Influence of different initiators on the degree of conversion of experimental adhesive blends in relation to their hydrophilicity and solvent content

Cadenaro, Milena; Antoniolli, Francesca; Codan, Barbara; Agee, Kelli; Tay, Franklin R.; Dorigo, Elettra De Stefano; Pashley, David H.; Breschi, Lorenzo

doi:10.1016/j.dental.2009.11.078

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Volume 26, Issue 4 , Pages 288-294, April 2010

Influence of different initiators on the degree of conversion of experimental adhesive blends in relation to their hydrophilicity and solvent content

Milena Cadenaro
- Unit of Dental Sciences and Biomaterials, Department of Biomedicine, University of Trieste, Italy
Francesca Antoniolli
- Unit of Dental Sciences and Biomaterials, Department of Biomedicine, University of Trieste, Italy
Barbara Codan
- Unit of Dental Sciences and Biomaterials, Department of Biomedicine, University of Trieste, Italy
Kelli Agee
- Department of Oral Biology, School of Dentistry, Medical College of Georgia, Augusta, GA, USA
Franklin R. Tay
- Department of Oral Biology, School of Dentistry, Medical College of Georgia, Augusta, GA, USA
Elettra De Stefano Dorigo
- Unit of Dental Sciences and Biomaterials, Department of Biomedicine, University of Trieste, Italy
David H. Pashley
- Department of Oral Biology, School of Dentistry, Medical College of Georgia, Augusta, GA, USA
Lorenzo Breschi
- Unit of Dental Sciences and Biomaterials, Department of Biomedicine, University of Trieste, Italy
- IGM-CNR, Unit of Bologna c/o IOR, Bologna, Italy
- Corresponding author at: Department of Biomedicine, Unit of Dental Sciences and Biomaterials, Clinica Stomatologica, University of Trieste, Piazza Ospedale, 1, I-34129 Trieste, Italy. Tel.: +39 0403992192; fax: +39 0403992665.

Received 18 June 2009; received in revised form 10 November 2009; accepted 16 November 2009.

Abstract

Objectives

The aim of this study was to compare the curing reaction of five experimental adhesive blends containing different photo-initiating systems. The hypothesis tested was that degree of conversion (DC) of resin blends is affected by resin type, solvent content and photo-initiating system.

Methods

The experimental methacrylate resin blends were ranked from hydrophobic (R2) to hydrophilic (R3 and R4) and tested as neat, or solvated with 10% or 20% ethanol, or 10% ethanol and 10% water. Three different photo-initiators were used: IS-1=0.25% CQ (camphorquinone)+1% EDMAB (ethyl 4-dimethylaminobenzoate); IS-2=1.25% TPO (diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide); IS-3=0.25% CQ+0.50% EDMAB+0.50% TPO. DC of resin blends was measured with a differential scanning calorimeter. Data were analyzed with a three-way ANOVA.

Results

Neat resin type influenced DC, as R4 showed the highest values compared to R2 and R3 (p<0.05). Solvent had a significant effect on DC (p<0.05): dilution of resin blends with 10% or 20% ethanol or 10% ethanol+10% water increased the DC of all resins, except for R4. Initiators influenced the polymerization since neat resins and mixtures solvated with 10% or 20% ethanol showed their highest DC values when polymerized with IS-1 or IS-3 (p>0.05), while IS-2 or IS-3 increased the DC values of resins diluted with 10% ethanol and 10% water (p<0.05).

Conclusions

Water-compatible photo-initiators such as TPO should be included in the hydrophilic solvated adhesive formulation to ensure an appropriate DC of the adhesive layer.

Keywords: Dentin-bonding agents, Degree of conversion, Initiators, Hydrophilicity, Solvent