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Daranee Versluis-Tantbirojn DENT 5302 TOPICS IN DENTAL BIOCHEMISTRY Dental caries • The caries process • Dietary factor and cariogenic aspects of dental plaque • Plaque fluid and the caries process Fluoride in dentistry • Fluoride and dental caries • Anticario mechanisms of fluoride • Fluoride metabolism • Fluoride toxicity • Application of fluoride (& Ca P) in caries control measures
DENT 5302 TOPICS IN DENTAL BIOCHEMISTRY 28 March 2007 The Caries Process Objectives: • Nature and character of dental caries • Factors influencing the caries process • Development of early caries lesion in enamel • Dentin caries
Outline • Nature of dental caries History & Epidemiology • Key features of dental caries Multi-factorial Site specific Dynamic • Demineralization-Remineralization • Formation of early enamel lesion • Microscopic features of early enamel lesion • Caries free vs Caries controlled • Dentin caries
1950 Epidemic 20 15 10 5 0 2000 1000 0 1000 2000 Carious Teeth (%) Industrialize Roman Percentage of carious teeth in English population
Less than high school High school At least some college Total children Dental caries: the most prevalent infectious disease • 5x > childhood asthma ; 7x > hay fever • Affects 85% of adults (>18 years old) in the US • 80% of caries occurs in 20% of the population www.surgeongeneral.gov/library/oralhealth/ Underprivileged population? Evans CA, Kleinman DV (2000). The Surgeon General's report on America's oral health: opportunities for the dental profession. J Am Dent Assoc. 131: 1721-8.
75% of children aged 5-11 years old were caries-free • 70% of 12-17 years old had caries • 94% of dentate adults (18 years or older) had caries The nature of caries has changed: Rapidly progressing childhood disease Slow but steadily progressing disease in adulthood
Discussion: Give some examples of using knowledge and understanding of dental caries in your future dental practice.
Characters of caries Dental caries is multifactorial Traditional concept Cariogenic bacteria (dental plaque) Diet: Fermentable carbohydrate Host factors: Tooth Saliva
Characters of caries Dental caries is multifactorial Social class Modern concept Flow rate Composition Buffer Education Income Saliva Fluoride Microbial species Biofilm Tooth Biological determinants Genetic Time Composition Sugar Frequency Diet Behavior Attitude Socio- economical factors Knowledge
Characters of caries Dental caries is site specific Dental caries: Localized destruction of tooth tissues Erosion Why localized? • Tooth morphology affects plaque accumulation • Metabolism of microorganisms in dental plaque (biofilm) • Microenvironment (plaque composition, thickness, diffusion properties) • Access to dietary substrates, saliva, anticaries agents
Characters of caries breakfast coffee break Net loss Mineral content lunch snack dinner brushing snack brushing midnight noon 6 pm 6 am Dental caries is dynamic Demineralization vs Remineralization
Brown spot (Arrested lesion) • Change in microenvironment • Reduced plaque accumulation • Access to saliva www.recaldent.com
Formation of early enamel lesion plaque saliva sound enamel subsurface lesion acid H+ + apatite diffuse & dissociate H2O OH- Ca2+ PO43- Ca2+ + PO43-+ OH- HPO42- F- surface zone (repair)
Microscopic features of early enamel lesion 1 2 3 2 3 4 1 2 3 4 1 4 1. Surface Zone Intact surface 20-100 mm thick, <10% mineral loss 2. Body of the Lesion Largest zone, highest mineral loss (24%) 3. Dark zone Very small pores, <10% mineral loss 4. Translucent zone Advancing front, 1% mineral loss
Clinical appearance: White spot lesion • First clinical signof enamel caries lesion • Not that early! • 300 – 500 mm depth to be visible Why are we interested in early caries lesion? • At this stage the lesion is reversible • Fluoride and preventive treatment are most effective at this stage
Early carious lesions are reversible Age 8 Age 15 Sound enamel 93 74 37 15 White spot 72 26 4 9 Cavitated lesion 19 19 111 sound enamel 41 white spots 32 cavitated lesions (Baker-Dirks, 1966) • Study done in community with water fluoridation • Only 9 of 72 white spot lesions became cavitated after 7 years • More than half of early lesions regressed to ‘normal’ enamel
Dr. J.P. Byers White spot lesions around orthodontic bracketts Dr. J.P. Byers
Discussion: ‘caries-free’ vs ‘caries-controlled’ Is there a ‘caries-free’ individual? Q1 Do you have any cavities or fillings Q2 Do you think you have demin-remin periods?
Progression of Carious Lesion How long? Proximal lesions in permanent teeth can take 3-4 years through enamel, unless in caries active individuals. (Pitts, 1983) 0 1 2 • Median survival time from stage 2 to 3 was ~ 3 years • Late teen Danish population • From 2 – 3: 9.2 surface % per year • From 3 – 4: 2.3 surface % per year 3 4
Dentin caries Microscopic features carious dentin A = zone of decomposed dentin B = zone of bacterial invasion C = zone of demineralization D = sclerotic dentin E = reparative dentin Outer carious dentin Inner carious dentin Progression of dentin caries • Demineralization of inorganic substance • Breakdown of organic matrix by proteolytic enzymes • Bacterial invasion
70 - 60 - 50 - 40 - 30 - 20 - 10 - Sound dentin Outer carious dentin infected nonremineralizable nonvital insensitive Knoop Hardness Number Pulp wall 3000 mm DEJ 1000 2000 Crystals in tubule lumen Bacteria Odontoblast Dentin caries Two layers of carious dentin Inner carious dentin uninfected remineralizable vital sensitive Sub- trans parent layer Turbid layer Transparent layer Fusayama T, Okuse K, Hosoda H. J Dent Res. 1966;45:1033-46. Relationship between hardness, discoloration, and microbial invasion in carious dentin.
Discussion: What do you learn today that can be used in future practice? 1. Why underprivileged population have more caries? 2. What should we do with white spot lesion? 3. How much carious dentin should be removed?
Recommended references • 1. Clarkson BH. Introduction to Cariology. Dent Clin North Am 1999;43(4):569-578. • 2. Zero DT. Dental Caries Process. Dent Clin North Am 1999;43(4):635-664. • 3. Featherstone JD. The science and practice of caries prevention. J Am Dent Assoc 2000;131:887-899. • 4. Gordon Nikiforuk. Understanding Dental Caries 1. Etiology and Mechanisms, Basic and Clinical Aspects. Basel; New York: Karger 1985. Chapter 10. • Gao W, Smales RJ, Yop HK. Demineralisation and remineralisation of dentine caries, and the role of glass-ionomer cements. Int Dent J 2000;50:51-56. • 6. Fejerskov O. Changing paradigms in concepts of dental caries: Consequences for oral health care. Caries Res 2004;38:182-191.