title: Properties of dental resins submitted to pH catalysed hydrolysis.
abstract: OBJECTIVE
  This study evaluated the surface microhardness (SM) and roughness (SR) alterations of dental resins submitted to pH catalysed degradation regimens.
  
  
  METHODS
  Thirty discs of each TPH Spectrum (Dentsply), Z100 (3M-ESPE), or an unfilled experimental bis-GMA/TEGDMA resin were fabricated, totaling 90 specimens. Each specimen was polymerized for 40 s, finished, polished, and individually stored in deionized water at 37 °C for 7 days. Specimens were randomly assigned to the following pH solutions: 1.0, 6.9 or 13, and for SM or SR evaluations (n = 5). Baseline Knoop-hardness of each specimen was obtained by the arithmetic mean of five random micro-indentations. For SR, mean baseline values were obtained by five random surface tracings (R(a)). Specimens were then soaked in one of the following storage media at 37 °C: (1) 0.1 M, pH 1.0 HCl, (2) 0.1 N, pH 13.0 NaOCl, and (3) deionized water (pH 6.9). Solutions were replaced daily. Repeated SM and SR measurements were performed at the 3-, 7- and 14-day storage time intervals. For each test and resin, data were analysed by two-way ANOVA followed by Tukey's test (α = 0.05).
  
  
  RESULTS
  There was significant decrease in SM and increase in SR values of composites after storage in alkaline medium. TPH and Z100 presented similar behaviour for SM and SR after immersion in the different media, whereas unfilled resin values showed no significant change.
  
  
  CONCLUSIONS
  Hydrolytic degradation of resin composites seems to begin with the silanized inorganic particles and therefore depend on their composition.
  
  
  CONCLUSIONS
  To accelerate composite hydrolysis and produce quick in vitro microstructural damage, alkaline medium appears to be more suitable than acidic medium. Contemporary resin composite properties seem to withstand neutral and acidic oral environments tolerably well.
authors.affiliation: Department of Dental Materials and Operative Dentistry, Faculty of Dentistry, University of Fortaleza, Fortaleza, Ceara, Brazil.
authors.forename: Renato
authors.initials: R
authors.lastname: Cilli
authors.forename: Jose Carlos
authors.initials: JC
authors.lastname: Pereira
authors.forename: Anuradha
authors.initials: A
authors.lastname: Prakki
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002424:Caustics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D055117:Curing Lights, Dental; D003764:Dental Materials / Q000737:chemistry*; D003775:Dental Polishing; D005898:Glass / Q000737:chemistry; D006244:Hardness; D006801:Humans; D006851:Hydrochloric Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008855:Microscopy, Electron, Scanning; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D012972:Sodium Hydroxide / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D002424:Caustics; D003188:Composite Resins; D003764:Dental Materials; D011109:Polymethacrylic Acids; C467914:TPH spectrum; C083568:Z100 composite resin; D014867:Water; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D012972:Sodium Hydroxide; D012822:Silicon Dioxide; D015040:Zirconium; D006851:Hydrochloric Acid; C028541:zirconium oxide