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Int Poster J Dent Oral Med 11 (2009), No. 1     15. Mar. 2009

Int Poster J Dent Oral Med 2009, Vol 11 No 1, Poster 433

Flexural-strength and E-modulus of hypo-allergic denture base materials

Language: English
 

Authors:
Dr. Sonia Mansour, Dr. Manar I. Jarkas, Prof. Dr. Jürgen M. Setz, Dr. Arne F. Boeckler,
Centre for Dentistry and Oral Medicine, Department of Prosthodontics, Martin-Luther-University Halle-Wittenberg
Dr. Christian Bierögel, Prof. Dr. Wolfgang Grellmann,
Center for Engineering Sciences, Martin-Luther-University Halle-Wittenberg

Date/Event/Venue:
July 2-5, 2008
86th General Session & Exhibition of the IADR
Toronto, Canada
 

Introduction

Many ingredients of acrylic resins denture base materials are suspicious to cause allergic reactions [1]. Except the complete polymerized PMMA all ingredients in methacrylate based denture resins such as residual monomer or BPO have allergic properties with different potentials. So, alternative products with no or only minor quantities of allergic components were developed. To fabricate these "hypo-allergic" denture base materials different technical and chemical processing's are applied. To serve as a clinically substitute conventional PMMA denture base resins hypo-allergic denture base materials should meet the standards for mechanical-physical properties of conventional denture base resins. Fundamental material properties are flexural strength (σfM) and flexural/elastic modulus (Ef). Flexural strength is equivalent to the maximum flexural stress during a bend test [2]. Flexural or E-modulus represents the relation between flexural stress and flexural strain in the elastic and visco-elastic region. So, it indicates the material's resistance against elastic deformation. High flexural strength and flexural modulus contribute to the preservation of edentulous jaw areas [3]. Flexural strength is an indicator of the load level and clinical work capability of denture materials finally. A high flexural modulus specifies rigidity as well as stiffness and represents denture base material's resistance to elastic as well as visco-elastic deformation.

The aim of this in-vitro study was to evaluate mechanical-physical properties of hypo-allergic denture base materials Additionally the results should be compared to the material properties of established PMMA denture base resins.
 

Material and Methods

Seven hypo-allergic denture base resins (Tab.1) different in configuration, chemical composition and processing procedure were tested for mechanical-physical properties. According to manufacturers the tested products were free from toxic or potential allergic substances. To evaluate the materials' properties three conventional PMMA denture base resins with different polymerization cycles and processing parameters represented the control group and provided the standard for comparison. To guarantee optimal processing and material quality specimens (Fig 1) were produced by the manufactures or an authorized laboratory.

To prevent the influence of preparation specimens were cut under water cooling (60x10x4mm). Six specimens from each product were tested in the three point bending test according to ISO178:2006 [Center for Engineering Sciences (Director: Prof. Dr. W. Grellmann)].

The distance between the supports was 50 mm. In an universal testing machine (Zwick, Germany, Fig 2) bending force and deflection were measured until break at a constant cross head speed of v=5 mm/min. The data were automatically recorded (software TestXpert 8.1, Zwick). σfM and Ef were calculated, analyzed and compared to the control level (T-test, < 0.05).

Hypo-allergic resins Basis Processing procedure Manufacturer
Acetal polyoxymethylene Injection Pressing Dental S.r.l.,
Dogana, San Marino
Erkocryl polymethyl methacrylate, partial of buthyl acrylate Injection-casting Erkodent Erich Kopp GmbH,
Pfalzgrafenweiler, Germany
Luxene polyvinyl copolymer Injection TopDent GmbH,
Mühlgraben Germany
Microbase diurethan diamethcrylate Injection DENTSPLY De Trey GmbH,
Konstanz, Germany
Polyan modified methyl methacrylate Injection-casting Polyapress GmbH,
Altkirchen, Germany
Sinomer polymethyl methacrylate, polyfunctional oligomers (acrylate/urethane based) Injection ALLDENT AG,
Ruggell, Liechtenstein
Versio.com dimethacrylate, polyfunctional methacrylates Casting Heraeus Kulzer GmbH & Co. KG,
Hanau, Germany
Conventional Resins Basis Processing procedure Manufacturer
Paladon 65 polyfunctional methacrylates Injection Heraeus Kulzer GmbH & Co. KG,
Hanau, Germany
PalaXpress polyfunctional methacrylates and copolymer Plug & press Heraeus Kulzer GmbH & Co. KG,
Hanau, Germany
SR-Ivocap polyfunctional methacrylates Injection Ivoclar Vivadent GmbH,
Ellwagen, Germany
Tab 1: Tested hypoallergenic denture base materials and PMMA based denture base resins
 
Fig 1: Specimens Fig 2: Three point bending test
 

Results

All tested hypo-allergic materials fulfilled the basic requirements according to DIN ISO 1567:2000. σfM standard of the conventional control group was in the range of 92.8 - 120.2 MPa (Fig 3). The average flexural strength of three tested products was within (100.5 - 116.0 MPa), two products were above (123.9 - 136.1 MPa) and two materials below (65.3 u. 71.4 MPa) the standardized control level.
Flexural modulus gained from the three point bending test characterizes material's stiffness. Ef standard level was between 2431 - 3180 MPa (Fig 4). The average flexural modulus of three products was within (2522 - 3020 MPa), two above (3234 - 3853 MPa) and one material below (2208 MPa) the respective control level.

Fig 3: Flexural strength Fig 4: Flexural modulus /elastic modulus
 

Conclusions

Flexural strength is an indicator of the load capacity and the resistance against stress cracking. Therefore it also indicates clinical work capability of resin dentures. A high flexural modulus value specifies rigidity as well as stiffness and represents denture base material\'s resistance to elastic and visco-elastic deformation. All tested products fulfilled the requirements of ISO 1567:2000. The flexural strength and flexural modulus of five tested hypo-allergic denture base materials were within or superior to the control levels established by the tested conventional PMMA denture base resins. Microbase exhibited insufficient flexural strength combined with high flexural modulus which indicates brittle material properties. Sinomer showed deficient values for flexural strength and flexural modulus.
 

Literature

  1. Wichelhaus A: Allergology in Dentistry. In: Heppt W, Bachart C (Eds) Allergology for ENT-Doctors. Thieme, Stuttgart, New York (1998) 142-147
  2. Grellmann W, Seidler S (Eds): Polymer Testing. Hanser, Munich, Wien, 2007
  3. Finger W: Mechanical and dynamic properties of denture base resins. Dtsch Zahnaerzt Z 30, (1975) 665-671
     

This Poster was submitted by Dr. Sonia Mansour.
 

Correspondence address:
Dr. Sonia Mansour
Martin-Luther-University Halle-Wittenberg
Centre for Dentistry and Oral Medicine, Department of Prosthodontics
Große Steinstraße 19
06108 Halle (Saale)
Germany