<prompt> To achieve the additional retention, following should be done while tooth preparation:Excessive occlusal preparationTapered preparationGrooves and boxesSupragingival finish line  <response>: Proximal grooves or boxes placed in healthy tooth structure are particularly effective in enhancing the resistance form of crown preparations, because these interfere with rotational movement tipping of the crown and thereby subject additional areas of the luting agent to compression.Ref: Stephen Rosenstiel, Martin Land, and Junhei Fujimoto, Contemporary Fixed Prosthodontics 5th Edition page 193 