Operative Lecture 4: Caries Preparations

What are the five indications of tooth preparations?

1. Cavity elimination

2. Repair fractured teeth

3. Congenital malformations

4. Defective restorations

5. Esthetic defect

What are the three available restorative materials?

1. Amalgam

2. Composite resin

3. Ceramics

Which phase of cavity preparation establishes the foundational form and design of the preparation?

Initial

Which phase of cavity preparation refines the preparation and prepares for restoration placement?

Final

What is the first step of tooth preparations?

Establish initial depth

What is reached when establishing the initial depth in tooth preparations?

Dentinoenamel junction

What are the guidelines for initial depth?

Occlusal Surface:

Root Surface:

Occlusal Surface: 0.2mm inside DEJ

Root Surface: 0.8mm inside external root surface

What dimension is needed for areas requiring secondary retention?

0.5mm inside DEJ

During outline formation, what must be removed?

All unsupported enamel and friable tooth structure

During outline formation, what must be included?

All faults, carious grooves, and defective restorations

During outline formation, what must be preserved?

Cuspal and marginal ridge strength

What is the goal of "Prevention of Extension"?

Conserve tooth structure

What are the three factors that extension of caries depends on?

1. Extent of caries/injury

2. Restorative material

3. Function/esthetics

What is the shape and placement of preparation walls to best enable both the tooth and restoration to withstand?

Primary resistance form

What are the three factors affecting primary resistance form?

1. Amount of occlusal contact

2. Type of restoration

3. Amount of remaining tooth structure

What shape should resistance form preparations be?

Box-shaped

What do box-shaped preparations help the tooth to resist?

Occlusal loading

What must be restricted for resistance forms for strong cusp and ridge areas?

Extension of external walls

What shape should internal line angles have in resistance forms to reduce stress?

Slight rounding

What in resistance forms prevent fracture due to load?

Thickness of restorative material

Should cusp capping be done if extension from a primary groove toward the cusp tip is no more than half the distance?

No

Should cusp capping be done if extension is one half to two thirds of the distance?

Consider

Should cusp capping be done if extension is more than two-thirds of the distance?

Yes

What are the three factors that affect resistance forms?

1. Occlusal contact

2. Amount of remaining tooth structure

3. Type of restorative material

What is the minimal occlusal thickness for amalgam restorations?

1.5mm

What is the minimal occlusal thickness for cast metal restorations?

1 - 2mm

What is the minimal occlusal thickness for ceramic restorations?

2mm

What is the minimal occlusal thickness for composite restorations?

1 - 2mm

What is primary resistance form dependent on?

Material

What is the chemical mean of retention?

Glass ionomers

What is the macromechanical mean of retention?

Amalgam-gold

What is the micromechanical mean of retention?

Composite

What are the four things that increases retention in amalgam restorations?

1. Occlusal convergence

2. Slight undercut in dentin

3. Conserved marginal ridges

4. Occlusal dovetail

What are the four things that increases retention in cast restorations?

1. Parallel opposing walls

2. Occlusal dovetail

3. Secondary retention

4. Reverse bevel

What are the four things that increases retention in composite restorations?

1. Micromechanical bonding

2. Enamel bevels

What is the form which provides visibility, accessibility and ease of operation during preparation and restoration?

Primary Convenience Form

What feature of convenience forms gives access to the deeper portion of the preparation?

Sufficient extension of walls

What is the access in Class II preparations made through in convenience forms?

Occlusal surface

What is provided by the adjoining tooth during Class II preparations in convenience forms?

Proximal clearance

What feature of convenience forms are in cast gold restorations?

Occlusal divergence

In which four events should you extend for convenience?

1. Margins are poorly visible

2. Bad access for instruments

3. Difficulty in proper material adaptation

4. Interfering anatomical contours

What are the four conservation strategies?

1. Magnification

2. Patient/practitioner positioning

3. Appropriate instruments/materials

4. Retraction techniques

Why is leaving carious dentin at the DEJ area unacceptable?

Enamel requires an uncompromised attachment to dentin

What can old restorative material serve as in restorations if it is intact and no caries are under it?

Base

What can be used as an adjunct to visual and tactile examination, but cannot replace clinical judgement?

Caries detector

What are the three techniques for caries removal?

1. Round bur in slow-speed

2. Chemochemical removal

3. Hand excavation

What are the three secondary resistance and retention forms?

1. Axial proximal grooves

2. Pins in dentin

3. Slots and coves

What is developed during finishing of enamel walls?

1. Cavosurface design

2. Smoothness

What are the two goals of enamel finishing?

1. Adjust CSA

2. Remove undermined enamel rods

Which bevel is part of the enamel thickness from the CSA?

Short

Which bevel is on the full enamel thickness?

Long

Which hand instruments are used in enamel finishing?

1. Chisel

2. Hatchet

Which rotary instruments are used in enamel finishing?

1. Fissure burs

2. Stones

What are Noye's three principles for strong enamel walls?

1. Enamel rests on sound dentin

2. Enamel rods inner ends rest on sound dentin

3. Strongest enamel margin has full length enamel rods supported by shorter rods

What are the six criteria for an ideal restoration according to the USPHSC?

1. Exact structure

2. Smooth margin without discrepancies

3. Smooth surface without discrepancies

4. Tight interproximal contact/compatible ridge height

5. Secure attachment to tooth

6. Asymptomatic restoration

What type of restoration is temporary between visits or therapeutic under restorations?

Intermediate

What type of restoration is placed as final restoration?

Permanent

What type of permanent restoration is fabricated and adjusted inside the patient's mouth?

Direct

What type of permanent restoration is fabricated outside the oral cavity?

Indirect

What are the two direct metallic restorative materials?

1. Amalgam

2. Gold foil

What are the two direct non-metallic restorative materials?

1. Resin composite

2. Glass ionomer

What are the two indirect metallic restorative materials?

1. Cast gold

2. Non-precious restorations

What are the two indirect non-metallic restorative materials?

1. Ceramics

2. Resin composite