Principles of cavity preparation

Question 1

Who classified cavity preparations according to location and size?

What year?

Answer 1

In 1896, Greene Vardiman (G.V.) Blackclassified cavity preparations according to location and size

Question 2

What are Black’s Classification of Cavities (1896)?

Answer 2

• Class I – Occlusal surfaces of molars and premolars, buccal pits of molars
• Class II – Approximal surfaces of molars and premolars
• Class III – Approximal surfaces of incisors and canines
• Class IV – Incisal edges of incisors and canines
• Class V – Cervical margins

Question 3

What are G.V. Black Principles Relating to Cavity Preparation?

Answer 3

• Outline Form
• Resistance Form (only for dental AMALGUM)
• Retention Form (only for dental AMALGUM)
• Treatment of Residual Caries
• Correction of Enamel Margins
• Cavity Debridement

Question 4

What is Outline form?

Answer 4

Gaining access to the caries.

• Dependent upon location of caries: either by direct access or by gaining access through another part of tooth (more destructive)
• Traditionally- by cutting through overlying enamel (high speed handpiece and diamond bur)

Question 5

What is resistance form?

Answer 5

To Resist Occlusal forces.

• To enable the restoration and remaining tooth structure to withstand masticatory forces.
• Cavity floor at right angle to the direction of the occlusal forces
• Sufficient depth of material compatible with its physical properties

only when using enamel

Question 6

What are the rules for Resistance Form for:

Amalgam

Adhesive Restorations (composite)

Answer 6

•Amalgam: enamel margins must be finished so that no unsupported / overhanging enamel remains (# if overloaded leaving a defect at cavity margin).

•Adhesive restorations:

not required to design retention & resistance form. However…achievement of a cavity which possesses some innate resistance & retention is desirable provided it does not req. removal of excessive tooth substance as this will ‘protect’ the bond – increasing longevity proven

Question 7

What are different forms of Retention?

Answer 7

• Grooves in cavity wall
• Use of undercut and occlusal keys
• Use of bonding agent and acid etch
• Dentine pins

Question 8

What is the Treatment of Residual Caries?

Answer 8

• Always remove caries from enamel-dentine junction first, then move on to the base of the cavity
• General rule of thumb – soft dentine is infected, and should therefore be removed
• Firm, but stained dentine in the base of the cavity can be left – should be removed in anterior teeth if it will show through enamel

Question 9

What instruments d you use when removing caries?

Answer 9

• Traditionally using a slow, rotating bur with rosehead
• Often finished off with use of hand excavator

Question 10

How do you correct enamel margins?

Answer 10

• Unsupported enamel is weak and prone to fracture
• Can be splinted by adhesive materials
• Remove weakened tooth substance
• Facilitate placement of matrix retainers
• Bevel to increase surface area for bonding

Question 11

What should be done throughtout the cavity preperation?

Answer 11

•Cavity should be thoroughly washed and dried to remove debris and bacteria

Question 12

What are parts 1 and 2?

what is the narrowest part of the restoration called?

Answer 12

For an Amalgam restoration…

narrowest part of restoration is called ISTHMUS

Question 13

Label the diagram…

Answer 13

Question 14

Cavity preperation diagram ..

Answer 14

Question 15

What is the Cavosurface angle?

Answer 15

•Cavosurface angle: where cavity wall meets tooth surface (crown of tooth)

– should be 90 - 110º for Amalgam