Six months is the number everyone knows, and almost nobody knows where it came from. It is not a clinical finding. It is a reasonable default that suits most mouths, and for some people it is too often, and for others not nearly enough.
What the interval depends on
Gum health more than anything. Someone with healthy gums, no history of decay and a good routine at home can go a year between visits without losing ground. Someone with gum disease, a dry mouth from medication, diabetes, or a run of fillings in the last few years is better seen every three or four months, because problems in those mouths move faster than the calendar.
The cleaning is the point
A check-up catches things; a cleaning prevents them. Tartar cannot be brushed off once it has set, and it is what gum disease grows under. If you have to choose between the two, choose the cleaning.
The right interval is the one at which your dentist keeps finding nothing. If every visit turns something up, the gap is too long.
Children
Children’s teeth change quickly and decay moves through them faster, so six months is a genuine minimum for kids, not a habit. The first visit should come by the first birthday — before there is anything to fix.
If it has been years
Go. Nobody at the clinic is going to lecture you; they see people who have been away for a decade every week. The first visit back is longer, and it may take two or three appointments to catch up. After that you are on the same schedule as everyone else.
