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Tooth Decay and
Stuff
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Tooth Decay
Tooth decay has been present sincethere have been teeth to decay.
Tooth decay, is an infectious disease thatdamages the structures of teeth
Pain
Tooth LossInfection
Death
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The Chemistry
Tooth decay is
Acid/Base
chemistryAcids dissolve the
enamel surface of
the tooth and
create holes in thetooth (cavities)
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What is Enamel?
Calcium hydroxyphosphate,Ca5(PO4)3OH, also known as mineral
apatiteAcid 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
anymoreNot bacterial growth in the mouth,
but alterations in internal body
chemistryBut 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 withanother metal or alloy.
Most metals are soluble in mercury.
Amalgams are commonly used in dentalfillings.
Dental amalgam consists of three solid phasesrepresented by Ag2Hg3, Ag3Sn, Sn8Hg
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Dental Amalgams
Dental amalgam is a stable alloy made bycombining 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 ofthe mouth
-They are well tolerated by patients, rareoccurrences of allergic response.
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Why Mercury?
Nearly every metal is soluble in mercury, iron is the onlyexception
Thus, a malleable paste before solidification can beformed
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 mercuryargue the long-term effects of mercurypoisoning
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 againstamalgam filling will cause pain
An electrochemical cell is created whenaluminum 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 anelectrical circuit, such as gold andsilver.
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Electricity in Your mouth
Silver and Gold have 3 different solidphases (volt potential):
Ag2Hg3 (0.85 v)Ag3Sn (-0.05 v)
Sn8Hg (-0.13)
Experiments you can do at home tocreate your very own circuit
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Experiments
No, not that if
you have a filling
or braces trychewing on
aluminum foil.
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The Corrosion
Sn8Hg --> Sn2++ 2e-
O2(g) + 4H+(aq) + 4e---> 2H2O (l)
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Grills Arent Dental Fillings!
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Sourceshttp://www.ada.org/public/topics/fillings.asp#restoring
http://en.wikipedia.org/wiki/Amalgam
Chang, Raymond. Chemistry; McGraw-Hill: San Francisco,2002.
http://en.wikipedia.org/wiki/Dental_fillings#Restoration_classifica
tionshttp://en.wikipedia.org/wiki/Dental_amalgam_controversy
http://www.madsci.org/posts/archives/oct2000/973002607.Ch.r.html
http://adr.iadrjournals.org/cgi/reprint/2/1/71.pdf
http://www.mercurypoisoned.com/dentists_disciplined/ImageDe
ntistNewsletter.jpghttp://lonestartimes.com/images/Weidenhof/grill.jpg
http://www.seemygrill.com/f/pics/114744405718814-
phpr0RvoL.jpghttp://farm1.static.flickr.com/35/72218577_035bb
4c2b5.jpg
http://farm1.static.flickr.com/35/72218577 035bb4c2b5.jpg
http://en.wikipedia.org/wiki/Dental_fillingshttp://en.wikipedia.org/wiki/Dental_fillings