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J Korean Acad Conserv Dent. 2011 Sep;36(5):377-384. English. Original Article.
Chang J , Baek SH , Lee IB .
Clinic for the Disabled, Seoul National University Dental Hospital, Seoul, Korea.
Department of Conservative Dentistry, Seoul National University School of Dentistry and Dental Research Institute, Seoul, Korea.

OBJECTIVES: The purpose of this study was to observe the change in the viscoelastic properties of thermoplasticized injectable root canal filling materials as a function of temperature and to compare the handling characteristics of these materials. MATERIALS AND METHODS: Three commercial gutta perchas and Resilon (Pentron Clinical Technologies) in a pellet form were heated in the Obtura-II system (Obtura Spartan) at 140degrees C and 200degrees C, and the extrusion temperature of the thermoplasticized materials was measured. The viscoelastic properties of the materials as a function of temperature were evaluated using a rheometer. The elastic modulus G', viscous modulus G", loss tangent tandelta, and complex viscosity eta* were determined. The phase transition temperature was determined by both the rheometer and a differential scanning calorimeter (DSC). The consistency of the materials was compared under compacting pressure at 60degrees C and 40degrees C by a squeeze test. RESULTS: The three gutta perchas had dissimilar profiles in viscoelastic properties with varying temperature. The phase transition of softened materials into solidification occurred at 40degrees C to 50degrees C, and the onset temperatures obtained by a rheometer and a DSC were similar to each other. The onset temperature of phase transition and the consistency upon compaction pressure were different among the materials (p < 0.05). Resilon had a rheologically similar pattern to the gutta perchas, and was featured between high and low-flow gutta perchas. CONCLUSIONS: The rheological characteristics of the thermoplasticized root canal filling materials changed under a cooling process. The dissimilar viscoelastic properties among the materials require different handling characteristics during an injecting and compacting procedure.

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