Fabrication of Denture Base Record Base Notes

Fabrication of Denture Base Record Base Introduction

The record base can be fabricated using various materials with various methods. This chapter demonstrates various methods of fabrication of record base.

Sprinkle-On Method

This is an excellent method for the fabrication of a record base. This method gives a record base of best fit and adaptation compared to finger adapted dough method. The operator can easily control the thickness of the record base. This is an easy method to fabricate a record base. This is an easy method for the fabrication of a record base and an ideal method for beginners/students.

Armamentarium:

• Maxillary final cast
• Self-cure acrylic resin in dispenser
• Self-cure monomer

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• Syringe
• Cold mold seal
• Painting brush
• Dappen dish.

Step 1:

Mark denture borders with an indelible pencil in the sulcus depth. Apply a cold mold seal (separating medium) on the maxillary cast with a painting brush. Repeat application 2–3 times to achieve an even coating of it.

Step 2:

Apply the desired quantity of self-cure polymer on a smaller area of the cast and saturate it with monomer liquid. Repeat the procedure as needed. A syringe can be used for dropping the monomer on the polymer.

Step 3:

Apply material in the sulcus in such a way that it fills the sulcus evenly. This will record the proper width and depth of the sulcus. Proper recording of the width and height of the sulcus is essential to achieve retention of the record base.

Note: Use a small plastic bottle with a nozzle to dispense polymer powder and a syringe with a needle to dispense monomer liquid drop by drop. Bend the needle as shown in the picture for easy use and visualization.

Step 4:

Repeat the procedure until even the thickness of the denture base of around 2–3 mm is achieved. Extend the procedure all over the cast to cover the entire denture foundation area with the acrylic resin

Step 5:

Cover it under the rubber bowl for 10–20 minutes to create monomer saturated environment under the rubber bowl to reduce surface porosity. The record base fabricated with self-cure acrylic resin can be cured in a pressure pot for 20 minutes at 20 psi pressure. Record bases cured under pressure have less porosity. The record base cured at normal atmospheric pressure has a better fit than cured under pressure.

Step 6:

Remove it carefully with a sharp instrument without damaging the cast or record base. Examine the cured record base carefully. Remove any excess material from borders using the acrylic trimmer. Make notches to relieve frenums. Notches are created using small straight fissure laboratory tungsten carbide bur. Finish and polish it. Store it in water while waiting for the next appointment/exercise.

Finger Adapted Dough Method

An alternate method of making a record base is finger adapted dough method. Instead of sprinkling on polymer and saturating it with monomer, mix the polymer and monomer together until the mixture attains dough consistency.

When the polymer-monomer mixture attains dough consistency, it is removed from the porcelain jar and adapted on cast in such a way that the record base of even thickness of 2–3 mm is fabricated.

The thickness of the record base is kept 1–1.5 mm over the crest and facial/buccal slopes of the ridge. This will prevent trimming of teeth (ridge lap area) while arranging in case of less interarch space.

Step 1:

Apply a cold mold seal (separating medium) on the maxillary cast with a painting brush. Repeat application 2–3 times to achieve even coating it.

Step 2:

Manipulate the required amount of self-cured polymer and monomer in a porcelain jar and wait till it attains dough consistency. Apply

Vaseline on palm and collect material from porcelain jar, mix it well using your finger.

Step 3:

Place the mixed material on the palatal part of the maxillary cast. Start spreading it and adapting it on the cast till it covers the full foundation area. Wetting fingers with monomer or water will
prevent material adhering to fingers or wear gloves to prevent adhesion. For fabrication of the mandibular record base, shape the acrylic resin in a rope shape place it on one end (retromolar pad) of the edentulous foundation, and start covering the whole foundation area

Step 4:

Remove excess material beyond the land area. If needed, cut the excess material with a paper cutter or BP blade. Ensure proper adaptation of resin in the vestibule area. Take care while adapting the resin not to reduce the thickness of the record base.

Step 5:

Allow the record base to cure under a rubber bowl or under pressure in the pressure pot.

Step 6:

Make notches to relieve all the frenum. Smooth rough surface if any

Forming Resin Sheet To Fabricate Record Base

A modification to finger finger-adapted dough method is to roll the acrylic dough in a sheet of desired thickness and adapt it on cast to fabricate the record base. Acrylic dough can be rolled into sheets by pressing it between two lubricated glass slabs or by using the stone mold. Resin sheets can also be fabricated by pressing the resin dough between two lubricated glass slabs.

Fabrication Of Record Base By Shellac Baseplate

Armamentarium:

• Final cast
• Shellac baseplate
• Slurry water
• Cotton
• Chip blower
• Curved scissors
• Wax Knife
• Wax Spatula
• Pencil to mark borders and frenum.

Shellac is available in the form of baseplates in different shapes for maxillary

and mandibular arch. It is made up of resinous exudate of a scale insect and added fillers such as talc and mica. When heated it becomes soft and can be easily adapted on cast, on cooling becomes rigid and dimensionally stable. It is easy to manipulate and adapt shellac. If needed, correction can be done by heating it again. The main disadvantage of shellac is that it may lose its initial adaptation to temperature changes while making wax rim on it or during adapting to different areas on the cast.

Step 1:

Soak the cast in slurry water to make it wet. This will prevent the sticking of shellac on the cast and damage to the cast.

Step 2:

Pass the shellac baseplate over the flame of the Bunsen burner till it becomes soft and moldable. Place it over the wet cast and try to adapt it to the cast. Apply heat as needed and continuously adapt it with your finger.

Step 3:

Use the curved end of a wax knife or wax spatula to adapt it into the sulcus.

Step 4:

Cut the excess shellac baseplate beyond the land area with curved scissors. Heat the material over a burner flame with a chip blower for easy cutting.

Step 5:

Fold the remaining shellac baseplate into the sulcus in such a way that it fills the sulcus. This is done to record the width and depth of the sulcus. Apply heat if needed and merge it nicely to remove rough area.

Step 6:

Allow it to cool and remove it carefully. Examine borders, if needed remove extra material with filling.

Note: The margin of the baseplate should be filled and flushed with the vestibular depth of the cast.

Step 7:

Provide enough clearance for all frenum.

Step 8:

Inspect the borders and smooth them with sandpaper wherever needed. Shellac record base is ready for use.

Fabrication Of Record Base By Light Cure Acrylic Resin

Light cure resin is available in sheets in a light-protected box. It is easy to adapt, shape, and adjust the light cure resin sheet on the cast. It is a very quick method for the fabrication of a record base but costly compared to other materials and methods. It requires special equipment for the polymerization of light cure resin. Sheets are available in uniform thickness

Step 1:

Take a sheet of light cure acrylic resin and adapt it to the cast.

Step 2:

Cut extra material beyond the land area with a BP blade.

Step 3:

Adapt material in the sulcus area with a wax spatula.

Step 4:

Cure it in a curing chamber for 10 minutes.

Step 5:

Inspect the borders. Trim and smoothen if needed. Light cure denture base is ready for use