The occlusal cavosurface bevel is prepared at an approximate angle of 45° to increase the surface area for enamel bonding and improve the mechanical retention of restorative materials. This bevel also helps to remove unsupported enamel rods, reducing the risk of enamel fracture. A 45° bevel provides an optimal balance between conservation of tooth structure and adequate retention, ensuring a durable and stable restoration margin.

Reference: Sturdevant's Art and Science of Operative Dentistry, 7th Edition.