artigo 15-melsen

Prévia do material em texto

ORIGINAL ARTICLE
Distal molar movement with Kloehn headgear:
Is it stable?
Birte Melsen, DDS, dr odont,a and Michel Dalstra, PhDb
Aarhus, Denmark
The aim of this study was to evaluate intramaxillary molar movement after 8 months of cervical traction and
posttreatment displacement 7 years later. The total molar displacements in relation to stable intraosseous
reference points were compared with those observed in an untreated control group that also had
intraosseous reference indicators inserted. During the headgear period, the type of molar displacement could
be predicted by the direction of the force system acting on the teeth. It was noted, however, that the variation
in the vertical development was related more to each patient’s growth pattern than to the force system applied.
After cessation of the headgear, intramaxillary displacement of the molars was noted, and the total displacement
of the molars did not differ from that of the untreated group. The indication for intramaxillary displacement of the
molars by means of extraoral traction is therefore questioned. (Am J Orthod Dentofacial Orthop 2003;123:374-8)
Distal displacement of the maxillary molars hasbeen an integral part of orthodontic treatmentfor patients with Class II malocclusions. It is
not surprising that a PubMed search on the keywords
distalizing molars and orthodontics resulted in 1747
references. Of these, 95 were related to headgear, but
only 4 represented controlled clinical trials, and only 4
reported posttreatment changes. The choice of appli-
ance for distal molar movement seems to be based more
on philosophy than on scientific data. Some clinicians
are dedicated to using extraoral traction,1-4 whereas
others, because of problems related to compliance,
prefer intermaxillary or intramaxillary appliances. Mc-
Sherry and Bradley5 published a comprehensive review
of the available techniques and listed indications and
contraindications. Although these appliances were all
designed to distally displace the maxillary molars, the
reactive forces also act on the occlusion, sometimes
favorably, sometimes unfavorably. Only when implants
or intraosseous screws are used can the reactive forces
be said to be fully controlled.6,7
Recent studies have shown that in more than 70%
of patients with Class II molar relationships, this
reflects a mesial rotation rather than a mesial position of
the molars because the lingual cusp of the maxillary
molar is in the central fossa of the mandibular molar.8
According to a split-line examination, the occlusal
forces acting on the molars are distributed to the facial
skeleton via the infrazygomatic crest.9 With reference
to this function, Atkinson10 defined the infrazygomatic
crest as the key ridge. Recently, finite element analysis
was used to simulate occlusal forces acting on molars
below the infrazygomatic crest, one cusp mesial or one
cusp distal; it was clearly demonstrated that the position
of the molar influenced the load transfer significantly.10
There seems to be general agreement that orthope-
dic alterations generated with functional or extraoral
appliances are highly reversible.12-15 An implant study
analyzing the alterations of the facial skeleton during
and after the use of cervical headgear clearly showed
that the posterior growth direction of the maxilla
reversed immediately after extraoral traction.16 The
same was observed in a group of patients treated with
a Thurov splint and extraoral traction.17
The posttreatment displacement of distalized mo-
lars has been subject to less interest. One reason could
be the difficulty in distinguishing intramaxillary move-
ments from the shift of the total maxillary complex due
to growth. With this background, the rationale behind
distal molar movement cannot be said to be evidence-
based.
This study will describe the intramaxillary molar
displacement 7 years after treatment with Kloehn head-
gear and cervical traction.
MATERIAL AND METHODS
The sample studied has previously been de-
scribed.18 Briefly, it consisted of 20 patients (12 boys
From the Department of Orthodontics, Royal Dental College, University of
Aarhus, Denmark.
aProfessor.
bAssociate professor.
Reprint requests to: Prof Birte Melsen, University of Aarhus, Royal Dental
College, Department of Orthodontics, Vennelyst Boulevard 9, DK-8000
Aarhus C, Denmark; e-mail, orthodpt@odont.au.dk.
Submitted, May 2002; revised and accepted, August 2002.
Copyright © 2003 by the American Association of Orthodontists.
0889-5406/2003/$30.00 � 0
doi:10.1067/mod.2003.72
374
and 8 girls) in the late mixed dentition, ranging in age
from 8.1 to 10.4 years. The sex distribution was
disregarded because no difference in growth intensity
between boys and girls has been shown in that age
group.19 All subjects had one-half to one cusp width
distal occlusion but no extreme overbite or overjet.
Skeletally, no patient deviated more than 2 SD from the
mean values of a Scandinavian population. The patients
had tantalum indicators inserted subperiosteally ac-
cording to Björk’s technique.20 Four indicators were
inserted in the maxilla—2 in the infrazygomatic crest
on the right, 1 on the left, and 1 below the anterior nasal
spine. Five indicators were inserted in the mandible.
After the insertion of the tantalum indicators, the
patients were treated with Kloehn headgear for 8
months, 12 hours per day. In 10 patients, the outer bow
was tilted upward 20°, and, in the remaining patients, it
was tilted downward 20°. The rationale for discontinu-
ing the headgear after 8 months was that most patients
had obtained a neutral molar relationship, and it was
considered unethical to continue treating the total
group. Posttreatment records were generated at that
time.
Four profile headfilms were taken in a cephalostat
with a film focus distance of 190 cm and a midsagittal
plane to film distance of 10 cm, giving a magnification
of the midsagittal structures of 5.6%, which was not
corrected for when the displacements of the molars
were evaluated. The first film was taken before insert-
ing the headgear, the second after 3 months to ensure
the stability of the reference indicators, the third after 8
months of treatment when the headgear was discontin-
ued, and the fourth 7 years after treatment, when the
patients were between 17 and 18 years of age.
The 21 patients described by Björk and Skieller21
served as the control group. These randomly selected
patients had the same ethnic backgrounds as the sample
studied. In addition, they had received implants identi-
cal to those used in the sample. The subjects described
by Björk and Skieller20 had been followed with radio-
graphs taken at 10, 13, and 16 years of age with the
same magnification used in the study group. The
intramaxillary tooth movement was estimated in the
same manner in the sample and the control group.
Because our intention was to evaluate the displace-
ment of the molars, individual templates indicating the
long axis of the molar intersecting the occlusal surface
in the center of the molar were made for each subject.
The templates were copied and positioned according to
the best fit on each headfilm from each patient. The
coordinate system in which the molar displacement was
expressed was defined as the x-axis corresponding to
the upper occlusal line and the y-axis a line through the
center of the molar’s occlusal surface at time point 1
(Fig 1). The radiographs were superimposed on the
maxillary implants. All measurements were repeated,
and the mean of the 2 measurements was used in the
results. To evaluate the correlation between the intra-
maxillary tooth movement during and after treatment,
the groups with the upward and downward extraoral
arms were pooled. The total intramaxillary tooth move-
ment in the pooled headgear groups and the control
group were compared with the Student t test.
RESULTS
The type of tooth movement during the headgear
period clearly reflected the line of action of the force in
the 2 groups (Figs 1 and 2). The patientswho had the
downward-tilting extraoral arms demonstrated a com-
bination of eruption and distal tipping of the molars,
whereas displacements in those with upward-tilting
extraoral arms were closer to a downward backward
translation. There was, however, no difference in the
amount of eruption. In both headgear groups, the
maxillary growth was altered into a downward back-
ward direction, but, probably because of the difference
in force distribution to the molars in the 2 groups, the
effect on the growth direction of the maxillary complex
was more pronounced in the second group (Fig 2).
During the posttreatment period, both molar displace-
ment and growth direction reversed, and a significant
Fig 1. Changes in position of molars during and after
treatment with cervical traction with extraoral arms bent
downwards. Note pronounced distal tipping of molars
during treatment followed by uprighting after cessation
of headgear.
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 123, Number 4
Melsen and Dalstra 375
inverse correlation was found between the treatment
and posttreatment changes horizontally (�0.58); no
significant relationship could be detected in the vertical
intramaxillary displacement (�0.21) (Fig 3).
When comparing the total intramaxillary displace-
ment of the molars during the treatment period plus the
7-year posttreatment period when the displacement
occurred without treatment, no significant difference
could be found (Tables I and II).
DISCUSSION
This study reported intramaxillary tooth movement
in a group of patients about 9 to 10 years of age using
cervical traction for 8 months and followed for 7 years
after treatment. Because our purpose was to analyze the
intramaxillary tooth movement, the use of fixed in-
traosseous references was necessary. Although alterna-
tive methods have been described,19,21 none can take
the modelling of the maxilla into consideration, be-
cause its exact modelling cannot be estimated. The use
of stable intraosseous implants is thus the only valid
method.19 The control group was not developed espe-
cially for this study because it would be impossible to
obtain permission to insert tantalum implants in un-
treated persons. The control group was, on the other
hand, representative of a random population followed
over the same period as the experimental group, with
implants inserted in the same areas.
The orthopedic effect of headgear during and after
treatment has previously been the subject of a thorough
study16 demonstrating that the backward downward
growth direction observed during treatment was re-
versed to a forward downward direction, catching up
with the delayed forward growth. This did not, how-
ever, lead to a relapse, because the mandibular forward
growth ensured the stability of the molar relationship
obtained by using the headgear.
The purpose of this study was not to focus on
growth but to study the relationship between the dis-
placements during and after extraoral traction; the
differences observed between the 2 groups of children
during treatment were not of interest. These differences
were related to the line of action of the force passing
below the center of resistance of the molars in one
group and through the center of resistance in the other
group. As expected, this resulted in distal tipping of the
molars in the first group. Although the vertical forces
acting on the molars also differed, they did not lead to
a difference in molar eruption, probably because of the
interaction with the occlusal forces.
Comparison of molar displacement in the headgear
and control groups showed that the molar that was
displaced distally by extraoral traction migrated mesi-
ally enough to regain a position comparable to that in
the untreated subjects. This did not indicate a relapse of
the Class I molar relationship obtained during treat-
ment. During the posttreatment period, the sagittal
molar relationship was maintained through forward
growth of the facial skeleton; this growth was more
pronounced in the mandible than in the maxilla, thus
accounting for the intramaxillary movement of the
maxillary first molars.16
Fig 2. Changes in position of molars during and after
treatment with cervical traction with extraoral arms bent
upwards. Note distal displacement of molars during
treatment followed by forward displacement after ces-
sation of headgear.
Fig 3. Changes in intramaxillary position of molars in
average control patient before and after peak of puber-
tal growth spurt. Reproduced with permission from
Bjørk and Skieller 1972 with kind permission by Am J
Orthod.
American Journal of Orthodontics and Dentofacial Orthopedics
April 2003
376 Melsen and Dalstra
CONCLUSIONS
The indication for intramaxillary distal movement
of the maxillary first molars should, on the basis of our
results, be reevaluated. For molars that have drifted
forward, an intramaxillary displacement might be de-
sirable. The question then would be whether the appli-
ance of choice is extraoral traction or 1 of those
recommended for noncompliance therapy.5 A strong
tendency of the molars to return to the key ridge was
demonstrated, and there is no evidence that the Class I
relationship obtained by extraoral traction is more
stable than that obtained by functional or intramaxillary
appliances. Because most Class II patients have a
mesial rotation of the molars, the need for true distal
movement8 of the maxillary molars might be limited.
This could indicate that prevention of the forward drift
would sufficiently correct the Class II relationships.
Considering the secondary effects that extraoral trac-
tion might have on head posture22 and tongue pres-
sure23 and the increased risk for developing sleep
apnea,24 the indication for Kloehn headgear should be
reconsidered.
REFERENCES
1. Pavlick CT. Cervical headgear usage and the bioprogressive
orthodontic philosophy. Semin Orthod 1998;4:219-30.
2. Ferro F, Monsurró A, Perillo L. Sagittal and vertical changes
after treatment of Class II Division 1 malocclusion according to
the Cetlin method. Am J Orthod Dentofacial Orthop 2000;118:
150-8.
3. Haas AJ. Headgear therapy: the most efficient way to distalize
molars. Semin Orthod 2000;6:79-90.
4. Schiavon Gandini MREA, Gandini LG Jr, da Rosa Martins JC,
Del Santo M Jr. Effects of cervical headgear and edgewise
appliances on growing patients. Am J Orthod Dentofacial Orthop
2001;119:531-9.
5. McSherry PF, Bradley H. Class II correction-reducing patient
compliance: a review of the available techniques. J Orthod
2000;27:219-25.
6. Diedrich P. Different orthodontic anchorage systems: a critical
examination. Fortschr Kieferorthop 1993;54:156-71.
7. Goodacre CJ, Brown DT, Roberts WE, Jeiroudi MT. Prosth-
odontic considerations when using implants for orthodontic
anchorage. J Prosthet Dent 1997;77:162-70.
8. Liu D, Melsen B. Reappraisal of Class II molar relationships
diagnosed from the lingual side. Clin Orthod Res 2001;4:97-104.
9. Seipel CM. Trajectories of the jaw. Acta Odontol Scand 1948;
8:81-191.
10. Atkinson SR. The mesio-buccal root of the maxillary first molar.
Am J Orthod 1951;38:642-52.
11. Cattaneo PM, Dalstra M, Melsen B. The transfer of occlusal
forces through the maxillary molars: a finite element study. Am
J Orthod Dentofacial Orthop 2003;123:367-73.
12. Tulloch JFC, Philips C, Proffit WR. Benefit of early Class II
treatment: progress report of a two-phase randomized clinical
trial. Am J Orthod Dentofacial Orthop 1998;113:62-72.
13. Boecler PR, Riolo ML, Keeling SD, TenHave TR. Skeletal
changes associated with extraoral appliance therapy: an evalua-
tion of 200 consecutively treated cases. Angle Orthod 1989;59:
263-70.
14. Keeling SD, Wheeler TT, King GJ, Garvan CW, Cohen DA,
Cabassa S, et al. Anteroposterior skeletal and dental changes
after early Class II treatment with bionators and headgear. Am J
Orthod Dentofacial Orthop 1998;113:40-50.
15. Ashmore JL, Kurland BF, King GJ, Wheeler TT, Ghafari J,
Ramsay DS. A 3-dimensional analysisof molar movement
during headgear treatment. Am J Orthod Dentofacial Orthop
2002;121:18-29.
Table I. Intramaxillary molar movement
Time (y) n
Horizontal movement Vertical movement
x SD Min-max y SD Min-max
Control 10-16 19 4.63 1.82 0.3-7.30 5.68 2.72 2.74-9.34
Sample 9-10 20 �3.23 1.07 0.5-5.50 2.61 1.7 0-3.60
10-17 20 8.04 3.11 2.4-11.1 5.35 3.0 3.4-10.23
9-17 20 5.42 1.91 1.0-11.1 8.01 3.7 3.4-10.23
Difference between total movement in experimental control group P � .10.
Min-max, Minimum and maximum.
Table II. Change in molar angulation
Time (y) x SD Minimum Maximum
Control 10-16 �8.10 4.3 �2 �12.0
Sample 9-10 5.75 4.4 �8 �17.5
10-17 �13.00 4.5 �3 �21.0
9-17 �7.25 4.8 �3 �15.0
Difference between total movement in experimental control group P � .10.
� � Distal; � � mesial.
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 123, Number 4
Melsen and Dalstra 377
16. Melsen B. Effects of cervical anchorage during and after treat-
ment: an implant study. Am J Orthod 1978;73:526-40.
17. Fotis V, Melsen B, Williams S. Posttreatment changes of skeletal
morphology following treatment aimed at restriction of maxillary
growth. Am J Orthod 1985;88:288-96.
18. Melsen B, Enemark H. Effect of cervical anchorage studied by
the implant method. Trans Eur Orthod Soc 1969;435-47.
19. Tanner JM. Growth at adolescence. 2nd ed. Oxford: Blackwell
Scientific Pub; 1964.
20. Björk A. The use of metallic implants in the study of facial
growth in children: method and application. Am J Phys An-
thropol 1969;29:243-54.
21. Björk A, Skieller V. Postnatal growth and development of the
maxillary complex. In: McNamara JA. Factors affecting the
growth of the midface. Monograph no. 6. Craniofacial growth
series. Ann Arbor: Center for Human Growth and Development;
University of Michigan; 1976 p. 61-99.
22. Björk A, Skieller V. Facial development and tooth eruption—an
implant study at the age of puberty. Am J Orthod 1972;62:339-83.
23. Baumrind S, Korn EL, Isaacson RJ, West EE, Molthen R.
Quantitative analysis of the orthodontic and orthopedic effects of
maxillary traction. Am J Orthod 1983;84:384-98.
24. Hiyama S, Ono T, Ishiwata Y, Kuroda T. Changes in mandibular
position and upper airway dimension by wearing cervical headgear
during sleep. Am J Orthod Dentofacial Orthop 2001;120:160-8.
25. Takahashi S, Ono T, Ishiwata Y, Kuroda T. Effect of wearing
cervical headgear on tongue pressure. J Orthod 2000;27:163-7.
26. Pirila-Parkkinen K, Pirttiniemi P, Nieminen P, Lopponen H,
Tolonen U, Uotila R, et al. Cervical headgear therapy as a factor in
obstructive sleep apnea syndrome. Pediatr Dent 1999;21:39-45.
BOUND VOLUMES AVAILABLE TO SUBSCRIBERS
Bound volumes of the American Journal of Orthodontics and Dentofacial Orthopedics are
available to subscribers (only) for the 2003 issues from the Publisher, at a cost of $96.00
($115.56 Canada and $108.00 international) for Vol. 123 (January-June) and Vol. 124
(July-December). Shipping charges are included. Each bound volume contains subject and
author indexes, and all advertising is removed. The binding is durable buckram, with the
journal name, volume number, and year stamped in gold on the spine. Payment must
accompany all orders. Contact Mosby, Subscription Customer Service, 6277 Sea Harbor Dr,
Orlando, FL 32887; phone 800-654-2452 or 407-345-4000.
Subscriptions must be in force to qualify. Bound volumes are not available in place
of a regular Journal subscription.
American Journal of Orthodontics and Dentofacial Orthopedics
April 2003
378 Melsen and Dalstra