Rheological characterization of thermoplasticized injectable gutta percha and resilon

Abstract

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 140℃ and 200℃, 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 tan δ , and complex viscosity η * 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 60℃ and 40℃ 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 40℃ to 50℃, 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.

Temperature‐dependent rheological property changes of thermoplastic gutta‐percha root filling materials

“…Previous studies have demonstrated that such thermoplastic behaviour is attributed to a transition of crystalline phase of GP polymer to amorphous phase (Deanin 1972, Schilder et al 1974. The phase transition temperatures of GP, trans-polyisoprene, from crystalline b-phase to aphase and further to amorphous phase are reported somewhat differently in studies using different test methods, such as X-ray diffraction (Leeper & Schlesinger 1953), thermo-mechanical methods (Schilder et al 1974, Tsukada et al 2004, Chang et al 2011 or calorimetric method (Marciano & Michailesco 1989, Combe et al 2001, Maniglia-Ferreira et al 2008, Ferrante et al 2011. The results of present study showed that thermoplastic GPs have already started to soften before 40°C as shown in Fig.…”

“…, Chang et al . ) or calorimetric method (Marciano & Michailesco , Kolokuris et al . , Combe et al .…”

“…Additionally, highly viscous materials are an ergonomic issue for the operator, requiring substantial manual force (Chang et al . ). Moreover, uncontrolled heat sources can overheat the gutta‐percha over the allowable temperature range, causing degradation (Maniglia‐Ferreira et al .…”

“…On the contrary, if the material is too viscous, the canal system may not be adequately filled with a greater chance of voids remaining within the canal. Additionally, highly viscous materials are an ergonomic issue for the operator, requiring substantial manual force (Chang et al 2011). Moreover, uncontrolled heat sources can overheat the gutta-percha over the allowable temperature range, causing degradation (Maniglia-Ferreira et al 2008) or elevation of root surface temperature (Lipski 2006) that may result in damage to the periodontium (Eriksson & Albrektsson 1983, Saunders 1990.…”

Comparison between Gutta-Percha and Resin-Coated Gutta-Percha using Different Obturation Techniques

“…A variety of materials and techniques have been developed to improve the sealing quality and reinforcing effect of root canal obturation (30). With the CLC technique, it has been shown that the apical seal is best produced when the spreader can be placed close to the working length (31). The spreader's shape and its depth of penetration are considered to be important factors in producing a more homogenous root canal filling (32).…”