Treatment of Class III Malocclusions Using Miniplate and Mini-Implant Anchorage Seung-Hak Baek, Il-Hyung Yang, Keun-Woo Kim, and Hyo-Won Ahn Orthodontic miniplates and mini-implants have become essential tools for anchorage management. This article presents the treatment of growing Class III patients with the use of the facemask in conjunction with the mini-plate (FM/MP), and also the treatment of postadolescent Class III patients camouflaged by the use of mini-implants as skeletal anchorage. For FM/MP therapy, an orthopedic force of more than 500 g per side with a vector of 30 downward and forward from the occlusal plane was applied 12-14 hours per day after placement of the curvilinear type surgical miniplates in the zygomatic buttress areas of the maxilla. After 16 months of maxillary protraction, significant forward displacement of the maxilla (point A) was found. Side effects of maxillary protraction, such as labial tipping of the upper incisors, extrusion of the upper molars, clockwise rotations of the mandibular plane, and bite opening, which are usually observed using tooth-borne anchorage, were minimized. Therefore, FM/MP can be an effective alternative treatment modality for maxillary hypoplasia with minimal unwanted side effects. Class III patients in the postadolescent period can be camouflaged with fixed appliance by the use of miniimplants as skeletal anchorage. The authors prefer to install the mini-implants in the buccal attached gingiva between the upper second premolar and the first molar. Class I intraarch elastics can be used to decompensate the already labially inclined upper incisors. Class III interarch elastics can be used for distal en masse movement of the lower dentition. Vertical elastics can be used to correct an open bite problem if present. Extrusion or intrusion of the lower molars can be controlled with strategic positioning of the mini-implants in the lower arch. With an understanding of biomechanics, the careful use of miniplates and mini-implants can expand the boundaries and scope of conventional fixed appliance therapy. (Semin Orthod 2011;17:98-107.) 2011 Elsevier Inc. All rights reserved. Associate Professor, Department of Orthodontics, School of Dentistry, Dental Research Institute, Seoul National University, Seoul, South Korea; Fellow Doctor and Graduate Student (PhD), Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, South Korea; Fellow Doctor and Graduate Student (PhD), Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, South Korea; Resident and Graduate Student (PhD), Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, South Korea. Address correspondence to Seung-Hak Baek, DDS, MSD, PhD, Associate Professor, Department of Oral and Maxillofacial Surgery, School of Dentistry, Dental Research Institute, Seoul National University, Yeonkun-dong 28, Jongro-ku, Seoul, South Korea. E-mail: drwhite@snu.ac.kr 2011 Elsevier Inc. All rights reserved. 1073-8746/11/1702-0$30.00/0 doi:10.1053/j.sodo.2010.12.003 Facemask in Conjunction with Miniplate as Skeletal Anchorage (FM/MP) Therapy for Growing Class III Patients The protraction facemask has been used to stimulate sutural growth at the circummaxillary suture sites in growing Class III patients with mild-to-moderate maxillary hypoplasia. 1-3 However, the use of tooth-borne devices as an anchor, such as palatal arches or expansion appliances, can lead to unwanted side effects, such as labioversion of the upper incisors, extrusion of the upper molars, counterclockwise rotation of the upper occlusal plane, and eventual clockwise rotation of the mandible. 3-6 98 Seminars in Orthodontics, Vol 17, No 2 (June), 2011: pp 98-107
Class III Malocclusion and Miniplate/Mini-Implant 99 Table 1. Skeletal and Dental Measurements Before and After Treatment Initial Debonding SNA 76.0 80.6 SNB 81.4 77.7 ANB 5.4 2.9 A-N perp 3.4 2.2 Pog-N perp 4.7 0.6 FMA 32.7 37.0 U1 to FH 123.14 119.48 IMPA 88.2 76.3 Interincisal angle 121.48 135.5 Figure 1. Schematic drawing of installation and force vector of the miniplate. (Courtesy of Professors BK Cha and SM Kim.) Placement of miniplates in the zygomatic buttress area or other areas in the maxilla can transmit the orthopedic force to the maxilla directly and minimize the rotational effect. 7-11 Growing patients with a Class III malocclusion and maxillary hypoplasia can be successfully treated with FM/MP. The protocols of FM/MP are as follows: under local anesthesia, a 1 2-cm horizontal vestibular incision is made just below the zygomatic buttress area and the zygomatic buttress is exposed with a subperiosteal flap. Curvilinear type surgical miniplates (Martin, Tuttlinger, Germany) are bent to conform to the anatomical shape of the zygomatic buttress. The bone of the zygomatic buttress has sufficient thickness and bone quality for attachment of the miniplates. 12 Placement of miniplates in this area is close to the center of resistance of the nasomaxillary complex so the force vector can be placed close to the center of rotation of the nasomaxillary complex. 7,13,14 The mesial end hole of the miniplate was modified to the shape of a hook for attachment of elastics. After the miniplates are Figure 2. Initial records. (A) Facial photographs; (B) Intraoral photographs; (C) Lateral cephalograms. (Color version of figure is available online.)
100 Baek et al Figure 3. Treatment progress. (A) After 15 months, the overjet was decreased. (B) The fixed appliance was placed. (C) Normal overbite and overjet were established. (Color version of figure is available online.) placed into the zygomatic buttress areas, 3 selftapping type screws per side are used to fix the miniplates. The mesial end of the miniplate should be exposed through the attached gingiva between the upper canine and the first premolar to control the vector of elastic traction. Four weeks after placement of the miniplates, the mobility of the miniplates is checked and an orthopedic force of more than 500 g per side with a vector of 30 downward and forward from Figure 4. Records at debonding. (A) Facial photographs. (B) Intraoral photographs. (C) Lateral cephalograms. (Color version of figure is available online.)
Class III Malocclusion and Miniplate/Mini-Implant 101 Figure 5. Evaluation of the treatment changes. (A) Superimposition between pre- (black) and post-treatment lateral cephalogram tracings (red in the online version). (B) Comparison of soft tissue profile between pre-, midand post-treatment. (Color version of figure is available online.) the occlusal plane is applied for 12-14 hours per day (Fig 1). It is recommended to overcorrect the malocclusion into a positive overjet and slight Class II canine and molar relationship. Patients with cleft lip and or palate often present with a Class III malocclusions with maxillary hypoplasia. Scar tissue that develops after cleft lip and palate surgery can disturb normal maxillary growth. Because of hypoplasia of the maxillary and relative prognathism of the mandible, treatment with conventional facemask therapy might not achieve satisfactory results. 15 The following Case 1 illustrates the treatment of a cleft palate patient diagnosed with skeletal Class III malocclusion and an anterior open bite using FM/MP. Case 1 Diagnosis and Treatment Plan Figure 2 shows a 12-year-old girl who presented with a history of a repaired cleft palate and a skeletal Class III malocclusion. The patient presented with a concave facial profile, an anterior crossbite, and an anterior open bite. The cervical vertebrae maturation index showed a stage 4 skeletal maturation, indicating that her skeletal Figure 6. Class III treatment mechanics using distal en masse movement of the lower dentition with Class III elastics and eventual counterclockwise rotation (flattening) of the occlusal plane. (Color version of figure is available online.)
102 Baek et al age was beyond her pubertal growth spurt. 16 The cephalometric analysis showed a skeletal Class III open-bite tendency with a steep mandibular plane angle. This hyperdivergent growth pattern contraindicated conventional facemask therapy (Table 1). Although growth observation for 2 years and then reassessment was proposed to the patient, the patient s parents elected to receive the FM/MP therapy. Treatment Progress FM/MP therapy was started 4 weeks after placement of the miniplates according to the protocol advocated by the authors (Fig 3A). During protraction, fixed appliances were placed to align the dentition (Fig 3B, C). Treatment Results Figures 4 and 5 and Table 1 show the results of treatment. There was significant forward movement of the A point (A-N perp, 5.6 mm; ANB angle, 8.3 ). Class II canine and molar relationships and normal overbite and overjet were obtained. A slight counterclockwise rotation of the occlusal plane angle occurred, indicating that there was a minimal side effect of extrusion of the upper molars as evidenced by the tracing superimpositions. Although the FMA angle was increased 4.3, the anterior open bite was corrected by downward and forward movement of the maxilla. Slight lingual tipping of the upper incisors (U1-FH, 3.7 ) occurred despite correction of the anterior cross bite and open bite. Figure 7. Schematic drawing of Class III camouflage treatment using mini-implant anchorage and elastics. (A) Mini-implant anchorage in the upper arches and elastics produce a similar result with conventional Class III mechanics without significant side effects. (B) Mini-implant anchorage between the lower second premolar and first molar and elastics produce intrusion of the lower molars and counterclockwise rotation of the occlusal plane. (C) Mini-implant anchorage in the retromolar pad area and elastics produce extrusion of the lower molars and clockwise rotation of the occlusal plane. (Color version of figure is available online.)
Class III Malocclusion and Miniplate/Mini-Implant 103 Figure 8. Initial records (T0). (A) Facial photographs. (B). Intraoral photographs. (C) Lateral cephalograms. (Color version of figure is available online.) Treatment of Postadolescent Class III Patients by the Use of Fixed Appliances in Conjunction with Mini-Implants as Skeletal Anchorage Class III patients with mild-to-moderate skeletal discrepancies can be camouflaged by orthodontic tooth movement. A half-step Class III molar relationship could be corrected into a Class I molar relationship by the use of distal en masse movement of the lower dentition with Class III elastics, counterclockwise rotation (flattening) of the occlusal plane, and dentoalveolar compensation (Fig 6). 17-25 However, this treatment mechanics has side effects, including labioversion of the upper incisors, extrusion of the upper molars, and clockwise rotation of the mandible. With recent development of mini-implant anchorage, the side effects of Class III camouflage treatment can be minimized. 26,27 The authors prefer to insert the mini-implants in the buccal attached gingiva between the upper second premolar and the first molar. Class I intraarch elastics can be used to decompensate the already labially inclined upper incisors. Class III interarch elastics can be used for distal en masse movement of the lower dentition. Vertical elastics can be used to correct open bite problem if present (Fig 7A). Extrusion or intrusion of the lower molars can be controlled with strategic positioning of the miniimplants in the lower arch (Fig 7B, C). The following Case 2 illustrates the camouflage treatment of a postadolescent Class III patient using fixed appliances in conjunction with mini-implants as skeletal anchorage. Case 2 Diagnosis and Treatment Plan Figure 8 shows an 18-year-old female patient who presented with lower anterior crowding, ectopic eruption of the upper second premolars, Table 2. Skeletal and Dental Measurements Before and After Treatment Initial Debonding SNA 73.8 75.2 SNB 73.5 73.6 ANB 0.3 1.6 A-N perp 2.0 0.8 Pog-N perp 0.1 1.5 FMA 27.1 27.2 U1 to FH 117.3 114.2 IMPA 83.0 82 Interincisal angle 132.5 136.6
104 Baek et al Figure 9. Treatment progress. (A) After extraction of the upper second premolars, leveling and alignment were started. (B) After leveling and alignment, there was no significant aggravation of the overbite and overjet. (C) The mini-implants were installed in the upper arch and Class (I) III and vertical elastics were used. (Color version of figure is available online.) protrusive lower lip, and mild skeletal Class III malocclusion. The cephalometric analysis showed a skeletal Class III open bite tendency with lingually inclined lower incisors (Table 2). Because the patient elected to receive a nonsurgical treatment option, the treatment plan was extraction of the upper second premolar teeth and Class III camouflage treatment with fixed appliances using mini-implants as skeletal anchorage. Treatment Progress After extraction of the upper second premolar teeth, leveling and alignment were started (Fig 9A). At the end of leveling and alignment, there was no significant aggravation of the overbite and overjet while the lower anterior crowding was resolved (Fig 9B). At the 17th month of treatment, 0.019 0.025 stainless-steel wires were used in both arches. The mini-implants were placed in the upper posterior area according to the protocol advocated by the authors and Class I intraarch elastics, Class III interarch elastics (1/4, 6 oz) and anterior vertical elastics (3/16, 6 oz) were used for key correction and occlusal settling (Fig 9C). Treatment Results Figures 10 and 11 and Table 2 show the results of treatment. After 25 months of fixed appliance treatment with mini-implants as skeletal anchorage, there was resolution of the anterior crowding, establishment of Class I canine and Class II molar relationship, and decrease of the lower lip protrusion. Significant distal en mass movement of the lower dentition resulted from mini-implants and Class III interarch elastics. Slight decompensation of the labially inclined upper incisors (U1-FH 3.0 ) occurred attributable to mini-implants and Class I intraarch elastics. Normal overbite was achieved by anterior vertical elastics. The treatment results were well maintained after 1 year of retention (Fig 12). Discussion Advantages of FM/MP Therapy for Growing Class III Patients Because the miniplates are independent of the dentition, there are several advantages in FM/
Class III Malocclusion and Miniplate/Mini-Implant 105 Figure 10. Records at debonding (T1). (A) Facial photographs. (B) Intraoral photographs. (C) Lateral cephalograms. (Color version of figure is available online.) MP. Firstly, simultaneous orthodontic treatment and maxillary protraction using FM/MP is possible. Secondly, FM/MP can be used for relatively longer periods than conventional facemask therapy and result in uniform advancement of the maxilla during the entire treatment period. Finally, MP/FM can minimize clockwise rotation of the mandible and prevent aggravation of the facial profile in the vertical growth pattern. Figure 11. Evaluation of the treatment changes. (A) Superimposition between T0 (black) and T1 lateral cephalogram tracings (red in the online version). (B) Distal en masse movement of the lower dentition (Left: T0; Right: T1). (Color version of figure is available online.)
106 Baek et al Conclusions Careful use of miniplates and mini-implants together with an understanding of the biomechanical principals involved can expand the boundaries and scope of conventional fixed appliance therapy. Figure 12. One-year retention records (T2). (A) Facial photographs. (B) Intraoral photographs. (Color version of figure is available online.) Advantages of Camouflage Treatment of Postadolescent Class III Patients Using Fixed Appliances in Conjunction with Mini-Implants as Skeletal Anchorage Insertion of mini-implants in the buccal attached gingiva between the upper second premolar and the first molar is relatively easier and shows a higher success rate than the lower posterior area. 28 When Class III interarch elastics are used for distal en masse movement of the lower dentition, the mini-implants inserted in the upper posterior area can decrease the side effects, such as labioversion of the upper incisors, extrusion of the upper molars, counterclockwise rotation of the upper occlusal plane, and eventual clockwise rotation of the mandible. In addition, Class I intraarch elastics from the mini-implants inserted in the upper area posterior to the upper archwire can decompensate the already labially inclined upper incisors and decrease upper lip protrusion and the nasolabial angle. This Class III mechanics with mini-implants can produce better changes in the both the upper and lower dentitions without significant side effects. References 1. McNamara JA: An orthopedic approach to the treatment of Class III malocclusion in young patients. J Clin Orthod 21:598-608, 1987 2. Delaire J: Maxillary development revisited: Relevance to the orthopaedic treatment of Class III malocclusions. Eur J Orthod 19:289-311, 1997 3. Nartallo-Turley PE, Turley PK: Cephalometric effects of combined palatal expansion and facemask therapy on Class III malocclusion. Angle Orthod 68:217-224, 1998 4. Baik HS: Clinical results of the maxillary protraction in Korean children. Am J Orthod Dentofac Orthop 108: 583-592, 1995 5. Kapust AJ, Sinclair PM, Turley PK: Cephalometric effects of face mask/expansion therapy in Class III children: A comparison of three age groups. Am J Orthod Dentofac Orthop 113:204-212, 1998 6. Hickham JH: Maxillary protraction therapy: Diagnosis and treatment. J Clin Orthod 25:102-113, 1991 7. Umemori M, Sugawara J, Mitani H, et al: Skeletal anchorage for open-bite correction. Am J Orthod Dentofac Orthop 115:166-174, 1999 8. Kircelli BH, Pektaş ZO, Uçkan S: Orthopedic protraction with skeletal anchorage in a patient with maxillary hypoplasia and hypodontia. Angle Orthod 76:156-163, 2006 9. Cha BK, Lee NK, Choi DS: Maxillary protraction treatment of skeletal Class III children using miniplates anchorage. Kor J Orthod 37:73-84, 2007 10. Kircelli BH, Pektas ZO: Midfacial protraction with skeletally anchored face mask therapy: A novel approach and preliminary results. Am J Orthod Dentofac Orthop 133:440-449, 2008 11. Lee NK, Baek SH, Choi DS, et al: Influence of miniplate shapes as skeletal anchorage for application of orthopedic force: a three-dimensional finite element analysis. J Korean Academy Maxillofac Plast Reconstr Surg 30:345-352, 2008 12. Sugawara J, Nishimura M, Nagasaka H, et al: Temporary Anchorage Devices in Orthodontics. Chapter 15: Skeletal Anchorage System Using Orthodontic Miniplates. St Louis, Mosby, 2009, p 320 13. Tanne K, Matsubara S, Sakuda M: Location of the centre of resistance for the nasomaxillary complex studied in a three dimensional finite element model. Br J Orthod 22:227-232, 1995 14. Ngan PW, Hagg U, Yiu C, et al: Treatment response and long-term dentofacial adaptations to maxillary expansion and protraction. Semin Orthod 3:255-264, 1997 15. Baek SH, Moon HS, Yang WS: Cleft type and Angle s classification of malocclusion in Korean cleft patients. Eur J Orthod 24:647-653, 2002
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