Aim. The purpose of this in vitro study was to evaluate microleakage of two different adhesive systems: self-etch and etch-and-rinse, using the optic microscopy. Materials and methods. Six sound upper premolar teeth had MOD cavities prepared. The teeth were divided into two groups of three teeth each and two restorative systems were used: 1) Filtek™ Silorane/Silorane System Adhesive (3M ESPE); 2) Premise™ Packable /OptiBond FL (KERR). All restorative materials were placed following manufacturers’ recommendations. After restoring them, the teeth were stored for 5 years in an oven in distilled water at 37°C. Before the tests, the apex was sealed with wax and the teeth were covered with nail polish except 1 mm around the edge restorations. Then, they were immersed in 0.5% alkaline solution of fuchsin for 24 hours. After sectioning, the microleakage evaluation at enamel margin was made using an optical microscope Olympus KCX41 (Olympus America Inc.) at a magnification of 4x and 10x, the method of granting a semiquantitative score of dye penetration on a scale from 0-3. Data were statistically analyzed using Kruskal-Wallis test. Results, conclusions. Microleakage was present in both groups, scores 2 (infiltration dye the entire length threshold cervical enamel) and 3 (infiltration threshold cervical enamel and expanding axial wall towards the pulp chamber), registering only in the Filtek Silorane (FS) group who applied to Silorane system, adhesive Self-etch adhesive system. The most effective adhesive system to reduce the microleakage at marginal threshold cervical MOD restorations on enamel, was etch-and-rinse system, OptiBond FL.
Aim: To assess thermal changes in composite fillings during light-curing process of two types of resin-based composites with low- polymerization shrinkage. Materials and methods: A thermocouple K was introduced apically through the pulp chamber of six extracted human upper premolars till the base of prepared MOD cavities, in order to measure the temperature developed in two restorative systems, a silorane-based composite (Filtek Silorane/3M EPSE - FS) and a dymethacrylate-based composite (Premise Packable/KERR - PP), during 5, 10 and 20 seconds light-curing process. For the light-curing of the adhesive systems and 9 increments of composites of the restorations was used a high power LED unit with a Periodic Level Shifting Light Technology from 1.100 mW/cm2 -1.330 mW/cm2 per second and a wave length of 450-470 nm. Results: The light-curing process caused an increase of the temperature in the restorative materials that was correlated to the increase of exposure time to the light, with almost doubled temperature values recorded for the silorane- based restorations compared to the dimethacrylate-based ones. The peak value was recorded for the horizontal base composite increment after 20 seconds of light-exposure, with a temperature mean value of 10.18 °C for FS composite compared to 4.91 °C mean temperature value recorded in PP composite. Conclusions: The ring opening Silorane cationic curing technology rises a concern regarding general accepted temperature values associated to its exothermic curing reaction during light-curing with a LED high-power and narrow wave length unit, compared to a highly-filled free-radical polymerization dimethacrylate-based resin system.
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