Class 2 Preparations

Question 1

Initial Caries-

Answer 1

entirely in enamel

Question 2

Moderate Caries-

Answer 2

lesion entering dentin

Question 3

Advanced Caries-

Answer 3

well into dentin, approaching pulp

Question 4

Root Caries-

Answer 4

lesion entering dentin

Question 5

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Interproximal Caries
Dentist’s goal:

Answer 5

• Remove carious tooth structure
• Remove least amount of tooth structure possible
• Prepare the tooth in a way that
• RESISTS fracture
  
  • Restorative material and tooth
  • =RESISTANCE form
• RETAINS the restoration
  
  • = RETENTION form
• Is possible clinically without detriment to patient or dentriment
  
  • = CONVENIENCE form

Question 6

Reverse S Curve (6)

Answer 6

• Shape in outline form, nearly always on buccal side of preparation
• Creates smoothly rounded form
• Improves resistance to amalgam fracture
• Keeps narrowest part of preparation away from axiopulpal line angle
• Improves resistance to amalgam fracture
• Allows preparation to break contact while allowing the buccal wall to meet the tooth surface at a 90 ̊ exit angle

Question 7

Buccal Contact is Open

Answer 7

0.2–0.5 mm.

Question 8

Gingival Contact

is Open at Least

Answer 8

0.5 mm

Question 9

Gingival Contact is Open at Least 0.5 mm

This ensures:

Answer 9

the etched,
caries-susceptible area below the
contact area is clear

Question 10

Lingual Contact is Open

Answer 10

.02–0.5 mm.

Question 11

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Class II Amalgam Preparation Steps (10)

Answer 11

Step 1: Complete a Class I Amalgam Preparation
Step 2: Widen the dovetail faciolingually and thin the
marginal ridge to about 0.5-0.8 mm mesiodistally.
Step 3: Ditch for the Box
Step 4: Break through the thin enamel wall
Step 5: Remove Undermined Enamel Hooks
Step 6: Smooth the Gingival Floor
Step 7: Bevel the Axiopulpal Line Angle
Step 8: Remove Undermined Enamel from the Gingival Margin
Step 9: Smooth Walls, Perfect Outline, and Finish the Prep.
Step 10: Place Retention Grooves

Question 12

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Step 2: Widen the dovetail faciolingually and thin the
marginal ridge to about 0.5-0.8 mm mesiodistally. (2)

Answer 12

Marginal Ridge Thinned
To .5-.8 mm. mesiodistally.
Dovetail widened.

Visualize the outline form
of the final prep. that you are
developing as you do this step.

Question 13

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Step 3: Ditch for the Box

Answer 13

Use a 169 bur approaching parallel to the long axis of the tooth to ditch for the box. Move the
bur in a pendulum motion so the bucco-lingual dimension of the gingival floor is wider than the
occlusal width of the box. Walls should converge 3 ̊-4 ̊each.

Question 14

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Step 4: Break through the thin enamel wall

Answer 14

Use the 169 bur and hand instruments to break through the thin shell of enamel that remains.
The round profile of the bur will have left “hooks” of undermined enamel on the buccal and
lingual margins that must be removed.

Question 15

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Step 5: Remove Undermined Enamel Hooks (2)

Answer 15

Use the enamel hatchet,with the
wide, flat side of the blade held
PERPENDICULAR to the surface of 
the tooth to remove the “hooks”
of undermined enamel

The preparation after removal
of undermined enamel

Question 16

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Step 6: Smooth the Gingival Floor
Option A: Use of 56 or 57 bur (3)

Answer 16

• The 56 or 57 straight fissure burs have broad, flat ends, and are useful for smoothing the floor of a box.
• These burs also have sharp edges thatwill leave sharp internal line angles which must be rounded.
• Enamel rods are inclined gingivally. Remaining undermined enamel on
the gingival margin will need to be trimmed away with a hand instrument.

Question 17

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Step 6: Smoothing the Gingival Floor
Option B: Use a 245 bur (3)

Answer 17

• The 245 bur has slightly rounded edges, naturally leaving more roundness at the buccal-gingival and
lingual-gingival internal line angles.
• It’send isn’t a large as that of a 56 or 57, making it more difficult for smoothing the gingival floor.
• Again, a hand Instrument will be needed to remove undermined enamel.

Question 18

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Step 7: Bevel the Axiopulpal Line Angle (2)

Answer 18

• Use the flat end of a 56 or 57 straight fissure
bur to put a 45 ̊ bevel on the axiopulpal line
angle.
• By approaching through the open portion of
the box and using the flat end of a bur, you
are less likely to nick surrounding tooth
structure (vs. using the side of a 169 or a
7902 flame bur)

Question 19

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Step 8: Remove Undermined Enamel from the Gingival
Margin

Answer 19

Use the gingival margin trimmer in a scraping motion to

Remove undermined enamel from the gingival margin.

Question 20

Purpose of Retention Grooves:

Answer 20

To retain the amalgam segment that fills the

box against INTERPROXIMAL displacement

Question 21

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Step 10, cont’d: Retention Grooves (4)

Answer 21

a. (We are going to place a buccal axial retention groove as an example) Place flutes of the 169 bur
right against the buccal axialline angle of the box.
b. Tip the bur mesially and lingually. Only the tip of the bur touches the tooth in the buccal-gingival-
axial point angle.
c. Activate the bur and push in a disto-buccal direction, bisecting the line angle on a conservative prep.
The groove should be JUST INSIDE THE D.-E. JUNCTION, ENTIRELY IN DENTIN.
d. Do a comparable groove in the lingual-axial line angle.
The grooves do NOT go into the gingival floor.

Question 22

The groove is at its deepest at

the —.

Answer 22

gingival

• It is the depth of the end of the 169 bur
(0.5 mm.)
• The groove fades out to nothing as it
reaches the axiopulpal line angle (or the
occlusal D.-E. junction). It does NOT go
into the gingival floor

Question 23

Path of Entry: Exception

• Mandibular First Premolar (3)

Answer 23

• The Long Axis of the crown of this tooth tilts lingually relative to Long Axis of the tooth root
• A Class I or II preparation should enter parallel to the long axis of the tooth CROWN
  
  • this will preserve strength in the small lingual cusp

Question 24

Composite preparations are different from amalgam

preparations BECAUSE

Answer 24

THE MATERIALS ARE DIFFERENT

Question 25

composite restoration vs amalgam (3)

Answer 25

Preparations can be more conservative Bonding capability of composite may strengthen supporting tooth structure Composite is a good insulator

Question 26

Indications for Composite (4)

Answer 26

Esthetics Light occlusal contacts Smaller restorations Isolation

Question 27

Esthetics (3)

Answer 27

◦ Anterior teeth ◦ Facial of premolars or first molar ◦ Patient desire

Question 28

Light occlusal contacts (2)

Answer 28

◦ Must have centric TOOTH SUPPORTED occlusion on marginal ridges and cusp tips ◦ Composite does not support occlusion

Question 29

Smaller restorations (5)

Answer 29

``` ◦ Class I occlusal, buccal pits, lingual pits ◦ Excellent prognosis ◦ Low stress areas ◦ Premolars > molars ◦ Small Class II restorations ```

Question 30

◦ Keep margins in

Answer 30

enamel | ◦ Don’t forget to bevel enamel

Question 31

= MINIMIZE (2)

Answer 31

microleakage and post-operative sensitivity

Question 32

skipped Possible Indications for Composite Special situations

Answer 32

◦ Crown foundation ◦ “Buildup” material ◦ Very large restorations ◦ To strengthen remaining weakened tooth structure ◦ Economic reasons or provisionally ◦ Conservative or Preventative restorations ◦ Can preserve tooth structure ◦ May be in conjunction with sealants ◦ Temperature sensitivity with metal restorations ◦ Cross reaction between nickel allergy and silver ◦ RARE and controversial

Question 33

NOT AN INDICATION FOR COMPOSITE (2)

Answer 33

Mercury fear ◦ Educate your patients ◦ Respect their autonomy ALS and MS patients ◦ Amyotrophic Lateral Sclerosis and Multiple Sclerosis ◦ Has not been conclusively shown to contribute to these conditions ◦ Multiple Sclerosis Society does not recommend removal of amalgam fillings to patients with MS.

Question 34

Contraindications to Composite (7)

Answer 34

Heavy occlusal forces Occlusal contacts entirely on composite Restorations extending to root surface Deep subgingival margins ``` Diet ◦ Highly acidic oral environment ◦ High alcohol consumption Poor Oral Hygiene Unable to isolate ```

Question 35

Why does composite fail? (5)

Answer 35

Dentin tubules ◦ More tubules as preparations get deeper= MORE FLUID Adhesives ◦ Water based adhesives undergo phase separation Etch ◦ Operator error- easier to etch dentin too long ◦ Collapse tubules Orientation of enamel vs. dentin Polymerization shrinkage

Question 36

Advantages of Composite (6)

Answer 36

``` Esthetic Conserves tooth structure Bonding ◦ Reduced microleakage and recurrent decay ◦ Increased retention No metal ◦ No mercury arguments from patients ◦ No corrosion ◦ No galvanic shock Can be economical ◦ Vs. crowns and inlays/onlays Preparation may be more forgiving ◦ RESTORATION IS NOT!!! ```

Question 37

Disadvantages of Composite (8)

Answer 37

``` Low modulus of elasticity Porous More technique sensitive placement More time-consuming placement Microleakage May stick to instrument, resulting in voids Can’t place in bulk Expensive compared to amalgam ```

Question 38

COMPOSITE PREPARATION/RESTORATION (4)

Answer 38

``` Remove defect Prepare tooth structure for adhesive Treat prepared tooth structure with adhesive Place composite ◦ Contour, finish, polish ```

Question 39

COMPOSITE PREPARATION | Clean tooth

Answer 39

◦ Pumice and water mixture

Question 40

skipped COMPOSITE PREPARATION Proximal outline form (3)

Answer 40

``` ◦ Must break gingival margin ◦ CARIES must be removed ◦ Occur just below contact ◦ Matrix band must fit passively ◦ Keep margins in enamel when possible ◦ Only remove carious tooth structure ```

Question 41

COMPOSITE PREPARATION | Proximal outline form: break...

Answer 41

◦ Break lingual contact | You will learn to break buccal contact AND to leave buccal contact intact

Question 42

COMPOSITE PREPARATION s curve? bevel? hooks?

Answer 42

``` Reverse S curve not necessary ◦ Flare buccal wall instead Bevel proximal lingual wall Same as amalgam: ◦ NO HOOKS ```

Question 43

COMPOSITE PREPARATION | Pulpal floor depth

Answer 43

◦ 1.5mm | ◦ Ideally, no greater than 2.5mm

Question 44

COMPOSITE PREPARATION | Axial Wall Depth

Answer 44

◦ 1.0mm

Question 45

COMPOSITE PREPARATION | BEVELS (3)

Answer 45

◦ Lingual wall bevel ◦ Gingival bevel ◦ Axial-pulpal line angle bevel

Question 46

``` COMPOSITE PREPARATION NO BEVEL (2) ```

Answer 46

if in the dentin/cementum

Question 47

``` COMPOSITE PREPARATION NO --- Dovetail --- Slightly --- or parallel occlusal walls No adjacent --- --- ```

Answer 47

HOOKS diverged converged tooth damage

Question 48

``` COMPOSITE PREPARATION Finish Preparation (2) ```

Answer 48

◦ Use flame shaped diamond bur | ◦ Use hatchet on proximal walls

Question 49

Can keep composite preparations

Answer 49

SMALL | ◦ Remove all caries, but keep preparation conservative

Question 50

INSPECT PREP BEFORE RESTORING (2)

Answer 50

◦ Free of debris, moisture | ◦ Blood and saliva