Biomedical subjects

M M Vrijhoef

Publications and source records attributed to M M Vrijhoef.

At least 19 recordsLinked to original sources

PubMed2000

Efficacy of preformed metal crowns vs. amalgam restorations in primary molars: a systematic review.

BACKGROUND: The authors evaluated the treatment efficacy of preformed metal crowns, or PMCs, vs. amalgam restorations in primary molars by means of a literature review and meta-analysis. TYPES OF STUDIES REVIEWED: From a literature search, the authors selected clinical studies that evaluated treatment with PMCs vs. amalgam control restorations in primary molars and provided data against which treatment outcomes could be compared. RESULTS: Ten studies with durations ranging from 1.6 to 10 years fulfilled the selection criteria. Their failure rates, based on need for subsequent treatment or retention of the restoration at final evaluation, ranged from 1.9 to 30.3 percent for PMCs and 11.6 to 88.7 percent for amalgam restorations. Overall, PMCs demonstrated greater longevity and reduced retreatment need compared with amalgam control restorations. The odds ratio for all studies fell within the boundary favoring treatment with PMCs. CLINICAL IMPLICATIONS: Analysis of the literature, though mainly retrospective studies, demonstrated evidence of a more favorable outcome for PMCs than for amalgam restorations in primary molars requiring multisurface restorations.

Crowns↗

PubMed1996

The influence of absolute humidity on shear bond adhesion.

OBJECTIVES: The purpose of this study was to investigate the relationship between dentine shear bond strength, using data from experiments performed according to a standard protocol, and the absolute humidity for a new, fourth generation dentine adhesive system. METHODS: Results of seven recently performed adhesion experiments using the same protocol and product were analysed. Groups of 10 human molars were each bonded in a humidity chamber. The temperature and relative humidity conditions varied from 23 to 37 degrees C and 30 to 95%. After bonding of the composite resin a shear bond test at a crosshead speed of 2.0 mm/min was performed. RESULTS: The bond strength levels of the dentine adhesive system were influenced significantly by extreme temperature and humidity differences. Adhesion levels varied from 27.8 (SD 8.5) MPA to 12.8 (SD 1.4) MPA. Isobond strength curves are a good method to gain insight into the humidity sensitivity of adhesive systems. CONCLUSIONS: Results of in vitro adhesive bonding procedures for a dentine adhesive can be significantly influenced by the absolute humidity levels at which the procedures are performed. Consequently "Materials and Methods" sections of publications should refer to absolute humidity or temperature and relative humidity levels as a relevant parameter.

Acid Etching, Dental↗

PubMed1994

Intraoral humidity during operative procedures.

Results of dentine adhesion studies are influenced by many factors such as intrinsic and extrinsic dentine wetness. Relative air humidity and temperature are extrinsic environmental factors whose influence on dentine bonding capability is not precisely known. It was the aim of this study to gain an understanding of these factors as present in the mouths of patients and as influenced by several variables. In six different experiments the influence of application of a rubber dam, high and low relative humidity in the dental surgery, nose and mouth breathing and tooth drying was investigated. The results show that without application of a rubber dam there was no statistically significant difference in temperature for the variables nose and mouth breathing and tooth drying (mean 27.7 +/- 1.5 degrees C). Only the difference in relative air humidity of the dental surgery was statistically significant. With the application of a rubber dam the relative air humidity and temperature were essentially the same as the dental surgery conditions. It is concluded that without rubber dam the intraoral environment in which bonding procedures are to be performed is comparable with a high humidity climate such as that of Central Africa or the South Pacific.

Analysis of Variance↗

PubMed1993

Loss of enamel due to etching with phosphoric or maleic acid.

In this study, the effect of enamel etching resulting in permanently lost enamel was investigated. Phosphoric acid and maleic acid were used as etchants. Also the etch duration was varied. The results of the study show that phosphoric acid removed significantly more enamel than maleic acid. The relationship found between the loss of enamel and the etch duration suggested that a diffusion controlled mechanism plays a role in the case of both acids. Morphological information obtained by scanning electron microscopy indicated that the surface structure resulting from etching with phosphoric acid and maleic acid is similar.

Acid Etching, Dental↗

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