Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to use teeth whitening strips [title] Read the instructions carefully. [step] Although most whitening strips are applied and used in a similar manner, some brands may have different instructions. Always read the instructions fully and be aware of any side effects before using any whitening strip or whitening product.

Ending1: Some brands of whitening strips may ask you to only use the strip for 2-3 days. [title] Use a baking soda whitening strip to fill in stains. Ending2: [substeps] Talk to your dentist if you are unsure what you should do with your teeth after using it. Some whitening strips may cause different side effects than others. Ending3: [substeps] Some versions of whitening strips are available over-the-counter and others are available over-the-counter. Be sure to read the manufacturer's instructions carefully and always follow these directions. Ending4: [substeps] Misuse can cause damage to your teeth, gums, and health. Instructions can vary between brands, always fully read the instructions before use.

Answer format: ending1/ending2/ending3/ending4