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Wax Shrinkage

Dental Materials Project

Yen Hoang

on 13 October 2013

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Transcript of Wax Shrinkage

WAx Shrinkage
Our Experiment
Baseplate Wax
Group 2
Bohdan Kobasko
Victoria Petrakis
Yanhong Wu
Yen Hoang
Problem with the wax
Main component is paraffin wax
Paraffin is a hard wax that is used in baseplate
to hold help artificial teeth in place for try-in dentures
Part of alkane group and is made of:
natural and synthetic waxes
Hydrocarbon waxes
used on a day to day base in a dental laboratory for many appliances.
is a pattern wax
Out of all the waxes used in dentistry, baseplate is used the most.
used as a support structure for artificial teeth in complete and partial dentures, try- in and occusal rims.
Also made up of beeswax, camauba, ceresin, natural synthetic resins, and microcrystalline, or synthetic waxes,
Other Components
The biggest problem with baseplate wax is the shrinkage that occurs after manipulating it. When the wax is heated, it expands, but when it cools, the wax shrinks. The reason this is such an issue is because it moves the teeth and changes our class one bites to some foreign bite.
Our experiment
Objective is to determine the amount of shrinkage due to the temperature changes
Our hypothesis is that the higher the temperature when melting wax, the higher amount of shrinkage that will take place.
Three metal cups 42g of baseplate wax
Scale Hot plate
Measuring cup Knife
Ruler Thermometer
Step 1
Cut up the wax in three quantities and weigh them, making sure each group is 14g.
Step 2
Place the wax in each cup, pushing them down to the bottom
Using a measuring cup filled to 80ml with water, pour the liquid into each cup and take note of the amount left in the measuring cup
Step 3
Heat up each cup to different temperatures, one at a time
Cup #1 -165.1°C
Cup #2 – 125°C
Cup #3 - 145°C
Allow the cups to sit overnight
Step 4
Step 5
Using the measuring cup filled to 80ml with water, pour it into each cup again
Step 6
Leave the cups to sit for another week and once again, using the measuring cup, pour water into each cup
Results, Discussion & Conclusion
Cup #1
was heated to the highest temperature of 165.1 °C
Before the experiment – 50ml
After one night – 50 ml  no change
After a week – 55ml  shrunk a total of 5 ml
Cup #2
Was heated to the lowest temperature of 125 °C
Before experiment – 53 ml
After one night – 49 ml  expanded 4ml
After one week – 54.5 ml  shrunk 1.5 ml
Cup #3
Heated to 145 °C
Before experiment – 48 ml
After one night – 50 ml  shrunk 2 ml
After one week – 53  shrunk a total of
5 ml
Cup #1 and Cup #3 both had the same amount of shrinkage while Cup #2, only shrunk 1.5 ml
Had the hypothesis been correct, the amount of shrinkage that occurred in Cup #1 and Cup #3 would have been different. Cup #1 had been heated to a temperature that was 20.1 degrees higher than that of Cup #3
From this experiment, it is assumed that after a certain temperature, the wax is unable to shrink anymore
Possible Errors
Water left from the previous measurement could have changed wax properties
Observation of water level was wrong
Did not pour water up to the same initial level
The hypothesis was correct in that the higher the temperature, the higher the amount of shrinkage. This can be seen by comparing Cup #1 and Cup #3 to Cup #2
However, we did not expect the wax to stop shrinking after a certain point

Therefore, from the results of this experiment, we have learned that when setting up teeth, heat the wax up to a minimum temperature to avoid too much movement.
Full transcript