Which of the following is not a common use of study models?

Study models, also known as dental casts or impressions, are three-dimensional representations of a patient's teeth and oral cavity, primarily used for various clinical and diagnostic purposes in dentistry. They play a crucial role in several areas of dental practice.

Denture design is a common use of study models, as they allow dental professionals to create custom-fitting dentures based on the specific contours and relationship of the patient's oral structures. Similarly, occlusal analysis, which focuses on assessing the relationship between the upper and lower teeth when biting down, also utilizes models to evaluate and adjust any occlusal discrepancies. Orthodontic assessment benefits greatly from study models as well, enabling orthodontists to analyze dental alignment, diagnose malocclusions, and plan treatments effectively.

In contrast, while periodontal diagnosis involves evaluating the condition of the gums and supporting structures of the teeth, it typically relies more on clinical examinations, probing, and radiographic analysis rather than the use of study models. Thus, the characterization of periodontal conditions and diagnoses does not usually incorporate study models in the same way as the aforementioned applications.

This distinction highlights why periodontal diagnosis is not a common use of study models, making it the correct choice in this context.