Extent of polymerization of experimental adhesive blends containing anhydrous QAMs

Objectives: This study examined the effect of anhydrous quaternary ammonium methacrylates (QAMs) on the extent of polymerization (Ep) of experimental light-cured adhesive resins by using differential scanning calorimetry (DSC). The hypothesis tested was that polymerization kinetics of the adhesive blends was not affected QAMs addition.

Methods: Light-curing experimental adhesive blends containing 70wt% resin (R2: 70wt% bisGMA, 28.75wt% TEGDMA; R3: 70wt% BisGMA, 28.75wt% HEMA; R4: 40wt% BisGMA, 30wt% TCDM, 28.75wt% TEGDMA; R5: 40wt% BisGMA, 30wt% BisMP, 28.75wt% HEMA), 20wt% ethanol (ETOH) and 10wt% QAMs in their anhydrous form (ATA or MCMS or METMAC) were prepared. All blends included 1wt% EDMAB+0.25wt% CQ. Resins with no QAMS were used as a control (80wt% R2-R5+20wt% ETOH). A DSC device was used to measure the Ep of the experimental adhesive blends. Curing was performed in the DSC chamber with a halogen curing light for 40s (600 mW/cm²) at 35°C under a nitrogen atmosphere. Data were analyzed by two-way ANOVA and Tukey's post hoc test.

Results: DSC data showed that Ep of all tested resins was higher when ATA was added (p<0.05) (Table 1). Ep of R5 was increased by QAMs addition independently from QAMs type (p<0.05).

Table 1. Means and standard deviations of Ep of the tested resin blends.

Resin blend	Ep (%)
80wt%R2+20wt%ETOH	59±5ab
80wt%R3+20wt%ETOH	63±5ab
80wt%R5+20wt%ETOH	60±7a
70wt%R2+20wt%ETOH+10wt%ATA	71±3bc
70wt%R3+20wt%ETOH+10wt%ATA	75±7c
70wt%R5+20wt%ETOH+10wt%ATA	66±2bc
70wt%R2+20wt%ETOH+10wt%MCMS	67±5bc
70wt%R3+20wt%ETOH+10wt%MCMS	70±2abc
70wt%R5+20wt%ETOH+10wt%MCMS	75±2abc
70wt%R2+20wt%ETOH+10wt%METMAC	64±3ab
70wt%R3+20wt%ETOH+10wt%METMAC	69±7abc
70wt%R5+20wt%ETOH+10wt%METMAC	69±6abc

Same superscript letters indicate no statistical difference (p>0.05).

Conclusions: The tested hypothesis was partially rejected since QAMs addition increased the Ep of some of the tested resin blends when QAMs were added. Further studies are needed to clarify if QAMs addition can affect the properties of adhesive resins. 

Supported, in part, by grants: FIRB RBAP1095CR, and PRIN 2009SAN9K5 and 2009FXT3WL from MIUR, Italy, R01DE015306 to DHP (PI), and #8126472 from the Academy of Finland to AT-M (PI).