dental caries

DENTAL CARIES

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Contents

Introduction Etiology of dental caries Histopathology of dental caries Diagnosis of dental caries References

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Introduction

Dental caries continues to be a major problem in dentistry and should receive significant attention in everyday practice, not only from the standpoint of restorative procedures but also in terms of preventive measures designed to reduce the problem.

Caries is on the decline in the industrial countries but it is on the increase in the developing countries due to increased sugar consumption.

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Dental caries is an irreversible microbial disease of the calcified tissues of the teeth, characterized by demineralisation of the inorganic portion and destruction of organic substance of the tooth , which often leads to cavitation.

It is essential to understand that cavitation in teeth are signs of bacterial infection.

It has effected humans since prehistoric times, but the prevalence of this disease has increased greatly in modern times due to dietary changes.

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Dental caries

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Tooth is covered by plaque, which consists mainly of bacteria. Plaque is often found close to the gum, in between teeth, in fissures and at other "hidden" sites.

Demineralization:When sugar and other fermentable carbohydrates reaches the bacteria, they form acids which start to dissolve the enamel - an early caries lesion occurs due to loss of Calcium and Phosphates

Remineralization:When sugar consumption has ceased, saliva can wash away sugars and buffer the acids. Calcium and Phosphates can again enter the tooth. The process is strongly facilitated by fluorides

A CAVITY occurs if the Demineralization "wins" over the Remineralization over time

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1. A tooth surface without caries.2. The first signs of demineralization.3. The enamel surface has broken down.4. A filling has been made but the demineralization has not been stopped.5. The demineralization proceeds and undermines the tooth.6. The tooth has fractured.

Progression of dental caries

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Acc. to WHO it is defined as a localized post eruptive pathological process of external origin involving softening of the hard tooth tissue and proceedings to the formation of a cavity.

It can also be defined as localized chemical dissolution of the tooth surface caused by metabolic events taking place in the biofilm (dental plaque) covering the affected area.

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It may develop at any tooth site where biofilm develops and remains for a period of time.

Biofilm is a prerequisite for caries lesion to occur. Biofilm is characterized by continued microbial activity resulting in continued metabolic events in the form of minute pH fluctuation.

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EPIDEMIOLOGY

Dental caries may be considered a disease of modern civilization , since prehistoric man rarely suffered from this form of tooth destruction . Anthropologic studies of VON LENHOSSEK revealed that the Dolicocephalic skulls of men from pre Neolithic periods (12000 BC) did not exhibit dental caries but skulls from Bracycephalic man of the Neolithic periods (12000 to 3000 BC) contained carious teeth. The cervical areas of teeth in older persons were frequently affected .

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CARIES SUSCEPTIBILITY OF INDIVIDUAL TEETH

BREKHUS (1931 ) studied a group of students at the university of Minnesota and reported the following caries susceptibility incidence of the teeth

Upper and lower first molar : 95 % Upper and lower second molars : 75 % Upper second bicuspids : 45% Upper first bicuspid :35% Lower second bicuspids : 35% Upper central and lateral incisor : 30 % Upper cuspids and lower first bicuspids : 10% Lower central and lateral incisors : 3 % Lower cuspids : 3%

ETIOLOGY OF DENTAL CARIES

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Etiology

Development of dental caries depends on :

1. Microflora: acidogenic bacteria that colonize the tooth surface.

2. Host :quantity and quality of saliva , quality of the tooth.

3. Diet : intake of fermentable carbohydrates, especially sucrose ,but also starch.

4. Time : total exposure time to acids produced by the bacteria of the dental plaque.

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Caries Tetralogy[Newbrun 1982]

Includes a fourth factor, time to the still existing concept of Keyes, depicting the significance of changes taking place over a period.

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Classification of dental caries ACCORDING TO MORPHOLOGY-Pit and fissure caries-Smooth surface caries ACCORDING TO CHRONICITY-Acute dental caries-Chronic dental caries ACCORDING TO PROGRESSION -Primary caries-Secondary (Recurrent )caries-Arrested caries

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ACCORDING TO SEVERITY AND PROGRESSION

-rampant caries-nursing caries-radiation caries ACCORDING TO PART OF TOOTH STRUCTURE

INVOLVED-Enamel caries-Dentinal caries-Cemental caries

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PIT AND FISSURE CARIES Pit and fissure with high steep walls and

narrow bases are prone to develop caries.

Retention of food debris and microorganisms.

Early caries appear brown or black, soft ‘catch’ of a fine explorer point.

Lateral spread of caries through a narrow opening at the DEJ.

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SMOOTH SURFACE CARIES Early appears as a faint white opacity of the

enamel without loss of the continuity of the surface.

Preceded by the formation of a microbial or dental plaque.

As caries penetrates enamel,it assumes bluish white appearance.

Proximal caries begins just below contact point. The typical cervical carious lesion is crescent

shaped cavity with chalky area.

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ACUTE DENTAL CARIES Rapid clinical course resulting in early

pulp involvement with pain. Progress rapidly so less time for

secondary dentin depositionis present E.g.Nursing bottle caries commonly

affects 4 deciduous maxillary incisors. It is a type of RAMPANT caries which primarily affects all deciduous incisors.

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CHRONIC DENTAL CARIES Progresses slowly and tends to involve

pulp much later. Sufficient time for sclerosis of dentinal

tubules and secondary dentin deposition.

Carious dentin stains deep brown. PAIN is not a common feature.

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RECURRENT CARIES Caries occuring in immediate vicinity of

a restoration. Usually due to inadequate extension of

the original restoration favoring retention of debris.

Poor adaptation of filling material to the cavity which produces a leaky margin.

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ARRESTED CARIES Static or stationary caries which do not

show any tendency for further progression. Occurs exclusively in caries of occlusal

surfaces characterised by a large open cavity which lack food retention.

EBURNATION OF DENTIN : gradual burnishing of superficial softened and decalcified dentin until it takes on a hard brown stained, polished appearance.

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RAMPANT CARIES It occurs as a sudden , rapid and almost

uncontrollable destruction of teeth , involving surfaces of teeth that are ordinarily caries free(proximal and cervical surfaces of anterior teeth including the mandibular incisors get affected)

A caries increment of 10 or more new lesions over a period of about a year is characteristic of rampant caries attack

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NURSING CARIES It is a specific form of rampant decay of

primary teeth of infants and toddlers. Affects maxillary primary incisors due to

prolonged nursing habit esp. when the child is sleeping

Also named as baby bottle tooth decay or early childhood caries

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RADIATION CARIES Common complication of radiotherapy of

oral cancer lesions and radiation induced xerostomia

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Hypothesis concerning the etiology of caries

Two hypothesis: Older one : promotes the universal

presence of potential pathogens in plaque and assumes that all accumulation of plaque are pathogenic.

Latter one promotes that accumulation of plaque could be regarded as normal in the absence of disease.

Plaque is assumed pathogenic only when signs of disease are present.

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The difference between two hypothesis was identified and discussed by Loesche:

First one : non specific plaque hypothesis Second one: specific plaque hypothesis Problem with non-specific hypothesis was

that it requires a therapeutic goal that completely eliminates plaque in all patients that requires a continuous therapy directed to total plaque elimination.

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Acc . to specific theory ,plaque can be identified as pathologic only when they are associated with clinical disease. So treatment can be aimed at elimination of the specific pathogenic organisms.

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Caries- latin word –rot or decay. Its etiology is agreed to be a complex

problem complicated by many indirect factors that obscure the direct causes.

Many theories have evolved through years of investigation and observation attempting to explain its etiology.

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The early theories

1. The legend of worms : the earliest reference is from the ancient sumerians known as legend of worms. This dates back around 5000 BC . The idea behind this was that caries was caused by worms and worms are the cause of toothache.

2. Endogenous theory: it was advocated by Greek physicians, who proposed that dental caries is produced by internal action of acids and corroding humors.They also proposed the Vital theory of tooth decay,which postulated that tooth decay originated from within the tooth itself.

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3. Chemical theory:Parmly in 1820 observed that dental decay affected externally and not internally. He proposed that unidentified chemical agent was responsible for caries.

4. Parasitic theory:Erdl in 1843 was first to relate microorganisms to caries as a positive agent. Ficnus in 1847 attributed dental caries to denticolae(decay related to microorganisms). But this was soon disseminated as it was proposed that dental caries commenced as a purely chemical process and bacteria were essential for caries as an exogenous source of the acids.

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Miller’s chemico-parasitic theory ORAcidogenic theory

Proposed by Willoughby D Miller in1882. He stated that caries is caused by acids

produced by microorganisms of the mouth. “Dental decay is a chemico-parasitic

process consisting of two stages , the de-calcification of enamel , which results in its total destruction and the de-calcification of dentin as a preliminary stage,followed by dissolution of the softened residue”

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The acid that affects the de-calcification is derived from the fermentation of starches and sugars lodged in the retaining centres of the teeth.

He isolated numerous microorganisms, some were acidogenic and others were proteolytic.

A no. of these bacteria were capable of producing lactic acid.

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He proposed that caries was not caused by any single organism but a variety of microorganisms.

Essential factors in caries process:1. Microorganisms2. Carbohydrate substrate3. Acid production

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This theory is the backbone of current knowledge and understanding of the etiology of dental caries.

Drawbacks : theory was unable to explain the predilection of specific sites on a tooth to caries and the initiation of smooth surfaces was not accounted by this theory.

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The proteolytic theory

The previous theory was not wholly accepted. Then this theory came into existence.

Proposed by Gottlieb and Gottlieb(1944). This theory proposed that the organic

material(enamel lamellae and rod sheaths) or protein elements are the initial pathway of invasion by microorganisms.

They also admit that acid formation accompanied the proteolysis.

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Pincus(1949) proposed that enamel proteins are mucoproteins, yielding sulphuric acid upon hydrolysis.

In support of this theory Gram negative bacilli capable of producing sulfatase were also isolated.

This acid dissolves the enamel, combining with the calcium to form calcium sulphate.

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Drawbacks : no sulfatase has been demonstrated at the site of carious lesion.

No such enzyme has also been demonstrated in the oral cavity.

The proteolysis of organic matrix of dentin may indeed occur after demineralization and there is no satisfactory evidence to support the claim that the initial attack on enamel is proteolytic.

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The proteolysis-chelation theory Proposed by Schatz et al (1955). Proposed a simultaneous microbial

degradation of the organic components (proteolysis) and the dissolution of minerals of the tooth by the process known as chelation.

Chelation is a process involving the complexing of a metallic ion to a complex substance through a coordinate covalent bond(highly stable , poorly dissociated).

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This theory considered caries to be a bacterial destruction of teeth where the initial attack is essentially on the organic components of the enamel. this breakdown product has chelating property hence dissolves the minerals in enamel (at a neutral or alkaline ph).

Thus this theory suggested that demineralization of enamel could arise without acid formation.

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Drawback : it was concluded that saliva and plaque do not contain substances in sufficient amount to chelate calcium in detectable amounts from enamel.

Also chelation is unlikely to be involved in the initiation of the lesion, it may play a minor role in the established lesion.

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Sucrose chelation theory

Proposed by Egglers-Lura (1967). He proposed that sucrose itself and not

the acid derived from it cause dissolution of enamel by forming an ionized calcium saccharates.

This theory stated that calcium saccharates and calcium complexing intermediaries require inorganic phosphate which is subsequentaly removed from the enamel by phosphorylating enzymes.

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Drawback : since saliva is an abundant source of inorganic phosphates for bacterial utilization, it is highly improbable that depletion of phosphate in plaque by oral microbial metabolism results in phosphate withdrawl from enamel.

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Role of plaque in dental caries

Dental plaque is soft, translucent and tenaciously adherent material accumulating on the surface of teeth and not readily removed by rinsing with water .

It is composed of bacteria and their by-products.

Accumulation of plaque on teeth is highly organized and ordered sequence of events

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It is estimated that 1mm³ of plaque weighing about 1mg contains more than 200 million bacteria.

A few specialized organisms (streptococci ) are able to adhere to oral surfaces like mucosa and tooth surface.

These bacteria produce a sticky matrix that allows them to coadhere to each other .

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Plaque growth

The initial bacteria are called pioneer bacteria or colonizers. (mainly streptococcal strains).

These bacteria proliferate and spread laterally to form a mat-like covering over the tooth surfaces.

When the entire surface is covered ,growth of colonies increases the thickness of plaque . Further growth of bacteria produces a vertical growth away from the tooth surface forming vertical columns called palisades .

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These bacteria allow the adherence of other organisms like filamentous bacteria,which are unable to adhere directly to the tooth surface. Proliferation of new invading bacteria produce entangled masses of filaments forming “corncob” like structure.

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Early stages of plaque succession

After professional removal of all organic material and bacteria from the tooth surface , a new coating of organic material begins to accumulate immediately.

Within 2 hrs, a cell free , structureless organic film, the pellicle, covers the tooth surface.

Some of the proteins of pellicle are biologically active and have a significant impact on microorganisms attemptimg to colonize the tooth surface.

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The early stages of recolonization of the cleaned tooth surface involves adhesion between the pellicle and the pioneering bacteria.

S. sangius , A. viscosus and peptostreptococcus are the main pioneering species capable of attaching to the pellicle within 1 hr after tooth cleaning.

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The adhesion process is selective and requires specific organism receptor capable of binding to certain areas on the precipitated salivary proteins of the pellicle.

The enzyme glucosyltransferase may be crucial in the adherence of organisms to the pellicle when sucrose is present as it enhances the polymerization of the extracellular matrix that helps in the formation of tenaciously adherent colonies.

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Late stages

Late stages are mainly responsible for causing caries.

In early stages there are primarily aerobic communities lacking pathogenic potential.

As the plaque matures,more and more acid is produced from metabolism mainly lactic acid.

This increased production of acid leads to prolonged drop in pH , increasing the potential for enamel demineraliztaion.

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Tooth habitat for pathogenic plaque

The tooth surface is stable and covered with the pellicle and thus the ideal site for the attachment of many oral streptococci.

If left undisturbed , plaque builds rapidly to sufficient depth to produce anaerobic environment.

Some favorable tooth habitats for plaque are:

Pit and fissures

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Smooth enamel surface immediately gingival to the contact area and in the gingival 1/3 of facial and lingual surface.

Root surface near the cervical line. Subgingival areas.

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Pits and fissures

Highest prevalence of all dental caries. Provide excellent shelter for organisms. The relative proportion of organisms

most probably determine the cariogenic potential of the pits and fissures.

The appearance of microorganisms in pits and fissures is followed by caries 6-24 months later.

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Sealing the pits and fissures just after tooth eruption may be the most important event in their resistance to caries.

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Smooth enamel surfaces

The proximal enamel surfaces gingival to the contact area are the 2nd most susceptible area to caries.

In very young patient,gingival papilla fills completely the interproximal spaces under the proximal contact.

So proximal caries are less likely to develop where the favorable soft tissue architecture exists.

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Conversely, apical migration of papilla creates more habitats for surface colonizing bacteria.

The gingival aspect of the facial and lingual smooth enamel surface is not rubbed by the bolus of food and not properly cleaned by the brush.

These surface areas are habitats for the caries- producing mature plaque.

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Root surface

The proximal root surface , often is unaffected by the action of oral hygiene procedures, because of its concave anatomic surface.

This favors the formation of mature, caries producing plaque and thus root caries lesion.

Also, the facial and lingual root surface when exposed to the oral environment harbors caries producing plaque.

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Role of microorganisms

To initiate carious lesion in enamel , the organisms must also be able to colonize the tooth surface.

The most important bacteria responsible for carious lesion are- Strepococcus mutans.

The second bacteria closely related to caries is Lactobacillus.

It was proposed that one or more organisms are implicated in the initiation of caries

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While others distinctly different organisms may influence the progression of disease.

Cariogenic bacteria: S . mutans S. salivarius S. mitior S.oralis S.milleri

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S. sangius Peptostreptococcus intermedius Lactobacillus acidophillus L . casei A. viscosus A. neaslundii

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Localization of bacteria related to caries

Type of caries

1. Pit and fissure

2. Smooth surface

organisms

S. mutans (very significant)

Lactobacillus (very significant)

S . Sangius (uncertain) Actinomyces (by chance) S. mutans (very

significant) S. salivarius (by chance)

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3. Root surface

4. Deep dentinal caries

A. viscosus (very significant)

A. naeslundii (very significant)

S. mutans (significant) Lactobacilli sp. (very

significant) A. naeslundii (very

significant)

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Role of acids

Carbohydrate degradation occurs through enzymatic breakdown and the acid formed are chiefly lactic acid although others such butyric acid are also formed.

The mere presence of acid in the oral cavity is of far less significance than the localization of acids upon the tooth surface.

Generally , monosaccharides and disaccarides result in the greatest fall in plaque pH.

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Anaerobic catabolism of carbohydrates called fermentation predominates in plaque. After breakdown one molecule of glucose breaks down into two molecules of lactic acid.

Bacteria : Homofermenters (streptococci,

lactobacilli) Heterofermenters

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Organisms which produce 90 % or more lactic acid as the end product are called homo-fermentative.

Organisms which produce a mixture of metabolites including other organic acids such as propionic , Butyric acid, Ethanol etc are called hetero-fermentative.

The proportion of lactic acid and other organic acid formed by plaque may be markedly affected by growth conditions and the type of bacteria present.

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Caries is a multifactorial disease in which there is interplay of four primary factors :

Host Microbial flora Substrate Time Thus, caries require a susceptible host, a

cariogenic flora, and a suitable substrate that must be present for a sufficent time.

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Factors

A. Tooth

B. Saliva

Components

Composition Morphologic

characteristics Position

Composition pH Quantity Viscosity Antibacterial factors

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C. Diet

D. Systemic conditions

Physical factors (quality of diet)

Local factors (carbohydrate content, Vitamin content,Fluoride content)

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Tooth factors

Composition of teeth : the composition of teeth undoubtedly influence the initiation and the rate of progression of a carious lesion .

Composition of enamel : enamel is the hardest calcified tissue in the body, because of its high content of mineral salts and their crystalline arrangement.

Enamel: inorganic=96%, organic=4%.

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Enamel attains a maximum thickness of 2.5mm on the cusps of the molars, thinning down to almost a knife edge at the neck of the tooth.

Acc. to Brudevold et al surface enamel is more resistant to caries than subsurface enamel.

Surface enamel is more highly mineralized .

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Tends to accumulate greater quantities of fluoride, zinc , lead, iron etc than subsurface enamel.

Also initial carious lesions indicate that marked decalcification is observed in subsurface enamel while the outer surface is relatively intact.

The surface dissolves at a slower rate in acids, Contains less water and has more organic material than subsurface enamel.

These factors apparently contribute to caries resistance and are partly responsible for slower degradation of surface enamel than the underlying enamel in initial carious lesion

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Composition of dentin: dentin forms the bulk and general form of the tooth.

Dentin : inorganic=65% organic=35% The dentinal tubules form a passage for

invading bacteria , resulting in rapid penetration and spread of caries to the pulp.

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Composition of cementum: cementum is the mineralized dental tissue, covering the anatomic roots of human teeth.

Cementum : inorganic=45-50% organic=50-55% Cementum has the highest fluoride

content of all the mineralised tissues.

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Physical characteristics

Tooth size:it has been assumed that low caries may have smaller teeth and the larger teeth were found more caries susceptible and are found in the oral cavity for a shorter time period .

the effect of tooth size would be negligible in comparison with the combined effects of other factors.

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Morphologic characteristics

The morphologic characteristics of tooth have been suggested as influencing the initiation of dental caries.

Caries susceptibility in the permanent dentition may be ranked in the following order :

1. Fissures of molars2. Mesial and distal surface of first molars.3. Mesial surface of 2nd molars and Distal

surface of 2nd premolars.

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4. Mesial and distal surfaces of the maxillary first premolars.

5. Distal surfaces of the canines and mesial surface of md. 1st premolar

6. Proximal surface of max. incisors.

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Fissures : the only morphologic feature which conceivably might predispose to the development of caries is the presence of deep, narrow, occlusal fissures or buccal or lingual pits.

Such fissures tend to trap food, bacteria and debris, so caries may develop rapidly in these areas.

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But as the attrition advances, the inclined planes become flattened , providing less opportunity for entrapment of food in the fissures, and the predisposition towards the caries diminishes.

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Surfaces: certain surfaces of teeth are more prone to decay , whereas other surfaces rarely show decay.

md. 1st molar: occlusal > buccal > mesial > distal >lingual.

Max. 1st molar: occlusal >mesial>lingual> buccal>distal.

Max. LI: lingual surfaces are more susceptible.

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All available evidences indicate that alteration of the tooth structure by disturbances in formation or in the calcification is of only secondary importance in dental caries. The rate of caries progression may be influenced , but caries initiation is affected only to a very little extent.

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Morphology of CEJ

An exposed CEJ is a potential area of plaque retention . So root caries tend to develop along the CEJ.

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Exposure of root surfaces

In the young , healthy adult, root surfaces like the CEJ are not exposed to the oral cavity.

Prevalence of exposed root surfaces is age-related or from gingival recession associated with periodontal disease.

Morphologically, the surface of intact cementum and the CEJ are very rough , compared to the enamel surface. And the rough surface is highly retentive to plaque .

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Position of tooth

Teeth which are malaligned, out of position , rotated or otherwise not normally situated may be difficult to cleanse and tend to favor the accumulation of food and debris.

This in susceptible persons would be sufficient to cause caries in a tooth .

The position seems to be a minor factor in the etiology of caries.

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Saliva and dental caries

Introduction :saliva is the primary means by which the pt. exerts control over its oral flora.

Who made the 1st observation of the influence of saliva on caries is hidden in the mists of time, but around 1900 there were several case reports on the deleterious effects of absence of saliva.

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Functions of saliva

Saliva has manifold functions in protecting the integrity of the oral cavity from food residue , debris and bacteria :

1. Saliva has some buffering effect against strong acids and bases.

2. Saliva provides the ions needed to remineralize the teeth.

3. Saliva has antibacterial, antifungal and antiviral capacities.

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The principal properties of saliva that protects the teeth against caries are:

1. Dilution and clearance of dietary sugars.

2. Neutralization and buffering of the acids in plaque.

3. Supply of ions for remineralization.4. Both endogenous and exogenous

antiplaque and antimicrobial factors.

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An important function of saliva is dilute and eliminate substances. This is a physiological process referred to as salivary clearance or oral clearance.

After an intake of sugar, the salivary glands will be stimulated by the taste or chewing to increase the flow rates, resulting in swallow, which eliminate some of the sugar from the oral cavity which inturn helps in caries prevention

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pH of saliva: The pH at which saliva ceases to be

saturated with calcium and phosphate is referred to as critical pH .

Critical pH= 5.5 The main determinants of critical pH are

the total calcium and phosphate conc. in saliva.

This value was determined by Schmidt-Neilsen, 1946.

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At this pH no demineralization or remineralization will take place.

Below this pH, demineralization occurs as phosphate ion of apatite crystals get converted to hydrogen phophates by increased hydrogen ion.

Thus, solubility of tooth depends on the pH of surrounding medium.

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In the pH range of 2-6 the solubility increases by a factor of 10 for each pH drop of one unit.

Stephan curve: he stated that inspite of saliva buffer capacity the plaque pH will drop immediately after the sugar intake to values below critical pH, whereafter it slowly returns to normal.

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Under resting conditions,pH of plaque is reasonably constant,6.9-7.2

Following exposure to sugars the pH drops very rapidly(in few minutes) to lowest level(5.5 to 5.2-critical pH) and at this pH,the tooth surface is at risk

During this critical period,the tooth mineral dissolves. Repeated fall of pH over a period of time leads o more and more mineral loss from the tooth surface,resulting in initiation of dental caries

Later slowly it returns to original value over a period of 30-60 minutes,approximately

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Quantity of saliva: In patients with reduced quantity of

saliva(salivary gland aplasia or xerostomia) , the cleaning properties of saliva in the mouth are impaired.

Which leads to low oral sugar clearance, which increases caries risk.

the unstimulated flow rates has been found to be diagnostically more important than the stimulated one.

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Individuals with unstimulated flow rates <0.2 ml/min have an elevated demineralization rate and a high risk of developing caries.

This low flow rates also favors acidic environment, with an increase in cariogenic microflora.

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Thus, a low saliva flow rate not only will prolong clearance time and periods with low plaque pH, but may also change the ecology of mouth.

In such cases the rate of progression of caries is also faster as compared to cases with normal flow rates.

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Viscosity : Occasional workers have reported that a

high caries incidence is associated with thick mucinous saliva.

The viscosity of saliva is due largely to the mucin content derived from submaxillary, sublingualand accessory glands.

The significance of this factor is not clear.

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Role of diet

The role of diet and nutrition factor deserves special consideration because of the often observed differences in caries incidence of various population who subsist on dissimiliar diets.

A diet rich in fermentable carbohydrate is indisputably a very powerful risk factor for caries.

Following consumption , depending on the quality of salivary gland function , a certain amount of saliva is stimulated by particular characteristic of food, such as taste, intensity of mastication.

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Fermentable carbohydrates

1.Monosaccharides Glucose Fructose2. Disaccharides Sucrose Maltose Lactose

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3. Polysaccharides Glucan Fructan Mutan Starch

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Sucrose is regarded as the most important in dental caries.

Sucrose is refined from sugar cane or beet and is the most common dietary sugar .

The dietary sugar all diffuse rapidly into the plaque and are fermented to lactic acid or can be stored as intracellular polysaccharides by the bacteria.

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This mechanism prolongs the fall in pH and promotes a suitable environment for acidogenic bacteria.

Sucrose is unique as it is the substrate for production of extracellular polysaccharide (fructans and glucan) and insoluble matrix polysaccharide (mutans).

Thus , sucrose favors colonization by oral microorganisms and increase the stickiness of plaque, allowing it to adhere in larger quantities to the teeth.

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Because of this effect on the quality of plaque , sucrose is considered to be somewhat more cariogenic than other sugars.

Also other dietary disaccharides and monosaccharides are regarded as risk factors.

All are rapidly fermented on plaque-covered tooth surfaces.

Glucose, fructose, maltose give identical fall in pH but for lactose fall in pH is smaller.

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In frequently consumed snack food such as sweets and drinks less fermentable and non-cariogenic sweeteners are increasingly being used as substitute for potentially cariogenic sugars.

These are : caloric or non-caloric sweeteners. Caloric: sorbitol, xylitol, mannitol Non-caloric : saccharin, cyclamate, aspartame They cannot be fermented by acidogenic

bacteria.

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Physical properties of food and cariogenicity: The Physical properties of food may be significant by

affecting food retention, food clearance, solubility and oral hygiene.

Physical properties of food may improve the cleansing action and reduce retention of food with in the oral cavity and increase saliva flow

Physical nature of Diet: Roughage food cleans the teeth from adherent debris

during mastication. Soft refined food tends to adhere to the teeth and are not

removed because of general lack of roughage. Mechanical cleansing by detergent foods may have some

role in caries control.

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Carbohydrate content of diet Most important factor in dental cariesVitamin content of Diet Vitamin A: Definite effect on developing teeth in

animals. No effect on humans. Vitamin D: Children suffering from Vit. D deficiency may

exhibit slightly higher degree of caries experience. Vitamin K: It may act as a anticaries agent by virtue of its

enzyme inhibiting activity in carbohydrate degradation cycle.

Vitamin B complex: Vit. B6 acts as an anticaries agent by selectively altering the oral flora by promoting the growth of non cariogenic organisms which suppress the non cariogenic forms.

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Calcium and phosphorus dietary intake : Disturbance in calcium and phosphorus metabolism during the period of tooth formation may result in severe enamel hypoplasia and defects of the dentin.

Fluorine content of diet: Dietary fluoride is relatively unimportant compared to fluoride in drinking water because of its metabolic unavailability.

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Dietary studies

Vipeholm study: (Gustafsson et al -1954):

This study was conducted in a mental institution for 5 yrs in Vipeholm hospital.

The institutional diet provided was nutritious , with little sugar, and no provision for between meal snacks.

The dental caries rate experienced was relatively low.

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7 groups:1. Control group2. Sucrose group(300gm sucrose)3. Bread group (345gm bread-50gm of sugar)4. Chocolate group(65gm – daily-for last 2yrs)5. Caramel group((22caramel-70gm sugar)6. 8-toffee group (60gm sugar- for 3 yrs)7. 24- toffee group(120 gm sugar-18 months)

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Conclusions

Increased caries risk- 1. Increase in sugar content.2. if sugar consumed in a form that will be

retained on tooth.3. If sugar is consumed in between meals.4. It varies widely in between individuals.5. Upon withdrawl of the sugar rich foods, the

increased caries activity rapidly disappears.6. Clearance time of the sugar correlates

closely with caries activity.

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This study showed that the physical form of carbohydrates is much more imporatnt in cariogenicity than the total amount of sugar ingested.

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Hopewood house study (Sullivan- 1958):

The dental status of children between 3-14 yrs of age at Hopewood house was studied for 10yrs.

All lived on a strictly institutional diet. The absence of meat and a rigid

restriction of refined carbohydrate were the two principal features.

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The meals were supplemented by vitamin concentrates and an occasional serving of nuts and a sweetening agent such as honey.

DMFT /child after 10 yrs -1.6 53% of the children were caries free. Conclusion: the children’s oral hygiene

was poor, calculus uncommon but gingivitis in 75% of children.

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This showed that dental caries can be reduced by diet control even in the presence of unfavourable oral hygiene.

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Turku sugar study (Scheinin, Makinen -1975):

This study was done to test the effects of chronic consumption of sucrose, fructose and xylitol on dental caries.

3 groups:1. Sucrose group-35 people2. Fructose group-38 people3. Xylitol group-52 people

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A dramatic reduction in the incidence of dental caries was found after 2 yrs of xylitol consumption.

Fructose was cariogenic as sucrose for the first 12 months but became less so at the end of 24 months.

It was also found that frequent between meal chewing of a xylitol gum produced an anticariogenic effect.

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Hereditary fructose intolerance (Froesch 1959): It is caused by the remarkably reduced levels of

hepatic, fructose -1-phosphate aldolase into two or three carbon fragments to be further metabolized.

Persons affected with this rare metabolic disorder have learned to avoid any food that contains fructose or sucrose, Because the ingestion of these foods causes symptoms of nausea, vomiting, malaise, tremor , excessive sweating , and even coma due to fructosemia.

Newburn 1969, found that caries prevalence was extremely low in persons with HFI.

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Systemic factors

Heredity :it has been linked with the dental caries incidence in scientific literature for many years.

In 1899, acc to GV Black when the family remains in one locality , the children living under the conditions similar to those of parents in their childhood , the susceptibility to caries will be very similar in the great majority of cases.

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But there is still no such evidence that heredity has a definite relation to dental caries incidence.the possibility exists that if there is such relation, it may be mediated through inheritance of tooth form structure, which predisposes to caries immunity or susceptibility.

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Pregnancy and lactation: it is a common clinical observation that a woman during the later stages of pregnancy or shortly after birth of the child will manifest a significant increase in caries activity.

In nearly all cases it is revealed that the woman has neglected her oral care.

So caries incidence is actually a local problem.

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Intake of medicine containing sucrose – fiber supplements for constipation, cough mixtures and antibiotics may affect caries risk

Psychiatric patients: carbohydrates favor uptake of tryptophan to the brain and serotonin production is enhanced. Thus its intake may induce relaxation.

Also psychiatric drugs impair salivary gland functioning.

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Occupation: in which frequent food sampling is required, may be associated with increased caries risk.Eg.Confectionary industry, bakery workers.

Socio-economic status: higher caries prevalence in children with low socio-economic background.

This is due to lesser parental knowledge , their lesser involvement in oral hygiene and lesser involvement in topical and supplementary F regimes.

HISTOPATHOLOGY OF DENTAL CARIES

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Caries of enamel

Smooth surface caries: The earliest manifestation of incipient enamel caries is the appearance of an area of decalcification, beneath the dental plaque, which resembles a smooth, chalky white area. There is loss of interprismatic substance, with increased prominence and roughening of the ends of the enamel rods.

It forms a cone shaped lesion with the Apex towards the DEJ and the base towards the surface of tooth. There is loss of continuity of the enamel surface and the surface feels rough to the point of an explorer.

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Pit and fissure caries: Pit and fissures are often of such depth that

food stagnation with bacterial decomposition in the base to be expected. The enamel in the bottom of the Pit or fissure may be very thin, so that early involvement frequently occurs.

When caries occurs it follows the direction of enamel rods and forms a cone shaped lesion with its apex at the outer surface and its base towards the DEJ. Because of its shape it tends to produce more undermining of enamel.

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Enamel Caries : Zone 1-translucent Zone Zone 2- Dark Zone Zone 3- Body Of The Lesion Zone 4- Surface Zone

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Four zones are clearly distinguishable.Zone 1: The translucent Zone: Advancing front of the enamel lesion. It is not always present.Zone 2: Dark Zone: It is referred to as the positive zone, because it is always present. It is formed as a result of demineralization.Zone 3: Body of the Lesion: It is the area of greatest demineralization.Zone 4: Surface Zone: Appears relatively unaffected.

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Caries of dentin

It begins with the natural spread of the process along the DEJ and the rapid involvement of great numbers of dentinal tubules. The initial penetration of the dentin by caries may result in dentinal sclerosis resulting in calcification of dentinal tubules, that tends to seal them off against further penetration by microorganisms. It most commonly occurs in older adults.

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The destruction of dentin through a process of decalcification followed by proteolysis, forming necrotic mass of dentin of a leathery consistency.

As the carious lesion progresses,

various zones of carious dentin may be distinguished which tends to assume a triangular shape with the apex towards the pulp and the base towards the enamel.

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Dentin caries: Zone 1: Zone of fatty degeneration

of Tomes fibres Zone 2: Zone of Dentinal sclerosis Zone 3: Zone of decalcification of

dentin Zone 4: Zone of bacterial invasion Zone 5: Zone of decomposed dentin

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Following zones are seen:Zone 1: Zone of fatty degeneration of Tomes fibres.Zone 2: Zone of Dentinal sclerosis- characterized by deposition of calcium salts in dentinal tubules.Zone 3: Zone of decalcification of dentin – a narrow zone, preceding bacterial invasion.Zone 4: Zone of bacterial invasion of decalcified but intact dentin.Zone 5: Zone of decomposed dentin.

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Caries of cementum (Root caries)

Dental plaque and microbial invasion are an essential part of the cause and progression of this lesion.

Microorganisms involved in root caries are filamentous rather than coccal. Microorganisms invade the cementum either along sharpey’s fibers or between bundles of fibers.

Lesion spreads laterally between the various layers. As carious process continues there is invasion of

microorganisms in to dentinal tubules, subsequent matrix destruction and finally pulp involvement.

DIAGNOSIS OF DENTAL CARIES

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Clinical inspection of the teeth at the chairside does not allow the dentist to observe the caries process itself. What dentists can do is to examine the consequences of microbial metabolic activity when looking for signs of lesions that have formed as a result of it. This is what caries diagnosis is about: detection of signs and symptoms of caries

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Diagnosis is defined as the “art or act of identifying a disease from its signs and symptoms”(Merriam-Webster,2003)

The logic is that the course of the diseases may be changed for the better if they are detected and treated before they reach a stage at which they elicit symptoms or require more invasive intervention. Therefore, in dental practice, diagnosis is closely linked with the management options.

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The primary objective of caries diagnosis is to identify those lesions that require surgical (restorative) treatment , those that require nonsurgical treatment , and those who are at high risk for developing carious lesions.

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Why do we diagnose caries?

Diagnosis is important in: Detecting and excluding disease Assesing prognosis Contributing to the decision making

process with regard to further diagnostic and therapeutic management

Informing the patient Monitoring the clinical course of the

disease

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Diagnostic tests need to be valid and reliable. Validity means that test should measure what

it is intended to measure e.g. a white spot lesion with a matt surface indicates an active lesion which has not yet cavitated

Reliability or reproducibility means that the test can be repeated with the same result e.g. dentist would recognize the same white spot lesion with matt surface as an active lesion. There should be intra- as well as inter-examiner reproducibility

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Differential diagnosis

When performing a caries diagnosis it should be appreciated that not all opaque lesions on the tooth surface represent dental caries.

All opacities reflect a decreased mineral content in the enamel, but may be caused by different mechanisms,either during enamel formation or posteruptively.

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Dental fluorosis has a symmetric distribution on homologous teeth & in mild cases,appears as fine white horizontal striae reflecting the perichymatal pattern of enamel.

When such white lines merge in the gingival part of the tooth,they are suggestive of inactive non-cavitated carious lesions(smooth on probing). Such lesion is arch,banana or kidney shaped, reflecting the retention of plaque along the curvature of the gingival margin

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Prerequisites for detection and diagnosis

The diagnosis of caries require good lighting and dry,clean teeth

When teeth have been cleaned,each quadrant of mouth is isolated with cotton wool rolls to prevent saliva wetting the teeth once they have been cleaned

Thorough drying should be carried out by gentle blast of air from three-in-one syringe as white spot lesions are more obvious when the teeth are dry and saliva can obscure small cavities

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Methods of caries detection

Conventional techniques: Visual observation Tactile inspection Radiography:• Intra-oral periapical radiographs• Bitewing radiographs

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Recent advances: Dental digital

radiography Caries-detector dyes Fiber-optic

transillumination Quantitative light-

induced fluorescence

Laser fluorescence Ultrasound Xeroradiography Electroconductivity

measurements Microbiologic

methods

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Visual observation

It encompasses the use of criteria such as detection of white spot, discoloration & frank cavitations.

Careful examination of teeth under clean & dry condition using good illumination reveal:-

- brownish discoloration of pit and fissures - opacity beneath pit & fissure or marginal

ridge. - frank cavitation of tooth surface.

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For practical purposes,begin with the upper right molars and move tooth by tooth and surface by surface to upper left molars,then jump to the lower left molars and finish up with the lower right molars. A consistent examination pattern ensures that no teeth or surfaces are missed

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Various aids- Magnification loupes Slides have been used to gather

information about caries. With the use of slides pictures of posterior teeth tell us more about discoloration, decalcification & translucencies

Use of separators in detection of proximal caries

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Magnification loupe

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Loupes are comfortable to wear Inexpensive Freely available in various magnifications E.g: • 2.5 Flip Up Loupes• 3.0x and 3.5x Galilean Flip-Up Optics• 2.5 Custom TTL Loupes• NEW Custom TTL Loupes on Safety Frame

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Tactile inspection

The teeth are examined by the aid of dental mouth mirror and a sharp probe

The mouth mirror is used to displace the cheeks and lips and to facilitate vision in difficult to reach areas on the teeth

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Reflected light from the mouth mirror can be applied to search for dark shadows,which may be suggestive of dentinal lesions

Transmitted light from the operating lamp is particularly helpful for examining the approximal surfaces of anterior teeth

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An explorer is useful in caries diagnosis as a tool to remove plaque and debris and check the surface characteristics of suspected carious lesions.

- curved explorer is used for examination of pit and fissures .

- inter proximal explorer is used to detect proximal caries.

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The surface texture of lesion is sensed through minute vibrations of the instrument by the supporting fingers when moving the tip of the probe at an angle of 20-40 degrees across the surface

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One should definitely abstain from poking vigorously into the tissue,thereby running the risk of causing irreversible damage to the surface layer of an incipient lesion,which may potentially accelerate localized lesion progression

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Some researchers are concerned that probing of suspected carious lesions may serve to spread infective plaque(i.e. mutans streptococci) to other teeth in the same mouth,thereby facilitating carious lesion development. However,this this concern has not been confirmed as transferred microorganisms would not survive unless their new econiche favored their existence

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Tactile finding suggestive of caries are:- • ‘binding’ or ‘catch’ of explorer tip• Frank cavitation at the base of pit or fissure • Softness at base of pit or fissure• Opacity surrounding the pit or fissure Feeling of ‘catch’ may be due to non carious

reasons also, this may depend on:• shape of fissure• sharpness of explorer• force of application• path of explorer placement

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Radiographs

Conventional , intra-oral periapical & bite wing radiographs are used to diagnose dental caries.

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Advantages:- - non-invasive method- disclose site inaccessible to other diagnostic

methods.- keeps a permanent record for maintaining progress

or arrest of carious lesions.Disadvantages:- - only a 2-D image of 3-D object. - doesn’t reveal the earliest stages of caries

development.. - radiolucency may be due to caries, wear, fracture,

or due to cervical burn out. - radiographic diagnosis is subjective , prone to

observer bias. - extent of caries as seen in the radiographs is

usually lesser than actual defect.

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BITEWING RADIOGRAPH:Role For detecting occlusal caries:-• Initial enamel caries are difficult to detect

on bitewing radiographs due to 3 D shape of occlusal surface.

• caries involving the buccal and lingual grooves on molars mimic occlusal lesions due to superimposition.

Role in detecting proximal caries:-• Early proximal enamel lesions are seen as

small radiolucent notch below contact area.• Advanced proximal caries are seen as dark

triangular area in proximal enamel with its base towards the external tooth surface.

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Diagrammatic representations of caries on bitewing radiograph

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Uses: Detecting incipient proximal caries. Examining many teeth in one

radiograph. Checking cervical margins of restoration. Noting the size of pulp chamber. Monitoring the progress or arrest of

caries.

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Fiberoptic transillumination

Diagnostic method by which visible light is transmitted through the tooth from an intense light source,e.g a fine probe with an exit diameter of 0.3-0.5 mm

Principle of it is that there is a different index of light transmission for decayed & sound tooth

Tooth which is decayed has a lower index of light transmission than the sound tooth structure

It is effective specially when used in anterior region.

It is used as an adjunct to visual and radiographic method

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If the transmitted light reveals a shadow when the tooth is observed from the occulusal surface this may be associated with the presence of a carious lesion

The narrow beam of light is of crucial importance when the technique is used in premolar and molar region

For optimal performance the probe should be brought in from the buccal or lingual aspect at an angle of about 45 degrees to the approximal surfaces pointing apically,while looking for dark shadows in the enamel or dentin

Shadows are best noticed when the office light is switched off

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Advantage: Does not produce overlapping images as

in case of posterior crowding Can be easily used in pregnant women

when radiation has to be avoidedDisadvantage : FOTI fails to detect incipient proximal

caries

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Digital fiberoptic Trans illumination Image captured by the camera are sent

to a computer for analysis , which produce digital images that can be viewed.

Advantages:- - instantaneous image projections - image quality is easy to control - can detect incipient & recurrent caries

very early - non invasive

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Disadvantages :- - doesn’t measure the depth of lesion- Difficult to distinguish between

deep fissure , stain and dental caries.

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Tooth separation

Neither radiographs nor FOTI can help to identify the presence of a cavity on contacting approximal surfaces. Therefore, tooth separation has been introduced

Orthodontic elastic separators are applied for 2-3 days around the contact areas of surfaces to be diagnosed,after which assess to inspection and probing is improved

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This technique may create some discomfort,especially in patients with established dentitions.

It requires an extra visit Therefore,at present this technique is

not recommended for routine use in general practice

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Xeroradiography

Advance technique alternative method to conventional radiography

In xero radiography image is recorded on photo conductive selenium coated plate rather than X ray film. Selenium coated plate is charged & placed in to light tight cassette. This photoreceptor is placed intra orally & exposed to X ray beam causing selective discharge. The amount of discharge is related to radiation striking photoreceptor.

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During developing the selenium plate is exposed to cloud of charged powder particle called TONER , next the plate is dried to remove the liquid vehicle of toner particles. Processed image is transferred to opaque elastic base with the help of clear adhesive tape.

USES: help to diagnose initial caries

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ADVANTAGES:--“Edge enhancement” can demarcate area of

varying dentition specially at margins.-Less radiation exposure.-no wet processing.-Both -ve & +ve prints are possible.

DISADVANTAGES:--Expensive-Development process should be completed

within 15 minutes-Electric charge over the film may cause

discomfort to the patient.

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Digital radiographic method

This method offer a more superior means of detecting caries than conventional radiographs.

Introduced in 1987 The application of computer technology to

radiography. Has allowed image acquistation,

manipulation, storage, retrieval & transmission to remote sites in digital format.

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Digital imaging sensor is used (CCD) instead of radiographic film.

The signal from CCD is sent to computer where it is digitized in 256 gray levels & is viewed on screen with enhanced density & contrast.

It is of two types:• Direct digital radiography• In-Direct digital radiography

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Direct digital radiography: Image is acquired by detector that is

sensitive to electro magnetic energy & data is converted into digitized form

It is of two types:1: photo stimulable phosphor {PSP}2: charged couple device sensor {CCD}Other type:-complementary metal oxide semiconductor

{CMOS}

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PSP: The interactions between X-ray photons &

crystals of PSP excite the electrons of phosphor. Further on irradiation with ruby laser,trapped electrons are released causing emission of shorter wave length of light in blue region of spectrum. The intensity of emitted blue light is proportional to amount of X ray absorbed by phosphor which can be detected by photo multiplier tube. The output of tube is digitized to form image.

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CCD: Consists of a chip of pure silicon. When CCD

interacts with X ray, an electric charge is created. After exposure, electric charge is sequentially transferred to computer which is acquired as an image later.

USES of digital radiography:1: Early detection of caries.2: In endodontics, it helps to measure root canal

length, working length & distance between apex and obturating material.

3: It also helps to assess bone loss.

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The software has been designed to assist in locating and classifying proximal surface caries in digital intraoral radiographs

The analysis is completed in seconds and an enlarged image of the radiograph being evaluated is displayed, along with the possible decay area

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This helps to identify and calculate the probability of enamel and dentin caries based on a unique histological database.

We simply select the area of interest and the software automatically outlines any consistent alignment of radiolucent features directing our attention to the area of interest for closer examination.

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ADVANTAGES:-- Reduce radiation dose.- Instant image visualization- No need for dark room- No processing error - Image can be magnified- Contrast and density of image can be

enhanced.DISADVANTAGES:-- Expensive

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Electric conductance measurement sound enamel is an insulator due to its

high inorganic content . On the other hand , carious enamel has a measurable conductivity which increase with degree of demineralization.

Two devices were developed in 1980’s - vanguard electronic caries detector. - caries meter

• Both instrument measures the electrical conductance between the tip of a probe placed in a fissure and connector attached to an area of high conductance.

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Low conductance of tooth is primarily caused by enamel

Increased conductance & decreased resistance are indicative of the presence of hypo &/or demineralization

When a potential of less 1volt applied, resistance of above 6,00,000 ohms indicates caries free tooth. Resistance below 2,50,000 indicates caries.

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Factors affecing electronic resistance measurement:

Porosity Surface area Thickness of tissues Hydration of enamel Temperature

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Advantages -More accurate in diagnosis of early occlusal

caries than visual method , radiographs or FOTI .

-Can monitor the progress of caries.Disadvantages -Hypomineralized area , enamel cracks can

cause misleading reading.-time consuming procedure -Requires the use of sharp metal explorer

which can cause traumatic defect in pits and fissures.

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Caries detecting dyes

Principle- Increased porosity- through the development of

capillary like micro voids- is earliest change in carious lesion

For detection of enamel caries• Calcien• Zyglozl-22

For detection of dentin caries• Fuschin• Acid red system• 9-aminoacridine

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Limitations: Does not stain bacteria but organic

collagen matrix of less mineralized dentine No differentiation between infected and

affected dentine possible High risk of over treatment Also stains healthy dentine with naturally

high collagen content: circumpulpal dentine

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Laser Fluorescence

Use of fluorescence for detection dates back 1929, when Benedict observed that normal teeth fluoresce under UV illumination.

Aids in the detection of occlusal caries The machine emits light at a wavelength

of 655nm and this is transported through a fibre bundle to the tip of a handpiece. The tip is placed against the tooth surface & rotated

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The laser light will penetrate the tooth. Different fibers in the tip receive the reflected light and fluorescence from the lesion,thought to be produced from bacterial porphyrins

The received light is measured & its intensity is an indication of size and depth of carious lesion

The machine does not detect the mineral loss Reproducibility has shown to be good but can

be confused by staining and calculus,giving high reading when active caries is not present

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Monochromatic light is used at 350,410 & 530nm on carious & non carious teeth.

In carious teeth emission spectra shifts to more than 540nm i.e. red range of EM spectrum.

It has been recently found that when illuminated with argon laser,carious tissue appears as dark, fiery, and orange-red in color.

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Diagnodent: Based on principle of fluorescence. It uses a diode laser light source & a fiber optic

cable that transmits light to a hand held probe.

Emitted fluorescence is collected at probe tip, processed & presented on display as an integer between -9 to99.

-9 indicates healthy teeth & increased fluorescence indicates caries particularly value above 20.

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The Diagnodent operates at a wavelength of 655 nm.

At this specific wavelength, clean healthy tooth structure exhibits little or no fluorescence, resulting in very low scale readings on the display.

However, carious tooth structure will exhibit fluorescence, proportionate to the degree of caries, resulting in elevated scale readings on the display of the Diagnodent.

An audio signal allows the operator to hear changes in the scale values. This enables the focus to be on the patient, not solely on the device.

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Limitations: Cannot determine the depth of lesion. Reading may alter due presence of food debris,

plaque. Not able to detect recurrent caries. Alloy restoration

exhibits little or no fluorescence, while the composites, ceramics & cements emit their own fluorescence.

Reading changes at different angulations of probe tip.

Caries indicator dyes cannot be used simultaneously with diagnodent.

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Quantitative light fluorescence

This methodology began with observation in1978 by a scientist in Sweden that the use of a laser light of selected wavelength markedly enhances the visibility of early non carious lesions

QLF uses light with wavelengths around 405 nm to excite yellow fluorescence at wavelengths above 520 nm.

Its diagnostic capacity is based on the mechanism that the intensity of natural fluorescence of a tooth is decreased by scattering due to a caries lesion.

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Two-photon image of a carious tooth Carious area shown in green

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The initial work was based around the use of multiphoton microscopy to build up a three dimensional image of the tooth.

This revolutionary technique enables the dentist to see right into the tooth but is complex to use and not suitable for general dental practitioners.

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Ultrasonography

Involves use of sound waves for detection

With the use of this instrument, sonic velocity & specific accoustic impedance can be determined for dentin & enamel as well as for soft tissue & bone.

In ultrasound frequency vibration is greater than 20 Khz. which is more than audible range{1500-20,000hz/sec}.

In sonography, sound waves are used in frequency of 1-20Mhz.

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Scanners used for sonography generate electric impulse that are connected into ultra –high frequency sound waves by transducer{ device which convert electric energy into sound energy}

Transducer is a thin piezo electric crystals made up of great number of dipoles arranged in geometric pattern. Electric impulse generated by scanner causes dipole in crystals to re-align themselves with electric field & thus sudden change causes a series of vibrations that produce the sound waves that are transmitted into the tissues being examined.

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When ultra sonography beam passes through or interacts with tissues of different sound, energy causes obstruction, reflection , refraction diffusion. Sonic waves that reflected back towards transducer cause change in the thickness of piezoelectric crystal, which produces an electric signal which is amplified and displayed on monitor.

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Fluorogenic enzyme assay: it is a new method to count cells “in situ”, based on a fluorogenic enzyme assay that measures the activity of alkaline phosphatase. Increasing cell number has close correlation with alkaline phosphatase activity and this relationship did not change with time in culture. This method is able to estimate relative cell numbers over a range from about 104 to 105×105 for many cell types. The method is rapid and efficient, making it a useful method for studying streptococcus and lactobacillus activity in active root lesions.

Microbiologic method

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Lactobacillus colony count test : This test estimates the number acidogenic Lactobacillus bacteria in the patient’s saliva by counting the number of colonies appearing on the tomato peptone agar plates (pH 5.0).

Streptococcus mutans count test: This test measures the number of S.mutans colony forming units per volume of saliva from the root lesion. It is cultured on the Mitis Salivarius Agar (MSA), selective streptococcal medium.

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All the above mentioned methods may be used as an adjunct to visual inspection. However to be used in practice the methods must be better than clinical-visual and radiographic examination.

They must be convenient to use,not too expensive and must be reproducible

Only laser fluorescence(diagnodent) and digital radiography are currently used in practice and seem to be suitable techniques for detection of caries

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References

Fejerskov Ole, Kidd Edwina.Dental caries:the disease and its clinical management.2nd Ed.

Roberson TM.Sturdevant’s Art & Science of Operative Dentistry.4th Ed.

Kidd Edwina. Essentials of dental caries Shafer, Hine, Levy.Textbook of oral pathology.5th Ed. Soben Peter. Preventive and Community Dentistry. 3rd

Ed. Nikiforuk Gordon. Understanding dental caries part1 Newbrun.Cariology Hiremath SS. Textbook of preventive and community

dentistry

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