# Injection Molding of Biodegradable Deciduous Teeth Dental Post
## 3 Results and Discussion
### Characterization of PLA/PCL/ACP Material
#### 3.1.2 Bending Test Results  
A three-point bending test was conducted to evaluate the flexural strength and modulus of the PLA/PCL/ACP composite material. The results indicate a flexural strength of 21.9 \(\pm\) 2.7 MPa and a flexural modulus of 2.08 \(\pm\) 0.13 GPa, as summarized in Table 2.  
Comparing these values with natural deciduous teeth, which exhibit a flexural modulus of 3.63 GPa [31], the PLA/PCL/ACP composite has a lower modulus. However, prior studies emphasize that dental post materials should not exceed the stiffness of natural teeth, as excessive rigidity increases the risk of tooth fractures [31; 32]. [PERSON] et al. [32] demonstrated that using lower-modulus materials for dental posts minimizes stress transmission to the tooth structure, thereby reducing root fracture risks and enhancing the longevity of the restoration. These findings align with the present study, suggesting that PLA/PCL/ACP's inherent flexibility may contribute to better shock absorption and improved clinical outcomes.  
Furthermore, when compared to fiber-reinforced dental posts, which typically have a modulus exceeding 5 GPa [21; 23], PLA/PCL/ACP offers significantly greater flexibility. While fiber posts provide structural reinforcement, their stiffness can potentially concentrate stress on the surrounding dentin, increasing the likelihood of microfractures [21]. The  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Sample \#** & **Flexural Strength (MPa)** & **Flexural Modulus (GPa)** \\ \hline
1 & 19.13 & 1.95 \\
2 & 25.69 & 2.28 \\
3 & 24.87 & 2.16 \\
4 & 19.42 & 2.08 \\
5 & 20.57 & 1.95 \\ Mean \(\pm\) SD & 21.934 \(\pm\) 2.70 & 2.08 \(\pm\) 0.13 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Flexural strength and modulus of PLA/PCL/ACP composites obtained from three-point bending tests.  
Figure 5: Shear viscosity of the PLA/PCL/ACP composite as a function of shear rate at 180 \({}^{\circ}\)C, 190 \({}^{\circ}\)C, and 200 \({}^{\circ}\)C. The temperature-dependent viscosity profiles were used to guide micromolding process settings.  
results of this study indicate that PLA/PCL/ACP may provide a safer alternative for primary teeth applications, as its lower modulus reduces excessive strain on the weakened dentin of deciduous teeth.  
Additionally, research on biodegradable implants suggests that PLA-based materials exhibit promising biocompatibility and controlled degradation behavior [20, 25]. [PERSON] et al. [20] highlighted the potential of PLA in biomedical applications, reinforcing the notion that a biodegradable dental post could facilitate natural healing while avoiding complications associated with permanent implants. Similarly, [PERSON] et al. [25] demonstrated that blending PLA with PCL can improve mechanical properties while maintaining flexibility, further supporting the viability of PLA/PCL/ACP as an optimized dental post material.  
In summary, the mechanical properties of PLA/PCL/ACP suggest that it is a suitable candidate for deciduous teeth applications, as its lower modulus reduces the risk of tooth fractures while maintaining sufficient structural integrity. The findings of this study align with prior studies in the literature supporting flexible post materials, reinforcing their potential in pediatric dentistry. To further contextualize its clinical relevance, a broader comparison with commercially available fiber posts, biodegradable PLA-based systems, and conventional metallic posts is presented in the following section.