An evaluation of extraoral combined high-pull traction and cervical traction to the maxilla Michael
C. Badell,
D.D.S.,
M.S.D.
Phoenix, Ariz.
E
xtraoral force to the maxillary denture has been used for many years to correct anteroposterior malrelationships of the jaws and teeth. The attitude of the orthodontic specialty has fluctuated with respect to the relative effects of extraoral anchorage on the growth and development of the dentoalveolar and craniofacial complexes. However, it has been rather widely accepted that extraoral force does influence growth and development while producing various amounts and directions of tooth movement. The degree and permanency of each of these factors have been the subject of hundreds of articles throughout the orthodontic literature and are as yet poorly documented. The purpose of this article is not to review these numerous references to extraoral traction, and the reader is referred to any number of standard orthodontic textbooks and journals if a more complete review is desired. In recent years, however, headgear therapy has consisted primarily of two types : 1. High-pull headgear which applies an upward and backward force to the maxilla and dentition. 2. Cervical headgear which applies a downward and backward force to the maxilla and dentition. Armstrong1 advocated the use of combined extraoral high-pull traction and cervical traction to the maxilla controlling the magnitude, direction, and duration of the force. It is the purpose of this investigation to describe the changes occurring in the dentition and associated structures during a period of continuous combined headgear wear and an average of 3.2 years after the headgear was discontinued. This article requirements Washington
is taken in part for the degree School of Dentistry.
from a thesis submitted of Master of Science
in in
partial Dentistry,
fulfillment University
of
the of
431
432
Bade11
Fig. 1. Photograph of a patient wearing and cervical headgear (16 ounces] with extraoral force.
Materials
and
the combination the resulting
high-pull direction
of
headgear pull for
(32 2:l
ounces) ratio of
methods
The sample for this study consisted of thirteen male and seventeen female orthodontic patients with an initial age range of 9 years 7 months to 12 years 11 months and a mean age of 11 years 2 months. Grouped according to Angle’s classification, there were twenty Class II, Division 1, three Class II, Division 2, and seven Class I malocclusions. Twenty-nine patients were treated on a nonextraction basis, and treatment of the remaining patient included the removal of one lower incisor after the initial treatment period.” All of the patients were treat,ed with extraoral combined high-pull traction and cervical traction to the maxillary first molars, utilizing a force that was periodically adjusted to 32 to 24 ounces per side for the high-pull component and 16 ounces per side for the cervical component. The double face-bow was also periodically adjusted so that the short outer bow was bent up at approximately 15 degrees to the straight 0.050 inch inner bow which was tied in to buccal tubes welded to the maxillary first molar bands (Fig. 1). All patients wore this appliance continuously (tied in) until the molar relationship was overcorrected (“super” Class I). Typically, the patient was then instructed to wear the appliance 14 hours per day for 3 weeks, after which he was to wear it during the sleeping hours only for an additional 9 weeks. During this time period, all patients had upper and lower incisor and first molar bands with 0.021 by 0.025 inch edgewise arches in place. No other types of “Patient Armstrong,
records were obtained Seattle, Wash.
from
the
private
orthodontic
practice
of
Dr.
Maclay
M.
Extraoml
high-pull
traction
and cervical traction
433
M
Fig. 2. Schematic diagram Fig. 3. Schematic diagram maxillary left first molar
illustrating illustrating (/6) and
the cephalometric the method used central incisor (1,.
points and to determine
landmarks utilized. the angulation of the
headgear and no interarch elastics were worn except in some cases for brief periods of time near the completion of orthodontic treatment. The effects of this extraoral combined high-pull traction and cervical traction were examined by means of serial lateral cephalometric radiographs taken before the extraoral force application, immediately after the prescribed period of continuous wear, and as long as possible after the extraoral force was completely discontinued. The interval between radiographs taken before and after the extraoral force application was defined as Interval I. This interval had a range from 60 days to 210 days, with a mean of 122 days. The interval following the complete discontinuance of extraoral force was defined as Interval II. This second interval had a range from 1 year 2 months to 4 years 4 months, with a mean of 3 years 2 months. The lateral head films were taken according to the method described by Broadbent and were traced on acetate paper with all bilateral images drawn as midline structures. The reader is referred to SalzmannZo for definitions of the standard cephalometric points and landmarks which were utilized. Individual teeth were traced by means of a template made from the head film which most clearly showed that particular tooth. Points used to measure tooth movement were marked on the template in order to transfer them more accurately to subsequent tracings (Fig. 2). In order to measure over-all growth and treatment changes, serial tracings were superimposed on the “ethmoid triad” and associated anterior cranial base landmarks according to the method described by Elmajian.6 This method was
434
Bade11
Fig. 4. Schematic the mandibular Fig. 5. Schematic to measure the molar (k) and
diagram illustrating the method used to determine first molar (p) and central incisor (il. diagram of the maxillary superimposition illustrating horizonal (horiz.) and vertical (vert.) movements of the central incisor [I-J.
the
angulation
of
left
the method used maxillary left first
also used to transfer the Frankfort horizontal plane from initial to subsequent tracings. The maxilla and mandible were superimposed separately in order to demonstrate tooth movement. The maxilla was superimposed on the anterior cranial base, the key ridges, the palate, and the infraorbital foramen according to the method described by Julius. I2 The mandible was superimposed on the cross section of the symphysis, the most inferior mandibular canal, and the distal portion of the mandibular third molar as described by Bj6rk.z The palatal plane (PP), occlusal plane (OP), and mandibular plane (MP) angles were measured relative to the Frankfort horizontal plane on the lateral head film taken at the beginning of Interval I. The angulations of the maxillary first molar and central incisor were also measured relative t,o this same Frankfort horizontal plane (Fig. 3). The mandibular first molar and central incisor angulations were measured relative to the mandibular plane (Fig. 4). For the maxillary superimposition, the horizontal and vertical movements of the upper first molar and central incisor were measured relative to t,he palatal plane on the lateral head film taken at the beginning of Interval I (Fig. 5). For the mandibular superimposition, the horizontal and vertical movements of the lower first molar and central incisor were measured relative to the mandibular plane on the lateral head film taken at the beginning of Interval I (Fig. 6).
All cephalometric points were digitized by means of the Benson Lehner recording system, which consists of the following equipment : 1. A 282M Telecordex 2. A Larr-M 3. A Richardson projector To determine technical error, a single operator traced, superimposed, and
Extraod
high-pull
tractio?b awl
i:
cervical traction
435
HORIZ. CcIcl
MP Fig. 6. Schematic to measure the first molar (p)
diagram horizontal and central
of the mandibular superimposition illustrating (horiz.) and vertical (vert.) movements of incisor (i).
the
the method mandibular
used left
digitized the three lateral head films of a randomly selected patient three separate times at 2-week intervals. The digitized points were converted into raw data using a coordinate conversion correction program (CCC computer program), Then a computational program (CPMB computer program) was used to convert raw data into the measured variables. Descriptive statistical analyses were then applied to the measured variables. The central tendency and variability of the observations were described by means, ranges, and standard deviations (SPSS computer program). The association of the variables was determined by Pearson product-moment correlation coefficients and stepwise linear regressions (BMD 025 computer program). The association was then tested for significance at the 1 per cent and 5 per cent levels. All computations were performed on the CDC 6400, University of Washington, Seattle, Washington. Observations
The mean change in the measured variables occurring during Interval I (period of continuous headgear wear) a.nd Interval II (postheadgear period) is recorded in Tables I and II. There were three variables which showed statistically significant differences between the three serial lateral cephalometric head films for the sample : 1. The maxillary first molar moved posteriorly 2.3 mm. and intruded 0.1 mm. while decreasing its angulation to Frankfort horizontal (FH) by 10.6 degrees during Interval I. This angulation to FH at the end of the period of continuous headgear wear was significantly different (0.001 level) from its inclination to FH for the other two serial lateral head films.
436
Bade11
Table
I. Mean
change
in variables
during
Interval
I
Variable
1. PP-FH angle (degrees) 2. OP-FH angle (degrees) 3. MP-FH angle (degrees) 4.
N-M (mm.)
5. Ar-PO (mm.) 6. A: Horizontal (mm.) 7. A: Vertical (mm.) 8. ANS: Horizontal (mm.) 9. ANS: Vertical (mm.) 10. B: Horizontal (mm.) 11. B: Vertical (mm.) 12. PO: Horizontal (mm.) 13. PO: Vertical (mm.) 14. .A-FH angle (degrees) 15. r: Horizontal (mm.) 16. & Vertical (mm.) 17. I-MP angle (degrees) 18. i: Horizontal (mm.) 19. i: Vertical (mm.) 20. l$-FH angle (degrees) 2 1. 14:Horizontal (mm.) 22. lfj: Vertical (mm.) 23. E-MP angle (degrees) 24. l$~ Horizontal (mm.) 25. r6: Vertical (mm.)
Change in angle formed by palatal plane and Frankfort plane Change in angle formed by occlusal plane and Frankfort plane Change in angle formed by mandibular plane and Frankfort plane Change in distance between points nasion and menton Change in distance between points articulare and pogonion Horizontal change in position of point A measured parallel to Frankfort plane Vertical change in position of point A measured perpendicular to Frankfort plane Horizontal change in position of ANS measured parallel to Frankfort plane Vertical change in position of ANS measured perpendicular to Frankfort plane Horizontal change in position of point B measured parallel to Frankfort plane Vertical change in position of point B measured perpendicular to Frankfort plane Horizontal change in position of pogonion measured parallel to Frankfort plane Vertical change in position of pogonion measured perpendicular to Frankfort plane (See Fig. 3) (See Fig. 5) (See Fig. 5) (See Fig. 4) (See Fig. 6) (See Fig. 6) (See Fig. 3) (See Fig. 5) (See Fig. 5) (See Fig. 4) (See Fig. 6) (See Fig. 6)
Mean
Standard deviation
f0.56
1.52
f1.16
2.29
+0.76
1.23
+1.14
1.44
+ 1.02
1.49
-0.71
1.03
+0.66
0.82
-0.45
1.54
+0.73
0.72
-0.06
1.41
+1.33
1.13
+0.08
1.78
t 1.30
1.10
-2.06 -0.76 -0.98 -1.24 -0.66 -0.17 -10.63 +2.28
8.43 2.32 1.16 5.13
1.99 0.85 10.54
-0.10
1.47 1.29
-3.52 +0.42 +0.93
7.95 0.98 0.92
2. The mandibular first molar moved 0.4 mm. posteriorly and 0.9 mm. superiorly while decreasing its angulation to the mandibular plane (MP) by 3.5 degrees during the first interval. This angulation to MP at the end of the period of continuous headgear wear was significantly different (0.02 level) from its angulation to MP for the other two serial lateral head films. 3. The occlusal plane increased 1.2 degrees to FH during Interval I. This occlusal plane angle at the end of Interval I was significantly different
Extraoral Table
II. Mean
change
Variable
1. PP-FH angle (degrees) 2. OP-FH angle (degrees) 3. MP-FH angle (degrees) 4. N-M (mm.) 5. Ar-Po (mm.) 6. A: Horizontal (mm.) 7. A: Vertical (mm.) 8. ANS: Horizontal (mm.) 9. ANS: Vertical (mm.) 10. B: Horizontal (mm.) 11. B: Vertical (mm.) 12. PO: Horizontal (mm.) 13. Po: Vertical (mm.) 14. I-FH angle (degrees) 15. r: Horizontal (mm.) 16. &I Vertical (mm.) 17. I-MP angle (degrees) 18. i: Horizontal (mm.) 19. i: Vertical (mm.) 20. M-FH angle (degrees) 2 1. M: Horizontal (mm.) 22. b Vertical (mm.) 23. k-MP angle (degrees) 24. k Horizontal (mm.) 25. E: Vertical (mm.)
in variables I
high-pull during
tractio?L and cervical traction
Interval Mean
+0.49 -3.35 -2.34 f7.45 +7.18 +2.61 +4.05 i-3.19
f3.00 +3.23 f4.57 +4.15 +6.85 -1.21 +0.96 +2.48 +1.54 +1.95 +2.55 + 13.55 -3.67 +3.03 -0.84 -1.05 +2.41
437
II I
Standard
deviation
1.76 2.78 2.28 4.89 4.18 2.29 2.74 2.93 2.09 2.79 3.20 3.85 4.64 7.37 2.13 2.21 6.14 2.31 1.94 9.13 2.33 2.21 6.99 1.66 2.01
(0.05 level) from its angulation for the other two serial lateral head films. No significant correlation was found except for the correlation of mandibular plane with anterior facial height (N-M) for Interval I with a coefficient of 0.71, which is significant at the 0.001 level. Discussion
Treatment changes (Interval I). Several additional factors must be taken into consideration in an evaluation of the treatment changes due to continuous combined extraoral high-pull traction and cervical traction to the maxillary first molars. Among these factors are : 1. The individual biologic variation between patients as partially reflected in the standard deviations of the mean changes in the measured variables for this sample (Table I). 2. The amount of anteroposterior movement of the incisors and molars as related to the initial malocclusion. 3. Tooth movement as influenced by additional appliance therapy (during the period of continuous headgear wear) consisting of upper and lower incisor bands with 0.021 by 0.025 inch edgewise arches in place.
438
Bade11
Clinical investigations’“* Ii. I83 z4 and experimental st~udies’“~2z demonstrated skeletal changes in response to cervical headgear therapy. In particular, the maxilla is commonly reported to be distally positioned with a clockwise rotation of the palatal plane. In addition, clinical investigations4 and experimental studies58 7 involving high-pull headgear confirm that the position of the maxilla may be changed upward and backward in the direction of the applied extraoral forces. For this investigation, all of the patients were treated with extraoral combined high-pull traction and cervical traction to the maxillary first molars (Fig. 1). The extraoral force was periodically adjusted to 24 to 32 ounces per side for the high-pull component and 16 ounces per side for the cervical component. This appliance was worn continuously (tied in) for a mean period of 122 days. During this period the mean change in the anteroposterior position of the maxilla relative to the cranial base was trot statistically significant as reflected in the small average distal and inferior changes in point A and ANS. The angulation of the palatal plane to FH increased in twenty cases (an average of only 0.6 degree) but decreased in ten cases. These small changes in the palatal plane relative to FH were not statistically significant. Graber” intimated changes in bony relationships resulting from “orthopedic forces” being applied to the maxilla. He suggested that a force of 1 to 2 pounds be applied to the maxillary teeth and indirectly to the basal bone in order to effect these “orthopedic changes.” The total force level utilized for this study was approximately 2.5 to 3 pounds per side. However, no statistically significant orthopedic changes were observed. This may be due in part to the relatively short period of time that the combined headgear was worn (mean, 122 days). Perhaps longer periods of wear would produce some degree of orthopedic changes. Damon,4 in a clinical study involving high-pull headgear, used a similar force level (approximately 3 pounds per side) over a similar treatment period which ranged from 92 to 169 days. In some cases, he was able to observe dramatic changes in the position of the maxilla. However, the extraoral force was delivered to the maxilla through the maxillary first molars and first premolars, which were splinted together for his investigation. Perhaps orthopedic changes can occur to a greater degree if the extraoral force is delivered to the maxilla by means of a dentition that is somehow splinted together rather than delivered directly to the maxillary first molars only, as was done for this investigation. Experimental studies involving cervical headgear’“, 22 and high-pull headgears, 7 have employed an appliance so that 300 to 800 grams per side of extraoral force was delivered to the maxilla of the Macaca muihtta monkey by means of a cast splint that encompassed the entire maxillary dentition. Significant orthopedic changes were demonstrated in the position of the maxilla and other bones in the craniofacial complex. Those changes may be partially attributable to the fact that the total extraoral force was delivered to a dentition
Extruora.1 high-pull
twction
rind cervical
tra8ction
439
that was completely splinted together. In addition, the extreme skeletal changes observed in the experimental studies may also be due in part to the relatively high ratio of total extraoral force to total body weight for the experimental animals in comparison to the force levels utilized for human patients in the clinical studies. For this investigation the total extraoral force (5 to 6 pounds) was only approximately 5 to 6 per cent of the total body weight of the patients, while for a typical experimental study5 the total extraoral force was approximately 20 per cent of the total body weight of the animals (Maca~ca mulntta~). The direction of pull of the extraoral force might also be a factor in the degree to which orthopedic changes occur. The tendency for the palatal plane to rotate clockwise (as associated with cervical headgear) or counterclockwise (as associated with high-pull headgear) might be minimized because of the direction of applied extraoral force to the maxilla resulting from the combination of cervical traction and high-pull traction for this study (Fig. 1). Extrusion and distal crown tipping of the maxillary molar in response to cervical headgear therapy have been reported by several authors.g~ 15,I4 For bhis sample of thirty cases, the maxillary first molar was moved distally an average of 2.4 mm. In twenty cases this was distal bodily movement as originally described by Armstrong,l while in ten cases there were varying degrees of distal crown tipping. Although approximately the same amount and direction of extraoral force were applied to each patient, the individual biologic variation could possibly account for this difference in the response of the maxillary first molar. In addition, proper positioning of the short outer bows more superior to the inner bows may have prevented or reduced the distal crown tipping which was observed in some cases. On the average, the maxillary first molar was also intruded slightly (0.1 mm.). This agrees with findings of experimental high-pull headgear studie$ 7 and clinical high-pull headgear studies4 which showed that the maxillary first molar root was also tipped distally. This intrusion is contrary to the extrusion commonly reported with cervical headgear therapy. Clinical investigatorPt I7 and experimental investigators’, 22 have reported increases in the mandibular plane angle and concurrent increases in anterior facial height as a result of headgear therapy. The mandibular plane angle did increase an average of 0.8 degree for this study, with a 1.1 mm. average increase in the anterior facial height (N-M). There was a biologically meaningful correlation (+O.i’l) between the increase in the mandibular plane angle and the increase in anterior facial height for the period of continuous headgear wear. Bite opening or clockwise rotation of the mandible was confirmed by changes in the position of point B and pogonion, both of which were 1.3 mm. inferior on the average at the end of Interval I. Bite opening may have been produced by occlusal interferences attributable to the “super” Class I buccal relationship to which all of the patients were treated. Frederick,7 in an experimental study involving high-pull headgear, demonstrated bite opening due to occlusal interferences in spite of the fact that the direction of the extraoral force utilized resulted primarily in intrusion.
440
Bad&
Am.
J. Orthod. April 19iG
Damon4 in a clinical study also involving high-pull headgear, found that the mandibular plane angle remained the same or decreased slightly. However, patients in his sample were not treated to a “super” Class I buccal relationship, and thus the occlusal interferences may have been minimized. On the average, the mandibular molar did not drift mesially during the period of continuous headgear wear. Tt remained unchanged or distally uprighted. This statistically significa,nt finding is in concordance with other studies59 8, 13,22 which demonstrated similar responses of the mandibular dentition to maxillary headgear therapy. The occlusal plane angle increased an average of 1.2 degrees to FH during the period of headgear wear, which was statistically significant and in agreement with the findings of Frederick.7 Mandibular length (Ar-Po) increased only slightly, on the average (1.0 mm.), for the sample. This is probably a reflection of the relatively short interval of time during which mandibular growth could occur. Axial inclinations and positions of the maxillary and mandibular central incisors were highly variable during the period of continuous headgear wear. This may be due to the initial alignment of the teeth and differences in the configuration of the arch wires used in addition to the individual biologic variation. Posttreatment changes (Zntervd ZZ). Certain other factors must be considered in order to evaluate completely the posttreatment changes following the period of continuous combined extraoral traction : 1. The individual biologic variation between patients as partially reflected in the standard deviations of the mean changes in the measured variables for this sample (Table II). 2. Changes in tooth position as influenced by continued appliance therapy after the initial period of continuous headgear wear. 3. The amount of anteroposterior movement of molars and incisors as related to available arch length in the interchange from mixed to permanent dentition. 4. Tooth movement as influenced by varying periods of retention with upper and lower removable appliances using no headgear. 5. The amount and direction of growth in the posttreatment period. During the postheadgear period, the maxilla moved downward and forward as reflected in the anterior and inferior positioning of point A and ANS. This is contrary to Tuenge and Elder’sZJ experimental finding that “the cephalometric growth pattern produced in the experimental group (utilizing high-pull headgear) showed an increasing difference from the control group during the entire posttreatment period.” However, this difference occurred at a decreasing rate during the last 4 months of the lo-month posttreatment period. The normal downward and forward movement of the maxilla in this sample may be attributed to the relatively long-term posttreatment period (average of 3 years 2 months) and the relatively minimal influence on the position of the maxilla (initially). The inferior movement of ANS (mean, 3.0 mm.) agrees with
Wieslander’sZ5 study of patients who wore cervical headgear. He found that ANS moved inferiorly an average of 7.3 mm. over a posttreatment period of 6 years. The palatal plane continued to increase its inclination to FH slightly (mean, 0.5 degree) which corresponds to results observed by Mitani and Brodie.lG Wieslande? found a similar mean increase of 0.8 degree in the posttreatment period. The maxillary molar showed a strong tendency to recover its original position and inclination during the postheadgear period. It uprighted an average of 13.6 degrees to FH and moved downward (mean 3.0 mm.) and forward (mean, 3.7 mm.). These findings agree with Tuenge and Elder’sZ3 results, which disclosed a “rapid cephalometric reversal of the maxillary tooth movement.” Part of this recovery was probably due to normal tooth eruption. Wieslander25 demonstrated a “minimal physiologic recovery” of the maxillary first molar following cervical headgear therapy. His sample consisted of twentyeight patients treated in the mixed dentition with cervical traction (10 to 15 ounces per side) 12 to 14 hours per day for an average of 2 years 8 months in order to restrain the forward movement of the maxillary dentition and/or maxilla. This contrasts with the sample for this investigation, where the purpose of the continuous combined extraoral traction (2.5 to 3 pounds per side) for an average of only 122 days was to bring about the distal bodily movement of the maxillary first molars. Therefore, it might be expected that more physiologic recovery of the dramatic tooth movement observed for this investigation (utilizing a much greater extraoral force over a shorter period of time) would occur than for Wieslander’s25 investigation (utilizing a much smaller extraoral force over a longer period of time). Anterior facial height (N-M) increased an average of 7.5 mm. during Interval II, and the mandibular length (Ar-Po) increased a mean of 7.2 mm. during this same period. Correspondingly, both point B and pogonion were located anteriorly and inferiorly at the end of the postheadgear period. The mean value for the anterior positioning of pogonion (4.2 mm.) agrees with the study by Wieslander,25 who found a mean value of 3.0 mm. Changes in anterior facial height, mandibular length, point B, and pogonion all reflect the tremendous amount of posttreatment growth that all the patients exhibited. The maintenance of the Class I relationship during the postheadgear period may be partially attributed to the favorable amount of downward and forward growth of the mandible. This agrees with findings of Riedellg and Herzberg.ll The mandibular plane angle decreased an average of 2.4 degrees during the postheadgear period. This decrease lends further support to the idea that the initial increase in the mandibular plane angle was due to occlusal interferences which were later resolved, allowing a subsequent decrease in the angle. The vertical component of growth which all the patients exhibited may also have contributed to this decrease. Simons and Joondeph,21 in an investigation of fully treated orthodontic cases 10 years postretention, found a decrease in the
442
Bade11
Fig. 7. Composite superimpositions changes in the measured variables
Am.
of a selected case that for both Interval I and
most closely Interval II.
represents
J. Orthod. April 1976
the
mean
mandibular plane angle. Wies1ander,25 in a posttreatment investigation of orthodontic patients treated in the mixed dentition with cervical headgear only, also found a decrease in the mandibular plane angle following treatment. The mandibular molar recovered from its distal uprighting during the first interval by moving, on the average, 1.1 mm. mesially and 2.4 mm. superiorly during the postheadgear period. Part of this recovery was probably attributable to normal tooth eruption. This finding agrees with Tuenge and Elder,23 who found a “rapid cephalometric reversal” of the mandibular tooth movement following treatment. The occlusal plane decreased 3.4 degrees (mean) to FH during the postheadgear period after an initial increase of 1.2 degrees during Interval I. There was no statistically significant difference between the initial occlusal plane angle and the occlusal plane angle at the end of the posttreatment period. This finding corresponds with findings by Mitani and Brodie16 and Simons and Joondeph*’ and may be attributed to continued appliance therapy during the second interval in addition to growth concomitant with normal tooth eruption. On the average, the maxillary central incisor moved downward and forward while the mandibular central incisor moved upward and backward during the postheadgear period. This may be due to normal tooth eruption in addition to continued appliance therapy during Interval II.
T’olume Number
69 4
Extraoral
high-pull 11-2
-
11-5 11-S
----I
traction
and cervical
traction I i
16-1 -.-.-. 16-1
413
\ ;
!
II i
!
\ ‘\ i \;
Fig. distal
8. Composite crown
tipping
superimpositions during
of Interval
a selected
case
that
shows
an
excessive
amount
of
I.
The axial inclinations of the maxillary and mandibular central incisors were highly variable. Their variability was similar to findings for the first interval and, again, may be attributed to different types of appliance therapy during the posttreatment period in addition to the individual biologic variation. Subjective examination of orthodontic study models for the sample at the end of the posttreatment period revealed that all of the maxillary second molars were in a reasonable occlusion. Thus, impaction of maxillary second molars in response to the extraoral force was not observed, even though the maxillary first molar crown was tipped distally to an excessive degree in some cases. This observation may be ascribed to the maxillary second molar tooth bud also moving distally in response to the extraoral force. Also, the fact that the maxillary first molars recovered mesially during the posttreatment period might have allowed for the normal eruption of the maxillary second molars, Clinical
implications
Continuous combined extraoral high-pull traction and cervical traction as described for this investigation may be particularly useful for orthodontic patients in the mixed dentition in which rapid distal movement of the maxillary first molars without any significant extrusion or skeletal change is desired. There are, of course, orthodontic patients for whom some degree of skeletal change (that is, restraint of the maxilla) in addition to distal movement of the maxiIlary first molars would be desirable. It is conceivable that this type
444
Fig.
Bade11
9.
pattern
;I 11,. J. Ol‘thod. Awil 19i6
Composite during
the
superimpositions
of
posttreatment
period.
a selected
case
that
demonstrates
a vertical
growth
of result could be achieved by wearing this same appliance for a longer period of time with less total force. Perhaps less “physiologic rec.overy” of maxillary first molars would occur with the appliance utilized in this manner. Skeletal changes might be effected by delivering combined extraoral force to a dentition which is splinted together. This could be accomplished by fabricating a custom splint for the patient, or it could be done by tying the entire maxillary dentition together with full orthodontic appliances in place. Individual
cases
Twenty patients in the sample demonstrated distal bodily movement of the maxillary first molar as originally described by Armstr0ng.l Fig. ‘7 depicts a selected case that most closely represents the mean changes in the measured variables for both Intervals I and II from this group. The other ten patients in the sample demonstrated varying degrees of distal crown tipping in response to the extraoral force during Interval I. Fig. 8 demonstrates a selected case from this group that shows an excessive amount (20.2 degrees) of distal crown tipping. Four patients exhibited a vertical growth pattern with little or no horizontal component of growth during the postheadgear period. In these cases the maxil-
Extraoral
high-pull
traction
awl
cervical
tmction
445
lary first molar tended to recover its original inclination and position, but to a lesser degree than the cases which demonstrated a more horizontal growth pattern. The mandibular first molars also tended to migrate mesially to a greater degree in these cases. Consequently, the Class I relationship achieved during Interval I was maintained. Fig. 9 shows a selected case that represents this group of patients. Summary
and
conclusions
The effects of extraoral combined high-pull traction and cervical traction of known duration (mean, 122 days) and magnitude (2.5 to 3 pounds total per side) were studied by means of serial lateral cephalometric head films of thirty patients. The lateral cephalometric head films used were taken at three different times: before the extraoral force was applied, after the prescribed period of continuous headgear wear, and as long as possible after the extraoral force was discontinued. Changes in the dentition and associated structures were described both for the period of continuous headgear wear and for an average of 3.2 years later. The following conclusions are based on statistical analysis of the observed changes : 1. The position of the maxilla and the palatal plane was not significantly affected by relatively short periods of extraoral combined high-pull traction and cervical traction to the maxillary first molars as used for this investigation. 2. The maxillary first molars can be moved distally and bodily with this appliance without extrusion. 3. On the average, the mandibular first molars uprighted distally in response to the extraoral force to the maxilla. 4. The maxillary and mandibular first molars demonstrated a strong tendency to recover to their original positions and inclinations relative to their respective bases during the posttreatment period. 5. The amount and direction of growth in the posttreatment period may be important in determining how the Class I relationship is maintained. I would like to thank Maclay provided the material for this the preparation of this manuscript.
M. Armstrong, investigation,
and
who developed Richard A.
the headgear and generously Riedel for his assistance in
REFERENCES
1. Armstrong, M. M.: Controlling the magnitude, direction, and duration of extraoral force, AK J. ORTHOD. 59: 217-243,1971. 2. Bjiirk, A.: Variations in the growth pattern of the human mandible; longitudinal radiographic study by the implant method, J. Dent. Res. 42: 400, 1963. 3. Broadbent, B. H.: A new x-ray technique and its application to orthodontics, Angle Orthod. 1: 45-66, 1931. 4. Damon, D. H.: A clinical study of extraoral high-pull traction to the maxilla utilizing a heavy force: A cephalometric analysis of the dentofacial changes, M.S.D. thesis, University of Washington. 5. Elder, J. R., and Tuenge, R. H.: Cephalometric and histologic changes produced by
446
Am
Bade11 extraoral
high-pull
traction
to the maxilla
in Macaca
mulattn,
AM.
J. ORTHOD.
66:
J. Orthod.
&Iv%1976
599-617,
1974.
6. Elmajian, K. E.: A serial study of facial growth as related to cranial base morphology, M.S.D. thesis, University of Washington, 1959. 7. Frederick, D. L.: Dentofacial changes produced by extraoral high-pull traction to the maxilla of the Yacaca mulatta; a histologic and serial cephalometric study, M.S.D. thesis, University of Washington, 1969. 8. Funk, A. C.: Mandibular response to headgear therapy and its clinical significance, A&I. J. ORTHOD. 53: 182.216,1967. 9. Graber, T. M.: Extraoral force-Facts and fallacies, AX J. ORTHOD. 41: 490-505, 1955. 10. Henry, H. L.: Craniofacial changes induced by “orthopedic forces” in the Macaca mzLZatta rhesus monkey, M.S.C. thesis, University of Manitoba, 1973. 11. Herzberg, R. : A cephalometric study of Class II relapse, Angle Orthod. 43: 112-118, 1973. 12. Julius, R. B.: A serial cephalometric study of the metallic implant technique and methods of maxillary and mandibular superimposition, M.S.D. thesis, University of Washington, 1972. 13. Lindquist, W. G.: An analysis of change in the mandibular arch, coincident with maxillary headgear therapy, M.&D. thesis, University of Washington, 1963. 14. Masumoto, G.: A serial cephalometric analysis of the dentofacial changes produced by extraoral cervical traction to the maxilla utilizing metallic implants, M.S.D. thesis, University of Washington, 1970. 15. Merrifield, L. L., and Cross, J. J.: Directional forces, Au. J. ORTHOD. 57: 435-464, 1970. 16. Mitani, H., and Brodie, A. G.: Three plane analysis of tooth movement, growth, and angular changes with cervical traction, Angle Orthod. 40: 80-94, 1970. 17. Moore, A. W.: Observations on facial growth and its clinical significance, Anr. J. ORTHOD. 45: 399-423, 1959. 18. Ricketts, R. M.: The influence of orthodontic treatment on facial growth and development, Angle Orthod. 30: 103, 1960. 19. Riedel, R. A.: A review of the retention problem, Angle Orthod. 30: 179-194, 1960. cephalometrics, Philadelphia 1961, J. B. Lippincott 20. Salzmann, J. A.: Roetgenographic Company. 21. Simons, M. E., and Joondeph, D. R.: Change in overbite: A ten-year postretention study, AM.
J. ORTHOD.
64:
349-367,1973.
Sproule, W. R.: Dentofacial changes produced by extraoral cervical traction to the maxilla of the Macaca mulotta monkey, M.S.D. thesis, University of Washington, 1968. 23. Tuenge, R. H., and Elder, J. R.: Posttreatment changes following high-pull traction to the maxilla of the Macaca mdatta, AM. J. ORTHOD. 66: 618-644, 1974. 24. Wieslander, L.: The effects of orthodontic treatment on the concurrent development of the craniofacialcomplex, AM. J. ORTKOD. 49: 15-27, 1963. 25. Wieslander, L.: Physiologic recovery after cervical traction therapy, AM. J. ORTHOD. 66: 22.
294-301, 65gO North
1974. 7th
Ave.
(85014)
C. Badell,
D.D.S.,
M.S.D.
Phoenix, Ariz.
E
xtraoral force to the maxillary denture has been used for many years to correct anteroposterior malrelationships of the jaws and teeth. The attitude of the orthodontic specialty has fluctuated with respect to the relative effects of extraoral anchorage on the growth and development of the dentoalveolar and craniofacial complexes. However, it has been rather widely accepted that extraoral force does influence growth and development while producing various amounts and directions of tooth movement. The degree and permanency of each of these factors have been the subject of hundreds of articles throughout the orthodontic literature and are as yet poorly documented. The purpose of this article is not to review these numerous references to extraoral traction, and the reader is referred to any number of standard orthodontic textbooks and journals if a more complete review is desired. In recent years, however, headgear therapy has consisted primarily of two types : 1. High-pull headgear which applies an upward and backward force to the maxilla and dentition. 2. Cervical headgear which applies a downward and backward force to the maxilla and dentition. Armstrong1 advocated the use of combined extraoral high-pull traction and cervical traction to the maxilla controlling the magnitude, direction, and duration of the force. It is the purpose of this investigation to describe the changes occurring in the dentition and associated structures during a period of continuous combined headgear wear and an average of 3.2 years after the headgear was discontinued. This article requirements Washington
is taken in part for the degree School of Dentistry.
from a thesis submitted of Master of Science
in in
partial Dentistry,
fulfillment University
of
the of
431
432
Bade11
Fig. 1. Photograph of a patient wearing and cervical headgear (16 ounces] with extraoral force.
Materials
and
the combination the resulting
high-pull direction
of
headgear pull for
(32 2:l
ounces) ratio of
methods
The sample for this study consisted of thirteen male and seventeen female orthodontic patients with an initial age range of 9 years 7 months to 12 years 11 months and a mean age of 11 years 2 months. Grouped according to Angle’s classification, there were twenty Class II, Division 1, three Class II, Division 2, and seven Class I malocclusions. Twenty-nine patients were treated on a nonextraction basis, and treatment of the remaining patient included the removal of one lower incisor after the initial treatment period.” All of the patients were treat,ed with extraoral combined high-pull traction and cervical traction to the maxillary first molars, utilizing a force that was periodically adjusted to 32 to 24 ounces per side for the high-pull component and 16 ounces per side for the cervical component. The double face-bow was also periodically adjusted so that the short outer bow was bent up at approximately 15 degrees to the straight 0.050 inch inner bow which was tied in to buccal tubes welded to the maxillary first molar bands (Fig. 1). All patients wore this appliance continuously (tied in) until the molar relationship was overcorrected (“super” Class I). Typically, the patient was then instructed to wear the appliance 14 hours per day for 3 weeks, after which he was to wear it during the sleeping hours only for an additional 9 weeks. During this time period, all patients had upper and lower incisor and first molar bands with 0.021 by 0.025 inch edgewise arches in place. No other types of “Patient Armstrong,
records were obtained Seattle, Wash.
from
the
private
orthodontic
practice
of
Dr.
Maclay
M.
Extraoml
high-pull
traction
and cervical traction
433
M
Fig. 2. Schematic diagram Fig. 3. Schematic diagram maxillary left first molar
illustrating illustrating (/6) and
the cephalometric the method used central incisor (1,.
points and to determine
landmarks utilized. the angulation of the
headgear and no interarch elastics were worn except in some cases for brief periods of time near the completion of orthodontic treatment. The effects of this extraoral combined high-pull traction and cervical traction were examined by means of serial lateral cephalometric radiographs taken before the extraoral force application, immediately after the prescribed period of continuous wear, and as long as possible after the extraoral force was completely discontinued. The interval between radiographs taken before and after the extraoral force application was defined as Interval I. This interval had a range from 60 days to 210 days, with a mean of 122 days. The interval following the complete discontinuance of extraoral force was defined as Interval II. This second interval had a range from 1 year 2 months to 4 years 4 months, with a mean of 3 years 2 months. The lateral head films were taken according to the method described by Broadbent and were traced on acetate paper with all bilateral images drawn as midline structures. The reader is referred to SalzmannZo for definitions of the standard cephalometric points and landmarks which were utilized. Individual teeth were traced by means of a template made from the head film which most clearly showed that particular tooth. Points used to measure tooth movement were marked on the template in order to transfer them more accurately to subsequent tracings (Fig. 2). In order to measure over-all growth and treatment changes, serial tracings were superimposed on the “ethmoid triad” and associated anterior cranial base landmarks according to the method described by Elmajian.6 This method was
434
Bade11
Fig. 4. Schematic the mandibular Fig. 5. Schematic to measure the molar (k) and
diagram illustrating the method used to determine first molar (p) and central incisor (il. diagram of the maxillary superimposition illustrating horizonal (horiz.) and vertical (vert.) movements of the central incisor [I-J.
the
angulation
of
left
the method used maxillary left first
also used to transfer the Frankfort horizontal plane from initial to subsequent tracings. The maxilla and mandible were superimposed separately in order to demonstrate tooth movement. The maxilla was superimposed on the anterior cranial base, the key ridges, the palate, and the infraorbital foramen according to the method described by Julius. I2 The mandible was superimposed on the cross section of the symphysis, the most inferior mandibular canal, and the distal portion of the mandibular third molar as described by Bj6rk.z The palatal plane (PP), occlusal plane (OP), and mandibular plane (MP) angles were measured relative to the Frankfort horizontal plane on the lateral head film taken at the beginning of Interval I. The angulations of the maxillary first molar and central incisor were also measured relative t,o this same Frankfort horizontal plane (Fig. 3). The mandibular first molar and central incisor angulations were measured relative to the mandibular plane (Fig. 4). For the maxillary superimposition, the horizontal and vertical movements of the upper first molar and central incisor were measured relative to t,he palatal plane on the lateral head film taken at the beginning of Interval I (Fig. 5). For the mandibular superimposition, the horizontal and vertical movements of the lower first molar and central incisor were measured relative to the mandibular plane on the lateral head film taken at the beginning of Interval I (Fig. 6).
All cephalometric points were digitized by means of the Benson Lehner recording system, which consists of the following equipment : 1. A 282M Telecordex 2. A Larr-M 3. A Richardson projector To determine technical error, a single operator traced, superimposed, and
Extraod
high-pull
tractio?b awl
i:
cervical traction
435
HORIZ. CcIcl
MP Fig. 6. Schematic to measure the first molar (p)
diagram horizontal and central
of the mandibular superimposition illustrating (horiz.) and vertical (vert.) movements of incisor (i).
the
the method mandibular
used left
digitized the three lateral head films of a randomly selected patient three separate times at 2-week intervals. The digitized points were converted into raw data using a coordinate conversion correction program (CCC computer program), Then a computational program (CPMB computer program) was used to convert raw data into the measured variables. Descriptive statistical analyses were then applied to the measured variables. The central tendency and variability of the observations were described by means, ranges, and standard deviations (SPSS computer program). The association of the variables was determined by Pearson product-moment correlation coefficients and stepwise linear regressions (BMD 025 computer program). The association was then tested for significance at the 1 per cent and 5 per cent levels. All computations were performed on the CDC 6400, University of Washington, Seattle, Washington. Observations
The mean change in the measured variables occurring during Interval I (period of continuous headgear wear) a.nd Interval II (postheadgear period) is recorded in Tables I and II. There were three variables which showed statistically significant differences between the three serial lateral cephalometric head films for the sample : 1. The maxillary first molar moved posteriorly 2.3 mm. and intruded 0.1 mm. while decreasing its angulation to Frankfort horizontal (FH) by 10.6 degrees during Interval I. This angulation to FH at the end of the period of continuous headgear wear was significantly different (0.001 level) from its inclination to FH for the other two serial lateral head films.
436
Bade11
Table
I. Mean
change
in variables
during
Interval
I
Variable
1. PP-FH angle (degrees) 2. OP-FH angle (degrees) 3. MP-FH angle (degrees) 4.
N-M (mm.)
5. Ar-PO (mm.) 6. A: Horizontal (mm.) 7. A: Vertical (mm.) 8. ANS: Horizontal (mm.) 9. ANS: Vertical (mm.) 10. B: Horizontal (mm.) 11. B: Vertical (mm.) 12. PO: Horizontal (mm.) 13. PO: Vertical (mm.) 14. .A-FH angle (degrees) 15. r: Horizontal (mm.) 16. & Vertical (mm.) 17. I-MP angle (degrees) 18. i: Horizontal (mm.) 19. i: Vertical (mm.) 20. l$-FH angle (degrees) 2 1. 14:Horizontal (mm.) 22. lfj: Vertical (mm.) 23. E-MP angle (degrees) 24. l$~ Horizontal (mm.) 25. r6: Vertical (mm.)
Change in angle formed by palatal plane and Frankfort plane Change in angle formed by occlusal plane and Frankfort plane Change in angle formed by mandibular plane and Frankfort plane Change in distance between points nasion and menton Change in distance between points articulare and pogonion Horizontal change in position of point A measured parallel to Frankfort plane Vertical change in position of point A measured perpendicular to Frankfort plane Horizontal change in position of ANS measured parallel to Frankfort plane Vertical change in position of ANS measured perpendicular to Frankfort plane Horizontal change in position of point B measured parallel to Frankfort plane Vertical change in position of point B measured perpendicular to Frankfort plane Horizontal change in position of pogonion measured parallel to Frankfort plane Vertical change in position of pogonion measured perpendicular to Frankfort plane (See Fig. 3) (See Fig. 5) (See Fig. 5) (See Fig. 4) (See Fig. 6) (See Fig. 6) (See Fig. 3) (See Fig. 5) (See Fig. 5) (See Fig. 4) (See Fig. 6) (See Fig. 6)
Mean
Standard deviation
f0.56
1.52
f1.16
2.29
+0.76
1.23
+1.14
1.44
+ 1.02
1.49
-0.71
1.03
+0.66
0.82
-0.45
1.54
+0.73
0.72
-0.06
1.41
+1.33
1.13
+0.08
1.78
t 1.30
1.10
-2.06 -0.76 -0.98 -1.24 -0.66 -0.17 -10.63 +2.28
8.43 2.32 1.16 5.13
1.99 0.85 10.54
-0.10
1.47 1.29
-3.52 +0.42 +0.93
7.95 0.98 0.92
2. The mandibular first molar moved 0.4 mm. posteriorly and 0.9 mm. superiorly while decreasing its angulation to the mandibular plane (MP) by 3.5 degrees during the first interval. This angulation to MP at the end of the period of continuous headgear wear was significantly different (0.02 level) from its angulation to MP for the other two serial lateral head films. 3. The occlusal plane increased 1.2 degrees to FH during Interval I. This occlusal plane angle at the end of Interval I was significantly different
Extraoral Table
II. Mean
change
Variable
1. PP-FH angle (degrees) 2. OP-FH angle (degrees) 3. MP-FH angle (degrees) 4. N-M (mm.) 5. Ar-Po (mm.) 6. A: Horizontal (mm.) 7. A: Vertical (mm.) 8. ANS: Horizontal (mm.) 9. ANS: Vertical (mm.) 10. B: Horizontal (mm.) 11. B: Vertical (mm.) 12. PO: Horizontal (mm.) 13. Po: Vertical (mm.) 14. I-FH angle (degrees) 15. r: Horizontal (mm.) 16. &I Vertical (mm.) 17. I-MP angle (degrees) 18. i: Horizontal (mm.) 19. i: Vertical (mm.) 20. M-FH angle (degrees) 2 1. M: Horizontal (mm.) 22. b Vertical (mm.) 23. k-MP angle (degrees) 24. k Horizontal (mm.) 25. E: Vertical (mm.)
in variables I
high-pull during
tractio?L and cervical traction
Interval Mean
+0.49 -3.35 -2.34 f7.45 +7.18 +2.61 +4.05 i-3.19
f3.00 +3.23 f4.57 +4.15 +6.85 -1.21 +0.96 +2.48 +1.54 +1.95 +2.55 + 13.55 -3.67 +3.03 -0.84 -1.05 +2.41
437
II I
Standard
deviation
1.76 2.78 2.28 4.89 4.18 2.29 2.74 2.93 2.09 2.79 3.20 3.85 4.64 7.37 2.13 2.21 6.14 2.31 1.94 9.13 2.33 2.21 6.99 1.66 2.01
(0.05 level) from its angulation for the other two serial lateral head films. No significant correlation was found except for the correlation of mandibular plane with anterior facial height (N-M) for Interval I with a coefficient of 0.71, which is significant at the 0.001 level. Discussion
Treatment changes (Interval I). Several additional factors must be taken into consideration in an evaluation of the treatment changes due to continuous combined extraoral high-pull traction and cervical traction to the maxillary first molars. Among these factors are : 1. The individual biologic variation between patients as partially reflected in the standard deviations of the mean changes in the measured variables for this sample (Table I). 2. The amount of anteroposterior movement of the incisors and molars as related to the initial malocclusion. 3. Tooth movement as influenced by additional appliance therapy (during the period of continuous headgear wear) consisting of upper and lower incisor bands with 0.021 by 0.025 inch edgewise arches in place.
438
Bade11
Clinical investigations’“* Ii. I83 z4 and experimental st~udies’“~2z demonstrated skeletal changes in response to cervical headgear therapy. In particular, the maxilla is commonly reported to be distally positioned with a clockwise rotation of the palatal plane. In addition, clinical investigations4 and experimental studies58 7 involving high-pull headgear confirm that the position of the maxilla may be changed upward and backward in the direction of the applied extraoral forces. For this investigation, all of the patients were treated with extraoral combined high-pull traction and cervical traction to the maxillary first molars (Fig. 1). The extraoral force was periodically adjusted to 24 to 32 ounces per side for the high-pull component and 16 ounces per side for the cervical component. This appliance was worn continuously (tied in) for a mean period of 122 days. During this period the mean change in the anteroposterior position of the maxilla relative to the cranial base was trot statistically significant as reflected in the small average distal and inferior changes in point A and ANS. The angulation of the palatal plane to FH increased in twenty cases (an average of only 0.6 degree) but decreased in ten cases. These small changes in the palatal plane relative to FH were not statistically significant. Graber” intimated changes in bony relationships resulting from “orthopedic forces” being applied to the maxilla. He suggested that a force of 1 to 2 pounds be applied to the maxillary teeth and indirectly to the basal bone in order to effect these “orthopedic changes.” The total force level utilized for this study was approximately 2.5 to 3 pounds per side. However, no statistically significant orthopedic changes were observed. This may be due in part to the relatively short period of time that the combined headgear was worn (mean, 122 days). Perhaps longer periods of wear would produce some degree of orthopedic changes. Damon,4 in a clinical study involving high-pull headgear, used a similar force level (approximately 3 pounds per side) over a similar treatment period which ranged from 92 to 169 days. In some cases, he was able to observe dramatic changes in the position of the maxilla. However, the extraoral force was delivered to the maxilla through the maxillary first molars and first premolars, which were splinted together for his investigation. Perhaps orthopedic changes can occur to a greater degree if the extraoral force is delivered to the maxilla by means of a dentition that is somehow splinted together rather than delivered directly to the maxillary first molars only, as was done for this investigation. Experimental studies involving cervical headgear’“, 22 and high-pull headgears, 7 have employed an appliance so that 300 to 800 grams per side of extraoral force was delivered to the maxilla of the Macaca muihtta monkey by means of a cast splint that encompassed the entire maxillary dentition. Significant orthopedic changes were demonstrated in the position of the maxilla and other bones in the craniofacial complex. Those changes may be partially attributable to the fact that the total extraoral force was delivered to a dentition
Extruora.1 high-pull
twction
rind cervical
tra8ction
439
that was completely splinted together. In addition, the extreme skeletal changes observed in the experimental studies may also be due in part to the relatively high ratio of total extraoral force to total body weight for the experimental animals in comparison to the force levels utilized for human patients in the clinical studies. For this investigation the total extraoral force (5 to 6 pounds) was only approximately 5 to 6 per cent of the total body weight of the patients, while for a typical experimental study5 the total extraoral force was approximately 20 per cent of the total body weight of the animals (Maca~ca mulntta~). The direction of pull of the extraoral force might also be a factor in the degree to which orthopedic changes occur. The tendency for the palatal plane to rotate clockwise (as associated with cervical headgear) or counterclockwise (as associated with high-pull headgear) might be minimized because of the direction of applied extraoral force to the maxilla resulting from the combination of cervical traction and high-pull traction for this study (Fig. 1). Extrusion and distal crown tipping of the maxillary molar in response to cervical headgear therapy have been reported by several authors.g~ 15,I4 For bhis sample of thirty cases, the maxillary first molar was moved distally an average of 2.4 mm. In twenty cases this was distal bodily movement as originally described by Armstrong,l while in ten cases there were varying degrees of distal crown tipping. Although approximately the same amount and direction of extraoral force were applied to each patient, the individual biologic variation could possibly account for this difference in the response of the maxillary first molar. In addition, proper positioning of the short outer bows more superior to the inner bows may have prevented or reduced the distal crown tipping which was observed in some cases. On the average, the maxillary first molar was also intruded slightly (0.1 mm.). This agrees with findings of experimental high-pull headgear studie$ 7 and clinical high-pull headgear studies4 which showed that the maxillary first molar root was also tipped distally. This intrusion is contrary to the extrusion commonly reported with cervical headgear therapy. Clinical investigatorPt I7 and experimental investigators’, 22 have reported increases in the mandibular plane angle and concurrent increases in anterior facial height as a result of headgear therapy. The mandibular plane angle did increase an average of 0.8 degree for this study, with a 1.1 mm. average increase in the anterior facial height (N-M). There was a biologically meaningful correlation (+O.i’l) between the increase in the mandibular plane angle and the increase in anterior facial height for the period of continuous headgear wear. Bite opening or clockwise rotation of the mandible was confirmed by changes in the position of point B and pogonion, both of which were 1.3 mm. inferior on the average at the end of Interval I. Bite opening may have been produced by occlusal interferences attributable to the “super” Class I buccal relationship to which all of the patients were treated. Frederick,7 in an experimental study involving high-pull headgear, demonstrated bite opening due to occlusal interferences in spite of the fact that the direction of the extraoral force utilized resulted primarily in intrusion.
440
Bad&
Am.
J. Orthod. April 19iG
Damon4 in a clinical study also involving high-pull headgear, found that the mandibular plane angle remained the same or decreased slightly. However, patients in his sample were not treated to a “super” Class I buccal relationship, and thus the occlusal interferences may have been minimized. On the average, the mandibular molar did not drift mesially during the period of continuous headgear wear. Tt remained unchanged or distally uprighted. This statistically significa,nt finding is in concordance with other studies59 8, 13,22 which demonstrated similar responses of the mandibular dentition to maxillary headgear therapy. The occlusal plane angle increased an average of 1.2 degrees to FH during the period of headgear wear, which was statistically significant and in agreement with the findings of Frederick.7 Mandibular length (Ar-Po) increased only slightly, on the average (1.0 mm.), for the sample. This is probably a reflection of the relatively short interval of time during which mandibular growth could occur. Axial inclinations and positions of the maxillary and mandibular central incisors were highly variable during the period of continuous headgear wear. This may be due to the initial alignment of the teeth and differences in the configuration of the arch wires used in addition to the individual biologic variation. Posttreatment changes (Zntervd ZZ). Certain other factors must be considered in order to evaluate completely the posttreatment changes following the period of continuous combined extraoral traction : 1. The individual biologic variation between patients as partially reflected in the standard deviations of the mean changes in the measured variables for this sample (Table II). 2. Changes in tooth position as influenced by continued appliance therapy after the initial period of continuous headgear wear. 3. The amount of anteroposterior movement of molars and incisors as related to available arch length in the interchange from mixed to permanent dentition. 4. Tooth movement as influenced by varying periods of retention with upper and lower removable appliances using no headgear. 5. The amount and direction of growth in the posttreatment period. During the postheadgear period, the maxilla moved downward and forward as reflected in the anterior and inferior positioning of point A and ANS. This is contrary to Tuenge and Elder’sZJ experimental finding that “the cephalometric growth pattern produced in the experimental group (utilizing high-pull headgear) showed an increasing difference from the control group during the entire posttreatment period.” However, this difference occurred at a decreasing rate during the last 4 months of the lo-month posttreatment period. The normal downward and forward movement of the maxilla in this sample may be attributed to the relatively long-term posttreatment period (average of 3 years 2 months) and the relatively minimal influence on the position of the maxilla (initially). The inferior movement of ANS (mean, 3.0 mm.) agrees with
Wieslander’sZ5 study of patients who wore cervical headgear. He found that ANS moved inferiorly an average of 7.3 mm. over a posttreatment period of 6 years. The palatal plane continued to increase its inclination to FH slightly (mean, 0.5 degree) which corresponds to results observed by Mitani and Brodie.lG Wieslande? found a similar mean increase of 0.8 degree in the posttreatment period. The maxillary molar showed a strong tendency to recover its original position and inclination during the postheadgear period. It uprighted an average of 13.6 degrees to FH and moved downward (mean 3.0 mm.) and forward (mean, 3.7 mm.). These findings agree with Tuenge and Elder’sZ3 results, which disclosed a “rapid cephalometric reversal of the maxillary tooth movement.” Part of this recovery was probably due to normal tooth eruption. Wieslander25 demonstrated a “minimal physiologic recovery” of the maxillary first molar following cervical headgear therapy. His sample consisted of twentyeight patients treated in the mixed dentition with cervical traction (10 to 15 ounces per side) 12 to 14 hours per day for an average of 2 years 8 months in order to restrain the forward movement of the maxillary dentition and/or maxilla. This contrasts with the sample for this investigation, where the purpose of the continuous combined extraoral traction (2.5 to 3 pounds per side) for an average of only 122 days was to bring about the distal bodily movement of the maxillary first molars. Therefore, it might be expected that more physiologic recovery of the dramatic tooth movement observed for this investigation (utilizing a much greater extraoral force over a shorter period of time) would occur than for Wieslander’s25 investigation (utilizing a much smaller extraoral force over a longer period of time). Anterior facial height (N-M) increased an average of 7.5 mm. during Interval II, and the mandibular length (Ar-Po) increased a mean of 7.2 mm. during this same period. Correspondingly, both point B and pogonion were located anteriorly and inferiorly at the end of the postheadgear period. The mean value for the anterior positioning of pogonion (4.2 mm.) agrees with the study by Wieslander,25 who found a mean value of 3.0 mm. Changes in anterior facial height, mandibular length, point B, and pogonion all reflect the tremendous amount of posttreatment growth that all the patients exhibited. The maintenance of the Class I relationship during the postheadgear period may be partially attributed to the favorable amount of downward and forward growth of the mandible. This agrees with findings of Riedellg and Herzberg.ll The mandibular plane angle decreased an average of 2.4 degrees during the postheadgear period. This decrease lends further support to the idea that the initial increase in the mandibular plane angle was due to occlusal interferences which were later resolved, allowing a subsequent decrease in the angle. The vertical component of growth which all the patients exhibited may also have contributed to this decrease. Simons and Joondeph,21 in an investigation of fully treated orthodontic cases 10 years postretention, found a decrease in the
442
Bade11
Fig. 7. Composite superimpositions changes in the measured variables
Am.
of a selected case that for both Interval I and
most closely Interval II.
represents
J. Orthod. April 1976
the
mean
mandibular plane angle. Wies1ander,25 in a posttreatment investigation of orthodontic patients treated in the mixed dentition with cervical headgear only, also found a decrease in the mandibular plane angle following treatment. The mandibular molar recovered from its distal uprighting during the first interval by moving, on the average, 1.1 mm. mesially and 2.4 mm. superiorly during the postheadgear period. Part of this recovery was probably attributable to normal tooth eruption. This finding agrees with Tuenge and Elder,23 who found a “rapid cephalometric reversal” of the mandibular tooth movement following treatment. The occlusal plane decreased 3.4 degrees (mean) to FH during the postheadgear period after an initial increase of 1.2 degrees during Interval I. There was no statistically significant difference between the initial occlusal plane angle and the occlusal plane angle at the end of the posttreatment period. This finding corresponds with findings by Mitani and Brodie16 and Simons and Joondeph*’ and may be attributed to continued appliance therapy during the second interval in addition to growth concomitant with normal tooth eruption. On the average, the maxillary central incisor moved downward and forward while the mandibular central incisor moved upward and backward during the postheadgear period. This may be due to normal tooth eruption in addition to continued appliance therapy during Interval II.
T’olume Number
69 4
Extraoral
high-pull 11-2
-
11-5 11-S
----I
traction
and cervical
traction I i
16-1 -.-.-. 16-1
413
\ ;
!
II i
!
\ ‘\ i \;
Fig. distal
8. Composite crown
tipping
superimpositions during
of Interval
a selected
case
that
shows
an
excessive
amount
of
I.
The axial inclinations of the maxillary and mandibular central incisors were highly variable. Their variability was similar to findings for the first interval and, again, may be attributed to different types of appliance therapy during the posttreatment period in addition to the individual biologic variation. Subjective examination of orthodontic study models for the sample at the end of the posttreatment period revealed that all of the maxillary second molars were in a reasonable occlusion. Thus, impaction of maxillary second molars in response to the extraoral force was not observed, even though the maxillary first molar crown was tipped distally to an excessive degree in some cases. This observation may be ascribed to the maxillary second molar tooth bud also moving distally in response to the extraoral force. Also, the fact that the maxillary first molars recovered mesially during the posttreatment period might have allowed for the normal eruption of the maxillary second molars, Clinical
implications
Continuous combined extraoral high-pull traction and cervical traction as described for this investigation may be particularly useful for orthodontic patients in the mixed dentition in which rapid distal movement of the maxillary first molars without any significant extrusion or skeletal change is desired. There are, of course, orthodontic patients for whom some degree of skeletal change (that is, restraint of the maxilla) in addition to distal movement of the maxiIlary first molars would be desirable. It is conceivable that this type
444
Fig.
Bade11
9.
pattern
;I 11,. J. Ol‘thod. Awil 19i6
Composite during
the
superimpositions
of
posttreatment
period.
a selected
case
that
demonstrates
a vertical
growth
of result could be achieved by wearing this same appliance for a longer period of time with less total force. Perhaps less “physiologic rec.overy” of maxillary first molars would occur with the appliance utilized in this manner. Skeletal changes might be effected by delivering combined extraoral force to a dentition which is splinted together. This could be accomplished by fabricating a custom splint for the patient, or it could be done by tying the entire maxillary dentition together with full orthodontic appliances in place. Individual
cases
Twenty patients in the sample demonstrated distal bodily movement of the maxillary first molar as originally described by Armstr0ng.l Fig. ‘7 depicts a selected case that most closely represents the mean changes in the measured variables for both Intervals I and II from this group. The other ten patients in the sample demonstrated varying degrees of distal crown tipping in response to the extraoral force during Interval I. Fig. 8 demonstrates a selected case from this group that shows an excessive amount (20.2 degrees) of distal crown tipping. Four patients exhibited a vertical growth pattern with little or no horizontal component of growth during the postheadgear period. In these cases the maxil-
Extraoral
high-pull
traction
awl
cervical
tmction
445
lary first molar tended to recover its original inclination and position, but to a lesser degree than the cases which demonstrated a more horizontal growth pattern. The mandibular first molars also tended to migrate mesially to a greater degree in these cases. Consequently, the Class I relationship achieved during Interval I was maintained. Fig. 9 shows a selected case that represents this group of patients. Summary
and
conclusions
The effects of extraoral combined high-pull traction and cervical traction of known duration (mean, 122 days) and magnitude (2.5 to 3 pounds total per side) were studied by means of serial lateral cephalometric head films of thirty patients. The lateral cephalometric head films used were taken at three different times: before the extraoral force was applied, after the prescribed period of continuous headgear wear, and as long as possible after the extraoral force was discontinued. Changes in the dentition and associated structures were described both for the period of continuous headgear wear and for an average of 3.2 years later. The following conclusions are based on statistical analysis of the observed changes : 1. The position of the maxilla and the palatal plane was not significantly affected by relatively short periods of extraoral combined high-pull traction and cervical traction to the maxillary first molars as used for this investigation. 2. The maxillary first molars can be moved distally and bodily with this appliance without extrusion. 3. On the average, the mandibular first molars uprighted distally in response to the extraoral force to the maxilla. 4. The maxillary and mandibular first molars demonstrated a strong tendency to recover to their original positions and inclinations relative to their respective bases during the posttreatment period. 5. The amount and direction of growth in the posttreatment period may be important in determining how the Class I relationship is maintained. I would like to thank Maclay provided the material for this the preparation of this manuscript.
M. Armstrong, investigation,
and
who developed Richard A.
the headgear and generously Riedel for his assistance in
REFERENCES
1. Armstrong, M. M.: Controlling the magnitude, direction, and duration of extraoral force, AK J. ORTHOD. 59: 217-243,1971. 2. Bjiirk, A.: Variations in the growth pattern of the human mandible; longitudinal radiographic study by the implant method, J. Dent. Res. 42: 400, 1963. 3. Broadbent, B. H.: A new x-ray technique and its application to orthodontics, Angle Orthod. 1: 45-66, 1931. 4. Damon, D. H.: A clinical study of extraoral high-pull traction to the maxilla utilizing a heavy force: A cephalometric analysis of the dentofacial changes, M.S.D. thesis, University of Washington. 5. Elder, J. R., and Tuenge, R. H.: Cephalometric and histologic changes produced by
446
Am
Bade11 extraoral
high-pull
traction
to the maxilla
in Macaca
mulattn,
AM.
J. ORTHOD.
66:
J. Orthod.
&Iv%1976
599-617,
1974.
6. Elmajian, K. E.: A serial study of facial growth as related to cranial base morphology, M.S.D. thesis, University of Washington, 1959. 7. Frederick, D. L.: Dentofacial changes produced by extraoral high-pull traction to the maxilla of the Yacaca mulatta; a histologic and serial cephalometric study, M.S.D. thesis, University of Washington, 1969. 8. Funk, A. C.: Mandibular response to headgear therapy and its clinical significance, A&I. J. ORTHOD. 53: 182.216,1967. 9. Graber, T. M.: Extraoral force-Facts and fallacies, AX J. ORTHOD. 41: 490-505, 1955. 10. Henry, H. L.: Craniofacial changes induced by “orthopedic forces” in the Macaca mzLZatta rhesus monkey, M.S.C. thesis, University of Manitoba, 1973. 11. Herzberg, R. : A cephalometric study of Class II relapse, Angle Orthod. 43: 112-118, 1973. 12. Julius, R. B.: A serial cephalometric study of the metallic implant technique and methods of maxillary and mandibular superimposition, M.S.D. thesis, University of Washington, 1972. 13. Lindquist, W. G.: An analysis of change in the mandibular arch, coincident with maxillary headgear therapy, M.&D. thesis, University of Washington, 1963. 14. Masumoto, G.: A serial cephalometric analysis of the dentofacial changes produced by extraoral cervical traction to the maxilla utilizing metallic implants, M.S.D. thesis, University of Washington, 1970. 15. Merrifield, L. L., and Cross, J. J.: Directional forces, Au. J. ORTHOD. 57: 435-464, 1970. 16. Mitani, H., and Brodie, A. G.: Three plane analysis of tooth movement, growth, and angular changes with cervical traction, Angle Orthod. 40: 80-94, 1970. 17. Moore, A. W.: Observations on facial growth and its clinical significance, Anr. J. ORTHOD. 45: 399-423, 1959. 18. Ricketts, R. M.: The influence of orthodontic treatment on facial growth and development, Angle Orthod. 30: 103, 1960. 19. Riedel, R. A.: A review of the retention problem, Angle Orthod. 30: 179-194, 1960. cephalometrics, Philadelphia 1961, J. B. Lippincott 20. Salzmann, J. A.: Roetgenographic Company. 21. Simons, M. E., and Joondeph, D. R.: Change in overbite: A ten-year postretention study, AM.
J. ORTHOD.
64:
349-367,1973.
Sproule, W. R.: Dentofacial changes produced by extraoral cervical traction to the maxilla of the Macaca mulotta monkey, M.S.D. thesis, University of Washington, 1968. 23. Tuenge, R. H., and Elder, J. R.: Posttreatment changes following high-pull traction to the maxilla of the Macaca mdatta, AM. J. ORTHOD. 66: 618-644, 1974. 24. Wieslander, L.: The effects of orthodontic treatment on the concurrent development of the craniofacialcomplex, AM. J. ORTKOD. 49: 15-27, 1963. 25. Wieslander, L.: Physiologic recovery after cervical traction therapy, AM. J. ORTHOD. 66: 22.
294-301, 65gO North
1974. 7th
Ave.
(85014)
