Dental Caries

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Dental Caries
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Definition

• Caries is a disease resulting in the destruction
  of the hard structure of the teeth

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Stages in the development of caries

1. The enamel becomes decalcified
2. A small white spot appear
3. Discoloration becomes pronounced
4. The tooth surface softens and decay penetrates
   through the enamel into the dentine
5. Caries spreads laterally and in depth
6. Cavitation occurs

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1. The lesion deepens, and pulp becomes affected,
   first reacting to stimuli (e.g.sweets, temp.),
   then damaged and dead
2. Bacteria travels down the root canal, out through
   the apex causing abscesses

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Factors determining the incidence of caries

• Micro organisms Acid producing bacteria,
  especially if they produce extracellular
  polysaccharides, will increase risk
• Host factors
• Decreased saliva secretion increase incidence
• Buffering power of saliva to raise pH decrease
  incidence

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1. The morphology of the teeth well spaced teeth
   decrease incidence, while fissures pits
   increase it.
2. The composition of the teeth certain trace
   elements decrease incidence (e.g. F, Mb and B),
   while others (e.g. Cu Mn) increase it

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1. Time frequency of consumption of carbohydrates,
   and length of time in the mouth are related to
   incidence. Good oral hygiene can counter act this
2. Substrates for acid production provided in diet

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Caries as a disease of civilization

• Evidence links caries to civilization
• This is due mainly to changes in dietary habits,
  e.g. increased carbohydrates intake by Eskimos
  and eating refined instead of natural forms of
  carbohydrates by African tribes

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Factors in unrefined food lead to decreased
incidence of caries

1. Substances that decrease solubility of calcium
   phosphate
2. More phytate /or calcium
3. Antibacterial substances
4. Substances that inhibit aggregation of bacteria
   - decrease plaque formation
5. Absence of free sugar (most important)

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Theories for the cause of caries

1. The proteolytic theory presence of proteolytic
   bacteria lead to hydrolysis of protein (collagen)
   leading to progression of caries
2. The phospho protein theory phospho protein
   phosphatse in plaque acts on phosphoproteins in
   enamel, but this is not tested in humans

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1. The proteolysis-chelation theory some products
   of bacterial action on enamel, dentine, saliva
   food constituents form complexes with calcium
   from plaque causing a decrease in the
   concentration required to maintain saturation,
   and leading to more solubility

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• The acid theory of caries Bacteria in saliva
  carbohydrate (sugar) lead to acid production
  dissolving appetite
• This the most likely theory

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Evidence

1. In thick plaque, pH below critical point
2. pH in carious cavities is lower
3. Caries intensity correlates with acid production
   and count of acid producing bacteria
4. In germ-free rats, caries was produced by
   inoculation with acid producing organisms

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The importance of diffusion

• Since caries is a penetrating lesion, the inward
  diffusion of the acid must play an important role
  in its development
• Evidence shows that the concentration of
  unionized lactic acid outside the enamel is more
  important than low pH

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• Unionized acid diffuses more easily inward,
  becomes diluted and ionized, allowing reaction
  with apatite to form free calcium and phosphate
• These ions diffuse outwards, and may precipitate
  as CaHPO4, explaining the apparently intact outer
  layer of enamel over the cavity
• Therefore, the critical pH may not only be the
  level at which the environment of enamel becomes
  unsaturated with apatite, but it also maybe the
  pH at which sufficient conc. Of unionized lactic
  acid exists to ensure inward diffusion

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The bacteria responsible for caries

• Two species were isolated from carious
  mouths and were suggested as causal organisms
• Streptococcus mutants, and
• Lactobacillus acidophilus or odontolyticus
• Other filamentous bacteria producing lactic
  acid were isolated from caries lesions of the
  root surfaces. These bacteria, the genus
  Actinomyces are of two species
• Actinomyces viscosus
• Actinomyces naeslundi , both are found
  predominantly in the gingival region and cause
  inaddition severe periodontal disease

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Relationship between lactobacilli and
streptococcus mutans

• streptococcus mutans alone can produce caries,
  but the combination is more effective
• streptococcus mutans stop acid production at pH
  4.3, but lactobacilli continue to below pH 4
• Therefore, the joint effect is more intense
• Lactobacilli seems to be involved in the initial
  attack, and is found at tha front of the lesion

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Local effects in caries

• Caries is localized, indicating the role of local
  conditions
• This might be partly due to differences in
  composition of plaque (bacterial and matrix)
• Evidence also suggests that different types of
  bacteria cause caries at different sites (e.g.
  tetracycline reduces smooth surface caries, to a
  greater extent than pit and fissure caries

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The role of diet in caries

• Diet has two types of effects
• Dietary effects local effects contributing to
  substrates for bacterial growth direct
  interaction with teeth
• Nutritional effects effects of assimilated food
  stuff

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1.Dietary effects

• There is evidence relating consumption of
  carbohydrates (particularly sucrose) to caries

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A- Indirect Evidence for importance of dietary
carbohydrates in caries

1. Eskimos, whose diet was formerly almost
   exclusively of fish, meat and fat, had a low
   incidence of dental caries while on their
   primitive diet
2. The prevalence of dental caries in different
   countries parallels the extent of sugar
   consumption in those countries

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1. In many areas of Europe where sucrose intake was
   severely restricted during World War II, caries
   incidence in children decreased dramatically
2. The study of human biochemical genetics has also
   provided evidence that sucrose plays a special
   role in caries. A rare enzyme deficiency
   involving a lack of fructose-I-phosphate aldolase
   results in hereditary fructose intolerance. Foods
   containing fructose cause nausea, vomiting,
   tremors, and convulsions in affected individuals.
   As sucrose is a glucose-fructose disaccharide, it
   also produces these effects, and is avoided by
   such pateints, who are often found to be
   caries-free or else have a very low caries
   prevalence

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1. Amongst present-day children of pre-school age
   there is a marked correlation between caries
   experience and the extent of eating between main
   meals
2. Rampant caries, in which the anterior teeth may
   be almost completely dissolved away, is found in
   babies who are given comforters filled with syrup
   or honey to suck for prolonged periods of time

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B- Populations on controlled diets

1. The caries score (decayed, missing and filled
   teeth, DMFT) was followed over years for
   different groups given carbohydrates sources of
   increasing degree of stickiness compared to a
   control group given a diet low in carbohydrates,
   with the calories supplied by sugar normally ,
   replaced by margarine

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1. A study conducted at an orphanage, indicated that
   refined carbohydrates increase the caries score.
   While resident, the children were given a diet
   that excluded refined carbohydrates , and had low
   caries score (DMFT), but this increased
   dramatically after they left and changed their
   diet to include sugar and refined carbohydrates

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Interaction between carbohydrates dental plaque

• Epidemiological evidence experimental studies
  indicated the following
• Carbohydrate free diet thin plaque
• Presence of sucrose more plaque
  (gelatinous)
• Sucrose is more cariogenic than glucose or
  fructose with respect to smooth surfaces

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• 4. Extra cellular polysaccharides are produced by
  bacteria from sucrose this help in
• Adherence to smooth surface
• Retain acid in close proximity to tooth surface
• Shield against buffering by saliva
• The above are less important in fissures

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Other dietary effects

• Addition of Calcium sucrose phosphate (CaSP)
  caries
• Acidic drink could dissolve enamel caries
  incidence
• Fibrous food reduce plaque formation , therfore,
  caries
• Foods that saliva flow caries e.g. salty
  foods
• Foods that pH increase Ca content caries
  e.g. cheese

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2- Nutritional effects

1. Vitamin D could lead to incidence of caries
2. Some trace elements caries some
   it

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• Minerals associated with increased caries
  include Copper, magnesium, Se, zinc, vanadium
  lead
• Minerals associated with decreased caries include
  
• F, Sr, B, K, nickel, Mo, Li
• Mechanism suggestion
• Effect morphology of teeth (rats)
• Effect crystal structure solubility

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Caries resistance

• Many factors not strong by themselves combine to
  caries e.g.
• Highly buffered saliva with high flow rate
• Ca, P, HCO3 in saliva
• High F/CO3 of enamel
• The most important factor is the type of bacteria
• presence of antibodies to cariogenic bacteria
  might help to caries also

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• Finally the morphology of teeth plays a role
• Note
• Cause of caries differs from person to another

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Remineralization

• Carious lesions up to white spot stage can cease
  to develop and might disappear
• Caries progresses by alternate demineralization,
  when pH falls, and partial remineralization when
  the pH rises
• Saliva could remineralization, but F speeds
  process