Before Midterm: Kennedy Classification/ Principles of Design I - Rest and Direct Retainers Flashcards
Kennedy Class, bilateral edentulous posterior to natural teeth:
Class 1
Type of denture to make for Class 1 and Class 2:
tissue supported
Kennedy Class, unilateral edentulous, posterior to natural teeth:
Class 2
Unilateral edentulous w natural teeth both anterior and posterior:
Class 3
Type of denture to make for Kennedy Class 3:
tooth supported partial
Kennedy Class, single bilateral edentulous crossing midline, anterior to natural teeth:
Class 4
Classification, before or after extractions?
after
If 3rd molar missing and not to be replaced is it considered in classification?
no
If 3rd molar is present and to be used as abutment is it considered in classification?
Yes
If 2nd molar missing & not to be replaced is it considered in classification
No
What determines classification?
Most posterior edentulous area(s)
How to name edentulous areas other than those determining classification:
modification spaces, designated by their #
When to replace 3rd molar via removable?
never
Options if 3rd is not in periodontally sound condition or if it s restoratively compromised.
May opt to place a rest on the tooth wo clasping it if you don’t want to use it as an abutment.
TF? Class IV will never have modification spaces.
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prepared surface of the abutment into which a rest fits.
rest seat
What is the rest:
component of RPD that transfers forces down long axis of abutment, fits into rest seats of teeth
5 fxns of rest:
vertical support, maintain position, maintain occlusal relationships by preventing settling of partial, prevent impinging on soft tissue, direct and distribute occlusal loads to abutment teeth
Rests transmit forces here:
PDL instead of soft tissue
How do rests prevent soft tiussue injury:
by minimizing vertical displacement
Is the retentive clasp above or below HOC?
below
Wo the non-retentiv clasp or rests what would happen?
partial would be forced down and impinge upon soft tissue
What state does a partial assume when a partial is seated properly?
passive state
When seated properly the retentive clasp is actively engaging the tooth.
F. not engaging
When does the retentive clasp engage the tooth?
only when unseating forces are exerted
List 4 types of rests:
occlusal, interproximal, lingual, incisal
Interproximal rest is aka:
embrasure rest
3 types of lingual rests:
cingulum rest, inverted V rest, anterior lingual rest
Cingulum rest is aka:
ledge rest
anterior lingual rest is aka:
spoon rest
2 ways to change HOC:
change path of insertion OR grind tooth
Occlusal rests:
Triangular or bell shape, angle of floor of rest and guide plane < 90°, rounded at marginal ridge (to prevent fracture?)
Fxn of angle of floor of rest and guide plane < 90°:
better mechanical locking
Where is force directed on an occlusal rest?
perpendicular to the direction of force: off tooth for the rest, into tooth for tooth
Depth of occlusal ridge at marginal ridge:
1-1.5mm
Thickness of occlusal rest at thinnest point:
0.5mm
Follow this when making rest seat:
natural anatomy, mesial pit is lower than MMR, most central portion of seat will be thinnest
B-L dimension of occlusal rest for premolars and molars:
2.5mm or 1/2 distance bw summit of cusps
M-D dimension of occlusal rest for premolars and molars:
premolars: 1/ M-D length, molars: 1/4 M-D length
Marginal ridge and B/L embrasure reduction for interproximal rests;
1.5mm
Beware of this when making interproximal embrasure:
don’t break contact
What would happen if contact is broken while making interproximal rests:
teeth drift
Where are interproximal rests typically found?
side of arch that is not edentulous, like two occlusal rests side by side
Shape of occlusal portion of interproximal rest when viewed from B:
semicircle
lingual/ cingulum/ ledge rest for MaxC:
1mm L-L, 1,5mm I-A, 2.5-3mm M-D following cingulum
When does the vertical dimension becomes relevant?
Only if rest were providing reciprocation and you had a clasp on the facial aspect
This type of rest typically is not used on mandibular canines:
Lingual/ cingulum, ledge rest
Why aren’t Lingual/ cingulum, ledge rests typically used on mandibular canines?
enamel thickness not enough
Type of rest to use for mandibular canines;
spoon rest
What to do if If dentin is exposed on mandibular canine
Place restoration to protect, sensitivity to pt and caries risk.
Shape of lingual/ cingulum rest in X-section:
V-shaped
Fxn of V-shaped lingual/ cingulum rest in X-section:
prevents migration of abutment away from framework
TF? If it is not possible to make floor of cingulum rest less than 90’ it is ok to make the floor flat.
T
Inverted V rest dimensions:
1mm L-L, 1.5mm I-A, 2.5-3mm M-D following congulum
When are inverted V rests most commonly done?
survey crowns
Why are inverted V rests less frequently done?
req more skil
Dimensions of Incisal rest, mandibular canine:
1/3 M-D width, 1.5mm I-A, wider L than B, gingival wall less that 90’ to POT, axial wall parallel to POT, internal line angles rounded
Can we have incisal rests on maxillary canines?
yes, more often mandibular though
Negative aspect of incisal rest, mandibular canine:
aggressive, unesthetic
Beware of this common mistake when making incisal rest on man canine:
creating UC’s
Teeth for lingual spoon rests:
Max and Man anteriors, sometimes used on canines
Beware of this common mistake when making ilingual spoon rests:
creating dimple that is UC that would not provide POI
Type of edge created by lingual spoon rest:
feather edge
Lingual spoon rest is this shape in appearance:
ovoid
DImensions of lingual spoon rest:
2mm wide, 1mm deep
Verify this when prepping a rest seat:
adequate interocclusal clearance
What does the depth of prep for rest seat depend upon?
Amount of space you have bw seat and opposing cusp
If the DMR is the only POC, when the partial is not in the mouth, the tooth will be prone to:
shifting and super-eruption, leading to issues with the partial seating properly
When to prepare away the only occlusal contact of a tooth?
Never
