## 3 Results  
The mean DC values and standard deviations (s.d.) of the five RBC materials placed with the three techniques and polymerized by the LED LCU at the top, middle, and bottom surfaces are shown in Table 3.  
In the study, different DC values were obtained for RBCs placed with the three placement techniques and polymerized by the LED LCU. When RBCs in 2 mm thickness \begin{table}
\begin{tabular}{c c c c c c} \hline
**Placement** & **Surface and** & & & **Mean DC\% \(\pm\) sd of RBCs** & \\
**Technique** & **Depth (mm)** & & & & \\ \hline \multirow{6}{*}{Standard} & \multirow{2}{*}{Top Surface (at 0.5 mm)} & **Micro-Hybrid** & **Packable** & **Ormocer** & **Hybrid** & **Flowable** \\  & & **Filtek Z250** & **Filtek P60** & **Admira** & **Tetric Ceram** & **Tetric Flow** \\ \hline \multirow{2}{*}{Bulk} & \multirow{2}{*}{Top Surface (at 0.5 mm)} & \multirow{2}{*}{48.6 \(\pm\) 0.10 \({}^{\text{A}}\)} & \multirow{2}{*}{62.8 \(\pm\) 0.17 \({}^{\text{B}}\)} & \multirow{2}{*}{51.0 \(\pm\) 0.10 \({}^{\text{Ca}}\)} & \multirow{2}{*}{44.6 \(\pm\) 0.10 \({}^{\text{D}}\)} & \multirow{2}{*}{32.3 \(\pm\) 0.10 \({}^{\text{E}}\)} \\  & Bottom Surface (at 2 mm) & & & & & \\  & Top Surface (at 0.5 mm) & & & & & \\  & Middle Surface (at 4 mm) & & & & & \\  & Bottom Surface (at 8 mm) & & & & & \\  & Top Surface (at 0.5 mm) & & & & & \\  & Middle Surface (at 4 mm) & & & & & \\  & Bottom Surface (at 8 mm) & & & & & \\  & Top Surface (at 0.5 mm) & & & & & \\  & Middle Surface (at 4 mm) & & & & & \\  & Bottom Surface (at 8 mm) & & & & & \\ \hline \end{tabular}  
Means followed by the same capital letters in the column indicate that no statistically significant difference among the different placement techniques at the same surfaces of the same RBC, while same small letters in the row show that no statistically significant difference among the different RBCs placed with same technique at same surfaces at \(p=0.05\) level.  
\end{table} 
Table 3: The Mean DC Values and Standart Deviations of RBCs Tested. were placed with the conventional standard technique, DC values varied from 62.8 \(\pm\) 0.17% to 32.3 \(\pm\) 0.10%. Each RBC exhibited the same DC value at the top (0.5 mm) and bottom (2 mm) surfaces. While the DC values of RBCs in 8 mm thickness placed with a single bulk technique varied from 59.0 \(\pm\) 0.10% to 32.1 \(\pm\) 0.10%, DC values of RBCs in 8 mm thickness placed by four horizontal incremental techniques varied from 53.5 \(\pm\) 0.10% to 29.2 \(\pm\) 0.00%. Different DC values were obtained at the top (0.5 mm), middle (4 mm), and bottom surfaces (8 mm) for each RBC in 8 mm thickness samples placed with bulk and incremental techniques, and the DC gradually decreased from the top surface to the bottom surface. The samples in 8 mm thickness placed with the bulk technique showed a higher DC than those placed with the incremental technique. For all tested surfaces, the highest DC was obtained with packable Filtek P60; ormocer Admira, micro-hybrid Filtek Z250, and hybrid Tetric Ceram followed, respectively, and the lowest DC was obtained by flowable Tetric Flow, regardless of the placement technique. The micro-hybrid Filtek Z 250 and ormocer-based Admira RBCs indicated similar DC values, and flowable Tetric Flow and hybrid Tetric Ceram exhibited significantly lower DCs than the other RBCs at all surfaces, regardless of the placement technique. Two-way analysis of variance (ANOVA) showed that the differences in the DCs of RBCs placed with the standard, bulk, and incremental techniques at the top surface were significant among the RBCs (\(p\) = 0.00 \(<\) 0.05, F = 47.254); however, the difference between the placement techniques was not statistically significant (\(p\) = 0.054 \(>\) 0.05, F = 4.295). Multiple comparisons showed that there was no statistical difference between the micro-hybrid Filtek Z 250 and ormocer-based Admira (\(p\) = 0.209 \(>\) 0.05), but the differences among the other RBCs were statistically significant (\(p\) = 0.00-0.019 \(<\) 0.05).