Relining and Rebasing

Question 1

Define “reline” vs “rebase” for dentures

Answer 1

Reline: Adding new base material to the tissue surface of an existing denture to fill the space between the original denture contour and altered tissue contour.

Rebase: Replacing the entire denture base material of an existing denture.

Note: Terms are often used interchangeably; chairside procedures are typically relines while laboratory-based ones are usually rebases.

Question 2

What are the four main categories of denture relines?

Answer 2

1) Temporary relines
2) Soft relines
3) Permanent relines,

4) Chairside vs Laboratory-based relines (classification by location)

Question 3

When are temporary relines indicated? (Give 3 situations)

Answer 3

1) Tissue conditioning when dentures are grossly ill-fitting
2) Post immediate dentures
3) After implant surgery

Question 4

What are the indications and disadvantages of soft relines?

Answer 4

Indications: Parafunctional habits, very atrophic ridges, cancer/cleft patients (obturators).

Disadvantages: Plasticizer leaches out, deteriorate with time, harbour microorganisms

Question 5

List the four types of soft lining materials and their activation methods

Answer 5

1) Heat-cured acrylics: methacrylate powder (polyethyl methacrylate) with benzoyl peroxide, activated by heat.

2) Self-cured acrylics: tertiary amine activates benzoyl peroxide.

3) Heat-cured silicones: siloxane with silica filler, processed against acrylic.

4) Self-cured silicones: similar composition to impression materials

Question 6

What are the indications for permanent (hard acrylic) relines?

Answer 6

Peripheral seal problems, correction of errors following inadequate master impression, immediate/post-immediate dentures, prolongs lifespan of older dentures. Usually laboratory-based.

Question 7

What are the first two clinical steps in the rebase technique before taking an impression?

Answer 7

1) Remove undercuts from the denture

2) Take a wash impression using closed mouth technique

Question 8

Describe the laboratory procedure after receiving the impression (first 4 steps)

Answer 8

1) Pour impression in stone

2) Create plaster overcast to maintain position and vertical dimension

3) Separate overcast

4) Remove denture to reveal working model

Question 9

What is carved at the junction of the hard and soft palate during rebasing?

Answer 9

A post-dam is carved at the junction of the hard and soft palate

Question 10

After carving the post-dam, what must be done to the denture before replacing it on the model?

Answer 10

The fitting surface and palate are removed from the denture to allow space for new acrylic

Question 11

How is the denture secured to the model and why is the overcast important?

Answer 11

Sticky wax holds the denture in place on the overcast. The overcast maintains the position of the denture in relation to the model and maintains the vertical dimension. Once the gap is filled with wax, the overcast can be removed.

Question 12

What flasking method is used in the demonstrated technique?

Answer 12

The Dundee injection method

Question 13

Describe the acrylic injection process in the rebase procedure

Answer 13

Mixed acrylic is placed in a plastic bag and inserted into the injector. The flask and injector are clamped, and the handle is turned slowly until acrylic flows out of the flask. The flask is then placed in a clamp and processed.

Question 14

What are the final clinical steps when the rebased denture returns from the laboratory?

Answer 14

Disinfect the denture, insert it, carry out insertion checks similar to finishing a new denture, arrange a review appointment in 1-2 weeks

Question 15

What is a key concern with patients self-relining dentures using internet materials?

Answer 15

Self-treatment may lead to negative consequences, highlighting the need for patient education about proper denture care and professional reline procedures