## 3 Results
### Dosimetric Comparison  
The dose distribution and dosimetry were reviewed as follows with the PTV D100%, PTVmax, PTVmin, CI, and HI of PTVH. The mean dose of the oral cavity and V26 of the bilateral parotid glands were also evaluated. For Patient 1, who was diagnosed with tongue cancer, cT2N0M0, stage II, he received composite resection for the primary tumour and neck lymph node dissection with pT2N0 Mb, stage II. Adjuvant RT was arranged for perineural invasion. The PTVH was the surgical bed of the primary tumour with margins. The dosimetry, when silicone 3D-printed bite blocks were used, showed better coverage of the PTVH and surface of the oral tongue than when conventional universal oral corks were used. The CIs of the PTVH of the plan with 3D printed bite blocks was 0.96, compared to the plan with conventional oral corks, 0.94. The HIs of the PTVH were 1.13 and 1.12. The median dose for the oral cavity was 45.7 Gy and 48.6 Gy (Table 1). The isodose line in 95% of the prescribed dose to the PTVH showed better coverage when silicone 3D printed bite blocks were used than conventional oral corks in the RT process (Figure 4a versus Figure 4b with arrowhead indicated). The dose scattered to the oral cavity was lower when silicone 3D printed bite blocks were used than conventional oral corks. The radiation dose and hot spot of the oral tongue were higher with better constraints of adjacent normal tissues when silicone 3D printed bite blocks functioned as boluses (Figure 4). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Patient 1** & **3D Printed Bite Blocks** & **Conventional Oral Corks** \\ \hline PTV D100\% & 95\% & 95\% \\ PTVmax & 107\% & 106.2\% \\ PTVmin & 82.7\% & 76.8\% \\ CI & 0.96 & 0.94 \\ HI & 1.13 & 1.12 \\ Median dose of oral cavity & 45.7 Gy & 48.6 Gy \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Dosimetry of Patient 1. Figure 4: _Cont._Patient 2, who was diagnosed as having left tonsil cancer, received an operation and a positive margin was noted in pathologic review. Adjuvant RT was arranged. The PTVH was the surgical bed of the primary tumour with margins. Dosimetry with the silicone 3D printing bite block showed similar distribution in PTVH to that with the conventional oral cork. In the DVH analysis, the RT dose, which scattered to adjacent normal tissues, such as bilateral parotid glands, was lower using the silicone 3D printing bite block than with conventional oral cork. The CIs of the PTVH of each plan were 0.99 and 1.00, and the HIs of the PTVH were 1.08 and 1.12. The HI was lower with 3D printed bite blocks, indicating a higher homogeneity. The V26 of the right parotid gland was 38% and 70%, and V26 of the left parotid gland was 34% and 68% (Table 2). The radiation dose to the bilateral parotid glands was lower with silicone 3D printing bite blocks (Figure 5). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Patient 2** & **3D Printed Bite Blocks** & **Conventional Oral Corks** \\ \hline PTV D100\% & 98\% & 97\% \\ PTVmax & 103\% & 106.1\% \\ PTVmin & 90.3\% & 89.3\% \\ CI & 0.99 & 1.00 \\ HI & 1.08 & 1.12 \\ V26 of right parotid gland & 38\% & 70\% \\ V26 of left parotid gland & 34\% & 68\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Dosimetry of Patient 2. Figure 4: Dose distributions of Patient 1 with two plans with silicone 3D printed bite blocks or conventional oral corks. **(a)** Dosimetry with the silicone 3D printing bite block showed better coverage of the PTVH and surface of the residual tongue compared to **(b)** that with the conventional oral cork. **(c)** In the DVH analysis, the radiation dose of the PTVH and residual tongue was higher and seemed to indicate that a lower dose had scattered to the oral cavity with the silicone 3D printing bite block than **(d)** with the conventional oral cork. Figure 5: Dose distributions of Patient 2 with two plans with silicone 3D printed bite blocks or conventional oral corks.