L 3&4 Flashcards
it is the application of mechanical principles on biological tissues while studying the biology from a functional viewpoint and then using these principles to design a stable prosthesis
BIOMECHANICS
an application of the principles of engineering design as implemented in living organisms
BIOMECHANICS
the RPD and their associated structures are subjected to various forms of stress; their ability to resist those stresses depends on:
o _____, ______, ______ and _____ of the stress
(force) being applied onto the denture and denture
bearing areas
direction, duration, magnitude, frequency
types of resistance generated:
o tooth-based
o tooth- and tissue-based
- displacing force
- dislodging force
A. vertical
B. horizontal
C. torsion
A
contributes mainly to resisting horizontal stress (direct retainers)
Tooth-Based Resistance
contributes to resisting vertical stress and torsion (major connectors and indirect retainers)
Tooth-Tissue Based Resistance
Fulcrum is located in the middle in between the load and the exerted effort.
CLASS I LEVER
Resistance is positioned in the middle in between the fulcrum and the exerted effort.
CLASS II LEVER
Exerted effort is applied in the middle in between the fulcrum and the resistance.
CLASS III LEVER
o unification of the major parts of the prosthesis
o distribution of the applied force throughout the arch to
selected teeth and tissue
o minimization of torque to individual teeth
MAJOR CONNECTOR
T/F
a rigid major connector limits movement possibilities by acting as a counteracting layer (cross-arch stability) that helps to resist displacement by functional stresses
T
Major connectors is made of?
Alloy
half pear shape, located above moving tissue but as far below the gingival tissue as possible
LINGUAL BAR
located at least 4 mm inferior to gingival margin and farther if possible
LINGUAL BAR
this major connector should be contoured with no presence of
sharp margin or any angular form to prevent irritation and
annoyance
LINGUAL BAR
superior border should be tapered towards the gingival tissue
superiorly with its greatest bulk of the inferior border
LINGUAL BAR
inferior border should be slightly rounded when the framework
is polished
LINGUAL BAR
INDICATION
→ when sufficient space exists between the slightly elevated alveolar lingual sulcus and the lingual gingival tissue
LINGUAL BAR
LINGUAL BAR
Use an individual impression tray for which lingual borders are ______mm short of the elevated floor of the mouth and then use an impression material that will permit the impression to be accurately molded as the patient licks the lips.
3 mm
should be made as thin as possible
LINGUOPLATE
upper border should follow the natural curvature of the
supracingular surfaces of the teeth and should not be located
above the middle third of the lingual surfaces
LINGUOPLATE
all gingival crevices and deep embrasure must be blocked out
parallel to the path of placement
LINGUOPLATE
apron is closely adapted to the teeth extending into
non-undercut interproximal embrasures resulting in scalloped form
LINGUOPLATE
INDICATION
→ when the alveolar lingual sulcus closely approximates the lingual gingival crevices
LINGUOPLATE
residual ridges in Class I arch have undergone such vertical resorption that offers minimal resistance to horizontal rotations
LINGUOPLATE
INDICATION
→ for using periodontally weakened teeth in group functions to support the prosthesis
→ overlapped anterior teeth
LINGUOPLATE
when the future replacement of one or more incisor teeth will be
facilitated by the addition of retention loops to an existing linguoplate
LINGUOPLATE
barshaperemainsthesameasthatofalingualbar
SUBLINGUAL BAR
when the height of the floor of the mouth in relation to the free gingival margin will be less than 6 mm
SUBLINGUAL BAR
if it is desirable to keep the free gingival margin of the remaining anterior teeth exposed and depth of the floor of the mouth is inadequate to place a lingual bar
SUBLINGUAL BAR
CONTRAINDICATION
→ remaining anterior teeth severely tilted towards the lingual
SUBLINGUAL BAR
CONTRAINDICATION
→ interfering lingual tori
→ high attachment lingual frenum
SUBLINGUAL BAR
CONTRAINDICATION
interference with elevation of the tongue during functional
movement
SUBLINGUAL BAR
shaped and located same as lingual bar
LINGUAL BAR WITH CONTINUOUS BAR
thin, narrow 3 mm metal strap located on the cingula of the
anterior teeth, scalloped to follow interproximal embrasure with
inferior and superior borders tapered to tooth surfaces
LINGUAL BAR WITH CONTINUOUS BAR
originates bilaterally
LINGUAL BAR WITH CONTINUOUS BAR
INDICATION
→ when linguoplate is indicated but the axial alignment of anterior teeth is such that excessive black out of interproximal undercuts would be required
LINGUAL BAR WITH CONTINUOUS BAR
INDICATION
wide diastema exists between mandibular anterior teeth and linguoplate would objectionably display metal in front view
LINGUAL BAR WITH CONTINUOUS BAR
located on or slightly above the cingula of the anterior teeth may be added to the lingual bar or can be used independently
CINGULUM BAR
INDICATION
→ when lingual plate or sublingual bar is indicated but the axial alignment of the anterior teeth is such excessive blockout of interproximal undercuts would be required
CINGULUM BAR
CONTRAINDICATION
→ anterior teeth severely tilted lingually
→ wide diastema exist between the mandibular anterior teeth and
the cingulum bar would objectionably display metal in front view
CINGULUM BAR
this concept is incorporated in the Swing-Lock design which consist labial or buccal bar that is connected to the major connector by a hinge at one end and a latch at the other end
LABIAL BAR
→ support is provided by multiple rests on the remaining natural teeth
→ retention is provided by a bar type retentive clasps with arms contacting the infrabulge areas on the labial surface
LABIAL BAR
INDICATION
→ lingual inclinations of remaining mandibular premolar and incisor teeth cannot be corrected
→ severe lingual tori cannot be removed
→ severe and abrupt lingual tissue undercuts
LABIAL BAR
CONTRAINDICATION
→ poor oral hygiene
→ presence of shallow or buccal vestibule
→ high frenal attachment
LABIAL BAR
INDICATION OF THE SWING-LOCK CONCEPT
→ missing key abutments
→ unfavorable tooth contours
→ unfavorable soft tissue contours
→ teeth with questionable prognosis
LABIAL BAR
→ cast framework material is distributed in 3 planes
→ should not be used to connect anterior replacements with distal
extension bases
SINGLE PALATAL STRAP
should have to be objectionably bulk to resist torque and
provide vertical support and horizontal stabilization but this
could interfere with speech
SINGLE PALATAL STRAP
strap should be 8 mm wide or approximately as wide as the
combined width maxillary premolar and first molar
SINGLE PALATAL STRAP
confined with an area bounded by 4 principal rests
SINGLE PALATAL STRAP
NDICATION
→ bilateral edentulous space of short span in a tooth-supported restoration
SINGLE PALATAL STRAP
relatively broad 8-10 mm
ANTERIOR-POSTERIOR STRAP
anterior part of the palatal strap located as far as possible to
void rugae and tongue interference
ANTERIOR-POSTERIOR STRAP
INDICATION
→ Class I and II arches in which excellent abutment and residual ridge and direct retention can be made without indirect retention
→ long edentulous span in Class II, Mod 1 arches
ANTERIOR-POSTERIOR STRAP
Class IV arches which anterior teeth must be replaced with RPD
ANTERIOR-POSTERIOR STRAP
inoperable palatal tori that does not extend posteriorly to the
junction of soft and hard palate
ANTERIOR-POSTERIOR STRAP
covering 2⁄3 of the palate
PALATAL PLATE
anterior border follows the valleys between rugae and does not
extend anteriorly to indirect retainers on the first premolar
PALATAL PLATE
INDICATION
→ Class I arch, remaining abutment is canine or first premolar
→ excessive vertical resorption
→ no palatal tori
PALATAL PLATE
ADVANTAGES
→ uniform thinness and thermal conductivity of metal makes readily acceptable to tongue and underlying tissues
→ corrugation in the anatomic replica adds strength to the casting
→ surface irregularities are intentional therefore electrolytic
polishing is all that is needed
→ greater retention
PALATAL PLATE
→ least desirable maxillary major connector
→ it should never be used arbitrarily
→ results to gingival irritation and periodontal damage
U-SHAPED PALATAL CONNECTOR
INDICATION
→ when a large inoperable palatal torus exist
→ several anterior teeth are to be replaced
U-SHAPED PALATAL CONNECTOR
PRINCIPAL OBJECTIONS
→ lack of rigidity
→ fails to provide good support and permits impingement of
underlying soft tissue
→ need of increase thickness that results to hindrance to the tongue
U-SHAPED PALATAL CONNECTOR
→ less than 8 mm in width
→ most widely used and yet the least logical
→ often too thin and flexible or too bulky and objectionable to the
tongue
SINGLE PALATAL BAR
→ exhibits many of the same disadvantage as the single palatal
bar
→ could be too bulky and interfere with tongue function
COMBINATION OF ANTERIOR AND POSTERIOR PALATAL BAR-TYPE CONNECTOR
is a term used to denote the scribing of a shallow groove on the maxillary master cast outlining the palatal major connector exclusive of rugae areas
beading
→ use of cleoid carver
→ care must be exercised to create a groove not larger than 0.5
mm in width or depth
BEADING OF MAXILLARY CAST
serves as the connecting link between major connector or the base of a RPD and other components of the prosthesis
MINOR CONNECTOR
functions:
o transfer functional stress to the abutment teeth
o transfer the effects of retainers, rests and stabilizing
components throughout the prosthesis
MINOR CONNECTOR
