MDSC study of melting and glass transitions in elastomeric dental impression materials

A modulated differential scanning calorimetric (MDSC) study was performed to investigate melting and glass transitions in vinyl polysiloxane, polyether and polysulfide dental elastomeric impression materials. The MDSC analyses were performed from −150 to 200°C, using heating-only modulation conditions and sufficient modulations to define the transitions. The two vinyl polysiloxane materials had a single melting peak near −50°C, whereas the polyether material had two melting peaks near −20 and 50°C. The polysulfide material had a small apparent melting peak near 70°C and an endothermic peak near 190°C that requires further investigation. Apparent crystallization peaks were observed on the nonreversing heat flow curves for the vinyl polysiloxane materials. These two silicones had glass transitions near −125°C that were very weak because of their high filler content. The polyether material had a glass transition near −80°C, and the polysulfide material had a glass transition near −55°C. More research is needed to elucidate the nature of the melting peaks in these elastomers and the relationships between polymer structural transformations and clinically relevant properties.