MARGINAL GEOMETRY

FINISH LINE CONFIGURATION

Chamfer

 It’s a finish line design for tooth preparation in which gingival aspect meets the external axial surface at an obtuse angle. This type is prepared with a tapered round ended fissure diamond bur.

Advantages

•         It provides distinct margin 

 •         Adequate bulk to the restoration

 •         Easier to control 

 •         Exhibits least stresse

Disadvantage

•         Care needed to avoid unsupported lip of enamel Indications:  

•         Cast metal restorations

•         Lingual margin of the metal ceramic crowns

Shoulder

        The shoulder finish line is a design for tooth preparation in which the gingival floor meets the external axial surfaces at approximately a right angle. This finishing line is prepared with flattened end tapered diamond fissure bur. 

Advantages

 •        Bulk of the restoration 

 •        Wide ledge provides resistance to occlusal forces 

 •       Provides space for healthy restorative contours 

 •        Maximum esthetics

 •        It offers resistance against distortion during processing  

Disadvantages

•        Less conservative of tooth structure

•        The sharp 90 internal line angle 

Indications:

 •        All ceramic restorations

  •        Facial margins of metal--ceramic crowns