Before midterm: Tooth Modification/ Principles of Design II Flashcards
Fxn of major connectors:
join components on both sides of arch
TF? All components of partial are directly or indirectly attached to the major connector.
T
5 types of Max major connectors:
palatal bar, palatal strap, Horse-shoe, A-P palatal strap, complete palate
Horse-shoe major connector is aka:
U-shaped
A-P palatal strap is aka:
A-P strap or O-Bar
When to use Palatal Bar:
Anchor-span Class III, 1-2 teeth missing on each side
Disadv of palatal bar:
little vertical support from palate, relatively bulky
Don’t position a palatal bar more anterior than:
2nd premolar, may affect speech
Why not to place palatal bar more anterior than 2nd premolar:
may affect speech
Which is thinner, palatal bar or palatal strap?
strap
Which Class partial are palatal strap typically used for?
Class II and III
Width of palatal strap should be at least:
8mm
Horse-shoe connector is indicated for:
prominent median palatine suture or an inoperable toris
TF? Horseshoe connector may be flexible.
T. bc it is curved
Contraindications of horse shoe connector:
Class I or II arches
Disadv of horseshoe connector:
little cross-arch stabilization
Adv of horseshoe connnetor:
may be flexible, rigid framework helps to distribute forces
This type of connector is preferred over Horseshoe connector:
rigid major connector
A-P palatal strap indications:
large edentulous span, prominent median palatine suture, inoperable torus
Width of each A-P palatal strap should be at least:
8mm
Open area on palatal region of A-P palatal strap should be at least:
15 X 20mm
Connectors to use for pts with inoperable torus or prominent median palatine suture:
horseshoe, A-P palatal strap
Posterior segment of the A-P palatal strap adds:
rigidity
Benefit of keeping open palatal portion bw straps of A-P palatal strap connector:
tongue / palate contact, taste, temperature
Connector that provides that greatest rigidity and support:
complete palate
Indications, complete palate
all posterior teeth replaced, perio compromised teeth, provides additional vertical support
Disadv of compete palate connector:
tissue health may be compromised POH
TF? Complete palate connector provides additional horizontal support.
F. Vertical
6 types of Man major connectors:
Lingual bar, lingual plate, sublingual bar, double lingual bar, cingulum bar, labial bar 5 bars and a plate)
double Lingual bar is aka:
continuous bar
Most freq used man major connector:
lingual bar
Adv of lingual bar for man major connector:
minimizes contact w teeth/ soft tissue
Contraindications of lingual bar:
lingual tori (usually)
Where to place bar for pt w lingual tori:
past contacting lingual aspect
Lingual bar requires at least __mm of space bw gingival margins and floor of mouth.
8mm
Lingual bar should be located here:
in the most apical position the movable soft tissues will allow
Type of man major connector to use if you don’t have room for the 8mm bw gingival margins and floor of mouth:
lingual plate
Shape of lingual bar in X-section:
half-pear
Adv of lingual bar:
wider, stronger at bottom
Indications for lingual plate
1’: less than 8mm for lingual bar, 2’: reduced perio support
Why is a lingual plate man major connector good if the remaining teeth have reduced perio support?
Force distribution over teeth and soft tissue
This man major connector scallops around anteriors:
Lingual plate
When to use lingual plate:
when not enough room for lingual bar
Disadv of Lingual plate:
covers a lot of tooth surface, minimizes cleansing action
TF? Teeth can easily be added to lingual plate.
T
TF? Lingual plate can often be used to avoid covering lingual tori.
T
Where should the inferior border of the lingual plate be positioned?
as low in the floor of the mouth as possible wo interfering w functional movements of tongue and soft tissues
TF? The major connector of the lingual plate should extend as far as movement allows.
T
From where to where is the superior border of the lingual plate scalloped?
from cingulum to interproximal contact
Lingual plate should eb supported by:
rests on mesial fossae of 1st premolars
What give vertical suppport for the lingual plate?
Rests on either end of plate
Disadv of lingual plate:
extensive coverage, decalcification, irritation of soft tisuse w POH
Scalloping of lingual plate is aka:
“step backs”
What are step backs of the lingual plate used for?
to accommodate diastemas (prevents display of metal)
TF? Lingual plate extends up to the cingulum and around the M and D surfaces of each tooth, but not into the interproximal area.
F. does not extend to M or D aspects of each tooth
Man major connector to use to maintain diastema.
lingual plate
Major connector is on the labial side of teeth for this type:
labial bar
Double lingual bar is aka:
continuous bar
What is the double lingual bar?
both sublingual bar and cingulum bar
When to use cingulum bar vs. lingual bar:
shallow floor of mouth (FOM)
Req’s of Major connector:
rigid, protects soft tissue, provides means for direct retention where indicated, and placement of a denture base, comfortable
Max major connector borders should be:
at least 6mm from free from, and parallel to, gingival margins
Man major connector borders should be:
at least 4mm from the free from, and parallel to, gingival margins.
Mandibular major connectors should be below:
sulcular depth, not occlusion blood supply
TF? Anterior border of man major connectors should end on anterior slope of rugae
F.
Anterior border of man major connector should end here:
posterior border of rugae
Man major connectors should be:
as symmetrical as possible, cross palatal midline at R angles
What happens when the length of the major connector is reduced?
red irritation potential (?)
Man major connector to avoid tori:
lingual plate w lingual connector
TF? Small torus can be covered.
T, but provide relief
Harder to avoid, man or max torus.
Man
TF? Mandibular tori usually require removal for partial fabrication.
T
Sharp corners on a partial can lead to:
Discomfort, stress concentration, susceptible to fracture
Fxn of minor connectors:
join partial to major connector
parts joined to major connector via minor connectors:
clasp assemblies, indirect retainers or auxiliary rests, denture bases, approach arms for infrabulge clasps
TF? Denture base joined via latice-work is consider a minor connector
T
minor connectors should have sufficient bulk of metal wo:
encroaching on tongue
Minor connectors are positioned in:
lingual embrasures
What to avoid when designing minor connectors:
narrow windows
Windows of minor connectors should be at least _mm wide.
5mm
how are rest seat connected?`
via minor connect + proximal plate`
Examples of minor connectors:
indirect retainer, proximal plate, latticework
Fxn of indirect retainers:
resist forces acting to dislodge prosthesis from seated
Forces attempting to dislodge prosthesis come from:
sticky foods, gravity, etc.
TF? Indirect retainer is considered a minor connector.
This is the framework component that resists rotational displacement of an extension base away from the supporting tissues
Forces exerted down the long axis of a tooth via the clasp lead to forces being exerted here:
up on the distal portion of distal extension
When does partial denture exhibit indirect retention?
When rotational forces are counteracted by placing indirect retainers
Which type of partials require indirect retention?
All Kennedy Class I, II, and IV (III doesn’t)
TF? The proximal plate is broad M-D and thin B-L
F. vice versa
Benefit of proximal plate being broad BL and thin MD:
easier to put denture tooth in natural position
M-D dimension should of proximal plate should be:
as narrow as possible, to preserve denture tooth space (about 1mm+)
GP criteria:
2/3 width of BL cusps, MR to junction of middle and gingival 3rd
GP criteria for GP adjacent to distal extension:
2/3 width of B-L cusps, Mr to middle 1/3
Benefit of GP adjacent to distal extenion being shorted I-G than all others:
Allows framework rotation
Types of lattice ork;
mesh, open loop
Lattice work to use w limited space:
mesh
Fxn of lattice work:
hold acrylic
How far to extend distal extension lattice work
2/3 of alveolar ridge, past most prominent area of tuberosity
TF? Extend lattice work to hamular notch.
F. to most prominent area of tuberosity
This is where the acrylic joins the framework:
finish lines: external and internal
What’s the difference bw the internal and external finish lines?
check?
Desired angulation of internal finish line:
<90’ for flush junction and mech retention
Function of internal finish line angulation less than 90’:
provide flush junction and provide mechanical retention
Open loop lattice work is only needed for:
distal extension
Fxns of tissue stops:
vertical stop on cast, flexing of framework during acrylic processing, stability to framework while setting teeth
TF? All cross bars of distal extension provide vertical stops.
F. not the most posterior portion
Tissue stops are only relevant:
during acrylic processing and evaluating on cast, not to support framework in mouth!!
What does it mean if the tissue stop is not contacting after processing of the cast?
Error during fabrication. in contact w cast
Only time to adjust the most distal portion of lattice work:
Pain and a pressure spot
When are abutment teeth prepared?
prior to tooth modifications
Before tx plan can be modified, you must:
mount dx cast, survey and design RPD
Steps that must be done bf tooth modifications:`
relief of pain/ infection, complete surgical proc, correction of occ plane/ malalignment
When to extract teeth for partials:
non-restorable, inadequate perio support unerupted/impacted
Do we have all unerupted 3rd molars extracted before any partial fabrication?
check. If so, why?
Surgeries that should be done before partial design:
extractions, tori / exostoses removal, reduction of enlarged tuberosities (no room for denture)
Issue for ppl w large tuberosities:
no space for dentures
How to manage minor supraeruption of teeth:
recontour occ surface (enamoplasty)
How to manage moderate supraeruption of teeth:
onlay or crown
How to manage severe supraeruption of teeth:
extraction
When to expose dentin when recontouring tooth to correct occlusal plane:
never
When is ortho indicated bf partial design:
distal molar tilted mesially, most pts won’t spend the $
Define enamelplasty:
recontouring of axial surface
TF? Enamelplasty requires local anesthetic.
F
Enamelplasty:
conservative, in enamel, polished, practice on cast if substantial recontouring needed bc you want to know if pt is becoming sensitive to adjustment
Why not to give pt LA for enamelplasty:
you want to know if the pt is becoming sensitive to the adjustments
one way to correct clinical orientation of crown to avoid over contouring (excessive or insufficient undercut):
Survey crown, optimally contoured
Survey sequence:
rest seat, GP, retention, reciprocation
Sequence of tooth mods:
GP, HOC, rest preps
GP of tooth mods for partial must allow:
direct seating and stabilize against lateral forces
GP criteria for tooth mods for partial insertion:
2/3 width of B-L cusps, MR to junction of middle and gingival 3rd
GP for tooth supported partial require GP with these dimensions:
2/3 width of B-L cusps, MR to junction of middle and gingival 3rd, maintain B-L contour
GP for distal extension (tissue supported partial, Class I or II:
MR to middle 3rd, permits rotation of framework
Benefit of additional rotation of distal extension:
minimizes torsion on abutment tooth (smaller GP)
Any partial that is supported by ___ will rotate.
tissue
TF. The bur should always be aligned with the long axis of tooth when making tooth mods.
F. with POI
Survey crown is indicated when:
modification would expose dentin and compromise contour bc crown is tilted too much
When to reduce on the cervical aspect of a tooth:
never, thin enamel
Desired edge when making GPs:
Featheredge
Location of retentive clasp:
gingival 3rd, 1.5-2mm from gingival margin
Location of middle/ shoulder region of retentive clasp:
above HOC
Reciprocal arm location:
junction of middle and gingival 3rd, always at or above HOC
Place ___ clasp as low as possible and __ clasp as high as possible.
retentive, reciprocal
Lateral force on tooth start when:
the retentive and reciprocal clasps touch the tooth for the first time and at same time
Ideal location of HOC undercut in relation to margin:
1.5-2mm from margin
When developing a retentive UC, this is the desired contour change:
Gradual, subtle contour change, not a semicircle 1.5-2mm away from gingival margin
Other indication for recontouring:
adjust excessively convex proximal surfaces for improved esthetics, mesially drifting tooth encroaching on edentulous area to idealize spacing, lingually tipped teeth, for better adaptation of minor connectors
When to recontour mesially tilted teeth:
to allow better adaptation of minor connectors or proper seating of major connector
When should aspects of framework crossing over undercut regions of tooth engage the UC region?
never
Minor connection in relation to tooth:
must be well off tooth, better to recontour tooth so framework components can be fabricated closer to tooth and not be annoying to pt
Pour cast in this stone to quickly check tooth mods against surveyor:
snap stone
When to do rest preps:
after verifying GP’s and HOC
How to get snap stone cast back in same orientation as the original cast:
no way to, reestablish based on new snap stone
Bur shape to use when making rest preps:
bullet shaped
Additional space must be allotted for this when prepping survey crown:
rest seat
Materials that can be used for survey crowns:
CCC, MCC
TF? Tooth mods on other abutment teeth should be done bf final impression for survey crown:
T
When doing SC, at what point do you do tooth modification?
Prior to survey crown bc it is more ideal to have already done tooth mods on all other teeth, then fabricate survey crown to develop ideal contours in relation to abutments and to utilize the contours of the other teeth (lab tech)
Which is better, to make tooth mods before or after survey crown is inserted?
before
Have these completed bf clinic for RPD pt:
mounted dx cast, surveyed, with drawn design (some faculty want mods done on duplicate cast), approved tx plan in Picasso, Chart design form, completed and signed
Instruments to bring to a RPD appt:
surveyor, proper burs and polishers, snap stone, stock impression trays, alginate
Common mistakes:
presenting tx plan to pt wo considering RPD design, make tooth mods prior to impression for survey crown, explain to pt the need for tooth mods
Pts most likely to object to tooth mods;
those w prior RPDs
How might the RPD design influence the overall tx plan?
need for survey crowns may not be obvious until surveying cast
TF? Finalization of tx plan can be done before surveying dx cast.
F.
Faculty to sign up w when working w RPD pts:
removable faculty
Which faculty can approve RPD final design?
only removable faculty
