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Distal molar movement with Kloehn headgear: Is it stable?
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)
D
istal displacement of the maxillary molars has been an integral part of orthodontic treatment for 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 appliance 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. McSherry 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 From the Department of Orthodontics, Royal Dental College, University of Aarhus, Denmark. a Professor. b Associate 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, [email protected]. 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
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 orthopedic 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 molars has been subject to less interest. One reason could be the difficulty in distinguishing intramaxillary movements 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 evidencebased. This study will describe the intramaxillary molar displacement 7 years after treatment with Kloehn headgear and cervical traction. MATERIAL AND METHODS
The sample studied has previously been described.18 Briefly, it consisted of 20 patients (12 boys
Melsen and Dalstra 375
American Journal of Orthodontics and Dentofacial Orthopedics Volume 123, Number 4
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 according to Bjo¨ rk’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 discontinuing 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 inserting 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 discontinued, and the fourth 7 years after treatment, when the patients were between 17 and 18 years of age. The 21 patients described by Bjo¨ rk 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 identical to those used in the sample. The subjects described by Bjo¨ rk and Skieller20 had been followed with radiographs 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 displacement 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
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.
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 intramaxillary tooth movement during and after treatment, the groups with the upward and downward extraoral arms were pooled. The total intramaxillary tooth movement 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 patients who had the downward-tilting extraoral arms demonstrated a combination 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 backward 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 displacement and growth direction reversed, and a significant
376 Melsen and Dalstra
American Journal of Orthodontics and Dentofacial Orthopedics April 2003
DISCUSSION
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 cessation of headgear.
Fig 3. Changes in intramaxillary position of molars in average control patient before and after peak of pubertal growth spurt. Reproduced with permission from Bjørk and Skieller 1972 with kind permission by Am J Orthod.
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 displacement 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).
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 intraosseous references was necessary. Although alternative methods have been described,19,21 none can take the modelling of the maxilla into consideration, because 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 especially for this study because it would be impossible to obtain permission to insert tantalum implants in untreated 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 reversed to a forward downward direction, catching up with the delayed forward growth. This did not, however, 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 displacements 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 mesially 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 treatment. 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
Melsen and Dalstra 377
American Journal of Orthodontics and Dentofacial Orthopedics Volume 123, Number 4
Table I.
Intramaxillary molar movement Horizontal movement
Control Sample
Vertical movement
Time (y)
n
x
SD
Min-max
y
SD
Min-max
10-16 9-10 10-17 9-17
19 20 20 20
4.63 ⫺3.23 8.04 5.42
1.82 1.07 3.11 1.91
0.3-7.30 0.5-5.50 2.4-11.1 1.0-11.1
5.68 2.61 5.35 8.01
2.72 1.7 3.0 3.7
2.74-9.34 0-3.60 3.4-10.23 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
Control Sample
Time (y)
x
SD
Minimum
Maximum
10-16 9-10 10-17 9-17
⫺8.10 5.75 ⫺13.00 ⫺7.25
4.3 4.4 4.5 4.8
⫹2 ⫹8 ⫹3 ⫹3
⫺12.0 ⫺17.5 ⫺21.0 ⫺15.0
Difference between total movement in experimental control group P ⬎ .10. ⫺ ⫽ Distal; ⫹ ⫽ mesial.
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 desirable. The question then would be whether the appliance 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 traction might have on head posture22 and tongue pressure23 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, Monsurro´ 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. Prosthodontic 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 evaluation 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 analysis of molar movement during headgear treatment. Am J Orthod Dentofacial Orthop 2002;121:18-29.
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American Journal of Orthodontics and Dentofacial Orthopedics April 2003
16. Melsen B. Effects of cervical anchorage during and after treatment: 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. Bjo¨ rk A. The use of metallic implants in the study of facial growth in children: method and application. Am J Phys Anthropol 1969;29:243-54. 21. Bjo¨ rk 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. Bjo¨ rk A, Skieller V. Facial development and tooth eruption—an implant study at the age of puberty. Am J Orthod 1972;62:339-83. 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. 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. Takahashi S, Ono T, Ishiwata Y, Kuroda T. Effect of wearing cervical headgear on tongue pressure. J Orthod 2000;27:163-7. 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.
22. 23.
24.
25. 26.
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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)
D
istal displacement of the maxillary molars has been an integral part of orthodontic treatment for 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 appliance 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. McSherry 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 From the Department of Orthodontics, Royal Dental College, University of Aarhus, Denmark. a Professor. b Associate 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, [email protected]. 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
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 orthopedic 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 molars has been subject to less interest. One reason could be the difficulty in distinguishing intramaxillary movements 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 evidencebased. This study will describe the intramaxillary molar displacement 7 years after treatment with Kloehn headgear and cervical traction. MATERIAL AND METHODS
The sample studied has previously been described.18 Briefly, it consisted of 20 patients (12 boys
Melsen and Dalstra 375
American Journal of Orthodontics and Dentofacial Orthopedics Volume 123, Number 4
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 according to Bjo¨ rk’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 discontinuing 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 inserting 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 discontinued, and the fourth 7 years after treatment, when the patients were between 17 and 18 years of age. The 21 patients described by Bjo¨ rk 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 identical to those used in the sample. The subjects described by Bjo¨ rk and Skieller20 had been followed with radiographs 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 displacement 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
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.
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 intramaxillary tooth movement during and after treatment, the groups with the upward and downward extraoral arms were pooled. The total intramaxillary tooth movement 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 patients who had the downward-tilting extraoral arms demonstrated a combination 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 backward 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 displacement and growth direction reversed, and a significant
376 Melsen and Dalstra
American Journal of Orthodontics and Dentofacial Orthopedics April 2003
DISCUSSION
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 cessation of headgear.
Fig 3. Changes in intramaxillary position of molars in average control patient before and after peak of pubertal growth spurt. Reproduced with permission from Bjørk and Skieller 1972 with kind permission by Am J Orthod.
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 displacement 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).
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 intraosseous references was necessary. Although alternative methods have been described,19,21 none can take the modelling of the maxilla into consideration, because 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 especially for this study because it would be impossible to obtain permission to insert tantalum implants in untreated 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 reversed to a forward downward direction, catching up with the delayed forward growth. This did not, however, 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 displacements 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 mesially 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 treatment. 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
Melsen and Dalstra 377
American Journal of Orthodontics and Dentofacial Orthopedics Volume 123, Number 4
Table I.
Intramaxillary molar movement Horizontal movement
Control Sample
Vertical movement
Time (y)
n
x
SD
Min-max
y
SD
Min-max
10-16 9-10 10-17 9-17
19 20 20 20
4.63 ⫺3.23 8.04 5.42
1.82 1.07 3.11 1.91
0.3-7.30 0.5-5.50 2.4-11.1 1.0-11.1
5.68 2.61 5.35 8.01
2.72 1.7 3.0 3.7
2.74-9.34 0-3.60 3.4-10.23 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
Control Sample
Time (y)
x
SD
Minimum
Maximum
10-16 9-10 10-17 9-17
⫺8.10 5.75 ⫺13.00 ⫺7.25
4.3 4.4 4.5 4.8
⫹2 ⫹8 ⫹3 ⫹3
⫺12.0 ⫺17.5 ⫺21.0 ⫺15.0
Difference between total movement in experimental control group P ⬎ .10. ⫺ ⫽ Distal; ⫹ ⫽ mesial.
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 desirable. The question then would be whether the appliance 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 traction might have on head posture22 and tongue pressure23 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, Monsurro´ 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. Prosthodontic 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 evaluation 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 analysis of molar movement during headgear treatment. Am J Orthod Dentofacial Orthop 2002;121:18-29.
378 Melsen and Dalstra
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16. Melsen B. Effects of cervical anchorage during and after treatment: 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. Bjo¨ rk A. The use of metallic implants in the study of facial growth in children: method and application. Am J Phys Anthropol 1969;29:243-54. 21. Bjo¨ rk 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. Bjo¨ rk A, Skieller V. Facial development and tooth eruption—an implant study at the age of puberty. Am J Orthod 1972;62:339-83. 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. 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. Takahashi S, Ono T, Ishiwata Y, Kuroda T. Effect of wearing cervical headgear on tongue pressure. J Orthod 2000;27:163-7. 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.
22. 23.
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