Dental caries , its etiology &

recent advances Garima singh

Pg student

Content • Introduction• Classification• Theories of dental caries • Etiology of dental caries• Microbilogy of dental plaque biofilm and role in dental

caries• The caries environment:

Saliva, pellicle, diet and hard tissue

• The chemistry of caries: remineralization and demineralization events with direct clinical relevance• Concluison• References

Introduction • Throughout the history of man, diseases have come and

diseases have disappeared. For most of the major diseases, it has been possible to clearly identify the underlying cause. • But for other diseases, it may be more difficult to

explain the reason. and this is particularly true for diseases with multifactorial background like dental caries.

• Word “caries” derived from latin word meaning ‘rot’ or ‘decay’.

• Shafer (1993) “ Dental caries is an irreversible microbial disease of calcified tissues of teeth, characterized by demineralization of inorganic portion and destruction of organic substance of tooth, which often leads to cavitation.”

• Dental caries is the localized destruction of susceptible dental hard tissue by acidic by-products from bacterial fermentation of dietary carbohydrates. • Thus , it is a bacterial driven, generally chronic, site

specific, multifactorial, dynamic disease process that results from the imbalance in the physiologic equilibrium between the tooth mineral and the plaque fluid

Classificaiton

• According to anatomic site:• Pit and fissure caries• Smooth surface caries• Root caries

• According to severity:• Incipient caries• Occult caries• cavitation

• According to age:• Early childhood caries two variant

• Nursing caries-unique pattern of dental decay in young children due to prolonged nursing habits

• Rampant caries-widespread rapidly borrowing type of caries resulting in early involvement of pulp and affecting those teeth which are usually immune to decay.

• Adolescent caries- variant of rampant caries where teeth are generally considered immune to decay• Senile caries-recession of gingiva

• According to progression:• Arrested caries• Recurrent caries• Radiation caries

Aetiology of dental caries• Early theories• The legend of the worm

• Endogenous theories• Humoral theory• Vital theory

• Exogenous theories• Chemical theory• Parasitic theory• Miller’s chemico parasitic theory• Proteolytic theory• Proteolysis- chelation theory

Theories of dental caries • The legend of the worm• Several early references to decay process include the

“legend of worm”• An equivalent of which was also found in Japanese

and Chinese literature• Also accepted in India and Egypt• Remedies were directed towards the “worms” eg.

Fumigaiton , acupuncture etc.

• Humoral theory• The four humors that were thought to maintain the

body health included ‘ blood, phlegm, black bile and yellow bile’.• All diseases including dental caries attributed to

imbalance between these factors.

• Vital theory• The tooth was thought to be the source and origin of

disorder in that the process started from the tooth within.

• Chemical theory

• Robertson 1835• Decay –due to acid production by fermentation of food

particles around teeth• Fermentation was strictly non-vital process.• Involvement of microorganism – not recognised

• Parasitic theory

• 1843, Erdl described filamentous parasites in the membrane removed from teeth.• Early microscopic observation of scrapings from teeth and

carious lesions, by Antonie Van Leeuwenhoek

Microorganism were associated with carious process

• Miller’s chemoparasitic theory

• In 1889 Miller, proposed that acid and microorganisms were involved in etiology of dental caries.• Dental decay is

Chemico-parasitic processConsist 2 stages

• Decalcificaiton of enamel and dentin• Dissolution of softened residue

• Significance: assigned an essential role to three factors-1. Role of microorganism in acid production and proteolysis2. Carbohydrate substrate 3. Acid which causes dissolution of tooth minerals.

• Accepted by majority of investigators

• Proteolysis: chelation theory

• Schatz et al, in 1955• Bacterial attack on enamel, initiated by keratinolytic

microorganisms, results in a breakdown of the protein and other organic components of enamel, chiefly “keratin”.

Formation of substances,- form soluble chelate with mineral component of tooth

Decalcifying enamel at a neutral or even alkaline pH

Levin's theory• He emphasized that demineralization and remineralization

of the enamel is a continuous process if in a given interval of time , more ions leave the enamel than entering it, then there is a net demineralization hence the carious process starts

• Three Important Factors• Ph of plaque• Ca&phospate ion concentration at the interface• Fluoride ion concentration

Aetiology of dental caries

susceptible Tooth

surface

Dietary fermentabl

e carbohydra

tes

Cariogenic bacteria

saliva

caries

Time

The caries environment: etiological factors • Saliva • Diet• Hard tissue ultrastructure• Role of plaque in etiology of dental caries

Saliva • Bathes the tooth surface.• Vehicle for solubilizing and transporting media for

various substances• Cleansing property• Clear the acids produced by microorganism

• Buffering property• Maintenance of pH

Saliva

Inorganic

Calcium , phosphate, fluoride, bi carbonate.

Related with maintaining the integrity of teeth

Provide buffer capacity

organic

Secretory IgALysozyme

LactoferrinLactoperoxidase

Proteins- statheins. PRP, histatin

• Mandel and colleagues & mandel and bennick • Could not observe differences between caries active

& caries resistant individuals when analysing salivary proteins and acidic PRPs, respectively.

• Vitorino & colleagues• Used spectrometer• Strong correlation between presence of

phosphorprotein and absence of caries• Phosphoprotein could contribute to more effective

remin. Process.

• Recently ,• Rundney and collegues• They identified statherin and cystatin as predictors of

occlusal caries.• Increased level is associated with high rates of

remineralisation.More

research is needed to

verify

Diet • Dental caries and fermentable carbohydrate• From etiology basis, it is still remain the main driver of

caries process.• Consideration on • Retentiveness of food• Presence of protective factors• Type of carbohydrate

ComplexSimple

Cariogenic properties of carbohydrates

Freely diffusible

Readily metabolized

Production of acids

demineralization

Synthesis of extracellular glucan

Favour accumulation of S. mutans and other cariogenic bacteria

• In previous study it has been shown that enhanced demineralization is associated with s.mutans.• This was attributed to alteration of diffusion properties

of plaque owing to presence of water insoluble extracellular matrix material synthesized from sucrose.

Tooth • Host factor involved in caries process are location,

morphology, composition, and posteruptive maturation.• Enamel is composed of mainly hydroxyapatite crystals,

but should not be considered as pure hydroxyapatite.• Chemically it is Ca10(PO4)2(OH)2

OH- F- PO43- CO3

2-

More resistant to caries

challenges

Less stable, susceptible to

demineralisation

Ion exchange in hydration

shell

Direct absorption on surface crystal

Substitution with similar

size and charge

Dental plaque and dental caries• "It is the soft tenacious material found on the tooth

surface and not readily removed by rinsing with water"……Dawes et al (1963)• Ecological plaque hypothesis

“critical role played by change to the oral environment in predisposing an individual to dental caries”

• Dental caries is a consequence of an imbalance in resident microflora due to enrichment within microbial community of potentially more cariogenic bacteria due to frequent conditions of low pH in plaque biofilms.

Chemistry of dental caries: reminerlaization & demineralization events

• Dental decay: demineralization of tooth surface goes beyond the mineral exchange• Mineral exchange-?• It occur regularly between tooth surface and

surrounding environment• From mechanistic aspect:• From clinical point of view:

Dynamic changes in Tooth surface• “not all mineral loss from tooth structure” is part of

pathologic process.• Tooth surface is a dynamic:• Periods of remineralisation (mineral gain) and

demineralization (mineral loss)• Particularly in surfaces covered by stagnant biofilms.

• Post-eruptive maturation:Tooth

eruption• Colonized by

bacteria

Conditions created by

bacteria

• In combination with saliva

More resistant enamel surface

Enamel-porous,Carbonate,

water, Mg etc

Remin and demin

less porous, decreased

content

Dynamic changes in crystals• Crystals on tooth surface are covered by stagnant

biofilm• likely to continue having mineral exchanges for as long

as the covering biofilms are able to create conditions of under saturation and supersaturating with respect to crystals.

Undersaturaiton:In acidic pH

Loss of Phosphate and hydroxyl ions

React with hydrogen ions

Mineral release from other sources

Mineral loss stops –saturation

Supersaturation pH incresed

remineralizationIf it occur for

long tymPrecipitation of minerals

Calculus formation

Although pH is strongest determinant for saturation level leading to demineralisation / remineralisation remain under clinical conditions

Change in pH and its role in dental caries• Acidogenic bacteria in dental plaque

rapidly metabolize fermentable carbohydrates producing acidic end products. In the mouth, these changes over time in response to a challenge (usually a cariogenic food) are known as Stephan responses or Stephan curves.

• Several factor affect this process:• Saliva flow • Intrinsic buffering capacity

• Urea- prevent fall in pH• Urea converted to ammonia by urease• Arginine-deaminase system

• Gorden at al found significantly higer level of urease activity in plaque in caries free subjects compared with caries active.

Carious lesion formation

Under cariogenic

environment

Balance lost b/wRemin/demin

Caries lesion

Development of subsurface

lesion

At higher magnification –enamel eroded

Proceed to dentin

Probably bacteria free

Remineralisation

Subsurface lesion

Consequences

• At some point , that three dimensional structure of a lesion is not able to withstand the stress created by external forces coming from mastication , bruising etc. , and surface collapses , crating an irreversible cavitation.

Conclusion • The caries process can be understood in very simple

terms as being the result of acids generated by dental biofilm from dietary fermentable carbohydrates causing demineralization of tooth mineral and ultimately leading to a caries lesion.

• However , the complex and dynamic environment created by various contributing factors must be taken into account to fully understand the caries disease process.

References :• Shafer ‘Textbook of Oral Pathology’• DCNA October 1999, 2010• Sturdevant ‘Art and Science of Operative Dentistry’• Gordon Nikiforuk ‘ Understanding Dental Caries’• Per Axelsson ‘preventive materials, methods, and programs.’