Effect of pre-heating on the viscosity and microhardness of a resin composite.
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 degrees C and compared with control groups (24 degrees 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.
Lucey
S
S
Restorative Dentistry, University Dental School and Hospital, Wilton, Cork, Ireland.
Lynch
C D
CD
Ray
N J
NJ
Burke
F M
FM
Hannigan
A
A
D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D003793:Dental Restoration, Permanent / Q000379:methods; D003799:Dental Stress Analysis; D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D014783:Viscosity
D003188:Composite Resins; C467914:TPH spectrum