How does silver dressing help with pressure sores?

Antimicrobial. Silvadene (silver sulfadiazine) cream is antimicrobial, keeping pressure sores from becoming infected. In addition, the emollient (cream or ointment) helps provide a moist wound bed for adjacent normal skin cells to migrate into the wound to heal the area.
Silver dressings. Dressings with silver have not shown, using statistical analysis, to be any better than their non-silver counterparts. They are not especially specific for pressure sores either. These types of dressings can be used on many types of wounds.
Natural antibiotic . Silver along with zinc have natural antibacterial properties. In and of themselves, they don't prevent pressure sores bit they keep existing pressure sores cleaner and less likely to become infected which will make a pressure sore worse, .