Aetiology of Dental Caries GN PDF

Ae5ology of Dental Caries Oral and Dental Science Josh Hudson GDC Learning Outcomes: Study of the causes, origins or reasons for something - 1.1.4 Explain ae-ology and pathogenesis of oral disease 1.1.11 Recognise psychological and sociological factors t...

Ae5ology of Dental Caries Oral and Dental Science Josh Hudson GDC Learning Outcomes: Study of the causes, origins or reasons for something - 1.1.4 Explain ae-ology 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 pa-ent assessment process 1.14.5 Explain the role of a dental therapist in restora-on of teeth Intended Learning Outcomes By the end of the session you will be able to; DeDne dental caries Explain the ae-ology of dental caries List and describe the 4 ae-ological factors leading to dental caries List the evidence available to support the proposed ae-ologies 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? Elec5ve Why do we lose our teeth? Caries The Burdon of Dental Caries So what? Why should I care? Why does it aGect me? To reduce carious tooth loss there are mul5ple 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 dissolu0on of a tooth surface brought about by metabolic ac0vity in a microbial deposit (a dental bio;lm) covering a tooth surface.” Kidd, E and Fejershov, O. 2016. Essen-als of Dental Caries 4th Edi-on What is the carious process? “The term dental caries is used to describe the results –signs and symptoms – of a localised chemical dissolu0on of the tooth surface caused by metabolic events taking place in the bio;lm (dental plaque) covering the aCected area.” Fejerskov O, Nyvad, B and Kidd E. 2015. Dental caries 3rd Edi-on What is the carious process? “Dental caries is a reversible (in its earliest stages) progressive disease of the dental hard 5ssues (enamel, den5ne, cementum) caused by the ac5ons of bacteria upon fermentable carbohydrates in the plaque bioQlm on tooth surfaces.” Baerjee A and Watson T. 2015. Pickard’s Guide to Minimally Invasive Opera-ve Den-stry 10th Edi-on Main points Chemical dissolution Involves Involves microbes & AGects all chemicals their hard 5ssue metabolites Involves OTen Involves Can be fermentable localized dissolu5on reversible Carbohydrates What are the ae5ological agents for caries? Ae5ology Suscep5ble tooth surface Plaque Bacteria Time Fermentable Carbohydrate Ae5ology These four things need to occur together for dental caries to occur Caries Susceptible tooth surface Plaque Bacteria Time Fermentable Carbohydrate All Encompassing DeQni5on Includes all four agents “A localised, chemical dissolu5on of a suscep5ble tooth surface over 5me brought about by metabolic ac5vity on fermentable carbohydrates in a microbial deposit (a dental bioQlm) covering a tooth surface.” True Extent 1. Suscep5ble Tooth Surface As men-oned in the deDni-ons, all dental hard -ssues are suscep-ble to some degree Some more than others (see histopathology of den-ne and enamel caries and [uoride lectures) However, some areas of the tooth have factors that make them more suscep-ble to dental caries. This is generally related to the ability for plaque bioQlm to accumulate Which areas of the tooth are considered ‘suscep5ble’?  What areas of the tooth are considered ‘suscep5ble’? Defec5ve margins Pits and Qssures Smooth surface Proximal Ledges/overhangs In between teeth where food and debris Secondary local factor - more plaque biofilm and food Grooved surfaces of the tooth - attract easily gets caught and plaque biofilm acclimates - more difficult for patient to clean. debris and plaque biofilm - more difficult easily acclimates - especially if lack of to removed interdental cleaning 2. Fermentable Carbohydrate Bacteria within the plaque bioDlm need food to survive. Sugars present in the diet provide the substrate for oral commensal bacteria to metabolise and produce lac-c acid. Bacteria like to eat the sugar in our diet 2. Fermentable Carbohydrate Sugars Not all carbohydrates are equally cariogenic Some worse than others Sucrose is most rapidly metabolised to produce extracellular polysaccharides compared to glucose, fructose or lactose Sucrose = Easiest sugar in mouths for bacteria to metabolise/break down - more caries potential than other sugars Complex carbohydrates (starch) are not completely digested within the mouth Complex (starch) - more difficult to break down so not easy for bacteria to metabolise/break down so not as easy to produce acid byproduct that produces dental caries. 2 di_erent kinds of sugars 1. Intrinsic sugars 2. Extrinsic sugars 2. Fermentable Carbohydrate Naturally occurring sugars or sugars contained within unprocessed foods are considered intrinsic Present in natural form - intrinsic sugars Only available for plaque bacteria to metabolise once released from cell they’re enclosed in Packaged intracellularly Present in fruit and vegetables Only become available when processed Lactose is an example but not contained within a cell Less cariogenic - due to process of cell around sugar needing to be broken down before the sugar is released and before plaque bacteria are able to metabolise it. This extra stage of breaking down the sugar for it to become available to plaque bacteria, makes it less cariogenic because it takes longer to happen and the longer it takes the happen, the more likely it has been swallowed and away from plaque bacteria before they have chance to metabolise it.  Already released - as soon as enter mouth the plaque bacteria and commensal bacteria can process these really quickly to cause dental caries. 2. Fermentable Carbohydrate Extrinsic sugars are not bound within a cellular structure Readily available to be broken down 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 -me 2. Fermentable Carbohydrate In Summary; Extrinsic Simple sugars (e.g. glucose, fructose and sucrose) di_use rapidly into the plaque and are metabolised quickly by bacteria to produce acid hence… Free and ready to be metabolised straight away Cariogenic! Intrinsic Complex carbohydrates such as starch (rice and potatoes) are not completely digested in the mouth and hence… Need to be broken down before the sugar is released - takes time - less cariogenic. Less Cariogenic! 2. Fermentable Carbohydrate 2. Fermentable Carbohydrate What type of sugars? Chocolate cake - extrinsic - ready to be metabolised - highly cariogenic 2. Fermentable Carbohydrate If bacteria is given sugar it will metabolise it to create acid = dental caries Bacteria + Simple sugars = Acid What does ‘cri5cal’ pH mean? At the point the acid production starts to cause damage to teeth 2.Fermentable Carbohydrates And over time a carious lesion When the PH becomes acidic, the saliva draws out these ions from the hydroxyapa-te causing tooth surface dissolu-on Saliva becomes supersaturated with phosphate & hydroxide ions in acidic environments Critical pH - acidity that needs to be reached before the The cri-cal PH is the point below which the tooth -ssue demineralisation can start to happen begins to lose mineral to saliva or plaque An acidic PH causes demineralisa-on of enamel and den-ne Bacteria metabolise bacteria and excrete acid - starts to dissolve surface of tooth - demineralisation  Dentine - dissolves more easily than enamel - higher pH - less acid needed in mouth for dentine to start dissolving - dentine more susceptible to caries than enamel. 2. Fermentable Carbohydrate Critial pH depends on type of tissue Cri-cal pH enamel is 5-5.5 Cri-cal pH den-ne is 6-6.5  If a tooth starts to dissolve it can remineralise and stop dissolving if mineral is If the tooth demineralises and hydroxyapatite breaks into free minerals and the minerals are washed not lost as part of the process. away (saliva, tooth brushing) - when the pH rises again, there is no minerals available to remineralise back into hydroxyapatite - remineralisation CANNOT occur. 2. Fermentable Carbohydrate As tooth disolves - shown as free minerals Tooth Hydroxyapa5te Free minerals Ca5(PO4)3OH 5 Ca2+ + 3 PO43- + OH- Greater When pH > Cri-cal pH = REMINERALISATION When pH < Cri-cal pH = DEMINERALISATION (CARIES) Less Acidic Environment = Shihs to the right and tooth dissolves Neutral Environment = Shihs to leh 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 euoride lectures)  How often the bacteria are given access to sugar to metabolise 3. Time We know -me plays a big part in the carious process Without all of the other factors being present for a period of -me, caries will not occur Need to consider frequency of acid aiack; Grazing, snacking, suckling 2-3 hours apart minimum 2-3 hours gaps between meals/snacks to protect teeth Aim for 4 acid aiacks a day More likely for tooth dissolution and Regular frequency = increased -me! dental caries. Aim to reduce frequency – diet analysis! Reduce sugar amount and frequency Why does 5me or frequency of intake maher? 3. Time But why does this all maier? Stephan Curve 3. Time In studies in the 1940’s, Stephen showed dental plaque had a res-ng 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 Plomng this graph became known as a Stephan’s curve  We want infrequent sugar attacks so less time for demineralisation of teeth 3. Time Infrequent aiacks mean less -me below cri-cal pH and less demineralisa-on (lower caries risk) Frequent aiacks mean more -me below the cri-cal PH and hence more demineralisa-on (higher caries risk) If constantly snacking - more time in the risky demineralisation zone - more likely and susceptible to dental caries  If there is sugar in the patients mouth but no plaque bacteria to metabolise it, no acid will be produced, if no acid being produced, no 4. Plaque Bacteria tooth dissolution The other factor needed is plaque bacteria. Please refer to your lectures on bioDlms for further informa-on on this area.  Low pH - selecting for bacteria that like low pH 4. Plaque Bacteria Thicker biofilm due to poor oral hygiene - selecting for anaerobic bacteria Both of these more readily produce lactic acid - increased the risk of acid production and tooth dissolution and dental caries. 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 suscep5ble tooth surface which is normally covered in plaque bioQlm Sugar present within the diet provides the substrate for oral commensal bacteria to metabolise and produce lac-c 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 remineralisa-on/demineralisa-on see-saw will favour remineralisa-on if the frequency of intake isNOTmore 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 con-nues over 5me, 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 bioQlm 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 Atlan-c Island caries free un-l Americans imported cariogenic food and drink – fermentable Vipeholm Study (1945-1952): Pa-ents in a Swedish mental hospital (no informed consent so now considered unethical) Division of pa-ents into several groups giving various amounts or sugar with varying frequencies Subjects given the most cariogenic food (to_ees) 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 5me Thank You!