I found this on the webpage:
https://www.dentalclaimsupport.com/blog/examining-cdt-code-d2940-do-you-place-protective-restorations-at-the-emergency-appointment#:~:text=The%20nomenclature%20defines%20D2940%20as%20a%20protective%20restoration.,outside%20the%20mouth%20then%20placed%20on%20the%20tooth

This type of restoration is accurately documented and reported to the payer using code D2940 which was revised a few years ago. The previous code nomenclature defined this code as a sedative filling. The current code language includes a revised nomenclature and a descriptor.
D2940 protective restoration
Direct placement of a restorative material to protect tooth and/or tissue form. This procedure may be used to relieve pain, promote healing, or prevent further deterioration. Not to be used for endodontic access closure, or as a base or liner under a restoration.
The nomenclature defines D2940 as a protective restoration. The current descriptor further defines the intended use of the code to give the treating provider guidance for proper coding.
It is a direct restoration, meaning that the restoration is placed directly on the tooth, not fabricated outside the mouth then placed on the tooth.
The type of restorative material is not specified. Any type of restorative material may be used when the purpose of the placement is to protect the tooth and/or tissue form. Tissue form protection could be filling a deep mesial fracture to keep the tissue from growing into the fractured portion of the tooth.
The descriptor then goes on to describe that the restoration may be used to relieve pain, perhaps in an emergency situation; promote healing as in the situation where the decay may be close to the nerve causing discomfort; or further deterioration of the tooth perhaps in the instance, the tooth is badly fractured and the restoration is placed to prevent further fracturing of the tooth until definitive treatment may be performed.
It is also important to note the descriptor makes it clear what procedures this code is not appropriate for. Code D2940 does not document and report a restoration placed for the purpose of closing an endodontic access hole. Nor is D2940 to be used to document the placement of a base or liner. Per CDT guidelines, placement of a base or liner is inclusive to the restoration and is not a separate procedure.