ELASTICS AND ELASTOMERICS
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INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
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CONTENTS 1.
INTRODUCTION.
2.
TERMINOLOGY
3.
HISTORY OF ELASTICS AND ELASTOMERICS
4.
PROPERTIES OF ELASTICS AND ELASTOMERICS
5.
ANALYSIS OF ELASTIC FORCE
6.
FORCE DEGRADATION www.indiandentalacademy.com
7.ELASTIC ERRORS 8. CLASSIFICATION OF ELASTICS 9.TYPES OF ELASTICS 10. PRE STRETCHED ELASTICS 11.FLUORIDE RELEASE FROM ORTHODONTIC ELASTIC CHAIN 12.CLASS II ELASTICS IN ORTHOPEDIC CORRECTION 13.CLASS II ELASTICS AND T M D 14.ELASTIC LIGATURE V/S WIRE LIGATURES www.indiandentalacademy.com
15.COIL SPRING V/S ELASTIC 16.ORTHODONTIST’S PART IN PATIENT WEARING ELASTICS 17.ARMAMENTARIUM 18.INSTRUCTION FOR WEARING ELASTICS 19.CONCLUSION 20.REFERENCES
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INTRODUCTION • Elastics and Elastomeric are routinely used as a active component of orthodontic therapy. Elastics have been a valuable adjunct of any orthodontic treatment for many years. There use, combined with good patient cooperation, provides the clinician with the ability to correct both Anteroposterior and vertical discrepancies. www.indiandentalacademy.com
• 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. www.indiandentalacademy.com
• The links of chain fit firmly under the wings of an edgewise bracket so that chain elastomers also serve to replace metal as the ligating force that holds the arch wire to the teeth. Since they are so positively located on the brackets it is usual for the chains to remain in situ until replaced by the orthodontist at the next visit of the patient. This routine differs from that usually followed for latex elastics, which are changed by the patient every one or two days. www.indiandentalacademy.com
The use of latex elastics in clinical practice is predicted on force extension values given by the manufactures for different sizes of elastics. The standard force index employed by suppliers indicates that at three times the original lumen size, elastics will exert the force stated on the package. From a clinician view it would be mandatory not only to know the clinical aspect of these elastics but also their basic properties, in order to extract the most out of these polymers. So in this seminar I hope I would succeed in www.indiandentalacademy.com presenting the overall aspects of elastics and elastomeric.
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 www.indiandentalacademy.com
• 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 www.indiandentalacademy.com
• 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. It is stressed not to www.indiandentalacademy.com exceed it proportional limit
• 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 became known as vulcanization.
• 1 ounce (oz) = 28.35grams. www.indiandentalacademy.com
HISTORY OF ELASTICS AND ELASTOMERICS • Elastomer is a general term that encompasses materials that, after substantial deformation, rapidly return to their original dimensions. • Natural rubber -the first known elastomer, used by the ancient Incan and Mayan civilizations. It had limited use because of its unfavorable temperature behavior and water absorption properties. • With the advent of vulcanization by Charles Goodyear in 1839, uses for natural rubber greatly increased. Early advocates of using natural latex rubber in orthodontics were Baker, Case and Angle. www.indiandentalacademy.com
Natural Rubber • When the early European explorers came to Central and South America, they saw the Indians playing with bouncing balls made of rubber. • The South American Indians called the rubber tree cahuchu, weeping wood. The drops of latex oozing from the bark made them think of big white tears. • A French explorer, Charles Marie de la Condamine, gathered the sample of hardened latex in Peru in 1735, called this new material caoutchouc. Variation in the French spellings are used as rubber in most European countries. • In 1770, the English chemist Joseph Priestley discovered that the materials could be used as an eraser to rub out pencil marks. From this use we get the name rubber. www.indiandentalacademy.com
• In 1846 E Baker in article on “the use of Indian rubber in regulating teeth” in New York dental recorder, he explained by cutting a narrow strip from thin sheet of Indian rubber and extending it to nearly its utmost capacity without breaking, fastened to the tooth to be regulated. • A French man JMA Strange in 1841 claimed that he used a rubber attached to some hooks on the appliance surrounding the molars for retention. • John Tomes in 1848 used the elastics springs with metal plates. www.indiandentalacademy.com
• It is also believed that the use of elasticity developed by Schange in 1948. The appliance designed by Farrar treated by the rubber plains in 1876. • Celvin Case discussed the use of intermaxillary elastics at the Columbia Dental Congress. However in 1893 Henry A Baker was credited with, originating the use of intermaxillary elastics with rubber bands and named it as Baker Anchorage. . Angle in1902 described the technique before the New York institute of www.indiandentalacademy.com Stomatology.
Synthetic Rubber • Synthetic rubber polymers developed from petrochemicals in the 1920’s have a weak molecular attraction consisting of primary and secondary bonds. • Elastomeric chains were introduced to dental profession in the 1960’s and have become integral part of orthodontic practice. They are used to generate light continuous forces. They are inexpensive, relatively hygienic, easily applied and required no patient cooperation. • From here and there have been numerous advances in manufacturing process which have let to a significant importance in their properties, with this there has been greater application of these elastics in clinics in variety of uses. www.indiandentalacademy.com
PROPERTIES OF ELASTICS AND ELASTOMERICS • 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. • Rubber is especially useful for several reasons:– it holds air – keeps out the moisture – does not readily conduct electricity.
•
But its chief www.indiandentalacademy.com importance to us is that it is elastic.
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 mineral matter. Latex holds little globules (particles) of rubber in the same way that milk holds butterfat. 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 thewww.indiandentalacademy.com rubber tree.
• In 1860, another Englishman, Greville Williams, heated some rubber and obtained a colourless liquid that he called isoperene. Each isoperene molecule contains five carbon atoms and eight hydrogen atoms (C5H8). The atom in the isoperene molecules always forms a definite pattern. Four of the carbon atoms form a chain. The fifth carbon atom branches off from one of the carbons in the chain. Three hydrogen atoms surround the fifth carbon atom to form a methyl group. : www.indiandentalacademy.com
The following chemical symbols show the arrangement of the five carbon and eight hydrogen atoms in the isoperene molecule 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 a giant, chainlike molecule, the rubber molecule. Chemists call such chainlike molecule polymers, meaning “many parts.� They call single molecules, such as isoperene, www.indiandentalacademy.com monomers.
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• 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. • Scientists have not discovered all the answers to the chemistry of rubber. For example, they once believed that sulphur atoms attached themselves to unsaturated carbon atoms during vulcanization. But the sulphur reaction that makes rubber hard now seems more complicated than this. In many other ways, the chemistry of natural rubber remains mystery.www.indiandentalacademy.com
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. • Manufacturers group synthetic rubbers into two classes: General-purpose and specialpurpose. www.indiandentalacademy.com
• 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 do. Also some of these specialpurpose rubberswww.indiandentalacademy.com have greater resistance to heat and cold.
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• Special-purpose rubbers include • • • • • • • • • •
butyl rubber cispolyisoperene rubber neoprene rubber nitrile rubber polysulphide rubbers polyurethane rubbers silicon rubber ethylene-propylene rubbers fluorocarbon rubbers thermoplastic rubbers www.indiandentalacademy.com
• Most of the elastics currently used in orthodontics are made up of polyurethane. • Polyurethane rubbers resist age and heat and withstand remarkable stresses and pressures.. Polyurethane foams come dense to light. The ingredients of polyurethane rubbers include ethylene, propylene, glycols, adipic acid, and diisocyanates. • 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. www.indiandentalacademy.com
• Structure of polyurethane being NH2(CH2)X NH2 + HOOC(CH2)X’COOH---------H(-NH(CH2)X NHCO(CH2)X’(CO-)Y OH + H2O HO(CH2) XOH + OCN(CH2)X’ CNO-------(-O(CH2)XOCONH(CH2)X;NHCO-)Y – Polyurethanes are polymers containing the group.
H
O
N
C
O
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• Formed typically through the reaction of a diisocyanate and a glycol. • XOCNRCNO + XHOR’OH----------[OCONHRNHCOOR’-]X
•
C2H6O2
+
– (GLYCOL GROUP)
CH2
CH2
OH
OH
C2H4(CNO)2 (DIISOCYANTI)
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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 and direction, length, diameter and contour of root, alveolar process, tooth rotation and health, age and above all the co-operation of the patient www.indiandentalacademy.com
• CL I elastic traction is judiciously combined with strong anchor bend. Deliberate consideration of anchorage conservation is essential, because the resultant of the retractive and intrusive forces that lies distant to the maxillary molars will induce adverse movements or anchorage loss of the maxillary molars. (Fig) • Intermaxillary elastic force exerts pressure on the incisor in a vertical direction bringing them into supraocclusion or accentuating supraocclusion already present. Tilting of anchor teeth may also occur. www.indiandentalacademy.com
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• BIEN analyzed elastic force under various conditions. He found intermaxillary elastics strength of 4oz, when the mouth is closed shows a distal driving force of 3.9oz or a loss of 2.5%. When the mouth is opened the distal force is 3oz or a loss of 25% with the head gear, with elastics parallel with maxillary arch, the driving force is 4oz and no loss. • The upward displacement force on mandibular molars is 2.6oz with mouth open and 0.9oz with closed mouth. With head gear, no displacement force on mandibular 1st molars. Fig www.indiandentalacademy.com
• Rotational force in the mandibular molars is 5.4oz with closed mouth and 4.1oz with open mouth. The downward displacement on molar teeth of 0.9oz is seen when mouth is closed. This pressure is neutralized by the upward pressure in the mandibular 1st molar. •
The rotational root force in maxillary molar is 8.4oz when mouth is closed and 13.7oz when mouth is open.
•
The arch wire force on the lower molar tends to tip the crown distally and root mesially. The forward pull of the elastic force tends to counteract distal crown tipping and to augment mesial root tipping. If the anchor bent and elastic forces are appropriate the tooth will remain upright. www.indiandentalacademy.com
• 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. •
A continuous force can bring about rapid intrusive movement. Each anterior tooth will intrude by a force as light as 20 to 30 gms. The light force produces very short hyalinizations periods and the anterior teeth will be intruded www.indiandentalacademy.com quite rapidly. (Fig).
• The tip back of the lower anchor molar in response to the anchorage bend can be controlled by CL II elastic force. When the elastic force is lower, the crown may tip back more and the root tip forward less. This is more often with 1 ½ to 2 ½ oz. (43 to 71 gms) elastics that usually sued in non extraction treatment. •
When the elastic force is greater, both crown and root may tip. It may upright the molar but imparting little or no net distal movement. This is observed with 2 ½ to 3 ½ oz.(71-99 gms) CL II elastic in extraction cases. www.indiandentalacademy.com
• The different amounts of elastics forces, increasing with the rapid restoration rate of crown tipping and the slower rate of root movement can bring about tooth movement differentials suitable for problems ranging from CL II extraction cases to CL I non extraction cases.
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FORCE DEGRADATION • Relaxation is defined as a decrease in force value carried or 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 www.indiandentalacademy.com the rest of the period .
• G. F Anderson and S. Bishara in 1970 compared (invitro) alastik chain with elastics when stretched to a maximum of 105mm from the molar on one side of the arch to the molar on the other side all along the arch. He observed that alastik chains were permanently deformed by approximately 50% of its original length as compared to 23% with elastics. Both took strain from saliva. • Under all conditions most of the loss or decay in force occurs in 24 hours, for elastic it is about 74% and 41% for ¾” elastics. The greatest force decay per unit of time occurred the 1st hour. They suggested that alastik chains are effective in condensing arches that have generalized spacing but less effective in retracting canines. www.indiandentalacademy.com
• An in-vitro study in Bapuji Dental College by Dr. Balajee Katta under the guidance of Dr. K Sadashiva Shetty, in 1993 shows continuous force decay throughout. An initial decay and most of this drop occurred during the 1st day. For alastiks 53% elasto force 48.6% and E-links 43.3%. Greatest percent of force decay per unit time occurred during the first hour for alastiks 47.7% elastoforce 40.6% and E-links 33.1% •
K.A. Russell et al 2001 conducted the study on the assessment of mechanical properties of latex and non latex orthodontic elastics. So there are few general conclusions that can be 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 www.indiandentalacademy.com
• After an exhaustive review of the literature regarding elastomeric chain, it can be 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
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ELASTIC ERRORS 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 3 rd report related to the development of stomatitis with acute swellings and erythematous buccal lesions to the use of www.indiandentalacademy.com orthodontic elastics
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C. Nattrass, A. J. Ireland, C.R. Lovell 1999; case report summary A nineteen years old girl with mild asthma had had 16 months of orthodontic treatment as a part of the joint orthodontic / orthognathic approach to her 9.5mm over jet. At the of banding her second molars she developed latex protein allergy as a reaction to the operator’s non sterile gloves she also gave a history of allergy to other substances as well as eczema. The patient was confirmed as allergic to latex protein by radioallergosorbent test (RAST) for IgE, requiring precautions be taken during further orthodontic procedures as well as during the subsequent surgery orthognathic surgery for underline class II skeletal pattern. www.indiandentalacademy.com
• Bruno W. Kwapis and John E . Knox. Case report: Rubber rings have several specific applications in dental practice. Displacement beneath the gingiva can lead to rapid destruction of the supporting tissues and subsequent loss of teeth. David C. Vandersall He studied about localized peritonitis induced by rubber elastics www.indiandentalacademy.com
• Frank G. Everett and Thurman L. Hice 1974 Case report: Contact stomatitis resulting from the use of orthodontic rubber elastics • John Holmes, et al 1993 concluded that in in-vitro conditions all orthodontic rubber bands cytotoxic. Clinically, however, this effect is not demonstrable. www.indiandentalacademy.com
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. It is because of the difference in the resilient properties. A study regarding staining in 1990 by Kenneth K. K. Lew divided into 3 categories. No staining: - With coco cola presumably most colorless food stuffs. Gradual staining: - With chocolate drink, red wine, tomato ketchup. Rapid staining: - With coffee and tea. www.indiandentalacademy.com
STORAGE According to the manufactures the orthodontic elastics should be stored in the refrigerator, because increased atmospheric temperature for a long period will decrease the strength. Keeping in refrigerator (cool and dry) will give long shelf life. www.indiandentalacademy.com
CLASSIFICATION OF ELASTICS
• Elastics can be classified in many ways. According to the material, their availability, there uses and force. www.indiandentalacademy.com
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 diol with a diisocynate. These are mainly used for elastic ligatures. www.indiandentalacademy.com
•ACCORDING TO THE AVAILABILITY Different makers have different sizes and force, and the colour coding and the name is also different. I have taken DENTARUM and T.P. elastics as an example. Others are B. M UNITEX, AMERICAN ORTHODONTICS, ORMCO and G,A.C www.indiandentalacademy.com
COLOUR
DIAMETER
FORCE
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
127.8
4.5
LAVENDER
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3/8
9.5
H E A V Y . E L A S T I C S
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
5/16
7.9
227.2
8.0
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• ACCORDING TO THE USES. 1) Intra oral 2) Extra oral
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INTRAORAL ELASTICS 1) CL I elastics or horizontal elastics or
intramaxillary elastics or intra-arch elastics:– The force recommended is 1 ½ to 2 ½ oz for non extraction cases and 2 to 4 oz. in extraction cases.
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2) CL II Elastics / intermaxillary elastics / interarch elastics The force recommended is 1 ½ to 2 ½ oz. in non extraction case and 2 to 4 in extraction cases.
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3) Class III elastics Recommended force is ¼” elastic with 3 ½ oz
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4)
Anterior Elastics.
(Force-1 to 2oz.)
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5) Zigzag 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. www.indiandentalacademy.com
– A significant extrusive effect on molar teeth was not observed. – In both groups the vertical position of the upper incisor showed a statistically significant increase. But this was greater in hypo divergent group. – As there was no unfavorable effects on the vertical jaw base relationship the zig zag elastic system is preferable especially in hyper divergent subjects.
Force recommended is 2.5 oz. www.indiandentalacademy.com
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6] Cross Bite Elastics Force recommended is 5-7 ounce
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7) Cross Palate Elastics
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8) Diagonal Elastics (Midline elastics)
Force used is 1 ½ to 2 ½ ounces.
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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 www.indiandentalacademy.com
10] Box Elastics
Force used ¼”
6 oz or 3/16” 6 oz.
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11) Triangular Elastics
Elastics of 1/8� 3 ½ oz is used.
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12) Vertical Elastics (Spaghetti) Force used is 3 ½ oz.
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13] M and W Elastics Force is ž� 2 ounce.
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14)Lingual Elastics
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15) Check Elastics
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16] 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.
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17)C1 II and C1 Pull Elastics
It is used for final setting of teeth. Usually ž�, 2 oz elastic is used. The elastic is used between each pair of teeth and hence on the central incisors on opposite sides of the midline. It starts from the 2nd molars. In c1 II pull upper 2nd molar is not included. www.indiandentalacademy.com
18)Elastics in removable appliance
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19)Half Strength Elastics The half strength c1 II elastics are used to distribute the tractive force more evenly, not to increase the amount of force. They are extended from hooks on the buccal tubes to the intermaxillary hooks on the arch wire and the other extend is from the lingual hook on the lower molars to the lingual cleat on the upper cuspids. Elastics with the force of 1-2 oz. are usually employed. www.indiandentalacademy.com
– Advantages:- Lower molars do not tend to tip lingually - Lower molars do not tend to rotate mesio-lingually and no toe in bent in the arch wire is required. - Buccal elastics on the intermaxillary hook tend to retract all of the upper anteriors, and lingual elastics tend to retract the cuspid, so it will be helpful to decrowd the anteriors.
• The basic principle should be observed in conjunction with the use of elastics, the force exerted on the anchor molar of the lower jaw must not be increased, and if two elastics of one are used, on each tooth, the elastic force should be half the strength. www.indiandentalacademy.com
20) 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 ž� or 2 oz www.indiandentalacademy.com
ACCORDING TO THE FORCE – High 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.
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Elastic separators Elastic separators
Dumbell separator
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TYPES OF ELASTICS INTRA ORAL ELASTICS: It can be of light, medium or heavy
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EXTRA ORAL ELASTICS: Heavy elastics and plastic chain are used with the head gear
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E-LINK : It is used as intermaxillary class II and class III applications. It is available in different lengths
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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. It also can be used for individual tooth rotation with placing.
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TIP EDGE RINGS: It can control and hold the desired degree of mesiodistal inclination. The cross bar can give up-righting forces.
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E-CHAIN: It is used for continuous ligation and consolidation etc. It is available in 3 types. Small (continuous) Medium (short)
Large (long)
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POWER THREAD: (ELASTIC LIGATURE)
This is polyurethane thread, used for rotating, extruding, losing minor spacing and to consolidate
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ELAST -O CHAIN: It is used for consolidation of arches. It gives a light continuous traction force. No solid bar between modules. It is stamped from translucent resilient elastomeric material
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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
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SLIP – NOT ELASTOMERIC THREAD: This is of tube in nature and during tying it will collapse. So single knot can hold properly. It can also use a tubing for ligature wire to tie the palately erupted cuspid to the arch wire. Heavy
Regular
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TUBING (SLEEVE): It is a flexible plastic tubing which slips over the arch wire to prevent irritation to the soft tissues. It is used with lip – bumper, utility arches etc. It can also prevent the over closure of spaces when used with the arch wires.
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SEPARATING RINGS: It gives a continuous force during contact opening. .Small – used in anterior region .Large – used in posterior region
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DUMBELL SEPARATORS: It is used for rapid opening of the contact points for the placement of bands. It is of two types. Small – for anterio Large – for posteriors
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ELASTIC SEPARATORS: It is also used for rapid opening of the contact points for the placement of bands. It is of two types and color coded for anteriors and posterio
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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.
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PLASTIC CHAIN: It is used extraoraly along with head gear, for the orthopedic correction using heavy forces.
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PRE STRETCHING OF ELASTICS – Brooks and Hershey reported in 1978 that pre stretching the plastic modules reduced the amount of force degradation. They found that modules pre-stretched for one day and immediately tested there after maintained 15 to 20 percent more of the initial force to the first day and 10 percent more the initial force. • J. Young and J. L. Sandrik suggested in 1979 that the chains should be pre-stretched by manufacturers orwww.indiandentalacademy.com operator, which would decrease the force loss of the elastic polymer
Allen. K. Wong suggested in 1976 that the elastomeric materials need to pr-stretched 1/3rd of their length to pre stress the molecular polymer chain. This procedure will increase the length of a material. If the material is over stretched a slow set will occur but will go back to original state in time. If the material is over stretched to near breaking point, over and over again permanent plastic deformation will occur. •
These means that the initial force may come to an effect during an pre stretched process. So when it is in use it will give more stable force. www.indiandentalacademy.com
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 or with a mechanical sealant layer • Controlled fluoride release device (CFRD) have been in use since 1980’s. in such device a copolymer membrane allows a reservoir of fluoride ions to migrate into oral environment rate. www.indiandentalacademy.com
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– The permanent study was designed to a 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. www.indiandentalacademy.com
CLASS II ELASTICS IN ORTHOPEDIC CORRECTION – In orthopedic treatment high priority is given to the establishment of optimal articulation and occlusion of teeth, as well as stability of the result achieved. – P. G. Sander in 1980 conducted a study on c1 II elastics on orthopedic correction. He tried a double plate appliance with and without elastics, in class II correction where activator is indicated. (Fig 61 a). – Hotz (1970) believed that a double plate appliance with class II elastics works in manner similar to that of an activator. www.indiandentalacademy.com
– Sander suggested that double plate appliance is equal to or better than activator. Activity will be greater with CL II elastics when compared to double plate appliances and activator. Asymmetrical jaw positions is much more common when CL II elastics were applied to double plate appliance. – Chewing pattern is difficult when CL II elastics are used during treatment. There was no discrete occlusal contact but rather a region of occlusion. The CL II elastics did not bring the lower jaw in to a stable position. – After treatment tooth positioner has to be advised. Chopper bite is often find in patients treated with CL II elastics. – Due to the proprioceptive guiding mechanism is altered with CL II elastics with straight wire appliance in www.indiandentalacademy.com growing patients will bring the mandible foreword.
– A study conducted by Petrovic and others in CL II elastics in orthopedic corrections, reveals that – )Intermaxillary elastics between upper and lower jaws not only move teeth but are also orthopedic appliances which are able to stimulate the growth amount and rate of the condylar cartilage. CL II elastics induced a posterior rotation in growing subject. – )CL II elastics on the growth rate of the condyle appears to be primarily through the menisco-temporocondylar frenum ( retrodiscal pad) CL II elastics elicit an earlier chondroblastic hypertrophy and an increased growth rate only when the retrodiscal pad is present. Intraoral CL II elastics stimulate the condylar cartilage growth rate and the lengthening of the mandible more strikingly than the extra oral elastics. www.indiandentalacademy.com
– In a case reported by Michael Kelly in 1986 explained the use of heavy CL II elastics in the correction of CL I division 1 subdivision. His findings indicates a reduction in maxillary forward growth and free mandibular forward development under 1½ to 3 oz of CL II elastics, along with Begg mechanotherapy. –
Dermaut L. R. and Breeden L., in 1981 conducted a study for measuring bone displacements due to orthodontic forces, by means of halographic interferometry, the effects of CL II elastics on a dry skull. The results reveal that sutures in the skull behave as weak structures. With regard to the nasofrontal sutures, the main movement was an anterioposterior displacement. This could be contributed to the force direction of the elastics. Related to the 1 st molar, as the anchor unit, the vertical displacement was most pronounced. The zygomaticotemporal suture was behaving as a hinge axis in a transversal direction.
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CL II ELASTICS AND T M D – Class II elastics and maxillary premolar extractions have been implicated as causes of temporomandibular disorders. Only anecdotal evidence has been offered supporting this claim. – A study on this been conducted by Maria T. O’reilly et.al in 1993. The study was mainly on the joint sounds, muscle tenderness and range of mandibular motion. – The only significant finding in this study was a mild pain on palpation lateral to the TMJ capsule at the 8-10 month period during orthodontic treatment. This was present for 40% of the subjects. www.indiandentalacademy.com
– There is no logical explanation for this findings. – These subjects were beginning to have the extraction spaces closed and their teeth and jaws may have been sore because of the tooth movement and changing proprioception. Possibly, their awareness of their TMJ’s was more pronounced. May be when they experience pain in one area. – They have concluded that orthodontic treatment involving extraction and CL II elastics having no effect or little effect. www.indiandentalacademy.com
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, higher force levels than elastomeric materials is required. With double 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. www.indiandentalacademy.com
– 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. www.indiandentalacademy.com
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 shows the following:- 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. www.indiandentalacademy.com – The force delivered is 90 to 100gm.
– In 1951 Walter R Bell conducted a research to determine the amount of force applied in the use of elastics and coil springs in orthodontic therapy. – He found that the spring will exert a denudable amount of force and may be relied upon to act constantly in the interval between appointments; oral fluids and long periods of use do not alter the efficiency of the steel coil. – The study conducted in our department in 1993 by Dr. Balajee Katta and Dr. K. Sadashiva Shetty observed that the force decay occurred during the first day while NiTi springs showed significant degradation from the first week. www.indiandentalacademy.com
ORTHODONTIST’S PART IN PATIENT WEARING ELASTICS – Educate the patient to wear the elastics continuously except while brushing and replacing. Occasionally there may be some exceptions. – Instruct the patient carefully where the elastics are to be attached and have him to do so before you. – Every visit check whether the patient is wearing elastics, properly or not. – Make sure that the patient can place his elastics easily and that they remain in place. www.indiandentalacademy.com
– Check whether the hooks, pins, tubes, cleats are easily accessible and remove all sharp edges that may cause breakage of elastics. – Caution the patient not to allow the lower jaw to come forward in response to the pulling force exerted by CL II elastics. Be sure that the patient closes in the proper retruded position. – It is most important to impress upon the patient and the parents, that if there is any difficulty inwww.indiandentalacademy.com wearing elastics it should be informed to your office immediately.
– Dispense sufficient amount of elastics required till the next visit. – Do not increase elastic force for a patient who shows unsatisfactory progress, before making sure that he is actually wearing the elastics already prescribed. – Patient who is slow or awkward in placing elastics, patient who leaves the office without replacing elastics, those patients appear at office without elastics, patients who claims that he wears elastics most of the time are showing a poor co-operation. www.indiandentalacademy.com
ARMAMENTARIUM – Dontrix Gauge:It is used to determine proper size elastic for each application by measuring the force. Measuring range is 28gm – 450gm.
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– Stress Gauge (cortex Gauge):The measuring range is 25-250gm or 100500gms or 200 – 1000 gm.
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– 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
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– 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.
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Module remover Double ended instrument for removing modules from the bracket.
Mosquito forces Having curved delicate serrated tips for applying modules
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Orthodontic wrench It is a double ended plastic instrument for the use of attaching and elastics by patient himself
Elastic positioner for power modules
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INSTRUCTION FOR WEARING ELASTICS • Louis Talmouis et al. (J.CLINICAL ORTHOD. 1995; 25; 49). as designed an instruction form for patients to understand instructions and demonstrate proper placement of elastics. The elastic configuration is hand – drawn on the form as the patient would seen in the mirror. Table 3 www.indiandentalacademy.com
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CONCLUSION • To put it in a nut shell elastics is a prime consideration in orthodontics. • Elastics are one of the most versatile material available to the orthodontist. • Its an invaluable tool of the orthodontist armamentarium. • An orthodontist who does not exploit these materials to the fullest is not doing justice to the patient. As a matter of fact I would think that it is all but not impossible to practice in this branch of dentistry without this material. www.indiandentalacademy.com
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