title: How should composite be layered to reduce shrinkage stress: incremental or bulk filling?
abstract: OBJECTIVE
  The purpose of this study was to determine the effect of different layering techniques on cuspal deflection in direct composite restorations.
  
  
  METHODS
  Aluminum blocks were used to prepare MOD cavities divided into three groups. Each cavity was restored with composite using three different filling techniques. Group 1 was filled in bulk, group 2 was restored by a horizontal increment technique, and group 3 by an oblique increment technique. Cuspal deflection was measured with LVDT probes and compared among groups using ANOVA and Scheffe's post hoc test (alpha = 0.05).
  
  
  RESULTS
  The cuspal deflections in groups 1-3 were 21.6+/-0.90 microm, 19.3+/-0.73 microm and 18.4+/-0.63 microm, respectively. The bulk filling technique yielded significantly more cuspal deflection than the incremental filling techniques, while there was no significant difference between the horizontal and oblique increment methods.
  
  
  CONCLUSIONS
  Cuspal deflection resulting from polymerization shrinkage can be reduced by incremental filling techniques to obtain optimal outcomes in clinical situations.
authors.affiliation: Department of Conservative Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, South Korea.
authors.forename: Junkyu
authors.initials: J
authors.lastname: Park
authors.forename: Juhea
authors.initials: J
authors.lastname: Chang
authors.forename: Jack
authors.initials: J
authors.lastname: Ferracane
authors.forename: In Bog
authors.initials: IB
authors.lastname: Lee
mesh_terms: D003188:Composite Resins / Q000008:administration & dosage*; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D044367:Phase Transition; D011897:Random Allocation
chemical_list: D003188:Composite Resins