Hard Resin Research Articles

Lemongrass (Cymbopogon citratus) oil nanoparticle synthesis, characteristic, and evaluation of antibacterial and antifungal effects and the influence on hardness of acrylic resin

Context: Acrylic resin is used in dentistry as a removable denture base. It can cause various pathologies when not properly cleaned. One of the pathologies is denture stomatitis caused by Candida albicans and Streptococcus mutans accumulation on the acrylic resin surface. Therefore, microbial agents such as denture cleansers are needed. Aims: To evaluate the characteristics of lemongrass (Cymbopogon citratus) nanoparticles as a better antibacterial and antifungal herbal ingredient and their relationship with acrylic hardness. Methods: C. citratus oil nanoparticles (LON) were synthesized and analyzed by transmission electron microscopy (TEM). Electrospray ionization tandem mass spectrometry (ESI-MS) analysis was used to analyze the characteristics of LON bioactive components. Minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) against C. albicans and S. mutans and mechanical hardness test of acrylic were performed. Results: The LON concentration of MIC and MBC against C. albicans and S. mutans was 25 and 100%, respectively. One-way ANOVA showed no significant difference between groups of LON with different concentrations (p=0.687). A paired t-test showed significant differences in acrylic resin hardness before and after treatment of LON with 100% (p=0.022) and 50% (p=0.021) concentration. There was no significant difference in hardness before and after treatment of other concentrations of LON and chlorhexidine as positive control. Conclusions: LON treatment on acrylic resin decreased the growth of C. albicans and S. mutans without altering the mechanical properties (hardness).

Wear and corrosion resistance of textured and functionally particle-enhanced multilayer dual-biomimetic polymer coatings

This study presents a dual-biomimetic polymer coating with improved wear and corrosion resistance, inspired by natural biological structures of shells and superhydrophobic surfaces. The coating is composed of alternating hard epoxy resin layers, modified with benzotriazole-functionalized silica for corrosion protection, and soft fluorocarbon resin layers, enhanced with graphene oxide for improved mechanical properties. Surface textures were added using a soft template method to boost hydrophobicity and reduce wear. The coating demonstrated excellent hardness, impact resistance, and corrosion protection, particularly in simulated seawater. Additionally, surface textures further minimized wear by trapping debris. This design strategy offers a promising approach for advanced polymer coatings in marine, machinery, and chemical applications, combining durability, protection, and self-healing properties.

Rehabilitation of Combined Hard and Soft Palate Defects with a Soft Relining Prosthesis: A Clinical Report.

It remains a significant challenge in prosthetic rehabilitation for combined hard and soft palate defects on account of two primary reasons. At first, conventional impressions can hardly get an accurate analogue and usually bring about a terrible experience for the patients. Secondly, conventional hard denture base resins used in obturator prostheses exhibit limitations in marginal sealing, undercut retention, and elastic buffering when in contact with the soft palate. This article presents a case where combined hard and soft palate defects were successfully and rapidly reconstructed by using digital intraoral impression technology and denture soft reline material.

Effect of Postrinsing Times and Methods on Surface Roughness, Hardness, and Polymerization of 3D-Printed Photopolymer Resin.

This in vitro study investigated the effects of different postrinsing times and methods on the surface roughness, surface hardness, and degree of polymerization of materials manufactured via stereolithography (SLA). A total of 288 disk-shaped specimens were manufactured using an SLA three-dimensional (3D) printer. The specimens were randomly divided into nine groups (n = 32) based on rinsing times and methods. The groups were categorized into three rinsing methods: automated, ultrasonic, and hand washing, with rinsing times of 5, 10, and 15 minutes using a 99% isopropanol alcohol as a solvent. Linear roughness (Ra) and area roughness (Sa) were measured using a 3D confocal laser microscopy; the roughness morphology was evaluated by using scanning electron microscopy. Vickers hardness (VHN) tests were performed using a Vickers microhardness tester. Fourier-transform infrared spectrometry was used to determine the degree of conversion of treated specimens. Data were statistically analyzed using two-way analysis of variance. The post hoc Tukey tests were conducted to compare the differences between groups (p < 0.05). The choice of the rinsing time and method affected the surface properties of the SLA photopolymer resin. The 15 minutes of ultrasonic method exhibited the highest Ra scores (0.86 ± 0.1 µm), while the 15 minutes of automated method presented the highest Sa scores (1.77 ± 0.35 µm). For the VHN test, the 15 minutes of ultrasonic method displayed the highest VHN score (18.26 ± 1.03 kgf/mm2). For the degree of polymerization, the 15 minutes of automated method was initially identified as the most effective (87.22 ± 6.80). To facilitate the overall surface roughness, surface hardness, and degree of polymerization, the optimal choice of postprocessing rinsing time and method for achieving a clear photopolymer resin was determined to be the ultrasonic method with a rinsing time of 15 minutes.

Longer light-curing time decreases the effect of ageing on composite resin hardness used in root reinforcement.

This study evaluated the hardness of a composite resin used for root reinforcement, considering the light-curing time, root canal region and ageing due to long-term storage. Twenty incisor roots were reinforced using composite resin, varying the photopolymerisation time (40 or 120 s). Following fibre post cementation, the roots were transversely sectioned into coronal, middle and apical regions. Composite hardness was measured initially and after 18 months of water storage. Data underwent repeated measures analysis of variance and Tukey's post hoc tests. The factors 'light-curing time', 'root region' and 'ageing' affected the hardness. Significant interactions were observed between 'light-curing time × root region' and 'ageing × light-curing time'. Regardless of time, resin hardness in the apical region was lower. After ageing, hardness in the coronal and middle regions decreased when the light-curing time was 40 s, while no significant effect on hardness was noted with a light-curing time of 120 s.

Investigation of microhardness, surface roughness, and color change of preheated composite resins

Aim: Applying heat is a method currently used to enhance the depth of polymerization in composite resin. This study aimed to evaluate the effects of heat treatment on resin hardness, color change, and surface roughness. Methodology: In this study, 64 samples (8 mm2 × 2 mm2) were produced (3M Filtek Universal, G-aenial A’CHORD, Neo Spectra and Clearfil Majesty ES-2) using a Teflon mold (n = 8). Half of the samples were preheated to 50oC, while the other half were polymerized at room temperature. Initial color measurements were performed using a spectrophotometer, the surface roughness was assessed with a profilometer, and the microhardness was determined using a Vickers microhardness device. Subsequently, all samples were immersed in a coffee solution at 37oC. The color changes were documented by the seventh day. The changes in color, roughness, and hardness of the materials were examined by the thirtieth day. Results: The groups that received heat treatment exhibited higher hardness values. The unheated G-aenial A’CHORD composite resin demonstrated the most significant color change by the end of the thirtieth day, while heated and unheated Clearfil Majesty ES-2 composite samples exhibited the least color change. By the end of the thirtieth day, the surface roughness of all samples increased significantly from the baseline, with the 3M Filtek Universal samples, both heated and unheated, showing the highest surface roughness. Conclusion: According to the results of this study, heat treatment of composite resins before polymerization reduces discoloration and improves hardness. Therefore, it is recommended to heat composite resins before application. How to cite this article: Çekmez MB, Karaoğlanoğlu S, Aybala Oktay E, Aydın N, Ersöz B. Investigation of microhardness, surface roughness, and color change of preheated composite resins. Int Dent Res 2024;14(1):42-49. https://doi.org/10.5577/intdentres.523

Investigation of the Effect of Denture Cleaning Solutions on Surface Hardness and Surface Roughness of Soft Lining Materials

Aim: The purpose of this study is to investigate the effects of commercial and non-commercial agents used to clean dentures on the surface roughness and hardness of two soft lining materials. Material and Methods: A total of 50 samples were used in this study. Samples were prepared from acrylic resin (Visco Gel) and silicone-based (Molloplast B) soft lining materials. The samples’ roughness and hardness values were measured. After the samples were kept in distilled water, white vinegar, denture cleanser tablet, 2% chlorhexidine gluconate, and 5% sodium hypochlorite for 15 minutes, 30 minutes, 45 minutes, 60 minutes, 2 hours, 8 hours, 24 hours, and 48 hours, roughness and hardness values were measured again. Statistical analysis was performed using the computer program SPSS Statistics 20.0 (SPSS Inc. Chicago, IL, USA) at a 95% confidence interval and p=0.05 significance level. Three-way ANOVA and Tukey’s multiple comparison tests were used for the statistical analysis of data. Results: The analysis of variance determined that the material type and time had a very significant effect (p&lt;.001) on surface roughness and hardness values, while the solutions in which samples were kept had an insignificant effect (p&gt;.05). Conclusion: The surface roughness and hardness of acrylic resin and silicone-based soft lining materials were affected by denture cleaning solutions to different extents.

Improving energy absorption and failure characteristic of additively manufactured lattice structures using hollow and curving techniques

Strut-based lattice structures of various types exhibited a common critical issue, namely, high tensile stress concentration occurred at node-to-strut sites, which often led to lowered energy absorbability as compared to triply periodic minimal surfaces structures. Therefore, this work aimed for improving the Octet-truss structure by a combined technique using hollow core and varying cross-section ratio. Firstly, test specimens were fabricated using a stereo-lithography based additive manufacturing of photopolymer hard resin. Elastic-plastic properties and damage criterion of the used polymer were experimentally determined and applied for finite element models. Validation by compressive tests of lattice samples showed deviations of stress–strain responses less than 12%, in which local deformation and subsequent damages were fairly predicted. Afterwards, finite element simulations of designed lattice structures subjected to compressive, combined shear, shear and tensile loads were performed and obtained stress–strain characteristics including total absorbed energies and deformation behaviors were studied. Under uniaxial compression and combined shear loads, modified Octet-truss structures exhibited considerable increases of energy absorptions up to 173% and 116%, respectively, and stress–strain responses were more stable. On the other hand, by tension mode peak stresses and elongations could be enhanced about 41% and 11%, accordingly. The improved performances of proposed strut-based structures were comparable to those of triply periodic minimal surfaces diamond structure. This was due to that local stress distributions in the structure became more uniform and previously dominated tensile stresses were switched to compressive stresses. Therefore, occurrences of shear bands and plastic hinges could be effectively inhibited.

Effect of Ethanol Addition on some Properties of Self-Polymerized Acrylic Resins

Background: Self-polymerized acrylic resins are widely utilized in dentistry. A higher residual monomer content is seen after polymerization of denture base resins. The literature showed that the ethanol solvent could rise the leaching of residual monomer from the polymer. The purpose of the current research was to investigate the influence of ethanol addition on hardness and roughness of acrylic resins. Materials and Methods: Sixty acrylic resin specimens were prepared and were divided into 2 main sets due to the kind of test used (surface hardness and surface roughness). There were three groups according to the ethanol concentrations. The first group was the control specimens with no ethanol, the second group was loaded with 10 ml of ethanol; and the third group was loaded with 15 ml of ethanol. The acrylic specimens were measured using the Shore A Durometer hardness and the surface roughness tester. Results: showed that the addition of ethanol significantly decrease the surface hardness of acrylic resins. The results indicated that there are significant differences between groups (P&lt; 0.0010). However, no significant differences between 10ml and 15 ml groups (P&gt;0.05). For surface roughness test, no significant differences were found among the studied groups (P&gt;0.05). Conclusions: The addition of ethanol to self-polymerized acrylic resins would significantly decrease the hardness and increases the surface roughness of acrylic resins

Effect of Ethanol Addition on some Properties of Self-Polymerized Acrylic Resins

Background: Self-polymerized acrylic resins are widely utilized in dentistry. A higher residual monomer content is seen after polymerization of denture base resins. The literature showed that the ethanol solvent could rise the leaching of residual monomer from the polymer. The purpose of the current research was to investigate the influence of ethanol addition on hardness and roughness of acrylic resins. Materials and Methods: Sixty acrylic resin specimens were prepared and were divided into 2 main sets due to the kind of test used (surface hardness and surface roughness). There were three groups according to the ethanol concentrations. The first group was the control specimens with no ethanol, the second group was loaded with 10 ml of ethanol; and the third group was loaded with 15 ml of ethanol. The acrylic specimens were measured using the Shore A Durometer hardness and the surface roughness tester. Results: showed that the addition of ethanol significantly decrease the surface hardness of acrylic resins. The results indicated that there are significant differences between groups (P&lt; 0.0010). However, no significant differences between 10ml and 15 ml groups (P&gt;0.05). For surface roughness test, no significant differences were found among the studied groups (P&gt;0.05). Conclusions: The addition of ethanol to self-polymerized acrylic resins would significantly decrease the hardness and increases the surface roughness of acrylic resins

Effect of duration and infection control barriers of light curing unit on hardness of Bulk Fill composite resin.

This study aimed to investigate the impact of the duration of light curing unit (LCU) usage and the use of infection control barriers on the hardness of Bulk Fill composite resin after curing. The hypotheses were that extended usage of the LCU would not reduces its output power and resin hardness, and that the presence of polyethylene film barriers exacerbates the reduction in resin hardness. Based on the absence or presence of polyethylene film (PE) and the number of layers used, a 3M LED curing light (EliparTM DeepCure-S; 3M ESPE, St Paul, MN, USA) was divided into three groups: PE0, PE1, and PE3. The curing light was used 30 times daily for 20 s per exposure, at frequencies of 0, 6, and 12 months. Maximum output power tests were conducted for each group of curing lights. Custom-made plastic modules were used to stack Bulk Fill composite resin (Filtek Bulk Fill Posterior Restorative; 3M ESPE) to a thickness of 4 mm. Each group of curing lights was used to cure the modules in a direct contact manner for 20 s. Vickers hardness measurements were taken at the top and bottom surfaces of the resin specimens using a digital microhardness tester. A one-way or two-way ANOVA analyzed the power of LCUs, Vickers hardness of Bulk Fill composite resin, and hardness decrease percentage across groups. Pairwise comparisons used the Tukey test (α = 0.05). As the duration of usage increased, both the power of the curing light and the hardness of the resin significantly decreased. Significant differences were observed in power and resin hardness among the PE0, PE1, and PE3 groups. When the duration of usage was 6 months or less, only multi-layered PE films led to a significant increase in the percentage decrease of hardness of cured resin from top to bottom. However, at 12 months, both single-layer and multi-layered PE films resulted in a significant increase in the percentage decrease of hardness of cured resin from top to bottom. The output power of the light curing unit decreases with prolonged usage, thereby failing to meet the curing requirements of Bulk Fill composite resin. The use of single-layer PE as an infection control barrier is recommended.

Assessment of the surface roughness and hardness of acrylic resin after incorporation of sodium fluoride salts (An In-vitro Study)

The control of oral hygiene is of great importance, particularly in dental work, to prevent caries caused by bacteria. One method to inhibit bacterial growth is usually by using fluoridated dental materials. The objectives are to assess the effect of sodium fluoride powder (NaF) inclusion with different concentrations on the surface roughness and hardness of heat-cured acrylic resins. A total of forty disc-shaped samples with a diameter of (12±0.1) mm and a thickness of (2±0.1) mm have been fabricated from heat cure acrylic resin. They were grouped into four subgroups according to different concentrations of NaF with 10 specimens for each group. Sodium fluoride powder (NaF) was incorporated into the monomer in concentrations of 0% (control group), 1%, 3%, and 5%. Then mixing was done with polymer according to manufacturer instructions and the conventional flasking, and packing procedures were used. Finally, the specimens are subjected to hardness and surface roughness tests. The results of this study revealed that the lowest mean value surface roughness (Ra) was with the (5%) group of NaF (7828). While, for the surface hardness test, the group (5%) of Naf showed the highest mean value among their subgroups (82.30). According to the results of the current study, sodium fluoride powder (NaF) has a positive effect on both the surface roughness and hardness of acrylic resin.

Fractionation of High-Value Compounds from Hops Using an Optimised Sequential Extraction Procedure.

This study describes the development and optimisation of a process for the extraction and fractionation of high-value compounds from hops. Firstly, the efficacy of ten organic solvents was compared for performing the initial solid-liquid extraction of compounds from hop pellets with subsequent fractionation steps. A methanol-dichloromethane mixture was selected and the extraction variables were optimised in order to maximise the recovery of valuable hop compounds separated into different streams (α- and β-acids in soft resins, xanthohumol in hard resins, and phenolics in spent solids) after fractionation steps. The optimisation results showed that extraction of hop pellets performed at room temperature with 19.7% (v/v) methanol for 89 min yielded recoveries of 86.57% α-acids and 89.14% β-acids in soft resins, 78.48% xanthohumol in hard resins and 67.10% phenolics in spent solids. These conditions were successfully validated using six hop varieties. Moreover, the antioxidant properties of all recovered fractions were compared and the soft resins showed the highest antioxidant activities, reaching values of 3.91 ± 0.10 g AAE/100 g for ferric reducing power (FRAP) and 0.10 ± 0.01 mg/mL for 50% of radical scavenging activity (EC50). The optimised sequential extraction could serve as a basis for larger scale-up for industrial production.

In Vitro Effect of Mouthrinses on the Microhardness of Three Different Nanohybrid Composite Resins.

Daily use of different mouthrinses at home or in the dental office can alter the properties of resin hardness. The present study aimed to compare Vickers microhardness (VHN) in vitro of nanohybrid composite resins (NCRs) immersed in mouthrinses. In total, 120 discs (10 ⨯ 2 mm) were prepared from three NCR shade A2 (n = 40/group) with FiltekTM Z350 XT (Z350XT), Tetric EvoCeram (TEC), and Polofil NHT (PNHT). The specimens were incubated in artificial saliva (37°C ⨯ 24 hr). Specimens were distributed into four mouthrinses (n = 10/group) of artificial saliva (control), chlorhexidine (CHX 0.12%, pH 5.6), cetylpyridine chloride (CPC 0.075%, pH 5.84), and CHX 0.12% + CPC 0.05% (pH 6.2) (2 times/day, 2' ⨯ 12 hr). The VHN (300 gf/10") was measured after 24 hr, 14, and 21 days. Data were analyzed by three-way analysis of variance, followed by post hoc Tukey analysis at 0.05 level of significance. The results revealed a global effect of the interaction of the mouthrinses ⨯ time between NRC evaluated (P=0.001). Baseline VHN in PNHT and Z350XT was higher than TEC. Within each group of NCR, VHN of CHX + CPC > other mouthrinses (PNHT/14 days; Z350XT/21 days), and >CPC (Z350XT/14 days). In mouthrinses-intragroups, VHN of PNHT and Z350XT decreased at 14 days (CHX, CPC) and was maintained over time in NCR (CHX + CPC). VHN-TEC was similar among groups. Microhardness showed differences due to the interaction of the type of NCR, the composition of the mouthrinses, and time. VHN decreased after 14 days and was more affected in composite resins with lower filler content and in mouthrinses with a lower pH.

Evaluation of Physical Properties of Denture Base Resins Containing Silver Nanoparticles of Aloe barbadensis Miller, Morinda citrifolia, and Boesenbergia rotunda and Its Anti-microbial Effect: An In Vitro Study.

Introduction The denture bases fabricated from polymethylmethacrylate (PMMA) have some disadvantages, such as surface prone to microbial growth and biofilm accumulation, which contributes to the onset and dissemination of infections among denture wearers. Therefore, the purpose of this in vitro study was to evaluate the flexural strength, hardness, and antimicrobial effect of denture base resin incorporated with 0.05% and 0.1% silver nanoparticles (AgNPs) of Aloe barbadensis miller (aloe vera), Morinda citrifolia (noni), and Boesenbergia rotunda (finger root). Materials and methods A total of 84 PMMAsamples were used and were divided into three groups. Flexural strength tests were performed on Group 1 PMMAblocks. Group 2 involved hardness testing of PMMAblocks, whereas Group 3 involved antimicrobial activity. Each group was subsequently split into seven subgroups with differing concentrations of AgNPs: Sub Group 1: control (no AgNPs),Sub Group 2: 0.05% aloe vera AgNPs, Sub Group 3: 0.1% aloe vera AgNPs, Sub Group 4: 0.05% noni AgNPs, Sub Group 5: 0.1% of noni AgNPs,Sub Group 6: 0.05%finger root AgNPs, and Sub Group 7: 0.1% finger root AgNPs.The flexural strength was evaluated usinga universal testing machine (Instron 8801). Surface hardness was measured using a Vickers tester (Tukon 1102). For the antimicrobial activity analysis, the samples were incubated in a suitable culture broth containing Candida albicans for 24 hours. Microbial colony count (colony-forming unit (CFU)/mL) was estimated to evaluate the microbial adhesion to the surface of the denture base materials. Statistical analysis The flexural strength, hardness, and CFU between the groups were analyzed using one-way analysis of variance (ANOVA) followed by multiple comparisons with Tukey's honest significant difference (HSD) test (α=0.05). The level of statistical significance was determined at p<0.05. Results It was observed that the mean flexural strength was maximum in PMMA incorporated with 0.05% of aloe vera AgNPs and least in PMMA incorporated with 0.1% noni AgNPs. It was seen that a steady loss in flexural strength is observed from 0.05% to 0.1%. The mean hardness was maximum in PMMA incorporated with 0.1% of noni AgNPs and least in PMMA incorporated with 0.05% aloe vera AgNPs. It was also found that the hardness was directly proportional to the number of nanoparticles. With an increase in the weight percentage of nanoparticles, a steady increase in hardness was seen in all the test groups. In our study, the results showed that finger root 0.1% showed the least CFU with a significant reduction of C. albicans adherence; therefore, it indicates higher anti-fungal activity. Aloe vera 0.05% showed the lowest inhibition of C. albicans,suggesting the least anti-fungal activity. Conclusion Within the limitations of this study, It can thus be concluded that the addition of AgNPs incorporated with plant extracts of Aloe barbadensis miller (aloe vera), Morinda citrifolia (noni), and Boesenbergia rotunda (finger root) can alter the flexural strength, hardness, and microbial adhesion of PMMA. In our study, it can be concluded that flexural strength increases with the addition of AgNPs of 0.5% concentration after which a steady loss is seen. However, the hardness and antimicrobial activity increased with an increase in the concentration of AgNPs in all three plant extracts.

The Influence of Incorporating Zno on The Surface Hardness of Poly Methyl Methacrylate. In Vitro Study

Introduction: Heat cured resins are commonly utilized for construction of complete and partial dentures. Such materials have poor mechanical properties and may be exposed to fracture. The present study, therefore, was conducted to evaluate the impact of incorporating ZnO on acrylic resins’ surface hardness. Materials and Methods: Twenty specimens were constructed in total. The study composed of 2 major sets, and each set had ten specimens. The 1st set had 1% zinc oxide and the second group had no zinc oxide and considered as control. All samples were subjected to the hardness test three times and average reading was recorded for all specimens. Results: a significant decrease in the surface hardness of acrylic re sins following the incorporation of ZnO (control group: 12 7.62+2.53 g/mm2, zinc oxide group: 106.67+ 1.51). Conc lusions: The addition of zinc oxide at 1 % would decrease the surface hardness of acrylic resins.

3D printed indirect bonding trays: Transfer accuracy of hard versus soft resin material in a prospective, randomized, single-blinded clinical study.

This prospective clinical study aimed to compare transfer accuracy and immediate loss rate of hard versus soft transfer trays utilizing a CAD/CAM workflow. We performed virtual bracket placement on intraoral scans of adolescent patients to create individual indirect bonding trays. Orthodontic software (Appliance Designer, 3Shape, Copenhagen, Denmark) was used to design the trays, which were then produced using 3D printing technology. Patients were randomly assigned to the hard or soft resin groups with a 1:1 allocation. Subgroups were determined based on the Little's Irregularity Index and distributed equally. 552 brackets were bonded onto adolescent patients using 46 CAD/CAM indirect bonding trays. The linear mean transfer errors ranged from -0.011mm (soft) to -0.162mm (hard) and angularly -0.255° (hard) and -0.243° (soft). No statistically significant differences were found between the subgroups or soft and hard resin groups. However, the transfer accuracy of molar brackets was significantly lower in the transversal and horizontal directions. All mean transfer errors were within the limits of clinical acceptability. The loss rate was 2.4 % in the hard resin group and 2.3 % in the soft resin group. The Intra Observer Correlation was excellent. CAD/CAM technology for indirect bracket bonding has been proven reliable in a randomized clinical trial. Both hard and soft resin showed a low rate of immediate loss compared to the current literature. Soft resin was more favorable than hard resin in terms of accuracy and usability. However, the indirect bonding of molar brackets is significantly less accurate than incisor brackets.

Adapted the Mechanical Characteristics of Bio-Composite Sisal Fibres Material by Adding Aluminum Particles for Structure

The e-bike structure is increasingly developing, especially in terms of design, its strength is around 300 MPa in a maximum application of around 160 MPa, as is the case with the scooter bike structure. The strength of sisal, which is a composite reinforcing component, is made from natural fiber from pineapple leaves, which is then mixed with hemp fiber and carbon fiber. In mechanical structure materials, apart from the material being expected to have high yield strength, it is also expected to have good ductility. The reinforcement is then mixed with hard epoxy resin, soft epoxy, and 9 µm aluminum particles which are then stirred for 12 hours, until smooth and even. Mathematically, the improvement in this bio-composite is quite significant, obtained from the addition of carbon fiber. The ductility of the material is obtained from sisal, hemp and ductile epoxy mixed with hard epoxy resin. Because the quality of crop yields greatly influences the quality of the fiber, future agricultural processes need to be provided with counseling. The sisal fiber is a leftover product from community farming in the Subang area (Indonesia). Research using local materials is still able to obtain strength reaching ~480 MPa so it is still good. In this research, tensile tests were carried out 3 times so that it was found that the fiber taken from the rope had the greatest tensile strength, reaching around 480 MPa.

CAD/CAM indirect bonding trays using hard versus soft resin material: a single-blinded in vitro study.

The present in vitro study aimed to evaluate the accuracy of three-dimensional (3D) printed indirect bonding trays consisting of hard or soft resin materials produced using computer-aided design and manufacturing (CAD/CAM). Forty-eight dental casts were 3D printed. Four groups based on frontal crowding were defined and divided into hard- and soft-resin groups. After virtual bracket positioning on the digital models, the transfer trays were 3D printed. To evaluate the accuracy of the procedure, measurements were performed using a digital overlay of the virtual (target) bracket position and a post-bonding scan. The horizontal, transverse, and vertical deviations and angular discrepancies were analyzed. The loss rate was evaluated descriptively as a percentage. A total of 553 brackets were bonded using 24 soft and 24 resilient indirect bonding trays. The mean deviations were of 0.05mm (transversal), 0.05mm (horizontal), 0.09mm (vertical), 0.13° (angulation) in the resilient resin group and of 0.01mm (transversal), 0.08mm (horizontal), 0.08mm (vertical), 0.37° (angular) in the soft resin group. The loss rate was 6.9% and 0.7% in the hard and soft resin groups, respectively. Angular deviations were significantly higher in the soft resin group (P=0.009), whereas the loss rate was considerably higher in the hard resin group (P<0.001). The findings indicate that indirect bonding using CAD/CAM is an accurate procedure in the laboratory setting. Soft resins are considered favorable for loss rate and useability.

The Effect of Bonding Surface Design on Shear Bond Strength of 3D-Printed Orthodontic Attachments.

This study compared the shear bond strength (SBS) of four innovative designs of the bonding surface of 3D-printed orthodontic attachments with conventional mesh design. In this in vitro study, the bonding surface design in different groups was as follows: Group 1, flat surface without any feature as a negative control; Group 2, concentric circles with no cuts; Group 3, concentric circles with 16 radial cuts; Group 4, concentric circles with 32 radial cuts; Group 5, small cones with a flat end and rounded edges; Group 6, mesh-based commercially available metal brackets of the maxillary central incisor (standard edgewise, Dentaurum®) as a positive control (n = 20). In Groups 1-5, attachments were designed with SolidWorks® Software and printed with a 2K DLP-LCD printer with hard tough resin (eSun®). All the samples were bonded to the restorative composite resin (Solafil®) surfaces with orthodontic composite resin (CuRAY-ECLIPSE®). The samples were examined for SBS with a universal testing machine after thermocycling (1,000 cycles of 5‒55°C). Data were analyzed with Shapiro-Wilk, one-way ANOVA, and Bonferroni tests. The statistical significance level was set at 0.05. The mean SBS was significantly different between all the groups (P < 0.001) except for Groups 2 and 5 (P = 1.00) and Groups 2 and 6 (P = 1.00). Group 4 had the highest mean of SBS. The bonding surface design significantly influenced the SBS of orthodontic attachments. The concentric circles with 32 cuts had higher bond strength than other designs and can be suggested as a new bonding surface design for orthodontic attachments.