Etiology of Dental Etiology of Dental CariesCaries

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

Micro-organisms

host & tooth

Sub-stratecaries

time

no caries

no caries

no caries

no caries

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

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.

Effect of desalivation on caries in hamsters

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 a

nd 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 fill

ed teeth prior to the antich

olinergic therapy obtained

from the patient’s dental r

ecords and roentgenograp

hs

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 cariesRelationship between salivary characteristics and caries prevalence

Property Relationship Property Relationship

Flow rate ± pH -Buffer capacity + Ca -

PO4 -

NH3 -

AmylaseViscosity -Urea -

+ positive relation; ± some relation; - no relation.

Why flow rate?

Flushing and neutralizing effect refered a

s “Salivary Clearance” or “Oral Clearanc

e 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 volu

me (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 molarsFUI=facial palatal upper incisorsLLM=lingual lower molarsFLM=facial lower molars

high flow ratehigh buffer capacityflow 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 Property Relationship

Flow rate ± pH -Buffer capacity + Ca -

PO4 -

NH3 -

AmylaseViscosity -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 N-acetylglucosamine and (N- 乙酰葡糖胺） , N-acetylmuramic 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

Thiocyanate ion (SCN-) from salivary glands硫氰酸盐

Hydrogen peroxide from bacteria

Salivary peroxidase system ( 唾液过氧化物酶系统）

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

Peroxidase

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 (enterocheli

ns) binding Fe++ more effectively

Some bacteria degraded LF and use the releas

ed Fe++

Amylase （淀粉酶）

A calcium metalloenzyme hydrolyses t

he alpha 1-4 bond of starch

Amylase may help clean the teeth of carbohyd

rate debris. But why appear in tears, serum, br

ohchial ( 支气管） , male and female urogeni

tal secretions?

Recent discovery: amylase may specifically bi

nds 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）

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.

StatherinsStatherins

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.

Why inhibiting precipitation?Why inhibiting precipitation?

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 ad

hesion of selected bacteria to tooth surface

The PRPs molecule is thought to bind to tooth surface via its amino-terminal segment.

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.

N C

Caries Immunology

Immunological prevention of infection disease achieved vast success in this century.

smallpox, poliomyelitis etc.

How about dental caries?

inhibit colonization, surface protein （表面蛋白） , glucosyltransferase （葡糖基转移酶 GTF ）

Opsonize （调理） bacteria, permitting phagocytosis

Theoretically, antibody may control cariogenic bacteria by

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.

Polypeptide chain structur

e of human IgA

Electron micrograph of a human dimeric IgA myeloma protein

Structure of human secretory IgA1 (sIgA1)

Animal studies

rodent or primates Diet containing sucrose (diet 2000) Infected test cariogenic bacteria Control group Caries development is determined by

Keyes method

Animial caries model

取唾液

取静脉血

本课题获国家自然科学基金重点项目资助

Whole cell Whole protein or peptide Part of peptide, one more dormain Cheramic peptide -- AgI/II~GTF DNA vaccin

Candidate antigen

SIgA, locally or via gut

serum antibody, via systematic

Passive immunization

Active immunization

Monoclonal antibody against S.mutans

Monoclonal antibody against the surface protein antigen of S.sobrinus (Pag)

Passive immunization

A 重组质粒 pCIA-P B 重组质粒 pCIA-PC 重组质粒 pCIA-P D 空载体制裁粒 pCIE 生理盐水

0

0. 5

1

1. 5

2

2. 5

3

3. 5

4

A B C D E

PAc - I gG血 清 抗PAc- I gA血 清 抗PAc- I gG唾 液 抗PAc- I gA唾 液 抗

各 实 验 组 大 鼠 血 清 及 唾 液 中 特 异 性 抗 体 水 平 分 析 （ O D 4 0 5）

0

10

20

30

40

50

60

70

80

A B C D E

E级龋损Ds级龋损Dm级龋损

各实验组大鼠磨牙龋齿计分分析

茸毛链球菌占总的可培养细菌的百分数

A 单抗处理组 B 腹水对照组 C PBS 处理组

A B C0

1

2

3

4

5 Series 1 Series 2

Series 3 Series 4

Series 5 Series 6

Series 7 Series 8

Series 9 Series 10

C. PBS处理组

Immunoelectron microscopy of PcAb against S.sobrinus 6715 whole cells reacted with the three bacteria

S.sobrinus S.mutans S.rattus

Immunoeletorn microscopy of McAb ZS2/286 reacted

with the three bacteria

S.sobrinus S.mutans 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

¡ý¡ý¡ý¡ý ¡ý¡ý ¡ý¡ý¡ý¡ý¡ý¡ý¡ý¡ý¡ý¡ý¡ý

immunization milk collection

Scheme of cow immunization

Two cows both immu

nized with the GTase o

ver-expression strain de

veloped good IgG in m

ilk.

Specific IgG level in bovine milk by ELISA

3 25 50 60 75 950

0.1

0.2

0.3

0.4

Series 1

OD(405nm)

days after parturition

4 30 62.5 1000

0.1

0.2

0.3

0.4

0.5OD405

temperature （℃）

The effects of temperature on IgG in milk

Effect of specific IgY on prevention of dental caries

killed S.mutans, S.sobrinus whole cells

egg yolk IgY

effect of specific IgY on S.mutans in vitro

effect of specific IgY on caries prevention in animal models

intramuscularimmunization

Host factors: tooth

Tooth morphology and arch form

Clinical Observation

Pit and fissure area o

f posterior teeth are h

ighly susceptible to c

aries. Food debris an

d microoganisms rea

dily impact in the fis

sures.

In same tooth, differences in surfaces regardin

g 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 for

m 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. Com

pare the extensive deminer

alization of the subsurface

enamel with the better min

eralized surface layer (orig

inal magnificaiton 100)

The surface enamel has more mineral and

organic matter but relatively less water. In

addition, certain elements, including

fluoride, chloride, zincaccumulate 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 pr

evalence, expressed as DM

F permanent teeth, in childr

en ages 11 to 12. Correspon

ding 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-fr

ee 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 sucros

e.

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, sorbito

l, 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 cariesVipeholm 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 a

ctivity in 5- to 6-year-o

ld children. The more s

nacks children eat, the

higher is the caries incr

ement. (def) Decayed, e

xtracted, 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

Micro-organisms

host & tooth

Sub-stratecaries

time

no caries

no caries

no caries

no caries

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, R

UG, 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 denti

n

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 br

own spot Dentin caries ( 中龋 ) cavitated lesion involving the up part of de

ntin 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.