Aous A. Abdulmajeed

Objectives: The aim was to evaluate the mechanical, physical, and surface properties, as well as the microstructure, of three direct resin composites with different formulations (CLEARFIL AP-X, MAJESTY ES Flow, and MAJESTY ES-2) from the same manufacturer. Methods: Mechanical properties, including flexural strength, flexural modulus, and fracture toughness, were determined for each material (n = 8/material) according to ISO standards. Fourier transform infrared (FTIR) spectroscopy was used to determine the degree of conversion (DC%). Two-body wear was evaluated using a ball-on-flat configuration in a chewing simulator for 15,000 cycles, and wear depth was measured using a non-contact 3D optical profilometer. Polymerization shrinkage stress was measured using a tensilometer. Surface roughness and gloss were evaluated on disk-shaped specimens (n = 5/material) after polishing with 2400- and 4000-grit abrasive papers. Microstructural characterization was performed using scanning electron microscopy. Data were analyzed using ANOVA followed by Tukey’s HSD test (α = 0.05). Results: CLEARFIL AP-X exhibited the highest flexural strength (186.95 MPa), flexural modulus (19.25 GPa), and fracture toughness (1.50 MPa m^1/2) among the tested materials (p < 0.05). However, it also showed the highest surface roughness and the lowest gloss values. MAJESTY ES Flow demonstrated the lowest wear depth and the highest gloss and polymerization shrinkage stress, whereas MAJESTY ES-2 exhibited the greatest wear and the lowest DC%. Conclusions: The three resin composites exhibited distinct mechanical, physical, surface, and microstructural characteristics associated with differences in their formulations, including filler content, filler morphology, and resin matrix composition. No single material demonstrated superior performance across all evaluated properties, highlighting the importance of selecting resin composites according to the specific clinical requirements.

Removing orthodontic brackets often presents clinical challenges, as it may cause patient discomfort, bracket fracture, or enamel damage resulting from strong adhesive bonds. Various techniques have been proposed to facilitate safer and more efficient debonding. Among them, laser-assisted methods have gained attention for their potential to minimize mechanical stress and improve patient comfort. The main objective of this study was to evaluate the effect of an erbium-doped yttrium–aluminum–garnet (Er:YAG) laser as an alternative to traditional mechanical methods for removing metal and ceramic orthodontic brackets. Materials and Methods: Thirty-six extracted premolars were prepared for bonding metal or ceramic brackets using a light-cure adhesive system. The control group consisted of six ceramic and six metal brackets removed with conventional orthodontic pliers. In the experimental groups, brackets were debonded using the Er:YAG laser (2940 nm, 0.6 mm spot size, 150 mJ; 15 Hz; (2.25 W) with an H14 handpiece. Irradiation time was recorded for each method, and teeth were rescanned to measure the surface area and volume of the crowns before and after bracket removal. Data were analyzed using one-way ANOVA and Tukey’s HSD test (p < 0.05). Scanning electron microscopy (SEM) was used for surface analysis. Results: A significant difference in debonding time (p = 0.001) was observed between the laser and traditional methods. The laser group took 52.5 s for metal and 56.25 s for ceramic brackets, compared to 1.05 s (metal) and 0.64 s (ceramic) in the traditional group. A significant difference in remaining cement volume was noted (p = 0.0002), but no differences were found between metal and ceramic brackets with laser removal. Conclusions: Er:YAG laser-assisted debonding is safe and minimally invasive but more time-consuming and costly than conventional methods, showing no improvement in clinical efficiency under current parameters.

Because of the evolvement of digitalized dentistry and the need of a restoration that is fixed, there has been an introduction of many materials related to 3D printing in today’s market. The purpose of this study is to evaluate the resistance of fractures by comparing materials of ceramic which are of four kinds and they are zirconia-reinforced lithium disilicate, also Emax cad, and IPSS emax as well as 3Dprinting nanoceramic. Methods: 24 crowns were prepared (6sample for each type of the material) used in the study. And undergone artificial ageing before testing using the universal testing machine. Submission of results in SPSS for tests like Kruskal-Wallis as well as nonparametric test proved the difference in each material of ceramics and it differed at p ≤ 0.05 whereas in the methods used there is no such difference. The material which showed a resistance for fractures with a high value was the samples of ZLS which was about 1473.1 and the material which showed a resistance for fractures with a low value was the Emax cad and it was about 1013.7. To conclude, Value of Fracture resistance can have an impact because of the kind of material whereas there is no significant impact because of the preparation method.

Titanium dioxide (TiO₂) nanotubes are emerging as a provocative target for oral implant research. The aim of this study was to evaluate the effect of UV on the wettability behavior, bacterial colonization, and fibroblast proliferation rate of TiO₂ nanotube surfaces prepared using different anodization voltages and aimed for use as implant abutment materials. Four different experimental materials were prepared: (1) TiO₂ nanotube 10 V; (2) TiO₂ nanotube 15 V; (3) TiO₂ nanotube 20 V; and (4) commercial pure titanium as a control group. TiO₂ nanotube arrays were prepared in an aqueous electrolyte solution of hydrofluoric acid (HF, 0.5 vol.%). Different anodization voltages were used to modify the morphology of the TiO₂ nanotubes. Equilibrium contact angles were measured using the sessile drop method with a contact angle meter. The investigated surfaces (n = 3) were incubated at 37 °C in a suspension of Streptococcus mutans (S. mutans) for 30 min for bacterial adhesion and 3 days for biofilm formation. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 7 days and the cell proliferation rate was assessed using the AlamarBlue assay^TM (BioSource International, Camarillo, CA, USA). The data were analyzed using one-way ANOVA followed by Tukey’s post-hoc test. Water contact angle measurements on the TiO₂ after UV treatment showed an overall hydrophilic behavior regardless of the anodization voltage. The ranking of the UV-treated surfaces of experimental groups from lowest to highest for bacterial adhesion was: TiO₂ nanotube 20 V < Ti and TiO₂ nanotube 15 V < TiO₂ nanotube 10 V (p < 0.05), and for bacterial biofilm formation was: TiO₂ nanotube 20 V-TiO₂ nanotube 10 V < Ti-TiO₂ nanotube 15 V (p < 0.05). Fibroblast cell proliferation was lower on TiO₂ nanotube surfaces throughout the incubation period and UV light treatment showed no enhancement in cellular response. UV treatment enhances the wettability behavior of TiO₂ nanotube surfaces and could result in lower bacterial adhesion and biofilm formation.

Purpose: To assess the effect of yttria mol% concentration and material thickness on the biaxial fracture load (N) of zirconia with and without mastication simulation.Materials and methods: Disk‐shaped specimens (N = 120) of 3 mol% yttria‐partially stabilized zirconia, 3Y‐PSZ (Katana High Translucent, Kuraray Noritake), 4 mol% yttria‐partially stabilized zirconia, 4Y‐PSZ (Katana Super Translucent Multi Layered) and 5 mol% Yttria‐partially stabilized zirconia, 5Y‐PSZ (Katana Ultra Translucent Multi Layered) were prepared to thicknesses of 0.7 and 1.2 mm. For each thickness, the biaxial fracture load (N) was measured with and without mastication simulation with 1.2 million cycles at a 110‐N load and simultaneous thermal cycling at 5°C to 55°C. The data were analyzed by three‐way Analysis of Variance (α = 0.05) and Tukey‐Kramer adjusted multiple comparison test.Results: Yttria mol% concentration and material thickness had a statistically significant effect on the mean biaxial fracture load (F = 388.16, p < 0.001 and F = 714.33, p < 0.001 respectively). The mean biaxial fracture load ranged from the highest to the lowest; 3Y‐PSZ, 4Y‐PSZ, and 5Y‐PSZ (p = 0.012). The mean biaxial fracture load of the 1.2 mm thickness groups was significantly higher than 0.7 mm thickness at any given condition (p = 0.002). Not all specimens survived the mastication simulation protocol. Fifty percent of the 0.7‐mm‐thick 4Y‐PSZ specimens, 70% of the 0.7‐mm‐thick 5Y‐PSZ specimens and 20% of 1.2‐mm‐thick 5Y‐PSZ specimens fractured during mastication simulation. Mastication simulation had no statistically significant effect on the biaxial fracture load (F = 1.24, p = 0.239) of the survived specimens.Conclusions: Lowering yttria mol% concentration and increasing material thickness significantly increases the fracture load of zirconia. At 0.7 mm thickness, only 3Y‐PSZ survived masticatory simulation. A minimum material thickness of 1.2 mm is required for 4Y‐PSZ or 5Y‐PSZ.

Purpose: To evaluate the effects of two postprocessing methods in terms of the overall, intaglio, and cameo surface dimensions of in‐office stereolithographic fabricated implant surgical guides.Materials and methods: Twenty identical implant surgical guides were fabricated using a stereolithographic printer. Ten guides were postprocessed using an automated method. The other ten guides were postprocessed using a series of hand washing in combination with ultrasonics. Each guide was then scanned using cone‐beam computed tomography to produce a set of digital imaging and communications in medicine (DICOM) files which were converted into standard tessellation language (STL) files. The STL file was then superimposed onto the original STL design file using the best fit alignment. The average positive and negative surface discrepancy differences in terms of means and variances were analyzed using t‐test (α = 0.05).Results: For the alternative group, the average positive and negative overall, intaglio, and cameo surface discrepancies were 77.38 ± 10.68 µm and –67.74 ± 6.55 µm; 78.83 ± 8.65 µm and –68.16 ± 5.26 µm; and 70.5 ± 8.48 µm –64.84 ± 5.55 µm, respectively. For the automated group, the average positive and negative overall, intaglio, and cameo surface discrepancies were 51.88 ± 4.38 µm and –170.7 ± 11.49 µm; 64.3 ± 4.44 µm and –89.45 ± 6.25 µm; and 83.59 ± 4.81 µm and –144.26 ± 13.19 µm, respectively. There was a statistical difference between the means of the two methods for the overall, intaglio, and cameo positive and negative discrepancies (p < 0.001).Conclusions: For a single implant tooth‐supported implant guide, using hand washing with ultrasonics appeared to be consistently better than the automated method. The manual method presented with more positive discrepancies, while the automated method presented with more negative discrepancies.

This in vitro study was designed to evaluate the effect of sol-gel derived TiO₂coating on blood coagulation, blood protein adsorption, and platelet response on zirconia surfaces. Square-shaped zirconia (n=96) (10x10x2 mm) was cut, ground, sintered, and finally cleansed ultrasonically in each of acetone and ethanol for 5 minutes. Three experimental groups (n=32) were fabricated: (a) zirconia coated with sol-gel derived TiO₂, (b) zirconia coated with sol-gel derived TiO₂and treated with ultraviolet (UV) irradiation for 1 hour, and (c) non-coated zirconia as control. The coatings were prepared from tetraisopropyl orthotitanate solution by dip-coating. The thrombogenicity of the specimens was evaluated using a whole blood kinetic clotting time method where the extent of blood clotting was evaluated at 10, 20, 30, 40, 50, and 60 minutes (n=4/time point, total n=24/group). Scanning electron microscope images were taken to observe platelet morphologies after 1-hour incubation with platelet-rich plasma (PRP) (n=5/group). Surface characteristics were visualized using atomic force microscopy (n=1/group). Adsorption of plasma proteins and fibronectin on each surface was studied by gel electrophoresis (n=2/group). Significant differences were observed in blood coagulation between the test groups at 20-, 30-, 40-, and 50-minute time points (p2coated specimens showed fastest blood coagulation followed by TiO₂coated and non-coated specimens. Furthermore, platelets appeared at a higher activation state on coated specimens. Gel electrophoresis revealed no difference in protein adsorption among the experimental groups. In summary, TiO₂coatings promoted blood coagulation, and it was further enhanced by UV treatment, which has the potential to hasten the wound healing process in vivo.

The biologic seal of peri-implant soft tissue is crucial for long-term prognosis of oral implants. This in vitro study describes a novel tissue culture model using porcine gingival explants to evaluate the soft tissue/implant interface. Two different types of substrates were investigated: (a) plain polymer: BisGMA–TEGDMA (50–50 %) and (b) unidirectional fiber-reinforced composite (FRC). Porcine gingival explants were obtained from a local slaughterhouse. The experimental implants (n = 4) were inserted into the middle of freshly excised porcine gingival explants and cultured at the air/liquid interface up to 14 days. Porcine gingival explants with no implants served as baseline controls. The specimens were fixed and processed for the preparation of undecalcified samples. Histological analysis of the soft tissue/implant interface was carried out using a light-microscope. Microscopic evaluation suggests that the gingival explants established epithelial and connective tissue attachment to both implant types over the incubation period. FRC surfaces seemed to have a favorable tissue response with a sign of an outward epithelial migration. However, tissue degeneration was observed at the end of the experiment. In conclusion, this in vitro model maintains mucosal viability and ability to histologically evaluate soft tissue attachment to biomaterials rendering it a time efficient and cost effective model that may reduce the need for animal experiments.