title: Impact of hydrophilicity and length of spacer chains on the bonding of functional monomers.
abstract: OBJECTIVE
  10-Methacryloyloxy-decyl-dihydrogen-phosphate (10-MDP) is currently considered as one of the most effective functional monomers for dental bonding, this in part thanks to its long and relatively hydrophobic spacer chain, adequately separating the polymerizable from the phosphate functionalities. This study compared functional monomers with different spacer chains' length and hydrophilicity to 10-MDP on their dentin and enamel bonding performance.
  
  
  METHODS
  Atomic absorption spectroscopy (AAS) was used to characterize the chemical interaction. Micro-tensile bond strength (μTBS) and fractographic analyses were performed after 24h and one year. Confocal micro-permeability and SEM nanoleakage assessments were also undertaken. The tested functional monomers were 2-MEP (2-carbon spacer), 10-MDP (10-carbon), 12-MDDP (12-carbon), MTEP (high hydrophilic polyether spacer chain) and CAP-P (intermediate hydrophilic ester spacer).
  
  
  RESULTS
  AAS revealed clear differences (p<0.05) in monomer-calcium salt formation in this order: 12-MDDP=10-MDP>CAP-P>MTEP>2-MEP. The highest initial dentin μTBS was obtained using 10-MDP or 12-MDDP. After 1-year aging, a significant drop (p<0.05) in μTBS was observed for the adhesives with MTEP (enamel and dentin), 2-MEP (enamel) and CAP-P (enamel). MTEP presented the highest micro-permeability, while 2-MEP, CAP-P and MTEP showed increased nanoleakage after aging.
  
  
  CONCLUSIONS
  These outcomes showed that more hydrophilic and shorter spacer chains may compromise the chemical interaction with calcium and the dentin/enamel bonding performance.
authors.affiliation: Piracicaba Dental School, State University of Campinas, Piracicaba, Brazil; King's College London Dental Institute, Biomaterials, Biomimetics and Biophotonics (B3) Group, London, United Kingdom. Electronic address: victorpfeitosa@hotmail.com.
authors.forename: Victor P
authors.initials: VP
authors.lastname: Feitosa
authors.affiliation: King's College London Dental Institute, Biomaterials, Biomimetics and Biophotonics (B3) Group, London, United Kingdom; Biomaterials and Minimally Invasive Dentistry - Departamento de Odontologia, Facultad de Ciencias de laSalud, Universidad CEU-Cardenal Herrera, Valencia, Spain.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Sauro
authors.affiliation: Federal University of Pelotas, Pelotas, Brazil.
authors.forename: Fabricio A
authors.initials: FA
authors.lastname: Ogliari
authors.affiliation: Federal University of Pelotas, Pelotas, Brazil.
authors.forename: Aline Oliveira
authors.initials: AO
authors.lastname: Ogliari
authors.affiliation: KU Leuven - BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven), Leuven, Belgium.
authors.forename: Kumiko
authors.initials: K
authors.lastname: Yoshihara
authors.affiliation: Federal University of Pelotas, Pelotas, Brazil.
authors.forename: Cesar H
authors.initials: CH
authors.lastname: Zanchi
authors.affiliation: Piracicaba Dental School, State University of Campinas, Piracicaba, Brazil.
authors.forename: Lourenço
authors.initials: L
authors.lastname: Correr-Sobrinho
authors.affiliation: Piracicaba Dental School, State University of Campinas, Piracicaba, Brazil.
authors.forename: Mário A
authors.initials: MA
authors.lastname: Sinhoreti
authors.affiliation: Piracicaba Dental School, State University of Campinas, Piracicaba, Brazil.
authors.forename: Américo B
authors.initials: AB
authors.lastname: Correr
authors.affiliation: King's College London Dental Institute, Biomaterials, Biomimetics and Biophotonics (B3) Group, London, United Kingdom.
authors.forename: Timothy F
authors.initials: TF
authors.lastname: Watson
authors.affiliation: KU Leuven - BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven), Leuven, Belgium.
authors.forename: Bart
authors.initials: B
authors.lastname: Van Meerbeek
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D002208:Caproates / Q000737:chemistry; D001840:Dental Bonding; D003743:Dental Enamel / Q000648:ultrastructure; D003763:Dental Leakage / Q000145:classification; D003804:Dentin / Q000648:ultrastructure; D057927:Hydrophobic and Hydrophilic Interactions; D007783:Lactones / Q000737:chemistry; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology; D010539:Permeability; D017553:Phosphorus Compounds / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry*; D013054:Spectrophotometry, Atomic; D013314:Stress, Mechanical; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D002208:Caproates; D007783:Lactones; D008689:Methacrylates; D017553:Phosphorus Compounds; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D019279:Resin Cements; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C012500:phosphorus pentoxide; C121056:caprolactone; C005044:hydroxyethyl methacrylate; C069749:methacryloyloxydecyl dihydrogen phosphate; D002118:Calcium
keywords: Adhesion; Durability; Functional monomer; Hydrophilicity; Micro-permeability; Self-etch adhesive