A Computed Tomographic (CT) and Pathological Study of Equine Cheek Teeth Infundibulae Extracted From Asymptomatic Horses. Part 1: Prevalence, Type and Location of Infundibular Lesions on CT Imaging

Abstract

Background: Equine maxillary cheek teeth infundibulae are frequently affected by developmental and acquired disorders, but the computed tomographic (CT) imaging features of normal and abnormal infundibulae remain incompletely understood. Objective: To examine infundibulae with various grades of occlusal caries and control teeth by standard CT in order to assess the prevalence, type and location of subocclusal infundibular lesions present. Study design: Ex vivo original study. Methods: One hundred maxillary cheek teeth, including 82 with, and 18 without infundibular occlusal caries, were extracted from horses of different ages and imaged by standard CT; 8 teeth were also imaged by MicroCT. Images were later assessed by Osirix® and the prevalence, characteristics and sites of infundibular lesions were assessed. Results: Teeth with shorter infundibulae (i.e., Triadan 09 position and older teeth) were more likely to have occlusal caries, as were the rostral infundibulae. Subocclusal developmental infundibular lesions, including cemental hypoplasia and caries, were present in 72% of infundibulae without occlusal caries. CT imaging confirmed two main patterns of developmental cemental hypoplasia, i.e., apical cemental hypoplasia usually involving the full width of the apical aspect of the infundibulum and central linear hypoplasia involving the central aspect of the infundibulum over most of its length, and combinations of these types. These developmental lesions could later be affected by (acquired) infundibular caries once occlusally exposed due to normal wear. Some “normal-sized” (i.e., circa 1 mm diameter) occlusal central vascular channels expanded subocclusally to the dimensions of central linear defects. Main Limitations: No clinical histories or accurate ages were available for these teeth. Conclusions: Hypoplastic cemental lesions, including at central linear, and apical sites, are common even in clinically normal maxillary cheek teeth infundibulae and caries can occur when these lesions contact the occlusal surface. Central linear defects are not always clearly distinguishable from “normal” central vascular channels.

A Computed Tomographic and Pathological Study of Equine Cheek Teeth Infundibulae Extracted From Asymptomatic Horses. Part 2: MicroCT, Gross, and Histological Findings

“…While a standard CT scan image volumes of 1 mm 3 , a microCT scanner can image sections as small as 1–5 μm 3 (16). Similar types of infundibular abnormalities were identified using micro-CT and standard CT imaging of in the companion study (8). However, MicroCT images allowed more detailed evaluation of infundibular anatomy and also allowed localized measurement of infundibular tissue attenuation.…”

“…A transverse histological section of a grossly normal infundibulum with a “normal” central vascular channel from a control tooth (no infundibular caries or subocclusal cemental defect) is shown in Figure 1. An example of a histological image of a food debris-filled, central linear cemental defect (linear defect wider than a “normal” central vascular channel) as described in an accompanying article (8) but without surrounding cemental caries is shown in Figure 2.…”

“…Micro-computed tomography (microCT) allowed assessment of cheek tooth anatomy in much greater detail than the conventional CT imaging used to examine 200 infundibulae in a companion study (8), without the physical disruption of dental structure (including complete enamel loss by the prolonged decalcification process) that is necessary for histological examination of these large calcified structures. While a standard CT scan image volumes of 1 mm 3 , a microCT scanner can image sections as small as 1–5 μm 3 (16).…”

“…Anatomical (1, 2) and computed tomographic (CT) studies (3–6) have shown that up to 90% of equine cheek teeth infundibulae, in particular the rostral (mesial) infundibulae of the Triadan 09 position, are incompletely filled with normal cementum, that preferably should completely fill the infundibulum. These infundibular defects, initially developmental in origin, include the very common presence of a fine central cemental defect (variously termed “central vascular channel,” “vascular channel,” or “central linear defect”) or larger areas of discolored hypoplastic cementum or even a total absence of cementum, as described (1, 2, 7) and also reported in the companion article (8).…”

“…Caries of infundibular cementum is an acquired, bacterial-acid mediated disorder that appears to preferentially affect infundibulae already affected by developmental defects that later trap food (8–10). Infundibular cemental caries can extend to the adjacent infundibular enamel and even to dentine and pulp where it can cause apical infection (without fracture development) (2, 7, 9–14).…”