Master of Science (M.S.) in Dentistry
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College of Dental Medicine
Jeffrey Y Thompson
Publication Date / Copyright Date
Nova Southeastern University
Najat Aldossarry. 2018. Depth of cure of resin composites: effect of incremental layering versus bulk placement and effect of curing light type. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, College of Dental Medicine. (85)
Background: The introduction of resin composite was a revolution in dentistry and it has shown a high level of success as a direct restorative material. Appropriate techniques and light curing units are essential for optimal clinical outcomes. Objective: To assess depth of cure of two bulk-fill composites and one nanofill resin composite, when photopolymerized with two different curing light units (CLU), placed with an incremental layering versus bulk-fill technique. Material and methods: Two Bulk-fill resin composites (Surefil SDR® Flow and Tetric EvoCeram®) and a conventional nanofill (FiltekTM Supreme Ultra) were used to prepare 90 cylindrical specimens. Specimens (n=5/group) were made using two placement techniques (incremental and bulk-fill). Each specimen was polymerized using one of two LCUs (Valo® LED [standard power or extra- power mode] and OptiLux 501® QTH), with irradiation times set according to the manufacturer recommendations. Vickers microhardness was evaluated starting from the top to the bottom surface of each specimen. Ten measurements were made sequentially (0.4 mm intervals). A three-way ANOVA and Tukey’s post hoc test was used (significance of 0.05) to analyze the DOC data. Results: All resin composite groups cured with LED CLU (extra-power for 3 sec) and placed using a bulk-fill technique showed significant differences (p<0.05) in hardness ratio (DOC analysis). Conclusions: An incremental insertion technique showed a significantly higher DOC for all composite resin groups when compared to bulk insertion. Therefore, it is not recommended to use a bulk-fill technique with conventional composite. Delivering high irradiance(3200 mW/cm2) and exposure time (3 sec) for LED CLU did not exceed the threshold value for bottom to top hardness ratio of 80% at 4 mm as claimed for Bulk-fill composites when using a bulk-fill insertion technique. Tetric EvoCeram Bulk Fill achieved a 3.2-mm DOC when LED CLU standard power was used for 10 seconds using a bulk-fill insertion technique. The best results were achieved with combinations of incremental insertion and use of a QTH curing light with extended curing time (40 sec).
Bulk-fill technique, Curing light, Depth of cure, Incremental technique, Vickers Hardness
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