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Biomedical subjects

A Guida

Publications and source records attributed to A Guida.

15 recordsLinked to original sources
PubMed2006

Calcium and zinc ion release from polyalkenoate cements formed from zinc oxide/apatite mixtures.

Calcium and zinc ion release from hydroxyapatite-zinc oxide-poly(acrylic acid) (HAZnO-PAA) composite cements into deionised water was investigated as a function of HA content, PAA concentration, PAA molecular weight and maturation time. At any given maturation time, zinc ion release was constant until the HA content was at the maximum loading (60 wt%) resulting in the cement matrix breaking up, allowing exacerbated ion release. The calcium ion release increased with increased HA content in the composite until the maximum loading where the release drops off. Up to this point, the release of both ionic species was proportional to square root time for the initial 24 hour period, indicating that the release is diffusion controlled. In agreement with related data from conventional Glass Polyalkenoate Cements (GPCs), it is the concentration of the PAA, not the molecular weight, that influences ion release from these materials. However, unlike GPCs, the release of the active ions results in a pH rise in the deionised water, more conventionally seen with Bioglass and related bioactive glasses. It is this pH rise, caused by the ion exchange of Zn(2+) and Ca(2+) for H(+) from the water, leaving an excess of OH(-), that should result in a favourable bioactive response both in vitro and in-vivo.

Apatites↗
PubMed2006

Mechanism of action of sodium hypochlorite and its effects on dentin.

The complex internal anatomy, host defences and the virulence of micro-organisms are important factors to consider in choosing a root canal treatment. The choice of an irrigation solution for use in infected root canals requires an exact knowledge of the micro-organisms responsible for the infective process, as well as the properties of different irrigation solutions in the treatment of teeth with asymptomatic apical periodontitis. Irrigation solutions must have a targeted antimicrobial action and the ability to dissolve organic tissues. Sodium hypochlorite (NaOCl) is the most used irrigation solution in endodontics and, because of its mechanism of action, it causes a biosynthetic alteration in cellular metabolism and a phospholipid destruction, a formation of chloramines which interferes in cellular metabolism, an oxidative action with irreversible enzymatic inactivation in bacteria, and a lipid and fatty acid degradation. However, it must be said that its use is able to remove collagen fibres and thereby to prevent the hybrid layer formation, which is considered by many authors as the fundamental qualification for a correct and adequate adhesion to dentin. The aim of this paper is to examine the mechanisms of action of sodium hypochlorite based on its antimicrobial and physical-chemical properties and to see how its action could interfere in the resistance of dentin adhesion. Scientific research has shown the now attested validity of sodium hypochlorite as an antibacterial agent with a proteolytic action, while other studies made on the adhesion strength on dentin surface have given conflicting results.

Collagen↗
PubMed2004

[Treatment of curved canals: from stainless steel to nickel titanium].

Endodontic treatment of curved canals is always more difficult than straight canals, especially for the apical zone preparation: root canals may present several curvatures in different space directions. From an anatomical point of view root canals with accentuated curvatures are a very frequent event (more than we might think); radiological exams, in fact, give us only a 2D image, and we can observe mesial or distal curvatures but not those in the oral or buccal direction. However, all root canals have curvatures of some degrees; even those that appear straight. Because of this, endodontitis have made many attempts to overcome these problems and manage to have a good preparation in curve canal. The authors analyse all endodontic techniques (step back, step down, crown down, balanced forces) codified in the course of the years, to prepare curved canals; they both in shape or in materials. It's fundamental for the endodontist to have a specific technique to treat curved canals to allow a good, wide preparation; in this way it's possible to make a better and tridimensional filling of the endodontic space above all in the tipical zone.

Dental Alloys↗
PubMed2003

[A SEM analysis of in vivo adhesive interface between a bonding agent and normal or sclerotic dentin].

AIM: Although dentine is a dynamic sub-stratum of the tooth, it seems correct to say that as far as etching and bonding to the sclerotic dentine is concerned, there are different micro-morphological aspects to be analysed in comparison to those on the healthy dentin. METHODS: This paper seeks to analysis the interface between the dentin and the adhesive bonding material resulting from in vivo placement of a 5(th) generation dentin bonding system on the base of cavities in 8 teeth. The teeth were removed for periodontal or orthodontic reasons and then examined by scanning electron microscopy. RESULTS: The results confirm the notable complexity of the dentin-adhesive interface that is developed or formed in-vivo and is due to the different state in which the dentine is found (healthy or sclerotic). CONCLUSION: It is underlined that the passage from the state of healthy to sclerotic dentin is very fast.

Bicuspid↗
PubMed2002

Fluoride release from model glass ionomer cements.

Glass ionomer cements (GICs) are an important class of biomedical material used extensively for color matched mercury free, dental restorations. GICs can release clinically beneficial amounts of fluoride and have acceptable handling properties which make them suitable as dental restoratives. The fluoride release of model GICs produced from specially synthesized fluoro-alumino-silicate glasses was studied. Nine glasses of varying fluoride content based on 4.5SiO(2)-3Al(2)O(3)-1.5P(2)O(5)-(5-Z)CaO-ZCaF(2) were synthesized and cement disks were prepared from them. The glass transition temperature reduced with increasing fluorine content of the glass. Fluoride ion release was measured into distilled water as a function of time for up to 140 days using a fluoride ion selective electrode. The quantity of fluoride released was found to be proportional to the fluorine content of the glass at all intervals time. The cumulative fluoride release was proportional to square root time. Substituting strontium for calcium in the glass had little influence on the fluoride release behavior of the cements.

Journal Article↗
PubMed2002

[Fluoride release properties of GRACs. A survey of the literature].

While numerous publications have documented the anticariogenic properties of GPACs through fluoride release measurements and artificial caries studies, considerable debate still exists concerning the fluoride release properties of these materials in terms of dissolution and diffusion mechanisms. This paper will review some of the more important aspects of GPAC fluoride release. Numerous studies have reported on the fluoride release properties of GPACs. The first point to note is that all the studies were performed on commercial materials. This approach has inherent difficulties as the main factor governing fluoride release is the GPAC composition and formulation. Traditional GPACs are two component systems, consisting essentially of a ion leachable fluoroaluminosilicate glass and a polymeric acid, especially a polycarboxylic acid; fluoride ions are of prime importance in this reaction, in that they have a major influence on the structure of the glass, its reactivity, cement formation and bioactivity. GPACs may be viewed as particle reinforced polymeric composites, in which the degraded residual glass particles with their silicious layer reinforce the polysalt matrix, improving mechanical properties.

Delayed-Action Preparations↗
PubMed2001

[Adolescents at the Lenval's children's hospital emergency unit in Nice in 1999].

OBJECTIVE: The goal of this survey was to investigate adolescents' health through their utilization of a pediatric emergency unit. METHODS: Prospective survey performed one week of each month in 1999 concerning the adolescents' (12 to 18 years) visits to the Lenval's children emergency care unit in Nice. RESULTS: During the study period, 1,096 adolescents were examinated and accounting for 18.6% of the children admitted in the year. The main reasons for visits were injury-related visits (55.5%), non-accidental somatic complaints (38.7%), psychiatric disorders (5.5%), and psychosocial problems (0.4%). Most adolescent visits (68.6%) were not severe emergencies requiring hospital technical equipment support; about one-third of the visits (28.6%) were non urgent consultations; severe emergencies were fewer than 1%; there was no death. Compared with the other pediatrics age groups, adolescents more often used the hospital technical equipment (65.1% vs 45.4%), required a longer visit (62 +/- 33 vs 57 +/- 37 min), and had a higher hospitalization rate (13.4% vs 10.1%). CONCLUSIONS: Adolescent emergency care requires multidisciplinary skills, such as traumatologic, gynecologic, psychiatric, and psychosocial compentence. Two units, absent at Lenval at the time of this survey, seem to be important for good care: space for very short hospitalization in the emergency unit and an adolescent-specific unit in the pediatric ward.

Adolescent↗
PubMed2001

[Main timetables of pediatric emergencies. Experience at the Lenval hospital in 1999].

OBJECTIVE: The purpose of the present study was to determine the main schedules of a visit in a paediatric emergency ward. PATIENTS AND METHODS: A prospective survey concerning the main schedules of the children examined in the paediatric emergency ward of the Lenval's hospital in Nice in 1999 was implemented. The study was conducted over a period of 84 days, one week per month, and included 6038 children analysed recording to the following criteria: 1) duration of the waiting; 2) duration of the radiological period; 3) duration of the medical advice and/or treatment period; 4) total time course of the visit. RESULTS: Data were collected in 66.6% of all cases for waiting (n = 4022), 52.1% for medical advice (n = 3149), in 44.1% for radiological time (n = 833 of 1888 children having radiological examination), in 58.1% for the total time course of the visit. Waiting for not severe emergencies was about one time out of three less than five minutes, more than one time out of two less than 15 minutes, and more than three times out of four less than 30 minutes. Mean radiological time course was 20 to 25 minutes. Mean medical advice was 15 minutes, for medical consultations such as surgical ones. Total time course of the visit was less than 30 minutes in 23.1% of all cases, 30 to 60 minutes in 38.5%, one to two hours in 31.3%, two to four hours in 6.8%, and more than four hours in 0.3% of all cases. Mean total time course of the visit was 45 minutes for medical emergencies and 55 minutes for surgical ones. CONCLUSION: This study shows the main schedules of a visit in a paediatric emergency ward which took care of 26,726 children in 1999. The results of this survey confirmed that waiting before consultation, for not severe emergencies, is sometimes long or very long because of a constant increasing number of patients and their preferential breakdown according to specific periods (weekends, public or school holidays, winter) which are the result of demographic, social and economic changes. At present, the only available possibility to control both phenomena consists in adjusting and adopting medical tools and staffs to crowds and flows. This study also confirms the usefulness for paediatric emergency ward to have a short hospitalization unit.

Appointments and Schedules↗
PubMed1997

Expression of interleukin-1beta in human breast carcinoma.

BACKGROUND: Interleukin 1beta (IL-1beta) is a multifunctional cytokine that up-regulates the inflammatory response. It is not known whether IL-1beta plays a major role in human malignancy. To determine whether IL-1beta might be involved in breast carcinoma progression, the authors measured the IL-1beta content in tissue extracts from >200 invasive breast carcinomas and smaller numbers of ductal carcinoma in situ (DCIS) and benign lesions. METHODS: IL-1beta content was measured by an enzyme-linked immunoadsorbent assay and analyzed to determine whether these values were correlated with the contents of scatter factor (SF) (an invasogenic and angiogenic cytokine), von Willebrand's factor (VWF) (a marker of endothelium), thrombospondin-1 (TSP1) (an antiadhesive and antiangiogenic glycoprotein), and tumor necrosis factor-alpha (TNF alpha) (another proinflammatory cytokine). Studies were also performed to determine whether IL-1beta content was correlated with other pathologic and immunochemical variables that have been utilized or proposed as prognostic indicators for breast carcinoma. RESULTS: The most important findings of these studies were: 1) immunoreactive IL-1beta was detected in approximately 90% of invasive breast carcinomas; 2) IL-1beta levels were significantly higher in invasive carcinomas than in a group of DCIS and benign lesions; 3) high IL-1beta content in invasive carcinomas was significantly associated with higher contents of SF, VWF, and TSP1, but not TNF alpha; and 4) there was a trend toward higher IL-1beta content in invasive carcinomas with a group of other parameters that suggest a biologically more aggressive tumor (estrogen receptor negativity, high tumor grade, p53 positivity, and bcl-2 negativity); and the proportion of invasive tumors with these characteristics was significantly increased in a subgroup of tumors having very high IL-1beta content. The authors also found a correlation between high IL-1beta content and CD68 positivity, suggesting that macrophages may account for some of the IL-1beta present in human breast carcinoma tissue. CONCLUSIONS: These findings suggest that significant titers of IL-1beta are present within the microenvironment of most breast carcinomas and that a high IL-1beta content is often associated with tumor invasiveness and with other pathologic features suggestive of an aggressive tumor biology.

Biomarkers↗
PubMed1995

[Isolated neurofibroma of the common bile duct].

The neurogenic tumors in the biliary tract are rare and usually are amputation neuroma that occur after cholecystectomy. We describe a case of isolated neurofibroma of the common bile duct in a young man not cholecystectomized. The patient suffered recurrent episodes of abdominal pain, vomiting and weight loss without clinical signs of Von Recklinghausen's disease or jaundice. The hepatogram was normal. The echography indicated a solid formation with obstruction of the proximal common bile duct. In the ERCP the stenosis was found. Surgical excision of the tumor and anastomosis of bilateral hepatic ducts and jejunum were carried out. At microscopic examination intraparietal neurofibroma of the common bile duct was found. As isolated entity, we know of only one reported case.

Adult↗
PubMedDate not supplied

[Septic complications of gallbladder lacerations during laparoscopic cholecystectomy].

The iatrogenic gallbladder perforation with bile and, eventually, gallstones loss in the peritoneal cavity happens in the laparoscopic cholecystectomies more frequently than in the laparotomic ones. The authors have reviewed their experience and recent bibliography with the aim to clarify factors that increase risks for this adverse effect; 579 patients subjected to laparoscopic cholecistectomy: in 81 cases (13.98%) the intra-peritoneal perforation of the gallbladder wall has happened, in 26 associated to gallstones loss; 12 of these last have developed abdominal wall infections. No case of intra-peritoneal abscess was observed. The Authors believe to be proper to select patients with the clinical and instrumental evaluation. They identify emergency and flogosis as risk factors for the perforations, as well the systemic illnesses for sepsis. They emphasize the role of antibiotic prophylaxis in the high risk subjects.

Adult↗
PubMedDate not supplied

[Intraoperative cholangiography in videolaparoscopic cholecystectomy: indications, advantages, and limitations].

Consensus doesn't exist about the intraoperative cholangiography specially if is need in every one laparoscopic cholecystectomy either exclusively in case of anatomical doubts or suspect of injures or stones of the common duct. We have considered 450 patient subjected to laparoscopic cholecystectomy during 1992-2000. Patients suspicious to be affected by common duct lithiasis (28 cases) are subjected to ERCP with cleaning of the biliary tree. In 18 patients (4%) it has been necessary the laparotomic conversion; 176 patients (39%) have been subjected to intraoperative cholangiography, selected on anatomical regional disposition or anamnesis and biochemical and instrumental results (history of jaundice or gallstones pancreatitis, abnormal serum level of the biliary stasis biochemistry, common bile duct major of 8 mm, michrolitiasis of the gallbladder). In 7 cases (4%) we have discovered common bile duct stones. We don't attempt intraoperative cholangiography in every one laparoscopic cholecystectomy, but only in cases where we suspect presence of common bile duct stones either iatrogenic injuries or when we retain it necessary to clarify the regional anatomy. Unlikely just in patients where would be more useful, causes major risk of intra- and post-operative complications, it is very difficult, often impossible, to attempt the intraoperative cholangiography. Routinary employing of the intraoperative cholangiography could be useful just for a little number of patients, while selective employing reduce 60% the X-ray. Collaboration with the radiologist is able to reduce the mistaken on the interpretation of the radiograms.

Cholangiography↗