3/20: Premature Contacts and Interferences Flashcards
What two things are coincident?
MIP and CR
- when the teeth meet in MIP, the condyles are in the CR position
What does the patient have when in MIP/CR?
Multiple, bilateral, even and simultaneous contacts
What does the patient have in the anterior teeth during MIP/CR?
“light occlusal contacts”
What does the patient have during protrusive and lateral excursive movements?
Anterior guidance
What are the types of occlusal interferences?
- Centric Interferences
- Working side Interferences
- Non-Working side Interferences
- Protrusive Interferences
What is occlusal interference?
An unwanted or premature interocclusal contact
What is also called premature contact?
Centric interference
What is centric interference?
Premature contact that occurs when the condyles are manipulated into CR
What teeth contact in centric interference?
Only one, maybe two teeth
What happens once the centric interference occurs?
The mandible moves forwards and upwards (and usually slightly laterally) into MIP
What teeth does centric interference occur on?
The mesial inclines of the maxillary teeth and distal inclines of the mandibular teeth
What is on the working side in lateral excursion?
Anterior guidance (canine guidance) on the working side
*****no other teeth on the working or non working side should contact
What teeth do working side interferences occur between?
Maxillary and mandibular posterior teeth on the working side as the patient makes a lateral movement
What can heavy contacts during working side interferences cause?
These contacts may be heavy enough to disclude the anterior teeth and interfere with the smooth harmonious movement of the NWS condyle
Which inclines do interferences occur between?
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
What is the difference between group function and working side interferences?
Different philosophies: canine guidance vs group function
What are examples of WS interferences?
Contacts further distal to the MB cusps of the first molars
Contacts on the WS that prevent the canines from guiding
What are non working side interferences?
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
What are the most destructive of all interferences?
Non-working side interferences
What do non-working side interferences change?
The lever system of the mandible and place considerable stress on the TMJ joints
Which incline do non-working side interferences occur on?
On the NW side between the inner inclines of the maxillary lingual cusps and the inner inclines of the mandibular buccal cusps
What is a protrusive interference?
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
Why are protrusive interferences very destructive?
because they are positioned close to the fulcrum (TMJs) and the resulting source of power (muscles) is large and destructive forces
On which inclines do protrusive interferences occur on?
- Between the posterior teeth
- Between the mesial inclines of the mandibular cusps and the distal inclines of the maxillary teeth
