3/20: Premature Contacts and Interferences

Question 1

What two things are coincident?

Answer 1

MIP and CR
- when the teeth meet in MIP, the condyles are in the CR position

Question 2

What does the patient have when in MIP/CR?

Answer 2

Multiple, bilateral, even and simultaneous contacts

Question 3

What does the patient have in the anterior teeth during MIP/CR?

Answer 3

“light occlusal contacts”

Question 4

What does the patient have during protrusive and lateral excursive movements?

Answer 4

Anterior guidance

Question 5

What are the types of occlusal interferences?

Answer 5

• Centric Interferences
• Working side Interferences
• Non-Working side Interferences
• Protrusive Interferences

Question 6

What is occlusal interference?

Answer 6

An unwanted or premature interocclusal contact

Question 7

What is also called premature contact?

Answer 7

Centric interference

Question 8

What is centric interference?

Answer 8

Premature contact that occurs when the condyles are manipulated into CR

Question 9

What teeth contact in centric interference?

Answer 9

Only one, maybe two teeth

Question 10

What happens once the centric interference occurs?

Answer 10

The mandible moves forwards and upwards (and usually slightly laterally) into MIP

Question 11

What teeth does centric interference occur on?

Answer 11

The mesial inclines of the maxillary teeth and distal inclines of the mandibular teeth

Question 12

What is on the working side in lateral excursion?

Answer 12

Anterior guidance (canine guidance) on the working side
*****no other teeth on the working or non working side should contact

Question 13

What teeth do working side interferences occur between?

Answer 13

Maxillary and mandibular posterior teeth on the working side as the patient makes a lateral movement

Question 14

What can heavy contacts during working side interferences cause?

Answer 14

These contacts may be heavy enough to disclude the anterior teeth and interfere with the smooth harmonious movement of the NWS condyle

Question 15

Which inclines do interferences occur between?

Answer 15

The outer incline of the mandibular buccal cusp and the inner inclines of the maxillary buccal cusp and/or between the outer inclines of the maxillary lingual cusps and the inner inclines of the mandibular lingual cusps

Question 16

What is the difference between group function and working side interferences?

Answer 16

Different philosophies: canine guidance vs group function

Question 17

What are examples of WS interferences?

Answer 17

Contacts further distal to the MB cusps of the first molars
Contacts on the WS that prevent the canines from guiding

Question 18

What are non working side interferences?

Answer 18

Any contact between the maxillary and mandibular teeth on the non-working side (side opposite to which the mandible moves) as the patient makes a lateral movement

Question 19

What are the most destructive of all interferences?

Answer 19

Non-working side interferences

Question 20

What do non-working side interferences change?

Answer 20

The lever system of the mandible and place considerable stress on the TMJ joints

Question 21

Which incline do non-working side interferences occur on?

Answer 21

On the NW side between the inner inclines of the maxillary lingual cusps and the inner inclines of the mandibular buccal cusps

Question 22

What is a protrusive interference?

Answer 22

Any contact between the posterior teeth as the
mandible moves forward in protrusion
**Sometimes the interference is so severe it will prevent contact between the anterior teeth

Question 23

Why are protrusive interferences very destructive?

Answer 23

because they are positioned close to the fulcrum (TMJs) and the resulting source of power (muscles) is large and destructive forces

Question 24

On which inclines do protrusive interferences occur on?

Answer 24

• Between the posterior teeth
• Between the mesial inclines of the mandibular cusps and the distal inclines of the maxillary teeth