The effect of delayed versus early loading on nitric oxide metabolism around dental implants: an 18-month comparative follow-up study.

PURPOSE: Nitrite is a stable end-product of nitric oxide oxidation. The aim of the present study was to quantitatively analyze peri-implant sulcular fluid (PISF) nitrite levels in a longitudinal study design to evaluate the potential changes in nitric oxide metabolism in relation to the clinical status of the peri-implant site and the loading style of the dental implants. MATERIALS AND METHODS: A total of 34 implants, either early loaded (EL) or delayed loaded (DL), in 17 patients were followed up for a period of 18 months. Clinical parameters were recorded, PISF samples were obtained, and PISF nitrite levels were spectrophotometrically determined. Clinical measurements and nitrite analysis were repeated at 1, 3, 6, 9, 12, and 18 months. RESULTS: Despite the gradual decrease in clinical parameters, fluctuations in PISF total nitrite levels were observed during follow-up. The pattern of nitric oxide metabolism, as reflected by PISF nitrite levels, also demonstrated differences between EL and DL implants that diminished toward the end of the experimental period. DISCUSSION: Although the presence of clinical and subclinical gingival inflammation contributes to the PISF total nitrite levels, nitric oxide metabolism is also associated with healing and bone remodeling, and the pattern of loading seemed to have an impact on nitric oxide production at dental implant sites. CONCLUSION: Nitric oxide production at dental implant sites seems to be tightly regulated to enable the maintenance of peri-implant bone.

Analysis of thte possible impact of inflammation severity and early and delayed loading on nitric oxide metabolism around dental implants.

PURPOSE: The aim of the present study was to analyze the possible impact of clinical status, presence and severity of inflammation, and loading on nitric oxide (NO) metabolism around mandibular dental implants. MATERIALS AND METHODS: A total of 34 implants in 17 patients, loaded either early (EL) or after a delay (DL), were classified according to the presence and severity of clinical inflammation in the peri-implant sites. Clinical parameters were recorded, peri-implant sulcular fluid (PISF) samples were obtained, and PISF nitrite levels were spectrophotometrically determined. Clinical measurements and nitrite analysis were repeated at 1, 3, 6, and 9 months postloading at available sites. RESULTS: Compared to noninflamed sites, inflamed sites demonstrated higher mean total nitrite levels (P = .032) that tended to increase with the severity of inflammation at both EL and DL implants. At noninflamed sites, EL implants provided significantly higher PISF volume than DL implants (P = .001). At noninflamed sites, EL implants revealed higher total nitrite levels; on the contrary, at inflamed sites, DL implants revealed higher total nitrite levels. In general, nitrite levels demonstrated a pattern of decrease followed by an increase during follow-up. DISCUSSION: Increased NO production with the presence and the severity of inflammation supports the contribution of NO in the peri-implant inflammatory process. Loading is also likely to have an impact on NO metabolism, which suggests a role for NO in remodeling and adaptation of bone around dental implants. CONCLUSION: Besides the presence of inflammation, the severity of inflammation and loading also seem to have an impact on NO metabolism around dental implants.

Correlation of injury severity and tissue Evans blue content, lipid peroxidation and clinical evaluation in acute spinal cord injury in rats.

OBJECTIVE: To demonstrate the changes in microvascular permeability occurring in association with graded acute spinal cord injury and to determine whether tissue Evans blue content is a useful indicator of the severity of spinal cord injury. The study also aimed to test the ability of the Evans blue method to demonstrate secondary injury after spinal cord contusion. METHODS: In step one of the study, spinal cord lipid peroxidation levels and spinal cord Evans blue content were evaluated at 2 h post-injury in five groups of rats: a control group, a laminectomy-only group and three trauma groups (10, 50, and 100 gcm). In step two, these rats were used for Evans blue assessment following clinical examination at 24 h post-injury. RESULTS: The laminectomy-only group showed no difference from the control group with regard to spinal cord lipid peroxidation levels, tissue Evans blue content, and clinical findings. Increase in spinal cord tissue Evans blue content and lipid peroxidation was correlated with increasing intensity of trauma. There was a negative correlation between trauma intensity and clinical findings, and there was an increase in spinal cord tissue Evans blue content at 24 h compared with that at 2 h. CONCLUSIONS: Determination of spinal cord tissue Evans blue content is a reliable, rapid, simple and inexpensive method that can be used in experimental spinal cord injury to assess the severity of injury and to evaluate neuroprotection studies. The present study is the first to show that the Evans blue technique is a useful method to demonstrate secondary injury of spinal cord tissue and vasculature.

Effects of carbon dioxide pneumoretroperitoneum on free radical formation in remote organs and use of verapamil as an antioxidant.

BACKGROUND AND PURPOSE: Pneumoretroperitoneum (Prp) acts as an ischemia/reperfusion (I/R) model. Ischemia/reperfusion (I/R) injury causes production of reactive oxygen species, which affect organs remote from the sites of I/R. The aim of this study was to assess the remote organ changes after Prp and to explore the effects of antioxidants. MATERIALS AND METHODS: Eighteen adult rabbits were randomized to three groups, each consisting of six rabbits. Group I (control) underwent balloon dissection of the left retroperitoneal space without gas insufflation. In group II (Prp), carbon dioxide at 10 mm Hg was applied for 2 hours after the balloon dissection (ischemia period) and for 1 hour after desufflation (reperfusion period). In group III (Prp + antioxidant), 5 minutes before the experiment, verapamil at 0.2 mg/kg was given intravenously and the same procedure was employed as in group II. Hepatic, pulmonary, opposite kidney, and treated kidney malondialdehyde (MDA) and reduced glutathione (GSH) levels were evaluated to show response to Prp. RESULTS: Pneumoretroperitoneum exerted oxidative stress on all tissues with an increase of MDA (P < 0.05) and a decrease of GSH (P < 0.05). The verapamil-treated group showed lower values of MDA (P < 0.05) and higher values of GSH (P < 0.05) than group II. CONCLUSION: Pneumoretroperitoneum increased oxidative stress in all remote organs tested. Verapamil reduced the oxidative stress. We concluded that Prp should be employed carefully in patients with limited vital organ capacity. Verapamil administration may be considered for protection against tissue injury attributable to oxidative stress in these patients.

Comparison of changes in tissue oxidative-stress markers in experimental model of open, laparoscopic, and retroperitoneoscopic donor nephrectomy.

PURPOSE: We evaluated the oxidative stress in renal tissue during three types of surgery: open donor nephrectomy (ODN), laparoscopic donor nephrectomy (LDN), and retroperitoneoscopic donor nephrectomy (RDN). The aim was to find out which is the appropriate procedure for harvesting a donor kidney. MATERIALS AND METHODS: Twenty-four New Zealand White rabbits were randomized to four groups, each consisting of six rabbits. Group I (control) was subjected to 180 minutes of anesthesia, and transperitoneal nephrectomy was performed without creation of warm ischemia. In group II (ODN), after 180 minutes of anesthesia, warm ischemia was created for 5 minutes, and nephrectomy was performed. Group III (LDN) was subjected to 5 minutes of warm ischemia after 180 minutes of pneumoperitoneum at 12 mm Hg, and the kidney was removed. In group IV (RDN), after pneumoretroperitoneum at 12 mm Hg for 180 minutes, warm ischemia was created for 5 minutes, and nephrectomy was performed. Renal tissues were analyzed to determine malondialdehyde (MDA) and reduced glutathione (GSH) as oxidative-stress markers. RESULTS: Renal tissue GSH levels were decreased, whereas MDA levels were increased in groups II through IV compared with the control group (p<0.05). There was no statistically significant difference between the ODN, LDN, and RDN groups in the renal oxidative-stress markers. CONCLUSION: No differences were detected in oxidative-stress markers in renal tissue samples between ODN, LDN, and RDN. Therefore, we believe LDN and RDN can be used for live donor kidney harvesting as effectively as ODN without creating greater oxidative stress, which can have deleterious effects on a donor kidney.

Orchidopexy or orchidectomy for preventing tissue hypoxia in contralateral testis following induction of ipsilateral abdominal testis associated with vas deferens obstruction.

INTRODUCTION: An experimental study was planned to evaluate and compare the effects of orchidopexy and orchidectomy on ipsilateral and contralateral testes in rats subjected to ipsilateral abdominal testis and vas deferens obstruction. MATERIALS AND METHODS: Four groups of 12 rats each were established. Sham operation, intra-abdominal testis with vas deferens obstruction and orchidopexy or orchidectomy for prior intra-abdominal testis with vas deferens obstruction were performed in groups 1, 2, 3 and 4, respectively. While testes were maintained for 8 weeks in the same position in groups 1 and 2, orchidopexy or orchidectomy was performed in groups 3 and 4 after the first 4 weeks, and the remaining testes were harvested after an additional 4 weeks. Lactic acid hypoxanthine contents were determined and the groups were compared with the paired t test. RESULTS: Maintaining intra-abdominal testis with vas deferens obstruction for 8 weeks and orchidopexy yielded the highest lactate values. However lactate levels in contralateral testes did not increase. On the other hand, hypoxanthine levels revealed the highest values after the initial 4 weeks. The 8-week study period resulted in increases of ipsilateral and contralateral testicular hypoxanthine levels. Orchidopexy caused a decrease in ipsilateral testicular values and ameliorated the increase in hypoxanthine levels in contralateral testes. CONCLUSIONS: Replacing an intra-abdominal testis with its vas deferens ligated into the scrotum ameliorates the oxidative stress in both ipsilateral and contralateral testes. Since orchidectomy does not result in better contralateral testicular values, orchidopexy should be preferred when treating an undescended testis with vasal obstruction.

Magnesium sulfate treatment in experimental spinal cord injury: emphasis on vascular changes and early clinical results.

Injury to the spinal cord results in disruption of neurons, cell membranes, axons, myelin, and endothelial cells. The aim of this study was to demonstrate the protective effect of magnesium sulfate on the blood-spinal cord barrier after acute spinal cord injury (SCI). This experiment was conducted in two parts. In the first, rats were injected intravenously with Evans blue 2 h after SCI. The laminectomy-only group had no trauma. Contusion injury (50 g-cm) was applied to the trauma and treatment groups. Magnesium sulfate (600 mg/kg) was given to the treatment group immediately after injury. For the second part, clinical evaluations were performed 24 h post surgery. Then, following Evans blue injection, spinal cord samples were obtained from the laminectomy-only, trauma, and treatment groups. For the control group, nontraumatized spinal cord samples were taken after Evans blue injection following clinical examination. Laminectomy did not affect the spinal cord Evans blue content in 2-h and 24-h groups. The trauma increased tissue Evans blue content, and 24-h samples showed more remarkable tissue Evans blue content, suggesting secondary injury. Application of 600 mg/kg of magnesium resulted in lower Evans blue content in the spinal cord than with injury. Remarkable clinical neuroprotection was observed in the treatment groups. Magnesium sulfate showed vaso- and neuroprotective properties after contusion injury to the rat spinal cord. The authors also demonstrated secondary injury of the blood-spinal cord barrier with the Evans blue clearance technique for the first time.

Different responsiveness of central nervous system tissues to oxidative conditions and to the antioxidant effect of melatonin.

Melatonin, a product of the pineal gland, is an effective free-radical scavenger both in vitro and in vivo. Free-radical-mediated lipid peroxidation has been increasingly considered as an important factor in post-traumatic neuronal degeneration. The aim of the present study was (i). to examine the responses of different regions of central nervous system (CNS) to free-radical generation induced in vitro and (ii). to test the efficacy of melatonin in reducing oxidative damage in different regions of the CNS. Rat brain, total spinal cord, spinal cord white matter and optic nerves were dissected with the rats under general anesthesia and immediately frozen at -20 degrees C. Thiobarbituric acid reactive substances were measured as an index of lipid peroxidation. Peroxidation was induced with ferrous iron (0.02 mm), ascorbate (1 mm), and hydrogen peroxide (H2O2) (0.5 mm). All tissue samples showed increased lipid peroxidation levels after treatment with free-radical generating agents. The highest amount of damage was observed in the presence of ferrous iron, ascorbate, and H2O2. Melatonin showed antioxidant effects in the brain, total spinal cord, optic nerve, and spinal cord white matter. The results show that melatonin has differential protective effects on CNS tissues in vitro and the most potent effect is observed in the spinal cord white matter.

Analysis of the relationship between the severity of periodontal destruction and proteoglycan metabolism of gingiva and gingival crevicular flu.

BACKGROUND: Although it is well-described that proteoglycans (PGs) are among the major non-collagenous components of the matrix which are degraded during periodontal diseases, the relationship between PG metabolism and seventy of periodontal breakdown, the extent of degradation of PGs together with the resulting end-products, and the elimination pathways of these catabolic end-products is likely to need further clarification. OBJECTIVE: The main aim of the present study was to analyze the possible impact of severity of periodontal destruction on PG metabolism of gingiva and gingival crevicular fluid (GCF). MATERIAL AND METHODS: For this purpose, gingiva and GCF samples obtained from patients (n = 45) exhibiting sites (n = 57) with moderate periodontal breakdown (MP) or severe periodontal breakdown (SP) were analyzed for PG metabolism via spectrophotometric determination of uronic acid levels. Gingiva and GCF samples were obtained from the same sites in every patient to analyze the possible relationship between uronic acid content of gingival tissue and GCF. RESULTS: No significant differences were found in uronic acid levels between sites with MP and SP (p > 0.05). The uronic acid content of GCF and gingiva showed significant overlaps between MP and SP sites and uronic acid levels did not present any constant correlation with the clinical parameters (p > 0.05). In a similar manner, uronic acid content of GCF and gingival tissue was not correlated (p > 0.05). CONCLUSION: The lack of a significant correlation between the uronic acid content of gingival tissue and GCF may suggest that the passage of PG metabolites from gingiva to GCF is likely to be under the influence of multifactorial interactions rather than being linear. As a general measure of PG metabolism, uronic acid levels do not seem to be related with the severity of periodontal destruction and tend to act as different measures when compared to traditional clinical parameters.