Dental Impressions Objectives



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Dental Impressions

Objectives:

By the end of the activity, you will be able to:

  1. Create a Styrofoam impression of your own bite marks or bite marks created from professional dental castings.

  2. Produce a transparency of your bite marks from your own dental impression or from the bite marks produced from professional dental castings.

  3. Match bite marks found on a victim with bite marks from a suspect.


Materials:

(Students will work in teams of two)

4 Styrofoam bite plates, approximately 6 cm by 7.5 cm

2 hand lenses tissues

5 transparency sheets (8x8cm)

2 permanent markers

Scissors

2 transparencies of bite marks from victim

1 re-sealable plastic bag (for garbage)

Two sets of professional dental impressions (optional)

2 metric rulers
Time Required to Complete Activity: 45 minutes
Safety Precautions:

Use tissues to wipe any residual saliva from the Styrofoam dental impressions. When the activity is completed, all tissues should be discarded in the trash (or in a re-sealable plastic bag) to avoid spreading bacteria. Students should wash their hands with soap and water after wiping their Styrofoam dental impressions.


Procedure:

Part A: Making Bite Plates

  1. Obtain two equally sized Styrofoam plates from our instructor. The plates must be large enough to be in contact with all of your teeth but small enough to fit in your mouth. If the pieces are too large, cut the Styrofoam plate with the scissors. You need to put in the largest size possible to get a good impression of your back teeth. It will be a tight fit and a little bit uncomfortable!

  2. Label one plate maxilla and the other mandible.

  3. With the upper and lower plates aligned, place both plates in your mouth at once. Make sure they are placed back far enough to sit between your back molars.

  4. Bite down firmly on the plates and gently grind your teeth. Do not chew on the Styrofoam or bite completely through the plates. Remember that all you are trying to do is get an impression of your teeth!

  5. Remove the plates and wipe off any residual saliva with a tissue. Immediately discard the used tissue and place it in a re-sealable bag.

  6. Examine the bite marks on the Styrofoam plates. Students should unbend the plate and use a ruler to make the required measurements for width and depth of the impressions on both jaws. They will also need to note any unique characteristics they observe, such as slanted teeth, spaces, evidence of braces, etc.


Part B: Identifying Dental Patterns

Compare the five dental tracings made from the upper and lower jaws of five different people.



  1. Obtain half sheet of transparency. Label both with your initials in the upper right hand corner. In the upper left hand corner, label one as upper and the other as lower.

  2. Place a transparency sheet labeled upper over the upper impressions.

  3. With a permanent pen, outline the pattern made by each of your upper teeth. Be careful to trace each tooth individually.

  4. Repeat process for your lower teeth.

  5. Compare your dental transparencies with those of your partner and record measurements in Data Table 1.

  6. Using your tracings of the upper jaws, attempt to match the upper jaw with the lower jaws labeled A through E. The lower teeth should fit into the arch of the upper teeth. This is called nesting. For most people, the upper teeth will extend beyond the lower teeth. Report your results in Data Table 2.

Part C: Bite Mark Identification

  1. For the challenge each group, will have to find and match a suspects bite mark to bite marks taken from a crime scene. Compare the labeled samples (suspects) to those found at the crime scene (Unknown).


Data Table 1:

Jaw

Width (cm)

Depth (cm)

Unique Characteristics

Maxillae









Mandible












Data Table 2:

Upper Teeth (number)

Lower Teeth (letter)



































Conclusion: Restate your objective/purpose. Discuss any scientific concepts that you might have covered in this lab. HIGHLIGHT THE #/LETTER of SUSPECT and THE NAME OF THE INDIVIDUAL GUILTY OF THE CRIME.  Describe what you learned in class from this lab and whether or not this lab was a success or a failure for you. Sources of error.




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