The final setting time of a mix of dental stone ends when the?

The final setting time of a mix of dental stone is defined by the completion of the exothermic reaction. During this process, as the dental stone reacts with water, it undergoes a chemical transformation that produces heat, indicating that the setting process is underway. This exothermic reaction results in the solidification of the material as it transitions from a pliable mix to a rigid form, thereby marking the end of the setting phase.

Understanding the timing of this reaction is crucial for dental professionals, as it influences the handling characteristics of the material and the overall quality of the dental impression or cast. Therefore, identifying the completion of the exothermic reaction as the point at which the final setting occurs allows for accurate timing in clinical settings to ensure optimal results.

The other options do not pinpoint the critical moment of final setting. While fluidity and cooling may occur during the setting process, they do not directly define the conclusion of the setting time, which is intrinsically linked to the chemical reaction rather than physical properties.