Canine retraction with J hook headgear

Canine retraction headgear

with J hook Dr. Ayala

Carlos Ayala Perez, D.D.S.* J. Alfred0 de Alba, D.D.S., M.S.,** Angelo A. Caputo, Ph.D.,*** and Spiro J. Chaconas, D.D.S., M.S.**** Los

Cul(f.

Angeles,

Several methods have been described for accomplishing distal movement of canines without losing posterior anchorage. An accepted method in canine retruction is the use of headgear with J hooks. Since it incorporates extraoral anchorage. it is most effective in maximum-anchorage cases. It was the purpose of this study to anulyze the distribution off&-ce transmitted to the alveolus und surrounding structures by means of photoelastic visuulization, utilizing J hook heudgear for maxillary clmine retraction. A three-dimensionul model representing a human skull was used. This model wus constructed with different birefringent materials to simulate bone, teeth, Lmd periodontul membranes. Three d$ferent vectors offorce were upplied repre.senting high-, medium-, and ION-pull headgear, which were placed at angles of 40, 20, and 0 degrees to the occlusal plane. The photoelastic analysis WCIS made by means ($cr circular-trunsmission polariscope arrangement, and the photoelastic duta \r*ere recorded photographically. The stress areas created by the three d(iferent vectors of ,force were associated with various degrees of canine tipping. This e$ect wus greater with the low-pull force component than with the medium-pull traction. The high-pull headgear produced the least tipping tendency, being closer to u bodily movement effect. Further, stresses were transmitted to deeper structures of’the simulated ficicd bones; these regions were the fronto:ygomatic. : ygomaticomaxillar~, and zygomaticotemporal sutures.

Key words: Canine retraction,

headgear, J hook, extraoral,

photoelastic

T

he canines share a very important role in oral function and esthetics. Their unique position connects anterior and posterior segments of the dental arch and makes their orthodontic movement of great clinical importance, especially in premolar-extraction cases. During retraction of canines, the maintenance of posterior tooth position has always been a major concern for the orthodontist, mainly in those cases in which maximum anchorage is needed. Throughout the literature several methods have been described to accomplish distal movement of canines without losing posterior anchorage. Distal tipping of posterior teeth, molar buccal root torque, and application of light forces are commonly *Formerly UCLA Orthodontic Associate; now in private practice in Mexico **Assistant Professorand Clinic Director, UCLA Section of Orthodontics. ***Professor and Chairman, UCLA Section of Biomaterials Science. ****Professor and Chairman, UCLA Section of Orthodontics.

538

0002-94161801

I10538+

10$01.00/O

0

City,

Mexico

1980 The C. V. Mosby

CO.

Volume 78 Number 5

Canine retraction

Fig. 1. J

hooks

used

with J hook headgear

539

for this study.

used by the clinician to counteract the mesial movement tendency of posterior teeth during retraction of canines. Also, numerous appliances, such as the Nance holding arch or palatal bar, have been designed for the same purpose. The space closure may be achieved with the use of elastic modules, open- or closed-coil springs, or sectional closing loops. Another method of canine retraction involves the use of headgear with J hooks, where the hooks attach to a continuous arch wire mesial to the canines and exert a force over them so that they will slide along the wire. Since this incorporates extraoral anchorage in canine retraction, it should be effective in maximum anchorage cases. The purpose of this study was to visualize photoelastically the distribution of forces transmitted to the alveolus and surrounding structures using J hook headgear for maxillary canine retraction. Review of the literature Numerous authorsrm3 have studied the effects produced by the application of forces with extraoral appliances. However, there is very little in the literature concerning headgear with J hooks (Fig. 1). Jarabak and Fizzel14 described the use of high-pull headgear to produce lingual root tipping of the maxillary incisors. Far-rant5 described the use of a high-pull headgear with J hooks for maxillary canine retraction combined with straight pull for mandibular canine retraction. HickamGes found that when the force vector of the J hooks for upper canine retraction was placed at a 15degree angle below the occlusal plane, the anterior segment tended to extrude. He recommended that retraction be started with the vector of force placed at a 15degree angle above the occlusal plane. Stress analysis by means of photoelastic visualization is not new in the dental field. Zak,*O in the 1930’s, introduced this technique to study some of the effects of orthodontic mechanics within the alveolus. Caputo and associates” studied the stresses produced by the application of forces to a canine tooth by various retraction sectional springs with different gable angles. Another study concerning the photoelastic visualization of orthodontic forces was performed by Chaconas and colleagues.12 Their study analyzed the distribution of stress areas within the craniofacial complex during application of occipital and cervical extraoral traction applied to the maxillary molars. Although the analysis of orthodontic forces with photoelasticity has been criticized by some authors,r3 the validity of this technique has been demonstrated by Glickman,r4 Standlee15 and Brodsky” and their co-workers. These authors found a correlation between the effects of the forces seen

540

Ayalu et al

Fig. 2.

Three-dimensional

Am. J. Orthod. Nownher 1980

photoelastic

model,

simulating

a human

skull,

with brackets

and arch wire

in

place.

in the photoelastic model and the in vivo histologic changes observed in the alveolar process. More recently, de Alba and associates,” with the aid of computerized cephalometrics, found a direct correlation between a photoelastic model using Class III mechanics and ten treated Class III cases. Material and methods A three-dimensional model representing a human skull was used (Fig. 2). This model was constructed of different birefringent materials to simulate bone, teeth, and periodontal membranes. Silicone rubber molds were made of various anatomic structures, such as the cranial base and portions of bones of the calvarium. Bones of the midface were molded separately and were reproduced with PLM-lZ* photoelastic material. Molds were also made for each individual tooth of the maxilla. The teeth were then reproduced from ivory-epoxy material.? On the basis of the aforementioned study which established the correlation of the photoelastic and histologic models, a soft birefringent urethane plastic$ was added to the maxillary alveolar sockets to represent the periodontal ligament. The teeth were then placed in their proper positions in the maxilla, leaving extraction spaces distal to the canines. After this procedure, all anatomic units were assembled together by applying an adhesive to the sutural areas. These simulated sutures were positioned in the *Photolastic, Inc., Malvern, Pa. +Resin Formulator Co., Culver City, Ca. SSolithane 113, Thiokol Chemical Corp., Trenton,

N. J

Volume 78 Number

Canine retraction

5

Fig. 3. Model traction.

and

aluminum

frame

with

the J hooks

in place

and ready

with J hook headgear

for testing

with

541

medium-pull

same direction as those found in the human skull and represented divisions between their respective bones. Twin 0.018 by 0.025 inch standard edgewise brackets were bonded to all posterior and canine teeth, and an arch wire was fabricated from 0.016 by 0.016 inch blue Elgiloy wire.* Some compensating bends were made in the arch wire to render it strictly passive. The arch wire was tied into place with ligature wire. A round aluminum stock was used to support the model through the foramen magnum; this was attached to an aluminum frame containing a series of pulleys so as to vary the direction of force applied to the J hooks (Fig. 3). The J hooks were positioned mesial to the canines, and three different vectors of force were used, simulating high-, medium-, and low-pull headgear (Fig. 4). The highpull force vector was placed at an angle of 40 degrees above the occlusal plane, the medium-pull at 20 degrees above, and the low-pull parallel to the occlusal plane. The force used was 200 Gm. on each side. In each case the model was submerged in a container with mineral oil. The temperature of the oil was increased at a rate of 5” C. per hour, until the stress-freezing temperature of the material was reached, and then brought down at the same rate to room temperature. This permitted the stresses to remain in place even after removal of the appliances. After each process, the photoelastic observations were made by means of a circular transmission polariscope arrangement (Fig. 5). The light-field method was used, and the data were recorded photographically. *Rocky

Mountain

Dental

Products

Co.,

Denver,

Colo.

542

Ayala

Am. J. Orrhod. November I980

et rd.

Fig.

4. Diagram

showing

the

high-,

medium-,

Fig. 5. Setup illustrating the circular transmission polariscope fuser. P, Polarizing lenses. Q, Quarter wave plates.

and

low-pull

arrangement.

force

vectors.

LS,

Light

source.

D, Dif-

Results Examination of the skull revealed that all areas were in an initial stress-free condition. After completion of the stress-freezing processes, stress patterns were observed in several areas of the craniofacial complex. Each anatomic area affected by the different types of headgear will now be discussed separately. Muxillaty teeth. During high-pull traction, stresses were recorded in the extraction sites distal to the canines around the apices and along the mesial and distal surfaces of the canine roots, extending posteriorly to the mesial root surfaces of the second premolar-s and the area between the premolar and molar roots (Fig. 6). These photoelastic fringe distributions were interpreted according to the methods used by Brodsky and associates.16 The areas that showed the maximum compression were at the coronal third of the distal surface of the canine root and the apical third of the mesial surface of the canine root. During application of the medium-pull headgear, compression was observed around the mesial surface of the apical third of the canine root, but the intensity was greater than with high-pull traction (Fig. 7). Also, compression was observed at the distal surface along the canine root, extending to the premolar. Stresses were recorded at the mesial aspect of the canine root and at the area between the premolar and molar roots.

Volume 78 Number 5

Canine retraction with J hook headgear 543

Fig. 6. Diagram of the areas of stress produced at the extraction site, distal to the canine, with application of high-pull traction. The dark area indicates high concentration of stress. The high dotted area indicates medium concentration, and the low dotted area denotes low stress concentration.

Fig.

7. Stress

areas

obtained

at the canine

area

with

application

of medium-pull

headgear.

During application of low-pull headgear, higher compressive stresses appeared at the apical third of the canine root and between the molar and premolar roots (Fig. 8). The areas showing the higher concentrations of stress were at the same sites as those produced with the other types of headgear; however, in this case the compressive stress was greater and extended along the mesial surface of the second premolar root, reaching the apical region. Frontozygomatic suture. Anterior and posterior views of this simulated suture showed concentration of stresses along the sutural area, extending to the superior orbital rim of the frontal bone and inferiorly through the body of the zygomatic bone. The distribution of the stress areas showed a greater concentration of stress at the sutural area with the application of a low-pull force vector (Fig. 9). The intensity was reduced when the medium-pull activation was applied, and it was lessened to a greater extent with the high-pull force vector (Fig. 10).

544

Fig. 8. Stress of the canine.

Fig.

Am. J. Orrhod. November 1980

Ayala et al

areas

9. Schematic

created

diagram

by the low-pull

of the anteromedial

force

component

aspect

indicating

of the simulated

severe

rotational

frontozygomatic

the stress areas produced at this sutural region and its vicinity with application Frontal bone. ZB, Zygomatic bone. FZS, Frontozygomatic suture.

(tipping)

suture,

of low-pull

effect

showing

traction.

MI,

With application of a medium-pull vector, fringe patterns were observed at the region of the simulated zygomaticotemporal suture and extended posteriorly along the zygomatic process of the temporal bone toward the mandibular fossa, with higher concentration at the inferior portion of this suture (Fig. 11). The high-and low-pull force vectors also created stress at this suture. However, the intensities were diminished as compared to the stressesproduced by the medium-pull traction and did not extend to the base of the zygomatic process of the temporal bone. Zygomaticomaxillary suture. Stress patterns were developed along the simulated zygomaticomaxillary suture, as observed from its posterior aspect, extending superiorly through the body of the zygomatic bone. Approximately the same intensity and location of stress patterns were observed for the three types of headgear. Zygomatic

arch.

Volume 78 Number 5

Fig.

10. Frontozygomatic

Canine retraction

sutural

area

simulated

as it was affected

with J hook headgear

by the high-pull

application

Fig. 11. Diagram of the simulated zygomatic arch, showing the stress areas produced tion of medium-pull traction. ZTS, Zygomaticotemporal suture. TB, Temporal bone. bone.

545

of force.

by the applicaZB, Zygomatic

Discussion The photoelastic model used in this study proved to be very satisfactory. Since it was three dimensional, it incorporated many geometric characteristics and spatial relationships of a human skull. As defined by Burstone, la the center of resistance of a single-rooted tooth of parabolic shape is situated at 0.4 the distance from the alveolar crest to the apex of the root. A force passing through the center of resistance would produce bodily movement. The stresses developed by the application of the high-pull headgear indicated less tipping tendency than with the other types of headgear as shown by the distribution of stress areas (less compression at the mesioapical part of the canine root than seen with the medium- and low-pull traction). This indicates that the force vector placed at a 40-degree angle above the occlusal plane was closer to the center of resistance. The concentration around the apices were indicative of a slight intrusion tendency. This finding correlates with the study

Am. J. Orthod Nowmber 1980

of Farrant,j who recommended the use of high-pull headgear with J hooks for upper canine retraction. The application of the medium-pull force vector produced a high tipping effect of the canine with less intrusion tendency than that produced by the high-pull traction. The low-pull traction produced the greater tipping effect. The stresses developed were also transmitted to other craniofacial structures, concentrating mainly at the region of the simulated zygomatic sutures. The zygomaticotemporal suture was less affected by the use of high- and low-pull headgear than with the mediumpull force vector, which produced a concentration of stresses that extended posteriorly toward the base of the zygomatic process of the temporal bone. This is of important clinical significance, since this portion of the temporal bone forms the articular eminence, an active component of the temporomandibular joint. From the observations of this study, it is recommended that a high-pull headgear be used for maxillary canine retraction, since its effects were closer to a bodily movement effect in the photoelastic model. This is an important clinical consideration during orthodontic therapy, where unnecessary root movement (round tripping) or tipping of roots into the cortical plate should be kept to a minimum, since these combinations of movements are more prone to cause root-resorption problems. Summary and conclusions A three-dimensional photoelastic model was reproduced from a human skull to permit an analysis of the effects of the forces transmitted to the alveolus and surrounding structures complex by the use of headgear with J hooks for maxillary canine retraction. Three different vectors of force, representing high-, medium-, and low-pull headgear, were applied. The stress areas created by the three different vectors of force showed various degrees of canine tipping. It was deduced from the photoelastic analysis that the high-pull headgear has a slight intrusion tendency which was lessened by the application of medium-pull traction. Tipping effect was observed when the low-pull force was applied. This effect was reduced with the medium-pull force component and was lessened to a greater extent with the application of high-pull traction. Therefore, it was concluded that the high-pull headgear produced the least tipping effect during maxillary canine retraction. Stresses were transmitted to deeper structures of the simulated facial bones; these regions were the frontozygomatic, zygomaticomaxillary , and zygomaticotemporal sutures. The differences regarding the intensity of the stress patterns developed at these sutural areas were at the region of the zygomaticofrontal suture in which the intensity was greater with the low-pull traction and lessened in severity as the medium- and high-pull headgears were applied. Stresses developed at the zygomaticotemporal suture region were higher with the application of the medium-pull traction and extended posteriorly to the base of the zygomatic process of the temporal bone. REFERENCES I. De Alba, J. A., Chaconas, S. J., and Caputo, A. A.: Orthopedic effect of the extraoral chincup appliance on the mandible, AM. J. ORTHOD. 69: 29-41, 1976. 2. Armstrong, M. M.: Controlling the magnitude, direction, and duration of extraoral force, AM. J. ORTHOD. 59: 217-243, 1971. 3. Greenspan, R. A.: Reference ORTHOD.

58: 486-491.

charts

for controlled

extraoral

force application

to maxillary

molars,

AM. J.

1970.

4. Jarabak, J. R., and Fizzell, J. A.: Technique 1972, The C. V. Mosby Company.

and treatment

with the light wire appliance,

ed. 2, St. Louis,

Volume 78 5

Number

5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.

Canine retraction

with J hook headgear

547

Farrant, S. D.: An evaluation of different methods of canine retraction, Br. .I. Orthod. 4: 5-15, 1977. Hickam, J. H.: Directional edgewise orthodontic approach. Part I, J. Clin. Orthod. 8: 617-633, 1974. Hickam, J. H.: Directional edgewise orthodontic approach. Part II, J. Clin. Chthod. 8: 617-633, 1974. Hickam, J. H.: Directional edgewise orthodontic approach. Part III, J. Clin. Orthod. 9: 42-55, 1975. Hickam, J. H.: Directional edgewise orthodontic approach. Part IV, J. Clin. Orthod. 9: 86-100, 197.5. Zak, B.: Photoelashtische analyse in der orthodontischen mechanik, A. Stomatol. 33: 22-37, 1935. Caputo, A. A., Chaconas, S. J., and Hayashi, R. K.: Photoelastic visualization of orthodontic forces during canine retraction, AM. J. ORTHOD. 65: 250-259, 1974. Chaconas, S. J., Caputo, A. A., and Davis, J. C.: The effect of orthopedic forces on the craniofacial complex utilizing cervical and headgear appliances, AM. J. ORTHOD. 69: 527-539, 1976. Evans, F. G.: Stress and strain in bones, Springfield, Ill., 1957, Charles C Thomas Publisher. Glickman, I., Roeber, F. W., Brion, M., and Pameijer, J.: Photoelastic analysis of internal stresses in the periodontum created by occlusal forces, J. Periodontol. 41: 30-35, 1970. Standlee, J. P., Collard, W. E., and Caputo, A. A.: Dentinal defects caused by some twist drills and retentive pins, J. Prosthet. Dent. 24: 192-195, 1970. Brodsky, J. K., Caputo, A. A., and Furstman, L. L.: Root tipping: A photoelastic-histopathologic correlation, AM. J. ORTHOD. 67: l-10, 1975. De Alba, J. A., Caputo, A. A., and Chaconas, S. J.: Effects of orthodontic intermaxillary Class III mechanics on craniofacial structures. Parts I and II, Angle Orthod. 49: 21-36, 1979. Burstone, C. J.: The biomechanics of tooth movement. In Kraus, B. S., and Reidel, R. A.: Vistas in orthodontics, Philadelphia, 1962, Lea & Febiger. Graber, T. M., and Swain, B. F.: Current orthodontic concepts and techniques, ed. 2, Philadelphia, 1975, W. B. Saunders Company. Tweed, C. H.: Clinical orthodontics, St. Louis, 1966, The C. V. Mosby Company. Poulton, D. R.: The influence of extraoral traction, AM. J. ORTHOD. 53: 8-18, 1967. Nikolai, R. J.: An optimum orthodontic force theory as applied to canine retraction, AM. J. ORTHOD. 68: 290-302, 1975. Introduction to stress analysis by the photoelastic coating technique, Technical Bulletin, TDG-1, Malvern, Pa., Photoelastic, Inc.