Name:



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Laboratory Instructions

Teeth

Observe

Dental remains are often used to identify deceased persons when other means of finding their identities are not available.

Materials

Supplied

Student Guide

graph paper

Laboratory Guidelines

Also Needed

tracing paper (or transparency sheets with markers)

metric ruler

Safety

Review the Laboratory Guidelines before conducting the lab.

Experiment: Precision and Accuracy of Measurements

Setup

Three burned bodies are discovered in a fire pit outside a remote mountain cabin. Local police believe that someone killed the people and burned their bodies to prevent their identification and to destroy evidence. Police arrested a suspect who has a suspicious wound, which he claims is a bite from his dog. As a forensic odontologist, you will analyze dental data to identify the bodies and possibly provide information about the crime.

Part A: Match Skulls to Victims

Evidence

A forensic odontologist drew these three dental sketches based on the three skulls recovered from the crime scene. Fillings appear as dark areas, and missing teeth appear as gray ovals in the sketch.

[pic] [pic]

Skull A Skull C

[pic]

Skull B

Dental Records of Possible Victims

|Police theorized that three names they discovered through investigation were|Key to Dental Charts |

|the names of the victims. A dentist gave investigators those individuals’ |[pic] |

|dental records. | |

|See the Key to Dental Charts below to learn how to interpret the dental | |

|records. Note that the key shows two teeth in each quadrant of the mouth. | |

|Molars and premolars have occlusal parts, which means the part used for | |

|chewing food. Incisors have either a point or a flat, cutting surface, which| |

|is the incisal part. | |

Possible Victim 1: Female, Age 43

|Dental Record |

|[pic] |

|Comments: |

|May 19, 1983 – mesial-occlusal restoration (filling) on 19, distal-occlusal restoration on 20, and mesial and distal restoration on 21 |

|April 10, 1985 – buccal restoration on 3, distal restoration on 4 |

|June 10, 1987 – extracted 18 (abscessed), 1, 16, 17, 32 came in with space. |

|July 13, 1992 - occlusal restoration on 30, mesial-occlusal restoration on 31 |

|May 10, 1995 – palatal restoration on 12, occlusal restoration on 13 |

|Dec. 8, 1999 – occlusal restoration on 14, mesial restoration on 15 |

|Oct. 12, 2004 – occlusal restoration on 16 |

Possible Victim 2: Female, Age 18

|Dental Record |

|[pic] |

|Comments: |

|May 17, 2006 – palatal restoration (filling) on 3, 4, 5 |

|Feb. 20, 2007 – extracted 19 (abscessed) |

|Aug. 9, 2007 – mesial restoration on 6 and 12 |

|March 10, 2008 – extracted 29 (abscessed) |

|June 8, 2010 – extracted 1, 16, 17, and 31 (abscessed) |

|Nov. 9, 2010 – roots filled (root canals) on 7, 8, 9, 10 |

Possible Victim 3: Male, Age 10

|Dental Record |

|[pic] |

|Comments: |

|Good dental health |

|2, 15, 18, 31 have not erupted |

|1, 16, 17, 32 have not developed |

|Note: 20, 21, 22 have not erupted (primary teeth are still in place) |

Procedure

1. Fill in the Blank postmortem dental charts below for Skulls A, B, and C using the sketches made by the forensic odontologist.

2. Use numbers to note the location of any teeth missing from each skull.

Skull A is missing ______________

Skull B is missing ______________

Skull B is missing ______________

3. Compare each sketch with dental records from each possible victim.

4. Determine if each sketch based on the crime scene evidence matches dental records for any of the possible victims.

Conclusion:

Skull A ( Matches possible victim #____ ( Does not match an available dental record

Skull B ( Matches possible victim #____ ( Does not match an available dental record

Skull C ( Matches possible victim #____ ( Does not match an available dental record

Blank postmortem dental chart for Skull A (to be filled in by forensic odontologist)

[pic]

Blank postmortem dental chart for Skull B (to be filled in by forensic odontologist)

[pic]

Blank postmortem dental chart for Skull C (to be filled in by forensic odontologist)

[pic]

Part B: Identify Bite Marks

Evidence

The following is a sketch of the bite mark found on the suspect:

[pic]

The following are drawings based on a cast taken from the suspect’s dog.

[pic] upper jaw

[pic]lower jaw

Procedure

1. With the tracing paper (or transparency sheet and marker), trace the bite patterns of the victims. Use the forensic odontologist’s drawings in Part A of the lab. Also, trace the set of canine teeth marks, upper jaw and lower jaw, above.

2. Working with each traced bite mark separately, compare each traced bite mark with the bite mark found on the suspect by laying each traced mark over the mark on the suspect (shown above).

3. Determine which, if any, of the five bite marks (three human and two canine) is a likely match.

Likely match is from _____________________________.

4. State whether it is possible that the bite came from the suspect’s dog, and support your argument with statements based on the data available.

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