RPD – THE SYSTEM OF DESIGN

GUEST APPEARANCE

PROFESSOR DAMIEN WALMSLEY

RPD – Top Tips for You

Do you have a diagnosis and a treatment plan?

What is the periodontal and restorative condition

of the teeth?

You have done Preliminary Impressions

Do you need to articulate models?

Have you surveyed the casts?

Learning Objectives

Top tip - take some time out to do a denture design

Learning Objectives

  Understand – Decision making process for

Removable Partial Dentures

– Stages of Partial Denture Design

  Communicate – Design instructions to Laboratory

Mucosa Tooth

Top tip decision Design Stages (after surveying mounted and articulated casts)

1. Saddles 2. Support 3. Retention 4. Reciprocation and Bracing 5. Connection 6. Indirect Retention

Essential Reading

A clinical guide to removable partial denture design Davenport et al. 2000 Ch 4 Saddles

pages 21-26

Buy the Books

http://www.nature.com/bdj/journal/v189/n11/full/4800838a.html

Read the free article

A clinical overview of removable prostheses McCord JF, Grey NJ, Winstanley RB, Johnson A. Introduction. Dental Update. 2002 Oct; 29 (8) :375. Followed by 5 articles

Reduce area of occlusal table Use narrow posterior teeth

Omit the last tooth

Creating success for mandibular RPD

1. Saddles 2. Support 3. Retention 4. Reciprocation & Bracing 5. Connection 6. Indirect Retention

Design Stages (after surveying mounted and articulated casts)

Essential Reading

A clinical guide to removable partial denture design Davenport et al. 2000 Ch 5 Support

pages 27-33

Classification of support

vertical force may be resisted by:-

  mucosa   tooth   tooth mucosa

  root area of the abutment teeth   extent of the saddles   expected force on the saddles

Quality of support

type of support available may vary and assessment of its quality is

made during design procedures

Tooth support Mucosa support Tooth-mucosa support

  rest design   tooth preparation

  saddle extension   quality of support

  free-end saddle   difficult to treat

The shortened dental arch concept was accepted by a great majority of dentists but not widely practised The shortened dental arch concept deserves to be included in all treatment planning for partially edentulous patients

Does it work?

Kanno T, Carlsson GE. A review of the shortened dental arch concept focusing on the work by the Kayser/Nijmegen group. J Oral Rehabil. 2006;33:850-62

Mucosa support

Walmsley AD Acrylic partial dentures Dental Update 2003; 30: 424-429

Distal Rest placement causes tilting

Free End Saddle

Mesial Rest placement prevents tilting

Foot Foot

Off the ridge retention of acrylic base

1. Saddles 2. Support 3. Retention 4. Reciprocation and Bracing 5. Connection 6. Indirect Retention

Design Stages (after surveying mounted and articulated casts)

Essential Reading

A clinical guide to removable partial denture design Davenport et al. 2000 Ch 6 Retention

pages 35-46

Types of RPD Retention

1. Clasps 2. Neuromuscular forces 3. Physical forces 4. Guide Surfaces 5. Attchments

Top Tip - Don’t just rely on clasps

www.dental-app.com

Keep to a minimum Use wrought where possible Watch the gum Use other forms of retention

Top tips 4 Clasps

Choice of Clasp

✖ ✔

Guide surfaces   2 or more parallel axial surfaces on abutment teeth

Guide surfaces: Benefits

  Increased stability   ‘frictional retention’

  Reciprocation   Prevent clasp deformation   Aesthetics

Benefits of Guide surfaces

  Natural

  Artificially prepared

Guide surfaces contour (shape)

How long should it be?

?

  Length guiding plane as long as possible (Kratochvil) – increased friction (retention & stability)

but will torque abutment tooth if free end saddle scenario.

Also consider periodontal support.

Other forms of mouth preparation

  Bonded metal Crowns

  Bonded composite contours

  Surveyed crowns

  Alginate

  First choice –  Tears rather than distort following removal

from DEEP undercuts.

  Silicone –  If undercut too severe, but more demanding

Make it so Final impressions

  Alginate   Individual (special) tray ensures even distribution

& thickness of material to ensure optimum elastic recovery on removal from mouth.

Final impressions

Chairside tray modification using cold curing acrylic resin or greenstick

Common faults

Metal Backings

Metal backings

Usually required for artificial maxillary anterior teeth, where lower teeth almost contact opposing mucosa……

Metal backings

…but how do you work out where the metal is meant to go??

1. Saddles 2. Support 3. Retention 4. Reciprocation and Bracing 5. Connection 6. Indirect Retention

Design Stages (after surveying mounted and articulated casts)

Essential Reading

A clinical guide to removable partial denture design Davenport et al. 2000 Ch 7 Bracing &

Reciprocation pages 47-51

Reciprocation

Prevents

tooth movement escape

1. Saddles 2. Support 3. Retention 4. Reciprocation and Bracing 6.  Indirect Retention 5. Connection

Design Stages (after surveying mounted and articulated casts)

Essential Reading

A clinical guide to removable partial denture design Davenport et al. 2000 Ch 9 Connectors

pages 57-64

Design for Upper jaw

Full coverage Ring connector Bar connectors

Anterior

Posterior

Mid palatal

Design for Lower jaw

1. Lingual bar

2. Sublingual bar

3. Lingual plate

4. Continuous or dental bar

5. Labial bar

1. Saddles 2. Support 3. Retention 4. Reciprocation and Bracing 5. Connection 6. Indirect Retention

Design Stages (after surveying mounted and articulated casts)

Essential Reading A clinical guide to removable partial denture design Davenport et al. 2000 Ch 8 Indirect

Retention pages 53-56

Support for indirect retainer

1. Tooth support

2. Mucosa support

System of Design

Top tip draw design on cast

Star Trek

2013