title: Monomer conversion, microhardness, internal marginal adaptation, and shrinkage stress of bulk-fill resin composites.
abstract: OBJECTIVE
  To evaluate degree of conversion (DC), Knoop microhardness (KHN), internal marginal adaptation (IA), and polymerization shrinkage stress (PS) of one conventional and four bulk-fill composites.
  
  
  METHODS
  Bulk-fill composites tested were Surefil SDR (SDR), Filtek Bulk-Fill (FBF), Tetric EvoCeram Bulk-Fill (TEC), and EverX Posterior (EXP). The conventional composite Herculite Classic (HER) was tested using both incremental and bulk-fill insertion techniques. Standardized Class I preparations (4-mm-depth) were made in extracted molars and restored with each product system (N=5). After 1-week wet storage, restorations were cross-sectioned and DC and KHN were evaluated at four depths (1, 2, 3, and 4mm) using confocal Raman spectroscopy and KHN techniques, respectively. Epoxy resin replicas of restorations were evaluated using scanning electron microscopy for IA. PS was determined using composite bonded to acrylic rods attached to a universal testing machine (N=5).
  
  
  RESULTS
  Within bulk-fill products, only SDR and FBF demonstrated similar DC at all depths, and KHN values did not statistically differ among depths, except for TEC. Neither placement method nor depth affected KHN or DC, except the DC of HER bulk-fill at 4mm. Incrementally layered HER, and bulk-fills SDR and TEC demonstrated the lowest proportion of internal gaps. Highest and lowest PS values were measured for EXP and TEC, respectively.
  
  
  CONCLUSIONS
  DC with depth was not uniform among all bulk-fill materials, although no difference in KHN was found. Higher PS correlated positively with higher proportion of interfacial gaps. The incremental technique using conventional composite showed reduced gap formation.
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Av. Limeira, 901, Piracicaba 13414-903, SP, Brazil. Electronic address: bruna.fronza@hotmail.com.
authors.forename: Bruna Marin
authors.initials: BM
authors.lastname: Fronza
authors.affiliation: Department of Oral Rehabilitation, College of Dental Medicine, Georgia Regents University, 1430 John Wesley Gilbert Dr, Augusta, GA 30912, USA. Electronic address: frueggeb@gru.edu.
authors.forename: Frederick Allen
authors.initials: FA
authors.lastname: Rueggeberg
authors.affiliation: Department of Biomaterials and Oral Biology, School of Dentistry, University of São Paulo, Av. Professor Lineu Prestes, 2227, São Paulo 05508-000, SP, Brazil. Electronic address: rrbraga@usp.br.
authors.forename: Roberto Ruggiero
authors.initials: RR
authors.lastname: Braga
authors.affiliation: Institute of Research and Development, University of Paraíba Valley, Av. Shishima Hifumi, 2911, São José dos Campos 12244-000, SP, Brazil. Electronic address: borysmog@gmail.com.
authors.forename: Borys
authors.initials: B
authors.lastname: Mogilevych
authors.affiliation: Institute of Research and Development, University of Paraíba Valley, Av. Shishima Hifumi, 2911, São José dos Campos 12244-000, SP, Brazil. Electronic address: lesoares@univap.br.
authors.forename: Luis Eduardo Silva
authors.initials: LE
authors.lastname: Soares
authors.affiliation: Institute of Research and Development, University of Paraíba Valley, Av. Shishima Hifumi, 2911, São José dos Campos 12244-000, SP, Brazil. Electronic address: amartin@univap.br.
authors.forename: Airton Abrahão
authors.initials: AA
authors.lastname: Martin
authors.affiliation: Department of Statistics, Piracicaba Dental School, State University of Campinas, Av. Limeira, 901, Piracicaba 13414-903, SP, Brazil. Electronic address: glaucia@fop.unicamp.br.
authors.forename: Gláucia
authors.initials: G
authors.lastname: Ambrosano
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Av. Limeira, 901, Piracicaba 13414-903, SP, Brazil. Electronic address: giannini@fop.unicamp.br.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Giannini
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry*; D003793:Dental Restoration, Permanent / Q000379:methods*; D006244:Hardness; D006801:Humans; D066298:In Vitro Techniques; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D008964:Molar, Third; D058105:Polymerization; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C000618653:EverX Posterior; C000614713:Filtek Bulk Fill; C539358:Herculite Ultra; C553871:Surefil SDR Flow; C501891:Tetric EvoCeram
keywords: Composite resin; Dental restoration; Gap formation; Hardness; Methacrylate; Polymerization; Stress