Plaque doesn't wait for your calendar
Plaque forms constantly on your teeth, and brushing and flossing remove most of it if you're genuinely consistent about it every single day, morning and night. But even a good home routine tends to miss the same spots over and over — between teeth, right along the gumline, and behind the lower front teeth where saliva glands concentrate minerals that speed up hardening. Within a matter of days, that missed plaque begins hardening into tartar, sometimes called calculus by dental staff. Once it's tartar, no amount of brushing pressure, a fancier toothbrush, or a stronger mouthwash removes it; only a professional cleaning with the right hand instruments or an ultrasonic scaler can actually take it off the tooth surface for good. This is exactly why the six-month interval most dentists recommend exists in the first place — it's roughly how long a diligent routine can hold the line before professional help is genuinely needed.