Thesis (M.Sc.) - Cairo University. Faculty of Oral and Dental Medicine. Department of Operative Dentistry.

Includes bibliographical references.

This study was performed to assess the effect of types of
composite, light intensities, curing modes and thermocycling on toothrestoration
interface. Methods: A total of 160 freshly extracted sound human
premolars were selected. Teeth were mounted individually in one inch
cylindrical acrylic blocks. Specimens were divided into 2 main groups 80 teeth
each according to type of resin composite i.e. either using nanofilled resin
composite or using microhybrid resin composite. Each group was further
subdivided into two subgroup 40 teeth each according to intensity of light i.e.
either low intensity or high intensity .Each subgroup was further divided into
two division 20 teeth each according to curing mode i.e. either soft- start
polymerization or snap shot polymerization .Each division was finally
classified into two classes 10 teeth each according to thermocycling i.e. either
did not subjected to thermocycling or subjected to thermocycling. Standardized
class v cavities were prepared on buccal surfaces of the teeth. Cavities were
restored with the different two types of resin composite using different light
intensities and different curing modes. Thermocycling was done for a total 500
cycles at 5ºC and 55ºC with one minute dwell time at each temperature. The
roots apices were sealed with wax and the teeth were covered with two coats of
nail varnish except 1mm around the restoration then immersed in 0.5 % basic
methylene blue for 24 hours, after rinsing the specimens were longitudinally
sectioned and dye penetration was assessed under a stereomicroscope(X 20).
Results: whether occlusal leakage or gingival leakage, there was no significant
difference in microleakage of the two types of resin composite when cured with
different light intensities of LED (low or high intensity) using different curing
modes ( snapshot or soft start curing modes).there was a significant difference
in microleakage between the non-thermocycled and thermocycled specimens.
Conclusion: 1-The tightness of seal of resin composites is not affected by the
variation in light intensity of light emitting diode.2-The curing modes of resin
composites have no influential effect on decreasing the marginal leakage of
resin composite.3-Thermocycling has an adverse effect on the marginal sealing
of resin composite restorations.

Text in English, abstracts in English & Arabic.