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Int Poster J Dent Oral Med 14 (2012), No. 4     15. Dec. 2012

Int Poster J Dent Oral Med 2012, Vol 14 No 4, Poster 627

Rheological properties of impression materials and shark-fin-test: A correlation analysis

Language: English
 

Authors:
Dr. Martha Zenginel, Ulrich Heun, Jürgen Stelzig, Dr. Markus Balkenhol, Prof. Dr. Bernd Wöstmann,
Justus-Liebig-University Giessen, Department of Prosthodontics, Gießen, Germany

Date/Event/Venue:
16.07.2010
IADR 2010
Barcelona, Spain.
 

Introduction

Rheological properties are regarded a major influencing factor which influences the accuracy of an impression material. The shark-fin-test has been introduced as a simple test to analyze flow properties of impression materials. However, there is a lack of evidence in the scientific literature on this subject, i.e. no information is available which physical properties or variables are reflected by the shark-fin-test.
 

Objectives

Thus it was the aim of this study to evaluate potential correlations of the rheological relevant parameters zero shear viscosity and yield stress between results obtained from the shark-fin-test and different rheological properties of elastomeric impression materials after mixing.
 

Material and Methods

Type 3 viscosities (acc. to ISO 4823) of chemically different impression materials (VPS: Flexitime, hybrid polyether/siloxane: Fusion, polyether: Impregum and P2) (Tab. 1) were subjected to the shark-fin-test (Fig. 1) as well as to two clinically relevant rheological test regimes (zero shear viscosity, yield stress). The rheological tests were conducted at defined 30 s intervals after mixing (n=6) until 150 s using a rotational rheometer (RS 600, Thermo Fisher Scientific) in a plate/plate configuration. All tests were carried out at ambient laboratory conditions (23 °C, 50 % rel. humidity). Median values and interquartile ranges were calculated. For statistical correlation analysis Spearman's Rho was used (α=0.05).

Impression material Manufacturer Type
Flexitime Correct Flow Heraeus Kulzer GmbH, Wehrheim, Germany Vinylpolysiloxane
Fusion Light Body GC Dental Products Corp. Hybrid Polyether/VPS
P2 light Heraeus Kulzer GmbH, Wehrheim, Germany Polyether
Impregum Garant L Duosoft 3M ESPE, Seefeld, Germany Polyether
Tab. 1: Impression materials
Fig. 1a-c: Procedure while operating the shark-fin-test
Fig. 1d-f: Procedure while operating the shark-fin-test
   
Fig. 1g: Procedure while operating the shark-fin-test
 
   

Results

Zero shear viscosity was lowest for Impregum at 30 s (321.9 Pa s) and increased for all materials over time. Highest values at 150 s were observed for Fusion (97120 Pa s). Yield stress was lowest for Impregum (17.18 Pa) and decreased over time. In contrast, all other materials showed an increase in yield stress (Fig. 2 and 3). Due to ongoing cross-linking reaction, yield stress could not be determined at progressed points in time for some of the materials.
A significant negative correlation was obvious between the rheological parameters on the one hand and the shark-fin-test on the other (p < 0.05).

Fig. 2: Zero shear viscosity and fin height of type 3 materials.
 
Fig. 3: Yield stress and fin height of type 3 materials.

Conclusions

Zero shear viscosity is affected by the Brownian motion and subsequently may be dependent on filler types and/ or the monomer properties of the impression materials tested. It was significantly negative correlated to the fin heights. Taking into consideration the clinical situation, zero shear viscosity describes the flowability of impression materials.
Yield stress was significantly negative correlated to the shark-fin-test. Chemically secondary bonds have to be resolved by measuring yield stress. The polyethers had by far the lowest values, though their yield stress could not be determined until the end of working time.
 

Literature

  1. Balkenhol M, Wöstmann B, Kanehira M, Finger WJ. Shark fin test and impression quality: a correlation analysis. J Dent 2007; 35 (5):409-415.
  2. German MJ, Carrick TE, McCabe JF. Surface detail reproduction of elastomeric impression materials related to rheological properties. Dent Mater 2008;24 (7):951-956.
  3. McCabe JF, Arikawa H. Rheological properties of elastomeric impression materials before and during setting. J Dent Res 1998;77 (11):1874-1880.
  4. McCabe JF, Carrick TE. Onset of elasticity in setting elastomers. J Dent Res 1990;69 (9):1573-1575.
  5. McCabe JF, Carrick TE. Rheological properties of elastomers during setting. J Dent Res 1989;68 (8):1218-1222.
  6. ISO DIN 4823. Elastomere Abformmassen, Zahnheilkunde 2001.
  7. Berg JC, Johnson GH, Lepe X, Adan-Plaza S. Temperature effects on the rheological properties of current polyether and polysiloxane impression materials during setting. J Prosthet Dent 2003;90 (2):150-161.
  8. Metzger T. Das Rheologie-Handbuch: für Anwender von Rotations-und Oszillationsrheometern. 2.Auflage. Vincentz Network, Hannover, 2006.
     

This Poster was submitted by Dr. Martha Zenginel.
 

Correspondence address:
Dr. Martha Zenginel
Justus-Liebig-University Giessen
Department of Prosthodontics
Schlangenzahl 14
35392 Gießen
Germany