Laikuan Zhu1, Yuping Li2, Carola A Carrera2, Yung-Chung Chen3, Mingyu Li4, Alex Fok5. 1. Department of Endodontics and Operative Dentistry, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Stomatology & Shanghai Research Institute of Stomatology, National Clinical Research Center of Stomatology, Shanghai, China. Electronic address: zhulk1997@163.com. 2. Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, Minneapolis, MN, USA. 3. Institute of Oral Medicine, College of Medicine National Cheng Kung University Taiwan, Taiwan. 4. Shanghai Key Laboratory of Stomatology & Shanghai Research Institute of Stomatology, National Clinical Research Center of Stomatology, Shanghai, China. 5. Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, Minneapolis, MN, USA. Electronic address: alexfok@umn.edu.
Abstract
OBJECTIVE: To verify and calibrate a chemical model for simulating the degradation of the dentin-composite interface induced by multi-species oral biofilms in vitro. METHODS: Dentin-composite disks (5-mm dia.×2-mm thick) were made from bovine incisor roots and filled with either Z100™ (Z100) or Filtek™ LS (LS) composite. The disks, which were covered with nail varnish, but with one of the dentin-composite margins exposed, were immersed in lactic acid solution at pH 4.5 for up to 48h. Diametral compression was performed to measure the reduction in bond strength of the dentin-composite disks following acid challenge. Scanning electron microscopy (SEM) was used to examine decalcification of dentin and fracture modes of the disks. To better understand the degradation process, micro-computed tomography, in combination with a radiopaque dye (AgNO3), was used to assess interfacial leakage in 3D longitudinally, while SEM was used to determine the path of leakage. One-way analysis of variance (ANOVA) was used to analyze the results, with the level of statistical significance set at p<0.05. The results were compared with those obtained previously using multi-species biofilms for verification and calibration purposes. RESULTS: After 48h of acid challenge, the debonding load of both the LS- and Z100-filled disks reduced significantly (p<0.05). In the Z100-filled disks, debonding mostly occurred at the adhesive-dentin interface, while in the LS-filled disks, this happened at the adhesive-composite interface, instead. The degree of dentin demineralization, the reduction in debonding load and the modes of failure observed were very similar to those induced by multi-species oral biofilms found in the previous work. Leakage of AgNO3 occurred mainly along the hybrid layer. The specimens filled with Z100 had a thicker hybrid layer (∼6.5μm), which exhibited more interfacial leakage than those filled with LS. SIGNIFICANCE: The chemical model with lactic acid used in this study can induce degradation to the dentin-composite interface similar to those produced by multi-species biofilms. With appropriate calibration, this could provide an effective in vitro method for ageing composite restorations in assessing their potential clinical performance.
OBJECTIVE: To verify and calibrate a chemical model for simulating the degradation of the dentin-composite interface induced by multi-species oral biofilms in vitro. METHODS: Dentin-composite disks (5-mm dia.×2-mm thick) were made from bovine incisor roots and filled with either Z100™ (Z100) or Filtek™ LS (LS) composite. The disks, which were covered with nail varnish, but with one of the dentin-composite margins exposed, were immersed in lactic acid solution at pH 4.5 for up to 48h. Diametral compression was performed to measure the reduction in bond strength of the dentin-composite disks following acid challenge. Scanning electron microscopy (SEM) was used to examine decalcification of dentin and fracture modes of the disks. To better understand the degradation process, micro-computed tomography, in combination with a radiopaque dye (AgNO3), was used to assess interfacial leakage in 3D longitudinally, while SEM was used to determine the path of leakage. One-way analysis of variance (ANOVA) was used to analyze the results, with the level of statistical significance set at p<0.05. The results were compared with those obtained previously using multi-species biofilms for verification and calibration purposes. RESULTS: After 48h of acid challenge, the debonding load of both the LS- and Z100-filled disks reduced significantly (p<0.05). In the Z100-filled disks, debonding mostly occurred at the adhesive-dentin interface, while in the LS-filled disks, this happened at the adhesive-composite interface, instead. The degree of dentin demineralization, the reduction in debonding load and the modes of failure observed were very similar to those induced by multi-species oral biofilms found in the previous work. Leakage of AgNO3 occurred mainly along the hybrid layer. The specimens filled with Z100 had a thicker hybrid layer (∼6.5μm), which exhibited more interfacial leakage than those filled with LS. SIGNIFICANCE: The chemical model with lactic acid used in this study can induce degradation to the dentin-composite interface similar to those produced by multi-species biofilms. With appropriate calibration, this could provide an effective in vitro method for ageing composite restorations in assessing their potential clinical performance.
Authors: C A B Cardoso; A R F de Castilho; P M A Salomão; E N Costa; A C Magalhães; M A R Buzalaf Journal: J Dent Date: 2014-08-23 Impact factor: 4.379
Authors: Carola A Carrera; Caixia Lan; David Escobar-Sanabria; Yuping Li; Joel Rudney; Conrado Aparicio; Alex Fok Journal: Dent Mater Date: 2015-01-30 Impact factor: 5.304