Mechanical properties of human oral mucosa tissues are site dependent: A combined biomechanical, histological and ultrastructural approach.

AIM: To investigate load-deformation properties of Thiel-embalmed human oral mucosa tissues and to compare three different anatomical regions in terms of mechanical, histological and ultrastructural characteristic with focus on the extracellular matrix. MATERIALS AND METHODS: Thirty specimens from three different regions of the oral cavity: attached gingiva, buccal mucosa and the hard palate were harvested from two Thiel-embalmed cadavers. Mechanical properties were obtained, combining strain evaluation and digital image correlation in a standardised approach. Elastic modulus, tensile strength, strain at maximum load and strain to failure were computed and analysed statistically. Subsamples were also analysed using scanning electron microscopy (SEM) and histological analysis. RESULTS: The highest elastic modulus of 37.36 ± 17.4 MPa was found in the attached gingiva group, followed by the hard palate and buccal mucosa. The elastic moduli of attached gingiva differed significantly to the buccal mucosa (p = .01) and hard palate (p = .021). However, there was no difference in the elastic moduli between the buccal mucosa and hard palate (p > .22). The tensile strength of the tissue samples ranged from 1.54 ± 0.5MPa to 3.81 ± 0.9 MPa, with a significant difference between gingiva group and buccal mucosa or hard palate (p = .001). No difference was found in the mean tensile strength between the buccal mucosa and hard palate (p = .92). Ultrastructural imaging yielded a morphological basis for the various mechanical properties found intraorally; the attached gingiva showed unidirectional collagen fibre network whereas the buccal mucosa and hard palate showed multi-directional network, which was more prone to tension failure and less elasticity. CONCLUSION: This is the first study assessing the various morphological-mechanical relationships of intraoral soft tissues, utilising Thiel-embalmed tissues. The findings of this study suggest that the tissues from different intraoral regions showed various morphological-mechanical behaviour which was also confirmed under the SEM and in the histological analysis.

Morphology and histology of the Anatolian bobcat (Lynx lynx) hard palate.

The aim of the research was to investigate the morphological and histological structure of the Anatolian bobcat (Lynx lynx) hard palate using light and scanning electron microscopy, in addition to gross examination. The Republic of Turkey Ministry of Agriculture and Forestry Work (Sivas Branch) provided three female Anatolian bobcat cadavers. The Anatolian bobcat hard palate consists of a narrow, rough part in the rostral region (including the incisive papilla, palatine ridges, and palatine raphe) and a wide, smooth part in the caudal part region. The gross examination revealed that the incisive papilla is small and shaped like a carboy icon, the primary and secondary palatine ridges have a serrated appearance, and the palatine raphe forms a single longitudinal row of conical papillae and a single transverse row of conical papillae (in the transverse groove that separates the two palatine ridges). In addition, the microscopy examination revealed microplicae in the epithelium, as well as abundant connective-tissue bundles running in various directions in the lamina propria and submucosa layer. These adaptations of the hard palate structures may increase efficiency during ingestion and help direct food backwards. This is the first study to provide detailed morphological and histological descriptions of the Anatolian bobcat hard palate.

Anatomical and mechanical properties of swine midpalatal suture in the premaxillary, maxillary, and palatine region.

The mechanical properties of the midpalatal suture and their relationship with anatomical parameters are relevant for both tissue engineering and clinical treatments, such as in sutural distraction osteogenesis. Soft tissues were dissected from ten swine heads and the hard palate was sliced perpendicularly to the midpalatal suture. Thirteen specimens were collected from each animal and analysed with micro-computed tomography and 4-point-bending for sutural width (Sw), interdigitation (LII), obliteration (LOI), failure stress (σ f ), elastic modulus (E), and bone mineral density (BMD). Values of the premaxillary, maxillary, and palatine region were compared with Kruskal-Wallis one-way ANOVA and Spearman's rank coefficient was used to analyse the correlation between parameters and their position along the suture (α = 0.05). LII had values of 1.0, 2.9, and 4.3, LOI had values of 0.0%, 2.5%, and 4.5%, and E had values of 12.5 MPa, 31.3 MPa, and 98.5 MPa, in the premaxillary, maxillary, and palatine region, respectively (p < 0.05). Failure stress and rigidity of the midpalatal suture increased from rostral to caudal, due to greater interdigitation and obliteration. These anatomical and mechanical findings contribute to characterise maxillary growth, and may help to understand its mechanical reaction during loading, and in virtual simulations.

Ultrastructural characterization of normal Merkel cells in the dog.

BACKGROUND: Involvement of Merkel cells (MKs) in different cutaneous diseases as well as in the growth, differentiation and homeostasis of the skin has been previously documented. HYPOTHESIS/OBJECTIVES: The aim was to assess the ultrastructural features of MKs in canine skin, including morphometrics, highlighting their similarities with and differences from those described for other mammals. ANIMALS: Hard palate, nasal planum, lower lip and whisker pad samples were taken from two healthy young dogs destined for academic purposes. METHODS: Ultrathin sections of samples fixed in osmium tetroxide and embedded in Epon 812 resin were stained with uranyl acetate and lead citrate and examined using a JEOL JEM 2010 transmission electron microscope. RESULTS: Ultrastructural characteristics included the following: (i) arrangement in clusters in the basal layer of the epidermis, oral mucosa and external follicular root sheath; (ii) inconstant link with nerve terminal; (iii) oval (10.27 ± 1.64 µm major axis) cell shape with large lobulated nuclei (5.98 ± 1.16 µm major axis); (iv) spine-like and thick cytoplasmic processes interdigitating with surrounding keratinocytes; (v) presence of desmosomes in the cell body or at the base of spine-like processes attaching to neighbouring keratinocytes; and (vi) cytoplasm containing loosely arranged intermediate filaments (10.04 ± 1.17 nm) and numerous dense-core granules (100.1 ± 17.12 nm) arranged in the basal portion of the cytoplasm. CONCLUSIONS AND CLINICAL IMPORTANCE: This study provides the first complete description of the ultrastructural characteristics of MKs in the dog, enhancing our knowledge of the skin structure in this species and providing a basis for future physiological and pathological studies of the role of these cells in normal and damaged canine tissues.

[An ultrastructure study on the palatomaxillary suture of dog expanded by NiTi-SMA].

OBJECTIVE: To explore the ultrastructure of the palate-maxillary sutures under tensile forces by transmission electron microscope (TEM). METHODS: The Suture expanders were made in NiTi-Shape memory alloy (NiTi-SMA). The maximum force was 3.5 N. Fourteen 8-month old mongrel dogs were used in the study. They were divided into three groups, (1) experimental group, (2) control group, (3) sham group. In the experiment and control groups, an 8 mm wide cleft was made by surgery. The suture expanders were fixed onto the palatine bones of the experimental group. The dogs of the experimental group were executed after 3, 7, 14, 28, 56 days of suture expansion. The change of suture tissue was examined by TEM. RESULTS: The cleft of the experiment group were closed at the ninth day of expansion. At the beginning, tissue rupture, exudation, death of fibroblasts, disruption of collagen and tear vessels were seen at the early stage of suture expansion. Then highly active functional manifestations were seen in both osteocytic and fibrocytic populations. At last, normal structure restored. CONCLUSIONS: Cell types and functional condition could be distinguished clearly by TEM. It suggests that the suture expansion should be the process of tissue repair and regeneration. The suture cells response, especially, the osteogenic response were the major factor of increasing suture width.

Revisión de la rugoscopía como método en la identificación humana / A review of rugoscopy as a method for human identification

El objetivo de esta revisión es demostrar la indivualidad de las rugas palatinas, observar si existe alguna relación hereditaria y proponer un rugograma que reproduzca las rugas y describa sus características. El estudio se divide en 2 partes. En la primera parte se tomaron 80 modelos de estudio del maxilar superior recolectados de los pacientes de las clínicas de la Facultad de Odontología UNC. A estos modelos se les realizó el rugograma, se elaboró una tabla de contingencia donde se cruzaron las variables de posición y tipo de ruga por medio de la prueba chi-cuadrado. Para la segunda parte se tomaron 9 familias con un total de 34 individuos, se aplicó un análisis discriminante para observar si existían características similares de las rugas entre los integrantes de una misma familia. A todos los modelos utilizadosen el estudio se les realizó el cotejo por medio de la superposición de acetatos (rugograma). Resultados: el tipo de ruga se encuentra relacionado con la posición, además se demostró que las rugas palatinas don únicas en cada individuo. Esto mismo se observó al realizar los cotejos. Las rugas que se presentaron con mayor frecuencia fueron sinuosa (4), curva (2), recta (1) y las menos frecuentes, raqueta (8), círculo (5) y punto (0). En el patrón hereditario se encontraron características similares entre los miembros de una misma familia, sin embargo no se puede determinar si un individuo externo pertenece o no a una determinada familia. En el cotejo se observó que ninguna de las rugas se repite en la misma posición y en la misma forma. Con esto se concluyó que la rugoscopía puede emplearse como método complementario en la identificación humana, pues es un instrumento por su accesibilidad, eficacia, fácil diligenciamiento, archivo y cotejo.

A comparative study of the surfaces of normal oral epithelia and inflammatory hyperplasias by scanning electron microscopy.

The oral epithelia may show epithelial changes induced by the inflammation of the underlying lamina propria. Light microscopically, the epithelial changes are similar to epithelial dysplasia seen in a premalignant lesion. A scanning electron microscope permits a resolution higher than that of a light microscope. Therefore, it may elucidate the changes observed light microscopically. The purpose of this study was to examine the surface changes of the epithelia of parulides (gum boils) compared with those of normal oral epithelia to see if there were any surface changes due to the underlying inflammatory processes. A total of 3 specimens (1 buccal mucosa, 1 gingiva, and 1 hard palate) taken from 3 patients, one specimen from each patient, were used as controls. A total of 2 parulides from 2 patients, 1 specimen from each patient, were used as experimentals. Each specimen was cut in two. One half was prepared for light microscopy and the other half was prepared for scanning electron microscopy. Light microscopically, it was confirmed that the buccal mucosa was nonkeratinized, the gingiva was parakeratinized, and the hard palate was orthokeratinized. The epithelium of the parulis was nonkeratinized to parakeratinized with increased intercellular spaces and distinct epithelial changes similar to epithelial dysplasia. By scanning electron microscopy, the nonkeratinized mucosa (buccal mucosa) showed that most of the ridges ran parallel to each other and the parakeratinized mucosa (gingiva) and the orthokeratinized mucosa (hard palate) exhibited ridges surrounding uniform pits. The surface of the parulis of the first patient showed relatively smooth areas with residual pits, reminiscent of that of keratinized mucosa, and the surface of the parulis of the second patient showed relatively smooth areas with residual parallel ridges, reminiscent of that of nonkeratinized mucosa. Light microscopically, the oral epithelia overlying the intensely inflamed lamina propria showed distinct epithelial changes similar to epithelial dysplasia seen in a precancerous lesion but appeared normal except for markedly decreased numbers of microridges by scanning electron microscopy.

Ultrastructural changes on the hard palatine mucosa of Calomys callosus after 120 days of experimental chronic alcoholism.

The present study analyzed the toxic effects of chronic alcohol ingestion on the ultrastructure of the lining epithelium of the hard palatine mucosa of the rodent Calomys callosus, in order to contribute to the understanding of the consequences of alcohol abuse for the morphology of the digestive system. Twenty-six adult animals aged three months were divided into two experimental groups. The control group received a solid diet and tap water, and the alcoholic group received the same solid diet and ethanol P.A. diluted 20% in water (v/v). After 120 days of treatment, all animals were anaesthetised, weighed and sacrificed. At the end of treatment, mean body weight did not differ between control and alcoholic animals. The epithelial cells of the alcoholic group showed many alterations such as the presence of lipid droplets, nuclei in corneum layer, nuclei with increase peripheral chromatin and greater electron density, altered mitochondria, and intense dilatation of the intercellular spaces. It was concluded that 20% ethanol provokes marked ultrastructural lesions in the hard palatine mucosa.

Merkel cells, corpuscular nerve endings and free nerve endings in the mouse palatine mucosa express three subtypes of vesicular glutamate transporters.

The hard palate of rodents is a mucous membrane covered by a keratinized epithelium that typically contains Merkel cell (MC)-neurite complexes. MCs have engendered considerable research activity because of their involvement in mechanoreception and possibly also Merkel cell carcinomas. MCs derive from the neural crest, differentiate under control of peripheral nerve factors, are enriched in large dense core vesicles, and secrete neuropeptides and other neuroactive molecules. Upon stimulation, MC-neurite complexes produce slowly adapting type I responses. Here we emphasize that the murine hard palate is a highly differentiated sensory region, as shown by intravital staining with a styryl dye and immunocytochemistry with antibodies to vesicular glutamate transporters (VGLUTs). The entire palate contained densities of sensory endings and MC-neurite complexes, that nearly paralleled in abundance the vibrissal pads. MCs were differentially distributed in the murine palate; clusters of MCs were most abundant in the antemolar and intermolar rugae, while individual MCs were particularly enriched in the rugae at the mid-portion of the palate and in the postrugal field. VGLUT1, VGLUT2 and VGLUT3 were expressed in MCs throughout, although immunostained MCs were most frequently encountered in intermolar than antemolar rugae. The same transporters were also present in corpuscular endings at the summit of the rugae and in intraepithelial free nerve endings throughout the palate. VGLUTs presumably load glutamate into large dense core vesicles in MCs and into small clear vesicles in corpuscular and free nerve endings. The data suggest that glutamate release, or co-release, is likely to represent an important functional aspect of palatine Merkel cells and neighboring corpuscular and free nerve endings.

Morphological effects on the hard palatine mucosa of Calomys callosus submitted to experimental chronic alcoholism.

The morphological effects of ethanol ingestion on the hard palatine mucosa of adult male Calomys callosus were observed. Twenty rodents were divided into two experimental groups: the control group received solid diet, Purina rat chow, and tap water ad libitum; the alcoholic group received the same solid diet and ethanol P.A. diluted 20% in water (v/v). After 270 days of treatment, all animals were sacrificed and the hard palatine mucosa were prepared for TEM and SEM methods. The epithelial cells of the alcoholic group showed some alterations like cytoplasmatic lipid droplets, pycnotic nucleus and increased mitochondrial size. The lamina propria also presented intense lipid droplets accumulation. The morphological changes suggested that chronic ethanol consumption was able to modify the integrity of the mucosa.

Epithelial cell proliferation and apoptosis in the developing murine palatal rugae.

Epithelial cell proliferation and apoptosis during morphogenesis of the murine palatal rugae (PR) were examined histochemically by using anti-bromodeoxyuridine (BrdU) and the terminal deoxynucleotidyl transferase-mediated UTP nick-end-labelling (TUNEL) technique. Formation of the PR rudiment was observed as an epithelial placode in fetuses at 12.5 days post-coitus (dpc). During the PR formation, BrdU-positive cells were detected mainly in the epithelium of the interplacode and interprotruding areas in fetuses administered BrdU maternally at 2 h before killing. TUNEL-positive cells were detected only at the epithelial placode area in 12.5-14.5 dpc. At 16.5-18.5 dpc, the BrdU-positive cells were decreased in number in the epithelial cells at the interprotruding area of the PR. Only a few TUNEL-positive cells were observed in the protruding area of the PR at 16.5 dpc. These results suggest that cell proliferation and apoptosis in the palatal epithelium are involved spatiotemporally in the murine PR morphogenesis.

[Distraction osteogenesis for the repair of cleft palate--an ultrastructural study].

OBJECTIVE: The aim of this study was to explore ultrastructural characters of the newly formed bone in the correction of cleft palate (CP) bone defect by distraction osteogenesis (DO). METHODS: The CP experimental animal models (12 cats) were established surgically, and were divided randomly into the experimental group (10 cats), in which the hard palate bone defects were corrected with DO procedure at the rate of 0.4 mm x 2/day. The specimen retrieval with euthanasia was carried out at 2, 4, 6, 8, 12 weeks after completion of distraction. Ultrastructural study was then performed; the experimental control group (2 cats) was kept for 6 weeks before euthanasia without any correction, the other extra 2 cats were used as the negative control. RESULTS: New bone formation appeared in early 2 weeks. Exclusively intramembranous bone formation was observed in all specimens. The remodeling activities were keep observed throughout the period of study, and the bone structure matured gradually till 12 weeks after the completion of DO. No repair was observed in experimental control group. CONCLUSION: The reconstruction of CP bone defect by means of DO could get active intramembranous bone formation and remodeling, which adapted to normal functional activities.