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BIOMECHANICS OF MOLAR DISTALIZATION APPLIANCE INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacadmy.com


CONTENTS • • • •

INTRODUCTION INDICATIONS AND CONTRAINDICATIONS BIOMECHANICS TYPES OF APPLIANCES -EXTRAORAL -INTRA ORAL • APPLIANCE SELECTION CRITERIA • CONCLUSION • REFERENCES www.indiandentalacadmy.com


INTRODUCTION Correction of class II malocclusion without extractions requires maxillary molar distalization by means intraoral or extraoral forces.

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• William Kingsley (1892) described for the first time headgear apparatus with which class I molar relationship could be achieved successfully.

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• Oppenheim advocated that position of mandibular teeth as being the most correct for individual and use of occipital anchorage for moving maxillary teeth distally into correct relationship without disturbing mandibular teeth. • In 1944, he treated a case with extra-oral anchorage for distalizing maxillary molar.

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• Kloehn in 1947 started a long and beneficial series of investigations and clinical applications of cervical anchorage to the maxillary dentition.

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• The headgears over the years have shown to be effective in maxillary molar distalization with movements in all planes of space. With the recent trend more towards non extraction treatment, several inter/intra arch devices have been advocated to distalize molars in the upper arch. www.indiandentalacadmy.com


• Researchers have focused on the simplicity and efficiency of these intra arch devices, which improves the continuity and constancy of forces. Oral hygiene is easier to maintain and the need for patient compliance is eliminated.

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• Molar distalization is a technique that has added a new column in the practice of every orthodontist to produce consistent, predictable and high quality results. The goals of practicing with efficiency and profitability are positively affected.

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• Since space is easier to gain in the maxillary arch than in the mandible because of increased trabecular structure of supporting bone and increased anchorage afforded by palatal vault, the distalization of maxillary molar becomes of significant value for the treatment of cases with mild to moderate arch discrepancy and class II molar relationship associated with a normal mandible. www.indiandentalacadmy.com


INDICATIONS •

Profile - should be acceptable with minimal facial change or straight profile

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• Functional – Normal TMJ

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• Skeletal - Class I skeletal pattern - Normal, short lower face height - Skeletal closed bite

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Dental • class II / End-on molar relationship

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Deep overbite Maxillary first molar mesially inclined Maxillary cuspids labially displaced

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• Loss of arch length due to premature loss of second deciduous molar • Mild to moderate discrepancy

arch

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perimeter


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UPPER MOLAR POSITION • This is a linear measurement between the distal surface of the maxillary first permanent molar and the pterygoid vertical line (PTV). • It is an indication of the forward position of the upper molar and illustrates to the clinician whether or not sufficient space is present for the second and third molars. www.indiandentalacadmy.com


• This measurement indicates or contraindicates molar distalization. • An interesting aspect of this measurement is that its mean value is the patient's age in years plus 3mm until growth is complete. Therefore the mean • measurement for nine - year old child is l2mm. www.indiandentalacadmy.com


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TIMING • A favorable time to move molars distally appears to be in mixed dentition, before the eruption of the second molars, and an efficient force system to move molars distally is a continuously acting force.

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CONTRAINDICATIONS • Profile:- Retrognathic profile

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• Functional:-abnormal temporomandibular Joint

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• Skeletal:- Class II skeletal - Skeletal open bite - Excess lower face height

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• Dental:-Class I or III molar relation. - Dental open bite/shallow bite

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BIOMECHANICS

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TYPES OF APPLIANCES • EXTRAORAL • INTRA ORAL

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EXTRA ORAL • Bilateral molar distalization a) Cervical pull head gear. b) Combi pull head gear. • Unilateral molar distalization with unilateral face bows a) power-arm face bow b) soldered offset face bow c) swivel-offset face bow d) spring-attachment face bow. www.indiandentalacadmy.com


INTRA ORAL • INTER ARCH • INTRA ARCH

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INTER ARCH    

Atkinson buccal bar Tandem yoke 3d biometric distalizing arch Modified herbst appliance for distalization of molars  Jasper jumper  Sliding jig  Crickett appliance www.indiandentalacadmy.com


INTRA ARCH  Sagittal appliance  Magnets  Modified lingual and Nance holding arches  Jones jig  NiTi coil springs

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Pendulum appliance Super elastic NiTi wires Molar distalizing bow Space regainers K-Loop Fixed piston appliance Distal jet www.indiandentalacadmy.com


 C-Space Regainer  Palatal orthodontic implants  First class appliance  Fixed palatal expander  Lokar molar distalisation  Transpalatal arch

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 Acrylic cervical occipital appliance  Rremovable molar distalization splint  Compressed springs  Mini distalization appliance  IBMD

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SPACE REGAINERS  Sling Shot Appliance  Modified Kings Appliance  Removable or fixed lingual arch with spring  Clasp ring

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MOLAR DISTALIZATION IN LOWER ARCH : • • • •

Lip bumper Modified lingual appliance Distal jet for lower molar Franzulum appliance

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EXTAORAL FORCES

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LOW-PULL HEADGEAR

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MEDIUM-PULL HEADGEAR

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HIGH-PULL HEADGEAR

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ASYMMETRIC HEADGEAR

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EXTRA ORAL • Bilateral molar distalization a) Cervical pull head gear. b) Combi pull head gear.

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Cervical pull head gear.

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Cervical Anchorage with low-pull Headgear

Translation

Clockwise Rotation

Anti-clockwise Rotation www.indiandentalacadmy.com


COMBI PULL HEAD GEAR

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combi-pull Headgear Translation

Clockwise Rotation

Anti-clockwise Rotation www.indiandentalacadmy.com


Unilateral molar distalization with unilateral face bows power-arm face bow

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soldered offset face bow

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swivel-offset face bow Swivel union

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spring-attachment face bow

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INTRA ORAL

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STANDARD PENDULUM APPLIANCE • In 1992, Hilgers • made of 0.032 TMA wire, • Springs deliver approximately 230 gms of force per side. • Springs have adjustment loop that can be manipulated to increase molar expansion, rotation and distal root tip. www.indiandentalacadmy.com


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MODIFIED PENDULUM APPLIANCE • • • •

M- pendulum Inverted loop Activation - 40-450 Springs deliver approximately 125 gms of force per side. • Springs have adjustment loop

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K -LOOP • By Kalra in 1995 • The appliance consists of a K-loop to provide the forces and moments and Nance button to resist anchorage

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K-loop made of .017”x.025”TMA wire with each loop 8mm long and 1.5mm wide

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Legs of appliance bent down 200

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Wire marked at mesial of molar tube distal of premolar bracket

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Bend placed 1 mm distal to distal mark and 1 mm mesial to mesial mark. Stop should be well defined and about 1.5mm long

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K-loop in place with 2mm activation

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Moments and forces produced by K-loop

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Reactivation sequence Open loop 1mm at (1); Open loop 1mm at (2); Open at (3) to regain the 200 bent of mesial and distal legs

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COMPRESSED SPRINGS • Gianelly and co-workers. • Springs made from compressed stainless steel or NiTi.

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• NiTi coil is activated to about 10 mm o produce 100 gm. • First premolars are anchored by Nance holding arch. • Coil springs can also be compressed by placing a sliding Gurin lock.

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REPELLING MAGNETIC APPLIANCE • First and second premolar are banded and an impression is made. A palatal stabilizing plate is fabricated and cemented in place. First molars are also banded.

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• An assembly containing repelling magnets is placed into the molar tubes on maxillary first molar and magnets are placed in a repelling portion facing by ligating a sliding yoke to an eyelet as premolar.

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• Activation every two or four weeks. • Not gained wide acceptance because the magnets tend to be expensive and bulky.

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SLIDING JIG • Auxillary sectional arch wires used to tip or move one or a group of teeth in buccal segments distally without disturbing anteriors. • Have bent in eyelets on each side. • To avoid friction or binding they should be made of 0.022 inch round wire and can also be made of rectangular wire. www.indiandentalacadmy.com


• Location of intermaxillary hook on the jig, soldered or bent-in, is on the occlusal area of anterior eyelet of jig. • To move maxillary molar distally, eyelet on distal end of jig must but against molar tube, mesial eyelet is located between cuspid and first premolar bracket at least 2 mm anterior to premolar bracket. www.indiandentalacadmy.com


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BIMETRIC DISTALIZING ARCH • Developed by Wilson and Wilson. • components

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• Distalizing force on the molars is produced by compression of push coil spring anchored by pull of class II elastics. The force of the elastics counteracts the forces of the push coil springs so that the anterior segment of the Wilson arch approximates the incisor brackets before ligation to the anterior teeth www.indiandentalacadmy.com


• Posterior ends of Omega loop should contact the face bow tubes on maxillary first molar, and anterior section of arch should approximate brackets on maxillary anterior teeth. 5 mm section of 0.010 x 0.045” open wound coil is placed over end of William’s arch bilaterally.

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• Advocated sequential use of elastics with decreasing force values i.e. 5/16� 6-oz in first week, similar size 4-oz in second and and similar size 2-oz in third and subsequent weeks of treatment.

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• Appliance is activated by placing loop forming pliers into Omega loop, forcing posterior leg distally. Elastic sequence begins again when reactivated. • Lower arch should have a stiffer rectangular arch wire or lingual arc.

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HERBST APPLIANCE • Emil Herbst in 1905. • Original design consisted of placement of bands on maxillary first premolar and molar and mandibular first premolar, which were connected with lingual bar to support anterior teeth.

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• The arches are connected with a telescopic adjustable piston mechanism to produce a protrusive force on mandible.

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• Class II correction is by equal amounts of dental and skeletal changes. • Dental changes include distalization of maxillary molar and mesial movement of mandibular molar and incisors.

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• Skeletal changes include inhibition of maxillary antero-posterior growth and to produce an increase in mandibular length and lower face height.

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MOLAR DISTALIZATION IN LOWER ARCH

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LIP BUMPER • used for molar anchorage, prevention of poor lip habits and creation of increased space for mandibular arch. • Made of 0.045” stainless steel that spans the facial structures of mandibular arch without contacting teeth and inserted into molar tubes.

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• Anteriorly wire is covered by plastic tubing or acrylic shield to hold lip away from incisors. • Force from mentalis muscle is transmitted to molar, enabling them to move to an upright and distal position

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APPLIANCE SELECTION CRITERIA • Regardless of approach, one should ponder several issues before considering any of these appliances for use Side effects Case types Arch length Treatment timing Co-operation www.indiandentalacadmy.com


Side Effects • Did incisors flare?

• If mandible is used as an anchor unit, did anything occur in that arch?

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• Side effects are a fact of life, especially in orthodontics. • There are some side effects that would be favorable in certain cases, while the same effects may be detrimental in others.

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• The key to correct appliance selection is to know, and be able to predict these effects. • For this a sound and thorough knowledge of biomechanics is essential.

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Case types • Consider an individual case at hand and his/her needs. • If mandibular dentition can be slightly mesialized, if this in the case then Herbst or BDA may be appliance of choice. • If not pendulum and other intra-arch appliances can be used. • If you may not afford flaring of incisors then headgear would be treatment of choice. www.indiandentalacadmy.com


Arch length How much distalization is required. TPA has limited application of 2-3 mm, if in need of greater amount of correction then Herbst and headgear are of choice followed by pendulum, Wilson BDA etc.

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Treatment timing Perhaps best time to initiate distalization is late mixed dentition and it may be too late after eruption of second molar. Some synergistic effect as dentition transits from primary to permanent as canines and premolars follow molars as they moved distally. Thus appliances that requires some anterior anchorage like pendulum may dilute these results. www.indiandentalacadmy.com


Co-operation • Invariably appliances that require least co-operation come with side effects that have to be considered.

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CONCLUSION • There are many advantages and disadvantages of both the intra-oral and extra-oral methods. • It should be remembered that patient selection for a particular method of distalization is of utmost importance and should not be overlooked .

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• Right appliance should be selected for the right patient and one should not select the patient for the appliance rather the appliance should be for the patient

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Biomechanics of molar distalisation appliance/ dental implant courses by Indian dental academy