Do I need a teeth cleaning if I brush every day?

Yes! You should still see your dentist twice a year for a cleaning. Brushing and flossing remove plaque but not all of it. As plaque is left to harden it creates tartar, only a dental hygienist or professional cleaning can remove tartar buildup. Additionally, it's important to see a dentist regularly to prevent any problems, like cavities, before the get worse.
Yes. Most people brush everyday however calcium phosphate or tarter slowly builds on the teeth. This scale cannot be brushed away but must be removed by scraping or use of ultrasonic vibration.