Cariology
and
Endodontics
A discipline to study the etiology,
pathogenic mechanism,pathology,
pathology-physiology,clinical
expression,treatment and favorable
turn etc,of the disease on dental
hard tissue and pulp tissue,
The content of the textbook
? Cariology
? Non-cariogenic disease of dental
hard tissue
? Endodontics
? Operative dentistry
History
In 50’s years
Oral medicine
?Cariology
?Operative dentistry
?Endodontics
?Non-cariogenic disease of dental hard tissue
?Disease of Oral mucosa
?Preventive dentistry
?Periodontology
?Paediatrics for dentistry
Stomatology in ancient times
Before Christ (B.C.)
There were some record about
caries
?Image liking character (script)
? worm + tooth
The chinese were known to have treated
dental ills with knife,cautery,and
acupuncture,a technique whereby they
punctured different areas of the body with
a needle.
In Dynasty Han (A.D.215~282)
There are some
record about
periodontology
Anno Domini
Pulpitis
In Han,Mr,Zhang Zhong Jing, Jin Gui
Yao lue,was a very famous writings in
which there was a record about arsenic
Arsenic is a toxicant medicine which
has been generally used for killing pulp
In Dynasty Tang (A.D.7~10 era)
the people use silver paste to fill tooth
decay
In Tang,tooth brush with willow twig
a toothbrush with hair planted was
invented in A.D.9~11 century from a
tomb of an emperor`s son-in-law of Liao
from Chi Fong city
3 events above described
reflected ancient civilization
of our country
Dentistry development
in West country
The first known dentist was an
Egyptian named Hesi-re (3000 B,C.),
He was chief toothist to the pharaohs,
he was also a physician,indicating
an association between medicine
and dentistry.
The Greeks
Hippocrates (500 B,C.)
appreciated the importance
of teeth,He accurately
described the technique for
reducing a fracture of the jaw
and also replacing a
dislocated mandible,He was
familiar with extraction
forceps for this is mentioned
in one of his writings.
Aristotle (384 B.C.) also
stated figs and soft
sweets produce decay.
Galen (200A,D,Romans)
was first to recognize that
toothache could be:
Pulpitis or pericementitis
He also classified teeth into centrals,
cuspids and molars.
B,Leonardo da
Vinci (end of 15th
Century) - he
described the anatomy
of the jaws,teeth and
maxillary sinus,These
drawings are the first
to accurately describe
the maxillary sinus,
However,credit has
been given to Dr,
Nathaniel Highmore of
England (1650).
D,Leeuwenhoek (17th Century)
- invented the microscope,He
described the dental tubuli and
was the first to see organisms of
the mouth
Anton van leeuwenhoek
K,John Greenwood (1789) -
dentures for George Washington
were made by him.
a red laser scans
George Washington's false teeth
not wooden
Laser scans find gold,ivory,lead,
human and animal teeth
L,Pierre Fauchard (18th Century - 1728)
- Father of Scientific Dentistry,Wrote a great
text "Surgeon Dentist",He also wrote a
complete work on Odontology in two volumes,
843 pages,He recognized the intimate
relationship between oral conditions and general
health,He advocated the use of lead to fill
cavities,He removed all decay and if the pulp
was exposed,he used the cautery,
Musee d'Art Dentaire Pierre Fauchard
at the Academie Nationale de Chirurgie Dentaire
22 Rue Emile Menier,75116,Paris France
He prescribed oil of cloves and
cinnamon for pulpitis,He described
partial dentures and full dentures in his
text,He constructed dentures with
springs and used human teeth,Gold
dowels were used in root canals filled
with lead,He was also known as Father
of Orthodontics,Fauchard died in 1768
at the age of 83,
1763 A.D
John Baker,M.D,Surgeon Dentist,
The earliest qualified dentist to practice
in Boston and in America,
1836 A.D.
Arsenic introduced for the killing
of pulps,by Spooner.
1840 A.D.
The American Society of Dental Surgeons,
first national dental organization,The
Baltimore College of Dental Surgery,the
first school in the world for the training of
dentists was founded by Harris and Harden.
Founded by Harris and Harden
1859 A.D.
Organization of American Dental
Association on a representative basis.
1890 W.D,Miller propose a
chemical-bacteria Paraorganism
theory to explain the mechanism
of caries
1891 A.D.
Extension for prevention
and scientific cavity
preparation promulgated
by G.V,Black,1892 A.D,
The establishment of a
three-year course in
dental colleges.
1906 A.D.
Einhorn recommends novacaine and
adrenalin combination for local
anesthesia.
1915 A.D.
McKay and Black
publish results of
investigation of
fluoride in drinking
water.
1956 A.D.
Air-rotor drill,250,000 RPM
Dr,Robert Borden.
Stomatology in China before 1949
? West China University (1910)
? Shanghai Second University(1920)
? 4th Military Medical University(1935)
? Beijing University(1943)
Shanghai Second University
West China University
1918(School 1910)
The first dental school in China
was founded in West China
Medical University in
1917,
A.W,Lindsay
A,W,Lindsay was teaching
After 1949
Hubei Medical College 1960
Founder
Prof,Xia Liang Cai
In recent 20 years,the science
and techniques got great progress
There are 1~2 faculties or dental
schools in each province
? Caries research
Caries Vaccine
Etiology & prevention
? Pulp disease
Modern root canal traitment
? Pulp biology
Stem cell – final target
Achievements
Craniofacial-oral-dental
research in the
century
21st
The leadership team of NIDR initiated
a strategic planning process in 1999
to identify
Where we are (strengths,weaknesses,
opportunities and threats)
Where we want to go (e.g.,mission and vision)
How we plan to get there (strategic plan)
Several scientific areas
will be concerned
in century 21st
From molecular biology to clinical investigations;
etiology,pathogenesis,epidemiology,prevention,
diagnosis and treatment of inherited craniofacial-
oral-dental diseases and disorders,e.g.,
ectodermic,dysplasia,cleft lip and palate,
amelogenesis imperfect,dentin genesis imperfect,
osteogenesis imperfect,and other inherited
diseases.
Inherited disease and disorders
Hereditary hypoplasia
Hereditary aplasia of the enamel
? dental caries
? Periodontitis
? Oral candidiasis
? Herpes
? Hepatitis,HIV/AIDS
Infections diseases
Viral,bacterial,fungal and parasitic such as
Diseased Periodontium
Primary herpetic stomatitis
Candidal stomatitis
Neoplastic disease
Supports basic,patient oriented,and
community-based research on the etiology,
pathogenesis and metastasis,epidemiology,
prevention,diagnosis,treatment of oral and
pharyngeal neoplastic diseases
Chronic disabling diseases
The full range of research involving
chronic disabling disease associated
with the craniofacial-oral-dental
complex
This includes osteoporosis,osteoarthritis
and related bone disorders,temporo-mandible
joint diseases and disorders,neuropathies and
neuro-degenerative diseases including those
involving oral sensory and motor functions and
autoimmune diseases such as sj?grens
syndrome,
Chronic diseases of cran-oral-
dental complex and other
systemic diseases (e.g.,diabetes)
Biomaterials,biomimetics
and tissue engineering
Biomaterials used for the repair,
regeneration,restoration and
reconstruction of craniofacial-oral-dental
molecules,cells,tissues and organs
The study of computer aid design
(CAD) computer aid manufacture
(CAM) for denture
Behavior,health promotion and environment
aimed at assessing the interactive roles of
sociological,behavior,economic,
environmental,genetic,and biomedical
factors in craniofacial-oral-dental diseases
and disorders
1996—
Diet and Oral Health
Cariology is a discipline within Stomatology
which deals with the complex interplaying
between the oral fluids and the microbial
deposits in relation to subsequent changes
in the dental hard tissues,
Several index have been used
in dental caries
Prevalence=
No of the patients with caries
No of the specific population in an area at risk of getting caries
at that time
Prevalence of caries,the total
caries experience of a population in
existence at a certain time in a
designated area.
Caries incidence is usually expressed
as the number of new decayed teeth or
surfaces per-a period in a
individual,group,or population,
Incidence of caries
DMF=Decayed teeth+Missing teeth+Filled
teeth/Number of subjects examined
DMFT
?If surface have been counted,then
we refer to the score as DMF-S
?If the teeth have been counted,
then it is refer to as DMF-T
The DMF-S or DMF-T are often
referred to as an,index”
The distribution of dental
caries in oral cavity
Reducing tendency
in developed country
The DMFT prevalence of 12-year-old children in the Nordic countries
in the period 1974-91.Denmark,Finland,Norway and Sweden seem to
follow the same downward trend,whereas Iceland has started a more
rapid decline somewhat later,
Increasing tendency
in developing country
95
84
98
95
98
92
95
98
1
3
Romania China Fuji Tonga Jordanian
4
5
6
2
7
8
83
85 86
62
DMFTs for 12 Years-old in Part of developing country
The caries prevalence of China
Time Population people with caries prevalence
Before 1949 32469 19258 59.30
1950~1959 219312 106781 48.70
1960~1969 544708 217774 40.00
1970~1979 3766290 1356362 36.00
1983 131340 40.54permanent teethCities 25080
Countryside 20636 29.70
Cities 19683 79.55
Countryside 16253 58.48
Deciduous teeth
The DMFT prevalence of 12-year-old children
in 11 provinces of China
Beijing 1.41 0.98
Shanghai 1.17 0.95
Tianjing 1.41 1.02
Gansu 0.36 0.8
Shandong 0.69 0.59
Yunnan 0.46 0.88
Liaoning 0.76 1.29
Zhejiang 1.22 1.46
Hubei 0.98 0.51
Guangdong 0.91 1.65
Sichuan 0.57 0.37
Account 0.67 0.88
Province DMFT(1983) DMFT(1995)
Age DMFT
12 1.03
15 1.42
18 1.60
35~44 2.11
65~74 2.49 (DFT)
The DMFT prevalence in 1995
Current concept of caries etiology
Dental caries is a multifactorial
disease in which there is an
interplay of three principal factors,
the host (primarily the saliva and
teeth),the microflora,and the
substrate,or diet,
A fourth factor time must be
considered in any discussion of the
etiology of caries,
Diagrammatically,these factors can
be portrayed as four overlapping
circles,
Micro-organisms
host
& tooth Sub-strate
The four circles diagrammatically represent the factors
involved in the carious process.all four factors must act
concurrently (overlapping of the circles)for caries to occur
time
nocariesnocaries
nocaries nocaries
caries
Caries requires a susceptible host,
a cariogenic oral flora and a
suitable substrate that must be
present for a sufficient length of
time
Saliva
the term saliva refers to the mixture
of secretions in the oral carity
?Saliva is produced day and night and it
is constantly swallowed
?Saliva is present as a proteinaceous
film covering all surfaces of oral cavity
This mixture consists of fluids
derived from
? the major salivary glands
? minor glands of oral mucose
? traces from gingival exudate
Effect of desalivation on incidence and
extent caries in animals
Effect of desalivation on caries in hamsters
Gruop No,
hamsters
Avg,no,
carious
teeth
Avg,caries
score
Intact Salivary
glands
20 2.3 4.0
Desalivated* 10 10.5 39.0
*Parotid,submandibular,and sublingual glands.
Decreased salivary flow
and caries in humans
?Sarcoidosis
?Sjogren’s syndrome
?Tharapeutic radiation
Hydrogen ion
Buffering ability
Calcium
Inorganic phosphate
Fluoricle
Inorganic components
Organic components
mucins
Glycoproteins
Statherin and acidic proline-rich
proteins
amylase
Antrmicrobial proteins
Saliva and dental caries
the quantity of saliva associated
with caries experience
Relationship between salivary
characteristics and caries prevalence
Property Relationship Property Relationshi
p
Flow rate ± pH
Ca
-
-
Buffer capacity + PO4
NH3
Amylase
Viscosity
Urea
-
-
-
-
Salivary composition and caries
Antibacterial factors of glandular
origin could protect oral mucosal
and hard surfaces by helping to
regulate the quantity and species
distribution of oral microbes
Oral Microorganisms
and
dental plaque
In contrast to mucosal surfaces,the
surfaces of teeth are not constantly
renewed by shedding of colonized
epithelial cells,
Surfaces of teeth
Some special sites
occlusal fissues
Approximal surface
Dental deposits
Biofilms on dental surface-matrix-
embedded microbial population,
adherent to each other and/or to
surface or interfaces
Acquired pellicle
Acellular,homogeneous organic film
that forms on enamel and other hard
surface by selective adsorption of
salivary proteins,
adsorption of salivary proteins
or glycoproteins
Origin
Immediately after cleaning and
polishing,salivary secrete deposit
in the defects of enamel.
? Surface pellicle
? Subsurface pellicle
Histological appearance
The surface pellicle appears acellular
and faintly granular under TEM
Surface Pellicle
Pellicles of unknown age may
vary in thickness from 50~1000nm.
globular
fibrillar
granular
Different morphological types
A subsurface pellicle
consisting of dendritic processes that
spread into the intercrystalline spaces
and extend to 3μm into the enamel.
90% water
10% solid material
composition
According to chemical analyses
amino acids account for 45% to 50%
carbohydrates amount 10% to 15%
of the dry weight
lipid
Function
?healing,repairing,or protecting the enamel
surface
?imparting selective permeability to the
enamel
?influencing the adherence of specific oral
microorganisms to the tooth surface
?serving as a substrate or nutrient for the
organisms
summary
?Organic deposit
?Naturally forms by selective adsorption
?Origin of protein from saliva
?After polishing,reforms rapidly
?Bacteria settle on the pellicle as soon as
it forms
?formation of dental plaque
Dental Plaque
In the fourth century B,C.
Aristotle related soft,adhere food
deposits to tooth decay,but it was
not until the advent of the microscope
in the seventeenth century that
“animalcules (microorganism) were
seen in these dental deposits.
Anton van leeuwenhoek,a draper and
sheriff`s chamberlain in Delft
recognized the limitation of mechanical
oral hygiene in removing these
deposits,
Anton Van leeuwenhoek saw large numbers
of living cells in scrapings from teeth:
I judge from myself that all the people living
in our united Netherlands are not as many
as the living animalcules that I carry in my
own mouth this very day.
Terminology
1847 Ficinus a slime coating denticulate
1897 Williams demonstrated the presence
of a mass of microorganisms
1895 G.V,Black gelatinous microbial
plaque
Dental plaque
Most figurative description:
a bacterial aspic with millions of
organisms standing shoulder to
shoulder
More formal definition by L?e,
plaque is the soft,non-mineralized,
bacterial deposit which forms on
teeth and dental prosthesis that are
not adequately cleaned
Morphology of dental plaque
A white or off-white accumulation
Variable thickness
Three main typies of organisms
coccoid
rod-shaped
filamentous
classification
?Supragingival plaque
?Subgingival plaque
?Dental calculus (calcified plaque)
Supragingival plaque
?Smooth surface plaque
?Fissure plaque
Supragingival smooth
surface plaque
Divided into 4 areas:
?plaque/tooth interface
?condensed microbial layer
?body of the plaque
?plaque surface
plaque/tooth interface
In some locations no pelicle
Higher magnification of plaque-enamel border,Microorganisms
that divide in horizontal planes are in direct contact with enamel
(1?30,000).
? Condensed microbial layer
a layer of very densely packed
coccoid organisms,from 3~20
cells thick
Part of a 7-day-old interdental plaque grown on enamel,The enamel matrix
(bottom),appearing as a fine meshwork,is covered by a thin electron-dense
and discontinuous pellicle,Immediately above this is the condensed microbial
layer which is covered by a layer of coccoid and filamentous micro-organisms
and probably Neisseria,The intermicrobial space is electron-lucent and reveals
cell remnants ( 1 ? 6,500).
?Body of the plaque
this occupies by far the largest portion
of the plaque
Thin section of plaque made of different
bacterial species-predominantly coccoidal.
Dense aggregation of microorganisms
at the enamel surface (lower left)
?Plaque surface
loosely arrangement
Great variety,coccoid,rod like,
“corncob”
In the surface layer of plaque some microorganisms
co-aggregate with other species,as visualized by the
presence of so-called corn cob structures
Magnified view of,corncob”
Free surface of plaque composed
of unidentified organisms
Free surface of plaque composed of
coccoid gram-positive (heavily stained
cell walls ) and unidentified gram-
negative microorganisms
Fissure plaque
Gram-positive cocci and short rods
predominate in a homogeneous,matrix,
with occasional yeast cells
Palisade and branching filaments
are absent within the fissures
A,survey of dental
plaque situated
within a deep,
narrow fissure of a
premolar
B,the upper half of
the fissure is filled
with dark material,
the lower half is
les dense
C,Higher
magnification
reveals a plaque
consisting of
mostly ghostlike
membrane and cell
wall structures
Subgingival plaque
? The matrix is sparse
? Organisms:filamentous organisms,
bacilli,cocci,spirochetes
? Gram negative bacteria
The filamentous nature of plaque associated with gingivitis,
Note attachment of smaller bacteria to filaments
Calcified plaque
Supragingival calcucus
white chalky yellow
Sub gingival calculus
greenish black
Dental calculus is plaque in which
mineralization has involved both the
plaque matrix and the microorganisms.
Formation and development
of dental plaques
? Uneven tooth surface
? Carious lesions
? ill-filling margins of restorations
? Irregularities in positioning of the
teeth
the location favoring plaque
formation:
?Pellicle formation
?Microbial colonization
Process of formation
Plaque formation can be
considered as three phases
? Initial colonization
? Rapid bacterial growth
? Remodeling
Bacteria are thought to be
unspecifically associated with the
tooth surface under the influence
of Van der wall`s attractive forces
as well as repulsive negative
electrostatic forces
Initial microbial colonization
Van der wall’s forces
There is a weakness forces between
the molecules to be equal to
1/10~1/100 energe of chemical bond
Depend on the cause and character
of producing the forces:
?Orientation force
?Induction force
?Dispersion force
Orientation force
Induction force
Dispersion force
A firm attachment may subsequently
be achieved by specific mechanisms
Ligands theory
Recognized system,adhesions”
→”receptors”
Simplified explanation of the principle of selective adherence
of bacteria to enamel,Successful attachment is achieved when
the surface characteristics of a bacterium fit with a component
in the pellicle (P)
Two-reaction process for S.mutans
initial weak attachment occurs
between bacterial cell proteins and
salivary glycoproteins of the
acquired pellicle and is followed by
cellular accumulation mediated by
sucrose-dependent glucans and cell
surface receptor ligands.
The adherence of selected oral
bacteria initially involves non specific,
low-affinity,very rapid binding
reactions followed by specific,high-
affinity,slower,but stronger
attachment to the acquired pellicle
Microbial succession
Receptors (oligossacharides)
S.Oralis has a glactose-hinding
adhesin
Actiuomyces viscosus → proline
rich protein
Statherin s.sangnis → sialic acid
Pioneer bacteria create an
environment which is either more
attractive for secondary invaders
or increase unfavorable condition
to themselves,
In this way the resident microbial
community is gradually replaced
by other species
In mature dental plaque there may
be a subtle balance(homeostasis)
that tends to eject invading species
not previously present.
Structural features of
microbial colonization
Initial microbial deposition
after a cleaned tooth surface has
been exposed for 4h to the oral
environment,surprisingly few
bacteria are found (one of reports)
After 4 hours exposure the enamel
is covered by pellicle which is a
granular deposit,primarily located in
Tomes processes pits (TP) and in
perikymatal grooves (P)
The first bacteria to colonize the tooth
surface are of the cocco-bacillary type
(B ).note that the granular deposit does
not cover the tooth surface in a uniform
layer (PE)
At this early stage bacteria are of the
coccid or cocco-bacillary type and
always reside in shallow depressions
on the surface
After 8h only a few smaller groups of
microorganisms have settled on the
surface sheltered by the perikymata
Numerous bacteria spread across
the surface as a monolayer
In 12-h-old bacterial deposits the microorganisms spread
in monolayer along the perikymata (P )
In same areas multiplying
microorganisms form multiplayer,
individual organisms are embedded
in an inter-microbial matrix,
The monolayer of bacteria (upper part) is gradually
replaced by a multiplayer (lower part )which is
embedded in an intermicrobial matrix (X)
? Within 1 day the tooth surface is
almost completely covered by
blanket of microorganisms
? monolayer are intermitted with
multilayers,
After 1 day the surface of the micro-
biota is mainly made up of coccoid
bacteria,with a few filaments
During the course of the 2nd day the
bacterial deposits are colonized by
multiple filamentous organisms with
a perpendicular orientation to the
surface
Distinct morphological changes may be recorded on the surface of the
microbiota when comparing the bacterial deposits after 24 (Fig,5-12) and
48 h(Fig.5-13),Whereas the 24-h-old bacterial deposit comprises a mass of
coccoid bacteria from which a few filaments extend,the 48-h-old microbiota
is almost entirely dominated by filamentous organisms28
Initial colonization of root cementum
occurs in principle as outline for
enamel surface,but process more
rapidly
Because of the irregular surface
to topography of root surfaces,
colonization does not take place
according to a particular pattern
48-h-old bacterial deposits on root cementum and enamel
surfaces from the same individual,Note that the microbial
deposits are thicker and more densely packed on root cementum
mature dental plaque
During the early days,plaque growth
occurs mainly as a result of cell
division,but continuous adsorption of
single microorganisms from saliva also
contributes to the expansion of the
bacterial deposit
The corn cob are composed of a central filament coated
with spherical organisms,and appear to have a direct
interspecies relationship machinated by surface fibrils
As the microbiota
grows older,
characteristic
structural changes
are noted deep to the
surface,The most
striking change is the
formation of an inner
layer of densely
packed gram-positive
pleomorphic bacteria
next to the tooth
surface
Ultrastructure
of 2 week-old
dental plaque
from 3
individuals with
different
colonization
patterns,Note
that,in
addition to
differences in
thickness,the
outer parts of
the deposits
vary in
composition
and structure,
Relative proportions of selected organisms in developing
supragingival plaque on the labial surface of incisors,Plaque samples
were obtained 1,3,5,7,and 9 days after thorough prophylaxis.
Chemical composition of plaque
plaque contain about 80% water
20% solids
protein 40% to 50%
carbohydrates account for 13% to 18%
lipids account for 10% to 14%
other
Direct smears
Count of 2 × 1011 microorganisms/g
In centrifuge
3× 1011 organisms/g
2/3 of plaque must consist of bacteria
that means 70% the area is composed
of microorganisms and 30% of
intercellular material (matrix)
Carbohydrates of plaque
?Glucose is the main carbohydrate found
in hydrolyzed extracts of plaque
?arabinose
?ribose
?galactose
?fucose
Much of the carbohydrate exists
in the form of extracellular
polymers
? glucans (homopolymers of glucose)
? fructans (homopolymers of fructose )
? Heteropolysaccharides
Plaque microorganisms forming
extracellular polysaccharides
Glucans Fructans Heteropolysaccharides
Streptococcus sanguis Actinomyces viscosus Actinomyces viscosus
Streptococcus mutans Streptococcus mutans Lactobacillus buclneri
Streptococcus salivarius Streptococcus salivarius lactobacillus cellobiosus
Streptococcus mitior Lactobacillus casei
Lactobacillus casei
Lactobacillus acidophilus
Neisseria sp,
Cariogenic bacteria
?Rats raised under bacteria-free conditions
did not develop caries
?In 1960 Keyes performed a series of
experiments that established dental caries
as infectious disease
Diagram of caries formation due to passage of bacteria from rat dams to
their pups,elimination of the disease by treatment of animals with
antibiotics,and the occurrence of caries following various types of
inoculations,The infection was reintroduced by contact with infected
animals,inoculation with isolated strains of,caries-inducing”streptococci,
and transfer of bacterial plaque or feces,
DR,ROBERT KOCH
The agent must be present in every case
of the disease;
The agent must be isolated from the host
and grown in a lab dish;
The disease must be reproduced when a
pure culture of the agent is inoculated into
a healthy susceptible host;
The same agent must be recovered again
from the experimentally infected host
Koch’s postulates
Specific bacteria and caries
Lactobacilli
these bacteria were thought to play an
important role in caries etiology when it
was first found that early carious plaque
contained elevated levels of lactobacilli
compared with plaque from non-carious
surfaces
Lactobacill
Caries free group,100/ml
Caries active group,100000/ml
In a group of caries-free children the
mean number of lactobacilli per 1ml
of saliva was in the hundreds,while
in caries active children the mean
number per1ml was in the range of
100,000.
The early observation on changes in
lactobacillus levels in the oral cavity
led many dental scientists to consider
these bacteria as the specific
microbial etiological factor in human
caries
For a number of reasons,the
lactobacilli failed to qualify as
an exclusive etiological agent
in human caries formation:
The affinity of lactobacilli for tooth
surface is low,<0.01%
High levels of lactobacilli tend to
exist after caries has developed,
caries can frequently be initiated
in the absence of detectable
lactobacilli,
The lactobacilli are secondary
invaders,they may contribute to
the progression of decay due to
their acidogenic and aciduric
properties
Conclusion
Streptococci
In vitro studies with the oral
streptococci have demonstrated
many features that support their
role as cariogenic agents
?Relatively rapid generation
?To produce large quantities of acid
?Aciduric
?To utilize a wide range of fermentable
carbohydrates
?To produce extracellular polysaccharides
?To store intracellular carbohydrate
?To form plaque matrix
Streptococcus mutans
In the early 1920’s,Clark attempted
to evaluate the etiology of caries by
analyzing the microbial content of
plaque from human carious lesions
A streptococcal bacterium was
consistently isolated from the samples
and its pleomorphic nature (range from
cocci to rods,depending on the culture
conditions) caused it to be named
Streptococcus mutans
Orland etc,demonstrated that
microorganisms were required for
imitation of dental caries in rats
In 1960’s at the NIDR got
a series of success
Keyes and Fitzgerald showed that
in rats,caries is an infectious and
transmissible disease,and that
specific streptococci from carious
lesion in animals could induce
extensive decay in hamsters,
S.mutans and Human caries
S.mutans represents less than
1% the flora in pooled plaque
from caries-inactive individuals
S.mutans normally makes up 5% to
10% of the total bacteria present in
pooled plaque samples obtained
from caries-active subjects
High concentrations of S,mutans
is found mainly at retentive sites
such as caries lesions,occlusal
surface,pits and fissures,and
approximal areas
A series studies indicate that
S.mutans is significant involved
in occlusal fissure decay
S.mutans and sucrose
One of the more unique features of
S.mutans is the ability to utilize dietary
sucrose to enhance colonization of
the oral cavity
S,mutans has the ability to
metabolize the disaccharide
sucrose by several pathways
Two extracellular sucrose-dependent
polysaccharide-forming enzymes are
constitutively produced and excreted
from the cell by S.mutans
Dextransucrase or
glucosyltransferase(GTF) is the
enzyme responsible for glucan
production,
When glucan is formed by GTF,the
products contain varying proportions
of ?(1?6) and ?(1 ?3) linkage
The ?(1 ?3) linkage are critically
important in that as their proportion
increases the glucan becomes less
soluble in water
Classification of mutans
streptococci
Other cariogenic bacteria
Bacteria capable of producing carious lesions at
different sites in the dentition of germ-free rats
site
Bacterium Smooth occlusal RootSurfaces Fissures Surfaces
Lactobacillus acidophlilus - + -
Lactobacillus casei - + -
Streptococcus mutans + + +
Streptococcus sanguis - + -
Streptococcus salivarius + + -
Streptococcus mitior - + -
Streptococcus milleri + + -
Streptococcus faecalis - + -
Actinomyces viscosus - + -
Actinomyces naeslundii - + +
Actinomyces israelii - + +
Rothia sp,- - +
The Actinomyces species and other
gram positive rods may be involved
in the initiation of lesions on root
surfaces of human teeth
Members of the genus veillonella
are obligate anaerobes and are
found in significant numbers in
dental plaque and saliva
Within plaque these bacteria have
the capacity to utilize lactic acid and
convert it to less harmful products
The progress
on bioflms research
Our understanding of biofilms has
been advanced over last decade
by the application of novel
techniques.
These include
non-invasive and
non-destructive
microscopic
techniques (e.g,
scanning
confocal laser
microscopy)
That biofilms are usually lightly
structured with channels traversing
the depth of biofilm,creating
primitive circulatory system.
What is the significance
of biofilms
Gene expression can alter markedly
when cell form a biofilm,resulting in
many organisms having a radically
different phenotype following
attachment to a surface.
DNA microarrays have show that 73
genes and 50% of the detectable
proteome were differentially
regulated in biofilms of P.aeruginosa
when compared with conventional
liquid grown (planktonic) cell.
Cell-cell communication
Gram-positive bacteria generally
communicate via small diffusible
peptides
Gram-negative bacteria secrete acyl
homoserine lactones (AHLS)
The MIC of an organism growing
on a surface can range from two-
to 1000-fold greater than the
same cells grown planktonically
What is the significance
of microbial communities
The component organisms are not
merely passive neighbors but rather
that they are involved in wide range
of physical,metabolic and molecular
interactions.
This community life-style provides
enormous potential benefits to the
participating organisms
?A broader habitat range for growth
?An increased metabolic deversity
and efficiency
?An enhanced resistanc to
environmental stress
Horizontal gene transfer is also
more feasible in multi-species
biofilms
Plaque structure
Confocal laser scanning microscopy
has revealed that supergingival plaque
can have a structured architecture.
Polymer-containing channels or
pores have been observed that
link the plaque/oral environment
interface.
Typical vertical (xz) section through a four-day human plaque sample
taken in reflected-light mode,Images were taken at 0.6-umintervals from
the top of the biofilm to the enamel surface underlying it,The image
clearly demonstrates the bacterial aggregates (grey-white) separated by
areas of low reflectance (arrowed) presumed to be channels,Inverted
biomass (M) and associated narrow attachment points (A) can also be
observed,Scale bar = 25 um
That bacterial vitality varies
throughout the biofilm,with the most
viable bacteria present in the central
part of plaque and lining the voids and
channels.
Two-color xy section of a
fluorescein-stained biofilm
showing reflected light (red)
and fluorescence (green)
at a depth of 20um below
the plaque surface.
Optical sections (1 um each) of biofilm 2,vital fluorescence visualization,
First layer starting adjacent to enamel (bottom,left),13th layer 25 um
apart from bottom (top,left).
Considerable heterogeneity in pH over
relatively short distances in model mixed
culture oral biofilms.
Such environmental heterogeneity will
allow fastidious bacteria to survive in
plaque,and enable microorganisms to
co-exist.
This explains how organisms with
apparently contradictory metabolic
and growth requirements are able
to persist at the same site.
Bacterial composition of
dental plaque biofilms
New techniques
?16s rRNA amplification
?FISH
?Checkboard DNA hybridization
?DNA microarray
That approximately 50% cells in
plaque cannot as yet be cultured
in the lab.
Around 40% of amplified clones
represent novel phynotypes.
These culture-independent studies
are changing our views on the role
of bacteria in disease.
That poorly classified organisms that
are currently difficult or impossible to
grow in the lab can predominate in
deep pockets.
Biofilm regulation of gene
experession
During the initial stages of biofilm formation
by S.mutans (first 2h following attachment),
33 proteins were differentially expressed
(25 proteins were up-regulated,8 proteins
down-regulated)
To communicate with one another in
a cell density-dependant manner via
small diffusible molecules.
Lysed cells in biofilms could act as
donors of chromosomal DNA,thereby
increasing the opportunity for horizontal
gene transfer in dental plaque.
That oral bacteria do not exist as
independent entities but rather function
as a co-ordinated,spetially organized
and metabolically integrated microbial
community.
Thanks
and
Endodontics
A discipline to study the etiology,
pathogenic mechanism,pathology,
pathology-physiology,clinical
expression,treatment and favorable
turn etc,of the disease on dental
hard tissue and pulp tissue,
The content of the textbook
? Cariology
? Non-cariogenic disease of dental
hard tissue
? Endodontics
? Operative dentistry
History
In 50’s years
Oral medicine
?Cariology
?Operative dentistry
?Endodontics
?Non-cariogenic disease of dental hard tissue
?Disease of Oral mucosa
?Preventive dentistry
?Periodontology
?Paediatrics for dentistry
Stomatology in ancient times
Before Christ (B.C.)
There were some record about
caries
?Image liking character (script)
? worm + tooth
The chinese were known to have treated
dental ills with knife,cautery,and
acupuncture,a technique whereby they
punctured different areas of the body with
a needle.
In Dynasty Han (A.D.215~282)
There are some
record about
periodontology
Anno Domini
Pulpitis
In Han,Mr,Zhang Zhong Jing, Jin Gui
Yao lue,was a very famous writings in
which there was a record about arsenic
Arsenic is a toxicant medicine which
has been generally used for killing pulp
In Dynasty Tang (A.D.7~10 era)
the people use silver paste to fill tooth
decay
In Tang,tooth brush with willow twig
a toothbrush with hair planted was
invented in A.D.9~11 century from a
tomb of an emperor`s son-in-law of Liao
from Chi Fong city
3 events above described
reflected ancient civilization
of our country
Dentistry development
in West country
The first known dentist was an
Egyptian named Hesi-re (3000 B,C.),
He was chief toothist to the pharaohs,
he was also a physician,indicating
an association between medicine
and dentistry.
The Greeks
Hippocrates (500 B,C.)
appreciated the importance
of teeth,He accurately
described the technique for
reducing a fracture of the jaw
and also replacing a
dislocated mandible,He was
familiar with extraction
forceps for this is mentioned
in one of his writings.
Aristotle (384 B.C.) also
stated figs and soft
sweets produce decay.
Galen (200A,D,Romans)
was first to recognize that
toothache could be:
Pulpitis or pericementitis
He also classified teeth into centrals,
cuspids and molars.
B,Leonardo da
Vinci (end of 15th
Century) - he
described the anatomy
of the jaws,teeth and
maxillary sinus,These
drawings are the first
to accurately describe
the maxillary sinus,
However,credit has
been given to Dr,
Nathaniel Highmore of
England (1650).
D,Leeuwenhoek (17th Century)
- invented the microscope,He
described the dental tubuli and
was the first to see organisms of
the mouth
Anton van leeuwenhoek
K,John Greenwood (1789) -
dentures for George Washington
were made by him.
a red laser scans
George Washington's false teeth
not wooden
Laser scans find gold,ivory,lead,
human and animal teeth
L,Pierre Fauchard (18th Century - 1728)
- Father of Scientific Dentistry,Wrote a great
text "Surgeon Dentist",He also wrote a
complete work on Odontology in two volumes,
843 pages,He recognized the intimate
relationship between oral conditions and general
health,He advocated the use of lead to fill
cavities,He removed all decay and if the pulp
was exposed,he used the cautery,
Musee d'Art Dentaire Pierre Fauchard
at the Academie Nationale de Chirurgie Dentaire
22 Rue Emile Menier,75116,Paris France
He prescribed oil of cloves and
cinnamon for pulpitis,He described
partial dentures and full dentures in his
text,He constructed dentures with
springs and used human teeth,Gold
dowels were used in root canals filled
with lead,He was also known as Father
of Orthodontics,Fauchard died in 1768
at the age of 83,
1763 A.D
John Baker,M.D,Surgeon Dentist,
The earliest qualified dentist to practice
in Boston and in America,
1836 A.D.
Arsenic introduced for the killing
of pulps,by Spooner.
1840 A.D.
The American Society of Dental Surgeons,
first national dental organization,The
Baltimore College of Dental Surgery,the
first school in the world for the training of
dentists was founded by Harris and Harden.
Founded by Harris and Harden
1859 A.D.
Organization of American Dental
Association on a representative basis.
1890 W.D,Miller propose a
chemical-bacteria Paraorganism
theory to explain the mechanism
of caries
1891 A.D.
Extension for prevention
and scientific cavity
preparation promulgated
by G.V,Black,1892 A.D,
The establishment of a
three-year course in
dental colleges.
1906 A.D.
Einhorn recommends novacaine and
adrenalin combination for local
anesthesia.
1915 A.D.
McKay and Black
publish results of
investigation of
fluoride in drinking
water.
1956 A.D.
Air-rotor drill,250,000 RPM
Dr,Robert Borden.
Stomatology in China before 1949
? West China University (1910)
? Shanghai Second University(1920)
? 4th Military Medical University(1935)
? Beijing University(1943)
Shanghai Second University
West China University
1918(School 1910)
The first dental school in China
was founded in West China
Medical University in
1917,
A.W,Lindsay
A,W,Lindsay was teaching
After 1949
Hubei Medical College 1960
Founder
Prof,Xia Liang Cai
In recent 20 years,the science
and techniques got great progress
There are 1~2 faculties or dental
schools in each province
? Caries research
Caries Vaccine
Etiology & prevention
? Pulp disease
Modern root canal traitment
? Pulp biology
Stem cell – final target
Achievements
Craniofacial-oral-dental
research in the
century
21st
The leadership team of NIDR initiated
a strategic planning process in 1999
to identify
Where we are (strengths,weaknesses,
opportunities and threats)
Where we want to go (e.g.,mission and vision)
How we plan to get there (strategic plan)
Several scientific areas
will be concerned
in century 21st
From molecular biology to clinical investigations;
etiology,pathogenesis,epidemiology,prevention,
diagnosis and treatment of inherited craniofacial-
oral-dental diseases and disorders,e.g.,
ectodermic,dysplasia,cleft lip and palate,
amelogenesis imperfect,dentin genesis imperfect,
osteogenesis imperfect,and other inherited
diseases.
Inherited disease and disorders
Hereditary hypoplasia
Hereditary aplasia of the enamel
? dental caries
? Periodontitis
? Oral candidiasis
? Herpes
? Hepatitis,HIV/AIDS
Infections diseases
Viral,bacterial,fungal and parasitic such as
Diseased Periodontium
Primary herpetic stomatitis
Candidal stomatitis
Neoplastic disease
Supports basic,patient oriented,and
community-based research on the etiology,
pathogenesis and metastasis,epidemiology,
prevention,diagnosis,treatment of oral and
pharyngeal neoplastic diseases
Chronic disabling diseases
The full range of research involving
chronic disabling disease associated
with the craniofacial-oral-dental
complex
This includes osteoporosis,osteoarthritis
and related bone disorders,temporo-mandible
joint diseases and disorders,neuropathies and
neuro-degenerative diseases including those
involving oral sensory and motor functions and
autoimmune diseases such as sj?grens
syndrome,
Chronic diseases of cran-oral-
dental complex and other
systemic diseases (e.g.,diabetes)
Biomaterials,biomimetics
and tissue engineering
Biomaterials used for the repair,
regeneration,restoration and
reconstruction of craniofacial-oral-dental
molecules,cells,tissues and organs
The study of computer aid design
(CAD) computer aid manufacture
(CAM) for denture
Behavior,health promotion and environment
aimed at assessing the interactive roles of
sociological,behavior,economic,
environmental,genetic,and biomedical
factors in craniofacial-oral-dental diseases
and disorders
1996—
Diet and Oral Health
Cariology is a discipline within Stomatology
which deals with the complex interplaying
between the oral fluids and the microbial
deposits in relation to subsequent changes
in the dental hard tissues,
Several index have been used
in dental caries
Prevalence=
No of the patients with caries
No of the specific population in an area at risk of getting caries
at that time
Prevalence of caries,the total
caries experience of a population in
existence at a certain time in a
designated area.
Caries incidence is usually expressed
as the number of new decayed teeth or
surfaces per-a period in a
individual,group,or population,
Incidence of caries
DMF=Decayed teeth+Missing teeth+Filled
teeth/Number of subjects examined
DMFT
?If surface have been counted,then
we refer to the score as DMF-S
?If the teeth have been counted,
then it is refer to as DMF-T
The DMF-S or DMF-T are often
referred to as an,index”
The distribution of dental
caries in oral cavity
Reducing tendency
in developed country
The DMFT prevalence of 12-year-old children in the Nordic countries
in the period 1974-91.Denmark,Finland,Norway and Sweden seem to
follow the same downward trend,whereas Iceland has started a more
rapid decline somewhat later,
Increasing tendency
in developing country
95
84
98
95
98
92
95
98
1
3
Romania China Fuji Tonga Jordanian
4
5
6
2
7
8
83
85 86
62
DMFTs for 12 Years-old in Part of developing country
The caries prevalence of China
Time Population people with caries prevalence
Before 1949 32469 19258 59.30
1950~1959 219312 106781 48.70
1960~1969 544708 217774 40.00
1970~1979 3766290 1356362 36.00
1983 131340 40.54permanent teethCities 25080
Countryside 20636 29.70
Cities 19683 79.55
Countryside 16253 58.48
Deciduous teeth
The DMFT prevalence of 12-year-old children
in 11 provinces of China
Beijing 1.41 0.98
Shanghai 1.17 0.95
Tianjing 1.41 1.02
Gansu 0.36 0.8
Shandong 0.69 0.59
Yunnan 0.46 0.88
Liaoning 0.76 1.29
Zhejiang 1.22 1.46
Hubei 0.98 0.51
Guangdong 0.91 1.65
Sichuan 0.57 0.37
Account 0.67 0.88
Province DMFT(1983) DMFT(1995)
Age DMFT
12 1.03
15 1.42
18 1.60
35~44 2.11
65~74 2.49 (DFT)
The DMFT prevalence in 1995
Current concept of caries etiology
Dental caries is a multifactorial
disease in which there is an
interplay of three principal factors,
the host (primarily the saliva and
teeth),the microflora,and the
substrate,or diet,
A fourth factor time must be
considered in any discussion of the
etiology of caries,
Diagrammatically,these factors can
be portrayed as four overlapping
circles,
Micro-organisms
host
& tooth Sub-strate
The four circles diagrammatically represent the factors
involved in the carious process.all four factors must act
concurrently (overlapping of the circles)for caries to occur
time
nocariesnocaries
nocaries nocaries
caries
Caries requires a susceptible host,
a cariogenic oral flora and a
suitable substrate that must be
present for a sufficient length of
time
Saliva
the term saliva refers to the mixture
of secretions in the oral carity
?Saliva is produced day and night and it
is constantly swallowed
?Saliva is present as a proteinaceous
film covering all surfaces of oral cavity
This mixture consists of fluids
derived from
? the major salivary glands
? minor glands of oral mucose
? traces from gingival exudate
Effect of desalivation on incidence and
extent caries in animals
Effect of desalivation on caries in hamsters
Gruop No,
hamsters
Avg,no,
carious
teeth
Avg,caries
score
Intact Salivary
glands
20 2.3 4.0
Desalivated* 10 10.5 39.0
*Parotid,submandibular,and sublingual glands.
Decreased salivary flow
and caries in humans
?Sarcoidosis
?Sjogren’s syndrome
?Tharapeutic radiation
Hydrogen ion
Buffering ability
Calcium
Inorganic phosphate
Fluoricle
Inorganic components
Organic components
mucins
Glycoproteins
Statherin and acidic proline-rich
proteins
amylase
Antrmicrobial proteins
Saliva and dental caries
the quantity of saliva associated
with caries experience
Relationship between salivary
characteristics and caries prevalence
Property Relationship Property Relationshi
p
Flow rate ± pH
Ca
-
-
Buffer capacity + PO4
NH3
Amylase
Viscosity
Urea
-
-
-
-
Salivary composition and caries
Antibacterial factors of glandular
origin could protect oral mucosal
and hard surfaces by helping to
regulate the quantity and species
distribution of oral microbes
Oral Microorganisms
and
dental plaque
In contrast to mucosal surfaces,the
surfaces of teeth are not constantly
renewed by shedding of colonized
epithelial cells,
Surfaces of teeth
Some special sites
occlusal fissues
Approximal surface
Dental deposits
Biofilms on dental surface-matrix-
embedded microbial population,
adherent to each other and/or to
surface or interfaces
Acquired pellicle
Acellular,homogeneous organic film
that forms on enamel and other hard
surface by selective adsorption of
salivary proteins,
adsorption of salivary proteins
or glycoproteins
Origin
Immediately after cleaning and
polishing,salivary secrete deposit
in the defects of enamel.
? Surface pellicle
? Subsurface pellicle
Histological appearance
The surface pellicle appears acellular
and faintly granular under TEM
Surface Pellicle
Pellicles of unknown age may
vary in thickness from 50~1000nm.
globular
fibrillar
granular
Different morphological types
A subsurface pellicle
consisting of dendritic processes that
spread into the intercrystalline spaces
and extend to 3μm into the enamel.
90% water
10% solid material
composition
According to chemical analyses
amino acids account for 45% to 50%
carbohydrates amount 10% to 15%
of the dry weight
lipid
Function
?healing,repairing,or protecting the enamel
surface
?imparting selective permeability to the
enamel
?influencing the adherence of specific oral
microorganisms to the tooth surface
?serving as a substrate or nutrient for the
organisms
summary
?Organic deposit
?Naturally forms by selective adsorption
?Origin of protein from saliva
?After polishing,reforms rapidly
?Bacteria settle on the pellicle as soon as
it forms
?formation of dental plaque
Dental Plaque
In the fourth century B,C.
Aristotle related soft,adhere food
deposits to tooth decay,but it was
not until the advent of the microscope
in the seventeenth century that
“animalcules (microorganism) were
seen in these dental deposits.
Anton van leeuwenhoek,a draper and
sheriff`s chamberlain in Delft
recognized the limitation of mechanical
oral hygiene in removing these
deposits,
Anton Van leeuwenhoek saw large numbers
of living cells in scrapings from teeth:
I judge from myself that all the people living
in our united Netherlands are not as many
as the living animalcules that I carry in my
own mouth this very day.
Terminology
1847 Ficinus a slime coating denticulate
1897 Williams demonstrated the presence
of a mass of microorganisms
1895 G.V,Black gelatinous microbial
plaque
Dental plaque
Most figurative description:
a bacterial aspic with millions of
organisms standing shoulder to
shoulder
More formal definition by L?e,
plaque is the soft,non-mineralized,
bacterial deposit which forms on
teeth and dental prosthesis that are
not adequately cleaned
Morphology of dental plaque
A white or off-white accumulation
Variable thickness
Three main typies of organisms
coccoid
rod-shaped
filamentous
classification
?Supragingival plaque
?Subgingival plaque
?Dental calculus (calcified plaque)
Supragingival plaque
?Smooth surface plaque
?Fissure plaque
Supragingival smooth
surface plaque
Divided into 4 areas:
?plaque/tooth interface
?condensed microbial layer
?body of the plaque
?plaque surface
plaque/tooth interface
In some locations no pelicle
Higher magnification of plaque-enamel border,Microorganisms
that divide in horizontal planes are in direct contact with enamel
(1?30,000).
? Condensed microbial layer
a layer of very densely packed
coccoid organisms,from 3~20
cells thick
Part of a 7-day-old interdental plaque grown on enamel,The enamel matrix
(bottom),appearing as a fine meshwork,is covered by a thin electron-dense
and discontinuous pellicle,Immediately above this is the condensed microbial
layer which is covered by a layer of coccoid and filamentous micro-organisms
and probably Neisseria,The intermicrobial space is electron-lucent and reveals
cell remnants ( 1 ? 6,500).
?Body of the plaque
this occupies by far the largest portion
of the plaque
Thin section of plaque made of different
bacterial species-predominantly coccoidal.
Dense aggregation of microorganisms
at the enamel surface (lower left)
?Plaque surface
loosely arrangement
Great variety,coccoid,rod like,
“corncob”
In the surface layer of plaque some microorganisms
co-aggregate with other species,as visualized by the
presence of so-called corn cob structures
Magnified view of,corncob”
Free surface of plaque composed
of unidentified organisms
Free surface of plaque composed of
coccoid gram-positive (heavily stained
cell walls ) and unidentified gram-
negative microorganisms
Fissure plaque
Gram-positive cocci and short rods
predominate in a homogeneous,matrix,
with occasional yeast cells
Palisade and branching filaments
are absent within the fissures
A,survey of dental
plaque situated
within a deep,
narrow fissure of a
premolar
B,the upper half of
the fissure is filled
with dark material,
the lower half is
les dense
C,Higher
magnification
reveals a plaque
consisting of
mostly ghostlike
membrane and cell
wall structures
Subgingival plaque
? The matrix is sparse
? Organisms:filamentous organisms,
bacilli,cocci,spirochetes
? Gram negative bacteria
The filamentous nature of plaque associated with gingivitis,
Note attachment of smaller bacteria to filaments
Calcified plaque
Supragingival calcucus
white chalky yellow
Sub gingival calculus
greenish black
Dental calculus is plaque in which
mineralization has involved both the
plaque matrix and the microorganisms.
Formation and development
of dental plaques
? Uneven tooth surface
? Carious lesions
? ill-filling margins of restorations
? Irregularities in positioning of the
teeth
the location favoring plaque
formation:
?Pellicle formation
?Microbial colonization
Process of formation
Plaque formation can be
considered as three phases
? Initial colonization
? Rapid bacterial growth
? Remodeling
Bacteria are thought to be
unspecifically associated with the
tooth surface under the influence
of Van der wall`s attractive forces
as well as repulsive negative
electrostatic forces
Initial microbial colonization
Van der wall’s forces
There is a weakness forces between
the molecules to be equal to
1/10~1/100 energe of chemical bond
Depend on the cause and character
of producing the forces:
?Orientation force
?Induction force
?Dispersion force
Orientation force
Induction force
Dispersion force
A firm attachment may subsequently
be achieved by specific mechanisms
Ligands theory
Recognized system,adhesions”
→”receptors”
Simplified explanation of the principle of selective adherence
of bacteria to enamel,Successful attachment is achieved when
the surface characteristics of a bacterium fit with a component
in the pellicle (P)
Two-reaction process for S.mutans
initial weak attachment occurs
between bacterial cell proteins and
salivary glycoproteins of the
acquired pellicle and is followed by
cellular accumulation mediated by
sucrose-dependent glucans and cell
surface receptor ligands.
The adherence of selected oral
bacteria initially involves non specific,
low-affinity,very rapid binding
reactions followed by specific,high-
affinity,slower,but stronger
attachment to the acquired pellicle
Microbial succession
Receptors (oligossacharides)
S.Oralis has a glactose-hinding
adhesin
Actiuomyces viscosus → proline
rich protein
Statherin s.sangnis → sialic acid
Pioneer bacteria create an
environment which is either more
attractive for secondary invaders
or increase unfavorable condition
to themselves,
In this way the resident microbial
community is gradually replaced
by other species
In mature dental plaque there may
be a subtle balance(homeostasis)
that tends to eject invading species
not previously present.
Structural features of
microbial colonization
Initial microbial deposition
after a cleaned tooth surface has
been exposed for 4h to the oral
environment,surprisingly few
bacteria are found (one of reports)
After 4 hours exposure the enamel
is covered by pellicle which is a
granular deposit,primarily located in
Tomes processes pits (TP) and in
perikymatal grooves (P)
The first bacteria to colonize the tooth
surface are of the cocco-bacillary type
(B ).note that the granular deposit does
not cover the tooth surface in a uniform
layer (PE)
At this early stage bacteria are of the
coccid or cocco-bacillary type and
always reside in shallow depressions
on the surface
After 8h only a few smaller groups of
microorganisms have settled on the
surface sheltered by the perikymata
Numerous bacteria spread across
the surface as a monolayer
In 12-h-old bacterial deposits the microorganisms spread
in monolayer along the perikymata (P )
In same areas multiplying
microorganisms form multiplayer,
individual organisms are embedded
in an inter-microbial matrix,
The monolayer of bacteria (upper part) is gradually
replaced by a multiplayer (lower part )which is
embedded in an intermicrobial matrix (X)
? Within 1 day the tooth surface is
almost completely covered by
blanket of microorganisms
? monolayer are intermitted with
multilayers,
After 1 day the surface of the micro-
biota is mainly made up of coccoid
bacteria,with a few filaments
During the course of the 2nd day the
bacterial deposits are colonized by
multiple filamentous organisms with
a perpendicular orientation to the
surface
Distinct morphological changes may be recorded on the surface of the
microbiota when comparing the bacterial deposits after 24 (Fig,5-12) and
48 h(Fig.5-13),Whereas the 24-h-old bacterial deposit comprises a mass of
coccoid bacteria from which a few filaments extend,the 48-h-old microbiota
is almost entirely dominated by filamentous organisms28
Initial colonization of root cementum
occurs in principle as outline for
enamel surface,but process more
rapidly
Because of the irregular surface
to topography of root surfaces,
colonization does not take place
according to a particular pattern
48-h-old bacterial deposits on root cementum and enamel
surfaces from the same individual,Note that the microbial
deposits are thicker and more densely packed on root cementum
mature dental plaque
During the early days,plaque growth
occurs mainly as a result of cell
division,but continuous adsorption of
single microorganisms from saliva also
contributes to the expansion of the
bacterial deposit
The corn cob are composed of a central filament coated
with spherical organisms,and appear to have a direct
interspecies relationship machinated by surface fibrils
As the microbiota
grows older,
characteristic
structural changes
are noted deep to the
surface,The most
striking change is the
formation of an inner
layer of densely
packed gram-positive
pleomorphic bacteria
next to the tooth
surface
Ultrastructure
of 2 week-old
dental plaque
from 3
individuals with
different
colonization
patterns,Note
that,in
addition to
differences in
thickness,the
outer parts of
the deposits
vary in
composition
and structure,
Relative proportions of selected organisms in developing
supragingival plaque on the labial surface of incisors,Plaque samples
were obtained 1,3,5,7,and 9 days after thorough prophylaxis.
Chemical composition of plaque
plaque contain about 80% water
20% solids
protein 40% to 50%
carbohydrates account for 13% to 18%
lipids account for 10% to 14%
other
Direct smears
Count of 2 × 1011 microorganisms/g
In centrifuge
3× 1011 organisms/g
2/3 of plaque must consist of bacteria
that means 70% the area is composed
of microorganisms and 30% of
intercellular material (matrix)
Carbohydrates of plaque
?Glucose is the main carbohydrate found
in hydrolyzed extracts of plaque
?arabinose
?ribose
?galactose
?fucose
Much of the carbohydrate exists
in the form of extracellular
polymers
? glucans (homopolymers of glucose)
? fructans (homopolymers of fructose )
? Heteropolysaccharides
Plaque microorganisms forming
extracellular polysaccharides
Glucans Fructans Heteropolysaccharides
Streptococcus sanguis Actinomyces viscosus Actinomyces viscosus
Streptococcus mutans Streptococcus mutans Lactobacillus buclneri
Streptococcus salivarius Streptococcus salivarius lactobacillus cellobiosus
Streptococcus mitior Lactobacillus casei
Lactobacillus casei
Lactobacillus acidophilus
Neisseria sp,
Cariogenic bacteria
?Rats raised under bacteria-free conditions
did not develop caries
?In 1960 Keyes performed a series of
experiments that established dental caries
as infectious disease
Diagram of caries formation due to passage of bacteria from rat dams to
their pups,elimination of the disease by treatment of animals with
antibiotics,and the occurrence of caries following various types of
inoculations,The infection was reintroduced by contact with infected
animals,inoculation with isolated strains of,caries-inducing”streptococci,
and transfer of bacterial plaque or feces,
DR,ROBERT KOCH
The agent must be present in every case
of the disease;
The agent must be isolated from the host
and grown in a lab dish;
The disease must be reproduced when a
pure culture of the agent is inoculated into
a healthy susceptible host;
The same agent must be recovered again
from the experimentally infected host
Koch’s postulates
Specific bacteria and caries
Lactobacilli
these bacteria were thought to play an
important role in caries etiology when it
was first found that early carious plaque
contained elevated levels of lactobacilli
compared with plaque from non-carious
surfaces
Lactobacill
Caries free group,100/ml
Caries active group,100000/ml
In a group of caries-free children the
mean number of lactobacilli per 1ml
of saliva was in the hundreds,while
in caries active children the mean
number per1ml was in the range of
100,000.
The early observation on changes in
lactobacillus levels in the oral cavity
led many dental scientists to consider
these bacteria as the specific
microbial etiological factor in human
caries
For a number of reasons,the
lactobacilli failed to qualify as
an exclusive etiological agent
in human caries formation:
The affinity of lactobacilli for tooth
surface is low,<0.01%
High levels of lactobacilli tend to
exist after caries has developed,
caries can frequently be initiated
in the absence of detectable
lactobacilli,
The lactobacilli are secondary
invaders,they may contribute to
the progression of decay due to
their acidogenic and aciduric
properties
Conclusion
Streptococci
In vitro studies with the oral
streptococci have demonstrated
many features that support their
role as cariogenic agents
?Relatively rapid generation
?To produce large quantities of acid
?Aciduric
?To utilize a wide range of fermentable
carbohydrates
?To produce extracellular polysaccharides
?To store intracellular carbohydrate
?To form plaque matrix
Streptococcus mutans
In the early 1920’s,Clark attempted
to evaluate the etiology of caries by
analyzing the microbial content of
plaque from human carious lesions
A streptococcal bacterium was
consistently isolated from the samples
and its pleomorphic nature (range from
cocci to rods,depending on the culture
conditions) caused it to be named
Streptococcus mutans
Orland etc,demonstrated that
microorganisms were required for
imitation of dental caries in rats
In 1960’s at the NIDR got
a series of success
Keyes and Fitzgerald showed that
in rats,caries is an infectious and
transmissible disease,and that
specific streptococci from carious
lesion in animals could induce
extensive decay in hamsters,
S.mutans and Human caries
S.mutans represents less than
1% the flora in pooled plaque
from caries-inactive individuals
S.mutans normally makes up 5% to
10% of the total bacteria present in
pooled plaque samples obtained
from caries-active subjects
High concentrations of S,mutans
is found mainly at retentive sites
such as caries lesions,occlusal
surface,pits and fissures,and
approximal areas
A series studies indicate that
S.mutans is significant involved
in occlusal fissure decay
S.mutans and sucrose
One of the more unique features of
S.mutans is the ability to utilize dietary
sucrose to enhance colonization of
the oral cavity
S,mutans has the ability to
metabolize the disaccharide
sucrose by several pathways
Two extracellular sucrose-dependent
polysaccharide-forming enzymes are
constitutively produced and excreted
from the cell by S.mutans
Dextransucrase or
glucosyltransferase(GTF) is the
enzyme responsible for glucan
production,
When glucan is formed by GTF,the
products contain varying proportions
of ?(1?6) and ?(1 ?3) linkage
The ?(1 ?3) linkage are critically
important in that as their proportion
increases the glucan becomes less
soluble in water
Classification of mutans
streptococci
Other cariogenic bacteria
Bacteria capable of producing carious lesions at
different sites in the dentition of germ-free rats
site
Bacterium Smooth occlusal RootSurfaces Fissures Surfaces
Lactobacillus acidophlilus - + -
Lactobacillus casei - + -
Streptococcus mutans + + +
Streptococcus sanguis - + -
Streptococcus salivarius + + -
Streptococcus mitior - + -
Streptococcus milleri + + -
Streptococcus faecalis - + -
Actinomyces viscosus - + -
Actinomyces naeslundii - + +
Actinomyces israelii - + +
Rothia sp,- - +
The Actinomyces species and other
gram positive rods may be involved
in the initiation of lesions on root
surfaces of human teeth
Members of the genus veillonella
are obligate anaerobes and are
found in significant numbers in
dental plaque and saliva
Within plaque these bacteria have
the capacity to utilize lactic acid and
convert it to less harmful products
The progress
on bioflms research
Our understanding of biofilms has
been advanced over last decade
by the application of novel
techniques.
These include
non-invasive and
non-destructive
microscopic
techniques (e.g,
scanning
confocal laser
microscopy)
That biofilms are usually lightly
structured with channels traversing
the depth of biofilm,creating
primitive circulatory system.
What is the significance
of biofilms
Gene expression can alter markedly
when cell form a biofilm,resulting in
many organisms having a radically
different phenotype following
attachment to a surface.
DNA microarrays have show that 73
genes and 50% of the detectable
proteome were differentially
regulated in biofilms of P.aeruginosa
when compared with conventional
liquid grown (planktonic) cell.
Cell-cell communication
Gram-positive bacteria generally
communicate via small diffusible
peptides
Gram-negative bacteria secrete acyl
homoserine lactones (AHLS)
The MIC of an organism growing
on a surface can range from two-
to 1000-fold greater than the
same cells grown planktonically
What is the significance
of microbial communities
The component organisms are not
merely passive neighbors but rather
that they are involved in wide range
of physical,metabolic and molecular
interactions.
This community life-style provides
enormous potential benefits to the
participating organisms
?A broader habitat range for growth
?An increased metabolic deversity
and efficiency
?An enhanced resistanc to
environmental stress
Horizontal gene transfer is also
more feasible in multi-species
biofilms
Plaque structure
Confocal laser scanning microscopy
has revealed that supergingival plaque
can have a structured architecture.
Polymer-containing channels or
pores have been observed that
link the plaque/oral environment
interface.
Typical vertical (xz) section through a four-day human plaque sample
taken in reflected-light mode,Images were taken at 0.6-umintervals from
the top of the biofilm to the enamel surface underlying it,The image
clearly demonstrates the bacterial aggregates (grey-white) separated by
areas of low reflectance (arrowed) presumed to be channels,Inverted
biomass (M) and associated narrow attachment points (A) can also be
observed,Scale bar = 25 um
That bacterial vitality varies
throughout the biofilm,with the most
viable bacteria present in the central
part of plaque and lining the voids and
channels.
Two-color xy section of a
fluorescein-stained biofilm
showing reflected light (red)
and fluorescence (green)
at a depth of 20um below
the plaque surface.
Optical sections (1 um each) of biofilm 2,vital fluorescence visualization,
First layer starting adjacent to enamel (bottom,left),13th layer 25 um
apart from bottom (top,left).
Considerable heterogeneity in pH over
relatively short distances in model mixed
culture oral biofilms.
Such environmental heterogeneity will
allow fastidious bacteria to survive in
plaque,and enable microorganisms to
co-exist.
This explains how organisms with
apparently contradictory metabolic
and growth requirements are able
to persist at the same site.
Bacterial composition of
dental plaque biofilms
New techniques
?16s rRNA amplification
?FISH
?Checkboard DNA hybridization
?DNA microarray
That approximately 50% cells in
plaque cannot as yet be cultured
in the lab.
Around 40% of amplified clones
represent novel phynotypes.
These culture-independent studies
are changing our views on the role
of bacteria in disease.
That poorly classified organisms that
are currently difficult or impossible to
grow in the lab can predominate in
deep pockets.
Biofilm regulation of gene
experession
During the initial stages of biofilm formation
by S.mutans (first 2h following attachment),
33 proteins were differentially expressed
(25 proteins were up-regulated,8 proteins
down-regulated)
To communicate with one another in
a cell density-dependant manner via
small diffusible molecules.
Lysed cells in biofilms could act as
donors of chromosomal DNA,thereby
increasing the opportunity for horizontal
gene transfer in dental plaque.
That oral bacteria do not exist as
independent entities but rather function
as a co-ordinated,spetially organized
and metabolically integrated microbial
community.
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