Changes of pharyngeal airway size and hyoid bone position following orthodontic treatment of Class I bimaxillary protrusion

The orthodontic extraction of second premolars: The influence on airway volume

INTRODUCTION

The extraction of second premolars and associated changes in the volume of the airway have not been previously explored. This retrospective study aimed to compare the volumetric changes of the airway preorthodontic and postorthodontic treatment in relevant extraction and control samples and to identify variables that may influence the outcome.

METHODS

Cone-beam computed radiography scans of 54 patients with second premolar extraction and 59 nonextraction patients treated in a private orthodontic practice were matched for crowding. The average age for both samples was 15 years. The images were individually landmarked and measured by applying volumetric, linear, and angular parameters. The results were analyzed using repeated measures, such as variance analysis, correlation testing, and regression statistical analyses.

RESULTS

There was a statistically significant increase in the airway volume for both groups (P <0.05). The difference in increase between the groups was not statistically significant. Seven variables demonstrated a collectively significant effect on changes to airway volume (F[7,112] = 38.48; P <0.001; r2 = 0.701), with 70% of the variation predicted by the variables. Multiple regression analyses indicated that changes to the area of minimum constriction (B = 32.45; t = 11.95; P <0.001) and changes to airway length (B = 94.75; t = 7.79; P <0.001) had a statistically significant effect on airway volume.

CONCLUSIONS

The volume of the airway increased in both the extraction and nonextraction samples. The biggest contributors to the increase were an increase in airway length and an increase in the area of minimum constriction, which likely occurred as a result of natural growth.

Comparative Analysis of Pharyngeal Airway Changes Following All Four Versus All Five Premolar Extractions in Orthodontic Treatments: A Cephalometric Study

BACKGROUND

Orthodontic treatment, particularly involving premolar extractions, has been a subject of ongoing debate within the orthodontic community. The impact of such interventions on the pharyngeal airway, a critical component of the respiratory system, remains a topic of exploration.

OBJECTIVE

This retrospective cephalometric study aims to investigate changes in pharyngeal airway dimensions following orthodontic treatment involving either all four or all five premolar extractions.

METHODS

A sample of 68 participants, extracted from orthodontic records, underwent cephalometric analysis to quantify changes in pharyngeal airway dimensions. The study compared two groups: those treated with all four premolar extractions (n=34) and those treated with all five premolar extractions (n=34). Cephalometric radiographs taken before and after treatment were analyzed, focusing on airway width, length, and volume.

RESULTS

Preliminary findings indicate significant changes in airway dimensions within each group. In the all four premolar extraction group, there was a statistically significant decrease in airway width (p=0.02) and volume (p=0.04). Similarly, the all five premolar extraction group exhibited significant reductions in airway width (p=0.03) and volume (p=0.02). However, the between-group comparisons revealed no significant differences in changes between the two groups.

CONCLUSION

This study sheds light on the intricate relationship between orthodontic interventions, specifically premolar extractions, and changes in pharyngeal airway dimensions. While significant changes were observed within each group, the lack of significant differences between the all four and all five premolar extraction groups raises intriguing questions about the specific impact of premolar extraction patterns on the upper airway.

Impact of palatopharyngeal sizes changing on pharyngeal airflow fluctuation and airway vibration in a pediatric airway

Snoring is common in children and is associated with many adverse consequences. One must study the relationships between pharyngeal morphology and snoring physics to understand snoring progression. Although some model studies have provided fluid-structure interaction dynamic descriptions for the correlation between airway size and snoring physics, the descriptions still need to be further investigated in patient-specific airway models. Fluid-structure interaction studies using patient-specific airway structures complement the above model studies. Based on reported cephalometric measurement methods, this study quantified and preset the size of the palatopharynx airway in a patient-specific airway and investigated how the palatopharynx size affects the pharyngeal airflow fluctuation, soft palate vibration, and glossopharynx vibration with the help of a verified FSI method. The results showed that the stenosis anterior airway of the soft palate increased airway resistance and airway resistance fluctuations, which can lead to increased sleep effort and frequent snoring. Widening of the anterior airway can reduce airflow resistance and avoid obstructing the anterior airway by the soft palate vibration. The pharyngeal airflow resistance, mouth inflow proportion, and soft palate apex displacement have components at the same frequencies in all airway models, and the glossopharynx vibration and instantaneous inflow rate have components at the same frequencies, too. The mechanism of this same frequency fluctuation phenomenon can be explained by the fluid-structure interaction dynamics of an ideal coupled model consisting of a flexible plate model and a collapsible tube model. The results of this study demonstrate the potential of FSI in studying snoring physics and clarify to some degree the mechanism of airway morphology affecting airway vibration physics.

Bone Remodeling of Maxilla after Retraction of Incisors during Orthodontic Treatment with Extraction of Premolars Based on CBCT Study: A Systematic Review

Background: Incisor retraction is often a crucial phase in ongoing orthodontic treatment, with significant implications for alveolar remodeling mechanisms. There are two prevailing theories which seek to explain this. According to the first, teeth move with the bone, while according to the second, teeth move within the bone. This systematic review seeks to assess morphometric changes in the maxillary alveolar process resulting from incisor retraction following premolar extraction and to evaluate the potential for bone remodeling associated with orthodontic movement. Methods: The study was conducted following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The following electronic databases were searched: PubMed, Google Scholar, Web of Science EMBASE and the Cochrane Central Register of Controlled Trials. The databases were searched using the following keywords: "Bone remodeling and retraction of incisors", "Alveolar bone and incisor retraction", "Bone thickness and incisor retraction", and "Bone changes and orthodontic treatment". Search filters were utilized to identify relevant papers and articles written in English and published during the last 10 years. Based on the information provided in their abstracts, papers and articles were selected according to the following criteria: randomized clinical trials (RCTs), controlled clinical prospective trials (CCTs), and retrospective studies. Articles unrelated to the study's scope or failing to meet inclusion criteria were excluded. These generally comprised individual case reports, case series reports, literature reviews, experimental studies, studies with limited data (including conference abstracts and journal writings), studies involving an unrepresentative group of patients (less than 10 patients), studies concerning patients with syndromes, and animal experiments. The remaining articles which were deemed relevant underwent comprehensive reference review and such journals as the American Journal of Orthodontics, Dentofacial Orthopedics, International Orthodontics, Journal of Clinical Orthodontics, and Angle Orthodontist were manually searched. Results: Seven articles meeting the inclusion criteria articles were selected for final evaluation, with a total of 284 participants, including 233 women and 51 men. During the analysis of the results included in the publications, a lack of homogeneity was observed, rendering a reliable statistical analysis and heterogeneity assessment unobtainable. Noteworthy disparities in methodologies and measurements posed a risk of drawing inappropriate conclusions. Consequently, emphasis was placed on qualitative analysis, emphasizing the need for standardization in future studies of a similar nature, to enable valid and comparable analyses. Conclusions: The research findings incorporated in this review demonstrate that significant bone loss occurs because of incisor retraction, which diminishes distance between the bone surface and the root surface on the palatal aspect. The magnitude of this change may vary, contingent upon both the extent of incisor displacement and alterations in their inclination, thereby affecting the positioning of the root tips. This change is significantly higher in adults than in growing adolescents. The rationale behind this assertion lies in the widely recognized phenomenon of declining cellular activity with advancing age. The decrease in the speed and intensity of cellular changes may explain the diminished capacity for remodeling as patient age increases. There is ongoing discourse regarding alterations in the volume of bone on the labial aspect of the alveolar process. Further research is necessary to measure whether bone remodeling during orthodontic movement is contingent upon other factors, such as the speed and biomechanics of retraction, the level of applied orthodontic force, and the patient age.

Influence of second premolar extractions on the volume of the oral cavity proper: a control comparative cone-beam computed tomography volumetric analysis study

OBJECTIVES

To compare the pre- and postorthodontic treatment volumetric changes of the oral cavity proper (OCP) in extraction and nonextraction patients and to identify influencing variables.

MATERIALS AND METHODS

Pre- and posttreatment cone-beam computed tomography (CBCT) scans of patients undergoing orthodontic treatment with fixed labial appliances and who satisfied the inclusion criteria were individually landmarked. Linear, angular, and volumetric measurements were determined. Descriptive statistics, repeated measure analyses of variance, correlations, and stepwise regression statistical analyses were applied.

RESULTS

The CBCT scans of 54 patients who underwent the extraction of second premolars and/or extraction of second primary molars associated with agenic second premolars, and 59 nonextraction patients matched for crowding, were assessed. The mean age for both groups was 15 years. There was a statistically significant increase in the volume of the OCP for both the extraction and nonextraction groups, with the nonextraction group demonstrating a larger increase in the volume of the OCP. Gender, age, changes in mandibular and maxillary arch length, and changes in mandibular and maxillary intermolar width all influenced the change in the OCP volume.

CONCLUSIONS

The volume of the OCP increased in growing patients with and without the extraction of the second premolars and/or extraction of second primary molars associated with agenic second premolars. Patients who did not have extractions as part of their orthodontic treatment demonstrated a greater overall increase in OCP volume.

Effect of premolar extraction and anchorage type for orthodontic space closure on upper airway dimensions and position of hyoid bone in adults: a retrospective cephalometric assessment

Background

This study aimed to assess the effect of premolar extraction and anchorage type for orthodontic space closure on upper airway dimensions and position of hyoid bone in adults by cephalometric assessment.

Methods

This retrospective study was conducted on 142 cephalograms of patients who underwent orthodontic treatment with premolar extraction in four groups of (I) 40 class I patients with bimaxillary protrusion and maximum anchorage, (II) 40 class I patients with moderate crowding and anchorage, (III) 40 class II patients with maximum anchorage, and (IV) 22 skeletal class III patients with maximum anchorage. The dimensions of the nasopharynx, velopharynx, oropharynx, and hypopharynx, and hyoid bone position were assessed on pre- and postoperative lateral cephalograms using AudaxCeph v6.1.4.3951 software. Data were analyzed by the Chi-square test, paired t-test, and Pearson's correlation test (alpha = 0.05).

Results

A significant reduction in oropharyngeal, velopharyngeal, and hypopharyngeal airway dimensions was noted in groups I, III, and IV (P < 0.001), which was correlated with the magnitude of retraction of upper and lower incisors (r = 0.6 - 0.8). In group II, a significant increase was observed in oropharyngeal and velopharyngeal dimensions (P < 0.001). A significant increase in nasopharyngeal dimensions occurred in all groups (P < 0.001). Also, in groups I and III, the position of hyoid bone changed downwards and backwards, which was correlated with reduction in airway dimensions (r = 0.4 - 0.6).

Conclusion

According to the present results, extraction orthodontic treatment affects upper airway dimensions and hyoid bone position. Maximum anchorage decreases airway dimensions while moderate anchorage increases airway dimensions.

Evaluation of pharyngeal airway space after orthodontic extraction treatment in class II malocclusion integrating with the subjective sleep quality assessment

Orthodontic treatment with premolar extractions is typically used to relieve dental crowding and retract anterior teeth for lip profile improvement. The aim of the study is to compare the changes in regional pharyngeal airway space (PAS) after orthodontic treatment with Class II malocclusion and to identify the correlations between questionnaire results and PAS dimensions after orthodontic treatment. In this retrospective cohort study, 79 consecutive patients were divided into normodivergent nonextraction, normodivergent extraction, and hyperdivergent extraction groups. Serial lateral cephalograms were used to evaluate the patients' PASs and hyoid bone positions. The Pittsburgh Sleep Quality Index and STOP-Bang questionnaire were used for sleep quality evaluation and obstructive sleep apnea (OSA) risk assessment, respectively, after treatment. The greatest airway reduction was observed in hyperdivergent extraction group. However, the changes in PAS and hyoid positions did not differ significantly among three groups. According to questionnaire results, all three groups had high sleep quality and low risk of OSA, with no significant intergroup differences. Moreover, pretreatment-to-posttreatment changes in PAS were not correlated with sleep quality or risk of OSA. Orthodontic retraction with premolar extractions nither exhibit significant reduction in airway dimensions nor increase their risk of OSA.

Effects of vertical control on anatomic and aerodynamic characteristics of the oropharyngeal airway during premolar extraction treatment of Class II hyperdivergent nonsevere crowding malocclusion

INTRODUCTION

This study aimed to analyze the effects of premolar extraction treatment with vertical control on changes in the anatomy and aerodynamics of the oropharynx in Class II hyperdivergent malocclusion with nonsevere crowding.

METHODS

Thirty-nine patients with Class II hyperdivergent malocclusion were enrolled consecutively. All the participants underwent 4 premolar extractions. The high-pull J-hook and mini-implants were used to provide vertical control. Cone-beam computed tomography was performed before and after treatment. The participants were divided into a decreased lower vertical facial height group (n = 23) and an increased lower vertical facial height group (n = 16) on the basis of superimposition. The aerodynamic characteristics, including airway resistance (inspiration, R_in; expiration, R_ex) and maximum velocity (inspiration, Vmax_in; expiration, Vmax_ex) at inspiration and expiration, were calculated using computational fluid dynamics. Anatomic characteristics, including volume and cross-sectional area (CSA_min), were measured using the Dolphin Imaging software (Dolphin Imaging and Management Solutions, Chatsworth, Calif).

RESULTS

After treatment, the median volume and CSA_min increased by 2357 mm³ and 43 mm², respectively, and median R_in and Vmax_ex decreased by 0.15 Pa/L/min and 0.24 m×s^-1, respectively, in decreased lower vertical facial height group. In contrast, the median CSA_min decreased by 9.5 mm² in the increased lower vertical facial height group. All the changes were statistically significant (all P <0.05). Significant differences in volume, CSA_min, R_in, and Vmax_ex were observed between the 2 groups.

CONCLUSIONS

Vertical control might improve the anatomic and aerodynamic characteristics of the oropharyngeal airway during premolar extraction treatment of Class II hyperdivergent malocclusion with nonsevere crowding.

Dentoalveolar, skeletal, pharyngeal airway, cervical posture, hyoid bone position, and soft palate changes with Myobrace and Twin-block: a retrospective study

BACKGROUND

The primary aim of this study was to evaluate the dentoalveolar, skeletal, pharyngeal airway, cervical posture, hyoid bone position, and soft palate effects of the Myobrace and Twin-block appliances. The second was to compare them in terms of ease of use by assessing the factors that may influence patient compliance.

METHODS

The study included thirty-six Class II division 1 patients (19 females, 17 males; mean age, 12.14 ± 1.23) who had previously been treated in the Orthodontic Clinic at Sivas Cumhuriyet University Faculty of Dentistry. The patients were divided into two groups: Group 1: Myobrace (n = 18), and Group 2: twin block (n = 18). The effects of the appliances on the skeletal, dentoalveolar, soft tissue, craniocervical, and other anatomic structures were assessed using 46 measurements (22 linear and 24 angular), on pre and post-treatment cephalometric radiographs. AudaxCeph 5.0 software (Ljubljana, Slovenia) was used for the analysis. To analyze the changes after one year of treatment, a paired sample t-test and Wilcoxon signed-rank test were used. Intergroup comparison was performed using the Student t-test and the Mann-Whitney U test.

RESULTS

In the Myobrace and Twin-block groups, there was a significant increase in SNB (°) (p = 0.004, p = 0.001), IMPA (°) (p = 0.005, p = 0.001) and a significant drop in U1/SN (°) (p = 0.021, p = 0.005). The lengths of Cd-Gn (mm), Go-Pg (mm), and Cd-Go (mm) increased significantly in the Twin-block group (p = 0.003, p = 0.010, p = 0.001), whereas the Myobrace group did not change. Similarly, there was no significant difference in pharyngeal and soft palate measurements in the Myobrace group but a statistically significant decrease in SP length and angle in the Twin-block group (p = 0.001, p = 0.006). Increases in SN/OPT (°) (p = 0.032, p = 0.001) and SN/CVT (°) (p = 0.012, p = 0.001) were statistically significant in both groups. Myobrace was more difficult to use while sleeping, whereas the twin block caused more nausea.

CONCLUSIONS

Both appliances can be used for mandibular advancement. The Twin-block appliance, on the other hand, was more effective and patient-friendly.

Study of pharyngeal airway morphology with CBCT: Benefits of four premolar extraction orthodontic treatments

BACKGROUND AND AIM

Four premolars extractions are routine procedures for correction of malocclusion, but will inevitably lead to a reduction of tongue space, whether this will weaken the pharyngeal airway remains a controversy.

PATIENTS AND METHODS

Cone-beam computed tomography (CBCT) radiographs of 80 patients who completed four premolar extraction orthodontic treatments were collected and divided into three anteroposterior skeletal groups according to the ANB (angle subspinale to nasion to supramentale) value. Linear, angular, cross-sectional area, and volumetric dimensions of the pharyngeal airway were measured using Dolphin Imaging 11.9 software. One-way analysis of variance and Pearson's correlation coefficient test were performed to assess the intergroup comparisons. Treatment changes were evaluated with two-sample t-tests.

RESULTS

In intergroup comparisons, vertical linear and cross-sectional area differences were identified in S-Go/N-Me, VD1, VD1/N-Me, VD2/N-Me, AA, OAA and OMINI (p<0.05), while other measurements showed no significant differences. Angle2, the tilting degree of the pharyngeal airway, showed a positive correlation with ANB (p<0.05). As for the treatment changes, a significant increase was found in the pharyngeal airway in the Class I group (OUA p<0.05, VD1 p<0.001, VD2 p<0.05) and Class II group (VD1 p<0.001. VD2, p<0.05), and inversely, a significant decrease was found in the pharyngeal airway in the Class III group (OAA p<0.05, OMINI p<0.05, OUA p<0.05). No volumetric difference was identified. Interestingly, regarding the preoperative pharyngeal airway size, values trended to the mean value significantly.

CONCLUSION

Four premolar extraction orthodontic treatments did not affect the pharyngeal airway volume except for the vertical liner and cross-sectional area dimensions. The trend of the gold standard suggested a positive influence of four premolar extraction orthodontic treatments.

Adaptive Changes in the Posterior Pharyngeal Wall Following Large Retraction of Incisors During Comprehensive Orthodontic Treatment

OBJECTIVE

To evaluate the effects of large retraction of incisors on the adaptive changes in the posterior pharyngeal wall and soft palate during comprehensive orthodontic treatment.

METHODS

Twenty-seven females with Class I mild crowding or spacing who required non-extraction treatment (group I) and 34 females with Class I bimaxillary dentoalveolar protrusion who required all first premolars extraction for the retraction of their incisors (group II) were included in the study. The effects of non-extraction and incisor retraction following all first premolars extraction orthodontic treatment on the sagittal dimensions of pharyngeal airway passage and posterior pharyngeal wall thickness were evaluated from pre- and post-treatment cephalograms.

RESULTS

The dimensions of pharyngeal airway passage were comparable among the groups. The length of the soft palate increased (P < .01) and the thickness of the soft palate decreased (P < .01) following retraction of incisors, and the difference between the groups was significant (P < .05). The posterior pharyngeal wall thickness was reduced significantly at PPWT2 (P < .05), PPWT3 (P < .001), PPWT4 (P < .001), PPWT5 (P < .001), and PPWT6 (P < .01) regions following retraction of the incisors, and the difference between the groups was statistically highly significant.

CONCLUSIONS

The large retraction of incisors during comprehensive orthodontic treatment in Class I bimaxillary dentoalveolar protrusion malocclusion subjects did not affect the sagittal dimensions of pharyngeal airway passage, but the thickness of the posterior pharyngeal wall reduced significantly as an adaptation to maintain the patency of the upper airway.

Changes in hyoid bone and tongue position in Class I subjects after orthodontic treatment with rapid palatal expander

OBJECTIVE

To evaluate the effects of the rapid palatal expander (RPE) on the hyoid bone and tongue position in skeletal Class I patients, compared to control groups.

METHODS

Eighty-four Class I subjects, aged 6-14, were selected. Among these, 28 patients were treated with RPE, 28 with function-generating bite (FGB) appliance, and 28 were untreated. Lateral cephalograms taken before (T0) and after (T1) treatment were retrieved. Changes in the hyoid bone and tongue position were evaluated, and the area above the tongue was measured.

RESULTS

No significant difference in the hyoid and tongue posture was observed across the groups. However, there were significant differences for HC3 (distance from H-point to the third cervical vertebrae), H2H (distance from H-point to SN plane), and TT-Eb (tongue length) between T0 and T1 in all groups.

CONCLUSION

The results suggest that hyoid bone and tongue position changes were related to growth rather than treatment.

Change in the Constricted Airway in Patients after Clear Aligner Treatment: A Retrospective Study

This retrospective study evaluated changes in the pharyngeal portion of the upper airway in patients with constricted and normal airways treated with clear aligners (Invisalign, Align). Additionally, we assessed the change of tongue position in the oral cavity from a lateral view. Evaluation was performed with specialized software (Invivo 6.0, Anatomage) on pretreatment and post-treatment pairs of cone beam computed tomography imaging (CBCT) data. The level of airway constriction, volume, cross-section minimal area and tongue profile were evaluated. Patients with malocclusion, with pair or initial and finishing CBCT and without significant weight change between the scans, treated with Invisalign clear aligners were distributed into two groups. Group A consisted of fifty-five patients with orthodontic malocclusion and constricted upper airway. Control group B consisted of thirty-one patients with orthodontic malocclusions without any airway constriction. In the group with airway constriction there was a statistically significant increase in volume during therapy (p < 0.001). The surface of the most constricted cross-section of the airway did not change significantly after treatment in any of the groups. The final tongue position was different from the initial position in 62.2% of all clear aligner treatments. The position of the smallest clearance of the airway in the pharynx was similar for both groups localized at the level of 2nd cervical vertebra.

Oropharynx and hyoid bone changes in female extraction patients with distinct sagittal and vertical skeletal patterns: a retrospective study

Background

Previous studies have reported inconsistent effects of premolar extraction on the oropharynx and hyoid bones. Currently, no strong evidence is available regarding the effect of extraction on upper airway size. Hence, the aim of this study was to analyse the effects of first premolar extraction on the oropharynx and hyoid bone positions in female adult patients, and further explored differences in oropharynx and hyoid bone changes among skeletal patterns.

Methods

The study population included 40 female adult patients who did not undergo extraction and 120 female adult patients who underwent extraction of four premolars; the including patients had four distinct sagittal and vertical skeletal patterns. Cone-beam computed tomography was performed before (T0) and after (T1) orthodontic treatment. Eight oropharynx variables and five hyoid bone variables were measured using Dolphin 3D Imaging software. Paired and independent t-tests were used to analyse measurements between timepoints and groups, respectively.

Results

The oropharynx volume increased significantly in the extraction group; changes did not differ significantly between extraction and non-extraction groups. Oropharynx variables did not differ significantly at T0 among the four skeletal pattern groups. After orthodontic extraction treatment, the oropharynx volume increased significantly in the class I-norm and class I-hyper subgroups, but not in the class II-norm and class II-hyper subgroups. Significant increases were observed in the oropharynx volume and most constricted axial area from T0 to T1 in the moderate retraction group, but not in the maximum retraction group. Extraction patients exhibited significant posterior movement of the hyoid, particularly among maximum retraction patients.

Conclusions

In female adult patients, first premolar extraction tends to increase the oropharynx size and cause posterior movement of the hyoid bone, particularly in skeletal class I patients. For skeletal class II and hyperdivergent patients with a narrow oropharynx, first premolar extraction does not negatively influence oropharynx size or hyoid bone position. The differences of oropharyngeal changes between moderate retraction patients and maximum retraction patients were not significant.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13005-022-00334-1.

Three-dimensional evaluation of hyoid bone position in nasal and mouth breathing subjects with skeletal Class I, and Class II

BACKGROUND

This retrospective study investigated the effect of breathing pattern, skeletal class (Class I, Class II), and age on the hyoid bone position (HBP) in normodivergent subjects.

METHODS

A total of 126 subjects (61 males, 65 females) aged 7-9 years and 10-12 years were scanned using cone-beam computed tomography (CBCT). All participants were classified according to the anteroposterior skeletal pattern into (Class I, Class II). Each skeletal group was further divided according to the breathing mode into mouth breathers (MB) and nasal breathers (NB). The HBP was measured accordingly. Independent sample t-test and Mann Whitney U test were used to detect significant differences between the groups, and binary logistic regression was used to identify MB predictive indicators.

RESULTS

The breathing mode and skeletal class affected the vertical HBP in subjects with 7-9 years, while they affected the anteroposterior HBP in subjects with 10-12 years. Regarding the age effect, hyoid bone was located more anteriorly in the older NB subjects, and hyoid bone was more inferiorly in the older age group. A regression equation of the significant variables was formulated, C3-Me (P: 001, OR: 2.27), and H-EB (P: 0.046, OR: 1.16) were positively correlated with occurrence of MB.

CONCLUSION

There were significantly different HBPs among subjects with different anteroposterior skeletal classes, breathing modes, and age cohorts. Moreover, C3-Me, and H-EB were significant predictors and correlated with increased likelihood of being MB subject.

Relationship between craniofacial and dental arch morphology with pharyngeal airway space in adolescents

PURPOSE

The aim of the study was to investigate a possible relationship between pharyngeal airway space, craniofacial variables, and dental arch form in adolescents grouped by sex.

METHODS

This cross-sectional study included 108 adolescents aged between 12 and 17 years. Lateral cephalometric radiographs were used to analyze sagittal craniofacial variables and the pharyngeal airway space. For evaluation of the dental arch form, we used plaster models. Statistical analysis included Student's t‑test and Pearson's correlation coefficient (r).

RESULTS

Maxillary length was directly proportional to upper nasopharyngeal airway dimensions in males (r = 0.312, p = 0.021) and females (r = 0.310, p = 0.022). In the female group, upper oropharyngeal measurements showed an inverse correlation with a labial inclination of the upper incisors (r = -0.415, p = 0.001), protrusion of the upper incisors (r = -0.364, p = 0.006), and soft palate thickness (r = -0.27, p = 0.043). In the male group, upper nasopharynx measurements showed an inverse correlation with soft palate thickness (r = -0.277, p = 0.042). The upper arch form appeared to be related to oropharyngeal measurements in females, while the lower arch form was related to oropharyngeal dimensions in males.

CONCLUSION

The findings suggest that there are sex-dependent correlations of the nasopharyngeal and oropharyngeal airway space with the sagittal craniofacial morphology and the transversal dental arch form.

Upper Airway Changes in Diverse Orthodontic Looms: A Systematic Review and Meta-Analysis

Upper airway assessment is particularly important in the daily work of orthodontists, because of its close connection with the development of craniofacial structures and with other pathologies such as Obstructive Sleep Apnea Syndrome (OSAS). Three-dimensional cone-beam computed tomography images provide a more reliable and comprehensive tool for airway assessment and volumetric measurements. However, the association between upper airway dimensions and skeletal malocclusion is unclear. Therefore, the current systematic review evaluates the effects of different surgical movements on the upper airway. Materials and Methods: Medline (PubMed, OVID Medline, and EBSCO), Cochrane Library (Cochrane Review and Trails), Web of Knowledge (social science, and conference abstracts), Embase (European studies, pharmacological literature, and conference abstracts), CINAHL (nursing and allied health), PsycInfo (psychology and psychiatry), SCOPUS (conference abstracts, and scientific web pages), and ERIC (education) databases were searched. Two authors independently performed the literature search, selection, quality assessment, and data extraction. Inclusion criteria encompassed computed tomography evaluations of the upper airway spaces with retrospective, prospective, and randomised clinical trial study designs. To grade the methodological quality of the included studies a GRADE risk of bias tool was used. Results and conclusion: In total, 29 studies were included. Among these, 17 studies had a low risk of bias, whereas 10 studies had a moderate risk of bias. A meta-analysis was performed with the mean differences using a fixed-effects model. Heterogeneity was assessed with the Q-test and the I2 index. The meta-analysis revealed significant (p ≤ 0.001, 95% confidence interval) increases in upper airway volume after rapid maxillary expansion and surgical advancement for the correction of Class II.

Comparison of anthropometric and conic beam computed tomography measurements of patients with and without difficult intubation risk according to modified mallampati score: New markers for difficult intubation

Background

The aim of this study was to compare the anthropometric and cone beam computed tomography (CBCT) measurements taken from risk-free and risky groups by using the modified Mallampati score (MMS).

Patients and Methods

A total of 176 volunteers between the ages of 18 and 65 in four different MMS classes were included in the study. The patients in classes MMS I and MMS II were accepted as risk-free and the patients in classes MMS III and MMS IV were accepted as risky for intubation. The Mann-Whitney U test was performed on the data to compare the anthropometric and radiological measurements taken from the risk-free and risky groups. A receiver operating characteristic (ROC) analysis was applied to the parameters that had a statistically significant difference.

Results

According to the analysis results, statistically significant differences were found in the neck circumference (NC), maximum interincisal distance (MID), thyromental distance (TMD) and sternomental distance (SMD) of the anthropometric measurements of men and women between the risk-free and risky groups (P < 0.05). In terms of CBCT measurements, the thickness of the tongue (TT), distance between the uvula and posterior wall of pharynx (U-Ph), distance between posterior nasal spine and nasopharynx (Snp-Nph) and length of the epiglottis (LE) were found to have statistically significant differences between the risk-free and risky groups of men and women (P < 0.05).

Conclusion

The NC, MID, TMD and SMD anthropometric measurements and TT, U-Ph, Snp-Nph and LE radiologic measurements were found to support MMS, which is one of the most widely used bedside intubation prediction tests. In addition to the inclusion of CBCT for intubation prediction, U-Ph and Snp-Nph radiologic measurements were added as difficult intubation markers.

Match of the Bimaxillary Basal Bone Arches and Its Variations among Individuals

INTRODUCTION

This study is aimed at illustrating the bimaxillary basal bone contours, to clarify the match of the basal bone arches of the upper and lower, especially the posterior segments, including the second molar and retromolar region.

METHODS

Based on 100 cone-beam computed tomography (CBCT) images (50 males and 50 females), we obtained 100 pairs of basal bone arches, which were the horizontal inner cortex contours passing the furcation of the first molar paralleled to the lower occlusal plane. The Generalized Procrustes Analysis (GPA) was applied to depict average contours and calculate the ratio and difference width of both upper and lower dental arches in different positions. Variations of the basal bone morphology among individuals were revealed using Principal Component Analysis (PCA).

RESULTS

The width discrepancy occurred at 7-7 segment (male: upper 65.62 mm and lower 68.81 mm and female: upper 62.98 mm and lower 68.38 mm) and the retromolar region (male: upper 64.67 mm and lower 71.96 mm and female: upper 62.34 mm and lower 71.44 mm). The ratio (p = 0.006) and difference value (p = 0.009) of 7-7 segment and the ratio of retromolar region (p = 0.044) differed in genders. Setting 2 mm overjet, the upper basal bone arch was wider than the lower by approximate 2 mm on both sides, except the second molar and retromolar region. According to PCA, the variation of basal bone arches appeared mainly at terminal segments.

CONCLUSIONS

For both male and female, the bimaxillary basal bone matched except terminal segments. Mismatch of female bimaxillary posterior basal bone was more pronounced than male. The basal bone arches of male were wider and longer than that of female.

Extraction vs. Nonextraction on Soft-Tissue Profile Change in Patients with Malocclusion: A Systematic Review and Meta-Analysis

Objectives

We aimed to summarize the current evidence regarding the impact of extraction vs. nonextraction in orthodontic treatment on patients' soft-tissue profile with malocclusion.

Methods

Between April 30^th and November 30^th, 2020, we searched PubMed and SCOPUS for published papers from inception to November 2020 using "orthodontic," "extraction," "nonextraction," and "Malocclusion." Included studies were summarized, and relevant data were extracted and analyzed using Review Manager 5.4.

Results

Pooled data from four controlled trials demonstrated a nonsignificant difference between extraction and nonextraction in terms of SNA (MD = 0.50, 95% CI: -0.37, 1.38; p = 0.26), SNB (MD = 0.11, 95% CI: -1.23, 1.44; p = 0.88), FMA (MD = 1.82, 95% CI: -2.39, 6.02; p = 0.40), IMPA (MD = 0.06, 95% CI: -8.83, -8.94; p = 0.99), overjet (MD = -1.47, 95% CI: -6.21, 3.26; p = 0.54), and overbite (MD = 0.50, 95% CI: -1.40, 2.40; p = 0.60). On the other hand, the extraction method significantly increased the ANB compared with the nonextraction group (MD = 0.78, 95% CI: 0.25, 1.31; p = 0.004).

Conclusion

The current evidence demonstrated that nonextraction protocols for orthodontic treatment are a safe and effective alternative to extraction protocols; individually tailored treatment strategies should be applied. More randomized controlled trials are critically needed to safely make an evidence-based treatment conclusion.

Pharyngeal airway dimensional changes after orthodontic treatment with premolar extractions: A systematic review with meta-analysis

INTRODUCTION

The objective of this research was to evaluate the effect of orthodontic extraction on the pharyngeal airway volume and Minimum cross-sectional area (MCA) in growing and adult patients.

METHODS

Seven databases, unpublished gray literature, and the references list of the identified articles were electronically searched for relevant studies that met our eligibility criteria. Included studies assessed the effect of dental extraction or sagittal dental movements on pharyngeal airway dimensions. The quality of the included studies was assessed using the methodological index for nonrandomized studies. In addition, a meta-analysis was conducted using the RevMan 5 (Nordic Cochrane Centre, Cochrane Collaboration, Copenhagen, Denmark).

RESULTS

In 7 studies, 268 treated patients with a mean age of 19.1 ± 7.6 years and 342 nonextraction control group subjects with a mean age of 19.3 ± 7.2 years were included. Compared with the control group, no statistically significant difference was found in total, nasopharyngeal, glossopharyngeal, oropharyngeal volume, or MCA (P >0.05) in the extraction group except in oropharyngeal volume in which a statistically significant increase in the volume 0.41 cm³ (95% CI, 0.05-0.80; P = 0.03) was detected. The clinical significance of this increase is questionable. Included studies showed a moderate to high risk of bias.

CONCLUSIONS

There is no strong evidence to support the concept that premolar extractions in bimaxillary protrusion or crowded growing and adult patients reduce either pharyngeal airway volume or MCA. Moreover, as the level of evidence was considered very low for all variables, the magnitude, and direction of the summaries have to be interpreted with caution. Future studies with better quality could significantly affect the direction and strength of the results.

TRIAL REGISTRATION NUMBER

PROSPERO CRD42018089924.

Effect of extraction treatment on upper airway dimensions in patients with bimaxillary skeletal protrusion relative to their vertical skeletal pattern

Objective

To investigate dimensional changes in regional pharyngeal airway spaces after premolar extraction in bimaxillary skeletal protrusion (BSP) patients according to vertical skeletal pattern, and to further identify dentoskeletal risk factors to predict posttreatment pharyngeal changes.

Methods

Fifty-five adults showing BSP treated with microimplant anchorage after four premolar extractions were included in this retrospective study. The subjects were divided into two groups according to the mandibular plane steepness hyperdivergent (Frankfort horizontal plane to mandibular plane [FH-MP] ≥ 30) and nonhyperdivergent groups (FH-MP < 30). The control group consisted of 20 untreated adults with skeletal Class I normodivergent pattern and favorable profile. Treatment changes in cephalometric variables were evaluated and compared. The association between posttreatment changes in the dentoskeletal and upper airway variables were analyzed using linear regression analysis.

Results

The BSP patients showed no significant decrease in the pharyngeal dimensions to the lower level in comparison with controls, except for middle airway space (MAS, p < 0.01). The upper airway variable representing greater decrease in the hyperdivergent group than in the nonhyperdivergent group was the MAS (p < 0.01). Posttreatment changes in FH-MP had negative correlation with changes in MAS (β = –0.42, p < 0.01) and inferior airway space (β = –0.52, p < 0.01) as a result of multivariable regression analysis adjusted for sagittal skeletal relationship.

Conclusions

Decreased pharyngeal dimensions after treatment in BSP patients showed no significant difference from the normal range of pharyngeal dimensions. However, the glossopharyngeal airway space may be susceptible to treatment when vertical dimension increased in hyperdivergent BSP patients.

Effects of miniscrew-assisted orthodontic treatment with premolar extractions on upper airway dimensions in adult patients with Class II high-angle malocclusion

INTRODUCTION

The primary aim of this study was to investigate the change in upper airway dimensions and in mandibular position after miniscrew-assisted treatment with premolar extractions in adult patients with Class II high-angle malocclusion. The secondary aim was to determine the correlation between changes in upper airway dimensions and changes in mandibular position in these patients.

METHODS

Eighteen adult patients with Class II high-angle malocclusion (mean ± standard deviation age = 21.2 ± 2.9 years) were selected retrospectively. All patients underwent 4 premolar extractions, and 2 miniscrews were implanted in the maxilla to intrude molar height. Cone beam computed tomography images were taken pretreatment and posttreatment for every patient. The primary outcome variable for the upper airway was the minimal cross-sectional area of the upper airway (CSA_min), and the primary outcome variables for the mandible were mandibular rotation (Mp-SN angle), mandibular horizontal position (SNB angle), and mandibular vertical position (ANS-Me distance).

RESULTS

The CSA_min significantly increased by 47.2 mm² (t = -2.26, P = 0.04) after orthodontic treatment. The mandible significantly rotated counterclockwise by 0.9° (t = 2.20, P = 0.04) after treatment, which consisted of forward movement of 1.2° (t = -4.30, P = 0.00) and upward movement of 1.3 mm (Z = -1.98, P = 0.05). Furthermore, the change of the CSA_min showed a significant correlation with the change of the ANS-Me (P = 0.01).

CONCLUSIONS

By using miniscrews to intrude maxillary molars, orthodontic premolar extraction treatment results in mandibular counterclockwise rotation, and upper airway dimensions increase in Class II high-angle young adult patients. The increase of the upper airway dimensions significantly correlates to the upward movement of the mandible.

Total maxillary arch distalization with modified C-palatal plates in adolescents: A long-term study using cone-beam computed tomography

INTRODUCTION

The aims of this study were to evaluate the long-term skeletodental effects, the volume of maxillary tuberosity, and airway space changes after maxillary molar distalization using modified C-palatal plate (MCPP) in adolescents with Class II malocclusion.

METHODS

The sample consisted of 20 adolescent patients (MCPP group; mean age, 12.9 ± 1.0 year) who underwent bilateral distalization of their maxillary dentition and 20 subjects as a control group. In the MCPP group, cone-beam computed tomography images were taken before distalization, at the end of the treatment, and during retention with a minimum of a 3-year posttreatment follow up period. Repeated measures ANOVA followed by post-hoc analysis with the Bonferroni test were used to identify significant differences between time points.

RESULTS

After the long-term observation period, sagittal skeletal and dental relationships were maintained (there were no significant changes in ANB, occlusal plane angle, and overjet postretention). The vertical skeletal dimension did not change during treatment and was stable at the long-term follow-up (the mandibular plane angle and ANS-Me were relatively well maintained). The volume of the maxillary tuberosity showed no significant change during long-term retention. However, the volume was significantly smaller in the treatment group than in the control group (P <0.0001). There were no significant airway space changes after distalization and the postretention period. In addition, there was no significant difference between the MCPP and control groups.

CONCLUSIONS

Improved sagittal skeletal and dental relationships because of treatment were maintained in the long-term evaluation. There was no negative long-term effect on airway space associated with the maxillary arch distalization. Therefore, these findings might be beneficial for clinicians in diagnosis and treatment planning for Class II malocclusion in adolescents.

Displacement in root apex and changes in incisor inclination affect alveolar bone remodeling in adult bimaxillary protrusion patients: a retrospective study

BACKGROUND

Periodontal health is of great concern for periodontists and orthodontists in the inter-disciplinary management of patients with bimaxillary protrusion. The aim of present study is to investigate changes in the alveolar bone in the maxillary incisor region and to explore its relationship with displacement of root apex as well as changes in the inclination of maxillary incisors during incisor retraction.

METHODS

Samples in this retrospective study consisted of 38 patients with bimaxillary protrusion. Cone-beam computed tomography (CBCT) images was taken before(T0) and after (T1) treatment. Alveolar bone thickness (ABT), height (ABH) and area (ABA) were utilized to evaluate changes in the alveolar bone, while incisor inclination and apex displacement were used to assess changes in the position of maxillary central and lateral incisors. Correlations between alveolar bone remodeling and apex displacement as well as changes in the inclination were investigated.

RESULTS

The labial ABT of central and lateral incisors at the mid-root third was increased. In contrast, the palatal ABT at crestal, mid-root and apical third level were consistently decreased. ABH was not altered on the labial side, while significantly decreased on the palatal side. ABA was not significantly increased on the labial side, but significantly decreased on the palatal side, leading to a significantly reduced total ABA. Orthodontic treatment significantly reduced inclination of upper incisors. Changes in the amount (T1-T0) of ABA was remarkably correlated with apex displacement and changes of inclination (T1-T0); in addition, using the multivariate linear regression analysis, changes of ABA on the palatal side (T1-T0) can be described by following equation: Changes of palatal ABA (T1-T0) = - 3.258- 0.139× changes of inclination (T1-T0) + 2.533 × apex displacement (T1-T0).

CONCLUSIONS

Retraction of incisors in bimaxillary protrusion patients may compromise periodontal bone support on the palatal side. An equation that incorporated the displacement of root apex and change in the incisor inclination may enable periodontist-orthodontist interdisciplinary coordination in assessing treatment risks and developing an individualized treatment plan for adult patients with bimaxillary protrusion. Moreover, the equation in predicating area of alveolar bone may reduce the risks of placing the teeth out of the bone boundary during 3D digital setups.

Evaluation of the airway space changes after extraction of four second premolars and orthodontic space closure in adult female patients with bimaxillary protrusion - A retrospective study

Background & objectives

Previous studies have found that first premolar extractions during orthodontic treatment may alter the upper airway dimensions. The objective of this study is to investigate the effects of second premolar extraction during orthodontic treatment on the dimensions of the upper airway in a sample of female adults.

Methods

Twenty-nine female adult patients with ages between 18 and 30 years old and incisor bimaxillary protrusion were included in this study. They were treated with comprehensive orthodontic treatment which included the extraction of four second premolars. Pre and post cephalometric radiographs were analyzed using Dolphin imaging software for changes in tongue length and height, soft palate thickness and length, the superior, middle, and inferior airway space, and vertical airway length. Descriptive statistics were used to characterize measurements. Student’s paired t-test was preformed to compare the pre- and post-test mean values of the dimensions.

Results

A significant increase in the vertical airway length was observed after the extraction of the second premolars (p = 0.02). The soft palate length showed a tendency towards an increase that did not reach statistical significance (p = 0.053). No other significant changes in the airway soft tissue measurements were observed. The proclination and protrusion of the upper and lower incisors were significantly decreased compared to pre-treatment measurements.

Interpretation & conclusions.

Orthodontic treatment involving the extraction of all four second premolars in females with bimaxillary protrusion increases the vertical airway length, which is the amount of distance between base of the tongue and posterior nasal spine. No other significant alterations in the upper airway measurements were observed.

Airway and cephalometric changes in adult orthodontic patients after premolar extractions

OBJECTIVE

To examine changes in the airway and cephalometric measurements associated with orthodontic treatment of adults with and without premolar extractions. The study investigated whether extractions had a direct or indirect effect on the airway and examined selected skeletal and dental features.

MATERIALS AND METHODS

This retrospective study used pre- (T1) and posttreatment (T2) cone-beam computed tomography scans of 83 adult patients matched for age and sex. A total of 15 airway and 10 skeletal and dental measures were analyzed by means of repeated-measures analysis of variance.

RESULTS

There were no results showing that extractions affected airway dimensions that could not be accounted for as reflections of measurement error. There was no evidence that extractions affected the airway indirectly through skeletal and dental changes. There were strong and consistent findings that patients with small airways showed larger ones after treatment and that patients with large airways showed smaller ones later. These effects were independent of whether or not extractions were part of treatment. The measurement phenomena of regression toward the mean and of differential unfolding of natural changes over time could have accounted for the results observed.

CONCLUSIONS

There was no evidence that extractions in nongrowing patients have negative consequences on the size of various airway measures in the nasopharynx, retropalatal, or retroglossal regions.

Maxillomandibular advancement surgery after long-term use of a mandibular advancement device in a post-adolescent patient with obstructive sleep apnea

Patients with obstructive sleep apnea (OSA) whose phenotype belongs to a craniofacial vulnerability are referred from sleep doctors to orthodontists. In adults, for osseo-pharyngeal reconstruction (OPR) treatment, permanent maxillomandibular advancement (MMA) surgery and use of a temporary mandibular advancement device (MAD) are applied. This case report demonstrates successful treatment of OSA through application of phased MAD and MMA in a 16-year-old male with craniofacial deformity and residual growth potential. This patient showed skeletal and dentoalveolar changes after 7-year MAD use throughout post-adolescence, which affected the design and timing of subsequent MMA surgery, as well as post-surgical orthodontic strategy. This case report suggests that OPR treatment can be useful for treatment of OSA in post-adolescent patients, from an orthodontic point of view, in close collaboration with sleep doctors for interdisciplinary diagnosis and treatment.

Effects of bicuspid extractions and incisor retraction on upper airway of Asian adults and late adolescents: A systematic review

OBJECTIVES

This systematic review aimed to assess the effects of bicuspid extractions and incisor retraction on airway dimension, hyoid position and breathing of adults and late adolescents.

METHODS

The review was conducted according to PRISMA guidelines. Eight databases including PubMed, EMBASE, Web of Science and Scopus were searched to August 2018. Minimum age of participants was 16 years. The intervention was dual-arch bicuspid extractions with incisor retraction. Outcomes were airway dimension, hyoid position and breathing assessment.

RESULTS

All nine publications meeting inclusion criteria were from Asia. They were divided into three Asian subregions. All East Asian lateral cephalometric studies reported anteroposterior airway narrowing at the oropharynx and sometimes the hypopharynx. However, the narrowing was small, comparable to measurement errors, and highly variable. Two out of three East Asian computed tomography (CT) studies described reductions in airway dimensions. The single functional breathing study showed increased simulated flow resistance after incisor retraction in East Asians. South Asian studies had mixed findings, with some reporting significant airway narrowing. The single study from West Asia found no significant airway or hyoid changes.

CONCLUSIONS

Airway response to bicuspid extractions and incisor retraction varied substantially when assessed with cephalometry. CT measurements present larger effect sizes and smaller variations, providing stronger evidence of airway narrowing. Orthodontic extractions for incisor retraction may be more frequently indicated in Asia, and East Asians seem particularly susceptible to airway narrowing and postero-inferior hyoid movement with incisor retraction. Better designed CT studies are needed for confirmation due to small effect size and large variability.

Airway increase after open bite closure with temporary anchorage devices for intrusion of the upper posteriors: Evidence from 2D cephalometric measurements and 3D magnetic resonance imaging

OBJECTIVE

The aim of this study was to analyse morphological changes in the upper airways in patients with anterior open bite treated with temporary anchorage devices for intrusion of upper posterior teeth.

MATERIALS AND METHODS

Twelve nonobese (body mass index: <25) anterior open bite patients between the ages of 19 and 44 years (mean age: 22.83 ± 8.19 years) were recruited for this study. Cephalometric radiographs and magnetic resonance imaging (MRI) scans before and after anterior bite closure without bracketing on anterior teeth were used to measure the upper airway, which was divided into retropalatal and retroglossal regions.

RESULTS

The mandibular plane angle and lower facial height were significantly reduced by intrusion of the upper posteriors and autorotation of the mandible. The retroglossal airway width (AW2) and retroglossal area (RG area) measured on cephalometric radiographs both increased significantly after treatment. Retroglossal volume increased and the retroglossal width/length ratio decreased significantly in MRI analysis. All other measurements were not significantly changed. However, no statistically significant correlations were observed between all measurements in 2D and 3D images, with the exception of the AW2 linear measurement in 2D images correlating with the AP length in MRI axial view images (r = 0.56, P = 0.0430).

CONCLUSION

Counterclockwise rotation of the mandible after anterior open bite closed using orthodontic treatment changed the airway morphology. Retroglossal volume significantly increased and the airway shape became less elliptical after bite closure.

Pharyngeal airway dimensional changes after premolar extraction in skeletal class II and class III orthodontic patients

OBJECTIVE

To assess and compare the changes in pharyngeal airway space dimensions following orthodontic treatment of skeletal class II and class III facial deformities with premolar extraction.

MATERIALS AND METHODS

Sixty pre and posttreatment lateral cephalometric radiographs of patients who underwent fixed orthodontic treatment with premolar extraction were collected. The sample was divided into two groups - 32 patients with skeletal class II and 28 patients with skeletal class III malocclusion. Both groups were subdivided into growing patients (<16 years old) and adults (>16 years old). Nasopharyngeal, palatopharyngeal, and glossopharyngeal airway space dimensions were measured in the pretreatment (T0) and posttreatment (T1) cephalometric radiographs using Dolphin Imaging 11.7 software. Two-way, repeated-measures analysis of variance was used to assess the in-treatment changes.

RESULTS

Nasopharyngeal airway dimension showed similar significant increase in class II (P = 0.042) and class III (P = 0.049) patients from T0 to T1, whereas palatopharyngeal and glossopharyngeal dimensions were insignificantly decreased in both groups. However, both malocclusions followed the same pattern of changes in relation to airway dimensions. In addition, no significant statistical difference was found in the airway spaces between growing and adult patients.

CONCLUSIONS

Extraction of premolars did not affect the pharyngeal dimensions except those of the nasopharynx, which showed a significant increase after extraction in both groups.

Three-dimensional evaluation of maxillary dentoalveolar changes and airway space after distalization in adults

OBJECTIVES

To evaluate the changes in position of the maxillary dentition and the airway space after distalization using a modified C-palatal plate (MCPP) in adult patients through CBCT images and to analyze the relationship between the amount of distalization and the changes in the airway space.

MATERIALS AND METHODS

CBCT images of 33 adult Class II patients (22.2 ± 4.0 years old; 27 women and 6 men) treated by total maxillary arch distalization using the MCPP were evaluated before and after distalization. The patients were divided into nonextraction and extraction groups. The changes in the airway space as well as the changes in the positions of the maxillary dentition were evaluated. The distalization effects were calculated and assessed using paired t-tests.

RESULTS

After distalization, the first molar showed significant distalization and intrusion ( P < .001) with no significant rotation of the crown and no significant buccal displacement of its root in the transverse dimension. There were no significant changes in the airway volume or the minimum cross-sectional area of the oropharynx.

CONCLUSIONS

The application of the MCPP resulted in significant total arch distalization without a significant effect on the transverse dimensions or changes in the oropharynx airway space. The MCPP can be considered a viable treatment option for patients with Class II malocclusion.

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.

Computational fluid dynamics simulation of the upper airway response to large incisor retraction in adult class I bimaxillary protrusion patients

The changes of the upper airway after large retraction of the incisors in adult class I bimaxillary protrusion patients were assessed mainly focused on the anatomic variation and ignored the functional changes. This study aimed to investigate the changes of the upper airway in adult class I bimaxillary protrusion patients after extraction treatment using the functional images based on computational fluid dynamics (CFD). CFD was implemented after 3D reconstruction based on the CBCT of 30 patients who have completed extraction treatment. After treatment, pressure drop in the minimum area, oropharynx, and hypopharynx increased significantly. The minimum pressure and the maximum velocity mainly located in the hypopharynx in pre-treatment while they mostly occured in the oropharynx after treatment. Statistically significant correlation between pressure drop and anatomic parameters, pressure drop and treatment outcomes was found. No statistical significance changes in pressure drop and volume of nasopharynx was found. This study suggested that the risk of pharyngeal collapsing become higher after extraction treatment with maximum anchorage in bimaxillary protrusion adult patients. Those adverse changes should be taken into consideration especially for high-risk patients to avoid undesired weakening of the respiratory function in clinical treatment.

Effect of orthodontic treatment on the upper airway volume in adults

INTRODUCTION

The aim of this study was to examine the effects of orthodontic treatment with and without extractions on the anatomic characteristics of the upper airway in adults.

METHODS

For this retrospective study, the pretreatment and posttreatment cone-beam computed tomography scans of 74 adult patients meeting defined eligibility criteria were analyzed. Imaging software was used to segment and measure upper airway regions including the nasopharynx, the retropalatal, and retroglossal areas of the oropharynx, as well as the total airway. The Wilcoxon signed rank test was used to compare volumetric and minimal cross-sectional area changes from pretreatment to posttreatment.

RESULTS

The reliability values were high for all measurements, with intraclass correlation coefficients of 0.82 or greater. The volumetric treatment changes for the extraction and nonextraction groups were as follows: total airway, 1039.6 ± 3674.3 mm³ vs 1719.2 ± 4979.2 mm³; nasopharynx, 136.1 ± 1379.3 mm³ vs -36.5 ± 1139.8 mm³; retropalatal, 412.7 ± 3042.5 mm³ vs 399.3 ± 3294.6 mm³; and retroglossal, 412.5 ± 1503.2 mm³ vs 1109.3 ± 2328.6 mm³. The treatment changes in volume or minimal cross-sectional area for all airway regions examined were not significantly (P >0.05) different between the extraction and nonextraction groups.

CONCLUSIONS

Orthodontic treatment in adults does not cause clinically significant changes to the volume or the minimally constricted area of the upper airway. These results suggest that dental extractions in conjunction with orthodontic treatment have a negligible effect on the upper airway in adults.

[Effect of dental arch length decrease during orthodontic treatment in the upper airway development. A review]

INTRODUCTION

A possible relation between an upper airway space decrease and the development of obstructive sleep apnea syndrom explains the importance to know the effect of the modification of dental arch length on the upper airway during orthodontic treatment.

OBJECTIVES

The aim of this article is to expose recent knowledge about upper airway development and dental arch length decrease factors, to determine the influence of this decrease on upper airway development.

METHODS

A review was done to determine the upper airway normal development, to define dental arch to specify if an ideal position of dental arch on apical base exists. All of the length dental arch decrease factors during orthodontic treatment (dental extraction, dental agenesis and dental malpositions) and their upper airway resounding were searched.

RESULTS

Some authors found a diminution of upper airway space after premolars extractions while others didn't found this diminution after extractions premolars when incisor retraction is finished. A decrease of transversal maxillary diameter and nasal cavity may be due to absence of permanent teeth.

CONCLUSION

The effect of dental arch length decrease during orthodontic treatment in the upper airway development was not scientifically proved. However we had to be vigilant and adapt our orthodontic treatment case by case to avoid an upper airway modification.

Effect of retraction of anterior teeth on pharyngeal airway and hyoid bone position in Class I bimaxillary dentoalveolar protrusion

BACKGROUND

To test the hypothesis that the retraction of anterior teeth has no effect on the dimensions of pharyngeal airway and to evaluate the retraction of anterior teeth on each parameter of pharyngeal airway.

METHODS

Twenty-two adult patients of Class I bimaxillary protrusion requiring first premolar extractions with maximum anchorage requirements were selected. The pharyngeal airway and dentofacial parameters of the patients were compared using pre- and post-treatment lateral cephalograms with the help of Student's paired t-test (P < 0.05). The relationship between airway size and dentofacial parameters was also evaluated using Pearson correlation coefficient.

RESULTS

The upper and lower lips were retracted by 2.25 and 5.4 mm after retraction of the incisors. The tips of upper and lower incisors were retracted by 7.75 and 7.15 mm, respectively. There was a statistically significant decrease in SPP-SPPW (P < 0.05), U-MPW (P < 0.001), TB-TPPW (P < 0.001), and change in HRGN (P < 0.01). A significant correlation was observed between the amount of retraction of lower incisor and decrease in the pharyngeal airway posterior to soft palate (r = 0.102), tongue (r = 0.322), and change in HRGN (r = 0.265).

CONCLUSIONS

The size of the pharyngeal (velopharyngeal and glossopharyngeal) airway reduced and hyoid bone position changed after retraction of the incisors in extraction space in bimaxillary protrusive adult patients.

There is Insufficient Evidence that Upper Airway Dimension Changes after Four Premolar Extraction Orthodontic Treatment

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION

The effect of teeth extraction for orthodontic treatment on the upper airway: a systematic review. Hu Z, Yin X, Liao J, Zhou C, Yang Z, Zou S. Sleep Breath 2015;19(2):441-51.

SOURCE OF FUNDING

The review was supported by the National Nature Science Foundation of China and the Research Fund for the Doctoral Program of Higher Education in China.

TYPE OF STUDY/DESIGN

Systematic review.

Airway Centric® TMJ philosophy/Airway Centric® orthodontics ushers in the post-retraction world of orthodontics

OBJECTIVE

Airway Centric® Dentistry/Orthodontics was defined in a previous article (Gelb M. Airway centric TMJ philosophy. CDA Journal. 2014) that also suggested airway considerations were more important than condylar position issues in determining patient health and welfare. Indeed, that article called for a new paradigm in the profession, but specific treatment techniques to achieve optimal airways and avoid reducing the airway were not discussed. The present article amplifies on that article and identifies specific orthodontic treatment methods, which are or are not, congruent with this new paradigm.

METHOD

The basis of traditional orthodontic diagnosis is outlined with references from the literature that show the scientific foundation for treatment is weak. A new approach to diagnosis and treatment with the goal of airway optimization is discussed.

DISCUSSION

Six keys for optimal orthodontic outcomes are presented as new goals, and none involve the teeth. Ten specific treatment goals are outlined, and some are the diametric opposite of the current standard of care in the profession.

CONCLUSION

We recommend that optimizing the airway for every patient and never doing any treatment which will diminish the airway, even minutely, needs to become the standard of care in Airway Centric® Dentistry.

How has our interest in the airway changed over 100 years?

Since the beginning of our specialty, our understanding of the link between function and facial growth and development has progressively improved. Today, we know that children with sleep-related breathing problems will often develop distinctive facial characteristics. In adults, sleep apnea can result in serious morbidity and mortality. Orthodontists can ask sleep-related questions in the health history to help identify sleep breathing disorders. Treating these patients presents unique opportunities for orthodontists to collaborate with other medical specialties to improve a patient's health and treatment outcome. Research presented in our Journal in the next century may shed new light that will help us better identify the problem and aid the specialty in developing more effective evidence-based treatment. Additional efforts are needed to understand the physiology, neurology, and genetics of sleep breathing disorders.

Evidence Supports No Relationship between Obstructive Sleep Apnea and Premolar Extraction: An Electronic Health Records Review

OBJECTIVE

A controversy exists concerning the relationship, if any, between obstructive sleep apnea (OSA) and the anatomical position of the anterior teeth. Specifically, there has been speculation that extraction orthodontics and retraction of the anterior teeth contributes to OSA by crowding the tongue and decreasing airway space. This retrospective study utilized electronic medical and dental health records to examine the association between missing premolars and OSA.

METHODS

The sample (n = 5,584) was obtained from the electronic medical and dental health records of HealthPartners in Minnesota. Half of the subjects (n = 2,792) had one missing premolar in each quadrant. The other half had no missing premolars. Cases and controls were paired in a 1:1 match on age range, gender, and body mass index (BMI) range. The outcome was the presence or absence of a diagnosis of OSA confirmed by polysomnography.

RESULTS

Of the subjects without missing premolars, 267 (9.56%) had received a diagnosis of OSA. Of the subjects with four missing premolars, 299 (10.71%) had received a diagnosis of OSA. The prevalence of OSA was not significantly different between the groups (OR = 1.14, p = 0.144).

CONCLUSION

The absence of four premolars (one from each quadrant), and therefore a presumed indicator of past "extraction orthodontic treatment," is not supported as a significant factor in the cause of OSA.

Upper Airway Changes after Orthodontic Extraction Treatment in Adults: A Preliminary Study using Cone Beam Computed Tomography

OBJECTIVE

Whether the orthodontic treatment with premolar extraction and maximum anchorage in adults will lead to a narrowed upper airway remains under debated. The study aims to investigate the airway changes after orthodontic extraction treatment in adult patients with Class II and hyperdivergent skeletal malocclusion.

MATERIALS AND METHODS

This retrospective study enrolled 18 adults with Class II and hyperdivergent skeletal malocclusion (5 males and 13 females, 24.1 ± 3.8 years of age, BMI 20.33 ± 1.77 kg/m2). And 18 untreated controls were matched 1:1 with the treated patients for age, sex, BMI, and skeletal pattern. CBCT images before and after treatment were obtained. DOLPHIN 11.7 software was used to reconstruct and measure the airway size, hyoid position, and craniofacial structures. Changes in the airway and craniofacial parameters from pre to post treatment were assessed by Wilcoxon signed rank test. Mann-Whitney U test was used in comparisons of the airway parameters between the treated patients and the untreated controls. Significant level was set at 0.05.

RESULTS

The upper and lower incisors retracted 7.87 mm and 6.10 mm based on the measurement of U1-VRL and L1-VRL (P < 0.01), while the positions of the upper and lower molars (U6-VRL, and L6-VRL) remained stable. Volume, height, and cross-sectional area of the airway were not significantly changed after treatment, while the sagittal dimensions of SPP-SPPW, U-MPW, PAS, and V-LPW were significantly decreased (P < 0.05), and the morphology of the cross sections passing through SPP-SPPW, U-MPW, PAS, and V-LPW became anteroposteriorly compressed (P <0.001). No significant differences in the airway volume, height, and cross-sectional area were found between the treated patients and untreated controls.

CONCLUSIONS

The airway changes after orthodontic treatment with premolar extraction and maximum anchorage in adults are mainly morphological changes with anteroposterior dimension compressed in airway cross sections, rather than a decrease in size.

Changes in airway dimensions and hyoid bone position following class II correction with forsus fatigue resistant device

OBJECTIVE

The objective of this study was to investigate the effects of fixed functional therapy on oropharyngeal airway dimensions and hyoid bone positions in Class II patients and make comparison with an untreated Class II group.

MATERIALS AND METHODS

Eighteen patients (8 girls, 10 boys; mean age 13.62 ± 1.92 years) who were treated with Forsus Fatique Resistant Device (FFRD) and 19 patients (11 girls, 8 boys; mean age 12.74 ± 0.91 years) who served as control were enrolled. Cephalograms were used to assess linear, angular, and area measurements. Intragroup comparisons were made by paired t and Wilcoxon tests and intergroup comparisons were performed by independent t test.

RESULTS

With respect to controls, FFRD group showed increased airway dimensions at soft palate (P < 0.05) and more forward positioning of the hyoid bone (P < 0.05). Dentoalveolar changes exhibited mesial movement of lower incisors and molars and reduction in overjet (P < 0.001) in FFRD group.

CONCLUSIONS

Positive effects in oropharyngeal airway dimensions and increased values of hyoid bone displacement to a more forward position were found after fixed functional therapy.

CLINICAL RELEVANCE

Treatment with fixed functional appliances is mostly based on mesial movement of mandibular dentition, which might influence changes in tongue posture. The present results might indicate that oropharyngeal airway dimensions may be affected by postural changes of the hyoid bone in consequence of dentoalveolar changes. Clinically, these may be considered especially in Class II cases with reduced airway dimensions.

The relevance analysis of hyoid bone position to skeletal or dental openbite and dentofacial characteristics

OBJECTIVE

The aim of this study was to investigate the relationship between the hyoid bone position and skeletal or dental openbite and to investigate dentofacial characteristics as indicated by the hyoid bone position.

STUDY DESIGN

In our study, 182 patients were included on the basis of skeletal and dental openbite. The hyoid bone position of the subjects was compared and evaluated. In addition, by dividing the samples according to the hyoid bone position, dentofacial characteristics of the subjects were compared and analyzed.

RESULTS

There were significant differences in the hyoid bone position according to the skeletal pattern, not dental pattern. The skeletal openbite group showed low hyoid bone position. In addition, the low hyoid bone group showed short ramus height, short posterior facial height, retrusive chin, and clockwise-rotated mandible.

CONCLUSIONS

Patients with low hyoid bone had a tendency toward skeletal openbite, even though there was no dental openbite. Moreover, low hyoid bone position had relevance to retrognathic dentofacial characteristics.

The effect of teeth extraction for orthodontic treatment on the upper airway: a systematic review

PURPOSE

The purpose of this study was to evaluate the effect of teeth extraction for orthodontic treatment on the upper airway.

METHODS

Relevant trials assessing the effect of orthodontic extractions on the upper airway were retrieved electronically through PubMed, Embase, Medline, Web of Knowledge, and the Cochrane Library. The processes of literature search, selection, quality assessment, and data extraction were performed by two authors independently.

RESULTS

Seven articles were included in this systematic review. They were categorized into three groups according to their indications for extractions, namely anteroposterior discrepancy (group 1), crowding (group 2), and unspecified indications (group 3). In group 1, enrolled patients were diagnosed with class I bimaxillary protrusion and had four first premolars extracted, with a significant decrease in upper airway dimension. In group 2, increase in the upper airway dimension was reported in patients who were diagnosed with class I crowding and four first premolars extracted. In group 3, all patients were adolescents and no significant change in the upper airway dimension was observed.

CONCLUSIONS

Currently, it is difficult to draw evidence-based conclusions because of the exceeding heterogeneity among included studies, and more qualified trials are required to provide reliable evidence. Extractions followed by large retraction of the anterior teeth in adult bimaxillary protrusion cases could possibly lead to narrowing of the upper airway. Mesial movement of the molars appeared to increase the posterior space for the tongue and enlarge the upper airway dimensions. Although the effect of teeth extraction on upper airway dimension seems to be related to indications for extraction, accepted scientific evidence is still insufficient owing to the limited number of included studies. The relationship between the upper airway size and the respiratory function has not been demonstrated. While there may be a decrease in the upper airway volume, there is no evidence that this would turn an airway more collapsible. None of the studies assessed in this review had actual functional assessment of breathing. Additional qualified trials are necessary to verify reliability.