Biomedical subjects

R Mongiorgi

Publications and source records attributed to R Mongiorgi.

At least 19 recordsLinked to original sources

PubMed2005

Fluoride release and absorption at different pH from glass-ionomer cements.

OBJECTIVE: The aim of this study was to evaluate the fluoride release (release-tests) from two glass-ionomer cements (GIC), before and after NaF solution treatment (fluoride treatment) in different pH environments. MATERIALS AND METHODS: After 21 days, every second sample was submitted to fluoride treatment to simulate a fluoride recharge. After fluoride treatment every second sample was submitted to a further three days of long release-tests. Sample surfaces were analyzed by SEM before and after the release-tests in all pH solutions studied. RESULTS: The present study showed that GICs released fluoride ions for the duration of the examination period. For both materials the amount of F(-) released at low pH was considerably greater than at higher pH. The massive superficial breaking up observed by SEM probably promoted the releasing processes. Recharge is possible at different pH levels using NaF solution. CONCLUSIONS: Fluoride release may depend on GICs surface degradation caused by pH in the solution. The use of this kind of material may be an important issue in patients with with low pH saliva and with a high risks caries.

Absorption↗

PubMed1999

The mechanical properties of fluoride-treated bone in the ovariectomized rat.

The effect of fluoride therapy on the osteopenic bone of the ovariectomized rat was studied by comparing the densitometric and biomechanical data. Forty retired breeder female Sprague-Dawley rats aged 10 months were randomly divided into five groups. One group (Group A) was killed at the beginning of the study and was used as a baseline. Three groups were ovariectomized and one was sham-operated (Group B) and observed for the same period as a sham-aged group. A group of ovariectomized rats was used as a sham therapy control (Group C) and received only deionized drinking water; the other two groups (F1 and F2) received L-glutamine monofluorophosphate and calcium at a rate of 1:30 F/Ca at different doses by gavage (0.57 mg F/17 mg Ca per kg/day-Group F1; 0.21 mg F/6.30 mg Ca per kg/day-Group F2). Densitometric and biomechanical (compression and three-point bending test) assays, X-ray diffraction, and Fourier transformed infrared spectroscopy were performed on femoral specimens. Biomechanical data showed that the femoral heads of Group F2 required a significantly greater energy-to-failure than Group C (P < 0.05) as well as treated femoral diaphysis when compared with the others (P < 0.01). Significant increases in the elastic modules were observed in fluoride-treated groups (P < 0.001) when compared with other groups. Diffractometric and spectroscopic data showed the presence of fluorine-apatite in both treated groups with a high component of carbonates. Also, fluoride therapy causes an increase of bone stiffness due to the presence of fluoroapatite. It seems to produce two opposed properties in the osteopenic rat bone: a higher resistance to compression loading and a greater frailty to flexion loading.

Animals↗

PubMed1999

Dentin permeability after toothbrushing with different toothpastes.

PURPOSE: To evaluate the interaction of smear layer produced during brushing and dentifrice particles. MATERIALS AND METHODS: Dentin disks were obtained from extracted human third molars. Dentin permeability was evaluated using a hydraulic pressure apparatus working at 1 psi of pressure. After preparation, each sample was connected to the hydraulic pressure apparatus to evaluate the permeability of dentin with the smear layer produced during specimen preparation. After 5 min of measurements dentin was etched with 37% phosphoric acid gel for 2 min, washed and gently dried with cotton to measure the permeability after smear layer removal. This was done to measure the maximum permeability of each specimen (expressed as 100%). Then a second smear layer was produced using a #400 carbide paper under water for 1 min. Dentin permeability of the smear layer covered dentin was then measured, and expressed as a percent of the maximum permeability of that specimen, permitting each specimen to serve as its own control. The three toothpastes used (Merfluan powder, Merfluan paste and Fluorigard) were applied on dentin surfaces using a small sponge to completely cover the dentin surface. After 5 s, each sample was connected to a mechanical device and brushed under water for 3 min with constant pressure of 250 gr using a Colgate medium toothbrush. After this treatment, each sample was gently washed with tap water, gently air dried for 3-5 s and connected with the pressure apparatus to remeasure the permeability after brushing. For SEM examination of dentin before and after treatment with toothpaste and brushing, each dentin and enamel sample was fixed in 2% buffered glutaraldehyde. RESULTS: Dentin permeability proved unaffected by dentifrice treatments. SEM observations demonstrated the presence of dentifrice particles on dentin surface and inside dentin tubules. Smear plugs produced during dentin brushing were not removed by dentifrices.

Dentin↗

PubMed1999

Calcium phosphates produced by physical methods in the treatment of dentin hypersensitivity.

BACKGROUND: The aim of this paper is to study the properties of innovative materials based on defective calcium phosphates produced by physical methods in the therapy of dentin hypersensitivity. METHODS: In particular, the effects of gels, aqueous solutions and toothpastes containing the above mentioned materials on dentinal permeability measured as dentin hydraulic conductance have been studied. The calcium phosphates have been characterized by X-ray powder diffraction (Rietveld analysis) and Fourier transform infra-red analysis. In addition, scanning electron microscopy has been performed to study the surface of dentin and enamel after treatment with the phosphates. In particular sound occlusal dentin, sound cervical dentin, carious occlusal dentin, sound buccal enamel and carious buccal enamel have been observed. RESULTS: The results have shown that these biocompatible materials can be produced with chemical and physical characteristics very similar to dentin and/or enamel. By forming a protective layer inside and outside the dentin tubuli, the calcium phosphates significantly reduce the dentinal hypersensitivity. CONCLUSIONS: These phosphates seem to be a promising material for clinical application.

Calcium Phosphates↗

PubMed1999

Bioactivity of chitosan in dentistry. Preliminary data on chitosan-based cements.

BACKGROUND: The chemical association of chitosan with inorganic salts, such as calcium phosphate, finds a promising application in dentistry as room-temperature self-hardening cement. We present the physical, chemical and crystallographic characterization of newly-developed cements made of 1) calcium-phosphate and a chitosan gel obtained by acetic acid treatment, and 2) calcium phosphate and a chitosan gel obtained by ascorbic acid treatment. Both cements are self-hardening at room temperature. METHODS: The cements were characterized by X-ray diffractography, scanning electron microscopy and fluorine-selective electrode analysis. RESULTS: The chitosan-hydroxyapatite cements had hardness comparable to spongy bone and above that of PMMA. CONCLUSIONS: The cements are promising for application in endodontics and restorative dentistry.

Biocompatible Materials↗

PubMed1997

[Effects of synthetic salmon calcitonin and alendronate on bone quality in ovariectomized rats].

BACKGROUND: The aim of this study was to assess the effect of calcitonin (CCT) and alendronate (ALN) on bone quality through histomorphometric, histological, densitometric and crystallographic evaluations in an experimental model of osteoporosis obtained in ovariectomized rats. METHODS: The animals were randomly assigned to the treatment with CCT (2 IU/kg/day, N-12) or with ALN (6 micrograms/kg/day, N-12) given subcutaneously, starting three months after ovariectomy: treatment lasted 60 days. Six rats untreated after ovariectomy and other 6 non ovariectomized (intact) were taken as controls. At the end of treatment the animals were sacrificed and femurs explanted for laboratory examinations. Results were evaluated by an ANOVA followed by the Tukey's test when appropriate. RESULTS: The histomorphometric analysis showed a significant increase of the trabecular bone volume and of the cortical bone thickness either with CCT and ALN in comparison with the ovariectomized untreated controls. Optic and electronic microscopy examinations suggest a higher bone remodeling after ALN than after CCT, but accompanied by areas of imperfect mineralization, and more irregular osteon and collagen fibres disposition. The densitometry carried out at the femoral head and diaphysis showed a similar bone mass increase following either CCT and ALN, but significantly higher in comparison to the untreated controls. At the diaphysis level ALN was superior in increasing the bone mass also when compared to the intact rats. The mineralogic exams showed that CCT acted on the re-elaboration of the mineral phase approaching the molar ratio Ca/PO4 to the physiological values typical of senescence, and crystallography revealed that the formation of hydroxyapatite crystals follows a physiological mineral redeposition: those phenomena were not observed for ALN. CONCLUSIONS: In conclusion both CCT and ALN could reduce the bone loss due to osteoporosis, by increasing the bone mass and thickness. Nevertheless the submicroscopic and chemical bone structure are less similar to the physiologic ones after treatment with ALN.

Alendronate↗

PubMed1997

Marginal morphology of Class V composite restorations.

PURPOSE: To evaluate the morphology of enamel and dentin margins of Class V restorations filled with different resin composites and glass ionomer cements by SEM examination of replicas. Microleakage was also evaluated between the restorative materials and dentin and enamel at different levels. MATERIALS AND METHODS: Non-retentive Class V cavities were prepared in extracted third molars on buccal and lingual surfaces at the CEJ level. Each material was used according to manufacturer's directions. Immediately after finishing, an impression of each restoration was made using a polyvinylsiloxane material to obtain an epoxy resin replica. Each replica was inspected under SEM to evaluate the morphology of the margin along the cervical-dentin and incisal-enamel junctions. Each tooth was then stored in dye solution (erythrosin B) for 24 hours. First an evaluation was made along the restoration margins to evaluate circumferential leakage. After longitudinal sectioning, leakage was calculated along the cavity wall in dentin and at the enamel interface (longitudinal leakage). RESULTS: Enamel margins were characterized (SEM) by prism fractures around restorations along with enamel chips and overhangs. These lesions were observed in about 30% of the samples. Dentin margins showed gaps along the dentin-bonding agents and fractures in the bonding agent/composite interface. Glass ionomers showed similar but fewer lesions both at enamel and dentin interfaces.

Adult↗

PubMed1997

[Treatment of dentin sensitivity with stannous fluoride gel. Electron microscopic study and evaluation of dentin permeability].

Dentine hypersensitivity still represent a major clinical problem only partially solved. The presence of exposed opened dentinal tubules has been demonstrated increase the dentine permeability and it is the responsible for pain and sensitivity. Stannous fluoride solution has been recently proposed to reduce dentine hypersensitivity. The aim of the present study was to evaluate the dentinal permeability of a new stannous fluoride gel proposed for the therapy of dentine hypersensitivity. Human extracted teeth have been used and mounted and connected with a hydraulic pressure apparatus working at 1 psi (70 cm of water pressure). It was calculated the permeability of untreated smear layer, treated smear layer (after gel application) and after acidic treatment. It was observed that gel treatment was able to reduce dentine permeability. Scanning electron microscopy demonstrated the presence of a homogeneous smear layer after treatment with gel. This in vitro study confirms that stannous fluoride treatment has the capacity to modify dentine permeability of sensitive dentine.

Dentin↗

PubMed1996

[Experimental osteoporosis caused by estrogen deficiency in rats. Role of a lactose, L-arginine and L-lysine combination in the prevention and therapy].

The role of a lactose, L-arginine and L-lysine association in the treatment of osteoporosis was evaluated in an in vivo model. Fifty Sprague Dawley female rats, 10 months age, were divided into 5 groups: 10 non-ovariectomized animals sacrificed at the beginning of the study (I group); 10 ovariectomized animals (OVX) without treatment and sacrificed at three months (II group); 10 OVX animals without treatment sacrificed at 6 months; 10 OVX animals treated starting from the I post-operative day with the association for three months (IV group, prevention) and 10 OVX animals treated like those of the IV group starting three months after surgery (V group, therapy). Animals were sacrificed in general anesthesia according to the scheduled times for radiologic, densitometric, histologic and mineralogic investigations. Preliminary results, which will need further researches, seem to show a progressive reduction of bone mass after ovariectomy in 10 months female rat and that the pharmacological association given as therapy (V group) may be able to lessen the reduction of bone mineral content.

Animals↗

PubMed1995

Dentine permeability and bond quality as affected by new bonding systems.

OBJECTIVES AND METHODS: The relationship between dentine bonding and the condition of dentine for four dentine bonding systems (All Bond 2, Clearfil Liner Bond, Scotchbond MP and XR Bond) has been examined. Different dentine conditions were evaluated and correlated with adhesion values. Dentine permeability was calculated using a hydraulic pressure apparatus working under physiological pulpal pressure (6.9 kPa), while remaining dentine thickness (RDT) was measured using pincer calipers. Scanning electron microscopic (SEM) examinations were effected to analyse dentine morphology. These evaluations were considered as an index of the condition of dentine. Shear bond strength tests were used to evaluate adhesion. Dentine samples after the bonding systems application were stored for 24 h under pulpal pressure before bond strength was tested. RESULTS: Scanning electron microscopy examinations indicated that the application of bonding system conditioners caused the removal of smear layer, the demineralization of dentine and the formation of a layer of collapsed collagen fibrils in the intertubular and peritubular dentine. Primers were able to infiltrate the collagen fibrils. A layer of resin infiltrated/reinforced dentine (the so-called 'hybrid layer') was observed for All Bond 2, Clearfil Linear Bond and Schotchbond MP. CONCLUSIONS: Significant correlations were observed only for XR Bond, which proved very sensitive to RDT and dentine permeability despite the presence of smear layer. The other three materials did not show any correlation with dentine conditions. By contrast they showed the highest bond values.

Acid Etching, Dental↗

PubMed1995

[A morphological analysis and assessment of the dentinal permeability of detergents and liners].

In this study we evaluated the morphological aspect at scanning electron microscopy (SEM) and the degree of permeability of the dentinal surface after treatment with different detergent solutions, liners and cleansers. In particular we tested new potassium oxalate products. The results obtained with in vitro tests showed that many detergents, liners and cleansers are able to maintain almost unaltered the smear layer, causing small modifications for the diameter and the number of dentinal tubules which are partially exposed. The materials we used were able to deterge the dentinal surface, as demonstrated by SEM analysis, but one of them was able to stabilize and to protect the surface. All tested products, except potassium oxalate, caused an increase in dentinal permeability, proving to exercise a potential by damaging action towards the dentine and the pulpal tissue. Only DDS was able to reduce the dentinal permeability, causing the formation of calcium oxalate precipitates which occlude the dentinal tubules.

Dentin↗

PubMed1994

Scanning electron microscopic evaluation of different endodontic procedures on dentin morphology of human teeth.

Four manual endodontic instruments, an ultrasonic and an endosonic system were studied with a view to evaluating the morphology of the smear layer and the amount of debris and pulpal residues in the apical third of human extracted straight teeth from 55- to 75-yr-old patients. The manual instruments were K files, Ergoflex files used with the step-back technique, Canal Master with its own technique, and Flex-R with the Roane technique. The ultrasonic system was Suprasson Piezo and the endosonic was Excalibur. Human extracted teeth with straight canals were used and examined under a scanning electron microscope. All manual instrumentations showed a homogeneous compact smear layer and no pulp residues. No statistical differences were observed among the four manual techniques. Ultrasonic technique showed the complete removal of the smear layer, leaving small amounts of pulp debris at the apical third, while the Excalibur showed an almost complete elimination of the smear layer, leaving a homogeneous layer of pulpal residues along the canal.

Aged↗

PubMed1994

Pathology from hydroxyapatite deposits in periarticular tissues. First conclusions on etiopathogenesis.

Biopsies of periarticular tissues from patients with episodes of chronic periarthritis were examinated by histological, ultrastructural and chemico-crystallographic methods. In all samples the mineralogical observations at the optical microscope, showed aggregates of microcrystalline incrustations, whose ultrastructural morphology has been characterized by SEM. The histological observations showed necrosis of collagen fibres and microcrystallization process in cavities and in metaplastic fibrocartilage. The HA deposits in the periarticular tissues, in the next stage of the process, are surrounded and demolished by macrophages and multinucleated giant cells. At the same time granulation tissue carries out the repair process, that begins with the formation of thin parallel collagen fibers interposed with many fibroblasts and numerous small vessels.

Biopsy↗

PubMed1994

A new material with theoretical osteoinductive properties: experimental evaluation.

An intensive research for bone substitutes has been in progress for several decades in order to find a new ideal material for bone replacement. In the present study the Authors report some data on a new developed material in comparison with synthetic hydroxyapatite. The new material was characterised by means of a crystallographic spectroscopic and chemical study. An in vitro test was also performed using murine fibroblasts. The results of this preliminary study showed that the sintered material has an and beta-tricalcium-phosphate (TCP) lattice depending on thermal treatment in accordance with literature data. Moreover, it showed a high level of biocompatibility. Though it is still in an investigation stage, perhaps this biomaterial is a highly reactive and unstable compound that could interact with CO2 and H2O.

Animals↗

PubMed1993

Chemical sorbents: official guidelines and experimental approach.

To evaluate the biocompatibility of an anionic exchange resin with active group trimethylammonium and charged with chloride ions an experimental study was performed with different tests to determine cytocompatibility, acute systemic toxicity, intracutaneous reactivity, allergic sensibilization, haemocompatibility and release of acetone, dichloromethane, quaternary amines and heavy metals (Pb, Cu, Cd) in eluate. Thus an anionic exchange resin can link all anionic substances; an ex vivo study on the participation of the dissociated sodic heparin in the anionic exchange was also conducted. In fact every time an extracorporeal circuit is made an anticoagulant must be administered to the patient and the removal of the drug could cause serious haemocoagulative problems. The results of the study showed a high biocompatibility of the resin that did not cause different significant reactions in comparison with negative control substances. The coating of the resin with poly-hydroxy-ethyl methacrilate with a separation phase technique avoided heparin removal from blood. Therefore adjustment of the dosage may not be necessary during further in vivo experiments. Future researches aiming to evaluate the the effectiveness and the biocompatibility of the sorbent in a living being will be performed in the next steps of the study.

Animals↗

PubMed1993

Morphological and structural characteristics of the myopathic bone.

The aim of the present paper was to study the myopathic bone both from the morphological and structural viewpoints. To this end, samples from 8 patients affected by different neuromuscular diseases (DMD, SMA and CMD) have been examined. Thus, by SEM analysis a quantitative reduction of the trabeculae and an increase in porosity of the myopathic bone were found and also, by diffractometric analysis, the presence of pathologic crystalline phases (beta-TCP and beta-TCP-Mg).

Adolescent↗

PubMed1993

Thermodynamical aspects of the polymerization reaction of PMMA cement mixed with phosphatic mineral phases.

The main problem related to the use of polymeric cement in orthopaedics is the high temperature reached during the polymerization, causing necrosis. This paper reports a thermodynamical study of the polymerization reaction of an acrylic cement mixed with powdered phosphatic phases. In particular, mixing of alpha-tricalciumphosphate, beta-tricalciumphosphate and hydroxyapatite was proposed. Important preliminary results indicated that amounts of about 66% by weight of alpha-tricalciumphosphate reduced the polymerization temperature to about 58 degrees C in respect to 100 degrees C of pure acrylic cement. In addition, a special chamber was designed and realized to monitor the temperature variations involved during the polymerization reaction of the different mixtures.

Bone Cements↗

PubMed1993

Chemistry and structure of a new canal sealer showing a dynamical behaviour.

The complete apical seal without percolation and transit of bacteria and their products along the wall of the endodontic canal is the fundamental condition to obtain a lasting result of a correct endodontic therapy. The aim of this study was to characterize a new formulation cement (PROENDO, VEBAS, Italy) with characteristics totally different from the conventional ones. Finally, we can assert that an alloplastic material like PROENDO, which is the subject of this study, bio-compatible, osteo-inductive, non-toxic, with adhesive capacities, is able to quicken the phenomena of restoration and recovery after an endodontic operation.

Calcium Phosphates↗