Evaluating flexure properties, hardness, roughness and microleakage of high-strength injectable dental composite: an in vitro study.

BACKGROUND: Recently, a new generation of high-strength flowable dental composites has been introduced by manufacturers. The manufacturers claim that these materials have enhanced mechanical and physical properties and are suitable for use in a wide range of direct anterior and posterior restorations, even in high-stress bearing areas. AIM: The objective of this study was to assess certain physical and mechanical properties of these recently introduced high-strength flowable composites in comparison to conventional multipurpose dental composites. METHODS: Four types of high-strength flowable composites (Genial Universal FLO, Gaenial Universal Injectable, Beautifil Injectable, and Beautifil Flow Plus) were tested in experimental groups, while a nanohybrid conventional composite (Filtek Z350 XT) was used as the control. For flexure properties, ten rectangular samples (2 × 2 × 25 mm) were prepared from each composite material and subjected to 5000 cycles of thermocycling. Samples were then subjected to flexural strength testing using the universal testing machine. Another twenty disc-shaped specimens of dimensions (5 mm diameter × 2 mm thickness) were fabricated from each composite material for surface roughness (Ra) (n = 10) and hardness (VHN) test (n = 10). All samples underwent 5000 cycles of thermocycling before testing. Additionally, microleakage testing was conducted on 60 standardized class V cavities prepared on molar teeth and divided randomly into five groups (n = 12). Cavities were then filled with composite according to the manufacturer's instructions and subjected to thermocycling for 1000 cycles before testing using methylene blue solution and a stereomicroscope. RESULTS: All tested materials were comparable to the control group in terms of flexural strength and surface roughness (p > 0.05), with Gaenial Universal FLO exhibiting significantly higher flexural strength compared to the other flowable composite materials tested. However, all tested materials demonstrated significantly lower elastic modulus and surface hardness than the control group (p < 0.05). The control group exhibited higher microleakage scores, while the lowest scores were observed in the Gaenial Universal FLO material (p < 0.05) CONCLUSION: The physical and mechanical behaviors of the different high-strength flowable composites investigated in this study varied. Some of these materials may serve as suitable alternatives to conventional composites in specific applications, emphasizing the importance of dentists being familiar with material properties before making material selections.

Effect of At-Home Versus Over-the-Counter Bleaching Agents on Enamel Color, Roughness, and Color Stability.

Background This study was designed to evaluate the efficacy of standard at-home bleaching agents in comparison to new over-the-counter (OTC) products on human enamel regarding color change, color stability, and surface roughness. Methodology A total of 80 extracted adult human maxillary central incisors were prepared and arbitrarily divided into the following four equal groups (N =20): group A: at-home opalescence boost containing 15% carbamide peroxide (CP); group B: crest whitening strips containing 6% hydrogen peroxide (HP); group C: light-emitted diode (LED) home tray with 20% CP + 4% HP; and group D: white and black toothpaste containing active charcoal components. Tooth color was measured using a spectrophotometer. Enamel surface roughness using a three-dimensional optical profilometer was measured before and after the bleaching procedure. To assess color stability, each bleached group was further subdivided into two equal subgroups (n = 10) according to the immersion media of either coffee or tea. Finally, the color was measured after 24 hours of immersion. Results All groups showed improvement in color from the baseline. The crest whitening strips group showed the lowest color improvement in comparison to all other groups. After staining, group C showed the lowest mean color change value ∆E2. No statistically significant difference was noted in surface roughness among all groups. Conclusions All OTC bleaching products as well as at-home bleaching improve teeth color and increase roughness on the enamel surface. Staining media has an adverse effect on the teeth after bleaching. The LED home tray showed a better whitening effect and color stability after bleaching.

Microhardness Evaluation of Microhybrid Versus Nanofilled Resin Composite After Exposure to Acidic Drinks.

Objective: To investigate the effect of two acidic agents on microhardness of nanofilled and microhybrid resin composite materials. Materials and Methods: 70 resin composite discs (10 mm diameter and 2 mm thick) were prepared from 2 resin composites (35 from each type), nanofilled (Z350XT) and microhybrid (Z250), 3M/ESPE. Ten discs (5 from each group) were used as control (tested at 1 h before immersion). Each group was divided into 3 subgroups (n = 10) according to the storage media: distilled water (control), box-type cola and orange juice. Each subgroup was further subdivided into 2 divisions (n = 5) according to microhardness testing at 24 h and 7days after immersions. Digital Vickers Microhardness Tester (FM-7, Future Tech, Tokyo, Japan) was used to measure surface microhardness with a Vickers diamond indenter. The surface of the specimens received a load of 200 g for 10 seconds. Three indentations not less than 1 mm from each other were placed on the surface of all specimens. Vickers hardness number (VHN) was calculated for each indentation Data were statistically analyzed using one- way ANOVA followed by Newman-keuls tests (P ≤ 0.05). Results: Orange juice showed statistically significantly the lowest VHN mean value (92.7) followed by the Cola group (95.15) then the water group (104.02) compared to the control group (117.4). Microhybrid composite groups showed statistically significant higher VHN mean value (108.1) than the nanofilled composite (100.2). The 7days groups showed statistically significant lower VHN mean value (97.3) than 24h groups (106.6). Conclusions: All storage media reduced hardness of resin composites with orange juice showing the highest reduction in hardness values. Microhybrid is more resistant to degradation than nanofilled composite. Over time, microhardness of resin composites decreased progressively.