Retention grooves for a Class V amalgam preparation are generally located at which line angles?

Retention grooves in a Class V amalgam preparation are strategically placed at the axio-occlusal and axio-gingival line angles. This specific placement is crucial for enhancing retention and resistance of the dental material within the preparation. The axio-occlusal angle provides support for the occlusal forces that may be exerted on the restoration, while the axio-gingival angle ensures that the restorative material firmly adheres to the tooth structure in the gingival area.

The rationale behind this design is to create a mechanical interlock that helps prevent the restoration from dislodging under the forces encountered during mastication, thereby increasing the longevity and effectiveness of the amalgam restoration.

In contrast, the other options do not accurately describe the optimal location for retention grooves in Class V preparations. For example, retaining grooves located at occluso-mesial and occluso-distal or axio-lingual and axio-buccal angles would not be effective in addressing the specific retention needs of a Class V preparation. This is largely due to the orientation of the forces acting on this area of the tooth and the unique anatomical considerations surrounding Class V preparations, which are typically found in the cervical region.