title: Polymerization shrinkage and depth of cure of packable composites.
abstract: OBJECTIVE
  This investigation evaluated polymerization shrinkage and depth of cure of five packable composites.
  
  
  METHODS
  Five materials were used for the investigation: Alert, Surefil, Solitaire, P60, and Prodigy Condensable. Groups of 10 specimens of each material were made measuring either 2 or 5 mm in thickness, mounted in a testing jig, and polymerized using a dental curing light. Linear shrinkage was recorded and converted to a volumetric value. To evaluate depth of cure, ten specimens of each material were fabricated in both 2- and 5-mm thicknesses, and a Knoop hardness number was recorded on the top and bottom surfaces 5 minutes after light curing. A one-way analysis of variance statistical test was used to determine if there was a significant difference among materials. A Tukey multiple comparison test was then used to determine where significant differences existed.
  
  
  RESULTS
  The volumetric shrinkage for the 2-mm-thick specimens from highest shrinkage to lowest were: Solitaire (3.3%), Prodigy Condensable (1.8%), Surefil (1.4%), P60 (1.2%), and Alert (0.2%). The 5-mm-thick specimens were ranked as follows: Solitaire (2.1%), Prodigy Condensable (1.0%), P60 (0.9%), Surefil (0.8%), and Alert (0.3%). Hardness for the bottom surface of the 2-mm-thick specimens showed that P60 (48.5) and Alert (42.6) had the highest values. Solitaire (11.2) had a significantly lower value. Hardness for the bottom surface at 5-mm thickness showed Alert (16.5) and P60 (16.3) with higher values than Surefil (8.9).
  
  
  CONCLUSIONS
  Solitaire had the most shrinkage and Alert the least at both 2- and 5-mm depths. Depth of cure was severely compromised for all materials at 5 mm.
authors.affiliation: University of Michigan School of Dentistry, Department of Biologic and Materials Science, Division of Prosthodontics, Ann Arbor 48109-1078, USA.
authors.forename: Alberto A
authors.initials: AA
authors.lastname: Herrero
authors.forename: Peter
authors.initials: P
authors.lastname: Yaman
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Dennison
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D006244:Hardness; D006801:Humans; D008029:Lighting / Q000295:instrumentation; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors
chemical_list: C406265:Alert composite resin; D003188:Composite Resins; C443708:P60 Condensible Resin Composite; D011108:Polymers; C477351:Prodigy Condensable; C113049:Solitaire composite resin; C403464:SureFil packable composite