title: Long-term surface hardness and monomer conversion of a nanoflled and a microhybrid composite resin.
abstract: OBJECTIVE
  This study aims to evaluate the degree of conversion (DC) and hydrolytic degradation through the Vickers hardness test (HV) of a nanoflled (Filtek(TM) Z-250, 3M) and a microhybrid (Filtek(TM)Supreme-XT, 3M) composite resin.
  
  
  METHODS
  Eight disk-shaped specimens (4 mm diameter × 2 mm thick, ISO 4049) of each material were prepared for each test. Composites were inserted into single increment in a metallic matrix and light-cured for 40 seconds. VH readings were performed for each specimen at predetermined intervals: immediately after polymerization (control), 1, 2, 3, 7, 14, 21, 30 and 180 days. After curing, initial hardness measurements were performed and the specimens were immersed in artifcial saliva at 37°C. For DC (%), specimens were ground, pressed with KBr and analyzed by FT-IR spectrophotometer.
  
  
  RESULTS
  Student t-test showed that there was no difference between the resins for DC (p = 0.252). ANOVA analysis revealed that Z-250 VH means were all greater than S-XT, for both top and bottom surfaces, whatever the storage-period in artifcial saliva (p < 0.001). After 180 days of storage, the hardness obtained for S-XT was similar with that at the baseline, for both top and bottom surfaces. While for Z-250 hardness was not signifcantly different from baseline only for top surface, but there was a signifcant decrease observed in hardness for bottom surface.
  
  
  CONCLUSIONS
  The materials tested showed no evidence of hydrolytic degradation in a signifcant way, in a 6-month storage-time in artifcial saliva. Nanoflled resin presents a monomer conversion comparable to the conventional microhybrid.
authors.affiliation: PhD Student, Department of Restorative Dentistry, São Paulo State University School of Dentistry, Araraquara, Brazil, Phone: +55 16 33016388 e-mail: fernandajasse@hotmail.com.
authors.forename: Fernanda Ferreira
authors.initials: FF
authors.lastname: Jassá
authors.affiliation: Master Student, Department of Restorative Dentistry, São Paulo State University School of Dentistry, Araraquara, SP, Brazil.
authors.forename: Carlos Henrique
authors.initials: CH
authors.lastname: Braga Borges
authors.affiliation: Professor of the Post Graduation in Integrated Dental Sciences University of Cuiaba, MT, Brazil.
authors.forename: Mateus Rodrigues
authors.initials: MR
authors.lastname: Tonetto
authors.affiliation: Professor, Department of Restorative Dentistry, São Paulo State University School of Dentistry, Araraquara, SP, Brazil.
authors.forename: Alessandra Nara
authors.initials: AN
authors.lastname: de Souza Rastelli
authors.affiliation: Chief, Optics Group from Institute of Physics of São Carlos, University of São Paulo, São Carlos, SP, Brazil.
authors.forename: Vanderlei Salvador
authors.initials: VS
authors.lastname: Bagnato
authors.affiliation: Professor, Department of Restorative Dentistry, São Paulo State University School of Dentistry, Araraquara, SP, Brazil.
authors.forename: Edson Alves
authors.initials: EA
authors.lastname: de Campos
authors.affiliation: Master Student, Post-Graduation in Dentistry, CEUMA University São Luis, MA, Brazil.
authors.forename: Reidson Stanley
authors.initials: RS
authors.lastname: Soares Dos Santos
authors.affiliation: Professor of the Post-Graduation in Dentistry, CEUMA University São Luis, MA, Brazil.
authors.forename: Matheus Coelho
authors.initials: MC
authors.lastname: Bandeca
authors.affiliation: Professor, Department of Restorative Dentistry, São Paulo State University School of Dentistry, Araraquara, SP, Brazil.
authors.forename: Josá Roberto
authors.initials: JR
authors.lastname: Cury Saad
mesh_terms: D002244:Carbon / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D006244:Hardness; D006801:Humans; D006868:Hydrolysis; D055115:Light-Curing of Dental Adhesives / Q000379:methods; D008422:Materials Testing; D053761:Nanocomposites / Q000737:chemistry*; D058105:Polymerization; D012464:Saliva, Artificial / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C474035:Filtek Supreme; C444701:Filtek Z250; D012464:Saliva, Artificial; D002244:Carbon