1147 Synthesis and Storage Stability of a Hydrolytically Stable Selfetching Primer
U. SALZ, A. GIANASMIDIS, N. MOSZNER, and V. RHEINBERGER, Ivoclar Vivadent AG, Schaan, Liechtenstein

Objectives: Acid monomers and hydrophilic (meth)acrylate crosslinkers used in selfetching primers are under acidic conditions not hydrolytically stable. To create adequate etch patterns on enamel and to dissolve the smeary layer on dentin strong acidic conditions with a pH-value in the range of 2 – 1 are required. Under these conditions conventional (meth)acrylates degrade by formation of the spacer (poly)ol and (meth)acrylic acid. Therefore a selfetching primer was developed based on hydrolytically stable components. A new synthesized acrylate etherphosphonic acid monomer (AEPA) and bis(meth)acryl amides (bis-MAA) were used to formulate a storage stable selfetching primer.

Methods: Long-term stability was investigated by HPLC at 23 and 42 oC for 16 weeks in comparison to a triethyleneglycol dimethacrylate (TEGDMA)/water based selfetching primer. The results of the HPLC-investigation could be confirmed by shear bond strength measurements.

Results: The results received by HPLC at a storage temp. of 42 oC are listed in the table below.

AEPA/bis-MAA-formulation

      
 

inital

4 weeks

8 weeks

12 weeks

16 weeks

AEPA (%)

40.0

26.9

17.9

12.0

9.5

Bis-MAA (%)

20.0

19.0

18.4

17.0

15.8

AEPA/TEGDMA-formulation

      

AEPA (%)

30.0

25.7

18.5

11.1

15.2

TEGDMA (%)

15.0

8.2

4.9

2.7

1.6

Under these strong acidic conditions about 90 % of the TEGDMA was saponified after 16 weeks at 42 oC, however only about 20% from the bisacryl amide were decomposed. In the case of the new acrylate etherphosphonic acid the link between the acid group and the polymerizable part of the molecule remained intact, but the acrylate ester bond was saponified too. Bond strength values were on enamel: 21.9 ± 6.0 MPa and on dentin 24.7 ± 2.2 MPa (two-way ANOVA significance level p < 0.05).

Conclusion: The use of new synthesized hydrolytically stable monomers resulted in a storage stable selfetching primer .

Seq #115 - "Self-etching" Adhesive Systems
3:45 PM-5:00 PM, Thursday, 7 March 2002 San Diego Convention Center Exhibit Hall C

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