Vytvrzování dentálních materiálů

Thomas HAENEL

Disertační práce

Curing of Visible Light Curing Resin Based Dental Composites

Abstract:

During the last 50 years, a broad range of visible light curing resin based composites (VLC RBC) was developed for restorative applications in dentistry. Correspondingly, the technologies of light curing units (LCU) have changed from UV to visible blue light, and there from quartz tungsten halogen over plasma arc to LED LCUs increasing their light intensity significantly. In this thesis, the influence of the curing conditions in terms of irradiance, exposure time and irradiance distribution of LCU on reaction kinetics as well as corresponding mechanical and viscoelastic properties were investigated. Different experimental methods were used to determine time dependent degree of conversion (DC), depth of cure (DoC), hardness distribution and post-curing kinetics. Dynamic mechanical indentation technique was implemented on a dynamic mechanical analyzer to determine local viscoelastic properties on a scale of 100 to 300 (mikro)m. To evaluate the data several quantitative approaches were applied. A novel DC-function based on a time dependent reaction constant is presented to produce intrinsically final DC-values less than 100 % and better representation DC-data. The novel DC-function shows that the kinetics of the curing reaction is mainly determined by the reaction time constant which depends on the irradiance of the LCU. The DC reached 45 % after time corresponding to the reaction time constant. It was shown that the reaction rate depends on the square root of irradiance for the investigated composites. A new method to determine DoC in a user-independent and automatized manner was presented which can be applied to any depth dependent property of light curing composites. Due to the mathematical description, the properties at DoC have decreased to 88 % of their plateau values, and are thus not arbitrary. Furthermore, the irradiance distribution of the LCU is reflected in the distribution of mechanical properties. Longer exposure times increase the hardness level, but do not level out the imprinted patterns. This is in accordance with long term hardness measurements revealing that the kinetics of the post-curing has a logarithmic time dependency, and is also determined by the locally introduced irradiance. Samples irradiated with different exposure times produced hardness curves which could be shifted to a master curve on the logarithmic time axis allowing for long term predictions of the hardness, and indirectly the DC.

Abstract:

Disertační práce řeší reakční kinetiku a výsledné mechanické vlastnosti fotokompozitů pro dentální aplikace. Cílem disertační práce je popsat a porozumět vytvrzovacího procesu se zaměřením na intenzitu a distribuci záření světelného zdroje a hloubku působení záření. Na základě získaných kinetických parametrů byla vytvořena nová hodnoticí metoda a ověřen teoretický model založený na reakční kinetice.

Keywords

Fotokompozit, vytvrzování světlem, dielektrická analýza, kinetika vytvrzování, distribuce záření, tvrdost, viskoelastické vlastnosti.

Jazyk práce: angličtina

Datum vytvoření / odevzdání či podání práce: 18. 7. 2016

Obhajoba závěrečné práce

• Obhajoba proběhla 13. 9. 2016
• Vedoucí: prof. Ing. Berenika Hausnerová, Ph.D.

Univerzita Tomáše Bati ve Zlíně

Fakulta technologická

Doktorský studijní program / obor:
Chemie a technologie materiálů / Technologie makromolekulárních látek