Effect of pre‐heating on the viscosity and microhardness of a resin composite

Abstract

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.

The Effect of Composition, Temperature and Post-Irradiation Curing of Bulk Fill Resin Composites on Polymerization Efficiency

“…In a recent research found that the increase of microhardness of two preheated conventional resin composites at 54 o C in comparison with room temperature specimens ranged from 9.6% to 23.8%. The explanation of this phenomenon may be that preheated RBCs present increased monomer mobility, due to their higher thermal energy, which leads to a lower viscosity and enhanced mobilities of growing chain moieties in the RBC material 37 . As a result, the degree of conversion increases and the surface microhardness, which indirectly expresses this property, also increases.…”

The Effect of Preheating on Light Cured Resin Composites

“…Finally, it increases the degree of conversion. The mechanical properties of the resin composite would go up with the increase of degree of conversion [4][5][6] . However, clinically we couldn't light-cure resins immediately after preheating due to the fact that they also have to be filled, carved.…”

Optimization of Heat-Dried Silane Application for CAD/CAM Ceramic Resin Bonding

“…[5] Film thickness, which is normally limitation with restorative composites resins, can be resolved using preheating. [3][4][5][6]13,22,26,46,48] When using EMAX, group E presented a stable SBS values after aging but was still significantly inferior to that of E/S+. This emphasizes the synergetic effect of etching and silane on that specific ceramic.…”