title: Time-dependent visco-elastic creep and recovery of flowable composites.
abstract: Creep behaviour of flowable composites was evaluated in relation to their filler fraction and the postcure period. Solid cylindrical specimens were prepared (4 x 6 mm) using steel moulds, with thorough light curing from multiple directions at 600 mW cm(-2). The specimens were divided into two groups (n=3/material) as follows: group I, loaded 5 min after preparation; and group II, loaded after storage for 1 month in water at 37+/-1 degrees C. A constant compressive stress of 36 MPa was applied to each specimen for 2 h followed by removal of the weight for 2 h of strain recovery. Axial strain measurements were obtained continuously over the total analysis time of 4 h. The maximum creep strain ranged from 2.04 to 7.69% and from 1.03 to 6.12% for groups I and II, respectively. Flowables that had the highest percentage of filler produced the lowest creep strain. The creep response decreased with 1 month of preload storage. Clinically, the finding of this study suggests that flowable composites are unsuitable for stress-bearing areas.
authors.affiliation: Department of Paediatric Dentistry, University of Al-Baath, School of Dentistry, Hama, Syria. d_kusai@yahoo.co.uk
authors.forename: Kusai
authors.initials: K
authors.lastname: Baroudi
authors.forename: Nick
authors.initials: N
authors.lastname: Silikas
authors.forename: David C
authors.initials: DC
authors.lastname: Watts
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D019245:Compressive Strength; D003764:Dental Materials / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000379:methods*; D004548:Elasticity; D008422:Materials Testing / Q000379:methods; D012212:Rheology; D013997:Time Factors; D014783:Viscosity; D016474:Weight-Bearing
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C111840:flowable hybrid composite