title: The effect of ageing on the elastic modulus and degree of conversion of two multistep adhesive systems.
abstract: During the curing reaction, the monomers of dentine bonding systems should cross-link sufficiently to strengthen an adhesive so that it is clinically reliable. This study evaluated how different storage conditions (air vs. water storage) affect the elastic modulus (E-modulus) and degree of conversion (DC) of a three-step etch-and-rinse adhesive and a two-step self-etch adhesive. The biaxial flexural test and Raman microscopy were performed on resin disks made from the bonding agents Adper Scotchbond Multi-Purpose (SBMP; 3M ESPE) and Clearfil Protect Bond (CPB; Kuraray). The measurements were repeated after storage in either air or water for 15 and 30 min and for 1, 24, and 72 h. At time 0, the E-modulus was not affected by the adhesive system, whilst the degree of cure of CPB was higher than that of SBMP. Air storage increased the E-modulus at each ageing interval. Storage in water increased the E-modulus until it reached a maximum at 24 h, after which it decreased significantly at 72 h. No linear correlation between the percentage DC and E-modulus of the two adhesives was found when stored in water. The results of this study indicate that the mechanical properties and polymerization kinetics of SBMP and CPB are affected by storage time and medium.
authors.affiliation: Division of Dental Sciences and Biomaterials, Department of Biomedicine, University of Trieste, Trieste, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Marchesi
authors.forename: Chiara O
authors.initials: CO
authors.lastname: Navarra
authors.forename: Milena
authors.initials: M
authors.lastname: Cadenaro
authors.forename: Marcela R
authors.initials: MR
authors.lastname: Carrilho
authors.forename: Barbara
authors.initials: B
authors.lastname: Codan
authors.forename: Valter
authors.initials: V
authors.lastname: Sergo
authors.forename: Roberto
authors.initials: R
authors.lastname: Di Lenarda
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Breschi
mesh_terms: D000388:Air; D055598:Chemical Phenomena; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D055119:Elastic Modulus; D006801:Humans; D008422:Materials Testing; D055668:Photochemical Processes; D018583:Pliability; D011108:Polymers / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: C503075:Clearfil Protect Bond; D017220:Dentin-Bonding Agents; D011108:Polymers; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; D014867:Water