title: Effect of heat on the flow of commercial composites.
abstract: OBJECTIVE
  This study compared the flowability of various commercial dental composites to flowable composites in response to warming in a composite warmer.
  
  
  METHODS
  18 conventional resin composites and four flowable composites were tested at room temperature (23 degrees C), and the conventional composites were tested after pre-heating in a Calset unit (Addent) to 54 degrees C or 68 degrees C. Flowability was determined by placing uncured composite onto plastic sheets and loading for 180 seconds (4 kg load) while maintained at 36 degrees C (conditioning temperature [n=3]) to simulate placing room temperature composite into a tooth. The composite was light-cured for 40 seconds. The thickness of the specimens were measured. Thickness/volume (T/V) were compared for the composites for the three temperatures, and between flowable and conventional composites at 23 degrees C (one-way ANOVA/Tukey's; P < 0.05).
  
  
  RESULTS
  At 23 degrees C, the flowable composites T/V were significantly less than the conventional composites (P < 0.001), ranging from 0.46 mm/cm3 (Perma Flo HV) to 1.43 mm/cm3 (Point 4 Flow), except for Z100 (1.48 mm/cm3/ +/-0.32), Z250 (1.79 mm/cm3/ +/-0.09), Gradia (1.53 mm/cm3/ +/-0.07), and Grandio (1.98 mm/cm3/ +/-0.07). The T/V of the conventional composites were not significantly different at all three temperatures (P> 0.05), except for Esthet-X which showed the greatest T/V decrease at 68 degrees C (3.84 mm/cm3/ +/-0.3) compared to 23 degrees C (6.44 mm/cm3/ +/-0.36) and 4 Seasons which showed the greatest T/V decrease at 54 degrees C (3 mm/cm3/ +/-0.1) compared to 23 degrees C (3.57 mm/cm3/ +/-0.1.4).
authors.affiliation: Department of Restorative Dentistry, Division of Operative Dentistry, OHSU School of Dentistry, 611 S.W. Campus Drive, Portland, OR 97369, USA. dacostaj@ohsu.edu
authors.forename: Juliana
authors.initials: J
authors.lastname: da Costa
authors.forename: Rose
authors.initials: R
authors.lastname: McPharlin
authors.forename: Thomas
authors.initials: T
authors.lastname: Hilton
authors.forename: Jack
authors.initials: J
authors.lastname: Ferracane
mesh_terms: D003188:Composite Resins / Q000737:chemistry; D006358:Hot Temperature; D008422:Materials Testing; D012212:Rheology; D014783:Viscosity
chemical_list: D003188:Composite Resins