Assessment of upper airway size after orthopedic treatment for maxillary protrusion or mandibular retrusion

Introduction

The aim of this retrospective study was to find out whether different Class II treatments would affect the airway sizes of patients having maxillary protrusion or mandibular retrusion.

Methods

The study sample comprised 57 Class II patients whose upper airway sizes were not significantly different at the start of treatment and whose sagittal skeletal jaw relationships showed that they had maxillary protrusion or mandibular retrusion. Twenty-two of them were treated with cervical headgear, 16 with activator, and 19 were selected as a control. Lateral cephalograms at the start of treatment and the end of orthopedic treatment were assessed. The intragroup comparisons were performed by using the paired-samples t test, and intergroup comparisons of the skeletal features and upper airways were performed with 1-way analysis of variance, with the Tukey test as a second step, at P < 0.05.

Results

The ANB angle decreased significantly in the treatment groups. The middle airway space and the SNB angle were significantly increased after the activator therapy ( P < 0.05). The SNB angle increased and SN-1 decreased in the mandibular retrusion group when compared with both maxillary protrusion and control groups. No statistically significant difference between the maxillary protrusion and the mandibular retrusion groups was found regarding the upper airway sizes after cervical headgear or activator treatments, respectively ( P > 0.05). The only significant differences observed in airway variables were at the middle airway space of the activator and control groups with an increase of 1.6 ± 2.5 mm and a decrease of 1.5 ± 2.3 mm, respectively.

Conclusions

Orthopedic treatment with either cervical headgear or activator did not result in different upper airway changes, but activator treatment resulted in increased middle airway space with regard to the Class II control group.

The skeletal and dentoalveolar effects of orthopedic treatment in subjects with Class II malocclusions have been well documented in the orthodontic literature. Headgear treatment has been used for treating growing skeletal Class II maxillary protrusion patients, and functional appliances were used for forward movement of the mandible in growing skeletal Class II mandibular retrusion patients. Studies have shown that continuous protraction force causes significant anterior displacement concurrently with histologic changes in the mandible and the mandibular condyle.

Initially, the major focus of the skeletal Class II treatment was related to skeletal correction and reduction in maxillomandibular relationship discrepancy. After a while, more attention has been paid to detect the Class II treatment effects, as the close association between malocclusion and upper airway morphology has been understood. Mergen and Jacobs reported that the nasopharyngeal area is significantly smaller in subjects with Class II malocclusion than in those with normal occlusion. More recently, the studies have intensively focused on assessing the upper airway changes associated with skeletal features.

The assessment of the nasal and pharyngeal airways from lateral cephalograms has shown that Class II patients have a tendency for narrower anteroposterior pharyngeal dimensions, specifically in the nasopharynx at the level of the hard palate and in the oropharynx at the level of the tip of the soft palate and the mandible. Muto et al identified a significant relationship between the posterior airway space and the position of the maxilla, mandible, and soft palate. Therefore, any alteration of the facial skeleton that is associated with these structures has been thought to result in a positive or negative effect on airway space.

In growing children with mandibular retrusion, functional appliances are thought to enlarge the upper airway by holding the mandible in a forward position, whereas forward growth of the mandible is maintained. This positive effect of functional appliances has gained popularity among researchers, since they are noninvasive and relatively risk free.

For a Class II malocclusion with maxillary prognathism, cervical headgear is a simple and commonly used appliance, which is directed to the maxilla to inhibit further maxillary growth or to perform distalization. Even without mandibular retrognathia, Class II Division 1 malocclusion is associated with a narrower upper airway structure. Therefore, maxillary orthopedic treatment procedures may induce an adverse change to the upper airway space that promotes or aggravates a breathing disorder, in contrast with the positive effects of mandibular orthopedic treatment procedures that were suggested to enhance the airway and lead to the resolution of preexisting airway disturbance.

The effects of orthopedic appliances used for Class II treatments, either with functional appliances or cervical headgear, have been reported in the literature. However, the influence of orthopedic appliances on the upper airway of patients with maxillary protrusion or mandibular retrusion in comparative studies is limited. The purpose of this study was to test the null hypothesis that the use of functional appliance for treatment of mandibular retrognathism or cervical headgear for maxillary prognathism causes no change on the upper airway in Class II malocclusion.

Material and methods

Class II subjects were selected from the archive of Department of Orthodontics, School of Dentistry, Hacettepe University, in Ankara, Turkey, according to the following selection criteria: (1) ANB angle greater than 5° with a clinically protrusive maxilla or retrognathic mandible, (2) Angle Class II molar relationship, and (3) no respiratory problems and no adenoidectomy or tonsillectomy before or during the treatment.

These subjects were then divided into control and orthopedic treatment groups. The patients who were either treated with fixed appliances or not treated because of lack of compliance and whose 1-year follow-up records were available were selected as controls (n = 19). The patients whose posttreatment records were available after orthopedic treatment were selected as the orthopedic treatment group. The orthopedic treatment group was then divided into cervical headgear (n = 22) and activator (n = 16) groups according to the treatment protocols.

The demographic data are shown in Table I . The mean ages of the subjects in the cervical headgear, activator, and control groups at the beginning of treatment were 10.6 ± 1.0, 10.3 ± 1.5, and 10.2 ± 1.4 years, respectively. The durations between pretreatment and follow-up records were 1.1, 1.3, and 1.0 years for the cervical headgear, activator, and control groups, respectively. Lateral cephalograms were assessed at pretreatment and posttreatment or follow-up. Cephalometric variables representing the dentoskeletal pattern ( Fig 1 ) were assessed by the combination of the cephalometric analyses of Steiner and Downs. Analysis of pharyngeal airway size ( Fig 2 ) was based on the method of Mochida et al. All lateral cephalometric radiographs were traced manually, and all angular and linear measurements were done by 1 author (H.G.C.).

Table I
Means, standard deviations, and multiple comparisons representing demographic variables at pretreatment among the 3 groups
Demographic variables Cervical headgear Activator Control Multiple comparisons
(n = 22) (mean ± SD) (n = 16) (mean ± SD) (n = 19) (mean ± SD)
Age (y) 10.6 ± 1.0 10.3 ± 1.5 10.2 ± 1.4 0.501
Sex (n) 0.18
Female 10 12 10
Male 12 4 9
Duration between records (y) 1.1 ± 0.6 1.3 ± 0.8 1.0 ± 0.0 0.259

Significant differences between the groups are presented.

Fig 1
Skeletodental measurements (°): 1, SNA: the angle between the SN and NA planes; 2 , SNB: the angle between the SN and NB planes; 3 , ANB: the angle between the NA and NB planes; 4, FMA: the angle between the Frankfort horizontal plane and the mandibular plane; 5 , SN-1: the angle between the maxillary incisor long axis and the SN plane; 6 , IMPA: the angle between the mandibular incisor long axis and the mandibular plane.

Fig 2
Pharyngeal airway measurements (mm): 7 , posterior airway space: the anteroposterior depth of the pharynx measured between the posterior pharyngeal wall and the posterior nasal spine on a line parallel to the Frankfort horizontal plane through the posterior nasal spine; 8 , superoposterior airway space: the anteroposterior depth of the pharynx measured between the posterior pharyngeal wall and the dorsum of the soft palate on a line parallel to the Frankfort horizontal plane through the middle of the line from the posterior nasal spine to the tip of the soft palate; 9 , middle airway space: the anteroposterior depth of the pharynx measured between the posterior pharyngeal wall and the dorsum of the tongue on a line parallel to the Frankfort horizontal plane through the tip of the soft palate; 10 , inferior airway space: the anteroposterior depth of the pharynx measured between the posterior pharyngeal wall and the surface of the tongue on a line parallel to the Frankfort horizontal plane through the most anteroinferior point on the body of the second cervical vertebra; 11 , epiglottic airway space: the anteroposterior depth of the pharynx measured between the posterior pharyngeal wall and the surface of the tongue on a line parallel to the Frankfort horizontal plane through the tip of the epiglottis.

Statistical analysis

The descriptive statistics were calculated as means and standard deviations. The data were analyzed using SPSS statistical software (version 21.0; IBM, Armonk, NY).

The intraclass correlation coefficients were calculated for the assessment of intraexaminer reliability. The intragroup comparisons were performed by using paired-samples t tests, and intergroup comparisons of the skeletal features and upper airways were performed with 1-way analysis of variance, with the Tukey test as a second step. P < 0.05 was considered statistically significant.

Results

The intraclass correlation coefficient values differed between 0.916 and 0.988 for airway variables and 0.941 and 0.991 for skeletodental variables.

Means, standard deviations, and multiple comparisons representing skeletal and airway differences at pretreatment among the 3 groups are shown in Table II . No statistically significant differences were found in SNA, SNB, ANB, FMA, and IMPA or in airway variables at pretreatment ( P > 0.05). The only statistically significant difference was in the SN-1 angle. The maxillary incisors had significantly greater protrusion in activator group than in the cervical headgear group ( P < 0.05).

Table II
Means, standard deviations, and multiple comparisons representing skeletal and airway differences at pretreatment among the 3 groups
Skeletodental variables Cervical headgear (n = 22) (mean ± SD) Activator (n = 16) (mean ± SD) Control (n = 19) (mean ± SD) Multiple comparisons
SNA (°) 81.2 ± 2.9 82.2 ± 3.4 80.2 ± 2.8
SNB (°) 75.2 ± 3.2 76.0 ± 3.2 75 ± 3.0
ANB (°) 5.9 ± 1.8 6.2 ± 1.2 5.3 ± 1.1
FMA (°) 24.1 ± 5.6 21.1 ± 4.4 24.8 ± 5.3
SN-1 (°) 104.3 ± 5.6 109.3 ± 6.1 106.1 ± 56.4 1-2
IMPA (°) 100.2 ± 6.7 99.5 ± 7.9 95.3 ± 6.2
Airway variables
PAS (mm) 23.9 ± 4.8 23.8 ± 5.1 24.4 ± 5.2
SPAS (mm) 11.7 ± 2.8 11.4 ± 2.5 11.9 ± 3.2
MAS (mm) 14.5 ± 4.0 13.8 ± 4.8 12.5 ± 3.2
IAS (mm) 10.4 ± 3.9 9.9 ± 3.0 11.6 ± 3.1
EAS (mm) 7.9 ± 3.8 7.3 ± 2.6 8.2 ± 3.5
PAS , Posterior airway space; SPAS , superoposterior airway space; MAS , middle airway space; IAS , inferior airway space; EAS , epiglottic airway space.

Significant differences between the groups are presented.

Mean changes from pretreatment to follow-up in skeletodental variables during the treatment and follow-up period are shown in Table III . Among the skeletodental variables, in the cervical headgear group, the SNA (−1.0° ± 1.4°) and ANB (−1.1° ± 0.7°) angles decreased significantly ( P < 0.05). In the activator group, there were statistically significant increases in the SNB angle and significant decreases in the ANB and SN-1 angles. No significant difference was seen in the control group at follow-up for the skeletodental variables.

Table III
Mean changes from pretreatment (T1) to follow-up (T2) in skeletodental and airway variables during treatment
Skeletodental variables Cervical headgear (n = 22) (mean ± SD) P value Activator (n = 16) (mean ± SD) P value Control (n = 19) (mean ± SD) P value
T1 T2 T1 T2 T1 T2
SNA (°) 81.2 ± 2.9 80.1 ± 3.3 0.03 82.2 ± 3.4 82.3 ± 3.1 80.2 ± 2.8 80.5 ± 2.8
SNB (°) 75.2 ± 3.2 75.3 ± 3.4 76.0 ± 3.2 77.6 ± 3.4 0.007 74.9 ± 3.0 75.2 ± 3.1
ANB (°) 5.9 ± 1.8 4.8 ± 1.9 0.00 6.2 ± 1.2 4.7 ± 1.5 0.00 5.3 ± 1.1 5.3 ± 1.3
FMA (°) 24.1 ± 5.6 24.2 ± 5.7 21.1 ± 4.4 21.2 ± 3.6 24.8 ± 5.3 24.7 ± 5.3
SN-1 (°) 104.3 ± 5.6 103.2 ± 4.7 109.3 ± 6.1 102.7 ± 5.9 0.00 106.1 ± 6.4 103.9 ± 6.6
IMPA (°) 100.2 ± 6.7 99.5 ± 7.2 99.5 ± 7.9 100.6 ± 8.0 95.3 ± 6.2 95.2 ± 6.9
Airway variables
PAS (mm) 23.9 ± 4.8 22.5 ± 6.1 23.8 ± 5.1 24.9 ± 6.3 24.4 ± 5.2 24.1 ± 5.4
SPAS (mm) 11.7 ± 2.8 11.3 ± 2.8 11.4 ± 2.5 12.3 ± 3.3 11.9 ± 3.2 12.2 ± 2.6
MAS (mm) 14.5 ± 4.0 14.6 ± 3.9 13.8 ± 4.8 15.4 ± 4.5 0.021 12.5 ± 3.2 10.9 ± 2.9 0.01
IAS (mm) 10.4 ± 3.9 10.1 ± 3.5 9.9 ± 3.0 10.4 ± 3.1 11.6 ± 3.1 10.7 ± 2.9
EAS (mm) 7.9 ± 3.8 7.9 ± 2.4 7.3 ± 2.6 7.4 ± 3.5 8.2 ± 3.5 7.5 ± 3.4
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Dec 19, 2018 | Posted by in Orthodontics | Comments Off on Assessment of upper airway size after orthopedic treatment for maxillary protrusion or mandibular retrusion
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