Hydraulic and Hydrophobic Impressions
(Continued)
Wash and dry the bite registration impression of the prepared tooth (Figure 3). This will act as a highly customized tray (Figure 4). Wash and dry the prepared tooth to remove excess blood and saliva. Inject a small amount of hydrophobic, low viscosity, vinylpolysiloxane material into the bite registration impression or the prepared tooth (Figure 5). Only a small amount of low viscosity material is required (Figure 6). Then have the patient close again all the way down into the bite registration impression (Figure 7).

Figure 3 |

Figure 4 |

Figure 5 |

Figure 6 |

Figure 7 |
In this second step of the impression procedure, when the patient closes into MI, the prepared tooth is thrust into the low viscosity impression material like a piston and generates a hydraulic force. This force propels the low viscosity material into the sulcus under sufficient pressure to displace blood and saliva. In fact, the low viscosity material is propelled under such a strong hydraulic force that it will fill the entire sulcus and will reproduce the entire subgingival finish line as well as the submarginal anatomy of the root. The subgingival finish lines will be reproduced with great detail and will be sharply defined. Since the low viscosity material is hydrophobic, it will not incorporate blood or saliva but rather will bodily displace them.