intro lecture Flashcards
types of removable protheses
complete and partial
types of RPD frames
cast metal, acrylic, flexible base
why not use flex base
hard to adjust and excess force on abutment teeth
metals used for cast frame, major one at UMKC
CoCr and NiCr, we use CoCr (Ni sensitivity)
kennedy classes
mod rules apply as well
clasp assemblies
major connector
Left: retentive and reciporcol cusp arms
Left: more of tooth wrapped
Principle of “Encirclement”
Clasp assembly needs to “wrap around” the tooth. at least 180 degrees
Prosthetics:
Prosthetics:
– art or science of replacing absent body parts
Prosthodontics:
– branch of dentistry that pertains to the replacement of missing teeth and oral tissues
Dental Prosthesis:
Dental Prosthesis:
– artificial replacement of 1 or more teeth and/or
associated structures
Fixed Partial Denture (FPD):
– Prosthesis replacing teeth in partially dentate arch.
– Not designed to be removed by patient.
Removable Partial Denture (RPD):
– Prosthesis replacing teeth in partially dentate arch.
– Designed to be removed by patient.
Abutment:
Abutment:
– Tooth used to support prosthesis
Centric Relation:
Maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterior-superior position against the slope of the articular eminence.
– Position independent of tooth contact.
– Position restricted to purely rotational motion.
Maximal intercuspal position
– Position with complete intercuspation of opposing teeth.
– Independent of condylar position
– Previously called Centric (Habitual) Occlusion
Diagnostic Cast vs Master Cast: .
Diagnostic Cast: Cast for the purpose of diagnosis & treatment planning.
Master Cast: Replica of teeth, residual ridges, & other parts of the dental arch used to
fabricate dental restoration or prosthesis.
Tooth-supported RPD:
Tooth-supported RPD:
– RPD that depends entirely
on natural teeth for support
Tooth-tissue supported RPD
Tooth-tissue supported RPD
– Extension base RPD
– RPD supported and retained by teeth at only one end.
– Denture base is supported by teeth & the residual ridge
indications for RPDs
Edentulous area(s) too long or numerous for a fixed prosthesis
• Need to restore lost soft and hard alveolar tissue, especially in the anterior region****
• Reduced periodontal support of remaining teeth
• Need to distribute masticatory stresses across the dental arch: cross-arch stabilization
No posterior abutment tooth
• Immediate replacement of teeth
• Attitude & desires of patient (economic considerations)
Disadvantages of RPDs
• Removable, not considered ‘part’ of patient
• May be lost or broken
• Clasps may be visible, less esthetic
• May dislodge during function
• May trap food while eating
Height of Contour/Survey Line
– Line encircling a tooth that designates its greatest diameter at a selected position
determined by a dental surveyor
– Height of contour will change if the axial inclination is changed
suprabulge area
Suprabulge Area
– Portion of tooth above the height of contour
infrabulge area, also called?
• Infrabulge Area
– Portion of tooth below the height of contour
– May also be referred to as Undercut:
• Surface of object below the height of contour in relation to the path of placement
RPD objectives
Restore anatomical defect
Restore function
Restore occlusal plane
Provide posterior occlusal support
Improve esthetics
Splint periodontally compromised teeth
RPD components
metal framework and denture base
metal framework components
-Major connector
-Minor connectors
-Rests
-Direct retainers
-Indirect retainers
denture base components
-Replacement teeth
-Supporting base
Material
MAJOR CONNECTOR
The component of an RPD that joins the units on one side of the dental arch with the units on the opposite side
maxillary major connectors
Palatal strap
Anterio-posterior Palatal Strap
Complete Palate
U-shaped (Horseshoe) connector
mandibular major connectors
lingual bar or plate
MINOR CONNECTOR
MINOR CONNECTOR
The connecting link between the major connector or base of a removable partial denture and the other units of the prosthesis, such as direct and indirect retainers and rests.
MINOR CONNECTOR
-Types
Guiding plane plates
Meshwork – to hold acrylic resin
Any unit connecting any type of rest to the major connector
REST:
REST: A component of a removable partial denture that serves to transfer forces occurring against the prosthesis down the long axis of the abutment teeth
REST SEAT:
REST SEAT: The prepared surface of a tooth or restoration to receive the rest, not a part of framework
Proximal Plate
A rigid extension from the major connector or base
Contacts the proximal surface of an abutment tooth
DIRECT RETAINERS
A component of a removable partial denture used to retain and prevent
dislodgement
Clasp Assembly
Two arms or other pieces, joined by a body which may connect a rest
May act as a retainer or stabilizer
INDIRECT RETAINERS
usually connected to?
usually a form of?
always needed in what classes?
A component of a removable partial denture that assists a direct retainer(s) in preventing displacement of a distal extension denture base by functioning through lever action on the opposite side of the fulcrum line
Usually connects to a major connector and is some form of rest
ALWAYS necessary in Class I or II situations
Denture Base
Part of the RPD that rests on the foundation tissues and to which teeth are attached.
– Polymer/Plastic or Metal
ACRYLIC RESIN ATTACHMENT
function?
The part of a RPD which rests on the oral mucosa and to which the teeth are attached
FUNCTION: Transmit stress to the supporting structure
Denture Base Retention
Part of framework to which the resin base is attached; lattice or mesh
Guiding Planes
Vertically parallel surfaces of abutment teeth oriented so as to contribute to the direction of the path of placement and dislodgement of removable partial dentures
guide planes exist or created?
Guiding Planes Must Be Created
Functions of Guiding Planes: (5)
POI?
actions of other components?
food traps?
Benefit for minor connectors?
prox surfaces/arms?
• Provide for one path of placement/removal
• Ensure the intended actions of the RPD components*
• Eliminate/decrease gross food traps**
• Increase frictional component of minor connectors
• Lowers the height of contour on proximal surfaces to allow better positioning of arms
reduction in undercuts with guide planes?
The large undercut adjacent to the proximal surface should be reduced in size.
how can reduction for guide planes be accomplished?
The reduction can be accomplished by altering the tilt of the cast or by selective grinding of the enamel surface.
Most often, using selective grinding, the undercut is reduced and a guiding plane is
prepared.
Location of Guiding Planes:
increased length results in?
Proximal surfaces of abutment teeth
• Parallel to long axis of teeth, if possible
• As length is increased, frictional retention is increased and resistance to rotation is
increased
As length (of guide plane) is increased:
frictional retention is increased and resistance to rotation is increased
Width of Guiding
Planes:•
• As wide as the widest portion of the occlusal rest
• One-third the bucco-lingual width of the tooth
• One-half the distance between the cusp tips
Length of Guiding Planes
(tooth-tissue vs tooth-tooth)
• Tooth supported abutments -3.0 to 4.0 mm
• Tooth-tissue supported abutments (distal extension abutments) -1.5 to 2.0 mm
DENTAL SURVEYOR FUNCTIONS
• Survey diagnostic cast
• Contour wax patterns
• Contour ceramic & cast restorations
• Place attachments requiring parallelism
• Survey master cast
OBJECTIVES OF SURVEYING DIAGNOSTIC CAST (7)
POI?
GP?
retention?
undercuts?
esthetics?
HOC?
tripod?
- Determine the most acceptable path of insertion
- Identify proximal tooth surfaces that can function as guiding planes
- Locate & measure areas of teeth that may be used for retention
- Determine if soft or bony areas of interference (undercuts) exist
- Determine most suitable path of insertion to satisfy esthetics
- Delineate height of contour on abutment teeth
- Record cast position to selected path of insertion (Tripod cast)
SURVEY PROCEDURE
- Path of Insertion Determined
- Mark the Height of Contour/Survey Line
- Measure/Mark Retentive Undercut
- Tripod Cast
Path of Insertion Determined based on?
• Based on Guiding Planes, Retentive Undercut, Interferences, Esthetics
PATH OF INSERTION
what to avoid when determining this? why?
• The direction in which the RPD is inserted & removed from the abutment teeth.
• Exaggerated tilt to path of insertion avoided
• Patient unable to open mouth sufficiently to accommodate
more GPs means?
Path of insertion more specific
• Increase RPD stability & retention
how are GP identified with the surveyor
• Identified by tilting cast in anterior-posterior direction until maximum parallelism of proximal surfaces
• Anterior-posterior tilt: as viewed from rear of cast table
• Analyzing rod used to identify potential surfaces that can be converted to guiding planes by selective grinding in occlusal 1/3-1/2
• Final orientation seldom >10-15° from horizontal
RETENTIVE UNDERCUT purpose
where found?
• RPD mechanical retention provided by clasp that engages retentive undercut
• Resist RPD dislodging forces
• Undercut area lies between survey line and gingival margin
HEIGHT OF CONTOUR/
SURVEY LINE
• Line encircling a tooth that designates its greatest diameter at a selected position determined by a dental surveyor
• Height of contour will change if the axial inclination is changed
Infrabulge Area, what can be found here?
• Portion of tooth below the height of contour in relation to path of insertion
• Retentive Undercut within this area
• Only Retentive clasp tips contact tooth below the Survey line
Areas of retentive undercut, where is it preferred on the tooth?
Areas of retentive undercut:
• Mesiofacial (A), Mid-facial (B), Distofacial (C) (Facial
undercut preferred)
ideal location undercuts
Ideally, within gingival 1/3, at least 1mm from gingival margin facially
finding the retentive undercuts with a surveyor
Manipulate mediolateral tilt of cast to equally distribute retentive undercut to abutments
• Cast tilt should not vary far from horizontal
False Undercut, results in?
• Illusion of undercut due to excessive cast tilt
• Will not exist clinically
• Awkward path of insertion
• Patient unable to place RPD
• Typical interference areas:
• Lingually-inclined mandibular teeth
• Buccally-inclined maxillary teeth
• Bony buccal exotoses, tori
• Height of contour too high, clasp placement too high
• Tissue undercut area of bar clasp
eliminate interferences by….
• Alter tilt of cast/Change path of insertion
• Maintain cast tilt, eliminate by surgery or recontouring of teeth
marking the height of contour
Side of carbon marker indicates survey line of abutment teeth
at chosen path of insertion
• Tip of marker will produce incorrect survey line
location of survey line and what is above/below survey line
All components (rigid) of RPD, except terminal 1/3 of retentive clasp, above survey line
• Ideally, survey line located at junction of middle & gingival 1/3
• Proximal 2/3 of retentive clasp & Reciprocal clasp in middle 1/3, above survey line.
• Retentive terminal 1/3 in gingival 1/3.
If survey line, at chosen path of insertion, too near occlusal surface:
clasp too high on the tooth
• May interfere with occlusion
• Increased leverage on tooth
• Tooth recontoured to lower survey line.
if survey line, at chosen path of insertion, too low:
no undercut exists
• Survey line at or near gingival margin
• No undercut exists for clasp retention
• Cannot use enamoplasty to change
• Requires surveyed crown
measuring retentive undercut
Measured with proper undercut gauge at chosen path of insertion
• Amount of undercut varies depending on clasp type
• 0.01” for Cr-Co or Ni-Cr cast clasp
• 0.02” or 0.03” for wrought wire clasp
fixing Inadequate Retentive Undercut
– Enamoplasty to create undercut
•“Dimple”
–Addition of composite at site to create undercut
–Surveyed crown
TRIPOD CAST
• Record tilt of cast at chosen path of insertion
• Clinician or Lab technician can re-establish path of insertion
• Draw vertical lines parallel to analyzing rod on 3 sides of cast
(Lines widely separated)
blue color code for RPD
- Metal framework outline
- Wrought wire clasp
red color code for RPD
- Indicate retentive undercut
- Indicate tooth modification areas
- Guiding planes, Survey line reposition, Rest
seat areas
black color code for RPD
-Survey line, tripod marks and soft tissue
undercuts
mouth preparations for RPD
• Perform indicated tooth modifications according to RPD
diagnostic cast design
• guiding planes, Survey line reposition, Rests
MASTER CAST
• Impression for master cast after mouth preparation
• Resurvey master cast
• Be sure mouth preparation adequate
• Align guiding planes
• Mark retentive undercuts
• Mark survey line
• Tripod cast
