The American dental association (ADA) specification number for non- aqueous elastomeric dental impression material is:

**Core Concept:**
The American Dental Association (ADA) specification number system is a method used for classifying dental materials based on their properties and performance. Non-aqueous elastomeric dental impression materials are a type of dental material used for creating dental impressions, which are essential for fabricating dental prostheses and restorations.

**Why the Correct Answer is Right:**
The correct answer, ADA Specification No. 54, refers to the elastomeric dental impression materials. These materials demonstrate high elasticity, which allows them to capture detailed anatomical details of the oral environment. Elastomeric materials also have good accuracy, stability, and dimensional accuracy during the impression-taking process.

**Why Each Wrong Option is Incorrect:**
A) ADA Specification No. 27 (for dental cements) and B) ADA Specification No. 51 (for dental impression materials) are incorrect because they refer to different categories of dental materials.
C) ADA Specification No. 17 (for dental fibers) is incorrect as it belongs to a different category of dental materials.
D) ADA Specification No. 26 (for dental composites) is incorrect, as it refers to a different category of dental materials.

**Clinical Pearl / High-Yield Fact:**
It is essential for dental professionals to understand the ADA Specification numbers for various dental materials to choose the appropriate material for specific dental procedures, ensuring optimal outcomes for patients.

**Correct Answer:** ADA Specification No. 54 (for elastomeric dental impression materials) is the correct answer as it represents the specification number assigned to non-aqueous elastomeric dental impression materials, which are widely used in clinical practice for their high elasticity, accuracy, stability, and dimensional accuracy.