Versatility of Skeletal Anchorage in Orthodontics

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Tony Cheuk-Kit Lee, BDS, MOrth, MOrthRCS1 VERSATILITY OF SKELETAL ANCHORAGE

Michael Tat-Chi Leung, IN ORTHODONTICS BDS, MOrth, MOrthRCS1 The purpose of this article is to update clinicians on the current con- Ricky Wing-Kit Wong, BDS, cepts and versatile uses and clinical applications of skeletal anchor- 2 MOrth, PhD, MOrthRCS age in orthodontics. Topics discussed include clinical indications, implant types, surgical sites, biomechanics, treatment time, and treat- A. Bakr M. Rabie, PhD, ment outcomes. World J Orthod 2008;9:221–232. MSc, Cert Ortho3

rthodontics is bound by biological minimize compliance concerns and may Oand physical constraints. Biologi- achieve a better outcome. These include cally, the response of periodontium sur- retraction of anterior teeth, lingual ortho- rounding the teeth to be moved has lim- dontics, orthopedics, and expansion. its; physical constraints can be largely 2. Procedures in which the results can- summed up by Newton’s third law, which not or can hardly be achieved with states that for every action, there is an conventional orthodontics, including equal but opposite reaction. When a retraction of the whole dentition and tooth is moved, an unwanted movement distalization of molars, intrusion of in the anchorage unit resulting from the posterior teeth, intrusion of anterior reaction force must be considered. Thus, teeth, and protraction of molars or skeletal anchorage is increasingly being the whole dentition. favored over tooth anchorage. This trend 3. Procedures in which the orthodontic represents an important paradigm shift movement of a single tooth is difficult in orthodontics. to achieve and the use of an implant Since the publication of a case report is adjunctive, including insufficient of the intrusion of maxillary incisors tooth anchorage and/or periodontal

1 with a bone screw by Creekmore and disease in adulthood, uprighting of Graduate Student, Discipline of 1 Orthodontics, Faculty of Dentistry, Eklund, there have been numerous molars and disimpaction, and extru- The University of Hong Kong, Hong reports concerning implant anchorage. sion and intrusion of individual teeth. Kong SAR, China. In the 1980s, conventional endosseous 2Associate Professor, Discipline of dental implants were the focus of the In this literature review, the available Orthodontics, Faculty of Dentistry, skeletal anchorage system.2–4 Recently, studies on skeletal anchorage in 11 The University of Hong Kong, Hong Kong SAR, China. skeletal anchorage systems, such as applications are collected and tabulated 5–7 8–10 3Professor, Discipline of Orthodon- onplants, miniplates, and micro- to provide orthodontists a concise sum- tics, Faculty of Dentistry, The Univer- implants,11–13 have been developed, mary of achievable treatment results. sity of Hong Kong, Hong Kong SAR, and many ongoing research studies on China. skeletal anchorage are beginning to CORRESPONDENCE show its versatility. Clinical applications RETRACTION Dr A. Bakr M. Rabie of skeletal anchorage in orthodontics OF ANTERIOR TEETH Discipline of Orthodontics can be divided into 3 main groups (Fig 1): Faculty of Dentistry Although the first report of the applica- The University of Hong Kong 1. Procedures in which the results could tion of a microimplant described the 2/F, Prince Philip Dental Hospital 34 Hospital Road, Sai Ying Pun be achieved by conventional orthodon- intrusion of maxillary anterior teeth, Hong Kong SAR, China tics without implants, but the applica- retraction of anterior teeth is still the prin- E-mail: [email protected] tion of skeletal anchorage would cipal orthodontic procedure that involves

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Fig 1 Clinical application of the skeletal anchorage system. Skeletal anchorage

Achievable by conventional mechanics?

Yes No, or hardly achievable

I. Minimize patient compliance II. Movement of group of III. Movement of individual and may achieve a better result teeth tooth

1. Retraction of anterior 5. Retraction of the whole 9. Insufficient tooth teeth dentition anchorage and/or periodontal disease in adulthood 6. Intrusion of posterior 2. Lingual orthodontics teeth 10. Uprighting of molars and disimpaction 7. Intrusion of anterior 3. Orthopedics teeth 11. Extrusion and intrusion of individual 8. Protraction of molars or 4. Expansion tooth the whole dentition

skeletal anchorage. Three systems can be ORTHOPEDICS used to retract the anterior teeth: palatal implants,4,14–18 miniscrews,11,13,19–25 mini- The main orthodpedic effect achievable plates,8 and the zygoma implant.26,27 The by the skeletal anchorage system is pro- use of implants provides absolute anchor- traction of the maxilla. Implants can be age, thereby enabling the premolar extrac- placed in different sites of the maxilla, tion spaces to be fully utilized for the dentoalveolus,32 processus pterygoi- retraction of maxillary anterior teeth so as deus,33 or lateral nasal wall of the max- to reduce lip protrusion and correct severe illa34 as anchorage during face mask pro- overjet (Table 1). traction. The technique can result in as much as 8 mm of protraction of the hypoplastic maxilla (Table 3). LINGUAL ORTHODONTICS

One of the difficulties in lingual orthodon- EXPANSION tics is controlling anchorage. Several case reports have described the use of The use of titanium screws as skeletal microimplants as a means toward achiev- anchorage during rapid maxillary expan- ing this end.21,28–31 Microimplants used sion (RPE) after surgical splitting of the in this way address esthetic and social maxilla can provide better anchorage and concerns, especially in anchorage- less buccal tilting of posterior teeth.35 A demanding cases, not only by eliminating study of this technique included 2 adults the use of headgear but also by making aged 21 and 23 years and achieved 8 treatment invisible (Table 2). mm of expansion after 21 and 45 days, respectively (Table 4).

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Table 1 Retraction of anterior teeth Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Palatal implant system Wehrbein et al, 19984 Palatal implant, Orthosys- Center of anterior Implant was connected to Not mentioned In the Class II case, overjet reduced by tem, Institute Straumann, palate transpalatal arch (TPA) and first 8 mm; in the Class III case, unilateral Waldenburg, Switzerland or second premolars as anchor- distalization of posterior teeth was (2 patients) age achieved. Implant-to-bone contact was between 34% and 93%, mean 75% Wehrbein et al, 199914 Palatal implant Center of anterior Implant was connected to a 11 months Ϯ 3 The right and left canines were (9 patients) palate TPA and second premolars as weeks (from start retracted 6.6 mm and 6.4 mm anchorage; ~1.5 N was applied of treatment to respectively, and the mean overjet per side to retract canine and correction of Class reduction was 6.2 mm then ~2 N to retract entire I canine relation- anterior segment ship and overjet) Wehrbein et al, 199615,16 Palatal implant Midsagittal anterior Implant was connected to TPA 9 months 8 mm retraction of incisors and (6 patients) palatal region and second premolars as canines anchorage; Sentalloy traction springs retracted canine and then entire anterior segment Bernhart et al, 200017 Brånemark, Nobel Biocare, Paramedian region of Mixed 5–22.8 months Time-related success probability was Sweden (21 patients) palate 84.8% after 22.9 months Miniscrew system Park et al, 200411 Microscrew, Stryker Patient 1: Bilaterally in Ni-Ti coil spring from implant for 19 months ANB angle decreased from 5 to 0.5 de- Leibinger, Portage, the alveolar bone en masse retraction of maxil- grees, SNA decreased by 2.5 degrees, Michigan, USA (3 patients) between maxillary sec- lary anterior teeth and SNB increased by 2 degrees; max- ond premolar and first illary anterior teeth retracted bodily by molar 7 mm, with 2 mm of intrusion Patient 2: Between the Intruding force was applied 21 months Mandibular molars were uprighted mandibular first and from the microscrew implants and moved mesially, followed by clo- second molars to a mandibular archwire distal sure of mandibular angle and an to the first molars increase in SNB angle Patient 3: Bilaterally in Ni-Ti coil spring from implant 34 months Maxillary teeth were distalized by 13 the alveolar bone retracted maxillary anterior mm with 2 mm of intrusion between maxillary sec- teeth ond premolar and first molar Bae et al, 200213 Microimplant, OsteoMed, Interradicular buccal Microimplant was connected to 11 months The maxillary anterior teeth retracted Addison, Texas, USA space between maxil- closing loops by overlay wire on bodily without any loss of anchorage (1 patient) lary second premolar maxillary posterior segment and first molar Chung et al, 200519 C-orthodontic microim- Interdental spaces C-implant was used with a hook 15 months Mandibular dentition was distalized 5 plants, Dentium between maxillary sec- for Class III elastics to distalize mm on the left side and 2 mm on the (1 patient) ond premolars and first mandibular dentition right side molars Costa A et al, 199820 Miniscrew, Cizeta, Bologna, Maxilla: inferior surface Mixed Not mentioned Miniscrew was an alternative to stan- Italy (19 patients) of the anterior nasal dard implants, special implants, spine (ANS), midpalatal onplants, miniplates, and zygoma suture, infrazygomatic wires crest Mandible: retromolar position, edentulous areas of the alveolar process, laterally in the molar and premolar region, symphysis Park et al, 200122 Microscrew, Stryker Buccal alveolar bone Ni-Ti coil spring from implant to Not mentioned Correction of bimaxillary protrusion; Leibinger, between maxillary sec- canine and hook in archwire for bodily retraction of maxillary anterior Microimplant, OsteoMed ond premolars and first retraction teeth and uprighting of mandibular (1 patient) molars and between molars mandibular first and second molars Park et al, 200523 Microscrew, Stryker Maxilla: Between sec- Partial canine retraction fol- 18 months Maxillary anterior teeth were Leibinger (1 patient) ond premolar and first lowed by en masse retraction retracted with 6-mm distal movement molar on both sides of 6 anterior teeth by Ni-Ti coil and 2-mm intrusion; maxillary poste- Mandible: between first spring attached to the micro- rior teeth moved 2.5 mm distally, con- and second molars on screw current with retraction of anterior both sides teeth Park et al, 200524 Miniscrew, Gebruder Buccally between sec- Elastics were attached between 14 months Upper lip was retracted by 3.8 mm Martin, Tuttlingen, ond premolars and first the lever arms in the acrylic and lower lip by 5.8 mm; significant Germany (1 patient) molars splints and miniscrews in the reduction in lip protrusion and an maxillary arch or the hooks on esthetic improvement in the profile the mandibular molar bands Thiruenkatachari et al, Titanium microimplants Buccal between roots of Ni-Ti coil spring from implant for 4–6 months No anchorage loss occurred on the 200625 (10 patients) second premolars and canine retraction side using the implant as anchorage first molars Miniplate system Chung et al, 20028 C-tube, Martin Medizin Tech- Buccal to second pre- Canine retraction by elastics to 6 months Reduced lip strain, mentolabial fold nik, Germany (1 patient) molars and first molar the C-tube created Zygoma implant system Bengi et al, 200626 Zygoma anchors Zygoma Zygomatic anchor was used dur- 5 months Overjet reduced from 10 mm to 3 Surgi-Tec, Bruges, Belgium ing rapid canine distalization mm (1 patient) Clerck et al, 200227 Zygoma anchors Inferior edge of zygo- A rigid power arm was fitted in Not mentioned Canines moved distally at a mean (27 patients) maticomaxillary but- the large vertical slot of a rate of 1.14 mm per month tress canine bracket; the hook at the end of the power arm was attached to the level of the canine's center of resistance

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Table 2 Lingual orthodontics Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Lee et al, 200121 Miniscrew, OsteoMed Palatal alveolar bone Ni-Ti coil springs were attached 16 months Retraction of 6 anterior teeth with no (1 patient) between maxillary first between microscrews and loss of anchorage; normalized overjet and second molars hooks on the anterior part of and overbite were achieved; improved the archwire profile by retraction of maxillary anterior teeth Kyung et al, 200428 Microimplant, Dentos, Palate between maxil- En masse retraction of maxil- 20 months Z-angle increased from 58 to 60 Daegu, Korea lary first and second lary anterior teeth degrees, indicating an improvement in (1 patient) molar roots profile Kawakami et al, 200429 Titanium screw, Martin, Buccal to maxillary and Force was applied to retract 12 months Facial profile improved with retraction Germany mandibular alveolar anterior teeth with anchorage of upper and lower lips; maxillary (1 patient) bones between first reinforcement by ligating the tita- molars showed little anchorage loss and second molars nium screws to the first molar hook with an elastic thread Hong et al, 200530 Mini-implant Patient 1: Palatal to Mushroom archwires with pow- 30 months Lip protrusion improved with a super maxillary first molars erchain for en masse retraction Class I molar relationship (2 patients) Patient 2: Palatal to Lever-arm and mini-implant 33 months Convex profile favorably improved; maxillary first molars were designed to achieve intru- axial inclination and dental height of sive tipping retraction of ante- maxillary incisors decreased by 11.9 rior teeth degrees and 1.3 mm, respectively Park et al, 200631 Palatal miniscrew, OSAS Midpalate Midpalatal screw was con- 8 months for ante- Upper lip retracted by 4.5 mm and (1 patient) nected directly to the trans- rior retraction; lower lip by 6.8 mm; patient's appear- platal arch (TPA) as anchorage total treatment ance improved considerably unit for maximum retraction of time, 23 months maxillary anterior teeth

Table 3 Orthopedics Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Henry et al, 199932 Cylindrical titanium screw- Maxillary molar alveolar Abutments on 2 molars were 8 months Maxilla moved anteriorly and inferiorly shaped implants, Bråne- area used as a means of applying 4 mm in a counter-clockwise direction mark (1 patient) elastic traction force from a face mask to protract the maxilla Enacar et al, 200333 Titanium lag screw Processus pterygoideus Petit face mask was attached 7 months ANS displaced 3 mm anteriorly and a (1 patient) to the hook of appliance to posterior rotation of mandible was protract the maxilla achieved as the chin displaced posteri- orly; SNB decreased from 83 to 81 degrees and ANB increased by 2 degrees Kircelli et al, 200634 Titanium miniplate; mini- Both sides of the aper- Elastic force from the miniplate 12 months 8 mm of maxillary advancement, 7 plate, MPI, Tasanmmed; ture piriformis and on extension to the face mask was mm of transversal expansion titanium screw, Leibinger the lateral nasal wall of used to protract the maxilla; (1 patient) maxilla rapid maxillary expander also used

Table 4 Expansion Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Harzer et al, 200435 EO implant, Straumann Palatally between roots Hyrax expansion screw was 21 and 45 days 8 mm of transveral expansion with (2 patients) of second premolars fixed on 1 side with an EO direct fixing of the transversal screw in and first molars implant and on the other side the palatal arch preventing buccal tip- with an osteosynthesis screw ping of the posterior teeth between the roots of the second premolars and first molars

RETRACTION OF THE implants—miniplates, palatal implants, and WHOLE DENTITION AND miniscrews—can retract teeth by either DISTALIZATION OF MOLARS direct or indirect anchorage (Table 5).

Retraction of the whole dentition and distalization of the molars are difficult ortho- INTRUSION dontic tasks. Since the introduction of OF POSTERIOR TEETH microimplants, these tasks are no longer impossible. Reports of retraction of the Pure molar intrusion has been a difficult whole dentition6,36,37 or distalization of task for orthodontists when correcting molars9,19,38–44 show that 3 main types of anterior open bite because of the diffi-

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Table 5 Retraction of whole dentition and distalization of molars Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Retraction of the whole dentition Armbruster et al, 200116 Onplant, Nobel Biocare Palate Transpalatal arch connected the onplant 23 months Correction of molar relationship from (2 patients) to maxillary first premolars as anchorage Class II to Class I unit. Molar distalization began with 200 g open-coil nickel-titanium springs Park et al, 200436 Microscrew, OsteoMed Patient 1: Interradicular Ni-Ti coils were attached from the micro- 7 months Entire maxillary dentition retracted by (3 patients) bone between maxillary screws to anteriorly soldered hooks on 2 mm second premolar and the maxillary archwire to retract maxillary first molars on both teeth sides Patient 2: Buccally Ni-Ti coils were attached from the micro- 11 months Maxillary anterior spaces closed; between maxillary sec- screws to anteriorly soldered hooks on maxillary arch moved 1 mm distally ond premolars and first the maxillary archwire to retract maxillary molars teeth Patient 3: Interradicular An elastomeric thread on the left side 5 months Correction of Class III molar to Class I bone between the roots and a Ni-Ti coil spring on the right side occlusion. Uprighting of the mandibu- of mandibular first and were attached between the microscrews lar dentition second molars and the mandibular dentition Park et al, 200437 Microscrew implant, Patient 1: Maxillary Elastomeric threads were used to apply 10 months 3 mm of posterior movement of max- OsteoMed implants were placed in orthodontic forces from the microscrew illary posterior teeth, as well as pos- (2 patients) the palatal alveolar implants to first premolars in the maxil- terior movement of the anterior teeth bone between the first lary arch and to a lingual button on sec- and a distal uprighting of mandibular and second molars; the ond premolars in the mandibular arch posterior teeth mandibular implants were placed in the alveolar bone distobuccally to the second molars Patient 2: Bilaterally in Ni-Ti coil springs and elastomeric forces 17 months Maxillary and mandibular posterior the buccal interradicu- were applied to canines in both maxillary teeth retracted by 2.0 and 2.5 mm, lar bone between maxil- and manidbular arches respectively lary second premolar and first molar Distalization of molar Sugawara et al, 20049 Titanium anchor plate and Behind second molars Single molar distalization: Anchor plate 19–29 Mean distal movement was monocortical screws, at the anterior border of was ligated with the first premolar via an months 3.5 Ϯ1.4 mm at crown level; mean Leibinger the manibular ramus open coil spring from first molar to dista- amount and rate of relapse 1 year (15 patients) lize second molar; after distalization of se- posttreatment were 0.3 mm and 9%, cond molars, distalization of the first mo- respectively lars was done with the same procedure. En masse distalization of the entire buccal segments: Direct retractive force from the anchor plate to the first premolars by elastic modules or Ni-Ti closed coil sprigs to perform en masse distalization of the whole buccal segment Byloff et al, 200038 Miniscrew, Mondeal Med- Bony palate in median Removable pendulum was placed over 22 months Molar relationship from Class II to ical System palatal area the 2 fixed cylinders of implants in the overcorrected Class I (1 patient) palate as an anchorage unit connecting lingual sheaths on maxillary first molars. A Ni-Ti pushing coil was inserted between maxillary first and second molars on the buccal side to distalize the second molar Keles et al, 200339 Stepped screw titanium Midpalatal suture Modified Keles Silder appliance with a 17 months Molars were distalized bodily by 3 (1 patient) Ni-Ti coil spring for maxillary molar distal- mm on both sides ization Gelgor et al, 200440 Intraosseous screw, (IMF Midpalatal suture Screw was connected to a TPA attached 3.0–6.2 Mean maxillary molar distalization Stryker (25 patients) behind incisive canal to the maxillary right and left first premo- months of was 3.9 mm; maxillary molar crowns lar and first molar bands; Ni-Ti coil springs active distal- tipped distally by a mean of 8.7 were inserted between the first premolar ization; 14 degrees; first premolars tipped and molar for molar distalization months of mesially by a mean of 2.8 degrees fixed appliance therapy Jenner et al, 198541 'Peri' bone plate Ramus of the mandible Elastic thread was used to apply a distal 5 months 3.5 mm of distal movement of (1 patient) during sagittal split force to first molar for distalization mandibular right first molar osteotomy Sugawara et al, 200642 Orthodontic titanium Zygomatic buttress Single molar distalization: Anchor plate 8 to 36 Mean amount of distalization of max- anchor plates, Leibinger was attached to maxillary first molar as months illary first molars was 3.78 mm at (25 patients) anchorage unit; Ni-Ti open-coil springs crown level and 3.2 mm at root level were inserted between maxillary first and second molars for distalization sliding mechanics. En-masse molar distalization: Anchor plate was attached to maxillary canines for en masse retraction Mannchen et al, 199943 Palatal implant Midpalatal suture Patient 1: Palatal implant was attached 2 months From a full Class II molar relationship (2 patients) to a palatal bar with 2 vertical legs and on the right and a 1.5 step on the left Ni-Ti pushing coil was placed on the legs to both Class I molar relationship to the maxillary molar for distalization Patient 2: Palatal implant was attached Not Incisors were torqued 7 degrees; to maxillary molars for molar stabilization mentioned maxillary incisal edge was retracted 2.5 mm and the apex retracted 5 mm, with no change in molar position Kyung et al, 200344 Miniscrew Midpalatal suture Patient 1: Midpalatal miniscrew was 17 months Maxillary molars moved distally 3.5 (2 patients) attached to transpalatal arch by power mm from the apices and 5 mm from chain for molar distalization the crowns Patient 2: 2 midpalatal screws were 5 months Maxillary molar moved distally 3.5 splinted attached to powerchain on max- mm from the apices and 5 mm from illary molars the crowns

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Table 6 Intrusion of posterior teeth Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Umemori et al, 199945 L-shaped miniplate, Buccal cortical bone Patient 1: Elastic orthodontic force from 18 months Mandibular molars were intruded Leibinger (2 patients) around the apical the miniplate to mandibular molars 3.5 mm; occlusal plane showed regions of lower first together with MEAW technique for molar counterclockwise rotation of 4.2 and second molars on intrusion degrees left and right sides Apical regions of man- Patient 2: Elastic orthodontic force from 26 months Mandibular second molars were dibular second molars the miniplate to mandibular molars intruded approximately 5 mm; together with an MEAW arch for molar mandibular and occlusal plane intrusion angles were flattened Sugawara et al, 200246 L-shaped miniplate, Below root apices Intrusive force was applied to each 9–22 months Mean amount of intrusion was 1.7 Leibinger (9 patients) around first and second mandibular molar by ligating with elastic mm and 2.8 mm at first and sec- mandibular molars on modules between stiff archwires and the ond molars, respectively; mean the cortical bone of the first hook of the miniplate amount of relapse was 0.5 mm and mandibular body 0.9 mm at first and second molars, respectively Sherwood et al, 200347 L-shaped titanium mini- Patient 1: Apical to An elastic thread was passed through 5.5 months of 4 mm of maxillary first molar intru- plate (2 patients) supererupted maxillary the exposed loop on the implanted mini- active intrusion sion first molar plate and tied tightly over the buccal Patient 2: Apical to tube of the extruded molar to initiate 7.5 months of 4.15 mm of mandibular first molar supererupted mandibu- intrusion active intrusion intrusion lar first molar Erverdi et al, 200448 I-shaped titanium mini- Zygomatic process 9-mm Ni-Ti coil springs were placed bilat- Anterior open All anterior open bites were cor- plate, Leibinger erally between the hole of the miniplate bite was corrected, with a mean of 1.7 degrees (10 patients) and the first molar buccal tube rected in a mean of clockwise mandibular rotation of 5.1 months; and 2.6 mm of maxillary molar mean total treat- intrusion ment duration was 18.3 months Kuroda et al, 200449 Titanium screw, Keisei Bilaterally in zygomatic Elastic chains were attached from the 19 months Maxillary and mandibular first Medical Industrial process of maxilla and titanium screw to the molars molars were intruded 3 mm toward (1 patient) buccal alveolar bone of the palatal plane and the mandibu- mandible lar plane with 5.6 degrees of clockwise rotation of the mandible Sherwood et al, 200550 L-shaped plate Patient 1: Zygomatic Elastic was threaded through the 5.5 months of Correction of anterior open bite (4 patients) strut in maxilla exposed loop of the miniplate to the active intrusion achieved bracket of the closest molars for intrusion 3 months of Mandible was able to autorotate, Patient 2: In mandible Elastic was threaded through the active intrusion allowing closure of the open bite to the level of the curve exposed loop of the miniplate to the of Spee bracket of the closest molars for intrusion Patient 3: Adjacent to Elastic was threaded through the 5 months of Anterior crossbite and 10-mm supererupted mandibu- exposed loop of the miniplate to the active intrusion mandibular midline discrepancy lar teeth bracket of the supererupted molars for were corrected intrusion; miniplate on the left side as anchorage to shift the entire mandibular dentition to the left Patient 4: Mandible Ni-Ti coil spring from the implant to Not mentioned Anterior crossbite corrected adjacent to mandibular mandibular anterior teeth for retraction right second molar

Chang et al, 200451 Microscrews, OSAS Buccal side, 1 between Powerchain from microscrews to maxil- 13 weeks Enough space for prosthesis con- (2 patients) maxillary left canine lary second molars for intrusion struction in the opposing counter- and first premolar, and part other between the first and second premolars. Palatal side, in midpalatal suture area Maxilla: between maxil- Not mentioned 5 months Adequate vertical space for con- lary left canine and first struction of a temporary crown on premolar mandibular left first molar Mandible: between mandibular left first and second premolars Paik et al, 200352 Miniscrew, OsteoMed Interdental septal bone A transpalatal arch was attached to the 27 months Maxillary first molar was intruded 3 between maxillary and maxillary molars. Elastic chain was con- mm. The anterior lower facial mandibular first and nected from the arch to the midpalatal height was reduced 2.5 mm. second molars; poste- screw for molar intrusion Autorotation of mandible; 4.9 mm rior midpalatal area of mandibular incisor intrusion

culty in vertical anchorage. Loss or INTRUSION OF ANTERIOR infraocclusion of opposing teeth can TEETH result in molar extrusion and contribute Gummy smiles and deep bite malocclu- to the difficulty in prosthetic replacement sions are commonly encountered clinical in the opposing jaw. Skeletal anchorage situations in orthodontics. Microimplants systems have provided a solution for can provide intrusion and retraction molar intrusion mechanics by means of forces simultaneously to deal with the miniplate or miniscrew anchorage45–52 vertical dentoalveolar excess and correct (Table 6). a severe gummy smile or protrusive lip (Table 7).1,53,54

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Table 7 Intrusion of anterior teeth Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Creekmore et al, 19831 Surgical vitallium bone Below anterior nasal Light elastic thread was tied 12 months Maxillary central incisors were ele- screw (1 patient) spine from head of screw to archwire vated approximately 6 mm and torqued lingually about 25 degrees Ohnishi et al, 200553 Mini-implant (1 patient) 3 mm above the root Mini-implant was tied to the 21 months Overbite and overjet changed from 7.2 apices of maxillary cen- main archwire in maxillary mm and 4.8 mm to 1.2 mm and 2.6 tral incisors anterior region for intrusion mm, respectively and proclination Lim, 200554 Mini-implant Buccal side between Powerchain from mini-implant Not mentioned Patient 1: Gummy smile was corrected (2 patients) first and second premo- to the hook of main archwire by decreasing the distance between lars above the center of between maxillary lateral maxillary incisor to Stm from 5.5 mm resistance of maxillary incisor and canine as force vec- to 2 mm; protrusive lip was corrected teeth tor pass through the center of by decreasing the maxillary incisor resistance of the maxillary angulation from 98.5 degrees to 93.5 anterior teeth degrees; Mn plane angle decreased from 45 degrees to 43 degrees Patient 2: Gummy smile corrected by decreasing the distance between maxillary incisor to Stm from 5.5 mm to 2.5 mm; maxillary incisor angulation decreased from 112.5 to 102 degrees

Table 8 Protraction molars/whole dentition Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Roberts et al, 19902 Endosseous implant, Tele- Mandibular left retro- Anchorage wire from the 39 months Intrusion of mandibular left third dyne molar area implant stopped the second molar 2 to 3 mm and mesial transla- (1 patient) premolar from moving distally tion of left second and third molars10 when the lingual arch and to 12 mm space closure loops were acti- vated for mesial translation of the mandibular left second and third molars Freudenthaler et al, Titanium screw, Leibinger Different for individuals: Ni-Ti closing coil spring from the Time of loading, Molar mesialization was achieved 200155 (8 patients) preferred position is implant to protract the 8–20 months between the roots of 2 mandibular molar mandibular premolars at the level of their apical thirds Kyung et al, 200356 Miniscrew, Martin Midway between lingual Elastic chain from the mini- 13 months Mandibular second molars were trans- (1 patient) side of first and second screw attached to the lingual lated mesially 9 mm into first molar premolar roots holding arch, which was extraction sites bonded to mandibular second molars for mesialization Roberts et al, 199457,58 Conventional dental Right retromolar area Anchorage wire from the 30 months of 8-mm mandibular first molar extrac- implant, Brånemark about 5 mm distal to implant, through the advancing active treatment tion space was closed to achieve Class (1 patient) mandibular third molar loop both on buccal and lingual I molar relationship side distal to the mandibular second molars for mesialization force

PROTRACTION OF INSUFFICIENT TOOTH MOLARS/WHOLE DENTITION ANCHORAGE AND/OR PERIODONTAL DISEASE The use of implants to protract molars and IN ADULTHOOD dentition started in 1990.2 There were 2 For patients with insufficient teeth for main ways to protract the mandibular anchorage or teeth that exhibit attach- molars: small miniscrews between ment loss and hence are not good as an roots55,56 and normal-sized implants in the anchorage unit, endosseous implants can retromolar area (Table 8).2,57,58 be useful.59,60 Such implants can serve not only as anchorage units, but also as abutments for a permanent prosthesis. Miniplates can also be used to manage malocclusion in patients with generalized horizontal bone loss and vertical bone loss, as anchorage to reduce overjet and to close spaces61 (Table 9).

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Table 9 Insufficient tooth anchorage and/or periodontal disease in adulthood Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Odman et al, 199459 Rehabilitation implant, Varied Varied 4–33 months 2D tooth movements varied between Br˚anemark 0.2 and 6.2 mm, whereas movements (9 patients) in the third dimension, extrusion and intrusion, ranged from 0.0 to 13.5 mm; movement in space for individual tooth was 3.9 mm Fukunaga et al, 200661 Y-shaped miniplates, Zygomatic process Retraction and intrusion of 21 months Maxillary incisors were inclined 9.5 Dentsply (1 patient) maxillary incisors by power- degrees lingually and intruded 2 mm chain from the miniplate to the at the apex main archwire

UPRIGHTING OF MOLARS CONCLUSION AND DISIMPACTION This literature review has shown that the Conventional orthodontics for uprighting application of skeletal anchorage can be molars or disimpacting teeth leads to versatile. The technique has been used adverse effects such as extrusion of the in conventional edgewise appliances to target molars and reciprocal actions on lingual orthodontics and as a biomechan- anchorage units. Nowadays, however, ical anchorage unit for retraction, protrac- microimplants can be used for skeletal tion, intrusion, and extrusion of teeth. It anchorage and eliminate such effects has also been applied in dentofacial because no orthodontic brackets are orthopedics and arch expansion, treat- used and no forces are applied to the ment of the whole dentition, and treat- anchor teeth62–67 (Table 10). ment of individual impacted or periodon- tally involved teeth. Thus, skeletal anchorage offers not EXTRUSION AND INTRUSION only absolute anchorage in orthodontics, OF INDIVIDUAL TEETH enabling clinicians to deal with anchorage-demanding cases, but it also acts as Vertical control is an essential compo- a powerful armamentarium to enable nent in orthodontic treatment. Intrusion orthodontists to tackle cases outside the and extrusion of individual teeth with scope of conventional mechanics. The microimplants not only provide good ultimate goal in skeletal anchorage will esthetic outcomes, but are also a practi- likely be to expand the scope of ortho- cal indication of available space to allow dontic and dentofacial orthopedic treat- prosthodontic work (Table 11).5,68–73 ment, thus minimizing the territory of orthognathic surgery.

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Table 10 Uprighting molars and disimpaction Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Park et al, 200262 Microscrew, OsteoMed (3 Patient 1: Retromolar Lingual button to mesiolingual 3 months Molar was uprighted, but showed a patients) area, distobuccally to surface of second molar mesiobuccal rotation mandibular first molar, attached to the microscrew 10 mm from distal surface of mandibular right second molar Patient 2: Retromolar A ligature wire was extended 8 months Molar was uprighted area distal to second outward for elastomeric force molar application Patient 3: Maxillary Super thread was applied 4 months Maxillary second molar was uprighted tuberosity between the microscrew and lingual cleats on buccal and lingual surfaces of second molar Giancotti et al, 200463 Miniscrew, Cizeta In left retromolar region Closed coil spring was tied from 9 months Mesial angulated impacted left (1 patient) the miniscrew to the orthodon- mandibular second molar was tics brackets on the mesial uprighted angulated left second molar for uprighting Park et al, 200464 Micro-implant, Absoranchor Maxilla: Distal half of Elastomeric thread was Not mentioned Second molars in maxillary and (1 patient) the interdental space attached from the microim- mandibular arches were uprighted between roots of first plants to the bonded buttons and second molars. on maxillary and mandibular Mandible: Buccal to second molars to provide a second molar crown buccally directed and an intrusive force Kokich et al, 199665 Titanium prosthetic implant Patient 1: Mesial to the Brackets on the prosthetic 8 months Third molars were uprighted and (3 patents) mandibular right third crown of the abutment acted as intruded molar anchorage to upright and intrude mandibular right third molar by the main archwire Patient 2: Both sides of Elastomeric chains were used Not mentioned Mandibular premolars had been posterior alveolus in to retract the anterior teeth retracted 4 mm and the incisors were area of mandibular from the abutments retracted 2.5 mm right second molar Patient 3: Mandibular A samarium-cobalt magnet was 8 months Maxillary first molar and second pre- right ridge placed in the occlusal surface molar intruded 3 mm between the implants and a removable segment stent con- taining a magnet was placed over the maxillary teeth. Repelling force provided an intrusive force to maxillary teeth Yun et al, 200566 Miniscrew, OSAS Patient 1: Between Miniscrew was attached to 8 months Mandibular right second molar was (2 patients) mandibular right sec- mandibular right first molar as uprighted ond premolar and first anchorage unit. A TMA upright- molar ing spring was attached to right mandibular first molar to upright right mandibular second molar Patient 2: Between Miniscrew was attached to 11 months Protraction of mandibular left molars mandibular left lateral mandibular left first premolar was successful incisor and canine as anchorage unit. Elastomeric chain was fitted from canine to mandibular left first molar for protraction Park et al, 200467 Microscrew, OsteoMed Patient 1: Buccal to Attachment bonded to labial 12 months Palatally impacted maxillary right (2 patients) maxillary right canine surface of exposed maxillary canine was brought into arch region right canine to apply buccal eruption force Patient 2: Buccal to Attachment bonded to labial 11 months in the In the maxilla, palatally impacted right maxillary right canine surface of exposed maxillary maxilla; 24 canine was brought into arch; in the region and buccal to right canine to apply buccal months in mandible, second and third molars the mandibular left eruption force; lever arm mandible were protracted forward without loss molar extraction site at extended gingivally from the of anchorage in the anterior segment the level of the center molar tube of mandibular sec- of resistance of molars ond molar at the level of resistance of molar to the microimplant for protraction force

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Table 11 Extrusion and intrusion of individual teeth Type of implant and Treatment Treatment Authors/year no. of patients Site of implant Biomechanics time results Janssens et al, 20025 Palatal onplant, Nobel Bio- Midsagittal palate Loops were extended from the 17 weeks Maxillary first molars were success- care (1 patient) onplant. Elastics from loops fully extruded were attached to lingual buttons of maxillary first molars for extrusive forces Roth et al, 200468 Microscrew, Jeil Alveolar bone area of Bridge of mandibular left 4 months Bridge of mandibular left canine to (1 patient) the mandibular left first canine to second premolar was second premolar was extruded with a premolar to be extruded by open-coil harmonious contour of the gingival spring from implant to cross- margins of mandibular left canine and tube bonded on bridge second premolar Da Costa Filho et al, Prosthetic implant Prosthetic implants of A metal core was constructed 19 days First premolar root reached the 200469 (1 patient) mandibular left second for the root canal-treated desired position and its metal core premolar and first mandibular left first premolar, was prepared to receive a conven- molar. with winglets to hold the elas- tional prosthetic crown tics from adjacent prosthetic implant teeth for extrusion Bae et al, 200670 Miniscrew, Absoanchor Buccal and lingual alve- A stainless steel wire was 6 months Mandibular left first and second (1 patient) olar bone between bonded to occlusal surfaces of molars were intruded enough to allow mandibular left first mandibular left first and sec- implant restorations of the maxillary and second molar ond molar. Elastic was molars attached between the 2 miniscrews, crossing over the bonded wire to apply an intrusive force Lin et al, 200671 Miniscrew, LOMAS Patient 1: 1 in the left Bilateral intrusive forces were 5 months Maxillary left second molar was (2 patients) tuberosity, the other delivered with powerchain from intruded in the desired position between the buccal the miniscew heads on both roots of the first and sides to bonded buttons on the second molars overerupted maxillary left second molar Patient 2: 1 in the right Bilateral intrusive forces were 8 months Maxillary right second molar was in infrazygomatic crest applied from the miniscrews to the desired position and adequate and the other in the bonded attachments on the space for the mandibular prosthesis right paramedian area overerupted molars by elastic was obtained of the palate chains Lee et al, 200472 Miniscrew, Two in midpalate, 3 on The 2 midpalatal miniscrews 7 months Maxillary first and second molars were Martin Tuttlingen buccal side mesodistal were splinted together with successfully intruded (1 patient) to extruded teeth extension arms; an intrusive force was applied from the extension arm and the buccal miniscrews to the maxillary left first and second molars by elastic chains Yao et al, 200473 L-shaped miniplate Miniplate was placed Powerchain from the miniplate 5 months First and second molars were success- and miniscrew, Leibinger buccal, miniscrew was and miniscrew was applied to fully intruded (1 patient) placed palatal to the the left first and second molars left maxillary first and second molar

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