Jaw Relations and Articulation

Question 1

What are non-contact relationships?

Answer 1

Movement governed by muscles of mastication and articular surfaces of TMJ

Question 2

Where is the axis of rotation in non-contact relationships?

Answer 2

Condylar heads

Question 3

What is the path followed by any point on mandible while rotating called?

Answer 3

Retruded arc of Closure

Question 4

What does opening of the mouth beyond 20mm cause?

Answer 4

Protrusion by translation and further rotation of both condyles establishing posterior guidance

Question 5

What is the inter-occlusal distance?

Answer 5

When muscles of mastication are at rest the space between the teeth is the inter-occlusal distance

Question 6

Describe the intercuspal position (ICP)

Answer 6

Relation of upper and lower jaws when teeth are in maximum intercuspation

Question 7

Describe the retruded contact point (RCP)

Answer 7

The most posterior position achievable by the mandible, usually 1mm distal to ICP

Question 8

What is protrusion?

Answer 8

Movement of mandible governed by palatal slopes of anterior teeth where posterior teeth separate from anterior

Question 9

What is lateral excursion?

Answer 9

Jaw working from side to side (side mandible moves to is working side and side moving away from is non-working side)

Question 10

Describe canine guidance lateral excursions

Answer 10

Separation of teeth by contact of canines on working side only

Question 11

What is group function lateral excursions

Answer 11

Contact of premolars and canines on working side only

Question 12

Name 3 parameters of jaw movement

Answer 12

1. TMJ
2. Teeth
3. Muscles of mastication

Question 13

What is the maximum envelope of movement?

Answer 13

Total mandibular movement which is limited by boarder positions and described by Posselt in 1952

Question 14

Describe the influence of contact relations of removable partial denture design - If the patient has an ICP

Answer 14

Reproduce this and set teeth to harmonise with existing occlusion - Conformative approach to occlusion

Question 15

Describe the influence of contact relations of removable partial denture design - If the patient has no ICP

Answer 15

Make denture occlusion correspond to RCP so new ICP = RCP - Reorganized approach to occlusion

Question 16

How may a patient’s mandibular movement be traced?

Answer 16

Electromagnetic techniques

Question 17

What is the function of articulating study casts?

Answer 17

Allow a design to avoid premature occlusion on any denture component

Question 18

What is the primary rule of articulated study casts?

Answer 18

Must maintain tooth-tooth ICP

Question 19

Name 2 ways study casts may be articulated

Answer 19

1. Hand alone if there is enough teeth present to do this

2. Wax registration rims if ICP not easily located by hand

Question 20

What allows study casts to be held reliably in ICP?

Answer 20

Articulators

Question 21

What is a surveyor?

Answer 21

A simple mechanical parallelometer with a vertical arm which can be brought against teeth or ridges of a cast to identify parallel surfaces and points of maximum contour

Question 22

Name 4 purposes of surveying study casts

Answer 22

1. Identify optimum path of insertion
2. Design, material and position of clasps
3. Allow blocking out of unwanted undercuts
4. Measure and mark correct position and depth of undercut

Question 23

Describe the initial survey

Answer 23

Always with the occlusal plane at right angles to the vertical because this is the most likely direction of displacement during function

Question 24

What is the function of blocking out unwanted undercuts?

Answer 24

Duplicate models can be made on which a prosthesis is constructed and subsequently seated upon and withdrawn from

Question 25

What is a survey line?

Answer 25

A mark around a tooth indicating its greatest circumfrence in any one position relative to the vertical

Question 26

What are undercut areas?

Answer 26

Areas below the survey line