Lecture 4

Dental Caries

Dental Caries

an infectious bacterial disease that has plagued humans since the beginning of recorded history

What is dental caries?

multifactorial, oral disease is caused primarily by an imbalance of the oral flora (biofilm) due to the presence of fermentable dietary carbohydrates on the tooth surface over time.

Four (4) factors in the causation of dental caries:

• host

• cariogenic film

• fermentable carbohydrates

• time

Host

• tooth

• oral fluids

• genes

Cariogenic film

oral organisms in the biofilm

Fermentable carbohydrates

• Cariogenicity of consumed carbohydrates

• Oral clearance

• Eating frequency

• Food detergency

Time

significant length for the 3 factors to interact

KEYES-JORDAN DIAGRAM

(Tooth-biofilm-carbohydrate-interaction)

Primary Modifying Factors:

• tooth anatomy

• saliva

• biofilm pH

• biofilm composition

• use of flouride

• diet Specifics

• oral Hygiene

• immune system

• genetic factors

Secondary Modifying Factors:

• socio economic factors

• education

• life style

• environment

• age

• ethnic group

• occupation

Localized Demineralization

loss of tooth structure → caries lesion

Bacteria (biofilm)

metabolize refined carbohydrates for energy and produce organic acids as by products.

Dental Plaque

also known as dental biofilm

Bio

means composition

Film

means structure

Biofilm: composition

• bacteria,

• their by products,

• extracellular matrix, &

• water

Critical pH level

enamel = 5.5

dentin = 6.2

below pH 5.5

• tooth mineral is dissolved;

• tooth mineral acts as buffer and loses calcium and phosphate ions into the plaque

pH 3.0 or 4.0

the surface of the enamel is etched or roughened.

pH 5.0

the surface remains intact while the subsurface mineral is lost

Demineralization

low pH drives calcium and phosphate from the tooth to the biofilm resulting in a net loss of minerals by the tooth

Remineralization

pH in the biofilms returns to neutral minerals can then be added back to partially demineralized enamel.

Dental Caries Lesion

results from a dynamic process of demineralization and remineralization

The caries process

formation of white spot lesion:

• acid

• calcium and phosphate

• fluoride, phosphate and calcium

The Caries Balance

caries does not result from a single factor: rather, it is the outcome of the complex interaction of pathologic and protective factors

Pathological factors involved in a carious lesion are:

• bacteria

• poor dietary habits

• xerostomia

Protective factors include

• saliva

• antimicrobial agents (chlorhexidine & xylitol)

• fluoride

• pit and fissure sealants

• effective diet

Etiology of Dental Caries

The etiological agents of dental caries are pathogenic bacterial dental plaque.

Two (2) Basic hypothesis concerning the pathogenicity of plaque:

• non-specific plaque hypothesis

• plaque and caries

Non-specific plaque hypothesis

• all plaques are pathogenic because pathogenic bacteria are universally present in plaque

• treatment of caries is total removal of plaque in all patients

Plaque and caries

• carious lesions started when specific bacteria in plaque are increased & active pH is decreased.

• plaque will become pathogenic when signs of caries develop

Theories of Etiology of Dental Caries

• Acidogenic /Chemicoparasitic theory

• Proteolytic theory

• Proteolysis-Chelation theory

Acidogenic /Chemicoparasitic theory

• most accepted theory given by Miller in 1890.

• Theory: Caries is caused by acids produced by microorganisms of the mouth.

Chemico-parasitic process consisting of two (2) stages:

• Preliminary Stage- decalcification of enamel & dentin

• Subsequent Stage- dissolution of the softened residue.

Acids

• lactic acid

• butyric acid

Proteolytic Theory

organic or portion elements of a tooth are the initial pathway of invasion by microorganisms

Chelation

process in which there is complexing of the metal ions to form complex substance through coordinate covalent bond which results in poorly dissociated/or weakly ionized compound.

Stephen Curve

relationship between change in plaque pH over a period of time following a glucose rinse in form a graph.

Acidogenic Nature

this means bacteria should be able to transport sugars and convert them to acid.

Aciduric Nature

bacteria should be able to thrive at low pH.

Clinical sites of Caries Initiation

• pits and fissures

• smooth enamel surface

• root surface

Pits and Fissures

found mainly on the occlusal surfaces in the teeth as well as in lingual pits of the maxillary incisors.

Wall lesions

caries lesions of pits and fissures develop from demineralization on their walls

White spot

usually found on the facial and lingual surfaces of the teeth.

Zone in enamel caries

• translucent zone

• dark zone

• body of the lesion

• surface zone

Secondary caries

occurs at the junction of a restoration and the tooth and may progress under restoration.

Rate (speed) of Caries

• acute

• chronic

• rampant

NON CARIOUS TOOTH DEFECTS TERMINOLOGY

• abrasion

• erosion

• attrition

• abfraction

Abrasion

abnormal tooth surface loss resulting from direct friction forces between the teeth and external objects or from frictional forces between contacting teeth components in the presence of abrasive medium.

Erosion

progressively loss of dentin tissue by chemical means not involving bacterial actions;

Attrition

mechanical wear of the incisal or occlusal surface as a result of FUNCTIONAL or PARAFUNCTIONAL MOVEMENTS of the mandible.

Abfraction

microfractures occur as the cervical of the tooth flexes under loads.