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Use of conventional tomography to evaluate changes in the nasal cavity with rapid palatal expansion
ORIGINAL ARTICLE
Use of conventional tomography to evaluate changes in the nasal cavity with rapid palatal expansion Jacqueline Palaisa,a Peter Ngan,b Chris Martin,c and Thomas Razmusd Sigonella, Italy, and Morgantown, WV Introduction: The relationship between nasal airway resistance and the use of rapid palatal expansion appliances remains controversial. The purpose of this study was to use conventional tomography to determine the anatomical changes in the nasal cavity after maxillary expansion. Methods: Nineteen patients (aged 8 –15 years) were included in the study. Tomograms were taken before expansion (T1), immediately after expansion (T2), and 3 months after expansion (T3). Areas for the left and right anterior, middle, and posterior nasal cavity and total volume were calculated by using the computer software, AutoCAD LT 2005. Data were analyzed with paired t tests. Results: Significant increases in area were found in the anterior nasal cavity from T1 to T2 (0.85 ⫾ 1.19 cm2, 11.7% increase), T2 to T3 (1.18 ⫾ 1.2 cm2, 22.2% increase), and T1 to T3 (2.6 ⫾ 1.7 cm2, 35.7% increase) (P ⬍.05). Similar increases were found in the middle and posterior nasal cavity. Significant increases in volume were found from T1 to T2 (2.1 ⫾ 2.7 cm3, 10.7% increase), T2 to T3 (4.9 ⫾ 2.3 cm3, 22.6% increase), and T1 to T3 (6.99 ⫾ 2.45 cm3, 27.8% increase). No significant differences were found in the area or the volume of the left and right sides of the nasal cavity. Individual variations in response to maxillary expansion were large for most of the parameters tested. Conclusions: These data suggest that rapid palatal expansion is usually accompanied by increases in area and volume of the nasal cavity, and these changes remain stable 3 months after maxillary expansion. (Am J Orthod Dentofacial Orthop 2007;132:458-66)
R
apid palatal expansion (RPE) is a commonly used orthodontic procedure for correcting maxillary transverse deficiency. It is often used in young patients with unilateral or bilateral crossbite in association with skeletal constriction of the palate. In the medical field, RPE has been suggested in the treatment of problems such as nasal airway insufficiency (mouth breathing), septal deformity, nasal infection, allergic rhinitis, and obstructive sleep apnea.1-9 Rationalization of the clinical use of RPE for its rhinological effects is controversial. Several studies reported an association between RPE and nasal airway resistance (NAR).2,8-12 Most of these studies found a decrease in NAR after treatment a
United States Navy LCDR, Sigonella, Italy. Professor and chair, Department of Orthodontics, School of Dentistry, West Virginia University, Morgantown. c Assistant professor, Department of Orthodontics, School of Dentistry, West Virginia University, Morgantown. d Professor, Department of Diagnostic Sciences, School of Dentistry, West Virginia University, Morgantown. Reprint requests to: Peter Ngan, West Virginia University, Department of Orthodontics, Health Sciences Center North, PO Box 9480, Morgantown, WV 26506; e-mail, [email protected]. Submitted, July 2005; revised and accepted, October 2005. 0889-5406/$32.00 Copyright © 2007 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2005.10.025 b
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with expansion appliances.12 However, individual variations in response to treatment were noted.7 It is also not clear whether the changes in NAR associated with RPE were stable over time.10-16 Anatomical changes in the nasal cavity are 1 way to explain the decrease in NAR with appliance therapy. Several studies used cephalometric and occlusal films to assess the stability of the nasal width increase after RPE treatment.3,17-19 Several studies found that the linear changes in nasal width were stable immediately after expansion,20-22 but others showed relapse after a few months.23,24 Posteroanterior (PA) cephalograms and occlusal films can show only the morphology of the nasal cavity in 2 planes of space.20 Computed tomography can provide 3-dimensional images to determine the changes in the nasal cavity. However, this method is more expensive, and the radiation level is substantially higher than that of cephalometric radiographs.25,26 Conventional tomography is an alternative approach to computed tomography and can provide similar diagnostic information with much less radiation exposure.27-29 Conventional tomography can provide images from many locations along the length of the nasal airway. It can also provide information on the effects of RPE on the area and the
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volume of the nasal cavity. This is the first study to use conventional tomography to assess changes in the nasal cavity with nonsurgical RPE. The objectives of this study were to determine with conventional tomography (1) the area and the volume of the nasal cavity before treatment (T1), immediately after expansion with RPE (T2), and 3 months after expansion (T3); (2) the area and the volume changes along the length of the nasal passage—ie, the anterior nasal cavity (ANC), the middle nasal cavity (MNC), and the posterior nasal cavity (PNC); and (3) the changes in area and volume in the right and left nasal cavities. MATERIAL AND METHODS
A cadaver skull was imaged on a complex motion tomography (CMT) plus machine (Panorex CMT Plus; Imaging Sciences Intl, Hatfield, Pa) to calibrate the machine and to test the operator’s ability to accurately reposition the skull in the machine. Three tomographic slices of the skull were imaged, and this procedure was repeated twice at 1-week intervals (t1, t2, and t3). The cross-sectional images were taken starting at the level of the canine eminence, 10 mm posterior to the first slice, and 10 mm posterior to the second slice. The first slice corresponded to the ANC, the second slice corresponded to the MNC, and the last slice corresponded to the PNC. After the 3 tomograms were taken, the nasal cavity in the ANC, MNC, and PNC slices was outlined by an examiner (J.P.) on matte acetate paper. These images were scanned into a computer and analyzed with software (AutoCAD LT 2005; Autodesk, Rafael, Calif). The areas of the left and right ANC, MNC, and PNC for each image were determined and recorded. The volume was calculated from these areas by using the formula: volume ⫽ area of ANC (thickness of tomographic slice ⫹ distance between ANC and MNC tomographic slices) ⫹ area of MNC (distance between ANC and MNC tomographic slices ⫹ thickness of tomographic slice ⫹ distance between MNC and PNC tomographic slices) ⫹ area of PNC (thickness of tomographic slice ⫹ distance between MNC and PNC tomographic slices). The areas measured in the ANC, MNC, and PNC at t1, t2, and t3 were compared to determine the operator’s reliability in repositioning the skull, tracing the nasal cavity, and measuring the area using paired correlations. Twenty patients, aged 8 to 15 years, were recruited for the in-vivo part of the study. All patients required a rapid palatal expander as part of their comprehensive orthodontic treatment in the Department of Orthodontics at West Virginia University. Approval for the study
was obtained from the Institutional Review Board of West Virginia University. One patient did not complete the study. The criteria of patient selection included those who required either a banded or a bonded hyrax expansion appliance for treatment, with at least 4 mm of maxillary expansion, and no previous orthodontic treatment or craniofacial or growth abnormalities. The CMT radiographic procedures involved 3 tomographic slices (10 mm apart) of the nasal cavity (ANC, MNC, and PNC) taken at 3 times. The first slice was taken at the level of the canine eminence. The T1 images were taken before expansion with RPE. The T2 images were taken immediately after expansion. The T3 images were taken 3 months after expansion. The location of the ANC tomographic slice was determined by measuring the distance between the anatomical landmarks, ala and tragus, clinically with a ruler. The MNC image was taken 10 mm posterior to the ANC image, and the PNC image was taken 10 mm posterior to the MNC image. The ala-tragus measurement was recorded for each patient, along with positioning measurements for the CMT machine to facilitate the most reproducible patient positioning for subsequent imaging at T2 and T3. When all films were imaged at T1, T2, and T3, 1 examiner (J.P.) traced the outlines of the nasal cavities on the films. The traced images were scanned with a scanner (Expression 1680; Epson America, Inc, Long Beach, Calif) imported into AutoCAD LT 2005 and analyzed to determine area in square centimeters. The area measurements of the left and right ANC, MNC, and PNC at T1, T2 and T3 were used to determine the volume in cubic centimeters at the various times. The volumes were calculated with the same formula as used in the calibration study. Statistical analysis
The data were analyzed by using statistical software (JMP; SAS Institute, Cary, NC). For the in-vitro calibration study, the reliability of the skull to be repositioned and traced in a repeatable manner was analyzed with pairwise correlations. Left, right, and total (left ⫹ right) areas and volumes were recorded and compared from t1 to t2 to t3. The images were highly correlated at all time intervals. The skull was not altered between weekly tomographic imaging; thus, the nasal cavity slices imaged at t1, t2, and t3 were the same on all films. The correlation coefficients of these images were 0.98 for t1 to t2, 0.99 for t2 to t3, and 0.99 for t1 to t3. The operator was reliable in repositioning the skull and tracing the areas of the nasal cavity consistently. For the in-vivo study, the left, right, and total (left ⫹ right) areas of the ANC, MNC, and PNC were
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Table I.
American Journal of Orthodontics and Dentofacial Orthopedics October 2007
Areas of right and left ANC, MNC, PNC at T1, T2, and T3 for the 19 patients (cm2) ANC
Time Patient 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Mean SD Minimum Maximum
Table II.
MNC
PNC
T1
T2
T3
T1
T2
T3
T1
T2
T3
8.29 5.13 5.9 5.78 9.06 7.45 9.28 9.04 6.96 5.93 8.26 6.21 5.66 8.48 10.42 8.95 6.34 5.53 6.26 7.31 1.56 5.53 10.42
9.61 5.12 6.69 5.86 10.17 9.22 10.41 7.66 6.39 6.65 10.87 7.9 7.59 9.46 9.43 8.97 7.58 8.96 6.54 8.16 1.67 5.12 10.87
11.94 7.55 8.81 6.62 11.71 12.75 13.53 8.17 9.59 7.87 13.19 8.67 6.49 9.313 11.47 11.99 9.67 11.62 7.96 9.94 2.25 6.49 13.53
8.98 9.55 7.1 5.77 10.56 8.42 12.19 8.88 8.16 7.8 9.16 9.31 7.93 8.1 11.85 12.35 7.44 6.12 6.89 8.77 1.9 5.77 12.35
8.86 10.41 7.12 7.00 11.3 8.36 13.93 8.96 7.06 8.03 10.77 9.2 9.45 9.69 11.31 12.99 7.76 11.44 8.31 9.58 1.99 7.00 12.99
11.55 14.99 9.22 8.13 14.48 11.86 15.68 11.28 10.39 10.52 12.36 11.14 10.87 11.24 14.75 17.18 9.78 12.75 9.44 11.98 2.43 8.13 17.18
7.63 11.06 8.47 7.51 10.79 8.72 9.86 8.54 9.32 7.43 8.09 7.5 10.35 7.45 11.3 12.72 8.96 8.81 8.92 9.13 1.52 7.43 12.72
8.82 11.91 7.66 8.07 15.21 10.51 12.64 8.22 9.88 6.93 8.83 7.82 15.02 7.42 10.68 12.62 10.11 11.73 10.77 10.26 2.46 7.42 15.21
12.85 14.42 9.54 10.47 18.87 12.34 14.47 10.3 12.45 10.02 10.91 10.01 12.35 10.41 15.6 16.95 10.28 11.8 9.73 12.3 2.66 9.54 16.95
Mean area changes of the right side for the 3 time periods Right ANC
Mean area change (cm2) SD (cm2) P value
Right MNC
Right PNC
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
0.41 0.50 .009
0.76 0.50 .0001
1.17 0.75 .0001
0.29 0.77 .060
1.28 0.76 .0001
1.57 0.76 .001
0.46 1.00 .036
1.03 0.94 .0001
1.49 1.08 .0001
measured for each patient. The means for the left, right, and total ANC, MNC, and PNC were then calculated. These means were used to find the differences in the areas for the time periods, T1 to T2 to T3. The patients’ nasal cavity volumes were calculated, and these were also grouped together to find the statistical mean for the volume. This mean was used to find the changes in volume for the group of patients over the time periods, T1 to T2 to T3. Paired t tests were used to compare changes in area and volume over the time intervals with a significance level of P ⬍.05. RESULTS
For the in-vitro study to calibrate the machine and determine the operator’s errors, the areas of ANC, MNC, and PNC at t1, t2, and t3 were compared. The correlation coefficients of the repeated area measurements were 0.98 from t1 to t2, 0.99 from t2 to t3, and 0.99 from t1 to t3.
For the in-vivo study, the average amount of expansion among the 19 subjects was 6.1 ⫾ 1.7 mm. The areas of ANC, MNC, and PNC (left and right) at T1, T2, and T3 for these patients are shown in Table I. These data were used to find the mean changes in areas of the various parts of the nasal cavity. As a group, the areas of the right nasal cavity increased significantly in the ANC, MNC, and PNC at all times (P ⬍.05) with the exception of the right MNC from T1 to T2 (Table II). The areas of the left nasal cavity increased significantly in the ANC, MNC, and PNC at all times (P ⬍.05, Table III). The area changes in the left ANC, MNC, and PNC increased significantly from T1 to T2 to T3 (P ⬍.05). The area of the left ANC increased from T1 to T3 by 1.46 ⫾ 1.14 cm2, or 39.6%. The area of the left MNC increased from T1 to T3 by 1.64 ⫾ 0.71 cm2, or 37.7%. The area of the left PNC increased from T1 to T3 by 1.64 ⫾ 0.92 cm2, or 36.6%. The areas of the right ANC, MNC, and PNC increased significantly T1 to T2 to T3
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Table III.
Mean area changes of the left side for the 3 time periods Left ANC
Mean area change (cm2) SD (cm2) P value
Table IV.
Left MNC
Left PNC
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
0.44 0.74 .009
1.08 0.90 .0001
1.46 1.14 .0001
0.52 0.69 .002
1.12 0.60 .0001
1.64 0.71 .001
0.67 0.70 .003
0.97 0.97 .0002
1.64 0.92 .0001
Mean area changes of the pooled right and left ANC, MNC, and PNC for the 3 time periods ANC
MNC
PNC
T
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
Mean area change (cm2) SD (cm2) P value
0.85 1.20 .003
1.78 1.20 .001
2.63 1.74 .0001
0.81 1.36 .0001
2.40 1.03 .0001
3.20 1.20 .0001
1.13 1.60 .003
2.05 1.85 .0001
3.18 1.68 .009
Fig 1. Percentage changes in area of ANC, MNC, and PNC for time periods T1 to T2, T2 to T3, and total change from T1 to T3.
(P ⬍.05) with the exception of the area of the right MNC, which did not increase significantly from T1 to T2. The area of the right ANC increased from T1 to T3 by 1.17 ⫾ 0.75 cm2, or 32.5 %. The area of the right MNC increased from T1 to T3 by 1.49 ⫾ 1.08 cm2, or 32.9%. The area of the right PNC increased from T1 to T3 by 1.57 ⫾ 0.76 cm2, or 35.7%. The pooled left and right area changes of the ANC, MNC, and PNC at the various times are shown in Table IV and Figure 1. The area changes of ANC, MNC, and PNC increased significantly from T1 to T2 to T3 (P ⬍.05). The area of the ANC increased from T1 to T3 by 2.63 ⫾ 1.74 cm2, or 36%. The area of the MNC increased from T1 to T3 by 3.2 ⫾ 1.2 cm2, or 36.6%. The area of the PNC increased from T1 to T3 by 3.18 ⫾1.68 cm2, or 35%. A comparison of the area
changes in the left and right nasal cavities at ANC, MNC, and PNC from T1 toT2 to T3 showed no significant differences. Correlation analysis showed no significant correlation between the amount of expansion and the increase of nasal cavity at any time periods (Table V). However, individual variations in response to maxillary expansion were large. Figure 2 shows the variability of shape and size changes in response to treatment for a typical patient. For most patients, the area increased from T1 to T2 to T3. However, in some time periods, the areas did not change. The volume of the left and right nasal cavities and the total volume (pooled left and right nasal cavities) for the 19 patients at T1, T2, and T3 are shown in Table VI. The changes in volume of the nasal cavity for the various time periods are shown in
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Table V.
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Correlation coefficients between expansion and increases in area and volume
Area of nasal cavity ANC Time period Correlation coefficient P value
MNC
PNC
Total volume
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
0.22 .34
0.29 .22
0.36 .13
⫺0.12 .61
0.24 .31
0.06 .78
⫺0.13 .58
0.29 .22
0.19 .42
⫺0.05 .82
0.30 .20
0.23 .34
Fig 2. Variability in shape and size changes in response to maxillary expansion for the anterior nasal cavity (ANC), middle nasal cavity (MNC), and posterior nasal cavity (PNC) from the time period A, T1 (solid line) to T2 (broken line); B, T2 (solid line) to T3 (broken line); and C, T1 (solid line) to T3 (broken line).
Table VII. As a group, the volume of the nasal cavity increased significantly from T1 to T2 to T3 (P ⬍.05). Figure 3 shows the percentage changes in volume from T1 to T2 to T3. The volume of the nasal cavity from T1 to T2 increased by 2.08 ⫾ 2.66 cm3, or 10.7%. The volume of the nasal cavity increased from T2 to T3 by 4.9 ⫾ 2.3 cm3, or 22.6%. The
volume of the nasal cavity increased from T1 to T3 by 6.99 ⫾ 2.45 cm3, or 27.8%. Correlation analysis showed no significant correlation between the amount of expansion and the increase in volume at any time periods (Table V). Individual variations in response to maxillary expansion were large. For most patients, the volume increased from T1 to T2 to T3.
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Table VI.
Volume of left and right nasal cavities and total nasal cavity at T1, T2, and T3 for the 19 patients (cm3) Left nasal cavity
Time Patient 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Mean SD Minimum Maximum
Right nasal cavity
Total
T1
T2
T3
T1
T2
T3
T1
T2
T3
10.4 9.8 7.44 6.7 11.49 10.19 11.05 9.53 9.74 8.22 9.19 8.31 10.07 10.0 14.12 13.98 9.17 7.61 8.16 9.75 1.96 6.7 14.12
11.39 9.71 7.71 8.01 13.73 12.23 13.54 9.02 9.33 8.86 12 9.63 12.47 11.31 13.06 14.48 10.19 12.83 9.19 10.98 2.06 7.71 14.48
15.13 13.62 10.78 9.95 15.58 15.96 15.96 10.73 13.77 11.15 13.47 10.76 12.38 13.15 17.04 18.52 11.17 14.63 11.16 13.42 2.48 9.95 18.52
9.03 10.4 8.99 7.61 12.03 8.78 13.84 10.79 9.0 8.38 10.7 10.16 8.26 8.47 11.94 12.61 8.2 7.73 8.53 9.76 1.80 7.61 12.61
9.41 11.96 8.72 8.04 13.92 8.8 15.61 10.37 8.2 8.12 11.67 9.92 11.49 9.48 11.44 12.76 8.97 12.17 10.33 10.59 2.09 8.04 15.61
12.45 16.05 010.37 9.25 18.69 12.25 18.19 12.10 11.65 10.57 14.36 12.86 11.67 11.91 14.65 17.25 11.84 12.38 10.03 13.08 2.74 9.25 18.69
19.43 20.22 16.43 14.32 23.03 18.96 24.89 20.32 18.74 16.6 19.89 18.47 18.33 18.47 26.07 26.59 17.36 15.34 16.69 19.51 3.48 14.32 26.59
20.8 21.67 16.44 16.06 27.66 21.03 29.15 19.38 17.53 16.98 23.67 19.55 23.96 20.79 24.51 27.24 19.15 25.0 19.53 21.58 3.89 16.06 29.15
27.58 29.67 21.15 19.19 34.27 28.21 34.156 22.84 25.42 21.72 27.83 23.62 24.05 25.06 31.69 35.77 23.0 27.01 21.18 26.50 4.86 19.19 35.77
Table VII.
Total volume changes in the nasal cavity for the 3 time periods
Mean area change (cm3) SD (cm3) P value
T2-T1
T3-T2
T3-T1
2.08 2.66 .0016
4.90 2.30 .0001
6.99 2.45 .0001
However, in a few, the volume decreased over the various time intervals. DISCUSSION
Several studies reported on the stability of maxillary width and the changes in the nasal structures after RPE treatment with PA cephalograms, occlusal films, or dental casts.25-27 Few studies used conventional tomography to examine the anatomical changes of the nasal cavity after maxillary expansion. One study used computed tomography to measure cross-sectional areas of the nasal airway of a patient from anterior to posterior at 4-mm intervals after RPE.30 According to pairwise correlations of the data from this study, the imaging technique used on the skull with conventional tomography was a reliable method to produce repeatable images of the nasal cavity. The area measurements from the skull images on the CMT machine had a correlation of 0.99. This demonstrates that the operator
was reliable in positioning, tracing, and measuring the areas on the images. Although computed tomography can provide accurate measurements on the area and volume of the nasal cavity, it is not practical because of its expense and the amount of radiation involved.25,26,30 Conventional tomography is more cost effective and can provide similar diagnostic information.23,24 In this study, 10% increases in area and 10% increases in volume were observed in ANC, MNC, and PNC at T2. This was followed by further increases of 25% in area and 15% in volume in the next 3 months when the expansion appliance was used as a retention device. No studies with conventional tomography have examined the stability of the nasal cavity expansion after removal of the expansion appliance.10,15,16 However, a study by Cameron et al35 using PA cephalograms examined changes in maxillary width and maxillary first molar width 8 years after removal of the expansion appliances. They found that the changes in maxillary width and maxillary first molar width exceeded the expected growth increment in the control group by 2.3 and 1.4 mm, respectively. A prospective study by Memikoglu and Iseri22 examined the changes in the transverse plane after bonded RPE and fixed appliance treatment. Using PA cephalograms and study casts obtained at pretreatment, postexpansion, and post-
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Fig 3. Percentage changes in volume from T1 to T2 to T3.
treatment (average treatment time, 3.08 years), the authors measured skeletal and dental reference points and found an increase in transverse linear measurements after expansion, and these changes were maintained and sometimes continued to increase until the end of conventional orthodontic treatment. They found no relapse after RPE and fixed therapy. Hershey et al10 performed linear measurements using PA cephalograms and models, and found that nasal cavity width increased 1 to 3 mm after expansion and another 0.33 mm during retention. On the other hand, Krebs23 and Thorn24 made linear measurements of the nasal cavity after expansion and found increases of 1.7 to 2.5 mm, but this initial expansion relapsed by 0.5 to 1.7 mm during retention. The conflicting results from these studies caused controversy about the benefits of expansion for the treatment of nasal airway resistance. All of these studies used 2-dimensional PA cephalograms or models to evaluate the changes after RPE. Conventional tomography was used to assess nasal septal deviation after surgically assisted RPE treatment. Schwarz et al29 examined 9 patients for septal deviation using 4 coronal tomograms taken within 4 months after surgical intervention. Linear measurements and the areas of the right and left airway spaces were recorded and compared with posttreatment measurements. Significant increases were found, but the mechanism was unknown. The authors speculated that it could be from expansion of the lateral walls, but they found no evidence to support this and concluded it might be due to tissue shrinkage. Many studies found decreases in NAR after RPE,7-10,12,17,18,21,31,32 but the stability of NAR has had conflicting results. Hershey et al10 and White et al11
studied the decrease in NAR after RPE. Both found that the reduction in NAR was stable over time (45% reduction in NAR 3 months later,33 and 48.7% reduction of NAR 1 year later11). Ngan et al34 found that orthopedic treatment directed at the maxilla in Class III malocclusions is stable despite some relapse. On the other hand, Wertz7 studied the effects of RPE on NAR and found inconclusive results that could not justify palatal expansion for the improvement of NAR. Individual variations in patients could be the cause of the controversial results in these studies. In our study, there were significant increases in the total volume from T1 to T2, T2 to T3, and T1 to T3. Increases in volume of the nasal cavity would support the studies that demonstrated a reduction in NAR after expansion.8-12,21,31,32 Volumetric data give a good indication of overall expansion and relapse but no information concerning expansion in various parts of the nasal cavity.35 We also found that the MNC and the PNC increased more than the ANC, even though the intermaxillary suture split with the RPE appliance decreases posteriorly. A possible explanation is that the MNC (mean, 8.77 cm2) and the PNC (mean, 9.13 cm2) are larger in area than the ANC (mean, 7.31 cm2). Consequently, the increase in area of the nasal cavity will be proportionally greater in the PNC even with a slightly greater intermaxillary suture split with the expansion appliance. There were no significant differences in the changes in the left vs the right nasal cavity in any measurements (areas of ANC, MNC, PNC, and total area) at the various time intervals. This finding was supported in a study by Bell36 that discussed the variability in the pattern of expansion depending on
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the patient’s age and maturity level, and by many cephalometric studies that show that the sutural separation of the maxilla is not uniform.3,10,25,27,36-40 Asanza et al41 found that the changes in expansion are not symmetrical, and the expansion varied from left to right and among patients. There were no significant correlations between the amount of expansion and the increases in nasal cavity area or volume for AMC, MNC, or PNC. This can be explained by the fact that the jackscrew is placed in the middle of the palate anteroposteriorly beneath the nasal airway. In the frontal plane, expansion is greater between the incisors and diminishes superiorly. The nasal septum, vomer, and perpendicular plate of the ethmoid bone typically do not completely detach but remain articulated to one of the separated maxillary and palatine bones. In the horizontal plane, expansion is greater in the anterior portion of the palate than the posterior. The posterior palate is more resistant to expansion because of the locking effect of the pyramidal processes of the palatal bones into the pterygoid plates of the sphenoid.41 From the data of this study, the area of the nasal cavity increased nonuniformly from the ANC to the PNC. Figure 2 also shows that the amount of expansion was not uniform superioinferiorly. Therefore, one cannot expect a direct correlation of either the area or the volume of the nasal cavity with the amount of palatal expansion beneath the nasal cavity. CONCLUSIONS
Conventional tomography was effective in evaluating the nasal cavity. It allowed for assessment in the transverse, vertical, and sagittal dimensions. Unlike frontal PA cephalograms, cross-sectional images can be made along the length of the nasal airway with tomograms. It was determined that the area and the volume increased significantly in all areas of the nasal cavity except for the right middle from T1 to T2. There appeared to be no relapse during the retention phase of 3 months after active expansion. The areas and the volumes increased significantly for all parts of the nasal cavity from T2 to T3. These results support previous studies that show continued reduction in NAR and airway obstruction symptoms long after expansion.
REFERENCES 1. Pfaff W. Stenosis of the nasal cavity by contraction of the palatal arch and abnormal position of the teeth. Dent Cosmos 1905;47: 570-3. 2. Brown GVI. The application of orthodontia principles to the prevention of nasal disease. Dent Cosmos 1903;45:765-75.
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3. Haas AJ. Rapid expansion of the maxillary dental arch and nasal cavity by opening the midpalatal suture. Angle Orthod 1961;31: 73-90. 4. Brogan WF. The stability of maxillary expansion. Aust Dent J 1977;22:92-9. 5. Gray LP. Septal deformity malocclusion and rapid maxillary expansion. Orthodontist 1972;4:2-14. 6. Black NM. The relation between deviation of nasal septum and irregularities of the teeth and jaw. JAMA 1909;52:943-5. 7. Wertz RA. Changes in nasal airflow incident to rapid maxillary expansion. Angle Orthod 1968;38:1-11. 8. Palmisano RG, Wilcox I, Sullivan CE, Cistulli PA. Treatment of snoring and obstructive sleep apnoea by rapid maxillary expansion. Aust N Z J Med 1996;26:428-9. 9. Cistulli PA, Palmisano RG, Poole MD. Treatment of obstructive sleep apnea syndrome by rapid maxillary expansion. Sleep 1998;21:831-5. 10. Hershey HG, Stewart BL, Warren DW. Changes in nasal airway resistance associated with rapid maxillary expansion. Am J Orthod 1976;69:274-84. 11. White BC, Woodside DG, Cole P. The effect of rapid maxillary expansion on nasal airway resistance. J Otolaryngol 1989;18: 137-43. 12. Gray LP. Results of 310 cases of rapid maxillary expansion selected for medical reasons. J Laryngol Otol 1975;89:601-14. 13. Turbyfill WJ. The long-term effect of rapid maxillary expansion [master’s thesis]. University of North Carolina; 1976. 14. Hartgerink DV, Vig PS, Abbott DW. The effect of rapid maxillary expansion on nasal airway resistance. Am J Orthod Dentofacial Orthop 1987;92:381-9. 15. Timms DJ. The reduction of nasal airway resistance by rapid maxillary expansion and its effect on respiratory disease. J Laryngol Otol 1984;98:357-62. 16. Timms DJ. Rapid maxillary expansion in the treatment of nasal obstruction and respiratory disease. Ear Nose Throat J 1987;66: 242-7. 17. Wright GH. A Group of deformities of the nasal respiratory tract, coincident with dental irregularities ii. a new instrument for comparative measurements. Dent Cosmos 1912;54:261-9. 18. Derichsweiler H. La disjonction de la suture palatine medane. Trans Eur Orthod Soc 1953;11:597-600. 19. Basciftci FA, Mutlu N, Karaman AI, Malkoc S, Kucukkolbasi H. Does the timing and method of rapid maxillary expansion have an effect on the changes in nasal dimensions? Angle Orthod 2002;72:118-23. 20. Cameron CG, Franchi L, Baccetti T, McNamara JA Jr. Longterm effects of rapid maxillary expansion: a posteroanterior cephalometric evaluation. Am J Orthod Dentofacial Orthop 2002;121:129-35. 21. Cross DL, McDonald JP. Effect of rapid maxillary expansion on skeletal, dental, and nasal structures: a postero-anterior cephalometric study. Eur J Orthod 2000;22:519-28. 22. Memikoglu TU, Iseri H. Effects of a bonded rapid maxillary expansion appliance during orthodontic treatment. Angle Orthod 1999;69:251-6. 23. Krebs A. Expansion of the midpalatal suture studied by means of metallic implants. Trans Eur Soc Orthod 1958;34:163-71. 24. Thorn NA. Expansion of maxilla spreading the midpalatal suture; measuring the widening of the apical base and the nasal cavity on serial roentgenograms [abstract]. Am J Orthod 1960;46:626. 25. Montgomery W. Computed Tomography: a three-dimensional study of the nasal airway. Am J Orthod 1979;76:363-75.
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26. Montgomery W. Rapid maxillary expansion effects on nasal cavity computed tomography study [abstract]. J Dent Res 1979; 58:1248. 27. Hamada MO. Implantology: radiographic resources. J Calif Dent Assoc 1989;17:20-31. 28. Clark DE. Radiation absorbed from dental implant radiography: a comparison of linear tomography, CT scan, and panoramic and intra-oral techniques. J Oral Implantol 1990;16:156-64. 29. Schwarz GM, Thrash WJ, Byrd DL, Jacobs JD. Tomographic assessment of nasal septal changes following surgical-orthodontic rapid maxillary expansion. Am J Orthod 1985;87:39-45. 30. Vig PS, Sarver DM, Hall DJ, Warren DW. Quantative evaluation of nasal airflow in relation to facial morphology. Am J Orthod 1981;79:263-72. 31. Gray LP. Rapid maxillary expansion and impaired nasal respiration. Ear Nose Throat J 1987;66:248-51. 32. Doruk C, Sokucu O, Sezer H, Canbay EI. Evaluation of nasal airway resistance during rapid maxillary expansion using acoustic rhinometry. Eur J Orthod 2004;26:397-401. 33. Hershey HG, Stewart BL, Warren DW. Changes in nasal airway resistance associated with rapid maxillary expansion.
Am J Orthod 1976 March;69(3):274-84. SAME AS 10, 16, 39, AND 48. Ngan P, Yiu C, Hu A, Hagg U, Wei SH, Gunel E. Cephalometric and occlusal changes following maxillary expansion and protraction. Eur J Orthod 1998;20:237-54. Tran A. Use of conventional tomography to evaluate changes in the nasal cavity with rapid palatal expansion [master’s thesis]. West Virginia University; 1997. Bell RA. A review of maxillary expansion in relation to the rate of expansion and patient’s age. Am J Orthod 1982;81:32-7. Haas AJ. Just the beginning of dentofacial orthopedics. Am J Orthod 1970;57:219-55. Krebs A. Midpalatal suture expansiion studied by the implant method over a seven-year period. Trans Eur Orthod Soc 1964; 40:131-42. Timms DJ. A study of basal movement with rapid maxillary expansion. Am J Orthod 1980;77:500-7. Wertz RA. Skeletal and dental changes accompanying rapid midpalatal suture opening. Am J Orthod 1970;58:41-66. Asanza S, Cisneros GJ, Nieberg LG. Comparison of hyrax and bonded expansion appliances. Angle Orthod 1997;67:15-22.
34.
35.
36. 37. 38.
39. 40. 41.
Use of conventional tomography to evaluate changes in the nasal cavity with rapid palatal expansion Jacqueline Palaisa,a Peter Ngan,b Chris Martin,c and Thomas Razmusd Sigonella, Italy, and Morgantown, WV Introduction: The relationship between nasal airway resistance and the use of rapid palatal expansion appliances remains controversial. The purpose of this study was to use conventional tomography to determine the anatomical changes in the nasal cavity after maxillary expansion. Methods: Nineteen patients (aged 8 –15 years) were included in the study. Tomograms were taken before expansion (T1), immediately after expansion (T2), and 3 months after expansion (T3). Areas for the left and right anterior, middle, and posterior nasal cavity and total volume were calculated by using the computer software, AutoCAD LT 2005. Data were analyzed with paired t tests. Results: Significant increases in area were found in the anterior nasal cavity from T1 to T2 (0.85 ⫾ 1.19 cm2, 11.7% increase), T2 to T3 (1.18 ⫾ 1.2 cm2, 22.2% increase), and T1 to T3 (2.6 ⫾ 1.7 cm2, 35.7% increase) (P ⬍.05). Similar increases were found in the middle and posterior nasal cavity. Significant increases in volume were found from T1 to T2 (2.1 ⫾ 2.7 cm3, 10.7% increase), T2 to T3 (4.9 ⫾ 2.3 cm3, 22.6% increase), and T1 to T3 (6.99 ⫾ 2.45 cm3, 27.8% increase). No significant differences were found in the area or the volume of the left and right sides of the nasal cavity. Individual variations in response to maxillary expansion were large for most of the parameters tested. Conclusions: These data suggest that rapid palatal expansion is usually accompanied by increases in area and volume of the nasal cavity, and these changes remain stable 3 months after maxillary expansion. (Am J Orthod Dentofacial Orthop 2007;132:458-66)
R
apid palatal expansion (RPE) is a commonly used orthodontic procedure for correcting maxillary transverse deficiency. It is often used in young patients with unilateral or bilateral crossbite in association with skeletal constriction of the palate. In the medical field, RPE has been suggested in the treatment of problems such as nasal airway insufficiency (mouth breathing), septal deformity, nasal infection, allergic rhinitis, and obstructive sleep apnea.1-9 Rationalization of the clinical use of RPE for its rhinological effects is controversial. Several studies reported an association between RPE and nasal airway resistance (NAR).2,8-12 Most of these studies found a decrease in NAR after treatment a
United States Navy LCDR, Sigonella, Italy. Professor and chair, Department of Orthodontics, School of Dentistry, West Virginia University, Morgantown. c Assistant professor, Department of Orthodontics, School of Dentistry, West Virginia University, Morgantown. d Professor, Department of Diagnostic Sciences, School of Dentistry, West Virginia University, Morgantown. Reprint requests to: Peter Ngan, West Virginia University, Department of Orthodontics, Health Sciences Center North, PO Box 9480, Morgantown, WV 26506; e-mail, [email protected]. Submitted, July 2005; revised and accepted, October 2005. 0889-5406/$32.00 Copyright © 2007 by the American Association of Orthodontists. doi:10.1016/j.ajodo.2005.10.025 b
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with expansion appliances.12 However, individual variations in response to treatment were noted.7 It is also not clear whether the changes in NAR associated with RPE were stable over time.10-16 Anatomical changes in the nasal cavity are 1 way to explain the decrease in NAR with appliance therapy. Several studies used cephalometric and occlusal films to assess the stability of the nasal width increase after RPE treatment.3,17-19 Several studies found that the linear changes in nasal width were stable immediately after expansion,20-22 but others showed relapse after a few months.23,24 Posteroanterior (PA) cephalograms and occlusal films can show only the morphology of the nasal cavity in 2 planes of space.20 Computed tomography can provide 3-dimensional images to determine the changes in the nasal cavity. However, this method is more expensive, and the radiation level is substantially higher than that of cephalometric radiographs.25,26 Conventional tomography is an alternative approach to computed tomography and can provide similar diagnostic information with much less radiation exposure.27-29 Conventional tomography can provide images from many locations along the length of the nasal airway. It can also provide information on the effects of RPE on the area and the
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volume of the nasal cavity. This is the first study to use conventional tomography to assess changes in the nasal cavity with nonsurgical RPE. The objectives of this study were to determine with conventional tomography (1) the area and the volume of the nasal cavity before treatment (T1), immediately after expansion with RPE (T2), and 3 months after expansion (T3); (2) the area and the volume changes along the length of the nasal passage—ie, the anterior nasal cavity (ANC), the middle nasal cavity (MNC), and the posterior nasal cavity (PNC); and (3) the changes in area and volume in the right and left nasal cavities. MATERIAL AND METHODS
A cadaver skull was imaged on a complex motion tomography (CMT) plus machine (Panorex CMT Plus; Imaging Sciences Intl, Hatfield, Pa) to calibrate the machine and to test the operator’s ability to accurately reposition the skull in the machine. Three tomographic slices of the skull were imaged, and this procedure was repeated twice at 1-week intervals (t1, t2, and t3). The cross-sectional images were taken starting at the level of the canine eminence, 10 mm posterior to the first slice, and 10 mm posterior to the second slice. The first slice corresponded to the ANC, the second slice corresponded to the MNC, and the last slice corresponded to the PNC. After the 3 tomograms were taken, the nasal cavity in the ANC, MNC, and PNC slices was outlined by an examiner (J.P.) on matte acetate paper. These images were scanned into a computer and analyzed with software (AutoCAD LT 2005; Autodesk, Rafael, Calif). The areas of the left and right ANC, MNC, and PNC for each image were determined and recorded. The volume was calculated from these areas by using the formula: volume ⫽ area of ANC (thickness of tomographic slice ⫹ distance between ANC and MNC tomographic slices) ⫹ area of MNC (distance between ANC and MNC tomographic slices ⫹ thickness of tomographic slice ⫹ distance between MNC and PNC tomographic slices) ⫹ area of PNC (thickness of tomographic slice ⫹ distance between MNC and PNC tomographic slices). The areas measured in the ANC, MNC, and PNC at t1, t2, and t3 were compared to determine the operator’s reliability in repositioning the skull, tracing the nasal cavity, and measuring the area using paired correlations. Twenty patients, aged 8 to 15 years, were recruited for the in-vivo part of the study. All patients required a rapid palatal expander as part of their comprehensive orthodontic treatment in the Department of Orthodontics at West Virginia University. Approval for the study
was obtained from the Institutional Review Board of West Virginia University. One patient did not complete the study. The criteria of patient selection included those who required either a banded or a bonded hyrax expansion appliance for treatment, with at least 4 mm of maxillary expansion, and no previous orthodontic treatment or craniofacial or growth abnormalities. The CMT radiographic procedures involved 3 tomographic slices (10 mm apart) of the nasal cavity (ANC, MNC, and PNC) taken at 3 times. The first slice was taken at the level of the canine eminence. The T1 images were taken before expansion with RPE. The T2 images were taken immediately after expansion. The T3 images were taken 3 months after expansion. The location of the ANC tomographic slice was determined by measuring the distance between the anatomical landmarks, ala and tragus, clinically with a ruler. The MNC image was taken 10 mm posterior to the ANC image, and the PNC image was taken 10 mm posterior to the MNC image. The ala-tragus measurement was recorded for each patient, along with positioning measurements for the CMT machine to facilitate the most reproducible patient positioning for subsequent imaging at T2 and T3. When all films were imaged at T1, T2, and T3, 1 examiner (J.P.) traced the outlines of the nasal cavities on the films. The traced images were scanned with a scanner (Expression 1680; Epson America, Inc, Long Beach, Calif) imported into AutoCAD LT 2005 and analyzed to determine area in square centimeters. The area measurements of the left and right ANC, MNC, and PNC at T1, T2 and T3 were used to determine the volume in cubic centimeters at the various times. The volumes were calculated with the same formula as used in the calibration study. Statistical analysis
The data were analyzed by using statistical software (JMP; SAS Institute, Cary, NC). For the in-vitro calibration study, the reliability of the skull to be repositioned and traced in a repeatable manner was analyzed with pairwise correlations. Left, right, and total (left ⫹ right) areas and volumes were recorded and compared from t1 to t2 to t3. The images were highly correlated at all time intervals. The skull was not altered between weekly tomographic imaging; thus, the nasal cavity slices imaged at t1, t2, and t3 were the same on all films. The correlation coefficients of these images were 0.98 for t1 to t2, 0.99 for t2 to t3, and 0.99 for t1 to t3. The operator was reliable in repositioning the skull and tracing the areas of the nasal cavity consistently. For the in-vivo study, the left, right, and total (left ⫹ right) areas of the ANC, MNC, and PNC were
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Table I.
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Areas of right and left ANC, MNC, PNC at T1, T2, and T3 for the 19 patients (cm2) ANC
Time Patient 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Mean SD Minimum Maximum
Table II.
MNC
PNC
T1
T2
T3
T1
T2
T3
T1
T2
T3
8.29 5.13 5.9 5.78 9.06 7.45 9.28 9.04 6.96 5.93 8.26 6.21 5.66 8.48 10.42 8.95 6.34 5.53 6.26 7.31 1.56 5.53 10.42
9.61 5.12 6.69 5.86 10.17 9.22 10.41 7.66 6.39 6.65 10.87 7.9 7.59 9.46 9.43 8.97 7.58 8.96 6.54 8.16 1.67 5.12 10.87
11.94 7.55 8.81 6.62 11.71 12.75 13.53 8.17 9.59 7.87 13.19 8.67 6.49 9.313 11.47 11.99 9.67 11.62 7.96 9.94 2.25 6.49 13.53
8.98 9.55 7.1 5.77 10.56 8.42 12.19 8.88 8.16 7.8 9.16 9.31 7.93 8.1 11.85 12.35 7.44 6.12 6.89 8.77 1.9 5.77 12.35
8.86 10.41 7.12 7.00 11.3 8.36 13.93 8.96 7.06 8.03 10.77 9.2 9.45 9.69 11.31 12.99 7.76 11.44 8.31 9.58 1.99 7.00 12.99
11.55 14.99 9.22 8.13 14.48 11.86 15.68 11.28 10.39 10.52 12.36 11.14 10.87 11.24 14.75 17.18 9.78 12.75 9.44 11.98 2.43 8.13 17.18
7.63 11.06 8.47 7.51 10.79 8.72 9.86 8.54 9.32 7.43 8.09 7.5 10.35 7.45 11.3 12.72 8.96 8.81 8.92 9.13 1.52 7.43 12.72
8.82 11.91 7.66 8.07 15.21 10.51 12.64 8.22 9.88 6.93 8.83 7.82 15.02 7.42 10.68 12.62 10.11 11.73 10.77 10.26 2.46 7.42 15.21
12.85 14.42 9.54 10.47 18.87 12.34 14.47 10.3 12.45 10.02 10.91 10.01 12.35 10.41 15.6 16.95 10.28 11.8 9.73 12.3 2.66 9.54 16.95
Mean area changes of the right side for the 3 time periods Right ANC
Mean area change (cm2) SD (cm2) P value
Right MNC
Right PNC
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
0.41 0.50 .009
0.76 0.50 .0001
1.17 0.75 .0001
0.29 0.77 .060
1.28 0.76 .0001
1.57 0.76 .001
0.46 1.00 .036
1.03 0.94 .0001
1.49 1.08 .0001
measured for each patient. The means for the left, right, and total ANC, MNC, and PNC were then calculated. These means were used to find the differences in the areas for the time periods, T1 to T2 to T3. The patients’ nasal cavity volumes were calculated, and these were also grouped together to find the statistical mean for the volume. This mean was used to find the changes in volume for the group of patients over the time periods, T1 to T2 to T3. Paired t tests were used to compare changes in area and volume over the time intervals with a significance level of P ⬍.05. RESULTS
For the in-vitro study to calibrate the machine and determine the operator’s errors, the areas of ANC, MNC, and PNC at t1, t2, and t3 were compared. The correlation coefficients of the repeated area measurements were 0.98 from t1 to t2, 0.99 from t2 to t3, and 0.99 from t1 to t3.
For the in-vivo study, the average amount of expansion among the 19 subjects was 6.1 ⫾ 1.7 mm. The areas of ANC, MNC, and PNC (left and right) at T1, T2, and T3 for these patients are shown in Table I. These data were used to find the mean changes in areas of the various parts of the nasal cavity. As a group, the areas of the right nasal cavity increased significantly in the ANC, MNC, and PNC at all times (P ⬍.05) with the exception of the right MNC from T1 to T2 (Table II). The areas of the left nasal cavity increased significantly in the ANC, MNC, and PNC at all times (P ⬍.05, Table III). The area changes in the left ANC, MNC, and PNC increased significantly from T1 to T2 to T3 (P ⬍.05). The area of the left ANC increased from T1 to T3 by 1.46 ⫾ 1.14 cm2, or 39.6%. The area of the left MNC increased from T1 to T3 by 1.64 ⫾ 0.71 cm2, or 37.7%. The area of the left PNC increased from T1 to T3 by 1.64 ⫾ 0.92 cm2, or 36.6%. The areas of the right ANC, MNC, and PNC increased significantly T1 to T2 to T3
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Table III.
Mean area changes of the left side for the 3 time periods Left ANC
Mean area change (cm2) SD (cm2) P value
Table IV.
Left MNC
Left PNC
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
0.44 0.74 .009
1.08 0.90 .0001
1.46 1.14 .0001
0.52 0.69 .002
1.12 0.60 .0001
1.64 0.71 .001
0.67 0.70 .003
0.97 0.97 .0002
1.64 0.92 .0001
Mean area changes of the pooled right and left ANC, MNC, and PNC for the 3 time periods ANC
MNC
PNC
T
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
Mean area change (cm2) SD (cm2) P value
0.85 1.20 .003
1.78 1.20 .001
2.63 1.74 .0001
0.81 1.36 .0001
2.40 1.03 .0001
3.20 1.20 .0001
1.13 1.60 .003
2.05 1.85 .0001
3.18 1.68 .009
Fig 1. Percentage changes in area of ANC, MNC, and PNC for time periods T1 to T2, T2 to T3, and total change from T1 to T3.
(P ⬍.05) with the exception of the area of the right MNC, which did not increase significantly from T1 to T2. The area of the right ANC increased from T1 to T3 by 1.17 ⫾ 0.75 cm2, or 32.5 %. The area of the right MNC increased from T1 to T3 by 1.49 ⫾ 1.08 cm2, or 32.9%. The area of the right PNC increased from T1 to T3 by 1.57 ⫾ 0.76 cm2, or 35.7%. The pooled left and right area changes of the ANC, MNC, and PNC at the various times are shown in Table IV and Figure 1. The area changes of ANC, MNC, and PNC increased significantly from T1 to T2 to T3 (P ⬍.05). The area of the ANC increased from T1 to T3 by 2.63 ⫾ 1.74 cm2, or 36%. The area of the MNC increased from T1 to T3 by 3.2 ⫾ 1.2 cm2, or 36.6%. The area of the PNC increased from T1 to T3 by 3.18 ⫾1.68 cm2, or 35%. A comparison of the area
changes in the left and right nasal cavities at ANC, MNC, and PNC from T1 toT2 to T3 showed no significant differences. Correlation analysis showed no significant correlation between the amount of expansion and the increase of nasal cavity at any time periods (Table V). However, individual variations in response to maxillary expansion were large. Figure 2 shows the variability of shape and size changes in response to treatment for a typical patient. For most patients, the area increased from T1 to T2 to T3. However, in some time periods, the areas did not change. The volume of the left and right nasal cavities and the total volume (pooled left and right nasal cavities) for the 19 patients at T1, T2, and T3 are shown in Table VI. The changes in volume of the nasal cavity for the various time periods are shown in
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Table V.
American Journal of Orthodontics and Dentofacial Orthopedics October 2007
Correlation coefficients between expansion and increases in area and volume
Area of nasal cavity ANC Time period Correlation coefficient P value
MNC
PNC
Total volume
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
T2-T1
T3-T2
T3-T1
0.22 .34
0.29 .22
0.36 .13
⫺0.12 .61
0.24 .31
0.06 .78
⫺0.13 .58
0.29 .22
0.19 .42
⫺0.05 .82
0.30 .20
0.23 .34
Fig 2. Variability in shape and size changes in response to maxillary expansion for the anterior nasal cavity (ANC), middle nasal cavity (MNC), and posterior nasal cavity (PNC) from the time period A, T1 (solid line) to T2 (broken line); B, T2 (solid line) to T3 (broken line); and C, T1 (solid line) to T3 (broken line).
Table VII. As a group, the volume of the nasal cavity increased significantly from T1 to T2 to T3 (P ⬍.05). Figure 3 shows the percentage changes in volume from T1 to T2 to T3. The volume of the nasal cavity from T1 to T2 increased by 2.08 ⫾ 2.66 cm3, or 10.7%. The volume of the nasal cavity increased from T2 to T3 by 4.9 ⫾ 2.3 cm3, or 22.6%. The
volume of the nasal cavity increased from T1 to T3 by 6.99 ⫾ 2.45 cm3, or 27.8%. Correlation analysis showed no significant correlation between the amount of expansion and the increase in volume at any time periods (Table V). Individual variations in response to maxillary expansion were large. For most patients, the volume increased from T1 to T2 to T3.
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Table VI.
Volume of left and right nasal cavities and total nasal cavity at T1, T2, and T3 for the 19 patients (cm3) Left nasal cavity
Time Patient 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Mean SD Minimum Maximum
Right nasal cavity
Total
T1
T2
T3
T1
T2
T3
T1
T2
T3
10.4 9.8 7.44 6.7 11.49 10.19 11.05 9.53 9.74 8.22 9.19 8.31 10.07 10.0 14.12 13.98 9.17 7.61 8.16 9.75 1.96 6.7 14.12
11.39 9.71 7.71 8.01 13.73 12.23 13.54 9.02 9.33 8.86 12 9.63 12.47 11.31 13.06 14.48 10.19 12.83 9.19 10.98 2.06 7.71 14.48
15.13 13.62 10.78 9.95 15.58 15.96 15.96 10.73 13.77 11.15 13.47 10.76 12.38 13.15 17.04 18.52 11.17 14.63 11.16 13.42 2.48 9.95 18.52
9.03 10.4 8.99 7.61 12.03 8.78 13.84 10.79 9.0 8.38 10.7 10.16 8.26 8.47 11.94 12.61 8.2 7.73 8.53 9.76 1.80 7.61 12.61
9.41 11.96 8.72 8.04 13.92 8.8 15.61 10.37 8.2 8.12 11.67 9.92 11.49 9.48 11.44 12.76 8.97 12.17 10.33 10.59 2.09 8.04 15.61
12.45 16.05 010.37 9.25 18.69 12.25 18.19 12.10 11.65 10.57 14.36 12.86 11.67 11.91 14.65 17.25 11.84 12.38 10.03 13.08 2.74 9.25 18.69
19.43 20.22 16.43 14.32 23.03 18.96 24.89 20.32 18.74 16.6 19.89 18.47 18.33 18.47 26.07 26.59 17.36 15.34 16.69 19.51 3.48 14.32 26.59
20.8 21.67 16.44 16.06 27.66 21.03 29.15 19.38 17.53 16.98 23.67 19.55 23.96 20.79 24.51 27.24 19.15 25.0 19.53 21.58 3.89 16.06 29.15
27.58 29.67 21.15 19.19 34.27 28.21 34.156 22.84 25.42 21.72 27.83 23.62 24.05 25.06 31.69 35.77 23.0 27.01 21.18 26.50 4.86 19.19 35.77
Table VII.
Total volume changes in the nasal cavity for the 3 time periods
Mean area change (cm3) SD (cm3) P value
T2-T1
T3-T2
T3-T1
2.08 2.66 .0016
4.90 2.30 .0001
6.99 2.45 .0001
However, in a few, the volume decreased over the various time intervals. DISCUSSION
Several studies reported on the stability of maxillary width and the changes in the nasal structures after RPE treatment with PA cephalograms, occlusal films, or dental casts.25-27 Few studies used conventional tomography to examine the anatomical changes of the nasal cavity after maxillary expansion. One study used computed tomography to measure cross-sectional areas of the nasal airway of a patient from anterior to posterior at 4-mm intervals after RPE.30 According to pairwise correlations of the data from this study, the imaging technique used on the skull with conventional tomography was a reliable method to produce repeatable images of the nasal cavity. The area measurements from the skull images on the CMT machine had a correlation of 0.99. This demonstrates that the operator
was reliable in positioning, tracing, and measuring the areas on the images. Although computed tomography can provide accurate measurements on the area and volume of the nasal cavity, it is not practical because of its expense and the amount of radiation involved.25,26,30 Conventional tomography is more cost effective and can provide similar diagnostic information.23,24 In this study, 10% increases in area and 10% increases in volume were observed in ANC, MNC, and PNC at T2. This was followed by further increases of 25% in area and 15% in volume in the next 3 months when the expansion appliance was used as a retention device. No studies with conventional tomography have examined the stability of the nasal cavity expansion after removal of the expansion appliance.10,15,16 However, a study by Cameron et al35 using PA cephalograms examined changes in maxillary width and maxillary first molar width 8 years after removal of the expansion appliances. They found that the changes in maxillary width and maxillary first molar width exceeded the expected growth increment in the control group by 2.3 and 1.4 mm, respectively. A prospective study by Memikoglu and Iseri22 examined the changes in the transverse plane after bonded RPE and fixed appliance treatment. Using PA cephalograms and study casts obtained at pretreatment, postexpansion, and post-
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Fig 3. Percentage changes in volume from T1 to T2 to T3.
treatment (average treatment time, 3.08 years), the authors measured skeletal and dental reference points and found an increase in transverse linear measurements after expansion, and these changes were maintained and sometimes continued to increase until the end of conventional orthodontic treatment. They found no relapse after RPE and fixed therapy. Hershey et al10 performed linear measurements using PA cephalograms and models, and found that nasal cavity width increased 1 to 3 mm after expansion and another 0.33 mm during retention. On the other hand, Krebs23 and Thorn24 made linear measurements of the nasal cavity after expansion and found increases of 1.7 to 2.5 mm, but this initial expansion relapsed by 0.5 to 1.7 mm during retention. The conflicting results from these studies caused controversy about the benefits of expansion for the treatment of nasal airway resistance. All of these studies used 2-dimensional PA cephalograms or models to evaluate the changes after RPE. Conventional tomography was used to assess nasal septal deviation after surgically assisted RPE treatment. Schwarz et al29 examined 9 patients for septal deviation using 4 coronal tomograms taken within 4 months after surgical intervention. Linear measurements and the areas of the right and left airway spaces were recorded and compared with posttreatment measurements. Significant increases were found, but the mechanism was unknown. The authors speculated that it could be from expansion of the lateral walls, but they found no evidence to support this and concluded it might be due to tissue shrinkage. Many studies found decreases in NAR after RPE,7-10,12,17,18,21,31,32 but the stability of NAR has had conflicting results. Hershey et al10 and White et al11
studied the decrease in NAR after RPE. Both found that the reduction in NAR was stable over time (45% reduction in NAR 3 months later,33 and 48.7% reduction of NAR 1 year later11). Ngan et al34 found that orthopedic treatment directed at the maxilla in Class III malocclusions is stable despite some relapse. On the other hand, Wertz7 studied the effects of RPE on NAR and found inconclusive results that could not justify palatal expansion for the improvement of NAR. Individual variations in patients could be the cause of the controversial results in these studies. In our study, there were significant increases in the total volume from T1 to T2, T2 to T3, and T1 to T3. Increases in volume of the nasal cavity would support the studies that demonstrated a reduction in NAR after expansion.8-12,21,31,32 Volumetric data give a good indication of overall expansion and relapse but no information concerning expansion in various parts of the nasal cavity.35 We also found that the MNC and the PNC increased more than the ANC, even though the intermaxillary suture split with the RPE appliance decreases posteriorly. A possible explanation is that the MNC (mean, 8.77 cm2) and the PNC (mean, 9.13 cm2) are larger in area than the ANC (mean, 7.31 cm2). Consequently, the increase in area of the nasal cavity will be proportionally greater in the PNC even with a slightly greater intermaxillary suture split with the expansion appliance. There were no significant differences in the changes in the left vs the right nasal cavity in any measurements (areas of ANC, MNC, PNC, and total area) at the various time intervals. This finding was supported in a study by Bell36 that discussed the variability in the pattern of expansion depending on
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the patient’s age and maturity level, and by many cephalometric studies that show that the sutural separation of the maxilla is not uniform.3,10,25,27,36-40 Asanza et al41 found that the changes in expansion are not symmetrical, and the expansion varied from left to right and among patients. There were no significant correlations between the amount of expansion and the increases in nasal cavity area or volume for AMC, MNC, or PNC. This can be explained by the fact that the jackscrew is placed in the middle of the palate anteroposteriorly beneath the nasal airway. In the frontal plane, expansion is greater between the incisors and diminishes superiorly. The nasal septum, vomer, and perpendicular plate of the ethmoid bone typically do not completely detach but remain articulated to one of the separated maxillary and palatine bones. In the horizontal plane, expansion is greater in the anterior portion of the palate than the posterior. The posterior palate is more resistant to expansion because of the locking effect of the pyramidal processes of the palatal bones into the pterygoid plates of the sphenoid.41 From the data of this study, the area of the nasal cavity increased nonuniformly from the ANC to the PNC. Figure 2 also shows that the amount of expansion was not uniform superioinferiorly. Therefore, one cannot expect a direct correlation of either the area or the volume of the nasal cavity with the amount of palatal expansion beneath the nasal cavity. CONCLUSIONS
Conventional tomography was effective in evaluating the nasal cavity. It allowed for assessment in the transverse, vertical, and sagittal dimensions. Unlike frontal PA cephalograms, cross-sectional images can be made along the length of the nasal airway with tomograms. It was determined that the area and the volume increased significantly in all areas of the nasal cavity except for the right middle from T1 to T2. There appeared to be no relapse during the retention phase of 3 months after active expansion. The areas and the volumes increased significantly for all parts of the nasal cavity from T2 to T3. These results support previous studies that show continued reduction in NAR and airway obstruction symptoms long after expansion.
REFERENCES 1. Pfaff W. Stenosis of the nasal cavity by contraction of the palatal arch and abnormal position of the teeth. Dent Cosmos 1905;47: 570-3. 2. Brown GVI. The application of orthodontia principles to the prevention of nasal disease. Dent Cosmos 1903;45:765-75.
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3. Haas AJ. Rapid expansion of the maxillary dental arch and nasal cavity by opening the midpalatal suture. Angle Orthod 1961;31: 73-90. 4. Brogan WF. The stability of maxillary expansion. Aust Dent J 1977;22:92-9. 5. Gray LP. Septal deformity malocclusion and rapid maxillary expansion. Orthodontist 1972;4:2-14. 6. Black NM. The relation between deviation of nasal septum and irregularities of the teeth and jaw. JAMA 1909;52:943-5. 7. Wertz RA. Changes in nasal airflow incident to rapid maxillary expansion. Angle Orthod 1968;38:1-11. 8. Palmisano RG, Wilcox I, Sullivan CE, Cistulli PA. Treatment of snoring and obstructive sleep apnoea by rapid maxillary expansion. Aust N Z J Med 1996;26:428-9. 9. Cistulli PA, Palmisano RG, Poole MD. Treatment of obstructive sleep apnea syndrome by rapid maxillary expansion. Sleep 1998;21:831-5. 10. Hershey HG, Stewart BL, Warren DW. Changes in nasal airway resistance associated with rapid maxillary expansion. Am J Orthod 1976;69:274-84. 11. White BC, Woodside DG, Cole P. The effect of rapid maxillary expansion on nasal airway resistance. J Otolaryngol 1989;18: 137-43. 12. Gray LP. Results of 310 cases of rapid maxillary expansion selected for medical reasons. J Laryngol Otol 1975;89:601-14. 13. Turbyfill WJ. The long-term effect of rapid maxillary expansion [master’s thesis]. University of North Carolina; 1976. 14. Hartgerink DV, Vig PS, Abbott DW. The effect of rapid maxillary expansion on nasal airway resistance. Am J Orthod Dentofacial Orthop 1987;92:381-9. 15. Timms DJ. The reduction of nasal airway resistance by rapid maxillary expansion and its effect on respiratory disease. J Laryngol Otol 1984;98:357-62. 16. Timms DJ. Rapid maxillary expansion in the treatment of nasal obstruction and respiratory disease. Ear Nose Throat J 1987;66: 242-7. 17. Wright GH. A Group of deformities of the nasal respiratory tract, coincident with dental irregularities ii. a new instrument for comparative measurements. Dent Cosmos 1912;54:261-9. 18. Derichsweiler H. La disjonction de la suture palatine medane. Trans Eur Orthod Soc 1953;11:597-600. 19. Basciftci FA, Mutlu N, Karaman AI, Malkoc S, Kucukkolbasi H. Does the timing and method of rapid maxillary expansion have an effect on the changes in nasal dimensions? Angle Orthod 2002;72:118-23. 20. Cameron CG, Franchi L, Baccetti T, McNamara JA Jr. Longterm effects of rapid maxillary expansion: a posteroanterior cephalometric evaluation. Am J Orthod Dentofacial Orthop 2002;121:129-35. 21. Cross DL, McDonald JP. Effect of rapid maxillary expansion on skeletal, dental, and nasal structures: a postero-anterior cephalometric study. Eur J Orthod 2000;22:519-28. 22. Memikoglu TU, Iseri H. Effects of a bonded rapid maxillary expansion appliance during orthodontic treatment. Angle Orthod 1999;69:251-6. 23. Krebs A. Expansion of the midpalatal suture studied by means of metallic implants. Trans Eur Soc Orthod 1958;34:163-71. 24. Thorn NA. Expansion of maxilla spreading the midpalatal suture; measuring the widening of the apical base and the nasal cavity on serial roentgenograms [abstract]. Am J Orthod 1960;46:626. 25. Montgomery W. Computed Tomography: a three-dimensional study of the nasal airway. Am J Orthod 1979;76:363-75.
466 Palaisa et al
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26. Montgomery W. Rapid maxillary expansion effects on nasal cavity computed tomography study [abstract]. J Dent Res 1979; 58:1248. 27. Hamada MO. Implantology: radiographic resources. J Calif Dent Assoc 1989;17:20-31. 28. Clark DE. Radiation absorbed from dental implant radiography: a comparison of linear tomography, CT scan, and panoramic and intra-oral techniques. J Oral Implantol 1990;16:156-64. 29. Schwarz GM, Thrash WJ, Byrd DL, Jacobs JD. Tomographic assessment of nasal septal changes following surgical-orthodontic rapid maxillary expansion. Am J Orthod 1985;87:39-45. 30. Vig PS, Sarver DM, Hall DJ, Warren DW. Quantative evaluation of nasal airflow in relation to facial morphology. Am J Orthod 1981;79:263-72. 31. Gray LP. Rapid maxillary expansion and impaired nasal respiration. Ear Nose Throat J 1987;66:248-51. 32. Doruk C, Sokucu O, Sezer H, Canbay EI. Evaluation of nasal airway resistance during rapid maxillary expansion using acoustic rhinometry. Eur J Orthod 2004;26:397-401. 33. Hershey HG, Stewart BL, Warren DW. Changes in nasal airway resistance associated with rapid maxillary expansion.
Am J Orthod 1976 March;69(3):274-84. SAME AS 10, 16, 39, AND 48. Ngan P, Yiu C, Hu A, Hagg U, Wei SH, Gunel E. Cephalometric and occlusal changes following maxillary expansion and protraction. Eur J Orthod 1998;20:237-54. Tran A. Use of conventional tomography to evaluate changes in the nasal cavity with rapid palatal expansion [master’s thesis]. West Virginia University; 1997. Bell RA. A review of maxillary expansion in relation to the rate of expansion and patient’s age. Am J Orthod 1982;81:32-7. Haas AJ. Just the beginning of dentofacial orthopedics. Am J Orthod 1970;57:219-55. Krebs A. Midpalatal suture expansiion studied by the implant method over a seven-year period. Trans Eur Orthod Soc 1964; 40:131-42. Timms DJ. A study of basal movement with rapid maxillary expansion. Am J Orthod 1980;77:500-7. Wertz RA. Skeletal and dental changes accompanying rapid midpalatal suture opening. Am J Orthod 1970;58:41-66. Asanza S, Cisneros GJ, Nieberg LG. Comparison of hyrax and bonded expansion appliances. Angle Orthod 1997;67:15-22.
34.
35.
36. 37. 38.
39. 40. 41.