SDA Flashcards
reasons for the concept
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
criticism from “traditionalist” prosthodontists
loss of molars associated with
- reduced masticatory efficiency
- mandibular displacement
- alterations in food selection
- aesthetic issues
- loss of occlusal stability
- TMJ problems
author
Kayser 1981
SDA concept
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
WHO oral health
“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”
SDA and oral fct and comfort
provide sufficient oral fct and comfort in terms of chewing fct, aesthetics, S+S of TMD
SDA and mandibular stability
the absence of molar support is not a risk factor for development of TMD
SDA and occlusal stability
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
occlusal attrition in SDAs
does not differ significantly from that of complete dental arches
alv bone height scores in SDAs
tend to decrease at the same degree as in complete dental arches
indications
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
contraindications
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
considerations
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
skeletal class
must be sufficient occlusal contact
severe malocclusion there may only be 2-3 pairs of occluding teeth
distal tooth migration occurs in SDA
increased anterior load
increased number and intensity of anterior occlusal contacts
increased interdental spacing
= exacerbated by inadequate perio support
caries
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?
toothwear
progressive toothwear contraindication
- long term threat to survival of teeth
- gradual loss of occluding contacts and occlusal stability
if stabilising occlusal contacts fail:
unplanned tooth loss may result
will lead to loss of occlusal stability
= undermines SDA, may require extensive prosthetic rehabilitation
EO exam
signs of TMD
- click/crepitus/deviation/pain in TMJ
- hypertrophy/tenderness of MofM
skeletal relationship
IO exam
signs of bruxism - buccal keratosis - scalloping - trauma - wear facets - fractured Rxs signs of TW PD assessment occlusal assessment teeth of poor prognosis
PD assessment - what must be done if there is active disease?
course of NST
- therapy aimed at stabilising the PD condition of all remaining teeth
- evaluate response
- must be able to maintain perio health
consequences of not having PD health
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
occlusal stability
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
5 requirements of occlusal stability
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
occlusal stability determined by number of factors
absence of pathology: TW, PDD PD support number of teeth in the dental arches ID spacing occlusal contacts mandibular stability
TMJ problems
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
traumatic occlusion manifestations
fracture of Rxs or teeth tooth mobility dental pain not explained by infection TW may also be a contributing factor to TMD
when can you consider a pts occlusion stable?
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
combination syndrome
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
extension of SDA
RRB
conventional bridgework (consider RPD)
implants
RPD
extension of SDA - RRB
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
extension of SDA - implants
single tooth in molar/premolar position
cantilever bridge
extension of SDA - RPD
bilateral free end saddle
RPI design
consider with Cu
non-compliance
