Oral Pathology

Acidogenic Theory or Chemicoparasitic theory of Dental Caries

Acidogenic Theory or the Chemicoparasitic theory explained by D Miller about the Etiology of Dental caries is the most widely accepted and most useful, which helps you understand the actual cause of Caries.
This theory is a blend of 2 theories explained in the earlier parts of 1800’s –

Chemicoparasitic Theory: Chemical Theory  + Parasitic Theory
Theory: Caries is caused by microorganisms of mouth.

Dental Decay is a chemicoparasitic process consisting of two stages:

  • Decalcification of enamel and dentin(preliminary stage)
  • Dissolution of the softned residue (subsequent stage)

Parasitic Theory says that: Micro organisms either directly or indirectly are the cause of caries
Chemical Theory said that: Unidentified chemical agents called ‘chymal agents’ are the cause of caries

D Miller hypothesis on Dental Caries:
“Dental decay is a chemico-parasitic process consisting of 2 stages, the decalcification of enamel which results in its total destruction and the decalcification of dentin in the preliminary stage, followed by dissolution of the softened residue. And the Decalcification of enamel signifying its total destruction”
The acid which affects this primary decalcificaton, is derived from the fermentation of starches and sugar lodged in the retaining centers of teeth.

Role Of Carbohydrates:
The carcinogenicity of a dietary carbohydrate varies with the frequency of ingestion, physical form and chemical composition, route of administration and presence of other food constituents.
Sticky, solid carbohydrates are more caries producing than those consumed as liquids.
Meals high in fat, protein or salt reduce the oral retentiveness of carbohydrates. Refined, pure carbohydrates are more caries producing than crude carbohydrates complex-ed with the other food elements.

Bacteria + Sugars + Teeth = Organic Acids + Caries

Role Of Microorganisms
Microorganisms dissolve sugars and produce acids which play a major role in producing caries.
Lactobacillus Acidophilus – Surface Caries and related to Initial Caries
Acidogenic Streptococci – Deeper carious lesions and related to more advanced lesions
Steptococcus Mutans – Smooth surface caries, Pit and Fissure caries, play an active role in caries initiation
Actinomyces Viscosus – Root surface caries

Role Of Acids:
The Acids formed mostly is Lactic acid which is formed through enzymatic breakdown of Sugars.
The Acid formation is slower upon application of cooked starch food
In plaque Anaerobic catabolism of Sugars is predominant which results in formation of one molecule of Glucose and 2 molecules of Lactic Acid.
Lactobacilli and Streptococci ferment sugars which produce more than 90% of Lactic acids

Role Of Dental Plaque:
Plaque Is a white, tenacious substance/deposit on tooth surface which contains glycoproteins derived from saliva
Also contains, micro-organisms, desquamated epithelial cells, Ca, Ph, etc
Causes dental caries & periodontal disease
Formed from structure called “acquired pellicle”
3 basic groups of micro-organisms in plaque
S.mutans, S.sangius, S.mitior, S.milleri, S.salivarius
A.viscocuc, A.naeslundi, A.israelli, Rothia dentocariosa
V.parvula, V.alcalescens
According to Stephan who modulated the Stephan’s curve
Graph showing behavior of pH in caries active
& immune ppl, after a 10% glucose rinse
Critical pH – 5.5
Resting pH in caries active ppl – 5.8
In caries immune ppl – 6.5
pH falls below 5.5, tissues’ destroyed
Caries active person – pH falls below 5 & takes long to return to 5.8
In immune persons – pH first falls below 5.5, but immediately returns to 6.5
pH due to acid formation on glucose intake, later pH ? due to diffusion of buffers into acid and acid into saliva
Carbohydrate meals given at regular intervals in caries active persons, pH remains below 5.5, thus, more decalcification occurs

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