Caries I 2021 PDF

‫بسم الله الرحمن‬ ‫الرحيم‬ Universit y 2022- Dental caries (I) By Prof. Dr. : NADIA LOTFY  Dental Caries Definition: It is progressive irreversible microbial disease of the calcified dental tissue Characterized by: 1- Demineralization of inorganic tis...

‫بسم الله الرحمن‬ ‫الرحيم‬ Universit y 2022- Dental caries (I) By Prof. Dr. : NADIA LOTFY  Dental Caries Definition: It is progressive irreversible microbial disease of the calcified dental tissue Characterized by: 1- Demineralization of inorganic tissue 2- Destruction of organic tissue  It is the most prevalent chronic disease affecting the human race. Once it occurs, its manifestations persist throughout life even the lesion is treated. It affects both sexes in all races, all social-economic traits and every age group. Requirements for development of dental caries A: Essential requirements: For caries to develop, some factors must occur at the same time: 1. A susceptible tooth. 2. Diet rich in fermentable carbohydrates. 3. Specific bacteria. 4. Dental plaque 5.Time  Contributing factors in dental caries These include A. Tooth 1. Composition( fluoride content) caries resistance) 2. Morphology: deep pits develops caries 3. Position: malalignment teeth develops caries B. Saliva 1. Composition: greater content of amonia caries resistance 2. pH: Low pH develops caries 3. Quantity: Xerostomia develops caries 4. Viscosity: thick saliva develops caries 5. Antibacterial factors. C. Diet 1. Physical factors Refined food develops caries 2. Local factors a. Carbohydrate content b. Vitamin content: Vitamin D,K and B6 reduce caries c. Fluorine content Enamel Hydroxyapat it e Fluoroapat it e  Etiology of dental caries No universally accepted opinion of etiology. Many theories have been proposed : I- Acidogenic theory (Miller’s chemico- parasitic theory). II- The proteolytic theory. III- The proteolysis - Chelation theory.  I- Acidogenic theory (Miller’s chemico- parasetic theory) It hypotheses that Dental decay consists of 2 stages: 1- Decalcification of calcified part. 2- Dissolution of residue. The acid is formed from the fermentation of sugar in the retained area of teeth. Acidogenic theory (Miller’s chemico- parasitic theory).  1) Role of Carbohydrates Tooth incubated with saliva + Sugar--- caries. Tooth incubated with saliva + meat ———> no caries Dietry CHOs is the origin since saliva contains negligible amount of CHO regardless its level in blood.  Factors affecting cariagenicety of CHOs 1) Type of CHOs monosaccharide give more caries as they are easily break down, diffuse rapidly into plaque and they are most frequently used. 2) Total amount of CHOs intake: Increased intake, increases caries activity 3) Frequent intake of CHOs between meals increases caries activity. 4) Texture of CHOs: Sticky CHOs increases caries as they remain attached to the tooth.  2) Role of micro organism Boiling of saliva & incubating it with sound tooth + CHOs—> no caries. So microorganisms must be present for caries production  Cariogenic bacteria Characteristics Of cariogenic bacteria: 1- Formation of acids (acidogenic). 2- Can live and grow in acid (aciduric). 3- Production of extra-cellular polysaccharides for formation of plaque for resisting dissolution.  Streptococcus mutans In early stages streptococcus mutans was isolated. Strongly acidogenic. Able to survive & continue to produce acid at low level of pH. It undergoes mutation from round to rod shape in different Ph. So, it is called mutants.  Streptococcus mutans  Able to produce adhesive, insoluble plaque  It has the ability to polymerize sucrose to give high molecular weight polysaccharide (dextran) Dextran is sticky, gelatinous substance that enable the microorganisms to adhere to the tooth and form the plaque that initiates caries in smooth surface.  2. Lactobacilli isolated from late stage dental caries. So, some bacteria are involved in initiation of caries & others for progression of caries Other cariogenic bacteria o Other streptococci e.g. strep. Sanguis, slivaries o Actinomyces, have a role in root surface caries & not in enamel caries.  3) Role of Acid It is formed by enzymatic breakdown of CHOs by bacteria. Acid formed is Lactic acid. Buteric acid may also be formed. Enamel Hydroxyapatite will become soluble in acidic environments. Enamel begins to demineralize at a pH 5.5 Acid should be localized to tooth surface for long period. This is done by dental plaque.  3.Role of dental plaque Dental plaque is a tenaciously adherent bacterial structure formed on tooth structure. It is soft, unmineralized, bacterial deposit which forms on teeth that are not adequately cleaned. It is removable by tooth brushing.  MECHANISM OF FORMATION 1- Deposition of a cell free layer ACQUIRED PELLICLE (salivary glycoproteins). This layer acts as nutrient for plaque bacteria. 2- Colonization of pellicle by bacteria. 3- Maturation of plaque by further colonization with filamentous and other bacteria.  Composition of dental plaque 1- Matrix : formed of : a) Water,80% b) protein: from saliva, bacteria. c) CHOs: in the from of polysaccharides formed from bacteria. Polysaccharides known as dextran d) Lipids: bacterial in origin. e) Inorganic components: Ca, phosphate, potassium Mg, Na, fluoride. 1- Bacteria: eg. Strepcoccus, filamentous and lactobacillus.  Role of plaque matrix 1) act as a diffusion limiting membrane, so retaining lactic acid for long period in high concentration. 2) slow down the entry of buffers from saliva. 3) contribute to adhesiveness. pH of plaque is 7.1 in caries free persons but 5.5 in persons with extreme caries.  4. Role of saliva in dental caries 1- Formation of pellicle from the salivary glycoprotein. 2- Washing effect. So (Xerostomia increases caries incidence) 3- Buffering effect. Depends on its bicarbonates & phosphate. 4- Saliva has antibodies that kills microorganisms 5- Other antibacterial substance like lysozyme, peroxidase & lactoferrin.  II- The proteolytic theory Enamel has some organic material e.g. E. lamellae and E. rod sheath. Microorganisms invade organic portion of E. and destroys the inorganic part and produce acid. This acid decalcifies the inorganic part of enamel  III- The proteolysis - Chelation theory Chelation: is a process of complexing of a metallic ion + complex substance—> highly stable compound. Examples are: 1. Chlorophyl: Protein + magnesium 2. Hemoglobin: Protein + Iron  bacterial attack organic part of enamel forming: 1- Chelates 2- Chelates unit with calcium ion from enamel leading to caries. Protein(organic substance of E )+C(from E) caries  The proteolysis - Chelation theory This theory solves the problem of initiation of caries, whether it is organic or inorganic. However, these theories do not solve some problems as: 1. Increase caries with increase sugar intake. 2. Increase lactobacillus count in high carious activity. Patients with high risk caries Patients about to undergo chemotherapy Patients who consume fermentable carbohydrates frequently Patients suffering from diseases of the autoimmune system. Pregnant patients Individuals taking medications that may affect the flow of saliva