Class I preparation

Question 1

What is a class I lesion?

Answer 1

A carrie that originates in structural defects of teeth…Pits and Fissures of the tooth’s natural anatomy

Question 2

List 3 general locations class I lesions are generally found in order of decreasing frequency.

Answer 2

1. Occlusal surfaces of posterior teeth (Most common)
2. Buccal and lingual surfaces of posterior teeth where grooves terminate
3. Lingual surface of anterior teeth - Most often maxillary lateral incisors

Question 3

Prepared cavities that involve only one tooth surface are classified as what? How are they named by surface?

Answer 3

Simple lesions take on the name of the surface with the lesion, i.e. a posterior tooth with only an occlusal lesion in the central groove is classified as Simple & Occlusal.

Question 4

What developmental condition makes people more susceptible to class I caries?

Answer 4

A failure in the fusion of enamel at the bottom of the grooves and fossae, causing the formation of deep invaginations that may extend as far as the DEJ.

Question 5

At the DEJ, what type of relationship do the cones of decay show during caries progression of a class I lesion?

Answer 5

Base to Base

Question 6

What bur should be used to make the initial outline?

Answer 6

330 bur on high speed w/ water.

Question 7

What is the optimal handpiece grip?

Answer 7

“modified” pen grasp

Question 8

What should the ideal isthmus width be for a class I prep? Extensions?

Answer 8

Isthmus should allow the large end of the 1P condenser to move through freely while the extensions should fit the 1P snuggly.

Question 9

What is retention form?

Answer 9

The shape of the cavity has to resist displacement or removal of the amalgam restoration.

Question 10

What is resistance form?

Answer 10

The cavity must be prepared in such a way that the tooth & the restoration withstand fracture against the applied forces during occlusion or mastication.

Question 11

What is the approximate required depth for resistance form of a class I prep?

Answer 11

.5 mm into the dentin

Question 12

What is the maximum width, in relation to occlusal table, you would want an occlusal prep to comply w/ resistance form?

Answer 12

Isthmus should be just slightly larger that the size of the 1P but no larger than 1/3 the width of the occlusal table.

Question 13

What is convenience form?

Answer 13

The shape of the cavity must allow adequate visibility and accessibility.

Question 14

For resistance form, how should the mesial and distal walls slant? What must be maintained in these regions?

Answer 14

The mesial and distal walls should have a slight divergence that parallels the enamel rods. However, you must ensure that the width of the marginal ridge is not compromised.

Question 15

To comply with retention form, how should the buccal and lingual walls slant?

Answer 15

The buccal and lingual walls should converge, again paralleling the enamel rods.

Question 16

While finishing/refining a preparation margins are planed to remove any unsupported enamel with what tool?

Answer 16

Hatchet

Question 17

What is unique about the preparation of an occlusal class I cavity for maxillary first molars, 3 & 14?

Answer 17

The prep is split into two cuts in order to preserve the large oblique ridge that is vital to the structural integrity of the maxillary first molars.

Question 18

Describe the mesial and distal portions of a maxillary 1st molar prep.

Answer 18

Mesial: Forms a L or C-like prep, b/c it wraps around the mesio-buccal cusp extending into mesial & buccal ridges
Distal: Extends onto lingual surface terminating in the middle 1/3 of the lingual wall. Has axial wall & gingival floor on lingual extension.

Question 19

For occlusal preparations of mandibular first molars, 19 & 30, what side, buccal or lingual, has two extensions?

Answer 19

The buccal wall has two buccal grooves that are included in the occlusal prep. The first is opposite the lingual groove in the middle of the tooth, while the 2nd is the distobuccal groove.