A pathological, histological and ultrastructural study of diseased equine cheek teeth

Abstract

The examination of 220 normal and 130 diseased equine (extracted) cheek teeth was performed using a variety of traditional and novel imaging techniques primarily to assess the aetiopathogenesis of the important dental disorders of apical infection and "idiopathic" dental fracture. Optimal settings for radiography and computer axial scanning of normal and diseased cheek teeth were determined. It was found that standard radiography of extracted cheek teeth was very poor at identifying intradental anatomical or pathological features, whilst computer axial scanning gave accurate information on both normal and abnormal radiographic features. Newly established histological techniques allowed preparation of undecalcified sections of 4-6 μm thickness, and undecalcified sections of 50-60 μm thickness. The current classification of equine dentine was modified, with primary, regular secondary, irregular secondary and tertiary dentine all being categorised separately. Previously undescribed histological features of normal and diseased equine teeth were identified such as dentinal pearls, interglobular dentine, caries and the presence of pioneer micro-organisms. The normal endodontic anatomy of all 24 cheek teeth was established, with individual pulp horns being identified using a unique numbering system. Anatomical parameters of dentine were established for normal cheek teeth, and these were compared to those of apically infected cheek teeth. A decreased presence of primary and secondary dentine, predentine and intertubular dentine was found in diseased teeth compared with normal cheek teeth, but increased number of resting lines were present in diseased cheek teeth. Analysis of 50 individual apically infected cheek teeth showed anachoretic pulpitis to be the most common aetiology, with occlusal pulp exposure often being a secondary finding. Apical infection caused by periodontal disease or infundibular caries was uncommon finding. Fracture patterns to the clinical crown of equine cheek teeth were grouped, with most fractures involving the buccal pulp horns of both maxillary and mandibular cheek teeth.