J Korean Acad Prosthodont.  1999 Oct;37(5):597-606.

EFFECTS OF AGING AND THERMAL CYCLING ON THE BIAXIAL RLEXURE STRENGTH OF VENEERING RESIN COMPOSITES FOR CROWN

• Jeong GY
• Ha IS
• Song KY

Abstract

This study was performed to evaluate the effect of aging and thermal cycling on the biaxial flexure strength of four commercially available veneering resin composites for crown(Dentacolor : DC, Artglass : AG, Esternia : ET and Targis : TG). Disc specimens were fabricated in a teflon mold giving 12mm in diameter and 1mm in thickness. All samples were divided into 4groups. Group 1 was dried in a dessicator at 25degrees C for 30 days. Group 2 was immersed in distilled water at 37degrees C for 30 days. Group 3 was immersed in distilled water at 65degrees C for 30 days. Group 4 was subjected to 10,000 thermal cycles between 5degrees C and 55degrees C, and the immersion time in each bath was 15 seconds per cycle. Biaxial flexure test was conducted using the ball-on-three-ball method at the cross head speed of 0.5mm/min and fracture surfaces were observed with scanning electoron microscope. The results obtained were summarized as follows ; 1. Weibull modulus values, except for the AG group, decreased after thermal cycling treatment. 2. Biaxial flexure strength values of aging group at 37degrees C were th lowest in all sample groups. Except for the DC group, strength values were significntly decreased for the drying group. 3. After thermal cycling test, the highest value of biaxial flexure strength of 188.8 MPa was observed in the ET group and the lowest value of 73.2 MPa was observed in the DC group. The strength values showed the significant differences in each group (p<0.05). 4. Observation of surfaces after thermal cycling test revealed the ditching in the part f surrounding large fillers.

MeSH Terms

Aging*
Baths
Crowns*
Fungi
Head
Immersion
Polytetrafluoroethylene
Water
Polytetrafluoroethylene
Water