Hello! This is a great question. For D4910, each insurance plan is different. If the patient has coverage for D4910, typically, the insurance will want the date of the initial scaling and root planing along with x-rays and perio charting less than 12 months old. When it comes to the perio maintenance frequency, that also differs by insurance plan. Some plans cover 4x/yr anytime, some are every 91 days, and some are every 6 months so this is another important piece of information to get when you verify the patient's insurance. To put it simply: there is no definitive answer and D4910 coverage varies from plan to plan. Hope this helps!