Dental Caries Important Question And Answers

Dental Caries

Question.1. Describe in brief etiology of dental caries.

Answer. Following is the etiology of dental caries:

Read And Learn More: Oral Pathology Question And Answers

Tooth
Composition

• Structure and composition of the teeth influence initiation and rate of progression of dental caries.
• Surface enamel is more resistant to caries as compared to subsurface enamel. Surface enamel consists of more quantity of fluoride, zinc, lead and iron.
  Concentration of carbonate, magnesium and sodium is lower in surface layer.
  Level of carbon dioxide is also lower in the surface layer which causes dissolution of surface layer by acids in lower rate and it consists of less organic and water content.
• Age changes in enamel such as decrease in the density and permeability and increase in nitrogen and fluoride content causes teeth to become more caries-resistant.

Morphologic Characteristic

• Deep and narrow occlusal fissures or buccal and lingual pits lead to development of dental caries.
• As age increases attrition of teeth occur and this leads to less accumulation of food in fissures, and there is less occurrence of caries.

Position

Malaligned tooth or rotated tooth has more chances of predisposition of caries as it tends to accumulate more food debris, cariogenic plaque and bacteria. In all these teeth cleaning cannot be done.

Saliva

Composition

• Inorganic components of saliva: In normal aspect saliva is supersaturated with calcium and phosphate ions.
  This causes prevention of dissolution of enamel and also precipitates apatite crystals in surface of enamel of carious lesion which helps in partial repair of tooth damaged by dental caries. During caries saliva is unsaturated with calcium and phosphate ions which lead to dissolution of enamel.
  Fluoride has also got excellent role in reduction of the dental caries.
• Organic components of saliva: High concentration of ammonia retards plaque formation and neutralizes acid.
• Urea increases the neutralizing power of saliva. Enzyme salivary amylase leads to the degradation of starch and makes it more soluble in this way starch is washed away from tooth surface.

pH

• Critical pH is the pH at which saliva appears to be saturated with the calcium and phosphorus ions.
  Value of critical pH is 5.5, below the critical pH inorganic portion of tooth starts dissolving. As there is increase in concentration of hydrogen ion in cariogenic plaque, this leads to the loss of more phosphate ions from the tooth.
• Buffering property of saliva leads to diffusion of bicarbonate ions in dental plaque and neutralizes the acid during caries process.

Quantity

• Quantity of saliva is inversely proportional to dental caries activity.
• More is the salivary flow less is the caries index.
• Hyposalivation occurs due to the conditions like diabetes mellitus, uremia and usage of anti­sialogogues.

Viscosity

If saliva is thick mucinous there is presence of high caries incidence.

Anti-Bacterial Factors

• Saliva consists of many anti­bacterial products such as lysozyme, salivary peroxidase and immunoglobulins.
• Lysozyme under the presence of sodium lauryl sulphate can lyse cariogenic streptococci.
• Salivary peroxidase inactivates bacterial enzymes of glycolytic pathway and inhibits their growth. This is more effctive against lactobacillus bacteria.
• IgA immunoglobulin inhibits S. mutants in saliva.

Diet

Physical Factors

• Raw unrefined food consists of roughage which clears the teeth but presence of soil and sand leads to attrition of occlusal and proximal surfaces of teeth and reduces dental caries.
• Soft and refined foods stick to the teeth and causes increased accumulation of debris which causes increased risk of dental caries.

Local Factors

• Carbohydrates, i.e. starch, sucrose, lactose, glucose, fructose or maltose play important role in process of dental
  caries. Synthesis of extracellular polysaccharides, glucAns and levan helps in adherence of bacteria to teeth.
• In lipids, medium chain fatt acids and their salts have anti­bacterial properties at low pH.
• Deficiency of Vitamin A and D can lead to enamel hypoplasia which can lead to dental caries in affected teeth.

Systemic Conditions

• Hereditary: There is the possibility of dental caries which leads to the inheritance of tooth form or structure which predisposes to dental caries.
• Pregnancy: In later stages of pregnancy because of lack of oral hygiene there is increased risk of dental caries.

 

Question.2. Describe the theories of etiology of dental caries.
Or
Defie dental caries and theories associated with dental caries.
Or
Describe the theories of dental caries.

Answer. “Dental caries is an irreversible progressive microbial disease of the calcified tissues of the teeth, characterized by the demineralization of the inorganic portion and distortion of the organic substances of the tooth, which often leads to cavitation”.

• Etiology of dental caries is a very complex process, which is often explained with the help of some theories.
  • Acidogenic theory
  • Proteolytic theory
  • Proteolytic chelation theory
  • Sucrose chelation theory
  • Autoimmune theory.

Acidogenic Theory

• This theory is also known as Miller’s chemicoparasitic theory.
• It proposes that acid formed due to the fermentation of dietary carbohydrates by oral bacteria leads to progressive decalcification of the tooth. Structures with subsequent degeneration of the organic matrix.
• Acidogenic theory states that the process of dental caries involves two stages.
  1. Initial stage: Production of organic acid occurs as a result of fermentation of the carbohydrates by the Plaque bacteria.
  2. Later stage: Acid causes decalcification of enamel followed by dentin and thereby causes total destruction of these two along with dissolution of their softened residues.
  Final result is cavity formation.
• According to Miller there are four important factors,which can influence the process of tooth destruction in dental caries.
  1. Dietary carbohydrates
  2. Microorganisms
  3. Acids
  4. Dental plaque.

Role of Carbohydrates

• Fermentable dietary carbohydrates play an important role in the causation of caries, e.g. glucose, fructose and sucrose.
• Among them sucrose is more potent.
• These sugars are easily and rapidly fermented by cariogenic bacteria in the oral cavity to produce acid at or near the tooth surface and causes dissolution of the hydroxyapatite crystal of the enamel followed by the dentin.
• Risk of caries incidence increases greatly if the dietary sugar is sticky in nature which remains adheres to the tooth surface for long time after taking the meal.
• Following the ingestion of these sugars the pH of the Plaque falls to 4.5 to 5 within 1 to 3 minutes and neutralization occurs after 10 to 30 minutes.
• Glucose, sucrose and fructose, etc. are rapidly defused into the plaque due to their low molecular weight.

Role of Microorganisms

• A large number of microorganisms play individual role in dental caries production and among them the most important one is Streptococcus mutans.
  • It readily ferments the dietary carbohydrate to produce acid, which causes tooth destruction.
  • It synthesizes dextran from sucrose, which helps in adhering the plaque bacteria as well as the acid on to the tooth surface.
  • S. mutAns has the ability to adhere and to grow on hard and smooth surface of the teeth.
• Actinomycosis group, e.g. Actinomycosis israelii, Actinomycosis viscosus, etc. are the important organisms to cause root caries.
• Lactobacillus acidophilus is important organism for the progress of dental caries.

Role of Acids

• During the process of caries formation, a large variety of acids are produced in the oral cavity due to the bacterial fermentation of dietary carbohydrate.
• These acids are lactic acid, aspartic acid, acetic acid, butyric acid, glutamic acid.
• They can cause demineralization of enamel and dentin and causes the tooth decay.

Role of Bacterial Plaque

• Plaque is a thin, transparent fim produced on tooth surface and it consists of microorganisms suspended in salivary mucin, also contain desquamated epithelial cells, leukocytes and food debris, etc.
• The dental plaque helps in initiation of dental caries by:
  • It harbors the cariogenic bacteria on the tooth surface.
  • It holds the acids on the tooth surface for long duration
  • It protects the acids from getting neutralized by buffering action of saliva.

Proteolytic Theory

According to this theory, the proteolytic enzymes liberated by cariogenic bacteria causes destruction of organic matrix of enamel, as a result of which the inorganic crystals of the enamel become detached form one another, and finally the whole structure collapse, leading to a cavity formation.

This theory cannot explain the role of sucrose, pH, fluoride, etc. in dental caries.

Proteolysis-Chelation Theory

• According to this theory during caries, fist of all pro­teolytic breakdown of the organic portion of the enamel matrix takes place.
• Following this a chelating agent is formed by the combination of the proteolytic breakdown products, acquired pellicle and food debris, etc.
• Chelating agent (negatively charged) release the calcium ion (positively charged) from enamel and dentin, this process is called as chelation and eventually results in tooth decay.

Sucrose Chelation Theory

• This theory propose that if there is very high concentration of sucrose in the mouth, there can be formation of complex substances like calcium saccharide and calcium complexing intermediaries.
• These complexes causes release of calcium and phosphorus ions from the enamel and thereby results in tooth decay.

Autoimmune Theory

This theory suggests that few odontoblast cells at some specific sites, within the pulp of few specifi teeth are damaged by autoimmune mechanisms.

Current Concept of Caries etiology

• Dental caries is a multifactorial disease in which there is interplay of three primary factors—the host, microflora, and the substrate. In addition a fourth factor, i.e. time.
• Caries formation requires a host, a cariogenic flora, and a suitable substrate that must be present for a sufficient length of time.

 

Question.3.Defie dental caries describe histopathology of caries in enamel and dentin.
Or
Describe in brief histopathology of dental caries.

Answer. “Dental caries is an irreversible progressive microbial disease of the calcified tissues of the teeth, characterized by the demineralization of the inorganic portion and distortion of the organic substances of the tooth, which often leads to cavitation”.

Histopathogical Features Of Caries In Enamel

Early Enamel Caries

• There will be loss of inter prismatic or inter rod substances with increase in prominence of these enamel rods.
• Dark line often appears at right angles of the enamel rods, suggesting segments.
• Accentuation of the incremental striae of retzus often occurs.

Advanced Enamel Caries

• It presents several zones in the tissues, out of which four zones are clearly visible, starting from the inner advancing front of the lesion the zones are:

Zone 1: translucent Zone

• It is the deepest zone lies at the advancing front of the enamel lesion.
• This zone is more porous than normal enamel.
• Pores are larger than the normal enamel.
• Pore volume is 1%.
• This zone appears structureless.
• This zone contains more fluoride than normal enamel.

Zone 2: Dark Zone

• Dark zone is located just superfiial to the translucent zone
  and its dark appearance is due to the excessive demineralization of the enamel.
• Zone is narrower in rapidly advancing caries and it is wider in slowly advancing lesion.
• Zone contains 2 to 4% pore volume.
• Pores are larger than normal but smaller than those of translucent zone.
• This zone reveals some degree of remineralization of carious lesion.

Zone 3: body of leison

• Zone is situated between the dark zone and the surface layer of enamel.
• It represents the area of greatest demineralization.
• Pore volume is 5 to 25%.
• This zone contains appetite crystals larger than those of the normal enamel.
• Large crystals results from the reprecipitation of minerals dissolved from the deeper zone.

Zone 4: surface Zone

• Surface zone when examined by the polarizing light appears relatively
• unaffected, it may be due to the surface remineralization by the salivary mineral ions.

Histological Features Of Caries In Dentin/Dentinal Caries

Dentinal caries histologically presents fie zones in the tissue, which are:

Zone 1: normal Dentin

• This zone represents the innermost layer of the carious dentin, here the dentinal tubules appears normal.
• There is evidence of fatt degeneration of the Tome’s process.
• No crystals in the lumen of the tubules.
• No bacteria in the tubules.
• Intertubular dentin has normal cross-banded collagen and normal dense appetite crystals.

Zone 2: sub-transparent Dentin

• This is the zone of dentinal sclerosis and is characterized by the deposition of very fine crystal structures within the dentinal tubules.
• Superficial layer shows area of demineralization and damage of the odontoblastic processes.
• No bacteria in the tubules.
• Dentin is capable of remineralization.

Zone 3: transparent Dentin

• This zone appears transparent and this is because of decalcification of dentin.
• It is softer than normal dentin.
• No bacteria in tubules.
  Cross-banded inter tubular collagen is still intact.
• This zone is capable of self-repair and remineralization.

Zone 4: turbid Dentin

• This zone is marked by widening and distortion of dentinal tubules, which are packed with microorganisms.
• There is very litte amount of minerals in dentin, denaturation of collagen fiers also takes place.
• Zone cannot undergo self repair or remineralization.
• This zone must be removed before restoration.

Zone 5: infected Dentin

• This is the outermost zone of the carious dentin.
• It is characterized by complete destruction of dentinal tubules.
• In this zone the area of decomposition of dentin, which occur along the direction of dentinal tubules are called “Liquefaction foci of Miller”, which occur perpendicular to dentinal tubules are called “Transverse clefts”.
• In the process, the entire dentinal structures become destroyed and cavitation begins from dentino enamel junction.

 

Question.4. Write short essay on caries activity test.
Or
Write short note on caries activity test.

Answer. A number of caries activity test have been evolved which are as follows:

Snyder Test

• This test measures the ability of salivary microorganisms to produce organic acids from carbohydrate metabolism.
• Glucose agar media containing an indicator dye, i.e. Bromocresol green is useful.
• The indicator dye changes from green to yellow in range of Ph between 5.4 to 3.8
• Paraffin-stimulated saliva is added into the medium,change of the medium from green to yellow is indicative of degree of caries activity.

Salivary Reductase Test

• It measures the activity of Reductase enzyme present in salivary bacteria.
• Paraff-stimulated saliva is collected in the plastic container and an indicator dye “Diazoresorcinol” is added to it which colors the saliva blue.
• The reductase enzyme liberated by the cariogenic bacteria causes color changes in the medium from blue to other colors, which indicates the caries “conductiveness” of the patients.

Microbiological Test

• Microbiological test helps to measure the number of Streptococcus mutAns and Lactobacillus acidophilus.
• Two samples of paraffin-stimulated saliva is collected and diluted 10 times and each is cultivated in two diffrent special media.
• Rogosa’s SL agar medium for Lactobacillus.
• Mit’s Salivarius agar medium for S. mutans.
• After incubation the numbers of colonies that develop in two separate media are counted and then are multiplied by 10 to estimate the number of bacteria in 1 ml of saliva.
• Result: If count is more than 10, 00,000 S. mutAns and more than 1,00,000 L. acidophilus, than the caries susceptibility of individual is very high.

Alban’S Test

It is the modification of synder test. It uses less agar, i.e. 5ml per tube. The saliva is drooled directly into the tubes and the tubes are incubated for 4 days at 37°C.
The color change is noted from bluish-green to yellow and the depth to which the change has occurred is noted.

Strip Test For S.MutAns Level In Saliva

Saliva/plaque samples are obtained by using tongue blades and toothpicks (after air drying the tooth for plaque samples) and are transferred to the S. mutants strip which is incubated in M.S.B.
agar (Mitis Salivarius Bacitracin agar).

The number of S. mutAns colonies are used to estimate the caries activity and more than 105 colonies per mL of saliva is indicative of high caries activity.

Buffer Capacity Test

10 mL of stimulated saliva is collected at least one after eating and stored under paraffin oil to prevent the loss of volatile bicarbonate ions, 4 mL of this is measured in beaker.

After correcting the pH meter to room temperature the pH of the saliva is adjusted to 7.0 by addition of acid or base.

The level of lactic acid in the graduated cylinder is then again recorded.

Lactic acid is then added to the sample until a pH of 6.0 is reached. The amount of lactic acid needed to reduce pH from 7.0 to 6.0 is the measure of the buffr capacity.

Fosdick Calcium Dissolution test

25 mL of gum-stimulated saliva is collected. Part of this is analyzed for calcium content.

The rest is placed in an 8 inch sterile test tube with about 0.1g of powdered human enamel.

The tube is sealed and shaken for four hours at body temperature after which it is again analyzed for calcium content.

If paraffin is used, a concentration of about 5% glucose is added. The amount
of enamel dissolution increases as the caries activity increases.

Dewar test

This test is similar to the Fosdick calcium dissolution test except that the fial pH after four hours is measured instead of the
calcium dissolved.

Swab Test

The swab test involves sampling of the oral flra by swabbing buccal tooth surfaces and placing it in the Snyder media.

This is incubated for 48 hours and the pH changes are read and correlated with the caries activity.

Interpretation

pH 4.1 and less than 4.1—Marked caries activity
pH 4.2–4.6—Active
pH 4.5–4.6—Slightly active
pH greater than 4.6—Caries active.

 

Question.5.Defie dental caries. Enumerate the theories associated with dental caries. Explain different measures in preventing and controlling dental caries.

Answer. “Dental caries is an irreversible progressive microbial disease of the calcifid tissues of the teeth, characterized by the demineralization of the inorganic portion and distortion of the organic substances of the tooth, which often leads to cavitation”.

Preventive And Controlling Methods Of Caries

• Chemical measures
• Nutritive measures
• Mechanical measures

Chemical measures

• Substances which alter the tooth surfaces or tooth structures.
  • Fluorine:
    • It has cariostatic activity
    • Fluorine makes the teeth more resistant to acid attck into oral cavity.
    • It decreases microbial acid production and enhance the remineralization of underlying enamel.
    • It is given in the form of:
    • Communal water floridation
    • Fluoride containing dentifrices
    • Fluoride mouth rinses
    • Dietary floride supplement.
  • Bis biguanides: Chlorhexidine and alexidine. They are antiplaque agents
  • Silver nitrate
  • Zinc chloride and ferrocyanide
• Substance which interfere with carbohydrate degradation
  through enzymatic alteration:
  • Vitamin K: It prevents acid formation in mixture of glucose into saliva.
  • Sarcosine.
• Substance which interfere with bacteria growth and metabolism:
• • Urea and ammonium compounds
  • Chlorophyll
  • Nitrofurans
  • Penicillin.

Nutritive Measures

• Groups of patients whose diet is high in fat, low in carbohydrate, and practically free from sugar have low caries activity.
• Phosphates diet causes signifiant reduction in indication of caries.

Mechanical Measures

• Tooth brushing: Tooth brushing reduces the number of oral microorganisms. If the teeth are brushed after each meal.
• Mouth rinsing: The use of mouthwash loses the food debris from the teeth and prevents the caries.
• Dental floss: It removes plaque from an area of gingiva to contact area on proximal surfaces of teeth, an area impossible to reach with the toothbrush.
• Detergent foods: Fibrous foods prevent lodging of food in the pit and fisures of the teeth and in addition acts as detergent.
• Pit and fissure sealants: The pits and fissures of occlusal surface are most difficult areas on teeth to keep clean, so pits and fissures sealants are generally used.

 

Question.6. Write short note on contributing factors in dental caries.

Answer. The following are the contributing factors in the dental caries.

• Dietary factors: Carbohydrates with types like monosaccharides, disaccharidase or polysaccharides and the amount consumed and whether it is between the meals.
• Microorganisms: Acidogenic Streptococcus mutants and Actinomycosis viscosus.
• Systemic factors: Hereditary, pregnancy and lactation factors have been suggested as etiological factors for dental caries.
• Host factors: Poor oral hygiene and improper brushing technique may lead to dental caries.
• Immunological factors: The functional role of circulating antibodies as protective agents against tooth decay has been demonstrated in nonhuman primates.

 

Question.7.Write notes on nursing bottle syndrome.

Answer. It is also called as nursing caries or baby bottle syndrome and bottle mouth syndrome.

This is a type of rampant caries affecting deciduous dentition.

Etiology

It occurs due to prolong use of:

• A nursing botte containing milk or milk like formula, fruit juice or sweetened water.
• Breastfeeding
• Sugar or honey-sweetened pacifiers.

Clinical Features

• The disease presents clinically as widespread carious destruction of deciduous tooth maxillary the fourth maxillary anterior followed by Ist molar and then the cuspid if the habit is prolonged.
• It has been emphasized that it is the absence of caries in mandibular incisors which distinguishes this disease from ordinary rampant caries.
• The carious process in affected teeth may be so sever that only root stumps remain
• The mandibular incisors usually escape because they are covered and protected by the tongue.

 

Question.8. Write note on microbial plaque.

Answer. Microbial plaque is also called as dental plaque or bacterial plaque.

• It was demonstrated first time by William in 1897.
• Microbial plaque is the soft, non-mineralized bacterial deposit which forms on teeth and dental prostheses that are not adequately cleaned. It is composed of 80% water and 20% solids.
• Bacterial and salivary proteins comprise one half of dry weight of plaque. Plaque has high concentration of protein, carbohydrates and lipids.
  Inorganic components of plaque are calcium and phosphate.
• It forms on the tooth surfaces which are not properly cleaned.
• Dental pellicle which is a glycoprotein and is derived from the saliva is adsorbed over the tooth surfaces and serve as nutrient for plaque microorganism.
• Plaque is classified into two types based on its anatomical location, i.e. supragingival plaque and subgingival plaque.
• Supragingival plaque play important role in origin of dental caries while subgingival plaque is responsible for the causation of periodontal diseases.

 

Question.9.Define and classify and write in detail on etiopathogenesis on dental caries.

Answer. “Dental caries is an irreversible progressive microbial disease of the calcified tissues of the teeth, characterized by the demineralization of the inorganic portion and distortion of the organic substances of the tooth, which often leads to cavitation”.

Classification of Dental Caries

• Based on location of the lesion
  • Pit and fisure caries
    • Occlusal
    • Buccal or lingual pit
  • Smooth surface caries
    • Proximal
    • Buccal or lingual surface
  • Root caries
• Based on tissue involved
  • Enamel caries
  • Dentinal caries
  • Cementum caries
• Based on virginity of the lesion
  • Primary caries
  • Secondary caries
• Based on progression of lesion
  • Progressive caries
    • Rapidly progressive like nursing caries and radiation caries
    • Slowly progressing
  • Arrested caries:

 

Question.10.Draw diagram of histopathology of pit and fisure caries and dentinal caries.

Answer. Pit and fissure caries:

 

Question.11. Write short note on streptococcus mutans in dental caries.

Answer. It was first isolated by Clarke in 1924 and is termed as Streptococcus mutans.

• It is a catalyse negative Gram-positive cocci forming short to medium chains.
• S. mutans synthesizes insoluble polysaccharides from sucrose and is homofermentative.
• Most important substrate for involvement of S. mutans in caries process is disaccharide sucrose.
• S. mutans produces acid from fermentation of sucrose, glucose, lactose, mannitol, etc. This leads to demineralization of tooth structure and fially caries.
• S. mutans can survive at pH as low as 4.2 and can demineralize the tooth causing dental caries.
• S. mutans synthesizes dextran which helps in adhering plaque bacteria to tooth surface which leads to more decay.
• S. mutans adhere to acquired pellicle and helps in plaque formation which fially cause caries.
• S. mutans has ability to adhere on hard and smooth surfaces of tooth structure.

 

Question.12.Defie dental caries. Describe microbiology and factors promoting dental caries.

Answer.

Microbiology Of Dental Caries

• In the pathogenesis of dental caries an important role play cariogenic bacteria, i.e. oral streptococci, especially of group mutants and lactic acid bacteria (Lactobacillus spp.).
• It is believed that bacteria of the species Streptococcus mutans is the main factor that initiates caries and very important factor of enamel decay.
• The bacteria of the genus Lactobacillus are important in further caries development, especially in the dentin.
• Streptococcus mutans and lactobacilli are characterized by the ability to grow in an acid environment and the property of rapid metabolism of sugars supplied in the diet to organic acids, including lactic acid.
• The microbial community from dentinal lesions is diverse and contains many facultatively and obligately anaerobic bacteria belonging to the genera Actinomyces,
  Bifiobacterium, Eubacterium, Lactobacillus, Parvimonas and Rothia.
• Streptococci are recovered less frequently. Caries can also be caused by other bacteria, including members of the mitis, anginosus and salivarius groups of streptococci,Propionibacterium, Enterococcus faecalis and Scardovia.

Streptococcus mutans

Streptococcus mutans are the most cariogenic pathogens as they are highly acidogenic, producing short­chain acids which dissolve hard tissues of teeth.

They metabolize sucrose to synthesize insoluble extracellular polysaccharides,which enhance their adherence to the tooth surface and encourage biofilm formation.

The reactions are catalyzed by three isozymes of glycosyltransferases.

The most important mutans streptococci isolated from tooth caries samples are S. mutans and S. sobrinus.

S. mutans is more cariogenic than S. sobrinus because of specific cell­surface proteins, which aid in its primary attachment to the tooth. S. sobrinus lacks such proteins.

S. mutans is able to metabolize a number of sugars and glycosides such as glucose, fructose, sucrose, lactose, galactose,mannose, etc.

In the presence of extracellular glucose and sucrose,S. mutans synthesizes intracellular glycogen­like polysaccharides (IPSs).

S. mutans produces also mutacins (bacteriocins), what is considered to be an important factor in the colonization and establishment of S. mutans in the dental biofilm.

Streptococcus Sobrinus

S. sobrinus has been implicated in caries development particularly in instances where caries development appears to be independent of S. mutans.

It is interesting that S. sobrinus displays higher acid production and acid tolerance compared to S. mutans.

Lactobacilli

Among the Lactobacillus rods in the oral cavity occur: L.acidophilus, L. casei, L. fermentum, L. delbrueckii, L. plantarum,L. jensenii, L. brevis, L. salivarius and L. gasseri.

Lactobacilli are divided into two main groups: homofermentative which in the fermentation process of glucose produce mainly lactic acid, e.g.

Lactobacillus casei, Lactobacillus acidophilus, heterofermentative which in addition to lactic acid produce acetate, ethanol and carbon dioxide, e.g. Lactobacillus fermentum.

Lactobacilli are isolated from deep caries lesions but rarely just before the development of dental caries and in the early tooth decay.

It is believed that they are pioneering microorganisms in the caries progress, especially in dentin.

Veillonella

It is a Gram­negative cocci which is commonly found in plaque.

It utilizes lactic acid by converting it to propionic acid and other weak acids.

Factors Promoting Dental Caries
Tooth Factors

• Tooth factors such as composition of tooth, structure of enamel, morphologic characteristics of tooth, position of tooth are the caries promoting factors.
• In composition of tooth surface enamel is more resistant to caries than subsurface enamel. This is because surface enamel is highly mineralized.
• Presence of deep, narrow occlusal fisures, buccal and lingual pits leads to the development of dental caries.
• Teeth which are malaligned, out of position, rotated or otherwise not normally situated are difficult to clean and favor accumulation of food and debris which lead to dental caries.

Salivary Factors

• Salivary factors such as composition of saliva, pH, quantity, viscosity and antibacterial factors in saliva play role in promotion of dental caries.
• When salivary flw rate is normal it leads to cleaning of bacteria from tooth surface and reduces the chances of dental caries while in xerostomia incidence of caries is high.
• As viscosity of saliva is increased deposition of plaque increases because thick saliva does not produce proper cleaning action.
  If viscosity of saliva is decreased normal contents of mineral is less and saliva does not produce anticaries functions.
• As the buffering action of saliva is decreased acid demineralization of tooth by dental caries become high this is because low concentration of salivary bicarbonate does not cause neutralization of acids which is produced by cariogenic bacteria.
  • Salivary enzymes such as amylase leads to breakdown of starch (which is a residual carbohydrate) from tooth surface which is washed easily from mouth. As if levels of salivary amylase are too low this will lead to dental caries.
  • Certain antibacterial agents are found in saliva such as lysozyme, thiocyanate, etc. These agents leads to the destruction of cariogenic bacteria by anti­bacterial action and reduces caries incidence. As if defiiency of such agents is present this will lead to the promotion of dental caries.
  • Salivary immunoglobulins such as IgA and IgG inhibit S. mutAns by facilitating destruction process through phagocytosis and lead to decrease in dental caries. If salivary immunoglobulin levels are decreased this leads to the increase in dental caries.

Diet Factors

• Diet factors such as physical nature, carbohydrates, vitamins and floride content play important role.
• More and more intake of soft and sticky food increases possibility of dental caries.
• Foods rich in carbohydrates lead to the dental caries.
• Physical nature of diet is important as soft refied foods cling to the teeth and are not removed because of lack of roughage. This collection of debris is due to reduction in mastication because of softness of diet. This leads to dental caries.
• Fluoride ions limit rate of carbohydrate metabolism by cariogenic bacteria and reduce acid attcks on tooth. Lagging of floride in diet leads to the increase incidence of dental caries.

Dental plaque

• Dental plaque is the soft, non­mineralized bacterial deposit which forms on teeth and dental prosthesis that are not adequately cleaned.
• Plaque harbors cariogenic bacteria on tooth surface.
• Rapid production of high amount of acids in plaque occur through fermentation of carbohydrates by cariogenic bacteria.
• Plaque hold the acids on tooth surfaces for longer duration.
• Increased thickness of plaque does not allow salivary buffrs to enter into neutralize the acids produced by the cariogenic bacteria.

 

Question.13. Write short note on sequel of dental caries.

Answer. Following is the sequel of dental caries

 

Question.14. Write short answer on role of carbohydrates in dental caries.

Answer. Fermentable dietary carbohydrates play an important role in the causation of caries, e.g. glucose, fructose and sucrose. Among them sucrose is more potent.

• Cariogenic carbohydrates are dietary in origin, as uncontaminated human saliva has negligible amount of carbohydrates regardless of blood sugar level.
• Salivary carbohydrates get bound to proteins as well as other compounds. They are not readily available for microbial degradation.
• Cariogenicity of dietary carbohydrates varies along with frequency of ingestion, physical form and the chemical composition, route of administration and presence of other food constituents.
• Sticky solid carbohydrates are more cariogenic as compared to their liquid form.
• Carbohydrates which get readily cleared from oral cavity via saliva and swallowing is less conducive to caries than to those which get slowly cleared.
• Polysaccharide gets less easily fermented by plaque bacteria as compared to monosaccharides and diasaccharides.
• Organisms of plaque release less acid from sugar alcohols,sorbitol, xylitol, mannitol. This implies that all these carbohydrates are non cariogenic.
• Carbohydrates which are fed through stomach tube or intravenously do not contribute to decay as they are unavailable for microbial breakdown.
• Food consisting of high fat, carbohydrate, protein or salt decreases oral retentiveness of carbohydrates.
• Refined pure carbohydrates are more carious as compared to crude carbohydrates which is complexed with other food elements which are capable of reducing enamel solubility or possessing antibacterial properties.