POINT/COUNTERPOINT
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Temporary skeletal anchorage devices: The case for miniplates Junji Sugawara Sendai, Japan, and Farmington, Conn
T
he desire to have complete control over anchorage is no doubt universal among orthodontists. About 100 years after orthodontists first started using tooth-borne anchorage for orthodontic treatment, temporary skeletal anchorage devices appeared. It was clear that orthodontics would be a completely new ball game; soon temporary skeletal anchorage devices had become indispensable modalities in modern orthodontic practices for adults. Beyond that, temporary skeletal anchorage devices are at the center of innovations of surgical orthodontics for jaw deformities and the orthopedic treatment of growing patients with skeletal disharmonies. As temporary skeletal anchorage devices were being developed in the 1990s, 2 types were widely put into use. There were great expectations for those that could osseointegrate with bone. This type included retromolar implants,1,2 palatal implants,3 and mini-implants.4 The other type, developing in parallel, was the mechanical retention type and included miniplates5-7 and miniscrews.8 Extensive clinical experience for a wide range of orthodontic problems and detailed evaluations of these modalities over the years have brought us to where we are now: the temporary skeletal anchorage devices in use are miniplates and miniscrews, and both offer mechanical retention. These 2 types of devices actually function best when they are working in collaboration with each other. They function differently, but both are indispensible in cutting-edge orthodontic treatment. Although the focus of this Counterpoint article is on miniplates, miniscrews also have a valuable role in modern orthodontics. Director, SAS Orthodontic Center, Ichiban-Cho Dental Clinic, Sendai, Japan; visiting clinical professor, Division of Orthodontics, Department of Craniofacial Science, School of Dental Medicine, University of Connecticut, Farmington, Conn. Address correspondence to: Junji Sugawara, SAS Orthodontic Center, IchibanCho Dental Clinic, 1-35-5F Hasekura-machi, Aoba-ku, Sendai 980-0824, Japan; e-mail, [email protected]. Am J Orthod Dentofacial Orthop 2014;145:558-65 0889-5406/$36.00 Copyright Ó 2014 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2014.03.010
STRUCTURE OF MINIPLATES
Miniplates are made of titanium or titanium alloys and come in various shapes and sizes. All miniplates have 3 parts: head, arm, and body. The head portion is intraorally exposed and positioned outside the dental arches. The head comes in a variety of shapes: circular,9 hooked,10-12 and tubular.13,14 Some are like bendable sticks that can be manipulated into the desired shape.15 The arm portion is transgingival or transmucosal and tends to be rectangular or round. The body portion is positioned subperiosteally, and its surface is attached to the bone. The body portions are classified into 4 basic shapes: T, L, Y, and I (straight). The body portion is fixed on the bone surface of the zygomatic buttress or the mandibular body with 2 or 3 miniscrews. Although there are many variations in miniplate heads, there are fewer variations in the body portions. SUCCESS RATES AND STABILITY
Perhaps the greatest advantage of miniplates is their high success rate. In a systematic review of temporary skeletal anchorage devices by Sch€atzle et al,16 the average failure rates of various devices were 7.3% for miniplates, 10.5% for palatal implants, and 16.4% for miniscrews. The authors concluded that based on the available evidence in the literature, miniplates provided reliable absolute orthodontic anchorage. In another report, Nagasaka et al17 reported that just 3 of 107 miniplates had to be replaced; this is equivalent to a failure rate of 2.8%. In another report by Choi et al,18 an average failure rate of 7% was reported for miniplates. The failure rates of miniplates were 6% according to Takaki et al19 and just 3% in a study by De Clerck and Swennen20 when miniplates were used as bone-anchored maxillary protraction for growing Class III patients. Clearly, although the numbers vary, all of these reports indicate the overwhelming success of miniplates, whether used in the maxilla or the mandible. Since miniplates are made of pure titanium or titanium alloy, they exhibit onplant effects on the bone surface, and the screws inserted into the cortical bone exhibit implant effects in addition to the mechanical retention effects. This means that in addition to their
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excellent mechanical properties, miniplates have more benefits because of this osseointegration. This double effect undoubtedly contributes to the much higher anchorage value and better stability of miniplates than other temporary skeletal anchorage devices, and this is what makes them the best choice among temporary skeletal anchorage devices. BIOMECHANICAL FEATURES OF MINIPLATES
For molar distalization, whereas the development of miniplates made it possible to predictably move all molars 3 dimensionally, they have been most frequently applied for distalizing the maxillary molars.21,22 The distalization of the maxillary molars is necessary in patients with Class II malocclusion or anterior crowding. The common features of those malocclusions are a narrow maxillary arch and mesial rotation of the maxillary molars. In such cases, the most rational approach is to distalize the maxillary molars using absolute anchorage placed in the buccal side rather than the lingual side. This makes it possible to distalize the molars and rotate them distally simultaneously; this in turn expands the maxillary dentition. To distalize the maxillary molars in such a way, absolute anchorage is put in place at the thick cortical bone of the zygomatic buttress. The placement of miniplates at the zygomatic buttresses presents no difficulty because the practitioner has a clear view of the bone. If miniscrews are used, the practitioner is going in blind. If miniscrews are the temporary skeletal anchorage device of choice, then they should be installed in the palate to distalize the maxillary molars.23 However, because the distalization mechanics with palatally installed miniscrews tends to aggravate the mesial rotation of the maxillary molars, complicated orthodontic mechanics are necessary to offset these undesirable side effects. Miniplates are simply a better option in such cases. The distalization of the mandibular molars is known to be much more difficult than that of the maxillary molars. Whereas traditional mechanotherapies gave practitioners no viable options, with orthodontic miniplates, the distalization of the mandibular molars is no longer a problem.24 All that is required is for patients to undergo minor surgery for the implantation of the miniplates. Since miniplates are put into place with short monocortical screws, there is no risk of injury to the roots or the inferior alveolar nerve. Thus, miniplates are frequently used to correct mandibular anterior crowding, an asymmetrical mandibular dentition, and an anterior crossbite with a Class III dentition, and for decompensation of the mandibular incisors in patients who need mandibular advancement.25
561
For molar intrusion, the incredible difficulty of intruding molars has seemed to practitioners to be an insurmountable obstacle in meeting their goals. With traditional orthodontic mechanics, it was all but impossible. Until recently, in all patients when intrusion of the posterior dentition was required for open-bite correction, orthognathic surgery was the only successful treatment option. At the end of the 1990s, Umemori et al6 reported an open-bite patient who was successfully corrected with miniplates. This was a milestone in the history of orthodontics. Ever since, with miniplates offering absolute anchorage, there has been a nonsurgical treatment option for adults with a skeletal open bite.26 Today, miniplates and miniscrews are indispensable in the treatment of open-bite patients not characterized by a severe anteroposterior jaw relationship. It must be conceded here that a nonsurgical approach with temporary skeletal anchorage devices is by no means easy: in addition to the obvious vertical problems, most open-bite patients also have various anteroposterior and transverse problems, including maxillary protrusion, anterior crossbite, asymmetric dentition, crowding, and congenitally missing teeth. To effectively address the multiple problems we are typically confronted with, the orthodontic mechanics for open-bite correction must be flexible. Miniplates, without doubt, are the most reliable, predictable, and effective modality available to us. In the correction of open-bite patients with relatively less complex orthodontic problems, the use of miniscrews has become a standard option. RECENT INDICATIONS FOR MINIPLATES
With improvements in the designs of miniscrews and new ideas for applications of these improved designs, the indications for miniplates are becoming fewer. Nevertheless, there are clear indications for miniplates, and it does not seem that their importance will dwindle with time. In such cases, the use of miniplates makes orthodontic treatment much shorter and more efficient than it would be if miniscrews were used instead. There are 4 particular areas in which miniplates are indispensable and will most likely remain indispensable. Backup system of miniscrews
Since miniplates are always placed where the cortical bone is relatively thick, such as the zygomatic buttress, the lateral wall of the piriform aperture rim, the mandibular basal bone, and the anterior border of the mandibular ramus, the success rate of miniplates is significantly higher than that of miniscrews. Therefore,
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miniplates function as a backup system, coming to the rescue when miniscrew installation is difficult because of low bone density, when miniscrews fail repeatedly, and when no area is found for miniscrew placement.27 Difficult cases with complex problems
Patients with difficult and complex problems require more thoughtful solutions. The practice of solely using miniscrews in patients with complex orthodontic problems often results in shortfalls. In such patients, miniplates offer more flexibility and allow us to solve problems efficiently. Examples of when miniplates are better options include patients who need their bimaxillary posterior teeth simultaneously distalized to avoid premolar extractions and skeletal open-bite patients with Class II malocclusion who require both distalization and intrusion of their molars. The use of miniplates is advised in patients with a borderline skeletal malocclusion who require camouflage treatment without premolar extractions. Miniscrews are applicable only for the camouflage treatment of borderline patients when the decision has been made for premolar extractions. Surgical orthodontics
In the surgery-first technique, orthognathic surgery is the first step in the correction of skeletal disharmony. In Class III patients, immediately after mandibular setback or maxillary advancement, the patient's profile is temporarily changed to Class II; because no decompensation of the incisors has taken place, occlusion is also altered to a Class II relationship. In the postsurgical orthodontic treatment, miniplates are applied to distalize and intrude the maxillary posterior teeth and/or protract the mandibular dentition. The miniplates are implanted at the zygomatic buttress and mandibular body during orthognathic surgery. With miniplates, premolar extraction tends not to be required for decompensation. Orthopedic treatment
Innovations in orthopedic therapy for growing patients with skeletal malocclusions are also being made thanks to the benefits of miniplates. A new orthopedic treatment for maxillary protraction using pure bone-borne orthopedic force between the maxilla and the mandible has been reported by De Clerck et al28,29 and Heymann et al.30 Orthopedic force is produced by Class III elastics connecting miniplates inserted into the infrazygomatic crests and between the mandibular canines and first premolars bilaterally. Since this intraoral appliance is invisible and completely
563
different from the traditional facemask, long-time use (24 hours per day) is expected. In addition, this appliance can prevent dentoalveolar compensation because the bone-borne anchorage uses miniplates and is not tooth-borne. A similar concept has been suggested by Wilmes et al,31 who reported on a technique characterized by skeletally borne maxillary protraction using miniplates (mentoplates) combined with bone-borne rapid maxillary expansion. There are expectations that a method such as these with miniplates will emerge for growing patients with a skeletal malocclusion, making it possible to avoid jaw surgery. IS IT ALL GOOD?
It would be somewhat deceitful to hail the glories of miniplates and fail to mention the problems that are sometimes associated with their use. In an honest assessment, one must concede that 2 definite problems with miniplates are not associated with miniscrews. The first is that the surgical intervention required for the placement of miniplates is more invasive than that for miniscrews. The other problem has to do with exactly who should put the miniplate into place. With regard to the surgical intervention, since miniplates are typically implanted at the zygomatic buttress and the mandibular body, a mucoperiosteal flap operation is inevitable. After implantation surgery, patients have facial swelling for about a week. These clear disadvantages come hand in hand with the use of miniplates. Thus, a risk-benefit analysis must be carefully carried out to clarify whether the patient will benefit significantly by the use of miniplates rather than miniscrews. So, once the decision is made to go ahead, who should put the miniplate into position? There is no doubt in my mind that orthodontists can confidently install miniscrews by themselves, but can they implant miniplates? The mucoperiosteal flap operation is definitely a challenge for orthodontists. Accordingly, orthodontists are best advised to refer the task of implanting miniplates to an oral surgeon, a periodontist, or an implantologist. However, the health care system in some countries or regions may make such collaboration difficult or expensive and hence create a hurdle for the use of miniplates. Recently, new miniplates have been developed that highlight their advantages and diminish their disadvantages. The feature of the miniplates reported by Chung et al27 is that they are easy for orthodontists to put into place, since they require minimal surgical intervention. We can expect that miniplates will continue to evolve and improve over time, and that this will translate into even greater benefits to our patients.
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ACKNOWLEDGMENTS
I want to express my condolences to the family, friends, and colleagues of Dr Vincent Kokich. He asked me to write this article, and we exchanged e-mails only hours before he passed away on July 24, 2013. News of his death came as quite a shock. He made a great impact not only in the world of orthodontics, but also in the lives of those who had the pleasure to work with him. May his soul rest in peace. REFERENCES 1. Roberts WE, Helm FR, Marshall KJ, Gongloff RK. Rigid endosseous implants for orthodontic and orthopedic anchorage. Angle Orthod 1989;59:247-56. 2. Roberts WE, Nelson CK, Goodacre CJ. Rigid implant anchorage to close a mandibular first molar extraction site. J Clin Orthod 1994; 28:693-704. 3. Wehrbein H, Merz BR, Diedrich P, Glatzmaier J. The use of palatal implants for orthodontic anchorage: design and clinical application of the orthosystem. Clin Oral Implants Res 1996;7:410-6. 4. Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod 1997;31:763-7. 5. Sugawara J, Umemori M, Mitani H, Nagasaka H, Kawamura H. Orthodontic treatment system for Class III malocclusion using a titanium miniplate as an anchorage. Orthod Waves 1998;57: 25-35. 6. 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. 7. Sugawara J. Dr. Junji Sugawara on the skeletal anchorage system. Interview by Dr. Larry W. White. J Clin Orthod 1999;33: 689-96. 8. Park H, Bae S, Kyung H, Sung J. Micro-implant anchorage for treatment of skeletal Class I bialveolar protrusion. J Clin Orthod 2001;35:417-22. 9. Sherwood KH, Burch J, Thompson W. Intrusion of supererupted molars with titanium miniplate anchorage. Angle Orthod 2003; 73:597-601. 10. Sugawara J. A bioefficient skeletal anchorage system. In: Nanda R, editor. Biomechanics and strategies in clinical orthodontics. St Louis: Elsevier Saunders, St. Louis; 2005. p. 295-309. 11. Sugawara J, Nishimura M. Minibone plates: the skeletal anchorage system. Semin Orthod 2005;11:47-56. 12. Sugawara J, Umemori M, Takahashi I, Nagasaka H, Kawamura H. The skeletal anchorage system. In: Cope BJ, editor. OrthoTADs: the clinical guide and atlas. Dallas, Tex: Under Dog Media; 2007. p. 449-532. 13. De Clerck HJ, Geerinckx V, Silicano S. The zygoma anchorage system. J Clin Orthod 2002;36:455-9. 14. Chung KR, Kim YS, Lee YJ. The miniplate with tube for skeletal anchorage. J Clin Orthod 2002;36:407-12. 15. Erverdi N, Tosun N, Keles A. A new anchorage site for the treatment of anterior open bite: zygomatic anchorage. A case report. World J Orthod 2002;3:147-53.
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16. Sch€atzle M, M€annchen R, Zwahlen M, Lang NP. Survival and failure rates of orthodontic temporary anchorage devices: a systematic review. Clin Oral Implants Res 2009;20:1351-9. 17. Nagasaka H, Sugawara J, Kawamura H, Kasahara T. A clinical evaluation on the efficacy of titanium miniplates as orthodontic anchorage. Orthod Waves 1999;58:136-47. 18. Choi BH, Zhu SJ, Kim YH. A clinical evaluation of titanium miniplates as anchors for orthodontic treatment. Am J Orthod Dentofacial Orthop 2005;128:382-4. 19. Takaki T, Tamura N, Yamamoto M, Takano N, Shibahara T, Yasumura T. Clinical study of temporary anchorage devices for orthodontic treatment-stability of micro/miniscrews and miniplates: experience with 455 cases. Bull Tokyo Dent Coll 2010; 5I:151-63. 20. De Clerck HJ, Swennen GR. Success rate of miniplate anchorage for bone anchored maxillary protraction. Angle Orthod 2011;81: 1010-3. 21. Sugawara J, Kanzaki R, Takahashi I, Nagasaka H, Nanda R. Distal movement of the maxillary molars in nongrowing patients with the skeletal anchorage system. Am J Orthod Dentofacial Orthop 2006;129:723-33. 22. Cornelis MA, De Clerck HJ. Maxillary molar distalization with miniplates assessed on digital models: a prospective clinical trial. Am J Orthod Dentofacial Orthop 2007;132:373-7. 23. Kyung SH, Hong SG, Park YC. Distalization of maxillary molars with a midpalatal miniscrew. J Clin Orthod 2003;37:22-6. 24. Sugawara J, Daimaruya T, Umemori M, Nagasaka H, Takahashi I, Kawamura H, et al. Distal movement of mandibular molars in adult patients with the skeletal anchorage system. Am J Orthod Dentofacial Orthop 2004;125:130-8. 25. Sugawara J, Nagasaka H, Kawamura H, Nanda R. Distalization of molars in nongrowing patients with skeletal anchorage. In: Nanda R, Kapila S, editors. Current therapy in orthodontics. St Louis: Mosby Elsevier; 2010. p. 301-20. 26. Sugawara J, Baik UB, Umemori M, Takahashi I, Nagasaka H, Kawamura H, et al. Treatment and posttreatment dentoalveolar changes following intrusion of mandibular molars with application of a skeletal anchorage system (SAS) for open bite correction. Int J Adult Orthod Orthognath Surg 2002; 17:243-53. 27. Chung KR, Kim SH, Kang YG, Nelson G. Orthodontic miniplate with tube as an efficient tool for borderline cases. Am J Orthod Dentofacial Orthop 2011;139:551-62. 28. De Clerck HJ, Cornelis MA, Cevidanes LH, Heymann GC, Tulloch CJ. Orthopedic traction of the maxilla with miniplates: a new perspective for treatment of midface deficiency. J Oral Maxillofac Surg 2009;67:2123-9. 29. De Clerck HJ, Cevidanes L, Baccetti T. Dentofacial effects of bone-anchored maxillary protraction: a controlled study of consecutively treated Class III patients. Am J Orthod Dentofacial Orthop 2010;138:577-81. 30. Heymann GC, Cevidanes LH, Cornelis MA, De Clerck HJ, Tulloch CJ. Three-dimensional analysis of maxillary protraction with intermaxillary elastics to miniplates. Am J Orthod Dentofacial Orthop 2010;137:274-84. 31. Wilmes B, Nienkemper M, Ludwig B, Kau CH, Drescher D. Early Class III treatment with a hybrid hyrax-mentoplate combination. J Clin Orthod 2011;45:15-21.
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Temporary skeletal anchorage devices: The case for miniplates Junji Sugawara Sendai, Japan, and Farmington, Conn
T
he desire to have complete control over anchorage is no doubt universal among orthodontists. About 100 years after orthodontists first started using tooth-borne anchorage for orthodontic treatment, temporary skeletal anchorage devices appeared. It was clear that orthodontics would be a completely new ball game; soon temporary skeletal anchorage devices had become indispensable modalities in modern orthodontic practices for adults. Beyond that, temporary skeletal anchorage devices are at the center of innovations of surgical orthodontics for jaw deformities and the orthopedic treatment of growing patients with skeletal disharmonies. As temporary skeletal anchorage devices were being developed in the 1990s, 2 types were widely put into use. There were great expectations for those that could osseointegrate with bone. This type included retromolar implants,1,2 palatal implants,3 and mini-implants.4 The other type, developing in parallel, was the mechanical retention type and included miniplates5-7 and miniscrews.8 Extensive clinical experience for a wide range of orthodontic problems and detailed evaluations of these modalities over the years have brought us to where we are now: the temporary skeletal anchorage devices in use are miniplates and miniscrews, and both offer mechanical retention. These 2 types of devices actually function best when they are working in collaboration with each other. They function differently, but both are indispensible in cutting-edge orthodontic treatment. Although the focus of this Counterpoint article is on miniplates, miniscrews also have a valuable role in modern orthodontics. Director, SAS Orthodontic Center, Ichiban-Cho Dental Clinic, Sendai, Japan; visiting clinical professor, Division of Orthodontics, Department of Craniofacial Science, School of Dental Medicine, University of Connecticut, Farmington, Conn. Address correspondence to: Junji Sugawara, SAS Orthodontic Center, IchibanCho Dental Clinic, 1-35-5F Hasekura-machi, Aoba-ku, Sendai 980-0824, Japan; e-mail, [email protected]. Am J Orthod Dentofacial Orthop 2014;145:558-65 0889-5406/$36.00 Copyright Ó 2014 by the American Association of Orthodontists. http://dx.doi.org/10.1016/j.ajodo.2014.03.010
STRUCTURE OF MINIPLATES
Miniplates are made of titanium or titanium alloys and come in various shapes and sizes. All miniplates have 3 parts: head, arm, and body. The head portion is intraorally exposed and positioned outside the dental arches. The head comes in a variety of shapes: circular,9 hooked,10-12 and tubular.13,14 Some are like bendable sticks that can be manipulated into the desired shape.15 The arm portion is transgingival or transmucosal and tends to be rectangular or round. The body portion is positioned subperiosteally, and its surface is attached to the bone. The body portions are classified into 4 basic shapes: T, L, Y, and I (straight). The body portion is fixed on the bone surface of the zygomatic buttress or the mandibular body with 2 or 3 miniscrews. Although there are many variations in miniplate heads, there are fewer variations in the body portions. SUCCESS RATES AND STABILITY
Perhaps the greatest advantage of miniplates is their high success rate. In a systematic review of temporary skeletal anchorage devices by Sch€atzle et al,16 the average failure rates of various devices were 7.3% for miniplates, 10.5% for palatal implants, and 16.4% for miniscrews. The authors concluded that based on the available evidence in the literature, miniplates provided reliable absolute orthodontic anchorage. In another report, Nagasaka et al17 reported that just 3 of 107 miniplates had to be replaced; this is equivalent to a failure rate of 2.8%. In another report by Choi et al,18 an average failure rate of 7% was reported for miniplates. The failure rates of miniplates were 6% according to Takaki et al19 and just 3% in a study by De Clerck and Swennen20 when miniplates were used as bone-anchored maxillary protraction for growing Class III patients. Clearly, although the numbers vary, all of these reports indicate the overwhelming success of miniplates, whether used in the maxilla or the mandible. Since miniplates are made of pure titanium or titanium alloy, they exhibit onplant effects on the bone surface, and the screws inserted into the cortical bone exhibit implant effects in addition to the mechanical retention effects. This means that in addition to their
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excellent mechanical properties, miniplates have more benefits because of this osseointegration. This double effect undoubtedly contributes to the much higher anchorage value and better stability of miniplates than other temporary skeletal anchorage devices, and this is what makes them the best choice among temporary skeletal anchorage devices. BIOMECHANICAL FEATURES OF MINIPLATES
For molar distalization, whereas the development of miniplates made it possible to predictably move all molars 3 dimensionally, they have been most frequently applied for distalizing the maxillary molars.21,22 The distalization of the maxillary molars is necessary in patients with Class II malocclusion or anterior crowding. The common features of those malocclusions are a narrow maxillary arch and mesial rotation of the maxillary molars. In such cases, the most rational approach is to distalize the maxillary molars using absolute anchorage placed in the buccal side rather than the lingual side. This makes it possible to distalize the molars and rotate them distally simultaneously; this in turn expands the maxillary dentition. To distalize the maxillary molars in such a way, absolute anchorage is put in place at the thick cortical bone of the zygomatic buttress. The placement of miniplates at the zygomatic buttresses presents no difficulty because the practitioner has a clear view of the bone. If miniscrews are used, the practitioner is going in blind. If miniscrews are the temporary skeletal anchorage device of choice, then they should be installed in the palate to distalize the maxillary molars.23 However, because the distalization mechanics with palatally installed miniscrews tends to aggravate the mesial rotation of the maxillary molars, complicated orthodontic mechanics are necessary to offset these undesirable side effects. Miniplates are simply a better option in such cases. The distalization of the mandibular molars is known to be much more difficult than that of the maxillary molars. Whereas traditional mechanotherapies gave practitioners no viable options, with orthodontic miniplates, the distalization of the mandibular molars is no longer a problem.24 All that is required is for patients to undergo minor surgery for the implantation of the miniplates. Since miniplates are put into place with short monocortical screws, there is no risk of injury to the roots or the inferior alveolar nerve. Thus, miniplates are frequently used to correct mandibular anterior crowding, an asymmetrical mandibular dentition, and an anterior crossbite with a Class III dentition, and for decompensation of the mandibular incisors in patients who need mandibular advancement.25
561
For molar intrusion, the incredible difficulty of intruding molars has seemed to practitioners to be an insurmountable obstacle in meeting their goals. With traditional orthodontic mechanics, it was all but impossible. Until recently, in all patients when intrusion of the posterior dentition was required for open-bite correction, orthognathic surgery was the only successful treatment option. At the end of the 1990s, Umemori et al6 reported an open-bite patient who was successfully corrected with miniplates. This was a milestone in the history of orthodontics. Ever since, with miniplates offering absolute anchorage, there has been a nonsurgical treatment option for adults with a skeletal open bite.26 Today, miniplates and miniscrews are indispensable in the treatment of open-bite patients not characterized by a severe anteroposterior jaw relationship. It must be conceded here that a nonsurgical approach with temporary skeletal anchorage devices is by no means easy: in addition to the obvious vertical problems, most open-bite patients also have various anteroposterior and transverse problems, including maxillary protrusion, anterior crossbite, asymmetric dentition, crowding, and congenitally missing teeth. To effectively address the multiple problems we are typically confronted with, the orthodontic mechanics for open-bite correction must be flexible. Miniplates, without doubt, are the most reliable, predictable, and effective modality available to us. In the correction of open-bite patients with relatively less complex orthodontic problems, the use of miniscrews has become a standard option. RECENT INDICATIONS FOR MINIPLATES
With improvements in the designs of miniscrews and new ideas for applications of these improved designs, the indications for miniplates are becoming fewer. Nevertheless, there are clear indications for miniplates, and it does not seem that their importance will dwindle with time. In such cases, the use of miniplates makes orthodontic treatment much shorter and more efficient than it would be if miniscrews were used instead. There are 4 particular areas in which miniplates are indispensable and will most likely remain indispensable. Backup system of miniscrews
Since miniplates are always placed where the cortical bone is relatively thick, such as the zygomatic buttress, the lateral wall of the piriform aperture rim, the mandibular basal bone, and the anterior border of the mandibular ramus, the success rate of miniplates is significantly higher than that of miniscrews. Therefore,
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miniplates function as a backup system, coming to the rescue when miniscrew installation is difficult because of low bone density, when miniscrews fail repeatedly, and when no area is found for miniscrew placement.27 Difficult cases with complex problems
Patients with difficult and complex problems require more thoughtful solutions. The practice of solely using miniscrews in patients with complex orthodontic problems often results in shortfalls. In such patients, miniplates offer more flexibility and allow us to solve problems efficiently. Examples of when miniplates are better options include patients who need their bimaxillary posterior teeth simultaneously distalized to avoid premolar extractions and skeletal open-bite patients with Class II malocclusion who require both distalization and intrusion of their molars. The use of miniplates is advised in patients with a borderline skeletal malocclusion who require camouflage treatment without premolar extractions. Miniscrews are applicable only for the camouflage treatment of borderline patients when the decision has been made for premolar extractions. Surgical orthodontics
In the surgery-first technique, orthognathic surgery is the first step in the correction of skeletal disharmony. In Class III patients, immediately after mandibular setback or maxillary advancement, the patient's profile is temporarily changed to Class II; because no decompensation of the incisors has taken place, occlusion is also altered to a Class II relationship. In the postsurgical orthodontic treatment, miniplates are applied to distalize and intrude the maxillary posterior teeth and/or protract the mandibular dentition. The miniplates are implanted at the zygomatic buttress and mandibular body during orthognathic surgery. With miniplates, premolar extraction tends not to be required for decompensation. Orthopedic treatment
Innovations in orthopedic therapy for growing patients with skeletal malocclusions are also being made thanks to the benefits of miniplates. A new orthopedic treatment for maxillary protraction using pure bone-borne orthopedic force between the maxilla and the mandible has been reported by De Clerck et al28,29 and Heymann et al.30 Orthopedic force is produced by Class III elastics connecting miniplates inserted into the infrazygomatic crests and between the mandibular canines and first premolars bilaterally. Since this intraoral appliance is invisible and completely
563
different from the traditional facemask, long-time use (24 hours per day) is expected. In addition, this appliance can prevent dentoalveolar compensation because the bone-borne anchorage uses miniplates and is not tooth-borne. A similar concept has been suggested by Wilmes et al,31 who reported on a technique characterized by skeletally borne maxillary protraction using miniplates (mentoplates) combined with bone-borne rapid maxillary expansion. There are expectations that a method such as these with miniplates will emerge for growing patients with a skeletal malocclusion, making it possible to avoid jaw surgery. IS IT ALL GOOD?
It would be somewhat deceitful to hail the glories of miniplates and fail to mention the problems that are sometimes associated with their use. In an honest assessment, one must concede that 2 definite problems with miniplates are not associated with miniscrews. The first is that the surgical intervention required for the placement of miniplates is more invasive than that for miniscrews. The other problem has to do with exactly who should put the miniplate into place. With regard to the surgical intervention, since miniplates are typically implanted at the zygomatic buttress and the mandibular body, a mucoperiosteal flap operation is inevitable. After implantation surgery, patients have facial swelling for about a week. These clear disadvantages come hand in hand with the use of miniplates. Thus, a risk-benefit analysis must be carefully carried out to clarify whether the patient will benefit significantly by the use of miniplates rather than miniscrews. So, once the decision is made to go ahead, who should put the miniplate into position? There is no doubt in my mind that orthodontists can confidently install miniscrews by themselves, but can they implant miniplates? The mucoperiosteal flap operation is definitely a challenge for orthodontists. Accordingly, orthodontists are best advised to refer the task of implanting miniplates to an oral surgeon, a periodontist, or an implantologist. However, the health care system in some countries or regions may make such collaboration difficult or expensive and hence create a hurdle for the use of miniplates. Recently, new miniplates have been developed that highlight their advantages and diminish their disadvantages. The feature of the miniplates reported by Chung et al27 is that they are easy for orthodontists to put into place, since they require minimal surgical intervention. We can expect that miniplates will continue to evolve and improve over time, and that this will translate into even greater benefits to our patients.
American Journal of Orthodontics and Dentofacial Orthopedics
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Counterpoint
ACKNOWLEDGMENTS
I want to express my condolences to the family, friends, and colleagues of Dr Vincent Kokich. He asked me to write this article, and we exchanged e-mails only hours before he passed away on July 24, 2013. News of his death came as quite a shock. He made a great impact not only in the world of orthodontics, but also in the lives of those who had the pleasure to work with him. May his soul rest in peace. REFERENCES 1. Roberts WE, Helm FR, Marshall KJ, Gongloff RK. Rigid endosseous implants for orthodontic and orthopedic anchorage. Angle Orthod 1989;59:247-56. 2. Roberts WE, Nelson CK, Goodacre CJ. Rigid implant anchorage to close a mandibular first molar extraction site. J Clin Orthod 1994; 28:693-704. 3. Wehrbein H, Merz BR, Diedrich P, Glatzmaier J. The use of palatal implants for orthodontic anchorage: design and clinical application of the orthosystem. Clin Oral Implants Res 1996;7:410-6. 4. Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod 1997;31:763-7. 5. Sugawara J, Umemori M, Mitani H, Nagasaka H, Kawamura H. Orthodontic treatment system for Class III malocclusion using a titanium miniplate as an anchorage. Orthod Waves 1998;57: 25-35. 6. 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. 7. Sugawara J. Dr. Junji Sugawara on the skeletal anchorage system. Interview by Dr. Larry W. White. J Clin Orthod 1999;33: 689-96. 8. Park H, Bae S, Kyung H, Sung J. Micro-implant anchorage for treatment of skeletal Class I bialveolar protrusion. J Clin Orthod 2001;35:417-22. 9. Sherwood KH, Burch J, Thompson W. Intrusion of supererupted molars with titanium miniplate anchorage. Angle Orthod 2003; 73:597-601. 10. Sugawara J. A bioefficient skeletal anchorage system. In: Nanda R, editor. Biomechanics and strategies in clinical orthodontics. St Louis: Elsevier Saunders, St. Louis; 2005. p. 295-309. 11. Sugawara J, Nishimura M. Minibone plates: the skeletal anchorage system. Semin Orthod 2005;11:47-56. 12. Sugawara J, Umemori M, Takahashi I, Nagasaka H, Kawamura H. The skeletal anchorage system. In: Cope BJ, editor. OrthoTADs: the clinical guide and atlas. Dallas, Tex: Under Dog Media; 2007. p. 449-532. 13. De Clerck HJ, Geerinckx V, Silicano S. The zygoma anchorage system. J Clin Orthod 2002;36:455-9. 14. Chung KR, Kim YS, Lee YJ. The miniplate with tube for skeletal anchorage. J Clin Orthod 2002;36:407-12. 15. Erverdi N, Tosun N, Keles A. A new anchorage site for the treatment of anterior open bite: zygomatic anchorage. A case report. World J Orthod 2002;3:147-53.
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16. Sch€atzle M, M€annchen R, Zwahlen M, Lang NP. Survival and failure rates of orthodontic temporary anchorage devices: a systematic review. Clin Oral Implants Res 2009;20:1351-9. 17. Nagasaka H, Sugawara J, Kawamura H, Kasahara T. A clinical evaluation on the efficacy of titanium miniplates as orthodontic anchorage. Orthod Waves 1999;58:136-47. 18. Choi BH, Zhu SJ, Kim YH. A clinical evaluation of titanium miniplates as anchors for orthodontic treatment. Am J Orthod Dentofacial Orthop 2005;128:382-4. 19. Takaki T, Tamura N, Yamamoto M, Takano N, Shibahara T, Yasumura T. Clinical study of temporary anchorage devices for orthodontic treatment-stability of micro/miniscrews and miniplates: experience with 455 cases. Bull Tokyo Dent Coll 2010; 5I:151-63. 20. De Clerck HJ, Swennen GR. Success rate of miniplate anchorage for bone anchored maxillary protraction. Angle Orthod 2011;81: 1010-3. 21. Sugawara J, Kanzaki R, Takahashi I, Nagasaka H, Nanda R. Distal movement of the maxillary molars in nongrowing patients with the skeletal anchorage system. Am J Orthod Dentofacial Orthop 2006;129:723-33. 22. Cornelis MA, De Clerck HJ. Maxillary molar distalization with miniplates assessed on digital models: a prospective clinical trial. Am J Orthod Dentofacial Orthop 2007;132:373-7. 23. Kyung SH, Hong SG, Park YC. Distalization of maxillary molars with a midpalatal miniscrew. J Clin Orthod 2003;37:22-6. 24. Sugawara J, Daimaruya T, Umemori M, Nagasaka H, Takahashi I, Kawamura H, et al. Distal movement of mandibular molars in adult patients with the skeletal anchorage system. Am J Orthod Dentofacial Orthop 2004;125:130-8. 25. Sugawara J, Nagasaka H, Kawamura H, Nanda R. Distalization of molars in nongrowing patients with skeletal anchorage. In: Nanda R, Kapila S, editors. Current therapy in orthodontics. St Louis: Mosby Elsevier; 2010. p. 301-20. 26. Sugawara J, Baik UB, Umemori M, Takahashi I, Nagasaka H, Kawamura H, et al. Treatment and posttreatment dentoalveolar changes following intrusion of mandibular molars with application of a skeletal anchorage system (SAS) for open bite correction. Int J Adult Orthod Orthognath Surg 2002; 17:243-53. 27. Chung KR, Kim SH, Kang YG, Nelson G. Orthodontic miniplate with tube as an efficient tool for borderline cases. Am J Orthod Dentofacial Orthop 2011;139:551-62. 28. De Clerck HJ, Cornelis MA, Cevidanes LH, Heymann GC, Tulloch CJ. Orthopedic traction of the maxilla with miniplates: a new perspective for treatment of midface deficiency. J Oral Maxillofac Surg 2009;67:2123-9. 29. De Clerck HJ, Cevidanes L, Baccetti T. Dentofacial effects of bone-anchored maxillary protraction: a controlled study of consecutively treated Class III patients. Am J Orthod Dentofacial Orthop 2010;138:577-81. 30. Heymann GC, Cevidanes LH, Cornelis MA, De Clerck HJ, Tulloch CJ. Three-dimensional analysis of maxillary protraction with intermaxillary elastics to miniplates. Am J Orthod Dentofacial Orthop 2010;137:274-84. 31. Wilmes B, Nienkemper M, Ludwig B, Kau CH, Drescher D. Early Class III treatment with a hybrid hyrax-mentoplate combination. J Clin Orthod 2011;45:15-21.
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May 2014 Vol 145 Issue 5
