Anatomical studies of maxillary cheek teeth infundibula in clinically normal horses

Reasons for performing study: Although clinical disorders of equine maxillary cheek teeth (CT) infundibula are common, anatomical knowledge of these structures is poor. Hypothesis: Anatomical examinations of sectioned CT infundibula will better define their shapes and sizes and allow identification of infundibular cemental variations and changes. Material and methods: Cheek teeth were extracted post mortem from 33 horses, aged 3-30 years, without a clinical history of dental disease. The CT were sectioned longitudinally in the bucco-palatal plane through the widest aspects of both infundibula. The infundibular surfaces were then assessed morphologically, including by measurements of areas of cemental variations and changes. Specimens from selected teeth were examined histologically. Results: Infundibular length and infundibular surface area, and infundibular length as a proportion of dental crown length progressively decreased with age, e.g. infundibular length was up to 89 mm after eruption to 2 mm in one older horse. Triadan 06 and 09 positions had significantly shorter CT and therefore infundibula, than the other 4 Triadan positions. Only 11.7% of infundibula were filled completely with normal appearing cementum, 8.2% of infundibula (especially the 09 position) had complete cemental caries; 22.6% of infundibula had areas with cemental hypoplasia and the remaining 57.5% of infundibulae had a variety of other cemental appearances, including the presence of central defects, localised occlusal caries and cemental discolourations. Histology showed the presence of an apical blood supply to infundibular cement in younger horses. Conclusions: Anatomical variations of CT infundibular cement are very common and some changes, such as areas of localised cemental hypoplasia, may predispose to the development of infundibular caries. Potential relevance: This more complete description and quantification of CT infundibular anatomy should allow more rational assessment and treatment of equine CT infundibular disorders.