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

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.

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.

Evaluation of pharyngeal airway dimensions and cephalometric changes after premolar extraction and nonextraction orthodontic treatment in adolescent and adult patients

PURPOSE

The purpose of this study was to investigate the effects of premolar extraction and non-extraction for orthodontic treatment on the skeletal, dentoalveolar and pharyngeal airway.

MATERIAL AND METHOD

The study was carried out with the radiographs of a total of 130 patients at the ages of 14 to 25, including 59 male and 71 female patients. The cases were divided into two groups as the "extraction" group(2 upper premolar teeth) (n = 66) and the "non extraction" group (n = 64).

RESULTS

Extraction Group:In both age groups, there was a statistically significant increase in the mean interincisal angle (U1xL1) and lower anterior facial height (ANS-Me) values(p < 0.05). In the 14-18 age group, there was a significant increase in the mean upper airway thickness, inferior airway space, hyoid position, soft palate length(PNSP) and upper pharynx values(p < 0.05). In both sexes, while the mean U1xL1 and ANS-Me values significantly increased, the mean upper incisors inclination values decreased significantly(p < 0.05). Non Extraction Group:In both age groups, the mean ANS-Me values increased significantly from T0 to T1(p < 0.05). In the 14-18 age group, the increase in the mean upper adenoid thickness, tongue length,PNSP, softpalate thickness and vertical airway length values was significant(p < 0.05). In the male patients, the mean U1xL1 value decreased significantly(p < 0.05).

CONCLUSION

The premolar teeth extraction performed in the patients receiving orthodontic treatment did not affect airway dimensions to a high extent.It was determined that the position of the hyoid bone and tongue length was not affected in the patients with premolar extraction and non extraction.

Treatment of an anterior open bite, bimaxillary protrusion and mesiocclusion by the extraction of premolars and the use of clear aligners

An anterior open bite may be orthodontically treated by either the intrusion of posterior teeth, the extrusion of anterior teeth, or a combination of both. An improvement in bimaxillary protrusion often involves the extraction of premolars and the retraction of the anterior teeth. The treatment of mesiocclusion mainly involves the mesial and/or distal movement of the molars. However, these three types of malocclusions pose significant treatment challenges when using clear aligners. The present case report describes the treatment of a 24-year-old female patient who presented with the above characteristics, which affected her confidence, willingness to smile and masticatory function. A four-premolar extraction plan was designed to resolve the problems using clear aligners as the patient rejected fixed or visible appliances. After 33 months of orthodontic therapy, except for the counter-clockwise rotation of the mandible and the decrease of facial height, the other objectives established in the pre-treatment plan were achieved, and the patient was satisfied with the results. The combination of clear aligners and premolar extractions effectively corrected the skeletal anterior open bite, bimaxillary dentoalveolar protrusion, and mesiocclusion.

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.

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.

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.

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.

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.

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.