Search PubMed⌕ Search

Biomedical subjects

A M Ubios

Publications and source records attributed to A M Ubios.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effect of compressive forces on a bone modelling surface.

The work presented herein, is an experimental study on the effect of an orthodontic appliance with a helicoidal spring designed to exert force toward palatine--i.e. in the opposite direction to the natural vestibular drift--on a bone remodelling surface. The appliance consists of two stainless steel molar bands, with a horizontal bracket tube welded to their palatal aspect through which the arms of the helicoidal spring are passed. Wistar rats, 250 g body weight, were fitted with the device for 48 and 96 hours. One group of rats was administered two doses of tetracycline hydrochloride prior to device placement, in order to label mineralizing fronts. Histomorphometric studies of the periodontal wall of the palatine alveolar bone showed a marked increase of bone resorption at both experimental time points together with an increase in the number of osteoclasts, and no tetracycline labelling after 48 hours. The results show that compressive forces are capable of stimulating resorption, even on bone modelling surfaces. The pressure applied would stimulate osteoblasts to send out signals for osteoclast recruitment and activity.

Alveolar Bone Loss↗
PubMed1996

An original orthodontic appliance for experimental mesial movements in rats.

The design of an original appliance to achieve mesial movement of the first upper molar on one side in rat is presented. The appliance is constructed in 0.4 mm stainless steel wire forming a parallelepiped 3 mm in width in its anterior sector, 4 mm in width in its posterior sector and 12 mm in length in its lateral branches. In addition a central longitudinal bar is welded to the structure. The lateral branches of the appliance slide freely through the tubes welded to the palatal aspect of the molar bands, cemented in turn to both first molars. A wire 2 mm in length is welded in the anchorage area to the mesial side of the molar tube at 3 mm from the anterior end of the appliance, which acts as a butt. A pre-formed nickel-titanium open coil spring 0.23 mm thick, lumen 0.60 mm and 5.00 mm in length is placed distal to the molar tube. The spring is compressed by 1 mm of its original length, the final force being approximately 50 g. The movement achieved was measured on plaster casts obtained from pre and postoperative impressions, and afforded values of 0.250 mm +/- 0.790 mm on the active side and 0.012 +/- 0.011 mm on the passive side. The histologic studies showed an extensive erosive area on the pressure side of the alveolar wall. The appliance presented will be useful to achieve models of experimental movements of only one molar towards mesial with a force of known magnitude.

Animals↗
PubMed1996

Impairment of molar tooth eruption caused by x-radiation.

The effect of x-radiation on erupting molars is presented. New born, 5 day old Wistar rats were locally irradiated in the molar area with doses of 20 Gy. They were killed in two groups, 30 and 60 days postirradiation respectively. Two other groups of non irradiated, age matched rats were killed at the given times. In addition a control group of 5 day old animals was also studied. Radiographic and histologic studies were performed. Odontoblastic atrophy, odontodysplasia, rootless formation, and ankylosis of tooth to bone by osteodentin formation with the resulting lack of tooth eruption were observed. The relation between the histologic alterations and tooth eruption is discussed.

Animals↗
PubMed1996

Suitability of different substrates for reliable bond strength tests.

The aim of the present study was to analyze different substrates used to determine composite-dentine bond strength. It comprises 3 parts. In the first, results obtained using bovine and human dentin are compared. In the second, bond strength of composite-bovine dentin sections cut at different angles was studied. In the third part, the effect of different storage solutions on bond strength was analysed. Two methods were used to study the capacity of bovine dentin to reproduce "in vivo" conditions as closely as possible: a) bond strength tests. Tensile strength of composite samples mounted on flat dentin surfaces, treated with bonding agents, stored in artificial saliva at 37 degrees C was measured. b) Observation of exposed surfaces by scanning electron microscopy. Results showed that more reliable values were obtained when using bovine dentin stored in distilled water at 4 degrees C sectioned at an angle of 125 degrees to vestibular face and not further than 7 mm from the incisal edge.

Animals↗
PubMed1994

Lethality due to uranium poisoning is prevented by ethane-1-hydroxy-1,1-biphosphonate (EHBP).

The processes of uranium extraction, purification, and manufacture involve the risk of chemical intoxication. Acute uranium poisoning elicits renal failure which in turn may lead to death. Great efforts have been put into the search for a protective agent for acute uranium poisoning. Several chelating agents such as EDTA, Tiron, DTPA, or aminosalicylic acid have been experimentally assayed. However, even when these agents are able to reduce the mortality none of them achieve 100% survival. We herein present the use of EHBP to prevent mortality due to uranium poisoning. Rats weighing 14 g were employed in two different experiments: A) The surviving animals were killed on the 60th day; and B) The animals were killed on the 9th day. In both experiments 4 groups were considered: 1. untreated control; 2. one intraperitoneal (IP) injection of uranyl nitrate (2 mg kg-1 of body weight); 3. 1 IP injection of EHBP (10 mg kg-1 of body weight); and 4. treatments 2 and 3 combined. In both experiments 50% of the animals in group 2 died on the eighth day. All the animals of the other groups were alive at the end of the experiment. Histological analysis of the kidneys of the animals of experiment B revealed renal damage in the exposed animals, whereas no structural alterations were detected in the kidneys of the other three groups, including those given uranyl nitrate and treated with EHBP. These results show the efficiency of only one injection of EHBP to avoid renal damage and to counteract the mortality due to uranium poisoning with a success rate of 100%.

Animals↗
PubMed1993

Early steps in bone resorption in experimental periodontitis: a histomorphometric study.

A histomorphometric study of the initial steps in the process of bone resorption of inflammatory origin is presented. The study was performed in a model of experimental periodontitis, in which plaque formation is induced by means of a cotton thread ligature placed around the neck of the first molar of Wistar rats. The treated animals were killed in groups after 24, 48, 72 and 96 hours. An equivalent number of untreated rats were employed as controls. After routine histologic processing mesiodistal sections were obtained. The histologic studies showed the sequence of events of the inflammatory process and bone resorption. The histomorphometric studies showed the concomitant increase in erosive areas and number of osteoclasts with the highest values at 72 hours. At 96 hours both parameters decreased. The results are discussed in the light of those afforded by other experimental models, in which bone resorption is induced by orthodontic forces. In these models the increase in the resorptive areas precedes the increase in the number of osteoclasts. The existence of two different mechanisms for the initiation of bone resorption, one which involves the action of an inflammatory environment and the other which results from the action of mechanical forces, is proposed.

Alveolar Bone Loss↗
PubMed1992

Mandibular growth and tooth eruption after localized x-radiation.

The effect of localized x-radiation on the growth of mandibular bone and molar eruption was evaluated by morphometric methods. A dose of 20 Gy of x-radiation was given to the molar zone of growing rats. The animals were then killed in groups at 30 and 60 days postirradiation. Two groups of nonirradiated, age-matched rats were used as controls. Parameters related to molar eruption, mandibular length, and mandibular height were measured on lateral radiographs. The results obtained showed that the values of the biometric parameters were lower in experimental than in control animals. Odontoblastic atrophy, alveolodentary ankylosis, and meager or no root formation were the most conspicuous histologic findings. Osteodentin was found between canaliculary dentin and bone in cases of ankylosis. The morphometric data presented confirm the probability of alterations in mandibular growth and tooth eruption following x-radiation and suggest that this be considered in planning radiotherapy in children.

Alveolar Process↗
PubMed1991

Uranium inhibits bone formation in physiologic alveolar bone modeling and remodeling.

The toxic effect of uranium (U) on bone modeling and remodeling was studied by performing histomorphometric measurements in the periodontal cortical bone of rats. Two different single intraperitoneal doses of uranyl nitrate (238U) were administered to two sets of rats respectively (2 and 0.8 mg/kg body wt). Rats treated with the first dose were killed 14 days postinjection (PI) and those treated with the second were killed 14, 30, and 60 days PI. The results revealed a decrease in bone formation in rats treated with uranium. On the remodeling side the decrease in bone formation was coupled to an increase in bone resorption on the 14th day PI. On the modeling side no bone resorption was observed and the decrease in bone formation was linked to an increase in resting bone zones. Bone formation depression as a key event in U intoxication is stressed.

Animals↗
PubMed1991

Effect of calcitonin on alveolar wound healing.

The effect of calcitonin (CT) on alveolar wound healing was studied with histomorphometric methods. Wistar rats weighing 80-90 g were submitted to extraction of the three mandibular molars. Half of them were injected intraperitoneally with daily therapeutic doses of CT. The control group received no further treatment. All the rats were killed 14 days after the onset of the experiment. Bone healing was impaired in CT treated animals and involved a more intense bone remodeling activity. Bone resorptive areas were present both on the profiles of the newly formed bone and on the alveolar ridge surface. These results suggest that CT would accelerate the process of bone healing.

Alveolar Process↗
PubMed1989

Tetracycline in uranyl nitrate intoxication: its action on renal damage and U retention in bone.

In acute intoxication, uranium (U) not only inhibits bone formation but its excretion in urine also causes renal damage. The former effect is ameliorated by tetracycline (TC), probably due to its chelation property, which might also prevent U deposition in bone. Chemical determination of U incorporated in bone and a histological study of the kidneys were performed on animals injected with U and then treated with TC. The results showed that TC was unable to prevent the binding of U to bone while it exacerbated U-induced renal damage.

Animals↗
PubMed1986

Alveolar wound healing after x-irradiation: a histologic, radiographic, and histometric study.

Healing of extraction wounds in rats following cephalic irradiation was studied by histologic, radiographic, and histometric methods 14 days after tooth extraction. Irradiation was given at 0, 3, and 7 days after surgery in doses of either 15, 20, or 30 Gy. No significant differences were seen with the different doses given seven days post-extraction. However, socket healing was delayed when irradiation was given immediately and three days after extraction. On the basis of these observations, it is recommended that radiation not begin until at least one week after the extraction of teeth.

Alveolar Process↗
PubMed1986

Effect of diphosphonate on the prevention of X-radiation-induced inhibition of bone formation in rats.

A histologic and histometric study of the effect of EHDP (ethane-1-hydroxy-1,1-diphosphonate) on the alveolar wound healing of irradiated animals is presented. This drug was selected based on its osteosclerotic effect when applied at low doses. The three left mandibular molars of 80 male Wistar rats were extracted. The rats were grouped into 4 sets of 20 rats each. Group I received no further treatment; Group II received daily intraperitoneal injections of EHDP (7.5 mg/Kg of body weight during 10 days); Group III: 15 Gy of X-radiation were applied to the head; and Group IV were irradiated and injected with EHDP as were animals of Groups III and II. Half of the animals were killed after 14 days and the other half 30 days post-extraction. Sections were made at the level of the mesial socket of the first molar in a bucco-lingual orientation, on which histometric determinations of bone activity were made. The results showed the attenuation of the inhibitory effect of radiation on bone formation when the animals were treated with EHDP.

Alveolar Process↗
PubMed1985

Alveolar wound healing alteration under uranyl nitrate intoxication.

The deposit of uranium compounds in calcifying zones has been demonstrated in bone. Nevertheless, no studies on the effect of uranium on osteogenesis have been performed. A histologic and histometric study of the effect of a single intraperitoneal injection of 2 mg/kg of body weight of uranyl nitrate on bone formation is presented. It was performed on rats' healing sockets, 14 days after tooth extraction. The alveolar bone volume (15 X 10(5) micron vs. 34 X 10(5) micron2), total bone formation areas (4.85% vs. 19.55%), and volume density of bone in the alveolar apical third (0.26 vs. 0.40) were significantly lower in intoxicated animals than in the controls. These results indicate the inhibitory effect of uranyl nitrate on bone formation.

Alveolar Process↗
PubMed1985

Scanning electron microscopy of human submandibular gland.

The fracture surface of human submandibular gland analyzed by scanning electron microscopy is studied here. Acini showed spherical granules of 0.7 +/- 0.28 micron diameter, their most distinctive feature. Some empty, septate cavities found contiguous to serous acini were considered to be mucous acini. Striated ducts had a circular lumen, with microvilli forming prominences. Blebs, some intact and others ruptured, were interpreted as apocrine secretion. The 'separating zone' of the striated cells was distinguishable from the rest of the cell because the structure of the cell was granular whereas the 'separating zone' was fibrillar.

Adult↗
PubMed1985

Microphotometric quantitation of succinic dehydrogenase in whole isolated osteoclasts.

The microphotometric quantitation of succinic dehydrogenase (SDH) in whole isolated osteoclasts was performed. Osteoclasts were obtained from imprints of the external metaphyseal area of tibia, a zone of physiological bone resorption. SDH was demonstrated histochemically and the reaction product was measured in a Zeiss Cytoscan microphotometer in arbitrary units (AU) of activity from 0 to 500. Total enzyme activity (TEA) was 10 to 50 AU in 78% of the cells. The enzyme concentration (MEC), taken as the activity per unit volume was 0.10 to 0.40 AU in 94% of the cells. Values of reactive cytoplasm area (RCA) were high for most of the cells, but lower for a few, probably mononuclear, osteoclasts. The correlation index for TEA vs RCA was significant. The study of enzyme activity in whole osteoclasts by microphotometric quantitation has been proven possible. This technique could be employed in further studies of enzyme activity of osteoclasts in other physiological or pathological states of bone resorption.

Animals↗
PubMed1985

Virus-like intranuclear inclusions in giant cell tumor of bone.

An ultrastructural study of 13 cases of typical giant cell tumor of bone (GCT) revealed the presence of virus-like intranuclear inclusions (INI), morphologically identical to those reported in Paget's disease of bone. In two giant cells of two different patients, INI were found only after careful survey of a great number of cells. This finding, coupled with the scarcity of GCT with similar inclusions reported in the literature, reveals the extreme rarity of this finding and leaves open to discussion the specificity of these INI even in Paget's disease, as well as the possible etiological significance in giant cell tumor of bone.

Bone Neoplasms↗