Aetiology of Dental Caries PDF

Aetiology of Dental Caries Oral and Dental Science Josh Hudson GDC Learning Outcomes: 1.1.4 Explain aetiology and pathogenesis of oral disease 1.1.11 Recognise psychological and sociological factors that contribute to poor oral health, the course of diseases and success of treatment 1.2.7 Discuss...

Aetiology of Dental Caries Oral and Dental Science Josh Hudson GDC Learning Outcomes: 1.1.4 Explain aetiology and pathogenesis of oral disease 1.1.11 Recognise psychological and sociological factors that contribute to poor oral health, the course of diseases and success of treatment 1.2.7 Discuss the importance of each component of the patient assessment process 1.14.5 Explain the role of a dental therapist in restoration of teeth Intended Learning Outcomes By the end of the session you will be able to; Define dental caries Explain the aetiology of dental caries List and describe the 4 aetiological factors leading to dental caries List the evidence available to support the proposed aetiologies Why do we lose our teeth? Why do we lose our teeth? Periodontal Disease Why do we lose our teeth? Trauma Why do we lose our teeth? Elective Why do we lose our teeth? Caries The Burdon of Dental Caries So what? Why should I care? Why does it affect me? To reduce carious tooth loss there are multiple factors we as professionals need to be able to do; Prevent Dental Caries Treat Dental caries Neither can be achieved without understanding dental caries What is the carious process? “A localised, chemical dissolution of a tooth surface brought about by metabolic activity in a microbial deposit (a dental biofilm) covering a tooth surface.” Kidd, E and Fejershov, O. 2016. Essentials of Dental Caries 4th Edition What is the carious process? “The term dental caries is used to describe the results –signs and symptoms – of a localised chemical dissolution of the tooth surface caused by metabolic events taking place in the biofilm (dental plaque) covering the affected area.” Fejerskov O, Nyvad, B and Kidd E. 2015. Dental caries 3rd Edition What is the carious process? “Dental caries is a reversible (in its earliest stages) progressive disease of the dental hard tissues (enamel, dentine, cementum) caused by the actions of bacteria upon fermentable carbohydrates in the plaque biofilm on tooth surfaces.” Baerjee A and Watson T. 2015. Pickard’s Guide to Minimally Invasive Operative Dentistry 10th Edition Main points Involves Involves microbes & Affects all chemicals their hard tissue metabolites Involves Often Involves Can be fermentable localized dissolution reversible Carbohydrates What are the aetiological agents for caries? Aetiology Susceptible tooth surface Plaque Bacteria Time Fermentable Carbohydrate Aetiology Caries Susceptible tooth surface Plaque Bacteria Time Fermentable Carbohydrate All Encompassing Definition “A localised, chemical dissolution of a susceptible tooth surface over time brought about by metabolic activity on fermentable carbohydrates in a microbial deposit (a dental biofilm) covering a tooth surface.” True Extent 1. Susceptible Tooth Surface As mentioned in the definitions, all dental hard tissues are susceptible to some degree Some more than others (see histopathology of dentine and enamel caries and fluoride lectures) However, some areas of the tooth have factors that make them more susceptible to dental caries. This is generally related to the ability for plaque biofilm to accumulate Which areas of the tooth are considered ‘susceptible’? What areas of the tooth are considered ‘susceptible’? Defective margins Pits and fissures Smooth surface Proximal Ledges/overhangs 2. Fermentable Carbohydrate Bacteria within the plaque biofilm need food to survive. Sugars present in the diet provide the substrate for oral commensal bacteria to metabolise and produce lactic acid. 2. Fermentable Carbohydrate Not all carbohydrates are equally cariogenic Sucrose is most rapidly metabolised to produce extracellular polysaccharides compared to glucose, fructose or lactose Complex carbohydrates (starch) are not completely digested within the mouth 2 different kinds of sugars 1. Intrinsic sugars 2. Extrinsic sugars 2. Fermentable Carbohydrate Naturally occurring sugars or sugars contained within unprocessed foods are considered intrinsic Packaged intracellularly Present in fruit and vegetables Only become available when processed Lactose is an example but not contained within a cell 2. Fermentable Carbohydrate Extrinsic sugars are not bound within a cellular structure Glucose – metabolised Sucrose – table sugar in the body to produce energy 2. Fermentable Carbohydrate Extrinsic sugars are not bound within a cellular structure Fructose – honey Starch – breads, wheat etc have large chains of glucose molecules. These are only slightly broken down by salivary amylase over time 2. Fermentable Carbohydrate In Summary; Simple sugars (e.g. glucose, fructose and sucrose) diffuse rapidly into the plaque and are metabolised quickly by bacteria to produce acid hence… Cariogenic! Complex carbohydrates such as starch (rice and potatoes) are not completely digested in the mouth and hence… Less Cariogenic! 2. Fermentable Carbohydrate 2. Fermentable Carbohydrate What type of sugars? 2. Fermentable Carbohydrate Bacteria + Simple sugars = Acid What does ‘critical’ pH mean? 2.Fermentable Carbohydrates When the PH becomes acidic, the saliva draws out these ions from the hydroxyapatite causing tooth surface dissolution Saliva becomes supersaturated with phosphate & hydroxide ions in acidic environments The critical PH is the point below which the tooth tissue begins to lose mineral to saliva or plaque An acidic PH causes demineralisation of enamel and dentine 2. Fermentable Carbohydrate Critical pH enamel is 5-5.5 Critical pH dentine is 6-6.5 2. Fermentable Carbohydrate Hydroxyapatite Free minerals Ca5(PO4)3OH 5 Ca2+ + 3 PO43- + OH- When pH > Critical pH = REMINERALISATION When pH < Critical pH = DEMINERALISATION (CARIES) Acidic Environment = Shifts to the right and tooth dissolves Neutral Environment = Shifts to left and tooth remineralises Importantly, the mineral can return to the tooth from the saliva when pH returns to normal as long as this hasn’t been removed or washed away (an important concept to understand prior to fluoride lectures) 3. Time We know time plays a big part in the carious process Without all of the other factors being present for a period of time, caries will not occur Need to consider frequency of acid attack; Grazing, snacking, suckling 2-3 hours apart minimum Aim for 4 acid attacks a day Regular frequency = increased time! Aim to reduce frequency – diet analysis! Why does time or frequency of intake matter? 3. Time But why does this all matter? Stephan Curve 3. Time In studies in the 1940’s, Stephen showed dental plaque had a resting pH of 6.5-7 When exposed to fermentable sugars, such as sucrose, fructose or glucose, the pH fell rapidly to a pH below 5 It then took up to an hour to return to normal Plotting this graph became known as a Stephan’s curve 3. Time Infrequent attacks mean less time below critical pH and less demineralisation (lower caries risk) Frequent attacks mean more time below the critical PH and hence more demineralisation (higher caries risk) 4. Plaque Bacteria The other factor needed is plaque bacteria. Please refer to your lectures on biofilms for further information on this area. 4. Plaque Bacteria As the PH drops, this favours certain caries causing bacteria (lactobacillus and strep mutans) causing the plaque biofilm microbial population to shift Also, as the biofilm becomes thicker, there is less oxygen in the deeper layers favouring anaerobic bacteria. This also causes the plaque biofilm microbial population to shift Anaerobic bacteria produce more lactic acid This causes a further drop in PH at the tooth surface causing demineralisation Summary Caries develops on a susceptible tooth surface which is normally covered in plaque biofilm Sugar present within the diet provides the substrate for oral commensal bacteria to metabolise and produce lactic acid The acid demineralises the enamel surface causing calcium ions to pass into the surrounding plaque Mutans streptococci are the bacteria commonly associated with enamel caries The remineralisation/demineralisation see-saw will favour remineralisation if the frequency of intake is more than ever 2-3 hours Summary If sugar is consumed at this frequency or less, the calcium ions in the plaque will move back into the tooth If consumed more frequently than this, more calcium ions will pass into the plaque than are readded and these are lost though swallowing of saliva If this process continues over time, the enamel becomes porous and white spot lesions develop How do we know this is all true? The Evidence Orland 1954 – Experiments with germ free rats demonstrated bacteria needed for caries to exist – Plaque biofilm Orland – Experiments with non germ free rats fed a sugar free diet to show sugar substate is needed for caries – fermentable carbohydrate Vipeholm study 1952 – Demonstrated sugar type and frequency is associated with caries - Time Tristan de Cunha – South Atlantic Island caries free until Americans imported cariogenic food and drink – fermentable Vipeholm Study (1945-1952): Patients in a Swedish mental hospital (no informed consent so now considered unethical) Division of patients into several groups giving various amounts or sugar with varying frequencies Subjects given the most cariogenic food (toffees) with the greatest frequency (meals and between meals) developed the most caries Those given less cariogenic food (e.g. bread) less frequently (meals only) developed less caries Those with increased frequency demonstrated more caries Demonstrated caries depends on substrate and time Thank You!