95 (NS)	0.99(NS)	0.92 (NS)
MICA	r	0.42	–0.40	0.11
	p-value	0.02[a]	0.03[a]	0.55 (NS)
PCA	r	0.30	–0.41	–0.19
	p-value	0.11 (NS)	0.03[a]	0.31 (NS)
ECA	r	–0.17	0.05	0.06
	p-value	0.37 (NS)	0.79 (NS)	0.74 (NS)

Abbreviations: ECA, epiglottis cross-sectional area; MACA, maximum cross-sectional area; MICA, minimum cross-sectional area; PCA, palatal cross-sectional area; NS, nonsignificant.

Note: Pearson's correlation test.

^a p < 0.05: statistically significant; p > 0.05 nonsignificant.

When the linear regression was used to predict the volume of the study variables, only MICA showed a significant association (p = 0.003), signifying that for every unit increase in the MICA, there was a 0.03 mm³ rise in the volume of the airway in the study cases. Similarly, for every degree of increase in the ANB angle, there was an 0.40 mm³ decrease in volume of the airway. No other parameter showed any significant prediction of the volume ([Table 7]).

Table 7 Linear regression to predict volume based on study variables

	Unstandardized coefficients		Standardized coefficients	T	p -value	95% confidence interval for B
	B	Standard error	Beta			Lower bound	Upper bound
Constant	25.81	2.55		10.12	< 0.001[a]	20.74	30.87
ANB	–0.71	0.17	–0.40	–4.12	< 0.001[a]	–1.05	–0.37
MICA (minimum cross-sectional area), mm2	0.03	0.009	0.30	3.05	0.003[a]	0.01	0.05

Note: Dependent variable: volume.

F(2, 89) = 24.79, p < 0.001, R ² = 0.36.

^a p < 0.05, statistically significant; p > 0.05: nonsignificant.

Discussion

Over the years, conventional radiology, nasal endoscopy, 3D computed tomography (CT), CBCT, and magnetic resonance imaging (MRI) have been used to evaluate oropharyngeal airway patency. Patency was usually measured in terms of linear measurements,[11] cross-sectional area, and airway volume.[12] However, it is imperative to note that in all the earlier studies[13] [14] [15] the airway cross-sectional areas were determined using reference lines parallel to the axial plane because the airway analysis software allowed measurements only in this dimension. In contrast to the present study, we used software functionality that allows the cross-sectional areas to be measured along the curvature of the upper airway. We analyzed the association of the airway cross-sections at different levels and the upper airway volume.

In the current study, there was no significant difference in the variables (MACA, MICA, PCA, ECA, and volume) between both genders of study subjects. Similar findings were observed by Yıldırım and Karaçay.[16] However, their study sample included class II patients only. Another Iranian study by Bronoosh and Khojastepour revealed that cross-sectional areas and volume of the upper airway had showed no significant gender-based differences.[6] In the same study, the pharyngeal airway area as measured on the lateral cephalogram showed a significant correlation with volumetric data on CBCT. A recent study conducted in Pakistan by Bokhari et al reported that there was no major difference in the upper airway volume between male and female patients.[17] Therefore, it can be stated that gender does not seem to have a significant impact on the airway dimensions irrespective of the type of malocclusion.

In our study, even though all the variables (except PCA) showed a significant difference during overall comparison. Similar findings were reported by El Rawdy and Elgemeeay.[7] They compared the total airway volume between class I and II cases and determined that class I cases have a significantly higher total airway volume than class II cases. Likewise, a study conducted on Indian patients by Vidya et al[13] found a statistically significant difference in the nasopharyngeal volume among the class I and II groups. Significantly lower cross-sectional areas and airway volumes were observed in class II patients when compared with class I patients in a Brazilian study by Alves et al.[18] The cross-sectional area and volume were measured using CBCT. Another study by Shokri et al[14] found out that there are significant alterations in airway volumes among class II and III patients, which are consistent with our study results. Significantly lower volumes in skeletal class II patients when equated to class III patients were also reported in a recently published Brazilian study.[19] The results from these studies are in concurrence with ours, thereby reiterating the finding that class II malocclusion is associated with significantly lower cross-sectional areas and volume.

In our study, the class III patients showed the highest values of the study variables, except for PCA. An Iranian study by Bronoosh and Khojastepour revealed that patients with class III malocclusion showed the highest airway volumes.[6] Iwasaki et al evaluated the form of the airways at two points and classified them into three patterns: wide, square, and long.[20] They found that patients with class III malocclusion displayed a significantly high number of wide patterns. A recent study performed on the Indian population using a CBCT-based airway tool also reported that class III patients showed higher volumes compared with class I and II study patients.[21]

Hong et al found that cross-sectional areas in the lower part of the pharyngeal airway in class III malocclusion patients were significantly higher than those of class I malocclusion inividuals.[8] In our study, the ECA value (epiglottis cross-section area), which is representative of the lower part of the airway, showed significantly higher values in class III patients than in class I study patients. Although the values of MACA, MICA, and volume were higher in the class III patients compared with class I patients, pairwise comparison found that the difference was not significant. This finding suggests that the cross-sectional areas in the lower part of the airway are more likely to show significant changes according to the type of malocclusion than the cross-sectional areas in the upper part of the airway.

In our study, the PCA, which corresponds to the upper part of the airway, did not show any significant changes between the study groups. Another study by Dogan et al reported similar findings regarding airway dimensions.[22]

In our study, there was an inverse association between the ANB angle and the airway volume. We observed that for every degree of increase in the ANB angle there was a 0.40 mm³ decrease in the volume of the airway. Only one study by Shokri et al[14] reported a similar finding; however, in their study, for every unit increase in the ANB angle, there was a 0.26 mm³ decrease in the volume of the airway. It is to be noted that both their study and ours were conducted on the Middle Eastern population. The findings of the study suggest that the ANB angle has an inverse association with the upper airway volume.

Another important finding of our study was that for every unit increase in the MICA there was a 0.03 mm³ rise in the volume of the airway in the study patients. In another study, Alhammadi et al observed an inverse correlation between the airway volume and the minimum constricted area.[23] The term “minimum constricted area” used in the study by Alhammadi et al is equivalent to the term MICA used in our study. Similarly, another study conducted on Thai population reported that the MICA was the most predictive variable for the respiratory disturbance index.[24] A recent study found that when a setback surgery of 1 mm was done to class III patients, there was a significant reduction in the most constricted level of the airway; which corresponds to the MICA in our study.[25] A Turkish study by Ünüvar et al reported that the sagittal position of the jaws influences the airway volume and the most constricted part of the airway, similar to the findings in our study.[26]

Al-Somairi et al[27] and Sprenger et al[28] suggested that class II malocclusions are associated with a deficient mandible often rotating in a downward and backward direction, thus reducing the oropharyngeal cross-sectional areas. Another recently published study found that class II patients had a significantly reduced tongue space in addition to the reduced upper airway volume.[29] These findings are suggestive of the fact that the MICA of the upper airway is a reliable predictor for airway volume.

However, not all studies have reported significant changes in the cross-sectional area and volume associated with malocclusions. A study by Dastan et al in 2021 found that there was no significant correlation between airway volume and angle of malocclusion.[30]

The airway dimension findings have clinical implications on orthodontic treatment planning and OSA management. A recent study revealed that OSA patients had a significantly narrower (p < 0.05) airway compared with patients without OSA.[31] Similarly, a recently published systematic review stated that the airway volume is maximum in class III malocclusion.[32]

One of the limitations of the study is that we used archived CBCT scans. The other limitation is the lack of diverse population sampling since the study was not multicentric in nature. Future work can focus on longitudinal studies on airway changes and the impact of treatment interventions on airway dimensions.

Conclusion

The results of the study revealed a significant difference in the cross-sectional airway variables (MACA, MICA, ECA) and pharyngeal volume in patients with different patterns of malocclusion.

• References

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