IADR Abstract Archives
The effect of resin composite pre-heating on monomer conversion
Objective: Recently, pre-heating of resin composites has been introduced as an effective means of increasing paste fluidity and monomer conversion. The aim of this study was to assess the monomer conversion of thermally conditioned specimens prior to light-curing.
Methods: Specimens (6x4x2mm, n=3 per group) were manufactured using the resin composite Tetric EvoCeram (Vivadent) after 5 min conditioning of the paste at temperatures 12, 25, 37, 54 and 68°C just before exposure to a halogen light-curing unit (40s @ 800mW/cm2). Monomer conversion was monitored 5min after irradiation and following 24h storage under dark and dry conditions at 37°C employing micro-MIR FTIR spectroscopy. The percentage degree of conversion (%DC) was measured by the two frequency technique on top and bottom surfaces and normalized vs. the monomer values. Statistical analysis was performed by 3-way ANOVA (α: 0.05).
Results: The results of %DC are listed below:
|
%DC (SD) |
12°C |
25°C |
37°C |
54°C |
68°C |
|
top/ 5 min |
14.5ac (13.5) |
16.6a (5.7) |
22.7abc (8.2) |
26.4abc (7.7) |
31.8c (15.3) |
|
2mm/ 5 min |
13.6a (15.2) |
16.6a (6.0) |
17.9abc (5.3) |
21.5abc (14.2) |
23.3abc (3.3) |
|
top/ 24 h |
41.8cd (5.5) |
41.6cd (5.3) |
51.8de (8.5) |
54.6de (3.7) |
57.7e (4.4) |
|
2mm/ 24 h |
29.9c (2.3) |
40.3cd (3.3) |
47.0de (1.9) |
49.6de (1.0) |
46.0de (2.6) |
Statistical homogenous groups are labelled with same superscript letters.
Conclusions: The hypothesis of improved monomer conversion at elevated temperatures has to be partly rejected since post-curing effects after 24 h led to assimilation of DC. At 5min, a linear correlation of the %DC on pre-heating temperatures (r2 = 0.982 (top)/ 0.924 (2mm)) was found. Improved conversion has been observed after 24 h, regardless of the conditioning temperature.