Dental Restoration Class 2 Preparation PDF

The Class 2 Preparation 1 Resistance form - Pulpal & gingival walls being flat and perpendicular to the forces directed to the long axis of the tooth. - Restrict the extension of the walls to allow strong cusps & ridges to remain with sufficient dentin support - providing enough thic...

The Class 2 Preparation 1 Resistance form - Pulpal & gingival walls being flat and perpendicular to the forces directed to the long axis of the tooth. - Restrict the extension of the walls to allow strong cusps & ridges to remain with sufficient dentin support - providing enough thickness of the restorative material. 2  If the restoration is extended into occlusal grooves, this extension will provide resistance to displacement of the restoration proximally (that is, toward the adjacent tooth ) 3 To provide enough resistance, the extension into the occlusal surface must have a faciolingual dimension of at least one forth the distance between the facial and lingual cusp tips (intercuspal distance). 4 And the facial and lingual margins of the occlusal extension must be approximately parallel to each other in a mesiodistal direction. 5 To provide resistance form for the Class2 amalgam restoration, the proximal preparation should have a mesiodistal dimension of about 1.5 mm or more. 6 The gingival wall, like the facial and lingual walls of the proximal preparation, should form an angle of approximately 90 degrees with the surface of the tooth. This provides strength to both the amalgam and enamel and prevents enamel not supported by sound dentin from being left at the margins of the restoration. 7  Reverse curve When the contact area is more buccally, extending the bucco-proximal wall into the embrasure lead to excessive cutting of the buccal cusps. To avoid this a reverse curve (S-shaped) is made in the buccal wall so as to have sufficient amount of dentin in that area. 8  Retention form - Occlusal convergence of facial & lingual walls. - Dovetail design of occlusal step. 9 10 Convergence toward the occlusal surface of the facial and lingual walls of the proximal slot preparation gives retention form to the restoration to keep it from dislodging occlusally. 11  Final tooth preparation - Removal of any remaining defective enamel and infected carious dentin. - Infected carious dentin is removed with a slowly revolving round bur or spoon excavator or both. 13  Pulp protection - Only on the pulpal walls (axiopulpal , occlusopulpal ) - Do not extend it until the margins. 14  Finishing external walls - Remove unsupported enamel. - 90 degree cavo surface angle at the margins. 15 16