Influence of different initiators on the degree of conversion of experimental adhesive blends in relation to their hydrophilicity and solvent content.
OBJECTIVE
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.
Cadenaro
Milena
M
Unit of Dental Sciences and Biomaterials, Department of Biomedicine, University of Trieste, Piazza Ospedale 1, Trieste, Italy.
Antoniolli
Francesca
F
Codan
Barbara
B
Agee
Kelli
K
Tay
Franklin R
FR
Dorigo
Elettra De Stefano
Ede S
Pashley
David H
DH
Breschi
Lorenzo
L
D000704:Analysis of Variance; D002152:Calorimetry, Differential Scanning; D017220:Dentin-Bonding Agents / Q000737:chemistry* / Q000528:radiation effects; D000431:Ethanol; D006244:Hardness; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D044367:Phase Transition; D010720:Phosphines; D019279:Resin Cements / Q000737:chemistry* / Q000528:radiation effects; D012997:Solvents; D013729:Terpenes; D014867:Water; D017155:Wettability
C520678:(2,4,6-trimethylbenzoyl) diphenylphosphine oxide; D017220:Dentin-Bonding Agents; D010720:Phosphines; D019279:Resin Cements; D012997:Solvents; D013729:Terpenes; D014867:Water; D000431:Ethanol; C048339:camphoroquinone