Effekt von bioaktiven Nanopartikeln auf die Struktur, die physikalischen und die mechanischen Eigenschaften von dentalen Adhäsiven
by Lisa Hohlfeld
Date of Examination:2023-04-06
Date of issue:2023-03-08
Advisor:Prof. Dr. Annette Wiegand
Referee:Prof. Dr. Sven Rinke
Referee:Prof. Dr. Thomas Meyer
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EnglishIn the present in vitro study, different nanoparticles were added to a commercial adhesive (Solobond Plus, VOCO GmbH, Cuxhaven, Germany). The modified adhesives were investigated with respect to their material properties and to a possible bioactive reaction. Solobond Plus was mixed with 0.1 m% or 1 m% bioactive glass with bismuth trioxide (BG-Bi), 10 m% or 20 m% monofunctional polyhedral oligomeric silsequioxanes (POSS-1) or 10 m% or 20 m% multifunctional polyhedral oligomeric silsequioxanes (POSS-8). Pure Solobond Plus adhesive was used as a control. The distribution and size of the different nanoparticles were investigated in the solvent of the adhesive (acetone) using dynamic light scattering. The degree of conversion was measured by Fourier transform infrared spectrometry. Viscosity was investigated on samples of experimental Solobond Plus adhesive (without photoinitiators) using a rheometer. Water absorption and sol fraction were performed on standardized test specimens. For this purpose, the polymerized specimens were incubated in distilled water at 37 °C and weighed every 2 - 3 d using a precision balance. Subsequently, the water uptake and the sol fraction were calculated. The bioactive potential was investigated on extracted bovine teeth. The modified adhesive was applied to dentin test specimens by the etch-and-rinse method. The test specimens were incubated in artificial saliva at 37 °C for 13 weeks and then examined for the formation of superficial calcium phosphate precipitates by scanning electron microscopy. The viscosity, degree of conversion, water uptake, and sol fraction were statistically analyzed by simple analysis of variance and Tukey post hoc test (α = 0.05). POSS-1 and POSS-8 showed good dispersion in acetone and had a size of < 2 nm. The dispersion and size of BG-Bi could not be measured due to its strong tendency to aggregate. Measurement of viscosity showed no significant change for all groups except 1 m% BG-Bi compared to the control and ranged from 19 +- 1 mPa s to 82 +- 2 mPa s. A significant increase in viscosity (334 +- 59 mPa s) was observed for 1 m% BG-Bi compared to the control. A significant decrease in the degree of conversion was detected for POSS-8 (10 m%: 43.8 +- 0.4%; 20 m%: 38.8 +- 0.3%) and POSS-1 (10 m%: 10.3 +- 1.9%; 20 m%: 9.3 +- 0.8%) compared to the control (53 +- 0.7%). No significant change in the degree of conversion was detected by addition of BG-Bi compared to the control. A significant decrease in water uptake was measured compared to the control (145 +- 10 µg/mm3) for both concentrations of POSS-1 (10 m%: 52 +- 4 µg/mm3; 20 m%: 48 +- 3 µg/mm3) and for 20 m% POSS-8 (96 +- 20 µg/mm3). No significant difference could be found for BG-Bi compared to the control. A significant reduction of the sol fraction compared to the control (110 +- 12 µg/mm3) was detected for 20 m% POSS-1 (56 +- 11 µg/mm3) and for both concentrations POSS-8 (10 m%: 75 +- 8 µg/mm3; 20 m%: 58 +- 6 µg/mm3). BG-Bi did not show a significant reduction of the sol fraction compared to the control. Calcium phosphate precipitate formation was detected in all groups. Low concentrations of POSS-8 seem most suitable to be applied in a commercial adhesive due to its multifunctional structure. POSS-1 seems to be less suitable, since the monofunctionality of the particles is expected to result in considerable losses in the degree of conversion. Due to the strong tendency to aggregation and the poor dispersibility, BG-Bi also seems unsuitable for use in the Solobond Plus adhesive according to this study.
Keywords: nanoparticle; adhesive