title: Bond strength of resin composite to differently conditioned amalgam.
abstract: Bulk fracture of teeth, where a part of the amalgam restoration and/or the cusp is fractured, is a common clinical problem. The aim of this study was to evaluate the effect of different surface conditioning methods on the shear bond strength of a hybrid resin composite to fresh amalgam. Amalgams (N=84) were condensed into acrylic and randomly assigned to one of the following treatments (N=6): (1) Alloy primer + opaquer, (2) Air-particle abrasion (50 micro m Al(2)O(3)) + alloy primer + opaquer, (3) Silica coating (30 micro m SiO(x)) + silanization + opaquer, (4) Opaquer + pre-impregnated continuous bidirectional E-glass fibre sheets, (5) Silica coating + silanization + fibre sheets, (6) Silica coating + silanization + opaquer + fibre sheet application. Non-conditioned amalgam surfaces were considered as control group (7). The mean surface roughness depth (R(Z)) was measured from the control group and air-abraded amalgam surfaces. The resin composite was bonded to the conditioned amalgam specimens using polyethylene molds. All specimens were tested under dry and thermocycled (6.000, 5-55 degrees C, 30 s) conditions. The shear bond strength of resin composite to amalgam substrates was measured in a universal testing machine (1 mm/min). Surface roughness values for the non-conditioned control group (R(Z) approximately 0.14 micro m) and for air-particle abraded surfaces with either Al(2)O(3) or SiO(x) (R(Z) approximately 0.19 micro m and R(Z) approximately 0.16 micro m, respectively) did not show significant differences (p=0.23) (One-way ANOVA). In dry conditions, silica coating and silanization followed by fibre sheet application exhibited significantly higher results (14.8+/-5.6 MPa) than those of the groups conditioned with alloy primer (2.2+/-0.7 MPa) (p<0.001), air-particle abrasion+alloy primer (4.4+/-2.0 MPa, p<0.001), silica coating+silanization alone (6.2+/-0.8 MPa, p=0.009) or non-conditioned group (1.4+/-0.6, p<0.001). Silica coating and silanization followed by additional fibre sheets with opaquer application (23.6+/-6.9 MPa) increased the bond strength significantly compared to those of other groups (group 5 vs group 6, p=0.007; other groups vs group 6, p<0.001). Thermocycling decreased the bond strengths significantly for all of the conditioning methods tested (for group 1, p<0.001; for group 2, p=0.013; for group 3, p=0.002; for group 4, p=0.026; for group 5, p=0.002; for group 6, p<0.001 and for group 7, p<0.001).
authors.affiliation: Department of Dentistry and Dental Hygiene, University of Groningen, Faculty of Medical Sciences, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands. mutluozcan@hotmail.com
authors.forename: M
authors.initials: M
authors.lastname: Ozcan
authors.forename: P K
authors.initials: PK
authors.lastname: Vallittu
authors.forename: M-C
authors.initials: MC
authors.lastname: Huysmans
authors.forename: W
authors.initials: W
authors.lastname: Kalk
authors.forename: T
authors.initials: T
authors.lastname: Vahlberg
mesh_terms: D020906:Air Abrasion, Dental; D000497:Alloys / Q000737:chemistry*; D000537:Aluminum Oxide / Q000737:chemistry; D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D003300:Copper / Q000737:chemistry; D001840:Dental Bonding; D003764:Dental Materials / Q000737:chemistry; D005069:Evaluation Studies as Topic; D005898:Glass / Q000737:chemistry; D006801:Humans; D008422:Materials Testing / Q000379:methods*; D033081:Shear Strength; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D012834:Silver / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature
chemical_list: D000497:Alloys; D003188:Composite Resins; D003764:Dental Materials; D012821:Silanes; D012834:Silver; D012822:Silicon Dioxide; D003300:Copper; D000537:Aluminum Oxide