Lab Techniques for

Flexible Partial Dentures

Introduction to Flexible Partials

• Simple solution to provide a removable restoration

• No tooth preparation needed• No metal frame needed• Finished partial with one trip through the

laboratory• Injection Technique• Valplast Partials are repairable and relinable• Guaranteed not to break

Type of Material

• Valplast is a type of Nylon Thermoplastic• Injection Molded• Denser than acrylic• Lower Water Absorption than PMMA• Flexural modulus around 470MPa at body

temperature (making it both flexible and sturdy)

• In use since 1953

Lab Procedure - Overview

• Design, block and relieve master model• Duplicate stone model• Try-in (if required) or Set-up on Master• Transfer set-up to duplicate model• Wax with prefabricated patterns• Invest, Sprue, Wax Elimination• Process with Manual Injector• Finish and Polish

Visually Survey Model

• Visualize design• Aesthetics• Path of Insertion• Comfort• Accuracy of Model

Remove Discrepancies

Wrap-Around Clasp• Most Common

Clasp• Hugs Tissue• Minimal Coverage of

Tooth• Stability against

vertical and rotational movement

Design is made with Red Pencil

Split Wrap-Around

• Clasp Separated from Flange

• Similar to “Roach” Clasp

• Flexibility along Horizontal and Vertical Axes

Spur

Anchor

Maxillary Wax Relief

• Relief Wax placed along Buccal Periphery

• Necessary on All Maxillary Cases

Use Hot Wax for Relief

Mandibular Wax Relief

• Junction of clasp with saddle is more rigid area.

• Undercut toward periphery must be relieved

Blocking and Relieving

• Lingual Undercuts Relieved

• Interproximal Spaces Closed

• Obstructive Undercuts Removed

Final Preparation

• Beading Post Dam• Etching Design

Duplication

• Soak Model• Prepare Flask• Pour Gel• Let set 15 minutes

in air…• …and 15 minutes

in water

Waxing After Setup

• Use of Prefabricated Forms is Recommended to Insure Proper Thickness and Uniformity

Palatal Waxing

• Soften Palate

• Press to Position

• Seal all Borders

Buccal Waxing

Using Prefabricated Form:

• Cut Form to Size

• Press to Model

• Seal all Borders

Bottom Half Investing

Spruing

Top Half Investing

Top Half Investing

Teeth Prepared for Retention

Processing

Melting - 11 Minutes

Injecting

Let’s See That Again...

After Processing

Pre-Finishing

Econo-Cutter

Trimmer

Dark Grinding Wheels

Fitting and Rubberizing

Brown Rubber Wheels

Vulcanite Burs

Polishing

Polishing Motion is Important

Advising Clinician on Insertion and Adjustment

• Partial must be placed in very hot water (150°F or more) for a minute prior to insertion and allowed to cool to a tolerable temperature.• This process makes the partial as flexible as it

would be at body temperature. This minimizes adjustments

Adjustments

• Minor clasp tightening or loosening can be done by heating the clasp again in very hot water and bending it severely in the needed direction. This will purposely warp the area enough to change its position

• Grinding should be done as a last resort.• Use a Standard Green Mounted Stone (used

usually for porcelain) to adjust Valplast. 20K to 30K rotation and constant motion

Small Additions - Welding

• Using hot air welder and welding rod, build up a boxing in the addition site to secure a new tooth

• Select a matching acrylic tooth.• Break a porcelain tooth to obtain pins• Heat each of two pins in flame to cherry red and

embed in the partial half way (pin head protruding)

• Cure scooped stock tooth over pins using tooth-shade or pink acrylic.

Large Additions – Injection

• Wax new section on duplicate model to original partial

• Invest, Sprue, Wash out wax• Prepare bonding site with acid etch

solution (Val-Fuse Repair Liquid)• Inject, finish, and polish

Relines

• Take Putty Matrix to record tooth position• Strip teeth from partial (in blocks) while

duplicating the model.• Rewax new base using matrix to position

teeth• Invest and process using repair technique

to bond top-half exposed Valplast to new base.

• Finish and Polish

Clinical Prep for Tooth Addition

• Clinician should take overall alginate impression to lift out case

• Counter-model for bite• Before pouring the model, any deposits or

adhesives should be removed from surface or the process will lead to an unintended reline.

Clinical Prep for Reline

• Closed-mouth rubber-base reline impression.

• Pick-up overall alginate impression.• Counter not necessary