Instructor Notes

Black's Principles of Cavity Preparation

Principle 1: Outline Form

The shape or outline of the cavity preparation as it meets the surface of the tooth. Final outline form may need to be refined after caries removal.

Principle 2: Resistance Form

Features of the preparation that resist fracture of the material and/or fracture of the remaining tooth structure.

Principle 3: Retention Form

Features of the preparation that retain the restoration (resist displacement or removal of the restoration).

Principle 4: Convenience Form

Extension of the preparation to allow access for operator instruments during the preparation and placement of the restoration.

Principle 5: Caries Removal

Removal of carious tooth structure.

Principle 6: Refinement

Removal of unsupported or fragile enamel to allow for a smooth restoration-tooth interface.

Principle 7: Cleansing

Washing the preparation of debris and drying it to allow for better visualization.

Design Features

Composite

The important concept to emphasize is the conservative nature of the composite preparation. Due to the micromechanical bond between the resin composite and the tooth structure (greater bond with enamel than with dentin), the preparation has very few design specificities. Minimum requirements include: removal of caries tooth structure, rounded internal features, and keeping restoration margins away from occlusal stress-bearing areas.

Amalgam

Due to the brittle nature of amalgam restorations under occlusal loads, a minimum thickness of 2mm of amalgam is required. Therefore, the amalgam preparation must be at least 2 mm deep. Since there is no bonding of the material to tooth structure, amalgam is retained by mechanical forces alone. The occlusally converging relationship of the internal walls, and any dovetail features are designed as a "locking" mechanism.

Cast gold

Although the cast gold preparation shares many similarities with the amalgam preparation, there are some important differences.

Similarities                                        Differences

Approximately 2 mm deep

Occlusal dovetail feature           

                                                  Gold can be drawn thin at gold-tooth margin

Internal walls must diverge toward the occlusal to allow for removal of the wax pattern and insertion of the gold restoration

 

 

 

References: Summitt JB, Robbins JW, Schwartz, RS. Fundamentals of operative dentistry: a contemporary approach. 2nd ed. Chicago. Quintessence. 2002

Kern GD. Lab Manual for Operative Dentistry Technique. Portland, OR. Oregon Health and Science University. 2003

Roberson TM, Heymann HO, Swift EJ, Jr. Sturdevant's Art and Science of Operative Dentistry. Mosby. 2001.