What is the main reason to conduct a visual inspection during an onlay preparation?

Conducting a visual inspection during an onlay preparation is primarily aimed at confirming that the occlusal surface has been properly prepared. This step is crucial because the occlusal surface must be shaped accurately to ensure a proper fit for the onlay, which contributes to both functionality and comfort for the patient. A well-prepared surface is critical for achieving optimal adhesion and longevity of the restoration. Inspecting the occlusal surface allows the practitioner to verify that the contours and dimensions meet the necessary specifications, minimizing the risk of complications that could arise from improper preparation.

The other aspects such as aesthetic considerations, durability of the material, or the need for additional materials, while important in their own right, are secondary to the immediate need to confirm that the foundational preparation is correct, as it directly impacts the success of the onlay procedure.