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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 7  |  Issue : 1  |  Page : 31-35  

Volumetric changes in pharyngeal airway in Class II division 1 patients treated with Forsus-fixed functional appliance: A three-dimensional cone-beam computed tomography study


Department of Orthodontics, Government Dental College, Jaipur, Rajasthan, India

Date of Web Publication22-Feb-2016

Correspondence Address:
Parul Temani
Department of Orthodontics, Government Dental College, Jaipur, Rajasthan
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0976-237X.177100

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   Abstract 


Objective: Recent years have witnessed a renewed interest to determine a quantifiable relationship between mandibular advancement performed with an orthodontic appliance and the resulting airway volume. The study was conducted to evaluate the volumetric changes in pharyngeal airway space using cone-beam computed tomography (CBCT) in Class II division 1 patients with retrognathic mandible treated by Forsus-fixed functional appliance and to compare them with their pretreatment findings. Materials and Methods: Thirty patients with Class II division 1 malocclusion of age group 10–17 years were selected randomly and evaluated for changes in pharyngeal airway volume with and without Forsus-fixed functional appliance. Patients in each group underwent CBCT scan of head and neck region at pretreatment stage and 6 months after the initial scan. Institutional approval for the project was obtained from the Ethical Committee. Volumetric changes of upper (oropharynx) and lower (hypopharynx) pharyngeal airways were measured on scanogram using computer software and intragroup comparisons were done. Results: There was a statistically significant increase in the volume of both hypopharynx and oropharynx and also total airway volume in patients treated with Forsus-fixed functional appliance. Three-dimensional reconstruction of the airway also demonstrates a considerable increase in pharyngeal airway space. Conclusion: Forsus-fixed functional appliance can be a promising appliance for improving pharyngeal airway volume in Class II division 1 patients with retrognathic mandible thus preventing obstructive sleep apnea and other respiratory problems in future. However, the long-term implications of this treatment modality need further consideration and a longer period of follow-up.

Keywords: Cone-beam computed tomography, Forsus-fixed functional appliance, pharyngeal airway


How to cite this article:
Temani P, Jain P, Rathee P, Temani R. Volumetric changes in pharyngeal airway in Class II division 1 patients treated with Forsus-fixed functional appliance: A three-dimensional cone-beam computed tomography study. Contemp Clin Dent 2016;7:31-5

How to cite this URL:
Temani P, Jain P, Rathee P, Temani R. Volumetric changes in pharyngeal airway in Class II division 1 patients treated with Forsus-fixed functional appliance: A three-dimensional cone-beam computed tomography study. Contemp Clin Dent [serial online] 2016 [cited 2019 Nov 18];7:31-5. Available from: http://www.contempclindent.org/text.asp?2016/7/1/31/177100




   Introduction Top


Class II division 1 malocclusion presents a common challenge to every orthodontist. Almost 60% of the skeletal Class II malocclusions are as a consequence of mandibular retrognathism.[1] Retrognathic mandible has also been found to be a contributing factor in obstructive sleep apnea (OSA) and other respiratory problems with patients having a shorter mandibular body length.[2] In skeletal Class II patients, the problem is likely caused by a posteriorly-oriented mandible that displaces the soft tissues attached to it, impinging on the airway space.[3] This can also lead to the systemic problems such as cardiac and respiratory ailments in such patients.[4] The oral and pharyngeal regions thus maintained in a state of equilibrium have a primary function in maintaining patent airway and the process of deglutition. Functional appliances form the optimum treatment option for mandibular retrognathism in growing children. Functional appliances also increase superior-posterior airway space, allows a larger lumen for air to pass through during inspiration, thereby decreasing the likelihood of an obstructive event. To make the treatment outcome more predictable, several “compliance free” fixed functional appliances have been introduced. The present study was aimed to evaluate the volumetric changes in pharyngeal airway with the help of cone-beam computed tomography (CBCT) in growing patients with retrognathic mandible treated by the Forsus-fixed functional appliance. The ability to perform precise measurements of various cross-sectional areas, three-dimensional (3D) reconstructions and volumetric measurements of the upper airway, and low radiation exposure are some of the advantages of CBCT technology when compared with other diagnostic radiological techniques.[5] The null hypothesis was that there was no significant increase in pharyngeal airway in patients treated with Forsus-fixed functional appliance.


   Materials and Methods Top


The present study was conducted with a sample consisting of 30 patients with Class II division 1 malocclusion of age group 10–17 years selected randomly from the patients of North Indian origin to evaluate the changes in pharyngeal airway dimensions with and without fixed functional appliance therapy (Forsus). Approval for the project was obtained from the Ethical Committee of the Institution.

All patients gave their consent as per the forms and regulations decided by the Ethical Committee of the Institute. Each subject filled out the consent form to individually participate in the present study. The subjects were explained about the purpose of the study which covered the points outlined in the information sheet.

Selection criteria

Inclusion criteria

  • Skeletal Class II division 1 malocclusion (ANB > 4°) with a clinically diagnosed retrognathic mandible
  • Class II division 1 dental malocclusion
  • Mandibular plane angle (Go-Me to FH plane) of 25 ± 5°
  • Overjet >5 mm
  • Age group: 10–17 years with significant growth potential at the beginning of treatment period.


Exclusion criteria

  • No sex difference taken into account
  • No prior orthodontic treatment and no permanent teeth extracted before and during Forsus-fixed functional appliance treatment
  • Patients having no congenital anomalies or facial asymmetries
  • Patients with no history of any serious trauma or surgery of orofacial region.


Methods

The maxillary and mandibular teeth were bonded with preadjusted edgewise appliance (roth prescription −0.022” × 0.028” slot). Leveling and alignment was completed with NiTi archwires and stabilized with 0.019” × 0.025” stainless steel archwires in both maxillary and mandibular arches. Forsus-fixed functional appliance was attached in the lower jaw onto a continuous 0.019” × 0.025” stainless steel archwire [Figure 1] and [Figure 2]. Prior to attachment of Forsus-fixed fuctional appliance, the lower arch was consolidated as one using the figure of “8” stainless steel ligature (0.009”) from 1st mandibular molar on one side to the other. The lower archwire was given a labial root torque of 10° and cinched back distal to first mandibular molar. The appliance was checked every 1 month and adjusted if necessary with a total time of 4–6 months for Forsus-fixed functional appliance therapy.
Figure 1: Forsus-fixed functional appliance-frontal view

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Figure 2: Forsus-fixed functional appliance-lateral view

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Installation of Forsus – Fatigue-resistant device

Once the correct size was selected, the appliance was inserted through the molar headgear tube from distal to mesial, push rod was inserted into the telescoping spring, and the mesial hook was looped over the mandibular archwire and crimped shut.

The records that were collected included a detailed clinical history, photographs, and CBCT scans at the beginning of the treatment and after completion of Class II correction with Forsus-fixed functional appliance therapy (within a week of appliance removal).

Cone-beam computed tomography scans

The CBCT scans used in the present study were obtained with Carestream CS9300 machine, which has a broad range of CBCT applications – such as paranasal sinus, temporal bone, dental implantology, trauma, and oral surgery. Ultrahigh CBCT resolution (0.09 mm) delivers superior fine bony structure visualization of temporal bone and radicular structures. Each compact disc having CBCT scan with digital imaging and communications in medicine images were loaded into 3D-Doctor Imaging Software (Able Software Corporation, USA) TM, which is an advanced 3D modeling, image processing, and measurement software for magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), microscopy, and scientific and industrial imaging applications. To build 3D models of the airways for the subjects, the CBCT data were loaded into 3D-Doctor software to allow semi-automatic segmentation of the airway in the sagittal view.

Oropharyngeal airway segmentation and volume measurement

The airway was visualized and then digitally excised by defining training area. The software was used to define the volume of the entire airway by first “segmenting” the regional space of interest by drawing a boundary in orthogonal planes. Because the airspace exhibits a significantly greater negative CT value than the more dense surrounding soft tissue, the sharp distinct high contrast border produces a clean segmentation of the airway.

Upper and lower landmarks for oropharynx were taken as the posterior most tip of the hard palate and tip of epiglottis, respectively. Hypopharynx was taken from the epiglottis to the lower border of sixth cervical vertebra [Figure 3]. After finishing the markings, volume viewer of the software measures the entire volume of the segmented region of the oropharynx and hypopharynx [Figure 4].
Figure 3: Segmentation of pharyngeal airway

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Figure 4: Three-dimensional volumetric measurement of pharyngeal airway

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Statistical analysis

Mean, standard deviation, and standard error were calculated, with the t-test used to determine the level of significance.


   Results Top


The changes in volume measurements of upper and lower pharyngeal airway in the sample have been summarized in [Table 1] and [Figure 5].
Table 1: Comparison of pre- and post-treatment values w.r.t. volume

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Figure 5: Graph depicting volumetric changes pre-and post-treatment

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It was seen that there was a significant increase (P< 0.001) in upper pharyngeal, lower pharyngeal, and total airway volume in treated cases after 6 months of Forsus-fixed functional appliance therapy [Figure 6] and [Figure 7].
Figure 6: Pretreatment three-.dimensional volumetric construction of airway. Volume: 748.32 mm3

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Figure 7: Posttreatment three-.dimensional volumetric construction of airway. Volume: 1012.83 mm3

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   Discussion Top


The pharyngeal airway has always been an area of interest for orthodontists because of the role played in the growth and development of the craniofacial and orodental complex and their primary functions in maintaining patent airway. Many previous studies have shown a possible relationship among pharyngeal airway and skeletal structures, soft tissues, and musculature.[6],[7] McNamara [1] stated that 60% of the skeletal Class II malocclusions are a consequence of mandibular retrognathism. Over the years, mandibular advancement appliances in the form of functional appliances are used in the dentofacial orthopedic treatment of growing children with hypoplastic and/or retrognathic mandible.[8]

Through this study, it was intended to evaluate the volumetric changes in pharyngeal airway space in Class II division 1 patients with retrognathic mandible treated by Forsus-fixed functional appliance and to compare them with their pretreatment values. The importance of the third dimension and the use of CT have been emphasized as early as 1979, highlighting important limitations of two-dimensional airway studies.[9]

The ability to perform precise measurements of various cross-sectional areas, 3D reconstructions and volumetric measurements of the upper airway are some of the advantages of CT technology when compared with cephalometric techniques. Following the introduction of CBCT, the main disadvantages of conventional CT devices, such as high radiation dose and longer exposure times, were eliminated.[10] CBCTs have led to a better understanding of upper airway anatomy and physiology. In addition, Aboudara et al. stated that CBCT is a simple and effective method for the evaluation of the upper airway.[9] This study used 3D-Doctor Imaging Software (Able Software Corporation, USA), which is an advanced 3D modeling, image processing, and measurement software for MRI, CT, PET, microscopy, and other imaging applications.

The purpose of this study was to try to understand the effect of fixed functional appliances; specifically Forsus in Class II division 1 patients on airway volume (oropharynx [upper pharynx] and hypopharynx [lower pharynx]) by 3D imaging and their efficacy in reducing obstructive respiratory problems in future. It was seen that there was a significant increase (P< 0.001) in upper pharyngeal, lower pharyngeal, and total airway volume in treated cases after Forsus-fixed functional appliance therapy.

These findings match with those observed by Haskell et al.[11] in their study on the effects of mandibular advancement device (MAD) on airway dimensions. They reported an average oropharyngeal volume increase of approximately 2800 mm 3 with MAD therapy.

Previous other authors have also suggested the improvement in volume in the oropharynx with MAD.[12],[13],[14]

Dolce [15] compared one phase versus two phase treatment effects in their study and showed that the skeletal effects of phase1treatment disappear by the end of fixed appliance treatment. This explains the rising trend toward a one phase treatment (combination of fixed functional appliance with fixed mechanotherapy) enabling simultaneous skeletal and dental correction. Moreover, the usage of fixed functional appliances has eliminated the onus of patient compliance factor from dictating treatment outcome, thus making the treatment more predictable and also quicker.[16],[17],[18]

Hence, Forsus-fixed functional appliance therapy is suitable for skeletal correction of Class II malocclusion by forward movement of mandibular bony base in younger age group which in turn leads to increase in pharyngeal airway volume thus preventing OSA and other respiratory problems in future.

This study was concerned with the immediate treatment effects of the Forsus-fixed functional appliance on pharyngeal airway. The long-term implications of this treatment method need further consideration.


   Conclusions Top


  • The null hypothesis was rejected
  • There was a statistically significant increase in the volume of both hypopharynx and oropharynx in patients treated with Forsus-fixed functional appliance.


Hence, it can be concluded that Forsus-fixed functional appliance can be a promising appliance for improving pharyngeal airway space in Class II division 1 patients with retrognathic mandible.

This study was concerned with the immediate treatment effects of the Forsus-fixed functional appliance on pharyngeal airway. The long-term implications of this treatment method need further consideration.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
McNamara J. Orthodontic and Orthopaedic Treatment in Mixed Dentition. Needham, MA: Needham Press Inc.; 1995.  Back to cited text no. 1
    
2.
Johal A, Conaghan C. Maxillary morphology in obstructive sleep apnea: A cephalometric and model study. Angle Orthod 2004;74:648-56.  Back to cited text no. 2
    
3.
Conley RS, Legan HL. Correction of severe obstructive sleep apnea with bimaxillary transverse distraction osteogenesis and maxillomandibular advancement. Am J Orthod Dentofacial Orthop 2006;129:283-92.  Back to cited text no. 3
    
4.
Sharabi Y, Dagan Y, Grossman E. Sleep apnea as a risk factor for hypertension. Curr Opin Nephrol Hypertens 2004;13:359-64.  Back to cited text no. 4
    
5.
Kau CH, Richmond S, Palomo JM, Hans MG. Three-dimensional cone beam computerized tomography in orthodontics. J Orthod 2005;32:282-93.  Back to cited text no. 5
    
6.
Kawakami M, Yamamoto K, Fujimoto M, Ohgi K, Inoue M, Kirita T. Changes in tongue and hyoid positions, and posterior airway space following mandibular setback surgery. J Craniomaxillofac Surg 2005;33:107-10.  Back to cited text no. 6
    
7.
Marsan G, Vasfi Kuvat S, Oztas E, Cura N, Süsal Z, Emekli U. Oropharyngeal airway changes following bimaxillary surgery in class III female adults. J Craniomaxillofac Surg 2009;37:69-73.  Back to cited text no. 7
    
8.
Graber TM, Rakosi T, Petrovic AG, editors. Dentofacial Orthopedics with Functional Appliances. St. Louis: CV Mosby Company; 1985.  Back to cited text no. 8
    
9.
Aboudara C, Nielsen I, Huang JC, Maki K, Miller AJ, Hatcher D. Comparison of airway space with conventional lateral headfilms and 3-dimensional reconstruction from cone-beam computed tomography. Am J Orthod Dentofacial Orthop 2009;135:468-79.  Back to cited text no. 9
    
10.
Celikoglu M, Bayram M, Sekerci AE, Buyuk SK, Toy E. Comparison of pharyngeal airway volume among different vertical skeletal patterns: A cone-beam computed tomography study. Angle Orthod 2014;84:782-7.  Back to cited text no. 10
    
11.
Haskell JA, McCrillis J, Haskell BS, Scheetz JP, Scarfe WC, Farman AG, et al. Effects of mandibular advancement device (MAD) on airway dimensions assessed with cone-beam computed tomography. Semin Orthod 2009;15:132-58.  Back to cited text no. 11
    
12.
Fransson AM, Tegelberg A, Johansson A, Wenneberg B. Influence on the masticatory system in treatment of obstructive sleep apnea and snoring with a mandibular protruding device: A 2-year follow-up. Am J Orthod Dentofacial Orthop 2004;126:687-93.  Back to cited text no. 12
    
13.
Bonham PE, Currier GF, Orr WC, Othman J, Nanda RS. The effect of a modified functional appliance on obstructive sleep apnea. Am J Orthod Dentofacial Orthop 1988;94:384-92.  Back to cited text no. 13
    
14.
Clark GT, Arand D, Chung E, Tong D. Effect of anterior mandibular positioning on obstructive sleep apnea. Am Rev Respir Dis 1993;147:624-9.  Back to cited text no. 14
    
15.
Dolce C, Schader RE, McGorray SP, Wheeler TT. Centrographic analysis of 1-phase versus 2-phase treatment for class II malocclusion. Am J Orthod Dentofacial Orthop 2005;128:195-200.  Back to cited text no. 15
    
16.
Pancherz H, Ruf S, Kohlhas P. “Effective condylar growth” and chin position changes in Herbst treatment: A cephalometric roentgenographic long-term study. Am J Orthod Dentofacial Orthop 1998;114:437-46.  Back to cited text no. 16
    
17.
Proffit WR, Tulloch JF. Preadolescent class II problems: Treat now or wait? Am J Orthod Dentofacial Orthop 2002;121:560-2.  Back to cited text no. 17
    
18.
Brandão M, Pinho HS, Urias D. Clinical and quantitative assessment of headgear compliance: A pilot study. Am J Orthod Dentofacial Orthop 2006;129:239-44.  Back to cited text no. 18
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
 
 
    Tables

  [Table 1]


This article has been cited by
1 Changes in airway dimensions following functional appliances in growing patients with skeletal class II malocclusion: A systematic review and meta-analysis
MingLi Xiang,Bo Hu,Yang Liu,Jicheng Sun,Jinlin Song
International Journal of Pediatric Otorhinolaryngology. 2017; 97: 170
[Pubmed] | [DOI]



 

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