Dielectric Analysis of Short-Term and Long-Term Curing of Novel Photo-Curing Dental Filling Materials

Transcription

1 European Polymer Congress 2009 Graz, Austria Dielectric Analysis of Short-Term and Long-Term Curing of Novel Photo-Curing Dental Filling Materials *, *Bernhard Möginger, **Matthias Frentzen, ***Martin Rosentritt *Bonn-Rhein-Sieg University of Applied Science, **University Hospital Bonn, ***University Hospital Regensburg, Germany Competence Platform Polymer Materialien Bonn-Rhein-Sieg University of Applied Sciences Tel.: / slide 1

2 Overview: - Introduction - Methods and materials - DEA (Dielectrical Analysis) In comparison to DEA: - DSC (Differential Scanning Calorimetry) - DMA (Dynamic Mechanical Analysis) - Results - Conclusion slide 2

3 Introduction Scope: Better understanding of the reaction kinetics of composite dental fillings Adaption of thermal analysis methods (e.g. DEA, DSC and DMA) Performed methods of investigation of the curing process of dental composites: DEA (Dielectrical Analysis) measurement of the time-dependent ion viscosity results are compared with DSC (Differential Scanning Calorimetry) calorimetric measurement of the reaction enthalpy DMA (Dynamic Mechanical Analysis) mechanical measurement of the stiffness increase Materials: VOCO, ARABESK TOP -product series slide 3

4 Introduction Application example: Dental filling with photo-cured composite material slide 4

5 Measurement methods DEA (Dielectrical Analysis): Measuring principle of the applied DEA sensor sample between capacitor electrodes Measuring quantities: ion viscosity µ dielectrical loss ε dielectrical constantε slide 5

6 Measurement methods DEA (Dielectrical Analysis): Measuring principle of the applied DEA sensor (different capacitor arrangement due to illumination of the sample) comblike Elektroden electrodes polymer Probe sample ~U d Isolationsmatrix insulation Sensorgehäuse sensor housing elektrisches alternating Wech electrical field slide 6

7 Measurement methods DEA (Dielectrical Analysis): sensor surfaces Foto von IDEX-Sensor Foto von TMS-Sensor 5 mm NETZSCH TMS sensor (Tool Mount Sensor; 1mm electrode distance) 2 mm NETZSCH IDEX sensor (interdigitated electrode; 115 µm electrode distance) slide 7

8 Measurement methods DEA (Dielectrical Analysis): experimental set-up DEA experimental set-up investigation of primary-curing DEA experimental set-up investigation of post curing 36 C slide 8

9 Measurement methods DSC (Differential Scanning Calorimetry): Measuring principle of the applied modified DSC device DSC measuring cell: oven covert (aluminium) reference pan (aluminium) thermocouple illumination device oven sample pan (aluminium) heating liquid nitrogen cooling slide 9

10 Measurement methods DMA (Dynamic Mechanical Analysis): Measuring principle of the applied modified DMA device (similar to a hardness test) dynamic testing load DMA set-up: measuring stamp cured polymer sample testing indentor (ø 1mm) steel frame sample holder slide 10

11 Results of the light induced curing DEA (Dielectrical Analysis) versus DSC (Differential Scanning Calorimetry) t 8s exothermal heat flow [W/g] slide 11

12 Results of the post-curing DEA (Dielectric Analysis): logarithmic time scale Post-curing of Arabesk Top OA2 1,6E+11 1,4E+11 µ(t) = µ 0 + µ * lg t ion viscoity [Ohm*cm] 1,2E+11 1E+11 8E+10 6E+10 4E+10 2E , time [h] Log IonViscosity 0,1 Hz (Ohm*cm) Log IonViscosity 1 Hz (Ohm*cm) Log IonViscosity 10 Hz (Ohm*cm) Temperature (C) slide 12

13 Evaluation of the post-curing DMA (Dynamic Mechanical Analysis): logarithmic time scale storage Speichermodul modulus [MPa] time Zeit [min] Unterseite 1Hz_UO(9%) Unterseite 1Hz_i(47%) Oberseite 1Hz_UO(9%) Oberseite 1Hz_i (47%) Abb. 7.2: Nachhärtverhalten von ARABESK TOP I und UO logarithmische Darstellung slope: post-curing behavior of ARABESK TOP I and UO (measurement of 2mm thick samples over 48 h on the upper light exposed and on the back side) (gemessen wurden 2mm dicke Plättchen über 48 h, jeweils auf der oberen belichteten und der unteren Seite) function of elastic modulus: ( ) ( ) [ ] E t = E0 + E lg t E = ( E ) 2 E1 ( t ) lg( t ) [ lg ] 2 1 slide 13

14 conclusion Most of the primary curing of the dental composites happens within the first 7-10s of illumination post-curing processes depend logarithmically on time DEA, DSC and DMA are appropriate methods to analyse the reaction kinetics of such dental composites Benefits in the future: precise studies of the curing kinetics of dental filling materials are possible kinetic models can be developed illumination strategies can be varified material development cycles can be shortened slide 14

15 Thank you very much for your attention! slide 15