It is sometimes surprising - and sad - to discover what Medicare will not cover. Given your low income do you qualify for Medicaid? In some states they will cover these types of expenses. It could be worth checking with your local Medicaid office to see if you qualify. You should also contact your local Office On Aging for leads in your area.
In some areas I have heard that the Lions Club has a program that matches seniors with free hearing aids. Check them out as well as other service organizations such as the Rotary Club and Catholic Charities.
With regard to needed dentures, check out this article about Free Dental Care. You might be able to find a free or very low-cost service near you. If they only offer care but not the dentures themselves, they would probably be able to refer you to an organization that would cover the dentures as well.
For both the hearing aids and dentures you should also consider applying to an organization like "modestneeds". This is a crowdfunding type of internet platform that matches people with needs and people who wish to help. You can learn more about them and other similar sites here.