Introduction to Occlusion

Question 1

Define occlusion

Answer 1

the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues

Question 2

dynamic relationship of the mandible to the maxilla is known as:

Answer 2

an articulation

Question 3

Components of masticatory system

Answer 3

Periodontium
articulatory sys
teeth

Question 4

Components of articulatory system

Answer 4

TMJ (hinges)
muscles (Motors)
occlusion (contacts)

Question 5

Components of TMJ

Answer 5

glenoid fossa
articular disc
condyle

Question 6

TMJ considered as ginglymoarthroidal, explain why.

Answer 6

In upper compartment only translational movements occur

In lower compartment rotational movements occur.

Question 7

Which muscle of mastication moves with condyle during function?

Answer 7

inferior lateral pterygoid

Question 8

functions of muscles of mastication

Answer 8

Masseter: elevation of mandible
Temporalis : retraction and elevation
Medial pterygoid: Grinding and Elevation
Lateral Pterygoid : Protraction and grinding

Question 9

Axes of mandibular rotational movements

Answer 9

saggital
horizontal (terminal hinge axis)
vertical

Question 10

Head region divided into three axes and three planes, name them.

Answer 10

sagittal axis is perpendicular to frontal plane,
vertical axis is perpendicular to horizontal plane, and
horizontal axis is perpendicular to sagittal plane

Question 11

when does horizontal axis movements occur?

Answer 11

in Centric Relation, making purely rotational opening and closing movements on the axis

Question 12

how big are the movements?

Answer 12

mvt is within 10 - 13 degree arc

separation is 20 - 25 mm

Question 13

When do Vertical movemnts occur

Answer 13

when mandible moves in a lateral excursion

Question 14

Where does the Vertical axis pass

Answer 14

on one side , working side/rotating side

Question 15

sagittal axis

Answer 15

when mandible moves on side, condyle on opposite side moves forward and donward simultaneously. this produces a downard arc when viewd in frontal plane

Question 16

mandibular movement to one side:

Answer 16

working side, laterotrusive relationship

Question 17

opposite side of mandible

Answer 17

nonworking side, Mediotrusive relationship

Question 18

What does a traditional Bennet angle measure? SCB

Answer 18

measures the angle from the sagittal plane to the endpoint of the movement of the condyle center.

Question 19

How is the bennet angle in articulators measured? S’PB

in articulators with an immediate lateral translation capability

Answer 19

measured from the sagittal plane after the immediate or early lateral translation (L) has occurred.

Question 20

What are the determinants of mandibular movements?

Answer 20

• posteriorly, the right and left TMJs;
• anteriorly, the teeth of the maxillary and mandibular arches;
• neuromuscular system

Question 21

Why do we put so much emphasis on harmony of TMJ and anterior guidance?

Answer 21

is because even the slightest disharmony can cause severe hyperactivity and incoordination of masticatory muscle function

Question 22

Anterior teeth are especially suited for guidance by virtue of:

Answer 22

• Canines having the longest, strongest roots in their respective arches
• The load being reduced by distance from the fulcrum (Class III lever)
• The proprioceptive threshold and concomitant reflexes reducing the load

Question 23

What are occlusal interferences ?

Answer 23

Interferences are undesirable occlusal contacts that may produce mandibular deviation during closure to maximal intercuspation or may hinder smooth passage to and from the intercuspal position

Question 24

what are they?

Answer 24

-centric
-non working
protrusive
-working

Question 25

centric interference

Answer 25

The centric interference is a premature contact that occurs when the mandible closes with the condyles in their optimum position in the glenoid fossae.

It will cause deflection of the mandible in a posterior, anterior, and/or lateral direction

Question 26

Working Intereference

Answer 26

occur when there is contact between the maxillary and mandibular posterior teeth on the same side of the arches as the direction in which the mandible has moved.
If that contact is heavy enough to disocclude anterior teeth, it is an interference

Question 27

Non working interfernce

Answer 27

is an occlusal contact between maxillary and mandibular teeth on the side of the arches opposite the direction in which the mandible has moved in a lateral excursion.
The nonworking interference is particularly destructive in nature
The potential for damaging the masticatory apparatus has been attributed to changes in the mandibular leverage, the placement of forces outside the long axes of the teeth, and disruption of normal muscle function

Question 28

Protrusive interference

Answer 28

is a premature contact occurring between the mesial aspects of mandibular posterior teeth and the distal aspects of maxillary posterior teeth.
potentially destructive and interfere with the patient’s ability to incise properly

Question 29

Organistions of occlusion

Answer 29

Unilateral / group function
bilateral
canine guided/mutually protected

Question 30

Canine guidance

Answer 30

Occlusal scheme where posterior teeth prevent execissive contact of the anterior teeth during MIP and then anterior teeth disengage posterior teeth from all excursive movemnts

Question 31

Group function

Answer 31

contacts are shared between teeth on the working side during a lateral excursion.
anterior group- hardest and earliest

Question 32

Analysis of occlusion

Answer 32

Static occlusion: contacts between teeth when mandible is closed and stationary
dynamic occlusiion: contacts between the teeth when mandible moves realtive to the maxilla.

Question 33

Centric occlusion (CO)

Answer 33

The occlusion of opposing teeth when the mandible is in centric relation;

Question 34

centric relation

Answer 34

Centric relation, which is an anteriorly, superiorly braced position along the articular eminence of the glenoid fossa, with the articular disc interposed between the condyle and eminence.

Question 35

MIP

Answer 35

The complete intercuspation of the opposing teeth independent of condylar position,

Question 36

What is the significance of Centric relation

Answer 36

• -Its a reproducible position of the mandible relative to the maxilla,
• Is reproducible irrespective of the guidance that the occlusal surfaces of the teeth may provide.
• Patients with no teeth still have a centric relation.
• There is inter- and intra operator reliability in finding it

Question 37

Freedom in centric occlusion

Answer 37

Occurs when mandible is able to move anteriorly for a short distance in the same horizontal and sagittal plane while maintaining tooth contact

Question 38

provision for long centric

Answer 38

moves the lingual incline forward so that the jaw is free to close without restriction either in centric relation or in the slightly protruded relationship that occurs at various postural positions of the head

Question 39

What is an articlator

Answer 39

Articulator: a mechanical instrument that represents the temporomandibular joints and jaws, to which maxillary and mandibular casts may be attached to simulate some or all mandibular movements;
Articulators are divisible into four classes;