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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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