What is a key factor that affects the dimensional changes of amalgam?

The dimensional changes of amalgam are significantly influenced by the mercury alloy ratio. This ratio determines the physical properties of the amalgam once it is mixed and set. A higher mercury content can lead to an increase in fluidity during the mixing process, which can affect the amalgam's ability to fill in the cavity preparation and adapt to tooth structure. However, this also can result in greater dimensional changes upon setting, such as expansion or contraction.

In contrast, variations in bonding agent types and surface polishing techniques impact the bond strength and the surface finish of the restoration but do not directly affect the internal characteristics of amalgam itself regarding dimensional stability. Enamel thickness is not related to the amalgam's properties but rather affects the overall structure and integrity of the tooth, influencing the placement and adaptation of the restoration rather than its dimensional changes. Therefore, the mercury alloy ratio is crucial, as it directly relates to how the material behaves physically under setting conditions.