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CPEBLS Stage 1 > Chapter 2 Dental caries > Flashcards

Chapter 2 Dental caries Flashcards

1
Q

What can result from the action of oral microorganisms as in dental caries?

A

Loss of tooth substance

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2
Q

Mechanical factors that result in loss of tooth substance

A
  • Attrition
  • Abrasion
  • Chemical erosion
  • Pathological resorption
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3
Q

Acidogenic theory as a cause of dental caries postulated by who?

A

W. D. Miller in 1889

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4
Q

Describe W. D. Miller’s acidogenic theory?

A

Acid formed from the fermentation of dietary carbohydrates by oral bacteria leads to a progressive decalcification of the tooth substance with a subsequent disintegration of the oral matrix.

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5
Q

What is dental plaque?

A

This is a biofilm consisting of a variety of different species of bacteria embedded in a matrix derived from salivary mucins and extracellular polysaccharide polymers (glucans and fructans) synthesized by the organisms.

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6
Q

A clean enamel surface is covered in a few seconds by ?

A

An adsorbed layer of molecules comprising mainly glycoproteins from saliva, the acquired pellicle, to which microorganisms initially adhere.

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7
Q

Describe what happens in an acquired pellicle?

A

As they multiply and synthesize extracellular matrix polymers other bacteria may bind to them, rather than to the pellicle, resulting in a complex biofilm of spatially arranged species.

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8
Q

Dietary sugars diffuse rapidly through plaque where they are converted to?

A

Acids (mainly lactic acid but also acetic and propionic acids) by bacterial metabolism.

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9
Q

pH of the plaque may fall by ?

A

As much as 2 units within 10 minutes after the ingestion of sugar, but over the next 30 to 60 minutes the pH slowly rises to its original figure, due to the diffusion of the sugar and some of the acid out of the plaque and the diffusion into the plaque of buffered saliva which helps to dilute and neutralize the acid.

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10
Q

At the critical pH of 5.5, mineral ions are?

A

Liberated from the hydroxyapatite crystals of the enamel and diffuse into the plaque.

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11
Q

What are Stephan’s curves?

A

pH curves of plaque in response to sugar are similar in shape in caries-free and caries-active individuals.

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12
Q

Since starting pH may be lower in caries-active mouths, what happens to the pH?

A

Reduction in pH will be greater and the pH will be depressed below the critical level for a greater period of time.

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13
Q

At a neutral or slightly alkaline pH, the plaque becomes?

A

Supersaturated with mineral ions derived both from the saliva and from those released from the hydroxyapatite crystals. Ions may now diffuse back into the enamel and be redeposited in the crystal structure, and this reprecipitation of mineral is aided by fluoride ions.

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14
Q

Once enamel caries has progressed to cavity formation, the plaque becomes?

A

Becomes progressively more removed from saliva and probably remains acidic for longer periods.

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15
Q

Many plaque bacteria store carbohydrate as?

A

As an intracellular glycogen-like polysaccharide which may be formed from a variety of sugars, and this may be broken down to acid when other sources of carbohydrate are absent, such as between meals.

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16
Q

Plaque organisms can synthesize extracellular glucans from dietary sugars which may also be metabolized to acid when?

A

When other sources of carbohydrate are absent.

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17
Q

Abundant extracellular polysaccharides markedly increase the bulk of?

A

Bulk of the plaque.

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18
Q

Fluoride ions are present in relatively high concentration in what?

A

in Plaque compared with saliva

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19
Q

Fluoride favours the precipitation of which ions from solution?

A

Calcium and phosphate

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20
Q

When fluoride, calcium and phosphate ions are present at the plaque-enamel interface, what happens?

A

The deposition of free mineral ions in the plaque as hydroxy- and fluorapatite on the remaining enamel crystals is encouraged.

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21
Q

If fluorides are administered systemically (for example by water fluoridation), what can form during enamel development?

A

Fluorapatite crystals

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22
Q

Which one is less soluble in acids? Fluorapatite or hydroxyapatite?

A

Fluorapatite

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23
Q

Systemic fluoride promotes formation of?

A

Hydroxyapatite crystals with a more stable crystal lattice.

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24
Q

Fluoride ions in plaque inhibit?

A

Inhibit bacterial metabolis and this provides an additional mechanism for the preventative action of fluoride in enamel caries.

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25
Q

Epidemiological data in humans indicates an association between the presence of which bacteria in plaque and the prevalence of caries?

A

S. mutans and S. sobrinus

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26
Q

Which organism are the pioneer organisms in dentine caries?

A

Lactobacilli

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27
Q

List key points in dental plaque

A
  • Cariogenic bacteria ferment carbohydrate ito acid
  • Cariogenic bacteria can store carbohydrate intra and extracellularly
  • Extracellular polysaccharides increase plaque bulk
  • Bulky plaques interfere with outward diffusion of acid and inward diffusion of salivary buffers
  • Frequent intakes of carbohydrate can depress the pH below the critical level for long periods
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28
Q

List key points in ionic exchanges in enamel caries

A
  • Ions see-saw across the plaque-enamel interface depending on pH
  • Ions in plaque can be redeposited into the enamel at a neutral pH or lost into the saliva
  • Enamel caries progresses when the net rate of loss of ions due to acid attack is greater than the net rate of gain due to remineralization
  • Fluoride ions encourage reprecipitation of minerals into enamel
  • Fluoride ions can replace hydroxyl ions in hydroxyapatite to form less acid-soluble fluorapatite
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29
Q

Which bacteria have been isolated from caries?

A
  • Several types of non-mutans streptococci: mitis, salivarius, anginosus, and saguinis groups, lactobacilli and actinomycetes
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30
Q

Species strongly implicated in dental caries

A
  • Mutans streptococci, especially S. mutans

- Lactobacilli

31
Q

Species that may be associated in dental caries

A
  • Non-mutans streptococci, e.g. mitis group

- Actinomycetes

32
Q

List other key points of microbiology of dental caries

A
  • Transmission of S. mutans occurs mainly from mother to child
  • Low plaque pH favours proliferation of mutans streptococci and lactobacilli
  • Level of mutans streptococci in plaque increased by sucrose consumption
33
Q

Which carbohydrate is more cariogenic than other sugars?

A

Sucrose, partly because it is readily fermented by plaque bacteria and partly because of its conversion by bacterial glucosyl transferase into extracellular glucans.

34
Q

Sucrose is also readily converted into?

A

Intracellular polymers

35
Q

Principal carbohydrates in human diets?

A

Sucrose and starches

36
Q

List other highly cariogenic carbohydrates

A
  • Glucose
  • Fructose
  • Maltose
  • Galactose
  • Lactose
37
Q

List sources of intrinsic and extrinsic dietary sugars

A
  • Intrinsic: mainly fruit and vegetables

- Extrinsic: sugars, milk, fruit juices

38
Q

Dietary advice recommends reduced consumption of?

A

Extrinsic sugars (except milk)

39
Q

What is hereditary fructose intolerance?

A

Those people who cannot tolerate fructose or sucrose (ingestion may lead to coma and death) but who are able to consume starches

Such individuals have little or no caries.

40
Q

Starch solutions applied to bacterial plaque produce no significant depression in pH due to?

A

Due to very slow diffusion of the polysaccharide into the plaque which must be hydrolysed by extracellular amylase before it can be assimilated and metabolized by plaque bacteria.

41
Q

Cooked highly refined starches can cause?

A

Caries, although much less than sucrose.

42
Q

Combination of cooked starch and sucrose together such as in cakes and biscuits is more _____ than sucrose alone.

A

Cariogenic

43
Q

Main alternative non-sugar sweeteners are?

A

Sorbitol and xylitol and are for all purposes and intents are non-cariogenic.

Xylitol is not fermented by oral bacteria and sorbitol is only fermented at a very slow rate.

44
Q

List key points in diet and dental caries

A
  • Caries prevalence increases when populations become exposed to sucrose-rich diets
  • Extrinsic sugars are more damaging than intrinsic sugars
  • sucrose is the most cariogenic sugar
  • Frequency of sugar intake is of more importance than total amount consumed.
45
Q

When is the risk of caries greatest?

A

If sugar is consumed between meals, thus supplying plaque bacteria with (in the case of habitual ‘snackers’ ) where there is an almost constant supply of carbohydrate.

46
Q

Risk of caries is increased when?

A

If sugar is consumed in a sticky form likely to be retained on the surfaces of the teeth.

47
Q

List factors intrinsic to the tooth enamel composition

A

There is an inverse relationship between enamel solubility and enamel fluoride concentration. A graded increase in enamel resistance with age might account for selectivity of site attack

48
Q

List factors intrinsic to the tooth enamel structure

A

Developmental enamel hypoplasia and hypomineralization may affect the rate of progression but not the initiation of caries

49
Q

List factors intrinsic to the tooth morphology

A

Deep marrow pits and fissures favour the retention of plaque and food.

50
Q

List factors intrinsic to tooth position

A

Malaligned teeth may predispose to the retention of plaque and food.

51
Q

Describe saliva as a factor extrinsic to the tooth

A

Flow rate, viscosity, buffering capacity, availability of calcium and phosphate ions for mineralization, and the presenceof antimicrobial agents such as immunoglobulins, thiocyanate ion, lactoferrin and lysozyme may affect caries pattern

52
Q

Describe how diet can be an extrinsic factor for caries

A

The most important factor is the frequency of intake of sugary foods and drinks. Chewing sugar-free gum or eating a small portion of cheese after meals helps protect against dental caries. Phosphates in the diet, either organically bound or inorganic, may also reduce the incidence of caries

53
Q

How can fluoride extrinsically affect the tooth?

A

Fluoride readily enters bacterial cells and can inhibit enzymes involved in the metabolism of sugar

54
Q

Where do pits and fissure caries occur?

A

Occlusal surfaces of molars and premolars, on the buccal and lingual surfaces of molars, and lingual surfaces of maxillary incisors.

55
Q

Early caries may be detected clinically by?

A

Brown or black discolouration of a fissure in which a probe ‘sticks’.

56
Q

Enamel directly bordering the pit or fissure may appear ?

A

Opaque, bluish-white as it becomes undermined by caries.

57
Q

Widespread use of fluoride-containing dentrifices makes _______ more difficult to diagnose.

A

Early occlusal caries

58
Q

Apparently clinically sound enamel can overlay extensive dentine caries because of?

A

Strengthening of the enamel by the formation of fluorapatite and the ability of fluoride to promote remineralization

59
Q

Smooth surface caries occurs on where?

A

Approximal surfaces, and on the gingival third of the buccal and lingual surfaces.

60
Q

Where do approximal caries begin?

A

Just below the contact point as a well-demarcated chalky-white opacity of the enamel. At this stage, there is no loss of continuity of the enamel surface and the lesion cannot be detected by a probe or on routine radiographs.

61
Q

White spot lesion may become?

A

Pigmented yellow or brown and may extend buccally and lingually into the embrasures.

62
Q

As smooth surface caries progresses, the surrounding enamel becomes?

A

bluish-white

63
Q

Surface of smooth surface caries becomes?

A

Roughed before frank cavitation occurs.

64
Q

On radiographs, lesions with an underlying radiolucency involving _________ is still intact.

A

Half or more of the dentine thickness

65
Q

Radiolucency limited to the outer half of the dentine, the probability of cavitation ranges from?

A

40 to 80 percent in different studies.

66
Q

Cervical caries extends occlusally from ?

A

From opposite the gingival margin on buccal and lingual tooth surfaces.

67
Q

Appearance of cervical caries ?

A

Similar to approximal caries, but almost always produces a wide open cavity.

68
Q

When do cemental or root caries occur?

A

Occurs when root face is exposed to the oral environment as a result of periodontal disease. Root face is softened and the cavities which may be extensive, are usually shallow, saucer-shaped with ill-defined boundaries.

69
Q

Recurrent caries occurs where?

A

Occurs around the margin or at the base of a previously existing restoration.

70
Q

Key points in diagnosis of caries?

A
  • Early occlusal caries may be difficult to detect
  • Radiolucencies in approximal enamel that do not reach the amelodentinal junction do not usually indicate enamel cavitation.
  • Approximal lesions which on radiographs do not extend into dentine should be treated by preventive measures.
71
Q

What is rampant or acute caries?

A

this is rapidly progressing caries involving many or all of the erupted teeth, often on surfaces normally immune to caries. The rapid coronal destruction and limited time for the protective responses of the pulpodentinal complex to occur lead to early involvement of the pulp.

72
Q

What is slowly progressive or chronic caries?

A

Caries that progresses slowly and involves the pulp much later than in acute caries. Most common in adults and the slow progress allows time for defence reactions of the pulpodentinal complex (sclerosis and reactionary dentine formation) to develop

73
Q

What is arrested caries?

A

Caries of enamel or dentine, including root caries, that becomes static and shows no tendency for further progression.

CPEBLS Stage 1 (7 decks)

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