Buy a new toothbrush and toothpaste somewhere else. You can find toothbrushes at convenience stores, grocery stores, pretty much any general store. Just start with brushing your teeth and rinsing with alcohol mouthwash, and your gums will probably repair themselves if it's only been a week. Go to a store as soon as you can to get a new toothbrush because it'll take too long to go back to your grandpa's house. If you feel you really do need a dentist appointment, show your mom your gums and tell her the longer she waits to make an appointment the larger the bill will be for dental care. If she still refuses, call somebody yourself to make an appointment. Try any relatives you have, such as your grandpa or your dad.