Oral microbial flora final/cosmetic dentistry courses

ORAL MICROBIAL
FLORA
www.indiandentalacademy.com
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education

contents
Introduction and history
Morphology of bacteria/viruses/fungi
General concepts of pathology
Host-parasite interaction
Immunity in the oral cavity
Development of oral flora
Factors affecting development of oral flora
The normal microbial flora of different sites of the
mouth

The principal microorganisms of the mouth
Dental plaque
Dental caries and periodontal disease
Bacterial/ viral/fungal infection of oral soft tissues
Prosthodontic considerations
-Infection control in dental laboratory and dental clinics
Conclusion
References

The Normal Flora
Our bodies are like mobile warm-
blooded coral reefs, rich in
microbial biodiversity and home to
vast numbers of bacterial cells
there are more bacterial cells (1014
)
associated with the human body
than there are human ones (only
1013
)!
composition of normal flora varies
from individual to individual
some bacterial species carried
only transiently
most fairly permanent

Disease can come about in several overlapping ways
1. Some bacteria are entirely adapted to the pathogenic way of life in
humans. They are never part of the normal flora but may cause
subclinical infection, e.g. M . tuberculosis
2. Some bacteria which are part of the normal flora acquire extra virulence
factors making them pathogenic, e.g. E. coli
3. Some bacteria which are part of the normal flora can cause disease if they
gain access to deep tissues by trauma, surgery, lines, e.g. S. epidermidis
4. In immunocompromised patients many free-living bacteria and
components of the normal flora can cause disease, especially if
introduced into deep tissues, e.g. Acinetobacter

Bacteria are single cell organisms that are found living throughout our
world. Bacteria eat everything from sugar, starch, sulfur and iron. There's
even a species of bacteria—Deinococcus radiodurans—that can withstand
blasts of radiation 1,000 times greater than a human being could survive!
What are bacteria?

Typical Bacteria Structure
Flagella- locomotion,
flagellin(protein)
Fimbriae- helps in
adhesion
Calpsule-mucoid
envelope, resists
phagocytosis, forms hapten
Cellwall-outermost layer
Cytoplasmic membrane
cytoplasm

Microbiologists classify bacteria according to their
shape: spherical, rod-shaped, and spiral-shaped.
Coccus Bacillus Spirillum
Types of Bacteria

Bacteria may be further classified according to
whether they require oxygen (aerobic) or no
oxygen (anaerobic)
Bacillus anthracis Peptostreptococcus
Anaerobic bacteriaAerobic bacteria

Morphology of viruses
Viruses are obligate intracellular parasites
Do not fall strictly into the category of unicellular
microorganisms as they do not possess a cellular
organisation
They contain only one type of nucleic acid either
DNA/RNA but never both
Much smaller than bacteria
Largest abt 300nm, poxviruses
Smallest abt 20nm,parvoviruses
Nucleicacid core surrounded by a protein coat, the
capsid
Capsid functions to introduce viral genome into host
cells by adsorbing readily to cell surfaces
DNA VIRUSES- poxvirus,herpes virus, adeno virus,
papova virus
RNA VIRUSES- picorna virus, orthomyxo virus,
paramyxo virus, retro virus, toga virus

Morphology of fungi
Unicellular with oval/spherical cells 2-5 micro mt
Produce a pseudomycelial form comprising of a network of
interlacing filaments

Normal Microbiota
Animals are generally free from microbes in utero.
After birth, microbial populations rapidly establish
themselves in the newborn’s body.
Feeding and breathing introduce many more microbes.
 E. coli and other bacteria colonize large intestine.
 Candida albicans colonizes mucous membranes.
Normal Microbiota or Flora: Microorganisms that remain
throughout an individual’s life.
Transient Microbiota: Microorganisms that are present for a
certain time period and then disappear.
Cells in human body: 1 x 1013
Microbes associated with human body: 1 x 1014
There are ~10 microorganisms/human body cell.

Why care about the normal flora?
colonization resistance:
competition for space and nutrients with pathogens
release of bacteriocins and colicins (antibacterial substances) to
prevent pathogen growth
vitamin K production in gut
continued antigenic stimulation from commensals
cross-reacting protective immunity against pathogens
commensal neisseriaceae and Neisseria meningitidis
Most complex and diverse…….
Oral cavity provides ideal enviornment…

Why care about the normal flora?
commensal bacteria may cause disease at their site of
carriage or nearby, e.g.
Streptococcus mutans (mouth)
 causes dental caries
Streptococcus pneumoniae (upper airways)
 causes otitis media, sinusitis
Some members of the normal flora can become
pathogenic if they acquire additional virulence factors
(e.g. E. coli) or are introduced into normally sterile sites
(e. g. Staphylococcus aureus)

Interaction Between the Normal Microbiota
and the Host
SYMBIOSIS: “Living together”.
1. Commensalism: One organism benefits, the other is
not affected (+/0).
Many microbes live off secretions and dead cells
and do not benefit or harm host.
2. Mutualism: Both organisms benefit from living
together (+/+).
E. coli synthesizes vitamin K and some B vitamins.
3. Parasitism: One organism benefits, the other is
harmed (+/-).
Most disease causing bacteria.

Opportunistic Pathogens
The nature of symbiotic relationships can change.
Opportunistic Pathogens: Organisms that normally do not
cause disease in their natural habitat in a healthy person.
They may cause disease if the host is weakened or if they
enter a different part of the body.
Pneumocystis carinii pneumonia in AIDS patients.
Tooth decay and gum disease caused by mouth flora.
Neisseria meningitidis is usually harmless in respiratory
tract, but can cause meningitis.

Etiology of Infectious Diseases
Diseases can be caused by many factors: infection,
genetics, degeneration, and others.
Koch’s Postulates
Developed by Robert Koch in 1877 to establish cause of
infectious diseases: anthrax and TB.
1. Same pathogen must be present in every case of the
disease.
2. Pathogen must be isolated from diseased host and
grown in pure culture.
3. Pathogen from pure culture must cause disease when
inoculated in healthy, susceptible laboratory animal.
4. Pathogen must be isolated from inoculated animal and
shown to be the original organism.

Koch’s Postulates for Infectious Diseases

Exceptions to Koch’s Postulates
Koch’s principles do not apply to all diseases.
1. Some microbes cannot be cultured in artificial media.
 Treponema pallidum (syphillis)
 Mycobacterium leprae (leprosy)
 Ricketsias, chlamydias, and viruses only multiply within cells.
2. One disease may involve several different pathogens.
 Diarrhea
 Pneumonia
 Meningitis
 Nephritis
3. Some pathogens may cause several different diseases.
 Streptococcus pyogenes: Scarlet fever, sore throat, skin infections,
bone infections, etc..

Transmission of Disease
I. Contact Transmission: Spread by direct contact,
indirect contact, or droplet transmission.
A. Direct Contact Transmission: Person-to-person
transmission. No intermediate object is involved. Examples:
Touching, kissing, sexual intercourse.
B. Indirect Contact Transmission: Agent is transferred via a
nonliving object (fomite).
Examples: Towels, eating utensils, thermometers,
stethoscopes, bedding, clothes, money, and syringes.
C. Droplet Transmission: Microbes are spread in mucus
droplets that travel short distances (less than 1 meter).
Examples: Sneezing, coughing, talking, and laughing.

Transmission of Disease (Continued)
II. Vehicle Transmission: Transmission of disease via
medium such as water, food, air, blood, body fluids,
and intravenous fluids.
 Waterborne Transmission: Usually caused by water
contaminated with sewage.
 Airborne Transmission: Spread of agents by droplets in
dust that travel more than 1 m to host.
III. Vectors: Animals that carry disease from one host to
another. Arthropods (insects) are most important
animal vectors.
 Mechanical Transmission: Passive transport of pathogens
on insect’s body.
 Biological Transmission: Pathogen spends part of its life
cycle in the vector.

CHAIN OF INFECTION
All links must be connected for infection to take place
PathogenPathogen
SourceSource
ModeModeEntryEntry
SusceptibleSusceptible HostHost
(sufficient virulence
& adequate numbers)
(allows pathogen to
survive & multiply)
(of transmission
from source to host)(portal that the
pathogen can
enter the host)
(i.e., one that is not immune)

Nosocomial (Hospital Acquired) Infections
“Nosocomial” Greek word for hospital.
Infections acquired at a health care facility.
According to Center for Disease Control (CDC), 5-15%
of all hospital patients acquire N.I.s.
Predisposing Factors:
 Wide variety of microbes in hospital environment
 Weakened or immunocompromised patients
 Chain of transmission: Mainly through direct or indirect
contact.
• From health care workers to patient
• From patient to patient
• Fomites: Catheters, needles, dressings, beds, wheelchairs
• Airborne transmission

Important Nosocomial Pathogens
Normal microbiota: Many are opportunistic pathogens
Antibiotic resistance: Very high due to the use of
antimicrobials in health care facilities.
Principle microorganisms: Used to be gram-positive
microbes. Today most are gram-negative bacteria.
 Enterobacteria: Over 40% of all infections. E. coli, Klebsiella
spp., Proteus spp., Enterobacter spp., and Serratia
marcescens.
 Staphylococcus aureus (11%)
 Fungi: (10%) C. albicans and others
 Enterococcus (10%)
 Pseudomonas aeruginosa (9%)

Control of Nosocomial Infections
Aseptic techniques to avoid contamination
Careful handling and disposal of contaminated material
Frequent and adequate hand washing
Proper infection control training of staff
Isolation wards and rooms
Avoid unnecessary antibiotic prescriptions
Avoid unnecessary invasive procedures
Regular disinfection of respirators and humidifiers and
maintenance of autoclaves
Use disposable and/or sterile supplies
Infection control committee

Development of Disease
1. Incubation Period: Time between initial infection and
appearance of signs and symptoms
2. Prodromal Period: Early, mild symptoms of disease.
3. Illness Period: Disease is most acute. Overt signs and
symptoms. Patient immune system actively fights off
infection. If not successful may die at this stage.
4. Decline Period: Signs and symptoms subside. Patient is
vulnerable to secondary infections.
5. Convalescence Period: Recovery. Body returns to predisease
state.

Immunity in the oral cavity
Non specific immunity
-intact mucosal barrier
-dental arches position
-saliva
-lysozyme
-peroxidase
-lactoferrin
Specific immune response
-tissues
-immunoglobulins and other soluble mediators

Development of the oral flora
Birth – sterile…..
- strep.salivarius, Nesseria, veillonella
- occasionally C.albicans…..
Infancy & early childhood
eruption of deciduous teeth
appearance of strep. Sanguis & mutans
Increasing no. of teeth and changes in diet…..
Few anaerobic become established…….

Development of oral flora contd
Adolescence
increase in no. of organisms occurs when permanent
teeth erupt
They have deep fissures, interproximal surfaces are
larger, gingival crevice is deeper---- increase in
anaerobic organisms
Bacteroides, leptotrichia, fusobacterium, spirochaetes
are found regularly
Lesions of dental caries………..

Development of oral flora contd
Adulthood
complexity is its characteristic
-Varying amounts of dp,chronic pdl disease, govern the no.
and type of organisms… carious
lesions, unsatisfactory restorations provides environments
for accumalations of bacteria
-Increase in bacteriodes and spirochaetes
-As teeth are lost……..
-Edentulous pts. harbour few spirochaetes or bacteroides.
Carriage of yeasts increases
-Dentures provide a protected environment in which yeasts
multiply…

Factors affecting the development of the oral
flora
Be introduced
Be retained
Be able to multiply in the conditions present in
the mouth

Factors affecting the development of the oral
flora contd..
Introduction
- although from birth a wide variety of microorganisms
are introduced into mouth, only certain species are able
to become established
Retention
- adherence eg.strep.salivarius
- protected sites
Sticky matrix of dental plaque and gingival crevices
bact.melaninogenicus and spirochates

Multiplication
Factors governing are
- availability of substrates
* increased carbohydrate in the diet, increases the no. of oral
bacteria
- ph
* bact. Melaninogenicus, veillonella are intolerent of ph below
5.5
* lactobacillus and C.albicans can tolerate very low ph values
- oxidation/reduction of the surroundings
* anaerobic organisms such as bacteroides, fusobacterium,
spirochaetes, actinomyces only multiply in reduced surroundings.
* gingival crevice and deeper layer of dental plaque are the
areas with low oxidation/reduction potential

Multiplication contd
Some of the interactions are nutritional such as
provision of PABA by strep.sanguis for strep.mutans in
reduced conditions.
The provision of vitamin k by several microorganisms
for bact.melaninogenicus
Some of the interactions are detrimental rather than
beneficial to a second species
eg. Production of H2O2 by strep.sanguis inhibit many
other streptococci and anaerobes
Microbial interactions

The normal microbial flora of different sites of the mouth
Lips
staph.albus and skin micro-cocci predominate with large no. of streptococci
typical of mouth
Cheeks
predominant bacterium is strep.mitior with strep.sanguis and salivarius
yeasts may isolated from carriers
Palate
streptococcal flora resembling cheek
haemophili, lactobacilli are common
yeasts and lactobacilli in denture wearers because of protected enviornment
Tongue
dorsal surface of the tongue is the ideal surface for retention of microorganisms
predominant organisms- strep.salivarius, strep.mitior, haemophilus, small no.
of C.albicans
micrococcus mucilageneous……..

The normal microbial flora of different sites of the mouth contd
Gingival crevices
-most numerous of any site in the mouth.
-1010
- 1011
organisms per gr. Wet wt. Of gingival debris
-well protected from forces that dislodge bacteria
-facultative gr+ve cocci 27, anaerobic gr+ve & gr-ve rods/filaments 40%
Teeth
# organisms attach through dental plaque
# build up as follows
- occlusal fissures and pits
- in enamel defects
- in interproximal spaces
- close to gingival margins
Saliva
# microbial count of saliva 107
- 108
org/ml
# for many years regarded as representative of oral flora….

Dentures and other intra oral appliances
Any appliance worn for considerable period, become colonized
with microorganisms and may alter the flora
Fixed appliances supports supra gingival plaque if poorly
constructed
Removable appliances have advantage of being able to be
cleansed properly…
Yeasts & lactobacilli multiply on any mucosal surface protected
from the flow of saliva
Acrylic appliances retain a denser flora than metal….
large no. of C.albicans can be cultured from the fitting surfaces of
the acrylic dentures.

Cocci
Gr+ve
strep.sanguis
strep.mutans
strep.mitior
strep.salivarius
strep.milleri
Gr-ve
neisseria
veillonella
Rods/filaments
Gr+ve
lactobacillus
corynebacterium
actinomyces
eubacterium
arachnia
propionibacterium
Gr-ve
haemophilus
eikenella
campylobacter
bacteroides
fusobacterium
actinobacillus
capnocytophaga
wolinellawww.indiandentalacademy.com

contd
Anaerobic bacteria- spirochaetes
Yeasts- C.albicans, tropicalis, krusei
Mycoplasma- M.orale, salivarium, faucium, buccale
Protozoa- Entamoeba gingivalis, trichomonas tenax
viruses

Dental plaque
Dental plaque is defined as soft deposits that form the biofilm
adhering to the tooth surface or other hard surfaces in the oral
cavity, including removable and fixed restoration
Dp is composed primarily of microorganisms 1gm plaque(wet wt)
contains 2*1011
bacteria
Meteria alba..
Plaque formation
-formation of pellicle coating
-initial colonization by bacteria
Gr+ bacteria, act.viscous. Strep.sanguis & other
streptoocci,vellonella,corynebacterium
-secondary colonization and plaque maturation
Gr- bacteria, P.intermedia, P.loscheii, capnocytophaga,
fusobacterium, porphyromonas gingivalis.www.indiandentalacademy.com

Microbial interactions in DP
Benificial or detrimental
Strep.mutans, sanguis & lactobacilli lowers the
ph by the fermentation of the carbohydrates to
produce an environment unsuitable for other
organisms like veillonella, bacteriodes
Hydrogen peroxide produced by strep.mutans
inhibits actinomcetes & a wide range of other
microorganisms
Vitamin k produced by corynebacterium stimulate
the growth of bact.melaninogenicus

calculus
Produced by calcification of supra & subgingival dental
plaque
Hardness varies as the deposition of calcium phosphate
occurs in patches
Local ph changes, saliva with super saturated solution
of calcium and phosphate provides enviornment for
plaque calcification
Bacterionema matruchoti along with veillonella,
nesseria, Haemophilus & bacteroides plays imp
role…….

Control of dental plaque
Diet
Physical removal
Ultrasonic scaling devices
Antiseptics
Antibiotics

Dental Caries
Odontopathic
Bacteria
Mutans group Lactobacillus
of Streptococci (acid-loving
bacteria)
Initiator of Caries Secondary invader

CARIOGENIC DENTAL PLAQUE
Bacteria produce a strong acid - Lactic Acid
Bacteria produce surface molecules which seal the
acid against the tooth and keep the saliva from
buffering the Lactic Acid
Bacteria are capable of continually producing the
Lactic Acid due to stores of glycogen within the
bacterial cells
Streptococcus mutans
Early colonizer of the tooth
Strong Protease Producer
Removes the salivary coat from its surface
Binds to Salivary coated tooth surfaces (only after
removing the coat of saliva on its surface)

LACTOBACILLUS
Acidophilic (acid-loving) environments
(Inside Deep Carious Lesions)
pH =
pH =
5.3
4.5
{
{4.5
3.7
LACTOBACILL
US

Dental caries
Microbiological aspect of caries prevention
diet
plaque control
immunisation against dental caries
based on belief that most carious lesions are initiated by
strep.mutans
vaccine to stimulate production of antibodies to organism, which
can then reach the site where caries is likely to develop and so
exert a protective effect

Periodontal disease
Acute
ANUG
periodontal abscess
Chronic
gingivitis
periodontitis
juvenile periodontitis

Periodontal disease contd
ANUG
Characterized by the destruction of interdental papillae and often
gingival margin
Isolated organisms are
Borrella vincenti
fusobacterium fusiforme
bact.melaninogenicus
Treatment
careful oral hygiene measures
metronidazole
Periodontal abscess
organisms isolated
Bact.gingivalis
Anaerobic cocci, Facultative cocci, actinomyceswww.indiandentalacademy.com

Gingivitis
Inflammation of gingivae appears to be caused by bacteria and
their products in dental plaque to gingival margin
Acute inflammatory response with dilatation of gingival capillaries
and exudaation of fluid containing IgG, complement,and PMN’s
No particular organism have been implicated….
Removal of dp…
Act.viscosus/naeslundi

chronic periodontitis
Gingivitis if not controlled leads to periodontitis
Attachment of junctional epithelium to the tooth migrates apically and gingival
pocket forms
This deepened pocket is colonised by dp bacteria and so a progressive
deepening of the pocket ensues
In the advance lesion the chronic inflammatory response leads to destruction of
collagen ane bone supporting the tooth.
Organisms isolated
anaerobic especially bact.gingivalis, eikenella corrodens,spirochaetes,
bact.melaninogenicus, act.viscous/naeslundi, act.israelli, veillonella
Treatment
control of plaque
elimination of pockets that cannot be kept clean
antibiotics have no role

Juvenile periodontitis
Some young patients develop a degree of pdl destruction well in advance of
that expected for their age
Two organisms predominate
-actinobacillus actinomycetem comitans
-capnocytophaga
Both organisms appear to promote the destruction of fibroblasts and activity of
osteoclasts

Bacterial infections of oral cavity
Syphilis
Actinomycoses
Tuberculosis
Diphteria
Scarlet fever
Leprosy
Tetanus

Candidiasis (oral thrush)
Caused by candida albicans
Common inhabitant of oral cavity
Most opportunistic infection in world
Causes- inadverent use of antibiotics,
immunosupressive drugs Eg. Corticosteroids, cytotoxic drugs
C/F – soft, white, slightly elavated plaque on buccal mucosa,
tongue. plaque
can be wiped away with gauze leaving erythematous area
Rx – antifungal drugs nystatin, chlortrimazoles, amphotericin B,
Iconozole
AIDS patients suffer an intractable form of oral thrush, caused by a newly-
described species, Candida dubliniensis. This organism is more resistant to
antifungal therapy than Candida albicans. AIDS patients may also present with
Kaposi sarcoma tumours in the oral cavity.

Types of Candidiasis
Pseudomembranous
candidiasis − Thrush
Hyperplastic candidiasis
Atrophic candidiasis

Viral infections of oral soft tissues
HSV-1 and/or HSV-2
Primary Infection
Secondary Infection
Varicella zoster virus (HHV-3)
Herpesvirus Infection
Primary Infection
Herpetic gingivostomatitis
Younger patients
Often asymptomatic
May be associated with fever,
chills, malaise
Vesicles-ulcers-crusting
Anywhere in the oral cavity

Herpesvirus Infection
Secondary Infection
Reactivation of latent virus
Not associated with
systemic symptoms
Small vesicles
Occur only on the hard
palate and gingiva
Prodromal signs
Varicella zoster virus

Herpangina
NOT caused by Herpesvirus
Coxsackie A virus
Children < 10 years of age
Common in summer and fall
Often subclinical presentation
Headache/Abdominal pain
48hrs prior to papulovesicular
lesions on tonsils and uvula.
Sore throat

Why Is Infection Control Important
in Dentistry?
Both patients and dental health care personnel (DHCP)
can be exposed to pathogens
Contact with blood, oral and respiratory secretions, and
contaminated equipment occurs
Proper procedures can prevent transmission of infections
among patients and DHCP

Modes of Transmission
Direct contact with blood or body fluids
Indirect contact with a contaminated
instrument or surface
Contact of mucosa of the eyes, nose, or
mouth with droplets or spatter
Inhalation of airborne microorganisms

Standard Precautions
Apply to all patients
•Elements of Standard Precautions
Handwashing
Use of gloves, masks, eye
protection, and gowns
Patient care equipment
Environmental surfaces
Injury prevention

Personal Protective Equipment
,

Sterilization and Disinfection
of Patient Care Items
Penetrate mucous membranes or contact bone, the bloodstream, or other
normally sterile tissues (of the mouth)
Heat sterilize between uses or use sterile single-use, disposable devices
Examples include surgical instruments, scalpel blades, periodontal scalers,
and surgical dental burs
Critical Instruments
•Semi-critical Instruments
Contact mucous membranes but do not penetrate soft
tissue
Heat sterilize or high-level disinfect
Examples: Dental mouth mirrors, amalgam condensers,
and dental handpieces

Noncritical Instruments and Devices
Contact intact skin
Clean and disinfect using a low to intermediate level disinfectant
Examples: X-ray heads, facebows, pulse oximeter, blood pressure cuff
Previously suctioned fluids might be
retracted into the patient’s mouth when
a seal is created
Do not advise patients to close their
lips tightly around the tip of the saliva
ejector
•Saliva Ejectors

Preprocedural Mouth Rinses
Present a risk for microorganisms to enter the body
Involve the incision, excision, or reflection of tissue that exposes normally
sterile areas of the oral cavity
Examples include biopsy, periodontal surgery,
implant surgery, apical surgery, and surgical
extractions of teeth
Oral Surgical
Procedures
Antimicrobial mouth rinses prior to a dental
procedure
Reduce number of microorganisms in
aerosols/spatter
Decrease the number of microorganisms
introduced into the bloodstream

Considered regulated medical waste
Do not incinerate extracted teeth containing amalgam
Clean and disinfect before sending to lab for shade
comparison
Can be given back to patient
Handling Extracted Teeth
in Educational Settings
Remove visible blood and debris
Maintain hydration
Autoclave (teeth with no amalgam)
Extracted Teeth

Automated Cleaning
Ultrasonic cleaner
Instrument washer
Washer-disinfector
Manual Cleaning
Soak until ready to clean
Wear heavy-duty utility gloves,
mask, eyewear, and protective
clothing

Heat-Based Sterilization
Steam under pressure (autoclaving)
Dry heat
Unsaturated chemical vapor
Liquid Chemical
Sterilant/Disinfectants
Only for heat-sensitive instruments
Powerful, toxic chemicals raise safety
concerns
Heat tolerant or disposable
alternatives are available

Disinfectants
Disinfectants are chemicals that destroy or inactivate most
species of pathogenic (disease-causing) microorganisms.
In dentistry, only those products that are Environmental
Protection Agency (EPA)-registered hospital disinfectants
with tuberculocidal claims (kills the tuberculosis bacteria)
should be used to disinfect dental treatment areas.
The Mycobacterium tuberculosis is highly resistant to
disinfectants, and if a disinfectant will inactivate the
M. tuberculosis, it will most certainly inactivate the less
resistant microbial families (such as bacteria, viruses, and
most fungi) on the treated surface.

Environmental Surfaces
May become contaminated
Not directly involved in infectious disease transmission
Do not require as stringent decontamination procedures
Clinical contact surfaces
High potential for direct contamination from
spray or spatter or by contact with DHCP’s
gloved hand
Housekeeping surfaces
Do not come into contact with patients or
devices
Limited risk of disease transmission

Clinical Contact Surfaces

Housekeeping Surfaces

Cleaning Clinical Contact Surfaces
Risk of transmitting infections greater than for
housekeeping surfaces
Surface barriers can be used and changed between
patients
OR
Clean then disinfect using an low- (HIV/HBV claim) to
intermediate-level (tuberculocidal claim) hospital
disinfectant
Cleaning Housekeeping Surfaces
Routinely clean with soap and water or an
detergent/hospital disinfectant routinely
Clean mops and cloths and allow to dry thoroughly
before re-using
Prepare fresh cleaning and disinfecting solutions
daily and per manufacturer recommendationswww.indiandentalacademy.com

Infection control in dental laboratory
Potential for disease transmission in the dental lab
is well documented
Potential pathogens can be transported to lab via
orally soiled impressions, dental
prostheses/appliances
Microorganisms can be transferred from
contaminated impressions to dental casts
Oral bacteria can remain viable in set gypsum
for up to 7 days
BASICS OF LABORATORY IC
Need coordination between dental office and lab
Use of proper methods/materials for handling and
decontaminating soiled incoming items
All contaminated incoming items should be cleaned and
disinfected before being handled by lab personnel, and before
being returned to the patient

MASK/PROTECTIVE
EYEWEAR/CLOTHING
Must be used when there is potential for splashes,
spray, spatter, or aerosols
Examples: when operating lathes, model trimmers, and other
rotary equipment
Lab coat/jacket should be worn at all times during
fabrication process
Change daily
Do not wear outside of the lab
Launder appropriately

IMPRESSIONS
Many studies have been performed to evaluate
effects of various disinfectants on different types
of impression materials
Research findings have been contradictory
No single disinfectant is compatible with all
impression materials
The least distortion is associated with products
having the shortest contact times

IMPRESSIONS
Many variables can affect impression materials
Composition and concentration of disinfectants
Exposure time and compatibility of various
disinfectants with specific impression materials
Physical/chemical properties can vary in a given
category of material or disinfectant
Consult dental materials’ manufacturers regarding
their compatibility with disinfectants

DISINFECTING IMPRESSIONS
Methods
Spraying, immersing
Exposure time should be that recommended by the
manufacturer of disinfectant for tuberculocidal
disinfection
Iodophors, sodium hypochlorite (1:10 concentration),
chlorine dioxide, phenols, and other approved products
are all acceptable

DISINFECTING IMPRESSIONS
Polyether materials cannot be immersed in disinfectants due to
potential for absorption and distortion
Immersion disinfectants can only be used once before discarding
(except for glutaraldehydes)
Most reports indicate dimensional stability is not significantly
affected by immersion technique
Clean and rinse impression in dental operatory
Cleaning efficiency can be improved by gently scrubbing
impression with camel’s hair brush and antimicrobial
detergent
Sprinkle dental stone into impression before rinsing to aid in
cleaning
Cleaning and rinsing
Reduces bioburden present
Lessens overall microbiologic challenge to disinfectantwww.indiandentalacademy.com

DENTAL CASTS
Very difficult to disinfect
It Is preferable to disinfect impression
If casts must be disinfected:
Place casts on end to facilitate drainage
Spray with iodophor or chlorine product, then rinse
Another option
Soak casts for 30 minutes in 0.5% concentration of sodium
hypochlorite and saturated calcium dihydrate solution (SDS)
SDS is produced by placing uncontaminated, set gypsum
(i.e. stone) in a container of water

ORALLY SOILED PROSTHESES
Scrub with brush and antimicrobial soap to
remove debris and contamination
Can be accomplished in operatory or
professional work area
Sterilize brush or store in approved
disinfectant
Place prosthesis in sealable plastic bag or
beaker filled with ultrasonic cleaning solution or
calculus remover
Place in ultrasonic cleaner for required time as
specified by manufacturer of ultrasonic cleaner
Place cover on ultrasonic cleaner to reduce
spatter potential
Remove and rinse under running tap water, dry,
and accomplish required work

LATHE
Ways to reduce risk of injury from aerosols, spatter, and macroscopic particles
Use protective eyewear
Ensure plexiglass shield is in position
Machine should be cleaned and disinfected daily
No need for separate pans for new and existing prostheses if isolated properly
At a minimum clean and disinfect pumice brushes and rag wheels daily. Daily
heat sterilization is preferable.
Change pumice daily

IMPRESSION TRAYS
Precleaning removes bioburden and any
adherent impression material
Ultrasonic cleaning can aid in removing
residual set gypsum
Chrome-plated or aluminum trays
Clean, package, heat sterilize
Single-use trays
Discard after one use
Custom acrylic trays
Can be disinfected (by spray or
immersion), then rinsed (if to be used
for second appointment)

DISINFECTION
Prosthodontic items contaminated by handling should be disinfected (by spray
or immersion technique based on type of item) after each use
Examples: alcohol torch, facebow, articulator, mixing spatula, mixing
bowl, lab knife, shade/mold guide
WAX BITES/RIMS,
BITE REGISTRATIONS
Immersion disinfection may cause distortion to some
items
Use spray disinfection
Heavy-body bite registration materials
Usually not susceptible to distortion and can be
disinfected in same manner as an impression of the
same material

PERSONAL HYGIENE
Refrain from the following activities while in the
lab where there is potential for occupational
exposure:
Eating
Drinking
Smoking
Applying cosmetics or lip balm
Handling contact lenses

conclusion
Very few microbes are
always pathogenic
Many microbes are
potentially pathogenic
Most microbes are
never pathogenic

References
Text book of microbiology; 5th
edition: ananthnarayan
Medical bacteriology; key and key
Oral microbiology & immunology; Micheal G Newmann
Microbiology in clinical dentistry; Frank J Orland
Clinical & oral microbiology; PW Ross
Clinical periodontology- Carranza
J periodontology 1971;42:485-94
Oral pathology: Shafer
Control of infection guidelines; 2 nd
edition:NHS

Oral microbial flora final/cosmetic dentistry courses

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