Hard Resin Research Articles

BASIC PROBLEMS WITH THE USE OF RESILIENT DENTURE LINING MATERIALS: LITERATURE REVIEW

Complicated cases in the treatment of totally edentulous patients, as well as in the fabrication of obturators and epitheses, require the use of resilient lining materials (RLMs). These materials have several disadvantages, which is why many dental practitioners do not recommend them. The tendency to breaking the bond between the hard acrylic resin and the resilient liner is a fact with unpleasant consequences, mainly found with the use of cold-curing silicone-based resilient liners. Methods to improve the bond between the hard denture base and the RLM have been the subject of numerous publications. The efforts of the authors are focused in two directions: mechanical or chemical treatment of the denture base or a combination of both. Other commonly discussed problems with the use of RLMs are the difficult and even impossible repair and the retention of oral fluids, fungi and other microorganisms due to the porosity of RLMs. Despite the wide variety of tools offered by different manufacturers, the issue of optimal and high-quality mechanical treatment of the polymerized resilient material has not yet been fully resolved.

Realization of a Novel Morphing Surface Using Additive Manufacturing and Its Active Control in Friction

Abstract As the need for higher efficiency of engineering components increases, so does the demand for functional surfaces. While various tribosurfaces (e.g., texturing and coatings) have been developed, many researches are aimed at static functionality. On the other hand, due to a wide range of environmental adaptability and active control, active-morphing surfaces can be highly efficient and robust. In this paper, we demonstrate a novel morphing surface and its realization using additive manufacturing (AM). By using a diaphragm structure, morphing performance is achieved even if a hard resin material is used. When air pressure is applied to the backside of the diaphragm, it changes to a convex shape and vice versa. The concept requires a complex structure for arranging airflow and a solid morphing system. The AM is one great technique to create such complex structures. As a result of actual manufacturing, the created morphing structure realizes a large morphing of 600 μm or more. In addition, the shape changes reversibly depending on the air pressure. The surface also exhibits very interesting tribological characteristics. The surface shows a friction coefficient of about 0.3 with a concavity, and then increases to 0.5–1.7 with a convexity. A real-contact area measurement reveals that the novel property occurs due to change in the real-contact area depending on surface morphology. In conclusion, the present paper provides a new concept of a novel morphing tribosurface, which selectively performs as a low-friction or break-like surface, created using AM.

Assessment and Determination of Bittering Agents, Essential Oils, and Antioxidants of Gesho (Rhamnus prinoides L. Herit) Collected from Amhara Region, Ethiopia

Rhamnus prinoides (Gesho) is an angiosperm dioecious plant, which is used for cash income, as a bittering agent for the preparation of the local alcoholic beverage and medicinal values. Although it has intense use, still its practical application is limited for local alcoholic beverage preparation, and there is no sufficient scientific report on the level and quantity of bittering agents, essential oils, and antioxidants of this plant. Therefore, the objective of this research was to assess and determine the bittering agents, essential oils, and antioxidants of R. prinoides. The leaves of R. prinoides were collected from eleven different sample sites and allowed to sun dry and then powdered. It was further dried in an oven at 60°C for 1 h, and then, total resin, essential oils, alpha acid, iso-alpha acid, beta acid, flavonoids, and polyphenols of R. prinoides were determined. All the data were analyzed using SPSS version 20.0. Based on this study finding, (16.03 ± 0.03–17.05 ± 0.04%) total resins, (10.00 ± 0.08–11.23 ± 0.07%) soft resins, (5.65 ± 0.11–6.40 ± 0.35%) hard resins, (1.82 ± 0.11–3.14 ± 0.02 mg/l) alpha acids, (2.26 ± 0.15–4.15 ± 0.10 mg/l) iso-alpha acids, (2.62 ± 0.04–4.29 ± 0.08 mg/l) beta acids, (7.74 ± 0.11–12.47 ± 0.13%) essential oils, (23.00 ± 0.14–25.01 ± 0.09%) flavonoids, and (2.11 ± 0.01–2.41 ± 0.02%) polyphenols were obtained in the leaves of R. prinoides. R. prinoides leaves taken from Tikledingay has shown statistically ( P ≤ 0.05 ) significant amount of soft resin (11.23 ± 0.07%), alpha acid (3.14 ± 0.02 mg/l), iso-alpha acid (4.15 ± 0.10 mg/l), essential oils (12.47 ± 0.13%), flavonoids (25.01 ± 0.09%), and polyphenols (2.41 ± 0.02%) in comparison with other samples. Generally, R. prinoides is a good source of bittering agents, essential oils, and antioxidants. However, the quantity of bittering agents, essential oils, and antioxidants in the leaves of R. prinoides was varied with sample collection sites. So R. prinoides can be used as a substitute for commercial hops used in the breweries, and promotion should be done to introduce the potential of Gesho as a bittering agent, source of aroma and flavor, and also antioxidant for beer and other alcoholic beverages.

The Photoinitiators Used in Resin Based Dental Composite-A Review and Future Perspectives.

The presented paper concerns current knowledge of commercial and alternative photoinitiator systems used in dentistry. It discusses alternative and commercial photoinitiators and focuses on mechanisms of polymerization process, in vitro measurement methods and factors influencing the degree of conversion and hardness of dental resins. PubMed, Academia.edu, Google Scholar, Elsevier, ResearchGate and Mendeley, analysis from 1985 to 2020 were searched electronically with appropriate keywords. Over 60 articles were chosen based on relevance to this review. Dental light-cured composites are the most common filling used in dentistry, but every photoinitiator system requires proper light-curing system with suitable spectrum of light. Alternation of photoinitiator might cause changing the values of biomechanical properties such as: degree of conversion, hardness, biocompatibility. This review contains comparison of biomechanical properties of dental composites including different photosensitizers among other: camphorquinone, phenanthrenequinone, benzophenone and 1-phenyl-1,2 propanedione, trimethylbenzoyl-diphenylphosphine oxide, benzoyl peroxide. The major aim of this article was to point out alternative photoinitiators which would compensate the disadvantages of camphorquinone such as: yellow staining or poor biocompatibility and also would have mechanical properties as satisfactory as camphorquinone. Research showed there is not an adequate photoinitiator which can be as sufficient as camphorquinone (CQ), but alternative photosensitizers like: benzoyl germanium or novel acylphosphine oxide photoinitiators used synergistically with CQ are able to improve aesthetic properties and degree of conversion of dental resin.

Physical and Mechanical Properties of Resins Blends Containing a Monomethacrylate with Low-polymerization Shrinkage.

Objectives The aim of this study was to evaluate the Knoop hardness (KH), cross-link density (CLD), water sorption (WS), water solubility (WSB), and volumetric shrinkage (VS) of experimental resins blends containing a monomethacrylate with low-polymerization shrinkage. Materials and Methods A blend of bisphenol glycidyl methacrylate (BisGMA) as base monomer was formulated with (Bis-GMA)/triethyleneglycol dimethacrylate (TEGDMA), Bis-GMA/isobornyl methacrylate (IBOMA), or Bis-GMA/TEGDMA/IBOMA in different concentrations (40, 50, or 60 wt%). The camphorquinone (CQ)/2-(dimethylamino) ethyl methacrylate (DMAEMA) was used as the photoinitiator system. The KH and CLD were measured at the top surface using an indenter. For WS and WSB, the volume of the samples was calculated in mm 3 . The samples were transferred to desiccators until a constant mass was obtained (m1) and were subsequently immersed in distilled water until no alteration in mass was detected (m2). The samples were reconditioned to constant mass in desiccators (m3). WS and WSB were determined using the equations m2 − m3/V and m1 − m3/V, respectively. VS results were calculated with the density parameters before and after curing. Statistical Analysis Data were submitted to ANOVA and Tukey’s test (α = 0.05). Results The resins containing IBOMA showed lower VS results. TEGDMA 40% and TEGDMA/IBOMA 20/20 wt% showed higher KH values. The IBOMA groups showed lower CLD, while TEGDMA groups had higher values of CLD. The BisGMA/TEGDMA resin presented the highest values of WS, and for WSB, all groups showed no significant differences among themselves. Conclusion The monomethacrylate with low-polymerization shrinkage IBOMA used alone or in combination with TEGDMA may decrease VS, WS, and CLD values.

Reduction of headache intensity and frequency with maxillary stabilization splint therapy in patients with temporomandibular disorders-headache comorbidity: a systematic review and meta-analysis.

This systematic review and meta-analysis aimed to analyze the effectiveness of maxillary stabilization splint (SS) therapy to reduce headache (HA) intensity and HA frequency in patients with temporomandibular disorders (TMD)-HA comorbidity. Randomized controlled trials (RCTs) using full-arch coverage, hard resin, and maxillary SS therapy were included. Electronic databases, including Cochrane Library, MEDLINE through PubMed, Web of Science, and EMBASE, were searched. The risk of bias was analyzed based on Cochrane's handbook. The search yielded 247 references up to January 28, 2020. Nine RCTs were included at a high risk of bias. The comparison groups included other splints, counseling, jaw exercises, medications, neurologic treatment, and occlusal equilibration. Four studies reported a statistically significant reduction in HA intensity, and five studies reported significant improvement in HA frequency from baseline at 2-12 months in patients with TMD-HA comorbidity treated with a full-arch hard maxillary SS. HA frequency in tension-type HA (TTH) comorbid with TMD diagnoses of myofascial pain (MFP) or capsulitis/synovitis improved significantly with SS than that with full-arch maxillary non-occluding splint (NOS) in two studies. Comparison groups receiving hard partial-arch maxillary splint nociceptive trigeminal inhibition (NTI) showed statistically significant improvements in HA intensity in patients with mixed TMD phenotypes of MFP and disc displacement comorbid with “general HA.” Comparison groups receiving partial-arch maxillary resilient/soft splint (Relax) showed significant improvements in both HA intensity and frequency in patients with HA concomitant with MFP. The meta-analysis showed no statistically significant difference in the improvement of pain intensity at 2-3 months with comparison of the splints (partial-arch soft [Relax], hard [NTI], and full-arch NOS) or splint use compliance at 6-12 months with comparison of the splints (partial-arch Relax and full-arch NOS) versus the SS groups in patients with various TMD-HA comorbidities. In conclusion, although SS therapy showed a statistically significant decrease in HA intensity and HA frequency when reported, the evidence quality was low due to the high bias risk and small sample size. Therefore, further studies are required.

A new teaching model with artificial teeth containing simulated pulpal tissue

This study aimed to evaluate the use of artificial teeth for endodontic training for dental students. The following aspects of the artificial teeth were approved by the endodontists in Isfahan University of Medical Science: internal and external anatomy; coronal pulp chambers regarding their size, shape, and canal path; the root canals regarding their size, shape, and position; filling the pulp chamber and root canals by considering the texture, quantity, color, and ease of handling; and resin hardness and visualization of the radiographic image. The results showed favorable opinions regarding the internal and external anatomy, coronal pulp chamber, root canal (s), handling, and radiographic imaging. The contents of the pulp space and hardness of the teeth were satisfactory. The artificial teeth tested have the potential to replace the natural teeth in preclinical training.

Electromyographic evaluation of the masseter and temporalis muscles activity in patients with complete denture, implant supported and implant retained mandibular overdentures. a cross-over study

This study was conducted to compare the electromyographic [EMG] activity of both masseter and the anterior temporalis muscles in patients with: Conventional complete dentures, Implant supported overdentures without attachments and, Implant retained overdentures with locator attachments. Material and methods: Six completely edentulous male patients with atrophied mandibular ridges received upper and lower conventional complete denture. EMG activity were measured for both masseter and the anterior temporalis muscles during clenching without food, clenching hard (carrot) and soft (banana) foods. Measurements were made at time of denture insertion, one month and two months after. Two implants were installed in canine regions of the mandible. After osteointegration, healing abutments were connected and the mandibular denture were relined with hard acrylic resin. Measurements were repeated, then healing abutments were replaced with locator attachments, and measurements were repeated again. Results: The highest EMG activity/amplitude of masseter and temporalis muscles, were noted with locator overdentures, and the lowest values were observed with conventional dentures. There was no statistically difference in muscle activity between implant supported overdentures and complete dentures. For all groups, muscle activity for masseter and temporalis muscles increased with advance of time. For both groups, muscle activity was significantly higher during clenching of hard food than clenching without food or with soft food Conclusion: Within the scope of this study, implant retained overdentures are recommended for edentulous patients rather than conventional complete dentures or implant supported overdentures as it improves EMG activity/amplitude of masseter and temporalis muscles.

Comparison of degradation behavior between soft and hard epoxy resins

ABSTRACT Soft and hard epoxy resins used as insulating sealants in nuclear power plants were aged simultaneously by heat and gamma rays at 80, 90, and 100°C, and the changes in their various properties induced as a result of their degradation were measured. The thermal, mechanical, dielectric, and spectroscopic properties hardly change in the hard epoxy resin, whereas they change drastically in the soft epoxy resin, indicating that the latter resin becomes hard and then brittle. This big difference in mechanical property between the two resins is attributable to a significantly low glass transition temperature of −30°C in the soft resin compared to that of 120°C in the hard resin. Although the hard epoxy resin with the high glass transition temperature exhibits thermal and mechanical properties insensitive to the aging conditions, its complex permittivity at temperatures higher than 140 °C shows an evident increase in accord with the progress of degradation. This phenomenon can be an indicator of the degradation of this resin. The effects of degradation on the absorption spectra in a THz frequency range are also examined.

THE EFFECT OF THE ACIDITY OF FERMENTED MILK AGAINST THE HARDNESS OF NANOHYBRID COMPOSITE RESIN

Background : The hardness of nanohybrid composite resin can decrease due to the acidic condition of the oral cavity. The acidic condition of the oral cavity can cause continuous degradation in composite resin. Fermented milk is a beverage that is widely sold in the market and is good for consumption however this beverage has the acid potential of hydrogen (pH) which can reduce the composite resin toughness. Aim : To determine the acidity effect of fermented milk on the hardness of nanohybrid composite resin. Method: Experimental study with a post test control group design. There were 27 samples of nanohybrid composite resin. One time immersion for three seconds in each group of beverages namely Milk, Cimory, and Yakult. After 15 days, a composite resin hardness test was performed using a Micro Vickers Hardness Tester with a load of 100 grams for 10 seconds. Statistical tests using One Way ANOVA. Results: The nanohybrid composite resin exhibited significant reduction in hardness between three beverage groups. Post hoc LSD test showed that there were significant differences between Milk with Yakult (p = 0.006) and Cimory with Yakult (p = 0.008) while Milk with Cimory (p = 0.907) did not have significant. Conclusions : There is a effect of fermented milk influences the hardness. There is a significant difference between Milk and Yakult and between Cimory and Yakult and there is no significant difference between Milk and Cimory.

Evaluation of Oral Splint in Treatment of Tempromandibular Disorders in Class I Malocclusion

Objective: This study was designed to evaluate the effect of occlusal splints used for treatment of tempromandibular disorders (TMD). Material and methods: Thirty class I malocclusion patients (ranging in age 20-30) suffering from signs of TMD attending at orthodontic department, faculty of dental medicine, Al Azhar university boys branch. The patients' complaints were crowding of teeth, limited mouth opening, tempromandibular joints (TMJ) pains, and joint noises during function. The patients will be divided randomly into three groups. Group I will have patients treated by hard rigid occlusal splint (heat cured tooth borne and occlusal surface). Group II will have patients treated by soft occlusal splint flexible and pliable tooth borne and occlusal surface. Group III will have patients treated by dual laminated occlusal surface, hard acrylic resin and soft material on tooth borne surface. Clinical evaluation was performed before the delivery of the splint and at 2, 4, 6 months. Maximum mouth opening and joint sound were recorded each follow up visit. Results: All groups of the study showed improvement in maximal mouth opening, TMJ pain, and clicking sounds with variable degrees according to treatment method. Conclusion: Dual laminated occlusal splint seemed to be superior in achieving rapid and prolonged improvement in TMD patients than other splints.

Effect of Exposure to Carbonated Beverages on the Surface Hardness of Acrylic Resins

The purpose of this study was to evaluate and compare the effect of carbonated beverage on the surface microhardness of two acrylic materials used to fabricate temporary restorations. The study was experimental in vitro. Forty blocks of acrylic resins used in provisional restorations were made, 20 from Alike® (GC AMERICA INC., Lot 1712161) and 20 from Acryptemp® (Zhermack S.P.A., Lot 302334). After that, the blocks were immersed in distilled water for 24 hours. After this time, the initial surface microhardness was measured. Then the 20 samples of the experimental group were immersed in a carbonated drink (coca cola - soda) for 12 minutes per day, for 5 days. Finally, the final surface microhardness was measured using the Vickers microdurometer. Measures of central tendency and dispersion were used, and the Student's t test and ANOVA were performed. A mean surface microhardness of 8.8 and 7.2HV was found for the PMMA resin group (Initial and final respectively), and 9.5 and 8HV for the bisacrylate group. Statistically significant differences were found when comparing the beginning and end of each group and when comparing the two materials. The acrylic resin of polymethylmethacrylate (Alike® GC AMERICA INC.) Presented higher surface microhardness compared to the bis acrylic resin (Acrytemp® Zhermack S.P.A), after being exposed to a carbonated drink.

A vat-polymerized 3-dimensionally printed dual-material occlusal device: A dental technique

A technique to additively manufacture an occlusal device by using a completely digital workflow is described. Using a computer-aided design program, information captured with an intraoral scanner was used to additively manufacture a dual-material occlusal device by using a vat-polymerization printer. This technique allows for the combination of 2 different materials, resulting in an occlusal device with a resilient intaglio and a hard resin exterior surface. Advantages of the resulting occlusal device compared with a single-material device include improved patient acceptance and comfort, better fit, and minimal adjustments to ensure fit.

The Analysis of the Differences between the Influence of Herbal Mouthwashes and the Chlorhexidine Mouthwash on the Physical Characteristics of Orthodontic Acrylic Resin

The present study, intended to compare the effects of immersion in herbal mouthwashes and the Chlorhexidine mouthwash on orthodontic acrylic resin, specifically with regard to alterations in its hardness, roughness and color. Seventy-two specimens of Orthodontic self-cured acrylic resin were used for the experiments. After preparation, specimens were placed in three types of mouthwash including Chlorhexidine 0.2 % (CHX), Persica and Matrica. The changes in microhardness (ΔKNH), Surface roughness (ΔRa) and color (ΔE) were evaluated prior to and following the immersion in mouthwashes. In order to analyze the data, we made use of SPSS version 22. One-Way ANOVA test was used to find the differences between groups. The Tukey test was conducted in the final stage. It was revealed that acrylic resins had lower microhardness when 12 hours after immersion had taken place. There were significant differences after 12h, 24h and 7 days between the groups in the softening of acrylic resins. The reduction in microhardness of acrylic resin with herbal mouthwashes in the three-time intervals was higher than CHX. With regard to increasing surface roughness, the disparity between herbal mouthwashes was insignificant. However herbal mouthwashes significantly increased the value of roughness more than CHX. Changes in color were significantly higher in all mouthwashes. Herbal mouthwashes caused more color variation than CHX. The color, roughness and hardness of acrylic resin undergo changes as a result of being immersed in the mouthwashes. However, the effect of herbal mouthwashes was more than that of CHX.

The Effect of Immersion of 12,5% Basil Leaves and 25% Mauli Banana Stem Mixture Extracts on Surface Hardness, Surface Roughness and Discoloration of Acrylic Resin

Background: The most used denture base is heat-cured acrylic resin. It can causes denture stomatitis. The action taken to prevent denture stomatitis is by cleaning the denture. Chemical denture cleansers can reduce surface hardness, increase the degree of surface roughness and may cause discoloration of acrylic resin surfaces. Alternative natural denture cleanser is used to minimize this effects. The natural denture cleanser is using 12,5% Basil leave and 25% Mauli banana stem extracts which are known to have antifungal effectiveness against Candida albicans. The combination of these two extracts is expected to have better effectiveness against Candida albicans without changing the nature of the acrylic resin base in surface roughness, hardness and color. Objective: This study aimed to analyze the comparison in surface hardness, surface roughness, and discoloration of a heat-cured acrylic resin which immersed in 12.5% Basil leave and 25% Mauli banana stem extracts with alkaline peroxide and distilled water. Methods: This study was a true experimental study with pre and posttest with control group design. Study on surface hardness used 24 cylindrical type heat-cured acrylic resin samples with a diameter of 30 mm and 5 mm thickness. Study on surface roughness used 24 acrylic resin rectangular 65 x 10 x 3.3 mm. Study on discoloration used 24 acrylic resin sized 15mm in diameter x 2mm thick; n=8/group. The study used 3 treatment groups: 12.5% Basil leaves and 25% Mauli banana stem extracts, alkaline peroxide, and distilled water. Hardness testing was measured using Vickers Hardness Testing and surface roughness measurement was performed using surface roughness tester. The value of discoloration was measured before and after the immersion for five days with the CIELab system using digital analysis tools. Result: The mean of the decrease in surface hardness value of heat-cured acrylic resin which was immersed in extract solution, alkaline peroxide, distilled water are 1.40, 1.38, and 0.60 respectively. The mean results of surface roughness increase in 12,5% Basil leave and 25% Mauli banana stem extracts, alkaline peroxide, and distilled water group were 0.0613 µm, 0.0663 µm, and 0.0425 µm respectively. Statistical tests on discoloration showed significant differences (p

Synthesis, characterization of Ag+ and Sn2+ complexes and their applications to improve the biological and mechanical properties of denture base materials

A new Ag+ and Sn2+ complexes of polymethyl methacrylate amide sulfadiazine (ligand H2L) were synthesized. The synthesized compounds were characterized by elemental analysis, TGA, SEM, TEM and spectral studies including 1H NMR, 13C NMR, FTIR, Electronic absorption and X-ray powder diffraction. The analytical and spectral technique used has identified that the H2L ligand acts as bidentate by amide group atoms of oxygen and nitrogen. For Ag+ and Sn2+ complexes the stoichiometry is 1:1 and 1:2 (M: Ligand) respectively. The results confirm the tetrahedral geometry of the Ag+ complex and an octahedral structure of the Sn2+ complex. The spectra of X-ray powder diffraction and TEM data show the nano-scale synthesized compounds. The antifungal activity of the synthesized ligand and its Ag+ and Sn2+ complexes was tested in vitro against the fungal Candida albicans before and after addition to the heat-polymerized acrylic denture base resin material. The data showed strong antifungal activity in the Sn2+ complex than in Ag+ complex and H2L ligand. Before and after combination with complexes H2L, Ag+, and Sn2+, the mechanical properties of acrylic denture base resin were studied. The results showed that the flexural strength, modulus, and hardness of acrylic denture base resin have improved than the control group. The addition of Sn2+ complex has decreased the deflection of acrylic resin more than H2L, while it has increased with the addition of Ag+ complex. Roughness decreased in heat-polymerized acrylic resin after adding H2L, Ag+, and Sn2+ complexes.

Pengaruh Aplikasi Gliserin pada Kekerasan Resin Komposit Nanofiller dengan Perendaman Cuka Apel

Composite resin is a type of filling material that is often used because it has good bonds with dentine and enamel and has a high aesthetic value. Nanofiller composite resin has high hardness, good polishing, color accuracy, and good translucency. The hardness of composite resins can change caused by low pH beverage. Purpose: To determine the differences in effect of glycerin application on hardness of nanofiller composite resins with immersion of apple cider vinegar. The type of research used was experimental laboratories with a pretest and post test group design. Samples were 24 immersion in apple vinegar for 60 and 120 minutes. Measurement of hardness using the Vicker Hardness Tester to determine the hardness value. Data analysis was performed using One Way Anova and Post-Hoc LSD tests.There is a significant difference in the value of composite resin hardness in the entire study group. The highest hardness value was found in the group with the application of glycerin and without immersion, while the lowest value was found in the group without the application of glycerin and immersion in 120 minutes.

Mechanical Behavior of PET-G Tooth Aligners Under Cyclic Loading

Invisible aligners are medical devices, which allow repositioning of teeth through a treatment designed by the orthodontists. During this orthodontic treatment, patients use several aligners each for a couple of weeks. The aligner will apply a system of forces on the teeth to shift them into desired position. Since aligners exert forces thanks to their particular shape, it is important that during lifetime's service they do not undergo significant deformations. This research aims to study the mechanical behavior of invisible aligners made by polyethylene terephthalate-glycol (PET-G), which is one of most used the plastic materials to produce these devices. In this study, cyclic compression tests in atmospheric environment (~25°C) as well as in the presence of saliva (to simulate intraoral environment) were performed. The mechanical behavior of two different thicknesses aligners (0.75 and 0.88 mm) was studied. In particular, each aligner was subjected to 22500 load cycles from 0 to 50 N. The number of load cycles simulates the average load history to which an aligner is subjected during its lifetime. The tests were performed on a testing machine, using a hard resin dental casts appropriately fixed to the machine. Analysis of the results shows that stiffness of aligners material increases during the cyclic test. In particular, it was observed a gradual reduction of crosshead displacement during the test, highlighting the occurrence of cyclic hardening phenomena. It was also found that the aligners show a residual strain recovery after removing the applied load. Moreover, in the analyzed load range rate, the aligners show a low tendency to accumulate residual strains as loading cycles progress.

3-D-Printed Registration Phantom for Combined Ultrasound and Optical Imaging of Biological Tissues

Efforts to develop quantitative ultrasound biomarkers would benefit from comparisons between ultrasound data and higher-resolution images of the tissue microstructure, such as from optical microscopy. However, only a few studies have used these methods for multiscale imaging because it is difficult to register low-resolution (>100 μm) ultrasound images to high-resolution microscopy images. To address this need, we have designed a 3-D-printed registration phantom that is made of a hard fluorescent resin, fits into a glass-bottom dish and can be used to calculate a coordinate system transform between ultrasound and optical microscopy. We report the phantom design, a registration protocol and an example registration using 18.5-MHz ultrasound and second harmonic generation microscopy. We evaluate the registration precision, achieving standard deviations smaller than the ultrasound resolution across all axes, and illustrate on a mouse mammary gland that this method yields results superior to those of manual landmark registration.

Evaluation of decontamination methods of oral biofilms formed on screw-shaped, rough and machined surface implants: an ex vivo study

BackgroundTo evaluate the effect of several representative decontamination methods of oral biofilms on different implant surfaces.Material and methodsEleven participants wore a hard resin splint carrying 6 rough (GC Aadva® implant; 3.3-mm diameter, 8-mm length) or machined (not commercially available) surface implants for 4 days to accumulate dental plaque naturally on the titanium surfaces of the implants. Apart from surface roughness, the morphology of all implants was identical. After detaching the implants from the splints, the ability of the following decontamination methods—gauze soaked in saline (G), ultrasonic scaler (US), air abrasive (Air), rotary stainless steel instrument (Rot), and Er:YAG laser (Las)—to cleanse the contaminated implant surface for 1 min extra-orally was tested. The control (Cont) group did not receive any decontamination. Scanning electron microscopic (SEM) investigation of one participant’s samples was employed to examine the post-instrumented implant surface for qualitative analysis, and bacterial culture of the remaining 10 participants’ samples was performed to count the number of colony-forming units (CFU) for quantitative analysis. The experimental sequence was initially performed for the rough surface implants and then similarly repeated for the machined surface implants. Bacterial CFU counts among the six groups were analyzed using the Steel-Dwass test, and differences between rough and machined surface implants were determined using the Mann-Whitney U test.ResultsG and Rot eliminated most biofilms on machined surface implants according to SEM analysis. G, Air, and Rot removed significantly more of the biofilms on rough and machined surface implants compared with US according to CFU counts. Moreover, G significantly reduced more biofilms than Las on machined surface implants. The analysis between rough and machined surface implants showed that Cont, G, and US were better able to cleanse biofilms on machined surface implants compared with rough surface implants.ConclusionsGauze soaked in saline and rotary stainless steel instruments may be advantageous for cleansing contaminated implant surfaces based on the qualitative and quantitative analyses. In contrast, air abrasives were not shown to be preferable in the qualitative analyses. Additionally, apart from the Er:YAG laser, the reduction of biofilms assessed in both qualitative and quantitative analyses demonstrated that all decontamination methods were better at cleansing machined surface implants compared with rough surface implants.