Fundamentals of Tooth Preparation

True / False: enamel is brittle

True

Enamel has --- elastic modulus and ---- tensile strength

high elastic modulus

low tensile strength

Fractures in enamel occur along ----

rods

True / False: dentin is compressive

True / False: amalgam is brittle

true

Amalgam requires --- for strength

bulk

Amalgam requires ---- margins for restorations

90 degree

Amalgam requires creating ---- for retention

undercuts

True / False: undercuts can exist because of natural tooth morphology and counter

Undercuts create ---- featureas

retentive

Composite is made of

filler particles embedded into a matrix

i.e glass in Bis-GMA

Amalgam is made of

silver/copper/tin/zinc in mercury

Amalgam is an

alloy = mercury and a metal

Composites bond to enamel and dentin using

acid etching

What are the initial stages of cavity preparation?

1. initial depth (0.2mm) and outline form

2. primary resistance form

3. primary retention form

4. convenience form

What are the final stages of cavity preparation?

5. remove decay and old restorative material

6. pulp protection

7. secondary resistance and retention

8. finish external walls

9. final procedure = cleaning and inspecting

True / False: When creating an outline form, material indicates --- depth

initial

When creating a restoration the most important aspect is to ---- tooth structure

conserve

How do you proceed from initial to final tooth preparation?

by extending the external margins to remove existing decay

Decay on internal walls is removed: first or last?

last

The initial depth for amalgam prep is --- mm into dentin

0.5mm

Isthmus

narrow anatomical part that connects two larger structures

The isthmus width for amalgam prep is --- mm

1 mm

True / False: composite preparations require varies initial depth and isthmus width

true

Ceramic requires --- mm initial depth and isthmus width

2 mm

Purpose of primary resistance form

The shape and placement of the preparation walls that enables the tooth structure and restoration to withstand masticatory forces

What is completed during primary resistance form?

Create the MINIMUM cavity depth / isthmus width for restorative material used

Remove unsupported enamel at cavomargins

Remove decay

Round internal and external line angles

Purpose of primary retention form

The shape and placement of the preparation walls that enables the tooth structure and restoration to withstand displacement via lifting or tipping

What is performed during primary retention form?

Mechanical undercuts for amalgam

Micro-mechanical and mechanical undercuts for composite = acid etching and undercuts

What 2 steps are completed in primary retention form?

Creating mechanical and micro-mechanical features to withstand displacement

Convenience form

form that allows for accessibility in preparing and restoring the tooth

When creating a convenience form the preparation must be opened enough for ----

adequate inspection

True / False: all staining is not considered decay

true - color of dentin changes due to mineralization and re-mineralization

Affected dentin can

remineralize

Does affected dentin have to be removed?

No can remain and re-mineralize if isolated from oral environment

Decay spreads at the ---

DEJ

When preparing a restoration the --- and --- must be free from caries

cavosurface margin and lateral walls

What is the heathy texture of dentin?

Dry and leathery

What is decayed texture of dentin?

Soft and moist

True / False: it is acceptable to probe the area over the pulp

FALSE = will cause penetration and exposure

Bases are used for ---- protection

thermal

Liners are used for ---- protection

Mechanical

Bases are not needed for ---- protection under ---

bases are not needed for thermal protection under composites

What occurs during secondary resistance and retention?

Macro-mechanical and micro-mechanical alterations

Macro-mechanical alterations refers to

grooves, slots, boxes, pins

Micro-mechanical alterations refers to

enamel and dentin conditioning = acid etching

Class 5 amalgam preparation requires ---- placement for proper retention

secondary groove placement

What are the two types of cavosurface margins?

1. Butt joint

2. Beveled

Class 5 composite preparterm-58ation extending below CEJ requires --- placement for proper retention

secondary groove placement

Butt joint margins have ---- degree angle between the restorative material and tooth

90 degree

Beveled margins have a ---- angle between the restorative material and tooth

sloped

When finishing the external walls of a preparation ceramic requires ---- margins

butt joint

When finishing the external walls of a preparation amalgam requires ---- margins

butt joint

When finishing the external walls of a preparation composite requires ---- margins

butt joint or beveled

When finishing the external walls of a preparation cast requires ---- margins

beveled

What is used under amalgam to minimize leakage / sensitivity?

Varnishes / bonding agents

What minimizes leakage in composites?

Acid etching improves bonding and decreases leakage

Never --- a preparation

Dessicate = dry

Why should a preparation never be dessicated (dried)?

causes collagen in dentin to collapse = decreases bond strength / pulp damage

A number 245 burr has a length of ---- mm

3 mm

A number 330 burr has a length of ---- mm

3 mm (pear shaped)

Cavity preparations begins with a --- cut

punch cut

The initial punch is done in the area of ----

decay

The initial depth of preparation is measured at the ---- area of the tooth, which would be the --- area

measured at the shallowest area of the tooth = pit area

The bur is oriented with its long axis ---- to the long axis of the tooth

parallel

True / False: the pulpal floor may measure greater than 2.0 mm in the area of the cusps and that is acceptable because it is the depth into dentin that is most important

true - the depth must be 0.5 mm into dentin with amalgam preparation

True / False: Multiple passes should be avoided because this can result in cavitypreparations with a wide faciolingual width, overconvergence ofthe facial and lingual walls and irregular internal line angles

True

Why should internal line angles be rounded?

to reduce stress concentration

materials condense more easily into rounded line angles

Once the initial depth is complete only areas requiring ---- removal should be deepened

decay

True / False: it is necessary to flatted the entire floor to the depth of the decay

True

What happens when the burr is tilted?

One wall severely undercut and the other wall severely over tapered

Primary retention is obtained by using a bur which produced cavity walls that ---- occlusally

converge

Tapered fissure burs produce walls that ---- occlusally

diverge

Pear shaped burs produce walls that ---- occlusally

converge

When should occlusal walls diverge?

when preparing indirect restorations

For class 1 preparations the buccolingual width should be less than ----- the buccolingual intercuspal dimensions

1/4

Why is flaring present in class 1 prep of mandibular first molar?

to incorporate pit without weakening the marginal ridge

The generic shape for a class 1 prep of a mandibular second molar is ---

plus shaped

For the class 1 prep of mandibular third molars outline generally follows the ---- and ----

deep fissures and pits

For the class 1 prep of mandibular second premolars the outline generally follows a ---- or ---- shape

Y or H shape

For the class 1 prep of mandibular first premolars it is important to not cross the ----

transverse ridge

For the class 1 prep of mandibular first premolar first prepare the --- and ---- pits

Mesial and distal pits

What happens if decay undermines the transverse ridge in a mandibular first premolar?

cross the transverse ridge from mesial to distal pits and create one large occlusal preparation

For the class 1 prep of maxillary first and second premolars the outline form follows the ----

primary fissure

For the class 1 prep of maxillary first and second molars the ---- should be preserved

oblique ridge

For the class 1 prep of maxillary first and second molars prepare separate ---- and ---- cavity preparations

O and OL

A caveated lesion is treated with an ----- procedure

Operative

A non-cavitated lesion that does not involve dentin is treated with a ---- procedure

Medical = non-invasive

Enamel that remains over carious dentin is described as

unsupported enamel

Carious lesions can be divided into 3 types

1. pits / fissures

2. smooth surface

3. root surface

Smooth surface lesions of enamel resembles an ----

irregular cone

The base of a smooth surface lesion is in the ----

The apex of a smooth surface lesion is in the ----

base = enamel

apex = DEJ

Cones of decay in smooth surface lesions are described as

apex to base

The base of a pits/fissure lesion is in the ----

The apex of a pits / fissure lesion is in the ----

base = DEJ

apex = enamel

Cones of decay in puts and fissures caries are described

base to base

Beginning carious lesions confined to enamel are known as

incipient

Incipient lesions are described as ---- or ----

E1 or E2

E1 lesions are

halfway into enamel

E2 lesions are

reach DEJ but do not extend into dentin

Reversible superficial lesions that often appear frosty white are called

white spot lesions