Study	Reason for exclusion
Akpata 2006	Liners not studied
Andersson‐Wenckert 2002	Sandwich technique study
Andersson‐Wenckert 2004	Sandwich technique study
Ernst 2002	Interventions not randomized
Ernst 2003	Interventions not randomized
Fagundes 2009	Liners not studied
Grogono 1990	Sandwich technique study
Huth 2003	No control or comparison group
Kaurani 2007	Interventions not randomized
Knibbs 1992	Sandwich technique study
Loguercio 2001	Liners not studied
Noro 1983	Interventions not randomized, restorative material no longer available (UV light‐cured RBC)
Rasmusson 1998	Inappropriate study design ‐ the study compared 1 brand of RBC placed without a liner to a second brand of RBC placed with a flowable composite as a liner
Shi 2010	Liners not studied
Unemori 2001	Interventions not randomized
van Dijken 1999	Sandwich technique study
Vilkinis 2000	Sandwich technique study
Whitworth 2005	Inappropriate study design ‐ the decision of which restoration to place (composite or amalgam) was left to the discretion of the operator and information regarding the decisions was not provided

RBC: resin‐based composite; UV: ultra violet.