IDA Disinfection Procedures Guide

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


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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


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

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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

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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

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






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Elastomerics
 Disadv –

absorb water & saliva
stain permanently
permanent deformation
rapid loss of force
temperature sensitive

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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
 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

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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

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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

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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

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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

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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

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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

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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
 Prevention
1. Effective plaque control
2. Fluoride release
a. fluoride varnishes
b. fluoride containing composites
c. fluoride releasing GIC
d. fluoride relesing elastomers



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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

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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

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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

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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

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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

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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

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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
 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

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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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

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

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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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 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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 Human exposure to Ni

- diet
- atmosphere
- jewelry
- water
- clothing
- fasteners

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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

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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
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

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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

84



Analyzed –
1,7,14,21,28 days

 Results –



Ni – peak level – day
7th
Park and Shearer
similar findings


85



Cr – peak level 14th
day


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.


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.

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

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

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

91

 16 patients no detectable Ni levels
 5 patients reduction in blood level

Higher values –

Contamination from venipuncture
needle

Diet


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.

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


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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

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

96


97

Composition of artificial saliva


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


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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


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


101

Iron Release – no
increase after 2
weeks – gp A
-- 3 days in gp B
-- 1 day in gp C & gp D


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

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

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105

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.


106


107

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.

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.


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


110

 Factors affecting development of

sensitization

 Raitt and Brostoff –
 Mechanical irritation
 Skin laceration
 Increased environmental temperature
 Increased intensity and duration of

exposure
 Genetic factors


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

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

113

Lack of intra oral response due to
Salivary glycoproteins -- barrier
difference of permeability
Cellular hypersensitivity btn skin & mucosa
difference in Langerhans distribution


114

 No

increase in blood level of Ni – 5
months of Ortho t/t - Bishara


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
,

116

Symptoms
 Contact dermatitis,
 Contact stomatitis,
 Loss of taste,
 Numbness, burning sensn,
 Angular chelitis
 Severe gingivitis,
 Mild erythema with or without edema

117

Immunologic mechanism
Ni – common cause – contact dermatitis
Delayed hypersensitivity reaction
Induction phase
Elucidation phase
Diagnosis –
ptn history
clinical findings
patch testing


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

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

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.

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.


122

Orthodontic appliances
Strong biologic sensitizers


123

.

Janson & Prystousky -- age range 10-20
years


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


125

Kawahara & Yamakawa – Ni –
moderately cytotoxic & Cr – little toxicity.

Grandjsan et al – avg dietary intake
Ni – 200 -300 micgms./day
Cr – 250 micgms/day


126

Benco – Ni concs – drinking water below
20 micgm/ltr.
-- below the normal dietary intake-not
clinically significant


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

128

Jacobson & Hensten –


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

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


131


132

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.

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

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

135

 Concluded – significant decrease in YS –

4 month period


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


137


138

 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

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


140

Surface characteristics


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

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

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

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


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-


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


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



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 .

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

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

151

 Torque meter assembly


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


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


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

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

156

results
 Significant alteration In the enamel surface

was not observed due to repeated
bonding - SEM


157

Thank you
Leader in continuing dental education


158

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