October/November 2015 Teacher's Guide for Tooth Decay: a delicate Balance Table of Contents



Download 323.18 Kb.
Page1/7
Date conversion23.11.2016
Size323.18 Kb.
  1   2   3   4   5   6   7
logo_chemmatters[1]

October/November 2015 Teacher's Guide for
Tooth Decay: A Delicate Balance
Table of Contents



In-Class Activities 39



About the Guide

Teacher’s Guide editors William Bleam, Regis Goode, Donald McKinney, Barbara Sitzman and Ronald Tempest created the Teacher’s Guide article material. E-mail: bbleam@verizon.net


Susan Cooper prepared the anticipation and reading guides.
Patrice Pages, ChemMatters editor, coordinated production and prepared the Teacher’s Guide. E-mail: chemmatters@acs.org
Articles from past issues of ChemMatters can be accessed from a DVD that is available from the American Chemical Society for $42. The DVD contains the entire 30-year publication of ChemMatters issues, from February 1983 to April 2013.
The ChemMatters DVD also includes Article, Title and Keyword Indexes that covers all issues from February 1983 to April 2013.
The ChemMatters DVD can be purchased by calling 1-800-227-5558.
Purchase information can be found online at www.acs.org/chemmatters.

Student Questions


    1. Name the three main constituents of the hard parts of the tooth.

    2. What is hydroxyapatite?

    3. Why does the author say the hydroxyapatite in your teeth “is dynamic”?

    4. What are the products of the demineralization of hydroxyapatite?

    5. How does pH differ between that of the mouth and that of the body?

    6. How do the lungs help to control blood pH (e.g., after exercising)?

    7. How does saliva maintain the pH of the mouth after bacteria produce acid from the carbohydrates we’ve consumed?

    8. What happens next to maintain equilibrium?

    9. What are the results of a consistently low pH in the mouth?

    10. What are the two main materials used to fill a decayed tooth, once the decay has been removed?

    11. Name three problems with the use of amalgams for filling teeth.


Answers to Student Questions


      1. Name the three main constituents of the hard parts of the tooth.

The three main constituents of the hard parts of the tooth are mineral, proteins and water.

      1. What is hydroxyapatite?

Hydroxyapatite is the mineral that makes tooth enamel hard. Its formula is Ca5(PO4)3(OH).

      1. Why does the author say the hydroxyapatite in your teeth “is dynamic”? The author mentions that the hydroxyapatite in your teeth “is dynamic” because there is an equilibrium occurring between demineralization and mineralization of the hydroxyapatite, as food is eaten which reduces pH that increases the rate of demineralization, and the subsequent release of saliva with a slightly higher pH that increases the rate of mineralization.

      2. What are the products of the demineralization of hydroxyapatite?

The products of the demineralization reaction of hydroxyapatite are calcium ions (Ca2+), phosphate ions (PO43–) and hydroxide ions (OH).

      1. How does pH differ between that of the mouth and that of the body?

The pH in the body differs from that in the mouth in that the blood pH is closely controlled at a slightly alkaline value of 7.4, while the pH of the mouth can vary between 6.2 and 7.4.

      1. How does the body control blood pH (e.g., after exercising)?

When exercising, lactic acid is produced in the muscles, adding H+ ions to the bloodstream. To relieve this equilibrium shift, according to Le Chatelier’s Principle, bicarbonate ions react with the H+ ions and produce carbonic acid. Then the carbonic acid build-up causes an increase in the amount of carbon dioxide and water (which is exhaled through the lungs). This returns the body to a new state of equilibrium and a normal pH.

      1. How does saliva maintain the pH of the mouth after bacteria produce acid from the carbohydrates we’ve consumed?

Saliva maintains the pH balance in the mouth by secreting bicarbonate ions, produced in the salivary ducts, which combine with and neutralize the H+ ions produced in the fermentation process.

      1. What happens next to maintain equilibrium?

As the excess H+ ions from the previous question are consumed, the amount of carbonic acid builds up. To maintain the right amount of carbonic acid in the mouth, some of the excess carbonic acid breaks back down into carbon dioxide and water. The excess carbon dioxide then diffuses out from the saliva.

      1. What are the results of a consistently low pH in the mouth?

Consistently low pH in the mouth results in small holes or pits to form in the enamel of the tooth, which eventually exposes the dentin below the enamel. Dentin, being less resistant to acid than enamel (only 70% hydroxyapatite vs. 96% for enamel), is more quickly and easily demineralized, resulting in more rapid tooth decay.

      1. What are the two main materials used to fill a decayed tooth, once the decay has been removed?

The two main materials used to fill a decayed tooth are composite resins and mercury amalgams.

      1. Name three problems with the use of amalgams for filling teeth.

Three problems with using amalgams to fill teeth are:

          1. More of the healthy part of a tooth must be removed in order to pack the amalgam into the cavity in such a way that it ensures no movement of the filling,

          2. Amalgams block X-rays, making it more difficult for the dentist to obtain a useful 3-dimensional panoramic picture of your entire mouth, and

          3. Amalgams need to be properly disposed of, since they contain hazardous mercury.

          4. (Not mentioned in article: Amalgam fillings appear silver or black, making them obvious and not very attractive.)



  1   2   3   4   5   6   7


The database is protected by copyright ©dentisty.org 2016
send message

    Main page