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Elastics in orthodontics /certified fixed orthodontic courses by Indian dental academy


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  • 1. ELASTICS IN ORTHODONTICS INDIAN DENTAL ACADEMY Leader in continuing dental education
  • 5. INTRODUCTION • Elastics and Elastomeric are routinely used as a active component of orthodontic therapy for many years. There use, combined with good patient cooperation, provides the clinician with the ability to correct both Antero-posterior and vertical discrepancies. 4
  • 6. • Both natural rubber and synthetic elastomers are widely used in orthodontic therapy. Naturally produced latex elastics are used in the Begg technique to provide intermaxillary traction and intramaxillary forces. Synthetic elastomeric materials in the form of chains find their greatest application with edgewise mechanics where they are used to move the teeth along the arch wire. 5
  • 7. TERMINOLOGY • Force : It is defined as an act upon a body that changes or tends to change the state of rest, or the motion of that body. Though defined in units of Newtons it is usually measured in units of grams or ounce. • Elastic: Is defined as the ability to return to its original length or shape after being stretched 6
  • 8. • Elasticity: The property of a substance that enables it to change its length, volume or shape in direct response to a force affecting such a change and recover its original form upon the removal of the force. • Elastic limit: The elastic limit is the maximum stress which a material can endure without undergoing permanent deformation 7
  • 9. • Elastic Modulus or Modulus of Elasticity: When a material is stressed it is usually found that the stress is usually proportional to the strain, so their ratio is constant. In other words the material deforms linearly and elastically. This can be represented by the expression E = stress/strain. • Resilience: [stored or spring energy] Resilience represents the energy storage capacity of a wire/ elastic. It is stressed not to exceed it proportional limit • CLAPEYRON”S theorem of reciprocity: When an elastic force is applied to two identical solids, the moving force is identical and reciprocal. 8
  • 10. • Plasticity: It is the property of any substance by which the material can be molded into various forms and then hardened for commercial use. • Relaxation: It is defined as decrease in force value carried or transmitted over time with the element maintained in a fixed activated state of constant strain. • Vulcanization: The process of heating sulphur-rubber mixtures is known as vulcanization. 9
  • 11. 10
  • 12. • 1728: Pierre FAUCHARD in his book proposed to close anterior diastema with silk ligature. • 1756: P BOURDET used a silk ligature to move teeth, prefiguring the straightwire era. • 1839: Charls GOODYEAR discovered vulcanization. • 1892: Calvin CASE was the first to use intermaxillary elastics to correct malocclusion. • 1904: H BAKER published in his international dental journal an article entiteled “treatment of protruding and receding jaws by the use of intermaxillary elastics”. 11
  • 13. • 1907: Edward H ANGLE in his book proposed the classification of malocclusion and the use of elastic forces. • 1958: Fred SHUDY recommended short class ll elastics in association with a high pull anterior extraoral force in order to control the vertical cases. • 1963: J.JARABAK described the biomechanics of class ll elastics for the first time. • 1965: R BEGG used class ll elastics which were changed every 5 days. 12
  • 14. • 1964-1970: Robert M RICKETTS originated the Bioprogressive segmental light square wire technique advising the closing elastics conduct in open bite cases. • 1972: Ron ROTH recommended short class ll intermaxillary elastics to help the curve of spee leveling . • 1973-1996: Michel LANGLADE developed the clinical applications of elastic forces in different situations such as occlusal elastics, cross bite elastics, proposing biomechanical comparison in clinical uses. 13
  • 15. Natural Rubber • Chemical analysis shows that about 30 to 35 percent of latex consists of pure rubber, water makes up another 60 to 65 percent. The remainder consists of small amount of other materials such as resins, proteins, sugar and minerals. Latex spoils easily and must therefore be processed into crude rubber as soon as possible after it has been tapped. This is done by separating the natural rubber in the latex from water and other materials. About 99 percent of all natural rubber comes from the latex of Hevea brasiliensis. This is the tree that we call the rubber tree. 16 Rubbers
  • 16. 19 •Rubber is one of our most interesting and most important raw materials. Natural rubber comes from the juice of a tree. Synthetic rubber is made from chemicals.
  • 17. H (Methyl Group) H C H H H H C=C C=C (Chain) H H In natural rubber thousands of tiny isoperene molecules link together in to a giant chainlike molecule,..the rubber molecule. 18 • In 1860, another Englishman, Greville Williams, heated some rubber and obtained a colourless liquid that he called isoperene.
  • 18. • Natural rubber has many unsaturated carbon atoms. Oxygen atoms from the air gradually attach themselves to these carbon atoms. This breaks down the rubber polymers so that the rubber becomes brittle or soft and loses elasticity. The addition of antioxidants during compounding prevents this action. 20
  • 19. Synthetic rubber • Rubber like materials which are made from chemicals were called synthetic rubbers because they were intended as substitutes for natural rubber. Chemists use the word elastomer for any substances, including rubber, which stretches easily to several times its length, and returns to its original shape. • Elastic Manufacturers group synthetic rubbers into two classes: General-purpose and special-purpose. 21
  • 20. • General purpose synthetic rubbers: The most important general purpose rubber is styrene-butadiene rubber (SBR). It usually consists of about three parts butadiene and one part styrene. Butadiene, a gas, is made from petroleum. It must be compressed or condensed into liquid form for use in making rubber. Styrene is a liquid made from coal tar or petroleum. Special purpose rubbers: Contact with petrol, oils, sunlight and air harms natural rubber. Special-purpose synthetic rubbers resist these “enemies” better than natural rubber or SBR. Also some of these special-purpose rubbers have greater resistance to heat and cold. 22
  • 21. Special-purpose rubbers include • butyl rubber • nitrile rubber • polysulphide rubbers • polyurethane rubbers • silicon rubber • fluorocarbon rubbers • thermoplastic rubbers 24
  • 22. • Most of the elastics currently used in orthodontics are made up of polyurethane. • Polyurethane rubbers resist heat and withstand remarkable stress and pressures. The ingredients of polyurethane rubbers include ethylene, propylene, glycols, adipic acid, and di-isocyanates. • It has got an excellent strength and resistance to abrasion when compared with natural rubber. They tend to permanently distort, following long periods of time in the mouth and often lose their elastic properties. This is mainly used for elastic ligatures. 25
  • 23. • Elastics can be classified in many ways. According to the material, their availability, there uses, there force … etc.
  • 24. ACCORDING TO THE MATERIAL Latex Elastics: These are made up of natural rubber materials, obtained from plants, the chemical structure of natural rubber is 1, 4 polyisoprene. Synthetic elastics: These are polyurethane rubber contains urethane linkage. This is synthesized by extending a polyester or a polyether glycol or polyhydrocarbon with a diisocynate. These are mainly used for elastic ligatures.
  • 25. •ACCORDING TO THE AVAILABILITY Different makers have different sizes and force, and the colour coding and the name is also different.
  • 29. DIAMETER FORCECOLOUR INCH MM GRAMS OUNCE WHITE 1/8 3.2 56.8 2.0 RED 3/16 4.6 99.4 3.5 GREY 3/16 4.6 127.8 4.5 BLUE 1/ 4 6.4 99.4 3.5 ORANGE 1/ 4 6.4 127.8 4.5 YELLOW 5/16 7.9 56.8 2.0 GREEN 5/16 7.9 99.4 3.5 TAN 5/16 7.9 127.8 4.5 PINK 3/8 9.5 99.4 3.5 LAVENDER 3/8 9.5 127.8 4.5 C O L O U R C O D I N G S
  • 30. DIAMETER FORCE INCH MM GRAMS OUNCE 3/16 4.6 56.8 2.0 5/16 7.9 95.4 3.5 3/16 4.6 113.6 4.0 5/16 7.9 170.4 6.0 H E A V Y . E L A S T I C S 5/16 7.9 227.2 8.0
  • 31. S p o r t s
  • 33.
  • 34. Risks of excessive elastics wear :- •An excessive correction (class ll becoming class lll) •An exaggerate tipping of lower or upper incisors. •Anchorage lost. •Undesirable extrusion / overbite. •Badly / incorrectly hooked elastics may change biomechanical effects complicating the treatment.
  • 35. ANALYSIS OF ELASTIC FORCE • Force produced by elastics on a tooth or teeth depends on its magnitude. The stress produced depends on the site of application, distribution through the periodontal ligament, direction, length, diameter, surface area and contour of root, alveolar process, health, age and above all the co- operation of the patient
  • 36. Force delivery:- Elastic Force application plays a strategic influence on orthodontic movement . Histologicaly optimum orthodontic force should not exceed the intact capillary blood pressure (20- 25 gm/cm2) in order to obtain optimum orthodontic tooth movement and bone remodeling with out perio ligament strangulation and root resorption . Z.DAVIDOVITCH has proposed intermittent forces as more suitable => because the duration will not be sufficient to produce anoxic destruction of the ligament and, the osteoclasts which are stimulated to function by force application would continue to resorb bone for a brief period of time, mobilizing the bone removing cells.
  • 37. The amount of light force exerted by the elastic is at an optimal level to tip the anterior crowns backward but a minimal level to move the lower molars forward bodily. Elastic force received by the molars and anteriors are equal and opposite, the resistance is not equal. So the crown tipping is relatively rapid and bodily movements are slow.
  • 38.
  • 39. Maxillary teeth Mandibular teeth Friction, continuous mechanics, ceramic brackets Heavy forces Frictionless biomechanics, segmented arch wires Light forces Basis of prescribed elastic forces:- Root rating scale in sagital movements
  • 40. Root rating scale in vertical movements
  • 41. Appointment Interval of Elastic wearers:- 1) Importance of movement to be obtained:-
  • 42. 2) The clinical goal to reach:- Orthodontist may advice the patient to schedule his next appointment only when the goal explained by him is achieved. 3) Exaggerated correction risks:- The danger of undesirable movement always persists when the patient walk out of the clinic. so the orthodontist should not hesitate to reduce the clinical visit interval / to reduce elastic wearing in an alternate way-night time only / every other night for example.
  • 43. • ACCORDING TO THE USES. 1) Intra oral 2) Extra oral
  • 44. INTRAORAL ELASTICS CL I elastics horizontal elastics intramaxillary elastics intra-arch elastics:- 1.
  • 45. •These extend with in each arch. • This is used for the space closure and to a certain extent; it can open the bite also. • It is placed from the molar tube to the intramaxillary hook of canine of the same side of the same arch.
  • 46. Different class l elastic uses:- Upper incisor tipping in class ll.2 Intrusion of molar / cuspid with a elastic tied to utility arch. Intrusion of lower incisors
  • 47. Class l elastics to rotate and bring forward the lateral incisor to the opened space by M utility arch. Class l elastic thru an utility helix to close a lower incisor diastema in moving distally the 41 Class l elastic tied to rotate 24 with an opposing force couple. Class l elastic to slide backward the right lower lateral incisor.
  • 48. Class l cross elastics to close diastema. Class l elastics to rotate a canine and a upper 1st premolar with a force couple.
  • 49. Bilateral buccal upper canine corrected with cross „O‟ shaped class l elastics. Correction of too buccal position of 1st premolars with an occlusal elastics
  • 50. Clinical uses of class I elastics :- 1. Space closing. 2. Dental movements 3. Extrusion 4. Intrusion 5. Tipping correction 6. Rotation 7. Strengthening force - minimize loosening anchorage - mid line shift correction
  • 51. Class l applications;-
  • 52. Clinical problems with class l elastics:- •Abnormal tipping •Exaggerated rotation •Exaggerated extrusion •Anchorage lose •Minor or insufficient displacement
  • 53. 2) CL II Elastics Intermaxillary elastics Interarch elastics
  • 54. This is extended from the lower molar teeth to upper cuspid which is placed from lower molar tube to the upper intermaxillary hook of the same side. They are primarily used to cause Antero-posterior tooth changes that aid in obtaining CL I cuspid relationship from a CL II relationship Indications:-
  • 55. . If the lower second molar are banded it is best to extend the elastic from the second molar to the upper cuspid if they are to be used for over two months of treatment. If the elastics are used for 2 to 6 weeks only, then one may extend them from the lower first molar to upper cuspid teeth. This treatment regimen minimizes the side effects from the use of elastics (extrusion of the lower posterior teeth and labial tipping of the lower anterior teeth, lowering of anterior occlusal plain and the creation of gummy smile).
  • 56.
  • 57. Biomechanic influence of mouth opening on class ll elastics force:- With 100gm elastic force 200 to centric occlusal plane:- =>A horizontal component force of: 100 Cos 200= 93.90 gm. => A vertical component force of: 100×Sin 200 = 34.20 gm 100gm With mouth open 10mm at incisor level, resulting in160gm elastic force at 290 to maxillary arch:- The 160gm elastic force makes 350 with the lower archwire:- =>A horizontal component of mesial force is: 160×Cos 350= 131 gm. =>A vertical component of extrusion force is: 160×Sin 350 = 91.8 gm 160gm 190gm 250 open =>maxilla (H-148gm, V-118gm), mandible (H-115gm, V-150gm) =>A horizontal component of distal force is: 160 Cos 290= 139.90 gm. =>A vertical component of extrusion force is: 160×Sin 290 = 77.60 gm Day time elastic wear VS Night time wear
  • 58. Facial type influence with Class ll elastic use and consequences on the antero superior occlusal plane when using continuous archwires
  • 59. Ch.TWEED class ll elastics F.SHUDY‟s 3 point class ll elastics R.ROTH‟s short class ll elastics. R.RICKETTS‟s bioprogressive teqn. Sectional maxillary wire. R.RICKETT‟s class ll utility arch. J.PHILIPPE‟s circummandibular arch
  • 60. Class ll elastic effects with continous archwires
  • 61. Class ll elsatics on sliding hook Class ll elastics placed on a sliding jig Class ll elastics placed on a utility arch. Class ll elastics placed on a Rickett‟s torquing utility arch.
  • 62. Class ll elastic placed on continous arch wire Class ll elastics placed on upper sectional to settle canine relationship with contraction class ll utility arch Class ll elastics placed on a sectional maxillary arch and mandibular utility arch.
  • 63. Bioprogressive torque Class ll elastics:- The continuous contraction arch when activated the anterior occlusal plane tips downwards during contraction. In Riskett‟s Bioprogressive torque utility arch, the class ll elastics pulls downwards and backwards the anterior loop which raises the anterior segment of the arch and increases the anterior torque progressively with contraction. 
  • 64. R.HOCEVAR class ll “check elastics” Class ll molar extrusion elastics. Triangular class ll elastics Influence of the hooked point of the class ll elastics= extrusive component In extraction case In non extraction case from M1 In non extraction case from M2
  • 65. 3) Class III elastics
  • 66. • Class III elastics are exact opposite of the class II‟s. • They extended from upper molar to the lower cuspid. • It is used in the treatment of CL III malocclusions. • It is attached from the maxillary molar to mandibular lateral incisor or canine. • They promote extrusion of upper posterior teeth and upper anteriors, along with lingual tipping of the lower anteriors.
  • 67. Indications 1. To avoid advance maxillary dentition and or retract the mandibular dentition. 2. To correct anterior cross bite. 3. Mandibular crowding in a non extraction case in which it is desired to eliminate the crowding without advancing the mandibular incisor appreciably. 4. In deep bite, low angle, crowded case early use of c1 III elastics will allow the bite open.
  • 68.
  • 69. Biomechanic influence of mouth opening on class lll elastics force:- 100gmWith 100gm elastic force 200 to centric occlusal plane:- =>A horizontal component force of: 100 Cos 200= 93.90 gm. => A vertical component force of: 100×Sin 200 = 34.20 gm With mouth open 25mm at incisor level, resulting in190gm elastic force at 450 to maxillary arch:- The 190gm elastic force makes 290 with the lower archwire:- =>A horizontal component of mesial force is: 190×Cos 290= 92.11 gm. =>A vertical component of extrusion force is: 190×Sin 290 = 166.17 gm 160gm 190gm =>A horizontal component of distal force is: 190 Cos 450= 131.98 gm. =>A vertical component of extrusion force is: 190×Sin 450 = 136.67 gm
  • 70. Influence of class lll on the occlusal plane tilting when using continuous archwire Influence of class lll elastic forces with different facial type and consequences on the vertical component of extrusion
  • 71. Class lll elastic effects with continuous archwires
  • 72. Conventional Class III elastics Regular class III elastic placed on maxillary mesial molar hook Class lll elastic to correct midline shift Class lll elastic placed behind the maxillary molar posteriorly and on anterior hook of a lower inclined bite plate in order to bring forward the upper arch.
  • 73. 4.ANTERIOR ELASTICS: 1. It is used to improve the over bite relationship of incisor teeth. 2. Open bite up to 2mm may be corrected with these elastics. 3. They may extend from the lower lateral incisor to the upper laterals or central incisor teeth or from the lower cuspid to the upper laterals. 4. It is used in conjunction with a plain arch wire for closing spaces between anterior teeth. It produces a reciprocal free tipping of anterior crowns, which closes the spaces. Anterior Elastics. (Force-1 to 2oz.)
  • 74.
  • 75.
  • 76. 5) ZigzagElastics/ Posterior elastics:- Aras A et al 2001 they have done pilot study of “The effect of zig zag elastics in the treatment of CL II div 1 malocclusion subjects with hypo and hyper divergent growth pattern”. The conclusion of this study can be summarized as follows. – Zig zag elastics thus was used in the last stage of fixed appliance treatment of CL II malocclusion in growing patient were effective in the correction of molar relationship. Establishing a good intercuspation as well as improving sagittal skeletal relationship. Force recommended is 2.5 oz.
  • 77.
  • 78.
  • 79. 6] Cross Bite Elastics •This is indicated in unilateral and bilateral cross bites, to expand and upright lower molars which have tipped lingually. • It is placed between the lingual aspect of the lingually placed molar and the buccal aspect of the opposing tooth. Force recommended is 5-7 ounce
  • 80.
  • 81. 7) Cross Palate Elastics • This is to correct the undesired expansion of the upper molars, during third stage. • This is placed between the lingual aspects of the upper molars. • Upper molar expansion during the 3rd stage is usually bilateral, the cross palate elastics is appropriate because the force it exerts in pulling one molar lingually is equal and opposite to the force it exerts in pulling the other lingually.
  • 82. 8) Diagonal Elastics (Midline elastics) Force used is 1 ½ to 2 ½ ounces.
  • 83.
  • 84. 9) Open Bite Elastics • These are used for the correction of open bite. • It can be carried out by a vertical elastic, triangular or box elastic. • Vertical elastic runs between the upper and lower brackets of each tooth.
  • 85. Force used ¼” 6 oz or 3/16” 6 oz.
  • 86.
  • 87.
  • 88. •Triangular elastics aid in the improvement of CL I cuspid intercuspation and increase the over bite relationship anteriorly by closing open bite in the range of 0.5 to 1.5 mm. • They extended from upper cuspid to the lower cuspid and first bicuspid teeth. • It is used for similar reasons of box elastics, but including only 3 teeth 10.Triangular elastics:
  • 89. Triangular Elastics Elastics of 1/8” 3 ½ oz is used.
  • 90. 11)Vertical Elastics(Spaghetti) Force used is 3 ½ oz. •This is useful in whom there is difficulty in closing the bite, whether anteriorly or posteriorly. • This type of elastic is contraindicated in malocclusions that were originally characterized by a deep bite
  • 91. 12] M and W Elastics Force is ¾” 2 ounce. •In an open bite or c1 III tendency, some amount of curve of spee should have been placed in the lower arch. Therefore some curve should be placed in the upper arch as well. • The arch wire is sectioned distal to laterals or cuspids and up and down elastics ( “M” with a tail) are worn. • In class I case M or W without a tail is used. The upper and lower arch wire is sectioned in which the teeth to be extruded. •In class II vector „W‟ with a tail is given.
  • 92.
  • 93. 13.Lingual elastics • This can be used as a supplement or a counter balancing agent to buccal elastic force, there by increasing the efficiency of force distribution. • Lingualy tipped lower molars can be uprighted by the use of class II elastics attached between to lingual hook of the lower molar and intermaxillary hook of upper arch wire on the same side. • Lingual elastics can be used as a substitute for buccal elastics like CL I and CL II elastics, provided the arch wire should be tied back to the cuspid bracket.
  • 94. Lingual Elastics
  • 95. 14) Check Elastics Check elastics can provide a potent mechanism for overbite reduction, causing extrusion of maxillary and mandibular molars and counteracting the tendency of the anchor bends to tip the molars distally plus aiding incisor intrusion.
  • 96. 15] Sling Shot Elastics( Molar distalizing) Two hook on buccal and lingual side of the molar to be incorporated in the acrylic plate to hold the elastic. The elastic is stretched at the mesial aspect of molar to distalize it.
  • 97. 16) Other elastics: Asymmetrical elastics: They are usually CL II on one side and CL III on other side. They are used to correct dental asymmetries. If a significant dental midline deviation is present (2mm or more), an anterior elastic from upper lateral to the lower contralateral lateral incisor should also be used. Finishing elastics: Are used at the end of the treatment for final posterior settling. Force recommended ¾” or 2 oz
  • 98. Midline shift correction Use as many contra lateral teeth possible in each segment
  • 99. ACCORDING TO THE FORCE – low Pull Ranges from 1/8” (3.2mm) to 3/8” (9.53mm). It gives 71 gm force (2 ½ oz) – Medium Pull Ranges from 1/8” (3.2mm) 3/8” (9.53 mm) it gives 128gm or 4 ½ oz force. – Heavy pull Ranges from1/8”(3.2mm) 3/8”(9.53 mm) It gives 184gm or 6 1/2oz force.
  • 100. TYPES OF ELASTICS INTRA ORAL ELASTICS: It can be of light, medium or heavy
  • 101. EXTRA ORAL ELASTICS: Heavy elastics and plastic chain are used with the head gear
  • 102.
  • 103. The twenty commandments of extra oral force application (E.O.F) 1. The E.O.F is a biologic orthopedic appliance. 2. Don‟t use E.O.F with 0.45 molar tube (extrusion / tipping) 3. Use an expansion of the inner face bow. 4. Use the natural musculature effects of cheeks. 5. Control the molar rotation. 6. Expand maxillary arch to avoid buccal eruption of second molars. 7. Keep away archwires when using E.O.F 8. Don‟t use any maxillary bite plate with E.O.F 9. Ask for 14-15 hrs daily wear 10. Don‟t use excessive forces (above 500 gm/ side) 11. Don‟t limit the treatment to E.O.F only. 12. Don‟t use E.O.F in maxillary incisor overbite. 13. Don‟t use E.O.F in every class ll with long range growth forcast. 14. Don‟t stop E.O.F abruptly. 15. Do overcorrect 16. Time needed to growth correction. 17. Don‟t use E.O.F on patients who is still thumbsucking. 18. Enchorage patient motivation. 19. Don‟t stop treatment after orthopedic correction. 20. Don‟t under estimate the simplicity of E.O.F EXTRA ORAL FORCE DELIVERY:- =>Juvenile preventive phase: 350 gm =>Interceptive phase: 400-500 gm =>Adolescent corrective phase:750 gm .in vertical excess tendencies:1000gm .in true vertical excess E.O.F is
  • 105.
  • 107. Elastic separators Elastic separators Dumbell separator
  • 108. E-LINK : It is used as intermaxillary class II and class III applications. It is available in different lengths
  • 109. LIG-A-RING: It is used for individual ligation of the tooth. It can be used in place of conventional ligature ties in straight wire therapy and for cuspid ties in Begg. It is of 1.5 – 2 mm in diameter.
  • 110. TIP EDGE RINGS: It can control and hold the desired degree of mesiodistal inclination. The cross bar can give up-righting forces.
  • 111. E-CHAIN:- (polyurethane) It is used for continuous ligation and consolidation etc. It is available in 3 types. Large (long filament chain) Medium (short filament chain) Small (closed loop chain) Longer the chain‟s filaments the lower the initial force
  • 112. The behaveiour of E-chain can be summarized as:- •A permanent deformation results after over extension of plastic module. •The degradation of force is increased over time. •The force exerted is unpredictable and inconstant over time. •The configuration of chain affects the behavior of the force. •After 3 weeks the residual force is generally about 5% so it is advised to change the E-chains at least every 3 weeks to obtain optimum results. •Oral environment ( such as PH, light, saliva, drinks, foods, dental plaque ) has been associated with degradation of the polyurethane elastomer. •The elastomeric chains must be kept in a container and protected from light. •Extension or prestretching has been advocated before inserting the chains.
  • 113. • Purpose is to improve the large initial force degradation & the constancy of force delivery • Wong – 1976 – pre stretching the elastic chains 1/3 of their original length – improve the strength • Brooks & Hershey – combination of pre - stretching and heat app n – reduced the amount of force degradation by 50 % at 1 hr and 31 % at 4 wks • E chains lose 50- 70 % of their initial force during the first day. • Longer filament chains deliver a lower initial force at the same extension than the closed loop chain • Pre stretching of these chains – means of reducing the rapid force decay rate & giving a constant force PRE STRETCHING OF ELASTICS
  • 114.
  • 115. POWER THREAD: (ELASTIC LIGATURE) This is polyurethane thread, used for rotating, extruding, closing minor spacing and to consolidate
  • 116. ELAST -O CHAIN: It is used for consolidation of arches. It gives a light continuous traction force.
  • 117. ELASTIC THREAD: This is an elastic ligature covered with silk or nylon. The nylon fibers is there to resist the unravelling and protect the latex core. It is available in 3 types. It is used for rotation correction, traction etc, both with fixed and removable appliance. Light Medium Heavy
  • 118. SEPARATING RINGS: – It gives a continuous force during contact opening. » .Small – used in anterior region » .Large – used in posterior region
  • 119. ROTATION WEDGES : It acts as a fulcrum between wire and bracket to correct the rotation. It is ligated to the tie wing of the bracket.
  • 120. PLASTIC CHAIN: It is used extraoraly along with head gear, for the orthopedic correction using heavy forces.
  • 121. FORCE DEGRADATION • Relaxation is defined as a decrease in force value transmitted over time with the element maintained in a fixed activated state of constant strain. • The force decay under constant force application to latex elastic, polymer chains and tied loops showed that the greatest amount of force decay occurred during the first three hours in water bath. The force remained relatively the same throughout the rest of the period.
  • 122. • K.A. Russell et al 2001 conducted the study on the assessment of mechanical properties of latex and non latex orthodontic elastics. • So there were few general conclusions drawn and applied clinically to all elastic types. Although all of elastics met the Australian standard for breaking force there was trend towards non latex elastics having lower breaking force than the latex elastics • After an exhaustive review of the literature regarding elastomeric chain, it is said that most marketed elastomeric chains generally loses 50% to 70% of their initial force during the first day of load application. At the end of three weeks they retained only 30 to 40% of original force
  • 123. In vivo aging phenomena:- electron images of an intermolecular link of a chain. 3 weeks of intraoral exposure. before afterMineralized precipitates electron images of an inter modular link of a chain. 50% elongation for 24 hrs. before after Stressed modular specimen showing regional failures with high percentage elongation without complete rupture. K, Na, Cl, S
  • 124. ELASTIC ALLERGY Latex allergy: Allergies to the latex proteins are increasing which has implication for dental practitioners because latex is ubiquitous in dental environment. K. A. Russel 2001 - reaction to the latex materials have become more prevalent and better recognized- since 1988 adoption of universal precautions. Only 3 reports have been cited in the literature relating latex allergies to orthodontic treatment. 2 of these studies related the allergic reactions to use of latex gloves, and 3rd report related to the development of stomatitis with acute swellings and erythematous buccal lesions to the use of orthodontic elastics
  • 125. Staining of elastics Elastomeric materials do stain from certain food such as mustard. The attempt to solve this problem by masking with metallic colour inclusions reduces the strength and elasticity because of the difference in the resilient properties. A study regarding staining in 1990 by Kenneth divided into 3 categories. No staining: - With coco cola and presumably most colorless food stuffs. Gradual staining: - With chocolate drink, red wine, tomato ketchup. Rapid staining: - With coffee and tea.
  • 126. FLUORIDE RELEASE FROM ORTHODONTIC ELASTIC CHAIN – Plaque accumulation around the fixed orthodontic appliance will cause dental and periodontal decease. • Decalcification can be avoided by mechanical removal of plaque or by topical fluoride application. • Controlled fluoride release device (CFRD) have been in use since 1980‟s. in such device a co-polymer membrane allows a reservoir of fluoride ions to migrate into oral environment .
  • 127. – A study was designed to know about stannous fluoride release from a fluoride impregnated elastic power chain. – The delivery of stannous fluoride by means of power chain would presumably reduce count and inhibit demineralization. – (An average of 0.025mg of fluoride is necessary for reminerilization). – But this protection is only temporary and of a continued exposure needs, the elastic should be replaced at weekly intervals. The force degradation property will be higher with the fluorinated elastic chain.
  • 128. ELASTIC LIGATURES Vs WIRE LIGATURES – Elastic ligature may be a substitute for the wire ligatures in most situations. – Elastic ligatures will give an easy work to the doctor and since no sharp ends it will be more acceptable by the patient. – In rotation control, during leveling and aligning higher force levels than elastomeric materials is required. The brackets in rotation cases the partial engagement of the arch wire will be difficult with elastic ligature, so in these cases wire ligature are advised.
  • 129. – When the sliding of a bracket on the arch wire is needed, it is advisable to use elastic ligature because of its smoothness. – The strength and inflexibility of wire ligatures may also provide more secured ligation. The relatively low strength of the elastic ligature is its major disadvantage. – Ligature wire can transfer elastic force from arch wire to tooth and for holding the engagement of the arch wire in the bracket.
  • 130. COIL SPRINGS Vs ELASTICS – To overcome the drawbacks of elastomeric material, Andrew L. Souis in 1994 conducted a study NiTi coil springs and elastics. – This study concluded that:- - NiTi coil springs have been shown to produce a constant force over varying length with no decay. - NiTi coil spring produced nearly twice rapid a rate of tooth movement as conventional elastics. - No patient co-operation needed. - Coil springs can stretch as much as 500% with out permanent deformation. – The force delivered is 90 to 100gm.
  • 131. ARMAMENTARIUM – Dontrix Gauge:- It is used to determine proper size elastic for each application by measuring the force. Measuring range is 28gm – 450gm. – Stress Gauge (correx Gauge):- The measuring range is 25-250gm or 100-500gms or 200 – 1000 gm.
  • 132. – Elastic separator placing pliers:- Pliers with the limit for excess expansion. Rounded beak protects patient‟s soft tissue. It can be used with large and small rings
  • 133. – Mathieu Forceps:- It is used for placing all types of elastomers. It has got a slip free grasping and quick release ratchets for fast operation. – Twirl on ligature:- It is used for placing elastomeric modules and can be preloaded.
  • 134. Module remover Double ended instrument for removing modules from the bracket. Mosquito forces Having curved delicate serrated tips for applying modules
  • 135. Orthodontic wrench It is a double ended plastic instrument for the use of attaching and elastics by patient himself Elastic positioner for power modules
  • 136. Disadvantages,and warning signal of elastics wearing 1. Muscular fatigue? - myalgia 2. TMJ arthalagia – pain 3. Functional mandibular limitations. 4. Mandibular dyskinesia. 5. Increased noise: -clicking –ligament laxity –crepitus. 6. Excessive dental tipping: - molar anchorage – forward/ backward incisors. 7. Teeth interferences: -mobility –dental pain –preiodontal problems. 8. Condyle loading signals with: -classlll elastics –chin cup 9. Improper incisor guidance: -openbite –overbite 10. Multiple root resorption (intrusion/ettrusion) 11. Chronic tongue interposition. 12. Excessive growth / insufficient growth.
  • 137. • To put it in a nut shell elastics is a prime consideration in orthodontics and is the most versatile material available to the orthodontist. • In treating our patients we have to make use of whole philosophy of elastic forces rather than a technique. • We have to use elastic forces carefully to get a mobile force without threatening anchorage. • An orthodontist who does not exploit these materials to the fullest is not doing justice to the patient. Always think of minimum effort maximum effect in short time possible to patient comfort.
  • 139. THE MOST IMPORTANT ELEMENT PATIENT COMPLIANCE! …….not a million dollar question!
  • 140. • Michel Langlade- “Optimization of orthodontic elastics” • William Brantly- “Orthodontic materials” scientific and clinical aspects. • Bishara Samir E. and Anderson George F., “A comparison of time re: • lated forces between plastic Elastics”. Angle Orthod. 1970; 40; 319-328. • Brantley William A.“Effects of pre-stretching on force degradation characteristics of plastic modules”. Angle Orthod. 1979; 49; 37-43. • David L. Baty, “Force delivery property of colored elastomeric modules”. Am J Orthod Dentofac Orthop., 1994; 106; 40-46. • David L. Baty, “ Synthetic Elastomeric chains a Literature Review” Am J Orthod Dentofac Orthop.1994:105:536-42. REFERENCES:
  • 141. • Aras. A et al “The zig zag elastics in the CL II div 1 malocclusion. Subject with hypo and hyper divergent growth pattern, a pilot study , Eur J orthod.: 2001; 23; 393-402. • Asbell M. B., “A brief history of orthodontist”. Am J Orthod Dentofac Orthop. 1990; 98; 176-182, 206-213.. • Bertl Wolfgang. H. and Droschl Helmut, “Forces produced by orthodontic elastics as a function of time and distance extended. Eur J Orthod. 1986; 8; 198-201. • Graber T.M. and Swain B.F., “Current orthodontic concepts and techniques”. second edition. Toronto; W.B. Sounders company; 1975. • Graber T. M and Bedrich Neuman, “Removable orthodontic appliances”, second edition London; W.B. sounders company; 1984. • Joseph V.P. “Fluoride release from orthodontic elastic chain”. J.Clin Orthod. 1993; 26; 101-105. • Kenneth K.K Lew, “Staining of clear elastomeric modules from certain- foods”. J.Clin Orthod. 1990; 24; 472-474. • Sonis. Andrew L. “comparison of NiTi coil springs Vs elastics in canine retraction”. J.Clin Orthod. 1994; 28; 293 – 295. • Taloumis Louis et al; “Instructions for wearing elastics”; J. Clin Orthod; 1995 ; 25; 49;.
  • 142. THANK YOU So ask your patients to bring back the worn out elastics when they return back next visit.