Shortened Dental Arch

Question 1

Kayser 1981 SDA concept

Answer 1

dentition where most posterior teeth are missing
satisfactory oral function without use of RPD
priority given to maintaining an anterior & premolar dentition in 1 or both jaws
in the 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:
- 1 unit = pair of occluding premolars
- 2 units = pair of occluding molars

Question 2

loss of molars associated with

Answer 2

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

Question 3

indications for SDA

Answer 3

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

Question 4

contraindications to SDA

Answer 4

• poor prognosis for remaining dentition
• untreated or advanced perio
• pre existing TMD
• signs of pathological tooth wear
• pt has significant malocclusion i.e. severe class II or class III
  *if any of above criteria are met consider replacing posterior teeth

Question 5

considerations when thinking of SDA

Answer 5

• problems chewing food?
• appearance / cosmetic concerns from missing teeth?
• discomfort arising from missing teeth?
• evidence of occlusal instability as a result of missing teeth?
  if answer is yes to any of the above then good cause to be made for replacing missing teeth

Question 6

EO exam for SDA

Answer 6

check for TMJ dysfunction:
click / crepitus / deviation / pain in TMJ
hypertrophy / tenderness of MoM
skeletal relationship

Question 7

IO exam for SDA

Answer 7

check for signs of bruxism - buccal keratosis, scalloping, trauma, wear facets, # restorations
tooth wear
perio assessment
occlusal assessment
teeth of poor prognosis

Question 8

failure to establish stable perio help has what consequences

Answer 8

1. drifting of periodontally compromised teeth under occlusal load
2. loss of alveolar bone leading to a compromised denture bearing area in the long term
3. loss of space (neutral zone) for denture teeth in the long term

Question 9

impact of perio on SDA

Answer 9

distal tooth migration occurs in SDA, this causes:
- increased anterior load
- increases number and intensity of anterior occlusal contacts
- increases interdental spacing
- exacerbated by inadequate perio support

Question 10

why is progressive tooth wear a contraindication to SDA

Answer 10

1. long term threat this poses to survival of teeth
2. gradual loss of occluding contacts & occlusal stability

Question 11

what is occlusal stability

Answer 11

the stability of tooth positioning relative to its spatial relationship in the occluding dental arches

Question 12

5 requirements of occlusal stability

Answer 12

1. stable contacts on all teeth of equal intensity in centric relation
2. anterior guidance in harmony with the envelope of function
3. disclusion of all posterior teeth during mandibular protrusive movement
4. disclusion of posterior teeth on the non working side during mandibular lateral movement
5. disclusion of posterior teeth on the working side during mandibular lateral movement

Question 13

occlusal stability determined by

Answer 13

1. absence of pathology: tooth wear, perio disease etc
2. periodontal support
3. no of teeth in dental arches
4. interdental spacing
5. occlusal contacts
6. mandibular stability

Question 14

manifestations from a traumatic occlusion include

Answer 14

of restorations and/or teeth
tooth mobility
dental pain not explained by infection
tooth wear
traumatic occlusion may also be a contributing factor to TMD

Question 15

options to extend SDA

Answer 15

1. resin retained bridgework
2. conventional bridgework
3. implants
4. RPD

Question 16

resin retained bridgework to extend SDA

Answer 16

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

Question 17

conventional bridgework as extension of SDA

Answer 17

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

Question 18

implants as extension of SDA

Answer 18

single tooth in molar / premolar position
cantilever bridge

Question 19

RPD as extension of SDA

Answer 19

bilateral free end saddle (kennedy class I)
RPI design
consider with CU
non compliance

Question 20

combination syndrome

Answer 20

care with unopposed SDA
instability CU in function
concentration of occlusal force anterior of CU
flabby ridge
consider extension of SDA
flimsy evidence