Dental Restoration Techniques: Amalgam, Gold Inlay, and Bleaching Agents

Difference in Cavity Preparation: Amalgam vs. Class II Inlay

Silver Amalgam Preparation

Silver amalgam preparations follow specific criteria designed for mechanical retention and resistance:

• Outline Form: Narrow, converging occlusally.
• Cavity Width: Kept at one-fourth the intercuspal distance.
• Burs Used: No. 245 and 330.
• Occlusal Cavosurface Angle (CSA): 90 degrees, establishing a butt joint with the amalgam.
• Gingival Bevel: In the range of 15 to 20 degrees.
• Retention: Undercuts in the preparation improve restoration retention.
• Proximal Clearance: Minimal clearance, not more than 0.5 mm from the adjacent tooth.
• Gingival Seat: Ideally kept supragingivally.
• Secondary Retention: Provided by grooves, slots, pins, and amalgam pins.
• Proximal Walls: Provide primary flare.
• Internal Angles: Rounded internal line angles.
• Reverse Curve: May be present in the proximal outline.
• Bevelling: Only done on the gingival cavosurface margin to remove unsupported enamel.

Class II Cast Gold Inlay Preparation

Class II cast gold inlays require a wider outline form and specific angles optimized for seating and frictional retention:

• Outline Form: Wide outline form, with cavity walls diverging occlusally.
• Cavity Width: May increase up to one-third the intercuspal distance.
• Burs Used: No. 271 and 169 L.
• Occlusal CSA: 135 to 145 degrees, designed to achieve a lap sliding fit with the inlay.
• Gingival Bevel: In the range of 20 to 30 degrees, which helps minimize the cement line.
• Retention: No undercuts should be present (retention relies on frictional fit).
• Proximal Clearance: Requires more proximal clearance.
• Gingival Seat: Requires subgingival extension of the gingival seat.
• Secondary Retention: Achieved through grooves, slots, boxes, skirt collars, and reverse bevels.
• Proximal Margins: Show 1/32 flare.
• Internal Angles: Defined internal angles.
• Reverse Curve: Not provided.
• Bevelling: Bevels are placed at both the occlusal and gingival cavosurface margins to provide frictional retention.

Role of Golden Proportions in Dental Aesthetics

The principle of Golden Proportions states that for objects to be proportional to one another, the ratio of 1:1.618 is aesthetically pleasing. As a general rule in dentistry, if the apparent size of each tooth is viewed from a frontal perspective, a 62 percent tooth size anterior to its relationship is considered aesthetically pleasing.