Anchorage preparation in PAE INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
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Topics of Discussion Anchorage. Classifications of anchorage Types of anchorage Anchorage for each stage followed in Roth Wick Alexander MBT Bioprogressive therapy 05/03/14
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Introduction Archemedes said, “ give me a lever long enough, a place to stand and I shall lift the earth.” “ a place to stand”is what we are going to talk about right now- simply put this is anchorage. 05/03/14
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When ever a force is applied , the stabilized site from where the force is exerted is the anchorage. For every force acting, there is an equal force acting in opposite direction.The undesirable actions must ideally be negated or at least kept at bare minimum. One effective way is to allow these reactionary forces to be dissipated over a large area. www.indiandentalacademy.com 05/03/14
Anchorage refers to the nature & degree of resistance to displacement offered by an anatomic unit when used for the purpose of effecting tooth movement. (Graber) According to Profitt anchorage can be defined as resistance to unwanted tooth movement. 05/03/14
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Classification of anchorage: Maximum posterior anchorage Reciprocal anchorage. Maximum anterior anchorage. 05/03/14
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Simple Stationary Reciprocal Intraoral Extra oral Intra maxillary Inter maxillary 05/03/14
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Simple
Stationary 05/03/14
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Reinforced anchorage
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Extra oral
Reciprocal 05/03/14
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Types of anchorage Dynamic anchorage: generated by applying moments or muscular forces. Moments can be generated through cantilever springs or base intrusion arches and applied to the anchor teeth. These create distal tipping forced,which help to resist anterior displacement of anchor unit Ex : tip back mechanics, lip bumper. 05/03/14
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Reinforced anchorage: the additional resistance to tooth movement gained when several teeth are joined together to act as one large , multirooted tooth. Prepared anchorage: anchorage control accomplished by tipping the teeth roots first, crowns second, to offer increased resistance to the later retraction of anterior teeth. 05/03/14
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Segmented mechanics: Three-dimensional control during retraction of the upper anterior teeth is essential not only for facial esthetics, but also for function of the stomatognathic system and stability of orthodontic treatment 05/03/14
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• A common orthodontic treatment goal is to combine retraction with intrusion and uprighting of the anterior teeth. • To achieve this goal, clinicians often bend the continuous archwire into a shape that is expected to deliver intrusive force. 05/03/14
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• Unfortunately, the many active and reactive forces produced by a continuous arch can combine to produce extrusion of the posterior teeth rather than intrusion of the incisors. 05/03/14
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• Controlled distribution of forces between the anterior and posterior parts of a fixed appliance can only be accomplished by dividing the arch into segments. • Each segment is consolidated into a rigid unit by a section of heavy rectangular wire, with little or no play between wire and bracket slot. 05/03/14
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• The anterior segment, usually including the four incisors and possibly the canines, forms the active unit, and the two posterior segments, including the premolars and molars, are the reactive units. When necessary, the reactive units are connected by a transpalatal bar to form a single rigid, multirooted entity. 05/03/14
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• The planned displacement of the anterior unit and the corresponding reaction of the posterior units are carried out by connecting the anterior and posterior units with active elements, such as retraction springs.
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• Clinically, the point of force application is the bracket. If a pure force is directed distally through the bracket, the tooth will undergo a distal tipping movement— a combination of distal translation and rotation around the CR . 05/03/14
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• The rotation is the result of a moment of the force (MF) produced because the force is applied at a distance (d) from CR. This moment is calculated as MF = F´d. • If a pure translational movement of the tooth is desired, the moment must be neutralized. This can be done by calibrating the retraction spring to produce a couple at the canine bracket. 05/03/14
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3 piece base intrusion arch wire • In non extraction cases in which flared incisors are associated with intra – arch spacing , full space closure is achieved only when deep over bite is corrected. • True intrusion is obtained by applying single intrusive force through the C.R of the anterior teeth. 05/03/14
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Base arch mechanism • The base arch mechanism is made of 0.018x 0.025ss with helices . It can also be fabricated from 0.017 x 0.025 tma with no helices. • It delivers 200 gm in the midline and 100 gm each side.
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T - loop • The T – loop can be used for 3 types of space closure • Anterior retraction • Symmetric space closure • Posterior protraction. • wire used is 0.017 x 0.025 TMA
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• T – loop is activated by 6mm for complete space closure. • Tooth movement occurs in 3 phases1.controlled tipping, • 2. translation and • 3.root uprighting.
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• Initial force system applies M/F ratio of 6 : 1 .this results in tipping. • With 2mm of space closure M/F is 10:1 resulting in translation. • Further space closure results in M/F ratio of 12:1 .this results in root uprighting.
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Anchorage for each stage followed in different systems
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Wick Alexander lewis
Lang brackets are used for canines & Lewis brackets are used for lower incisors as well as premolars.
lang 05/03/14
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Inter bracket distance Increased inter bracket distance increases flexibility of the wire hence the forces applied are less.
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Mini-diamond brackets are used in central & lateral brackets.lateral bracket has a hook attached to it for engaging class II elastics.
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r a l u b i d Initial arch wire n a M a rc h 0.17 x 0.025 multi stranded D – Rect wire is used as the first wire if torque control is important & the mandibular arch is not too crowded. In case of moderate to severe crowding 0.16 x 0.022 D – Rect wire is used.
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0.0175 multi stranded respond wire is used as initial wire in maxillary arch. A round wire used in maxillary arch especially in early treatment tends to promote anterior dental advancement. This is desirable in class II div 2 cases. 05/03/14
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Driftodontics : The mandibular anterior teeth have a tendency to drift distally. The mandibular posterior teeth will drift mesially, but much more slowly. Appliances are placed only on the maxillary arch until a class I cuspid relation is achieved. The late placement of mandibular appliance is referred to as driftodontics. 05/03/14
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Individual canine retraction: re
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More control over molar anchorage Cuspid is the largest rooted tooth in the mouth, it is important to put it into position as quickly as possible. By retracting cuspids first incisor retraction can be achieved with out significant loss of torque.
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Anchorage conservation in mandible: Mandibular molar has – 6 degree tip incorporated in it which promotes leveling & helps in gaining arch length (Tweed’s philosophy). 05/03/14
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Anchorage conservation in maxilla: Omega loops are bent into many various vari – simplex discipline arch wires mesially to the terminal molars. Omega loop is generally the preferred method of tying back. Omega loops are placed in 0.016 ss wires . In average case this is supported with a face bow.
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An orthopedic effect occurs while the cuspids are retracted & molars do not advance. If pt does not wear the face bow the molar advances till the molar buccal tube is in flush with the omega loops. Any further mesial molar movement is accompanied by maxillary incisor advancement. 05/03/14
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retractor Retractor is one of the most important elements of varisimplex discipline. It is the only appliance with which the orthodontist can control all 3 dimensions – vertical , sagittal & transverse both skeletally & dentally.
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Advantage of face bow is that opposing force is applied to the back of the neck or top of the head. Maxillary molar buccal tube is placed either occlusally or gingivally. Adv of gingival placement – tube is closer to the C.Rot which reduces the molar tipping effect. 05/03/14
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Advantage of occlusal placement Vari- simplex discipline includes the use of omega loops in the posterior segment. Omega loops can block gingivally placed headgear tubes. Pt finds it easy to insert the inner bow into the tubes. 05/03/14
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Cleaning around the tubes is easier.
The retractor is usually placed 2 weeks after the brackets are bonded & banded to the maxillary arch. When given initially light force is applied. The neck strap is adjusted so that no more than 8 ounces of force is transmitted through the appliance. 05/03/14
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At the next appointment , 4 weeks later the neck strap is tightened to produce a pull of approx 16 ounces. The elastic strap will fatigue over time. As it stretches it has to be adjusted to preserve a constant force. Severity of class II pattern affects the optimal amount of daily facebow wear. 05/03/14
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Pre treatment ANB is the ceph measurement used to establish daily requirements. If ANB is 3 or less , the pt will sleep with the retractor but will not wear it when he is awake. If ANB is 3 – 5 pt will wear it approx 10 hrs per night. If ANB is > 5 pt will wear the retractor 14 hrs per day or more 05/03/14
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Incisor retraction: 0.018 x 0.025 ss closing loop arch wire is used to retract the incisors. Tear drop loops of approximately 5mm in height are used. Before the wire is engaged the wire distal to the cuspids is reduced to approx 0.016 x 0.023. 05/03/14
The closing loop is activated by about www.indiandentalacademy.com 1mm per month.
Roth : The various factors which prevent drifting of mandibular dentition forward are facial type, amount of over bite & occlusal forces. Any orthodontic appliance forces that tend to overcome these will result in mesial migration of the dentition. 05/03/14
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Factors that cause posterior tooth to move forward are Attempting to upright extremely distally tipped canines. Pulling distally with posterior teeth against extremely procumbent or labially inclined incisors. 05/03/14
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Attempting to level the curve of spee with a continuous wire with out the use of distal traction. Attempting to do any of the first three tooth movements utilizing either a stiff or a resilient wire. Attempting to move lingually or torque the maxillary incisor roots. Attempting to expand the mandibular arch with a labial arch wire 05/03/14
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Stages Leveling and aligning Retraction Finishing. 05/03/14
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Leveling & aligning Start aligning with 0.015 wild cat or 0.015 respond followed by 0.017 or 0.019 respond. Anterior facebow is used to upright lower anteriors. Band the 2nd molars. 05/03/14
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Intrusion utility arch is used to level the curve of spee followed by a small continuous wire. Goshgarian TPA 05/03/14
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To widen a narrow mandibular arch, place lingual arch with recurved finger springs to widen the premolars prior to insertion of labial arch wire. To correct the cant of occlusion short class II elastics 1/8 inch in diameter applying 48 oz of force www.indiandentalacademy.com are used.
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Double key hole looped arch wire is used for retraction. Advantage – complete space closure with single set of arch wires with out coming back & changing the arch wire. 05/03/14
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MBT Anchorage control according to MBT:
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The maneuvers used to restrict undesirable changes during the opening phase of treatment , so that leveling & aligning is achieved with out the key features of malocclusion becoming worse. www.indiandentalacademy.com
Horizontally AC is used to achieve a correct AP position of teeth in the profile at the end of the treatment. Vertically AC is involves the need to try to influence the vertical skeletal & dental development in the posterior segments & at times attempts to limit vertical eruption of anterior segments or even intrude these. 05/03/14
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Laterally , AC involves the maintenance of expansion procedures , primarily in the maxillary arch & the avoidance of tipping and extrusion of posterior teeth during any 05/03/14
expansionwww.indiandentalacademy.com phase.
Anchorage in horizontal plane Control of anterior segments: • Lacebacks ,bend backs • Reduce the anchorage needs during leveling & aligning. • Bracket design – reduced tip. • Arch wire forces – use of very light arch wire forces. • Avoidance of elastic chain 05/03/14
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Upper molar Post anchorage control in upper arch is more than the lower arch because UM moves mesially more easily than the lower molars. Upper anterior teeth are bigger. UA have more tip built into them 05/03/14
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UI require more torque control & bodily movement than lower incisors which require distal tipping or uprighting. Most of cases are class II type of malocclusion. Because of these factors EO force is normally the most effective method of posterior anchorage control 05/03/14
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Lower molars Lingual arch – in the mixed dentition cases it prevents the lower molars from drifting mesially. Class III elastics Head gear. 05/03/14
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Vertical control of incisors: If the canines are distally tipped in the starting, in such cases , as the arch wire passes through the canine bracket slot it will lay incisally to the incisor bracket slot causing extrusion if the wire is fully engaged. 05/03/14
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Vertical control of canines: High labial canines should not be engaged with arch wire because it causes unwanted vertical movement of lateral incisors and premolars.
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Vertical control of molars in high angle cases: Upper 2nd molars are generally not initially banded , to minimize extrusion of these teeth. If upper molars require expansion, an attempt is made to achieve bodily movement rather than tipping. 05/03/14
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Palatal bar should lie about 2mm away from palate so that the tongue can exert a vertical intrussive effect. When head- gears are used in high – angle cases either a combination pull or a high pull headgear is used.cervical pull headgear is avoided. Upper or lower posterior bite planes in molar region is helpful to minimize extrusion of molars.
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Anchorage control in lateral(coronal) plane: Intercanine width: it should be kept as close as possible to starting dimensions for stability. Crowding is not relieved by uncontrolled expansion of the upper & lower arches. Molar cross bites: molar cross bites should be corrected by bodily movement of molars. As far as possible tipping should be avoided. 05/03/14
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Narrow maxillary arch: If maxilla is too narrow, early rapid expansion should be considered prior to leveling & aligning. If adequate maxillary bone exists , a fixed quad helix expander is used. minimal molar cross bites are usually corrected by using rectangular wires which are slightly expanded from normal & which carry buccal root torque. 05/03/14
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Bioprogressive therapy Cortical bone anchorage: The concept of cortical bone anchorage implies that , to anchor a tooth , its roots are placed in proximity to the dense cortical bone under a heavy force that will further squeeze out the already limited blood supply and thus anchor the tooth by restricting the physiological activity in an area of dense laminated bone.
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Three main aspects of tooth movement & cortical bone support: Avoid cortical bone support where ever possible & direct the roots through the less dense & more vascular trabecular bone. Light forces are used. 05/03/14
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Anchor tooth by placing their roots adjacent to the denser cortical bone . When treatment objectives require that we move teeth through the supporting cortical bone, where the dense bone cannot be avoided but must be remodeled,the forces must be kept even lighter to respect the character of bone and its limited blood supply & physiological response. 05/03/14
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Muscular anchorage The facial type described by the cephalometric morphology reflects the musculature which supports the occlusion. When the musculature is strong as characterized by the deep bite, low mandibular plane angle, brachy facial type,the teeth demonstrate a natural anchorage. 05/03/14
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In the open bite vertical dolichofacial patterns, the musculature seems weaker & less able to over come the molar extruding & bite opening effect 05/03/14
of our treatment mechanics. www.indiandentalacademy.com
Upper molar anchorage Maximum upper molar anchorage: Nance plastic button followed by headgear. Modification of nance lingual arch , with plastic button against the rugae is the addition of a distal loop on the mesial lingual of the upper molar bands which allows the molar teeth to be expanded & rotated. 05/03/14
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Nance plastic button followed by head gear
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Adv of expansion & rotation of molars Expansion places the molar roots out under the zygomatic process where cortical bone support resists change & thus anchors & limits their movements. The molars, placed in distal rotation, tend to resist the forward mesial pull as the cuspids are being retracted on sectional arch springs. 05/03/14
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For the final positioning in the finishing occlusion . The finishing alignment & details of occlusion should be kept in mind even in the first basic treatment movements. 05/03/14
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Moderate upper molar anchorage: Quad helix expansion arch. palatal bar without plastic button support will stabilize the molar & give moderate anchorage support. The lingual arch limits molar eruption & vertical height development. 05/03/14
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Use of upper utility arch during cuspid retraction with or with out the lingual arch has a moderate anchorage effect to the upper molars, since the intrusion action to the upper incisors produces a tip back to the upper molars, which acts to stabilize them 05/03/14
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Quad helix
Upper utility arch Sectional retraction then anterior retraction
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Minimum upper molar anchorage: Class III extraction treatment usually calls for upper second bicuspid extraction with advancement of 1st molar. Since upper molar has a natural tendency to rotate & migrate mesially as it erupts, the advancement of upper molar is a matter of encouraging & supporting this natural process 05/03/14
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A vertical closing loop or double delta loop will assist in its forward closure. The forward migration of the upper molar usually carries it into mesial rotation & treatment mechanics will need to compensate by uprighting with distal rotations for a better final fit & occlusion. 05/03/14
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Reciprocal closing mechanics
Protraction of molar forward after extraction of 5’s. 05/03/14
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Lower molar anchorage: Maximum molar anchorage: maintained through the action of long lever arm of the lower utility arch. Buccal root torque that places roots against the cortical support to limit their movement. Up to 45 degrees buccal root torque is placed in a 0.016 * 0.016 elgiloywww.indiandentalacademy.com wire.
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• Buccal expansion of the molar section of 10mm on each side is necessary to support the buccal torque. • Tip back of 30 – 40 degrees keeps the molar upright & resists the forward pull in response to the cuspid retraction springs. • Distal molar rotation of 30 – 45 degrees is placed in the molar section of the utility arch 05/03/14
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in extraction cases.
Moderate lower molar anchorage: Modifies the lower utility arch mechanics to allow the molar to come forward during cuspid &incisor retraction. A contraction utility arch is stepped ahead of the molar tube to advance the molar. 05/03/14
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Minimum anchorage mechanics: To advance the lower molar forward the four anchoring factors of torque, tip back, expansion & rotation are minimized. Round wire in the molar tube may be used to eliminate the binding & torquing to the molar & there by reduce the anchorage. 05/03/14 www.indiandentalacademy.com
Conclusion: • In many cases , the successful outcome of the treatment depends on treatment planning. • In PAE, anchorage should be planned and taken care of from the first day of treatment. 05/03/14
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