Focus on the vibration frequency, which typically ranges from 20,000 to 30,000 strokes per minute for battery-powered models. Ensure the motor is a high-efficiency micro-motor to maximize battery life. For the bristles, prioritize DuPont Tynex nylon or charcoal-infused bristles with end-rounded tips to prevent gingival recession. Additionally, verify the IPX7 waterproof rating, which allows the device to be submerged in water up to 1 meter for 30 minutes, ensuring safety and durability in bathroom environments.