Biomedical subjects

M J Braem

Publications and source records attributed to M J Braem.

5 recordsLinked to original sources

PubMed2001

Dynamic elastic modulus of 'packable' composites.

OBJECTIVE: A new type of so-called 'packable', 'condensable' or 'mouldable' composite has been developed and aims at replacing amalgam for posterior restorations. The purpose of the present investigation was to study the dynamic elastic modulus of 12 packable composites, and to follow the evolution of this property following prolonged water absorption. METHODS: Of each material ten rectangular samples (1.5x5x35 mm) were prepared. The elastic modulus (GPa) of each sample was determined with a non-destructive dynamic method using a Grindo-Sonic after 24 h of dry storage at room temperature, and after 24h, 1, 3 and 6 months of wet storage at 37 degrees C. All data were analyzed using two-way ANOVA, Bonferroni/Dunn's test for multiple comparisons and paired t-test with a significance level of p<0.05. In addition, inorganic filler volume percentages were derived from the phenomenological model introduced by Braem et al. [11]. RESULTS: The studied materials varied widely in terms of elastic modulus, ranging between composites classified as Compact-Filled Densified (elastic modulus of 23.4+/-2.4 GPa) and as Microfine (elastic modulus of 8.5+/-2.1 GPa). SIGNIFICANCE: The great diversity observed in the elastic modulus of this type of composites necessitates clear specifications with regard to 'first' the definition of marketing terms such as packable and so on, and 'second' the justified use in posterior teeth.

Analysis of Variance↗

PubMed1996

[Damage to composite restorations].

The expression of damage in dental composite restoratives varies widely, going from some local damage as in attrition facets, to generalized failure or collapes of a restoration. However, crack growth lies on the basis of both aforementioned phenomena. It is therefore of primary importance to gain insight in the way structurally differing materials respond to external stress. It is the aim of the present review to summarize some recent in vitro studies that deal with simulation of wear and fatigue phenomena in dental composite restorative materials.

Composite Resins↗

PubMed1995

In vitro fatigue behavior of restorative composites and glass ionomers.

OBJECTIVES: This in vitro study was conducted to investigate the fatigue behavior of several dental restoratives, including composites, glass ionomers and a resin-reinforced glass ionomer. METHODS: Fatigue was imposed under a reverse stress-controlled regimen, following a staircase approach. Samples were stored and tested under both dry and wet conditions. The following parameters were measured and analyzed: Young's modulus, restrained fracture strength, and flexural fatigue limit. RESULTS: As a general trend, all products showed a decrease in Young's modulus following water sorption. For all products except the resin-reinforced glass ionomer, the same trend was seen in the restrained fracture strength. This is, however, no longer valid for the flexural fatigue limit: the trend is steady-state for the glass ionomers, status quo for the resin-reinforced glass ionomer, and all composites tested show a decrease. SIGNIFICANCE: The diversity in structure of both composites and glass ionomers does not allow findings for one product to be extrapolated to other similar products.

Bisphenol A-Glycidyl Methacrylate↗

PubMed1994

In vitro flexural fatigue limits of dental composites.

The flexural fatigue test equipment developed was used to study the fatigue behavior of dental restorative composites, using a "staircase" approach. Three commercial composites were tested after dry and wet storage conditions. The findings indicate that the method is accurate and reliable, and that changes due to water sorption are clearly reflected: The flexural fatigue limit decreases after water sorption. From the present results it seems that under environmentally controlled conditions, the fatigue behavior is characterized by a well-defined fatigue stress level above which the composites tested fail rapidly, and below which they survive.

Dental Materials↗

PubMed1993

Derangement of composite filler distribution inside syringe-type delivery systems.

Used and almost emptied syringes of two brands of composites contained material close to the pestle-head that appeared to be more granular and dry, as compared to the composite obtained from unused syringes. The present results suggest that a derangement of filler and matrix phases occurred inside the used syringes when compared to unused controls. Stress imposed on the composite material inside the unused syringes resulted in a comparable derangement of filler and matrix phases. Although this derangement was limited, the effect could contribute to intra- and interlaboratory scattering of data.

Analysis of Variance↗