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Effect of pre‐heating on the viscosity and microhardness of a resin composite
Author(s) -
LUCEY S.,
LYNCH C. D.,
RAY N. J.,
BURKE F. M.,
HANNIGAN A.
Publication year - 2010
Publication title -
journal of oral rehabilitation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 93
eISSN - 1365-2842
pISSN - 0305-182X
DOI - 10.1111/j.1365-2842.2009.02045.x
Subject(s) - indentation hardness , materials science , composite material , composite number , viscosity , hardness , curing (chemistry) , vickers hardness test , significant difference , knoop hardness test , microstructure , mathematics , statistics
Summary The effect of pre‐heating resin composite on pre‐cured viscosity and post‐cured surface hardness was evaluated. Groups of uncured specimens were heated to 60 °C and compared with control groups (24 °C) with respect to viscosity and surface hardness. Mean (SD) viscosities of the pre‐heated specimens ( n = 15) were in the range of 285 (13)–377 (11) (Pa) compared with 642 (35)–800 (23) (Pa) at ambient temperature. There was a statistically significant difference between the two groups ( P < 0·001). Mean (SD) Vickers microhardness (VHN) of the pre‐heated group ( n = 15) was 68·6 (2·3) for the top surface and 68·7 (1·8) for the bottom surface measured at 24 h post curing (specimen thickness = 1·5 mm). The corresponding values for the room temperature group were 60·6 (1·4) and 59·0 (3·5). There was a statistically significant difference between corresponding measurements taken at the top and bottom for the pre‐heated and room temperature groups ( P < 0·001). There was no significant difference between top and bottom measurements within each group. Pre‐heating resin composite reduces its pre‐cured viscosity and enhances its subsequent surface hardness. These effects may translate as easier placement together with an increased degree of polymerization and depth‐of‐cure.