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Biomedical subjects

M Pezzoli

Publications and source records attributed to M Pezzoli.

At least 19 recordsLinked to original sources
PubMed1997

[In vitro evaluation of the cytotoxicity of composite resin in the presence or absence of smear layer].

BACKGROUND: The aim of the present research was to investigate the cytotoxicity of the composite resins applied on dentine samples with different smear layer removal, by using cell cultures and LDH determination. MATERIALS AND METHODS: Ninety-eight caries-free third molars recently extracted were used. Transversal sections, 500 mu thick, were obtained. A simulated pulpar chamber was constructed allowing to give lodging in the inferior side to the cell culture and in the superior side to the dentine section with the composite resin. LDH activity was then determined by using a spectrophotometer. BACKGROUND: The results show that the composite resins are surely cytotoxic if directly applied on the dentine. The smear layer is able to reduce the transdentinal diffusion of composite resin toxicity. On the basis of the data obtained it is suggested that in vivo, being necessary to eliminate the smear layer due to its bacterial contents, it is possible in the deep cavities, to partially remove with EDTA maintaining the smear plugs after their disinfection. Nevertheless EDTA application should not exceed 30 seconds.

Cell Culture Techniques↗
PubMed1997

[Study of compression resistance of conventional or passive post and core reconstructed roots].

BACKGROUND: The object of this study is to estimate if the reconstructed roots with passive post and core have a greater resistance to compression in relation to reconstructed roots with traditional post and core. MATERIALS AND METHODS: Experimental situations have been reproduced as close as possible to real clinical situations simulating the cervical edge of the crown with a supporting cervical ring. A comparative analysis of the resistance to compression has been carried out using three groups of roots: the first group constructed from reconstructed roots with traditional post and core; the second group of reconstructed roots with passive post and core; the third group of roots were not reconstructed. RESULTS: Our results have shown that if the root reconstruction includes a metallic support ring that goes beyond the root plate by at least 1 mm there is no difference in the resistance to compression of statistical significance between reconstructed roots with passive post and core and reconstructed roots with traditional post and core. It turns out instead that there is a significant increase in resistance to compression of the reconstructed roots (because of the presence of the cervical support ring) in respect of the third group of unreconstructed roots.

Analysis of Variance↗
PubMed1993

Load transmission evaluation by removable distal-extension partial dentures using holographic interferometry.

Five pairs of bilateral distal-extension removable partial dentures with different clasp designs were constructed on the same dried human mandible in order to compare their load distribution characteristics. The technique of holographic interferometry was used. Among the dentures tested, those with RPI and back action clasps having mesial rests provided the best results from the mechanical point of view. The most unfavourable behaviour was presented by the Akers clasps design. The RPA design and dentures having clasps with continuous MOD rest gave intermediate results.

Dental Clasps↗
PubMed1992

[Epidemiological studies of the dental-periodontal health conditions in 2 samples of the school-age population of the city of Turin].

The paper reports the results of a study of the prevalence of teeth-parodontal diseases found in two groups from the school population, aged between 13 and 19, resident in Turin. The structure of the survey, the clinical methods of collecting data and the statistical processing of data were carried out according to OMS directives regarding the study of oral pathologies.

Adolescent↗
PubMed1991

Influence of corrosion on brazed joints' strength.

The influence of corrosion on the bond strength of different brazed joints commonly used in dentistry has been investigated by means of accelerated immersion tests in artificial saliva buffered at pH 2, and in Ringer's solution, both kept at 37 degrees C. Two Co-Cr base metal alloys were brazed with a gold and a non-precious alloy. After 60 days' immersion the tensile strength of the samples brazed with the gold alloy was dramatically reduced because of galvanic corrosion phenomena. The bond strength of the specimens brazed with the non-precious alloy was largely unaffected. Corrosion products rich in nickel were detected. The electrochemical characterization of the base metal alloys and brazing materials was performed by means of polarization curves in the two media investigated. High short circuit currents were only produced with the gold brazing materials.

Corrosion↗
PubMed1991

Corrosion under static and dynamic conditions of alloys used for magnetic retention in dentistry.

In recent years magnetic retention has gained increasing popularity in dental practice. This investigation compared the corrosion resistance of the palladium-cobalt ferromagnetic alloy (constituent of the keeper cemented on the abutment teeth) coupled with the samarium-cobalt magnets embedded in the removable part of the denture. The behavior of three couples (cobalt-palladium, cobalt-palladium/titanium, and cobalt-palladium/palladium) has been studied. The magnets, because of their poor corrosion resistance, are encapsulated in various materials. To simulate clinical conditions, characterized by the continuous movement of the keeper with respect to the magnet, the experiments were conducted in artificial saliva under intermittent and continuous wear.

Cobalt↗
PubMed1990

[Dentin-dentinal adhesive interaction. Calorimetric measurement].

Among the tests employed to evaluate the bond strength between dentine and dental adhesives (tensile or shear bond strength measurements, marginal leakage measurements) a general accordance on their reliability cannot be found. Calorimetric measurement may be useful in deciding if the adhesion is mechanical or chemical. In this preliminary study, calorimetric measurements have been performed on three adhesive systems commonly employed: Scotchbond, Gluma, Dentin Adhesit. A calorimeter, equipped with reaction vessels which allow the contact between the two reactants after the thermostatisation has been reached, was used. A thermal effect was observed in all cases, greater for Scotchbond and Gluma, poor for Dentin Adhesit. These values are the sum of different contributes of various reaction paths.

Acrylic Resins↗
PubMed1989

Metal-porcelain bonding to a magnetizable alloy.

The bond strength of porcelain to a magnetizable Pd-Co alloy was compared with that of a precious and nonprecious ceramic alloy by using the four-point flexure test and a direct shear test. The test procedure consisted of continuous loading until a bond failure occurred. The fractured surfaces were then examined with a scanning electron microscope. A good strength of the magnetizable Pd-Co alloy comparable to that of two specific ceramic alloys and intermediate between precious and nonprecious alloys was observed. Most of the failures of the precious alloy occurred at the oxide-porcelain interface. The preferential fracture paths were observed for the nonprecious alloy between the metal fracture and the oxide layer. The fractures of the magnetizable alloy occurred at the oxide-porcelain interface and in the bulk of the porcelain, clearly pointing out the possibility of using magnetizable Pd-Co alloy for metal ceramic abutment crowns.

Cobalt↗
PubMed1989

Tensile strength of Cr-Co dental alloys solder joints.

Modifications and repairs of removable partial dentures usually involve solder joints. It is important to know the combination of solder and alloy that will provide the strongest junction. The purpose of this work was to investigate the mechanical strengths of different solders commonly used in dental practice. Specimens of three removable partial denture alloys (Dentitan, Crutanium, Wisil) were soldered with various solders having different melting temperatures. The soldered specimens were subjected to tensile testing, and the fracture surfaces were examined by means of scanning electron microscopy. Most of the failures occurred within the soldered joint, which is the weakest portion of a removable partial denture. Excessive use of flux to achieve an adequate flow of solder produced defects in the solder joint. A relationship was found between joint strength and solder fusion temperature for Crutanium and Wisil--the higher the fusion temperature, the higher the joint strength.

Chromium Alloys↗
PubMed1989

[Magnets used in dentistry. Preliminary data on in vitro biocompatibility].

The biocompatibility of various magnetic materials used in dentistry to secure prostheses was assessed. In vitro cell cultures were performed on coated and uncoated covered and uncovered rare earth magnets. These studies were completed by essays of the lactic dehydrogenase used as an indicator of membrane damage. The various analyses indicate that the magnets in common clinical use are not significantly cytotoxic.

Animals↗
PubMed1989

[A clinical-statistical study on oral health of a sample of young population].

The hygienic-health condition of the oral cavity in a sample of the youth population has been assessed. Eating habits, preventive measures taken with regard to the teeth and condition of the dental arch were all considered. Sociocultural differences were observed in the distribution of the incidence of caries, poor knowledge of correct oral hygiene techniques and little motivation.

Adolescent↗
PubMed1989

[Electrochemical behavior of 3 magnetic alloys used for prosthetic retention].

By means of potentiodynamic techniques the electrochemical behaviour of a ferromagnetic alloy Pd-Co and three types of caps (AISI 316 stainless steel, Pd, Ti) for permanent Sm-Co magnets has been investigated in artificial saliva and in Ringer's solution. In addition short-circuit measurements were performed on several couples Pd-Co/AISI 316, Ti, Pd caps. From our findings a good corrosion resistance of all the materials is evidenced in artificial saliva. In Ringer's solution, which is more aggressive, Pd-Co shows no tendency to passivity.

Cobalt↗
PubMed1989

[Comparative study of manual and mechanical insertion of self-threading parapulpal pins].

Analysis of the traction resistance of 18 TMS Link-Plus self-threading pulp pins (Whaledent Int.) some inserted manually, others using a low-speed device in a group of extracted teeth revealed no statistically significant differences between the two groups. It therefore seems that the tiny fractures observed under microscopic examination are caused by the threading mechanism per se and not by the way it is carried out.

Dental Pins↗
PubMed1988

Retention magnets in guiding plates of distal-extension removable partial dentures.

This investigation studied vertically placed magnets that act simultaneously as guiding plates and retentive devices. The retention of vertically placed magnets was less than that of horizontally or obliquely placed magnets, but comparable to that of I-bar retainers. Load-induced stresses were lower, transmitted more axially to the abutments and were generally more equitably distributed than stresses produced by magnets in other orientations to the abutment tooth. The force distribution characteristics were less stressful than those of a comparable RPD with distal guiding plates, mesial rests, and I-bar retainers. Although the investigators were initially concerned about the relative capabilities of the vertically placed magnets, in vitro and in vivo studies demonstrated that retention was as good if not better than that of conventional clasp designs.

Dental Stress Analysis↗
PubMed1986

Magnetizable abutment crowns for distal-extension removable partial dentures.

A study of the retention and load-distributing characteristics of bilateral distal-extension dentures with magnetizable abutment crowns revealed the following findings: Comparable retention was obtained with the horizontal and oblique pedestals. Decreased retention was noted when there was space between the magnet and pedestal. The retention values were substantially higher than reported values for the I-bar retainer. For the space and no-space situations, the horizontal pedestal design provided better stress results than the oblique design. Better stress-distributing properties for horizontal and oblique pedestals were obtained with the presence of a space between the magnets and pedestals. Of all the designs tested, the horizontal pedestal with a space demonstrated the best load-transmission characteristics.

Dental Abutments↗