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Biomedical subjects

A Stavropoulos

Publications and source records attributed to A Stavropoulos.

17 recordsLinked to original sources
PubMed2005

Formation of human cementum following different modalities of regenerative therapy.

The aim of the present study was to compare newly formed cementum following different types of regenerative therapy in humans. Eighteen patients, each displaying one advanced intrabony defect around teeth scheduled for extraction, were included in this study. The defects were treated with either guided tissue regeneration (GTR), enamel matrix protein derivative (EMD), EMD plus bioactive glass, bovine-derived xenograft (BDX), BDX plus GTR, or BDX plus EMD. After healing, the teeth were removed together with their surrounding soft and hard tissues. Cellular content, presence of artifactual splits between the new cementum and the old one or the dentin surface, and thickness of the new cementum were evaluated. Irrespective of treatment, the new cementum was of a reparative, cellular, extrinsic and intrinsic fiber type. There were no differences in cementum thickness among treatments. These findings indicate that in humans, (a) the new cementum formed after different types of regenerative therapy was, irrespective of the treatment, of a reparative, cellular, extrinsic and intrinsic fiber type, and (b) the regenerative modality does not seem to influence the type of newly formed cementum.

Animals↗
PubMed2004

Healing of human intrabony defects following regenerative periodontal therapy with a bovine-derived xenograft and guided tissue regeneration.

The purpose of the present study was to histologically evaluate the healing of human intrabony defects following treatment with either a bovine-derived xenograft (BDX) and guided tissue regeneration (GTR) [BDX + GTR] or a bovine-derived xenograft mixed with collagen (BDX Coll) and GTR [BDX Coll + GTR]. Eight patients with chronic periodontitis and each with one very deep intrabony defect around a tooth scheduled for extraction were treated with either a combination of BDX + GTR (five patients) or with BDX Coll + GTR (three patients). The postoperative healing was uneventful in all eight cases. After a healing period of 6 months, the teeth or roots were extracted together with some of their surrounding soft and hard tissues and subsequently fixed in 10% buffered formalin. Following decalcification in EDTA, the specimens were embedded in paraffin and 8-microm histological sections were cut in the mesio-distal direction, parallel to the long axes of the teeth. The sections were alternatively stained with hematoxylin and eosin, van Giesson's connective tissue stain or with the Ladevig's connective tissue staining method and examined under the light microscope. Generally, formation of new cementum with inserting collagen fibers was found in seven out of the eight treated cases, whereas in the remaining case (treated with BDX + GTR) the healing was characterized by formation of a long junctional epithelium along the debrided root surface and no formation of cementum or bone. In the specimens demonstrating periodontal regeneration the new cementum was always of a cellular type. In most cases, the graft particles were surrounded by bone. In some areas, the bone tissue around the graft particles was connected by perpendicularly inserting collagen fibers to the newly formed cementum on the root surface. The epithelium downgrowth stopped always at the most coronal part of the newly formed cementum. No remnants of the membrane material were observed in any of the biopsies. Connective tissue encapsulation of the graft particles was rarely observed and was limited to the most coronal part of the defects. The findings of the present study provide evidence that treatment of intrabony defects with both BDX + GTR and BDX Coll + GTR may enhance periodontal regeneration in humans.

Alveolar Bone Loss↗
PubMed2003

Deproteinized bovine bone and gentamicin as an adjunct to GTR in the treatment of intrabony defects: a randomized controlled clinical study.

OBJECTIVES: To evaluate whether Bio-Oss used as an adjunct to guided tissue regeneration (GTR) improves the healing of 1- or 2-wall intrabony defects as compared with GTR alone, and to examine whether impregnation of Bio-Oss with gentamicin may have an added effect. MATERIAL AND METHODS: Sixty patients, with at least one interproximal intrabony defect with probing pocket depth (PPD) > or =7 mm and radiographic evidence of an intrabony component (IC) > or =4 mm, were treated at random with either a resorbable membrane (GTR), a resorbable membrane in combination with Bio-Oss impregnated with saline (DBB-), a resorbable membrane in combination with Bio-Oss impregnated with gentamicin (DBB+), or with flap surgery (RBF). RESULTS: All treatment modalities resulted in statistically significant clinical improvements after 1 year. Defects treated with GTR alone presented a probing attachment level (PAL) gain of 2.9 mm, a residual PPD (PPD12) of 4.9 mm, a radiographic bone level (RBL) gain of 3.1 mm, and a residual IC (IC12) of 2.7 mm. GTR combined with Bio-Oss did not improve the healing outcome (PAL gain: 2.5 mm; PPD12: 4.9 mm; RBL gain: 2.8 mm; IC12: 3.3 mm). Impregnation of the Bio-Oss with gentamicin 2% mg/ml resulted in clinical improvements (PAL gain: 3.8 mm; PPD12: 4.2 mm; RBL gain: 4.7 mm; IC12: 2.1 mm), superior to those of the other treatment modalities, but the difference was not statistically significant. Defects treated with only flap surgery showed the most inferior clinical response (PAL gain: 1.5 mm; PPD12: 5.1 mm; RBL gain: 1.2 mm; IC12: 4.2 mm) of all groups. CONCLUSION: The results failed to demonstrate an added effect of Bio-Oss implantation in combination with GTR on the healing of deep interproximal 1- or 2-wall, or combined 1- and 2-wall intrabony defects compared with GTR alone. Local application of gentamicin, on the other hand, improved the treatment outcome but not to an extent that it was statistically significant.

Absorbable Implants↗
PubMed2003

Gentamicin used as an adjunct to GTR.

OBJECTIVES: To evaluate in a discriminating "capsule" model whether local application of gentamicin may have an added effect on bone formation produced by Bio-Oss and guide tissue regeneration (GTR). MATERIAL AND METHODS: Thirty male 3-month-old Wistar rats were used. After elevation of muscle-periosteal flaps, a rigid hemispherical Teflon capsule, loosely packed with 0.025 g of Bio-Oss impregnated with 2 mg/ml gentamicin sulfate (Garamycin), was placed with its open part facing the lateral bone surface of the mandibular ramus (test) in one side of the jaw. A capsule filled only with Bio-Oss (control) was placed on the contralateral side of the jaw. After healing periods of 1, 2 and 4 months, groups of 10 animals were sacrificed and the specimens were processed for histological examination. The volumes of (1) the space created by the capsule, (2) newly formed bone, (3) Bio-Oss particles, (4) loose connective tissue, and (5) acellular space in the capsule were estimated by a point-counting technique in three to four histological sections of each specimen, taken by uniformly random sampling. RESULTS: The histological evaluation showed limited but increasing bone fill in the capsules from 1 to 4 months in both the test and control sides. After 4 months, the newly formed bone occupied 11.9% (CV: 0.39) of the space created by the capsules at the test sides versus 13.2% (CV: 0.41) at the control sides. There was no statistical significant difference between test and control specimens at any observation time (p>0.05). CONCLUSION: It is concluded that local application of gentamicin has no added effect on bone formation when combined with Bio-Oss and GTR.

Animals↗
PubMed2003

Osteogenesis by guided tissue regeneration and demineralized bone matrix.

AIM: To evaluate in a discriminating capsule model whether bone formation by guided tissue regeneration (GTR) may be influenced by concomitant implantation of demineralized bone matrix (DBM). MATERIALS AND METHODS: Thirty 4-month-old male albino rats of the Wistar strain were used in the study. Following surgical exposure of the mandibular ramus, a hemispherical, Teflon capsule (5.0 mm in diameter), loosely packed with a standardized amount of DBM, was placed with its open part facing the lateral bone surface of the ramus. At the contralateral side, an empty capsule was placed, serving as control. After healing periods of 15, 30, and 120 days, groups of 10 animals were sacrificed and 40-70 microm thick undecalcified sections of the capsules were produced. In the sections, the cross-sectional areas of (1) the space created by the capsule, (2) newly formed bone, (3) DBM particles, (4) loose connective tissue as well as the (5) height of the capsules, and (6) that of the newly formed bone were measured. RESULTS: Increasing bone fill was observed in both test and control sites from 30 to 120 days. After 30 days of healing, the mean amount of bone was approx. 3% of the cross-sectional area of the capsules at the test sites while it was 8% in the control sites (p<0.05). However, no statistically significant differences were observed between the test (46%) and control (64%) sites after 120 days regarding any of the measured parameters (p>0.05). The newly formed bone in the DBM group at 120 days, on the other hand, appeared more dense than that in the control capsules. CONCLUSION: DBM used as an adjunct to GTR did not provide any added effect on bone formation but increased the density of the newly formed bone.

Animals↗
PubMed2003

Denaturation of demineralized bone matrix significantly reduces bone formation by guided tissue regeneration.

AIM: To examine in a discriminating capsule model whether denaturation of demineralized bone matrix (DBM) by heating may influence bone formation. MATERIALS AND METHODS: DBM was produced from the long bones of rats. Half the portion of DBM was denatured by heating in distilled water for 20 min at temperatures between 70 degrees C and 90 degrees C. Prior to the study, the destruction of the osteoinductive properties of the DBM was confirmed in three rats following intramuscular implantation. Thirty, 4-month-old, male albino rats of the Wistar strain were used in the study. Following surgical exposure of the mandibular ramus, a hemispherical Teflon capsule (internal diameter = 5.0 mm) was placed, with its open part facing the lateral aspect of the ramus. On one side (test side), the capsule was loosely packed with denatured DBM, while on the contralateral side, serving as control, the capsule was loosely packed with the same amount of non-denatured DBM. After healing periods of 30, 60, and 120 days, groups of 10 animals were killed and 40-70 microm thick undecalcified sections of the capsules were produced. Three sections from each specimen, representing the mid-portion of the capsule, were subjected to histological analysis and computer-assisted planimetric measurements. RESULTS: Increasing amounts of newly formed bone were observed in both test and control capsules during the experimental period. At 4 months, the new bone formed in the control capsules occupied 46.7% of the cross-sectional area of the capsules, while it was only 19.1% in the test capsules (P<0.05). CONCLUSION: Denaturation of DBM by heating significantly reduces bone formation by guided tissue regeneration.

Animals↗
PubMed2003

Evaluation of a cell-permeable barrier for guided tissue regeneration combined with demineralized bone matrix.

AIM: To evaluate whether bone formation by guided tissue regeneration (GTR) and demineralized bone matrix (DBM) can be enhanced by the use of a cell-permeable Teflon barrier allowing the penetration of undifferentiated mesenchymal cells from the surrounding soft tissues. MATERIAL AND METHODS: DBM was produced from the long bones of rats, and its bone-inductive properties were tested in three rats prior to the study by intramuscular implantation. Thirty, 4-month-old, male albino rats of the Wistar strain were used. Following surgical exposure of the mandibular ramus, a cell-permeable Teflon capsule, loosely packed with DBM, was placed with its opening facing the lateral surface of the ramus (test side). At the contralateral side, serving as control, a non-perforated (cell-occlusive) Teflon capsule, loosely packed with the same amount of DBM, was placed. After healing periods of 30, 60, and 120 days, groups of 10 animals were killed, and 40-70 microm thick undecalcified sections of the capsules were produced. RESULTS: Computer-assisted planimetric measurements on the histological sections disclosed similar amounts of newly formed bone in both test and control capsules. After 4 months, the new bone in the control capsules occupied 45.0% of the cross-sectional area of the capsule, while it was 50.5% in the test capsules. This difference was not statistically significant (P<0.05). CONCLUSION: Similar amounts of bone formed in cell-permeable and cell-occlusive capsules grafted with DBM, suggesting that invasion of undifferentiated mesenchymal cells from the surrounding soft tissues into the barrier-protected area is unnecessary for bone formation with GTR.

Animals↗
PubMed2001

Deproteinized bovine bone used as an adjunct to guided bone augmentation: an experimental study in the rat.

BACKGROUND: Promising results have been reported following treatment of periodontal and peri-implant bone defects with deproteinized bovine bone grafts, but their influence on bone formation has not been clarified. PURPOSE: The goal of this study was to examine whether implantation of deproteinized bovine bone (Bio-Oss, Geistlich AG, Wolhusen, Switzerland) influences bone formation when used as an adjunct to guided bone augmentation (GBA). MATERIALS AND METHODS: A rigid, hemispherical, Teflon capsule was loosely packed with a standardized quantity of Bio-Oss and placed with its open part facing the lateral surface of the mandibular ramus (test) in 30 rats. At the contralateral side of the jaw, an empty capsule was placed (control). Groups of 10 animals were sacrificed after 1, 2, and 4 months. The volumes of the space created by the capsule and of the (1) newly formed bone, (2) remaining Bio-Oss particles, (3) soft connective tissue, and (4) acellular space in the capsule were estimated by a point-counting technique in three or four histologic sections, taken by uniformly random sampling. RESULTS: Bone formation at 1 month was limited in both tests and controls. After 2 months, the mean volume of the newly formed bone occupied 9.0% of the space created by the capsule in the test specimens compared with 23.8% in the control specimens (p < .01). After 4 months, the respective figures were 11.6% (tests) versus 38.7% (controls) (p < .01). CONCLUSION: It can be concluded that Bio-Oss, used as an adjunct to GBA, interferes with bone formation.

Animals↗
PubMed1997

The effects of slow waves in the screening EEGs of pilot cadets on P300 ERP and memory scanning performance.

BACKGROUND: Electroencephalography (EEG) screening of pilot candidates has long been established but remains controversial. The EEG records of 0-15% of the test population demonstrate the presence of brief periods of slow waves (theta, 4-7.9 Hz and delta, 0-3.9 Hz). The significance of these EEG findings for pilot selection has not been defined. HYPOTHESIS: We investigated whether the existence of slow waves in the EEG records of cadet pilots was related to differences in their cognitive performance. If so, the EEG could serve as a tool for cognitive assessment in candidate pilot screening. The relationship between spontaneous EEG slowing and cognitive performance has not been investigated although there is evidence of EEG slowing during the performance of short-term memory tasks. METHODS: Some 116 screening EEG records were re-evaluated for the presence of slow wave activity. Cadets with positive records and a control group performed: a) a modified version of Sternberg's visual memory scanning task on a PC computer; and b) the auditory "OddBall" behavioral task for eliciting the P300 evoked response using the Nicolet Spirit Evoked Potential System. RESULTS: Analysis of the behavioral and electrophysiological data was divided in EEG groups: a) Normal; b) Bilateral slowing only during hyperventilation; c) Bilateral slowing; d) Slowing with right dominance; and e) Slowing with left dominance, showed no significant difference among the groups for all parameters measured. CONCLUSIONS: Brief periods of bilateral or focal EEG slow activity in the records of pilot cadets could not predict differences in cognitive function as this was assessed in these experiments. Specific neuropsychological screening procedures might be more valuable for this purpose than the standard EEG screening.

Adolescent↗