Histopathology of Dental Caries

Dr .Intisar Ben Amer

Department of Oral Pathology

Dental Caries

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Dental caries or tooth decay is one of

the most common of all disorders,

second only to common cold.

►Dental caries is one of the most common of all diseases and still a major cause of loss of teeth. ► Affects both sexes and all races, all socio-economic and people of all ages.

What is Dental Caries?

• It is a microbial disease of the calcified tissues of the teeth, characterized by demineralization of the inorganic portion and destruction of the organic substance of the tooth.

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Etiology of Dental Caries Miller concluded that caries could result from decalcification caused by the bacterial acid production followed by invasion and destruction of any remaining tissue . In 1954,Orland and his associates in USA showed that caries did not develop in germ-free animals. However, dental caries develops only in the presence of several interacting variables.

Essential requirements for the development of dental caries 1. Cariogenic bacteria 2. Diet 3. Bacterial plaque 4. Susceptible tooth surface

Etiology of Dental Caries

Teeth

Time

Carbohydrate

Bacteria

caries

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1. The Role of Bacteria Bacteriological studies have indicated some certain types of microorganisms as being intimately associated with dental caries . These organisms are mainly streptococci (s.mutans, s.sangius, s.mitis, s.oralis), lactobacilli and actinomyces . Some are implicated in the initiation of the carious lesion such as s.mutans, where as lactobacilli contribute to tooth destruction after the process has started. Cariogenic bacteria differ according to their site . For instance, in root caries as well in rampant caries actinomyces are the predominant. Where as, in occlusal and smooth surface caries, s.mutans are mostly involved.

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1. The Role of Bacteria

The essential features of cariogenic bacteria are:

• 1. Acidogenic : have the ability to produce acid.

• 2. Aciduric: have the ability to survive at a PH as low as 4.2

• 3. they form large amounts of extra-cellular sticky and insoluble glucan plaque matrix.

• 4.they are able to form and store intra-cellular polysaccharides.

• 5. they have a proteolytic property .

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2.Role of carbohydrates

There is a direct relationship between fermentable carbohydrates (CHO) in diet and dental caries. Different CHO also have different cariogenic properties. For instance, sucrose is more cariogenic than other sugars. This is because it is readily converted by bacterial glucosyl transferse into extra-cellular glucans as well as intracellular polymers, which in turn is broken down into acid when other sources of CHOs are absent, such as in between meals.

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3.The role of dental plaque Clinically , dental plaque has a thin yellow film on the surface of the teeth.

With time , it undergoes mineralization to form dental calculus .

Stages of plaque formation Stage I

The process of plaque formation starts with the deposition of the acquired dental pellicle. This a structure less, cell-free layer of salivary glucoproteins adsorbed on the tooth surface .

Stage II

The acquired dental pellicle becomes visible when tooth brushing stops for 12-24 hours. Colonization of the acquired pellicle by bacterial flora, particularly by streptococcal strains occurs.

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The role of dental plaque

Plaque microorganisms can synthesize extra-cellular glucans from dietary sugars which help attach the plaque to the tooth and may also be metabolized to acid when other sources of CHOs are absent. Stage III maturation of the dental plaque takes place by the proliferation of the heterogeneous flora.

(1) The enamel (e) has plaque biofilm (b) growing at the border of the inflamed gingival (g).

(2) Same plaque at closer look. There is a ‘white spot’ lesion (w) developing at the margin of

the gingiva, and brown calculus (c) developing in the sulcus attached to the tooth.

(3) Close-up view of plaque. Biofilm bacteria, which

consists of several species of bacteria (cocci, rods, motile spirochetes),

organic material (salivary proteins) and organic matter secreted by the bacteria (yellow-

stained)

Figure shows an illustration of dental plaque at

the gingival margin.

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The role of dental plaque

Dental plaque is important in the mechanism of dental caries as follow:- dietary sugars diffuse rapidly through plaque, where the bacterial

enzymes breakdown this sugar into acids and glucans . at a critical PH (it is usually 5.5)the acids attacks E resulting in the

liberation of the mineral ions from the hydroxyapatite crystals and their diffusion into plaque .

slowing down the arrival of the salivary buffers from saliva thus delaying their neutralization action .

A detail of a tooth (to the right = enamel). It 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

4.The influence of susceptible tooth surface

Factors Extrinsic to

the tooth

saliva

diet

Factors intrinsic to the tooth

Enamel structure

Enamel composition

Tooth morphology

Tooth position

According to the location of the of

the lesion According to the

rate of attack

1. Pit and fissure caries

2. Smooth surface caries

3. Cemental /root caries

4. Recurrent caries

1.Acute /rampant caries

2. Chronic /slowly progressive

caries

3. Arrested caries

• According to the location of the of the lesion

• 1.Pit and fissure caries:-

• This occurs on the occlusal surfaces of molars and premolars ,on buccal and lingual surfaces of molars and on the lingual surfaces of maxillary incisors

• 2. Smooth surface caries :-

• This occurs on the proximal surfaces of all teeth and on the gingival third of the buccal and lingual aspects.it begins below the contact area as a well- demarcated chalky-white.

• Cervical caries extends occlusally from the gingival margin on buccal and lingual tooth surfaces. It is usually crescent in shape.

• 3. Cemental /root caries:-

• This occurs when the root surface is exposed to the oral environment because of a periodontal disease.

• 4. Recurrent caries:-

• It occurs around the margins or at the base of a previously existing restoration.

Pit and fissure caries

Smooth surface caries

Pit and fissure caries and

Smooth surface caries

Recurrent caries

Cemental /root caries

• According to the rate of attack

• 1. Acute /rampant caries:-

• It is rapidly progression caries that involves many or all of the

erupted teeth .

• 2. Chronic /slowly progressive caries:-

• This is slowly progression caries .

• 3. Arrested caries:-

• This is caries of E,D,or C, which has become static , with no

tendency for further progression, mostly because of the re-

mineralization, which has occurred from the precipition of ions from

saliva.

Rampant caries

Rampant caries /RADIATION CARIES

Arrested caries