Polymerization kinetics of dental adhesives cured with LED: Correlation between extent of conversion and permeability

Lorenzo Breschi, Milena Cadenaro, Francesca Antoniolli, Salvatore Sauro, Matteo Biasotto, Carlo Prati, Franklin R. Tay, Roberto Di Lenarda

Research output: Contribution to journalArticlepeer-review

74 Scopus citations


Objectives: The aim of this study was to analyze the polymerization kinetics of different adhesive films in relation to their permeability after exposure to different LED curing units. Methods: One adhesive from each class was analyzed: a three-step etch-and-rinse (OptiBond FL; Sybron-Kerr), a two-step etch-and-rinse (One-Step, Bisco), a two-step self-etch (Clearfil Protect Bond, Kuraray) and a one-step self-etch adhesive (Xeno III; Dentsply DeTrey). Adhesive films were prepared and cured with SmartLite IQ (Dentsply) or L.E.Demetron I (Demetron Kerr) up to complete curing. Polymerization kinetic curves of the tested adhesives were obtained with differential scanning calorimetry (DSC). In particular, total reaction time and extent of polymerization (Ep) at 20, 40 or 60 s were compared. Permeability of the adhesive films was evaluated on flat dentin surfaces of human extracted teeth connected to a permeability device and statistically analyzed. Results: Total reaction time differed among the adhesives tested: OptiBond FL < Clearfil Protect Bond < One-Step < Xeno III with both curing units (p < 0.05). At 20 s OptiBond FL showed the highest Ep, while the lowest values were obtained with One-Step and Xeno III (p < 0.05). Ep increased when curing time was prolonged (40 and 60 s) for all adhesives tested (p < 0.05), however, on simplified adhesives, incomplete polymerization took place even after prolonged exposure intervals. An inverse correlation was found between Ep of the adhesives and their permeability using LED curing units. Significance: This study supports the hypothesis that, longer curing times than those recommended by the respective manufacturer decrease permeability of the bonded interfaces.

Original languageEnglish (US)
Pages (from-to)1066-1072
Number of pages7
JournalDental Materials
Issue number9
StatePublished - Sep 2007


  • Dentin
  • Dentin adhesives
  • Extent of polymerization
  • LED curing units
  • Permeability

ASJC Scopus subject areas

  • General Materials Science
  • General Dentistry
  • Mechanics of Materials


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