IADR Abstract Archives
Effect of Lithium-Disilicate thickness on DC and MH of cements
To evaluate conversion degree (DC) and micro-hardness (MH) of a dual- and a light-curing cement under lithium disilicate of different thickness. The null hypothesis is that (1) thickness influence resin cement curing and (2) dual-cements reach higher DC
Method:
60 Lithium Disilicate (E-Max CAD) discs 2cm of diameter, A2 shade LT were prepared and divided into three groups (n=20) according to the thickness: A 0.6 mm; B 1mm; C 1.5mm. Each group wasdivided into two subgroups (n=10) according to the resin cement employed: 1, NX3 dual cement (Kerr); 2 Choice2 light-curing cement (Bisco). A single surface of all samples was treated with 4% phosphoric acid, silane and etch-and-rinse (Optibond FL) adhesive. DC was evaluated with ATR FT-IR spectrophotometer: a 0.2mm cement layer was applied, and samples were placed on the FT-IR light beam. Curing was performed with a multiLED polywave lamp (Valo) for 60sec at 1700mW/cm2 with the lamp in slight contact with the opposite surface towards the cement layer. Once the DC was established, a Vickers Test was performed on the cement with a nano-indentometer. Statistical analysis was performed with ANOVA test (p<0.05)
Result:
means and standard deviations of DC (Table1) and MH (table2)
0,6 mm Dual |
0,6 mm Light-Curing |
1 mm Dual |
1 mm Light-Curing |
1,5 mm Dual |
1,5 mm Light-Curing |
56,98 |
60,62
|
50,64
|
59,55
|
45,40
|
52,32 |
2,64(SD)
|
4,42(SD)
|
12,76(SD)
|
2,50(SD)
|
7,58(SD)
|
6,86(SD)
|
0,6 mm Dual |
0,6 mm Light-Curing |
1 mm Dual |
1 mm Light-Curing |
1,5 mm Dual |
1,5 mm Light-Curing |
35,76 |
61,09 |
31,34 |
57,73 |
36,30 |
52,18 |
4,63(SD)
|
14,30(SD)
|
2,83(SD)
|
4,88(SD)
|
10,51(SD)
|
6,60(SD)
|
Conclusion:
null hypothesis(1) was partially accepted since thickness influences DC only of light curing cements. MH is significantly higher for light curing cement. Null hypothesis(2) was rejected since there is no difference between the DC of the two cements