chap3 edited

THE ROLE OF CARBOHYDRATES IN

DENTAL CARIES

Definition

It is an irreversible microbial disease of the calcified tissues of the inorganic portion and destruction of the organic substance of the tooth, which often leads to cavitations.

ETIOLOGY OF DENTAL CARIES

The Early Theories:

The legend of the worms

Endogenous theories Chemical theories Parasitic theories

The Recent Theories:

The Acidogenic theory The Proteolytic theory The Proteolysis-

chelation theory Sucrose chelation

theory

Miller’s Chemico-parasitic Theory or Acidogenic Theory (1882)

“Dental decay is a chemico-parasitic process consisting of two stages:

the decalcification of enamel, which results in its total destruction and the decalcification of dentin as a preliminary stage

the second stage is the dissolution of enamel signifying its total destruction.”

Important factors

According to Millers’ there are five important factors which can influence the process of tooth destruction:

1. Dietary carbohydrates 2. Microorganisms3. Acids (Saliva)4. Dental Plaque Bacteria5. Tooth Structure

Role of Dietary carbohydrates

Fermentable dietary carbohydrates play an important role in causation of caries:

1. Glucose2. Fructose3. Sucrose (most potent) etc.These sugars are easily and rapidly fermented by

cariogenic bacteria to produce acids at or near the tooth surface & cause dissolution of hydroxyappetite crystals followed by dentin

Rate of caries attack depends on the form of carbohydrate & the frequency of intake of such carbohydrate

Risk of caries increases if sugar is taken repeatedly in between the two major meals

Risk of caries increases greatly if the dietary sugar is sticky in nature which can remain adhered to the tooth surface for a long time

Fermentable dietary carbohydrate due to their low molecular weight gets rapidly diffused into the plaque & hence are easily available for fermentation

Following the ingestion of these sugars the pH of plaque falls to 4.5-5 within 1-3 mins. & it takes another 10-30 mins. To return to neutrality

The pH alteration can be recorded with the help of graph called “Stephens curve”

Starches produce little or no caries as they are very slowly diffused into the plaque and also require extra cellular amylase to become hydrolyzed before they can be metabolized by plaque bacteria

When sucrose is replaced by sorbitol or xylitol (non fermentable) caries formation is greatly reduced

Role of micro organisms

Streptococcus mutans plays very role to facilitate in caries formation:

1. It can readily ferment dietary carbohydrate to produce acid

2. It can synthesize dextran from sucrose, the later helps in adhering the bacteria as well as acid on to the tooth surface

3. It has ability to adhere & grow even on hard and smooth surfaces of the teeth

Actinomycotic group( A.israelii, A.viscosus, A.nasulandii, etc.) Produce caries in the root portion of the teeth A.viscosus-most active agent to cause root

caries Lactobacillus acidophilus- progression of dentinal caries higher lactobacillus counts in saliva indicates

the presence of more active carious lesions in the oral cavity.

Role of acids

A large variety of acids are produced in the oral cavity during the process of caries formation due to bacterial fermentation of carbohydrates

Eg. Lactic acid, Aspartic acid,

Butyric acid, Acetic acid,

Propionic acid, Glutamic acid

Metabolism of carbohydrate by bacteria produces organic acid which result in highly localized drop in the pH at plaque- tooth interface

A drop in local pH causes demineralization of tooth surface

Below the critical pH (5.5) the tooth minerals act as buffers and loose calcium and phosphate ions into the plaque

When the local pH falls to about 5.0 subsurface demineralization is inevitable in the enamel, which results in formation of incipient caries (where the surface of the enamel remains intact but it is demineralized in the area below the surface the process is called subsurface demineralization)

When the pH is lower further at the level of about 3.0-4.0 the surface of enamel begins to get etched & resorbed

Role of bacterial plaque

The plaque is a thin, transparent film produced on tooth surface consisting predominantly of microorganisms suspended in salivary mucins & extra cellular bacterial polysaccharides

Also presence of desquamated epithelial cells, leukocytes & food debris, etc.

One hour after formation of acquired pellicle (component of dental plaque) various organisms become attached to it, these organisms are called “pioneering organisms” in dental caries

These initial organisms lack in caries producing potential since they are mostly aerobic in nature & produce very little amount of acid

As the plaque matures with time, S.mutuans group becomes more predominant within the plaque & produce organic acids

The dental plaque helps initiation of caries by following ways:

1. It harbors the cariogenic bacteria on the tooth surface

2. It holds the acids on the tooth surface for a long duration

3. It protects the acids produced by the bacteria from getting neutralized

Limitations of acidogenic theory

1. Unable to explain specific areas on the tooth (initiation of smooth surface caries)

2. Phenomenon of arrested caries

3. Cannot explain subsurface demineralization

4. Fails to justify rampant caries

5. Cannot explain caries in impacted tooth

6. Why some population are caries free?

Classification of dental caries

1. Based on location of the lesion Pit and fissure caries Smooth surface caries Root caries

2. Based on the rate of carious progression Acute dental caries Chronic dental caries

Classification (cont.)

3. Based on virginity of the lesion Primary caries Secondary caries

4. Based on chronology Infancy (soother or nursing bottle caries) Adolescent caries

Pit & fissure caries

This type of lesions occurs in the developmental pit & fissure of the teeth

Pit & fissure caries of the primary type develops in the occlusal surface of molars and premolars, in the buccal; and lingual surface of the molars and in the lingual surface of the maxillary incisors

This lesion usually appears brown or black, with little softening and opaqueness of the surface when the lesion is examined by a fine explorer tip, a catch point is often felt

The lesion are smaller in the beginning but become wider as they spread towards the dentin

Smooth surface caries

This type of caries develops on the proximal surfaces of the teeth or on the gingival third of the buccal and lingual surfaces

Proximal caries usually begin just below the contact point, and appears in the early stage as a faint white opacity of the enamel without apparent loss of the continuity of the enamel surface and in some cases yellow or brown pigmented area

As the caries penetrate the enamel, the enamel surrounding the lesion assumes a bluish-white appearance. This is particularly apparent as lateral spread of caries at the DEJ occurs

Root caries

Can be defined as ‘a soft, progressive lesion that is found anywhere on the root surface that has lost connective tissue attachment and is exposed to the oral environment’

It is predominantly found in dentition of older age groups with significant gingival recession and exposed root surface

Root caries initiates on mineralized cementum and dentin surfaces which have greater organic component then enamel tissue

Involvement of pulp occurs within a few days (mostly because of the softer nature of the cementum and dentin)

Enamel may become secondarily involvedClinically these lesions are extensive, shallow

and saucer shaped, with ill defined margins

Rampant dental caries

An acute fulminating type of carious process which is characterized by simultaneous involvement of multiple number of teeth in multiple surfaces

Rapid coronal destruction occurs within a short span of time, causing early involvement of the pulp

The common age of occurrence of rampant caries is about 4-8 years for the deciduous teeth & 11-19 years for the permanent teeth

This type of caries attacks those surfaces of teeth, which are otherwise considered immune to the disease

Nursing bottle caries

Acute caries lesions which occurs among those children which take milk or fruit juices by the nursing bottle for a considerable longer duration of time preferably during sleep

It commonly occurs in the upper anterior teeth (as these are constantly coming in contact with the sweetened milk) while the lower teeth are not usually affected as they remain under the cover of the tongue

It causes early pulp involvement because they spread at a very rapid pace and as a result the pulp hardly gets any time to protect itself

Arrested caries

It is a lesion whose progression is ceased after the initial development

It can occur both in enamel and dentin

Recurrent caries

It refers to a carious lesion that begins around the margins or at the base of a preexisting defective restoration

Radiation caries

Patients receiving large doses of radiation in the head & neck region often develop a specific type of large “caries like lesions” in the cervical of teeth

They often surround the entire crowns of the affected teeth

It may be due to the reduced salivary secretions, secondary to the radiotherapy

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