Biomedical subjects

M M Vrijhoef

Publications and source records attributed to M M Vrijhoef.

At least 19 recordsLinked to original sources

PubMed1989

Transverse resistance of composite resin restorations on dentin.

The transverse resistance of a dentin-bonded composite resin restoration was tested. Dentin and enamel surfaces of human molars were pre-treated differently. The specimens were stored for various periods. The presence of enamel led to a transverse resistance significantly higher than when only dentin was present. When enamel was present, additional etching of dentin gave a lower resistance. This was possibly caused by the formation of a soluble monite precipitate. Etching of dentin without the presence of enamel gave a value significantly higher than the bond strength to unetched dentin.

Composite Resins↗

PubMed1989

The corrosion behavior of palladium-silver-ceramic alloys.

Five commercial Pd-Ag alloys were investigated. Their electrochemical behavior was tested with standard potentiodynamic techniques in 0.9% saline solution and an artificial saliva and compared with high-Pd systems. Corrosion characteristics of the Pd-Ag alloys were quite similar regardless of microstructural and compositional differences. In the area of oral interest, all alloys showed a sufficient corrosion resistance. The alloys were, unlike their high-Pd counterparts, adversely affected by a high Cl- content under more extreme conditions, and a visible film formed.

Ceramics↗

PubMed1989

A controlled clinical study of amalgam restorations: survival, failures, and causes of failure.

The survival and modes of failure of amalgam restorations were investigated retrospectively. 2660 Class I or II lesions were restored and evaluated yearly or half-yearly for failures during the 30- to 84-month follow-up. Restorations with unacceptable margins were not counted as failures if no traces of secondary caries could be seen. 8% of the restorations were lost because of patient drop-out. Of the remaining restorations, 1% was replaced due to primary caries. Of the remaining number (2431), 9% failed because of all other reasons. The leading mode of failure was bulk fracture (4.6%), followed by tooth fracture (1.9%), and marginal ridge fracture (1.3%). For all other reasons, 0.8% of the restorations failed. Only two restorations were replaced because of secondary caries. The alloy selection in both conventional and high-copper categories significantly influenced the survival of the restorations for reasons directly related to the restoration.

Dental Amalgam↗

PubMed1989

The corrosion behaviour of high-palladium porcelain-bonding alloys.

The corrosion behaviour of eight commercial high-Pd alloys was investigated and compared to that of Pd-Ag systems. They were tested with standard potentiodynamic techniques in 0.9 per cent saline solution and an artificial saliva. The corrosion behaviour of the high-Pd alloys was satisfactory and essentially equivalent. In more systems anodic overloading in 0.9 per cent saline in this alloy group seemed to be superior compared to the Pd-Ag alloy group. Within the high-Pd alloy systems compositional and constitutional variations were apparently too small to result in substantial electrochemical effects.

Corrosion↗

PubMed1989

Metallurgical aspects of palladium-silver porcelain-bonding alloys.

Metallurgical aspects of five commercial Pd-Ag porcelain-bonding alloys have been investigated using X-ray diffraction, light microscopy and X-ray microanalysis. All alloys are mainly single-phase systems, but they appear to be inhomogeneous due to constitutional supercooling. Porcelain firing times are presumably insufficient to reach homogeneity. Two alloys show a virtually identical chemical composition but a differing amount of segregation which should be attributed to minor components controlling the solid diffusion process. Both indium-containing alloys show signs of a minor second phase which could not be identified due to its finely dispersed character.

Dental Alloys↗

PubMed1989

[Dowel and core systems for endodontically treated molars--in vitro loading].

The restoration of broken down pulpless molar teeth generally implies the provision of a cast post and core with a crown. In this experiment the failure resistance of some restoration methods utilizing amalgam and composite resin was investigated under an oblique load. Significant differences could be detected between the cast dowel and core, the methods utilizing composite resin and the methods utilizing amalgam. All systems could resist forces of more than 1000 Newton.

Crowns↗

PubMed1989

[Dimensional accuracy and stability of the complete denture impression tray].

When recording final impressions for complete dentures, the dimensional stability of the tray material is of significance for the final result. The aim of this study was to measure the dimensional changes in different tray materials prior to and after border moulding. Self-curing acrylic, thermoplastic acrylic and shellac were measured at fixed intervals with the aid of a measuring microscope. The trays were constructed on metal master models with respectively nine reference points for the upper tray and eight points for the lower tray. Self-curing acrylic produces the most contraction as a function of time, followed by thermoplastic acrylic. Shellac exhibits the least contraction c.q. dimensional change. Thermoplastic acrylic material proved to be the most stable after border moulding. Shellac was totally unreliable due to the major changes following border moulding.

Dental Impression Technique↗

PubMed1988