Influence of different sterilization procedures and partial demineralization of screws made of bone on their mechanical properties.

Since 1992, screws made of allogenic, autoclaved human cortical bone have been employed as osteosynthesis materials. Autoclaving at 134 degrees C for 5 min makes them microbiologically safe, but on the other hand it reduces both their mechanical properties and osteoconductive capacity. The aim of this in vitro study was to determine if the mechanical properties of these screws could be improved after receiving different autoclaving procedures and partial inner demineralization, the latter additionally tending to increase their osteoconductive potential. 132 screws made of bovine cortical bone were employed. Some of them were partially demineralized with 0.6 N HCl from an inner canal performed following their longitudinal axis. All the specimens were autoclaved at 134 degrees C but under different vacuum conditions and sterilization time (A1-A2). They were then subjected to tension, shear and torque tests. A difference between both sterilization procedures was observed. Samples sterilized at 134 degrees C, 2-2.4 mbars for 5 min (A1) showed better mechanical properties than those autoclaved for longer time and higher vacuum conditions (A2). Demineralization also influenced their mechanical properties, being less resistant with increasing time. Based on these results, a standard screw made of bone and autoclaved at 134 degrees C, 2-2.4 mbars, 5 min seems to be the most appropriate, from a biomechanical point of view, to be used as osteosynthesis material.

Proliferación y apoptosis en epitelio lingual de ratones con tumores salivales inducidos por dimetilbenzantraceno (DMBA) y modulados por lípidos dietarios / Proliferation and apoptosis in tongue epithelium of mice bearing salivary tumors induced by dimetilbenzantraceno (DMBA) and modulated by dietary lipids

INTRODUCTION: According to the concept of field defects during the carcinogenesis process, excessive epithelial proliferation/apoptosis may exist in areas near tumors. Proliferation or apoptosis could be modified by dietary lipids. PURPOSE: The present study was designed to analyze proliferation and apoptosis in tongue epithelium of mice fed diets based on different lipids followed by induction of salivary tumors with DMBA. MATERIALS AND METHODS: Forty-five days after weaning, ten BALB/c mice were assigned to two diets: corn oil (CO) and fish oil (cod liver, FO). Two weeks later, DMBA was injected in the submandibular area. Animals were sacrificed at the 13th post-injection week. Samples of tongue were fixed in formalin-ethanol and immunohistochemically stained for proliferation (Ki-67) and apoptosis (Bax). By light microscopy, the number of nuclei positive for these markers were counted out of three-hundred total interphase cells both in dorsal and in ventral tongue surfaces. Results were analyzed through Analysis of Variance and t Test. RESULTS: Cell proliferation was greater in dorsal than in ventral tongue surfaces (p < 0.0001) with no diet difference. Apoptosis was significantly greater in mice fed FO than CO, particularly in tongue dorsal epithelia (p < 0.018). CONCLUSIONS: This study shows that FO diet induces higher levels of apoptosis in tongue epithelia suggesting a tissue defensive mechanism when exposed to a carcinogenic-tumoral agent.

Introducción: Según el concepto de cancerización de campo, existría alteración en la proliferación epitelial en áreas cercanas a tumores. Dicha proliferación podría ser modificada por lípidos dietarios. Objetivos: este estudio fue diseñado para analizar proliferación y apoptosis en epitelio lingual de ratones portadores de tumores salivalesinducidos por DMBA y alimentados con dietas a base de diferentes lípidos. Materiales y Métodos: Cuarenta y cinco días posteriores al destete, diez ratones BALB/c fueron asignados a dos dietas: maíz(M) y bacalao (B). Dos semanas después se inyectó DMBA en la zona submandibular. Los animales fueron sacrificados a ala 13º semana post-inyección. Muestras de lengua fueron fijadas en formal-etanl y procesadas inmunohistoquímicamente con marcadores de proliferación (Ki-67) y apoptosis. Mediante microscopia óptica, se efectuó un conteo de núcleos positivos a ambos marcadosres en un total de trecientas células en interfase, tanto en cara dorsal como ventral de lengua. Los resultados fueron analizados mediante Anális de Varianza y Test t. Resultados: La proliferación celular fue mayor en cara dorsal que en ventral (p> 0.001), sin diferencias por dieta. La apoptosis fue significativamentes mayor en ratones alimentados con B que M, en particular en cara dorsal (p<0.018). Conclusiones: Este estudio demuestra que la dieta B induce mayor apoptosis en ela epitelio lingua, sgiriendo un mecanismo defensivo de los tejidos ante el agente cancerígeno-tumoral.

Proliferación y apoptosis en epitelio lingual de ratones con tumores salivales inducidos por dimetilbenzantraceno (DMBA) y modulados por lípidos dietarios / Proliferation and apoptosis in tongue epithelium of mice bearing salivary tumors induced by dimetilbenzantraceno (DMBA) and modulated by dietary lipids

INTRODUCTION: According to the concept of field defects during the carcinogenesis process, excessive epithelial proliferation/apoptosis may exist in areas near tumors. Proliferation or apoptosis could be modified by dietary lipids. PURPOSE: The present study was designed to analyze proliferation and apoptosis in tongue epithelium of mice fed diets based on different lipids followed by induction of salivary tumors with DMBA. MATERIALS AND METHODS: Forty-five days after weaning, ten BALB/c mice were assigned to two diets: corn oil (CO) and fish oil (cod liver, FO). Two weeks later, DMBA was injected in the submandibular area. Animals were sacrificed at the 13th post-injection week. Samples of tongue were fixed in formalin-ethanol and immunohistochemically stained for proliferation (Ki-67) and apoptosis (Bax). By light microscopy, the number of nuclei positive for these markers were counted out of three-hundred total interphase cells both in dorsal and in ventral tongue surfaces. Results were analyzed through Analysis of Variance and t Test. RESULTS: Cell proliferation was greater in dorsal than in ventral tongue surfaces (p < 0.0001) with no diet difference. Apoptosis was significantly greater in mice fed FO than CO, particularly in tongue dorsal epithelia (p < 0.018). CONCLUSIONS: This study shows that FO diet induces higher levels of apoptosis in tongue epithelia suggesting a tissue defensive mechanism when exposed to a carcinogenic-tumoral agent.(AU)

Introducción: Según el concepto de cancerización de campo, existría alteración en la proliferación epitelial en áreas cercanas a tumores. Dicha proliferación podría ser modificada por lípidos dietarios. Objetivos: este estudio fue diseñado para analizar proliferación y apoptosis en epitelio lingual de ratones portadores de tumores salivalesinducidos por DMBA y alimentados con dietas a base de diferentes lípidos. Materiales y Métodos: Cuarenta y cinco días posteriores al destete, diez ratones BALB/c fueron asignados a dos dietas: maíz(M) y bacalao (B). Dos semanas después se inyectó DMBA en la zona submandibular. Los animales fueron sacrificados a ala 13º semana post-inyección. Muestras de lengua fueron fijadas en formal-etanl y procesadas inmunohistoquímicamente con marcadores de proliferación (Ki-67) y apoptosis. Mediante microscopia óptica, se efectuó un conteo de núcleos positivos a ambos marcadosres en un total de trecientas células en interfase, tanto en cara dorsal como ventral de lengua. Los resultados fueron analizados mediante Anális de Varianza y Test t. Resultados: La proliferación celular fue mayor en cara dorsal que en ventral (p> 0.001), sin diferencias por dieta. La apoptosis fue significativamentes mayor en ratones alimentados con B que M, en particular en cara dorsal (p<0.018). Conclusiones: Este estudio demuestra que la dieta B induce mayor apoptosis en ela epitelio lingua, sgiriendo un mecanismo defensivo de los tejidos ante el agente cancerígeno-tumoral. (AU)

Effects of enzymatic treatments on the biomechanical properties of screws made of bone.

Nowadays, bone tissue employed to manufacture screws used as osteosynthesis material is obtained from organ donors. But in different medical fields there is an increasing need to use xenogenic grafts and implants, which still imply risks of transmission of some diseases and antigenicity. Two different autoclaving programs (A1, A2) and an alternative to reduce the antigenicity of screws made of xenogenic bone based on enzymatic treatment are analyzed from a biomechanical point of view. 128 screws made of bovine femur bone were employed. Some of them were partially demineralized with 0.6 N HCl, enzymatically digested with collagenase (specific) and pepsin (nonspecific) and then autoclaved. The specimens were subjected to tension, shear and screw torque tests and histologically evaluated. Compared to A1, A2 sterilization method (134 degrees C but higher vacuum and longer time) considerably reduced the mechanical strength of specimens. The enzymatic digestion, expected to reduce antigenicity, did not affect the screw superficial structure and would not modify the bone biomechanical properties per se, but maybe because of the association with autoclaving and partial demineralization.

Volume variations of bone tissue after undergoing different physical and chemical treatments.

Both autogenic and allogenic bone has been employed through different surgical procedures to fill different defects or as osteosynthesis materials. Some physical and/or chemical treatments are usually necessary before its use. Since bone volume is important from a surgical point of view, the present study was designed to analyse its possible variations when subjected to certain procedures. Screws made of bovine cortical bone were autoclaved in different conditions regarding time and vacuum (A1-A2), cryopreserved, demineralised, enzymatically digested and rehydrated. The samples were measured before and after every treatment. Sterilisation caused a volume reduction more marked with method A1 than A2 whereas freezing allowed to obtain the original size. No volumetric changes were registered after demineralisation and enzymatic digestion. Rehydration significantly increased their volume already during the first hour but the maximum value was reached at 24 h. Thus, autoclaving was the only treatment able to reduce the bone volume whilst freezing and rehydration allowed the samples to return to their original size.

Cellular basis and clinical implications of biological markers in salivary tissues: their topological distribution in murine submandibular gland.

Cell proliferation and apoptosis as well as cell-cell adhesion and communication are essential processes that assure cell survival, renewal and coordination. Since junctional proteins have a tumor suppressor activity, their immunohistochemical characterization has diagnostic and prognostic value. The purpose of this report is to review the role played by junctional and proliferation-related proteins in the salivary glands and to illustrate their immunohistochemical localisation in normal murine submandibular gland. Normal salivary gland tissue was obtained from normal adult male BALB/c mice. After immediate fixation in formalin and ethanol, the samples were immunohistochemically stained for E-cadherin (HECD-1), Bcl-2, Ki67 (MIB-1), connexin26 and connexin 32, beta-catenin and gamma-catenin. Their topological distribution and reactivity were evaluated by light microscopy. The nuclei of submandibular acinar cells exhibited low to moderate staining for Ki67, but no reaction was observed in ductal cells. Murine Bcl-2 was light to moderately expressed in the latero-basal domain of cells of submandibular acini but was only lightly expressed in striated and eosinophilic ducts. The lateral domain of acinar cells were heavily stained with anti-E-cadherin, while only low levels were expressed at the cellular surface of ducts. beta-Catenin was consistently and evenly distributed along the latero-apical boundaries of eosinophilic secretory duct cells as well as on the lateral domain of acinar cells. On the contrary, gamma-catenin was generally expressed at lower levels than beta-catenin, was not expressed in ductal cells and was only lightly stained on the lateral membranes of acinar cells. No expression of connexin 32 was observed in ducts but it was significantly expressed in a spotted pattern along the plasma membrane of acinic cells. Connexin 26 showed similar localization to that of connexin 32 but the staining was much more intense. Since these proteins have been reported to play key roles in maintaining homeostasis via control of cell growth, differentiation and death, their analysis in normal salivary tissue will hopefully contribute to the study of salivary tumorigenesis.

Effects of dietary lipids on cell proliferation of murine oral mucosa.

BACKGROUND: The lack of certain essential polyunsaturated fatty acids (PUFAs) induces perturbation in cell proliferation, apoptosis and dedifferentiation that could be linked to an increased protumorigenic trend. Contrarily, n-3 essential fatty acids (EFAs) arrest cell proliferation in several tumor models. According to the concept of field cancerization, multiple patches of abnormal epithelial proliferation may coexist in the vicinity of oropharyngeal neoplasms. The purpose of the present study is to determine whether certain dietary PUFAs differentially modulate the patterns of cell proliferation and apoptosis at non-tumoral sites of the oral mucosa in mice bearing DMBA induced salivary tumors. After weaning, BALB/c mice were assigned to four diets: Control (C), Corn Oil (CO), Fish (FO) and Olein (O). Two weeks later, DMBA was injected into the submandibular area. The animals were sacrificed between 94 and 184 days at 4-6 PM. Fixed samples of lip, tongue and palate were stained using H-E and a silver technique. A quantification of AgNORs in the basal (BS) and suprabasal stratum (SBS) of the covering squamous epithelia as well as of mitosis and apoptosis was performed. RESULTS: Analysis of Variance showed greater proliferation in tongue than in palate or lip. According to the diet, a significant difference was found in the Fish Oil, in which palate exhibited fewer AgNOR particles than that of the control group, both for BS and SBS (p < 0.05 and 0.152, respectively), indicating a reduced cell proliferation. CONCLUSIONS: These results corroborate and reaffirm that the patterns of cell proliferation, apoptosis and differentiation of the oral stratified squamous epithelium may be differentially modulated by dietary lipids, and arrested by n-3 fatty acids, as shown in several other cell populations.

Influence of environmental and nutritional factors on salivary gland tumorigenesis with a special reference to dietary lipids.

Salivary gland cancer is a rare condition whose incidence varies according to different geographical regions. Several environmental factors, such as ionizing radiation and some occupational aspects, as well as habits like smoking and alcohol consumption, are related to salivary tumorigenesis. Both acinar and ductal cells may be involved in the origin of salivary gland tumours. Even though laboratory and epidemiological evidence indicates that diet and nutritional habits may modulate the tumorigenesis at different sites, little is known about this effect on salivary glands, mainly in regard to dietary lipids. However, the fact that monounsaturated fatty acids behave as protumorigenic and, on the contrary, certain polyunsaturated fatty acids exert beneficial effects, demonstrated on breast, colon and even oral cancer, gives support to our hypothesis. The suggested relationship between environmental and nutritional factors, mainly dietary lipids, and salivary gland cancer constitutes the aim of the present work.

N-3, n-6 and n-9 dietary fatty acids modulate the growth parameters of murine salivary gland tumors induced by dimethylbenzanthracene.

Variations in dietary fatty acid composition influence the biological behaviour of certain tumours. Diets enriched with oleic acid (18:1 n-9) seem to promote tumour progression on several lines due perhaps to the development of essential fatty acid deficiency (EFAD), whereas n-3 fatty acids have a protective effect. Since the role played by lipids on salivary gland tumorigenesis has not yet been studied, an experimental model is presented. BALB/c mice were fed on four different diets: control, corn oil, fish oil and olein groups. Salivary gland adenocarcinomas were chemically induced by using 9,10-dimethyl-1,2-benzanthracene. Animals were sacrificed at the 20th post-injection week and several tumour parameters were analysed. Linoleic acid showed no promoting activity. Tumour size was larger in the olein group than in fish oil fed mice, indicating that the oleic acid, linked to the induced EFAD condition, has a protumorigenic activity whereas n-3 polyunsaturated fatty acids appear to exert a protective effect.

Neodymium-YAG and CO2 lasers in treatment of pre-cancerous lesions of the oral cavity.

The oral mucosa is an area of premalignant lesions such as leukoplakias and lichens. This work analyzes results obtained from patients who are carriers of these premalignant lesions treated with 1,060 and 1,320 nm Nd-YAG and CO2 lasers. Certain immediate and mediate post-op symptoms such as pain edema, hemorrhage, recidivism and scar fibrosis were studied and favorable results were obtained with this therapy.