RPD MUST KNOW

Dimensions of Occlusal Rest

- Shape: Triangular Shape - Width: 1/3 B-L - Depth: 1-1.5 mm depth - Angle: Less than 90 degree angle

Word association: Bar clasp

-Infrabulge clasp -"Push" clasp

Word association: Circumferential clasp

-Suprabulge clasp -"Pull" clasp

_______" undercut for cast half-round clasp.

0.01

_______" undercut for wrought wire clasp.

0.02

Micro era requires ______ mm resiliency of tissues.

0.4mm

For an ERA attachment, you need ____ mm below for stability and at least ____-____ mm on top for the tooth.

1 mm below for stability at least 4-5 mm on top for the tooth

Mandibular Major Connector Design Specifications

1. Borders 4mm away from gingiva 2. Tissue relief 3. Highly polished tissue surface

Maxillary Major Connector Design Specifications

1. Borders 6mm away from gingiva 2. End before vibrating line 3. Cross midline at right angle (perpendicular) 4. Beaded

What design features in an RPD provide reciprocation?

1. Clasp assembly 2. Major connector 3. Minor connector

Why are guiding planes important?

1. Contribute to stability of thepartial 2. Ensure positive clasp action

What are the two types of ERA used for RPD?

1. ERA-RV (reduced vertical dimension) 2. Micro ERA (20% smaller than the RV in every direction)Comes with plastic pattern and inserts of different degrees of retention which connect to RPDInserts are casted together using same metal alloy as framework

What are 10 indications for RPD?

1. Edentulous areas that are too long for a fixed prosthesis 2. Need to restore soft and hard tissue 3. Absence of adequate periodontal support 4. Compromised abutment teeth 5. Need for cross arch stabilization 6. Need for a distal extension base 7. Anterior esthetics 8. Physical and emotional problems precluding FDPs 9. Ease of plaque removal from the natural teeth and partial denture 10. Economics

What are the 5 types of retention attachment classifications?

1. Frictional : resistance to relative motion of two or more surfaces in intimate contact with each other 2. Mechanical: Resistance to removal due to physical undercut 3. Frictional and Mechanical: combines features of both above 4. Magnetic: resistance to movement is due to magnetic attraction of certain materials 5. Suction: force created by a vacuum

Rotational movement around this fulcrum line is the greatest in magnitude but is not necessarily the most damaging.

Transverse axis

T/F: Occlusal forms of the teeth on RPD must be made to conform to an already established occlusal pattern.

True. Ensure that teeth be placed such that forces of mastication are directed to the load bearing anatomical areas.

How can you regain retention of natural tooth attachment after plastic inserts are worn?

YOU CANNOT! Nothing you can do unless you redo the crown and bridge or cut off the attachment. Could try to cement onto the ERA rings to regain retention, but cannot be done if limited space Reason why attachment on implant is preferred because it can be easily replaced.

Why do we need altered cast if the framework fits?

1. Improve adaptation of the denture base to the ridge to minimize movement during function 2. Equalize stress between ridge and abutments 3. Improve contours of peripheriesChallenges of taking final impression on Class I or II. Goal is to eliminate incorrect area on cast.

What are the advantages of implant for IRPO?

1. Improved support, retention, stability 2. Improved esthetics 3. Improved patient comfort 4. Decreased need for reline

Major Connector Types (Mandibular)

1. Lingual bar 2. Lingual plate (i..e tori exist or high lingual frenum) 3. Sublingual bar (i.e. more posterior and inferior of regular lingual bar) 4. Lingual bar with cingulum bar 5. Cingulum bar 6. Labial bar

When is an attachment application needed?

1. Long span fixed partial denture 2. Removal partial denture 3. Overdenture -Teeth retained / supported overdenture -Implant retained / supported overdenture -Implant retained partial overdenture

Altered casts are most indicated for:

1. Mandibular distal extensions (Class I & II) 2. Extensive edentulous spans 3. Any case where periphery is distorted & needs correction 4. Less necessary in maxilla due to major connector contact with palate

Steps for RPD Design Sequence

1. Outline Rests 2. Outline minor connectors and proximal plates 3. Outline major connector 4. Outline base retention 5. Outline clasp assembly 6. Abutment teeth preparation 7. Custom tray 8. Border molding 9. Final impression 10. Master cast 11. Laboratory prescription 12. Framework fabrication 13. Adjusting framework 14. Jaw relation (triad + occlusal wax rim) 15. Mounting 16. Patient try-in of tooth set up 17. Festooning 18. Processing 19. Denture placement 20. Post placement adjustments

Major Connector Types (Maxillary)

1. Palatal plate (covers at least 50% of palate) 2. Complete palatal coverage (covers 100% of palate) 3. Single palatal strap (covers less than 50% of palate; at least 8mm wide) 4. Anterior-posterior palatal strap (i.e. used when there is mandibular tori or patient has Kennedy III) -15 mm diameter -Width A-P straps = 8-10mm -Lateral palatal straps = 7-9mm -Torus not extending within 8mm of vibrating line 5. U-shaped palatal connector (i.e. used when there is mandibular tori) 6. Single palatal bar (i.e. if patient has strong gag reflex) 7. Anterior-posterior palatal bar

What are the 3 consideration in clasp design for distal extension Classes I and II?

1. RPI- mesial rest, proximal plate, I-bar (mod T bar if pt does not have an undercut) 2. RPA- mesial rest, proximal plate, Akers clasp 3. Combination clasp- mesial rest, proximal plate, wrought wire

What 3 clinical situations are contraindications of infrabulge clasps, thus, opting for a combination clasp assemble?

1. Shallow vestibular depth- less than 5mm to horizontal arm of infrabulge clasp 2. Immediate undercut below gingival margin of abutment teeth 3. Mispositioning of the abutment tooth

What are 3 indications for a fixed dental prosthetic?

1. Short tooth bound space 2. Anterior modification spaces 3. Esthetics

What are the limitations of intraoral attachments?

1. Size of the pulp 2. Length of the clinical crown 3. Cost

Why would you use it on a long span fixed partial denture?

1. To Avoid A Pier Abutment (use attachment as a stress breaker to avoid rocking) 2. To Correct Angulation

What is an attachment?

A connector consists of two or more parts. One part is connected to a root, tooth, or implant and the other part to a prosthesis. Contributes to the fixation, retention, stabilization, and support of a dental prosthesis.

Denture Base: Acrylic vs. Metal

Acrylic 1. Extension base RPD 2. "Snowshoe" effect (suggests that broad coverage furnishes the best support with the least load per unit area) 3. Long span tooth borne RPD 4. Restoration of anatomy 5. Need for reline 6. Anticipated tooth loss Metal 1. Short span 2. Limited space 3. Vertical overlap of anterior teeth 4. Metal pontics 5. Metal backed composite 6. Strength 7. No reline

What are the considerations for indirect retention?

Indirect retention is mandatory in class 1, 2, 4 situations. Not necessary in class 3 situation due to the absence of a fulcrum line. Prevents the lifting of the distal extension by providing the teeth anterior to the fulcrum line with a rest (mesial, occlusal, incisal, etc.)

Why not do a flexible partial if it is more comfortable for the patient?

It is generally unhealthy to remaining dentition. Lack of rests result in unresisted support to occlusal forces, may result in "stripping" the attached tissues from teeth.

What is the most common obstacle for attachments?

Available space

All of the following are philosophies of RPD design except: A. Minimal tooth coverage B. Minimal gingival coverage C. Minimal distribution of force D. Minimal strain to the abutment teeth

C. MAXIMAL/EQUITABLE distribution of force

Which teeth are favored positions for implant for better support and stability?

Canine and molar

What class is used the most for locator attachments?

Class 5: Rotational and Vertical resilient attachment Allows for rotation and vertical movement

Kennedy Class that requires maxillary cast mounting via record base + wax rim + face bow

Class I and II

Tooth-Tissue Borne Kennedy Classes

Class I and II

Kennedy Class that requires hand articulation

Class III and IV

Tooth-Born Kennedy Classes

Class III and IV

The three class of levers are based on:

FLE (123) 1. Location of fulcrum 2. Resistance (load) 3. Direction of effort (force)

T/F: Altered casts can be used when any part of the RPD does not fit correctly in the patient's mouth.

False. Altered casts can only be used when the edentulous area does not fit properly on the patient's tissues. Minor connector, major connector, and rest seat issues --> new RPD fabrication

T/F: The main advantage of RPD attachments is allowing for a favorable distribution of forces.

False. The main advantage of attachments is the elimination of visible clasp arms. Attachments have unpredictable or unfavorable distribution of forces.

T/F: We can use altered casts on all Kennedy classifications.

False. We do not do altered cast on Class III, because it is only used for distal edentulous areas.

These forces can be extremely dangerous and should receive significant attention during the design process

Horizontal axis

What is 2-2-2?

Implant overdenture 2 implants + 2 prefabricated attachments + 2 dentures Connect the attachment to the implant and the other part to the dentures so when they snap together it has a lot of retention. UAB standard of care

Why would you use it on an RPD?

In the instance the patient is of high esthetic command and wants to eliminate visibility of metal clasps

Why is Cr-Co a desirable metal for RPD framework?

Most desirable due to corrosion resistant, high strength, high modulus, low density, low cost

Precision vs Semi-Precision Attachments

Precision: (solid) -Machine-made in special metal alloy (both pieces) -Within 0.01mm tolerance -Must be cast to, soldered, or welded Semi-Precision: (resilient) -Fabricated by direct casting of plastic, wax, or refractory patterns (one or both pieces) -Plastic insert and wax pattern. -Can be cast with PFM framework.

What is reciprocation?

Resistance to horizontal forces exerted on a tooth by an active retentive element Purpose: 1. Prevents tooth movement as the clasp flexes over the HOC 2. Rigid (cast clasp) 3. Contacts the tooth above the HOC (non-retentive) 4. Takes the form of a clasp, plate, or vertical minor connector 5. Provides resistance to lateral movement

Solid vs. Resilient

Solid 1. Solid allows little or no movement 2. Abutment/tooth supported are considered solid 3. Class I 4. Solid = Precision Resilient 1. Resilient allows for some movement 2. Abutment/tooth/tissue supported are considered resilient. 4. Class 2-6 5. Resilient = Semi-Precision

Why is it important for the distal extension Class I and II to have a short guide plane?

This ensures equal distribution of stress between the abutment tooth and residual alveolar ridge.

What is considered when selecting which attachment to use?

•Conditions of the oral cavity •Vertical space •Facio-Lingual Space •Path of placement •Retention •Resilient or non-resilient