Three-dimensional computed tomographic evaluation of morphologic airway changes after mandibular setback osteotomy for prognathism

Linear and volumetric airway changes after maxillomandibular advancement for obstructive sleep apnea

PURPOSE

Maxillomandibular advancement (MMA) surgery is a well-established treatment of obstructive sleep apnea (OSA). Although many studies have assessed the efficacy of MMA in treating OSA, very few studies have quantified the magnitude of its changes to airway morphology. Therefore, the present study investigated the linear and volumetric morphologic changes that occur in the pharyngeal airway after treatment of OSA using MMA.

MATERIALS AND METHODS

A retrospective cohort study of patients with OSA treated from May 2010 to February 2014 was performed. Each patient underwent preoperative clinical and fiberoptic nasopharyngoscopic examinations. Pre- and postoperative polysomnograms, lateral cephalograms, and cone-beam computed tomography scans were acquired. The radiographic images were used to determine the linear and volumetric airway measurements. The time and magnitude of skeletal movement were used as the independent variables. The dependent variables included assessment of success or cure, apnea hypopnea index (AHI), cephalometric changes, Epworth score, rapid eye movement sleep, body mass index, and various airway morphologic parameters.

RESULTS

A total of 15 patients (13 men and 2 women) participated in the present study. The surgical success and cure rate was 73.33% and 40.00%, respectively. Statistically significant improvements were found in the airway total volume, minimal cross-sectional area, anteroposterior and lateral dimensions, airway index, airway length, posterior airway space morphology, AHI, and Epworth sleepiness score.

CONCLUSIONS

MMA is a highly successful surgical treatment of OSA that improves airway morphology and sleep quality. MMA results in a shorter and broader airway and associated improvements in the AHI.

Effects of mandibular setback surgery on upper airway dimensions and their influence on obstructive sleep apnoea - a systematic review

BACKGROUND

Mandibular setback used to be the traditional treatment of choice for correcting mandibular prognathism. Nowadays, bimaxillary surgery is preferred. Several authors have asserted that mandibular setback causes a relative narrowing of the upper airway (UA) that could trigger obstructive sleep apnoea (OSA); however, its potential role in OSA development is still much debated. Another controversial subject is whether changes in airway space caused by the procedure are permanent.

OBJECTIVES

To ascertain the consequences for UA size and shape of mandibular setback surgery in comparison with bimaxillary surgery (maxillary advancement with Le Fort I and mandibular setback), and to analyse the changes in oximetric indices and their relationship with OSA.

SEARCH METHODS

A systematic review was made of the bibliography in 4 databases: Medline, Scopus, Embase and Cochrane.

SELECTION CRITERIA

Systematic reviews, meta-analyses, clinical trials and cohort and case-control studies of adults published in the past 15 years were included.

DATA COLLECTION AND ANALYSIS

The initial search yielded 668 articles, of which 498 were eliminated because of duplication and 123 on the basis of their titles and abstracts or summaries. The remaining 47 papers were read in their entirety, and 14 were included in the final selection.

RESULTS

According to our observations, the nasopharyngeal space does not undergo significant changes after either of the two surgical procedures. In the oropharynx and hypopharynx, none of the measurements changed significantly with maxillary advancement; however, persistent and significant decreases in the area, horizontal linear dimensions, and volume of these spaces are encountered after mandibular setback alone. No long-term changes in oximetric indices were found.

CONCLUSIONS

Morphological changes are more pronounced following exclusively mandibular surgery. A decrease in the UA does take place but appears not to affect the patient's sleep quality. This study found no evidence to confirm that bimaxillary or mandibular orthognathic surgery predisposes to obstructive sleep apnoea development.

A 2-year follow-up of changes after bimaxillary surgery in patients with mandibular prognathism: 3-dimensional analysis of pharyngeal airway volume and hyoid bone position

PURPOSE

The aims of this study were to use 3-dimensional cone-beam computed tomography (CBCT) to evaluate how the upper airway and hyoid bone position changed after orthognathic surgery in patients with skeletal Class III malocclusions and to analyze the relations among upper airway changes, the change in the position of the hyoid bone, and postsurgical stability.

MATERIALS AND METHODS

CBCT scans were obtained from 15 patients with mandibular prognathism before surgery (T0), 6 months after surgery (T1), 1 year after surgery (T2), and 2 years after surgery (T3). Positional displacement of the hyoid bone was assessed using the coordinates at T0, T1, T2, and T3. In addition, the volume of each patient's pharyngeal airway was measured. Differences in CBCT scans at the established time points were determined by the Wilcoxon signed rank test. The Spearman correlation coefficient was used to determine the relations among changes in hyoid bone position, airway volume, and skeletal reference points.

RESULTS

The hyoid bone moved backward at 6 months after surgery (T0 to T1), and the total volume of the pharyngeal airway was considerably decreased at the same time points. At 1 year after surgery (T1 to T2), although the hyoid moved more posteriorly and the total volume of the pharyngeal airway was decreased, the changes were not major. At 2 years after surgery, the hyoid bone moved anteriorly and the size of the upper pharyngeal airway was increased (T2 to T3).

CONCLUSION

The hyoid bone moved posteriorly and the pharyngeal airway volume was decreased at 6 months after bimaxillary surgery. These measurements had a tendency to recover at 2 years postoperatively. The decrease in pharyngeal airway volume was not correlated with positional changes of the hyoid bone.

Changes of the Airway Space and the Position of Hyoid Bone after Mandibular Set Back Surgery Using Bilateral Sagittal Split Ramus Osteotomy Technique

Purpose:

Although there have been several studies of reduced airway space after mandibular setback surgery using the sagittal split ramus osteotomy technique, research on the risk factors for changes of the airway space is lacking. Therefore, this study was performed to examine airway changes and the position of the hyoid bone after orthognathic surgery, and to assess possible risk factors.

Methods:

In this retrospective study, 50 patients who underwent posterior displacement of the mandible by the bilateral sagittal split ramus osteotomy technique were included. Changes of the position of the hyoid bone and the airway space were analyzed over various follow-up periods, using cephalometric radiography taken preoperatively, immediately after surgery, eight weeks after surgery, six months after surgery, and one year after surgery. To identify risk factors, multiple regression analysis of age, gender, body mass index (BMI), posterior mandibular movement, and the presence of genioplasty was performed.

Results:

Inferor and posterior movement of the hyoid bone was observed postoperatively, but subsequent observations showed regression towards the anterosuperior aspect. The airway space also significantly decreased after surgery (P <0.05), and increased slightly up until six months after surgery. The airway space significantly decreased (β=0.47, P <0.01) as the amount of mandibular setback increased. However, age, sex, BMI, and presence of genioplasty were not associated with airway reduction.

Conclusion:

The amount of mandibular set back was significantly associated with postoperative reduction of airway space. It is necessary to establish a treatment plan considering this factor.

Cephalometric evaluation of the pharyngeal airway space after orthognathic surgery and distraction osteogenesis of the jaw bones

OBJECTIVE

Orthognathic surgeries and distraction osteogenesis (DO) of the jaw bones cause a change in the pharyngeal airway space (PAS). The aim of our study was to evaluate the magnitude of changes occurring in the pharyngeal airway after mandibular set-back surgeries and DO of maxilla/mandible.

MATERIALS AND METHODS

The study undertaken was a retrospective cephalometric study. Subjects included in our study had undergone mandibular set-back surgery or DO of maxilla/mandible. Lateral cephalograms of the subjects taken pre-operatively (T0), immediate post-operatively (T1) and after a minimum follow-up period of 6 months (T2) were studied. The cephalograms were traced manually and the following parameters were evaluated: Surface area of the PAS, pharyngeal airway width at the level of the base of the tongue, position of the hyoid bone and the tongue. Repeated measure ANOVA test was done to assess the presence of any significant changes in the proposed parameters at T0, T1 and T2. A correlation analysis was made between the mandibular/maxillary movements and the corresponding changes in the PAS.

RESULTS

Surgical movements of maxilla and mandible do have an effect on the pharyngeal airway.

CONCLUSION

It was clearly evident that the effects of mandibular movements on the PAS and the hyoid bone is more significant than the maxillary movements.

Pharyngeal airway space, hyoid bone position, and head posture after bimaxillary orthognathic surgery in Class III patients: long-term evaluation

OBJECTIVE

(1) To determine the effect of bimaxillary orthognathic surgery on pharyngeal airway, hyoid bone, and craniocervical posture in Class III bimaxillary surgery patients. (2) To evaluate short-term and long-term results. (3) To compare short- and long-term values.

MATERIALS AND METHODS

Twenty-six Class III adult patients treated with bimaxillary surgery were included in the study. Cephalometric records were taken before treatment (T1), before surgery (T2), and 5 months (T3), 1.4 years (T4), 3 years (T5), and 5 years (T6) postsurgery.

RESULTS

No significant differences were identified in craniocervical angulation between time intervals. There was a significant superior movement of hyoid bone at postsurgery (T3; P < .05); however, adaptation occurred to the normal position in the long term. A nonsignificant decrease occurred at the oropharyngeal middle pharyngeal distance parameter; however, this was compensated with a significant increase between T5 and T6 (P < .001). A significant decrease was observed in the hypopharyngeal Go-P parameter between T3 and T1 (P < .01), but it recovered with a nonsignificant increase in the long term. A significant increase in nasopharyngeal area was observed between T3 and T1 (P < .05). The hypopharyngeal area significantly increased between T5 and T6, and PNS-R significantly increased between T3 and T1 (P < .05).

CONCLUSION

The pharyngeal areas adversely affected after surgery recover at long-term follow-up; thus, adaptation occurs after bimaxillary surgery.

3-Dimensional analysis for class III malocclusion patients with facial asymmetry

OBJECTIVES

The aim of this study is to investigate the correlation between 2-dimensional (2D) cephalometric measurement and 3-dimensional (3D) cone beam computed tomography (CBCT) measurement, and to evaluate the availability of 3D analysis for asymmetry patients.

MATERIALS AND METHODS

A total of Twenty-seven patients were evaluated for facial asymmetry by photograph and cephalometric radiograph, and CBCT. The 14 measurements values were evaluated and those for 2D and 3D were compared. The patients were classified into two groups. Patients in group 1 were evaluated for symmetry in the middle 1/3 of the face and asymmetry in the lower 1/3 of the face, and those in group 2 for asymmetry of both the middle and lower 1/3 of the face.

RESULTS

In group 1, significant differences were observed in nine values out of 14 values. Values included three from anteroposterior cephalometric radiograph measurement values (cant and both body height) and six from lateral cephalometric radiographs (both ramus length, both lateral ramal inclination, and both gonial angles). In group 2, comparison between 2D and 3D showed significant difference in 10 factors. Values included four from anteroposterior cephalometric radiograph measurement values (both maxillary height, both body height) and six from lateral cephalometric radiographs (both ramus length, both lateral ramal inclination, and both gonial angles).

CONCLUSION

Information from 2D analysis was inaccurate in several measurements. Therefore, in asymmetry patients, 3D analysis is useful in diagnosis of asymmetry.

Reduction of atlantoaxial subluxation causes airway stenosis

STUDY DESIGN

A cross-sectional study.

OBJECTIVE

The purpose of this study was to investigate the effect of reduction of anterior atlantoaxial subluxation (AAS) on the oropharyngeal airway space.

SUMMARY OF BACKGROUND DATA

Our previous studies have shown that reduction of the occipito-C2 angle (O-C2A) makes the mandible shift posteriorly, resulting in oropharyngeal airway stenosis, which occasionally causes postoperative dysphagia after occipitocervical fusion. Based on this background, we hypothesized that reduction of AAS would also cause oropharyngeal airway stenosis independent of the O-C2A, because it also shifts the mandible posteriorly. To our knowledge, there are no data demonstrating an association between reduction of AAS and the oropharyngeal airway space.

METHODS

The authors prospectively evaluated 64 patients with rheumatoid arthritis. We analyzed lateral cervical plain radiographs of 5 different positions (neutral, flexion, extension, retraction, and protrusion), and measured the O-C2A, C2-C6 angle, anterior atlantodental interval, anteroposterior distance of the narrowest oropharyngeal airway space (nPAS), and so on. The subjects were classified into 2 groups: group R comprised patients with a "reducible AAS" in dynamic cervical movement, and group N comprised "patients without AAS" patients.

RESULTS

In the multiple regression analysis, the change in the O-C2A was the only significant independent variable related to the percentage change in the nPAS from the neutral position in group N. On the contrary, the change in the anterior atlantodental interval and change in the O-C2A were significantly related to the percentage change in the nPAS in group R. No cases in group N and 7 cases (28%) in group R showed a paradoxical decrease in the nPAS in extension, in which the O-C2A is largest and reduction of AAS is obtained.

CONCLUSION

Reduction of AAS has a negative effect on the oropharyngeal airway space. Therefore, reduction of AAS during occipitocervical fusion may cause postoperative dysphagia despite maintenance of the O-C2A.

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

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

Pharyngeal airway space, hyoid bone position and head posture after orthognathic surgery in Class III patients

OBJECTIVE

To determine the effect of orthognathic surgery on pharyngeal airway in Class III patients and to (1) compare the results of different surgical techniques, (2) determine the change at the position of the hyoid bone, and (3) evaluate the craniocervical posture changes related to pharyngeal airway change.

MATERIALS AND METHODS

Forty-eight Class III adult patients were included in the study to assess airway space after orthognathic surgery. Nine patients were treated with maxillary advancement, seven patients were treated with mandibular set back, and 32 patients were treated with bimaxillary surgery. Cephalometric records were taken before treatment, after surgery, and about 1 year after surgery (at the end of the treatment).

RESULTS

No differences were determined at the position of hyoid bone and craniocervical posture. Nasopharyngeal area was significantly increased in all groups (P < .05). Oropharyngeal area and SPSS and IPS parameters were significantly decreased after mandibular set back operation (P < .05). In bimaxillary and maxillary advancement groups, PPS parameter was significantly increased (P < .01), and IPS parameter was significantly decreased (P < .05). No differences were detected at oropharyngeal and hypopharyngeal areas in bimaxillary and maxillary advancement groups.

CONCLUSION

Different surgical procedures have different effects on pharyngeal airway space.

Effect of large incisor retraction on upper airway morphology in adult bimaxillary protrusion patients

OBJECTIVE

To evaluate, using multislice computed tomography (MSCT), the morphologic changes in the upper airway after large incisor retraction in adult bimaxillary protrusion patients.

MATERIALS AND METHODS

Thirty adult patients with bimaxillary protrusion had four first premolars extracted, and then miniscrews were placed to provide anchorage. A CT scan was performed before incisor retraction and again posttreatment. Three-dimensional (3D) reconstruction of the pre- (T1) and post- (T2) CT data was used to assess for morphological changes of the upper airway. A paired t-test was used to compare changes from T1 to T2. The relationship among the three variables (upper incisor retraction amount, upper airway size, and hyoid position) was analyzed by Pearson correlation coefficient.

RESULTS

The amounts of upper incisor retraction at the incisal edge and apex were 7.64 ± 1.68 mm and 3.91 ± 2.10 mm, respectively. The hyoid was retracted 2.96 ± 0.54 mm and 9.87 ± 2.92 mm, respectively, in the horizontal and vertical directions. No significant difference was observed in the mean cross-sectional area of the nasopharynx (P > .05) between T1 and T2, while significant differences between T1 and T2 were found in the mean cross-sectional areas of the palatopharynx, glossopharynx, and hypopharynx (P < .05); these mean cross-sectional areas were decreased by 21.02% ± 7.89%, 25.18% ± 13.51%, and 38.19% ± 5.51%, respectively. The largest change in the cross-sectional area is always noted in the hypopharynx. There was a significant correlation among the retraction distance of the upper incisor at its edge, the retraction distance of the hyoid in the horizontal direction, and the decrease of the hypopharynx.

CONCLUSION

Large incisor retraction leads to narrowing of the upper airway in adult bimaxillary protrusion patients.

Análise cefalométrica das vias aéreas superiores de pacientes Classe III submetidos a tratamento ortocirúrgico

OBJETIVO: o objetivo deste estudo foi avaliar as alterações causadas por cirurgia ortognática de recuo mandibular associada ou não à cirurgia maxilar combinada nas vias aéreas superiores (VAS). MÉTODOS: foram avaliadas radiografias cefalométricas de perfil pré-cirúrgicas e pós-cirúrgicas imediatas de 17 pacientes com Classe III. Foram realizadas medições do diâmetro do espaço aéreo (EA) no plano sagital, nas regiões correspondentes à hipofaringe e à orofaringe; também foram registradas as alterações na posição do osso hioide. Utilizou-se o teste t pareado e o coeficiente Pearson, buscando possíveis associações entre as alterações esqueléticas e as ocorridas no EA. RESULTADOS: observou-se redução significativa do EA na região da hipofaringe (média de 3,10mm, p=0,024). O osso hioide sofreu deslocamento inferior e posterior, além de diminuição da distância entre o mesmo e a região anterior da mandíbula. Não foi possível correlacionar, quantitativamente, a redução anteroposterior do EA com o recuo mandibular. Entretanto, observou-se correlação forte entre o diâmetro inicial do EA e a quantidade de redução observada ao nível da hipofaringe, e moderada em relação à orofaringe. CONCLUSÕES: o recuo mandibular pode causar estreitamento significativo das VAS, principalmente na porção mais inferior (hipofaringe). Portanto, deve-se atentar para sua avaliação durante o plano de tratamento ortocirúrgico, já que não foram descartados possíveis efeitos deletérios dessas alterações nas funções do indivíduo.

Effects of orthognathic surgery on oropharyngeal airway: a meta-analysis

Oropharyngeal changes caused by orthognathic surgery have been a concern because the sleep quality of patients may be enhanced or worsened by these changes. The purpose of this meta-analysis was to identify, review and compare scientific literature about changes in airway in adult patients undergoing orthognathic surgery to correct anteroposterior osseous discrepancies. An electronic search of four databases was carried out up to July 2010, with supplemental hand searching of the references of the retrieved articles. Quality assessment of the included articles was carried out. Data were extracted and a meta-analysis was performed. Heterogeneity was assessed amongst the studies and results were presented in forest plots. 49 studies met the inclusion criteria. Only studies with moderate or high methodological soundness were included in the review. Moderate evidence was found to support a significant decrease in the oropharyngeal airway in mandibular setback surgery, a milder decrease in bimaxillary surgery to correct Class III and an increase in maxillomandibular advancement surgery. Evidence is lacking on airway volume changes after orthognathic surgery.

Three-dimensional changes in pharyngeal airway in skeletal class III patients undergoing orthognathic surgery

PURPOSE

It has often been hypothesized that mandibular setback surgery causes narrowing of the pharyngeal airway. We examined whether the pharyngeal airway narrowed after orthognathic surgery in patients undergoing either mandibular setback surgery or bimaxillary surgery and whether the amount of narrowing of the pharyngeal airway was any different after mandibular setback surgery or bimaxillary surgery.

MATERIALS AND METHODS

Cone-beam computed tomography scans were obtained for 21 patients who were assigned to either mandibular setback surgery or bimaxillary surgery. The anteroposterior dimension, lateral width, cross-sectional area, and volume of each subject's pharyngeal airway were measured before and after surgery.

RESULTS

The pharyngeal airway showed significant narrowing after both mandibular setback surgery and bimaxillary surgery. The amount of change in the anteroposterior dimension and cross-sectional area on the posterior nasal spine plane and the length of the pharyngeal airway showed significant differences between the 2 groups.

CONCLUSION

The amount of narrowing of the pharyngeal airway was smaller in patients undergoing bimaxillary surgery than in the patients undergoing mandibular setback surgery.

Changes in the pharyngeal airway space and hyoid bone position after mandibular setback surgery for skeletal Class III jaw deformity in Japanese women

INTRODUCTION

The purpose of the study was to examine the changes in stability of pharyngeal airway space (PAS) and hyoid bone position after 2 types of mandibular osteotomies in comparison with a control group.

METHODS

The subjects included 46 Japanese women with skeletal Class III malocclusion. Twenty-five patients with mandibular prognathism underwent single-jaw surgery with bilateral sagittal split ramus osteotomy (SSRO), and 21 patients underwent bilateral intraoral vertical ramus osteotomy (IVRO). The control subjects included 30 volunteer women with normal occlusion. The treated subjects were assessed at the beginning of treatment, immediately after surgery, and after postsurgical treatment.

RESULTS

The Class III subjects had a significantly wider PAS than did the control subjects. Significant decreases in the lower PAS were observed after orthognathic surgery. The hyoid bone showed upward and forward movement with upward movement of the lower border of the PAS during the postsurgical stage in the SSRO group. In contrast, the anterior border of the PAS and the hyoid bone showed considerable backward movement in the IVRO group.

CONCLUSIONS

The posttreatment morphology of the PAS in both Class III groups approached that of the control group. The IVRO group showed a reduction in the airway dimensions, especially during the postsurgical period, which occurred during surgery in the SSRO group.

Effects of extraction versus non-extraction treatment on oropharyngeal airway volume

OBJECTIVE

To compare the effects of extraction vs nonextraction orthodontic treatments on oropharyngeal airway volume.

MATERIALS AND METHODS

An existing patient database was screened for pretreatment (T0) and posttreatment (T1) cone beam computed tomography (CBCT) scans and complete medical histories. Twenty patients treated with removal of four premolars (ExtG) and 20 controls (NExtG), were matched for age, gender, ethnicity, height, weight, body mass index, and oropharyngeal (OP) volumes, among other variables. Constructed lateral cephalograms (three skeletal and four dental variables) and OP volumes were measured at T0 and T1 using Dolphin Imaging 11.0. Independent sample t-tests were used to compare the groups at T0 and the outcome variables at T1. Paired sample t-tests were used to compare the mean changes from T0 to T1. Statistical significance was set at P < or = .05.

RESULTS

Changes from T0 to T1 were found to be significant in both groups for CoA, CoGn, U1-FH, and IMPA. In the ExtG alone, U1-Na Perp and L1-Na Perp were also significantly different from T0 to T1. Despite the observed differences, no significant differences were found at the end of treatment between the mean OP volumes for either group (12,675.6 +/- 4483.6 for ExtG; 12,002.7 +/- 2857.0 for NExtG, P > .05). Similarly, the mean changes in OP volume (1082.6 mm(3) and 1701.1 mm(3) for ExtG and NExtG, respectively) and increase in mean minimal constricted axial areas (17.4 mm(2) and 1.9 mm(2) for ExtG and NExtG, respectively, P > .05) from T0 to T1 were not significant for the two groups.

CONCLUSION

Extraction of four premolars with retraction of incisors does not affect OP airway volume.

Three-dimensional airway changes after Le Fort III advancement in syndromic craniosynostosis patients

BACKGROUND

To investigate the changes of upper airway volume in syndromic craniosynostosis patients following Le Fort III advancement, computed tomographic scans were analyzed and related to the amount of advancement.

METHODS

In this retrospective study, the preoperative and postoperative computed tomographic scans of 19 patients with syndromic craniosynostosis who underwent Le Fort III advancement were analyzed. In four cases, preoperative polysomnography demonstrated obstructive sleep apnea. The airway was segmented using a semiautomatic region growing method with a fixed Hounsfield threshold value. Airway volumes of hypopharynx and oropharynx (compartment A) and nasopharynx and nasal cavity (compartment B) were analyzed separately, as was the total airway volume. Advancement of the midface was recorded using lateral skull radiographs. Data were analyzed for all patients together and for patients with Crouzon/Pfeiffer and Apert syndromes separately.

RESULTS

Airway volume increased significantly in compartment A (20 percent; p = 0.044) and compartment B (48 percent; p < 0.001), as did total airway volume in (37 percent; p < 0.001) in the total study group. No significant differences in volume changes were found comparing Apert with Crouzon/Pfeiffer patients. No distinct relation could be found between advancement of the midface and volume gain either in the total study group or in Apert and Crouzon/Pfeiffer patient groups separately. Postoperative polysomnography showed significant improvement of obstructive sleep apnea in all four patients.

CONCLUSIONS

A significant improvement of the upper airway after Le Fort III advancement in syndromic craniosynostosis patients is demonstrated. No distinct relation could be observed between advancement and airway volume changes.

Two- and three-dimensional evaluation of the upper airway after bimaxillary correction of Class III malocclusion

OBJECTIVE

The aim the study was to evaluate area and volumetric changes in the upper airway after bimaxillary correction of Class III malocclusion by the means of computer tomography (CT), and to compare these to the changes in linear measurements from lateral cephalograms.

STUDY DESIGN

This was a prospective clinical trial. Lateral cephalograms and CT scans of 10 Class III patients were evaluated 1 week before and 6 months after surgery. Wilcoxon matched pairs signed ranks test was used to determine the differences in measurements pre- and postoperatively. Spearman's rank correlation was used to test the association between the CT and cephalometric measurements.

RESULTS

CT measurements: The oropharyngeal and hypopharyngeal volumes increased by 3.98 +/- 4.18 cm(3) (P = .015) and 2.51 +/- 1.92 cm(3) (P = .021), respectively. The total volume of the posterior airway space increased, but the increase was not statistically significant. After surgery no change in the cross-sectional area of the upper airway was recorded at the retropalatal, oropharyngeal, or hypopharyngeal levels. Cephalometric measurements: The nasopharyngeal space increased 4.08 +/- 5.07 mm (P = .039) and the tongue increased in length by 4.84 +/- 5.93 mm (P = .22). No correlation was found between the measurements on CT scans and corresponding measurements on the lateral cephalograms.

CONCLUSIONS

Bimaxillary surgery for correction of Class III malocclusion did not cause decrease of the posterior airway space. Three-dimensional imaging techniques are preferable to 2-dimensional lateral cephalograms for evaluation of the upper airway after orthognathic procedures.

Pharyngeal airway dimensions after chin cup treatment in Class III malocclusion subjects

The objective of this study was to examine if chin cup therapy have any adverse effect on the sagittal pharyngeal dimensions in Class III malocclusion patients. Twenty patients (10 girls and 10 boys; mean age 10.31 +/- 1.15 years) with skeletal Class III malocclusion, and an untreated control group (8 girls and 10 boys, mean age 9.89 +/- 1.55 years) were evaluated. The chin cup appliance and an occlusal bite plate with 600 grams totally was used for 9.78 +/- 0.93 months. Linear, angular and area measurements were evaluated on the cephalometric radiographs taken before and after observation and treatment periods. Treatment changes showed significant increases in maxillary forward position, effective length of the maxilla and the mandible, and vertical facial height measurements. The mandible showed a clockwise rotation revealed by the decrease in SNB and the increase in mandibular plane angles. Significant increase in the nasopharyngeal area was found when the treatment and control groups were compared. The nasopharyngeal airway area was affected by chin cup treatment, without any adverse effect on the pharyngeal airway dimensions in the short term.

Changes in head posture and hyoid bone position in Turkish Class III patients after mandibular setback surgery

The aim of this study was to determine the changes in head posture and hyoid bone position after mandibular setback osteotomy in Turkish adult Class III patients. Serial lateral cephalograms of 42 Turkish Class III patients (24 female, 18 male patients, mean age: 25.4+/-1.2 years) who underwent mandibular setback surgery were evaluated preoperatively, 1.2+/-0.6 years, 2.3+/-0.8 and 4.2+/-0.9 years postoperatively. A mean mandibular setback of 5.6+/-0.8mm was associated with a posterior and inferior movement of the hyoid bone and a significant flexion in the neck posture. Surgical correction of mandibular prognathism altered the position of the hyoid bone by downward repositioning carrying the root of the tongue downwards immediately postoperatively, but followed with a tendency to return to its original position.

Effect of Orthognathic Surgery on the Posterior Airway Space (PAS)

Orthognathic surgery has been used regularly to treat dentofacial deformities. The surgical procedures affect both the facial appearance as well as the posterior airway space (PAS). Our current literature indicates that setback procedures produce an inferior repositioning of the hyoid bone and posterior displacement of the tongue and the soft palate. These movements cause anteroposterior and lateral narrowing of the PAS. Most authors agree that these effects are permanent. The PAS changes in turn produce an adaptive posturing, with an increased craniocervical angle to open up the PAS. Even though most patients do not display snoring and obstructive sleep apnoea (OSA) post-surgery, there is certainly an increased possibility in patients with already compromised airways. Therefore, patients who are undergoing orthognathic surgery should be screened for excessive daytime somnolence, snoring, increased body mass index (BMI) and medical conditions related to OSA and sent for an overnight polysomnography (PSG) if OSA is suspected. Then the proposed treatment plan may be modified according to the risk of potential airway compromise or even to improve it. Conversely, advancement of the maxilla and mandible causes widening of the airway in both the anteroposterior and lateral dimensions. This effect would translate to better airflow and decreased airway resistance. This is supported by the evidence showing high success rates when orthognathic surgery, especially maxillomandibular advancement (MMA), is utilised to treat OSA. Key words: Airway changes, Cephalometrics, Maxillomandibular advancement, Obstructive sleep apnoea, Orthognathic surgery

Positional changes of oropharyngeal structures due to gravity in the upright and supine positions

OBJECTIVES

To compare the responses of oropharyngeal structures to gravity while sitting upright or lying down in a supine position.

METHODS

Seven subjects were evaluated by cone beam CT (CBCT) while in the upright position and by a four-row multidetector helical CT (MDCT) while in the supine position. All of the voxel sizes were adjusted to be 0.3x0.3x0.3 mm3 in the x-y-z axis. The posterior nasal spine, basion and fourth cervical bone were used as references to measure positional changes in the oropharyngeal structures between the upright and supine positions. The smallest areas in the oropharynx were also evaluated.

RESULTS

The soft palate, epiglottis and entrance of the oesophagus moved caudally with the positional change from supine to sitting upright, and moved posteriorly when the position changed from an upright to a supine position. The hyoid bone moved caudally but not posteriorly in response to the same positional changes. The width and length of the smallest area present in the oropharynx was larger in the upright position than in the supine position.

CONCLUSIONS

Gravity can produce movements in oropharyngeal structures in response to postural changes between sitting upright and lying in the supine position.

A proposal for a new analysis of craniofacial morphology by 3-dimensional computed tomography

INTRODUCTION

Three-dimensional (3D) analysis is essential for making a precise diagnosis of craniofacial morphology. Two-dimensional (2D) x-ray films are used to understand 3D structures. However, 2D images have several limitations. This article proposes a new type of cephalometric analysis by using 3D computed tomography.

METHODS

Axial images of 30 subjects (16 men; mean age, 19.2 years; 14 women, mean age, 20.5 years) were reconstructed into 3D models by using Vworks 4.0 (Cybermed, Seoul, Korea). The 3D models were measured with Vsurgery (Cybermed). The zygoma, maxilla, mandible, and facial convexity were analyzed.

RESULTS

The measurements were compared with Korean normal averages, and no statistically significant differences were found. Landmark identification was reproducible.

CONCLUSIONS

Three-dimensional computed tomography can provide information for use in diagnosis and treatment planning.

Condylar head remodeling following mandibular setback osteotomy for prognathism: A comparative study of different imaging modalities

PURPOSE

Condylar remodeling, which develops after mandibular setback osteotomy, was evaluated and compared in CT, plain film radiographs, and MR images acquired postoperatively.

METHODS

Thirty-nine patients treated with sagittal split ramus osteotomy (SSRO) and 46 patients treated with intraoral vertical ramus osteotomy (IVRO) were studied. Remodeling as seen in the images and the diagnostic agreement between imaging modalities was evaluated.

RESULTS

A newly formed bone layer in the posterior part of the condylar head was identified as a sign suggestive of remodeling. This sign was seen predominantly at periods over 6 months postoperatively. IVRO subjects had a higher incidence of remodeling than did the SSRO group. The diagnostic agreement between the 3 imaging modalities was substantial. There was a positive correlation between postoperative condylar displacement and the incidence of remodeling.

CONCLUSIONS

The incidence of postoperative condylar head remodeling may be predictable. High-dose postoperative imaging studies to assess the TMJ should be restricted to those cases having a clear need for such studies.

Cirurgia ortognática: orientações legais aos ortodontistas e cirurgiões bucofaciais

Os autores entrevistaram especialistas em Ortodontia e em Cirurgia Bucomaxilofacial, elaboraram uma lista de ocorrências específicas do dia-a-dia do exercício da especialidade, redigindo, com base na legislação vigente e na literatura, uma série de orientações, atitudes e comportamentos que sugerem como rotina aos profissionais.

Assessment of Three-dimensional X-ray Images: Reconstruction From Conventional Tomograms, Compact Computerized Tomography Images, and Multislice Helical Computerized Tomography Images

Three-dimensional X-ray images (3D images) were used for imaging diagnosis in the oral and maxillofacial region. These images could be fundamentally reconstructed from various tomograms, though clinical 3D images were mainly reconstructed from computerized tomography (CT) images. In this investigation, 3D images were reconstructed from conventional tomograms with a panoramic unit, compact CT images, and multislice helical CT images, and the usefulness of each system was subjectively assessed for dental implant treatment. Three hemilateral dried human mandibles were used and were examined by linear tomography with a panoramic unit, compact CT, and multislice helical CT, and 3D images were reconstructed by using the rendering software for each system. The 3D images were visually evaluated on a 5-point scale covering the alveolar ridge, buccal and lingual bone surface, mental foramen, and tooth sockets. As a result, 3D images reconstructed from conventional tomograms with the panoramic unit were assessed as fair to unsure, compact CT 3D images were assessed as unsure to good, and multislice helical CT 3D images were assessed as good to excellent. It was concluded that compact CT 3D images and multislice helical CT 3D images were useful in dental implant treatment.