Does using a soft toothbrush lessen gum disease or increase tooth decay?

Less inflammation.: The best is probably a soft toothbrush, because it does not damage and inflame the gums. It also is unlikely to damage the tooth enamel where another toothbrush would.

Soft cleans better!: Soft toothbrush bristles bend easier and are able to get into the nooks and crannies on and between the tooth and gum. The key is angulating the toothbrush correctly, about 45 degrees to the gum line and move the brush gently to dislodge and food or bacteria in the area. You'll need other tools to clean inbetween teeth. Even if you have root exposed, soft bristles will not damage the root surface.

Does not injure gum: According to research, brushing with soft bristle prevent damage and injury to the gum tissue and thus prevent the gingival recession from hard brushing. With the today advance technology, the brisle size can be thinner and still have a memory or springiness capability. Soft bristle brush allow us to use the bass technique, i.e., brushing parallel to the gum line without causing recession.

Neither: They are unrelated. Soft tooth brush are not associated with either one. There are many factors that dictates gum disease like bad oral hygine or genetics. A soft tooth brush only lessens the mechanical abrasion of the tooth or the gum line.