Which type of matrix retainer is placed from the lingual?

The correct choice regarding the type of matrix retainer that is placed from the lingual is indeed the contra angle matrix retainer. This type of retainer is designed to allow for the placement of a matrix band on the tooth in a way that is more accessible from the lingual side, particularly useful for posterior teeth where the lingual approach can provide a better angle for placement.

The contra angle design provides an adjustable mechanism that permits the assistant to secure the band tightly around the tooth while minimizing difficulty during positioning. This design is advantageous for specific clinical situations, such as preparing for restorative work, where visibility and accessibility are limited.

Other types of retainers, like the universal matrix, are typically used on the buccal side and may not accommodate the same placement angle as the contra angle design. Crown retainers are specifically designed for use with crowns and do not follow the same placement principles as a contra angle. Wedges are utilized to help seal the margins of a matrix band but do not refer to a retainer type at all. They serve a different purpose in the matrix placement process.