If a horse reads the anatomy book...
the roots of his/her 1st two upper cheek teeth should reside in the Maxillary Bone,
the roots of his/her 2nd two upper cheek teeth in the Rostral Sinus Compartment,
and the roots of his/her 3rd two upper cheek teeth in the Caudal Sinus Compartment!
They don't all read the Book!
Veterinary Dentistry includes the evaluation, diagnosis, prevention, & treatment of oral disease that extends into regional tissues; therefore, veterinary dentistry specialists are specifically trained to treat orofacial and sinonasal disease. Sinoscopy is a minimally invasive procedure performed on a sedated horse that is primarily used to visually evaluate a horse's sinuses. Rigid and/or flexible endoscopes are passed through small holes cut into the facial bones or sometimes through the nose to access the sinus compartments.
Looking down into Caudal Sinus Compartment. (Frontal Portal) Mucopurulent fluid in Caudal Sinus Compartment (Frontal Portal)
Pus & Grass in Rostral Sinus Compartment (Frontal Portal) Bone Sequestrum of facial bone viewed from sinus. (via rhinoscopy)
Bacterial Plaque viewed from Rostral Sinus Compartment (RMS Portal)