ORTHODONTIC CORRECTION Of OCCLUSAL CANT USING MINI IMPLANTS:A CASE REPORT Gupta J*, Makhija P.G.**, Jain V*** Abstract: The inability of orthodontists to change the cant of the maxillary occlusal plane without surgical intervention is a limitation of orthodontic treatment. LeFort I osteotomy with asymmetric maxillary impaction is often used to correct this problem. However, canting caused by extruded teeth can be corrected easily with normal orthodontic appliances and temporary anchorage devices. The correction occurs through intrusion of the extruded teeth on one side of the maxilla. A 16- year-old female with canted maxillary occlusal plane was treated in this manner showing the possibility of correcting occlusal plane canting with mini implants thus avoiding surgical intervention. Key Words: Canting, Mini implants, intrusion Introduction Many patients have canted occlusal planes caused by unilaterally extruded maxillary molars or asymmetric mandibular vertical development. Until recently, there was no reliable nonsurgical method to correct this condition. Various methods of molar intrusion have been introduced, including posterior bite blocks, highpull headgear, posterior bite blocks with high-pull headgear, and active vertical correctors with magnets. Unfortunately, there are limitations to these methods in adult patients, and the appliances are highly *senior lecturer ** Professor & HOD, Modern Dental College & Research Center, Indore (M.P) ***Post graduate student, Dept of Peridontics, Saims Indore (M.P.) dependent on patient cooperation 1-3. Recently, miniscrews and miniplates have been introduced to aid orthodontic mechanics, and they have been reported to provide skeletal anchorage to permit molar intrusion 4-15. Sherwood et al 7 described a method of maxillary molar intrusion for open-bite patients, and Umemori et al 8 reported mandibular molar intrusion. Both studies showed good control of vertical excess through molar intrusion. In this case report, we describe a new approach for correcting a canted occlusal plane using miniscrews thus avoiding the possibility of surgical intervention making this an attractive treatment alternative. NJDSR. Volume 3, Number 1, 2015 Page 57
DIAGNOSIS: A 16-year-old female reported with chief complaint of forwardly placed upper front teeth (Fig 1). anteriors, premolars and molars on same side(fig 2,3). Figure 3: Extraoral front smiling Figure 1: Extraoral front Extra oral examination reveals convex profile, high clinical Frankfurt mandibular angle, incompetent lips, increased nasolabial angle. Intraoral examination reveals class I molar relation on right side and class II on left side. Class I canine relation on right side and class II on left side. Mild crowding is present with upper and lower anteriors. There is highly placed canine on left side. The lower midline was shifted towards left side by 2mm. The maxillary occlusal plane is canted on right side due to extrusion of Figure 2: Extraoral profile Cephalometrically patient presents with skeletal class II pattern, vertical growth pattern, proclined upper and lower anteriors and protruded upper and lower lips. TREATMENT OBJECTIVES: The treatment objectives for this patient were to: 1. Correct the upper and lower crowding. 2. Correct the increased overjet. 3. Correct the molar and canine relation on left side. 4. Correct the canted maxillary occlusal plane. 5. Correct the lower midline shift. TREATMENT PLAN: The treatment plan included extraction of upper I premolars, lower I premolar on right side and II premolar on left side. Cant correction using miniscrews by intruding upper right quadrant. NJDSR. Volume 3, Number 1, 2015 Page 58
TREATMENT PROGRESS: After extraction of upper I premolars, lower I premolar on right side and II premolar on left side, treatment began by bonding both arches with MBT 0.022 X 0.028 prescription. Initial leveling and aligning was accomplished in 4 months with 0.014 -in and 0.018-in round nickel titanium wires followed by 0.017 X 0.025- in rectangular nickel titanium wires and then followed by 0.019 X 0.025 stainless steel working wire. Anchorage control was done by transpalatal arch. Initially, two 8 mm miniscrews with a diameter of 1.2mm were implanted on the upper right quadrant between upper right lateral incisor and canine and upper right second premolar and first molar(fig 4). required amount of intrusion achieved the elastics were removed and ligature wire was tied from miniscrews to arch wire to maintain the intrusion achieved(fig 5). A B Figure 5: Intraoral front showing corrected maxillary cant (A & B) Figure 4: Intraoral right side showing implants with elastics for intrusion The miniscrews were implanted at chair side under local anaesthesia. Elastics were used to intrude the teeth and changed every 2 to 3 weeks. The intrusion of the upper right quadrant took approximately 6 months. After the A 3.5-mm posterior open bite was achieved on the right side by intrusion. The remaining space was closed by active tiebacks and overjet was corrected. The miniscrews were removed before the finishing stage(fig 6). DISCUSSION: Changing a canted occlusal plane requires either intrusion of extruded molars or extrusion of intruded molars. Extrusion of teeth can cause clockwise NJDSR. Volume 3, Number 1, 2015 Page 59
A B Figure 6: Extraoral front showing pre(a) and post(b) correction rotation of the mandible, producing a longer face. Intrusion of molars is more stable and reduces facial height 11. Because this patient would benefit from a reduction in facial height intrusion of molars was temporary anchorage and force applied are much lower. Complete osseous integration therefore is not necessary. Orthodontic forces of 250 grams or less have been successfully applied to miniscrews after preferred. Previous studies showed soft tissue healing 12,15,16. In our patient excellent intrusion of molars by using skeletal anchorage with miniplates 5,7,8. For our patient, miniscrews were chosen for skeletal anchorage. The placement and force was applied immediately after loading the miniscrews. One theory that supports early loading is that mechanical retention between the screw and the bone removal of miniscrews require less surgery is sufficient to withstand normal and are easier than placement of orthodontic force levels 17. miniplates 4,6,11. Intrusive mechanics: Prior to the placement of miniscrews Conventional mechanics essentially periapical x ray films are taken to evaluate consist of characterstics of extrusive the space between the roots. In the maxilla mechanics. Conversely the TAD is there are relatively narrow spaces followed by large convex root curvature and distally tipped molar angulation.kyung et al 15 recommended 30 to 40 degree angulations in the maxillary teeth. generally located apically compared with the brackets and in this location the mechanics are advantageous in achieving intrusion. When considering the effects of molar Traditional oral implants require a intrusion to decide whether a molar should waiting period of at least 4 months before occlusal loading. Miniscrews, however are different because they have been used for be intruded the intermaxillary occlusal relationship should be considered along with condition of bone and attached NJDSR. Volume 3, Number 1, 2015 Page 60
gingival should be evaluated. Stability of molar intrusion can be achieved by overcorrection 18. To avoid root resorption, intrusive force levels should be kept near optimal 19. Burstone 19 suggested applying 20 grams of intrusion force for an incisor. Melsen and Fiorelli 20 used about 50 grams buccolingually in an adult. About 200 grams force was used to intrude molars in this study. There are no long-term studies about the stability of intrusion with miniscrews in the orthodontic literature. It has been suggested, however, that normal occlusal forces might help prevent relapse of the intruded teeth. Proffit 21 stated the equilibrium theory: occlusal forces can assist in maintaining the correction. Intrusive forces applied apically to the buccal tooth surface result in rotational movement, leading to molar flaring. Therefore, intrusive forces should be applied to both the buccal and lingual surfaces 4,6. This allowed the use of a transpalatal arch to control the buccal flaring of the maxillary molars instead of adding intrusive forces on the lingual surface along with buccal root torque This mechanical system worked well and eliminated the need for a miniscrew in the midpalatal suture area. Before treatment, there were concerns about mild gingival inflammation around the miniscrews, but no adverse gingival reactions occurred. Gingival infection of the implanted site should not be a concern in patients with good oral hygiene. All miniscrews used in this patient showed no clinically discernible mobility and provided good skeletal anchorage during treatment. CONCLUSION: The inability of orthodontists to change the cant of the maxillary occlusal plane without surgical intervention has been accepted as a limitation of orthodontic treatment but mechanics using TADS following general biomechanical principles has provided a new alternative for cant correction without surgical intervention. REFERENCES: 1. Proffit WR. Contemporary orthodontics. 2nd ed. 1993. Mosby Year Book; St Louis: p. 226-7. 2. Noar JH, Shell N, Hunt NP. The performance of bonded magnets used in the treatment of anterior open bite. Am J Orthod Dentofacial Orthop 1996;110:145-54. 3. Hwang HS, Lee KH. Intrusion of overerupted molars by corticotomy and magnets. Am J Orthod Dentofacial Orthop 2001; 120:209-16. 4. Park YC, Lee SY, Kim DH, Jee SH. Intrusion of posterior teeth using miniscrew implants. Am J NJDSR. Volume 3, Number 1, 2015 Page 61
Orthod Dentofacial Orthop 2003;123:690-4. 5. Sherwood KH, Burch J, Thompson W. Intrusion of supererupted molars with titanium miniplate anchorage. Angle Orthod 2003;73:597-601. 6. Chang YJ, Lee HS, Chun YS. Microscrew anchorage for molar intrusion. J Clin Orthod 2004;38:325-30. 7. Sherwood KH, Burch JG, Thompson WJ. Closing anterior open bites by intrusion of molars using titanium miniplate anchorage. Am J Orthod Dentofacial Orthop 2002;122:593-600. 8. Umemori M, Sugawara J, Mitani H, Nagasaka H, Kawamura H. Skeletal anchorage system for open-bite correction. Am J Orthod Dentofacial Orthop 1999;115:166-74. 9. Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod 1997;31:763-7. 10. Miyawaki S, Koyama I, Inoue M, Mishima K, Sugahara T, Takano- Yamamoto T. Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage. Am J Orthod Dentofacial Orthop 2003;124:373-8. 11. Paik CH, Woo YJ, Boyd RL. Treatment of an adult patient with vertical maxillary excess using miniscrew fixation. J Clin Orthod 2003;37:423-8. 12. Liou EJ, Pai BC, Lin JC. Do miniscrews remain stationary under orthodontic forces? Am J Orthod Dentofacial Orthop 2004;126: 42-7. 13. Deguchi T, Takano-Yamamoto T, Kanomi R, Hartsfield JK, Roberts WE, Garetto LP. The use of small titanium screws for orthodontic anchorage. J Dent Res 2003;82:377-81. 14. Lin JC, Liou EJ. A new bone screw for orthodontic anchorage. J Clin Orthod 2003;37:676-81. 15. Kyung HM, Park HS, Bae SM, Sung JH, Kim IB. Development of orthodontic micro-implants for intraoral anchorage. J Clin Orthod 2003;37:321-8. 16. Roberts WE. When planning to use an implant for anchorage, how long do you have to wait to apply force after implant placement? (letter to the editor). Am J Orthod Dentofacial Orthop 2002;121(1):14A. 17. Costa A, Raffainl M, Melsen B. Miniscrews as orthodontic anchorage: a preliminary report. Int J Adult Orthod Orthognath Surg 1998:13:201-9. 18. Graber V Orthodontics current principles and techniques 5 th ed 2012. Moasby Inc; page 381 19. Burstone CR. Deep overbite correction by intrusion. Am J Orthod Dentofacial Orthop 1977;72:1-22. 20. Melsen B, Fiorelli G. Upper molar intrusion. J Clin Orthod 1996;30:91-6. 21. Proffit WR. Equilibrium theory revisited. Angle Orthod 1978; 48:175-86. Corresponding Author Dr. Jeenal Gupta Senior Lecturer Dept Of Orthodontics Modern Dental College & Research Center, Indore (M.P) EMAIL :- jeenu_85@yahoo.co.in NJDSR. Volume 3, Number 1, 2015 Page 62