Effect of universal adhesives on microtensile bond strength to hybrid ceramic.

Background The aim of this study was to evaluate the effect of universal adhesives (UA) and silane on the microtensile bond strength (μTBS) of resin cement to a hybrid ceramic Vita Enamic (VE). Methods VE specimens were acid etched using hydrofluoric acid (HF) and were assigned to three groups (n = 10) based on the applied bonding technique. In group 1 (S), a silane-based primer was used as a surface treatment prior to the application of a resin cement (Variolink Esthetic DC). In group 2, a silane-containing UA, Clearfil Universal Bond (CUB) was used for the surface treatment, and in group 3, A silane-free UA, Tetric N-Bond Universal (TNU) was used for surface treatment. Resin cement build-ups were prepared. The bonded specimens were sectioned into resin-ceramic beams. Half of the beams of each group were stored for 24 h at 37 °C and the other half were subjected to a thermo-cycling aging. The microtensile bond strength (μTBS) was measured at a crosshead speed of 0.5 mm/min. Failure modes were assessed accordingly. Data were analyzed using a) two-way analysis of variance ANOVA followed by one-way ANOVA and Tukey tests between groups and b) independent t-test to detect differences (α = 0.05) for each group. The surface topographies of the ceramic surface were evaluated using scanning electron microscopy. Results The results showed that silane-based primer (S) application resulted in significantly higher (p < 0.05) μTBS values after 24 h and after thermocycling compared to both silane-containing UA (CUB) and silane-free UA (TNU). The μTBS values of all groups were significantly reduced after thermocycling. No statistically significant difference was observed between the μTBS of CUB and TNU after 24 h. However, TNU showed significantly higher μTBS after thermocycling. Different failure modes were observed, and adhesive failure was the most common in all groups. Marked surface topographic changes were observed following HF etching. Conclusion It is concluded that, the UAs tested cannot be recommended as substitutes to the silanization of Hybrid ceramic

Six-month color change and water sorption of 9 new-generation flowable composites in 6 staining solutions

Abstract Color match and water sorption are two factors that affect restorative materials. Discoloration is essential in the lifespan of restorations. The aim of this study was to evaluate color change and water sorption of nine flowable composites at multiple time points over 6 months. 60 samples of each composite were divided into two groups (Color Change and Water Sorption/Solubility). Each Color Change group was divided into six subgroups, which were immersed in distilled water (DW), coffee (CF), Coca-Cola (CC), red wine (RW), tea (TE) and orange juice (OJ). The color was measured at the baseline, 1, 2, 3 and 4 weeks, and 3 and 6 months and color change values (ΔE) were calculated. Each Water Sorption [WS]/Solubility [WL] group was tested according to ISO 4049:2009. The data were evaluated using two-way ANOVA, Fisher’s post-hoc test and Pearson’s correlation test. The composite with the lowest ΔE differed for each solution: Filtek™ Bulk Fill in DW (∆E = 0.73 (0.17–1.759)); Vertise Flow in CF (∆E = 14.75 (7.91–27.41)), in TE (∆E = 7.27 (2.81–24.81)) and OJ (∆E = 3.17 (0.87–9.92)); Tetric EvoFlow® in CC (∆E = 1.27 (0.45–4.02)); and Filtek™ Supreme XTE in RW (∆E = 8.88 (5.23–19.59)). RW caused the most discoloration (∆E = 23.62 (4.93–51.36)). Vertise Flow showed the highest water sorption (WS = 69.10 ± 7.19). The Pearson test showed statistically significant positive correlations between water sorption and solubility and between water sorption and ∆E; the positive solubility-∆E correlation was not statistically significant. The findings suggest that water sorption is one factor associated with the ability of composites to discolor; however, discoloration is a multifactorial problem

The impact of motivational factors on research productivity of dental faculty members: A qualitative study

AbstractObjectivesIn light of the scarcity of literature regarding the impact of motivational factors on research productivity among dental faculty members, this research examined the link between dental faculty members' motivation in the KSA and their self-efficacy about research. This study also analysed the factors that may contribute to the need for conducting more in-depth research.MethodsA qualitative study was performed on a group of 21 respondents working in different dental colleges in the KSA.ResultsThe fundamental needs for faculty members in dental schools include good remuneration, adequate research facilities, funding for research, and support. Some of the researchers clearly showed a greater need for increasing their own research productivity. These researchers felt that enhancing research productivity would benefit them positively because it would increase their scope of knowledge, which in turn would make them better faculty members. In addition, increased research productivity would also improve their status within the global academic community.ConclusionsThis study has clearly identified the lack of proper funding and support along with a lack of adequate research facilities as barriers to their research productivity. Dental colleges in the KSA need to promote faculty efforts and provide facilities to motivate their faculty members to perform more research

Hygroscopic expansion kinetics of dental resin-composites

Objective To evaluate the extent and rate of hygroscopic expansion of resin composites at 37 C. Methods Eight resin composites were examined: 1 micro-hybrid (Bright Light®), 5 nano-hybrids (Experimental Vertise™; Nanoceram-Bright®; Tetric EvoCeram®; Grandio® SO; Ceram X™ duo) and 2 flowables (X-tra base; Venus® Diamond Flow). Five disks (15 mm × 2 mm) of each material were prepared. The mean change in specimen diameter was recorded by a custom-built non-contact laser micrometer. Specimens were initially measured dry and then at fixed time intervals, over 150 days, after storage in distilled water at 37 ± 1 C. Data were re-expressed in volumetric terms and analysed by repeated measures ANOVA, one-way ANOVA and Tukey's post hoc test (α = 0.05). Results The volumetric hygroscopic expansion ranged from 0.58 to 2.26 and can be considered in three bands. First, Experimental Vertise had the highest expansion (p <0.001). Venus Diamond Flow, Tetric EvoCeram and Ceram X duo were the second band. The third band, with still lower expansion, consisted of Bright light, Grandio So, Nanoceram-Bright and X-tra base, with no significant difference between them. Conclusion For the size (2 mm thickness) and shape of specimen measured, equilibrium was attained in all cases by 60 days. Within this set of resin-composites the equilibrium expansion varied by almost 400% of the lowest material. © 2013 Academy of Dental Materials

Effect of self-etching ceramic primer on bond strength of zirconia-reinforced lithium silicate ceramics

This study evaluated the effect of self-etching ceramic primer (SECP) on shear bond strength (SBS) of zirconia-reinforced lithium silicate (ZLS) ceramics. Two hundred and seventy block-specimens of two types of ZLS ceramics and one type of lithium disilicate (LS) ceramics were prepared. Ninety blocks of each material were divided into three groups (n = 30), namely group 1: no surface treatment (control), group 2: hydrofluoric acid (HF), silane-based primer (S), and group 3: SECP. Resin cement was applied, and light-cured for build-up. Shear bond strength (SBS) test was used. Half of the bonded specimens (n = 15) were tested after storage in distilled water for 24 h, whereas the other half were tested after 5000 thermo-cycles. The failure modes were evaluated using scanning electron microscope (SEM). The SBS values for samples treated with SECP and HF + S within the respective materials were statistically comparable (p > 0.05). Thermocycling significantly reduced the SBS (p < 0.05) for all ceramic materials in groups 2 and 3. Mixed failure followed by adhesive failure were the most common failure modes in groups 2 and 3, whereas pretest failure was only detected in group 1. Considering the limitations of the study, with respect to in vitro bond strength, the SECP is an alternative for the conditioning of internal surface of glass ceramics

Use of Reparative Agents Topical Fluoride Activated by CO₂ Laser and Curodont™ Repair and NR-5™ on Vickers Hardness and Micro-Shear Bond Strength of Eroded Enamel to Composite Restoration

Aim: This study aims to assess the impact of various reparative remineralizing agents, specifically topical fluoride (TF) and a combination of a carbon dioxide laser (CO2 laser) with TF, as well as regenerative agents such as Curodont™ Repair and NR-5™, on two key factors—the micro-Vickers hardness (VH) of eroded enamel and the micro-shear bond strength (µSBS) of composite restoration. Materials and Methods: A total of 50 single-rooted premolars with intact enamel were sectioned mesiodistally into two halves, making a sample size of 100 specimens. All of the samples were then exposed to Coca-ColaTM for 2 min each day over 1 month to induce erosion on the enamel surface. The specimens were then embedded in acrylic cold-cure resin facing a flat surface upward. The samples were then arbitrarily divided into five groups based on the remineralizing and regenerative agents used, as follows (n = 20): Group 1: No remineralizing agent, Group 2: Curodont™ Repair, Group 3: NR-5™, Group 4: TF, and Group 5: CO2 laser + TF. The VH of the pretreated enamel surfaces was analyzed and µSBS testing and failure mode of composite restoration were performed using a universal testing machine (UTM) and stereomicroscope. ANOVA and Tukey’s post hoc were performed for data analysis. Results: In Group 3, the (NR-5™)-treated teeth exhibited the highest VH values and µSBS. In Group 1, the (No remineralizing agent)-treated specimens displayed the lowest VH and the lowest µSBS. An intergroup comparison analysis unveiled that Group 3, Group 4 (TF), and Group 5 (CO2 laser + TF) presented comparable outcomes of microhardness and bond strength. The Group 2 (Curodont™ Repair) samples exhibited no significant difference in VH and µSBS, as compared to Group 1. Conclusions: The use of a combination of NR-5™ technology and a CO2 laser in conjunction with TF has been shown to significantly augment the natural mineralization process. This enhancement results in increased microhardness and an improved bond strength in the treated enamel

Efficiency of the new reciprocating and rotary systems with or without ultrasonics in removing root-canals filling with calcium silicate-based sealer (MTA)

Abstract Background To compare the efficiency of endodontic rotary and reciprocating systems in removing calcium silicate-sealer based fillings and to investigate the impact of passive ultrasonic irrigation (PUI) on their efficiency. Materials and methods 160 root-canals were instrumented, filled with gutta-percha and calcium silicate based-sealer and divided into 10 equal groups. Five groups in which the reciprocating systems (WaveOne-Gold, Reciproc-Blue and R-Motion) and rotary systems (Fanta-AF-One and Tango-Endo) were used to remove root-canals’ fillings. In the other five groups the fillings were removed by the same systems then additionally with PUI. The times to complete retreatments procedures were recorded. Micro-computed tomography’s analysis of the root-canals fillings’ volume before and after retreatments was used to determine the remaining filling materials (RFMs) volumes. Results The RFMs after using rotary systems (10.1%) was greater than after using reciprocating systems (3.8%) (P &lt; 0.001). The RFMs after using WOG (2%) and RB systems (2.6%) were less than those in the RM (6.8%), TE (9.5%) and FAFO (10.7%) systems [P &lt; 0.05]. The times required to remove the filling materials using the TE (3.7 min), FAFO (4.1 min) and RM (4.1 min) systems were shorter than those required by the RB (5.4 min) and WOG (4.9 min) systems [P &lt; 0.05]. Using PUI resulted in less RFMs (1.44%) when compared to using only rotary or reciprocating systems (6.27%) [P &lt; 0.001]. Conclusions Endodontic reciprocation systems were more effective, but needed longer times than rotary systems in removing calcium silicate based- sealers fillings. The PUI significantly improved removal of the root-canals’ filling materials. Clinical relevance: Reciprocating systems and PUI are recommended whenever root-canals retreatment is considered regardless of using calcium silicate-based sealers. </jats:sec

Effects of Er, Cr: YSGG Laser on Shear Bond Strength of the Orthodontic Brackets for 5 and 10 Seconds: An In Vitro Study

Objectives. The study designed to compare the effect of erbium, chromium: yttrium-scandium-gallium-garnet (Er, Cr: YSGG) laser at different power outputs and short periods of time (5 and 10 s) and acid etching on the shear bond strength (SBS) and failure mode of metallic orthodontic brackets. Material and methods. A total of sixty-nine human premolars extracted for orthodontic purposes were used. 60 teeth were randomly assigned to one of the five treatment groups. (n = 12): group 1: 37% phosphoric acid etching and groups 2–5: the enamel surface irradiated by the Er, Cr: YSGG laser operated at different power outputs (1 W, 1.5 W, 2 W, and 2.5 W), each laser group was divided into two subgroups (n = 6) according to exposure time (5 s and 10 s). Nine teeth were not subjected to SBS testing but were prepared for scanning electron microscopy (SEM). The nonparametric Kruskal–Wallis test was used to evaluate the data; the SBS and adhesive remanent index (ADI) were evaluated. Results. The mean SBS for all laser groups and the acid-etched group were comparable, with no significant differences except for the 1 W group for 5 and 10 s and the 1.5 W group for 5 s. For the ARI scores, no statistically significant difference was found among the groups ( P = 0.059 ), and the majority of the samples had ARI type 2 or 3. Conclusion. The laser irradiation at 2 and 2.5 W for 5 s was similar to that produced by acid etching, whereas the laser irradiation at 2 and 2.5 W at 10 s was higher compared with that obtained with acid etching and adequate to etch the enamel.</jats:p