title: Microcomputed Tomography Evaluation of Volumetric Shrinkage of Bulk-Fill Composites in Class II Cavities.
abstract: OBJECTIVE
  This study aimed to quantify polymerization shrinkage of one conventional and three bulk-fill composites, under bonded and unbonded conditions, in Class II preparations using 3D microcomputed tomography (μCT) and report its location.
  
  
  METHODS
  Preparations (2.5 mm occlusal depth × 4 mm wide × 4 mm mesial box and 1 mm beyond the CEJ distal box depth) were made in 48 human extracted molars (n = 6). Four composites were tested, one regular (Vitalescence/VIT) and three bulk-fill: SureFil SDR Flow (SDR), Tetric EvoCeram Bulk Fill (TET), and Filtek flowable Bulk Fill (FIL). Teeth were divided into four groups according to restorative material used and subdivided into two subgroups, according to the presence of an adhesive system (XP Bond) application (bonded [-B]) or its absence (unbonded [-U]). Each tooth was scanned three times: (1) after cavity preparation, (2) before and (3) after composite light-curing. Acquired μCT images were imported into 2D and 3D software for analysis.
  
  
  RESULTS
  Significantly different volumetric shrinkage between bonded and unbonded conditions was observed only for TET group (p < 0.05), unbonded presenting significantly higher volumetric shrinkage. Among the bonded groups, TET-B presented significantly lower shrinkage than both SDR-B and FIL-B but not significantly different from VIT-B. Generally, shrinkage occurred at occlusal and distal surfaces.
  
  
  CONCLUSIONS
  When applied to bonded Class II cavities, TET exhibited significantly lower volumetric shrinkage compared to the other bulk-fill composites. However, it also exhibited the highest difference of volumetric shrinkage values between unbonded and bonded cavities.
  
  
  CONCLUSIONS
  Volumetric polymerization shrinkage occurred with all composites tested, regardless of material type (conventional or bulk-fill) or presence or absence of bonding. However, volumetric shrinkage has been reduced or at least maintained when bulk-fill composites were used compared to a conventional composite resin, which makes them a potential time saving alternative for clinicians. (J Esthet Restor Dent 29:118-127, 2017).
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA.|Department of Restorative Dental Science, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Hamad
authors.initials: H
authors.lastname: Algamaiah
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA.|Research Professor, Department of Biomaterials, Universidad de Los Andes, Santiago, Chile.|Department of Restorative Dentistry, Piracicaba Dental School, UNICAMP, Piracicaba, SP, Brazil.
authors.forename: Camila S
authors.initials: CS
authors.lastname: Sampaio
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA.
authors.forename: Lindiane C
authors.initials: LC
authors.lastname: Rigo
authors.affiliation: Department of Epidemiology and Health Promotion, New York University College of Dentistry, New York, NY, USA.
authors.forename: Malvin N
authors.initials: MN
authors.lastname: Janal
authors.affiliation: Associate Professor, Department of Restorative Dentistry, State University of Campinas, Piracicaba Dental School, Piracicaba, SP, Brazil.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Giannini
authors.affiliation: Assistant Professor, Department of Phosthodontics, University of São Paulo, Bauru School of Dentistry, Bauru, SP, Brazil.
authors.forename: Estevam A
authors.initials: EA
authors.lastname: Bonfante
authors.affiliation: Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA.
authors.forename: Paulo G
authors.initials: PG
authors.lastname: Coelho
authors.affiliation: Associate Professor, Department of Operative Dentistry, Guarulhos University, Guarulhos, SP, Brazil.
authors.forename: Andre F
authors.initials: AF
authors.lastname: Reis
authors.affiliation: Assistant Professor, Department of Biomaterials and Biomimetics, New York University College of Dentistry, New York, NY, USA.
authors.forename: Ronaldo
authors.initials: R
authors.lastname: Hirata
mesh_terms: D003188:Composite Resins / Q000737:chemistry; D003731:Dental Caries / Q000000981:diagnostic imaging* / Q000473:pathology*; D006801:Humans; D058105:Polymerization; D055114:X-Ray Microtomography / Q000379:methods*
chemical_list: D003188:Composite Resins; C000614713:Filtek Bulk Fill; C553871:Surefil SDR Flow; C501891:Tetric EvoCeram