**3.1 Silicone/powder ratio by weight**

As the starch powder implicated in fabrication of 3 dimensional soft tissue prostheses, it was necessary to determine the average amount of this powder within the total weight of prosthesis and their percentages by weight in the final prosthesis. in this investigation, 8 printed blocks of the starch powder (45 × 45 × 4 mm) were produced by Z510 printer. The blocks weighed using a sensitive digital balance (Mettler AJ100). Then the samples infiltrated with Sil-25 maxillofacial silicone polymers according to infiltration protocol mentioned in the previous section (3 bars for 25 minutes left for 25 hours) final setting time. Then the infiltrated blocks weighed again and percentage of each component within an infiltrated block was determined. **Table 2** shows weight in gram, standard deviation and percentage of each component. The powder adds up to 40% of the total weight of the fully infiltrated blocks, whereas the silicone polymers comprising only 60%.


**Table 2.**

*Percentage of silicone polymers and starch powder in fully infiltrated blocks.*

## **3.2 Depth of infiltration of the silicone polymers into 3D printed facial prosthesis**

As the printed starch models produced by the Z-Corp printer are solid and fragile, therefore, it was necessary to apply a specific protocol for infiltration of the silicone polymers into the printed models. For this purpose a set of 30 cubes measuring 20 × 20 × 20 mm were printed in starch, using Z-Corp (Z510) 3D printer, the starch cubes were infiltrated with Sil-25 maxillofacial silicone polymer under different conditions. One group served as control group, the cubes were infiltrated with Sil-25 maxillofacial silicone polymers, ratio (1–10) according to manufacturing standard. The cubes were then submerged in the polymer mixture and left under atmospheric air pressure at room temperature for a scheduled time, 5 minutes (*n* = 6), 10 minutes (*n* = 6), 15 minutes (*n* = 6), 20 minutes (*n* = 6) and 25 minutes (*n* = 6), and then left to set for 24 hours. The cubes then bisected with surgical blade No. 11. The inner part of the cube stained to color and highlight the non-infiltrated parts of the cubes in order to measure infiltration depth of the silicone polymers inside the cubes (**Figure 8**).

Three other groups were served as test groups, testing infiltration depth was repeated on 30 cubes measuring 20 × 20 × 20 mm for each test group, but in this group the cubes were placed in a pressure vessel under 1, 2 and 3 bars pressure for a similar time schedule, 5 minutes (*n* = 6), 10 minutes (*n* = 6), 15 minutes (*n* = 6), 20 minutes (*n* = 6) and 25 minutes (*n* = 6). After 24 hours the cubes were bisected and the inner part of the cubes colored then Traveling microscope (Mitutoyo TM) with X-Y coordinate, used to measure the infiltration depth, 12 measurements on each sectioned cube (**Figure 9**).

Result of this study is shown in **Figure 10** and **Table 3**, minimum depth of infiltration was detected under normal atmospheric pressure and room temperature, which was around 1 mm, this was slightly affected by length of time the cubes staid sank in the silicone polymers. Whereas, 2 and 3 bars pressure increased the infiltration depth of the silicone polymers significantly, which was also affected by length of time. Maximum infiltration depth was recorded for 3 bars pressure and at 25 minutes time. Results showed that pressure and time have significant effect on the depth of infiltration of the silicone polymers inside the powder cubes. Two ways ANOVA implied significant differences (*p* < 0.05) between the three groups of the current study, normal pressure, 2 and 3 bars pressure.

#### **Figure 8.**

*Bisected cubes stained to identify the depth of infiltration of silicone polymers, the dye is taken up by the hydrophilic starch, whereas the infiltrated area is hydrophobic and does not take up the dye.*

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facial prostheses.

tissue facial prostheses.

*Optimization of Maxillofacial Prosthesis DOI: http://dx.doi.org/10.5772/intechopen.85034*

*measurements on each sectioned cube.*

**Figure 9.**

**Figure 10.**

According to result obtained from this study, it can be concluded that infiltration depth of Sil-25 silicone polymers is significantly influenced by pressure applied. Under 3 bars and 25 minutes time, the infiltration depth recorded more than 8 mm from all sides, this would suggest that infiltration depth inside a prosthesis would be around 16 mm and reasonably this depth will be sufficient for soft

*Infiltration of Sil-25 under normal air, 2 and 3 bars pressure and 5-time schedule.*

*Traveling microscope (Mitutoyo TM) with X-Y coordinate, used to measure the infiltration depth, 12* 

**3.3 Quality of infiltration of the elastomer into 3D printed facial prosthesis**

Evaluation of the infiltration quality of silicone polymers inside the 3D printed starch powder was required to characterize the interaction between the hydrophobic silicone polymers and the hydrophilic starch powder. It is acknowledged that the mechanical and optical properties of the 3D printed prostheses depend basically on material properties and characterization, which consequently determine the service life of the prostheses and determine its ability to resist the environmental factors such as UV from sunlight humidity, body secretion and weathering temperature. The previous section determined depth of infiltration of the infiltrate inside the printing powder, 8 mm penetration depth was achieved. However, we did not realize how consistent/homogeneous this infiltration was. Therefore, SEM was carried out to characterize an important aspect of 3D color printing facial prostheses and to detect any flaw in the structure of the composite that is utilized in fabrication of

#### **Figure 9.**

*Prosthesis*

**Table 2.**

**3.2 Depth of infiltration of the silicone polymers into 3D printed facial prosthesis**

**Starch Starch + Silicone pressure Starch Silicone pressure** 3.5 ± 0.04 8.50 ± 0.07 41.5% 58.5%

**Weight in gram and SD % By wight**

*Percentage of silicone polymers and starch powder in fully infiltrated blocks.*

As the printed starch models produced by the Z-Corp printer are solid and fragile, therefore, it was necessary to apply a specific protocol for infiltration of the silicone polymers into the printed models. For this purpose a set of 30 cubes measuring 20 × 20 × 20 mm were printed in starch, using Z-Corp (Z510) 3D printer, the starch cubes were infiltrated with Sil-25 maxillofacial silicone polymer under different conditions. One group served as control group, the cubes were infiltrated with Sil-25 maxillofacial silicone polymers, ratio (1–10) according to manufacturing standard. The cubes were then submerged in the polymer mixture and left under atmospheric air pressure at room temperature for a scheduled time, 5 minutes (*n* = 6), 10 minutes (*n* = 6), 15 minutes (*n* = 6), 20 minutes (*n* = 6) and 25 minutes (*n* = 6), and then left to set for 24 hours. The cubes then bisected with surgical blade No. 11. The inner part of the cube stained to color and highlight the non-infiltrated parts of the cubes in order to

measure infiltration depth of the silicone polymers inside the cubes (**Figure 8**). Three other groups were served as test groups, testing infiltration depth was repeated on 30 cubes measuring 20 × 20 × 20 mm for each test group, but in this group the cubes were placed in a pressure vessel under 1, 2 and 3 bars pressure for a similar time schedule, 5 minutes (*n* = 6), 10 minutes (*n* = 6), 15 minutes (*n* = 6), 20 minutes (*n* = 6) and 25 minutes (*n* = 6). After 24 hours the cubes were bisected and the inner part of the cubes colored then Traveling microscope (Mitutoyo TM) with X-Y coordinate, used to measure the infiltration depth, 12 measurements on

Result of this study is shown in **Figure 10** and **Table 3**, minimum depth of infiltration was detected under normal atmospheric pressure and room temperature, which was around 1 mm, this was slightly affected by length of time the cubes staid sank in the silicone polymers. Whereas, 2 and 3 bars pressure increased the infiltration depth of the silicone polymers significantly, which was also affected by length of time. Maximum infiltration depth was recorded for 3 bars pressure and at 25 minutes time. Results showed that pressure and time have significant effect on the depth of infiltration of the silicone polymers inside the powder cubes. Two ways ANOVA implied significant differences (*p* < 0.05) between the three groups of the

*Bisected cubes stained to identify the depth of infiltration of silicone polymers, the dye is taken up by the* 

*hydrophilic starch, whereas the infiltrated area is hydrophobic and does not take up the dye.*

each sectioned cube (**Figure 9**).

current study, normal pressure, 2 and 3 bars pressure.

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**Figure 8.**

*Traveling microscope (Mitutoyo TM) with X-Y coordinate, used to measure the infiltration depth, 12 measurements on each sectioned cube.*

#### **Figure 10.**

*Infiltration of Sil-25 under normal air, 2 and 3 bars pressure and 5-time schedule.*

According to result obtained from this study, it can be concluded that infiltration depth of Sil-25 silicone polymers is significantly influenced by pressure applied. Under 3 bars and 25 minutes time, the infiltration depth recorded more than 8 mm from all sides, this would suggest that infiltration depth inside a prosthesis would be around 16 mm and reasonably this depth will be sufficient for soft tissue facial prostheses.

## **3.3 Quality of infiltration of the elastomer into 3D printed facial prosthesis**

Evaluation of the infiltration quality of silicone polymers inside the 3D printed starch powder was required to characterize the interaction between the hydrophobic silicone polymers and the hydrophilic starch powder. It is acknowledged that the mechanical and optical properties of the 3D printed prostheses depend basically on material properties and characterization, which consequently determine the service life of the prostheses and determine its ability to resist the environmental factors such as UV from sunlight humidity, body secretion and weathering temperature. The previous section determined depth of infiltration of the infiltrate inside the printing powder, 8 mm penetration depth was achieved. However, we did not realize how consistent/homogeneous this infiltration was. Therefore, SEM was carried out to characterize an important aspect of 3D color printing facial prostheses and to detect any flaw in the structure of the composite that is utilized in fabrication of facial prostheses.


**Table 3.**

*Infiltration depth of Sil-25 inside 3D printed starch blocks under different pressure and at different time schedule.*

#### *3.3.1 Slide preparation for SEM*

Scanning Electron Microscopy SEM was applied for this purpose to prepare and obtain various samples of printed starch blocks infiltrated with two different maxillofacial silicone polymers (Sil25 and Promax 10) in order to examine the quality of the infiltration inside the starch printed blocks. SEM pictures of the printed blocks were compared with hand mixed of 40% starch powder and 60% Sil25 silicone polymers. Hand mixed blocks were prepared by mixing the starch and the silicone polymers for 1 minute to obtain a homogenous mixture, then the mixture poured into a 75 × 75 × 4 mm stainless steel mold, pressed and left for 24 hours in ambient temperature. Then slices from the three blocks were prepared using surgical blade number 11 and send for SEM to be examined with SEM of starch powder alone.

#### *3.3.2 SEM interpretation*

SEM analysis of the starch powder, 3D printed blocks infiltrated Sil-25 and Promax10 plus the hand mixed blocks are shown in **Figure 11**, the SEM of the powder and of the infiltrated powder blocks showed amorphous, non-crystalline shaped particles with different particle sizes varies from very small to relatively large particles. These particles appeared to be loosely arranged and randomly orientated with some spaces in between these particles and disorganized spreading of the starch powder within the silicone polymers leaving big gaps between the powder particles. Incorporation of starch powder with Sil-25 maxillofacial silicone and Promax10 under 3 bar pressure are seen in **Figure 11A** and **B**, showing almost similar distribution of the powder within the infiltrates. However, better incorporation and more homogenous distribution of starch particles within the silicone polymers in hand mixed of 40% powder incorporated into 60% infiltrate of silicone polymers by weight (**Figure 11C**). This could be attributed to the layer of binder on the outer surfaces of the printed blocks that might an obstacle for the infiltration process.

#### *3.3.3 Final analysis of SEM*

**Figure 12** is a magnified SEM image (×707) of hand mixed starch powder and Sil-25 silicone polymers. Although at a lower magnification the sample apparently seems to be very properly infiltrated having smooth texture, however, under higher

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prostheses.

**Figure 11.**

**Figure 12.**

*Optimization of Maxillofacial Prosthesis DOI: http://dx.doi.org/10.5772/intechopen.85034*

magnification the composite shows evidence of porosity and spaces between the powder particles and the silicone polymers within the composite. This phenomenon indicates lack of coherence and integrity between the hydrophobic silicone polymers and the hydrophilic starch powder, which, is related to the wettability and viscosity between silicone polymers that have low surface energy and strongly

*SEM for (A) 3D printed starch block infiltrated Sil-25 SP (×180), (B) 3D printed starch block infiltrated Promax10 (×189), (C) hand mixed starch powder and Sil-25 SP (×178), (D) starch powder particles (×341).*

Furthermore SEM sections (**Figures 11C** and **12**) showing gaps and voids, which indicate tripping of air especially in central parts of the blocks under infiltration pressure. Lack of interaction and incorporation between the starch powder particles and the silicone polymers that are utilized by Z-Corp printer and employed for fabrication of soft tissue facial prostheses will influence the general properties and material's integrity, which my finally affect the durability of the prostheses. Therefore, it was necessary to test the mechanical properties of the 3D printed samples that are going to be used for fabrication of soft tissue facial

hydrophobic [37] and starch powder is hydrophilic in nature [38].

*SEM for Sil-25 hand mixed samples showing spaces around the starch particles (×707).*

#### **Figure 11.**

*Prosthesis*

Infiltration time (minutes)

Silicone polymer

**Table 3.**

*schedule.*

Sil-25 Air

*3.3.1 Slide preparation for SEM*

Pressure

pressure

0.94 (0.08)

*3.3.2 SEM interpretation*

infiltration process.

*3.3.3 Final analysis of SEM*

Scanning Electron Microscopy SEM was applied for this purpose to prepare and obtain various samples of printed starch blocks infiltrated with two different maxillofacial silicone polymers (Sil25 and Promax 10) in order to examine the quality of the infiltration inside the starch printed blocks. SEM pictures of the printed blocks were compared with hand mixed of 40% starch powder and 60% Sil25 silicone polymers. Hand mixed blocks were prepared by mixing the starch and the silicone polymers for 1 minute to obtain a homogenous mixture, then the mixture poured into a 75 × 75 × 4 mm stainless steel mold, pressed and left for 24 hours in ambient temperature. Then slices from the three blocks were prepared using surgical blade number 11 and send for SEM to be examined with SEM of starch powder alone.

Sil-25 2 Bar 1.99 (0.10) 2.76 (0.23) 3.30 (0.28) 3.75 (0.19) 3.88 (0.17) Sil-25 3 Bar 3.94 (0.15) 5.43 (0.20) 6.36 (0.51) 7.71 (0.27) 8.65 (0.49)

*Infiltration depth of Sil-25 inside 3D printed starch blocks under different pressure and at different time* 

**Infiltration depth in (mm) and SD**

5 minutes 10 minutes 15 minutes 20 minutes 25 minutes

1.19 (0.01) 1.16 (0.05) 1.27 (0.13) 1.35 (0.08)

SEM analysis of the starch powder, 3D printed blocks infiltrated Sil-25 and Promax10 plus the hand mixed blocks are shown in **Figure 11**, the SEM of the powder and of the infiltrated powder blocks showed amorphous, non-crystalline shaped particles with different particle sizes varies from very small to relatively large particles. These particles appeared to be loosely arranged and randomly orientated with some spaces in between these particles and disorganized spreading of the starch powder within the silicone polymers leaving big gaps between the powder particles. Incorporation of starch powder with Sil-25 maxillofacial silicone and Promax10 under 3 bar pressure are seen in **Figure 11A** and **B**, showing almost similar distribution of the powder within the infiltrates. However, better incorporation and more homogenous distribution of starch particles within the silicone polymers in hand mixed of 40% powder incorporated into 60% infiltrate of silicone polymers by weight (**Figure 11C**). This could be attributed to the layer of binder on the outer surfaces of the printed blocks that might an obstacle for the

**Figure 12** is a magnified SEM image (×707) of hand mixed starch powder and Sil-25 silicone polymers. Although at a lower magnification the sample apparently seems to be very properly infiltrated having smooth texture, however, under higher

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*SEM for (A) 3D printed starch block infiltrated Sil-25 SP (×180), (B) 3D printed starch block infiltrated Promax10 (×189), (C) hand mixed starch powder and Sil-25 SP (×178), (D) starch powder particles (×341).*

**Figure 12.** *SEM for Sil-25 hand mixed samples showing spaces around the starch particles (×707).*

magnification the composite shows evidence of porosity and spaces between the powder particles and the silicone polymers within the composite. This phenomenon indicates lack of coherence and integrity between the hydrophobic silicone polymers and the hydrophilic starch powder, which, is related to the wettability and viscosity between silicone polymers that have low surface energy and strongly hydrophobic [37] and starch powder is hydrophilic in nature [38].

Furthermore SEM sections (**Figures 11C** and **12**) showing gaps and voids, which indicate tripping of air especially in central parts of the blocks under infiltration pressure. Lack of interaction and incorporation between the starch powder particles and the silicone polymers that are utilized by Z-Corp printer and employed for fabrication of soft tissue facial prostheses will influence the general properties and material's integrity, which my finally affect the durability of the prostheses. Therefore, it was necessary to test the mechanical properties of the 3D printed samples that are going to be used for fabrication of soft tissue facial prostheses.
