Effect of radiotherapy on the surface roughness and microhardness of contemporary bioactive restorative materials.

OBJECTIVE: The aim of this in vitro study was to evaluate the effect of radiotherapy on the surface microhardness and roughness of different bioactive restorative materials. MATERIALS AND METHODS: A total of 60-disc specimens (5 mm × 2 mm) were performed in four groups (n = 15 each) from Equia Forte HT, Cention N, Activa Bioactive Restorative, and Beautifil II. Following the polishing procedure (600, 1000, 1200 grit silicon carbide papers), all specimens were irradiated at 2 Gy per fraction, five times a week for a total dose of 70 Gy in 30 fractions over 7 weeks. Before and after the irradiation, the specimens were analyzed regarding the surface roughness and microhardness. Surface morphology was also analyzed by scanning electron microscopy. Kruskal-Wallis test, Wilcoxon test, and paired sample t-test were used for statistical analysis. RESULTS: Significant differences were found after radiation with increased mean roughness of both Cention N (p = 0.001) and Beautifil II (p < 0.001) groups. In terms of microhardness, only the Beautifil II group showed significant differences with decreased values after radiation. There were statistically significant differences among the groups' roughness and microhardness data before and after radiotherapy (p < 0.05). CONCLUSION: The effect of radiotherapy might differ according to the type of the restorative material. Although results may differ for other tested materials, giomer tends to exhibit worse behaviour in terms of both surface roughness and microhardness. CLINICAL RELEVANCE: In patients undergoing head and neck radiotherapy, it should be taken into consideration that the treatment process may also have negative effects on the surface properties of anti-caries restorative materials.

Investigating the impact of post-curing cycles on surface hardness and color stability in 3D printed resin crowns.

This study evaluated the effect of different post-curing cycles on the Vickers hardness, color change, and translucency value of 3D printed methacrylic acid ester-based temporary and permanent crown resins. A total of 300 samples were printed in disk shape (ø:8 mm, thickness: 2 mm) using VarseoSmile Crown Plus (VSC) and VarseoSmile Temp (VST) materials from a 3D printer. These disks were divided into five subgroups (n = 30 each) based on flash-curing cycles (0, 750, 1500, 2250, and 3000). Surface hardness tests and color tests were conducted on both the green state and flash-cured groups. The data were analyzed using univariate analysis of variance (ANOVA). The hardness of 3D printed temporary and permanent crown resin increased with post-curing time. Compared to the post-curing cycle recommended by the manufacturer, no clinically significant color change (ΔE00 ≥ 2.25) was observed in any of the polymerized groups. It was determined that permanent crown material had a more translucent structure than temporary crown material. The interaction between material and post-curing had significant effects on surface hardness, color (ΔE00), and translucency of 3D printed methacrylic acid ester-based resins.

Enhancing the antibacterial and surface hardness of glass ionomer cement modified with Salvadora persica and Chlorhexidine: An in vitro study.

Objective: This laboratory study evaluated the effect of Salvadora persica (S. persica) root extracts and Chlorhexidine Digluconate (CHX) on the antibacterial and surface hardness properties of glass ionomer cement (GIC). Methods: The in vitro experimental study was conducted at the Baqai Institute of Pharmaceutical Sciences of Baqai Medical University, Karachi, Pakistan, from October 2022 to March 2023. There were a total four experimental groups. The first group consisted of ethanol extract (GIC-SPEE) and second group consisted of hexane extract as (GIC-SPHE) both prepared from Salvadora persica root respectively, and mixed with liquid of GIC separately. The third group comprised chlorhexidine (GIC-CHX) that was also mixing into liquid portion of GIC and the last group was Control i.e. (cGIC). The GIC samples were prepared by using stainless steel metallic moulds with dimension (5mm x 2mm), following the manufacturer guidelines. Antibacterial activity against Streptococcus mutans was done by disc diffusion test (DDT), and surface hardness test was done by Vickers hardness tester. Statistical analysis was performed using One-Way ANOVA and Tukey's post hoc tests (p<0.05). Results: The antibacterial activity against S. mutans reported that the maximum zone of inhibition was obtained at 3 wt% by the GIC-SPEE, when compared with other experimental groups. For surface hardness, the highest mean and standard deviation and significant findings was reported by the group GIC-SPEE. Conclusions: Considering the outcome of this in vitro study, it can be concluded that the addition of 3 wt% GIC-SPEE increased the surface hardness and antibacterial activity against Streptococcus mutans.

Temperature changes and hardness of resin-based composites light-cured with laser diode or light-emitting diode curing lights.

The temperature and Vickers Hardness (VH) at the top and bottom surfaces of three resin-based composites (RBCs) were measured when light-cured using five light-curing units (LCUs). The spectrum, power, and energy delivered to the top of the RBCs and transmitted through the RBCs were measured. Starting at 32℃, the temperature rise produced by the Monet Laser (ML-1 s and 3 s), Valo Grand (VG-3 s and 10 s), DeepCure (DC-10 s), PowerCure, (PC-3 s and 10 s) and PinkWave (PW-10 s) were measured at the bottom of specimens 2 mm deep × 6 mm wide made of Filtek Universal A2, Tetric Evoceram A2 and an experimental RBC codenamed Transcend UB. The VH values measured at the top and bottom of these RBCs were analyzed using ANOVA and Scheffe's post hoc test (p < 0.05) to determine the effects of the LCUs on the RBCs. The transmitted power from the ML was reduced by 77.4% through 2 mm of Filtek Universal, whereas light from PW decreased by only 36.8% through Transcend. The highest temperature increases from the LCU combined with the exothermic reaction occurred for Transcend, and overall, no significant differences were detected between Filtek Universal and Tetric Evoceram (p = 0.9756). Transcend achieved the highest VH values at the top and bottom surfaces. The PinkWave used for 10 s produced the largest temperature increase (20.2℃) in Transcend. The Monet used for 1 s produced the smallest increase (7.8℃) and the lowest bottom:top VH ratios.

Effect of graphene on the mechanical and anisotropic thermal properties of Cu-Ta composites.

Strong interfacial bonding is the basic requirement for metal-graphene composites for higher thermo-mechanical properties. In the present work, a novel metal tantalum is introduced in the metal-graphene composites prepared by (ball-milling + molecular level mixing) followed by hot press sintering. SEM, transmission electron microscopy and high transmission electron microscopy are observed to check the interface area which shows the presence of tantalum carbide on the interface area which is formed during the sintering process. The formation of the carbide element significantly enhances the mechanical properties of composites. The addition of a very low amount of 0.1 vol% of rGO give the very high yield strength 200 MPa and ultimate tensile strength value 375 MPa with the good agreement of ductility, Vickers hardness 95 HV and bending strength 617 MPa which are much higher than unreinforced copper-tantalum composites and even from pure copper. The anisotropic thermal conductivity values are also significantly improving due to the better interfacial bonding and the ratio was 5 which is just 1.01 for pure copper. The formation of carbide elements and extraordinary high mechanical values with good ductility and anisotropic thermal conductivity ratio can lead to these materials used in thermal packaging systems and the electronic industry.

Impact of adhesive primer and light-curing on polymerization kinetics of self-adhesive resin cement in association with free radical reaction.

This study analyzed the impact of adhesive primer and light-curing on the polymerization kinetics of urethane dimethacrylate-based self-adhesive resin cement combined with free radical reaction. Specimens were prepared by mixing the cement paste with or without adhesive primer. Subsequently, specimens were light-cured or set without light-curing. The degree of conversion (DC), Vickers hardness (Hv), and free radical concentrations were repeatedly measured up to 168 h after the curing initiation. Irrespective of the curing procedures, DC, Hv, and free radical concentration rapidly increased during the initial 30 min of curing. The specimens cured with adhesive primer and/or light-curing generally showed higher values of DC, Hv, and radical concentration than those set by chemical curing alone, especially during the initial polymerization phase. Kinetic analysis using a linear mixed model revealed that the adhesive primer had a higher coefficient estimate than light-curing, indicating that the former had a higher impact on the polymerization. Additionally, the adhesive primer alleviated the Hv reduction caused by water and air during the initial polymerization phase, although light-curing hardly prevented the polymerization inhibition. Therefore, we suggest that application of adhesive primer is beneficial to achieve higher degree of conversion and better mechanical properties of self-adhesive resin cements by enhancing free radical reactions.

The existence of butterfly effect and its impact on the dentinal microhardness and crack formation after root canal instrumentation.

To compare the microhardness and crack formation in root dentine presented with butterfly effect in lower premolars. Sixty mature lower premolars were selected and divided into the control and experimental groups. Teeth in the experimental group were instrumented up to size 30/.04. The roots were cut horizontally into twelve parts of 1-mm-thick cross-section and were numbered accordingly. They were divided into coronal, middle, and apical root sections. Sections were then viewed under a microscope to determine the presence of butterfly effect and subsequently scored. 8 teeth from both control and experimental groups with the highest and lowest score were selected. Crack formation was inspected and classified into four different types of cracks. Microhardness test was performed using a Vickers hardness test. Higher frequency of butterfly effect was found in the apical root section and root dentine with butterfly effect were harder mesiodistally. The middle and apical root sections with butterfly effect were harder than the coronal section. No significant difference of dentine hardness between the control and experimental groups. Cracks only occurred in the experimental group and presented in buccolingual direction with a higher rate of Type 1 and Type 2 cracks. Prevalence of butterfly effect in lower premolars increased from coronal to apical with increased hardness mesiodistally. More buccolingual cracks were found in radicular dentine with butterfly effect and most of them exhibited Type 1 and Type 2 cracks. Roots of lower premolar with butterfly effect may be susceptible to a higher rate of vertical root fracture in buccolingual direction, especially after root canal treatment. Thus, special attention should be given not to overload instruments during root canal preparation.

Effect of pressure and light curing of composite micro hardness.

The aim of this study is to evaluate the micro hardness Vickers of a composite micro hybrid polymerized under constant pressure. Twelve experimental samples were made equally divided into two groups: an experimental group and a control. Enamel plus HRi (Micerium) microbiotic composite resin, UD3 colour, was inserted into a syringe heater (ENA HEAT Composite Heating Conditioner) so that the material could be brought to a temperature of 39°C. A defined amount of composite resin is taken from the syringe with a Heidemann spatula and placed between two slides, previously cleaned with 90 ° alcohol. The samples are then inserted one at a time into a special device for constant pressure application. Vickers hardness measurements were made on the top of surfaces. The mean value of the samples belonging to the experimental group is 56.81 ± 0.71. The mean value of the control samples is 52.02 ± 2. The results obtained allow us to state that applying a constant pressure during the cementation phase of indirect adhesive restorations allows to obtain better mechanical characteristics of the composite used as a cementing agent.

Revealing the Unusual Rigid Boron Chain Substructure in Hard and Superconductive Tantalum Monoboride.

Poor electrical conductivity severely limits the diverse applications of high hardness materials in situations where electrical conductivities are highly desired. A "covalent metal" TaB with metallic electrical conductivity and high hardness has been fabricated by a high pressure and high temperature method. The bulk modulus, 302.0(4.9) GPa, and Vickers hardness, 21.3 GPa, approaches and even exceeds that of traditional insulating hard materials. Meanwhile, temperature-dependent electrical resistivity measurements show that TaB possesses metallic conductivity that rivals some widely-used conductors, and it will transform into a superconductor at Tc =7.8 K. Contrary to common understanding, the hardness of TaB is higher than that of TaB2 , which indicates that low boron concentration borides could be mechanically better than the higher boron concentration counterparts. Compression behavior and first principles calculations denote that the high hardness is associated with the ultra-rigid covalent boron chain substructure. The hardness of TaB with different topologies of boron substructure shows that besides incorporating higher boron content, manipulating light element backbone configurations is also critical for higher hardness amongst transition metal borides with identical boron content.

Effect of Aging Time and Thickness on Low-Temperature Degradation of Dental Zirconia.

PURPOSE: To evaluate the influence of specimen thickness and low-temperature degradation (LTD) on yttrium-stabilized tetragonal zirconia polycrystals (Y-TZP). MATERIALS AND METHODS: Thin discs of Y-TZP from four manufacturers were sintered according to each manufacturer's recommendations, cut into 23 mm (length) × 4 mm (width) × 0.8 mm/1.5 mm (thickness) specimens, artificially aged under standard autoclave sterilization conditions (34°C at 0.2 MPa for 10 and 20 hours), and finally ground and polished. Tetragonal to monoclinic transformation was confirmed by X-ray diffraction (XRD) analysis. Flexural strength was measured by 3-point bending tests and Vickers hardness measurements. Fracture surfaces were examined by scanning electron microscopy (SEM). RESULTS: SEM investigation revealed that with increasing aging time, the surface defects and grain size increased, particularly in the 20-hour group. Compared with the 1.5 mm group, the 0.8 mm group showed more significant defects, irrespective of aging time. The flexural strengths of Y-TZP materials decreased with a decrease in the thickness. Moreover, LTD of Y-TZP can cause significant tetragonal to monoclinic transformation, which also results in a statistically significant decrease in the flexural strength. CONCLUSION: A thinner Y-TZP specimen was likely to present surface defects and microcracks after aging. In addition, the flexural strengths decreased with a decrease in the thickness, a notable fact for further studies.

Does the Translucency of Novel Monolithic CAD/CAM Materials Affect Resin Cement Polymerization with Different Curing Modes?

PURPOSE: The translucency of CAD/CAM blocks influences the polymerization efficiency of resin cement used underneath. The aim of this study is to evaluate the influence of the translucency parameters (TPs) of current monolithic CAD/CAM blocks on the microhardness of light-cured or dual-cured resin cement. MATERIALS AND METHODS: 100 specimens were prepared from five types of CAD/CAM blocks (Mark II, Suprinity, Enamic, e.max, Ultimate), and their TP values were measured by spectrophotometry; 100 resin cement specimens (Duolink) were cured underneath five ceramic specimen groups by indirect LED light for 40 seconds with dual-cure (with catalyst) and light-cure (without catalyst) polymerization modes. Control group resin cement specimens (n = 20) were cured with both polymerization modes by direct LED light without any ceramic disc, making 120 resin cement specimens in total. The specimens were then stored in a dry environment for 24 hours before measurement of the polymerization depth with a digital micrometer. Vickers hardness measurements were performed at different resin cement sections. The results were statistically analyzed with 1-, 2-, and 3-way ANOVA, Student's t-test and Tukey's HSD test (α = 0.05). RESULTS: The highest TP values occurred for Suprinity and Ultimate, whereas the lowest TP value occurred for Enamic (p < 0.01). The depth of cure and Vickers hardness values changed proportionally with TP value. In all specimens, dual polymerization provided higher depth of cure and Vickers hardness values than those obtained using light polymerization (p < 0.01). In all specimens except Enamic, the hardness value differences between the sections were statistically insignificant (p > 0.05). In Enamic, the hardness values for both polymerization types decreased significantly in the deeper sections (p < 0.01). CONCLUSIONS: Lower depth of cure was observed as the amount of transmitted light decreased in the investigated materials. In clinical practice, light-cured resin cements may result in inadequate polymerization for ceramic materials with lower TP values. Zirconia-reinforced lithium silicate and nanoceramic resins may be reliable restorative materials for a restoration with both optimal esthetics and sufficient mechanical strength resulting from proper polymerization.

An in vitro study to compare the influence of different all-ceramic systems on the polymerization of dual-cure resin cement.

AIM: The aim of the study is to compare the effect of composition of three different all-ceramic systems on the polymerization of dual-cure resin cement, using different curing cycles and evaluated immediately within 15 min and after 24 h. MATERIALS AND METHODS: Resin cement disc samples were fabricated by polymerization through three different all-ceramic disc, namely: lithium disilicate discs - IPS e.max (Group B), leucitereinforced discs - IPS Empress (Group C), zirconia discs - Cercon (Group D), and without an intervening ceramic disc, as control (Group A). A total of 80 resin cement disc samples were fabricated for fur groups (n = 20). Each group further consisted of two subgroups (n = 10), t10 and t20 according to two different exposure times of 10 and 20 s, respectively. Each of the 80 resin disc samples was evaluated for their degree of polymerization achieved, by measuring the microhardness(Vickers hardness number) of the samples immediately within 15 min and after 24 h, giving us a total of 160 readings. Oneway analysis of variance test, ttest, and paired ttest were used for multiple group comparisons followed by Tukey's post hoc for groupwise comparison. RESULTS: Direct activation of the resin cement samples of control (Group A) showed statistically significant higher mean microhardness values followed by Groups C then B and D, both immediately and after 24 h. The mean microhardness for immediate post-activation was always inferior to the 24 h post-activation test. For both 10 and 20 s curing cycle, there was a significant increase in the microhardness of the resin cement discs cured for 20 s through the different ceramics. CONCLUSION: Ceramic composition affected the polymerization of dual cured resin cement. Doubling the light irradiation time or curing cycle significantly increased mean microhardness value. Greater degree of conversion leading to an increase in hardness was observed when the resin cement discs were evaluated after 24 h.

In vitro Fracture strength and hardness of different computer-aided design/computer-aided manufacturing inlays.

OBJECTIVE: The purpose of this study was to examine the fracture strength and surface microhardness of computer-aided design/computer-aided manufacturing (CAD/CAM) materials in vitro. MATERIALS AND METHODS: Mesial-occlusal-distal inlays were made from five different CAD/CAM materials (feldspathic ceramic, CEREC blocs; leucite-reinforced ceramic, IPS Empress CAD; resin nano ceramic, 3M ESPE Lava Ultimate; hybrid ceramic, VITA Enamic; and lithium disilicate ceramic, IPS e.max CAD) using CEREC 4 CAD/CAM system. Samples were adhesively cemented to metal analogs with a resin cement (3M ESPE, U200). The fracture tests were carried out with a universal testing machine. Furthermore, five samples were prepared from each CAD/CAM material for micro-Vickers hardness test. Data were analyzed with statistics software SPSS 20 (IBM Corp., New York, USA). RESULTS: Fracture strength of lithium disilicate inlays (3949 N) was found to be higher than other ceramic inlays (P < 0.05). There was no difference between other inlays statistically (P > 0.05). The highest micro-Vickers hardness was measured in lithium disilicate samples, and the lowest was in resin nano ceramic samples. CONCLUSION: Fracture strength results demonstrate that inlays can withstand the forces in the mouth. Statistical results showed that fracture strength and micro-Vickers hardness of feldspathic ceramic, leucite-reinforced ceramic, and lithium disilicate ceramic materials had a positive correlation.

Light energy attenuation through orthodontic ceramic brackets at different irradiation times.

OBJECTIVE: To evaluate the total light energy (TLE) transmission through three types of ceramic brackets with, bracket alone and with the addition of orthodontic adhesive, at different exposure durations, and to compare the microhardness of the cured adhesive. MATERIALS AND METHODS: Three different makes of ceramic brackets, Pure Sapphire(M), Clarity™ ADVANCED(P) and Dual Ceramic(P) were used. Eighteen specimens of each make were prepared and allocated to three groups (n = 6). MARC(®)-resin calibrator was used to determine the light curing unit (LCU) tip irradiance (mW/cm(2)) and TLE (J/cm(2)) transmitted through the ceramic brackets, and through ceramic bracket plus Transbond™ XT Light Cure Adhesive, for 5, 10 and 20 s. Vickers-hardness values at the bottom of the cured adhesive were determined. Statistical analysis used one-way analysis of variance (ANOVA); P = 0.05. RESULTS: TLE transmission rose significantly among all samples with increasing exposure durations. TLE reaching the adhesive- enamel interface was less than 10 J/cm(2), and through monocrystalline and polycrystalline ceramic brackets was significantly different (P < 0.05). Pure Sapphire(M) showed the highest amount of TLE transmission and Vickers-hardness values for 5, 10 and 20 s. CONCLUSION: Following manufacturer's recommendations, insufficient TLE may be delivered to the adhesive: increasing the exposure durations may be required when adhesive is cured through ceramic brackets. Clinicians are advised to measure the tip irradiance of their LCUs and increase curing time beyond 5 s. Orthodontic clinicians should understand the type of light curing device and the orthodontic adhesive used in their practice.

The Effect of Irradiation Distance on Light Transmittance and Vickers Hardness Ratio of Two Bulk-fill Resin-based Composites.

The aims of this study were to assess the light energy transmission and Vickers hardness (VH) ratio of two bulk-fill resin-based composites (RBCs) (Tetric EvoCeram and Filtek) cured at different distances between the light curing unit's (LCU) tip and the surface of the restoration (T-S) using either a Bluephase G2, Bluephase® 'turbo tip' or Bluephase Style LCU. Samples were cured from the top at T-S distances of 2mm, 6mm and 10mm for 20 seconds. A MARC-Resin-Calibrator™ recorded the transmitted irradiance reaching the bottom of the sample, in real time. The VH was measured at the top and bottom after 24h of dark storage. Both the total light energy (TLE) transmitted through the samples and their VH ratios were reduced with increasing T-S distance. At 10mm T-S distance, the VH ratio values of samples cured with Bluephase G2 LCU were significantly greater than the samples cured with the other LCUs while the samples cured with Bluephase® 'turbo tip' showed the lowest values. It can be concluded that TLE transmitted through bulk-fill RBCs and their VH ratio reduces with increasing T-S distance but the rate of decline is LCU dependent. Bluephase G2 was associated with the smallest light attenuation.

Addition of benzalkonium chloride to self-adhesive resin-cements: some clinically relevant properties.

OBJECTIVE: The clinical survival rates of the adhesive restorations are limited due to the deterioration of resin-dentin bonds over time, partly due to the endogenous enzymatic activity of dentin. Recently, benzalkonium chloride (BAC) has been shown to effectively inhibit endogenous protease activity of dentin. This study evaluated the effect of different concentrations of benzalkonium chloride (BAC) on the degree of conversion (DC), vickers hardness (VH), setting time (ST) and biaxial flexural strength (FS) of two self-adhesive resin luting cements (RC). METHODS: Two RC SpeedCEM (Ivoclar-Vivadent) and BisCem (Bisco) were modified by addition of 0.1, 0.5, 1, 1.5, 2 wt% BAC. The luting cements without the addition of BAC served as control. The DC (FT-IR/ATR from the bottom of the resin disc), vickers hardness (from top and bottom of the light-cured specimen), setting time (ISO 4049) and biaxial flexural strength (0.6 × 6 mm discs) of the specimens were tested. Data were analyzed using ANOVA and Tukeys HSD. RESULTS: DC results were in the range of 70-80%, with some significant changes in BisCem (p < 0.05). VH values of both materials increased significantly compared to control, with no significant change as the BAC percentage increases. BAC addition influenced the ST differently for both materials. For BisCem, a gradual decrease (p < 0.05) was observed whereas, for SpeedCEM, a gradual increase was observed until 1% BAC (p < 0.05). For FS values, a gradual decrease was observed for both materials with increased amounts of BAC (p < 0.05), compared to the control group. CONCLUSIONS: BAC addition of up to 1% seems to be acceptable considering the properties tested. Clinical significance. Incorporation of benzalkonium chloride to self-adhesive resin luting cements during the mixing procedure does not significantly affect the degree of conversion or flexural strength of the luting agent and may be a good option to improve the durability of adhesive interface.

Synthesis of a resin monomer-soluble polyrotaxane crosslinker containing cleavable end groups.

A resin monomer-soluble polyrotaxane (PRX) crosslinker with cleavable end groups was synthesized to develop degradable photosetting composite resins. The PRX containing 50 α-cyclodextrins (α-CDs) with disulfide end groups was initially modified with n-butylamine to obtain a resin monomer-soluble PRX. The PRX containing 13 n-butyl groups per α-CD molecule was completely soluble in conventional resin monomers such as 2-hydroxyethyl methacrylate (HEMA) and urethane dimethacrylate (UDMA). The synthesized n-butyl-containing PRX was further modified with 2-aminoethyl methacrylate to provide crosslinkable acrylic groups onto PRX. The prepared resin monomer-soluble PRX crosslinker was successfully polymerized with a mixture of HEMA and UDMA to provide photosetting plastic. It was confirmed that the Vickers hardness of the prepared plastic was greatly decreased after treatment with dithiothreitol. This indicates that the resin monomer-soluble PRX crosslinker can be applied to design degradable photosetting plastics potentially used in the industrial or biomedical field.

Comparative Evaluation of Dental Enamel Microhardness Following Various Methods of Interproximal Reduction: A Vickers Hardness Tester Investigation.

Interproximal enamel reduction, also known as stripping, is a common orthodontic procedure that reduces the mesiodistal diameter of teeth, allowing for a balance of available space in dental arches. The aim of this study was to assess the enamel surface microhardness resulting from the application of currently available methods for interproximal reduction. Forty-two extracted human permanent teeth were divided into six different groups, each subjected to a therapeutic stripping procedure using various methods (i.e., diamond burs, abrasive strips of 90 µm, 60 µm, 40 µm, and 15 µm, and abrasive discs). Stripping was performed by a single individual in accordance with the manufacturers' recommendations for the various systems used. One of the proximal faces of the tooth underwent IPR, while the other side remained untreated for control. The hardness of the enamel surface was measured using a Vickers hardness tester. The control group achieved the hardest enamel surface (354.4 ± 41.02 HV1), while the lowest was observed for enamel surfaces treated with 90 µm abrasive strips (213.7 ± 118.6). The only statistically significant difference was identified in comparisons between the values measured for the control group and those obtained after stripping with diamond burs (p = 0.0159). Enamel microhardness varied depending on the stripping instrument used, but no statistically significant differences were found (p > 0.05). Optimal microhardness values, close to those of healthy enamel, were achieved after mechanical treatment with 15 µm abrasive strips and abrasive discs. Dental stripping is a safe therapeutic procedure that has a relatively minor influence on the microhardness of surface enamel.

Crystal growth, Hirshfeld analysis, optical, thermal, mechanical, and third-order non-linear optical properties of Cyclohexylammonium picrate (CHAP) single crystal.

The organic single crystals of Cyclohexylammonium picrate (CHAP) had been grown using the method of slow evaporation solution growth. A determination was made regarding the solubility of the substance. The crystal's lattice cell parameters and morphology were characterized using single-crystal X-ray diffraction and powder X-ray diffraction techniques. The HRXRD techniques were utilized to assess the crystal quality. The functional groups of CHAP material were identified through the use of FT-IR and FT-Raman analysis. A Hirshfeld surface analysis was performed to investigate the formation of hydrogen bonds between N-H⋯O and C-H⋯O molecules. The grown crystals were examined in optical and thermal investigations utilizing UV-visible and TGA, DSC techniques. Mechanical analysis is used to quantify surface properties, such as work hardening coefficient and void volume. Z-scan analysis was utilized to calculate the non-linear refractive index (n2), nonlinear absorption (ß), and third-order non-linear susceptibility (χ3).

Effects of CAD/CAM restorative materials and thickness on the depth of cure of various light-cured resin composite materials.

The study assessed the depth of cure (DOC) of different resin composites light-cured through different types of CAD/CAM materials of variable thickness. Three CAD/CAM materials (multilayer zirconia, lithium disilicate glass ceramic, composite) of three thicknesses (2-, 3-, and 4-mm) were prepared and their translucency parameter (TP) were measured. A light-curable and a dual-curable resin cement (Variolink Esthetic LC and DC) and a bulk-fill resin composite with a higher Ivocerin concentration (Tetric PowerFill) were used to mimic luting agents. DOC was assessed via Vickers microhardness testing. Increased thickness of CAD/CAM specimen was associated with decreased DOC. The chemical composition of the resin composites affected their curing performance depending on the light curing mode. Tetric PowerFill presented the greater DOC among the other resin composites. Receiver operating characteristic models of curing status appeared to provide better insight in predicting the DOC of luting agent according to TP than linear regression.