D C Watts1, B K Kisumbi, G K Toworfe. 1. University of Manchester Dental School, Higher Cambridge Street, Manchester M15 6FH, UK. david.watts@man.ac.uk
Abstract
OBJECTIVES: The aim was to study dimensional time-dependence of resin/ionomer formulations from 5 min age to one month and to separate out the intrinsic setting shrinkage and hygroscopic expansion effects, by using non-aqueous and aqueous storage media, respectively. METHODS: Materials studied included: A: resin-, B: metal- and C: polyphosphonate-modified glass-ionomer cements [GICs]; and controls of D: poly-acid modified composite [compomer]; and E: resin-composite. Separate specimen groups (n = 5) were stored in different storage-media: (i) silicone fluid; (ii) de-ionized water. Experiments were repeated at 23 and 37 degrees C. Volumetric changes of specimens (4 mm diameter x 6 mm height) were obtained via accurate mass measurements (to 10(-4) g), using Archimedes principle, with silicone or water also used as the Archimedean fluid. These measurements were made periodically over a 30 day period, post fabrication. RESULTS: In silicone at 23 degrees C, all materials underwent further gradual intrinsic shrinkage (after 5 min from mix). This was highly significant (p < 0.05) for the RM-GIC (A). At 37 degrees C, however the RM-GIC expanded, indicating that its cure is temperature-sensitive. In water, at 23 and 37 degrees C, the shrinkage was either partially offset (materials C, D, E), or replaced by appreciable expansions (materials A and B). Differences between RM-GIC (A) and MM-GIC (B) were significant (p < 0.05). SIGNIFICANCE: The deployment of dual storage media made an important contribution to the separate analysis of the volumetric changes due to the on-going setting chemistry in these systems and the time-dependent effects of an aqueous environment.
OBJECTIVES: The aim was to study dimensional time-dependence of resin/ionomer formulations from 5 min age to one month and to separate out the intrinsic setting shrinkage and hygroscopic expansion effects, by using non-aqueous and aqueous storage media, respectively. METHODS: Materials studied included: A: resin-, B: metal- and C: polyphosphonate-modified glass-ionomer cements [GICs]; and controls of D: poly-acid modified composite [compomer]; and E: resin-composite. Separate specimen groups (n = 5) were stored in different storage-media: (i) silicone fluid; (ii) de-ionizedwater. Experiments were repeated at 23 and 37 degrees C. Volumetric changes of specimens (4 mm diameter x 6 mm height) were obtained via accurate mass measurements (to 10(-4) g), using Archimedes principle, with silicone or water also used as the Archimedean fluid. These measurements were made periodically over a 30 day period, post fabrication. RESULTS: In silicone at 23 degrees C, all materials underwent further gradual intrinsic shrinkage (after 5 min from mix). This was highly significant (p < 0.05) for the RM-GIC (A). At 37 degrees C, however the RM-GIC expanded, indicating that its cure is temperature-sensitive. In water, at 23 and 37 degrees C, the shrinkage was either partially offset (materials C, D, E), or replaced by appreciable expansions (materials A and B). Differences between RM-GIC (A) and MM-GIC (B) were significant (p < 0.05). SIGNIFICANCE: The deployment of dual storage media made an important contribution to the separate analysis of the volumetric changes due to the on-going setting chemistry in these systems and the time-dependent effects of an aqueous environment.
Authors: Susana María Salazar Marocho; Mutlu Ozcan; Regina Amaral; Luiz Felipe Valandro; Marco Antonio Bottino Journal: Clin Oral Investig Date: 2012-01-13 Impact factor: 3.573
Authors: Cina Mehrvar; Emily Deignan; Mark Hurtig; Gideon Cohen; Paul Zalzal; Oleg Safir; Adel Alhalawani; Marcello Papini; Mark R Towler Journal: J Mater Sci Mater Med Date: 2021-04-29 Impact factor: 3.896