٢١2أیار، ٢٥

Preventive Dentistry Fifth class

Nutrition, diet & oral health2nd lecture2020-2021

By Dr. Adil Ghalib FadhilCollege of DentistryUniversity of Basrah

Objectives

• Type of sugars • The roles of dietary sugars• Stephan curve• Practical ways to reduce dental caries

The goals of preventive dentistry are to avoid disease altogether.

The goal of primary prevention is never to have had

any kind of dental disease.

• Dietary carbohydrates exert their cariogeniceffect locally on tooth surface by influence thequality and quantity of dental plaque. Dentalcaries occurs as plaque bacteria metabolizefermentable carbohydrate, producing organicacids. These acids diffuse through the plaque intothe enamel and dissolve mineral. If mineraldiffuses out of the tooth and into the oralenvironment, then demineralization occurs. If theprocess is reversed the damaged crystal arerebuilt (remineralization).

• Caries occurs when demineralization exceedsremineralization.

Role of carbohydrates incaries development

Fermentable carbohydrate: anycarbohydrate that can be hydrolyzed by salivary amylase and subsequently

fermented by bacteria

Carbohydrate is an essential nutrient and can:be classified in to three main categories

1- Free-form monosaccharide (simple sugars) includeglucose and fructose which are found naturally in fruit,vegetables and honey while galactose occur only as aresult of the breakdown during digestion of lactose.2-Disaccharides (two simple sugar molecules linkedtogether): the most common: Sucrose (refined fromsugar cane or sugar beets, it’s a major part of dietarysugar) formed when one molecules of glucose combinewith one molecules of fructose. Lactose is formed when amolecule of glucose combine in a molecules of galactose(milk sugar). Maltose is formed when two molecules ofglucose combine; it is mainly derived from hydrolysis ofthe starch.

3-Polysaccharides: the polysaccharides notsugar.All polysaccharides are made up of manyindividual sugar molecules, usually glucose,joined together. The digestible forms includestarch, which is found in rice, potatoes, peas;about half of dietary carbohydrates arecomposed of starch.

This is a convenient analogy to understand and is anoffshoot of the classic Venn diagram ( first introduced by Keyes (1962).

Not all sugars are cariogenic.

The role of dietary sugars

The more common dietary sugars are presented.The cariogenic potential of carbohydrates are presented too.

The sugars with the most cariogenicity are sucrose

and glucose (red).

Other carbohydrates (maltose, lactose, fructose, and starch)

are less cariogenic.

The sugar alcohols, such as sorbitol and mannitol, are the

least cariogenic (yellow)

Xylitol has even been shown to be anticariogenic (green).

The disaccharide sucrose and the monosaccharide glucose ( a component of sucrose), are most cariogenic.

Frequent ingestion, can cause severe damage to the tooth.

There is no question that carbohydrates arethe main etiological reason for the development of caries.One of the strategies in prevention of caries is to limitaccess to the more cariogenic sugars and substitute themwith the anti-cariogentic ones.Not only does their conversion to acid result inenamel dissolution, but they also encourage the growthof more virulent cariogenic bacteria.

The demineralization–remineralizationbalance in caries

• The plaque thickness dominated by cariogenic bacteria, can effectivelykeep the saliva from reaching the enamel surface.

• In addition, the more plaque there is, the more acid is produced.

• These acids have a longer time to penetrate into the enamel underthick biofilm - This allows the tooth to demineralize!!!!

• If the saliva reaches the acids they are washed away and neutralized bythe salivary buffers - This allows the tooth to remineralize.

• The cycle repeats itself over and over withevery sweet snack and meal containingfermentable sugars

• Caries occurs when the frequency of sugarexposure during the day is high.

The repeated cycle of ‘sugar attacks.’

The pH of dental plaque in response to glucose has been studied using the classic Stephan curve

The diagram illustrates the plaque pH response curves that have been obtained from patients with differentrisks for caries.

Stephan curve

The resting PH of dental plaque wasmostly between pH( 6.5 and 7 ), theterm resting plaque refers to plaque 2-2.5 hours after the last intake ofcarbohydrate. But when the plaqueexposed to sucrose or glucose the pH ofplaque falls rapidly below the criticalvalue within 2-5 minutes.

(The value of pH 5,5 has become accepted ascritical pH below which dental enamel willbegin to dissolve because the environment isno longer saturated with enamel mineral),this rapid fall was then followed by slowrecovery over the next 30-60minutes. plot ofplaque PH against time has become known asthe Stephan curve.

The slow rate of recovery to the resting pH ,depend onRapid production of acid , overcome bufferingsystemDelay of escape of acid into saliva,Diffusion of salivary buffers in to plaque isdelayedContinued sugar production from bacterialintracellular poly saccharide

Lack of saliva means long and deep Stephancurve, lengthening the time ofdemineralization and reducing the time whenremineralization can occur.

Caries free subjects tend to have a slightlyhigher resting plaque pH, a higher minimumpH following consumption of fermentablecarbohydrate and a faster return to restinglevels, when compared with caries susceptiblesubjects (as shown in figure below).

•A high-risk individual, when given a glucose rinse , will

experience a dramatic drop in the plaque pH well below the

critical pH of 5.5.

•The recovery to neutral pH in the high risk individual will be

slow.

The area under the pH-time curve(AUC)representing the time spend atpH lower than the critical pH.

The AUC for a high riskindividual will be very large.

AUC is a better measure of total cariesrisk.

The person with a high risk for caries snacksfrequently during the day,and the total AUCs clearly are excessiveand will not allow remineralization to occur.

If that daily trend continues, the person willexperience dental decay.

For a moderate risk individual (yellow), the initial pH drop may only be a little lower than the critical pH, and the AUC will be much less.

For a caries-resistant person (green),the initial pH drop of that person’s plaque maynot even reach the critical pH, and the recovery will be very quick.

The person with moderate caries risk might havethree meals and one snack of moderate cariogenicpotential on a daily basis,and the AUCs below the critical pH might result in a net loss of mineral.

At this stage, remineralizationstrategies might work.

• Тhe person at low risk may not snack at all and has three meals of low cariogenicity spread apart during the day.

• This allow remineralization to occur.

• Researchers have determined that:it is not only the frequency of ingestion that isimportant, but it is alsothe type of fermentable carbohydrate that is ingested.

• Preventive interventions aim to modify the steps in the repeat demineralization and remineralization cycles.

Physical form of food and clearance time:

In addition to the chemical composition of food,physical and organoleptic properties .(particle size, solubility, adhesiveness, textureand taste) are important for cariogenicity, sincethey influence eating pattern and oral retentionof the foods. Diets that results in the greaterretention of refined carbohydrate over thelongest period are the most cariogenic.

The carbohydrate in various drink areeliminated within 5 minutes while sweetsuch as sugar containing chewing gum,toffees, lozenges generally give high oralsucrose concentration and clearance timefrom 40 minutes for chewing gum to 15-20minutes for other sweets.

The texture of the diet is also important, forboth salivary secretion and elimination offermentable carbohydrate from the oral cavity.A diet that require thorough chewing willresult in the secretion of large amount ofsaliva with a high pH and strong bufferingcapacity, in contrast to a finely textured dietthat require little mastication tends to beretained in the oral cavity and eliminatedslowly

Practical way to speed up carbohydrateclearance are

tooth brushing immediately after meal, orinduction of rapid salivary flow by mechanicalor gustatory stimuli through eating tough orhighly flavored foods at the end of mealsChewing sugar free chewing gum or peanutsimmediately after eating sugar also speed upsugar clearance and neutralization of plaqueacid through saliva stimulation

end