cross contamination in Prosthodontic set up

1. -Rani Ranabhatt
JR l
Department of Prosthodontics

2.  Introduction
 Aim & Rationale
 History
 Definitions
 Patient care items & Levels of disinfections
 Unit dose concept
 Sterilization methods
 Instrument processing
 Infection control in dental setting
 Infection control in dental laboratory
 Problems with chemical disinfectants use
 Dimensional changes of disinfected impressions
 Conclusion
 References

3.  Infection control has become one of the most
discussed topics in dentistry. Much of this
discussion has been dedicated to general
dentistry and oral surgery.
 Little has been discussed about infection
control in other disciplines, such as
Prosthodontics

4.  As more evidence has been gained
concerning the pathogenicity and
invasiveness of hepatitis-B ,TB & AIDS in
Prosthodontics, research is evolving that
relates directly to this previously neglected
discipline.

5.  The aim of today’s discussion is to provide a
background about the possible ways of
transmission of infection spreading, and
procedures recommended for preventing their
spread during Prosthodontic treament

6.  The answer lies in the fact that we sterilize to minimise
and eliminate the spread of infection and disease
 Infectious agents can spread by direct contact, indirect
contact via a contaminated surface or material
 Every effort therefore must be made to avoid cross
contamination of these microorganisms and to prevent
the potential transfer of diseases in Prosthodontic
setting

7.  Zaccharias Jansen in 1590 and Robert Hooke in 1660-
invented Microscopes
 Anthony Van Lewenhouk - first described
microorganisms
 Joseph Lister -asepsis
 Louis Pasteur added new dimensions to the field of
sterilisation
 John Tyndall, Robert Koch etc further accelerated the
progress advent of steam sterilisers, sterile gowns,
drapes and gloves emerged

8.  The modern infection control prevention and
sterilisation guidelines were stated by the CDC
(Centre for Disease Control) in 1973 and specific
dental infection control guidelines by the ADA and
OSHA and EPA in 1978 revised in 1985 and 1988

9.  The destruction or removal of all pathogenic organisms,
or organisms capable of giving rise to infection.
 Disinfection is applicable to all inanimate objects
 Disinfectant is an agent accomplishing disinfection

10.  A classification of chemical disinfectants was
proposed by Spaulding in 1972
 It was originally developed for classifying hospital
instruments but now has been modified for dental
instruments
 Patient care items are classified --
1.Critical
2.Semicritical
3.Non critical
Three levels of disinfection are
1.High
2.Intermediate
3.low

11. CRITICAL:-
 Penetrate or touch broken skin or mucous
membranes.
 Needles, Scalpels, surgical instruments, mirrors,
dental explorers.
SEMICRITICAL:-
 Touch intact mucous membranes.
 Amalgam condensers, handpieces ultrasonic
cleaners.
NON CRITICAL:-
 That do not touch mucous membranes.
 Counter tops, light handles, chair surfaces.

12.  Scalpel blades
 Implant drills
 Suturing kit
 Dental explorer etc

13.  Impressions
 Prosthesis
 Face bow fork
 Wax knife
 Bite blocks
 Polishing stones and rag
wheels
 Impression trays returned
from laboratory

14.  Articulators and
facebows
 Mixing bowl and
spatulas
 Shade and mold
guides
 Prosthetic rulers
 Wax rims

15.  This means dispensing , prior to patient
contact , a sufficient amount of a material
needed to accomplish a procedure
 Any excess is discarded on completion
 The unit dose concept minimizes the chances
of cross infection during prosthetic
procedures

16. 1. High level disinfection – these disinfectants must
inactivate resistant bacterial spores and all other
microbial forms
E.g. ethylene oxide gas, immersion
gluteraldehyde solutions
2. Intermediate level disinfection– these disinfectants
do not inactivate spores during routine use but
they destroy other forms of microbes
E.g. formaldehyde, chlorine compounds,
iodophors, alcohols, phenolic compounds

17. 3. Low level disinfectants provide the narrowest
antimicrobial range
E.g. quaternary ammonium compounds, simple phenols
and detergents
Most of the dental disinfectants come under
intermediate/medium level of disinfectants, but a
minimum standard of intermediate/medium level
disinfection can be exceeded by using high level
disinfectants like glutaraldehydes

18.  It is an ill defined term, used in close relation to
disinfectants
 They are generally considered to be substances that kill
or inhibit microorganisms, especially in contact with
body, without causing extensive damage to the flesh

19. The process by which an article, surface or
medium is freed of all living microorganisms either
in the vegetative or spore state.
OR
It is defined as freeing the object or substance
from all life of any kind

20. Sterilization can be classified as
 Mechanical
 Chemical

21. further classified into
1. Sunlight
2. Drying
3. Dry heat
4. Moist heat
5. Filtration
6. Radiation
7. Ultrasonic and sonic vibrations

22. 1. Alcohol
2. Aldehyde
3. Dyes
4. Halogens
5. Phenols
6. Surface active agents
7. Metallic salts
8. Gases

23.  A simple & effective
method
 Tips of the instruments
are held in a Bunsen
flame till they become
red-hot.
 These materials may
be dipped in a
disinfectant before
flaming

24.  This is an excellent method for safely destroying
materials such as contaminated cloth, animal
carcasses and pathologic materials.
Newspaper photograph showing
Spanish-American war performing
incineration

25.  This is the most widely
used method of
sterilization by dry
heat.
 A holding period of
160oC( 320oF) for 1 hr
is used to sterilize
glassware, swabs,
liquid paraffin, dusting
powder, fats and
grease

26.  The glass bead
steriliser uses a metal
cup with glass beads of
1 mm diameter in it
 The hot salt container
uses ordinary table salt
 The temperature range
for both varies from
425oF TO 475oF
 Both are used to
sterilise endodontic
instruments

27.  Moist heat kills microorganisms by denaturing
proteins..
 Moist heat penetrates material much more rapidly
than dry heat because water molecules conduct
heat better than air.
 Broadly divided into 3- below , at and above
1000C

28. PASTEURIZATION
 Its purpose is to reduce the
bacterial population of a
liquid such as milk and
destroy organisms that may
cause spoilage
 .Spores are not affected by
this method .

29.  Vegetative bacteria are killed almost immediately at 90-
1000C, but sporing bacteria require prolonged periods
of boiling.
 Boiling water is not considered as a sterilizing agent. It
is considered as a method for disinfection
 A minimum exposure period of 30min. is
recommended to kill vegetative bacteria.
 Sodium bicarbonate 2% conc. is added to increase the
efficiency of process.

30.  Also known as compressed or saturated steam
 This is an inexpensive method using a Koch or
Arnold steamer.
 Principle used is steam under pressure is hotter
and higher the pressure the higher the temperature
 Liquids were sterilized by this method at 1000C for
30min on each of 3 successive days.
 Also called Tyndallization

32.  Moist heat in the form of pressurized steam is
regarded as the most dependable method for
destruction of all forms of bacterial life including
spores.
 This method is incorporated into a device called
the autoclave. .
 The basic principle is that when the pressure of a
gas increases the temperature increases

33.  Pressure in autoclave –
15lbs/sq. inch
 Temperature - 1210C
 Time - 15 min
 FLASH METHOD
30lbs,3 min,1310C

34.  This method can be used for a broad variety of
items such as instruments, clothing, glassware and
intravenous solutions , handpieces ,burs etc
 Limitations ;
 Plastic ware melts in high heat
 Sharp instruments become dull ( corrosion )
 oily substances cannot be treated since they do not
mix with water.
 A new form of autoclave called the Prevacuum
autoclave has been developed, which draws air out
of the chamber at the beginning of the cycle. The
major advantage of this is minimal exposure

35. 1. Chlorine compounds( Hypochlorites)
2. Iodophors
3. Combination synthetic phenolics
4. Glutaraldehydes
5. Phenolic/alcohol combinations.
 These chemical disinfectants can be used by
different methods of disinfection such as
spraying and immersion techniques

36. GLUTERALDEHYDE
 2% solution is effective. It destroys vegetative cells
within 10 min to 30min and spores in 10 hrs
 It is recommended for use on surgical instruments
where residual blood may be present.
 It does not damage delicate objects, and therefore it
can be used to sterilize optical equipment such as the
optic fiber endoscopes.

37. DISADVANTAGE
 It can damage many metal items.
 E.g. nickel coated impression trays
& carbon steel burs will often
discolour and corrode, respectively
when immersed in gluteraldehyde
solution for prolonged periods
 It can cause hypersensitivity on
exposure

38. FORMALDEHYDE
In aqueous solutions, it is bactericidal, sporicidal
and virucidal.
 When 37 gms. of the solid are suspended in 100ml
of water a solution called formalin results.
 Formalin is utilized for inactivating virus in
vaccines & producing toxoids from toxins. .
 In the gaseous form, formaldehyde is expelled into
a closed chamber where it is used as a sterilant
for surgical equipment, hospital gowns, Dental
operatory and operation theatres
 Main drawback : CARCINOGENIC

39.  Available as -- gas
-- organic compound
-- inorganic compounds
 Most commonly used as hypochlorites(DAKIN’s
solution)
 The disinfectant action results from it’s ability to
liberate free chlorine.

40.  Iodine is more reactive and more germicidal..
 Tincture of iodine
2% iodine solution in ethyl alcohol used as an
antiseptic for application over skin and mucous
membrane
 Iodophors
They are compounds of iodine with non ionic
surface active agents that release iodine over a long
period of time
 ADVANTAGES
 Less allergic
 Less irritating to tissues
 Do not stain clothes
 Sustained release

41.  This compound was approved in 1976
by FDA as surgical scrub, hand wash,
and superficial skin wound cleanser.
 Chlorhexidine in a conc. of 0.2% is also
most effective antiplaque &
antigingivitis agent

42.  Three MOST commonly used
methods of sterilisation in
dentistry are
1. Steam autoclave
2. Unsaturated chemical vapor
3. Dry heat oven

43.  The steps involved are
1. Presoaking
2. Cleaning
3. Corrosion control and lubrication
4. Packaging
5. Sterilization
6. Sterilization monitoring
7. Drying or cooling
8. Storage
9. Distribution
10. Sharpening

44.  Alpha-hemolytic streptococcus species
 Staphylococcus species
 Micrococcus
 Diphtheriods
 Bacillus species
 Pseudomonas
 Nisseria
 Enterobacter species
 Corynebacterium species,
 Escherichia coli
 Gamma-hemolytic streptococcus species,
 Klebsiella oxytoca
were found on crowns, wax occlusal rims, dentures,
rubber base impressions, irreversible hydrocolloids,
impressions, relining materials and artificial stone
casts

45. 1. All dental treatment
personnel should wear
latex examination gloves
during patient
examination.
2. All dental treatment
personnel should wear
masks covering nose and
mouth during treatment
of patients.

46. 3. All dental treatment
personnel should wear
protective eye wear during
patient treatment.
4. All items used in the oral
cavity should be properly
sterilized.

47. 5. All “touch and splash”
surfaces should be
disinfected with agents like
glutaraldehyde, sodium
hypochlorite.iodophoros,
and synthetic phenolics.
6. Contaminated material
should be disposed carefully
by placing in sealed,
appropriately marked
containers.
7. Immunization programs
have been scheduled for the
active immunization against
hepatitis, HIV, tetanus,
chicken pox, influenza

48. 1. All prosthesis removed
from the mouth should be
carefully rinsed under
running water, cleaned of
debris in an ultrasonic
cleaner whenever possible,
and disinfected.
2. All impressions should be
rinsed and disinfected
before dental stone models
are fabricated.

49. 3. Working pumice should be
discarded after use.
4. Lathe attachments, such
as stones, acrylic burs, and
rag wheels, should be
removed from the lathe
after each use and stored
in a disinfectant
5. Lathe shields and air
filtrations should be used
to contain contaminated
splashes, and airborne
contamination.
.

50. 6.Care should be exercised to
clean and disinfect touch
and splash surfaces in the
laboratory.
7. Clothing worn during
patient treatment should be
covered with a disposable
apron specially when
contaminated prosthesis
and impressions are
handled

51.  Impressions can also
be disinfected and
sterilized using
 ultra-violet radiation
and
 gas (ethylene-di-
oxide) in closed
chambers.

52.  this method can be used to eliminate cross-
contamination via the cast, because it can be
repeated at every stage as required
 in contrast to the presently described
chemical disinfection procedures, microwave
irradiation of the casts for 5 minutes at 900
W gives high level disinfection of the gypsum
casts .

53.  ADA RECOMMENDATIONS FOR STERILIZATION
AND DISINFECTION OF DENTAL
INSTRUMETNS, MATERIALS
COMMONLY USED

54. Instruments Steam
autoclave
Dry heat
oven
Chemical
vapor
Ethyleneoxid
e gas
Burs –carbon
steel - ++ ++ ++
steel
+ ++ ++ ++
Tungsten
carbide + ++ + ++
Stone diamond
+ ++ ++ ++
Polishing
++ + ++ ++
Sharpening
++ ++ ++ -
Flouridee gel
trays heat
resistant
++ - - ++

55. Non reistant
trays
- - - ++
Hand inst
carbon steel
- ++ ++ ++
Stainless
steel
++ ++ ++ ++
Hand pieces
(++) - (+) -
Contra angle
++ - ++ -
Prophylaxis
angle
+ + + -
Imp trays Al
++ + ++ ++
Chrome
plated
++ ++ ++ ++
Custom
acrylic resin
- - - ++

56. plastic
- - - ++
mirrors
- ++ ++ ++
Polishing
garnet
- - - -
Rubber
+ - - -
Prophylaxis
cup
- - - -
Saliva
ejectors
- - - -
Air H2O
syringe t
++ ++ ++ --
X ray film
holders
(++) - (+) ++
Collimating
device
- - - ++

57.  In contrast to dental treatment room and
surgical operatory , the dental laboratory is
often overlooked when planning effective
infection control and exposure control
measures

58. IMPRESSIONS:-
 Alginate:- ( for limited period)
Sodium hypo chlorite sprays/immersed
Iodophors
glutaraldehyde
 Polysulphide:-
Sodium hypochlorite Immersed
Chlorine dioxide
Phenols
 Reversible hydrocolloid
iodophor
bleach
glutaraldehyde sprays/immersed

59.  Gypsum casts:-
Iodophor - (Sprayed or
soaked10mins)
 Resin dentures:-
Sodium hypo chlorite
(Immersed)
 Wax records:-
Iodophor
Sodium hypo chlorite
(Immersed.)

60. impres
sion
glutaralde
hyde
Iodophors Cl compd Phenol Phenolic
gluteralde
hyde
Alginate - - + - -
Polysulphi
de
+ + + + +
Silicon
rubber
+ + + + +
ZOE + + - ? +
Agar - + + ? +
Compoun
d
- + + - +

61. prosthes
is
glutarald
ehyde
Iodopho
rs
Cl
compou
nd
phenols Phenolic
glutarald
ehyde
Fixed(met
al/porecel
ain)
+ +/- - ? +
Removabl
e
(acrylic/po
recelain)
- + + - -
Removabl
e
(metal/acr
ylic)
- +/- +/- - -

62.  Time taking
 expensive to perform in a dental practice
 all chemical disinfectants are potentially
harmful to the health of the user and the
environment
 unpleasant odour
 Not readily compatible with irreversible
hydrocolloids, which is one of the most
frequently used impression materials.

63.  Even a cast from a properly
disinfected impression may
subsequently become
contaminated by a
technician or clinician.
 Also, the prosthesis will
become contaminated by
the patients after trial and
adjustment in the mouth
and will recontaminate the
cast after repositioning.

64.  In practice contaminated
gypsum casts are difficult
to disinfect chemically.
 If elimination of cross-
contamination is
considered a
requirement, then
disinfection measures
should be applied
through out all phases of
treatment to both the
cast and the prosthesis

65.  Critical qualities affected during disinfection
detail reproduction
surface roughness
wettability
accuracy and stability
 It was reported that the disinfection
discrepancies were well within the acceptable
limits for production of adequately fitting
prosthesis

66.  Surgical field (OT v/s
dental chair)
 Chlorhexidine rinse
 Single use drills
 Systemic Antibiotic

67.  “PREVENTION IS BETTER THAN CURE”- a proverb
well suited to sterilisation
 A thorough understanding of the application of
sterilisation will help ensure safety from the invisible
but deadly world of microbial pathogens
 Hence utilisation of proper sterilization, disinfectants
and aseptic procedures helps us achieve the safety our
profession Demands ......

68.  Textbook of microbiology- R.Anantnarayan 5th Edition Orient
Longman
 Infection control and office safety- DCNA April 1991
 Endodontic practice- Loius Grossman 11th Edition Varghese
publishing House
 Kotsiomiti E et al. accuracy and stability of impression
materials subjected to chemical disinfection – a literature
review. J Oral Rehab 2008
 Bhat V et al. Infection control in the prosthodontic laboratory.
JIPS june 2007

69. THANK YOU