Thermal diffusion in some polyelectrolyte dental cements: the effect of powder/liquid ratio

Watts, D.C.; Smith, Robert S.

doi:10.1111/j.1365-2842.1984.tb00578.x

Cited by 15 publications

(8 citation statements)

References 14 publications

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“…The rise in thermal diffusivity of the polycarboxylate cement was particularly steep when compared with those of the glass-ionomer cements. The same effect was observed by Watts and Smith (1984) and by Braden (1964) ain Civjan et al (1972) with zinc phosphate and zinc oxide/eugenol cements. Watts and Smith attributed this effect to the fact that most zinc-oxide-based cements contain a small amount of magnesium oxide, 5% in the case of zinc polycarboxylate (Bertenshaw and Combe, 1972).…”

Section: Discussionsupporting

confidence: 86%

“…(1973) gave the thermal diffusivity of magnesium oxide as (.14 cm2 sec-I at 20TC, a high figure when compared with that of 0.0024 cm2 sec, 1 for zinc oxide. Watts and Smith suggested that this exceptionally high diffusivity could perhaps account for a four-fold rise in iffisivity of the polycarboxylate cement, in spiw of magnesium oxide forming only 5% of the -(D ZOE (Braden, 1964) E]-W ZOE (Civjan, 1972) A A ZnPO4 (Braden, 1964) v V ZnPO4 (Ciyjan, 1972) X X Zn POLYCARBOXYLATE (Watts, 1984) + + Zn POLYCARBOXYLATE (Tay) total oxide/powder mixture. However, similar effects are noted in zinc oxide/eugenol cements, where no magnesium oxide is present.…”

Section: Discussionmentioning

confidence: 98%

“…I was noted, indicating that the influences of magnesium oxide and water were probably slight. Additional plots extrapolated from the results of Braden (1964), Civjan et al (1972, and Watts and Smith (1984) are included for comparison.…”

Section: Discussionmentioning

confidence: 99%

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Thermal Diffusivity of Glass-ionomer Cements

Tay

Braden

1987

J Dent Res

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Thermal diffusivity, a property related to the thermal insulative efficiency of a material, was measured in nine glass-ionomer cements and compared with results from a silicate and a polycarboxylate cement. Each cement was mixed at various powder-liquid ratios (P/L) and moulded into a rectangular prism of approximate dimensions 2 cm cube with a thermocouple embedded in it. The prism was immersed in a constant-temperature bath at 1 degree C, and the fall in temperature was observed over a period of three min. Except for the initial and later stages, the plot of the logarithmic difference between external and internal temperatures of each block of cement against time showed a straight line in accord with theoretical prediction. From the slope, the thermal diffusivity of the material was calculated. The values for the silicate, polycarboxylate, and glass-ionomer-metal (cermet) showed a marked rise with increasing P/L, whereas at higher P/L, glass ionomer cements showed gradual change, with values being only slightly higher than the thermal diffusivity of dentin. Glass-ionomer cements are good thermal insulators over a wide range of P/L, and close agreement between experimental and theoretical data shows that glass-ionomer cements are homogenous isotropic materials.

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Section: Discussionsupporting

confidence: 86%

Section: Discussionmentioning

confidence: 98%

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Thermal Diffusivity of Glass-ionomer Cements

Tay

Braden

1987

J Dent Res

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“…the measure of how quickly a material reacts to a change in temperature [14] and showed it to be low for some of the earliest commercial brands of glass-ionomer cement. This study also reported that glass-ionomers were good thermal insulators [14], a finding that has been confirmed in other studies concerned mainly with thermal diffusivity [12,13,23].…”

Section: Discussionsupporting

confidence: 79%

“…These effects relate to the thermal properties of the glass powders in these cements, and showed that increases in the powder:liquid ratio reduce the temperature rise for a given input of heat, but increases the rate at which heat spreads through the material. These effects, particularly for thermal diffusivity, have been confirmed by other workers [12][13][14].…”

Section: Introductionsupporting

confidence: 75%

Heat transfer properties and thermal cure of glass-ionomer dental cements

Gavić

Goršeta

Glavina

et al. 2015

J Mater Sci: Mater Med

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Under clinical conditions, conventional glass-ionomer dental cements can be cured by application of heat from dental cure lamps, which causes acceleration in the setting. In order for this to be successful, such heat must be able to spread sufficiently through the cement to enhance cure, but not transmit heat so effectively that the underlying dental pulp of the tooth is damaged. The current study was aimed at measuring heat transfer properties of modern restorative glass-ionomers to determine the extent to which they meet these twin requirements. Three commercial glass ionomer cements (Ionofil Molar, Ketac Molar and Equia™ Fill) were used in association with three different light emitting diode cure lamps designed for clinical use. In addition, for each cement, one set of specimens was allowed to cure without application of a lamp. Temperature changes were measured at three different depths (2, 3 and 4 mm) after cure times of 20, 40 and 60 s. The difference among the tested groups was evaluated by ANOVA (P < 0.05) and post hoc Newman-Keuls test. All brands of glass-ionomer showed a small inherent setting exotherm in the absence of heat irradiation, but much greater temperature increases when exposed to the cure lamp. However, temperature rises did not exceed 12.9 °C. Application of the cure lamp led to the establishment of a temperature gradient throughout each specimen. Differences were typically significant (P < 0.05) and did not reflect the nominal power of the lamps, because those lamps have variable cooling systems, and are designed to optimize light output, not heating effect. Because the thermal conductivity of glass-ionomers is low, temperature rises at 4 mm depths were much lower than at 2 mm. At no time did the temperature rise sufficiently to cause concern about potential damage to the pulp.

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Dental Restorative Materials

Watts

2006

Materials Science and Technology

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Thermal diffusion in some polyelectrolyte dental cements: the effect of powder/liquid ratio

Cited by 15 publications

References 14 publications

Thermal Diffusivity of Glass-ionomer Cements

Thermal Diffusivity of Glass-ionomer Cements

Heat transfer properties and thermal cure of glass-ionomer dental cements

Dental Restorative Materials

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