METHODICAL ELABORATION 5 & 6
METHODICAL ELABORATION #5
1. Biomechanics of partial removable acrylic prosthesis.
a. https://www.slideshare.net/TaseefHasan/biomechanics-in-removable-partialdenture
b. Biomechanics is the movements(forces) in response to function that will help
design a stable prosthesis
c. Biomechanical consideration
i.
Direction, Duration, Magnitude, and frequency of stress being applied
ii.
Capacity of the denture and denture bearing areas is to resist the
forces/stress
iii.
Changes due to resistance will occur over time
iv.
Types of resistance
1. Tooth based - mainly contributes to horizontal stress(direct
retainer)
2. Tooth and tissue based - mainly contributes to vertical stress and
torsion(major connectors and indirect retainer)
d. Type of stress forces
i.
Vertical
1. Displacing force
2. Dislodging force
ii.
Horizontal
iii.
Torsion
2. Maintaining, stability, balance of the partial removable acrylic denture, notion,
practical importance
a. Notion: when the mouth is opened the trail denture stays in its position
b. Practical importance
i.
Maintain the prosthetic in place for function
c. Important def
i.
Stability: resistance to movement in horizontal direction (anteriorposteriorly or medio-laterally)
ii.
Retention: resistance to removal from the tissues or teeth
iii.
Support: resistance to the movement towards tissue or teeth
d. Retention:
i.
Interfacial surface tension
1. Thin layer of water spreading uniformly throughout denture
a. Water is not compressible & results in better retention and
adaptation
ii.
Adhesion
1. Ability of water/saliva to be attracted to water
iii.
Cohesion
1. Ability of water/saliva to be attracted to gingiva
iv.
Atmospheric Pressure
1. Negative pressure created by vacuum from gravity of dentures
pulling the denture away pulls denture back
v.
Mechanical
METHODICAL ELABORATION 5 & 6
1. Direct/Indirect retainers
2. Frictional fit
3. Undercuts
vi.
Physical
1. Adhesion
2. Cohesion
3. Interfacial surface tension
4. Atmospheric pressure ATM
5. Gravity
vii.
Physiological
1. Molding of tissue around polished surface
2. Neuromuscular control
3. Enumerate component elements of partial removable acrylic denture, practical
value.
a. Components
i.
Denture base - covers the residual ridges and support the denture teeth
ii.
Artificial Teeth - acrylic, porcelain, metal
iii.
Clasps(Direct retainer) - provide retention against dislodging forces
iv.
Rest(Indirect retainer) - prevent or resists movement or rotation of the
base away from the residual ridge
v.
Major Connector - connects parts of one side of the dental arch to those
of the other side
vi.
Minor Connectors - unit that connects other components
b. ACCORDING TO TEACHER:
1. Base (attaches all the saddles together)
2. Prosthetic Teeth
3. Clasps
4. Types of clasps used in the construction of partial removable acrylic denture,
general characteristics.
a. Clasps prevent dislodgement of the prosthesis without damage to the abutment
teeth
b. Types - page 45 http://removpros.dentistry.dal.ca/ewExternalFiles/RPD%20Manual%2011.pdf
i.
Circumferential(circle or Akers) clasp
ii.
Ring clasps
iii.
Embrasure(Double Akers) clasp
iv.
“C” clasps( hair-pin or Reverse action)
v.
Bar clasps - T ,Y, L, I, U, S
vi.
R-P-I clasp
vii.
RPA clasp
viii.
Combined clasps
METHODICAL ELABORATION 5 & 6
c.
d. Requirements to clasps
i.
Dental segment
1. Have close contact with tooth tissue and its free end should be
located in the retention zone occupying not less than 2/3rd of
mesio-distal part of vestibular surface
ii.
Elastic segment
1. Should not be in contact with marginal periodontium of support
tooth and should be located in above equatorial zone
iii.
Fixing segment
1. Specific retention for fixing in the base of artificial removable
denture
5. Special systems used in the construction of partial removable acrylic denture,
general characteristics.
a. They mean special bone attachments
b. Dowler System
i.
c. Hinge Attachment
i.
Provides more mobility less ridged in case of very long edentulous spans
6. Enumerate stabilising and supporting elements of partial removable acrylic
denture. general characteristics and practical value.
- By Lecture
- Stabilizing & Supporting Elements of Partial Removable Acrylic Denture
- Periodontal support & Muco-periosteal support
- Fixation Systems:
- Screwing
- Friction - telescoping caps, attachments, bars, clasps
- Anchoring with Clasps
- Root & periodontal Ligaments
METHODICAL ELABORATION 5 & 6
High quality - sufficient surface area & structure, Ante’s Law, 1:3
Ratio
Implants, Posts & core
Alveolar ridge - Must be well defined & not hyper/atrophied
Good non-diseased mucosa (better stickiness)
Saliva quality - thick but not to thick is best for adhesion forces
Cheeks, tongue, vestibule, lips, muscles - keep denture in place
Path of insertion
-
-
METHODICAL ELABORATION #6
1. Laboratory stage for manufacturing of the wax composition, general characteristics,
importance.
- Manufacturing:
- Impression + Model Fabrication
- Survey
- Surveyor: determines height of contour with common path of insertion
- Waxing
- Setup
- Flasking
- De-Waxing
- Boilout in hot water bath
- Application of separating media
- Packing with acrylic (& use bench press to pack it)
- Curing
- Deflasking
- Finish & polish
2.Preventive modeling of the wax composition, general characteristics, importance.
- Preliminary*
3.Qualitative determination of wax composition on the model fixed in the simulator.
- Composition = wax up
4.Qualitative determination of wax composition in the oral cavity.
- Extraoral Determination:
- Determine possible technological errors and inaccuracies in time of
manufacturing prosthesis & remove blemish, trauma factors
- Thickness of base, quality of surface, sharp edges, sagging plastic
- Polymerization defects - porosity
- Color, size, shape of artificial teeth to natural teeth
- Clasps, location degree of fixation, sharp edges
- Quality of artificial teeth arrangement & fixation
- Intraoral Determination
- Check fit, extension, retention, stability,
- Esthetics, phonetics,
- Physiognomy restoration
- Vertical & horizontal component of jaw relationship
- Clasps arms must be non-traumatic for their placement (relative to gingival
margins)
- Centric occlusion must have maximum occlusion
METHODICAL ELABORATION 5 & 6
- Functional occlusion must correspond to principles of dynamic occlusion
- Check with Spatulae Test
5.Definitive modeling of the wax composition, general characteristics, importance.
6.Techniques of manufacturing of PRAD.
- Compression Molding Technique
- Injection Molding Technique
- Microwave Energy
- Heat activated
- Chemical/Cold activated
7.Individualization of the base of PRAD to the prosthetic field. Techniques of realization
- Adjust
- Teeth or acrylic base
- Proper polishing & smoothing
- (smooth surface allows for better adhesion)
- Intra-oral adaptation:
- Carbon paper/articulating paper
- Correct clasps
- Individualization of occlusion
- Polish inner surfaces - avoid mucosa trauma
- Technique for Base to Prosthetic Field
- Spatulae Test
- Determines quality of contact of prosthesis base with the prosthetic field
- It attempts to displace wax composition with the top of the spatulae by
introducing it between the occlusal surfaces of lateral teeth of both
hemiarches while the patient i keeping dental arches in maximum contact
8.Individualization of the clasps of PRAD to support teeth. Tools and techniques of
realization.
- Clasps of PRAD (Direct retainers)
- Dental segment:
- Close contact with tooth tissues
- Free end should be located in retention zone & occupy less than ⅔ of
mesio-distal region of vestibular surface
- Elastic Segment:
- No contact with marginal periodontium of support tooth
- Located above equatorial zone
- Fixing Segment:
- Specific retention form for fixing base of PRD
- Clasps Adjustment Technique:
- Bend clasp for better partial adaptation
-
Dental Tools: dental pliers
- Adam plier
- Adam clasp bending plier
- Adams clasp former
- Adams Spring forming plier
9.Individualization of occlusion. Tools and techniques of realization.
- Artificial Tooth Alignment Techniques:
METHODICAL ELABORATION 5 & 6
-
Maxilla & Mandibular Artificial Teeth Alignment
- Maxillary Central incisors:
- Parallel to profile line
- Maxillary lateral Incisors
- Cervically inward
- Maxillary Canines
- Cervically outward
- Mandibular central incisors
- Cervically inward
- Mandibular lateral incisors
- Cervically outward
- Mandibular canine
- Cervically outward