Toothwear - Indirect Restorations - Mods To Standard Preps

Question 1

When can fixed restorations usually be possible in toothwear cases?

Answer 1

When 50% of crown structure remains above the gingival margin

Question 2

What are the issues with prepping a tooth in a toothwear case?

Answer 2

Lack of occlusal-gingival height

Lack of occlusal space

Severely compromised tooth

Must maximise retention with what structure you have

Question 3

What material is best for use in severe bruxists in toothwear?

Why?

Considerations?

Answer 3

Metal used on biting surfaces
- more ductile than porcelain
- stronger

Less prone to fracture

Aesthetic considerations, e.g. have the cusp that facing smile line in porcelain, and functional cusps in metal

Question 4

How can retention be maximised in a crown prep on worn teeth?

Answer 4

Grooves parallel to POI of crown

Small inlay prep within the crown prep

More parallel crown preps - less space for aesthetic porcelain but more retentive

Question 5

What is resistance form?

Answer 5

Shape of a cavity / preparation giving it the best resistance to masticatory forces and rotational forces.

Question 6

What margin is needed for metal?

Porcelain?

Answer 6

Chamfer for metal

Shoulder for porcelain

Question 7

When is a metal margin more preferable on a crown?

Answer 7

Posterior tooth with no aesthetic concern, in a toothwear patient.

Chamfer finish aids retention and less tooth structure removal.

Question 8

What is a last resort of toothwear case?

Considerations?

Answer 8

Surgical crown lengthening
- removal of bone around tooth
- increase Occluso-gingival height

• takes 3 months for gingiva to stabilise, no definitive crowns in this time
• root cementum exposed can give rise to sensibility

Question 9

How can an existing bilateral free end saddle denture have its OVD increased slightly?

Answer 9

Inverted cone bur to drill small retentive holes into the top of acrylic teeth. Add composite to these