bTime Determinants of Dental Caries

8/2/2019 bTime Determinants of Dental Caries

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Time Determinants of

Dental CariesDr.Ghada Maghaireh

BDS,MS,ABOD


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Factors involved in the caries process

Tooth

Plaque

Diet CariesToothPlaque

Diet


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CariesPlaque Tooth

Diet

Topical Fluoride

Saliva

Time

Im

muneSystem

Socioeconomic Status

Attitude


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Time

Caries can be arrested or completely repaired if enough

time is given for remineralization.

Caries lesion dose not develop over night, but take time.

It may takes years for cavitation to occur which gives the

dentist and the patient time for preventive treatmentstrategies.


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Teeth

Teeth consists of a calcium phosphate mineral

that demineralizes when the environmental pH

lowers.

As the environmental pH recovers, dissolved

calcium and phosphate can repriciptate on

remaining mineral crystals (remineralization).

Remineralization is a slower process than

demineralization.


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Chemically

Demineralization and Remineralization

Ca10(PO4)6(OH)2 10Ca+2 + 6PO4-3 +2OH-

Tooth Mineral Ions Dissolved in the Oral Fluids


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Teeth

When Remineralization is given enough time, it can

eliminate the damage done during Demineralization, but

in the absence of this the caries process will progress and

a lesion will develop.

For many years, much emphasis was given to the pre-

eruptive effect of fluoride improving the quality of the

dental hard tissues.

It is now clear that posteruptively used fluoride is more

protective against caries.


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Fluoride

It was noticed that excessive fluoride in thedrinking water (>2.0 part per million ppm F)resulted in mottling appearance of enamel(enamel fluorosis).

Enamel fluorosis was related to lowprevalence of dental caries.

Later on studies found that when the drinkingwater contained about 1 ppm fluoride, theteeth of the inhabitants of that area had a low

caries prevalence but no signs of dentalfluorosis.

Because of some problems with waterfluoridation, alternative methods ofsupplementing fluoride intake has been

developed.


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Crystalline Structure of Enamel

Enamel is composed of hydroxyapatite crystals (Ca10

(PO4)6(OH)2).

It is not a pure hydroxyapatite since it also has a non-apatite phase (amorphous calcium phosphate or

carbonate).

Enamel is porous allowing ions to diffuse into it, so thecomposition of the hydroxyapatite lattice can vary

throughout its structure.


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Crystalline Structure of Enamel

The crystal lattice has the capacity to substitute

other ions of appropriate size and shape.

within the lattice calcium can be exchanged for

radium, strontium and hydrogen ions and

phosphate can be exchanged for carbonate andhydroxyl for fluoride.


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Deposition of Fluoride in Enamel

During tooth formation: low concentrations deposited during toothformation because of low fluoride concentrations in tissue fluids.

After calcification but before eruption: more fluoride is taken up by

the surface enamel which is in contact with tissue fluids.

After eruption and throughout life: the enamel continue to take upfluoride from the external environment.

The fluoride content of intact surface is much higher than theinterior enamel but tends to be extremely variable (between primaryand permanent, between individuals, different teeth in the sameindividual, different surfaces of the tooth).


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Cariostatic Mechanisms of Fluoride

1. Once teeth have erupted, fluoride promote Remineralization (byreprecipitation of dissolved calcium and phosphate).

2. And inhibit demineralization (part of the reprecipitation is on thesurface which narrow the pores on the enamel surface whichprevents acid penetration), thus encouraging repair or arrest ofcarious lesions, delaying lesion progression.

3. Fluoride can exert a bactericidal or antienzymatic effect.

4. Interferes with ionic bonding during pellicle and plaque formationon tooth surface.

5. Improves enamel crystal structure (fluorapatite).


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Rate of Caries Progression

Caries lesion progress more slowly than they did several

decades ago which may be related to the increase use of

fluoride.

About 50% of the enamel fissure lesions had progressed to

involve dentin within 2 years while 75% had become

dentinal lesions after 4 years.

It needs about 3 to 4 years for proximal carious lesions to

reach dentin.


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Rate of Caries Progression

Caries on free smooth surfaces seems toprogress more slowly than on proximalsurfaces or in fissures.

Along with the decline in caries prevalencehas come a decline in caries progression rate.

Between the initiation of caries and theinvolvement of dentin in the caries process,there is ample time for preventivemanagement strategy.


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The Prognosis of Caries Lesions

While free smooth caries seemed to benefited the most

from the apparent caries decline, occlusal surfaces of molar

and premolars seem to have the least benefit.

The degree of destruction caused by caries that allows the

lesion to heal to be arrested is an important question.

The point of no return means a need for restoration whichis very crucial decision in the life of any tooth.


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Secular Trends in Dental Caries

The encouraging decline in caries prevalence in

children and adolescents during the 1970s and

most of the 1980s in industrialized countries has

leveled off.

Variations exist for a variety of reasons both

between and within countries.There are indications , particularly for young

children, that the caries prevalence is rising again.


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Secular Trends in Dental Caries

The decline in caries in 20 to 25 years old in

industrialized countries is most probably attributed to the

synergistic effect of improved plaque control, topical use

of fluoride and well-organized school-based preventiveprograms.

Fluoride toothpaste is by far the most frequently used

fluoride agent in the world, but it is used regularly byfewer than 10% of the world's population and about a

third of the population of the industrialized countries.


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bTime Determinants of Dental Caries

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