Biomedical subjects

G Abbas

Publications and source records attributed to G Abbas.

8 recordsLinked to original sources

PubMed2006

Human microvascular endothelial cellular interaction with atomic N-doped DLC compared with Si-doped DLC thin films.

This article reports results of endothelial cell interaction with atom beam source N-doped a-C:H (diamond-like carbon, DLC) as it compares with that of Si-doped DLC thin films. The RF plasma source exhibits up to 40% N-dissociation and N-atomic fluxes of approximately 0.85 x 10(18) atoms/s, which ensures better atomic nitrogen incorporation. Two different types of nitrogen species (with and without the use of sweep plates to remove charged ions) were employed for nitrogen doping. The number of attached endothelial cells is highest on Si-DLC, followed by the N-DLC (where the sweep plates were used to remove ions), the N-DLC (without the use of sweep plates), undoped DLC, and finally the uncoated sample. The contact angle values for these films suggest that water contact angle is higher in the atomic nitrogen neutral films and Si-DLC films compared to the ionized-nitrogen specie doped films and undoped DLC thin films, suggesting that the more hydrophobic films, semiconducting films, and film with relieved stress have better interaction with human microvascular endothelial cells. It seems evident that N-doping increases the Raman I(D)/I(G) ratios, whereas N-neutral doping decreases it slightly and Si-doping decreases it even further. In this study, lower Raman I(D)/I(G) ratios are associated with increased sp(3)/sp(2) ratio, an increased H concentration, photoluminescence intensity, and a higher endothelial cellular adhesion. These investigations could be relevant to biocompatibility assessment of nanostructured biomaterials and tissue engineering.

Cell Adhesion↗

PubMed2006

Effectiveness of a self-adhesive resin luting system on fracture resistance of teeth restored with dentin-bonded crowns.

Laboratory studies have demonstrated satisfactory fracture resistance of all-ceramic crowns placed using a conventional resin-composite luting material and a dentine bonding system. This study investigated the fracture resistance of teeth restored with dentine-bonded ceramic crowns luted with a self-etching luting material. Standardized preparations were carried out on two groups of ten sound, unrestored, maxillary premolar teeth. Ceramic crowns were constructed, their internal surfaces etched and placed using two luting system combinations. Compressive fracture resistance was determined for each group using a Universal Testing Machine. Mean compressive fracture resistance of 890 (222) N and 760 (271) N were recorded for the RelyX Unicem Aplicap and Mirage groups, respectively. There was no significant difference in the mean compressive fracture resistance of the restored teeth in both groups (P<0.05). The failure modes were different for each cements with more severe (Mode V)failures associated with the Mirage group compared with the consistent Mode II failures associated with RelyX Unicem Aplicap. We conclude that the fracture resistance of dentine-bonded crowns luted with a self-adhesive resin-based luting material was no different from that of a conventional resin-based luting system. The fracture resistance of dentine-bonded ceramic crowns may be clinically satisfactory when a self-adhesive resin-based luting material is utilised.

Analysis of Variance↗

PubMed2004

Macrophage responses to vascular stent coatings.

Diamond-like carbon (DLC) films have been proposed as potential coatings for blood-contacting devices. In this study, tetrahedral amorphous carbon (ta-C) films deposited by filtered cathodic vacuum arc system (FCVA) were compared with commercially deposited polyurethane coatings (PU) and uncoated stainless steel samples. X-ray reflectivity (XRR) measurements were performed to check density and thickness of the ta-C coatings, and contact angles measurements were used to assess surface wettability. J774 macrophages were used to assess the cell responses to the materials. Cell number, metabolic activity, and hydrogen peroxide production were measured by using biochemical assays, and the cell attachment and morphology were determined by using scanning electron microscopy and confocal laser scanning microscopy. Wettability measurements showed that of the materials, the stainless steel was the most hydrophilic, and the ta-C coatings were the most hydrophobic. Although the initial attachment and morphology did not appear to be dependent on the wettability, the cell numbers did increase with increasing wettability. Macrophages on the stainless steel samples were the most active in producing hydrogen peroxide. These data show that ta-C samples performed as well as commercial PU-coated samples in blocking cell reactions to the substrate and may prove to be effective coatings for blood-contacting materials.

Animals↗

PubMed2003

Cuspal movement and microleakage in premolar teeth restored with a packable composite cured in bulk or in increments.

INTRODUCTION: The aim of this study was to investigate the effect of two novel curing systems (a plasma arc light, and a 'turbo-boosted' conventional curing light) on cuspal movement and gingival microleakage of 'packable' resin-based composite (RBC) restorations placed in extracted maxillary premolar teeth. MATERIALS AND METHODS: Forty sound extracted upper premolar teeth were subjected to standardised preparation of a large mesio-occlusal-distal cavity before restoration with a RBC. Four curing regimens were used. Either the RBC was placed in bulk and light-cured in one increment using (a). the plasma arc light; (b). the 'turbo-boosted' curing light, or the RBC was placed in eight increments using (c). the plasma arc light; (d). the 'turbo-boosted' curing light. A deflection measuring gauge allowed a measurement of cuspal deflection at each stage of polymerisation. Restored teeth were thermocycled before immersion in a 0.2% basic fuchsin dye for 24 h. After sagittal sectioning of the restored teeth in a mesio-distal plane, the sectioned restorations were examined to assess cervical microleakage. RESULTS: Cuspal deflection measurements were significantly increased when the 'turbo-boosted' halogen curing light was compared with the plasma arc light. Total mean cuspal deflection measurements obtained with incremental cure were significantly increased compared with bulk cure for both light sources. Gingival microleakage for bulk restored teeth was significantly increased compared with teeth restored incrementally. Incremental restoration with the plasma arc light had significantly increased gingival microleakage compared with the 'turbo-boosted' halogen curing light. CONCLUSIONS: The packable composite tested could not be cured adequately to a depth of 5 mm with the plasma arc light within the specified irradiation time. Under the test conditions of the current investigation, bulk curing only appeared to be practical with the high intensity halogen light (40 s activation). Incremental build-up and polymerisation optimised marginal seal for the high intensity halogen light but led to greater cuspal deflection.

Bicuspid↗

PubMed2001

Re-operation for bleeding after thyroidectomy and parathyroidectomy.

BACKGROUND: This study was undertaken to determine the frequency and timing of re-operation for bleeding following thyroidectomy (THY) and parathyroidectomy (PARA) as well as the implications of this concerning the safety of ambulatory surgery. METHODS: Patients requiring re-operation after THY and PARA were identified from a computerized database of patients undergoing surgery between 3/l/95 and 12/31/99. The medical records of these patients were reviewed in detail. RESULTS: Six of 918 THY (0.7%) and 4 of 350 PARA (1.1%) required re-operation for bleeding. In two cases the wounds were opened emergently at the bedside due to worsening airway obstruction. One patient required an emergency tracheostomy. There were no deaths. Excluding one patient who bled five days post-operatively, the time interval from the completion of surgery to the identification of postoperative hematoma ranged from 2 to 48 hours, the median being 16 hours. CONCLUSIONS: Postoperative bleeding is an uncommon but unavoidable complication of THY and PARA. If treated promptly, serious consequences can be avoided. The relatively long interval between the initial operation and the development of the hematoma needs to be considered when recommending the performance of these procedures on an ambulatory basis.

Hemorrhage↗

PubMed2001

The incidence of carcinoma in cytologically benign thyroid cysts.

BACKGROUND: The management of cytologically benign thyroid cysts is controversial. Treatment options include observation, chemical sclerosis, and surgery. This study was undertaken to determine the incidence of carcinoma in cytologically benign thyroid cysts that recur after complete aspiration and to determine the indications for surgery in these patients. METHODS: The medical records of 1189 consecutive patients undergoing thyroid surgery between July 1995 and November 2000 were reviewed. In 34 patients the indication for surgery was a thyroid cyst with benign cytologic findings that refilled at least once after complete aspiration. These patients were selected for further study. RESULTS: The 26 women and 8 men had a median age of 42 years. Fine-needle aspiration cytology was consistent with a benign cyst in all these cases. Final pathologic findings revealed the nodule to be a papillary carcinoma in 4 patients (12%). In another 4 patients (12%) an incidental microscopic papillary carcinoma, separate from the cyst, was identified on final pathologic findings. In all 4 patients with papillary carcinoma the cyst size was greater than 3 cm (range, 3.4 to 5.0 cm). CONCLUSIONS: The incidence of malignancy in cytologically benign thyroid cysts that recur after aspiration is high enough to warrant surgical excision, especially if the cyst is greater than 3 cm in size.

Adult↗

PubMed2001

Utility of PCR in diagnosis of problematic cases of typhoid.

Typhoid is a global problem. Conventional diagnostic methods have limitations. The Widal test gives a high proportion of false positive results, and indiscriminate use of antibiotics has reduced the utility of blood culture. Consequently, these procedures are inadequate for diagnosing suspected cases of typhoid that do not present clear-cut symptoms. We previously showed that PCR-based diagnosis of typhoid targeting the flagellin gene has unparalleled specificity. We assessed the utility of this method for diagnosis of problematic cases of typhoid. A comparative study of PCR, blood culture, and Widal test was carried out on 55 cases of suspected typhoid with fever for 3-30 days and possessing an ambiguous clinical picture. A control group comprised of 20 healthy persons was also included. The respective positive results by PCR, blood culture, and Widal test for these groups were 58.2 and 0%, 14.5 and 0%, and 52.7 and 45%. Sensitivity of PCR as compared with that of blood culture was significantly better. We concluded that PCR is much superior to conventional methods and, due to its high sensitivity and specificity, can be of great use for rapid and definitive diagnosis of problematic cases of typhoid.

Case-Control Studies↗

PubMed1995

Repair of chronic tympanic membrane perforations with long-term epidermal growth factor.

Chronic tympanic membrane (TM) perforation is a common problem worldwide. Recent reports have shown epidermal growth factor (EGF) to stimulate healing in approximately 80% of chronic TM perforations in chinchillas when applied in three doses over 1 week. The objective of this controlled study is to evaluate the efficacy of long-term EGF in the closure of TM perforations. Chronic chinchilla TM perforations were treated with EGF for up to 6 weeks. One hundred percent (17 of 17) of treatment group perforations completely healed. However, two new findings with this long dosing scheme were reperforation on long-term follow-up and three TMs with cholesteatomas. It is likely that reperforation was due to a progressive thinning seen with prolonged EGF application. Long-term EGF use is not recommended for the treatment of TM perforations because of possible wound healing impairment and possible cholesteatoma induction.

Animals↗