SDA

Question 1

reasons for the concept

Answer 1

many not happy with wearing dentures
non-compliance with wearing of dentures as high as 40%
high incidence of dental disease in RPD wearers
- root caries, PDD
- harder to keep clean

Question 2

criticism from “traditionalist” prosthodontists

Answer 2

loss of molars associated with

• reduced masticatory efficiency
• mandibular displacement
• alterations in food selection
• aesthetic issues
• loss of occlusal stability
• TMJ problems

Question 3

author

Answer 3

Kayser 1981

Question 4

SDA concept

Answer 4

a dentition where most posterior teeth are missing
satisfactory oral fct without RPD
priority given to maintaining an anterior and premolar dentition in one or both jaws
right circumstances - non-replacement of posterior missing teeth can provide a stable and acceptable dentition
sufficient adaptive capacity in subjects when 3-5 occlusal units are left
- pair of occluding premolars 1 unit
- pair of occluding molars 2 units

Question 5

WHO oral health

Answer 5

“the retention, throughout life, of a fct, aesthetic, natural dentition of not less than 20 teeth and not requiring recourse to prostheses should be the tx goal for oral health”

Question 6

SDA and oral fct and comfort

Answer 6

provide sufficient oral fct and comfort in terms of chewing fct, aesthetics, S+S of TMD

Question 7

SDA and mandibular stability

Answer 7

the absence of molar support is not a risk factor for development of TMD

Question 8

SDA and occlusal stability

Answer 8

provide sufficient occlusal stability
minor changes in ID spacing occur shortly after ets leading to a SDA, but a new occlusal equilibrium remains stable and these changes do not pose any problem to the oral fct
vertical overbite not influenced by the SDA

Question 9

occlusal attrition in SDAs

Answer 9

does not differ significantly from that of complete dental arches

Question 10

alv bone height scores in SDAs

Answer 10

tend to decrease at the same degree as in complete dental arches

Question 11

indications

Answer 11

missing posterior teeth with 3-5OU remaining
sufficient occlusal contacts to provide a large enough occ table
favourable prognosis for remaining anterior and premolar teeth
pt not motivated to pursue complex Rx plan
limited financial resources for dental care
= will only work long term if the remaining natural dentition can be preserved for the remainder of the lifetime of the pt

Question 12

contraindications

Answer 12

poor prognosis for remaining dentition
untreated or advanced PDD
pre-existing TMD
signs of pathological TW
significant malocclusion - severe class 2/3
= if meet any of above consider replacing posterior teeth

Question 13

considerations

Answer 13

does pt have any problems chewing food?
does pt have any aesthetic concerns arising from the missing teeth?
any discomfort arising from the missing teeth?
- food crunching on gums -v pt dependent
any evidence of occlusal instability as a result of the missing teeth/
- teeth not meeting properly / pt struggling to find a comfortable position
= if any of these yes, good case to be made for replacing the missing teeth

Question 14

skeletal class

Answer 14

must be sufficient occlusal contact

severe malocclusion there may only be 2-3 pairs of occluding teeth

Question 15

distal tooth migration occurs in SDA

Answer 15

increased anterior load
increased number and intensity of anterior occlusal contacts
increased interdental spacing
= exacerbated by inadequate perio support

Question 16

caries

Answer 16

must be controlled and stable
prev caries tx may result in heavily restored teeth which are structurally weak
- is the heavily restored tooth capable of withstanding occlusal loads of an SDA?
- if tooth non-vital and has RCT can it cope with forces?

Question 17

toothwear

Answer 17

progressive toothwear contraindication

• long term threat to survival of teeth
• gradual loss of occluding contacts and occlusal stability

Question 18

if stabilising occlusal contacts fail:

Answer 18

unplanned tooth loss may result
will lead to loss of occlusal stability
= undermines SDA, may require extensive prosthetic rehabilitation

Question 19

EO exam

Answer 19

signs of TMD
- click/crepitus/deviation/pain in TMJ
- hypertrophy/tenderness of MofM
skeletal relationship

Question 20

IO exam

Answer 20

signs of bruxism
 - buccal keratosis
 - scalloping
 - trauma
 - wear facets
 - fractured Rxs
signs of TW
PD assessment
occlusal assessment
teeth of poor prognosis

Question 21

PD assessment - what must be done if there is active disease?

Answer 21

course of NST

• therapy aimed at stabilising the PD condition of all remaining teeth
• evaluate response
• must be able to maintain perio health

Question 22

consequences of not having PD health

Answer 22

drifting of PD compromised teeth under occlusal load
loss of alveolar bone leading to a compromised denture-bearing area in the long-term
loss of space (neutral zone) for denture teeth in the long term
- PD drifting, loss of OVD

Question 23

occlusal stability

Answer 23

stability of tooth positioning relative to its spatial relationship in the occluding dental arches
absence of tendency for teeth to migrate other than the normal physiologic compensatory movements occurring over time

Question 24

5 requirements of occlusal stability

Answer 24

stable contacts on all teeth of equal intensity in centric relation
anterior guidance in harmony with the envelope of fct
disclusion of all posterior teeth during mandibular protrusive movement
disclusion of posterior teeth on the NWS during mandibular lateral movement
disclusion of posterior teeth on the WS during mandibular lateral movement

Question 25

occlusal stability determined by number of factors

Answer 25

absence of pathology: TW, PDD
PD support
number of teeth in the dental arches
ID spacing
occlusal contacts
mandibular stability

Question 26

TMJ problems

Answer 26

does pt have an existing TMD problem?
is this associated with bruxism/TW?
lack of posterior support may be contributing to TMD
replacement of missing teeth and correction of occlusal derangement may reduce TMD symptoms
little evidence to support increased TMD problems with SDA

if they don’t have TW SDA won’t cause TW

Question 27

traumatic occlusion manifestations

Answer 27

fracture of Rxs or teeth
tooth mobility
dental pain not explained by infection
TW
may also be a contributing factor to TMD

Question 28

when can you consider a pts occlusion stable?

Answer 28

if pt can achieve a reproducible ICP without evidence of these pathological manifestations of trauma
in a natural dentition, this can be achieved for most pts with 10 occluding pairs of teeth

Question 29

combination syndrome

Answer 29

care with unopposed SDA
instability Cu in fct
concentration of occlusal force anterior of Cu
- teeth vs denture - denture-bearing area less resilient to occlusal force
- overload bony tissues - gradually turn into fibrous tissue
flabby ridge
consider extension of SDA
- dissipate forces round whole arch
flimsy evidence

Question 30

extension of SDA

Answer 30

RRB
conventional bridgework (consider RPD)
implants
RPD

Question 31

extension of SDA - RRB

Answer 31

distal cantilever
max 1 unit each side of arch
light contact on cantilevered pontics in ICP
minimal contacts in excursive movements
heavy contacts may lead to failure

Question 32

extension of SDA - implants

Answer 32

single tooth in molar/premolar position

cantilever bridge

Question 33

extension of SDA - RPD

Answer 33

bilateral free end saddle
RPI design
consider with Cu
non-compliance