Tooth Decay and Stuff

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Tooth Decay and Stuff
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Tooth Decay

• Tooth decay has been present since there have
  been teeth to decay.
• Tooth decay, is an infectious disease that
  damages the structures of teeth
• Pain
• Tooth Loss
• Infection
• Death

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The Chemistry

• Tooth decay is Acid/Base chemistry
• Acids dissolve the enamel surface of the tooth
  and create holes in the tooth (cavities)

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What is Enamel?

• Calcium hydroxyphosphate, Ca5(PO4)3OH, also known
  as mineral apatite
• Acid attacks apatite
• Ca5(PO4)3OH(s) (Tooth enamel) H (Acid) (aq) ?
  Ca5(PO4)3(aq) H2O(l)
• Reaction is reversible saliva

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Fluoride is your friend

• If fluoride, F-, ions are present in saliva,
  fluorapatite, Ca5(PO4)3F, also forms.
• Ca5(PO4)3(aq) F-(aq) ? Ca5(PO4)3F (s)
• Fluorapatite better than apatite itself (fluoride
  treatments)

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Tooth decay, not just candy anymore

• Not bacterial growth in the mouth, but
  alterations in internal body chemistry
• But candy doesnt help!

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What is a Dental Filling?

• Dental material used to restore the
  function/integrity/morphology of missing tooth
  structure
• -Indirect and direct restoration
• -Numerous types of methods

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Amalgams?

• An amalgam is a mixture of mercury with another
  metal or alloy.
• Most metals are soluble in mercury.
• Amalgams are commonly used in dental fillings.
• Dental amalgam consists of three solid phases
  represented by Ag2Hg3, Ag3Sn, Sn8Hg

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Dental Amalgams

• Dental amalgam is a stable alloy made by
  combining elemental mercury, silver, tin, copper
  and possibly other metallic elements.
• 65 minimum, silver copper
• 6 maximum, copper
• 2 minimum, zinc
• 25 maximum, tin
• 45 liquid mercury

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Why Dental Amalgams?

• -Amalgams withstand chewing loads
• -Useful for restoring molars in the back of the
  mouth
• -They are well tolerated by patients, rare
  occurrences of allergic response.

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Why Mercury?

• Nearly every metal is soluble in mercury, iron is
  the only exception
• Thus, a malleable paste before solidification can
  be formed
• As silver dissolves, flexible but firm structure
  is molded
• Adheres to tooth enamel
• Forms high-strength compound

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Primary controversy

• Opponents of dental amalgams with mercury argue
  the long-term effects of mercury poisoning
• Combination of metals should be safe
• Some action taken before to ban mercury fillings
  internationally, but FDA, USPHS, CDC-approved
• Not enough research to fully support either side

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Controversy
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Battery in your mouth?

• Try this at home! Aluminum foil pressing against
  amalgam filling will cause pain
• An electrochemical cell is created when aluminum
  foil contacts a dental amalgam. Aluminum contacts
  Sn8Hg phase
• Aluminum becomes the anode and the filling as the
  cathode.
• Saliva acts as an electrolyte.
• The contact between the metals acts as a
  short-circuit

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Dental Filling Corrosion

• Dental filling can corrode over time
• Different metals can create an electrical
  circuit, such as gold and silver.

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Electricity in Your mouth

• Silver and Gold have 3 different solid phases
  (volt potential)
• Ag2Hg3 (0.85 v)
• Ag3Sn (-0.05 v)
• Sn8Hg (-0.13)
• Experiments you can do at home to create your
  very own circuit

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Experiments

• No, not that if you have a filling or braces try
  chewing on aluminum foil.

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The Corrosion

• Sn8Hg --gt Sn2 2e-
• O2(g) 4H(aq) 4e- --gt 2H2O (l)

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Grills Arent Dental Fillings!
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Sources

• http//www.ada.org/public/topics/fillings.asprest
  oring
• http//en.wikipedia.org/wiki/Amalgam
• Chang, Raymond. Chemistry McGraw-Hill San
  Francisco, 2002.
• http//en.wikipedia.org/wiki/Dental_fillingsResto
  ration_classifications
• http//en.wikipedia.org/wiki/Dental_amalgam_contro
  versy
• http//www.madsci.org/posts/archives/oct2000/97300
  2607.Ch.r.html
• http//adr.iadrjournals.org/cgi/reprint/2/1/71.pdf
  
• http//www.mercurypoisoned.com/dentists_discipline
  d/ImageDentistNewsletter.jpg
• http//lonestartimes.com/images/Weidenhof/grill.jp
  g
• http//www.seemygrill.com/f/pics/114744405718814-p
  hpr0RvoL.jpghttp//farm1.static.flickr.com/35/7221
  8577_035bb4c2b5.jpg
• http//farm1.static.flickr.com/35/72218577_035bb4c
  2b5.jpg