Please choose the correct ending to complete the given sentence: Health: [header] How to choose a toothpaste [title] Check for fluoride. [step] It's important that your toothpaste contains fluoride, as it helps strengthen the enamel of your teeth. Your enamel is under constant attack from acids, and fluoride remineralizes the entire structure.

Ending1: Some types of toothpaste may develop a enamel buildup if its fluoride content is low. [substeps] Sprinkle a small amount of fluoride on top of a gums brush to give the flavor consistent throughout throughout the day. Ending2: Look for a toothpaste that contains fluoride, as fluoride is mildly abrasive. [substeps] Human gums can easily be damaged by acids, so make sure you treat them sparingly. Ending3: While fluoride treats plaque buildup in the mouth, it can have a lasting impact on the health of your teeth. [substeps] When you have weakened enamel, you may consider switching to white toothpaste or whole toothpaste. Ending4: Make sure fluoride is an ingredient in any toothpaste you buy. It should be 1 , 000 parts per million in your toothpaste.

Answer format: ending1/ending2/ending3/ending4