Teeth set the pace for almost everything else in an older horse's life, because a horse that cannot grind fiber properly cannot hold condition no matter how good the feed looks in the bucket. The comparison at the heart of this question is simple, but the reasoning behind it matters: younger mouths change slowly and predictably, while elderly mouths change on several fronts at once, and the checking rhythm has to match that speed.
The Comparison, Quantified
Prime-age horses typically follow a roughly annual rhythm for dental checks, and that pace catches the sharp enamel points that develop as teeth erupt and grind, long before they cut cheeks or change his chewing. Once a horse is elderly, the rhythm typically halves to an examination about every six months, because his teeth are worn shorter, surfaces are uneven, and the margin between a manageable finding and a mouth that hurts is far smaller. Treat both figures as typical patterns for a healthy mouth rather than guarantees, since a prime horse with a known problem may be seen more often on professional advice, and a senior whose mouth has stabilized may be given a slightly longer gap by the clinician who knows him. What should not happen is an elderly horse drifting onto the prime horse's annual rhythm by default, simply because nobody updated the schedule when he aged.
What Each Check Actually Covers
A dental check examines the whole mouth with a speculum and light, not just the front teeth an owner can see. The clinician looks for sharp points along the cheek teeth that lacerate the cheek or tongue, uneven wear such as waves or steps that stop the jaw moving freely, and missing teeth that leave gaps where food packs and ferments against the gum. The soft tissues matter as much as the teeth: sores on the tongue, ulcers on the cheeks, and inflamed gums all explain a horse that has started dropping feed or resisting the bit. In an elderly horse, loose teeth are a particular focus, because a tooth moving under chewing pressure is painful long before it falls out, and the socket left behind needs watching. Between professional checks, watch him eat: quidding, where wads of chewed hay are dropped, slow eating, tilting the head to one side, and losing condition despite a full ration are the everyday signs that the next check should come early.
Routing Problems to the Right Professional
The bit and bridle, for a senior still ridden lightly, add another reason to keep the shorter rhythm. A mouth carrying sharp points or a loose tooth meets bit pressure unevenly, and resistance blamed on attitude in an older horse is often discomfort that a six-month check would have caught at the previous visit. Tell the clinician if he has begun leaning on one rein, tossing his head at contact, or eating happily from a bucket while leaving hay, because those details direct attention to the exact area that hurts him.
Loose or painful findings route to the vet or the equine dentist promptly, not onto a list for next time. A horse that stops eating comfortably, drops weight quickly, develops a foul smell from the mouth, or shows swelling along the jaw deserves a same-week conversation, because mouth pain suppresses appetite and an elderly horse has little condition to spare. Keep the record of each check, including which teeth were treated, any gaps or loose teeth noted, and the date the next check is due, so a change of clinician does not restart his history from memory. Feeding changes recommended after a check, such as softer or shorter fiber, belong in that same record where everyone who feeds him will see them. Clinicians reviewing the Pet Passport record on KinsLe can compare successive examinations, track mouth changes over time, and plan the next appointment sooner.