Hydrophilicity of elastomeric non-aqueous impression materials during setting.

Objectives: Clinically relevant accuracy of dental impressions depends on flowing and wetting properties of the applied impression materials. The major objective of this study was to develop an experimental set-up and an analysis strategy for wettability measurements of impression materials during their working time.

Methods: High-resolution drop shape analysis was used to study contact angles on thin unset films of two polyether and two vinyl polysiloxane (VPS) impression materials. Qualitative and quantitative analysis of the contact angle evolution in terms of initial values and the equilibrium state of hydrophilicity, as well as in terms of kinetics of hydrophilization were extended using a mathematical model approach.

Results: Compared to VPS impression materials, polyethers show pronounced and constant initial hydrophilicity throughout prescribed working time. The kinetics of the VPS impression materials towards more hydrophilic equilibrium surface states is very fast compared to polyethers. This possibly balances the disadvantage of the initial VPS impression materials hydrophobicity. Generally, the experimental and analytical methods have proven to yield detailed insights into the wetting characteristics during setting.

Significance: Both, high initial and a fast kinetics towards increased hydrophilicity may improve flowing and wetting processes during impression taking. Therefore, time-resolved wettability studies should be regarded when developing advanced impression materials and defining working times. They may supplement rheological studies.