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Elastomeric & new materials, recycling and biodegradation of materials /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

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    Elastomeric & new materials, recycling and biodegradation of materials /certified fixed orthodontic courses by Indian dental academy Elastomeric & new materials, recycling and biodegradation of materials /certified fixed orthodontic courses by Indian dental academy Presentation Transcript

    • Elastomeric and newer materials Recycling of materials Biodegradation of materials Hypersensitivity reactions Disinfection procedures www.indiandentalacademy.com 1
    • INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com 2
    • DISINFECTION PROCEDURES Objective of sterilization –Removal of microorganisms or destroy them from materials or from areas since they cause contamination, infection and decay. In microbiology Surgery Drug & food - to prevent contamination - to maintain asepsis -for ensuring the safety www.indiandentalacademy.com 3
    •  Sterilization – The process by which an article, surface, or medium is freed of all living microorganisms either in the vegetative or spore state  Disinfection – The destruction or removal of all pathogenic organisms, or organisms capable of giving rise to infection www.indiandentalacademy.com 4
    •  Antisepsis – used to indicate the prevention of infection, usually by inhibiting the growth of bacteria in wounds or tissues SEPS ( A Greek word ) – PUTRID  Bactericidal agents  Bacteriostatic agents www.indiandentalacademy.com 5
    • Elastomerics  Elastomer is a material that after substantial deformation rapidly returns to its original dimensions.  Natural rubber- ancient Incan & Mayan civilization- 1st known elastomer  Charles goodyear- 1839vulcanization www.indiandentalacademy.com 6
    • Elastomerics  Natural rubber latex elastics- Baker, Case, Angle- early advocates  Polymer rubbers – developed from petrochemicals – 1920 www.indiandentalacademy.com 7
    • Structure  Primary + secondary bonds- weak molecular attraction  At rest – folded linear molecule  On extension – unfold- expense of secondary bonds www.indiandentalacademy.com 8
    • Elastomerics  If primary bonds are broken- permanent deformation  Synthetic polymers – sensitive to free radical generating systems ozone uv light  Decrease in flexibility & tensile strength  Addition of antioxidants & anti ozonates www.indiandentalacademy.com 9
    • Elastomerics  Introduced to dental profession – 1960’s  Generate light continuous forces Uses – canine retraction diastema closure rotational correction space closure Advinexpensive relatively hygienic easily applied ptn co operation   www.indiandentalacademy.com 10
    • Elastomerics  Disadv – absorb water & saliva stain permanently permanent deformation rapid loss of force temperature sensitive www.indiandentalacademy.com 11
    • Elastomerics www.indiandentalacademy.com 12
    • Elastomerics www.indiandentalacademy.com 13
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    • Elastomerics www.indiandentalacademy.com 15
    • Elastomerics Force degradation and force delivery of elastomeric chains  Inability to deliver a continuous force level  Bishara & Anderson-1970- compared latex & unitek alastik modules  After 24 hrs alastiks 74 % force decay latex elastics 42 % loss www.indiandentalacademy.com 16
    • Force Decay www.indiandentalacademy.com 17
    • Elastomerics  After 1st day- force decay relatively stable  Hershey & Reynolds- 1975 – compared chains – framework- simulating tooth movement  Conclusion 1st day- 50% force loss 4 wks – 40% original force remains more consistent force- by stamping manufacture – than injection molded www.indiandentalacademy.com 18
    • Elastomerics  Wong1976 – compared two commercial chains  Chains distracted & maintained at 17 mm in water at 37 C  Result – 1st 3 hrs – greatest amount of force lost  Kovach et al – evaluated initial force values of unitek alastiks stretched to 30 % of their original length at rates of .2 , 2 & 20” / min www.indiandentalacademy.com 19
    •  Conclusion – rapidly extended chains – greater initial force levels At 1 wk the chain stretched at slow rateexhibited less force decay Recommended slow stretching www.indiandentalacademy.com 20
    •  Ash & Nikolai-1978 – compared force decay of chains – stored in air , water and vivo  In vivo environment – significantly more force decay after 30 mins than those kept in air  After 3 wks – chains in vivo – greater force loss than those stored in water  Both maintained force levels of more than 160 gms www.indiandentalacademy.com 21
    •  Due to effects of mastication oral hygiene , salivary enzymes & temp variations  Genova et al – 1985 – investigated force degradation of chains - artificial saliva  Conclusion chains subjected to tooth movement retained 913 % less force than held at constant length short filament chains – higher initial force levels & retain higher % of remaining force www.indiandentalacademy.com 22
    •  Rock et al – tested 13 commercially available elastics  Regardless of the no. of loops , the force values at 100% extension were constant  Short filament chains – higher initial force level at 100 % extension-403 to 625gms  Recommended 50 – 75 % extensiondesired force of 300 gms www.indiandentalacademy.com 23
    •  Killiany et al – 1986 – force delivery and decay characteristics of RMO – ENERGY chain – compared with short loop chain from American orthodontics  After 4 wks – simulated oral environment – ENERGY chain – retained 66 % of initial force short loop chain retained 33 % of original force www.indiandentalacademy.com 24
    •  Kuster etal 1986- compared chains of 2 companies stored in air & in vivo  At 100% extension force levels 315gm 279gm  Initial extension of 50 -75% not supported www.indiandentalacademy.com 25
    •  Storie & Fraunhofer – compared gray chain & fluoride releasing chain from ortho arch  conclusion fluoride releasing chain – higher initial force level at 100 % extension gray chain – retain 38 % of its initial force fluoride releasing chain – 14 % of initial force after 1 wk in 37 C distilled water www.indiandentalacademy.com 26
    •  Baty & Fraunhofer- compared 3 colour of elastomeric chains with std gray chains  Conclusion  Colouring had little effect on initial force delivery of chains www.indiandentalacademy.com 27
    • Pre- stretching effects  Purpose – 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 www.indiandentalacademy.com 28
    •  Heat appln alone – increased rate of force decay  Storie et al – pre stretched gray and fluoride releasing chains – 50 % for 5 secs Immersed in 3 fluid environments  Reported no clinical benefit www.indiandentalacademy.com 29
    • Environmental effects  Ferriter – 1990 – effect of ph extremes of plaque (4.95) & saliva (7.26)  Chains – basic soln – exhibited more force decay  Jefferies et al – simulated disinfection 30 mins & sterilization (10 hrs & 1 wk ) using gluteraldehyde soln  Use of gluteraldehyde – no deleterious effect on properties www.indiandentalacademy.com 30
    •  Coffelt et al – subjected chains to 31 % APF 4 % SNF 0.4 % Kcl soln  Concluded 31% APF had some effect on the force delivery & decay rate www.indiandentalacademy.com 31
    • summary     E chains lose 50- 70 % of their initial force during the first day and at 3 wks retain only 30 -40 % of the original force Force guage should be used to determine the desired initial force 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 & a constant force www.indiandentalacademy.com 32
    • summary  Environmental factors – associated with deformation & force degradation  The synthetic elastomeric chains – protected from direct light  E chains – convenient , inexpensive method – continuous force system over a 3-4 wk period www.indiandentalacademy.com 33
    • White spot lesion Enamel de mineralization  Prevention 1. Effective plaque control 2. Fluoride release a. fluoride varnishes b. fluoride containing composites c. fluoride releasing GIC d. fluoride relesing elastomers  www.indiandentalacademy.com 34
    •  Enamel sealants – minimal benefit (Banks & Richmond)  Fluoride releasing composites – ineffective in preventing enamel damage ( Mitchel , Turner – 1993 )  GIC – provides greater fluoride release  Inadequate bond strength  Featherstone – 1985 – long duration low dose fluoride release – reduces demineralization www.indiandentalacademy.com 35
    •  Fluoride releasing elastomeric modules – provide such conditions  Joseph & Gobler – 1993 – study on the rate and amount of SNF release from a fluoride impregnated elastic power chain  Material 5 experimental groups & 1 control group 12 unit length of F power chain (CFRD) studied 37 C in a incubator & 100 rpm agitation www.indiandentalacademy.com 36
    • Conclusion fluoride release initially high – very low levels – after 1 wk Minimum continuous level of 0.25 mg of fluoride – necessary for remineralization Bactericidal effect at low levels of fluoride  www.indiandentalacademy.com 37
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    •  Protection only temporary  Max benefit – elastics to be replaced at wkly intervals  Regular topical appln of fluoride still necessary www.indiandentalacademy.com 39
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    •  William wiltshire – 1996 – measured release of fluoride from fluoride releasing elastomeric modules ( fluor-I ties) in vitro  Results initial burst of fluoride during the 1 st and 2nd day foll by a logarithmic decrease  35 % - total fluoride at day 1  63 % - 1st wk  83 % - 1st month  88 % - 2nd month  At 6 months – 0.19 +/- 0.03 micro gms www.indiandentalacademy.com 41
    •  For optimal clinical benefit – replace fluoride releasing ligature monthly  Banks , Chadwik, Asher prospective controlled clinical trial To evaluate the effectiveness of SNF releasing modules & chain Materials 49 ptns, 782 teeth- exptl group 45 ptns, 740 teeth – control group, non fluoride releasing elastomerics www.indiandentalacademy.com 42
    •  After bonding excess composite removed  Etching confined  Standardized dietary & hygiene instructions  Ptns scored by EDI ( Enamel Decalcification Index) – Banks & Richmond – 1994 www.indiandentalacademy.com 43
    • EDI www.indiandentalacademy.com 44
    •  Conclusion     The use of fluoride releasing elastomeric modules – reduced enamel decalcification per tooth by 49 % Enamel decalcification control group – 26 % of teeth & 73 % ptns exptl group – 16 % of teeth & 63 % ptns Occlusal zones showed no difference Fluoride releasing elastomerics – effective in reducing enamel decalcification www.indiandentalacademy.com 45
    • Fibre reinforced composite  Poly( ethylene tere phthalate glycol) & poly (1,4 cyclohexylene dimethylene tere phthalate glycol) reinforced with continuous glass fibres  FRC contained -43-45 vol% fiber  Flexural strength -565 MPa  Requisites proper wetting of glass fibres proper orientation of glass fibres www.indiandentalacademy.com 46
    • pultrusion  Fibre bundles – pulled through an extruder simultaneously with the extrusion of the polymer.  Fibre bundles impregnated by the polymer  Exiting dies determine cross section shape and size www.indiandentalacademy.com 47
    • Electro micrograph www.indiandentalacademy.com 48
    • Fibre reinforced composite    Burstone & Gunther 2001 Enhanced mech. properties A metal attachment pad- FRC strip – exhibited superior bonding strength www.indiandentalacademy.com 49
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    •   Highest failure – with loadings parallel to the tooth surface Less shear strength www.indiandentalacademy.com 51
    • Charles Burstone& Kuhlberg  Pre impregnated material – PREG partially polymerised fibre matrix complex Applications 1. Bonded cuspid to cuspid retainers 2. Bridges active applications - adjuncts for active tooth movements www.indiandentalacademy.com 52
    •  Matrix – light cured thermoset Bisgma  Splint it – long fibre reinforced composite  S glass fiber- bar more esthetic  Two stages of polymerization  Initial polymerization- matrix flexible www.indiandentalacademy.com 53
    • Properties  ME – 70 % > highly filled composite  YS – 6 times >  Resiliency – 24 times > www.indiandentalacademy.com 54
    •  Clinical use - 3 configurations rope wide strip woven pattern www.indiandentalacademy.com 55
    •  Technique        FRC rope cut to length Transparent foil removed Tooth prepared for bonding FRC placed & contoured to tooth Attachments are directly bonded to FRC Low viscosity adhesive – protective layer Indirect or direct bonding www.indiandentalacademy.com 56
    • Active application FRC full arch www.indiandentalacademy.com 57
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    • Attachments www.indiandentalacademy.com 59
    • Intermaxillary elastics www.indiandentalacademy.com 60
    • Vertical elastics- open bite www.indiandentalacademy.com 61
    • Extrusion of maxillary incisor segment www.indiandentalacademy.com 62
    • Space closure www.indiandentalacademy.com 63
    • Space closure www.indiandentalacademy.com 64
    • Molar uprighting www.indiandentalacademy.com 65
    • Uprighting posterior segment with tip back spring www.indiandentalacademy.com 66
    • Anterior lingual root torquing spring combination with stainless steel arch wire www.indiandentalacademy.com 67
    • Maxillary incisor intrusion TMA intrusion arch www.indiandentalacademy.com 68
    • Mandibular incisor intrusion arch www.indiandentalacademy.com 69
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    • Replacement connectors www.indiandentalacademy.com 71
    • Maxillary lingual bonded FRC retainer www.indiandentalacademy.com 72
    • Connecting FRC framework www.indiandentalacademy.com 73
    • summary  Long fibre reinforced materials have the potential to replace metals in clinical orthodontics  Biocompatibility not a concern  FRC materials are superior to polymers  Increased rigidity and strength  Highly formable – fabricated in complex shapes www.indiandentalacademy.com 74
    •  Layers can be added to change the shape - improve rigidity  Precise contour to the teeth  Potential to alter some of the current methods of active treatment  Esthetic alternative to lingual orthodontics www.indiandentalacademy.com 75
    •  Ptns who need only partial or compromised treatment are good candidates for FRC appliances  Mixed dentition cases  FRC bars- alternative to bands www.indiandentalacademy.com 76
    •  Disadvantage weakest in shear Shear loads to be minimized as much as possible Requires good bonding conditions eg – bridges and retainers www.indiandentalacademy.com 77
    • Biodegradation Orthodontic materials – Universally austentic SS - 18% chromium - 8% nickel NiTi – 1970s Oral environment – ionic properties thermal properties microbiologic enzymatic Ideal for biodegradation  www.indiandentalacademy.com 78
    •  Human exposure to Ni - diet - atmosphere - jewelry - water - clothing - fasteners www.indiandentalacademy.com 79
    •  Dietary intake - Ni – 200 -300 microgms / day - Cr – 280 microgms / day - Ti – 300 – 2000 microgms/day Water – 20 microgms / l – Ni - 0.43 microgms/l- Cr www.indiandentalacademy.com 80
    •  Iatrogenic exposure Joint prosthesis Dental implants Orthopedic plates Surgical clips Pace maker leads Prosthetic heart valves orthodontic appliances Ni release – dental alloy – 4.2 www.indiandentalacademy.com microgms/cm/day 81
    •  36micgms/day – Cr  Full mouth ortho appliances – 40micgms/day – Ni  Heat treated-SS arch wire- 0.26micgms/cm/day www.indiandentalacademy.com 82
    •  Bishara , Barret – 1993 : Purpose – Compare in vitro corrosion rate for std orthodontic appliances Appliance immersed – prepared artificial saliva at 37c Materials 10 sets of bands and brackets Both SS & NiTi archwires www.indiandentalacademy.com 83
    • -Type 305 – SS – bands AISI -Type 316 – SS – brackets and tubes AISI -Bands not covered from inner surface -17- 25 wires -5 sets – rectangular SS wires -5 sets – Ni Ti – Unitek Polyethylene tubes – 100 ml Artificial saliva – pH – 6.75 www.indiandentalacademy.com 84
    •  Analyzed – 1,7,14,21,28 days  Results –   Ni – peak level – day 7th Park and Shearer similar findings www.indiandentalacademy.com 85
    •  Cr – peak level 14th day www.indiandentalacademy.com 86
    • Conclusion     Orthodontic appliances -reasonable amts of Ni & Cr when placed in a artificial saliva medium Ni release reaches max after 1 week then diminishes Cr release increases during the first 2 weeks and levels off during subsequent 2 weeks Release rates of Ni & Cr from SS or NiTi wire – not significantly different. www.indiandentalacademy.com 87
    • Conclusion  For both archwire types the release rate for Ni averaged 37 times greater than that for Cr.  The release rates for full mouth orthodontic appliances are less than 10% of the reported average daily dietary intake for Ni & .25% of those reported for Cr. www.indiandentalacademy.com 88
    •  Changes in the blood level of nickel Bishara,Barret Purpose: to determine whether orthodontic patients accumulate measurable concentrations of Ni in blood. Materials: 31 subjects – 18 females & 13 males. Blood samples collected 1 – before placement of orthodontic appliance 2 – 2 months after placement 3 – 4-5 months after placement www.indiandentalacademy.com 89
    • Blood analyzed – atomic absorption spectro photometry Nickel and Chromium carcinogenicity Ni – risk inversely proportional to solubility in aqueous media Cr – hexavalent oxidation state Normal Ni & Cr conc in blood Ni – 2.4 +/- 0.5 ng/ml & 30 +/- 19 ng/ml Cr – 0.371 ng/ml www.indiandentalacademy.com 90
    •   Hexavalant Cr – readily absorbed Elimination – urine. Results –  Ni levels in blood  All blood levels below normal  17.2% of blood samples – above detection limit of .4 ppb  never exceeded 1.3ppb www.indiandentalacademy.com 91
    •  16 patients no detectable Ni levels  5 patients reduction in blood level Higher values –  Contamination from venipuncture needle  Diet www.indiandentalacademy.com 92
    • SUMMARY  Patients with fully banded & bonded appliances did not show a significant increase in the Ni blood level during the 1 st 4-5 mnts of orthodontic therapy  Orthodontic therapy using appliances made of alloys containing Ni-Ti did not result in significant increase in the blood levels of Ni. www.indiandentalacademy.com 93
    • Grimsdottir 1992  Facebows,archwires,brackets& molar bands analyzed  Most appliances – variable amount –Ag solder  14days in 0.9Nacl  Facebows – highest amount of NI &Cr  Archwires- least www.indiandentalacademy.com 94
    • Park & Shearer  Ni &Cr release-simulated ortho appliance  incubated in 0.05%Nacl  Ni-40micgms/day  Cr-36 micgms/day  below the daily dietary intake  may sensitize patients www.indiandentalacademy.com 95
    • Metal release from simulated fixed orthodontic appliances – AJO 2001 Hwang etal Method Simulated fixed orthodontic appliances ---soaked in 50 ml of artificial saliva pH – 6.75 +/- .15 at 37 C Time period – 3 months 4 groups ( 16 – 22) 2 SS wires 2 Ni-Ti arch wires www.indiandentalacademy.com 96
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    • Composition of artificial saliva www.indiandentalacademy.com 98
    • 320 polyethylene tubes – 50 ml artificial saliva Method Metal release – plasma mass spectrometry Analyzed on 1st, 3rd days, 1st 2nd 3rd 4th 8th &12th weeks www.indiandentalacademy.com 99
    • Results Cr release – no increase after 4 weeks – gp A -- 2 weeks in gp B -- 3 weeks in gp C -- 8 weeks in gp D www.indiandentalacademy.com 100
    • Ni release – no increase after 2 weeks – gp A -- 3 days in gp B -- 7 days in gp C -- 3 weeks in gp D www.indiandentalacademy.com 101
    • Iron Release – no increase after 2 weeks – gp A -- 3 days in gp B -- 1 day in gp C & gp D www.indiandentalacademy.com 102
    • CONCLUSION The daily amount of Cr & Ni released – insignificant when compared with – daily dietary intake of these metals Such a small amount of release might produce sensitivity when the orthodontic appliance are in place for 2-3 years For an allergic reaction in the oral mucosa an antigen must be 5 – 12 times greater than that needed for a skin allergy www.indiandentalacademy.com 103
    • Leaching of Ni Cr and Be ions from base metal alloy in an artificial oral environment --Yong Tai, Ralf D Long, J PROST DENT 1992 Method Artificial oral environment – 3D force movement cycles of mastication 12 pairs of crowns articulated Metal vs metal Metal vs enamel Metal vs procelain Metal vs metal without chewing as a control www.indiandentalacademy.com 104
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    • 1 year simulated – period of mastication Results In vitro analysis in artificial environment – release of Ni & Be from base metal alloy Dissolution & Occlusal wear are both factors in the release of Ni & Be metals Occlusal wear increases the concs 2-3 times more – than with dissolution alone. www.indiandentalacademy.com 106
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    • Hypersensitivity Refers to the injurious consequences in the sensitized host following contact with specific antigens. Incidence of Ni sensitivity Greg, Dulap, Moffa – allergic response to Ni containing dental alloys. www.indiandentalacademy.com 108
    •  Ni toxicity – moderately cytotoxic  Cr toxicity – little Grimsdotir & Hansten – saliva -connecting medium – discharge of ions & metal compounds – combine with chemically corroded metal – attach to mucosa. www.indiandentalacademy.com 109
    • Alan & Smith – incidence rate of hypersensitivity – 10% Blane & Peltonon – estimated that 4.5 – 28.5 of popln – have sensitivity to Ni Higher prevalence in females  Janson & Park – hypersensitivity in females – related to environmental exposure – contact with detergents jewellery & other metallic objects www.indiandentalacademy.com 110
    •  Factors affecting development of sensitization  Raitt and Brostoff –  Mechanical irritation  Skin laceration  Increased environmental temperature  Increased intensity and duration of exposure  Genetic factors www.indiandentalacademy.com 111
    • Dietary intake     Ni - 200 – 300 micgms / day Cr – 250 micgms / day Drinking water – 20 micgms / l – Ni (Bencho ) Amount of Ni release  Grims Dottar – largest amount of Ni – released from facebow – silver solder Brackets -- .3-.9 micgms/day SS archwire -- .26 micgms/cm.sq/day www.indiandentalacademy.com 112
    •  Form of release - Ni – soluble  Cr – insoluble  Allergy more common in extra oral -- intra oral appliances – 6 times 5-12 times higher conc needed – oral mucosa www.indiandentalacademy.com 113
    • Lack of intra oral response due to Salivary glycoproteins -- barrier difference of permeability Cellular hypersensitivity btn skin & mucosa difference in Langerhans distribution www.indiandentalacademy.com 114
    •  No increase in blood level of Ni – 5 months of Ortho t/t - Bishara www.indiandentalacademy.com 115
    • Hypersensitivity reactions         Dental Alloys Symptoms of allergic reactions – dental alloys Inflammed hyperplastic gingival tissue Alveolar bone loss -- crowns Edema of throat, palate, gums Osteomyelitis – SS bone fixation wires Orthodontic appliances – face bows & neck straps, Ni-Ti arch wires , www.indiandentalacademy.com 116
    • Symptoms  Contact dermatitis,  Contact stomatitis,  Loss of taste,  Numbness, burning sensn,  Angular chelitis  Severe gingivitis,  Mild erythema with or without edema www.indiandentalacademy.com 117
    • Immunologic mechanism Ni – common cause – contact dermatitis Delayed hypersensitivity reaction Induction phase Elucidation phase Diagnosis – ptn history clinical findings patch testing www.indiandentalacademy.com 118
    • Different corrosion resistant materials – used in Hypersensitivity ptns AISI 316 L steel – most corrosion resistant AISI 304 L steel PIA 17 – 4 Bio force ion guard wire – 3 micron nitrogen coating Pyramid manufacturers – steel -- hypo allergic www.indiandentalacademy.com 119
    • Conclusions The daily amount of Cr & Ni released – insignificant when compared with – daily dietary intake of these metals Such a small amount of release might produce sensitivity when the orthodontic appliance are in place for 2-3 years For an allergic reaction in the oral mucosa an antigen must be 5 – 12 times greater than that needed for a skin allergy www.indiandentalacademy.com 120
    •  Patients with fully banded & bonded appliances did not show a significant increase in the Ni blood level during the 1 st 4-5 mnts of orthodontic therapy  Orthodontic therapy using appliances made of alloys containing Ni-Ti did not result in significant increase in the blood levels of Ni. www.indiandentalacademy.com 121
    •  The release rates for full mouth orthodontic appliances are less than 10% of the reported average daily dietary intake for Ni & .25% of those reported for Cr. www.indiandentalacademy.com 122
    • Orthodontic appliances Strong biologic sensitizers www.indiandentalacademy.com 123
    • . Janson & Prystousky -- age range 10-20 years www.indiandentalacademy.com 124
    •  Raitt and Brostoff – several factors for the development of sensitization  Mechanical irritation  Skin laceration  Increased environmental temperature  Increased intensity and duration of exposure  Genetic factors www.indiandentalacademy.com 125
    • Kawahara & Yamakawa – Ni – moderately cytotoxic & Cr – little toxicity. Grandjsan et al – avg dietary intake Ni – 200 -300 micgms./day Cr – 250 micgms/day www.indiandentalacademy.com 126
    • Benco – Ni concs – drinking water below 20 micgm/ltr. -- below the normal dietary intake-not clinically significant www.indiandentalacademy.com 127
    • Majjer & Smith – Ni released – soluble compound Cr – insoluble form Greg & Temovari – reaction – use of facebow – Ni-Ti arch wires Moffa et al – allergic response to Ni containing dental alloys Dulap et al – allergic reaction – insertion of Ni-Ti wire in sensitive patient www.indiandentalacademy.com 128
    • Jacobson & Hensten – www.indiandentalacademy.com 129
    • Park & Shearer -- Ni from orthodontic bands – sensitized ptns. – cause hypersensitivity reactions in ptns with prior h/o hs. James et al – no relationship betwn a +ve recn to Ni & a clinical response to Ni containing dental alloy Stearh Jear et al – no risk involved for Ni sensitive ptns www.indiandentalacademy.com 130
    • Bishara, Barrete – no increase in blood level of Ni – 5 months of orthodontic treatment. Magnuson & Neilson – higher level of Ni conc – needed to elicit – intra oral response www.indiandentalacademy.com 131
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    • Fischer – sensitivity test – not to be used indiscriminately Vijayabasava, Surendra Shetty – decrease in pH – increase in Ni Highest – pH 5.8 Ni release – less than 5-10% daily dietary intake Ross Levy et al – orthodontic appliance – induce sensitivity – little or no effect on the gingiva of the ptn. www.indiandentalacademy.com 133
    • Recycling “ Involves repeated exposure of the appliance for several wks to mechanical stresses or elements of the oral environment as well as sterilization b/w uses. May result in corrosion and biodegradation of the wire Alteration in properties www.indiandentalacademy.com 134
    • Recycling  Niti – desirable mechanical prop      Relatively high cost Buckthal et al – 52% orthodontists recycle Ni ti wires 80% cold methods – disinfection Cold & heat sterilization – don’t affect mechanical properties Harris et al – simulated oral environment 0.016 Nitinol wires www.indiandentalacademy.com 135
    •  Concluded – significant decrease in YS – 4 month period www.indiandentalacademy.com 136
    • Effects of clinical recycling on mechanical properties of Niti alloy wires -sunil kapila-1991  Materials and methods 60 wires – Nitinol & Niti wires 3 point bending test – mechanical properties SEM – surface characteristics www.indiandentalacademy.com 137
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    •  Wires To – as received condition T1 – 8 wks of clinical exposure ( 1 cycle) T2 – 2 cycles Cold recycled after one clinical cycleisopropyl alcohol Results Nitinol wires subjected to 1 or 2 recycles demonstrated statistically significant differences during loading then control To www.indiandentalacademy.com 139
    •  SEM of both Nitinol and Niti wires demonstrated increased pitting of wires after clinical exposure  Some smoothening of Nitinol wires were also observed in localised regions of the wire www.indiandentalacademy.com 140
    • Surface characteristics www.indiandentalacademy.com 141
    • Recycling of orthodontic brackets  British survey – 47.5 % of clinicians recycle metal brackets   recycled brackets – accelerates corrosion process wheeler and Ackermann – reduction in mesh diameter – recycling – no significant change in bond strength www.indiandentalacademy.com 142
    •  Mascia and chen – decrease in shear bond strength  Hixon et al – studied change in bracket slot tolerance after recycling of brackets  concluded – no statistically significant change in the tolerance through two successive recycles  Chapman – bracket slot - increase in width – proportionate to no. of times it is recycled www.indiandentalacademy.com 143
    • comparison of iron release from new and recycled orthodontic brackets-Huang & Yen- AJO2001  purpose – compare release of ions Ni, Mn , Fe    materials and methods – 12 wk period recycle brackets – coated with adhesive and heat treated atomic absorption – detection of ions www.indiandentalacademy.com 144
    •  surface characteristics – energy dispersive radiographic analysis  Results – recycled brackets released more ions than new brackets  Both new and recycled brackets can degrade in solns  Greater amounts of Ni, Mn and Fe ions were released in the artificial saliva soln than in other buffer solns www.indiandentalacademy.com 145
    •  The brackets release greater amounts of ions in a ph 4 buffer than in ph 7 or 10 buffer  As the immersion time increased so did the ion release  After 12 wk immersion the total amount of ion release was less than the cumulative daily intake- www.indiandentalacademy.com 146
    • Effect of recycling on the mechanical properties and surface topography of Niti alloy wires Sung ho lee & Chang – AJO 2001 Parameters – mechanical properties surface topography frictional forces www.indiandentalacademy.com 147
    • Materials 3 types of Niti wires – 60 wires 16. 22 rectangular wires 1. As received condition – To - control group 2. Treated in artificial saliva for 4 wks – T1 3. Treated in artificial saliva & autoclaved – T2 Method – maintained in a incubator at 37 C  www.indiandentalacademy.com 148
    •  Results – Niti wires demonstrated no statistically significant differences in max tensile strength , ME and bending fatigue  Niti and Optimalloy demonstrated increased pitting and corrosion on recycling , Sent alloy did not  Recycled NIti and Optimalloy demonstrated greater surface roughness , Sent alloy did not . www.indiandentalacademy.com 149
    •  Recycled Niti and Optimalloy demonstrated significantly greater max frictional co.eff s than did the control group.  Sent alloy showed no difference.  Surface roughness and frictional co.eff of recycled Niti and Optimalloy were not more than those of Sent alloy control group www.indiandentalacademy.com 150
    • changes in bracket slot tolerence following recycling of direct bond metallic orthodontic appliances -Mark Hixson Materials and methods – Stainless steel – direct bond brackets – 3 different companies Evaluated for changes in ability to be torqued by rectangular arch wire after being recycled 75 0.022 * 0.028 brackets www.indiandentalacademy.com 151
    •  Torque meter assembly www.indiandentalacademy.com 152
    •  conclusion – recycling of brackets results in no significant change in the tolerance through two successive recycles  The max increase in tolerance after 2 recycles was approximately 3 degrees www.indiandentalacademy.com 153
    • Effect of recycling on shear bond strength – D N Kapoor, Pradeep Tandon – JIOS sep 03  Purpose – compare the reconditioning methods like flaming ,sand blasting and solvent disolution  Bond strength – universal instron testing machine www.indiandentalacademy.com 154
    • Results  New brackets bonded to freshly extracted teeth produce higher shear bond strength when compared to re-bonded brackets bonded to freshly extracted teeth and/or reconditioned enamel surface  Flaming and sand blasting method for re conditioning of brackets demonstrates highest shear bond strength www.indiandentalacademy.com 155
    • Results  Rebonded brackets after re conditioning by solvent disolution method exhibit more than optimum shear bond strength and can be an effective chemical method for reconditioning  Lowest value of shear bond strength was seen when the bracket - reconditioned by flaming was bonded to reconditioned enamel surface www.indiandentalacademy.com 156
    • results  Significant alteration In the enamel surface was not observed due to repeated bonding - SEM www.indiandentalacademy.com 157
    • Thank you www.indiandentalacademy.com Leader in continuing dental education www.indiandentalacademy.com 158