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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 8  |  Issue : 1  |  Page : 21-25

Cephalometric evaluation of soft palate changes after maxillary advancement in lip and palate cleft patients


1 Department of Oral and Maxillofacial Surgery, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran
2 Department of Orthodontics, Dental Faculty, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran
3 Department of Oral and Maxillofacial Surgery, Implant Research Center, Dental Faculty, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran
4 Craniomaxillofacial Research Center, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran

Date of Submission07-Mar-2020
Date of Acceptance25-Jun-2020
Date of Web Publication13-Jan-2021

Correspondence Address:
Dr. Hamidreza Mahaseni Aghdam
Department of Oral and Maxillofacial Surgery, Dental Faculty, Tehran Medical Sciences, Islamic Azad University, Tehran
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jclpca.jclpca_6_20

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  Abstract 


Introduction: Changes in the soft palate and velopharyngeal function are among the most important concerns for maxillofacial surgeons in patients with midface deficiency, especially in those with cleft palate who needed maxillary advancement. In this study, we evaluated cephalometric changes in soft palate after maxillary advancement. Materials and Methods: This study included 16 cleft patients (7 females and 9 males), with a mean age of 22 ± 3.47. The maxillary advancement alone was done in 10 patients and bimaxillary osteotomy in the other six patients. Cephalometric characteristics were assessed before and 6 months after the surgery, and the results were analyzed using paired t-test or Wilcoxon test. Results: The results showed a 6% increase (P < 0.05) for PNS-U (soft palate length) index. In addition, PTM-UPW (upper pharyngeal space) and U-MPW (middle pharyngeal space) increased by 5% (P < 0.05) and 5% (P < 0.08), respectively, after the surgery. V-LPW (lower pharyngeal space) also increased by 0.6% but was not statically significant. Conclusions: According to the results of this study, after surgical maxillary advancement, changes were observed in upper and middle pharyngeal spaces, soft palate length, and inclination, but lower pharyngeal space remained unchanged.

Keywords: Cephalometric changes, cleft lip and palate, maxillary advancement


How to cite this article:
Qaranizade K, Jafari A, Farahmand M, Aghdam HM, Shooshtari LT. Cephalometric evaluation of soft palate changes after maxillary advancement in lip and palate cleft patients. J Cleft Lip Palate Craniofac Anomal 2021;8:21-5

How to cite this URL:
Qaranizade K, Jafari A, Farahmand M, Aghdam HM, Shooshtari LT. Cephalometric evaluation of soft palate changes after maxillary advancement in lip and palate cleft patients. J Cleft Lip Palate Craniofac Anomal [serial online] 2021 [cited 2021 Jan 21];8:21-5. Available from: https://www.jclpca.org/text.asp?2021/8/1/21/295378




  Introduction Top


Changes in the soft palate and velopharyngeal function are one of the most important concerns of maxillofacial surgeons in patients with midface deficiency, especially in those with cleft palate who needed maxillary advancement.[1],[2],[3] The prevalence of skeletal class III deformity among different communities and races has been reported between 5% and 14%[4] The average prevalence of cleft lip with or without cleft palate is 7.75/10,000 live birth in the united states,[5] while the highest percentage of these patients is seen in Asia.[6] One of the main surgical procedures in treatment of maxillary deficiency in these patients is maxillary advancement that could have an effect on soft palate position and therefore velopharyngeal function.[7]

One of the most common problems in patients with palatal cleft is hypernasal speech due to velopharyngeal insufficiency because there is nasal air escape during speech.[8],[9]

One of the concerns in maxillary advancement surgery is the effect of hard palate elongation that can pull the soft palate forward, resulting in velopharyngeal insufficiency.[10] Tensor veli palatini as a main muscle in the soft palate is able to compensate anatomic changes to maintain velopharyngeal function in healthy individuals, but in patients with cleft palate, atrophy and disorientation of these muscles, in addition to the presence of scar tissue, can impair the ability of compensation and velopharyngeal function. Therefore, after repositioning maxilla, velopharyngeal insufficiency may worsen.[7] Some researchers have reported no evidence of significant changes in velopharyngeal function,[11] while others stated problems in velopharyngeal function after maxillary advancement.[7]

The purpose of this study is to evaluate cephalometric changes in soft palate and velopharyngeal area after maxillary advancement.


  Materials and Methods Top


This cross-sectional clinical trial was approved by local board of ethics and research method of Azad University of Medical Sciences. Completion of questionnaire was based on required information in patients' medical and cephalometric records.

This study was done on 16 patients (9 males and 7 females). The selection criteria were patients with maxillary deficiency (skeletal Class III malformation) as a result of unilateral cleft lip and palate that underwent mono-maxillary advancement or bimaxillary surgery (maxillary advancement and mandibular setback) based on their medical records. The palatal cleft had been treated surgically during the first stages of their treatment, and there was no residual palatal cleft or fistula before our orthognathic surgery. Presurgical orthodontic treatment had been done in all patients with the aim of decompensation, leveling, tooth alignment, and arch coordination. All needed information such as age, sex, past medical and surgical history such as alveolar graft, pharyngeal flap, and the presence of hypernasal speech were completed. Lateral cephalometric radiographs were available, and images obtained after the surgery were in the same position as those taken before the surgery. All radiographs were obtained with the imaging system Orthophos XG 3D Ready Ceph (Sirona Dental Systems, Bensheim, Germany) at 72 kV, 15 mA, with the source to midsagittal plane distance of 1.5 m. One calibration ruler for magnification correction was used in all samples.

All the radiographs were obtained at natural head position (NHP) at the same center before and after the surgery. NHP is a standardized and reproducible position, with the patient head in an upright position and the eyes focused on the mirror in front of the patient.

Six patients underwent bimaxillary surgery, and maxillary osteotomy was performed on the rest of the patients. All the cases were treated by Le Fort 1 maxillary advancement. In the cases that needed mandibular setback, the surgery was done with bilateral sagittal split ramus osteotomy. Rigid fixation with plates and screws was done in all cases. All the surgeries had been done by the same surgeon. None of our patients underwent distraction osteogenesis.

They all had previous alveolar graft surgery, without history of previous pharyngeal flap. They all had some degree of hypernasal speech. The average maxillary advancement and mandibular setback in the aforementioned patients were 4.6 and 4 mm, respectively.

Cephalometric images obtained in NHP were studied, and patients with radiographic images not taken in NHP method or cases in which time interval between surgery and imaging was more than 6 months were not included in this study. Tracing was done on cephalograms by two observers. The scaled ruler that already exists in lateral cephalometries was used to assess whether the lateral cephalograms were of true size or not. In cases of dissimilarity, the smaller image was copied with higher magnification percentage, then the two images were superimposed on the SN line and unified according to size. Subsequently, the desired measurements were done.

The palate cephalometric indices and related factors such as SNA, SNB, MNB, the Jarabak ratio, inclination angle, soft palate length, soft palate inclination, PTM-UPW, U-MPW, and V-LPW were determined before and after the surgery, and changes were statistically analyzed using paired t-test and Wilcoxon test (statistically significant differences were set at P < 0.05) [Figure 1]. Data were analyzed using the IBM SPSS Statistics for Windows, version 22 (IBM Corp., Armonk, N.Y., USA). Then, factors such as age, sex, type of surgery, history of previous surgeries, existence of hypernasality, alveolar graft, and pharyngeal flap were statistically analyzed using Chi-square test and Fisher's exact test to determine if there is any correlation between these factors and the effects of surgery on palatal soft tissue changes. (Statistically significant differences were set at P = 0.4.)
Figure 1: Cephalometric landmarks that were used in this study. Cephalometric index: (1) PNS-U: soft palate length (2) Sper × PNS-U: soft palate inclination (3) Ptm-upw: nasopharynx (4) U-Mpw: oropharynx (5) V-Lpw: hypopharynx (6) Ptm-M: maxillary advancement

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  Results Top


This study was done on 16 patients (9 males [56%] and 7 females [44%], with a mean age of 22 ± 3.47) with maxillary deficiency (skeletal Class III malformation) as a result of unilateral cleft lip and palate.

The following indices had more than 5% changes, either positive or negative: PNS-U, SN × M-PNS, MNB, SNM, U-MPW, PTM-UPW, and PTM-M, and the rest of the indices presented <5% transformation, as shown in [Table 1].
Table 1: Cephalometric indices based on follow-up periods after surgery

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MNB, PNS-U, PTM-M, and PTM-UPW landmarks showed more than 5% change, and the difference between pre- and postoperative measurements was statistically significant. Even though SNM, SN × M-PNS, and U-MPW landmarks also had more than 5% change, no statistically significant difference was seen.

Indices with more than 5% changes and statistically significant were evaluated according to their age, sex, and type of surgery, as demonstrated in [Table 2], representing that NWB and PTM-M landmarks showed more than 50% variation in all cases, regardless of age, sex, and surgery type. The rest of the landmarks, whether changed or not, were not influenced by age, sex, and type of surgery, and their variation was not statistically significant. Therefore, related factors such as age, sex, type of surgery, history of previous surgeries, existence of hypernasality, alveolar graft, and pharyngeal flap had no correlation with the results of soft palate changes in this study.
Table 2: Patient distribution according to the changes of the indices and segregation of the related factors

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  Discussion Top


One of the concerns for maxillofacial surgeons after treatment of Class III skeletal abnormalities in patients with cleft lip and palate, by means of maxillary advancement surgery, is the unpredictable changes in soft palate and velopharyngeal function. Hypoplasia and decrease in maxillary growth are common deformities among patients with cleft lip and palate.[12],[13] Maxillary advancement surgery is the best way to correct these deformities. In total maxillary advancement surgery, sometimes, it is difficult to achieve more than 6 mm advancement, and also, 20%–25% relapse is reported in these patients because of previous scars.[14] On the other hand, this surgery may affect the velopharyngeal and soft palate position and therefore could cause some changes in the dimension of airway and also velopharyngeal function.[10],[15] Therefore, the aim of this study was to evaluate the cephalometric changes in the soft palate in patients with cleft lip and palate after maxillary advancement.

In the present study, the length of soft palate (PNS-U) was increased by 1.81 mm or 6% after surgery (average maxillary advancement was 4.06 mm), which is statistically significant. This finding was compatible with findings by Utreja et al.,[1] Mason et al.,[16] and also Schendel et al.[17] and in conflict with the studies of Heliövaara et al.[18],[19] and Ko et al.[20] that did not find any significant changes in soft palate length after surgery.

Mason et al.[16] and Kummer et al.[21] stated that when the maxilla moves forward, the distance between pharyngeal wall and soft palate increases. Furthermore, the length of soft palate increases through an adaptive mechanism, in order to compensate the changes that have occurred. The latter can be due to elasticity of the soft palate rather than its growth. In this study, the inclination of the soft palate increased 1.84° clockwise (4.5%), which was consistent with the research of Utreja et al.,[1] Schendel et al.,[17] and Ko et al.[20] This increase can be an adaptive mechanism to preserve velopharyngeal function.

The upper pharyngeal airway passage (PTM-UPW) showed 1-mm (5%) increase after surgery, which was statistically significant, similar to the findings of Heliövaara et al.,[18],[19] Ko et al.,[20] and Mochida et al.[22] Furthermore, a 0.53-mm (5%) increase in oropharynx (U-PMW) or middle pharyngeal airway passage was observed after surgery but was not statistically significant, matching the results of previous studies. In a similar study, Utreja et al.[1] showed an increase in the oropharynx after surgery, but this finding was statistically insignificant. Heliövaara et al.[18] did not find any considerable changes in the oropharynx. This increase in the oropharynx after surgery may be the result of PNS and soft palate protrusion after maxillary advancement.

Schendel et al.[17] claimed a 84% deterioration of the velopharyngeal function just 4 months after maxillary advancement in cleft lip and palate patients, while in another study, Kanno et al.[11] experienced no deterioration following the advancement procedure.

Based on Kim et al.,[23] there was no velopharyngeal functional disorder either in patients with cleft lip and palate or in noncleft patients after surgery. Even though there might be a small disturbance in velopharyngeal function due to the maxillary advancement, it is less significant, when considering the esthetic improvements gained from maxillary advancement surgery in treatment of midface deficiency in these patients.

In spite of similar and contradictory views in previous studies, explaining changes in the inclination and length of soft palate and pharyngeal spaces, no one discusses the adaptive mechanism of the soft palate after maxillary advancement; they only mentioned the adaptation of soft palate after advancement which has no effect on hypernasality. Local anatomy should be given more consideration in order to interpret this fact. The remarkable point is that following maxillary advancement, soft palate composed of palatal aponeurosis along with the attached muscles moves forward. However, since the position of posterior osteotomy line, from the maxillary tuberosity, locates anteriorly to the pterygoid process, the attachments of muscles such as tensor veli palatini, levator veli palatini, palatopharyngeus, palatoglossus, and superior pharyngeal constrictor, are moved posteriorly in relation to the osteotomy line.

Tensor veli palatini, the sheath of which turns around the pterygoid hamulus, will elongate anteriorly as a result of maxillary advancement. Tensor veli palatini and palatopharyngeus muscle cause the posterior and upside elongation of the soft palate and resist against palatal tension after osteotomy. This causes elongation of the soft palate and changes its inclination in an ascending direction. In fact, even recuperation of hypernasality in patients with cleft lip and palate has been observed after maxillary advancement, which may be the result of tension of the soft palate that may cause indirect reinforcement of atrophic muscles. Thus, like the preceding studies, using Le Fort I osteotomy to correct maxillary growth defect, will not cause hypernasality. Previous research has also emphasized on the fact that if a patient does not represent hypernasality before the surgery, he or she will not have this condition after the surgery either.[23] Meanwhile, existence of muscles such as palatopharyngeus and superior pharyngeal constrictor causes narrowing of the lateral pharyngeal space following osteotomy, which reduces hypernasality.

Since previous palatal surgeries in our subjects had been performed by different surgeons using various different undocumented techniques, it is not possible to find an exact relationship among the existing data. For instance, osteotomy of the pterygoid hamulus or section of the tensor veli palatini tendon is done in some surgeries, which may all influence velopharyngeal function. In addition, since we cannot predict the repair of the displaced muscles in cleft patients as a result of their previous palatal cleft repair surgery, whether completely healed or not, we are often faced with misplaced and atrophic muscles, and hypernasality may result from the dysfunction of these aforementioned muscles.

Regarding the current study, maxillary advancement in patients with cleft lip and palate results in elongation of soft palate and reinforcement of the atrophic muscles, which can recapture hypernasality. In addition, pharyngeal airway and morphology of the soft palate along with its muscles should be evaluated before the surgery, and more attention should be given to the local anatomy.


  Conclusion Top


Therefor due to the lack of comprehensive information about the changes in upper and middle pharyngeal spaces, soft palate length, and inclination, we decided to search about the effect of surgical maxillary advancement on these parameters.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



Utreja AK, Jena AK, Rattan V, Singh SP. Immediate and long-term changes in the pharyngeal airway passage following maxillary advancement with distraction osteogenesis in adult patients with cleft lip and palate. J Ind Orthod Soc 2012;45:219-23.

McComb RW, Marrinan EM, Nuss RC, Labrie RA, Mulliken JB, Padwa BL. Predictors of velopharyngeal insufficiency after Le Fort I maxillary advancement in patients with cleft palate. J Oral Maxillofac Surg 2011;69:2226-32.

Danaei SM, Maram SS, Zamiri B, Tehranchi A. Assessment of the changes in the dimensions of the soft palate following orthognathic surgery in class III patients. J Dent Shiraz Univ Med Sci 2012;13:1-8.

Mouakeh M. Cephalometric evaluation of craniofacial pattern of Syrian children with Class III malocclusion. Am J Orthod Dentofacial Orthop 2001;119:640-9.

Tanaka SA, Mahabir RC, Jupiter DC, Menezes JM. Updating the epidemiology of cleft lip with or without cleft palate. Plast Reconstr Surg 2012;129:511e-8e.

Gorlin RJ, Cohen MM, Hennekam RC, Raoul CM. Syndromes of the Head and Neck. New York: Oxford University Press; 2001. p. 822-8.

Janulewicz J, Costello BJ, Buckley MJ, Ford MD, Close J, Gassner R. The effects of Le Fort I osteotomies on velopharyngeal and speech functions in cleft patients. J Oral Maxillofac Surg 2004;62:308-14.

Dotevall H, Lohmander-Agerskov A, Ejnell H, Bake B. Perceptual evaluation of speech and velopharyngeal function in children with and without cleft palate and the relationship to nasal airflow patterns. Cleft Palate Craniofac J 2002;39:409-24.

Kuehn DP, Moller KT. Speech and language issues in the cleft palate population: The state of the art. Cleft Palate Craniofac J 2000;37:1-35.

Witzel MA, Munro IR. Velopharyngeal insufficiency after maxillary advancement. Cleft Palate J 1977;14:176-80.

Kanno T, Mitsugi M, Hosoe M, Sukegawa S, Yamauchi K, Furuki Y. Long-term skeletal stability after maxillary advancement with distraction osteogenesis in nongrowing patients. J Oral Maxillofac Surg 2008;66:1833-46.

Saito K, Ono T, Mochida M, Ohyama K. Changes in nasorespiratory function in association with maxillary distraction osteogenesis in subjects with cleft lip and palate. Cleft Palate Craniofac J 2006;43:75-83.

Rachmiel A, Aizenbud D, Peled M. Long-term results in maxillary deficiency using intraoral devices. Int J Oral Maxillofac Surg 2005;34:473-9.

Gateno J, Engel ER, Teichgraeber JF, Yamaji KE, Xia JJ. A new le fort I internal distraction device in the treatment of severe maxillary hypoplasia. J Oral Maxillofac Surg 2005;63:148-54.

Tahmasbi S, Jamilian A, Showkatbakhsh R, Pourdanesh F, Behnaz M. Cephalometric changes in nasopharyngeal area after anterior maxillary segmental distraction versus Le Fort I osteotomy in patients with cleft lip and palate. Eur J Dent 2018;12:393-7.

Mason R, Turvey TA, Warren DW. Speech considerations with maxillary advancement procedures. J Oral Surg 1980;38:752-8.

Schendel SA, Oeschlaeger M, Wolford LM, Epker BN. Velopharyngeal anatomy and maxillary advancement. J Maxillofac Surg 1979;7:116-24.

Heliövaara A, Ranta R, Hukki J, Haapanen ML. Cephalometric pharyngeal changes after Le Fort I osteotomy in patients with unilateral cleft lip and palate. Acta Odontol Scand 2002;60:141-5.

Heliövaara A, Hukki J, Ranta R, Haapanen ML. Cephalometric pharyngeal changes after Le Fort I osteotomy in different types of clefts. Scand J Plast Reconstr Surg Hand Surg 2004;38:5-10.

Ko EW, Figueroa AA, Guyette TW, Polley JW, Law WR. Velopharyngeal changes after maxillary advancement in cleft patients with distraction osteogenesis using a rigid external distraction device: A 1-year cephalometric follow-up. J Craniofac Surg 1999;10:312-20.

Kummer AW, Strife JL, Grau WH, Creaghead NA, Lee L. The effects of Le Fort I osteotomy with maxillary movement on articulation, resonance, and velopharyngeal function. Cleft Palate J 1989;26:193-9.

Mochida M, Ono T, Saito K, Tsuiki S, Ohyama K. Effects of maxillary distraction osteogenesis on the upper-airway size and nasal resistance in subjects with cleft lip and palate. Orthod Craniofac Res 2004;7:189-97.

Kim SK, Kim JC, Moon JB, Lee KC. Perceptual speech assessment after maxillary advancement osteotomy in patients with a repaired cleft lip and palate. Arch Plast Surg 2012;39:198-202.





 
  References Top

1.
Utreja AK, Jena AK, Rattan V, Singh SP. Immediate and long-term changes in the pharyngeal airway passage following maxillary advancement with distraction osteogenesis in adult patients with cleft lip and palate. J Ind Orthod Soc 2012;45:219-23.  Back to cited text no. 1
    
2.
McComb RW, Marrinan EM, Nuss RC, Labrie RA, Mulliken JB, Padwa BL. Predictors of velopharyngeal insufficiency after Le Fort I maxillary advancement in patients with cleft palate. J Oral Maxillofac Surg 2011;69:2226-32.  Back to cited text no. 2
    
3.
Danaei SM, Maram SS, Zamiri B, Tehranchi A. Assessment of the changes in the dimensions of the soft palate following orthognathic surgery in class III patients. J Dent Shiraz Univ Med Sci 2012;13:1-8.  Back to cited text no. 3
    
4.
Mouakeh M. Cephalometric evaluation of craniofacial pattern of Syrian children with Class III malocclusion. Am J Orthod Dentofacial Orthop 2001;119:640-9.  Back to cited text no. 4
    
5.
Tanaka SA, Mahabir RC, Jupiter DC, Menezes JM. Updating the epidemiology of cleft lip with or without cleft palate. Plast Reconstr Surg 2012;129:511e-8e.  Back to cited text no. 5
    
6.
Gorlin RJ, Cohen MM, Hennekam RC, Raoul CM. Syndromes of the Head and Neck. New York: Oxford University Press; 2001. p. 822-8.  Back to cited text no. 6
    
7.
Janulewicz J, Costello BJ, Buckley MJ, Ford MD, Close J, Gassner R. The effects of Le Fort I osteotomies on velopharyngeal and speech functions in cleft patients. J Oral Maxillofac Surg 2004;62:308-14.  Back to cited text no. 7
    
8.
Dotevall H, Lohmander-Agerskov A, Ejnell H, Bake B. Perceptual evaluation of speech and velopharyngeal function in children with and without cleft palate and the relationship to nasal airflow patterns. Cleft Palate Craniofac J 2002;39:409-24.  Back to cited text no. 8
    
9.
Kuehn DP, Moller KT. Speech and language issues in the cleft palate population: The state of the art. Cleft Palate Craniofac J 2000;37:1-35.  Back to cited text no. 9
    
10.
Witzel MA, Munro IR. Velopharyngeal insufficiency after maxillary advancement. Cleft Palate J 1977;14:176-80.  Back to cited text no. 10
    
11.
Kanno T, Mitsugi M, Hosoe M, Sukegawa S, Yamauchi K, Furuki Y. Long-term skeletal stability after maxillary advancement with distraction osteogenesis in nongrowing patients. J Oral Maxillofac Surg 2008;66:1833-46.  Back to cited text no. 11
    
12.
Saito K, Ono T, Mochida M, Ohyama K. Changes in nasorespiratory function in association with maxillary distraction osteogenesis in subjects with cleft lip and palate. Cleft Palate Craniofac J 2006;43:75-83.  Back to cited text no. 12
    
13.
Rachmiel A, Aizenbud D, Peled M. Long-term results in maxillary deficiency using intraoral devices. Int J Oral Maxillofac Surg 2005;34:473-9.  Back to cited text no. 13
    
14.
Gateno J, Engel ER, Teichgraeber JF, Yamaji KE, Xia JJ. A new le fort I internal distraction device in the treatment of severe maxillary hypoplasia. J Oral Maxillofac Surg 2005;63:148-54.  Back to cited text no. 14
    
15.
Tahmasbi S, Jamilian A, Showkatbakhsh R, Pourdanesh F, Behnaz M. Cephalometric changes in nasopharyngeal area after anterior maxillary segmental distraction versus Le Fort I osteotomy in patients with cleft lip and palate. Eur J Dent 2018;12:393-7.  Back to cited text no. 15
[PUBMED]  [Full text]  
16.
Mason R, Turvey TA, Warren DW. Speech considerations with maxillary advancement procedures. J Oral Surg 1980;38:752-8.  Back to cited text no. 16
    
17.
Schendel SA, Oeschlaeger M, Wolford LM, Epker BN. Velopharyngeal anatomy and maxillary advancement. J Maxillofac Surg 1979;7:116-24.  Back to cited text no. 17
    
18.
Heliövaara A, Ranta R, Hukki J, Haapanen ML. Cephalometric pharyngeal changes after Le Fort I osteotomy in patients with unilateral cleft lip and palate. Acta Odontol Scand 2002;60:141-5.  Back to cited text no. 18
    
19.
Heliövaara A, Hukki J, Ranta R, Haapanen ML. Cephalometric pharyngeal changes after Le Fort I osteotomy in different types of clefts. Scand J Plast Reconstr Surg Hand Surg 2004;38:5-10.  Back to cited text no. 19
    
20.
Ko EW, Figueroa AA, Guyette TW, Polley JW, Law WR. Velopharyngeal changes after maxillary advancement in cleft patients with distraction osteogenesis using a rigid external distraction device: A 1-year cephalometric follow-up. J Craniofac Surg 1999;10:312-20.  Back to cited text no. 20
    
21.
Kummer AW, Strife JL, Grau WH, Creaghead NA, Lee L. The effects of Le Fort I osteotomy with maxillary movement on articulation, resonance, and velopharyngeal function. Cleft Palate J 1989;26:193-9.  Back to cited text no. 21
    
22.
Mochida M, Ono T, Saito K, Tsuiki S, Ohyama K. Effects of maxillary distraction osteogenesis on the upper-airway size and nasal resistance in subjects with cleft lip and palate. Orthod Craniofac Res 2004;7:189-97.  Back to cited text no. 22
    
23.
Kim SK, Kim JC, Moon JB, Lee KC. Perceptual speech assessment after maxillary advancement osteotomy in patients with a repaired cleft lip and palate. Arch Plast Surg 2012;39:198-202.  Back to cited text no. 23
    


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