I.T. Dacre

Pathological studies of cheek teeth apical infections in the horse: 5. Aetiopathological findings in 57 apically infected maxillary cheek teeth and histological and ultrastructural findings

Examination of 57 apically infected maxillary cheek teeth (CT) showed one or more viable pulps and minimal apical calcified tissue changes present in recently infected CT. With chronic infections, pulps were necrotic or absent, pulp horns were filled with food if occlusal pulpar exposure was present, and gross caries of dentine was occasionally present. With chronic infections, the apical changes varied from gross destructive changes in some teeth, to extensive proliferative calcified apical changes in others. Infundibular caries was believed to cause apical infection in just 16% of infected (maxillary) CT, anachoretic infection in 51%, periodontal spread in 12%, fractures and fissures in 9%, dysplasia in 5% and miscellaneous or undiagnosed causes in 7%. Histology showed viable pulp and absence of circumpulpar dentinal changes in some recently infected CT, but chronically infected teeth had loss of predentine and progressive destruction of the circumpulpar secondary, and even primary dentine, with bacteria identified within the dentinal tubules surrounding infected pulps. Tertiary dentine deposition was rarely detected. Scanning and transmission electron microscopy confirmed these histological findings and showed extensive destructive changes, especially to the dentinal architecture surrounding the pulp chambers of some infected teeth.

Equine idiopathic cheek teeth fractures. Part 1: Pathological studies on 35 fractured cheek teeth

REASONS FOR PERFORMING STUDY There is little published information on the pathology of idiopathic fractures of cheek teeth (CT). OBJECTIVES To perform pathological examinations on equine CT with idiopathic fractures in order to establish fracture patterns and to gain information on their aetiopathogenesis. HYPOTHESIS Gross and histological examination of CT with idiopathic fractures, including measurements of dentinal thickness, will provide information on fracture patterns, and on the duration and aetiopathogenesis of these fractures. METHODS Of 35 CT with idiopathic fractures that were examined to determine their fracture patterns, 20 underwent gross, histological and ultrastructural examinations, including dentinal thickness measurements, with the latter compared to dentinal measurements of dental age and Triadan position matched control CT, to help determine the duration of any pre-existing endodontic disease. RESULTS The fracture planes involved the pulp chambers in 30 out of 35 CT examined, and ran through coalesced, carious infundibula in the other 5 (maxillary) CT. The maxillary CT, particularly the Triadan 09 position were preferentially affected. The most common fracture plane, which was termed a maxillary buccal slab fracture, occurred through the 2 lateral (1st and 2nd) pulp chambers of maxillary CT and usually involved only the clinical crown. Buccal slab fractures of mandibular CT (through 4th and 5th pulp chambers) and midline sagittal fractures through the infundibula (of maxillary CT) were the next most common fracture patterns. Reduced dentinal thickness (probably indicating prior pathological changes in the fractured CT) was present in 25% of fractured CT. CONCLUSIONS Most idiopathic equine CT fractures involve the pulp chambers, especially those on the buccal aspect of both upper and lower CT. No predisposition to fracture was found in the majority of affected CT that appeared to have a normal endodontic appearance prior to development of fractures through their pulp chambers. The remaining idiopathic CT fractures were caused by advanced infundibular caries. POTENTIAL RELEVANCE All CT with idiopathic fractures are all at risk of pulpar or even apical infection.

Pathological studies of cheek teeth apical infections in the horse: 4. Aetiopathological findings in 41 apically infected mandibular cheek teeth

Examination of 41 extracted, apically infected mandibular cheek teeth (CT) without obvious causes of infection included radiography, computerised axial tomography and decalcified and undecalcified histology. In CT with recent infections, some pulps remained viable, with proliferative soft and calcified tissue changes confined to the apex. With more advanced CT infections, occlusal pulpar exposure was sometimes present (in 34% of the 41 CT), some infected pulp chambers were filled with necrotic pulp or food, and extensive destructive or proliferative changes were present in the calcified apical tissues. No physical route of infection to the apex was found in 24 CT (59%) that consequently were believed to have anachoretic infections. Fractures involving pulps, including fissure fractures between the clinical crown and infected pulps, were found in eight (20%) CT. Some CT had vertical, full length periodontal destruction between the infected apex and the gingival margin that were believed to be the route of infection in four (19%) CT and dysplastic changes were believed to have caused one (2%) infections.

Pathological studies of cheek teeth apical infections in the horse: 1. Normal endodontic anatomy and dentinal structure of equine cheek teeth.

Morphological examinations were performed on 100 normal equine cheek teeth (CT) of 1-12 years dental age (i.e. time since eruption), using gross examination, dissection microscopy, computerised axial tomography, and decalcified and undecalcified histology. The CT in Triadan 07-10 positions consistently had five pulp horns, but the 06 CT had an additional pulp horn more rostrally. Mandibular and maxillary Triadan 11s had six and seven pulp horns, respectively. Sections of CT taken 2-6mm below the occlusal surface (variation due to normal undulating occlusal surface) showed the presence of pulp in up to 50% of individual maxillary CT pulp horns, and in up to 25% of individual mandibular CT pulp horns. The histological appearances of primary and secondary dentine were described and it is proposed that the type of dentine present most centrally in every pulp chamber examined, currently termed tertiary dentine, should be re-classified as irregular secondary dentine, and that the term tertiary dentine be reserved for the focal areas of dentine laid down following insult to dentine or pulp.

Pathological studies of cheek teeth apical infections in the horse: 2. Quantitative measurements in normal equine dentine.

Measurements of primary, regular and irregular secondary dentine and pulp dimensions were made on transverse, sub-occlusal and mid-tooth sections, of 40 maxillary and 42 mandibular control equine cheek teeth (CT) of different ages. Maxillary and mandibular CT primary dentine in different age groups had a mean thickness of 922-1,065 microm and 1099-1,179 microm, respectively, on the lateral aspects, and 1,574-2,035 microm and 1155-1,330 microm, respectively, on the medial aspects of pulp horns. Surprisingly, some increase in thickness was found in some mandibular CT primary enamel in the first few years following eruption. Regular secondary dentine thickness increased with age, for example at mid-tooth level in mandibular CT from 124 microm at 3 years dental age to 290 microm at >7 years dental age on the lateral aspect of pulp horns, and from 166 microm to 509 microm on the medial aspects of pulp horns, indicating a deposition rate of 0.5-10 microm/day. This type of dentine was thicker sub-occlusally than in the mid-tooth region. Maxillary dentinal dimensions showed a similar age-related increase in thickness. Maxillary CT dentine was significantly thicker (72% in primary, 43% in regular secondary dentine) on the medial compared to the lateral aspects of pulp horns, but mandibular CT dentine was just 15% and 14% thicker in primary and regular secondary dentine thickness, respectively, on the their medial as compared to their lateral aspects. Dentinal and pulp dimensions varied between individual pulp horns, Triadan tooth position, and dental age, with complex interactions between these variables for some parameters.

The Effect of Three Types of Rasps on the Occlusal Surface of Equine Cheek Teeth: A Scanning Electron Microscopic Study

Two hand rasps (tungsten chip blade, solid carbide blade) and an electrically-driven solid carbide axial bur were used to treat the cheek teeth of 2 horses immediately postmortem. All teeth were normal and were rasped to a standard considered satisfactory in practice. Six teeth from each horse served as untreated controls. Following treatment, the teeth were extracted and the clinical crown removed and prepared for scanning electron microscopy. Teeth were also extracted and examined from a horse that had excessive dental treatment previously. Dental debris created by the procedures was collected and examined. All three rasp techniques resulted in amputation of odontoblast processes. The solid carbide blade cut deep gouges and grooves into the surface of the dentin, chipping the enamel and peripheral cement. No smear layer was created. Rasping with a tungsten chip blade created a partial smear layer and a smoother surface than the solid carbide blade. The electrically-driven bur produced a complete smear layer and removed all dental tissues to a smooth layer. The enamel had also been damaged by the electric bur. Crown particles collected after the procedures were larger following hand rasping compared with particles produced by the electric bur. The extent of damage to sensitive and vital dentin tissue was of concern. Further studies are required to establish the optimum technique for rasping equine cheek teeth.

Pathological studies of cheek teeth apical infections in the horse: 3. Quantitative measurements of dentine in apically infected cheek teeth

Histological measurements of dimensions of primary, regular secondary and irregular secondary dentine, pulp diameter and assessment of the levels of predentine, resting lines and enlarged areas of intertubular dentine were performed in apically infected mandibular and maxillary cheek teeth (CT). These examinations showed significantly reduced regular and irregular secondary dentine thickness in diseased as compared to control CT, with 21/26 infected maxillary CT and 15/18 infected mandibular CT having reduced regular secondary dentine (varying between 27.4% and 89.1% reduced secondary dentine levels compared to age and site matched control CT values). As a result of decreased dentinal deposition, significantly wider pulp horns were present in diseased compared to control CT. No significant differences were found between diseased and control primary dentine thickness in maxillary CT, and minor differences in mandibular CT were not believed to be clinically significant. The significantly reduced presence of predentine and of intertubular dentine and the increased presence of resting lines in diseased compared to control CT confirms that long-term disruption of normal dentine deposition had occurred in many infected CT.