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Maxillary and cranial base changes during treatment with functional appliances
Maxillary and cranial base changes during treatment with functional appliances Michael Courtney, MDS, Michael Harkness, BDS, MSc, PhD, DOrth, and Peter Herbison, MSc a Dunedin, New Zealand The purpose of this prospective study was to investigate the maxillary and the cranial base changes after treatment with the Harvold activator and the Fr&nkel function regulator appliances. Forty-two children, who are 10 to 13 years old, with Class II, Division 1 malocclusions were matched in triads according to age and sex and randomly assigned to either the control, Harvo~d activator, or Fr&nkel function regulator group. Lateral cephalometric radiographs were taken at the start of the study and 18 months later. Both appliances reduced the overjet by tipping the maxillary incisors palatally and, as a consequence, the length of the maxillary arch was reduced. The appliances had no effect on either the horizontal or vertical position of the maxillary molars. Small, but statistically significant, changes in the cranial base angle in the Fr&nkel function regulator group were attributed to relatively large changes at basion in several children, influencing the results because of the small size of the sample. The appliances had no effect on the position of the maxilla. (Am J Orthod Dentofac Orthop 1996;109:616-24.) D u r i n g treatment with functional appliances, it is claimed that forward growth of the maxilla may be either inhibited, 1-4 redirected downward, 3 or that the effects are principally dentoalveolar. 5-8 These conflicting claims have been attributed to shortcomings in the research methods employed and, in particular, to biased methods of sample selection. 9"1° It is claimed that samples selected on the basis of successful treatment results are likely to reflect orthopedic changes, when in fact they may indicate nothing more than a favorable growth pattern. 4'11"12To overcome these problems, random allocation of subjects to experimental and control groups is regarded as the best method of eliminating many of the biases that lead to false results in nonrandomized trials. 9'13 The aims of this prospective investigation are to determine the changes in the maxilla and the cranial base in children with Class II, Division 1 malocclusion, treated with either the Frfinkel function regulator or the Harvold activator.
SUBJECTS AND METHODS Subjects The subjects who participated in this trial were 50 schoolchildren with Class II, Division 1 malocclusions) 4 The children, who were between 10 and 13 years of age From the Department of Orthodontics, School of Dentistry, University of Otago. This research was supported by the Medical Research Council of New Zealand. aDepartment of Preventive and Social Medicine, University of Otago. Copyright © 1996 by the American Association of Orthodontists. 0889-5406•96/$5.00 + 0 8/1/59177
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(mean age of 11.6 years), were matched in triads according to age and sex and randomly assigned to either the control group (C), the Fr~inkel function regulator group (FFR), or the Harvold activator group (HA). After 18 months there were 42 children remaining in the study. Of these, 17 children (11 boys and 6 girls) were in the control group, 13 children (7 boys and 6 girls) in the Fr~inkel function regulator group, and 12 children (7 boys and 5 girls) in the Harvold activator group. Six children were removed from the study because they either repeatedly failed appointments or refused to wear the appliance as instructed. Two children moved to another region. Each subject was either treated or supervised, without extraction of teeth, for 18 months by a randomly assigned orthodontist.
Methods The Fr~inkel appliance (FR-2) used in the study was constructed according to the descriptions given by McNamara and Huge 15 and Eirew, McDowell, and Phillips, 16 and the Harvold activators were constructed according to the description given by Harvold. 17 For each subject, records were taken at the beginning of the study and at 6, 12, and 18 months later. Although only the initial and 18-month lateral cephalometric radiographs and stature measurements were analyzed in the present study, all cephalometric radiographs were used to aid identification of the reference points and anatomically stable structures. The anterior wall of sella turcica, SE point, the cribriform plate of the ethmoid bone, the bilateral frontoethmoidal crests, and the superior surfaces of the orbits were traced onto mylar film and superimposed on the initial radiograph? '1s'~9 Individual templates were then made of the anatomically stable structures in the maxilla, 2° the most prominent maxillary central incisor,
American Journal of Orthodontics and Dentofacial Orthopedics Volume 109, No. 6
the maxillary first permanent molar, the maxillary first premolar, and the posterior outline of the maxilla. A 2 cm long maxillary reference plane, extending anteriorly from the base of the zygomatic process and parallel to the floor of the nose, was drawn. A second template was constructed of the anatomically stable structures in the mandible, ~9'21the condyle, the most prominent mandibular central incisor, and the mandibular first permanent molar. The templates, with the reference points marked in, were overlaid on the structures on the initial radiograph, and the cephalometric points and reference planes were transferred to the overlying mylar film. The mylar film was then positioned on the 18-month radiograph to obtain the best fit of the stable structures in the anterior cranial base. The templates were then superimposed on the relevant structures in turn and the reference points transferred to the overlying mylar film. The points on each tracing were digitized three times with a reflex metrograph and the coordinates converted to angular and linear measurements. = The definitions of the reference points and the measurements used are given in Fig. 1 and Tables I and II. The data collected from the lateral cephalometric radiographs were not corrected for magnification. Further details of the subjects and methods are given by Nelson et al. '° Between 4 and 8 weeks later, all radiographs were retraced and remeasured, using the methods described previously. The combined errors in identification of the reference points, tracing, superimposition and digitization were calculated with the Dahlberg formula. 23 The largest errors were the angular measurements for the maxillary first molar to the palatal plane (U6/ANS-PNS, initial, 2.27°; 18 months, 1.80°). There were no statistically significant differences between the two sets of measurements. To further enhance the accuracy of the method, the means of both sets of measurements have been used in all subsequent calculations.
Statistical analysis The study was large enough to have a power of about 80% of detecting a one standard deviation difference with p < 0.05. The matching of subjects was discarded for the final analysis. Unpaired Student's t tests were used to compare the differences between the boys and girls at the beginning of the study. An analysis of variance was used to determine whether any statistically significant differences existed between the groups at the beginning of the study and in the magnitude of the changes over the 18 months. Duncan's new multiple range test was then used to determine which groups were different. The increase in stature was used as the covariate in an analysis of covariance to determine whether the rate of growth of the subjects in the Harvold group contributed to the significant differences between the Harvold activator and the control groups, m
RESULTS T h e results are given in Tables III, IV, and V. T h e use o f the increase in stature as a covariate
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Fig. 1. Reference points and planes.
had no effect on the findings. M e a s u r e m e n t s below the cranial base and maxillary reference planes and to the left of the vertical reference planes are negative values. T h e changes were calculated by subtracting the initial values f r o m the 18-month values.
Pretreatment comparisons T h e r e were five statistically significant differences (age, S-N length, A N S horizontal, A point horizontal, A N S - P N S length) b e t w e e n the boys and girls at the beginning of the study (Table III). A l t h o u g h the girls were 6 m o n t h s older t h a n the boys, the cephalometric variables were slightly larger in the boys as c o m p a r e d with the girls. T h e s e sex differences are c o m p a r a b l e to the values given by Riolo et al. 24 for N o r t h A m e r i c a n children of similar ages. T h e data f r o m the boys and girls were then c o m b i n e d and the groups c o m p a r e d with the analysis o f variance. T h e r e were no significant differences b e t w e e n the groups at the beginning of the study (Table IV).
Treatment comparisons T h e r e were 21 statistically significant differences b e t w e e n the groups after 18 months. Nine of these changes were b e t w e e n the Harvold activator g r o u p and the control group, (ANS-Me, N-Me, maxillary arch length, Uie horizontal, Uia horizontal, overbite, overjet, U I A / I Z plane, and U I A / A N S -
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Table I.
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Reference points
S SE
Sella - The centre of sella turcica, S p h e n o - e t h m o i d registration p o i n t -
determined by inspection. Intersection of the sphenoidal plane with the averaged
N ANS A IZO)
Nasion - The most anterior point on the frontonasal suture. Anterior nasal spine - The tip of the anterior nasal spine in the mid-sagittal plane. A p o i n t - The most posterior point on the anterior contour of the upper alveolar process.
greater sphenoid wings.
Inferior zygoma (1) -
The lower most point on the average of the right and left outlines of the
zygoma. IZ(2) PNS Uia Uie U6MCpt U6DCT U6Apt Me Ba Go
He Lia UPmCT OB point OJ point
constructed point two centimetres rostral to IZ(1) along the line parallel to the floor of the nose through IZ(1). Posterior nasal spine - The point of intersection of the hard palate, soft palate, and the downward projection, perpendicular to the line of the palate, of the pterygomaxillary fissure. Upper inc&or apex - The root tip of the most prominent maxillary central incisor. Upper incisor incisal edge - The incisal tip of the most prominent maxillary central incisor. Upper m o l a r mesial contact p o i n t - The mesial contact point of the maxillary first molar. Upper m o l a r distal cusp tip - The tip of the distal cusp of the maxillary first molar. Upper m o l a r a p i c a l p o i n t - The root tip of the maxillary first molar. M e n t o n - The most inferior point on the symphyseal outline. Basion - The most inferior, posterior point on the anterior margin of foramen magnum. G o n i o n - The midpoint of the angle of the mandible. Determined by bisecting the angle formed by the mandibular line and the tangent to the posterior outline of the angle from the mandibular condyles. L o w e r incisor edge - The incisal tip of the most prominent mandibular central incisor. L o w e r incisor apex - The root tip of the most prominent mandibular central incisor. Upper p r e m o l a r cusp tip - The tip of the cusp of the upper first premolar or the tip of the mesial cusp of the upper first deciduous molar. Overbite p o i n t - The point of intersection between the perpendicular through Uie and a line drawn parallel to the functional occlusal plane through the point Lie. O v e r j e t p o i n t - The point of intersection of the line drawn parallel to the functional occlusal plane through Uie and the labial surface of the most prominent mandibular incisor. Inferior zygoma (2) - T h e
NOTE: OB point and OJ point were used to facilitate the calculation of overbite and overjet.
PNS), nine between the Fr~inkel function regulator and the control group (Ba horizontal, NSBa angle, ANS-Me, N-Me, maxillary arch length, Uie horizontal, overjet, UIA/IZ plane, and UIAJANSPNS), and three were between the Harvold activator and the Fr/inkel function regulator groups (NSBa angle, overbite and overjet). Cranial base. The horizontal position of basion moved 0.86 mm further posteriorly in the Fr/inkel function regulator group than in the control group. The cranial base angle opened by 0.44° in the Fr/inkel function regulator group and closed by 0.19° and 0.35 °, respectively, in the control and Harvold activator groups. The small differences between the control and the Frfinkel function regulator groups and the Fr/inkel function regulator and the Harvold activator groups were statistically significant. Maxilla. There were no statistically significant changes in the positions of ANS, A point, PNS, and IZ(1) relative to the two cranial base reference planes. Lower anterior face height (ANS-Me) and total anterior face height (N-Me) increased by 1.25
mm and 1.65 mm, respectively, in the Frfinkel function regulator group and by 2.5 mm and 3.00 mm, respectively, in the Harvold activator group, as compared with the control group. These differences were statistically significant. Although posterior face height (S-Go) increased more in both appliance groups than in the control group, this increase was not statistically significant. There were no statistically significant differences between the groups in either SNA angle or in maxillary rotation (S-N/ANS-PNS). Dentoalveolar. Maxillary arch length, measured from the incisal edge of the most prominent maxillary central incisor to the mesial contact point of the upper first molar, decreased by 1.59 mm in the Frfinkel function regulator group and by 1.89 mm in the Harvold activator group, as compared with the control group. The inclination of the upper incisors to the maxillary reference plane (IZ(1)IZ(2)) and to the palatal plane (ANS-PNS) also decreased significantly in both appliance groups. Although the upper incisor edges moved palatally in both appliance groups, the upper incisor apices
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Table II. M e a s u r e m e n t s Cranial base
NSBa Ba-N S-N S-Ba Ba vertical Ba horizontal
The angle between N, S and Ba. The distance between Ba and N. The distance between S and N. The distance between S and Ba. The perpendicular distance from Ba to the cranial base reference plane, S-SE. The perpendicular distance from Ba to the perpendicular to the cranial base reference plane through S.
Maxilla
ANS vertical ANS horizontal A point vertical A point horizontal PNS vertical PNS horizontal IZ(1) vertical IZ(1) horizontal N-ANS
The perpendicular distance from ANS to the cranial base reference plane. The perpendicular distance from ANS to the perpendicular to the cranial base reference plane through S. The perpendicular distance from A point to the cranial base reference plane. The perpendicular distance from A point to the perpendicular to the cranial base reference plane through S. The perpendicular distance from PNS to the cranial base reference plane. The perpendicular distance from PNS to the perpendicular to the cranial base reference plane through S. The perpendicular distance from IZ(1) to the cranial base reference plane. The perpendicular distance from IZ(1) to the perpendicular to the cranial base reference plane through S. The distance between N and ANS; designated the upper anterior face height
(UAFH). ANS-Me N-Me S-Go ANS-PNS SNA S-N/ANS-PNS S-SE/ANS-PNS S-SE/IZ plane
The distance between ANS and Me; designated the lower anterior face height (LAFH). The distance between N and Me; designated the total anterior face height (TFH). The distance between S and Go; designated the posterior face height (PFH). The distance between ANS and PNS. The angle between S, N, and A. The angle between S-N and ANS-PNS. The angle between the cranial base reference plane and ANS-PNS. The angle between the cranial base reference plane and IZ(1)-IZ(2).
Dentoalveolar
Arch length Uie vertical Uie horizontal Uia horizontal Overbite Overjet UIA/IZ plane UIA/ANS-PNS U6/IZ plane U6/ANS-PNS U6DCT vertical U6MCpt horizontal
The distance between Uie-U6MCPt. The perpendicular distance from Uie to the maxillary reference plane. The perpendicular distance from Uie to the perpendicular to the maxillary reference plane through IZ(1). The perpendicular distance from Uia to the perpendicular to the maxillary reference plane through IZ(1) The distance between OB point and Uie. The distance between OJ point and Uie. The angle between Uie-Uia and IZ(1)-IZ(2). The angle between Uie-Uia and ANS-PNS. The angle between U6DCT-U6Apt and IZ(1)-IZ(2). The angle between U6DCT-U6Apt and ANS-PNS. The perpendicular distance from U6DCT to the maxillary reference plane. The perpendicular distance from U6MCPt to the perpendicular to the maxillary reference plane through IZ(1).
o n l y m o v e d l a b i a l l y in t h e H a r v o l d a c t i v a t o r g r o u p , compared with the control group. Overbite was r e d u c e d s i g n i f i c a n t l y m o r e in t h e H a r v o l d a c t i v a t o r g r o u p as c o m p a r e d w i t h b o t h t h e c o n t r o l a n d t h e Fr~inkel f u n c t i o n r e g u l a t o r g r o u p s . T h e r e d u c t i o n in o v e r j e t in t h e H a r v o l d a c t i v a t o r g r o u p w a s also s i g n i f i c a n t l y g r e a t e r t h a n in t h e F r g n k e l f u n c t i o n r e g u l a t o r g r o u p . T h e r e w e r e n o s t a t i s t i c a l l y signif-
i c a n t d i f f e r e n c e s in t h e h o r i z o n t a l a n d v e r t i c a l m o v e m e n t s o f t h e m a x i l l a r y first p e r m a n e n t m o l a r between the groups.
DISCUSSION T h e r e s u l t s o f this p r o s p e c t i v e study, in c o m b i n a t i o n w i t h o u r e a r l i e r study, 1° c o n f i r m e d B j o r k ' s speculation 5 that the treatment effects of functional
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Table III. C o m p a r i s o n of the boys a n d girls at the b e g i n n i n g of the study Boys (n = 25) Variables
Age (yr) Stature (cm)
Girls (n = 17)
Mean
SD
Mean
SD
11.28 145.70
0.91 5.54
11.89 148.65
0.68 7.24
0.024 0.143
108.72 73.23 45.36 32.97 30.81 131.76
3.07 2.52 3.05 4.42 3.29 5.00
107.34 70.93 45.70 31.61 32.71 133.15
3.99 3.32 2.51 3.98 3.17 5.76
0.215 0.015 0.702 0.315 0.315 0.412
54.29 70.21 58.78 62.65 45.25 11.85 47.04 36.94 52.77 65.33 114.67 73.12 59.27 81.15 7.42 9.12 6.69
5.66 5.40 5.08 6.27 2.24 3.98 3.94 4.75 3.27 4.37 5.11 3.56 2.62 2.35 3.18 4.33 4.24
54.36 65.45 58.99 58.02 44.24 9.82 46.41 34.13 51.17 63.28 111.91 72.24 56.69 80.10 7.38 10.28 8.41
4.63 4.00 4.41 4.53 2.56 3.36 2.78 3.10 2.53 6.68 6.10 3.73 1.53 3.65 2.36 4.25 4.37
0.969 0.004 0.894 0.013 0.185 0.092 0.575 0.052 0.097 0.235 0.120 0.441 0.001 0.261 0.969 0.396 0.209
35.99 32.19 30.82 20.15 4.35 9.06 2.96 20.04 112.49 115.12 107.43 104.80
2.64 2.59 4.06 2.97 2.92 2.11 2.74 1.88 5.33 5.52 4.69 4.41
34.89 30.88 30.48 19.05 3.30 9.66 2.86 20.69 115.91 118.28 105.05 102.68
2.75 3.79 3.01 2.49 2.45 1.93 2.42 2.33 6.55 7.04 4.80 5.73
0.197 0.189 0.770 0.215 0.232 0.354 0.906 0.321 0.071 0.111 0.117 0.182
Cranial base
Ba-N (mm) S-N (ram) S-Ba (mm) Ba vertical (.mrn) Ba horizontal (mm) NSBa (°) Maxilla
ANS vertical (mm) ANS horizontal (mm) A point vertical (nun) A point horizontal (mm) PNS vertical (mm) PNS horizontal (mm) IZ(1) vertical (mm) IZ(1) horizontal (mm) N-ANS (mm) ANS-Me (mm) N-Me (mm) S-Go (mm) ANS-PNS (mm) SNA (°) S-N/ANS-PNS (°) S-SE/ANS-PNS (°) S-SE/IZ plane (°) Dentoalveolar
Max archlength (mm) Uie vertical (mm) Uie horizontal (ram) Uia horizontal (ram) Overbite (mm) Overjet (mm) U6MCpt horizontal (mm) U6DCT vertical (mm) UIA/IZ plane (°) UIA/ANS-PNS (°) U6/IZ plane (°) U6/ANS-PNS (°)
Significant values are in bold type; unpaired t test.
a p p l i a n c e s are m a i n l y c o n f i n e d to the d e n t o a l v e o l a r structures. T h e small, b u t statistically significant, o p e n i n g of the c r a n i a l base angle in the Frfinkel f u n c t i o n r e g u l a t o r g r o u p was d u e to posterior m o v e m e n t of b a s i o n r a t h e r t h a n a c h a n g e in the p o s i t i o n of n a s i o n . B a s i o n m o v e d posteriorly by m o r e t h a n 2.5 m m in several subjects in the Frfinkel f u n c t i o n r e g u l a t o r group, w h e r e a s t h e r e was n o significant
difference a m o n g the t h r e e groups in the position of n a s i o n relative to the c r a n i a l base r e f e r e n c e p l a n e s ( A N O V A , N vertical, p = 0.285; N horizontal, p = 0.505). W e p o s t u l a t e it was the m a g n i t u d e of these changes in some subjects, relative to the sample size, that was r e s p o n s i b l e for the significant findings in this group r a t h e r t h a n the i n f l u e n c e of the a p p l i a n c e s o n the c r a n i a l base. Previous longit u d i n a l studies have shown that the cranial base
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Table IV. Comparison of the groups at the beginning of the study Control (n = 17)
FFR (n = 13)
ANOVA
SD
Mean
SD
108.24 72.44 45.05 31.44 32.04 133.16
3.03 2.35 2.97 3.71 3.26 5.54
107.28 71.55 45.70 33.51 30.80 131.53
3.38 3.23 2.27 3.40 3.32 6.47
0.558 0.602 0.801 0.490 0.631 0.752
4.86 5.94 4.26 6.73 2.38 4.45 3.16 5.16 3.70 4.35 6.06 3.94 2.85 2.87 4.68 5.38 2.14
54.66 67.56 58.83 59.91 44.39 10.82 46.08 35.15 52.00 63.59 112.48 72.04 80.07 7.85 10.81 7.98 57.92
6.43 5.56 5.57 6.21 2.45 3.85 3.47 4.55 2.64 6.09 5.50 3.72 3.22 2.72 4.30 4.13 2.91
53.54 69.77 57.88 62.56 44.58 11.80 45.79 36.65 52.33 64.39 113.46 73.30 82.27 7.73 8.82 6.52 58.77
4.52 4.41 4.74 4.75 2.43 2.97 3.71 4.14 2.71 6.36 5.41 3.16 2.38 3.05 3.70 2.81 2.86
0.836 0.534 0.651 0.485 0.502 0.714 0.162 0.726 0.962 0.710 0.437 0.669 0.097 0.566 0.465 0.697 0.682
2.60 3.17 3.54 2.61 1.77 1.87 3.17 2.43 4.64 5.07 5.47 5.14
35.72 32.50 30.44 20.24 4.55 9.27 3.10 20.79 112.03 114.87 106.56 103.72
2.60 3.70 3.64 3.05 3.39 2.34 2.65 1.89 6.56 6.80 4.44 5.29
35.10 31.58 31.63 19.94 3.18 9.30 2.28 20.04 115.50 118.52 107.15 104.13
3.10 2.49 3.88 2.91 3.21 2.10 1.67 1.79 7.06 7.22 4.53 5.03
0.663 0.480 0.570 0.547 0.475 0.997 0.706 0.661 0.353 0.344 0.798 0.979
Mean
SD
Mean
Cranial base Ba-N (ram) S-N (ram) S-Ba (ram) Ba vertical (rain) Ba horizontal (rnra) NSBa (°)
108.72 72.70 45.70 32.40 31.77 132.23
3.95 3.45 3.16 5.13 3.50 4.36
Maxilla ANS vertical (ram) ANS horizontal (ram) A point vertical (mm) A point horizontal (mm) PNS vertical (ram) PNS horizontal (ram) IZ(1) vertical (ram) IZ(1) horizontal (nun) N-ANS (mra) ANS-Me (mra) N-Me (ram) S-Go (mm) SNA (°) S-N/ANS-PNS (°) S-SE/ANS-PNS (°) S-SE/IZ-IZ (°) ANS-PNS (ram)
54.60 67.78 59.58 60.17 45.37 10.64 48.03 35.72 52.07 65.28 114.44 72.94 80.13 6.83 9.20 7.55 58.07
Dentoalveolar Max archlength (ram) Uie vertical (ram) Uie horizontal (ram) Uia horizontal (mm) Overbite (ram) Overjet (mm) U6MCpt horizontal (mm) U6DCT vertical (mm) UIA/IZ plane (°) UIA/ANS-PNS (°) U6/IZ plane (°) U6/ANS-PNS (°)
35.09 31.07 30.21 19.13 3.97 9.33 2.98 20.13 114.13 116.06 105.91 103.98
Variables
H A (n = 12)
angle in untreated persons may change with age. 25,z6
In contrast to a number of studies, 1-4 we could find no evidence of orthopedic changes in the maxilla. For example, Jakobsson I reported that ANS and A point were prevented from moving forward by approximately 1.1 and 0.7 mm, respectively, in his activator group as compared with his control group. However, in agreement with the present study, others 6'ev have reported that growth of the maxilla was not restricted horizontally during treatment. Total anterior face height (N-Me) and lower
I
anterior face height (ANS-Me) increased significantly in both appliance groups. Others have reported similar increases in lower anterior face height. 2'6'2s There were no significant differences between the groups in either upper anterior face height (N-ANS) or posterior face height (S-Go). The larger increase in total and lower anterior face heights in the Harvold activator group, as compared with the Frfinkel function regulator group, is attributed to the greater bite opening used with this appliance. Our finding that eruption of the maxillary molar played little part in the significant increase in vertical dimension supports Nel-
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Table V. Comparison of the groups using the differences between measurements at the start and 18
months later Control (n = 17) Variables
FFR (n = 13)
HA (n = 12)
ANOVA
Mean
SD
Mean
SD
Mean
SD
P
Ba-N (mm) S-N (ram) S-Ba (mm) Ba vertical (rnm) Ba horizontal (mm)
1.92 1.04 1.18 - 0.89 -0.72
1.22 0.53 1.00 0.91 0.76
2.81 1.27 1.65 - 0.70 - 1.58
0.77 0.35 0.79 1.05 0.67
2.34 1.19 1.54 - 1.25 -0.89
1.79 0.72 1.22 0.90 1.16
0.194 0.501 0.412 0.353 0.031
NSBa (°)
- 0.19
0.57
0.44
0.78
- 0.35
0.76
0.014
1.59 1.37 1.47 L16 0.72 0.75 0.70 0.81 1.43 2.50
0.561 0.314 0.646 0.295 0.377 0.233 0.365 0.219 0.517 0.001
Cranial base change
t
t
t Maxillary skeletal change ANS vertical (mm) ANS horizontal (mm) A point vertical (mm) A point horizontal (ram) PNS vertical (ram) PNS horizontal (ram) IZ(1) vertical (mm) IZ(1) horizontal (mm) N-ANS (mm) ANS-Me (mm)
1.18 1.54 0.98 0.86 0.39 0.70 0.94 0.58 0.97 0.97
- 2.23 0.68 - 2.78 0.28 - 1.46 - 0.99 - 1.53 0.38 1.86 2.84
1.18 1.10 1.17 0.99 0.97 1.29 1.16 0.79 0.77 1.46
- 2.28 1.48 - 2.57 0.46 - 1.06 - 0.68 - 1.03 0.41 2.19 4.09
3.30
1.43
4.95
1.64
6.30
3.05
0.001
3.19 1.75 0.35 0.20 0.25 - 0.06
1.51 1.71 0.73 0.86 0.99 1.05
4.39 1.80 - 0.09 0.16 0.37 - 0.30
1.33 1.33 0.76 1.13 1.46 1.44
4.46 2.34 - 0.24 0.75 0.84 0.06
1.97 1.55 0.79 1.04 1.20 1.81
0.063 0.565 0.097 0.259 0.428 0.847
Max arch length (ram)
- 0.51
1.26
- 2.10
1.41
- 2.40
1.68
0.001
Uie vertical (mm) Uie horizontal (mm)
- 1.40 0.41
1.05 1.10
- 2.15 - 1.16
1.38 1.79
- 2.37 - 1.92
1.42 1.96
0.103 0.001
Uia horizontal (mm)
t 0.03 t
0.86
0.54
0.73
0.99
1.13
0.027
0.94
0.25
1.83
t t
- 1.99
2.52
0.002
0.21
1.21
- 2.24
2.23
- 5.17
3.75
0.000
0.80 - 2.03 0.94
1.09 1.19 2.49
0.95 - 2.27 - 3.98
0.89 1.09 5.01
0.50 - 2.58 - 6.59
1.01 1.75 6.13
0.533 0.568 0.000
1.74
2.14
- 3.38
4.70
- 6.00
6.66
0.000
2.38 2.45
0.628 0.463
N-Me (ram) S-Go (mm) ANS-PNS (ram) SNA (°) S-N/ANS-PNS (°) S-SE/ANS-PNS (°) S-SE/IZ -IZ (°)
- 1.81 1.28 - 2.37 0.84 - 1.31 - 0.39 - 1.10 0.80 1.72 1.59
t
*
t
Dentoalveolar change
Overbite (mm) Overjet (ram) U 6 M C p t horizontal (mm) U 6 D C T vertical (mm) U I A / I Z plane (°) UIA/ANS-PNS (°)
0.34
t
tt
r
* U6 /IZ plane (°) U6/ANS-PNS (°)
- 0.64 - 1.43
2.48 2.05
- 0.19 - 0.80
t
t 2.71 2.81
0.28 - 0.31
Significant values are in bold type. The bars indicate groups found by Duncan's new multiple range test to be different at the 5% level of significance.
American Journal of Orthodontics and Dentofacial Orthopedics Volume 109, No. 6
son et al. 1° view that the increase in face height was due primarily to increased eruption of the mandibular molar. This finding is not surprising because both appliances have extensions to prevent the maxillary teeth from erupting and is supported by others. 2~'29 On the other hand, several authors 3°'31 have reported that the eruption of the maxillary molar was inhibited. The greater bite opening incorporated in the Harvold activator appliance would account for the significant reduction in overbite in the Harvold group. In agreement with a number of previous studies, 3z-34 the overjet was reduced by tipping the maxillary incisors palatally and the mandibular incisors labially. 1° The significant reduction in maxillary arch length in both appliance groups is due, almost entirely, to thi s palatal movement. The apices of the maxillary incisors tipped labially approximately 1 mm in the Harvold activator group and approximately 0.5 mm in the Frfinkel function regulator group. Our finding that there were no significant differences between the groups in forward movement of the maxillary molars agrees with Wieslander and Lagerstrom6 and disagrees with Jakobsson 1 and Johnston4 who reported that the maxillary molar was restrained. Others have also reported that the mandibular incisors are proclined during functional appliance treatment. ~'2~ This effect is almost certainly due to the use of the mandibular arch as anchorage to treat the maxillary arch. Therefore, on the basis of the results of this and our previous study, 1° we recommend that these appliances should be used to treat Class II, Division 1 malocclusions in growing persons with Skeletal I or mild Skeletal II dental bases. It would also be an advantage to have a relatively low vertical face height and increased overbite because these appliances allow the mandibular molars to erupt and, by so doing, increase the height of the face. As these appliances reduce an overjet by tipping maxillary and mandibular incisors, the increased overjet should be due to proclined maxillary incisors, which can be tipped palatally into position, and retroclined or upright mandibular incisors, which may be proclined successfully.35 Modifications to the appliances, such as incisor capping or the addition of an extraoral force, may prevent or limit the amount of mandibular incisor proclination. Spaced and well-aligned arches are also desirable, first to lessen or prevent crowding from developing in the
Courtnc~, Harkness, and Herbison
623
maxillary arch when the maxillary incisors are tipped palatally and second, to accommodate the mandibular incisors should they relapse toward their pretreatment positions?2"34 CONCLUSIONS
After 18 months' wear, the effects of both appliances were confined mainly to the dentition. The larger increase in anterior face height and significant reduction in overbite in the Harvold activator group, compared with the Frfinkel function regulator group, were attributed to the greater bite opening obtained with this appliance. The Harvold activator also reduced the overjet, by tipping the maxillary incisors palatally, more than the Fr~nkel function regulator. The length of the maxillary arch was reduced as a consequence. The small, but statistically significant, changes at basion in the Frfinkel function regulator group are attributed to large cranial base changes in several subjects influencing the results because of the small size of the sample. We are indebted to Drs. John C. Muir and Heli Vinkka-Puhakka who participated in the planning and conduct of this trial. REFERENCES 1. Jakobsson SO. Cephalometric evaluation of treatment effect on Class II, Division 1 malocclusions. Am J Orthod 1967; 53:446-57. 2. Harvold EP, Vargervik K. Morphogenic response to activator treatment. Am J Orthod 1971;60:478-90. 3. Woodside DG, Reed RT, Doucet JD, Thompson GW. Some effects of activator treatment on growth rate of the mandible and position of the midface. In: Cook JT. Transactions of the Third International Orthodontic Conference. London: Crosby, Lockwood and Staples, 1975:459-80. 4. Johnston LE. A comparative analysis of Class II treatments. In: Vig PS, Ribbens KA. Science and clinical judgement in orthodontics. Monograph 19. Craniofacial Growth Series. Ann Arbor: Center for Human Growth and Development, University of Michigan, 1986:103-48. 5. Bjork A. The principle of the Andresen method of orthodontic treatment, a discussion based on cephalometric x-ray analysis of treated cases. Am J Orthod 1951;37:437-58. 6. Wieslander L, Lagerstrom L. The effect of activator treatment on Class II malocclusions. Am J Orthod 1979;75: 20-6. 7. Calvert FJ. An assessment of Andresen therapy on class II division 1 malocclusion. Br J Orthod 1982;9:149-53. 8. Robertson NRE. An examination of treatment changes in children treated with the function regulator of Frankel. Am J Orthod 1983;83:299-310. 9. Tulloch JFC, Medland W, Tuncay OC. Methods used to
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17. 18.
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20.
21. 22. 23.
Courtn~ Harkness, and Herbison
evaluate growth modification in Class II malocclusion. Am J Orthod Dentofac Orthop 1990;98:340-7. Nelson C, Harkness M, Herbison P. Mandibular changes during functional appliance treatment. Am J Orthod Dentofac Orthop 1993;104:153-61. Cohen AM. A study of Class II division 1 malocclusions treated by the Andresen appliance. Br J Orthod 1981;8:15963. Mills JRE. Clinical control of craniofacial growth: a skeptic's viewpoint. In: McNamara JA, Ribbens KA, Howe RP. Clinical alteration of the growing face. Monograph 14. Craniofacial Growth Series. Ann Arbor: University of Michigan, 1983:17-39. Sackett DL, Hayes RB, Tugwell P. Clinical epidemiology: a basic science for clinical medicine. Boston: Little, Brown and Co., 1985. British Standards Institution 1983 BS4492. British standard glossary of terms relating to dentistry. London: British Standards Institution, 1983. McNamara JA, Huge SA. The Frankel appliance (FR-2): model preparation and appliance construction. Am J Orthod 1981;80:478-95. Eirew HL, McDowell F, Phillips JG. The Fraenkel appliance-avoidance of lower incisor proclination. Br J Orthod 1981;8:189-91. Harvold EP. The activator in interceptive orthodontics. St Louis: CV Mosby, 1974. Melsen B. The cranial base: the postnatal development of the cranial base studied histologically on human autopsy material. Acta Odont Scand 1974;32(Suppl 62):1-126. Bjork A, Skieller V. Normal and abnormal growth of the mandible. A synthesis of longitudinal cephalometric implant studies over a period of 25 years. Eur J Orthod 1983;5:1-46. Bjork A, Skieller V. Growth of the maxilla in three dimensions as revealed radiographically by the implant method. Br J Orthod 1977;4:53-64. Bjork A. Prediction of mandibular growth rotation. Am J Orthod 1969;55:585-99. Scott PJ. The reflex plotters: measurement without photographs. Photogram Rec 1981;10:435-46. Dahlberg G. Statistical methods for medical and biological students. New York: Interscience Publications, 1940.
American Journal of Orthodontics and Dentofacial Orthopedics June 1996 24. Riolo ML, Moyers RE, McNamara JA, Hunter WS. An atlas of craniofacial growth. Monograph 2. Craniofacial Growth Series. Ann Arbor: Center for Human Growth and Development, University of Michigan, 1974. 25. Bjork A. Cranial base development. Am J Orthod 1955;41: 198-225. 26. Brodie AG. The behavior of the cranial base and its components as revealed by serial cephalometric roentgenograms. Angle Orthod 1955;25:148-60. 27. Derringer K. A cephalometric study to compare the effects of cervical traction and Andresen therapy in the treatment of Class II division 1 malocclusion. Part 1 - skeletal changes. Br J Orthod 1990;17:33-46. 28. Chang H, Wu K, Chen K, Cheng M. Effects of activator treatment on Class II, division I malocclusion. J Clin Orthod 1989;23:560-3. 29. McNamara JA, Bookstein FL, Shaughnessy TG. Skeletal and dental changes following functional regulator therapy on Class II patients. Am J Orthod 1985;88:91-110. 30. Baumrind S, Korn EL, Molthen R, West EE. Changes in facial dimensions associated with the use of forces to retract the maxilla. Am J Orthod 1981;80:17-30. 31. Righellis EG. Treatment effects of Frankel, activator and extra oral traction appliances. Angle Orthod 1983;53:10721. 32. Ahlgren F, Laurin C. Late results of activator treatment: a cephalometric study. Br J Orthod 1976:3:181-7. 33. Reey RW, Eastwood A. The passive activator: case selection, treatment response, and corrective mechanics. Am J Orthod 1978;73:378-409. 34. Derringer K. A cephalometric study to compare the effects of cervical traction and Andresen therapy in the treatment of Class II division 1 malocclusion. Part 2-dentoalveolar changes. Br J Orthod 1990;17:89-99. 35. Mills JRE. The stability of the lower labial segment. A cephalometric survey. Dent Pract 1968;18:293-305.
Reprint requests to: Dr. E. M. Harkness School of Dentistry PO Box 647 Dunedin, New Zealand
SUBJECTS AND METHODS Subjects The subjects who participated in this trial were 50 schoolchildren with Class II, Division 1 malocclusions) 4 The children, who were between 10 and 13 years of age From the Department of Orthodontics, School of Dentistry, University of Otago. This research was supported by the Medical Research Council of New Zealand. aDepartment of Preventive and Social Medicine, University of Otago. Copyright © 1996 by the American Association of Orthodontists. 0889-5406•96/$5.00 + 0 8/1/59177
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(mean age of 11.6 years), were matched in triads according to age and sex and randomly assigned to either the control group (C), the Fr~inkel function regulator group (FFR), or the Harvold activator group (HA). After 18 months there were 42 children remaining in the study. Of these, 17 children (11 boys and 6 girls) were in the control group, 13 children (7 boys and 6 girls) in the Fr~inkel function regulator group, and 12 children (7 boys and 5 girls) in the Harvold activator group. Six children were removed from the study because they either repeatedly failed appointments or refused to wear the appliance as instructed. Two children moved to another region. Each subject was either treated or supervised, without extraction of teeth, for 18 months by a randomly assigned orthodontist.
Methods The Fr~inkel appliance (FR-2) used in the study was constructed according to the descriptions given by McNamara and Huge 15 and Eirew, McDowell, and Phillips, 16 and the Harvold activators were constructed according to the description given by Harvold. 17 For each subject, records were taken at the beginning of the study and at 6, 12, and 18 months later. Although only the initial and 18-month lateral cephalometric radiographs and stature measurements were analyzed in the present study, all cephalometric radiographs were used to aid identification of the reference points and anatomically stable structures. The anterior wall of sella turcica, SE point, the cribriform plate of the ethmoid bone, the bilateral frontoethmoidal crests, and the superior surfaces of the orbits were traced onto mylar film and superimposed on the initial radiograph? '1s'~9 Individual templates were then made of the anatomically stable structures in the maxilla, 2° the most prominent maxillary central incisor,
American Journal of Orthodontics and Dentofacial Orthopedics Volume 109, No. 6
the maxillary first permanent molar, the maxillary first premolar, and the posterior outline of the maxilla. A 2 cm long maxillary reference plane, extending anteriorly from the base of the zygomatic process and parallel to the floor of the nose, was drawn. A second template was constructed of the anatomically stable structures in the mandible, ~9'21the condyle, the most prominent mandibular central incisor, and the mandibular first permanent molar. The templates, with the reference points marked in, were overlaid on the structures on the initial radiograph, and the cephalometric points and reference planes were transferred to the overlying mylar film. The mylar film was then positioned on the 18-month radiograph to obtain the best fit of the stable structures in the anterior cranial base. The templates were then superimposed on the relevant structures in turn and the reference points transferred to the overlying mylar film. The points on each tracing were digitized three times with a reflex metrograph and the coordinates converted to angular and linear measurements. = The definitions of the reference points and the measurements used are given in Fig. 1 and Tables I and II. The data collected from the lateral cephalometric radiographs were not corrected for magnification. Further details of the subjects and methods are given by Nelson et al. '° Between 4 and 8 weeks later, all radiographs were retraced and remeasured, using the methods described previously. The combined errors in identification of the reference points, tracing, superimposition and digitization were calculated with the Dahlberg formula. 23 The largest errors were the angular measurements for the maxillary first molar to the palatal plane (U6/ANS-PNS, initial, 2.27°; 18 months, 1.80°). There were no statistically significant differences between the two sets of measurements. To further enhance the accuracy of the method, the means of both sets of measurements have been used in all subsequent calculations.
Statistical analysis The study was large enough to have a power of about 80% of detecting a one standard deviation difference with p < 0.05. The matching of subjects was discarded for the final analysis. Unpaired Student's t tests were used to compare the differences between the boys and girls at the beginning of the study. An analysis of variance was used to determine whether any statistically significant differences existed between the groups at the beginning of the study and in the magnitude of the changes over the 18 months. Duncan's new multiple range test was then used to determine which groups were different. The increase in stature was used as the covariate in an analysis of covariance to determine whether the rate of growth of the subjects in the Harvold group contributed to the significant differences between the Harvold activator and the control groups, m
RESULTS T h e results are given in Tables III, IV, and V. T h e use o f the increase in stature as a covariate
Courtney~ Harkness, and Herbison
617
Fig. 1. Reference points and planes.
had no effect on the findings. M e a s u r e m e n t s below the cranial base and maxillary reference planes and to the left of the vertical reference planes are negative values. T h e changes were calculated by subtracting the initial values f r o m the 18-month values.
Pretreatment comparisons T h e r e were five statistically significant differences (age, S-N length, A N S horizontal, A point horizontal, A N S - P N S length) b e t w e e n the boys and girls at the beginning of the study (Table III). A l t h o u g h the girls were 6 m o n t h s older t h a n the boys, the cephalometric variables were slightly larger in the boys as c o m p a r e d with the girls. T h e s e sex differences are c o m p a r a b l e to the values given by Riolo et al. 24 for N o r t h A m e r i c a n children of similar ages. T h e data f r o m the boys and girls were then c o m b i n e d and the groups c o m p a r e d with the analysis o f variance. T h e r e were no significant differences b e t w e e n the groups at the beginning of the study (Table IV).
Treatment comparisons T h e r e were 21 statistically significant differences b e t w e e n the groups after 18 months. Nine of these changes were b e t w e e n the Harvold activator g r o u p and the control group, (ANS-Me, N-Me, maxillary arch length, Uie horizontal, Uia horizontal, overbite, overjet, U I A / I Z plane, and U I A / A N S -
618
Courtn~
Table I.
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American Journal of Orthodontics and Dentofacial Orthopedics June 1996
Reference points
S SE
Sella - The centre of sella turcica, S p h e n o - e t h m o i d registration p o i n t -
determined by inspection. Intersection of the sphenoidal plane with the averaged
N ANS A IZO)
Nasion - The most anterior point on the frontonasal suture. Anterior nasal spine - The tip of the anterior nasal spine in the mid-sagittal plane. A p o i n t - The most posterior point on the anterior contour of the upper alveolar process.
greater sphenoid wings.
Inferior zygoma (1) -
The lower most point on the average of the right and left outlines of the
zygoma. IZ(2) PNS Uia Uie U6MCpt U6DCT U6Apt Me Ba Go
He Lia UPmCT OB point OJ point
constructed point two centimetres rostral to IZ(1) along the line parallel to the floor of the nose through IZ(1). Posterior nasal spine - The point of intersection of the hard palate, soft palate, and the downward projection, perpendicular to the line of the palate, of the pterygomaxillary fissure. Upper inc&or apex - The root tip of the most prominent maxillary central incisor. Upper incisor incisal edge - The incisal tip of the most prominent maxillary central incisor. Upper m o l a r mesial contact p o i n t - The mesial contact point of the maxillary first molar. Upper m o l a r distal cusp tip - The tip of the distal cusp of the maxillary first molar. Upper m o l a r a p i c a l p o i n t - The root tip of the maxillary first molar. M e n t o n - The most inferior point on the symphyseal outline. Basion - The most inferior, posterior point on the anterior margin of foramen magnum. G o n i o n - The midpoint of the angle of the mandible. Determined by bisecting the angle formed by the mandibular line and the tangent to the posterior outline of the angle from the mandibular condyles. L o w e r incisor edge - The incisal tip of the most prominent mandibular central incisor. L o w e r incisor apex - The root tip of the most prominent mandibular central incisor. Upper p r e m o l a r cusp tip - The tip of the cusp of the upper first premolar or the tip of the mesial cusp of the upper first deciduous molar. Overbite p o i n t - The point of intersection between the perpendicular through Uie and a line drawn parallel to the functional occlusal plane through the point Lie. O v e r j e t p o i n t - The point of intersection of the line drawn parallel to the functional occlusal plane through Uie and the labial surface of the most prominent mandibular incisor. Inferior zygoma (2) - T h e
NOTE: OB point and OJ point were used to facilitate the calculation of overbite and overjet.
PNS), nine between the Fr~inkel function regulator and the control group (Ba horizontal, NSBa angle, ANS-Me, N-Me, maxillary arch length, Uie horizontal, overjet, UIA/IZ plane, and UIAJANSPNS), and three were between the Harvold activator and the Fr/inkel function regulator groups (NSBa angle, overbite and overjet). Cranial base. The horizontal position of basion moved 0.86 mm further posteriorly in the Fr/inkel function regulator group than in the control group. The cranial base angle opened by 0.44° in the Fr/inkel function regulator group and closed by 0.19° and 0.35 °, respectively, in the control and Harvold activator groups. The small differences between the control and the Frfinkel function regulator groups and the Fr/inkel function regulator and the Harvold activator groups were statistically significant. Maxilla. There were no statistically significant changes in the positions of ANS, A point, PNS, and IZ(1) relative to the two cranial base reference planes. Lower anterior face height (ANS-Me) and total anterior face height (N-Me) increased by 1.25
mm and 1.65 mm, respectively, in the Frfinkel function regulator group and by 2.5 mm and 3.00 mm, respectively, in the Harvold activator group, as compared with the control group. These differences were statistically significant. Although posterior face height (S-Go) increased more in both appliance groups than in the control group, this increase was not statistically significant. There were no statistically significant differences between the groups in either SNA angle or in maxillary rotation (S-N/ANS-PNS). Dentoalveolar. Maxillary arch length, measured from the incisal edge of the most prominent maxillary central incisor to the mesial contact point of the upper first molar, decreased by 1.59 mm in the Frfinkel function regulator group and by 1.89 mm in the Harvold activator group, as compared with the control group. The inclination of the upper incisors to the maxillary reference plane (IZ(1)IZ(2)) and to the palatal plane (ANS-PNS) also decreased significantly in both appliance groups. Although the upper incisor edges moved palatally in both appliance groups, the upper incisor apices
American Journal of Orthodontics and Dentofacial Orthopedics Volume 109, No. 6
Courtne)~ Harkness, and Herbison
619
Table II. M e a s u r e m e n t s Cranial base
NSBa Ba-N S-N S-Ba Ba vertical Ba horizontal
The angle between N, S and Ba. The distance between Ba and N. The distance between S and N. The distance between S and Ba. The perpendicular distance from Ba to the cranial base reference plane, S-SE. The perpendicular distance from Ba to the perpendicular to the cranial base reference plane through S.
Maxilla
ANS vertical ANS horizontal A point vertical A point horizontal PNS vertical PNS horizontal IZ(1) vertical IZ(1) horizontal N-ANS
The perpendicular distance from ANS to the cranial base reference plane. The perpendicular distance from ANS to the perpendicular to the cranial base reference plane through S. The perpendicular distance from A point to the cranial base reference plane. The perpendicular distance from A point to the perpendicular to the cranial base reference plane through S. The perpendicular distance from PNS to the cranial base reference plane. The perpendicular distance from PNS to the perpendicular to the cranial base reference plane through S. The perpendicular distance from IZ(1) to the cranial base reference plane. The perpendicular distance from IZ(1) to the perpendicular to the cranial base reference plane through S. The distance between N and ANS; designated the upper anterior face height
(UAFH). ANS-Me N-Me S-Go ANS-PNS SNA S-N/ANS-PNS S-SE/ANS-PNS S-SE/IZ plane
The distance between ANS and Me; designated the lower anterior face height (LAFH). The distance between N and Me; designated the total anterior face height (TFH). The distance between S and Go; designated the posterior face height (PFH). The distance between ANS and PNS. The angle between S, N, and A. The angle between S-N and ANS-PNS. The angle between the cranial base reference plane and ANS-PNS. The angle between the cranial base reference plane and IZ(1)-IZ(2).
Dentoalveolar
Arch length Uie vertical Uie horizontal Uia horizontal Overbite Overjet UIA/IZ plane UIA/ANS-PNS U6/IZ plane U6/ANS-PNS U6DCT vertical U6MCpt horizontal
The distance between Uie-U6MCPt. The perpendicular distance from Uie to the maxillary reference plane. The perpendicular distance from Uie to the perpendicular to the maxillary reference plane through IZ(1). The perpendicular distance from Uia to the perpendicular to the maxillary reference plane through IZ(1) The distance between OB point and Uie. The distance between OJ point and Uie. The angle between Uie-Uia and IZ(1)-IZ(2). The angle between Uie-Uia and ANS-PNS. The angle between U6DCT-U6Apt and IZ(1)-IZ(2). The angle between U6DCT-U6Apt and ANS-PNS. The perpendicular distance from U6DCT to the maxillary reference plane. The perpendicular distance from U6MCPt to the perpendicular to the maxillary reference plane through IZ(1).
o n l y m o v e d l a b i a l l y in t h e H a r v o l d a c t i v a t o r g r o u p , compared with the control group. Overbite was r e d u c e d s i g n i f i c a n t l y m o r e in t h e H a r v o l d a c t i v a t o r g r o u p as c o m p a r e d w i t h b o t h t h e c o n t r o l a n d t h e Fr~inkel f u n c t i o n r e g u l a t o r g r o u p s . T h e r e d u c t i o n in o v e r j e t in t h e H a r v o l d a c t i v a t o r g r o u p w a s also s i g n i f i c a n t l y g r e a t e r t h a n in t h e F r g n k e l f u n c t i o n r e g u l a t o r g r o u p . T h e r e w e r e n o s t a t i s t i c a l l y signif-
i c a n t d i f f e r e n c e s in t h e h o r i z o n t a l a n d v e r t i c a l m o v e m e n t s o f t h e m a x i l l a r y first p e r m a n e n t m o l a r between the groups.
DISCUSSION T h e r e s u l t s o f this p r o s p e c t i v e study, in c o m b i n a t i o n w i t h o u r e a r l i e r study, 1° c o n f i r m e d B j o r k ' s speculation 5 that the treatment effects of functional
620
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American Journal of Orthodontics and Dentofacial Orthopedics June 1996
Table III. C o m p a r i s o n of the boys a n d girls at the b e g i n n i n g of the study Boys (n = 25) Variables
Age (yr) Stature (cm)
Girls (n = 17)
Mean
SD
Mean
SD
11.28 145.70
0.91 5.54
11.89 148.65
0.68 7.24
0.024 0.143
108.72 73.23 45.36 32.97 30.81 131.76
3.07 2.52 3.05 4.42 3.29 5.00
107.34 70.93 45.70 31.61 32.71 133.15
3.99 3.32 2.51 3.98 3.17 5.76
0.215 0.015 0.702 0.315 0.315 0.412
54.29 70.21 58.78 62.65 45.25 11.85 47.04 36.94 52.77 65.33 114.67 73.12 59.27 81.15 7.42 9.12 6.69
5.66 5.40 5.08 6.27 2.24 3.98 3.94 4.75 3.27 4.37 5.11 3.56 2.62 2.35 3.18 4.33 4.24
54.36 65.45 58.99 58.02 44.24 9.82 46.41 34.13 51.17 63.28 111.91 72.24 56.69 80.10 7.38 10.28 8.41
4.63 4.00 4.41 4.53 2.56 3.36 2.78 3.10 2.53 6.68 6.10 3.73 1.53 3.65 2.36 4.25 4.37
0.969 0.004 0.894 0.013 0.185 0.092 0.575 0.052 0.097 0.235 0.120 0.441 0.001 0.261 0.969 0.396 0.209
35.99 32.19 30.82 20.15 4.35 9.06 2.96 20.04 112.49 115.12 107.43 104.80
2.64 2.59 4.06 2.97 2.92 2.11 2.74 1.88 5.33 5.52 4.69 4.41
34.89 30.88 30.48 19.05 3.30 9.66 2.86 20.69 115.91 118.28 105.05 102.68
2.75 3.79 3.01 2.49 2.45 1.93 2.42 2.33 6.55 7.04 4.80 5.73
0.197 0.189 0.770 0.215 0.232 0.354 0.906 0.321 0.071 0.111 0.117 0.182
Cranial base
Ba-N (mm) S-N (ram) S-Ba (mm) Ba vertical (.mrn) Ba horizontal (mm) NSBa (°) Maxilla
ANS vertical (mm) ANS horizontal (mm) A point vertical (nun) A point horizontal (mm) PNS vertical (mm) PNS horizontal (mm) IZ(1) vertical (mm) IZ(1) horizontal (mm) N-ANS (mm) ANS-Me (mm) N-Me (mm) S-Go (mm) ANS-PNS (mm) SNA (°) S-N/ANS-PNS (°) S-SE/ANS-PNS (°) S-SE/IZ plane (°) Dentoalveolar
Max archlength (mm) Uie vertical (mm) Uie horizontal (ram) Uia horizontal (ram) Overbite (mm) Overjet (mm) U6MCpt horizontal (mm) U6DCT vertical (mm) UIA/IZ plane (°) UIA/ANS-PNS (°) U6/IZ plane (°) U6/ANS-PNS (°)
Significant values are in bold type; unpaired t test.
a p p l i a n c e s are m a i n l y c o n f i n e d to the d e n t o a l v e o l a r structures. T h e small, b u t statistically significant, o p e n i n g of the c r a n i a l base angle in the Frfinkel f u n c t i o n r e g u l a t o r g r o u p was d u e to posterior m o v e m e n t of b a s i o n r a t h e r t h a n a c h a n g e in the p o s i t i o n of n a s i o n . B a s i o n m o v e d posteriorly by m o r e t h a n 2.5 m m in several subjects in the Frfinkel f u n c t i o n r e g u l a t o r group, w h e r e a s t h e r e was n o significant
difference a m o n g the t h r e e groups in the position of n a s i o n relative to the c r a n i a l base r e f e r e n c e p l a n e s ( A N O V A , N vertical, p = 0.285; N horizontal, p = 0.505). W e p o s t u l a t e it was the m a g n i t u d e of these changes in some subjects, relative to the sample size, that was r e s p o n s i b l e for the significant findings in this group r a t h e r t h a n the i n f l u e n c e of the a p p l i a n c e s o n the c r a n i a l base. Previous longit u d i n a l studies have shown that the cranial base
American Journal of Orthodontics and Dentofacial Orthopedics Volume 109, No. 6
Courtne~ Harkness, and Herbison
621
Table IV. Comparison of the groups at the beginning of the study Control (n = 17)
FFR (n = 13)
ANOVA
SD
Mean
SD
108.24 72.44 45.05 31.44 32.04 133.16
3.03 2.35 2.97 3.71 3.26 5.54
107.28 71.55 45.70 33.51 30.80 131.53
3.38 3.23 2.27 3.40 3.32 6.47
0.558 0.602 0.801 0.490 0.631 0.752
4.86 5.94 4.26 6.73 2.38 4.45 3.16 5.16 3.70 4.35 6.06 3.94 2.85 2.87 4.68 5.38 2.14
54.66 67.56 58.83 59.91 44.39 10.82 46.08 35.15 52.00 63.59 112.48 72.04 80.07 7.85 10.81 7.98 57.92
6.43 5.56 5.57 6.21 2.45 3.85 3.47 4.55 2.64 6.09 5.50 3.72 3.22 2.72 4.30 4.13 2.91
53.54 69.77 57.88 62.56 44.58 11.80 45.79 36.65 52.33 64.39 113.46 73.30 82.27 7.73 8.82 6.52 58.77
4.52 4.41 4.74 4.75 2.43 2.97 3.71 4.14 2.71 6.36 5.41 3.16 2.38 3.05 3.70 2.81 2.86
0.836 0.534 0.651 0.485 0.502 0.714 0.162 0.726 0.962 0.710 0.437 0.669 0.097 0.566 0.465 0.697 0.682
2.60 3.17 3.54 2.61 1.77 1.87 3.17 2.43 4.64 5.07 5.47 5.14
35.72 32.50 30.44 20.24 4.55 9.27 3.10 20.79 112.03 114.87 106.56 103.72
2.60 3.70 3.64 3.05 3.39 2.34 2.65 1.89 6.56 6.80 4.44 5.29
35.10 31.58 31.63 19.94 3.18 9.30 2.28 20.04 115.50 118.52 107.15 104.13
3.10 2.49 3.88 2.91 3.21 2.10 1.67 1.79 7.06 7.22 4.53 5.03
0.663 0.480 0.570 0.547 0.475 0.997 0.706 0.661 0.353 0.344 0.798 0.979
Mean
SD
Mean
Cranial base Ba-N (ram) S-N (ram) S-Ba (ram) Ba vertical (rain) Ba horizontal (rnra) NSBa (°)
108.72 72.70 45.70 32.40 31.77 132.23
3.95 3.45 3.16 5.13 3.50 4.36
Maxilla ANS vertical (ram) ANS horizontal (ram) A point vertical (mm) A point horizontal (mm) PNS vertical (ram) PNS horizontal (ram) IZ(1) vertical (ram) IZ(1) horizontal (nun) N-ANS (mra) ANS-Me (mra) N-Me (ram) S-Go (mm) SNA (°) S-N/ANS-PNS (°) S-SE/ANS-PNS (°) S-SE/IZ-IZ (°) ANS-PNS (ram)
54.60 67.78 59.58 60.17 45.37 10.64 48.03 35.72 52.07 65.28 114.44 72.94 80.13 6.83 9.20 7.55 58.07
Dentoalveolar Max archlength (ram) Uie vertical (ram) Uie horizontal (ram) Uia horizontal (mm) Overbite (ram) Overjet (mm) U6MCpt horizontal (mm) U6DCT vertical (mm) UIA/IZ plane (°) UIA/ANS-PNS (°) U6/IZ plane (°) U6/ANS-PNS (°)
35.09 31.07 30.21 19.13 3.97 9.33 2.98 20.13 114.13 116.06 105.91 103.98
Variables
H A (n = 12)
angle in untreated persons may change with age. 25,z6
In contrast to a number of studies, 1-4 we could find no evidence of orthopedic changes in the maxilla. For example, Jakobsson I reported that ANS and A point were prevented from moving forward by approximately 1.1 and 0.7 mm, respectively, in his activator group as compared with his control group. However, in agreement with the present study, others 6'ev have reported that growth of the maxilla was not restricted horizontally during treatment. Total anterior face height (N-Me) and lower
I
anterior face height (ANS-Me) increased significantly in both appliance groups. Others have reported similar increases in lower anterior face height. 2'6'2s There were no significant differences between the groups in either upper anterior face height (N-ANS) or posterior face height (S-Go). The larger increase in total and lower anterior face heights in the Harvold activator group, as compared with the Frfinkel function regulator group, is attributed to the greater bite opening used with this appliance. Our finding that eruption of the maxillary molar played little part in the significant increase in vertical dimension supports Nel-
622
Courtne)4, Harkness, and Herbison
American Journal of Orthodontics and Dentofacial Orthopedics June 1996
Table V. Comparison of the groups using the differences between measurements at the start and 18
months later Control (n = 17) Variables
FFR (n = 13)
HA (n = 12)
ANOVA
Mean
SD
Mean
SD
Mean
SD
P
Ba-N (mm) S-N (ram) S-Ba (mm) Ba vertical (rnm) Ba horizontal (mm)
1.92 1.04 1.18 - 0.89 -0.72
1.22 0.53 1.00 0.91 0.76
2.81 1.27 1.65 - 0.70 - 1.58
0.77 0.35 0.79 1.05 0.67
2.34 1.19 1.54 - 1.25 -0.89
1.79 0.72 1.22 0.90 1.16
0.194 0.501 0.412 0.353 0.031
NSBa (°)
- 0.19
0.57
0.44
0.78
- 0.35
0.76
0.014
1.59 1.37 1.47 L16 0.72 0.75 0.70 0.81 1.43 2.50
0.561 0.314 0.646 0.295 0.377 0.233 0.365 0.219 0.517 0.001
Cranial base change
t
t
t Maxillary skeletal change ANS vertical (mm) ANS horizontal (mm) A point vertical (mm) A point horizontal (ram) PNS vertical (ram) PNS horizontal (ram) IZ(1) vertical (mm) IZ(1) horizontal (mm) N-ANS (mm) ANS-Me (mm)
1.18 1.54 0.98 0.86 0.39 0.70 0.94 0.58 0.97 0.97
- 2.23 0.68 - 2.78 0.28 - 1.46 - 0.99 - 1.53 0.38 1.86 2.84
1.18 1.10 1.17 0.99 0.97 1.29 1.16 0.79 0.77 1.46
- 2.28 1.48 - 2.57 0.46 - 1.06 - 0.68 - 1.03 0.41 2.19 4.09
3.30
1.43
4.95
1.64
6.30
3.05
0.001
3.19 1.75 0.35 0.20 0.25 - 0.06
1.51 1.71 0.73 0.86 0.99 1.05
4.39 1.80 - 0.09 0.16 0.37 - 0.30
1.33 1.33 0.76 1.13 1.46 1.44
4.46 2.34 - 0.24 0.75 0.84 0.06
1.97 1.55 0.79 1.04 1.20 1.81
0.063 0.565 0.097 0.259 0.428 0.847
Max arch length (ram)
- 0.51
1.26
- 2.10
1.41
- 2.40
1.68
0.001
Uie vertical (mm) Uie horizontal (mm)
- 1.40 0.41
1.05 1.10
- 2.15 - 1.16
1.38 1.79
- 2.37 - 1.92
1.42 1.96
0.103 0.001
Uia horizontal (mm)
t 0.03 t
0.86
0.54
0.73
0.99
1.13
0.027
0.94
0.25
1.83
t t
- 1.99
2.52
0.002
0.21
1.21
- 2.24
2.23
- 5.17
3.75
0.000
0.80 - 2.03 0.94
1.09 1.19 2.49
0.95 - 2.27 - 3.98
0.89 1.09 5.01
0.50 - 2.58 - 6.59
1.01 1.75 6.13
0.533 0.568 0.000
1.74
2.14
- 3.38
4.70
- 6.00
6.66
0.000
2.38 2.45
0.628 0.463
N-Me (ram) S-Go (mm) ANS-PNS (ram) SNA (°) S-N/ANS-PNS (°) S-SE/ANS-PNS (°) S-SE/IZ -IZ (°)
- 1.81 1.28 - 2.37 0.84 - 1.31 - 0.39 - 1.10 0.80 1.72 1.59
t
*
t
Dentoalveolar change
Overbite (mm) Overjet (ram) U 6 M C p t horizontal (mm) U 6 D C T vertical (mm) U I A / I Z plane (°) UIA/ANS-PNS (°)
0.34
t
tt
r
* U6 /IZ plane (°) U6/ANS-PNS (°)
- 0.64 - 1.43
2.48 2.05
- 0.19 - 0.80
t
t 2.71 2.81
0.28 - 0.31
Significant values are in bold type. The bars indicate groups found by Duncan's new multiple range test to be different at the 5% level of significance.
American Journal of Orthodontics and Dentofacial Orthopedics Volume 109, No. 6
son et al. 1° view that the increase in face height was due primarily to increased eruption of the mandibular molar. This finding is not surprising because both appliances have extensions to prevent the maxillary teeth from erupting and is supported by others. 2~'29 On the other hand, several authors 3°'31 have reported that the eruption of the maxillary molar was inhibited. The greater bite opening incorporated in the Harvold activator appliance would account for the significant reduction in overbite in the Harvold group. In agreement with a number of previous studies, 3z-34 the overjet was reduced by tipping the maxillary incisors palatally and the mandibular incisors labially. 1° The significant reduction in maxillary arch length in both appliance groups is due, almost entirely, to thi s palatal movement. The apices of the maxillary incisors tipped labially approximately 1 mm in the Harvold activator group and approximately 0.5 mm in the Frfinkel function regulator group. Our finding that there were no significant differences between the groups in forward movement of the maxillary molars agrees with Wieslander and Lagerstrom6 and disagrees with Jakobsson 1 and Johnston4 who reported that the maxillary molar was restrained. Others have also reported that the mandibular incisors are proclined during functional appliance treatment. ~'2~ This effect is almost certainly due to the use of the mandibular arch as anchorage to treat the maxillary arch. Therefore, on the basis of the results of this and our previous study, 1° we recommend that these appliances should be used to treat Class II, Division 1 malocclusions in growing persons with Skeletal I or mild Skeletal II dental bases. It would also be an advantage to have a relatively low vertical face height and increased overbite because these appliances allow the mandibular molars to erupt and, by so doing, increase the height of the face. As these appliances reduce an overjet by tipping maxillary and mandibular incisors, the increased overjet should be due to proclined maxillary incisors, which can be tipped palatally into position, and retroclined or upright mandibular incisors, which may be proclined successfully.35 Modifications to the appliances, such as incisor capping or the addition of an extraoral force, may prevent or limit the amount of mandibular incisor proclination. Spaced and well-aligned arches are also desirable, first to lessen or prevent crowding from developing in the
Courtnc~, Harkness, and Herbison
623
maxillary arch when the maxillary incisors are tipped palatally and second, to accommodate the mandibular incisors should they relapse toward their pretreatment positions?2"34 CONCLUSIONS
After 18 months' wear, the effects of both appliances were confined mainly to the dentition. The larger increase in anterior face height and significant reduction in overbite in the Harvold activator group, compared with the Frfinkel function regulator group, were attributed to the greater bite opening obtained with this appliance. The Harvold activator also reduced the overjet, by tipping the maxillary incisors palatally, more than the Fr~nkel function regulator. The length of the maxillary arch was reduced as a consequence. The small, but statistically significant, changes at basion in the Frfinkel function regulator group are attributed to large cranial base changes in several subjects influencing the results because of the small size of the sample. We are indebted to Drs. John C. Muir and Heli Vinkka-Puhakka who participated in the planning and conduct of this trial. REFERENCES 1. Jakobsson SO. Cephalometric evaluation of treatment effect on Class II, Division 1 malocclusions. Am J Orthod 1967; 53:446-57. 2. Harvold EP, Vargervik K. Morphogenic response to activator treatment. Am J Orthod 1971;60:478-90. 3. Woodside DG, Reed RT, Doucet JD, Thompson GW. Some effects of activator treatment on growth rate of the mandible and position of the midface. In: Cook JT. Transactions of the Third International Orthodontic Conference. London: Crosby, Lockwood and Staples, 1975:459-80. 4. Johnston LE. A comparative analysis of Class II treatments. In: Vig PS, Ribbens KA. Science and clinical judgement in orthodontics. Monograph 19. Craniofacial Growth Series. Ann Arbor: Center for Human Growth and Development, University of Michigan, 1986:103-48. 5. Bjork A. The principle of the Andresen method of orthodontic treatment, a discussion based on cephalometric x-ray analysis of treated cases. Am J Orthod 1951;37:437-58. 6. Wieslander L, Lagerstrom L. The effect of activator treatment on Class II malocclusions. Am J Orthod 1979;75: 20-6. 7. Calvert FJ. An assessment of Andresen therapy on class II division 1 malocclusion. Br J Orthod 1982;9:149-53. 8. Robertson NRE. An examination of treatment changes in children treated with the function regulator of Frankel. Am J Orthod 1983;83:299-310. 9. Tulloch JFC, Medland W, Tuncay OC. Methods used to
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American Journal of Orthodontics and Dentofacial Orthopedics June 1996 24. Riolo ML, Moyers RE, McNamara JA, Hunter WS. An atlas of craniofacial growth. Monograph 2. Craniofacial Growth Series. Ann Arbor: Center for Human Growth and Development, University of Michigan, 1974. 25. Bjork A. Cranial base development. Am J Orthod 1955;41: 198-225. 26. Brodie AG. The behavior of the cranial base and its components as revealed by serial cephalometric roentgenograms. Angle Orthod 1955;25:148-60. 27. Derringer K. A cephalometric study to compare the effects of cervical traction and Andresen therapy in the treatment of Class II division 1 malocclusion. Part 1 - skeletal changes. Br J Orthod 1990;17:33-46. 28. Chang H, Wu K, Chen K, Cheng M. Effects of activator treatment on Class II, division I malocclusion. J Clin Orthod 1989;23:560-3. 29. McNamara JA, Bookstein FL, Shaughnessy TG. Skeletal and dental changes following functional regulator therapy on Class II patients. Am J Orthod 1985;88:91-110. 30. Baumrind S, Korn EL, Molthen R, West EE. Changes in facial dimensions associated with the use of forces to retract the maxilla. Am J Orthod 1981;80:17-30. 31. Righellis EG. Treatment effects of Frankel, activator and extra oral traction appliances. Angle Orthod 1983;53:10721. 32. Ahlgren F, Laurin C. Late results of activator treatment: a cephalometric study. Br J Orthod 1976:3:181-7. 33. Reey RW, Eastwood A. The passive activator: case selection, treatment response, and corrective mechanics. Am J Orthod 1978;73:378-409. 34. Derringer K. A cephalometric study to compare the effects of cervical traction and Andresen therapy in the treatment of Class II division 1 malocclusion. Part 2-dentoalveolar changes. Br J Orthod 1990;17:89-99. 35. Mills JRE. The stability of the lower labial segment. A cephalometric survey. Dent Pract 1968;18:293-305.
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