Biomedical subjects

B Van Meerbeek

Publications and source records attributed to B Van Meerbeek.

9 recordsLinked to original sources

PubMed1992

Marginal adaptation of four tooth-coloured inlay systems in vivo.

This study investigates the margin quality of four different tooth-coloured inlay systems using computer-aided quantitative margin analysis under scanning electron microscopy. Three types of restorations involved chairside procedures using a commercial CAD-CAM apparatus: one type of inlay restoration was milled from preformed glass ceramic blocks, the other two inlay types were milled from preformed porcelain blocks. The fourth system was based on an experimental indirect composite inlay system. Each inlay type was luted with its respective dual-curing luting composite, which was supplied with the system. After 6 months of clinical service, all four systems revealed a significant percentage of submargination indicating occlusal wear of the luting composite. The porcelain inlays and the composite inlays luted with their respective experimental luting composite showed the best marginal adaptation. Luted glass ceramic inlays, in particular, suffered from a significantly higher percentage of inlay margin fractures (9 per cent) and marginal openings (4 per cent) than the other systems. A possible explanation is that the glass ceramic subsurface structure at the inlay-lute interface was weakened by etching with ammonium bifluoride.

Acid Etching, Dental↗

PubMed1992

Marginal accuracy of CAD/CAM inlays made with the original and the updated software.

The software driving the Cerec CAD/CAM system has recently been updated. In this study, the marginal accuracy of computer-machined porcelain inlays was determined using the original and the updated software. Two types of MOD cavities in Frasaco resin teeth were prepared with either sharp or rounded box corners. The distance of the occlusal and proximal marginal interface was determined using a measuring microscope. The mean occlusal interfacial distance was 52 microns for both programs. Only the box corners showed a significantly larger space, of which the mean value was approximately 200 microns. The updated version improved the marginal accuracy at the box corners. Further reduction of the interfacial distance was accomplished by rounding the sharp box corners.

Bicuspid↗

PubMed1992

Morphological aspects of the resin-dentin interdiffusion zone with different dentin adhesive systems.

Cross-sections of resin-dentin interfaces were etched with an argon-ion beam to make their substructure detectable by scanning electron microscopy. The dentin adhesive systems were categorized morphologically into three groups, and an attempt was made to clarify their adhesive mechanism. The first group of products removed the smear layer. The argon-ion bombardment clearly disclosed a hybrid or resin-impregnated dentin layer. It is hypothesized that conditioning with acidic or chelating agents demineralized the dentin surface-layer to a certain depth, leaving behind a collagen-rich mesh-work. Hydrophilic monomers are then believed to alter this collagen-fiber arrangement in a way that facilitates penetration of the adhesive resin, resulting in a mechanical, intermingled link between collagen and the adhesive resin. The second group preserved the smear layer. In this case, the dentinal tubules were obliterated with globular particles at their orifices and remained patent underneath these smear plugs. This type of adhesive system aims at the incorporation of the smear layer into the hydrophilic monomers, which have an affinity for the organic and/or inorganic components of the underlying dentin. Finally, a third, small group only partly dissolved the smear layer, creating a thin resin-impregnated dentin layer and a resin-impregnated smear plug. This study clearly showed that the application of recent adhesive systems induced structural changes in the dentin surface morphology, creating a retentive interface, called the inter-diffusion zone, between the deep, untouched dentin layers and the composite filling material. This resin-dentin interdiffusion zone offers bonding sites for copolymerization with the resin composite and, concurrently, might have protective potential for the pulp tissues.

Acid Etching, Dental↗

PubMed1992

Factors affecting adhesion to mineralized tissues.

The objective of this paper is to review the literature concerning factors affecting adhesion to mineralized tissues. Factors related to the physicochemical structure of the adherents and to the inherent properties of composite restorative materials, along with the postulated bonding mechanisms of current adhesive systems, are discussed.

Acid Etching, Dental↗

PubMed1992

Dentin- and enamel-bonding agents.

The introduction of bonding agents in restorative dentistry has made it possible to adhere restorative materials to tooth structure. Since bonded restorations were introduced by Buonocore in 1955, extensive research has been conducted to develop systems that bond equally effectively to enamel and dentin. Researchers have identified a micromechanical retention mechanism for the attachment of hydrophobic resin restorative materials to both enamel and dentin that works if appropriate conditioning or priming steps are applied. At the dentin site, the modes of action of current adhesive systems converge to create a resin-dentin interdiffusion zone between the deep dentin structures and the filling material. To incorporate or remove the smear layer in this interdiffusion zone, different adhesion strategies are followed to obtain a resin-dentin bond. In the clinical situation, these modern dentin-bonding systems are more technique sensitive; the thickness of the interface, its elastic capacity, the polymerization efficiency and initiation of the bonding agent, and, finally, the application technique used for the restorative material play an important role in the final result.

Acid Etching, Dental↗

PubMed1991

Radiopacity of composites compared with human enamel and dentine.

A 99.5 per cent pure aluminium step-wedge served as reference for evaluating the radiopacity of 55 anterior and posterior composites. The radiopacity of all materials evaluated was compared with the radiopacity of human enamel and human dentine of equivalent sample thickness. Seventeen composites exhibited a radiopacity significantly greater than that of enamel. Some composites intended for posterior use lack the radiopacity required for posterior composite restorations.

Analysis of Variance↗

PubMed1991

Trends in the selection of dental filling materials.

In 1983 and 1988 a questionnaire was sent to a random sample of Belgian dentists to compare the selection of filling materials such as amalgam and gold with the tooth-coloured filling materials, composites and glass polyalkenoate (ionomer) cements, for the restoration of Class II lesions in premolar and permanent molar teeth. Despite the increasing demand for aesthetics to be considered, the use of composite resins in the posterior region only increased moderately over the assessment period, while amalgam maintained its leading position as the restorative material of choice in premolar and molar teeth. Only in situations where aesthetics played a primary role did composite resins gain over silver-based fillings. There was no change in the use of gold as an indirect restorative material. Finally, the selection rate of glass ionomers increased slightly.

Acid Etching, Dental↗

PubMed1990

[Marginal adaptation of posterior composites. A complex clinical problem].

In this article, the authors deal with the problem of marginal fit for posterior composites, where direct class-II aesthetic restoration is involved. For different materials, they analyse and discuss the influence of their physicochemical properties, the contour of preparations, and composite handling. Three types of clinical cases are described: preparation using the tunneling technique, adhesive preparation, conventional preparation.

Bicuspid↗

PubMed1990

[Dental adhesion: foundations and clinical results].

Adhesion is one of the most frequently used words nowadays in dentistry. Although our knowledge on adhesion continues to improve daily, the situation is, however, far from understood. There is still confusion over what adhesion really is, what it means, and how it should be evaluated. The first part of this article deals with the general principles of adhesion and the specific within the dental profession over the clinical efficiency of available adhesive dentinal restorative systems. The second part of this paper presents the 2-year in-vivo results of four commercially available dentinal adhesive systems. From this trial, it seems that the more recent approach in obtaining adhesion to dentine is the most promising in terms of retentive capacities.

Adhesiveness↗