Keywords mouth breathing - skeletal class II malocclusion - pharyngeal airway
Introduction
During the course of growth period, diverse etiologic features like dentoalveolar
development, maxillary and mandibular growth, tongue and lips functions, and eruption
of the teeth may cause malocclusion. The features in sagittal malocclusions are proclination
of incisors, short and hypotonic upper lip, and incompetent lips with convex profile.[1 ]
Correct muscle activity stimulates proper facial growth and bone development when
nose breathing is combined with regular eating and swallowing processes, as well as
posture of the tongue and lips.[2 ] However, depending on the severity, duration, and time of occurrence, dysfunctions
such as nasorespiratory blockage can affect dentofacial morphology.[3 ] Ricketts observed that the key features of the respiratory obstruction syndrome
are presence of hypertrophied tonsils or adenoids, mouth breathing, open bite, cross
bite, and narrow external nares.[4 ] Mouth breathing can cause postural changes such as the mandible being lowered, the
head being lifted, the hyoid bone being lowered, and the tongue becoming anterior
inferior.[2 ]
[3 ]
Mouth breathing has also been shown to alter the lower third face, mandibular rotation,
and excessive mandibular angle in studies. Nasal obstruction affects muscular function,
which can lead to dentofacial abnormalities.[5 ]
[6 ]
The size of the pharyngeal space is mostly influenced by the growth and size of the
soft tissues that surround the dentofacial skeleton.[7 ] Reduced pharyngeal airway passage can be caused by cranial anomalies such as mandibular
or maxillary retrognathism, small mandibular body, and backward and downward rotation
of the jaw.[8 ] Reduced space between the mandibular corpus and the cervical column may cause posterior
changes in tongue and soft palate posture, impair respiratory function during the
day, and possibly cause nocturnal problems such as snoring, upper airway resistance
syndrome, and obstructive sleep apnea.[9 ]
The occlusion of the upper and lower pharyngeal airways, as well as mouth breathing,
is linked to vertical growth pattern. Vertical growth patterns and class II malocclusions
are necessary to indicate anatomic predisposing factors if this association exists.[10 ] Early diagnosis, evidence-based explanation of etiology, and assessment of functional
aspects may be critical for the restoration of normal craniofacial growth and stability
of treatment needs in growing patients with skeletal discrepancies and clinical symptoms
of adenoid facies.[11 ]
[12 ]
[13 ]
The aim of this prospective cross-sectional clinical investigation was to compare
dentofacial features and pharyngeal airway in children with skeletal class II malocclusion
with or without mouth breathing habit to healthy children with normal craniofacial
relationship. Any significant correlations between the various cephalometric characteristics
and the airway morphology of the children were also examined.
Materials and Methods
The Research Ethics Committee of our Institution approved the study (Cert. No. ABSM/EC/2011),
which was in accordance with the 1964 Helsinki declaration and its later amendments.
Informed written consent from the parents and oral assent from the participating children
were obtained.
Source of Data
Data source comprised of children aged 9 to 13 years with normal skeletal jaw relation
(class I) and untreated class II malocclusion reporting to the Outpatient Department
of Pediatric and Preventive Dentistry of our Institution. The selected children required
interceptive orthodontic therapy and therefore needed radiographic investigation.
Experimental Design
Sample Size Estimation
Based on the expected difference in the airway volume, the sample size estimation
is done.
Sp = 1,836
Mean difference = 2,027
z value of œ – 5% = 1.96
z value of β – 20% = 0.84
n = 2(1.96 + 0.84)2 *(1,836)/(2,027)2
= 12.86, which is rounded off to 20 per group.
The sample size was estimated using the formula:
n = 2s
p
2 [Z
1–α /2 + Z
1–β
]2
µ
2
d
S
2
p
= S
2
1 + S
2
2
2
Where,
S
2
1 : Standard deviation in the first group
S
2
2 : Standard deviation in the second group
α : Significance level
1–β : Power
Sixty children were thus selected and grouped as follows:
Group 1: 20 children clinically and radiographically diagnosed with class I molar
relation bilaterally and class I skeletal relationship, served as the control group.
Group 2: 20 children clinically and radiographically diagnosed with skeletal class
II malocclusion.
Group 3: 20 children clinically and radiographically diagnosed with skeletal class
II malocclusion and with confirmed mouth breathing habit.
The presence of mouth breathing was confirmed by standardized tests.[14 ]
[15 ]
[16 ]
Eligibility Criteria
1 Children with normal skeletal class I jaw relation (difference between SNA and SNB
(ANB) angle between 0° and 3°).
2 Children with untreated skeletal class II division I malocclusion (ANB > 5°) and point of contact on the occlusal plane from A (AO) ahead of point of contact
on the occlusal plane from B (BO) (>1 mm).
3 Children with untreated skeletal class II division I malocclusion (ANB > 5°) and AO ahead of BO (>1 mm) with confirmed mouth breathing habit.
Anteroposterior jaw relationship (ANB angle, [Fig. 1 ]) was corroborated by the Wits appraisal.
Fig. 1 Cephalometric tracing of angular measurements. Cephalometric landmarks and reference
planes for angular measurements: (1) SNA, (2) SNB, (3) ANB, (4) gonial angle, (5)
articular angle, (6) saddle angle, (7) upper incisor to NA, (8) lower incisor to NB,
(9) upper incisor to SN, (10) upper incisor to palatal plane, (11) lower incisor to
mandibular plane, (12) interincisal angle, (13) SN-MP, (14) mandibular plane to palatal
plane, (15) occlusal to mandibular plane angle, and (16) (N-S-Gn) Y-axis. Abbreviations:
ANB, difference between SNA and SNB; NA, Nasion - point A; NB, Nasion - point B; SN,
Sella - Nasion; SNA, Sella - Nasion - point A; SNB, Sella - Nasion - point B; SN-MP,
Sella Nasion- Mandibular plane angle.
Exclusion Criteria
Lateral cephalograms were obtained under standardized conditions.[17 ] All subjects were positioned in the cephalostat with the sagittal plane at a right
angle to the path of X-rays. The Frankfort plane was parallel to the horizontal plane,
the teeth were in centric occlusion, and lips were lightly closed.
All radiographs were manually traced with a 2H lead pencil on 0.003 inch acetate paper,
and the following angular and linear measurements were recorded by a single investigator
and double-checked by other investigators for proper landmark identification. Each
patient in our study had a total of 31 cephalometric measurements, 16 of which were
angular and 15 of which were linear[18 ] ([Figs. 1 ] and [2 ]). McNamara analysis was used to determine upper and lower airway width[19 ] ([Fig. 3 ]).
Fig. 2 Cephalometric tracing of linear measurements. Cephalometric landmarks and reference
planes for linear measurements: (1) anterior facial height, (2) posterior facial height,
(3) facial height ratio, (4) length of maxillary base, (5) length of mandibular base,
(6) SN, (7) point A to Nasion perpendicular, (8) PoG to N perpendicular, (9) sella
to articulare, (10) articulare to gonial angle, (11) gonial angle to gnathion, (12)
nasion to gonial angle, (13) sella to gnathion, (14) overjet, and (15) overbite. Abbreviations:
PoG, Pogonion; SN, Sella- Nasion.
Fig. 3 Cephalometric measurements for airway. (1) McNamara's upper pharynx dimension (PM-UPAW:
minimum distance between the upper soft palate and the nearest point on the posterior
pharynx wall). (2) McNamara's lower pharynx dimension (U-MPAW: minimum distance between
the point where the posterior tongue contour crosses the mandible and the nearest
point on the posterior pharynx wall). Abbreviations: PM-UPAW, Pterygomaxillare-upper
pharyngeal airway; U-MPAW, Uvula - middle pharyngeal airway.
Statistical Analysis
All statistical analyses were performed using the Statistical Package for the Social Sciences , version 20.0. Arithmetic mean and standard deviation values were calculated for
each measurement. For multiple comparisons, one-way analysis of variance and a post
hoc Tukey honestly significant difference (HSD) test was used. Pearson's correlation
was done to correlate the significant variables with airway width. When the p -value was less than 0.05, it was considered to be significant.
Results
A total of 60 children were included in this study. The mean age of the children was
11 ± 1.44 years, while the gender distribution was 33 boys and 27 girls. Intergroup
comparison of age and gender revealed that there were statistically no significant
differences between the groups.
When angular measurements in groups II and III were compared with those in group I,
we found statistically significant differences in the following measurements: Sella
- Nasion- point B (SNB) ANB, lower gonial angle, saddle angle, interincisal angle,
mandibular plane to palatal plane angle, y -axis (p < 0.001, [Table 1 ]), mandibular plane angle, occlusal plane to mandibular plane angle, upper incisor
to NA, and lower incisor to NB (p < 0.05, [Table 1 ]).
Table 1
Intergroup comparison of various angular dentofacial measurements
Group I
Group II
Group III
Statistical significance (p -Value)
Groups I–II
Groups I–III
SNA
82.85
82.9
83.15
0.998
0.928
SNB
80.65
77
77.2
<0.001
<0.001
ANB
2.2
5.85
6
<0.001
<0.001
Upper gonial angle
54.95
51.95
58.15
0.117
0.089
Lower gonial angle
76
69.55
78.75
<0.001
0.065
Articular angle
144.7
148.45
144.6
0.092
0.998
Saddle angle
119.95
121.05
126.3
0.775
<0.001
Upper incisor to NA (angular)
28.2
31.7
32.6
0.025
0.004
Upper incisor to NA (linear)
5.2
5.45
6.9
0.933
0.05
Lower incisor to NB (angular)
27.2
34.3
30.45
<0.001
0.009
Lower incisor to NB (linear)
5.7
5.5
5.9
0.952
0.952
Upper incisor to SN
112
111.1
112.2
0.865
0.993
Upper incisor to palatal plane
65.9
68.6
69.85
0.428
0.169
Lower incisor to mandibular plane
100.45
108.3
100.05
0.002
0.982
Interincisal angle
124.65
119.85
113.45
0.135
<0.001
SN-MP
33.8
34.6
39.8
0.928
0.021
Mandibular plane to palatal plane
34.25
25.1
33.15
<0.001
0.572
Occlusal to mandibular plane angle
16.6
13.5
20.2
0.055
0.022
Y -axis
64.4
64.9
0.859
<0.001
Abbreviations: ANB, difference between SNA and SNB; NA, Nasion - point A; NB, Nasion
- point B; SN, Sella - Nasion; SNA, Sella - Nasion - point A; SNB, Sella - Nasion
- point B; SN-MP, Sella Nasion- Mandibular plane angle.
Note: Statistically significant differences in the following dentofacial measurements:
p < 0.001 = highly significant; p < 0.05 = significant.
When linear measurements between group II and group III were compared and analyzed
with group I, we found statistically significant differences in the Jarabak's ratio,
N-Go, overjet, and overbite (p < 0.001, [Table 2 ]).
Table 2
Intergroup comparison of various linear measurements
Group I
Group II
Group III
Statistical significance (p -Value)
Groups I–II
Groups I–III
Jarabak's ratio
0.639
0.71
0.5955
<0.001
<0.001
Length of maxillary base
52.25
51.8
53.15
0.956
0.835
Length of mandibular base
67.55
70.1
69.25
0.217
0.501
SN
71.1
72.7
71.2
0.343
0.996
point A to Nasion perpendicular
1.45
3.32
4.73
0.005
<0.001
PoG to N perpendicular
–2.1
–1.9
–5.31
0.965
<0.001
Sella to articulare
36.15
36.2
32.65
0.998
0.001
Articulare to gonial angle
42.25
46.65
43.5
0.002
0.563
Gonial angle to gnathion
70.95
68.6
67.05
0.223
0.02
Nasion to gonial angle
107.75
116.95
109.5
0.364
<0.001
Sella to gnathion
117.3
118.3
112.9
0.85
0.052
Overjet
3.1
3.75
7.95
0.425
<0.001
Overbite
2.4
4.3
1.45
0.001
0.12
Abbreviations: PoG, pogonion; SN, Sella - Nasion.
Note: p < 0.001 = highly significant; p < 0.05 = significant.
In the present study, children in group I recorded a mean upper airway measurement
of 16.25 ± 2.573 mm, which was within normal range values. Intergroup comparison revealed
statistically significant differences in upper pharyngeal airway widths among the
three groups. Upper pharyngeal airway width was found to be significantly decreased
in group III (mean = 9.85 ± 1.785 mm, p < 0.001, [Table 3 ]) followed by group II (mean = 11.05 ± 2.012 mm, p < 0.001, [Table 3 ]).
Table 3
Comparison of upper and lower airway width between three groups
Upper airway
Lower airway
N
Mean (mm)
Standard deviation
N
Mean (mm)
Standard deviation
Group I
20
16.25
2.573
20
9.8
1.399
Group II
20
11.05
2.012
20
9.65
1.309
Group III
20
9.85
1.785
20
9.05
1.05
Children in group I recorded a mean lower airway measurement of 9.8 ± 1.399 mm, which
was within normal range values. However, there were no statistically significant differences
in lower pharyngeal airway widths across the groups in our study, and there were no
correlations between lower pharyngeal airway width space and craniofacial growth pattern
or malocclusion types.
Post hoc Tukey HSD analysis of the intergroup comparison of the results revealed significant
differences between groups II and III in certain dentofacial measurements such as
upper and lower gonial angles and saddle angle (major angles); vertical measurements
such as mandibular plane to palatal plane and y -axis; and dental measurements such as overbite, overjet, and lower incisor to NB
and Mandibulae plane (MP) ([Table 4 ]).
Table 4
Post hoc analysis of results
Dependent variable
(I) Group
(J) Group
Mean difference (I–J)
Standard error
p -Value
SNA
Class I
Class II
–0.05
0.815
0.998
Class II with mouth breathing
–0.3
0.815
0.928
Class II
Class II with mouth breathing
–0.25
0.815
0.95
SNB
Class I
Class II
3.65
0.852
<0.001
Class II with mouth breathing
3.45
0.852
<0.001
Class II
Class II with mouth breathing
–0.2
0.852
0.97
ANB
Class I
Class II
–3.65
0.41
<0.001
Class II with mouth breathing
–3.8
0.41
<0.001
Class II
Class II with mouth breathing
–0.15
0.41
0.929
Upper gonial angle
Class I
Class II
3
1.487
0.117
Class II with mouth breathing
–3.2
1.487
0.089
Class II
Class II with mouth breathing
–6.2
1.487
<0.001
Lower gonial angle
Class I
Class II
6.45
1.198
<0.001
Class II with mouth breathing
–2.75
1.198
0.065
Class II
Class II with mouth breathing
–9.2
1.198
<0.001
Articulare angle
Class I
Class II
–3.75
1.758
0.092
Class II with mouth breathing
0.1
1.758
0.998
Class II
Class II with mouth breathing
3.85
1.758
0.082
Saddle angle
Class I
Class II
–1.1
1.536
0.755
Class II with mouth breathing
–6.35
1.536
<0.001
Class II
Class II with mouth breathing
–5.25
1.536
0.003
Upper incisor to NA angle
Class I
Class II
–3.5
1.299
0.025
Class II with mouth breathing
–4.4
1.299
0.004
Class II
Class II with mouth breathing
–0.9
1.299
0.769
Upper incisor to NA linear
Class I
Class II
–0.25
0.706
0.933
Class II with mouth breathing
–1.7
0.706
0.05
Class II
Class II with mouth breathing
–1.45
0.706
0.109
Lower incisor to NB angle
Class I
Class II
–7.1
1.055
<0.001
Class II with mouth breathing
–3.25
1.055
0.009
Class II
Class II with mouth breathing
3.85
1.055
0.002
Lower incisor to NB linear
Class I
Class II
0.2
0.669
0.952
Class II with mouth breathing
–0.2
0.669
0.952
Class II
Class II with mouth breathing
–0.4
0.669
0.822
Upper incisor to SN
Class I
Class II
0.9
1.75
0.865
Class II with mouth breathing
–0.2
1.75
0.993
Class II
Class II with mouth breathing
–1.1
1.75
0.805
Upper incisor to palatal plane
Class I
Class II
–2.7
2.157
0.428
Class II with mouth breathing
–3.95
2.157
0.169
Class II
Class II with mouth breathing
–1.25
2.157
0.832
Lower incisor to mandibular plane
Class I
Class II
–7.85
2.181
0.002
Class II with mouth breathing
0.4
2.181
0.982
Class II
Class II with mouth breathing
8.25
2.181
0.001
Interincisal angle
Class I
Class II
4.8
2.467
0.135
Class II with mouth breathing
11.2
2.467
<0.001
Class II
Class II with mouth breathing
6.4
2.467
0.032
Mandibular plane
Class I
Class II
–0.8
2.17
0.928
Class II with mouth breathing
–6
2.17
0.021
Class II
Class II with mouth breathing
–5.2
2.17
0.051
Mandibular plane to palatal plane
Class I
Class II
9.15
1.086
<0.001
Class II with mouth breathing
1.1
1.086
0.572
Class II
Class II with mouth breathing
–8.05
1.086
<0.001
Occlusal to mandibular plane angle
Class I
Class II
3.1
1.311
0.055
Class II with mouth breathing
–3.6
1.311
0.022
Class II
Class II with mouth breathing
–6.7
1.311
<0.001
Y
-axis
Class I
Class II
–0.5
0.949
0.859
Class II with mouth breathing
–6.4
0.949
<0.001
Class II
Class II with mouth breathing
–5.9
0.949
<0.001
Jarabak 's ratio
Class I
Class II
–7.10%
0.94%
<0.001
Class II with mouth breathing
4.35%
0.94%
<0.001
Class II
Class II with mouth breathing
11.45%
0.94%
<0.001
Length of maxillary base
Class I
Class II
0.45
1.573
0.956
Class II with mouth breathing
–0.9
1.573
0.835
Class II
Class II with mouth breathing
–1.35
1.573
0.668
Length of mandibular base
Class I
Class II
–2.55
1.508
0.217
Class II with mouth breathing
–1.7
1.508
0.501
Class II
Class II with mouth breathing
0.85
1.508
0.84
SN
Class I
Class II
–1.6
1.136
0.343
Class II with mouth breathing
–0.1
1.136
0.996
Class II
Class II with mouth breathing
1.5
1.136
0.39
point A to Nasion perpendicular
Class II
Class II
–1.87
0.571
0.005
Class II with mouth breathing
–3.28
0.571
<0.001
Class II
Class II with mouth breathing
–1.41
0.571
0.043
PoG to Nasion perpendicular
Class I
Class II
–0.2
0.788
0.965
Class II with mouth breathing
3.215
0.788
<0.001
Class II
Class II with mouth breathing
3.415
0.788
<0.001
Sella to Articulare
Class I
Class II
–0.05
0.95
0.998
Class II with mouth breathing
3.5
0.95
0.001
Class II
Class II with mouth breathing
3.55
0.95
0.001
Articulare to gonial angle
Class I
Class II
–4.4
1.216
0.002
Class II with mouth breathing
–1.25
1.216
0.563
Class II
Class II with mouth breathing
3.15
1.216
0.032
Gonial to gnathion
Class I
Class II
2.35
1.401
0.223
Class II with mouth breathing
3.9
1.401
0.02
Class II
Class II with mouth breathing
1.55
1.401
0.514
Nasion to gonial
Class I
Class II
–9.2
1.278
<0.001
Class II with mouth breathing
–1.75
1.278
0.364
Class II
Class II with mouth breathing
7.45
1.278
<0.001
Sella to gnathion
Class I
Class II
–1
1.839
0.85
Class II with mouth breathing
4.4
1.839
0.052
Class II
Class II with mouth breathing
5.4
1.839
0.013
Overjet
Class I
Class II
–0.65
0.517
0.425
Class II with mouth breathing
–4.85
0.517
<0.001
Class II
Class II with mouth breathing
–4.2
0.517
<0.001
Overbite
Class I
Class II
–1.9
0.474
0.001
Class II with mouth breathing
0.95
0.474
0.12
Class II
Class II with mouth breathing
2.85
0.474
<0.001
Upper airway
Class I
Class II
5.2
0.68
<0.001
Class II with mouth breathing
6.4
0.68
<0.001
Class II
Class II with mouth breathing
1.2
0.68
0.19
Lower airway
Class I
Class II
0.15
0.399
0.925
Class II with mouth breathing
0.75
0.399
0.154
Class II
Class II with mouth breathing
0.6
0.399
0.297
Abbreviations: ANB, difference between SNA and SNB; NA, Nasion – point A; NB, Nasion
– point B; PoG, Pogonion; SN, Sella – Nasion; SNA, Sella – Nasion – point A; SNB,
Sella – Nasion – point B; SN-MP, Sella Nasion- Mandibular plane angle.
When correlations among dentofacial variables and upper airway were analyzed in children
of group II, we observed that the variables like upper incisor to NA, lower incisor
to NB, lower incisor to MP, overbite, and interincisal angle showed a fair to good
correlation with upper airway width ([Table 5 ]).
Table 5
Significant correlation among the dentofacial variables and upper airway width in
Group II
Group II
Upper airway
Upper incisor to NA linear
Pearson's correlation
0.373
Significance: two-tailed
0.105
N
20
Lower incisor to NB angle
Pearson's correlation
–0.348
Significance: two-tailed
0.133
N
20
Lower incisor to NB linear
Pearson's correlation
0.316
Significance: two-tailed
0.175
N
20
Interincisal angle
Pearson's correlation
0.56
Significance: two-tailed
0.01
N
20
Point A to Nasion perpendicular
Pearson's correlation
0.406
Significance: two-tailed
0.076
N
20
Sella-Articulare
Pearson's correlation
0.598
Significance: two-tailed
0.005
N
20
Overjet
Pearson's correlation
–0.431
Significance: two-tailed
0.057
N
20
Negative correlation if sign is negative of the Pearson's correlation
–0.1
–0.3
–0.5
–0.7
–0.9
Positive correlation if sign is positive of the Pearson's correlation
0.1
0.3
0.5
0.7
0.9
Poor correlation
Fair correlation
Good correlation
Very good correlation
Excellent correlation
Abbreviations: NA, Nasion – point A; NB, Nasion – point B.
Note: Negative correlation means if one increases, the other decreases. Positive correlation
means if one increases or decreases, the other also increases or decreases.
When correlations among dentofacial variables and upper airway were analyzed in children
of group III, ANB, as length of ramus (ar – Go) angle, upper incisor to palatal plane,
overjet, and overbite showed a good correlation with upper airway width ([Table 6 ]). However, we found a fair correlation between SN-MP and Nasion – gonion (N-Go)
measurements with the upper pharyngeal airway width ([Table 6 ]).
Table 6
Significant correlation among the dentofacial variables and upper airway width in
Group III
Group III
Upper airway
ANB
Pearson's correlation
–0.575
Significance: two-tailed
0.008
N
20
Upper incisor to palatal plane
Pearson's correlation
0.536
Significance: two-tailed
0.015
N
20
Lower incisor to mandibular plane
Pearson's correlation
0.305
Significance: two-tailed
0.191
N
20
Mandibular plane
Pearson's correlation
–0.219
Significance: two-tailed
0.353
N
20
Nasion to Gonion
Pearson's correlation
0.32
Significance: two-tailed
0.169
N
20
Articulare to gonial angle angle
Pearson's correlation
0.421
Significance: two-tailed
0.065
N
20
Overjet
Pearson's correlation
–0.102
Significance: two-tailed
0.668
N
20
Overbite
Pearson's correlation
–0.013
Significance: two-tailed
0.957
N
20
Negative correlation if sign is negative of the Pearson's correlation
–0.1
–0.3
–0.5
–0.7
–0.9
Positive correlation if sign is positive of the Pearson's correlation
0.1
0.3
0.5
0.7
0.9
Poor correlation
Fair correlation
Good correlation
Very good correlation
Excellent correlation
Abbreviations: ANB, difference between Sella – Nasion – point A (SNA) and Sella –
Nasion – point B (SNB).
Note: Negative correlation means if one increases, the other decreases. Positive correlation
means if one increases or decreases, the other also increases or decreases.
Discussion
The growth and function of the nasal cavities, nasopharynx, and oropharynx are all
tightly linked to appropriate skull growth. Several studies have found a link between
pharyngeal structures and dentofacial and craniofacial structures in both adults and
children.[20 ]
[21 ]
It has also been discovered that certain dentofacial features and morphological changes
are linked to postural modifications.[22 ] Because of a possible link between upper airway size and structure and sleep-induced
breathing difficulties, attention has recently been drawn to uvulo-glosso-pharyngeal
dimensions. Obstructive sleep apnea sufferers have abnormal skeletal and soft tissue
patterns that restrict airway space, according to research.[23 ]
[24 ]
We chose children aged 9 to 13 years for our study because these preadolescents have
the best chance of receiving early diagnosis and timely care.
The ANB angle was used to determine the anteroposterior skeletal jaw relationship
in our investigation, and the Wits appraisal confirmed it. Rotation and vertical growth
of the jaws, anteroposterior position of the nasion, and vertical distance between
points A and B are all factors that influence the ANB angle, according to Hussels
and Nanda.[25 ] The ANB angle, on the other hand, has been described by Oktay[26 ] and Ishikawa et al[27 ] as one of the most trustworthy and accurate assessments of the anteroposterior jaw
relationship. As the ANB angle is a popular cephalometric parameter in clinical orthodontics,
it was used to categorize the children in our study.[2 ]
Our findings revealed substantial variations in numerous dentofacial and airway width
parameters across the three groups of youngsters in both angular and linear measurements.
Average values for upper and lower airway width in this age group are stated to be
in the range of 15 to 20 mm and 9 to 15 mm, respectively.[19 ]
[28 ] Children of group I exhibited upper and lower airway measurements within normal
range values. However, intergroup comparison revealed statistically significant differences
in upper pharyngeal airway widths among the three groups, with group III children
obtaining the narrowest measurements, followed by group II (p < 0.001, [Table 3 ]). This was in accordance with a previous study by Paul and Nanda who found greater
prevalence of mouth breathing and nasopharyngeal airway obstruction in subjects with
class II malocclusions.[29 ]
There were no statistically significant differences in lower pharyngeal airway widths
across groups in our study, and there were no correlations between lower pharyngeal
airway width space and craniofacial growth pattern or malocclusion type. This backs
up prior research.[21 ]
[28 ]
[30 ]
In this study, we found that children in group III had significantly larger ANB angles
(p < 0.001, [Table 1 ]), which showed a strong negative correlation with upper pharyngeal airway width
(–0.575, [Tables 6 ]). These findings are in accordance with those of Ceylan and Oktay who reported that
the oropharyngeal space was reduced in subjects with an enlarged ANB angle.[21 ] Subjects with posterior mandibular rotation exhibited smaller upper airway dimensions,
according to Akcam et al.[31 ] This demonstrates a close link between the upper airway dimension and the jaws'
posture.
According to Ferrario et al, orthodontic diagnosis should be based on more than one
anteroposterior examination.[32 ] Other anteroposterior determinants such as the Wits assessment, SNB, A-N Perpendicular,
and Pog-N Perpendicular showed statistically significant differences in both groups
II and III, supporting the reliability of the ANB angle, which was utilized to identify
our participants. Furthermore, the upper airway width was found to have a significant
correlation with all of the above anteroposterior tests ([Tables 5 ] and [6 ]).
From these findings, we can infer that children with increased anteroposterior jaw
measurements and skeletal mandibular retrognathism were more likely to have narrower
upper pharyngeal airway space.
Although our study did not classify children according to their growth patterns, we
observed significant increases in the following (vertical) dentofacial measurements,
namely SN-MP and y -axis, with the greatest increase in group III. The SN-MP and N-Go measurements in
group III showed a fair correlation with the upper pharyngeal airway width ([Table 6 ]). Further, a significantly smaller Jarabak's ratio was found in group III as compared
with group I, reflecting a significantly shorter posterior face height and a vertical
growth pattern in this group (p < 0.001, [Table 2 ]).
Our findings were in accordance with another study[8 ] that reported that the nasopharyngeal airway in hyperdivergent individuals was significantly
narrower than that in normo-divergent individuals.
In our study, we found that preadolescent children with skeletal class II and skeletal
class II with mouth breathing had narrower upper pharyngeal airways, which significantly
correlated with key anteroposterior and vertical dentofacial measurements, specifically
SNB, ANB, SN-MP, and N-Go. These children's dental measurements, such as upper incisor
to NA, lower incisor to NB, lower incisor to MP, overbite, and interincisal angle,
showed a fair correlation with upper airway width ([Tables 5 ] and [6 ]).
In our study, it is possible that the retruded position of the jaw in children in
groups II and III caused the tongue base to be positioned more posteriorly and inferiorly,
reducing oropharyngeal airway space. In people with mandibular retrognathism, it is
known that the tongue position is more backward, and that contact with the soft palate
might result in a posterior placement of the soft palate and restriction of the oropharyngeal
airway.[33 ]
To breathe through the mouth, one must maintain an oral airway, which is achieved
by shifting the mandible and tongue downward and backward, as well as tilting the
head back. These variations in posture could have an impact on the connection between
teeth as well as the direction of jaw growth, which could shift lower and backward.[34 ]
This work used two-dimensional cephalometric films to assess pharyngeal airway width
rather than airway flow capacity, which would have necessitated a more complicated
three-dimensional cone-beam computed tomography and dynamic estimation.[35 ] Further, as we had used lateral head films for airway measurement, we could not
measure the anteroposterior dimensions of the airway, and therefore could not determine
three-dimensional volumetric measurements. While the cephalometric view produces a
two-dimensional image that is unavoidably constrained, it has the advantage of being
simpler and more easily available than computed tomography scanning or magnetic resonance
imaging. Although we found significant correlations between many dentofacial measurements
and upper pharyngeal airway widths among children with skeletal class II with and
without mouth breathing, we recommend that further investigations including a larger
sample size of children as well as evaluation of other airway parameters such as airway
volume and airflow capacity will allow a better understanding of the relationship
between respiratory function and craniofacial morphology.
Conclusion
Our study found significant differences in many of the dentofacial measurements between
the children of the three groups, with greater sagittal as well as vertical jaw discrepancies
in children with malocclusion. Children with class II malocclusion with mouth breathing
had the greatest vertical jaw discrepancy.
We found a significantly decreased upper pharyngeal airway width in children with
malocclusion, with the narrowest airway observed in children with class II malocclusion
with mouth breathing. No significant differences were observed in lower airway widths
among the groups.
Based on the findings of this study, we may conclude that children with class II malocclusion
with mouth breathing seemed to have significant narrowing of the upper airways. Certain
dentofacial characteristics such as increased sagittal and vertical discrepancy and
anterior tooth proclination seem to be definitely correlated with a decreased upper
pharyngeal airway width, which could help identify children at increased risk of sleep
disordered breathing.
