UNASSIGNED: Plaster of Paris splints are commonly utilised for foot and ankle injuries. However, during follow-ups, some of these splints were found to be broken. Various methods, including splint form or augmentation changes, have been explored to enhance flexural strength. However, the impact of water temperature on the splint\'s flexural strength still needs to be studied. This research aimed to investigate the effect of water temperature on the flexural strength of the Plaster of Paris splint.
UNASSIGNED: Three groups were set up based on different water temperatures: cold, hot, and room temperature. Posterior ankle splints were created and immersed in water at these varying temperatures, with five pieces tested per group. The splints were then allowed to harden fully over three days. Each splint underwent a tensile strength test using an axial pressure machine, which recorded their flexural strength data.
UNASSIGNED: There were no statistically significant differences in the general characteristics of the splints. The flexural strengths of the three splint groups (pre-cooled, pre-heated, and room temperature) were 182.6N, 162.45N, and 228.91N, respectively. Statistical analysis revealed that room-temperature splints demonstrated a statistically significant increase in flexural strength compared to pre-heated splints (p<0.05). However, they did not differ significantly from pre-cooled splints.
UNASSIGNED: The highest flexural strength was observed in splints immersed in room-temperature water.

BACKGROUND: To evaluate the flexural strength of digitally milled and printed denture base materials.
METHODS: The materials tested were Lucitone 199 denture base disc (Dentsply Sirona), AvaDent denture base puck (AvaDent), KeyMill denture base disc (Keystone), Lucitone digital print denture base resin (Dentsply Sirona), Formlab denture base resin (Formlabs), and Dentca base resin II (Dentca). Sixty bar-shaped specimens of each material were prepared for flexural strength testing and were divided into five groups: control, thermocycled, fatigue cycled, and repair using two different materials. The flexural strength and modulus were tested using a 3-point bend test performed on an Instron Universal Testing Machine with a 1kN load cell. The specimens were centered under a loading apparatus with a perpendicular alignment. The loading rate was a crosshead speed of 0.5 mm/min. Each specimen was loaded with a force until failure occurred. A one-way ANOVA test was used to analyze the data, followed by Tukey\'s HSD test (α = 0.05).
RESULTS: The milled materials exhibited higher flexural strength than the printed materials. Thermocycling and fatigue reduce the flexural strengths of printed and milled materials. The repaired groups exhibited flexural strengths of 32.80% and 30.67% of the original flexural strengths of printed and milled materials, respectively. Nevertheless, the type of repair material affected the flexural strength of the printed materials; the composite resin exhibited higher flexural strength values than the acrylic resin.
CONCLUSIONS: The milled denture base materials showed higher flexural strength than the printed ones.

This study aimed to evaluate the effect of airborne particle abrasion with different particles on the surface free energy, roughness, and biaxial flexural strength of a feldspathic ceramic by comparing it with hydrofluoric acid etching, the standard surface treatment, and polishing. Square-shaped feldspathic ceramic specimens (12 mm × 12 mm × 1.2 mm) were divided into subgroups as airborne particles abraded with alumina (AO3a, AO3b, AO25, AO50a, AO50b, AO90, AO110a, AO110b, AO120a, and AO120b), silica (SO50a, SO50b, SO100, and SO100/200), or nutshell granule (NS100/200), hydrofluoric acid etched, and polished (n = 12). Surface free energy (n = 5), roughness (n = 5), biaxial flexural strength (n = 12), and Weibull moduli (n = 12) were investigated. Data were evaluated with 1-way ANOVA and Tukey HSD tests, and possible correlations were investigated with Pearson\'s correlation (α = 0.05). SO100/200 mostly had lower surface free energy (p ≤ 0.011), and polishing and etching led to higher surface free energy than AO3a, AO3b, and AO120a (p ≤ 0.031). Polished, SO100, and SO50b specimens mostly had lower roughness and AO125 had the highest roughness (p ≤ 0.029). SO100/200 mostly had lower biaxial flexural strength (p ≤ 0.041), and etched specimens had higher biaxial flexural strength than AO120a, AO120b, and SO50b (p ≤ 0.043). AO3b had the highest (33.56) and AO120b had the lowest (11.8) Weibull modulus. There was a weak positive correlation between the surface free energy and the biaxial flexural strength (r = 0.267, p = 0.011). A larger particle size mostly resulted in higher roughness, which was also affected by the particle shape. Most of the test groups had similar biaxial flexural strength to that of the hydrofluoric acid-etched group. Therefore, for tested feldspathic ceramic, airborne particle abrasion with tested parameters may be a suitable alternative without causing any further damage.

OBJECTIVE: 3D printing found its way into various medical applications and could be particularly beneficial for dentistry. Currently, materials for 3D printing of occlusal splints lack mechanical strength compared to polymethyl methacrylate (PMMA) used for standard milling of occlusal splints. It is known that print orientation and graphene nanoplatelets (GNP) can increase biaxial strength in a variety of materials. Thus, the aim of this study was to assess if adjustment of print orientation and addition of GNP improve biaxial strength and if they affect cytotoxicity of a 3D printable resin for occlusal splints.
METHODS: Specimens were printed vertically and horizontally with a stereolithography (SLA) printer and multilayered GNP powder was added to the resin at different concentrations. Printed specimens were characterized by Raman spectroscopy, optical profilometer analysis and scanning electron microscopy. Biaxial strength was evaluated by biaxial flexural testing. Cytotoxicity of specimens on L929 and gingival stromal cells (GSC) was assessed by the toxdent test, the resazurin-based toxicity assay and live-dead staining.
RESULTS: Horizontally printed specimens showed significantly higher biaxial strength and lower deformation. GNP did not improve biaxial strength and material deformation of 3D-printed resins. None of the specimens were cytotoxic to L929 cells or GSC.
CONCLUSIONS: Print orientation in SLA printing has a significant impact on biaxial strength and material deformation. 3D printable materials can reach comparable or even improved biaxial strength compared to PMMA when using the optimal print orientation while GNP has no beneficial effects on the biaxial strength of resins for 3D printing of occlusal splints.

The mechanical properties and thickness of adult temporal and occipital bones were examined in modern Japanese forensic samples. Cranial bones were obtained from 293 Japanese corpses (179 men and 114 women). During autopsy, left temporal (LT), right temporal (RT), and occipital (O) bone samples were extracted from each skull. Sample thickness (ST) was measured using multidetector computed tomographic imaging. The fracture load (FL) of each sample was measured by a bending test, in which the flexural strength (FS) was calculated. The FL and ST values for O were significantly greater compared with those of the LT and RT bones. The temporal bones were thinner compared with other parts of the skull and at greater risk for fracture. There is a need to take precautions to prevent temporal bone fractures. There were no significant differences in any of the values between LT and RT, indicating bilateral symmetry of the temporal bones. There were significant negative correlations between age and the FL and FS values for all sites in both sexes, except for O in the male samples, suggesting that older individuals are at increased risk for fractures. No significant correlations were observed between age and ST values in any of the samples. There were significantly positive correlations between FL and ST values at all sites regardless of sex.

Purpose: Sintering procedures influence the properties of zirconia. This study evaluated the effect of varying sintering rates on flexural strength (σ) of 3, 4, and 5 mol% yttria (Y) containing monochrome (Mo) and multilayer (Mu) zirconia. Materials and Methods: 270 specimens (width×length×thickness = 11.2×20×1.5 mm) were prepared from Mo and Mu of 3Y, 4Y, and 5Y zirconia and randomly sintered at regular (RS: 10 °C/min), fast (FS: 35 °C/min), and speed (SS: 70 °C/min) sintering (n = 15/group). Three-point bending test was determined for σ. ANOVA and Bonferroni test were analyzed for significant differences of σ (a=0.05). The microstructure and crystalline [monoclinic (m), tetragonal (t), and cubic (c)] phases were evaluated by SEM and XRD.Results: σ of zirconia was affected by zirconia type, shade pattern, and sintering rate. Significant higher σ for 3Y>4Y>5Y (p<0.05). Significant greater σ for Mu>Mo (p<0.05). Significant reduction of σ upon SS than RS and FS (p<0.05). However, no significant effect on σ upon varying sintering rates within each type of zirconia (p>0.05). SEM indicated greater grain size in 5Y than in 4Y and 3Y. XRD indicated higher t phase in 3Y, whereas higher c phase in 5Y. Mo indicated a higher c phase than Mu.Conclusions: σ was influenced by Y content (3Y>4Y>5Y), shade pattern (Mu>Mo), and sintering rate (RS@FS>SS). Nonetheless, no influence of varying sintering rates on σ for each type of zirconia, suggesting sintering zirconia with RS and FS for expecting higher σ and at SS for acceptable σ for chair-side cost-effective restoration.

Objectives: The use of fiber posts in endodontically treated primary maxillary central incisors improves the retention of composite resin restorations. The purpose of this study was to evaluate the effect of 4 different luting cements on fracture resistance of primary maxillary central incisors with fiber posts. Materials and Methods: In this in vitro study, 40 primary maxillary central incisors were endodontically treated and obturated with Metapex. They were then randomly divided into four groups (n=10) for cementation of fiber posts with GC Fuji I glass ionomer luting cement, Panavia F2.0 dual-cure luting cement, Panavia SA Luting Plus cement (self-adhesive), and TotalCem self-adhesive cement. After 1000 thermal cycles, the fracture resistance was measured. Data were statistically analyzed using ANOVA (alpha=0.05). Results: The mean fracture resistance was 267.07±130.01N in TotalCem, 257.27±102.56N in Panavia F2.0 dual-cure cement, 227.82±110.40N in Panavia SA Luting Plus self-adhesive cement, and 220.89±59.96N in GC Fuji I glass ionomer group. There was no statistically significant difference in fracture resistance among the four groups (P=0.714). Conclusion: Type of luting cement had no significant effect on fracture resistance of primary maxillary central incisors with fiber posts. Nonetheless, TotalCem yielded the highest fracture resistance. Considering its self-adhesive property and easy workability, it can be a good option for cementation of fiber posts in endodontically treated primary central incisors.

Polylactic acid (PLA) models of normal human femoral diaphyses were designed using three-dimensional (3D) printing technology to create inexpensive, accessible, and reproducible specimens for flexural biomechanical studies. These models were subjected to three-point bending and their response to loading was characterized. The anisotropic mechanical behavior of the 3D-printed femurs and the influence of printing orientations, infill density, wall layers, resolution, and other printing parameters were explored to develop a design space. The objective of the design space was set to emulate the flexural biomechanical response of the normal human femur bones. Results show the 3D-printed PLA diaphyseal femurs with 5% infill density, two-four wall layers, and a resolution of 200 µm resulted in a flexural strength of 184.8 ± 8.18 MPa. Models with 20% infill density and six wall layers resulted in a flexural modulus of 18.54 ± 0.543 GPa. These results emulate the biomechanical response of the normal human femur, as determined by historical target values derived from prior cadaveric and 3D printing data. With further research, inclusive of modeling the proximal and distal femur and more comprehensive biomechanical testing, 3D-printed femurs may ultimately serve as a cheap, accessible biomechanical resource for surgeons and researchers.

BACKGROUND: Polymethylmethacrylate (PMMA) bone cement is used in orthopedics and dentistry to get primary fixation to bone but doesn\'t provide a mechanically and biologically stable bone interface. Therefore, there was a great demand to improve the properties of the PMMA bone cement to reduce its clinical usage limitations and enhance its success rate. Recent studies demonstrated that the addition of halloysite nanotubes (HNTs) to a polymeric-based material can improve its mechanical and thermal characteristics.
OBJECTIVE: The purpose of the study is to assess the compressive strength, flexural strength, maximum temperature, and setting time of traditional PMMA bone cements that have been manually blended with 7 wt% HNT fillers.
METHODS: PMMA powder and monomer liquid were combined to create the control group, the reinforced group was made by mixing the PMMA powder with 7 wt% HNT fillers before liquid mixing. Chemical characterization of the HNT fillers was employed by X-ray fluorescence (XRF). The morphological examination of the cements was done using a scanning electron microscope (SEM). Analytical measurements were made for the compressive strength, flexural strength, maximum temperature, and setting time. Utilizing independent sample t-tests, the data was statistically assessed to compare mean values (p < 0.05).
RESULTS: The findings demonstrated that the novel reinforced PMMA-based bone cement with 7 wt% HNT fillers showed higher mean compressive strength values (93 MPa) and higher flexural strength (72 MPa). and lower maximum temperature values (34.8 °C) than the conventional PMMA bone cement control group, which was (76 MPa), (51 MPa), and (40 °C), respectively (P < 0.05). While there was no significant difference in the setting time between the control and the modified groups.
CONCLUSIONS: The novel PMMA-based bone cement with the addition of 7 wt% HNTs can effectively be used in orthopedic and dental applications, as they have the potential to enhance the compressive and flexural strength and reduce the maximum temperatures.

Cerium oxide nanoparticles are known for their antibacterial effects resulting from Ce3+ to Ce4+ conversion. Application of such cerium oxide nanoparticles in dentistry has been previously considered but limited due to deterioration of mechanical properties. Hence, this study aimed to examine mesoporous silica (MCM-41) coated with cerium oxide nanoparticles and evaluate the antibacterial effects and mechanical properties when applied to dental composite resin. Cerium oxide nanoparticles were coated on the MCM-41 surface using the sol-gel method by adding cerium oxide nanoparticle precursor to the MCM-41 dispersion. The samples were tested for antibacterial activity against Streptococcus mutans via CFU and MTT assays. The mechanical properties were assessed by flexural strength and depth of cure according to ISO 4049. Data were analyzed using a t-test, one-way ANOVA, and Tukey\'s post-hoc test (p = 0.05). The experimental group showed significantly increased antibacterial properties compared to the control groups (p < 0.005). The flexural strength exhibited a decreasing trend as the amount of cerium oxide nanoparticle-coated MCM-41 increased. However, the flexural strength and depth of cure values of the silane group met the ISO 4049 standard. Antibacterial properties increased with increasing amounts of cerium oxide nanoparticles. Although the mechanical properties decreased, silane treatment overcame this drawback. Hence, the cerium oxide nanoparticles coated on MCM-41 may be used for dental resin composite.