Mattresses that are made from memory foam are denser than traditional foam mattresses. The memory foam that is used in mattresses usually ranges from 1.5 lb to 8 lb density. This makes them quite heavy, but they are also incredibly supportive. Memory foam is known to help relieve pressure points and even prevent bedsores. The third generation of memory foam was released in 2006 and includes gels that prevent body heat from being trapped. This allows users of the best memory foam mattresses to sleep cool by preventing overheating during the night.