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DENT 5302 TOPICS IN DENTAL BIOCHEMISTRY

The caries process

Dietary factor and cariogenic aspects of dental plaque

Plaque fluid and the caries process

Fluoride and dental caries

Anticario mechanisms of fluoride

Fluoride metabolism

Fluoride toxicity

Application of fluoride (& Ca P) in caries control measures

DENT 5302 TOPICS IN DENTAL BIOCHEMISTRY

28 March 2007

• Nature and character of dental caries

• Factors influencing the caries process

• Development of early caries lesion in enamel

• Dentin caries

Objectives:

Outline

Nature of dental caries

Key features of dental cariesMulti-factorial

Site specific

Dynamic

Formation of early enamel lesion

Microscopic features of early enamel lesion

Demineralization-Remineralization

History & Epidemiology

Dentin caries

Caries free vs Caries controlled

Roman

IndustrializeCarious Teeth (%)

1950

Epidemic

Percentage of carious teeth in English population

0 2000100010002000

20

15

10

5

0

Evans CA, Kleinman DV (2000). The Surgeon General's report on

America's oral health: opportunities for the dental profession.

J Am Dent Assoc. 131: 1721-8.

Dental caries: the most prevalent infectious disease

• 5x > childhood asthma ; 7x > hay fever

• Affects 85% of adults (>18 years old) in the US

• 80% of caries occurs in 20% of the population

Less than high school High school

At least some college Total children

www.surgeongeneral.gov/library/oralhealth/

Underprivileged population?

70% of 12-17 years old had caries

94% of dentate adults (18 years or older) had caries

The nature of caries has changed:

Rapidly progressing childhood disease

Slow but steadily progressing disease in adulthood

75% of children aged 5-11 years old were caries-free

Discussion:

Give some examples of using knowledge and understanding

of dental caries in your future dental practice.

Cariogenic bacteria (dental

plaque)

Host factors:ToothSaliva

Diet:Fermentable carbohydrate

Dental caries is multifactorialCharactersof caries

Charactersof caries

Traditional concept

Social classSocial class

EducationEducation

BehaviorBehaviorAttitudeAttitude

KnowledgeKnowledge

IncomeIncome

Biofilm Tooth

Saliva

FluorideMicrobialspecies

Diet

Flow rateCompositionBuffer

CompositionSugarFrequency

Time

Genetic

Dental caries is multifactorialCharactersof caries

Charactersof caries

Modern concept

Biological determinants

Socio- economical factors

Erosion

Tooth morphology affects plaque accumulation

Metabolism of microorganisms in dental plaque (biofilm)

Microenvironment (plaque composition, thickness, diffusion properties)

Access to dietary substrates, saliva, anticaries agents

Dental caries: Localized destruction of tooth tissues

Why localized?

Charactersof caries

Charactersof caries Dental caries is site specific

Demineralization vs Remineralization

breakfast

lunch

coffee break

snackdinner

snack

mid

night

6 am

brushing

brushing

noon6 p

m

Min

eral

con

tent

Netloss

Charactersof caries

Charactersof caries Dental caries is dynamic

Brown spot (Arrested lesion)

• Change in microenvironment

• Reduced plaque accumulation

• Access to saliva

www.recaldent.com

Application

acid H+ + apatite

Ca2+ + PO43- + OH-

saliva plaque sound enamel

subsurface lesion

OH-

Ca2+

PO43-

F-

surface zone (repair)

H2O

HPO42-

diffuse & dissociate

Formation of early enamel lesion

1

1

1

2

2

2

3

33 4

44

1. Surface Zone Intact surface 20-100 m thick, <10% mineral

loss

2. Body of the Lesion Largest zone, highest mineral loss (24%)

3. Dark zone Very small pores, <10% mineral loss

4. Translucent zone Advancing front, 1% mineral loss

Microscopic features of early enamel lesionMicroscopic features of early enamel lesion

At this stage the lesion is reversible

Fluoride and preventive treatment are most effective at this stage

Clinical appearance: White spot lesion

First clinical sign of enamel caries lesion

Not that early!

300 – 500 m depth to be visible

Why are we interested in early caries lesion?Why are we interested in early caries lesion?

Study done in community with water fluoridation

Only 9 of 72 white spot lesions became cavitated after 7 years

More than half of early lesions regressed to ‘normal’ enamel

(Baker-Dirks, 1966)

Age 8 Age 15

Sound enamel 93 74 37

15

White spot 72 26 4 9

Cavitated lesion 19 19

111 sound enamel

41 white spots

32 cavitated lesions

Early carious lesions are reversible

White spot lesions

around orthodontic

bracketts

Dr. J.P. ByersDr. J.P. Byers

Dr. J.P. ByersDr. J.P. Byers

Is there a ‘caries-free’ individual?

Discussion: ‘caries-free’ vs ‘caries-controlled’

Q1 Do you have any cavities or fillings

Q2 Do you think you have demin-remin periods?

Progression of Carious Lesion

0 1 2

3 4

Proximal lesions in permanent

teeth can take 3-4 years through

enamel, unless in caries active

individuals. (Pitts, 1983)

How long?

Late teen Danish population

From 2 – 3: 9.2 surface % per year

From 3 – 4: 2.3 surface % per year

Median survival time from

stage 2 to 3 was ~ 3 years

Rampant caries in Mountain Dew drinker

A = zone of decomposed dentin

B = zone of bacterial invasion

C = zone of demineralization

D = sclerotic dentin

E = reparative dentin

Microscopic features carious dentin

Outer carious dentin

Inner carious dentin

Dentin cariesDentin caries

Progression of dentin caries

Demineralization of inorganic substance

Breakdown of organic matrix by proteolytic enzymes

Bacterial invasion

Inner carious dentin

uninfected

remineralizable

vital

sensitive

Fusayama T, Okuse K, Hosoda H. J Dent Res. 1966;45:1033-46.

Relationship between hardness, discoloration, and microbial invasion in carious dentin.

Turbid layer

Transparentlayer

Sub-trans parentlayer

Crystals in tubule lumen

PulpwallPulpwall

Sound dentin

DEJ 1000 2000 3000 m

Kn

oo

p H

ard

nes

s N

um

be

r 70 -

60 -

50 -

40 -

30 -

20 -

10 -

Odontoblast

Outer carious dentin

infected

nonremineralizable

nonvital

insensitive

Bacteria

Two layers of carious dentinTwo layers of carious dentinDentin cariesDentin caries

Discussion:

What do you learn today that can be used in future practice?

2. What should we do with white spot

lesion?

1. Why underprivileged population have more caries?

3. How much carious dentin should be removed?

Recommended references

1. Clarkson BH. Introduction to Cariology. Dent Clin North Am 1999;43(4):569-578.

2. Zero DT. Dental Caries Process. Dent Clin North Am 1999;43(4):635-664.

3. Featherstone JD. The science and practice of caries prevention. J Am Dent Assoc 2000;131:887-899.

4. Gordon Nikiforuk. Understanding Dental Caries 1. Etiology and Mechanisms, Basic and Clinical Aspects. Basel; New York: Karger 1985. Chapter 10.

5. Gao W, Smales RJ, Yop HK. Demineralisation and remineralisation of dentine caries, and the role of glass-ionomer cements. Int Dent J 2000;50:51-56.

6. Fejerskov O. Changing paradigms in concepts of dental caries: Consequences for oral health care. Caries Res 2004;38:182-191.