Elastomeric and newer materials Recycling of materials Biodegradation of materials Hypersensitivity reactions Disinfection procedures
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INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com
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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
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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
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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
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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
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Elastomerics Natural rubber latex elastics- Baker, Case,
Angle- early advocates Polymer rubbers – developed from petrochemicals – 1920
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Structure Primary + secondary bonds- weak
molecular attraction At rest – folded linear molecule On extension – unfold- expense of secondary bonds
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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
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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
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Elastomerics ďƒ˜ Disadv –
absorb water & saliva stain permanently permanent deformation rapid loss of force temperature sensitive www.indiandentalacademy.com
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Elastomerics
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Elastomerics
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Elastomerics
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Elastomerics Force degradation and force delivery of elastomeric chains ďƒ˜ Inability to deliver a continuous force level ďƒ˜ Bishara & Anderson-1970- compared latex & unitek alastik modules ďƒ˜ After 24 hrs alastiks 74 % force decay latex elastics 42 % loss www.indiandentalacademy.com
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Force Decay
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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
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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
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Conclusion –
rapidly extended chains – greater initial force levels At 1 wk the chain stretched at slow rateexhibited less force decay Recommended slow stretching
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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
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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
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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
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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
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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
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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
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Baty & Fraunhofer- compared 3
colour of elastomeric chains with std gray chains Conclusion
Colouring had little effect on initial force delivery of chains
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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
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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
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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
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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
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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
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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
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White spot lesion Enamel de mineralization ďƒ˜ Prevention 1. Effective plaque control 2. Fluoride release a. fluoride varnishes b. fluoride containing composites c. fluoride releasing GIC d. fluoride relesing elastomers ďƒ˜
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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
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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
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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
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Protection
only temporary Max benefit – elastics to be replaced at wkly intervals Regular topical appln of fluoride still necessary
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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
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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
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After bonding excess composite removed Etching confined Standardized dietary & hygiene
instructions Ptns scored by EDI ( Enamel
Decalcification Index) – Banks & Richmond – 1994 www.indiandentalacademy.com
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EDI
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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
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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
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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
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Electro micrograph
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Fibre reinforced composite
Burstone & Gunther 2001 Enhanced mech. properties A metal attachment pad- FRC strip – exhibited superior bonding strength
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Highest failure – with loadings parallel to the tooth surface Less shear strength
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Charles Burstone& Kuhlberg ďƒ˜ 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
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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
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Properties ME – 70 % > highly filled composite YS – 6 times > Resiliency – 24 times >
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ďƒ˜
Clinical use - 3 configurations rope wide strip woven pattern
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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
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Active application FRC full arch
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Attachments
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Intermaxillary elastics
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Vertical elastics- open bite
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Extrusion of maxillary incisor segment
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Space closure
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Space closure
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Molar uprighting
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Uprighting posterior segment with tip back spring
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Anterior lingual root torquing spring combination with stainless steel arch wire
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Maxillary incisor intrusion TMA intrusion arch
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Mandibular incisor intrusion arch
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Replacement connectors
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Maxillary lingual bonded FRC retainer
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Connecting FRC framework
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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
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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
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Ptns who need only partial or
compromised treatment are good candidates for FRC appliances Mixed dentition cases FRC bars- alternative to bands
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ďƒ˜ Disadvantage
weakest in shear Shear loads to be minimized as much as possible Requires good bonding conditions eg – bridges and retainers
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Biodegradation Orthodontic materials – Universally austentic SS - 18% chromium - 8% nickel NiTi – 1970s Oral environment – ionic properties thermal properties microbiologic enzymatic Ideal for biodegradation
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ďƒ˜ Human exposure to Ni
- diet - atmosphere - jewelry - water - clothing - fasteners www.indiandentalacademy.com
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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
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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
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36micgms/day – Cr Full mouth ortho appliances –
40micgms/day – Ni Heat treated-SS arch wire-
0.26micgms/cm/day www.indiandentalacademy.com
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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
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-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
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Analyzed – 1,7,14,21,28 days
Results –
Ni – peak level – day 7th Park and Shearer similar findings
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Cr – peak level 14th day
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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.
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Conclusion ďƒ˜ For both archwire types the release rate
for Ni averaged 37 times greater than that for Cr. ďƒ˜ 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
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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
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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
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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
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16 patients no detectable Ni levels 5 patients reduction in blood level
Higher values – Contamination from venipuncture needle Diet
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SUMMARY ďƒ˜ 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 ďƒ˜ 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
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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
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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
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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
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Composition of artificial saliva
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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
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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
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Ni release – no increase after 2 weeks – gp A -- 3 days in gp B -- 7 days in gp C -- 3 weeks in gp D
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Iron Release – no increase after 2 weeks – gp A -- 3 days in gp B -- 1 day in gp C & gp D
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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
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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
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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.
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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
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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.
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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
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Factors affecting development of
sensitization
Raitt and Brostoff – Mechanical irritation Skin laceration Increased environmental temperature Increased intensity and duration of
exposure Genetic factors
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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
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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
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Lack of intra oral response due to Salivary glycoproteins -- barrier difference of permeability Cellular hypersensitivity btn skin & mucosa difference in Langerhans distribution
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No
increase in blood level of Ni – 5 months of Ortho t/t - Bishara
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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
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Symptoms Contact dermatitis, Contact stomatitis, Loss of taste, Numbness, burning sensn, Angular chelitis Severe gingivitis, Mild erythema with or without edema www.indiandentalacademy.com
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Immunologic mechanism Ni – common cause – contact dermatitis Delayed hypersensitivity reaction Induction phase Elucidation phase Diagnosis – ptn history clinical findings patch testing
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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
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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
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ďƒ˜ 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 ďƒ˜ 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
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ďƒ˜ 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.
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Orthodontic appliances Strong biologic sensitizers
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Janson & Prystousky -- age range 10-20 years
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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
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Kawahara & Yamakawa – Ni – moderately cytotoxic & Cr – little toxicity.
Grandjsan et al – avg dietary intake Ni – 200 -300 micgms./day Cr – 250 micgms/day
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Benco – Ni concs – drinking water below 20 micgm/ltr. -- below the normal dietary intake-not clinically significant
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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
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Jacobson & Hensten –
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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
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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
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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
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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
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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
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Concluded – significant decrease in YS –
4 month period
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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
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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
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ďƒ˜ SEM of both Nitinol and Niti wires
demonstrated increased pitting of wires after clinical exposure
ďƒ˜ Some smoothening of Nitinol wires were
also observed in localised regions of the wire
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Surface characteristics
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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
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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
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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
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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
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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-
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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
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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
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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
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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
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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
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ďƒ˜ Torque meter assembly
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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
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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
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Results ďƒ˜ 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 ďƒ˜ Flaming and sand blasting method for re conditioning of brackets demonstrates highest shear bond strength www.indiandentalacademy.com
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Results ďƒ˜ 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 ďƒ˜ Lowest value of shear bond strength was seen when the bracket - reconditioned by flaming was bonded to reconditioned enamel surface www.indiandentalacademy.com
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results ďƒ˜ Significant alteration In the enamel surface
was not observed due to repeated bonding - SEM
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Thank you www.indiandentalacademy.com Leader in continuing dental education
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