Three-dimensional cephalometric study of upper airway space in skeletal class II and III healthy patients

Impact of class II and class III skeletal malocclusion on pharyngeal airway dimensions: A systematic literature review and meta-analysis

Background

This study is a pioneer systematic review and meta-analysis aimed at comparing the influence of Class II and Class III skeletal malocclusions on pharyngeal airway dimensions. It stands as the inaugural comprehensive assessment to collate and analyze the disparate findings from previously published articles on this topic. The objective of this study was to identify published articles that compare the effects of class II and class III skeletal malocclusion on the pharyngeal airway dimensions.

Methods

An all-inclusive search for existing published studies was done to identify peer-reviewed scholarly articles that compared the influence of class II and class III skeletal malocclusion on pharyngeal airway dimensions. The search was done via five electronic databases: Cochrane Library, EMBASE, Scopus, Web of Science, and PubMed. Screening of the articles was done and the eligible studies were critically assessed using the Joanna Briggs Institute (JBI) Critical Appraisal Checklist.

Results

The initial search yielded 476 potential articles of which, nine were finally included in this study for a total of 866 patients. Three studies were of cross-sectional design and six were of retrospective study design. Following a critical analysis and review of the studies, class III skeletal malocclusion had significantly larger volume and area measurements compared to class II skeletal malocclusion.

Conclusion

Research in the field of literature has established that variations in skeletal classifications have a discernible effect on the size of the pharyngeal airways. With the advancement of skeletal malocclusions to a class III, there is an observed increase in both the volume and cross-sectional area of the airways.

Three-dimensional evaluation of the pharyngeal airway space in patients with anterior open bite

Objective

: This study aimed to three-dimensionally evaluate the pharyngeal airway space (PAS) of patients with anterior open bite (AOB) by using cone-beam computed tomography (CBCT) and compare the findings with those obtained in individuals with normal occlusion.

Methods

: The open bite group (OBG, n = 25) consisted of patients with an anterior overbite of -3 mm or less, while the control group (n = 25) consisted of age- and sex-matched individuals with an anterior overbite of 1-3 mm, Angle Class I malocclusion (1° ≤ point A-nasion-point B angle ≤ 4°), and a normodivergent profile (22° ≤ Frankfort mandibular plane angle ≤ 28°). After the CBCT data were reconstructed into a three-dimensional image, the PAS was segmented into four parts, and the volume of each part was measured. Pharyngeal airway length (PAL) and the area and transverse width of the part showing minimal constriction were also measured. Pearson's correlation analysis was used to evaluate the correlation between changes in the PAS and the amount of anterior overbite.

Results

: The OBG showed a significantly narrower airway space in the nasopharyngeal, hypopharyngeal, and total airway volumes. The OBG also showed a significantly smaller area and transverse width of the part with minimal constriction. The OBG showed a significantly longer PAL, but there was no correlation between the amount of anterior overbite and the changes in PAS.

Conclusions

: The PAS was associated with AOB. Patients with AOB had a narrower PAS and a smaller part showing minimal constriction.

Three-dimensional evaluation of the effects of Bionator and Forsus appliances on oropharyngeal airway volume in patients with mandibular retrognathia

OBJECTIVE

To evaluate whether there is a difference between the effects of Bionator and Forsus appliances on airway volume.

METHODS

Forty patients with mandibular retrognathia were divided into two groups. The Bionator appliance was applied to Group 1, while the Forsus FRD EZ2 appliance was applied to Group 2. Three-dimensional images were captured before and after functional appliance use in both groups. Dolphin 3D software was used for airway measurements.

RESULTS

No statistically significant difference was found between the groups in terms of volumetric and area measurements. There was a statistically significant difference between the minimum axial T and O-N border T measurements of the groups.

CONCLUSION

The use of functional appliances may contribute to an increase in oropharyngeal airway dimensions, but there was no difference between the Bionator and Forsus groups in terms of volumetric measurements.

Does Head and Neck Posture Affect Cone-Beam Computed Tomography Assessment of the Upper Airway?

PURPOSE

Radiographic analysis is often used as a screening tool to assess for risk of sleep-related breathing disorders. This study aimed to address 2 questions: (1) Does head posture significantly affect the minimum cross-sectional area (MCA)? and (2) Is the NBC3 (nasion-basion-C3) angle a reliable measurement to control for alteration of head position in cone-beam computed tomography (CBCT) scans?

METHODS

Study design: prospective cohort study.

SETTING

Private practices affiliated with a research institution.

PARTICIPANTS

convenience sample of adult volunteers.

VARIABLES

CBCT scans were taken in 2 conditions: baseline (natural head position, NHP) and 1 of 5 experimental conditions (head tilted up, head tilted down, sitting vs standing, use of chin-rest, and swallow variation). For the primary aim of our study, the primary predictor variable was head posture and the main outcome variable was percentage change in MCA. For the secondary aim, the primary predictor variable was head posture and the main outcome variable was degree change in NBC3 angle.

RESULTS

Ninety subjects were included (age 40.7 ± 13.7 years, 70% female). Mean NBC3 at baseline was 112.4 ± 8.3°. Head tilted down significantly decreased (-41.4 ± 18.5 mm², P = .03∗) and head tilted up significantly increased MCA (+147.4 ± 43.3 mm², P = .0018∗). Head tilted down significantly reduced the NBC3 angle measurement (-10.5 ± 6.8°, P = .006) and head tilted up significantly increased the NBC3 angle measurement (+14.4 ± 5.8°, P = .0004). A quadratic regression model was fitted with moderately strong correlation (R² = 0.54) showing an exponential effect of small changes in the NBC3 angle on MCA, P < .0001. The model predicts that increasing NBC3 by +5 and + 10° resulted in MCA changes of +25% and +88%, whereas a decrease in NBC3 by -5 and -10° results in MCA changes of -21% and -23%, respectively.

CONCLUSION

Alterations in head posture significantly affect the MCA of the upper airway on CBCT. The NBC3 angle can be used to reliably assess changes in cranio-cervical extension and validate comparisons of MCA between CBCT scans for the same patient. A standardized protocol for CBCT acquisition is proposed.

Analysis of maxillary arch morphology and its relationship with upper airway in mouth breathing subjects with different sagittal growth patterns

OBJECTIVE

This three-dimensional cone beam computed tomography(CBCT) study assessed pharyngeal airway and maxillary arch in mouth breathing subjects with different skeletal classifications and analyzed the factors associated with the upper airway morphological variations in mouth breathing (MB) and nasal breathing (NB) subjects.

METHODS

One hundred and five subjects (52 MB and 53 NB children), divided into three skeletal groups: Class I (1° ≤ ANB° ≤ 5°), Class II (ANB° >5°), and Class III (ANB°<1°). An independent t-test and one-way ANOVA test were utilized in the group analysis of normal distributed data. The linear multiple regression test was applied to create a model for the airway volumes based on the maxillary arch parameters in different skeletal groups.

RESULTS

In three skeletal groups, NB individuals had greater oropharyngeal airway volume (OPV) and total pharyngeal airway volume (TPV) than MB. Maxillary arch parameters of intermolar width (IMW), intercanine width (ICW), and maxillary width of canines (MWC) were larger in NB participants than in MB subjects. In the MB group, we discovered that Class II individuals had lower NPV (nasopharyngeal airway volume) than Class I and Class III. MWC was lower in Class II subjects compared to Class I and Class III in both the NB and MB groups.

CONCLUSION

NB individuals had greater pharyngeal airway and maxillary arch parameters than MB subjects. Our model equation revealed that the inter-molar width (IMW) and palatal area (PA) parameters were the strongest predictors of total pharyngeal airway volume (TPV) in the skeletal Class II and Class I groups.

Three-dimensional evaluation of pharyngeal airway and maxillary arch in mouth and nasal breathing children with skeletal Class I and II

Objective

This study aimed to investigate whether the subjects with mouth breathing (MB) or nasal breathing (NB) with different sagittal skeletal patterns showed different maxillary arch and pharyngeal airway characteristics.

Methods

Cone-beam computed tomography scans from 70 children aged 10 to 12 years with sagittal skeletal Classes I and II were used to measure the pharyngeal airway, maxillary width, palatal area, and height. The independent t-test and the Mann–Whitney U test were used for the intragroup analysis of pharyngeal airway and maxillary arch parameters.

Results

In the Skeletal Class I group, nasopharyngeal airway volume (P < 0.01), oropharyngeal airway volume (OPV), and total pharyngeal airway volume (TPV) (all P < 0.001) were significantly greater in subjects with NB than in those with MB. Furthermore, intermolar width, maxillary width at the molars, intercanine width, maxillary width at the canines, and palatal area were significantly larger in subjects with NB than in those with MB (all P < 0.001). In the Skeletal Class II group, OPV, TPV (both P < 0.05) were significantly greater in subjects with NB than in those with MB. No significant differences in pharyngeal airway parameters in the MB group between subjects with Skeletal Class I and those with Skeletal Class II.

Conclusion

Regardless of sagittal Skeletal Class I or II, the pharyngeal airway and maxillary arch in children with MB differ from those with NB. However, the pharyngeal airway was not significantly different between Skeletal Class I and II in children with MB.

A Comparative Assessment of the Upper Pharyngeal Airway Dimensions among Different Anteroposterior Skeletal Patterns in 7–14-Year-Old Children: A Cephalometric Study

Background: The pharyngeal airway is a crucial part of the respiratory system’s function. Assessing the pharyngeal airway dimensions in different skeletal types is important in the orthodontic treatment of growing patients. The aim of this study was to compare the upper pharyngeal airway dimensions of 7–14-year-old children with different skeletal types. Methods: Three-hundred-sixty-one lateral cephalometric radiographs were grouped based on their skeletal patterns determined by the ANB angle as skeletal type I (n = 123), type II (n = 121), and type III (n = 117). The radiographs were divided into 4 groups: 7/8 YO (7–8 years old), 9/10 YO, 11/12 YO, and 13/14 YO. The cephalometric measurements comprised SNA, SNB, ANB, Ad1-PNS, Ad2-PNS, McUP, and McLP. An ANOVA was used to compare the group results. Results: Significant differences in Ad1-PNS, Ad2-PNS, McUP, and McLP in skeletal types II and III were found between age groups. Most upper pharyngeal airway dimensions in skeletal types II and III children were significantly wider in the 13/14 YO group than in the other age groups. Conclusion: The upper pharyngeal airway dimensions increased age-dependently in 7–14-year-old children, especially in skeletal types II and III. The upper pharyngeal airway dimensions could serve as a guide in differentiating the different skeletal classes in clinical settings.

Long-term three-dimensional effects of orthognathic surgery on the pharyngeal airways: a prospective study in 128 healthy patients

OBJECTIVE

To investigate volumetric and circumferential pharyngeal airway space (PAS) changes and stability over time as evaluated with cone beam computed tomography (CBCT) before and after orthognathic surgery 2 years postoperatively.

MATERIALS AND METHODS

One hundred twenty-eight patients underwent bimaxillary orthognathic surgery at the Department of Maxillofacial Surgery of University Hospitals, Leuven, Belgium, were recruited prospectively. Patients were divided into 4 groups based on the amount of mandibular advancement in 5 mm increments (< 0 mm, 0-5 mm, 5-10 mm, or > 10 mm). CBCT data was acquired preoperatively and 1-6 weeks, 6 months, 1 year, and 2 years postoperatively. Patients with a history of maxillofacial trauma or surgery, obstructive sleep apnoea syndrome, or craniofacial anomalies were excluded. Nasopharyngeal, oropharyngeal, and hypopharyngeal PAS volumes and constriction surface areas (mCSA) were measured and compared between each time point with a paired t-test.

RESULTS

The largest significant increase in oropharyngeal volume and mCSA were observed in the 5-10 mm (+ 13.3-21.7%, + 51.3-83.0%)) and > 10 mm (+ 23.3-44.6%, + 92.3-130.0%) mandibular advancement groups. This increase only remained stable 2 years postoperatively in the > 10 mm group. In other mandibular advancement groups, short-term oropharyngeal volume and mCSA increases were noticed, which returned to baseline levels 6 months to 1 year postoperatively.

CONCLUSION

Bimaxillary advancement osteotomy significantly increases oropharyngeal volume and mCSA, which remains stable between 6 months to 1 year postoperatively.

CLINICAL RELEVANCE

Long-term stable volumetric and mCSA enlargements were found with > 10 mm mandibular advancements over a period of 2 years. Return towards baseline levels was observed in the other mandibular advancement groups.

The upper airway volume effects produced by Hyrax, Hybrid-Hyrax, and Keles keyless expanders: a single-centre randomized controlled trial

OBJECTIVE

To assess upper airway volume changes after rapid maxillary expansion (RME) with three different expanders.

TRIAL DESIGN

Three-arm parallel randomized clinical trial.

METHODS

Sixty-six patients, 10-16 years old, in permanent dentition, with maxillary transverse deficiency were recruited and assigned with block randomization (1:1:1 ratio) and allocation concealment to three groups of 22 patients each (Hyrax, Hybrid-Hyrax, and Keles keyless expander). The primary outcome (overall upper airway volume change) and secondary outcomes (volume changes in the nasal cavity, nasopharynx, oropharynx, and hypopharynx) were blindly assessed on the initial (T0) and final (T1, 6 months at appliance removal) cone beam computed tomography. Differences across groups were assessed with crude or adjusted for confounders (gender, age, growth stage, skeletal pattern, baseline airway volume, and amount of expansion) linear regression models.

RESULTS

Fifty-one patients were analysed (19, 19, and 13 in the Hyrax, Hybrid-Hyrax, and Keles groups). Maxillary expansion resulted in considerable increases in total airway volume in the Hybrid-Hyrax group (+5902.1 mm3) and less in the Hyrax group (+2537.9 mm3) or the Keles group (+3001.4 mm3). However, treatment-induced changes for the primary and all secondary outcomes were of small magnitude and no significant difference was seen among the three expanderes in the total airway volume in either crude or adjusted analyses (P > 0.05 in all instances). Finally, among pre-peak patients (CVM 1-3), the Hybrid-Hyrax expander was associated with significantly greater increases in total airway volume compared to the Hyrax expander (P = 0.02).

CONCLUSIONS

RME resulted in relatively small increases in total upper airway volume and its separate compartments, with mostly no statistically significant differences across the Hyrax, Hybrid-Hyrax, and Keles groups.

LIMITATIONS

Significantly greater attrition was found in the Keles group due to appliance failure. The current trial might possibly be under-powered to detect differences between groups, if such exist.

HARMS

Keles expanders blocked during activations and required substitution for completion of treatment.

PROTOCOL

The protocol was not published before trial commencement.

REGISTRATION

Australian and New Zealand Clinical Trial Registry (ACTRN12617001136392).

A community detection analysis of malocclusion classes from orthodontics and upper airway data

OBJECTIVE

The interaction between skeletal class and upper airway has been extensively studied. Nevertheless, this relationship has not been clearly elucidated, with the heterogeneity of results suggesting the existence of different patterns for patients' classification, which has been elusive so far, probably due to oversimplified approaches. Hence, a network analysis was applied to test whether different patterns in patients' grouping exist.

SETTINGS AND SAMPLE POPULATION

Ninety young adult patients with no obvious signs of respiratory diseases and no previous adeno-tonsillectomy procedures, with thirty patients characterized as Class I (0 < ANB < 4); 30 Class II (ANB > 4); and 30 as Class III (ANB < 0).

MATERIALS AND METHODS

A community detection approach was applied on a graph obtained from a previously analysed sample: thirty-two measurements (nineteen cephalometric and thirteen upper airways data) were considered.

RESULTS

An airway-orthodontic complex network has been obtained by cross-correlating patients. Before entering the correlation, data were controlled for age and gender using linear regression and standardized. By including or not the upper airway measurements as independent variables, two different community structures were obtained. Each contained five modules, though with different patients' assignments.

CONCLUSION

The community detection algorithm found the existence of more than the three classical skeletal classifications. These results support the development of alternative tools to classify subjects according to their craniofacial morphology. This approach could offer a powerful tool for implementing novel strategies for clinical and research in orthodontics.

Comparing Pharyngeal Airway Dimensions and Hyoid Bone Position in the Subgroups of Skeletal Class III Malocclusions: A Cephalometric Study

Aim:

To examine pharyngeal airway dimensions and hyoid bone position according to the subgroups of Class III malocclusion.

Materials and Methods:

This retrospective study consisted of patients divided into three subgroups with skeletal Class III malocclusion. The study included a total of 151 individuals (61 females and 90 males). The authors divided individuals with skeletal Class III malocclusion into three subgroups: maxillary retrognathia, mandibular prognathia, and combined. The study’s cephalometric analysis used eight nasopharyngeal, seven oropharyngeal, two hypopharyngeal, nine hyoid, and four area measurements. One-way analysis of variance was used to evaluate patients. Tukey’s post-hoc tests were used for bilateral comparisons of significant parameters. The results were considered statistically significant at a P < .05 significance level.

Results:

The study found no significant differences between the groups’ pharyngeal airway and area measurements ( P > .05). When the authors evaluated hyoid bone position, a statistically significant difference was found between the three groups’ Hy-A (mm), Hy-S (mm), Hy-SN (mm), and Hy-FH (mm) measurements ( P < .05).

Conclusion:

Linear and areal pharyngeal airway dimensions are similar in subgroups of Class III malocclusions, while the hyoid bone is vertically higher in individuals with maxillary retrognathia.

Effect of functional appliances on the airway in Class II malocclusions

The proximity of the orofacial structures to the upper airway has led to enormous interest in their influence on the airway maintenance mechanism. The recognition of Sleep disorders and the evolution of dental sleep medicine has fueled further interest in the role of orthodontic treatment on the airway particularly in Class II malocclusions. With abundant literature on class II malocclusions and growth modification, it is natural that focus would shift on the effect of functional appliances on the airway. Most studies on the subject show an improvement in the airway in response to functional appliances and these include both two dimensional and three dimensional study of the airway. This review showcases the most significant literature on this field of study against the background of the information that is needed to gauge its clinical relevance.

A cross-sectional retrospective study of normal changes in the pharyngeal airway volume in white children with 3 different skeletal patterns from age 9 to 15 years: Part 1

INTRODUCTION

This study investigated correlations between airway size and age, sex, and skeletal patterns; identified airway change trends; and measured volumetric norms in children via cone-beam computed tomography.

METHODS

Four hundred twenty nontreated white patients were stratified by age, sex, and anteroposterior skeletal pattern. The nasopharyngeal airway (NPA), oropharyngeal airway (OPA), and total pharyngeal airway (TPA) volumes were delineated on 3-dimensional digital cephalograms. SPSS (SPSS, Chicago, Ill) was used to run an analysis of variance and post-hoc analyses.

RESULTS

The Class III group had significantly larger OPA volumes than Class I and II groups. Male subjects had considerably larger NPA volumes than female subjects. Age was significantly associated with all 3 airway volumes (P <0.05). The young cohort (ages, 9-10 years) had a mean TPA of 11,435.34 ± 484.45 mm³, the middle cohort (ages, 11-13 years) had a mean TPA of 14,152.07 ± 395.46 mm³, and the older cohort (ages, 14-15 years) had a mean TPA of 18,057.99 ± 484.25 mm³.

CONCLUSIONS

An effect of skeletal classification on OPA and a sex effect on NPA were observed. The annual change in the mean of TPA volume decreased in subjects aged 10-12 years, then rebounded until 14 years. TPA change peaked in female subjects 1 year before male subjects.

Analysis of the middle region of the pharynx in adolescents with different anteroposterior craniofacial skeletal patterns

Objective:

To assess the volume and morphology of the middle region of the pharynx (MRP) in adolescents with different anteroposterior craniofacial skeletal patterns.

Methods:

One hundred twenty-six patients (56 male and 70 female), who had cone-beam computed tomography (CBCT) within their records, were selected for this cross-sectional study. Participants were classified, according to their ANB angle value, in Class I (1^o ≤ ANB ≤ 3^o), Class II (ANB > 3^o) and Class III (ANB < 1^o). The total volume (tV), minimum axial area (AxMin) and morphology of the MRP and its subdivisions - velopharynx (VP) and oropharynx (OP) - were characterized by CBCT and 3-dimensional image reconstruction software. Intergroup comparisons were performed by ANOVA and Tukey post-hoc tests. Correlations between tV and Axmin with the ANB angle values were tested using linear regression analysis, considering sex as covariable.

Results:

Statistically significant difference between groups were observed in tV only for the VP region; Class II individuals presented significantly lower tV (6863.75 ± 2627.20 mm³) than Class III subjects (9011.62 ± 3442.56 mm³) (p< 0.05). No significant differences were observed between groups for any other variable assessed, neither in MRP nor in the OP region (p> 0.05). A significant negative correlation was evidenced between tV and Axmin and the ANB angle values; sexual dimorphism was observed for some variables.

Conclusions:

Class II subjects have smaller tV in the VP region. tV and Axmin tend to decrease in all evaluated regions when the ANB angle values increase.

Comparison of pharyngeal airway volume in different skeletal facial patterns using cone beam computed tomography

Background

This study aimed to compare the pharyngeal airway volume in class I,II and III skeletal malocclusion patients using cone beam computed tomography (CBCT).

Material and Methods

This retrospective, cross sectional study was conducted on lateral cephalograms of 71 patients derived from their CBCT scans. Using the ANB angle, the patients were divided into class I,II and III malocclusion. Two observers used Dolphin 3D software to calculate the pharyngeal airway volume, airway area, minimum axial area, minimum area location, airway length and morphology. Data were analyzed using one-way ANOVA, Kruskal-Wallis test, Tukey’s test, Spearman’s correlation coefficient and multiple regression analysis.

Results

The three skeletal classes were significantly different in airway volume, minimum axial area, mean airway area and airway morphology (P<0.05). Significant differences were found in airway volume and mean airway area between class II and III patients (P<0.05). The minimum axial area and airway morphology in class III patients were greater than those in class I and II patients (P<0.05). Every one unit increase in the ANB angle decreased the airway volume by 0.261 units. The effect of ANB angle on airway volume was statistically significant and it was shown that one unit increase in the angle decreased the airway volume by 453.509 units.

Conclusions

A significant correlation exists between the skeletal facial pattern and upper airway dimensions. In our study, the total airway volume and the mean airway area of class III patients were larger than those in class II patients.

Key words:Cone-Beam computed tomography, malocclusion, pharyngeal airway volume.

Evaluation of Nasal Obstruction in Various Sagittal Skeletal Deformity of Jaws

Nasal obstruction (NO) is a common symptom present in 25% of the general population, which significantly interferes with the quality of life. The different facial profiles and malocclusion patterns could be associated with the degree of NO. In order to evaluate the nasal function in patients with different facial morphology patterns, the authors developed a prospective study in which 88 patients from a dentofacial deformities center were included. These patients were submitted to fibrorhinoscopy (Mashida, ENT PIII) with a 3.2-mm cannula under topical anesthesia to evaluate septal deviation, inferior and medium turbinates, and pharyngeal tonsils. The 88 patients included in the study were divided into 3 groups according to the classification of the facial profile, distributed as follows: 32 class I, 28 class II, and 28 class III; the data collected was statistically analyzed by analysis of variance and the results are shown. The patients included in this study presented similar prevalence of NO with the reduction of airway function efficiency. Although it was not a statistically different, the group II presented higher mean Nasal Obstruction Syndrome Evaluation scores.

Effects of bodily retraction of mandibular incisors versus mandibular setback surgery on pharyngeal airway space: A comparative study

OBJECTIVE

The purpose of this study was to compare the changes induced in the pharyngeal airway space by orthodontic treatment with bodily retraction of the mandibular incisors and mandibular setback surgery without extraction.

METHODS

This retrospective study included 63 adult patients (32 men and 31 women). Thirty-three patients who had been treated via four-bicuspid extraction and bodily retraction of the mandibular incisors (incisor retraction, IR group) were compared with 30 patients who had been treated via mandibular setback surgery (MS group) without extraction. Lateral cephalograms were acquired and analyzed before (T1) and after treatment (T2).

RESULTS

The superior pharyngeal airway space did not change significantly in either group during treatment. The middle pharyngeal airway space decreased by 1.15 ± 1.17 mm and 1.25 ± 1.35 mm after treatment in the IR and MS groups, respectively, and the decrease was comparable between the two groups. In the MS group, the inferior pharyngeal airway space (E-IPW) decreased by 0.88 ± 1.67 mm after treatment (p < 0.01). The E-IPW was larger in the MS group than in IR group at T1, but it did not differ significantly between the two groups at T2. No significant correlation was observed between changes in the pharyngeal airway space and the skeletal and dental variables in each group.

CONCLUSIONS

The middle pharyngeal airway space decreased because of the posterior displacement of the mandibular incisors and/or the mandibular body. The E-IPW decreased only in the MS group because of the posterior displacement of only the mandibular body.

Correlation between the position of hyoid bone and subregions of the pharyngeal airway space in lateral cephalometry and cone beam computed tomography

OBJECTIVE

To correlate the pharyngeal airway subregions with the positioning of the hyoid bone.

MATERIAL AND METHODS

The study examined 107 lateral cephalometric (LC) and cone beam computed tomography (CBCT) images. Linear and volumetric measurements of the pharyngeal subregions were made and correlated to linear measurements using hyoid triangle analysis on images of LC and multiplanar (MPR) and three-dimensional (3D) reconstructions of CBCT.

RESULTS

There was significant correlation between linear measurements of the pharyngeal subregions and hyoid bone position in LC images and in MPR and 3D reconstructions of the CBCT. Correlations were more frequent in the oropharynx and hypopharynx, especially for LC images. No correlations were observed between LC images or CBCT reconstructions and the volumetric measurements of the pharyngeal subregions and the position of the hyoid bone.

CONCLUSION

The hyoid bone position showed more correlations with oropharynx and hypopharynx airway measurements. The hyoid triangle method was not applicable to 3D images, since it showed a smaller number of measures correlated to the hyoid bone position.

Long-term influence of mandibular advancement on the volume of the posterior airway in skeletal Class II-patients: a retrospective analysis

In the past, maxillomandibular advancement has resulted in considerable improvement in the volume of the posterior airway space. The objective of the present study was to find out how mandibular advancement without maxillary involvement would affect the posterior airway space in patients with mandibular retrognathism. Cone-beam computed tomographic (CT) scans were done for 20 patients before, and six months after, mandibular advancement. Cephalometric analysis at both time points included 2-dimensional and 3-dimensional assessment of the upper airway. Eight men and 12 women presented a preoperative mean (SD) Wits value of 7.4 (1.54) mm, with an airway area of 7.11 (1.88) cm² and a volume of 14.92 (4.46) cm³. Six months postoperatively they showed a Wits value of 2.7 (0.41) mm, an airway area of 11.33 (3.49) cm², and a volume of 25.7 (6.10) cm³. There was a mean (range) enlargement of 59 (22-82) % of the area and 73 (29-108) % of the volume. A preoperative Wits value of 8mm or more correlated significantly with a larger increase of the posterior airway space (p=0.002). At the same time, an improvement in the Wits value of 4.5mm or more correlated significantly with an increase in volume (p=0.016). The effect of mandibular advancement on the posterior airway space was significant, and the volumetric effect seems to be even more relevant than the two-dimensional changes.

Pharyngeal airway dimensions in skeletal class II: A cephalometric growth study

Purpose

This retrospective study aimed to evaluate the nasopharyngeal and oropharyngeal dimensions of individuals with skeletal class II, division 1 and division 2 patterns during the pre-peak, peak, and post-peak growth periods for comparison with a skeletal class I control group.

Materials and Methods

Totally 124 lateral cephalograms (47 for skeletal class I; 45 for skeletal class II, division 1; and 32 for skeletal class II, division 2) in pre-peak, peak, and post-peak growth periods were selected from the department archives. Thirteen landmarks, 4 angular and 4 linear measurements, and 4 proportional calculations were obtained. The ANOVA and Duncan test were applied to compare the differences among the study groups during the growth periods.

Results

Statistically significant differences were found between the skeletal class II, division 2 group and other groups for the gonion-gnathion/sella-nasion angle. The sella-nasion-B-point angle was different among the groups, while the A-point-nasion-B-point angle was significantly different for all 3 groups. The nasopharyngeal airway space showed a statistically significant difference among the groups throughout the growth periods. The interaction among the growth periods and study groups was statistically significant regarding the upper oropharyngeal airway space measurement. The lower oropharyngeal airway space measurement showed a statistically significant difference among the groups, with the smallest dimension observed in the skeletal class II, division 2 group.

Conclusion

The naso-oropharyngeal airway dimensions showed a statistically significant difference among the class II, division 1; class II, division 2; and class I groups during different growth periods.

Cephalometrics of Pharyngeal Airway Space in Lebanese Adults

Purpose. The upper airway space is significant in orthodontic diagnosis and treatment planning. The objectives of this study are to assess the dimensions of soft tissue elements of the upper pharyngeal space and evaluate potential correlations with modifying variables such as gender, skeletal class, and anthropometric parameters. Materials and Methods. Lateral cephalograms were obtained from 117 healthy young adult Lebanese subjects. Nineteen cephalometric linear/angular measurements of the nasopharynx, oropharynx, and hypopharynx were recorded. Anthropometric parameters including body mass index and neck circumference were measured. Results. Significant differences were demonstrated for 12 out of the 19 parameters considered between genders. Uvula and tongue dimensions and the distances between epiglottis-posterior pharyngeal wall and epiglottis-posterior nasal spine were significantly larger in males. The anteroposterior inclination of the uvula and the distances between the uvula and posterior pharyngeal wall were significantly greater in females. No significant differences were found between skeletal classes relative to most of the variables. Body mass index and neck circumference were positively correlated with the dimensions of tongue and uvula. Conclusions. Sexual dimorphism relative to some cephalometric variables and anthropometric parameters may account partly for larger oronasopharyngeal spaces in females. Anthropometric data need to be accounted for in population-related comparisons.

A comparative study of the pharyngeal airway space, measured with cone beam computed tomography, between patients with different craniofacial morphologies

PURPOSE

The present study aims to determine any existing association between airway dimensions, measured with cone beam computed tomography (CBCT), and the different patient craniofacial morphologies.

MATERIAL AND METHODS

Sixty CBCT (Dental Picasso Master 3D) images, from patients treated at the Orthodontics Master at Valencia University were selected. The program InVivoDental 5.1 was used to visualize sections, analyze three-dimensional images, and perform airway measurements in the three planes of the space. Intra- and interobserver error methods were recorded. After that, measurements at three different levels of the airway (upper, medium, lower) were taken, in both the anteroposterior and transversal directions of the airway space. The area (mm(2)) of the airway space at the three levels was also measured.

RESULTS

In the anteroposterior airway measurements, there were differences between the measurements by level. The magnitude of these differences depended on the skeletal pattern of the individual. In the transversal airway measurements and in the area airway measurements, there were no differences according to the skeletal pattern. However, in the transversal direction, measurements in the lower level were significantly higher than in the superior level in all cases. When measuring the area, significantly higher measurements in the upper level were recorded. The homogeneity between medium and lower levels decreased gradually from class I to class III subjects.

CONCLUSIONS

No statistically significant results were observed that related the anteroposterior and vertical skeletal craniofacial morphology with airway dimensions, although some specific associations have been detected for certain airway levels or for pattern combinations.

Three-dimensional upper-airway assessment in patients with bronchial asthma

OBJECTIVE

To assess the upper airway (UAW) total volume (TV), the nasopharyngeal narrowest area (NNA), and the oropharyngeal narrowest area (ONA) in patients with bronchial asthma.

MATERIALS AND METHODS

The sample consisted of 52 patients divided into two groups: the control group (n  =  26; mean age  =  14.85 years), which consisted of patients not suffering from bronchial asthma; and the asthmatic group (n  =  26; mean age  =  16.65 years), which consisted of patients with bronchial asthma. To assess UAW-related variables (TV, NNA, and ONA), cone-beam computed tomography scans of the patients were evaluated by means of the Dolphin Imaging software 11.5. All measurements were repeated after 30 days, and the results were submitted to reliability tests by means of the intraclass correlation coefficient and the Bland-Altman agreement test. The values obtained for TV, NNA, and ONA for each group were compared by using Student's t-test for independent samples (5% level of significance).

RESULTS

The results showed that the groups were matched concerning gender, cephalometric characteristics, and type of malocclusion. The asthmatic group had significantly lower TV (P  =  .01) and ONA (P  =  .007) than the control group. However, no significant difference was observed for NNA between the groups (P  =  .54).

CONCLUSIONS

Bronchial asthma may be a determining factor for the reduction of UAW dimensions, as patients with asthma showed significant reductions in TV and ONA dimensions.

The influence of craniofacial morphology on the upper airway dimensions

Objective: 

To evaluate the influence of craniofacial morphology on the upper airway dimensions in healthy adult subjects.

Materials and Methods: 

The records of 276 healthy 17- to 27-year-old patients were extracted from the cone-beam computed tomography image database of the Institute of Stomatology, Riga Stradins University. Dolphin 11.7 software was used to evaluate craniofacial anatomy and semiautomatic segmentation of the upper airway. Measurements of oropharyngeal airway volume (OPV), minimal cross-sectional area (CSAmin), and nasopharyngeal airway volume (NPV) were obtained. The presence of adenoid tissues was recorded. Associations between variables were analyzed by Spearman's correlation coefficients, and multivariate linear regression analysis was used to identify factors that had a possible influence on upper airway dimensions.

Results: 

The following factors were identified as influencing the variability of NPV (23%): SNA angle, gender, and presence of adenoids. Statistically significant, although weak, correlations were found between SNB angle and OPV (r  =  0.144, P &lt; .05) and CSAmin (r  =  0.182, P &lt; .01).

Conclusion: 

The results suggest that craniofacial morphology alone does not have a significant influence on upper airway dimensions.

The relationship between upper airways and craniofacial morphology studied in 3D. A CBCT study

OBJECTIVES

To assess whether morphology and dimension of the upper airway differ between patients characterized by various craniofacial morphology.

SETTING AND SAMPLE POPULATION

Ninety young adult patients from the Postgraduate Clinic, Section of Orthodontics, Department of Dentistry, Health, Aarhus University, Denmark, with no obvious signs of respiratory diseases and no previous adeno-tonsillectomy procedures. Thirty patients were characterized as Class I (-0.5 < ANB < 4.5), 30 as Class II (ANB > 4.5), and 30 as Class III (ANB < -0.5).

MATERIAL AND METHODS

Cone-beam computed tomography (CBCT) scans obtained in a supine position for all patients. Cephalometric landmarks were identified in 3D. Sagittal and transversal dimensions, cross sections, and partial and total volumes of the upper airway were correlated with the cephalometric measurements in all three planes of space. The cross-sectional minimal area of the upper airway was assessed as well.

RESULTS

No statistical significant relationships between dimension and morphology of upper airways and skeletal malocclusion were found.

CONCLUSION

Differences in craniofacial morphology as identified by the sagittal jaw relationship were not correlated with variation in upper airway volumes. A clinical significant relation was detected between minimal area and total upper airway volume.

Effects of first premolar extraction on airway dimensions in young adolescents: A retrospective cephalometric appraisal

OBJECTIVE

To evaluate the upper airway dimensions in adolescents treated for bimaxillary proclination with first premolar extraction.

MATERIALS AND METHODS

A retrospective cephalometric evaluation was carried out on the available pre and post orthodontic treatment records of 150 patients (12-18 years of age) who had bimaxillary proclination and were treated with fixed orthodontic therapy. Cephalometric landmarks for sagittal airway measurements and hyoid bone were identified; linear and angular measurements were obtained. Descriptive statistics using paired t-test was used to assess changes in pre and post treatment values and Pearson's correlation coefficient was calculated to evaluate the reliability of observations. The method error calculations were performed using the Dahlberg formula.

RESULTS

It was observed that the mean values of nasopharyngeal dimension and Total Airway Length (TAL) showed no statistically significant difference in pre and post treatment groups. All other airway and hyoid parameters showed statistically significant difference. Pearson's correlation coefficient showed statistically significant correlations in all the airway and hyoid parameters.

CONCLUSIONS

In the present study, the nasopharyngeal dimension and TAL were not found to be directly affected by the retraction of anterior teeth, This can be attributed to the fact that nasopharyngeal dimension and TAL are not under direct influence of tongue position. The other findings also indicated direct correlation of tongue position to oropharynx and hypopharynx. Consequently, we emphasize clinically relevant anatomic risk factors that should be given prime importance and serious consideration on the decision whether to extract or not in growing patients.

Role of mandibular displacement and airway size in improving breathing after rapid maxillary expansion

BACKGROUND

Oral breathing and maxillary deficiency are often associated with steep mandibular plane angle, and retrognathic mandible compared with the faces of healthy controls. Some studies suggested that after rapid maxillary expansion, improvement in nasal breathing and repositioning of mandible with transitory increasing of facial height and, in some cases, spontaneous forward repositioning might occur. The above-mentioned mandibular effects could contribute to enlarge oropharynx volume with repositioning of tongue and soft palate with an improvement of upper airway volume after treatment. The aim of this study was to investigate by cone beam computed tomography the role of oropharyngeal volume and mandibular position changes after rapid maxillary expansion in patients showing improved breathing pattern confirmed by polysomnography exam.

METHODS

The final sample of this retrospective study comprised 14 Caucasian patients (mean age 7.6 years) who undergone rapid maxillary expansion with Haas-type expander banded on second deciduous upper molars. Cone beam computed tomography scans and polysomnography exams were collected before placing the appliance (T0) and after 12 months (T1). Mandibular landmarks localization and airway semiautomatic segmentation on cone beam computed tomography scans allowed airway volume computing and measurements.

RESULTS

No significant differences were found between oropharyngeal airway changes and mandibular displacement after rapid maxillary expansion in growing patients.

CONCLUSIONS

The suggested improvement in upper airway and breathing after rapid maxillary expansion should be further related to different compartments of airway such as rhinopharynx and nasal cavity.

Three-dimensional evaluation of upper airway in patients with different anteroposterior skeletal patterns

OBJECTIVES

To investigate variability in the upper airway of subjects with different anteroposterior skeletal patterns by evaluating the volume and the most constricted cross-sectional area of the pharyngeal airway and defining correlations between the different variables.

MATERIAL AND METHODS

The study sample consisted of 60 patients (29 boys, 31 girls) divided into three groups: Class I (1 ≤ ANB ≤ 3), Class II (ANB>3), and Class III (ANB<1), to evaluate how the jaw relationship affects the airway volume and the most constricted cross-sectional area (Min-CSA). Differences between groups were determined using the Tukey-Kramer test. Correlations between variables were tested using Pearson's correlation coefficient.

RESULTS

The volume and the Min-CSA of the pharyngeal airway (PA) were significantly related to anteroposterior skeletal patterns (p < 0.05). The nasopharyngeal airway (NA) volume of Class I and Class III subjects was significantly larger than that of Class II subjects (p < 0.05). The Min-CSA and the length of PA were significantly related to the volume of PA (p < 0.05). The site and the size of the Min-CSA varied among the three groups.

CONCLUSIONS

The volume and the most constricted cross-sectional area of the airway varied with different anteroposterior skeletal patterns. The NA volume of Class I and Class III subjects was significantly larger than that of patients with a Class II skeletal pattern.

Short-term pharyngeal airway changes after mandibular advancement surgery in adult Class II-Patients--a three-dimensional retrospective study

The purpose of this study was to investigate volume changes in posterior airway space (PAS) after bilateral mandibular advancement surgery. Measurements were taken based on three-dimensional (3D) records available for a large and homogeneous cohort of patients. Pre- and postoperative CBCT scans of 102 adult patients with Class II dysgnathia were visualized and analyzed using 3D software (Mimics® Innovation Suite 14.1; Materialise, Leuven, Belgium). The PAS was divided into three segments by three planes parallel and one plane perpendicular to the Frankfort horizontal plane. Total volume, partial volumes, and cross-sectional areas were calculated from the pre- and postoperative scans. Dahlberg coefficients were obtained to verify each parameter for the measurements' reliability. The statistical significance of the changes observed was analyzed by Wilcoxon's rank-sum test. Highly significant (p=0.000) increases in total posterior airway volume (+32.0%) were noted as an effect of mandibular advancement surgery, amounting to 45.6% in the lower PAS third compared to 38.8% in the middle and 12.5% in the upper PAS third. We also obtained highly significant (p=0.000) increases in all the cross-sectional areas investigated, amounting to 48.5% on the soft-palate level compared to 21.6% on the level of the epiglottis tip, and 14.6% on the hard-palate level. These results demonstrate that bilateral mandibular advancement surgery in Class II-Patients leads to significant increases in PAS volume and significant widening of the narrower sites inside the pharynx.

Comparative Evaluation of Nasopharyngeal Airways of Unilateral Cleft Lip and Palate Patients Using Three-Dimensional and Two-Dimensional Methods

Aim

Comparison of nasopharyngeal airway dimensions among UCLP patients and the control group.

Materials and Methods

Computed tomography imaging data and cephalometric films of 20 patients with UCLP and 20 controls were acquired prior to treatment. Three-dimensional (3D) reconstructions of nasal, superior, middle, and inferior pharyngeal airways were carried out from dicom data, and volumes of these compartments were calculated. Nasal width and superior, middle, and inferior nasopharyngeal areas were calculated from cephalometric films.

Results

The only statistically significant difference among the cleft and noncleft patients was detected in nasal volume ( p < .01). Upper and middle pharyngeal airway areas were found to display significant larger areas in the noncleft group on cephalometric appraisal. Nonsignificantly larger nasal widths were measured in the cleft group.

Discussion and Conclusion

Evaluation of the nasopharyngeal airways of cleft and noncleft patients was done, resulting in only the nasal region showing statistically significant difference. Our results showed significantly lower nasal volume measurements of cleft patients when compared with the healthy individuals (p < .01). This inadequacy can be interpreted as an outcome of the deficiency. The controversy among results of cephalometric appraisal and 3D imaging can be associated with superimpositions, density, and contrast inadequacies and obscured landmarks. When 2D data are compared with 3D data, the former can be insufficient and therefore deceiving. Consequently, although the radiation dose of 3D imaging systems is greater, they have the advantage of superior diagnostic outputs.

Relationship between Class III malocclusion and hyoid bone displacement during swallowing: a cine-magnetic resonance imaging study

Objective

The displacement of the hyoid bone (HB) is a critical biomechanical component of the swallowing function. The aim of this study was to evaluate the swallowing-induced vertical and horizontal displacements of the HB in subjects with 2 different magnitudes of skeletal Class III malocclusion, by means of real-time, balanced turbo-field-echo (B-TFE) cine-magnetic resonance imaging.

Methods

The study population comprised 19 patients with mild skeletal Class III malocclusion, 16 with severe skeletal Class III malocclusion, and 20 with a skeletal Class I relationship. Before the commencement of the study, all subjects underwent cephalometric analysis to identify the nature of skeletal malformations. B-TFE images were obtained for the 4 consecutive stages of deglutition as each patient swallowed 10 mL of water, and the vertical and horizontal displacements of the HB were measured at each stage.

Results

At all stages of swallowing, the vertical position of the HB in the severe Class III malocclusion group was significantly lower than those in the mild Class III and Class I malocclusion groups. Similarly, the horizontal displacement of the HB was found to be significantly associated with the severity of malocclusion, i.e., the degree of Class III malocclusion, while the amount of anterior displacement of the HB decreased with an increase in the severity of the Class III deformity.

Conclusions

Our findings indicate the existence of a relationship between the magnitude of Class III malocclusion and HB displacement during swallowing.

Three-dimensional computed tomography analysis of airway volume changes after rapid maxillary expansion

INTRODUCTION

In this retrospective study with 3-dimensional computed tomography, we evaluated airway volume, soft-palate area, and soft-tissue thickness changes before and after rapid maxillary expansion in adolescents. Another purpose was to determine whether rapid maxillary expansion caused changes in the palatal and mandibular planes and facial height.

METHODS

The sample comprised 20 patients who were treated with rapid maxillary expansion. Spiral tomographs were taken before and 3 months after treatment. Reliability studies were performed, and then volumetric, soft-palate area, soft-tissue thickness, and cephalometric parameters were compared on the tomographs. Intraclass correlations were performed on the reliability measurements. Before and after rapid maxillary expansion measurements were compared by using Wilcoxon signed rank tests. Spearman correlation coefficients were used to evaluate the associations among the airway volume, soft-palate area, soft-tissue thickness, and cephalometric measurements. Significance was accepted at P ≤0.05 for all tests.

RESULTS

Intraclass correlation coefficients were ≥0.90 for all reliability measures. Significant increases from before to after rapid maxillary expansion were found in nasal cavity and nasopharynx volumes, and for the measurements of MP-SN, S-PNS, N-ANS, ANS-Me, and N-Me. Significant positive correlations existed between changes in PP-SN and N-ANS, and ANS-Me and N-Me.

CONCLUSIONS

Rapid maxillary expansion causes significant increases in nasal cavity volume, nasopharynx volume, anterior and posterior facial heights, and palatal and mandibular planes.

Cephalometric analysis of pharyngeal airway space dimensions in Turner syndrome

Turner syndrome (TS) that is due to a total or partial lack of an X chromosome affects about 1 in 2000 girls. The syndrome is characterized by short stature and gonadal dysgenesis. Its documented craniofacial features include retrognathic jaws, a short mandible, and a large cranial base angle. Our aim was to find out whether the syndrome also has an effect on the pharyngeal airway space. We retrospectively analysed lateral cephalograms of 35 TS subjects whose age ranged from 6.5 to 21 years and of 35 healthy female controls matched for age. On those, we did 7 linear and 10 angular cephalometric measurements and 9 pharyngeal measurements. Differences between the subjects with TS and their controls were assessed by paired two-tailed T-test. In the girls with TS, both the maxilla and the mandible were more retrognathic (SNA, P = 0.015 and SNB, P < 0.001), the mandible was shorter (TM-Pgn, P = 0.016), and the cranial base angle was larger (SNBa, P = 0.025) than in the controls, confirming the results of earlier studies. Notably, all six pharyngeal airway measurements were smaller in girls with TS. Two of them, PNS-ad2 and PAS, were statistically significantly smaller (P = 0.019 and P = 0.012, respectively). Thus, a narrow pharynx, either as a primary finding or as a consequence of the maxillo-mandibular retrognathism, further delineates the phenotype. This may imply an elevated risk of sleep apnoea in females with TS.

Does rapid maxillary expansion have long-term effects on airway dimensions and breathing?

INTRODUCTION

In this systematic review, we identified and qualified the evidence of long-term reports on the effects of rapid maxillary expansion (RME) on airway dimensions and functions.

METHODS

Electronic databases (Ovid, Scirus, Scopus, Virtual Health Library, and Cochrane Library) were searched from 1900 to September 2010. Clinical trials that assessed airway changes at least 6 months after RME in growing children with rhinomanometry, acoustic rhinometry, computed tomography, or posteroanterior and lateral radiographs were selected. Studies that used surgically assisted RME and evaluated other simultaneous treatments during expansion, systemically compromised subjects, or cleft patients were excluded. A methodologic-quality scoring process was used to identify which studies would be most valuable.

RESULTS

Fifteen articles fulfilled the inclusion criteria, and full texts were assessed. Three were excluded, and 12 were assessed for eligibility. Four articles with low methodologic quality were not considered. The remaining 8 were qualified as moderate. The posteroanterior radiographs showed that nasal cavity width increases; in the lateral radiographs, decreased craniocervical angulation was associated with increases of posterior nasal space. Cone-beam computed tomography did not show significant increases of nasal cavity volume. Rhinomanometry showed reduction of nasal airway resistance and increase of total nasal flow, and acoustic rhinometry detected increases of minimal cross-sectional area and nasal cavity volume.

CONCLUSIONS

There is moderate evidence that changes after RME in growing children improve the conditions for nasal breathing and the results can be expected to be stable for at least 11 months after therapy.

Airway volume for different dentofacial skeletal patterns

INTRODUCTION

Our objective was to evaluate the nasal passage (NP) and oropharyngeal (OP) volumes of patients with different dentofacial skeletal patterns.

METHODS

The study sample consisted of 140 patients (70 boys, 70 girls), divided into 3 groups as Class I (1 ≤ ANB ≤ 3), Class II (ANB > 3), and Class III (ANB < 1), and then further divided into 4 groups as SNA angle ≥ 80°, SNA angle <80°, SNB angle ≥78°, and SNB angle < 78° to evaluate how the positional changes in the maxilla and the mandible affect the OP and NP variables. Differences between groups were determined by using the Kruskal-Wallis test. Correlations between the variables were tested with the Spearman correlation coefficient. The linear multiple regression test was applied to create a model for the airway volumes separately.

RESULTS

The OP volume of the Class II subjects (n = 50) was significantly lower when compared with that of the Class I (n = 46) and Class III subjects (n = 44). The only statistically significant difference for NP volume was observed between the Class I and Class II groups. The mean OP airway volume of subjects with retruded mandibular positions was statistically significantly smaller when compared with the subjects with higher SNB angles. The area of the most constricted region at the base of the tongue (minAx) had a high potential in explaining the OP volume, whereas the NP volume models were not as successful as the OP counterpart. However, minAx was also entered into the NP volume equations as an explanatory variable.

CONCLUSIONS

The OP airway volumes of Class II patients were smaller when compared with Class I and Class III patients. It was observed that mandibular position with respect to cranial base had an effect on the OP airway volume. The only significant difference for the NP volume was between the Class I and Class II groups, with a smaller volume observed for the Class II group.

Interaction between otorhinolaryngology and orthodontics: correlation between the nasopharyngeal airway and the craniofacial complex

In terms of pathophysiology, an anatomically narrow airway is a predisposing factor for obstruction of the upper respiratory tract. The correlation between the nasopharyngeal airway and the craniofacial structures is discussed in this context. Thus a mutual interaction between the pharynx and the mandibular position was demonstrated, whereby the transverse dimension of the nasopharynx was significantly larger in patients with prognathism than in patients with retrognathism. The influence of chronic obstruction of the nasal airway on craniofacial development was also discussed. The form-and-function interaction, which ought to explain the causal relationship between nasal obstruction and craniofacial growth, appears to be of a multifactorial rather than a one-dimensional, linear nature. It is not disputed, however, that expanding the maxilla improves not only nasal volume and nasal flow, but also the subjective sensation of patients, although it is not possible to make a prognostic statement about the extent of this improvement because of the differing reactions of individuals. Orthodontic appliances for advancing the mandible can also be successfully used in the treatment of mild obstructive sleep apnea syndrome. This treatment method should be considered particularly for patients who are unwilling to undergo or cannot tolerate CPAP (continuous positive airway pressure) treatment.

An analysis of different approaches to the assessment of upper airway morphology: a CBCT study

BACKGROUND

Upper airway morphology and respiration have been assigned an important role in the development of the craniofacial complex. Several studies advocate lateral cephalograms to evaluate the upper airway. Although this method has been widely used, a two-dimensional projection of a three-dimensional anatomical structure is questionable.

OBJECTIVE

To correlate linear measurements (sagittal and transversal), cross-sectional areas, and volumes of the upper airway determined on Cone Beam CT (CBCT) data sets.

MATERIAL AND METHODS

CBCT-scans of 34 patients were used to perform a 3D evaluation of the upper airway. Linear sagittal measurements reproducing those usually performed on lateral cephalograms, linear transversal measurements, cross-sectional areas, partial and total volumes (TV) were computed.

RESULTS

The analysis showed a weak correlation (r < 0.8) between most of the linear measurements. The correlations between sagittal, transversal, and cross-sectional area with partial volumes were weak, except for the lower part of the nasopharynx which was highly correlated (r > 0.9) with sagittal measurement and with area. The upper part of the velopharynx presented a good correlation (0.8 < r < 0.9) between area and volume. Good correlation between most transversal measurements and the corresponding areas was found. Minimal sagittal, minimal transversal, and minimal area were weakly correlated with TV.

CONCLUSIONS

Upper airway cannot be accurately expressed by single linear measurements as performed on cephalograms. The TV alone does not depict the morphology of the airway. A CBCT-based 3D analysis gives a better picture of the anatomical characteristics of the upper airways and therefore can lead to an improvement of the diagnosis.