title: Acoustic properties of interfacial debonding and their relationship with shrinkage stress in Class-I restorations.
abstract: (1) To investigate the properties, and their correlations, of the acoustic emission (AE) from interfacial debonding of Class-I composite restorations during curing. (2) To establish the relationship between the theoretical shrinkage stress and the level of interfacial debonding in such restorations as determined by AE measurement.
  
  
  
  An AE sensor was attached onto the surface of human molars with a Class-I composite restoration of 4mm (length)×3mm (width)×2mm (depth) to monitor their debonding from the tooth tissues during curing. Background signals were analyzed before curing to determine the threshold amplitude for noise filtering. Three groups (n=3) of composites with different levels of shrinkage were tested: (1) Z100™, (2) Filtek™ Z250, and (3) Filtek™ LS. All restorations were cured with an LED blue light operated at 1200mW/cm(2) for 40s. AE signals were recorded continuously from the start of curing for 10min, and their frequency, amplitude and duration were analyzed. Finally, the cumulative number of AE events was compared with the theoretical maximum shrinkage stress that could be generated by the composites.
  
  
  
  The amplitude of the background signals was below 30dB, which was chosen as the threshold for noise filtering. The amplitude of all debonding events ranged from 30 to 50dB, and their duration was below 100μs. The peak frequency had two main bands: 100-200kHz and 700-800kHz. The duration time increased with increasing amplitude, but no correlation was found between the peak frequency and the other two parameters. The cumulative number of AE events was 30.67±2.31, 14.00±7.81 and 5.67±3.06 for Z100, Z250 and LS, respectively, which corresponded well with the theoretical maximum shrinkage stress they could produce, i.e. 42.5, 97.5 and 182.5MPa. R(2)=0.9955 for the linear regression. The theoretical shrinkage stress below which no AE events were detected was about 14.3MPa.
  
  
  
  For the materials considered, the amount of interfacial debonding produced in a Class-I restoration during curing increased linearly with the theoretical maximum shrinkage stress of the composite. The theoretical stress below which no AE events were detected was similar to composite-dentin bond strength reported in the literature.
authors.affiliation: Department of Prosthodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.affiliation: Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, State Key Laboratory of Military Stomatology, Xi'an, China.
authors.forename: Jiawen
authors.initials: J
authors.lastname: Guo
authors.affiliation: Department of Prosthodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Huang
authors.affiliation: Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Young
authors.initials: Y
authors.lastname: Heo
authors.affiliation: Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, Minneapolis, MN, USA.. Electronic address: alexfok@umn.edu.
authors.forename: Alex
authors.initials: A
authors.lastname: Fok
authors.affiliation: Department of Prosthodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China. Electronic address: wyan65@163.com.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000162:Acoustics; D003188:Composite Resins; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D003804:Dentin; D006801:Humans; D008422:Materials Testing; D013499:Surface Properties
chemical_list: D003188:Composite Resins
keywords: Acoustic emission; Interfacial debonding; Resin composite; Shrinkage stress