Read more about our ongoing projects:
- Light curing devices used in dentistry – intensity correlated to heat – a risk for patients?
The aim of the study is to develop a technique using both infrared thermography and thermocouples to investigate temperature and distribution of temperature on natural teeth subjected to light curing with different LED curing devices. The preliminary results show a correlation between the time of curing and temperature increase as expected. At a irradiance above 1200mW/cm2, the surface temperature was measured to be over 50°C. The distance of the light tip seems to have less importance at distances below 4 mm. With only a thin dentinal wall left (0,6mm), there seem to be a risk for occurrence of severe pulp damage.
LED curing devices- Temperature distribution on natural teeth correlated to intensity and distances (presented at The 47th meeting of the Continental European Division of the International Association for Dental Research (CED-IADR), 2015)
- Adverse effects of dental polymer resin-based materials - causes and mechanisms
With a well-established method (SILAC), the effect on cells of monomers common in dental materials is investigated by changes in protein levels. Preliminary results show changes in protein expression depending on time and concentration of the monomer tested (i.e. HEMA). The method is not previously described for dental materials.
- Toxicological reactions related to dental monomers - Analysis of cellular mechanisms
The present study aim to contribute toxicological data on dental monomers that are consistent with NRC (National Research Council) recommendation to identify molecular mechanisms related to substances biological effects, and EU REACH regulation that would cut down on animal experiments to assess the toxicity of chemicals. Data from the project may help to increase understanding of how dental monomers at the molecular level creates unwanted reactions. The data can potentially be used in a future mapping of the human toxomet where the use of free concentrators ions is very important for in-vitro in-vivo extrapolation. The objective of the survey is to facilitating methods that help to prevent and solve problems as well as increase adverse knowledge about the various dental materials.
- Release of substances from dental substances - quality assurance of analytical methods
The project carried out identification and quantification of potential harmful organic substances (monomers, Bisphenol A, etc.) released from the dental polymer-based materials by various handling procedures and different material compositions using well validated analysis methods. Preliminary result achieved show that leakage of organic substances is affected by changes in monomer distribution of the composites tested. A validated GC-MS based method for analysis of Bisphenol-A and other organic substances have been developed.
- Mechanical and Microstructural Properties of Monolithic Zirconia: Crown Fracture Resistance and Impact of Low-Temperature Degradation
Zirconia has been widely used in dentistry to improve the strength of ceramic restorations maintaining aesthetics. In addition, zirconia is increasingly being used for monolithic crowns without veneering porcelain. However, there is a lack of scientific information regarding whether or not monolithic zirconia crowns can function with sufficient durability, especially in the molar regions. The overall aim of this project was to analyze factors that would affect mechanical and microstructural properties of monolithic zirconia crowns. Material testing was performed to evaluate the influence of sintering temperature, additional heat treatment, coloring procedure and autoclaving-induced low-temperature degradation (LTD) on the biaxial flexural strength of zirconia. Additional heat treatment did not reduce the strength, but the strength was found to decrease as the sintering temperature increased. The tooth-colored zirconia possessed equivalent strength to the non-colored zirconia. In addition, X-ray diffraction analysis and scanning electron microscopy showed that the tooth-colored zirconia had higher resistance to LTD.Crown fracture testing showed that the fracture resistance of the monolithic zirconia crowns with an occlusal thickness of 0.5 mm was significantly higher than that of lithium disilicate crowns with an occlusal thickness of 1.5 mm. The types of cements did not significantly affect the fracture resistance of monolithic zirconia crowns. When subjected to autoclaving-induced LTD, the fracture resistance of the monolithic zirconia crowns significantly decreased. By contrast, cyclic loading with a load of 300 N for 240,000 cycles did not significantly affect the fracture resistance of the crowns.The knowledge obtained by the laboratory studies performed suggests that monolithic zirconia crowns with a minimal thickness of 0.5 mm will have the capability of being applied to the molar region with sufficient durability, providing there is a properly controlled fabrication process to avoid unexpected degradation of the material.