1-Diet is one of the most important factors that contributes in the development of dental caries. Like fermentable carbohydrates.2-The change in plaque pH is represented graphically over a period of time following the sucrose rinse. Such a graph is called a "Stephan's curve"3-"Stephan's curve" Gives the relation between the drop in pH and the ingestion and intake of sugars and carbohydrates mainly the sucrose.4-A rinse of sucrose for seconds can cause a great drop in the pH lasts between twenty minutes to several hours.5-The most important interval on the X-axis "Time in minutes" is that facing the curve below the critical pH "5.5" point on the Y-axis.6- the critical demineralization level (pH 5.5 to 5.0) are considered Acidogenic food.7-Since the caries is a multifactorial disease, there are many factors that are required for the development of caries not only the acidogenisty of food.8-Acidogenicity: is the ability of the food to produce acids and lowering the pH below the critical point.9-Cariogenicity: is the ability of the food to produce acids and lowering the pH below the critical point causing caries along with the other factors specific to the individual who eats the food and the food itself10- factors cause caries :a. Predominant bacterial flora.b. Saliva: Flow rate and buffering capacity.c. Fluoride availability.d. Oral hygiene.e. Individual immune factors.f. Food: quantity, nature and frequency."Will be discussed below"11-Sucrose: is a disaccharide that is the most common form of sugarconsumed by humans.12-Sucrose is considered the most blamed sugar for caries formation..13-Sucrose enhances the colonization and growth of MS in dental plaque more than other monosaccharides and disaccharides.14- High Fructose Corn Syrup (HFCS consists mostly of (50% fructose and 50% glucose).15-These sugars do not cause any production of extracellular polysaccharides that enhance more colonization of bacteria in the plaque of the tooth surface inside the oral cavity and therefore its cariogenic potential has been estimated to be 20-25% less that of sucrose.

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16-The starch products are fermented and degraded mainly in thestomach not in the oral cavity, but they cause lowering the ph for alonger time.17- sucrose is still has higher cariogenic potential than other sugars.18-Because of the production of extracellular polysaccharides depends on sucrose and that smooth surface caries can only develop with plaque thatadheres by means of extracellular polysaccharides (plaque formation).

19-Frequent between-meal snaking on sugars or processed starchcontaining sugars increases plaque formation and extends the length of time that bacterial acid production can occur where enamel and dentin demineralization happens.20-Peanuts is an example of food that can neutralize the acidic condition back to its normal21- Protein, fat, phosphorous and calcium inhibit caries in rats.Aged natural cheese has been shown to be Cariostatic.22-The protective effect of cheese is attributed to their texture thatsimulate salivary flow and their protein, calcium and phosphate content that neutralize plaque acids.23-Lipids Seem to accelerate oral clearance of food particles.24-Some fatty acids in low concentrations inhibit growth of MS.25-FluorideIncreases the tooth’s resistance to acid attack, and enhances remineralization of carious lesion.26-Milk "unsweetened" is anti-cariogenic since it contains protective factors due to the presence of calcium, phosphate, casein and lipids.27-The sugar in milk is lactose, which is the least cariogenic sugar.28-Despite being one of the most sources of sugar, it is anti-cariogenic.

Caries in Enamelintercrystalline spaces more water in these spaces become more porous. Clinically by naked eyes White spot lesion

the earliest microscopic evidence of caries in enamel. Best seen on dried tooth as a small, opaque, white area.

Later on brown or black in color if not arrested then cavitation happens dentine develops caries faster

4 zones based on its histological appearance Zone 1 : TZ

Zone 2 : The dark zone (DZ) -superficial to the TZ Toward the base of the lesion -More porous than the translucent zone.

• Zone 3 : The body of the lesion(B) - The largest portion of the lesion. - Superficial to DZ. -Increase in porosity from the peripheries to the center. - Most porosity in the center.

• Zone 4: the surface zone (SZ). - Intact unaffected surface layer that cover the small lesion. - High degree of mineralization than subsurface enamel. ''That is why it is called white spot lesion'' 

- If the lesion progress the surface layer will be destroyed and a cavity formed.

• Cavitation :

IF the lesion progress, the surface zone (Zone 4 ) breaks down and a cavity forms.

- When a cavity is formed there will be NO reverse process "Remineralization, only treated by fillings and restorations.

* Dentine caries As caries reaches the enamel dentine junction , the caries spread laterally and RAPIDLY to the junction because the dentine is more organic in nature and has less minerals than the enamel .

- Sound enamel appears to be undermined by the process of dentine .

-Undermined enamel is brittle and can be fractured producing a large cavity

The Classification of Dental caries.no universally accepted classification of (caries).clinical features dental caries may be classifiedin many ways:1. Morphology (Anatomical site of the Lesion).2. Prior condition of the tooth.3. Dynamics (Rate of destruction of the lesion).4. Extent of the lesion.5. Chronology (age).

1. Classification Based on Morphology (according to the anatomical site).

-Crown caries (Enamel) cementoenamel junction 'CEJ' Root caries (Cementum).Enamel/Crowncaries, Pits or fissures( occlusal caries)

_ Occlusal caries usually appears earlier in life before smooth surfacemore easily in irregular surfaces ( Pits and fissures) and they are noteasily cleaned with more time therefore the carious process is initiated.

_Smooth surfaces caries.

-Interproximal surface caries

-Cervical and gingival surface called Self Cleansing surfaces

_Root caries.must start at root portion predominantly found in teeth of older age group with significant gingival recession leading to exposed root surfaces which means exposed root cementum and dentine.-The bacterial flora causing the root caries may be different from the flora that initiate enamel caries.

2. Classification Based on Prior condition of the tooth.

_Primary (initial) Caries:first time, regardless of progression or extent.Denotes lesion on unrestored surfaces.

_Secondary (Recurrent ) Caries: margins of an existing restoration, regardless of extension or progression.•Denotes lesion developing adjacent to fillings or restorations._Residual caries:It is a demineralized tissue left in place (cavity) before a filling is placed.

3. Classification Based on Severity and Rate Progression.

•Acute Caries (Rampant caries) : characterized by sudden, rapid, and almost uncontrollable destruction of teeth Because there are multiple active carious lesions occurring in the same patient at the same time:

•Chronic Caries Severity: much more than the time for the acute caries and Much smaller than acute caries ''Because it is slower''

•Active Caries : Describe lesion that progressively destroys more tooth structure, Ongoing.

•Arrested Caries:•Occurs when the active degradative process is interrupted or ceases. Some re-mineralization and discoloration usually characterize it.

4. Classification Based on Extent of the lesion.- Size of lesion or where it reaches.Incipient caries:The lesion is confined to enamel and doesnot penetrate the DEJ.

The early carious lesion on visible smooth surfaces of teeth is clinically manifested as a white, opaque region.

An important feature of the early lesion is the apparently intact surface layer overlying subsurface of demineralization.

-Can be stopped "Called arrested caries''.-Can be remineralized.-Advanced caries:-The lesion penetrates the DEJ.-Cavitation happens.-Can't be remineralized.-Creates a lesion that usually requires restoration.

5. Classification based on Chronology (age).

-Infancy caries.•The four maxillary anterior incisors are affected first; these teeth areanatomically positioned in the mouth that is frequently bathed by afeeding formula. *before the molars.

It has been reported that prolonged and unrestricted night-time breastfeedingresult in increased caries rate.

Other names: Bottle caries or nursing caries or toddler who

Particular form of rampant caries in the primary dentition of infantsand young children. (Rapid and on the caries free surfaces.)

-Adolescent Caries.Acute exacerbation in caries rate is usually seen at 4-8 years of age and at 11-18 years of age.

The acute attack in the period of 11-18 years of age usually characterized as adolescent caries.

•The characteristic features of this type of caries are:- Lesions are in teeth and surfaces that are relatively immune to caries.-Caries free surfaces.-Lesions had relatively small opening in enamel with extensive undermining.-Carious lesion distributes under the enamel rapidly and demineralizes a high percent of the dentine inorganic content.---So the enamel here is called undermined enamel.- There is rapid penetration of enamel and extensive involvement of dentin.- Particular form of rampant caries "Rapid and on the caries free surfaces''.

1- Causes of dental caries: - Diet: Intake of sucrose. - Quantity and quality of saliva, the quality of tooth.- Microflora or microorganisms: Infection by a specific set of cariogenic bacteria within dental plaque.

2- To make the caries these causes come together with enough time.

3- The first isolation of cariogenic bacteria from caries lesions ,By Clark, 1924.

4- Discovery of Mutans Streptococci, abbreviated as (MS) which is a gram-positive bacteria .

5- (MS) is mostly involved in the initiation of dental caries.

6- Used to be called streptococcus mutans but now it is called mutans streptococci. ( The species then the name of the bacteria)

7- Streptococci .

- Not all the 25 present in the oral cavity.

8- The most prominent streptococcus found in the oral cavity include:

1. S. mutans. 2. S. sanguis. 3. S. mitoir. 4. S. salivarius. 5. S. milleri. 5. S. stands for streptococci.

9- Mutans streptococci form 39% of the total streptococci in the oral cavity.

10- MS does not colonize the mouth of infants prior to the eruption of teeth.

11- 6 months after the delivery the mouth will be free of MS because of no presence of teeth in this period

12- MS disappears from the mouth following extraction of all teeth for example old people who need full-mouth extractions "called clearance "

13- Infants most likely become infected from their parents by kissing him or feeding him with their spoon , because of the permanent contact with each other .

14- The scientist found that the MS bacteria in infants whose mothers' harbor higher levels of MS in saliva become colonized more rapidly than infants of mothers with low salivary MS levels

15- MS are transmitted vertically, from mother to child.

16- Mother’s with high caries experience tend to have children with high caries.

17- The genetic inheritance from both the mother and father has an influence on caries susceptibility of the child.

18- However, children's caries pattern more closely follows the mother’s, not the father’s caries experience because the mother takes care of the child more than the father.

19- MS does not colonize teeth uniformly. 20- The organism "MS" may be more frequently isolated from fissures and interproximal surfaces, so those areas most frequently involved in caries, than from buccal or lingual smooth surfaces.

21- in "fissures and interproximal surfaces" there are more accumulations of dental plaque.

22- the levels of MS depend on the accumulation of plaque not the surface of the tooth . 23- its suggested that MS does not spread readily from one tooth surface to another.

24- MS Classifications: serological and genetics.(( It depends on the local micro environment of the surface itself)) :

A. MS have been divided into 5 genetic groups based on DNA base composition and hybridization (I, II, III, IV, and V). B. Strains have also been divided into 8 serotypes designated a through h strains of MS isolated from individuals. C. In North America and Europe most commonly belong to genetic group I, serotype c and this differs according to races or nations.

25- Class I & III >>> from humans26- class II & IV >> from rats and hamesters , rare in humans27- class V >> only from wild rats 28- These classifications help in preventing caries programs by researchers.

29- Acidogenicity: fermentation >> CRIES PRODUCE ACID >> demineralization of the enamel >> initial carious process .

30- Aciduricity: is the ability of bacteria to grow and metabolize under highly acidic conditions since bacteria cannot stand acidic condition that affects the membrane of the bacteria and leave it to die.

31- Lower the pH to below "5.5, the critical pH*" which drives the dissolution of calcium phosphate (hydroxyapatite) of the tooth enamel (demineralization) .

32- The decrease in the pH inhibits the growth of beneficial bacteria.

33- Further lower the pH, promote progression of the carious lesion or the demineralization.

34- The capacity of oral bacteria to tolerate acidic environment is of a major importance to the ecology of plaque communication and is directly related to caries pathogenesis.

35- SM has constitutive acid tolerance (Aciduricity) properties: 36- MS has an enzyme called F-ATPase that can produce protons to keep the surrounding "Local" environment neutral.

37- The MS metabolize the sucrose (found in the fermentable carbohydrates that come from diets) producing the lactic acid which is responsible for lowering pH and demineralization of the enamel. 38- the most important substrate for the involvement of MS in the caries process is the (disaccharide sucrose = glucose + fructose).

39- MS dissimulates sucrose in 3 different pathways:

A- accompanied or followed by direct phosphorylation for energy utilization through the glycolytic pathway leading to lactic acid production.

- This lactic acid will be released to the environment lowering the pH below the critical and this will initiate the demineralization and the carious process, as well. - This pathway is called "Lactic acid production".

B- The sucrose will not be transported into the cell interior instead it will be converted extracellularly to adhesive extracellular carbohydrates polymers by cell bound extracellular enzymes.

- Extracellular carbohydrates polymers includes two types: a. Glucans b. Fructans.

- Extracellular carbohydrates polymers >> sticky >> this will enhance the adherence of more MS and accumulation of MS on the tooth surface , - The initiator for the carious process is lactic acid .

- This pathway is called "Synthesis of carbohydrate polymer".

C- The sucrose will be degenerated to free glucose and fructose by an enzyme called invertase. - The intermediary metabolites from sucrose enter the glycolytic cycle or maybe utilized in intercellular polymer synthesis in order to provide a reservoir for energy.

- This pathway is called "Invertase activity in S. Mutans".

Other types of bacteria associated with dental caries.

40- Lactobacillus is a Gram-positive rod-shaped bacteria. 41 - Lactobacilli are strong acid producers and are among the most Aciduric and Acidogenic bacteria. 42- Restriction of dietary carbohydrates intake or restoration of carious lesions often led to diminution of oral lactobacillus population.

. 43- Several types of filamentous organisms will initiate root caries in experimental animals. 43- Actinomyces and Rothia species have been found in dental plaque and root caries.

45- Veillonella is a Gram negative cocci.