Operative I: 5.1 Class II Preparations

What is the outline form of Class II Amalgam Preparations?

- Extend into all caries-prone areas, including the pits and deep grooves, and include all proximal contact areas

- Extend the box floor gingivally to be gingival to the proximal contact, but occlusally to the gingiva

- Extend to self-cleansing areas (remove proximal contacts)

- Extend so all enamel is supported by dentin

How far should the prep be from the adjacent tooth in a Class II Amalgam Preparation?

At least 0.5 mm from the adjacent tooth

How far should the prep be from the proximal contact in a Class II Amalgam Preparation?

At least 0.5 mm gingival to proximal contact

How far should the prep be from the gingiva in a Class II Amalgam Preparation?

At least 0.5 mm occlusal to ginival margin

What is the resistance form of Class II Amalgam Preparations?

- conserve tooth structure by circumventing cuspal inclines

- 90-degree cavosurface margins

- Prepare a reverse curve if needed

- Maintain 2 mm of marginal ridge width

- Pulpal floor parallel to the cuspal plane

- Gingival floors perpendicular to occlusal forces

- Bevel the axio-pulpal line angle to prevent concentration/fracture of restoration

- Rounded free-flowing cavosurface margin

When do you place a reverse curve?

In Class II amalgam preparations (depends on location of proximal contact)

- conserves tooth structure

- establishes 90 degree cavosurface margins

- allows for bulk of amalgam

T/F. You need reverse curves in both composite and amalgam preparations.

False. Only for amalgam and only sometimes, depending on proximal contact

What should the pulpal floor be in Class II Amalgam Preparations?

Pulpal floor parallel to the cuspal plane

What should the gingival floor be in Class II Amalgam Preparations?

Gingival floors perpendicular to occusal forces

How much marginal ridge do you want to leave in a Class II Amalgam Preparation?

Maintain 2 mm of marginal ridge width

What should the axial wall and depth be in a Class II Amalgam Preparation?

The axial wall should mimic convexity of external tooth suface in order to establish uniform depths and it should be a depth (space between axial wall and external tooth) of 1 mm

How are the ways that we make sure there is enough bulk of amalgam?

- pulpal depth of 1.5 to 2mm

- axial depth of 1 to 2 mm

- establish a "rectangle shape" to box by defining internal line angles

- axial wall should mimic convexity of external tooth surface in order to establish uniform depth

In a Class II Amalgam Preparation, what is important for the axio-pulpal line angle?

To bevel it to prevent stress concentration/fracture of the restoration.

In a Class II Amalgam Preparation, what should the shape of the box be?

retangle shape box

What is the retention form of Class II Amalgam Preparations?

- Occlusal should have converging buccal and lingual walls (NOT the mesial and distal walls)

- Proximal walls should parallel the buccal and lingual surfaces of the tooth

What should the buccal and lingual surfaces be related to in a Class II Amalgam Preparation?

Proximal walls should parallel the buccal and lingual surfaces of the tooth and converge

T/F. All walls in a class II Amalgam Preparation should be converging.

False. NOT the mesial and distal walls should be straight or diverging because we do not want unsupported enamel)

Which contact should you break first in a class II Amalgam Preparation?

Break the gingival contact before breaking the buccal and lingual contacts

Where should you initiate the vertical extension in a class II Amalgam Preparation?

-initiate the vertical extension in the middle of the marginal ridge and not at the contact (this prevents damage to the adjacent tooth)

What are the functions of the enamel hatchet?

- remove unsupported enamel

- smooth walls and floor of box

- bevel axio-pulpal line angle

What preparation extensions do you need to consider for the mandibular 1st premolar?

Transverse ridge

What preparation extensions do you need to consider for the maxillary molars?

Oblique ridge, lingual groove

What preparation extensions do you need to consider for the mandibular 1st molars?

distal cusp and buccal groove

What preparation extensions do you need to consider for the maxillary 1st premolar?

mesial marginal ridge groove

What are the things to consider when you have special morphology you are thinking about including in your prep?

- is it undermined with caries

- depth of groove is high risk for caries

- remaning tooth structure is thin

- remaining tooth structure is unsupported