principles of occlusion

Question 1

Occlusion

Answer 1

• act or process of closure or of being closed of shut off (without inclusion of teeth)
• static relation between the incising or masticating surfaces of the maxillary or mandibular or tooth analogues (with inclusion of teeth)
• i.e. closure of the mouth until teeth come into contact

Question 2

ICP intercuspal position

Answer 2

• complete intercuspation of the opposing teeth independent of condylar position, sometimes referred as the best fit of the teeth regardless of condylar position
• i.e. habitual bite

Question 3

Physiologic rest position

Answer 3

• the postural position. of the mandible when an individual is resting comfortably in an upright position and the associated muscles are in a state of minimal contractual activity
• position of jaw when we are comfortable, teeth are not together during the day, mandible is resting in a position

Question 4

vertical dimension

Answer 4

• distance between two seated anatomic or marked points (usually one on the tip of the nose and other on the chin)

Question 5

resting vertical dimension

Answer 5

• same points, whilst jaw is in physiological rest position

Question 6

occlusal vertical dimension

Answer 6

• same points, ask patient to close together into ICP

Question 7

what is the free way space on average

Answer 7

2-4mm

Question 8

what is freeway spac

Answer 8

space between two positoons

VD-OVD = FWS

Question 9

types of excursions

Answer 9

protrusion
latterotrusion
recursion (posterior movement of jaw_

Question 10

Laterial excursion sub types

Answer 10

mediotrusion

laterotrusion

Question 11

mediotrusion

Answer 11

side moving towards the midline

Question 12

laterotrsusion

Answer 12

side moving away from the midline

Question 13

what happens in the Codyls during lateral excursion

Answer 13

mediotrusion
- condyle moves out from the glenoid bossa onto articular eminane
laterotrusion
- condyle remains on fossa purely rotates

Question 14

centric relation

Answer 14

• Maxillomandibular relationship, independent of tooth contact, in which the condyles articulate in the anterior superior position against the posterior slopes of the articular eminences, in this position the mandible restricted to a purely rotary movement
• i.e. a maxillomandibular relationship not a tooth based position, relationship when the condyles are in the glenoid fossa in the anterior and superior position, against the posterior surface of the articular eminence

Question 15

RCP

Answer 15

• contact of a tooth or teeth along the retruded path of closure, initial contact of a tooth or teeth during closure around the transverse horizontal axis
• tooth contact whilst mandible is in CR, condyle is in the glenoid fossa, unstrained and comfortable, as the jaw closes RCP is the first tooth contact that occurs

Question 16

RCP vs iCP

Answer 16

RCP is tooth contact whist mandible is in centric relation

ICP is habitual bite, tooth contact when we close toegher

Question 17

mandibular rest postions

Answer 17

Physiologic rest position
CR
mandibular protrusion
Mandibular laterotrusion
LVD

Question 18

tooth contact relationships

Answer 18

ICP
Tooth contacts during protrusive excursions
RCP
OVD

Question 19

anterior guidance and poster guidance

Answer 19

Pathway taken by the mandible is guided anteriorly by the teeth (anterior guidance) and also by the condyles (posterior guidance)

Question 20

why is anterior guidance with incisors better

Answer 20

incisors further from the hinge therefore load is reduced
morhoplogy - longer roots help in distributing lateral loads rather than facial or compressive loads on posterior teeth in ICP

Question 21

anterior guidance in anterior open bites

Answer 21

reverse and large overset involves posterior teeth

Question 22

Ideal protrusion steps

Answer 22

• anterior teeth come into contact and guide the mandible anteriorly
• condyle comes out of the glenoid fossa and onto the articular eminence
• typically causes posterior teeth to disclude (christensens phenonmenon)
• This is ideal as posterior teeth are not ideal to revive lateral loads in mandibular movements and are closer to the hinge, therefore would receive higher loads

Question 23

lateral excursion teeth used

Answer 23

canines

• when this occurs the canines (in contact) guide on the working side only (side which the jaw is moving to), all other teeth are discluded
• Most optimum anterior guidance relationship in lateral excursions

Question 24

why is canine guidance for lateral ideal

Answer 24

1) Morphology
- very strong tooth with long roots
2) Favourable crown to root ratio
3) distant from the hinge of the mandible
4) distance from the powerful muscles of mastication

Question 25

group function

Answer 25

canine guidance not always present
guidance provided by a number of teeth on the working side
no contacts on balancing side

Question 26

significance of RCP

Answer 26

often only involved 2 opposing teeth
- these teeth carry all load of occlusion when patientslides from RCP to ICP (vice versa)
if these are unrestored tsound teeth no problem, restored failure of restoration is liekly

Question 27

classifications of occlusion

Answer 27

skeletal
incisor
angle

Question 28

skeletal classification of occlusion

Answer 28

relationship between md and mx

no association to teeth

Question 29

incisor classification of occlusion

Answer 29

class 1/2/3
nbeween incisors

Question 30

Angle classification of occlusion

Answer 30

molar relationship between upper 1st molar and lower 1st molar

Question 31

ideal occlusion (e.g. one to make dentures)

Answer 31

1) Multiple simultaneous contact
2) no cuspal incline contact
3) occlusal contacts that are in line with long axis of the tooth
4) ICP=CR
5) Anterior guidance on anterior teeth (canine during lateral excursions, anterior during protrusion) and posterior disclusion
6) Mutually protected occlusion

Question 32

mutually protected occlusion

Answer 32

posterior teeth protect anterior in ICP

anterior protect poster teeth during excursions

Question 33

why are the anterior teeth capable of taking load whilst in protrusive excursion

Answer 33

• ther are the furtherest away from the hinge of the mandible and therefore the force exerted is limited
• they are distant from the massester and therefore the force exerted is limited

Question 34

High restorations can lead to

Answer 34

• Patient discomfort/pain (muscle soreness, pain on biting, headache)
• tooth fracture
• tooth mobility
• additional time and money
• professional pride?

Question 35

what happens if a restoration is not in occlusion

Answer 35

• tooth drifting
• overeruption (teeth continue to erupt until they reach a contact
• further occlusal issues may stem from this (interferences or suboptimal contacts)

Question 36

restoration aims

Answer 36

• Contact in ICP
• Maintaining contacts on all other teeth (not changing the occlusal schemes)
• fitting our restoration within the existing scheme
• contact in protrusion or laterotrusion, in most cases no unless the tooth previously had these contacts

Question 37

how to measure occlusion

Answer 37

• mark up occlusion with articulating paper
• use of shimstock foil to feel contacts between the teeth
  May also measure
• skeletal/incisor/angle classifications
• signs of occlusion issues (wear facets, craze or fracture lines, fremintus)
• OVD (occlusal vertical dimension) – can often be decreased due to tooth wear

Question 38

Additional record taking

Answer 38

• photographs
• impression and mounting of study models on an articulator
• facebow record (generally used if we are restoring num. of teeth that are involved in the occlusal movements)