• Identify the types of human teeth and describe their structure and function
• State the causes of dental decay and describe the proper care of teeth
• Describe how flouride reduces tooth decay and explain arguments for and against the addition of flouride to public water supplies

Teeth are more complicated than they look! They have nerves, a blood supply and there are different types of teeth.

They can be divided into two basic parts

1. Crown (the visible part)
   
2. Root (embedded in the jaw and not usually visible)
   

Have a look at the picture below, it shows a full set of permanent human teeth as they appear in the human mouth.

Each different structure is adapted to a particular function;

Incisors and canines are sharp so they can tear into food.

Molars have a flatter shaped crown for crushing and grinding up food

Now scroll back up to the photograph of the real teeth, can you identify the name of each tooth from the diagram?

• Most people could probably tell you that teeth are made of calcium, which is pretty much correct......in fact tooth enamel is mostly made up of calcium phosphate.
  

• Check out this link below for some basic information about teeth and then copy the diagram into your notes.
  

You will be provided with the following list of equipment for your experiment;

5 (real) teeth

Lemon juice

2 (well know) fizzy soda drinks

Sparkling water

Electronic balance (units in grams)

Flouride solution

Set of small beakers

Design an experiment to investigate tooth decay, don't forget to identify your variables and consider how you will present your data.

Here are the key points....

Results

• Should include a table, and a paragraph that describes what is shown in the table. This is not where you explain your results (that is done in the evaluation/conclusion).
  

• You also need to describe any qualitative data - colour, appearance, smell etc.
  

Conclusion

• This is where you explain and your results in terms of scientific content. Use your knowledge of causes of tooth decay, (sugar, acidity, bacteria) and try to relate it to your results.
  

• Remember you NEVER state that your hypothesis was proved right or wrong, but you can state if your results support your hypothesis.
  

Evaluation

• Comment on any experimental error/human error
  

• How could improvement be made to the procedure/equipment/organisation of the experiment.
  

• What would be the next logical investigation to find out more?
  

• Teeth contain a lot of calcium.....this is something to remember when thinking about how tooth decay occurs.
  

• After consuming food/drinks that are high in sugar, molecules called glycoproteins stick to the teeth (a glycoprotein is combination of a carbohydrate and a protein molecule).

• Then millions of a type of bacteria Streptococcus mutans then stick to the glycoprotein molecule, and use the sugar from the glycoprotein molecule in respiration
  

• Because they perform anaerobic respiration they make lactic acid.

• Anaerobic respiration

  When there is a lack of oxygen, glucose is broken down to release some energy but less energy than aerobic respiration (C6H12O6 + 6O2 -> 6H20 + 6CO2)

  Anaerobic respiration involves the incomplete breakdown of glucose. It releases around 5% of the energy released by aerobic respiration, per molecule of glucose. The waste product is lactic acid rather than carbon dioxide and water:

  glucose → lactic acid (+ little energy)

• Lactic acid lowers pH (because it is an acid!) and this causes calcium phosphate in teeth to dissolve which can cause a cavity to form.
  

• Flouride is a naturally occuring mineral (F-) found in many foods and water.

• Flouride helps to prevent tooth decay by strengthening the tooth enamel, by making the tooth more resistant to the acid attacks from bacteria (Streptococus mutans) and sugars.

• Flouride can even reverse the damage from the early stages of tooth decay.
  

Look under the 'ate' in Colgate (below).

We are going to debate the arguments for and against the addition of flouride to public water supplies.

You will each be given a side of the debate to research, and take part in a class debate.

• Check your answers to the exam questions using the iGCSE mark scheme below.
  
• AVP stands for any valid argument (we can discuss any AVP issues in class).