Saliva and Dental Caries

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Saliva and Dental

CariesDr.Ghada Maghaireh

BDS,MS,ABOD


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Anatomy

Major salivary glands

Minor salivary glands


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The Oral Cavity and Saliva

Whole saliva is the mixed fluid in the mouth incontact with the teeth and mucosa whichderived from the major salivary glands, minor

salivary gland and certain gingival cervicularfluid.

The daily production of saliva ranges between0.5 and 1.0 liter and it is composed of more than99% water and less than 1% solids (proteins andelectrolytes).


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Functions of Saliva

Rinsing effect.

Solubilization of food taste-substances.

Bolus formation.

Food and bacterial clearance.

Dilution ofdebris.

Lubrication of oral soft tissue.

Facilitation of mastication, swallowing and speech.

Protection of the teeth by neutralizationof acid by bufferingaction and by maintaining supersaturated calcium phosphate

concentrations and by participating in pellicle formation.


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Salivary Clearance

Salivary clearance or oral clearance is aphysiological process in which saliva dilute and

eliminate substances to the oral cavity.

Bacteria: Bacteria is removed from the mouth tothe stomach by saliva.

Food debris: Saliva clears the mouth from fooddebris.


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Symptoms of Xerostomia

1. The oral mucosa is thin and pale and withoutthe usual glistening appearance.

2. The saliva appears thick and foamy, and formwhitish threads on mucosa.

3.

Xerostomic patients suffer from symptoms ofburning mouth, taste disturbances and dryeyes.


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Causes of Salivary Gland Hypofunction

1. Medication with a side effect of decline insalivary secretion rate (e.g. antidepressants,

diuretics, antihistamines, antihypertensive,antiemetics and narcotics).

2. Radiation therapyto the head and neck area.

3. Autoimmune diseases (e.g. rheumatoid arthritis,

Sjogrens syndrom, sarcoidosis).


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Effect of Age on Salivary flow Rate

Age dose not notably affect salivary flow in aclinical situation.

The flow rate of stimulated whole saliva dose notdecline with age.

Decrease in secretion of submandibular and minorsalivary glands which may explain the feel of drymouth in elderly even when the stimulated whole

salivary flow rate shows normal values.


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Components of Saliva

Water

Organic Components

Inorganic Components


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Inorganic Components of Saliva

Hydrogen ion

Calcium

Inorganic phosphate

Fluoride


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Hydrogen ion

Sources of hydrogen ions: secreted from the gland inthe form of organic and inorganic acids, produced bythe oral microorganisms, or taken to the oral cavity.

The acid-base balance of the oral cavity is verycomplicated and variable.

After an intake of fermentable carbohydrate:Locations of the oral cavity with very highconcentrations of hydrogen ions will present low pH,

while other locations may have lower hydrogen ionsconcentration due may be to access to saliva will have

high pH.


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Hydrogen ion

The pH of saliva depends on secreted acids and basesmostly the bicarbonate ion.

The bicarbonate ion concentration in unstimulatedsaliva is one-tenth of the plasma level.

The more the salivary flow is stimulated the closer the

salivary bicarbonate to the plasma concentration. Therefore, the pH of stimulated and unstimulated saliva

can differ up to 2 pH units.


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The Buffering Ability of Saliva

The most important buffering system in saliva isthe carbonic acid/bicarbonate system.

The bicarbonate has the ability to take up thehydrogen ions to form carbonic acid.

The enzyme carbonic anhydrase, which is presentin saliva, catalyze the reaction forming carbondioxide from carbonic acid.


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The Buffering Ability of Saliva

After a certain amount of acid has been added to saliva,the pH starts to fall rapidly.

This rapid decrease is caused by a depletion of the

bicarbonate and inorganic phosphate ions.

Around pH 4, the buffering ability of saliva is mainlycaused by macromolecules such as proteins.

The buffering of saliva is complicated by transport ofbuffer substances between the many compartments ofthe oral cavity.


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Calcium

Salivary calcium is distributed as free, ionized calcium and boundcalcium depending on the salivary pH value.

The free, ionized calcium is important in caries (establish theequilibrium between the calcium phosphate of the dental hard tissue

and the surrounding).

In normal saliva, ionized calcium is about 50%, as pH decrease, theionized form increase.

At pH value below 4 most of the salivary calcium is in ionized form.

The amount of calcium in the pellicle layer is higher than that in thesaliva.


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Calcium

Calcium caries two positive charges which can

bind by chelation to certain chelating agents (e.g.citrate in citric acid found in citrus fruits orjuices).

This may result in the dissolution of the calciumphosphate of the tooth surface.


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Inorganic Phosphate

The inorganic phosphate found in saliva consists ofphosphoric acid, primary, secondary and tertiaryphosphate ions.

The concentrations of total inorganic phosphatedecreases with increasing flow rate.

The most important function of inorganic phosphate is

participating in the maintenance of the tooth structure. Buffering of the saliva.

Phosphate is a nutrient to the oral microflora.


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Fluoride

The Fluoride concentration in saliva ranged0.01-0.03 ppm, which considered negligible.

Fluoride concentration in saliva depend onfluoride in the environment (drinking water,dentifrices and other products).

Fluoride diffuse from the saliva into the plaquecausing elevation of fluoride level in plaque.


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Organic Components

Mucins and other glycoproteins.: Lubricating and maintaining amoist mucosal surface. Help protecting the mucosa from infectionand prevent bacterial adhesion to tooth structure.

Statherin and acidic proline-rich proteins: Theses are calcium-bindingproteins that inhibit spontaneous precipitation of calcium phosphatesalts on tooth.

Amylase : Amylase split starch into maltose, maltotrios and dextrin.Clear food debris containing starch in the mouth by which acids can

form, so starch has some cariogenic potential.

Other antimicrobial proteins: The most of these proteins can inhibitthe metabolism, adherence, and the variability of cariogenicmicroorganisms.


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Dental Caries and the Quantity of Saliva

Reduced ability to produce saliva is associated with increased cariesexperience.

In patients with reduced quantity of saliva the mechanistic andclearing properties of saliva are impaired.

The unstimulated flow rate has been found to be more importantthan the stimulated.

The buffering capacity of saliva depends on the concatenation ofbicarbonate which is strongly dependent on the secretion rate (the

lowest concentrations are found at low secretion rates).

High lactobacillus counts are marks of low saliva production andnumber of lactobacilli in saliva has been found to correlate positively

with caries activity.


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Effect of Salivary Gland Hypofunction

The lack of saliva leads to rapidly developingcaries in atypical places such as lingual, incisal,and cuspal tooth surfaces.

Patients with impaired salivary secretion shouldreceive an individual prophylactic dentalprogram including intensive caries preventivecare.


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Saliva and Caries

Chewing Action:- Stimulate saliva flow.

- Stimulated saliva has higher buffer capacity.

- Food (fermentable carbohydrates) is more rapidly cleared.

- Acids are neutralized and cleared more rapidly.

Saliva and Dental Caries

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