occlusion and Rx dentistry (3rd year)

Question 1

muscles involved in mandibular movement

Answer 1

MofM

suprahyoids

Question 2

muscles involved in mandibular movement - MofM

Answer 2

temporalis - elevates and retracts
LP - protrudes, depresses, lat movement
MP - elevates, lat movement
masseter - elevates and protracts

Question 3

muscles involved in mandibular movement - suprahyoids

Answer 3

elevate hyoid bone/depress mandible

Question 4

mandibular movements

Answer 4

rotation

translocation

Question 5

rotation

Answer 5

small amount of mouth opening (up to 20mm)
condyle and disc remains within the articular fossa
no downwards or forwards movement
“hinge movement”

Question 6

hinge movements and terminal hinge axis

Answer 6

rotation of condylar heads around the imaginary horizontal line through rotational centres of the condyles
imaginary line - terminal hinge axis

Question 7

facebow

Answer 7

records relationship of maxilla to the hinge axis of rotation of the mandible

• terminal hinge axis
• inter-condylar distance

Question 8

translocation

Answer 8

LP contracts
articular disc and condyle begin to move
travel downwards and forwards along incline of the articular eminence
may also travel laterally (laterotrusive movement)

Question 9

condylar guidance angle

Answer 9

condyle sliding down the articular eminence
anatomy varies (av value)

Question 10

ICP-RCP slide

Answer 10

ICP about 1mm anterior to RCP in 90% of the pop

RCP and ICP not coincident so mandible slides forward to achieve ICP - anterior slide

Question 11

ICP-RCP slide and restoring last tooth in arch

Answer 11

if pt has a large bite and you don’t take a facebow before crowns then you may prop open

Question 12

describe the working and non-working sides if the mandible moves to the right

Answer 12

RS - working side

LS - non-working side

Question 13

Posselt’s envelope

Answer 13

extremes of mandibular movement

border movements of the mandible in the sagittal plane

Question 14

border movements of the mandible - positions

Answer 14

ICP
E (edge to edge)
Pr
T (max opening)
R (retruded axis position)
RCP

Question 15

ICP

Answer 15

tooth position regardless of the condylar position

max interdigitation

Question 16

edge to edge

Answer 16

tooth position
teeth slide forward from ICP guiding on palatal surfaces of anterior teeth
incisal edges of U and L incisors touch

Question 17

Protrusion

Answer 17

condyle moves forwards and downwards on articular eminence
only incisors +/- canines touch
no posterior tooth contacts
eventually no tooth contacts

Question 18

max opening

Answer 18

no tooth contacts
mouth wide open
full translocation of the condyle over the articular eminence

Question 19

retruded axis position

Answer 19

reproducible - used in dentures and toothwear
no tooth contacts
most superior anterior position of the condylar head in the fossa
terminal hinge axis

Question 20

RCP

Answer 20

1st tooth contact when the mandible is in R

ICP is about 1mm anterior to RCP in 90% of population - in 10% RCP and ICP are the same

Question 21

marking tooth contacts

Answer 21

dry teeth
Millers forceps and fine articulating paper
for ICP contacts just get them to tap
if want guidance get ICP in blue then get them to grind using red

Question 22

when to mark tooth contacts

Answer 22

before
 - preparing a tooth
 - removing a restoration
after
 - placement of a crown
 - placement of a restoration

Question 23

what to look at in the static occlusion

Answer 23

incisor relationship
molar relationship
OJ/OB
cross bites
open bites
individual tooth contacts
RCP-ICP slide (freedom in static)

Question 24

functional (working) cusps

Answer 24

cusps that occlude with the opposing teeth in ICP

lingual cusps of U posteriors and buccal cusps of L posteriors

Question 25

non-functional (balancing) cusps

Answer 25

cusps that do not occlude with the opposing teeth in ICP | buccal cusps of U posteriors and lingual cusps of L posteriors

Question 26

fossa

Answer 26

depression/concavity | fct cusp of a tooth contacts fossa of opposing tooth

Question 27

ICP contacts

Answer 27

lingual cusp of U molar contacts fossa of L molar | buccal cusp of L molar contacts fossa of U molar

Question 28

normal overbite

Answer 28

2-4mm

Question 29

Ackerly classification of complete traumatic overbites

Answer 29

1 - palatal mucosa 2 - gingival crevice 3 - stripping 4 - palatal abrasion

Question 30

crossbite

Answer 30

where one or more teeth may be abnormally malpositioned bucally/lingually/labially with reference to opposing teeth

Question 31

mutually protected dynamic occlusion - gold standard

Answer 31

canine guidance posterior disocclusion in lateral excursions no non-working/working side contacts no protrusive interferences

Question 32

canine guidance

Answer 32

when mandible moves to one side, contact only between canines no posterior tooth contacts (a space)

Question 33

why are canines chosen as guidance for lateral excursions?

Answer 33

longest and largest roots (C:R) dense compact bone surrounding them fewer muscles are active when canines contact during eccentric movements than when posterior teeth contact dissipate horizontal forces while disoccluding posterior teeth

Question 34

what is it important that canine/group function provide enough guidance for?

Answer 34

to disocclude teeth on the NW side which are not desirable contacts

Question 35

group function

Answer 35

mandible moves to left (WS), multiple teeth in contact on left several teeth on WS contact during laterotrusive movement

Question 36

when is bilateral group function seen often?

Answer 36

toothwear

Question 37

what is the most favourable alternative to canine guidance?

Answer 37

group function

Question 38

best teeth for group function

Answer 38

3,4,5,MB cusp 6 any contact more posterior not desirable as increased force due to closeness of fulcrum buccal cusp to buccal cusp is more desirable contact during movement than lingual to lingual cusp

Question 39

occlusal interferences

Answer 39

undesirable tooth contacts that may produce mandibular deviation during closure to ICP or may hinder smooth passage to and from ICP

Question 40

types of occlusal interferences

Answer 40

working side - similar cusps contact non-working side - dissimilar cusps contact protrusive - any posterior contact during protrusion

Question 41

why avoid posterior contacts?

Answer 41

teeth designed to absorb heavy forces in direction of long axis of tooth most teeth not designed to absorb significant lateral forces generated by occlusal interferences musculature gets a rest as less activity if not undesirable posterior contacts occlusal trauma and undesirable tooth movements

Question 42

eccentric bruxism

Answer 42

moving away from CO, dynamic parafunctional grinding involuntary rhythmic/spasmoidic/fct gnashing/grinding/clenching in other than chewing movements

Question 43

centric bruxism

Answer 43

clenching | freq associated with acute nervous tension or physical effort

Question 44

S and S of bruxism

Answer 44

``` toothwear fractured restorations tooth mobility - often absence of PDD tooth migration muscle pain and fatigue headache - worse at end of day earache pain and stiffness in TMJ and surrounding muscles ```

Question 45

occlusal trauma

Answer 45

injury resulting in tissue changes within the attachment apparatus, inc PDL, supporting alv bone and cementum, as a result of occlusal force(s) primary - intact periodontium secondary - reduced periodontium

Question 46

fremitus

Answer 46

presence/absence palpable/visible movement of a tooth when subjected to occlusal forces finger on cervical 1/3 and ask pt to close together

Question 47

examining the occlusion

Answer 47

``` incisor relationship guidance OJ/OB ICP contacts W/NW/P contacts pathology ```