Temporomandibular joint biomechanics and equine incisor occlusal plane maintenance

In equine dentistry, the physiological incisor occlusal surface is visually perceived as a plane with a distinct inclination to the head’s coronal plane, extending rostro-ventrally to caudo-dorsally. To better understand the formation of this inclined plane and its connection to dental wear, we investigated the hypothesis that it arises from masticatory movements and the considerable distance between mandibular articular heads and the incisor occlusal surfaces, acting as the three points of support for the mandibles. Leveraging data from a large-scale clinical study involving static and dynamic orthodontic measurements in horses, we approximated the mandibular movement range where incisor occlusion and dental wear occur. By introducing and testing a segment coordinate system, we explored possible angular deviations from the occlusal plane caused by mandibular roll and pitch rotations during two lateral mandibular movement patterns, protrusion and retrusion. Theoretical biomechanical calculations and simulations confirmed the visual perception of the incisor occlusal surface as a plane. To further examine our assumptions, we employed a simple mechanical simulator to assess incisor normal occlusion and provoked malocclusions (diagonal, smile, and frown bite) by modifying temporomandibular joint (TMJ) movement patterns. The results from clinical investigations were corroborated by both the theoretical analysis and mechanical simulations, strengthening our understanding of the biomechanical basis behind the physiological incisor occlusal plane maintenance in horses. These findings have significant implications for equine dental health and contribute to a thorough understanding of TMJ dynamics

Temporomandibular joint biomechanics and equine incisor occlusal plane maintenance

In equine dentistry, the physiological incisor occlusal surface is visually perceived as a plane with a distinct inclination to the head\u27s coronal plane, extending rostro-ventrally to caudo-dorsally. To better understand the formation of this inclined plane and its connection to dental wear, we investigated the hypothesis that it arises from masticatory movements and the considerable distance between mandibular articular heads and the incisor occlusal surfaces, acting as the three points of support for the mandibles. Leveraging data from a large-scale clinical study involving static and dynamic orthodontic measurements in horses, we approximated the mandibular movement range where incisor occlusion and dental wear occur. By introducing and testing a segment coordinate system, we explored possible angular deviations from the occlusal plane caused by mandibular roll and pitch rotations during two lateral mandibular movement patterns, protrusion and retrusion. Theoretical biomechanical calculations and simulations confirmed the visual perception of the incisor occlusal surface as a plane. To further examine our assumptions, we employed a simple mechanical simulator to assess incisor normal occlusion and provoked malocclusions (diagonal, smile, and frown bite) by modifying temporomandibular joint (TMJ) movement patterns. The results from clinical investigations were corroborated by both the theoretical analysis and mechanical simulations, strengthening our understanding of the biomechanical basis behind the physiological incisor occlusal plane maintenance in horses. These findings have significant implications for equine dental health and contribute to a thorough understanding of TMJ dynamics

Unique expression patterns of the embryonal stem cell marker SOX2 and hormone receptors suggest the existence of a subpopulation of epithelial stem/progenitor cells in porcine and bovine endometrium

There are currently insufficient data on the population of endometrial epithelial stem/progenitor cells in farm animals.With the aim of identifying a potential population of epithelial stem/progenitor cells in the porcine and bovine endometrium, this study immunohistochemically examined the expression patterns of the oestrogen and progesterone receptors, as well as that of the embryonal stem cell marker SOX2.A total of 24 endometrial tissue samples obtained from cycling pigs (n = 12) and cows (n = 12) were included in our study. Each endometrium was divided into basal, middle and luminal portions. The percentage of marker-positive cells and the intensity of the immunoreaction in each portion of the endometrium were determined.Inverse expression patterns of SOX2 and progesterone receptors were found in both animal species throughout the oestrous cycle. Strong diffuse SOX2 expression was detected in the basal portions of the glands, while a significant decrease in positivity and a weak immunoreaction were found in the luminal two thirds of the glandular epithelium. Strong progesterone receptor expression was observed in at least 90% of glandular cells in the middle and luminal portions, whereas weak staining and significant decrease in positivity were detected in the basal portions of the glands. One oestrogen receptor expression pattern resembled that of progesterone receptors.The inverse expression patterns of SOX2 and hormone (especially progesterone) receptors suggest that endometrial epithelial stem/progenitor cells represent a subset of cells that reside in the basal portions of the endometrial glands in both the bovine and porcine endometrium

Effects of different fixatives over different fixation times, including Antigenfix, on immunohistochemical studies

Tissue fixation is an essential step in the performance of ancillary studies, including immunohistochemistry. The aim of this study was to compare the effect of various fixatives and fixative times on immunohistochemistry (IHC) in bovine and porcine endometrium using progesterone receptors and SOX2 antibodies. Immunohistochemical staining with progesterone receptors and SOX2 was performed on tissue samples fixed in formalin, Antigenfix, Greenfix, Bouin\u27s solution and methacarn at 1.5, 8.5, 15.5, 29.5, 64.5, 189.5, 249.5, 309.5 and 369.5 days of fixation. Formalin and Antigenfix proved to be the best fixative for both short-term and long-term fixation for IHC. Bouin\u27s solution was partially applicable for short-term (24 h) fixation. Greenfix and methacarn were absolutely inappropriate fixatives for IHC (completely negative staining using methacarn). These results were obtained on an automated immunostainer using EDTA buffer pH 8.4 as the antigen retrieval solution. When the staining procedure was performed manually and citrate buffer with different pH values was used, weakly positive results were obtained with both progesterone receptors (pH 8 and 9) and SOX2 (pH 7.2); however, significantly lower staining quality was obtained using the methacarn fixative compared to aldehyde fixatives. The reported findings demonstrated the superiority of aldehyde fixatives (formalin and Antigenfix) over alcohol fixatives (methacarn) and fixatives combining both denaturing and cross-linking proteins (Greenfix and Bouin\u27s solution) for IHC. Antigen retrieval-IHC using EDTA buffer was found to be excellent for aldehyde fixatives, but proved to be completely unsuitable for methacarn, Greenfix, and Bouin\u27s solution