Changes in nasal structures following orthopaedic and surgically assisted rapid maxillary expansion

Abstract

The aim of this study was to investigate and compare changes in the nasomaxillary complex substructures following orthopaedic rapid maxillary expansion (RME) and surgically assisted RME (SARME). 10 patients received RME, 10 patients received SARME, and 10 patients served as an untreated control group. Lateral and posteroanterior cephalograms were obtained for each individual at pre-expansion/pre-control (T1) and post-expansion/post-control (T2). Descriptive parameters and transversal measurements on maxillo-mandibular dentoalveolar structures and skeletal bases, right and left nasal cavity angles (NC/Lom/VL and CN/Lom/VL, respectively), total nasal cavity angle (NC/Lom/CN), nasal cavity width (NC-CN) and nasal septum angle (sn/Lom/VL) were also calculated. Paired t -tests were used to evaluate changes within groups following treatment/control. Analysis of variance (ANOVA) and Duncan’s tests were used to compare changes between groups. With the exception of nasal septum deviation, all nasal parameters significantly increased following RME and SARME. The increases in the SARME group were greater than in the other groups, but no statistically significant differences were recorded between the RME and SARME groups. Neither RME nor SARME created positional changes in the nasal septum.

Rapid maxillary expansion (RME) has been the gold standard for maxillary expansion in children and adolescents. Surgically assisted rapid maxillary expansion (SARME), which involves surgical weakening of certain anatomic structures of the midface prior to RME, has been proposed as a means of obtaining better results in adults and avoiding bone fracture, pain and gingival complications .

RME and SARME have been successful in the treatment of maxillary transverse deficiency, nasal airway resistance , nasal septum deviation and obstructive sleep apnea . Patients presenting with maxillary transverse deficiency have also been reported to have small nasal cross-sectional areas . It has been suggested that by gradually increasing nasal volume and reducing nasal airway resistance , maxillary expanders lead to improved breathing, physical development, athletic performance and general health .

No differences have been reported between RME and SARME with the exception of indication , which is based on the facial skeleton’s increased resistance to maxillary expansion that occurs with age and skeletal maturation. It is possible that SARME could be more effective than RME in increasing nasal dimensions because it offers more parallel expanded maxillary bony segments. The objective of the present study was to determine if there is a difference between the effects of orthopaedic RME and SARME on nasal structures.

Materials and methods

Subjects

This study examined lateral cephalometric radiographs from 30 subjects ( Table 1 ). 20 subjects were patients at the Ankara University, Faculty of Dentistry, and 10 subjects were randomly selected from the Faculty’s longitudinal archives as controls. Inclusion criteria for the maxillary expansion groups were: presence of posterior bilateral cross-bite with skeletal involvement; no future orthognathic surgery required; and no pre-expansion orthodontics applied.

Table 1
The mean (X), standard errors (Sx), minimum (min) and maximum (max) values of the ages of the subjects in SARME, RME and control groups.
Groups N Chronological age (years)
X Sx Min Max
SARME 10 ♀: 7 19.01 1.22 16.25 25.58
♂: 3
RME 10 ♀: 6 15.51 1.09 13.33 17.58
♂: 4
Control 10 ♀: 6 15.27 1.43 13.42 17.00
♂: 4

The RME group comprised 10 patients (six male, four female) with a mean age of 15.51 years (range 13.33–17.58 years) and a minimum skeletal age of 15 years, according to Greulich–Pyle hand–wrist analysis . The SARME group comprised 10 patients (seven male, three female) with a mean age of 19.01 years (range 16.25–25.58 years) and a minimum skeletal age of 17 years, according to Greulich–Pyle hand–wrist analysis . Of the 10 patients in the SARME group, six patients were older than 17 years and four patients were 17 years or younger. The latter four patients were initially treated by RME, but their treatment was continued with surgical assistance due to discomfort, pain and resistance to expansion. Patients in the RME group had completed 99.2% (minimum: 98.6%, maximum: 99.8%) of their growth potential, and the patients in the SARME group had completed 99.5% (minimum: 99.1%, maximum: 100%) of their growth potential . The control group comprised 10 untreated subjects (six male, four female) matched to the RME group for sex and age ( Table 1 ) in order to assess the effects of nasopharyngeal growth over a 1-year follow-up period. (Growth of the airway is complete at approximately 15 years of age , so controls were not required for the SARME group.) The same type of expansion appliance and surgical procedure was used in all cases ( Fig. 1 ).

Fig. 1
A patient treated with SARME. (a) Occlusal photograph. (b) Occlusal radiograph.

RME

An occlusal-coverage Hyrax-type palatal expander was used to eliminate premature contacts during expansion. After bonding of the appliances, patients and their parents were instructed to activate the screws one full turn in the morning and one full turn in the evening (one turn equals 0.25 mm).

RME

An occlusal-coverage Hyrax-type palatal expander was used to eliminate premature contacts during expansion. After bonding of the appliances, patients and their parents were instructed to activate the screws one full turn in the morning and one full turn in the evening (one turn equals 0.25 mm).

SARME

Subjects in this group received occlusal-coverage Hyrax-type palatal expanders. Surgery was performed under local anaesthesia. Bilateral incisions were made at the depth of the vestibule from the first molar area to the distal aspect of the lateral incisor. The mucoperiosteum was elevated, and the maxillary bone exposed from the piriform aperture to the pterygomaxillary fissure. After identifying the infraorbital nerve, an osteotomy was performed horizontally from the piriform aperture to the pterygomaxillary fissure well above the apices of the teeth. The pterygoid plates were not separated from the maxilla. An additional vertical incision was made parallel to the labial frenulum, and the maxilla was separated by malleting a thin osteotome between the central incisors at a level below the anterior nasal spine. The surgical sites were irrigated and sutured. An anterior nasal package and pressure bandage was applied to patients for 24 h, and antibiotics, analgesics and oroantral regime were prescribed.

Screws were activated immediately after bonding in the RME group and after surgery in the SARME group. For both groups, activation consisted of two turns per day and was performed for 2–3 weeks until the necessary amount of expansion was achieved. Upon completion of expansion, appliances were left in place for 12 weeks. At the end of the 12-week post-expansion period (T2), the appliances were removed and replaced by transpalatal arches for the remainder of the conventional orthodontic treatment period.

Cephalometric evaluation

Pre-expansion/pre-control (T1) and post-expansion/post-control (T2) posteroanterior and lateral cephalograms were taken from all subjects. Occlusal radiographs were also obtained from patients in the RME and SARME groups.

Posteroanterior and lateral cephalograms were traced, and cephalometric reference points were identified using a 0.3 mm lead pencil on 0.003-in. frosted acetate tracing paper. Craniofacial ( Fig. 2 ) and nasal ( Figs 3 and 4 ) measurements were made on all cephalograms using the PorDios cephalometric analysis program (Purpose on Request Digitizer Input Output System, Institute of Orthodontic Computer Science, Aarhus, Denmark). The linear and angular measurements of nasal structures presented in Figs 3 and 4 were previously reported in studies by Altug-Atac et al. and Kyrkanides et al. .

Fig. 2
Skeletal and dentoalveolar measurements: (1) SNA; (2) SNB; (3) ANB; (4) SN/GoGn; (5) overjet; (6) overbite.

Fig. 3
Posteroanterior cephalometric measurements on maxillo-mandibular dentoalveolar structures and skeletal bases: (7) MxR-MxL (basal maxillary width); (8) ApR-ApL (linear distances between right and left maxillary central incisor apices); (9) UmolR-UmolL (maxillary dentoalveolar width), in mm; (10) MxR/cg/MxL (the angle between crista galli and maxillary base points); (11) UmolR/cg/UmolL (the angle between crista galli and maxillary molar points), in degrees.

Fig. 4
Transverse measurements of nasal structures: (12) NC/Lom/VL (right nasal cavity angle); (13) CN/Lom/VL (left nasal cavity angle); (14) NC/Lom/CN (total nasal cavity angle), in degrees; (15) NC-CN (nasal cavity width), in millimeters; (16) sn/Lom/VL (nasal septum angle), in degrees.

Statistical analysis

Mean values and standard errors were examined to compare linear changes both within and between groups. Analysis of variance (ANOVA) and Duncan’s tests were used to make comparisons between groups at T1 ( Table 2 ) and within groups between T1 and T2 ( Table 3 ). Paired t -tests were also used to analyze changes between T1 and T2 within each group ( Table 3 ).

Table 2
The comparison of SARME, RME and control groups at T1 (pre-expansion/pre-control) by analysis of variance (ANOVA) and Duncan tests.
Parameters SARME RME Control Test SARME vs. RME RME vs. control SARME vs. control
X ±Sx X ±Sx X ±Sx
Lateral cephalometric measurements
Maxilla
1. SNA deg 75.28 0.94 74.57 0.96 80.77 3.32 * * *
Mandible
2. SNB deg 75.20 1.32 77.56 1.07 77.97 2.36
Maxillo-mandibular relations
3. ANB deg 0.08 0.67 −2.98 1.30 2.80 1.94 ** ** ** **
4. SN/GoGn deg 42.80 1.32 41.90 1.08 31.46 3.58 *** *** ***
5. Overjet mm 1.92 0.82 −1.82 1.67 3.01 1.64 ** ** **
6. Overbite mm −1.61 1.48 1.15 0.52 1.85 1.98 ** ** **
Posteroanterior radiographic measurements
Maxillary skeletal and dentoalveolar measurements
7. MxR-MxL mm 66.79 2.16 62.80 0.56 71.18 0.17 ** ** *
8. ApR-ApL mm 7.79 0.33 6.76 0.44 7.03 0.47
9. UmolR-UmolL mm 54.88 2.38 55.04 0.93 60.19 0.71 * * *
10. MxR/cg/MxL deg 50.61 1.24 48.93 1.41 53.27 1.02 * *
11.UmolR/cg/UmolL deg 34.13 1.50 36.30 0.80 39.41 2.11 * *
Measurements of nasal structures
12. NC-Lom-VML deg 16.91 0.65 18.20 0.56 17.75 0.82
13. CN-Lom-VML deg 19.27 0.51 19.15 0.94 17.60 0.82
14. NC-Lom-CN deg 36.18 0.81 37.35 1.46 35.35 1.07
15. NC-CN mm 32.15 1.02 31.75 0.83 32.01 0.74
16. sn-Lom-VML deg 0.93 1.53 1.05 0.91 0.78 1.23
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Feb 8, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Changes in nasal structures following orthopaedic and surgically assisted rapid maxillary expansion

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