Der Einfluss von bioaktiven und antimikrobiellen Nanopartikeln auf die Eigenschaften und Anwendbarkeit eines experimentellen Dentaladhäsives

The influence of bioactive and antimicrobial nanoparticles on the properties and applicability of an experimental dental adhesive

by Christian Kreutz
Doctoral thesis
Date of Examination:2024-08-13
Date of issue:2024-08-06
Advisor:Prof. Dr. Annette Wiegand
Referee:Prof. Dr. Matthias Rödiger
Referee:Prof. Dr. Ralf Dressel
Persistent Address: http://dx.doi.org/10.53846/goediss-10658

 

 

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Abstract

English

Background: The degradation of the hybrid layer is a main cause of early loss of bonded restorations. Through the addition of nanoparticles such as bioactive glass (BG), calcium phosphate particles (CAP) and methacryl-functionalized polyhedral oligomeric silsesquioxanes (MA-POSS- 8) the hybrid layer should be stabilized. At the same time, minimally invasive caries therapy concepts require new properties from the adhesive systems. During selective caries removal, microorganisms are left close to the pulp and covered with a dense filling. To ensure that infected dentin does not lead to a local inflammation of the pulp, antimicrobial properties of the adhesive could be advantageous. Positive antimicrobial properties could be demonstrated with silicate-coated silver particles (SiO2@Ag). Aim: The aim of the study was to investigate the influence of the combination of different nanoparticles on the properties and applicability of a dental adhesive. Methods: An experimental adhesive was prepared based on bisphenol A glycidyl dimethacrylate (60 wt%), triethylene glycol (15 wt%) and 2-hydroxyethyl methacrylate (25 wt%). Camphorquinone and 2-dimethylaminoethyl methacrylate were added as photoinitiators at 0.5 wt% each. In each test group, 5 wt% methacrylic-functionalized polyhedral oligomeric silsesquioxanes were mixed with the experimental adhesive and combined with additional nanoparticles (1 wt% BG, 1 wt% CAP or 1 wt% SiO2@Ag). The adhesive without fillers served as control. The physicochemical properties (degree of conversion, linear shrinkage, water sorption, sol fraction, complex and shear viscosity), the antimicrobial effect and bioactivity after storage in artificial saliva and artificial dentinal fluid were examined. Statistical analysis of the physicochemical properties and the antimicrobial effect was performed by using Kruskal-Wallis test and pairwise comparisons. The results of the pairwise comparisons were corrected according to Bonferroni (p < 0.05). Results: The combination of BG and MA-POSS-8 increases water sorption (from 87,5 µg/mm3 to 117,1 µg/mm3) and solubility (from 0,5 µg/mm3 to 17,1 µg/mm3), while the combination of CAP and MA-POSS-8 as well as SiO2@Ag and MA-POSS-8 showed no significant effect on water sorption and solubility compared to the unfilled adhesive. Also, the combination of CAP and MA-POSS-8 resulted in a increased shear viscosity of the adhesive (from 386,9 mPa*s to 475,7 mPa*s). Complex viscosity and linear shrinkage were not affected by the addition of the nanoparticles/fillers compared to the unfilled adhesive. The degree of conversion ranged between 51,7 and 54,4% in all adhesives. After storage in artificial saliva, significant mineral precipitates were observed on the surface of the filled adhesives which could not be detected on the surface of the unfilled adhesive. After storage in artificial dentinal fluid, calcium phosphate precipitates were observed on the surface of adhesives. However, there were significantly more precipitates on the surface of the filled adhesives compared to the unfilled adhesive. No antimicrobial effect was observed for any combination of nanoparticles compared to the unfilled adhesive. Conclusion: The combination of bioactive and/or antibacterial nanoparticles have only slightly effects on the physicochemical properties and improved bioactivity was detected. No antibacterial effect could be observed.
Keywords: MA-POSS-8; core-shell silica-silver; bioactive glass; calcium phosphate; antimicrobial effect; bioactivity; hybrid layer; adhesive
Schlagwörter: MA-POSS-8; ummantelte Silbernanopartikel; bioaktives Glas; Kalziumphosphat; antimikrobieller Effekt; Bioaktivität; Hybridschicht; Adhäsivtechnik
 
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