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Etiology of Dental Caries
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
Microorganisms
no
caries
host
& tooth
no
caries
Substrate
caries
no
caries
no
caries
time
Host factor: saliva
What is saliva here mean?
a. major saliva glands
Saliva
parotid, submandibular, sublingual
b. minor gland
c. gingival exudate
Why Saliva?
 Animal

experiments
Clinical observations
Animal experiment
Effect of desalivation on caries in hamsters
Group
No. hamsters
Avg. no.
Avg. caries
carious teeth
score
Intact salivary glands
20
2.3
4.0
Desalivated*
10
10.5
39.0
* Parotid, submandibular, and sublingual glands.
Clinical observations
Xerostomia:
decreased or lack of salivary secretion
Cause: therapeutic radiation
salivary glands disorder
(e.g. sjogren syndrome)
taking medicine
Clinical observation
Caries in a patient with impaired salivary function as
result of radiation therapy (courtesy of Drs Jansma
and Vissink, RUG, the Netherlands.
The caries is different from common.
Decay offer seen in cervical area, a rapid
demineralization over broad surfaces with
no cavity. the huge change in quantity of
saliva is responsible.
In xerostomia
The amount of bacteria
The quality of plaque change
S.mutans, Lactobacillus, Yeast, Actinomyce
S. sanguis, Veillonella, Neisseria
A case report
Decayed, missing, and
filled teeth prior to the
anticholinergic therapy
obtained from the
patient’s dental records
and roentgenographs
Full-mouth
roentgenographs of
patient showing
rampant caries and
pulpal involvement
of mandibular
anterior teeth
Decayed, missing, and
filled teeth of a patient
who received prolonged
anticholinergic therapy
for a duodenal ulcer.
Note the steep caries
increment (DMFT 27)
that occurred during the
time of xerostomia
Salivary composition and caries
Relationship between salivary characteristics and caries prevalence
Property
Relationship
Flow rate
±
Buffer capacity
+
Property
Relationship
pH
Ca
PO4
NH3
Amylase
Viscosity
Urea
+ positive relation; ± some relation; - no relation.
-
-
Why flow rate?
Flushing and neutralizing effect refered
as “Salivary Clearance” or “Oral
Clearance Capacity”
The Dawes (1983) model of oral clearance. Saliva is produced
at a rate dependent on the concentration of sugar in the saliva.
When a maximum volume of saliva (Vmax) is reached, a
swallow occurs and the salivary volume decreases to a residual
volume (Resid), thereby eliminating some of the sugar
Flow rate of saliva
Unstimulated
0.3ml/min
0.7~1.5L/day
Severe xerostomia
0.05ml/min
A computer
simulation of the
effect of changes in
the unstimulated
flow rate on the
clearance of
sucrose after a 10%
sucrose mouthrinse.
The simulation
assumed average
values for Resid
(0.8ml), and Vmax
(1.1 ml)
Sucrose concentrations in
saliva at different sites and
times after a 10% sucrose
mouthrinse
WS=whole saliva;
FUM=facial upper molars
FUI=facial palatal upper incisors
LLM=lingual lower molars
FLM=facial lower molars
high flow rate
high buffer capacity
flow rate
bicarbonate concentration
Na+
Electrolyte concentration as a function of
salivary flow rate. See also chapter 3
Salivary composition and caries :
contradictory results, because of the
difficulties in study
Relationship between salivary characteristics and caries prevalence
Property
Relationship
Flow rate
±
Buffer capacity
+
Property
Relationship
pH
Ca
PO4
NH3
Amylase
Viscosity
Urea
+ positive relation; ± some relation; - no relation.
-
Salivary buffers
In saliva, two chief buffer system,
bicarbonate-carbonic acid (HCO3/H2CO3, PK1=6.1) AND phosphate
(HPO4=/H2PO4-, PK2=6.8)
Bicarbonate is most important
buffer system
Dialysis of saliva, remove all ion, keep
protein , no buffer capacity remained.
Diagram of a
Stephan curve – the
plaque pH response
to a 10% glucose
solution (Redrawn
from Jenkins, The
physiology and
biochemistry of the
mouth. Blackwell,
London, 1978).
The effect of restricting the access of saliva to plaque
upon the shape of the Stephan curve (Reproduced
from) Jenkins, the physiology and biocbemistry of
the mouth. Black well, London, 1978)
Mean Stephan
curved following
rinsing with sucrose
alone and following
parafilm chewing or
cheese chewing.
Reproduced from
Higham and Edgar;
Caries Res
1989;23:42-48
Concept of “Critical pH”
In normal concentration of calcium
and phosphate, the critical pH is
5.5.
Antibacterial factor of
glandular origin
Lysozyme （溶菌酶）
Hydrolytic enzyme,
cleaves the 1-4 linkage
between Nacetylglucosamine and (N乙酰葡糖胺）, Nacetylmuramic acid (N-乙
酰胞壁酸）a structure of
cell wall of bacteria.




lysozyme, exist in many tissue fluid such as
tear, egg, saliva etc.
Many bacteria is resistant to lysozyme by
capsule and extracellular polymers.
Animal test show lysozyme alone could not
prevent caries.
Lysozyme function by affecting the
ecological balance between microorganism.
Salivary peroxidase system
(唾液过氧化物酶系统）
Salivary peroxidase
Thiocyanate ion (SCN-)
硫氰酸盐
from salivary glands
Hydrogen peroxide from bacteria
Peroxidase
H2O+SCN-
OSCN-+H2O
OSCN- 硫氰酸盐中间产物，包括二氰代
硫、氰亚磺酸、氰磺酸等
OSCN- inactivate various enzyme
of the glycolytic pathway and
therefore inhibit growth, respiration
and metabolism of many bacteria.
Lactoferrin（乳铁蛋白）
Ferric iron (Fe3+) is an essential microbial
nutrient
 Lactoferrin binds ferric iron, make it
unavailable for microbial use.
 Unbound lactoferrin may also have
bactericidal effect on some microorganisms
such as S.mutans

Microorganism’s policy against LF

Some bacteria produce a protein
(enterochelins) binding Fe++ more effectively

Some bacteria degraded LF and use the
released Fe++
Amylase （淀粉酶）
A calcium metalloenzyme hydrolyses
the alpha 1-4 bond of starch
Amylase may help clean the teeth of
carbohydrate debris. But why appear in tears,
serum, brohchial (支气管）, male and female
urogenital secretions?
Recent discovery: amylase may specifically
binds to some oral micro-organism.
Histatins （富组蛋白）
A group of small histidin-rich protein.
Inhibitor of candida albicans (白色念珠菌）
and S.mutans.
Unstimulate saliva: 2~30nmol/ml
Statherins （富酪蛋白）
Statherins
a 43 residue protein, produced
by acinar cell

Inhibit primary precipitation of calcium
phosphate, entire molecule is needed.

Inhibit secondary precipitation (crystal
growth). Only first six residues are
needed.
Why inhibiting precipitation?
In a given pH, only supersaturated saliva
would prevent demineralization (脱矿) and
promote remineralization (再矿化).
However, supersaturated with calcium
phosphate will promote crystallization of
calcium phosphate salts onto tooth surface.
Proline-rich proteins (PRPs,富脯蛋白)
3
PRPs was identified, with around 150 amino
acid residues.
 Inhibition of crystal growth calculus formation,
remineralization and calcium phosphate
precipitation
the first by 30 residues at the amino-terminal part
 Important
constituent of acquired pellicle
 Interaction with oral bacteria, modulation of
adhesion of selected bacteria to tooth surface
The PRPs molecule is
thought to bind to tooth
surface via its aminoterminal segment.
N
C
tooth
Binding of this segment is sufficient to fulfill
the primary role (inhibition of crystal growth),
and leaves the carboxy-terminal region of the
molecule, which has a different composition,
directed to the oral cavity, and free to interact
with oral bacteria.
Caries Immunology
Immunological prevention of infection
disease achieved vast success in this century.
smallpox, poliomyelitis etc.
How about dental caries?
Theoretically, antibody may control cariogenic
bacteria by


inhibit colonization, surface protein（表面
蛋白）, glucosyltransferase（葡糖基转移
酶GTF）
Opsonize（调理）bacteria, permitting
phagocytosis
Humoral and cellular
factors at the plaque/
tooth interface. Saliva
provides secretory IgA,
which can reach plaque
both at the gingiva and
at occlusal fissures.
Gingival exudate provides both humoral (IgG, IgM,
and IgA) antibodies and cellular components
(neutrophils, lymphocytes), but only to plaque in the
gingival region.
Electron micrograph
of a human dimeric
IgA myeloma protein
Polypeptide chain
structure of human IgA
Structure of human secretory IgA1 (sIgA1)
Animal studies
Animial caries model





rodent or primates
Diet containing sucrose (diet 2000)
Infected test cariogenic bacteria
Control group
Caries development is determined by
Keyes method
取唾液
本课题获国家自然科学
基金重点项目资助
取静脉血
Candidate antigen





Whole cell
Whole protein or peptide
Part of peptide, one more dormain
Cheramic peptide -- AgI/II~GTF
DNA vaccin
Active immunization
SIgA, locally or via gut
serum antibody, via systematic
Passive immunization
Passive immunization
 Monoclonal antibody against S.mutans
 Monoclonal antibody against the surface
protein antigen of S.sobrinus (Pag)
4
3.5
3
2.5
血清抗PAc -IgG
血清抗PAc-IgA
唾液抗PAc-IgG
唾液抗PAc-IgA
2
1.5
1
0.5
0
A
B
C
D
E
各实验组大鼠血清及唾液中特异性抗体水平分析（OD405）
A 重组质粒pCIA-P
C 重组质粒pCIA-P
E 生理盐水
B 重组质粒pCIA-P
D 空载体制裁粒pCI
80
70
60
50
E级龋损
Ds级龋损
Dm级龋损
40
30
20
10
0
A
B
C
D
E
各实验组大鼠磨牙龋齿计分分析
5
4
Series 1
Series 2
Series 3
Series 4
Series 5
Series 6
Series 7
Series 8
Series 9
Series 10
3
2
1
0
A
B
C
茸毛链球菌占总的可培养细菌的百分数
C. PBS处理组
A 单抗处理组
B 腹水对照组
C PBS处理组
S.sobrinus
S.mutans
S.rattus
Immunoelectron microscopy of PcAb against S.sobrinus 6715 whole cells reacted
with the three bacteria
S.sobrinus
S.mutans
Immunoeletorn microscopy of McAb ZS2/286 reacted
with the three bacteria
S.rattus
Immunoeletorn microscopy of non-specific mice ascites reacted
with S.sobrinus 6715
 Polyclonal
antibody against a S.mutans
GTase-I overexpression strain
 Polyclonal antibody against caries in milk
 IgY against caries in hen egg-yolk
Western blot of overexpress GTase-I strain
Effect of specific bovine milk antibodies against dental caries
construction of GTase-I overexpressing strain B29-33

intramuscular immunization

specific cow milk antibodies

mouse rinsing

colonization level of S.mutan on teeth surface 
immunization
milk collection
¡ý¡ý¡ý¡ý ¡ý¡ý ¡ý¡ý¡ý¡ý¡ý¡ý¡ý¡ý¡ý¡ý¡ý
Scheme of cow immunization
OD(405nm)
0.4
0.3
Two cows both
immunized with the
GTase over-expression
strain developed good
IgG in milk.
0.2
0.1
Series 1
0
3
25
50
60
75
days after parturition
Specific IgG level in bovine milk by ELISA
95
OD405
0.5
0.4
0.3
0.2
0.1
0
4
30
62.5
temperature（℃）
The effects of temperature on IgG in milk
100
Effect of specific IgY on prevention of dental caries
killed S.mutans, S.sobrinus whole cells

intramuscular
immunization

egg yolk IgY

effect of specific IgY on S.mutans in vitro

effect of specific IgY on caries
prevention in animal models
Host factors: tooth
Tooth morphology and arch form
Clinical Observation

Pit and fissure area
of posterior teeth are
highly susceptible to
caries. Food debris
and microoganisms
readily impact in the
fissures.

In same tooth, differences in surfaces
regarding to susceptible to caries

In mandibular first molars
occlusal > buccal > mesial > distal > lingual

In maxillary first molar
occlusal > mesial > lingual (palatal) > distal > buccal
Reason:

Partly due to tooth morphology
pit and fissure > smooth
few caries in cuspal area

In first molar, distal area is free to saliva
for 4-5 year, whereas the mesia area readily
form dental plaque in 4~5 day after eruption.
Defect in tooth
Plaque growth 24
hours after cleaning,
on a central maxillary
incisor of a patient
who is an “abundant”
plaque former. Note
the spread along the
gingival margin, the
crack, and other
surface defects.
Extensive dental caries on the left side of maxilla
and mandible in a patient who has received > 40 Gy
radiation dose to the area of the left parotid gland
Where dental plaque likely to form?
Stagnation area (滞留区）
Photograph of plaque
accumulation in stagnation
areas after omission of
toothbrushing for 3 days.
Note that accumulations
preferentially occur along the
gingival margin and
interproximal spaces whereas
no plaque accumulates in
cuspal and incisal areas due to
continuous mechanical wear
on these areas
Irregularities in arch form, crowding
and over lapping of the teeth also favor
the development of carious lesions.
Because of more stagnation areas
Clinical features immediately after
removal of orthodontic appliances and
cleaning. The orthodontic treatrment
had lasted for 2 years. Noe the marked
gingival reaction and the characteristic
chalky surface appearance of the active
enamel lesion.
After 3 months with careful oral
hygiene the gingival tissues have
recovered and the active lesion has been
completely arrested. The white
appearance of the lesion has diminished
markedly due to polishing away of the
eroded outermost enamel surface
Tooth composition
Enamal surface is more caries-resistant than
the subsurface
Microradiograph of white
spot lesionof enamel.
Compare the extensive
demineralization of the
subsurface enamel with
the better mineralized
surface layer (original
magnificaiton  100)
The surface enamel has more mineral and
organic matter but relatively less water. In
addition, certain elements, including
fluoride, chloride, zincaccumulate in
the enamel surface.
A-C Concentration
gradients of
different elements
in enamel from the
surface towards the
enamel-dentinal
junction
Changes of the enamel, such as a decrease
in density and permeability and a increase
in nitrogen and fluoride content occur with
age. This “maturation” maker the tooth
more resistant to caries.
Fluoride concentrations in
surface enamel of deciduous
canines as a function of dental
caries prevalence in the
deciduous dentition at the age
of 6 years. No straightforward
relationship to illustrate that a
high fluoride concentration
should be linked to a low
caries prevalence is seen.
However, when the caries
experience is high, the fluoride
concentration in enamel
becomes high as well.
Substrate: Diet and Caries
Diet: food and drink taken by any person
from day to day.
Function: locally
systemic
Locally:
react with the enamel surface and by
serving as a substrate for cariogenic
microoganisms.
Systemically:
Nutrition, on melabolic processes
Difficulties in identify diet role in
influencing caries
Reason:
difficulties in control diet for a long time
information only from diet history
Many researches indicate the sucrose
in the “arch criminal” in the etiology
of caries.
Cumulative dental decay
prevalence, expressed as
DMF permanent teeth, in
children ages 11 to 12.
Corresponding annual 1959
per capita sucrose
utilization data for 18
countries and the state of
Hawaii, from the food and
Agriculture Organization of
the United ations. (Courtesy
of Dr. T. Marthaler.)
Relationship between dental caries and mean sugar intake (g/day) for
South African males (16 to 17 years old) of four different ethnic
groups. There is a direct relationship between percent population
caries-free and sugar intake. (Drawn from the data of Retief et al.)
Interventional human studies
Vipeholm study
Hopewood House study
Plot of the mean number of
DMF teeth per child versus
chronological age in state
schools of Australia and in
children of Hopewood House
(with standard error of means).
Note the extremely low caries
increment of the
institutionalized children while
under strict dietary control and
the steep increase in caries
experience when dietary
supervision was no longer in
effect – at above 13 years of age.
(Courtesy of T. Marthaler)
Special population groups
hereditary fructose intolerance (HFI)
Assessment of cariogenic
potential of foodsuffs

In vitro model of caries
adhesiveness of food
enamel demineralization
production of titratable acid

Monitoring of plaque pH changes
acidogenicity is measured

Animal testing
Adhesiveness of foods
adhesiveness:
attacment between food and the tooth
surface, sticky food
Determining sucrose content
Plaque-pH curves following the application of A: lactose, glucose, maltose,
fructore and sucrose, and B: raw starch, cooked starch, maltose and sucrose.
Telemetrically recorded pH of interdental plaque (5 days old) in a subject during and
17 min after rinsing with 15ml of 10 per cent test solutions of Lycasin, xylitol,
sorbitol, sorbose and sucrose. PC=3min paraffin chewing; U=2 min urea rinse.
Other dietary components
and caries
Phosphates
cariostatic activity
animal experiment support that adding
phosphate in diet reduce caries in animal,
by local effect.
Human study: not convincing
Reason: difference in animal and human
and in experiment.
Trace elements
Relationship of mineral elements to caries
Frequency of eating and caries
Vipeholm study
Results of the Vipeholm
dental caries study. Sugar in
various forms was given
either between or with meals
over several years, and the
rate of caries increase was
studied. The caries increment
was much lower wen sugar
was given with meals
compared with sugar between
meals. (courtesy of B.E.
Gustafsson.)
The effect of between –
meal eating on caries
activity in 5- to 6-yearold children. The more
snacks children eat, the
higher is the caries
increment. (def)
Decayed, extracted,
filled (teeth). (Courtesy
of Weiss and Trithart.)
Animal studies
Early theories of caries etiology
Worms:
虫牙学说
Humors体液学说:
ancient greek; four fluid of body
are not in balance
Vital theory (活体学说)
18 century, disease originate tooth itself.
Chemieal theory (化学酸学说)
parmly (1819) suggest acid may induce caries.
Parasitic or septic theory (寄生腐败学说)
microorganism may play role, by microscope,
many bacteria on tooth were found.
proteolysis-chelation theory
First organic matter dissolved, degraded,
then, the end product may have chelating
effect and thereby dissolve the minerals
in the enamel.
This process may happen at neutral or
alkaline pH
Miller chemico-parasitic theory
 acid
was present in caries
 many
food mixed with salive and incubate
at 37℃ could decalcify tooth
 Several
oral bacteria could produce acid to
cause caries
 Different
bacteria invade caries lesion
Current concepts of caries etiology
Microorganisms
no
caries
host
& tooth
no
caries
Substrate
caries
no
caries
no
caries
time
Clinical classification of caries
Rate of caries progression
1950’s study:
it took one year the enamel fissure caries
develop into dentine.
1989’s study:
only 50% fissure developed into dentine within
2 years.
Fluoride application may retard caries progression
The progression rates of proximal caries
lesions from initial enamel caries to
dentinal caries in permanent dentition
was estimate to 68 (2 years at age 7, 4
years at age 12).
Classification according to progression rate
Acute caries:
progress fast, often
in children and teenagers,
light colored cavity.
Rampant caries, many tooth involved
at same time acute caries feature often
accompanied by systematic disorder.
Such as sjogren syndrome or saliva
reduction after radiation.
Caries in a patient with
impaired salivary function as
result of radiation therapy
(courtesy of Drs Jansma and
Vissink, RUG, the
Netherlands).
Chronic caries
progress slowly, black or brown colored
cavity hard remaining dentine
Arrested caries
caries stop progressing because of
the local etiological change
Secondary caries (recurrent caries)
caries recurred after treatment. Often at the
margin the filling materials restoration or
beneath
The shadow located on the
mesiolingual cusp adjacent
to the larger occlusal
amalgam restoration on the
maxillary right first molar
indicates the presence of
carious dentin
Classification according to the involving site
Occlusal caries
Root caries
Smooth surface caries
Classification according to the deepness
 Superfacial caries(浅龋)
white spot lesions, visibly frosted surface
brown spot
 Dentin caries (中龋)
cavitated lesion involving the up part of
dentin
 Deep caries (深龋)
cavitated lesion involving the pupal third of
dentin
Diagnosis
• Visual change
•Probing: rough surface or trapping point
pain upon probing
• Temperature test
• X-ray examination
• Transillumination
 Visual
change
Matte, white, active cervical lesions
 Probing:
rough surface or trapping point
pain upon probing
The explorer tip
can easily damage
white spot lesions
 Temperature
test
 X-ray
examination
 transillumination
Proximal caries lesion is
detected in an anterior
tooth with the use of
transillumination
Superfacial caries(浅龋)
White spot or brown, dark lesion, rough
upon probing
No complaint, no hyper sensitivity
Dentin caries (中龋)
Cavity, hypersensitivity upon probing,
hot or cold stimulus.
Deep caries (深龋)
Deep cavity, very sensitive and some
pain upon stimulus, however the pain
disappear as soon as the stimulus is
taken away.