Base & Rim

Record Bases

used to establish the proper dimension between upper and lower arches

rigid, temporary form that represents the base of a denture and fits directly onto the master cast

RB Function

provides a stable foundation to support the occlusal rim and helps register accurate jaw relations without rocking or shifting

interim denture base that supports the occlusal rim

RB are used to facilitate ___ records

maxillomandibular relation

MMR

the spatial position and orientation of the upper jaw (maxilla) relative to the lower jaw (mandible)

What is RB made of?

a rigid, relatively thin layer of wax, shellac or thermoplastic polmyer (Triad)

Occlusal Rims

wax placed on baseplate to measure height & width of missing teeth

occluding surface or block—typically constructed from baseplate wax—built on top of the record base

OR Function

simulates the space of missing teeth and tissues to record vertical dimension, jaw orientation, lip support, and the plane of occlusion

joins RB in facilitating MMR record, as well as shows how teeth of the denture should be arranged

Breakdown the OR functions in more detail:

• Used to relate casts on an articulator

• Wax occlusion rims simulate the position of the teeth

• Determination of midline of the arch

• Determination of smiling (high) lip line and speaking (low) lip line

• Determination of canine eminences

• Provide proper support of the lips and cheeks when appropriately contoured

• Aid in orientation of the

occlusal plane

• Serve as a means of transfer of the facebow record

• Used in determining vertical and horizontal jaw relationships: VDO, VDR, freeway space, CR

By convention, OR are slightly ___ than the dentition to be replaced

bulkier

Why bulkier?

provides additional stability during the bite records procedure

OR is basically ___

wax that is placed on top of RB

So, essentially, our master cast is just a mold of the patient's mouth that determines the shape/fit of the overall denture, while the BP and OR will show how we fill that denture in with teeth, as well as how that denture will occlude/move/fit in mouth?

yes

the master cast is a guide, but of course it is not at all a part of the ultimate denture... it is the segue between mouth and denture product

mouth —> custom impression —> master cast —> RB & OR .... —> eventually —> final denture to give to patient.. we will learn more about what comes next, next :)

Explain RB and OR very simply:

🪙 The Record Base (The Foundation)

What it is: A hard, rigid plastic pattern that is custom-molded to fit perfectly over your bare gums.

What it does: It acts like a temporary, tight-fitting foundation. It mimics the base of the future denture so the dentist can test how well it sits on your gums.

🕯️ The Occlusal Rim (The Wax Wall)

What it is: A block of dental wax shaped like a horseshoe that is built on top of the record base.

What it does: It takes the place of your missing teeth during the planning phase. Because wax is easy to melt and shape, the dentist can trim it down or add to it.

🤝 How They Work Together

The dentist places the combined wax-and-plastic piece into your mouth to record vital measurements:

Bite height: Finding how far apart your upper and lower jaws should sit.

Jaw alignment: Seeing how your upper and lower jaws come together.

Tooth placement: Marking where your centerline is and where your new teeth should eventually be placed in the wax.

What instruments do we need

• Separating medium (Vaseline)

• Baseplate wax

• Sticky Wax

• Wax spatula

• Hanau torch

• Red handled knife / Buffalo knife

• Acrylic burs

• mm Ruler

• Bunsen burner

• Triad resin

• Rim former / Putty knife / Hot

plate

Let's talk about making an RB: Step 1

block out master cast

Areas that may require blockout:

undercuts

frenum attachments

rugae

irregular soft/hard tissue surfaces

redundant soft tissue areas

However, you don't want to block out "too much" ... why?

because then RB won't stay in the mouth

Wax should be ___

thin enough to see through

RB: Step 2

lubricate casts

thin layer

RB: Step 3

adapt Triad to master cast

When adapting the Triad material, the Triad overlying the palate of the maxilla should be consistently ___ thick

1-2 mm

Why?

to facilitate speech

An XS thick RB may precipitate ___... you don't want this

gagging

XS thickness may also lead to RB impinging upon the tongue space, thus preventing the patient from articulating speech sounds in a normal fashion

Last but not least, ___ and ___ records made from overly thick RB may be inaccurate

VDO

CR

RB: Step 4

cure Triad RB in machine

RB: Step 5

trim borders of RB

— mark XS with pencil and trim this XS with flash

The XS that extends onto the ___ of the cast should be trimmed preferentially

land area

The only portion of the RB that is highly polished is the ___

periphery

— there is no need to use pumice to polish the RB (doing too much)

After you complete making the RB, it is optional to ___ in the RB — before you cure it

make dots

What for?

to gain more retention for upcoming wax placement of the OR

Characteristics of a proper, complete RB:

• Strength and rigidity

• Accuracy (closely approximates the contours of the final cast it was fabricated from) → Stability and Retention

• Smooth, rounded, well polished borders

• Thickness of borders and palate must resemble those of

the finished dentures

• Palate must be 1-2mm thick

• Thickness and contour of the denture borders are defined by the land area of the master cast

___ RBs are required for establishing MMR and verifying phonetics

Retentive

If RB is loose, the denture will be inaccurate. Accoridngly, you need to check the flanges for ___

overextension

After adjustment, if the record base is only slightly loose,

use ___ to help retain the record base

denture adhesive

What if the denture still has pronounced looseness?

you need to remake it

Let's pivot... what are the ideal dimensions for a maxillary OR?

22 mm base height

3-5 mm width at front

6 mm width moving towards back

8 mm at back

How about for a mandibular OR?

18 mm height

3-5 mm wide up front

6 mm wide moving towards back

8 mm wide at back

Why 18 mm for mandible?

1/2 to 2/3 up to the retromolar pad

Now, just like we did for the RB, let's detail the steps used to create OR... Step 1:

apply baseplate wax to RB

— over alveolar ridge areas

OR: Step 2

heat a sheet of baseplate wax over a Bunsen Burner until it is pliable, then roll or fold it into a long tube

OR: Step 3

starting from one end (tuberosity), press this roll of wax along the crest of the ridge

OR: Step 4

seal the wax to the RB with a hot wax spatula

Just to clarify, what is this wax?

the OR!! this is what composes it

OR: Step 5

adjust vertical dimensions of wax

OR: Step 6

contour — buccals and labials —the baseplate wax of the OR

fill in voids with additional wax

OR: Step 7

establish anterior overjet/inclination

The anterior extension of the wax rim should measure ___ from the incisive papilla

7-9 mm

This measurement can be performed with a ___ or ___ gauge

Boley

Alma

You want the anterior extension to be slightly ___, as well

proclined

— angled/tipped forward

The inclination of the wax rim is determined by the ___

ridge relationship

classes I - III

OR: Step 8

adjust horizontal dimensions of the wax rim

Give the ideal thickness per region:

• Anterior region: 3-5mm

• Premolar region: 6mm

• Molar region: 8mm

Lingual contours must not impinge on the ___

tongue spce

Before you begin making BP and OR, make sure to ___ on the master cast

mark landmarks

using red-blue pencil

Completed mandibular OR should have highest height at the ___ region

posterior