6. Make a lemon paste. Make a paste from the juice of one lemon and some salt. Mix it well and apply to your teeth. Let it sit for a few minutes and gargle with warm water to rinse it off. 1  Lemons offer a win-win solution for treating gum disease.2  First, they're an anti-inflammatory, which makes them helpful in treating infected gums.et it sit for a few minutes and gargle with warm water to rinse it off. 1  Lemons offer a win-win solution for treating gum disease. 2  First, they're an anti-inflammatory, which makes them helpful in treating infected gums.