What critical factor distinguishes different composite materials?

The critical factor that distinguishes different composite materials is particle size. In composite dental materials, especially those used for restorations, particle size plays a significant role in determining the mechanical properties, aesthetics, and handling characteristics of the composite.

Different particle sizes affect the strength, polishability, and viscosity of the material. For instance, smaller particles can create a smoother finish and improve the material's aesthetics, making it less noticeable in the dental restoration. Conversely, larger particles can contribute to the strength and durability of the composite, but may compromise the smoothness and overall appearance.

While color, volume, and manufacturer can influence the appearance and specific use-case of a composite material, they are not as critical to differentiating the fundamental properties and performance characteristics of the materials themselves as particle size is. Each composite formulation caters to different clinical needs based on these minute variations in particle size, which ultimately impact the success of dental restorations.