Biomedical subjects

L Breschi

Publications and source records attributed to L Breschi.

36 records · Page 2Linked to original sources

PubMed2001

Evaluation of the F2000 bonding procedure: a high resolution SEM study.

OBJECTIVES: The aim of this study was to define the morphological bonding of the F2000 Restorative System (3M Dental Product) to enamel and dentin. For this purpose, high resolution scanning electron microscope (SEM) in conjunction with a tensile bond strength analysis was used to correlate the morphological findings to the bonding potential. Scotchbond 1 (SB1) adhesive system was utilized as a control. MATERIALS AND METHODS: Teeth were prepared in vivo and prepared as: (1) F2000 PA for 15s, (2) F2000 PA for 30s, (3) 35% phosphoric acid for 15s and SB1 and (4) 35% phosphoric acid for 30s and SB1. All teeth were then restored with the F2000 compomer restorative material, extracted, sectioned and analyzed by means of a field emission in-lens SEM (FEISEM). The conditioning/etching patterns of the two adhesive systems were also evaluated in vitro on dentin disks in order to show high resolution details of every single step of the bonding procedure. RESULTS: FEISEM images showed a repetitive pattern of the enamel crystals with several microporosities after the 30s application of F2000 PA; moreover a good adaptation of the adhesive resin on the conditioned enamel was observable. FEISEM analysis of the dentin surface revealed no evidence of a smear layer after the application of F2000 PA for 30s. Residual smear plugs were partially obliterating the tubule orifices when F2000 PA was used, while they were completely absent after etching with 35% phosphoric acid. The total etching technique revealed open tubules and resin tags formation after the application of SB1. CONCLUSIONS: The one step etching/priming/bonding procedure of the F2000 PA showed favorable results at ultra-structural level when applied on both the enamel and the dentin surface for 30s (as per manufacturers' instructions), but the bond strength analysis showed higher values of bonding of the F2000 compomer when the SB1 adhesive agent (after etching with 35% phosphoric acid) was used (7.7+/-2.2 vs 19.0+/-4.4MPa).

Acid Etching, Dental↗

PubMed2000

Cyclosporin A upregulates phospholipase C beta1 in fibroblasts from gingival overgrowth.

BACKGROUND: In an attempt to evaluate the influence of cyclosporin A (CsA) on fibroblast metabolism, the phospholipase C beta1, (PLC beta1) nuclear expression was evaluated in fibroblasts from heart transplantation patients treated with CsA who exhibited gingival overgrowth (GO) and from controls. METHODS: PLC beta1 was assessed by immunoblotting and immunocytochemistry means. RESULTS: Findings did not show any difference in terms of PLC beta1 expression between the 2 groups when fibroblasts were incubated in media without CsA, while the addition of CsA highly stimulated the fibroblasts from CsA-treated patients compared to controls. The abnormal fibroblastic response in CsA-treated patients was detected both in cells from enlarged gingival sites and in cells from clinically healthy gingival sites. CONCLUSIONS: These results do not explain whether the exaggerated reactivity to in vitro CsA is the consequence of a genetically transmitted susceptibility to CsA that identifies those subjects at risk for developing GO, or whether it is a secondary effect of the long-term in vivo exposure to CsA. However, the present data underline the lack of any close relationship between enhanced fibroblast activity and clinical signs of GO and support the hypothesis that some other factors, together with CsA, are involved in the pathogenesis of CsA-induced GO.

Adult↗

PubMed2000

New trends in dentin/enamel adhesion.

The acid-etch-technique has provided an ideal surface for bonding to enamel by using 30-40% phosphoric acid. The resulting etch pattern is characterized by the profuse formation of microporosities which allow the penetration of monomers into those porosities to form resin tags that provide micromechanical retention. Successful attempts of bonding to dentin in a similar fashion have been reported more recently. Due to the specific properties of dentin, such as its tubular structure and its intrinsic wetness, bonding to dentin has not yet reached the ideal characteristics. In spite of the existing deficiencies in dentin adhesion, the increasing demand for esthetic restorations has generated intensive research on new esthetic materials with special focus on amalgam alternatives. The bonding mechanism of recent dentin bonding agents is based on the penetration of ambiphilic molecules into acid-etched dentin to form a lacework of dentin collagen and polymerized monomers. Dentin adhesive systems that contain a multitude of different bottles of different colors and shapes belong to the past. Because clinicians are increasingly eager to try new materials, the actual tendency calls for simplification of the bonding procedure e.g. one-bottle adhesive systems and all-in-one no-bottle materials. In spite of simpler materials, a separate etching step is still needed for one-bottle systems. Nevertheless, manufacturers of these simplified one-bottle materials recommend their use to bond polyacid-modified composites (compomers) without a separate etching step. The most recent addition to the group of simplified adhesives is the all-in-one no-bottle adhesives; one of these all-in-one systems, Prompt L-Pop (ESPE) has resulted in very promising laboratory results when used on enamel. In spite of the uncertainty about the capacity of all-in-one adhesives to etch enamel adequately in vivo, scanning electron microscopy studies have resulted in an enamel-etching pattern morphologically similar to that corresponding to phosphoric acid-etched enamel. While all-in-one adhesive systems have been reported to result in very satisfactory dentin bond strengths, results from other laboratories suggest that bonding to dentin with all-in-one adhesive systems will need to be somewhat improved. Clinical studies, which are the ultimate test for the acceptance of dentin adhesives, are now underway in several centers. Six-month data showed a very good clinical performance for this ultra-simplified all-in-one adhesive system.

Acid Etching, Dental↗

PubMed1999

Field emission in-lens SEM study of enamel and dentin.

This investigation used field emission in-lens scanning electron microscopy (FEISEM) for the study of tooth surfaces, with particular reference to adhesive bonding and acid conditioning. Dentin wafers with an intact enamel periphery were treated by either ethylenediaminetetraacetic acid (EDTA) (pH 7.4) or phosphoric acid (pH 0.7). The samples were then fixed, sequentially dehydrated in alcohol, and either air- or critical point-dried. After coating, surfaces were examined by FEISEM. For enamel, intraprismatic crystals were clearly recognizable, with the crystals showing both a longitudinal and parallel orientation to the long axis of the prisms. For dentin, the surface ultrastructure (mineral crystals and collagen banding) for the both untreated and treated samples was observed. Fine structures measuring on the order of 6 nm were also observed on samples treated by EDTA. We conclude that FEISEM can routinely provide high-resolution images of enamel and dentin, and that it has the capability of revealing the defined distribution of crystals and collagen fibers in dental tissues.

Acid Etching, Dental↗

PubMed1999

Cusp fracture resistance in composite-amalgam combined restorations.

OBJECTIVE: To evaluate the in vitro resistance to fracture and microleakage in composite-amalgam combined restorations. METHODS: Seventeen Class I cavities with unsupported enamel walls prepared in extracted permanent molar teeth were treated with a bonding agent (Scotchbond MP, 3M Dental), the buccal cusps were reinforced with a composite resin (Z-100, 3M Dental) and the cavities were then restored with amalgam (Permite, Oral B). All teeth were load tested using a special fatigue-stress apparatus, immersed in a dye solution and then sectioned for examination by stereomicroscopy and scanning electron microscopy (SEM). RESULTS: Fractures in enamel supported by composite were present in 11 cases while 12 specimens included fractures in enamel supported by bonded amalgam. Microleakage was observed in 16% of the enamel-amalgam interfaces, 10% of the dentin-amalgam interfaces, 7% of the amalgam-composite interfaces, 4% of the composite-enamel interfaces and 11% of the composite-dentin interfaces. CONCLUSIONS: Bonded amalgam appears to be as effective as bonded composite in supporting undermined enamel in terms of resistance to fracture, but composite may have better marginal adaptation to enamel compared to bonded amalgam. Good marginal adaptation may be observed between amalgam and composite in composite-amalgam restorations.

Adult↗

PubMed1998

Ultrastructural aspects of the DNA polymerase alpha distribution during the cell cycle.

We studied the nuclear topography of the replicating enzyme DNA polymerase alpha in HeLa cells by transmission electron microscopy and field emission in lens scanning electron microscopy. Cells were synchronized at the G1/S-phase boundary and samples of the different phases of the cell cycle were labeled with an anti-DNA polymerase alpha antibody detected by an immunogold reaction. DNA synthesis was detected by immunogold labeling after bromodeoxyuridine administration. The typical labeling pattern of DNA polymerase alpha observed in G1- and S-phase cells was represented by circular structures 80-100 nm in diameter surrounding an electron-dense area. In double labeled samples these circular structures were associated with bromodeoxyuridine-containing DNA replication sites, forming rosette-like structures. Field emission scanning electron microscopy performed on ultrathin cryosections revealed the chromatin fibers underlying DNA polymerase alpha complexes and showed that the size of the rosette-like structures corresponded to the diameter of chromatin foldings. G2- and M-phase cells showed a spread distribution of DNA polymerase alpha. The evidence of DNA polymerase alpha circular arrangement exclusively in G1- and S-phase cells, obtained by such different approaches, allowed us to consider the three-dimensional structures as DNA replication areas.

Bromodeoxyuridine↗

PubMed1998

Immunocytochemical discrimination between early and late S phase: a new approach to the study of gingival epithelium proliferation in rats.

The renewal of the free gingival margin epithelium in rats was studied evaluating 5-bromodeoxyuridine (BrdU) incorporation in proliferating cells by means of an immunocytochemical method. We found a close correspondence between light and electron microscopy patterns of BrdU incorporation at a nuclear level. BrdU was localized in the inner interchromatin regions in cells starting DNA synthesis, while it was localized in the peripheral heterochromatin domains in cells terminating the S phase. This possibility of discriminating cells in early S phase from cells in late S is able to provide far more information as to the time at which a labeled cell starts proliferation than that obtainable with 3H-thymidine autoradiography. This, in turn, permits detection of cells that start proliferation in a wide period of time by means of a single BrdU administration. Rats treated at 7 a.m. demonstrated higher proliferation than rats treated at 7 p.m., supporting the existence of circadian variations in the epithelial renewal. Proliferative events take place by consecutive activation of at least three replication waves, producing clusters of labeled cells which could be observed in rats sacrificed at 10 a.m. In rats treated once with BrdU at 7 a.m., the clusters were localized in both the basal and suprabasal layer of the epithelium; in rats further injected with BrdU at the same time, the clusters increased in size, progressively extending throughout the epithelium. In this way, the renewal of the free gingival margin epithelium does not proceed randomly, but by consecutive activation of discrete units or clusters of basal cells, which then extend to the upper layers. This can be followed at a morphological level as a progression of labeled cells, which move from the basal layer to the epithelium surface in approximately 82-85 hours.

Animals↗

PubMed1995

Effects of acid-etching solutions on human enamel and dentin.

Nine noncarious human molars were extracted and stored in saline solution. Three standard occlusal cavities with beveled enamel margins were prepared on each tooth and etched with the etching solutions of three dentinal adhesive systems: (1) 37% phosphoric acid solution, (2) 4.3% oxalic acid and 2.6% aluminum salts solution, and (3) 10% maleic acid solution. Scanning electron microscopic analysis revealed that all the etching solutions affected the enamel surface morphology. The solution of oxalic acid and aluminum salts removed primarily the prism core material and partially the periphery of the prisms, but did not affect the nonbeveled enamel surface. Phosphoric and maleic acids removed both prism core materials and prism periphery; these specimens also showed areas in which no prism morphology could be detected. These two acids also removed apatite crystals from the prism core of the intact enamel surface.

Acid Etching, Dental↗

PubMed1983