Depending on the case, resin composite fillings initially designed for human dentistry might be the solution for managing these equine tooth cavities, said Christopher Pearce, MRCVS, specialist dental veterinarian and director of The Equine Dental Clinic, in Wimborne, U.K.

If the developmental cavity is large enough to threaten tooth health and hasn’t yet become infected, resin composite fillings can solve equine dental problems before they start, Pearce said. Solid and adherent—yet able to wear away at the same natural rate as horses’ teeth—composite fillings can stop the pain, disease, and breakage infundibular caries can cause.

“We know enough to know that when we see cavities of a certain size in a certain tooth, we can say to clients with pretty high degree of confidence, ‘Okay, I know your horse seems fine and is performing well, and he or she just won the competition at the weekend, but he’s got a large cavity in the 109 cheek tooth, and he’s 14 years of age,’” Pearce said. “Teeth with cavities of that size within the next two or three years may develop sinusitis or a root abscess, or they may fracture their tooth. So, now we have the same options that a human dentist would give you,” including not only extraction or waiting it out but also filling the cavity.

Infundibular Caries: A Developmental Cavity

Unlike humans, horses have upper cheek teeth that develop deep infoldings called infundibula, Pearce explained. In young horses upper teeth grow the outer walls first and then fill with a dental material known as cementum. For reasons yet to be determined, some horses lack cementum in their upper cheek teeth—especially in the first cheek teeth to erupt—leaving an empty space, usually deep inside the tooth. This gives the appearance of a solid tooth, even though it’s somewhat hollow.

Because horses’ teeth erupt continually, as their surfaces wear away these hollow spaces progress toward the surface little by little, Pearce said. Eventually, depending on the cavity size, the surface wears away enough to expose the hole beneath—often when the horse has reached his teenage years.

These cavities might not cause problems if they’re small, he said. But when infundibular cavities are large, they can pack with food, which, when combined with bacteria naturally present in the mouth, can start to ferment and create acid. When that happens the horse can develop pain, sinus infections, and/or oral infections, he said. In some cases the tooth can break in two.

Saving Infundibular-Caries-Affected Teeth With Fillings

While eventually it might be necessary to remove teeth affected by pathogenic infundibula, Pearce said it’s possible to save the teeth by filling them before problems arise. He and his fellow researchers adapted techniques used previously by equine dentists and researchers to fill such cavities, he said. That includes removing impacted food, thoroughly cleaning the cavity, and filling the hole with a solid, adhesive, form-fitting material.

Although they originally considered using hard materials like glass-ionomer cements and porcelain, the scientists realized flowable and compactible resin—the “white” composite fillings used in human dentistry—were better adapted to equine dentistry because they’re slightly less hard and wear away with use, said Pearce.

Between 2006 and 2012 Pearce and his colleagues followed the progress of 92 horses (with an average age of 14 at the time of treatment and a range of 6 to 25 years) with 223 cheek teeth fillings. They didn’t know, however, whether the resin filling was a successful long-term solution, he said. So the research group looked back at those previously treated horses to see how they fared over the years.

They found that even up to 11 years later, 99% of the treated horses—all with at least a five-year history of fillings—experienced no adverse effects or abnormalities as a result of the fillings. Nearly 85% of the fillings were fully intact, with a wear rate similar to that of the surrounding tooth.

Even so, filling infundibula requires significant training in equine veterinary and dental medicine as well as in the technique itself, Pearce said. Practitioners should also be skilled in identifying ideal candidates based on the severity of the infundibular caries and its associated risks if left untreated.

Pearce CJ, Brooks N. Long-Term Follow-Up of Restorations of Equine Cheek Teeth Infundibula (2006-2017). Front Vet Sci. 2022 Jan 14;8:793631. doi: 10.3389/fvets.2021.793631. PMID: 35127882; PMCID: PMC8809405.