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Cephalometric changes in nasopharyngeal area after anterior maxillary segmental distraction versus Le Fort I osteotomy in patients with cleft lip and palate

Objective: The present study was designed to compare the effects of two surgical methods, anterior maxillary segmental distraction (AMSD) versus conventional Le Fort I osteotomy, on cephalometric changes of velopharyngeal area of patients with cleft lip and palate. Materials and Methods: This study was conducted on 20 CLP in two groups. The first group had classic Le Fort I maxillary advancement and the second group had AMSD with a modified hyrax as an intraoral tooth-borne distractor. In the second group, 1 week after the surgery, activation of hyrax screw was started with the rate of 2 times a day for about 10 days. Initial and final lateral cephalograms were traced and analyzed by OrthoSurgerX software. Results: The changes in variables evaluating velopharyngeal status showed a significant difference between the two groups. In Group A (conventional), the mean of nasopharyngeal area and Nasopharynx floor length showed a significant increase (P < 0.05) after the surgery, while in Group B (DO), the trend of changes was vice-versa. The changes in SNA, overjet, and soft-tissue convexity were similar in both groups. Conclusion: AMSD can improve facial profile, almost similar to the conventional Le Fort I advancement, while there is a significant decrease in nasopharyngeal; hereby there is no increase in the velopharyngeal sphincter.


INTRODUCTION
Most of the Patients with cleft lip and palate suffer from maxillary hypoplasia mostly due to soft-tissue scarring from lip and palate repair. [1] This problem should be addressed by orthopedic advancement of the maxilla during the growth Total maxillary advancement could be accomplished instantly by conventional orthognathic surgery or gradually through distraction osteogenesis (DO). [1] Le Fort I osteotomy offers some advantages over DO method including more predictable and precise results, less office time, and less need to patient cooperation but has some disadvantages such as longer surgery time and relapse tendency specially in CLP patients. [4] It is usually difficult to achieve >6 mm maxillary advancement in these patients and about 20%-25% relapse is reported after conventional surgery mostly as a result of previous scars. [5] Forward movement of the soft palate following the anterior repositioning of the entire maxilla may have an adverse effect on the velopharyngeal function (VPF) which is the most important factor influencing the speech in CLP patients. [6,7] There is controversy over this effect in the literature. [8] While some studies have reported no effect on velopharyngeal status and speech after maxillary advancement, others claimed deterioration of VF and triggering or worsening of speech problems in these patients. [9][10][11] Taha and Elsheikh found a positive correlation between the amount of maxillary advancement by DO and the increase in hypernasality and nasopharyngeal depth. [6] The results of another study [12] showed that the hypernasality is not always proportional to the extent of advancement, but it depends on the posterior pharyngeal wall position and rotation of the palatal plane.
Entire maxillary advancement through conventional Le Fort I osteotomy or DO could be replaced by anterior maxillary segmental distraction (AMSD) in CLP patients to maintain the velopharyngeal area intact. [13] Block and Brister reported the first successful clinical application of AMSD in dogs [14] followed by the experience of Dolanmaz on humans in 2003 [15] Various studies have been launched on the optimal protocols and ideal patients for AMSD. [2,13,[16][17][18][19] The present study aimed at evaluating the cephalometric changes of velopharyngeal area following AMSD and comparing them with conventional maxillary advancement in CLP patients. To the best of our knowledge, no other study has been performed such evaluation.

MATERIALS AND METHODS
This study was approved by the Ethics Committee of Shahid Beheshti University of Medical Sciences in Iran (code IR.SBMU.RIDS.REC.1394.12). This retrospective study was conducted on 20 CLP patients who had surgery for correction of maxillary deficiency and orthodontic treatment. All patients had severe maxillary hypoplasia (SNA <76) and negative overjet (at least -4 mm). All patients were treated in Dental School of Shahid Beheshti University and their surgeries were performed in Taleghani hospital. According to the surgery method, the patients were divided into two groups of 10. The first group had classic Le Fort I maxillary advancement and the second group had AMSD with an intraoral tooth-borne distractor (without downfracture).
In the first group, after preoperative orthodontic treatment, routine maxillary advancement was done and followed by postoperative orthodontics (Group A). For the other group (Group B), preoperative orthodontic treatment created a space of about 2 mm between the maxillary first and second molars. Then, during the surgery, anterior maxillary segmental osteotomy was performed anterior to the second molars with an extra vertical cut between first and second molars. A tooth-borne anteroposterior distractor (a hyrax appliance with 90° rotation), [20] which was made in advance on a plaster model, was cemented in place in operation room [ Figure 1]. One week after the surgery, activation of hyrax screw was started with the rate of 2 times a day for about 10 days until at least edge-to-edge incisal relation was achieved. Afterward, distractor was remained in place for about 4 months. The interdental space created by distraction at the osteotomy site was utilized to correct dental crowding orthodontically, without the need for tooth extraction. A functionally stable occlusion with the alignment of teeth in the arch and a positive overjet were established at the end of 1-year postsurgery in all patients. Final records were prepared approximately 12 months postsurgery.
All initial and final lateral cephalograms were traced and analyzed by OrthoSurgerX software, [21] which was prepared for airway evaluation according to Linder-Aronson and Henrikson, [22] Tobias, [23] and Bergland [24] studies. Reference points were marked, yielding 22 linear and seven angular measurements [ . Linear measurements were adjusted according to SN.
Soft-tissue convexity angle was obtained by Dolphin software (version 10.5, Canoga Park, CA).

Statistical analysis
Data were analyzed using the SPSS software (SPSS version 22.0, SPSS, Chicago, IL, USA). Among all measurements, the changes in nasopharyngeal area as the most important variable for airway evaluation and also palatal length, nasopharynx floor length, and total maxillary length as linear measurements were analyzed in both groups [ Figure 2]. For detecting the amount of maxillary advancement following the surgery, SNA as angular measurement was assessed. Descriptive statistics were calculated in the form of mean and standard deviation. As all variables' distribution was normal, the significance of difference was tested using the repeated measurement ANOVA, considering α = 0.05 and β = 0.2.

RESULTS
The two groups were matched according to age, sex, severity of maxillary deficiency, and type of CLP. The mean age in Group A and B was 19.3 and 20.5 years, respectively. In Group A, there were 7 men and 3 women, and in Group B, there were 6 men and 4 women. Furthermore, in the first group, there were 8 patients with bilateral CLP and 2 patients with unilateral CLP, while these amounts were 9 and 1 in the second group.
Pretreatment and posttreatment mean cephalometric and P values are presented in Table 1. Pretreatment values for SNA, overjet, and soft-tissue convexity in Group A were 72.06°, −5.42 mm, and 178.2°, respectively, while these amounts in Group B were 69.66°, −5.97 mm, and 176.69°.
In Group A, the changes in nasopharyngeal area, nasopharynx floor length, effective length of maxilla, and SNA were significant, comparing pre-and postsurgery. Following AMSD in Group B, nasopharyngeal area, length of palate, and SNA changed significantly. The changes in all variables     Table 1 showed a significant difference between the two groups. In Group A (conventional method), the mean of nasopharyngeal area pre-and post-treatment was 628.7 mm 2 and 818.94 mm 2 , respectively, which shows significant increase (P < 0.05) after the surgery, while in Group B (DO method), the trend of changes was vice versa and these amounts were 708.2 mm 2 (before surgery) and 581.8 mm 2 (after surgery) indicating significant decrease (P < 0.05) following the distraction.
Another important variable is SNA which indicates these methods' success in maxillary advancement. Following conventional advancement in Group A, the SNA mean changed from 72.06° to 77.94° (P < 0.05), whereas DO method in Group B changed the mean SNA from 69.66° presurgery to 72.89° postsurgery (P < 0.05). Comparison between the two groups showed no significant difference (P = 0.073). The changes in overjet and soft-tissue convexity were also similar in both groups (P = 0.953 and P = 0.552, respectively).

DISCUSSION
Changes in speech and velopharyngeal function (VPF) after maxillary advancement through conventional Le Fort I or even distraction of total maxillae have been reported in CLP patients. [9][10][11]25] AMSD has been proposed to advance the anterior segment of the maxillae and create the space in maxillary arch without deterioration of the velopharyngeal function. Patients with anterior crossbite, concave profile due to maxillary deficiency, crowding or tooth impaction in the upper arch, and velopharyngeal insufficiency are good candidates for this technique. [13,19,26] In the present study, we compared the effect of AMSD and conventional maxillary advancement on changes in cephalometric variables evaluating the amount of advancement and velopharyngeal status which was performed in no previous study. Various appliances including external and internal distractors such as the Dynaform system, modified hyrax appliance, and the hybrid distractors have been reported to be used for anterior maxillary distraction. [27,28] The modified hyrax appliance, which was used as the distractor in this study, had the advantage of easy fabrication, minimal expense, and good patient tolerance.
In both groups, analysis of the sagittal position of the maxilla through SNA, soft-tissue convexity, and overjet showed significant changes, which were expected as a result of distraction or surgical advancement, while these changes had no significant difference between the two groups. This fact shows that the amount of A point advancement was almost the same in both groups. Other studies also showed significant facial profile improvement following AMSD. [2,13,17] When the maxilla was brought forward by conventional advancement, the nasopharyngeal area was increased significantly, which shows that velopharyngeal function probably has been adversely affected. This effect has been reported in previous studies following Le Fort I osteotomy [29,30] or even after maxillary advancement by distraction. [6,12,31] They found a significant positive correlation between the amount of forward skeletal movement and postdistraction hypernasality and pharyngeal depth. [6,31] Chua et al. concluded that total maxillary distraction has no advantage over conventional advancement for the purpose of preventing velopharyngeal incompetence and speech disturbance in moderate cleft maxillary advancement. [9] On the contrary, in the AMSD group, the nasopharyngeal area was decreased significantly and nasopharynx floor length also showed an insignificant decrease, which are favorable changes in the velopharyngeal sphincter. Furthermore, length This proposes no detrimental effect on speech. To the best of our knowledge, just one study by Rao Janardhan et al. had been evaluated the effect of AMSD on speech, and they found no deterioration of speech after AMSD. [2] CONCLUSION AMSD of the hypoplastic cleft maxilla can improve facial balance and esthetics, almost similar to the conventional Le Fort I advancement, while there is a significant decrease in nasopharyngeal; hereby, there is no increase in the velopharyngeal sphincter.

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