Abstract
During restorative treatment, premolars restored with resin filling materials using the conventional incremental-fill technique take longer restoration time and undermine the integrity of the tooth. The aim of this study was to assess fracture resistance of premolars restored by various types of novel bulk-fill composite resin materials. Forty-eight (n = 48) freshly extracted sound maxillary first premolars were used in this in vitro study. The teeth were divided into six groups, each having 8 specimens. Group A (positive control) was allocated for the intact teeth. For specimens in Groups B to F, a large cavity (Class-II MOD) was prepared with a standardized dimension of cavity (3 mm depth on the pulpal floor, 4 mm at the gingival seat, and 3 mm cavity width). Group B represented prepared teeth without any restoration. Group C, Group D, Group E, and Group F were restored with Tetric EvoCeram® incremental-fill (conventional), Beautifil bulk-fill, Filtek posterior bulk-fill, and SonicFill 2 bulk-fill restorative materials, respectively. All samples were finished and polished with an enhanced finishing kit and stored in distilled water for a month before the fracture resistance testing. All the samples were exposed to the axial loading (the speed of crosshead was 1 mm/min) in a computer-controlled universal testing machine (LARYEE, China) via a steel bar (6 mm in diameter) and the maximum applied force in Newton was recorded as the fracture resistance. One-way analysis of variance (SPSS 21) was used to compare the fracture resistance within the groups, and Tukey's post hoc test was used to determine the difference between the groups. The lowest value of fracture resistance was recorded for Group B, and the highest value was recorded for Group A followed by the values of Group D, Group C, Group F, and Group E. One-way ANOVA revealed a statistically significant difference between the groups (P < 0.05). Nonsignificant difference was found between the premolars restored by bulk-fill and conventional composites. Among the bulk-fill restored specimens, Beautifil restorative demonstrated significantly higher fracture resistance in comparison with the other two bulk-fill restored specimen groups (SonicFill 2 and Filtek). Bulk-fill composite such as Beautifil could be an alternative option to conventional incremental-fill composite for premolar restoration.
Highlights
Modification or damage in structure of the tooth due to trauma, dental caries, and endodontic and restorative procedures has an undesirable effect on its fracture strength and increases the risk of cusp cracks and fracture
The Class-II mesio-occlusodistal (MOD) cavity in maxillary premolar creates a particular challenge for the filling materials in concern of resistance to tooth fracture and longevity. erefore, the damaged posterior teeth need to be filled with a restoration material that is capable of withstanding fracture when receiving a great amount of occlusal pressure
One-way analysis of variance was conducted using IBM SPSS 21 software to compare the fracture resistance of the groups and Tukey’s honestly significant difference (HSD) post hoc test at a 95% significance level to determine the difference between groups
Summary
Modification or damage in structure of the tooth due to trauma, dental caries, and endodontic and restorative procedures has an undesirable effect on its fracture strength and increases the risk of cusp cracks and fracture. New classes of dental restoration products have been developed to overcome these challenges associated with the incremental technique by simplifying the procedures resulting in the reduced number of restoration steps and shorter clinical time. Beautifil bulk-fill restorative (Shofu, Japan) is classified as multifunctional giomer composites and produced with a complex balance by combination of fillers with dissimilar types of monomers to reduce shrinkage and stress associated with the polymerization process. Many studies have been conducted on assessing the fracture resistance of different types of bulk-fill composites as premolar restoration materials [10], further understanding is still required on bulk-fill deep and large restorations with new generation nanocomposites. E aim of this study was to test the fracture resistance of maxillary first premolar restored using multiple types of bulk-fill composite resin materials. (1) ere would be nonsignificant difference in the resistance to fracture of sound teeth and all restored teeth (2) ere would be nonsignificant difference in the resistance to fracture of specimens restored by multiple types of conventional and bulk-fill composite materials (3) ere would be nonsignificant difference in the resistance to fracture of specimens restored by different bulk-fill composite materials
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