Effect of an RMGI Liner on Polymerization Shrinkage of Composites

Objective:  Evaluate the effect of a new resin-modified glass ionomer liner (3M™ ESPE™ Vitrebond™ Plus Liner, VBP)  on the polymerization shrinkage stress of composites with a range of shrinkage (3M™ ESPE™ Supreme™, SUP; Ivoclar™ Tetric™ EvoCeram, EVO; Dentsply™ EsthetX™, EX), compared with three RMGI liners (3M™ ESPE™ Vitrebond™ Liner, VB; GC™ Fuji™ Paste Pak Liner, FPP; GC™ Fuji™ Lining LC, FLC)  and two flowable composites (Kerr™ Revolution™, REV; 3M™ ESPE™ Supreme™ Flow, SPF).

Methods:   The deflecting disc method [Watts & Cash. Dent Mater 1991;7:281] was used to measure volumetric polymerization shrinkage of a 2mm thickness of composite alone, and of 2mm thickness of composite combined with 0.5mm thickness of each test material; n=5 per group. Percent reduction in shrinkage for composite combined  with each liner was calculated.   Data were analyzed via one-way ANOVA and Tukey's T-test (p<0.05).

Results:  Table shows mean volumetric %shrinkage(stdev), and %reduction in shrinkage over composite alone.  These results can be closely correlated to flexural modulus data (Rusin et al., 2007)

	%Shrinkage, SUP+liner.	%reduction over SUP alone	%Shrinkage, EVO+liner.	%reduction over EVO alone	%Shrinkage,  EX+liner.	%reduction over EX alone
VBP	1.48(0.20)	52.7%	1.47(0.07)	35.4%	1.84(0.11)	38.7%
VB	1.11(0.20)	64.6%	1.21(0.15)	46.6%	1.49(0.22)	50.2%
FPP	2.14(0.13)	31.4%	1.91(0.17)	15.9%	2.47(0.46)	17.5%
FLC	2.03(0.21)	34.9%	1.75(0.19)	23.0%	2.20(0.15)	26.5%
REV	2.25(0.09)	27.9%	1.90(0.10)	16.3%	2.81(0.11)	6.3%
SPF	2.56(0.05)	18.2%	1.99(0.06)	12.5%	2.82(0.11)	6.1%
Composite alone	3.13(0.10)	--	2.27(0.12)	--	3.00(0.18)	--

Conclusions:   Use of RMGI liners VBP, VB, FPP and FLC resulted in a statistically significant reduction in the volumetric shrinkage of composites, with VBP and VB having the greatest effect.  Shrinkage reduction was greater for VBP and VB than for FPP and flowables REV and SPF when used with SUP, EVO, and EX.