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Biomedical subjects

M Araújo

Publications and source records attributed to M Araújo.

11 recordsLinked to original sources
PubMed2005

Healing of extraction sockets and surgically produced - augmented and non-augmented - defects in the alveolar ridge. An experimental study in the dog.

OBJECTIVES: The current experiments had three aims (i) to determine whether the absence of the periodontal ligament (PDL) may alter features of the healing of an extraction socket, (ii) to examine if there were differences in the proportion of different tissues in resolved extraction sockets and surgically produced defects after 3 months of healing, (iii) to study the influence of different biomaterials on the healing of surgically produced bone defects. MATERIAL AND METHODS: Extraction sites: In five dogs, the 4th mandibular pre-molars were hemi-sected and the distal roots were removed. The extraction socket of one of the pre-molars was instrumented to eliminate all remnants of the PDL tissue. The socket of the contra-lateral pre-molar was left without instrumentation. The dogs were sacrificed after 3 months of healing. Defect sites: In five dogs, the pre-molars and 1st molars on both sides of the mandible were first removed and 3 months of healing allowed. After this interval three standardized cylindrical defects were prepared in each side of the mandible. The defects were 3.5 mm in diameter and 8 mm deep. In each quadrant one defect was grafted with Bio-Oss Collagen, one with Collagen Sponge and one defect was left non-grafted. The dogs were sacrificed 3 months after the grafting procedure. RESULTS: Extraction sites: The two categories of extraction sockets did not differ with respect to gross morphological features. The tissue of the extraction sites, apical of a newly formed bone bridge, was dominated by bone marrow. Few trabeculae of lamellar bone were also present. Defect sites: The non-augmented defect was sealed by a hard-tissue bridge. In the central and apical portions of the defect bone marrow made up about 61%, and mineralized bone 39% of the tissues. The invagination of the surface of this crestal bone was 0.8+/-0.3 mm. The defect augmented with Collagen Sponge was covered by a hard-tissue bridge 38% of the tissue within the defect was made up of bone marrow while the remaining 62% was occupied by mineralized bone. The invagination of the hard-tissue bridge was on the average 0.6+/-0.1 mm. In defects augmented with Bio-Oss Collagen the biomaterial occupied a substantial portion of the tissue volume. Eighty-five percent of the periphery of the Bio-Oss particles were found to be in direct contact with newly formed mineralized bone. Woven bone and bone marrow made up 47% and 26% of the newly formed tissue. The invagination of the most coronal part of the bone defect was 0.1+/-0.1 mm. CONCLUSION: Sockets that following tooth removal had their PDL tissue removed exhibited similar features of healing after 3 months as sockets which had the PDL retained. The tissues present in an extraction site appeared to be more mature than those present in a surgically produced defect of similar dimension. The Bio-Oss Collagen augmented defect exhibited less wound shrinkage than the non-augmented defect.

Alveolar Process↗
PubMed2004

Tuberculosis in renal transplants in Rio de Janeiro.

Retrospective analysis of 982 renal transplants over 21 years (1981 to 2002) sought to evaluate the prevalence of tuberculosis (TB). This analysis included 74 patients: 30 with a past TB history, who had INH prophylaxis since the beginning of immunosuppression, and 44 who only became TB infected after receiving transplants. The diagnosis of TB was made by a compatible medical situation with bacteriological/histological confirmation, which when not possible, underwent a therapeutic test occur. The average time for the illness to surge was 3 years. The mortality rate was 34.9% (15/44). Patients with hepatitis C were more affected. Among those who used INH prophylaxis only one contracted TB, showing that the drug displayed a protection rate of 96.6% (29/30).

Antitubercular Agents↗
PubMed2003

Dynamics of bone tissue formation in tooth extraction sites. An experimental study in dogs.

OBJECTIVES: The aim of the present experiment was to study events involved in the healing of marginal, central and apical compartments of an extraction socket, from the formation of a blood clot, to bone tissue formation and remodeling of the newly formed hard tissue. MATERIAL AND METHODS: Nine mongrel dogs were used for the experiment. The fourth mandibular premolars were selected for study and were divided into one mesial and one distal portion. The distal root was removed and the socket with surrounding soft and mineralized tissue was denoted "experimental unit". The dogs were killed 1, 3, 7, 14, 30, 60, 90, 120 and 180 days after the root extractions. Biopsies including the experimental units were demineralized in EDTA, dehydrated in ethanol and embedded in paraffin. Serial sections 7 microm thick were cut in a mesio-distal plane. From each biopsy, three sections representing the central part of the socket were selected for histological examination. Morphometric measurements were performed to determine the volume occupied by different types of tissues in the marginal, central and apical compartments of the extraction socket at different intervals. RESULTS: During the first 3 days of healing, a blood clot was found to occupy most of the extraction site. After seven days this clot was in part replaced with a provisional matrix (PCT). On day 14, the tissue of the socket was comprised of PM and woven bone. On day 30, mineralized bone occupied 88% of the socket volume. This tissue had decreased to 15% on day 180. The portion occupied by bone marrow (BM) in the day 60 specimens was about 75%, but had increased to 85% on day 180. CONCLUSION: The healing of an extraction socket involved a series of events including the formation of a coagulum that was replaced by (i) a provisional connective tissue matrix, (ii) woven bone, and (iii) lamellar bone and BM. During the healing process a hard tissue bridge--cortical bone--formed, which "closed" the socket.

Animals↗
PubMed2003

Effect of enamel matrix proteins (Emdogain') on healing after re-implantation of "periodontally compromised" roots. An experimental study in the dog.

OBJECTIVE: The present experiment was performed to assess whether Emdogain applied on the root surface of extracted teeth or teeth previously exposed to root planning can protect the tooth from ankylosis following re-implantation. MATERIAL AND METHODS: The experiment included two groups of dogs, including five animals each. The root canals of all mandibular third premolars (3 P 3) were reamed and filled with gutta-percha. A crestal incision was placed from the area of the second to the fourth premolar. Buccal and lingual full thickness flaps were elevated. With the use of a fissure bur, the crown and furcation area of 3 P 3 were severed in an apico-coronal cut. The distal and mesial tooth segments were luxated with an elevator and extracted with forceps. Group A: The mesial and distal segments of 3 P 3 were air dried on a glass surface for 60 min. The roots from the right side were conditioned and exposed to Emdogain application. The roots from the left side received the same treatment with the exception of Emdogain application. The mesial and distal tooth segments were re-implanted and the crown portions were severed with a horizontal cut and removed. The buccal and lingual flaps were mobilized and sutured to obtain complete coverage of the submerged roots. Group B: A notch was prepared in each root, 4-5 mm apical of the cemento-enamel junction. The area of the root that was located coronal to the notch was scaled and planned. The roots in the right side of the mandible were treated with Emdogain, while the roots in the left side served as controls. After 6 months of healing, the dogs were killed and blocks containing one root with surrounding tissues were harvested, and prepared for histological examination, which also included morphometric assessments. Thus, the proportions of the roots that exhibited signs of (i) replacement (ii) inflammatory and (iii) surface resorption were calculated. RESULTS AND CONCLUSION: It was demonstrated that healing of a re-implanted root that had been extracted and deprived of vital cementoblasts was characterized by processes that included root resorption, ankylosis and new attachment formation. It was also demonstrated that Emdogain treatment, i.e. conditioning with EDTA and placement of enamel matrix proteins on the detached root surface, failed to interfere with the healing process.

Animals↗
PubMed2001

[Influence of dose regimen on gentamycin nephrotoxicity in rats].

The acute renal failure (ARF), that still presents a right mortality rate (50%) can be defined as an abrupt decline of the glomerular filtration, resultant of ischemic or toxicity event. The drugs nephrotoxicity is one of the most frequent cause (27%) of ARF and it is suggested that the interval of administration of the drug can interfere in this side effect, however the best administration regimen is not very well established. This study evaluated the renal function of rats that received gentamicin (100 mg/kg) in one dose or in two doses (2 x 50 mg/kg), by intraperitoneal infusion. The results obtained in this research, indicated that the single infusion of gentamicin determined smaller nephrotoxicity by the reduction of serum concentration of this drug in 24 hours, decreasing the intracellular accumulation of this gentamicin, which is one of the main cellular mechanisms of this renal injury. The single dose treatment regime, otherwise, shows advantages not only related to the nephrotoxicity effect, but also it is relevant to the cost and safety, which can be rationable factors in the administration of this drug.

Acute Kidney Injury↗
PubMed2000

Bone healing around implants placed in a jaw defect augmented with Bio-Oss. An experimental study in dogs.

The present experiment was carried out to study some tissue reactions around implants that were placed in an edentulous ridge which had been augmented with deproteinized natural bovine cancellous bone mineral. In 4 male beagle dogs, the premolars in the right side of the mandible were extracted and a large buccal ridge defect was created by mechanical means. The bone plate at the lingual aspect of the defect was left intact. 5 months later, the distal 2/3 of the defect area was augmented with Bio-Oss (Geistlich Sons Ltd, Wolhusen, Switzerland) mixed with a fibrin sealer (Tisseel, Immuno AG, Vienna, Austria). After 3 months of healing, 3 fixtures (Astra Tech AB, Mölndal, Sweden; TiO-blast; 8x3.5 mm) were installed in the mandible; 2 were placed in the augmented portion and I was placed in the non-augmented portion of the defect. After a healing period of 3 months, abutment connection was performed and a plaque control period initiated. 4 months later, the dogs were sacrificed and each implant region was dissected. The tissue samples were dehydrated, embedded in plastic, sectioned in the bucco-lingual plane and examined in the light microscope. It was observed that osseointegration failed to occur to implant surfaces within an alveolar ridge portion previously augmented with Bio-Oss. In the augmented portion of the crest, the graft particles were separated from the host tissue as well as from the implant by a well-defined connective tissue capsule. Although the lingual aspect of all fixtures (test and control) was in contact with hard tissue at the time of installation, after 4 months of function, a deep vertical bone defect frequently had formed at the lingual surface of the implants. It was concluded that in this model (i) Bio-Oss failed to integrate with the host bone tissue and (ii) no osseo-integration occurred to the implants within the augmented portion of the crest.

Alveolar Ridge Augmentation↗
PubMed1999

Bone tissue reaction around implants placed in a compromised jaw.

The present experiment was carried out to examine bone tissue alterations that occurred around implants at which the marginal level of bone support at fixture installation was different at buccal and lingual surfaces. 8 beagle dogs were randomly divided into one test group and one control group. The mandibular premolars in the left side of the mandible (P1, P2, P3, P4) were extracted. In the 4 dogs of the test group, the buccal bone plate in the mandibular premolar region was removed to establish a bone defect that was about 25 mm long, about 5-6 mm high, and about 4 mm wide. In the 4 dogs of the control group, no bone resection was performed. 8 months after tooth extraction, 3 fixtures (Astra Tech AB, Mölndal, Sweden:TiO-blast: 8x3.5 mm) were installed in each dog. In the 4 dogs of the test group, the implants were positioned in the defect sites in such a way that (i) mechanical stability was achieved and (ii) their lingual surfaces were entirely invested in bone. At the buccal and approximal surfaces of the fixtures, however, the unthreaded portion (2 mm) and the 3 marginal threads remained exposed. In the control group, all implants were following installation entirely surrounded by bone tissue. After a healing period of 3 months, abutment connection was performed and a plaque control program initiated. 4 months later, the dogs were sacrificed. The mandibles were removed and placed in a fixative. Each implant region was dissected, the tissue samples were dehydrated, embedded, sectioned in a bucco-lingual plane and used for light microscopic examination. The findings demonstrated that osseointegration occurred at implants, placed in a chronic defect with large discrepancies between the buccal and lingual bone. During the process of healing and function, however, marked modeling and remodeling of the bone tissue took place. Thus, at the buccal surface, some bone regrowth and osseointegration occurred while at the lingual wall, there was a substantial resorption of the marginal bone and an enhanced number of bone multicellular units. Concomitant with the bone tissue alterations described, there was some recession of the peri-implant mucosa.

Animals↗
PubMed1996

The periodontal tissues in healed degree III furcation defects. An experimental study in dogs.

The aim of the present study was (i) to describe the periodontal tissue that formed in degree III furcation defects in mandibular molars of dogs following GTR therapy and (ii) to compare this healed periodontium to the corresponding tissue of pristine furcations. The study was performed in 10 mongrels dogs. In 6 of the dogs (group A), the 2nd and 4th premolars in both sides of the mandible were extracted 2 months prior to the start of the study. The 4 remaining dogs (group B) were used as normal untreated controls. In the dogs of group A, a furcation defect was produced in the 3rd mandibular premolars and reconstructive surgery was later performed in accordance with the GTR technique. 5 months after reconstructive surgery, all 10 animals (groups A+B) were sacrificed and perfused with a solution of 10% neutral, buffered formalin through the carotid arteries. Tissue blocks containing the experimental teeth were excised, demineralized in EDTA, embedded in paraffin. Serial sections were cut in the mesiodistal plane and parallel with the long axis of the roots. The microtome was set at 7 microns. The sections were stained in hematoxyline and eosin or Van Gieson's connective tissue staining. From each biopsy, 3 sections, 14 microns apart, and representing the central part of the furcation, were selected for light microscopic examination. In the healed furcation sites, histometric and morphometric measurements were performed at different levels (zones), either at the mesial or distal root surfaces; (zone 1) immediately apical of the notch; (zone 2) coronal to the notch where the newly formed alveolar bone was in continuity with the reduced bone crest; (zone 3) coronal to the notch; representing the most coronally positioned area of new bone formation; (zone 4) coronal to the notch; representing areas with no alveolar bone present. In the pristine furcation sites, the measurements were made at zones which corresponded to the location of the zones in the healed furcations. The present data demonstrated that all furcation sites in group A after 5 months of healing exhibited comprehensive de novo cementum formation in the previously exposed parts of the intraradicular root surfaces, and that collagen fibers invested in the newly formed cementum. Comparisons between the pristine and the healed furcations disclosed that the periodontal ligament of the healed furcations was poorly organised, and that bone formation was frequently incomplete.

Alveolar Process↗
PubMed1993

[Incidence of bacterial contamination in the Ares-Betanzos estuary (NW Spain)].

The presence of bacterial indicators of fecal pollution and V. parahaemolyticus in the estuary of Ares-Betanzos (ría de Ares-Betanzos, NW of Spain) was investigated. Resistance patterns of coliform bacteria to eight antibacterial agents were also determined. In general, high numbers of indicator bacteria were found; for instance, heterotrophic bacteria ranged between 1.82 x 10(2) to 1.9 x 10(4) CFU/ml and up to 4.6 x 10(3)/100 ml fecal coliforms in surface waters and 1.2 x 10(4)/100 ml fecal streptococci in sediment could be found. Surface waters of sampling points 2 and 7, located at the inner part of the estuary, were more polluted than the corresponding ones in the mouth (sampling points, 1, 3, 4 and 9), whereas the sediment showed just the opposite distribution. An 88.5% of isolated coliforms were resistant to one or more antibacterial agents. The MAR index points to urban wastewaters as the probable origin of pollution. The low incidence of V. parahaemolyticus and the lack of correlation with any of the fecal indicator bacteria determined, discard its use as indicative of fecal pollution in marine environments.

Drug Resistance, Microbial↗