Dalia Kaisarly1,2, Moataz El Gezawi3, Andreas Keßler4, Peter Rösch5, Karl-Heinz Kunzelmann4. 1. Department of Conservative Dentistry and Periodontology, University Hospital, LMU Munich, Goethestrasse 70, 80336, Munich, Germany. kaisarly@dent.med.uni-muenchen.de. 2. Biomaterials Department, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt. kaisarly@dent.med.uni-muenchen.de. 3. Department of Restorative Dental Sciences, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia. 4. Department of Conservative Dentistry and Periodontology, University Hospital, LMU Munich, Goethestrasse 70, 80336, Munich, Germany. 5. Faculty of Computer Science, University of Applied Sciences, Augsburg, Germany.
Abstract
OBJECTIVES: Sufficient depth of cure allows bulk-fill composites to be placed with a 4-mm thickness. This study investigated bulk versus incremental application methods by visualizing shrinkage vectors in flowable bulk-fill and conventional composites. MATERIALS AND METHODS: Cylindrical cavities (diameter = 6 mm, depth = 4 mm) were prepared in 24 teeth and then etched and bonded with OptiBond FL (Kerr, Italy). The composites were mixed with 2 wt% radiolucent glass beads. In one group, smart dentin replacement (SDR, Dentsply) was applied in bulk "SDR-bulk" (n = 8). In two groups, SDR and Tetric EvoFlow (Ivoclar Vivadent) were applied in two 2-mm-thick increments: "SDR-incremental" and "EvoFlow-incremental." Each material application was scanned with a micro-CT before and after light-curing (40 s, 1100 mW/cm2), and the shrinkage vectors were computed via image segmentation. Thereafter, linear polymerization shrinkage, shrinkage stress and gelation time were measured (n = 10). RESULTS: The greatest shrinkage vectors were found in "SDR-bulk" and "SDR-increment2," and the smallest were found in "SDR-increment1-covered" and "EvoFlow-increment1-covered." Shrinkage away from and toward the cavity floor was greatest in "SDR-bulk" and "EvoFlow-increment2," respectively. The mean values of the shrinkage vectors were significantly different between groups (one-way ANOVA, Tamhane's T2 test, p < 0.05). The linear polymerization shrinkage and shrinkage stress were greatest in Tetric EvoFlow, and the gelation time was greatest in "SDR-bulk." CONCLUSIONS: The bulk application method had greater values of shrinkage vectors and a higher debonding tendency at the cavity floor. CLINICAL RELEVANCE: Incremental application remains the gold standard of composite insertion.
OBJECTIVES: Sufficient depth of cure allows bulk-fill composites to be placed with a 4-mm thickness. This study investigated bulk versus incremental application methods by visualizing shrinkage vectors in flowable bulk-fill and conventional composites. MATERIALS AND METHODS: Cylindrical cavities (diameter = 6 mm, depth = 4 mm) were prepared in 24 teeth and then etched and bonded with OptiBond FL (Kerr, Italy). The composites were mixed with 2 wt% radiolucent glass beads. In one group, smart dentin replacement (SDR, Dentsply) was applied in bulk "SDR-bulk" (n = 8). In two groups, SDR and Tetric EvoFlow (Ivoclar Vivadent) were applied in two 2-mm-thick increments: "SDR-incremental" and "EvoFlow-incremental." Each material application was scanned with a micro-CT before and after light-curing (40 s, 1100 mW/cm2), and the shrinkage vectors were computed via image segmentation. Thereafter, linear polymerization shrinkage, shrinkage stress and gelation time were measured (n = 10). RESULTS: The greatest shrinkage vectors were found in "SDR-bulk" and "SDR-increment2," and the smallest were found in "SDR-increment1-covered" and "EvoFlow-increment1-covered." Shrinkage away from and toward the cavity floor was greatest in "SDR-bulk" and "EvoFlow-increment2," respectively. The mean values of the shrinkage vectors were significantly different between groups (one-way ANOVA, Tamhane's T2 test, p < 0.05). The linear polymerization shrinkage and shrinkage stress were greatest in Tetric EvoFlow, and the gelation time was greatest in "SDR-bulk." CONCLUSIONS: The bulk application method had greater values of shrinkage vectors and a higher debonding tendency at the cavity floor. CLINICAL RELEVANCE: Incremental application remains the gold standard of composite insertion.
Authors: Daranee Tantbirojn; Antheunis Versluis; Maria R Pintado; Ralph DeLong; William H Douglas Journal: Dent Mater Date: 2004-07 Impact factor: 5.304