class IV preparation

Question 1

class IV lesion

Answer 1

a proximal lesion of anterior teeth that involves one or more incisal angles

Question 2

what can cause a class IV lesion?

Answer 2

• caries
• trauma
• occlusal interferences
• grinding
• or any combo of the above

Question 3

type of preparation and restoration can vary based on the:

Answer 3

• cause
• esthetics
• occlusal scheme
• finances

Question 4

when should you check the occlusion of a class IV?

Answer 4

BEFORE preparation

Question 5

when should you choose a composite body shade?

Answer 5

• prior to beginning
• in proper light

Question 6

classifications of fractures of a class IV

Answer 6

• Ellis Classifications: bases on extent of fracture
• Class I
• Class II
• Class III

Question 7

class I fracture of a class IV prep

Answer 7

• in enamel only
• best pulpal prognosis
• retention can be challenging due to occlusion

Question 8

class II fracture of a class IV prep

Answer 8

• fracture extends through enamel into dentin
• risk of pulpal involvement long term increases (due to original trauma)
• can be restored with direct composite, veneers, or crowns

Question 9

class III fracture of a class IV prep

Answer 9

• extends through enamel and dentin and exposed pulpal tissue clinically
• minimally requires pulpal protection prior to retoration
• need for root canal increases
• long term, may require crown

Question 10

other classifications according to trauma (non class IV lesion)

Answer 10

1. non vital tooth without loss of tooth structure
2. total tooth loss (avulsion)
3. displacement of tooth without fracture of crown or root
4. fracture of entire crown

Question 11

before treatment with trauma:

Answer 11

• must evaluate for other injuries (lacerations, head injury, jaw fractures, etc.)
• must evaluate tooth for vitality (if vital = re-test vitality as it may become non-vital)
• radiographic exam (!!! - look for widened PDL, caries, root fractures)
• discuss options with patient

Question 12

before class IV treatment consider:

Answer 12

• consider nature of injury
• need for root canal now or in future
• prep design
• restorative material
• patient occlusion!!!!

Question 13

complications

Answer 13

• retention?
• root canal?
• post and core?
• crown?
• veneer?
• patient’s bite

Question 14

bite classification

Answer 14

class I: normal
class II: overbite
class III: underbite
open bite

Question 15

complications with bite:

Answer 15

• laterotrusive or protrusive interferences
• severely worn dentition (bruxism)
• collapsed bite

Question 16

considerations (of variation)

Answer 16

• “young” tooth will have a large pulp chamber and high pulp horns
• tooth’s apex may not be closed and will require treatment prior to root canal
• consider pulpal protection even in a moderate fracture (CaOH as liner, glass ionomer as a base)

Question 17

what must you recognize in a class IV:

Answer 17

• signs of pulpal injury from trauma
• receded pulp
• widened PDL and Periapical periodontitis
• may require root canal
• tooth may present with a darkened color

Question 18

Class IV preparation of a #8 composite

Answer 18

• shaped according to extent of fracture
• retention is placed internally in the dentin area, and the entire external cavosurface margin has a continuous bevel

Question 19

outline form for class IV fracture (MIFL) of tooth #8

Answer 19

Question 20

how to create the fracture

Answer 20

remove the blackened area (as seen in outline form) with a tapered diamond rotary instrument

Question 21

class IV preparation after creating the fracture:

Answer 21

• remove tooth from typodont
• draw the area of the dentin with a pencil
• replace tooth into typodont
• place rubber dam

Question 22

after drawing on the dentin and placing the rubber dam:

Answer 22

• use 35 carbide bur
• remove dentin to a depth of 1mm
• measure depth with perio probe

Question 23

after drilling into dentin:

Answer 23

use hand instruments (hatchet and hoe) to smooth the axial wall of prepared dentin

Question 24

after smoothin with hatchet/hoe to smooth dentin:

Answer 24

• use 1/2 round bur
• place retention at axio-gingival line angle and at axio-incisal point angle

Question 25

after placing retention:

Answer 25

- use tapered diamond rotary instrument - begin beveling on the external facial surface

Question 26

the bevel being placed should be:

Answer 26

- 1mm wide around the entire cavosurface margin except for GINGIVAL (incisal, lingual, facial)

Question 27

class IV finished prep criteria

Answer 27

1. follows outline form of the fracture 2. 1/2mm into dentin 3. smooth internal surfaces 4. retention at the axio-gingivial line angle and at the axio-incisal point angle 5. 1mm bevel around the facial, lingual, and incisal margins

Question 28

Class IV composite restoration (only for preclinic purposes - no acid etching):

Answer 28

- use bonding agent and apply small amount for 20 seconds - air thin - cure for 20 seconds - place mylar strip interproximally and place wedge to hold

Question 29

construction of the lingual matrix is made with what material?

Answer 29

polyvinyl siloxane putty

Question 30

what can the lingual matrix be constructed from?

Answer 30

- a waxed up model of the desired final contour of the restoration - a properly contoured existing restoration that needs to be replaced

Question 31

how is the polyvinyl siloxane putty used?

Answer 31

- should cover lingual surface of the tooth to be restored - preferably includes at least one tooth adjacent on each side - putty should extend to gingival portion and cover incisal edge (end @ facio-incisal line angle)

Question 32

what does the lingual matrix correctly reproduce?

Answer 32

- contour of the lingual surface - embrasures - marginal ridges - helps confine material to restored area

Question 33

what does the lingual matrix NOT provide?

Answer 33

- proximal contact - proximal contour - seal the gingival margin

Question 34

application of composite onto prep:

Answer 34

1. choose capsule 2. place small amount into retentive areas (WHILE holding matrix against facial surface) 3. light cure 4. continue adding in increments no more than 2mm 5. fold matrix over facial and lingual surfaces of tooth for proper contour 6. light cure through matrix 7. repeat until slightly overbuilt (for polishing) 8. polish

Question 35

what is the oxygen inhibition layer?

Answer 35

- occurs when light cured - oxygen in the air interferes with polymerization - located on surface of composite - this layer is removed during finishing and polishing

Question 36

the anatomical contours must _________ the contralateral tooth.

Answer 36

MIRROR

Question 37

what burs do you use for contouring the facial and incisal surfaces?

Answer 37

tapered diamonds

Question 38

what burs do you use for contouring the lingual cavity?

Answer 38

football shaped diamond

Question 39

why is anatomy important?

Answer 39

- esthetics - function - preventing future fractures - occlusion

Question 40

final restoration must be checked for:

Answer 40

interferences in MIP, protrusion, and lateral excursion

Question 41

polishing:

Answer 41

1. soflex discs (coarse to very fine = dark to light) 2. wipe off restoration with gauze between disc changes 3. flame shape/point rubber abrasive for lingual cavity 4. enhance bur on slow speed to pre-polish lingual fossa and MR area 5. abrasive strip for interproximal surface (coarse to fine) 6. luminescence

Question 42

finished restoration criteria

Answer 42

1. smooth and shiny 2. no pits or scratches 3. natural contour that mirrors contralateral tooth 4. no excess composite 5. natural shape (embrasures) 6. no ditching 7. strong interproximal contacts