Comparison of the Degree of Conversion of Resin Based Endodontic Sealers Using the DSC Technique

Abstract

Objectives:The aim of this study was to determine the degree of conversion (DC) of three resin based endodontic sealers using the DSC technique.Methods:The sealers tested were: EndoREZ (ER) (Ultradent, South Jordan, UT); EndoREZ with Accelerator (ER+A) (Ultradent, South Jordan, UT); RealSeal (RS) (SybronEndo, Orange, CA). Two LED units were used to activate the sealers: UltraLume LED 5 (Ultradent, South Jordan, UT, USA); Mini LED Satelec (Satelec Acteon Group, Mérignac Cedex, France). Samples of 4.0 mg were analyzed with a DSC 7 calorimeter (Perkin Elmer Inc., Wellesley, MA, US). Each specimen was irradiated by each lamp four times for 20 seconds at an interval of 2 mins, while the DSC 7 recorded the heat flow developed during the treatment. The degree of conversion and the kinetic curves were calculated from the values of heat developed during each polymerization. The data were statistically analysed with a Kruskal-Wallis one-way ANOVA multiple range and Student-Newman-Keuls (SNK) tests at a P value of .05.Results:Statistically significant differences were found in the degree of conversion among the sealers: ER+A showed the highest values with both lamps.Conclusions:The higher polymerization rate in resin sealers is obtained with the addition of a catalyst.

Polymerization behavior and thermal characteristics of two new composites at five temperatures: refrigeration to preheating

“…It has been shown that the DC can be accelerated by dynamic heating of composite materials 4,5,7-10,22. This study, as well, showed that preheating the composites may increase the extent of polymerization for both of the composites examined.…”

“…The only significant increase in heat produced by King Dental composite was at 60℃ (compared to the heat flow level at 15℃), where as Core Max II showed a considerable increase in polymerization by increasing the environment temperature. The difference between the materials is attributed to their chemical compositions and viscosities which might affect the polymerization of self-cured composites 5,8,10,16,20,21. The higher variation observed among KD specimens may be relevant to preparation techniques of the materials (CM was available in the form of powder and liquid with superior homogeneity, KD had 2 pastes), and probably lower viscosity of CM components.…”

“…The DC is the ratio of single carbon-carbon bonds in a polymer structure to double carbon-carbon bonds among monomers 4. It indicates the percentage of monomer-to-polymer conversion and is a qualitative and quantitative index for the extent of the polymerization 3,5. Mechanical-physical characteristics and clinical performance of dental composites are compromised by a low DC;5 the residual monomers might act as plasticizers, reducing mechanical properties and increasing swelling 4,6.…”

“…The heat of polymerization (HP) is proportional to the percentage of reacted monomers 3,5. If there is no other thermal sources in the reaction (such as light curing units), the energy released during composite polymerization is directly associated with both the DC and the increase in the temperature of adjacent tissues during chair-side operations.…”

“…If there is no other thermal sources in the reaction (such as light curing units), the energy released during composite polymerization is directly associated with both the DC and the increase in the temperature of adjacent tissues during chair-side operations. This energy may be measured by differential scanning calorimetry (DSC) which is a thermal analysis method and can provide the variation of enthalpy in the exothermic polymerization reaction, indicating thermal and physical characterizations 5,16. The DSC is known as a highly sensitive approach and as one of the most reliable direct methodologies for assessment of thermal and physical characterizations of the materials such as DC 5,16-19.…”