title: Chemical degradation of composite restoratives.
abstract: The chemical environment is one aspect of the oral environment, which could have an appreciable influence on the in vivo degradation of composite restoratives. The effects of chemical media on surface hardness of four composite restoratives (Silux [SX], Z100 [ZO], Ariston [AR] and Surefil [SF]) were investigated. The relationship between hardness and the thickness of the degradation layer was also studied. Thirty six specimens (3 x 4 x 2 mm) were made for each material. Following polymerization, the specimens were stored in artificial saliva at 37 degrees C for 24 h. The specimens were then randomly divided into six groups of six, subjected to microhardness testing (load = 500 gf, dwell time = 15 s) and stored in the following chemicals for 1 week at 37 degrees C: artificial saliva (S), distilled water (W), 0.02 N citric acid (C), 0.02 N lactic acid (L), heptane (H) and 75-25% ethanol-water solution (E). After conditioning, the specimens were again subjected to hardness testing and sectioned. Change in hardness (DH) was computed and the thickness of the degradation layer (DL) was measured using a computerized image analysis system at 600x magnification. Results of statistical analysis (ANOVA/Scheffe's [P < 0.05]) of DH based on materials were as follows: SX - E > all other mediums; ZO - W > C; and AR - S, W, E > H (> indicates significantly greater hardness change). No significant difference in DH was observed between the different chemicals for SF. The effects of chemical media on DH were found to be material dependent. A significant but weak positive correlation (Pearson's correlation [P < 0.05]) exists between change in hardness and thickness of the degradation layer.
authors.affiliation: Department of Restorative Dentistry, Faculty of Dentistry, National University of Singapore, Singapore. rsdyapuj@nus.edu.sg
authors.forename: A U
authors.initials: AU
authors.lastname: Yap
authors.forename: S H
authors.initials: SH
authors.lastname: Tan
authors.forename: S S
authors.initials: SS
authors.lastname: Wee
authors.forename: C W
authors.initials: CW
authors.lastname: Lee
authors.forename: E L
authors.initials: EL
authors.lastname: Lim
authors.forename: K Y
authors.initials: KY
authors.lastname: Zeng
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D019343:Citric Acid / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent; D000431:Ethanol / Q000737:chemistry; D006244:Hardness; D006536:Heptanes / Q000737:chemistry; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019344:Lactic Acid / Q000737:chemistry; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D012464:Saliva, Artificial / Q000737:chemistry; D012822:Silicon Dioxide; D012997:Solvents / Q000737:chemistry; D013223:Statistics as Topic; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry; D015040:Zirconium
chemical_list: C409382:Ariston pHc; D003188:Composite Resins; D003764:Dental Materials; D006536:Heptanes; D008689:Methacrylates; D011108:Polymers; D012464:Saliva, Artificial; D012997:Solvents; C403464:SureFil packable composite; C083568:Z100 composite resin; D014867:Water; D019343:Citric Acid; D019344:Lactic Acid; D000431:Ethanol; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; D015040:Zirconium