Standard Wax Research Articles

Novel solid inks based on beeswax, graphite and graphene applied to the fabrication of paper-based sensor for galactose determination

In this study, we present for the first time a simple and novel method for the fabrication of paper-based electrochemical sensors. The device development was carried out in a single stage with a standard wax printer. Hydrophobic zones were delimited with commercial solid ink, while electrodes were generated using new composite solid inks of graphene oxide/graphite/beeswax (GO/GRA/beeswax) and graphite/beeswax (GRA/beeswax). Subsequently, the electrodes were electrochemically activated by applying an overpotential. Various experimental variables for the GO/GRA/beeswax composite synthesis and electrochemical system obtention were evaluated. The activation process was examined by SEM, FTIR, cyclic voltammetry, electrochemical impedance spectroscopy and contact angle measurement. These studies showed morphological and chemical changes in the electrode active surface. As a result, the activation stage considerably improved the electron transfer on the electrode. The manufactured device was successfully applied for galactose (Gal) determination. This method presented a linear relation in the Gal concentration range from 84 to 1736 μmol L−1, with a LOD of 0.1 μmol L−1. The variation within and between-assay coefficients were 5.3% and 6.8%, respectively. The strategy here exposed for paper-based electrochemical sensors design is an unprecedented alternative system and represents a promising tool for mass production of economic analytical devices.

Requirements for Hybrid Technology Enabling the Production of High-Precision Thin-Wall Castings.

Prototypes and small series production of metal thin-walled components is a field for the use of a number of additive technologies. This method has certain limits related to the size and price of the parts, productivity, or the type of requested material. On the other hand, conventional production methods encounter the limits of shape, which are currently associated with the implementation of optimization methods such as topological optimization or generative design. An effective solution is employing hybrid technology, which combines the advantages of 3D model printing and conventional casting production methods. This paper describes the design of aluminum casting using topological optimization and technological co-design for the purpose of switching to new manufacturing technology. It characterizes the requirements of hybrid technology for the material and properties of the model in relation to the production operations of the investment casting technology. Optical roughness measurement compares the surface quality in a standard wax model and a model obtained by additive manufacturing (AM) of polymethyl methacrylate (PMMA) using the binder jetting method. The surface quality results of the 3D printed model evaluated by measuring the surface roughness are lower than for the standard wax model; however, they still meet the requirements of prototype production technology. The measurements proved that the PMMA model has half the thermal expansion in the measured interval compared to the wax model, which was confirmed by minimal shape deviations in the dimensional analysis.

Guidelines for the choice of circumferential wrought wire and cast clasp arms for removable partial dentures

PurposeThe aim of this study was to establish guidelines for the selection of cast and wrought-wire clasps for removable partial dentures (RPDs) that would be appropriate for clinically encountered undercuts and facial curvatures. MethodsRandomly selected discarded casts were collected and 30 premolars and 30 molars were surveyed, sectioned to a line representing the clasp and scanned using a flatbed scanner. The average clasp curvature and length for each group was determined and a three-dimensional model printed, to which wrought wire clasps of 0.9- and 1.0-mm diameter were adapted. Standard wax clasp patterns were adapted and cast in a stellite alloy. Each clasp was deformed beyond its proportional limit; and the forces exerted at that limit and at deflections of 0.25 mm, 0.5 mm, and 0.75 mm were measured, and a safety limit was calculated that would ensure elastic deformation at the required undercuts. ResultsA table was produced with guidelines for those clasps that would provide the highest retentive force within the proposed safety limit. The highest forces were provided by cast clasps in a 0.25-mm undercut. Wrought round wire of 1-mm diameter provided the next highest retentive forces, in a 0.25-mm undercut for premolar clasps arms and 0.5-mm for molar clasps. ConclusionsThe results provide valid guidelines for the use of combinations of clasp material and undercut that would exert the maximum retentive force without deformation for both short (premolar) as well as long (molar) clasps, for wrought and cast clasps.

The Economic Impact of Paraffin Type and Substrate Mixture on the Production of Grafted Vines—Case Study Muscat Ottonel

The study focussed on a nursery by analyzing its strategic choices to obtain the best profit on grapevine planting material. The production of grapevine grafts involves high labor and material costs. In this study, Muscat Ottonel grape variety grafted on Oppenheim Sellection 4 rootstock was paraffined with different types of wax: standard wax (SW), paraffin with 8-chinolinol (8C) and paraffin with oxiquinolein (OX) (before callusing), and silver color (S), blue color (B) and standard (SW) paraffin (after grafting callusing and before planting in field nursery). After uprooting from the field nursery, all variants were paraffined with red paraffin for storage. The unit cost price was calculated based on total expenses and the yield of grafts obtained in the vine field nursery. The lowest price per unit cost was recorded for the 8C/S variant, directly related to the first quality yield after uprooting from the nursery. The highest profit rate was for the 8C/S variant, while the lowest was registered to the SW/SW variant. The grafts of the 8C/S variant were potted in three rooting mixtures. Variant B (forest ground 60% + black peat 25% + river sand 10% + conifer sawdust 5%) generated the highest yield of the potted grafted vine with a rate of profit of over 170%, due to the lower production cost and high yield of potted vines, while variant C (forest ground 70% + river sand 15% + conifer sawdust 15%), determinate the lowest yield. Results may be useful in orienting the small-to-medium grapevine planting materials producers to choose the best cooperative strategies, which nurseries might implement to enhance their competitiveness and survive in the long-run.

Comparative Analysis of Marginal Accuracy of Complete Crowns Fabricated by Using Ringless and Metal Ring Investment Systems: An In Vitro Study

To compare the vertical margin accuracy of lost wax castings produced by the conventional casting technique with all metal (WIRONIUM®) and PFM alloy (WIRON®99) using a metal ring and ringless system. A brass die assembly was used to fabricate standardized wax pattern crowns. A total of 100 wax patterns were made with both ringless and metal ring investment systems. Wax patterns were readapted and refined on the master die and divided into two groups, namely, group I and group II with 50 wax patterns in each group. Group I (ringless system) and group II (metal ring system) were further divided into subgroups having a sample size of 25 in each group. Each coping was invested and cast individually. The marginal discrepancy between the metal die and the castings were measured by a stereomicroscope and AutoCAD software 2013. Measurement was made on the facial area of the metal die. The resultant casts obtained from different casting systems show statistically significant difference found between the marginal discrepancies using metal ring and ringless castings system, and statistically nonsignificant difference was found between the marginal discrepancies using all metal alloy (WIRONIUM®) and PFM alloy (WIRON®99) within the same group. The marginal discrepancy for castings made with ringless casting system was less when compared to metal ring casting system, and there was no difference in marginal discrepancy when compared to all metal alloy (WIRONIUM®) and PFM alloy (WIRON®99) within the same group. Marginal fit is influenced by several factors including type of crown, tooth preparation geometry, dimensional accuracy of impression materials, factors related to dental casting, type of cement, luting pressure, duration of cementation, and use of occlusal vents or die spacers.

Formulation of date pit oil‐based edible wax coating for extending the storage stability of guava fruit

The study was planned to formulate edible wax coating by utilizing date pit oil. Date pit oil was extracted from three date varieties (Aseel, Hallawi, and Dhakki) through solvent extraction method. One variety was selected on the basis of physicochemical analysis of date pit oil. The different treatments (T1, T2, T3, and T4) of wax coating were formulated by replacing water in standard wax formulation with date pit oil as 0.5%, 1%, 1.5%, and 2%, respectively. The storage studies were carried out for 16 days; different fruit parameters like pH, weight loss, total soluble solids (TSS), titratable acidity, fruit firmness, and vitamin C content were studied. Results indicated significant improvement in the shelf life of coated guava fruits as compared to uncoated guava fruits.T4 showed highest keeping quality as compared to T3, T2, and T1. Practical applications This research work is novel in the field of edible coating by using date pit oil as natural barrier against environmental factors affecting the shelf life of guava fruit. There is immense potential in this new commodity to explore more applications of promising importance. Moreover, this study can be replicated for other fruits and vegetables to curtail postharvest losses and supplementing economic benefits.

Influence of angulation and vertical misfit in the evaluation of micro-deformations around implants

Objective: This in vitro study was to evaluate micro-strains around of implant, under the influence of angulations and vertical misfit in three-element implant-supported fixed partial dentures during axial loading by using strain gauge analysis. Materials and Methods: Three external hexagon implants with straight configuration and three external hexagon implants with angled (17°) configuration were inserted into two polyurethane blocks. To measure micro-strain, four strain gauges were bonded onto the surface of each block. Plastic copings were adapted to a standard wax pattern and cast. An axial load of 30 kgf was applied on the center of each implant for 10 seconds, using a load application device. The vertical misfit was measured at six different points by using a stereo microscope with 100-X magnification. Results: The results showed that the values for different implant angulations were significant (P= 0.0086). The Pearson’s correlation test between micro-strain and vertical misfit revealed no correlation between angled configuration (P= 0.891) and straight configuration (P= 0.568). Conclusion: The micro strain was higher for angled implants; no correlation was found between the vertical misfit and the micro strain values.

An in vitro Comparative Study to evaluate the Marginal Fit of Castings using Ring and Ringless Casting Techniques with varying Sprue Diameter

ABSTRACT Introduction The ultimate success of fixed prosthesis is to pay meticulous attention to the detailed production of the missing tooth structure. Such an accurate replication is technically demanding. Hence, the aim of the study was to evaluate the accuracy of marginal fit of castings with varying sprue diameter and using ring and ringless techniques. Materials and methods Forty standardized wax copings were fabricated on a stainless steel die and divided into two groups. The first group was cast using the metal ring investment technique; the second group was cast using the ringless investment technique. Both the groups were further divided into two groups, each based on the diameter of the sprue (groups I and III: 4.5 mm and groups II and IV: 2.5 mm). The vertical marginal gap was measured at three sites per specimen, using a digital optical microscope at ×100 magnification. The results were analyzed using two-way analysis of variance and independent t-test to determine statistical significance. Results The vertical marginal gaps of castings fabricated using the ringless technique (0.145 ± 0.072 mm) were significantly less (p < 0.001) than those castings fabricated using the conventional metal ring technique (0.264 ± 0.100 mm); however, the vertical marginal gaps of the 2.5 mm sprue diameter (0.199 ± 0.092 mm) and 4.5 mm sprue diameter (0.211 ± 0.118 mm) castings were not statistically significant (p > 0.05). There was also statistically significant interaction (p < 0.001) between group IIA (0.120 ± 0.038 mm) and group IA (0.302 ± 0.098 mm), which was analyzed using the independent t-test. Conclusion It can be concluded that the ringless casting technique in comparison to metal ring technique produces metal castings of better marginal adaptation. Furthermore, the sprue diameter had significant difference wherein the 4.5 mm diameter produced the least vertical discrepancies in the ringless casting technique and 2.5 mm produced lesser vertical discrepancies in the metal ring. Clinical significance One of the key factors that decides the success of a metal-ceramic restoration is the marginal fit. The accurate fit of the restoration greatly minimizes the plaque accumulation, offers good mechanical properties, and reduces micro-leakage and development of secondary caries. The techniques of casting procedure and sprue diameter can have an influence on the outcome. Hence, the current research was undertaken to study the influence of these factors on marginal fit. How to cite this article Dutta T, George VT, Balakrishnan D, Narayan AI. An in vitro Comparative Study to evaluate the Marginal Fit of Castings using Ring and Ringless Casting Techniques with Varying Sprue Diameter. World J Dent 2017;8(2):109-113.

Comparison of denture base adaptation between CAD-CAM and conventional fabrication techniques

Statement of problemCurrently no data comparing the denture base adaptation of CAD-CAM and conventional denture processing techniques have been reported. PurposeThe purpose of this in vitro study was to compare the denture base adaptation of pack and press, pour, injection, and CAD-CAM techniques for fabricating dentures to determine which process produces the most accurate and reproducible adaptation. Material and methodsA definitive cast was duplicated to create 40 gypsum casts that were laser scanned before any fabrication procedures were initiated. A master denture was made using the CAD-CAM process and was then used to create a putty mold for the fabrication of 30 standardized wax festooned dentures, 10 for each of the conventional processing techniques (pack and press, pour, injection). Scan files from 10 casts were sent to Global Dental Science, LLC for fabrication of the CAD-CAM test specimens. After specimens for each of the 4 techniques had been fabricated, they were hydrated for 24 hours and the intaglio surface laser scanned. The scan file of each denture was superimposed on the scan file of the corresponding preprocessing cast using surface matching software. Measurements were made at 60 locations, providing evaluation of fit discrepancies at the following areas: apex of the denture border, 6 mm from the denture border, crest of the ridge, palate, and posterior palatal seal. The use of median and interquartile range was used to assess accuracy and reproducibility. The Levine and Kruskal-Wallis analysis of variance was used to evaluate differences between processing techniques at the 5 specified locations (α=.05). ResultsThe ranking of results based on median and interquartile range determined that the accuracy and reproducibility of the CAD-CAM technique was more consistently localized around zero at 3 of the 5 locations. Therefore, the CAD-CAM technique showed the best combination of accuracy and reproducibility among the tested fabrication techniques. The pack and press technique was more accurate at 2 of the 5 locations; however, its interquartile range (reproducibility) was the greatest of the 4 tested processing techniques. The pour technique was the most reproducible at 2 of the 5 locations; however, its accuracy was the lowest of the tested techniques. ConclusionsThe CAD-CAM fabrication process was the most accurate and reproducible denture fabrication technique when compared with pack and press, pour, and injection denture base processing techniques.

Accuracy of Ringless Casting and Accelerated Wax‐Elimination Technique: A Comparative In Vitro Study

The purpose of this study was to determine whether the ringless casting and accelerated wax-elimination techniques can be combined to offer a cost-effective, clinically acceptable, and time-saving alternative for fabricating single unit castings in fixed prosthodontics. Sixty standardized wax copings were fabricated on a type IV stone replica of a stainless steel die. The wax patterns were divided into four groups. The first group was cast using the ringless investment technique and conventional wax-elimination method; the second group was cast using the ringless investment technique and accelerated wax-elimination method; the third group was cast using the conventional metal ring investment technique and conventional wax-elimination method; the fourth group was cast using the metal ring investment technique and accelerated wax-elimination method. The vertical marginal gap was measured at four sites per specimen, using a digital optical microscope at 100× magnification. The results were analyzed using two-way ANOVA to determine statistical significance. The vertical marginal gaps of castings fabricated using the ringless technique (76.98 ± 7.59 μm) were significantly less (p < 0.05) than those castings fabricated using the conventional metal ring technique (138.44 ± 28.59 μm); however, the vertical marginal gaps of the conventional (102.63 ± 36.12 μm) and accelerated wax-elimination (112.79 ± 38.34 μm) castings were not statistically significant (p > 0.05). The ringless investment technique can produce castings with higher accuracy and can be favorably combined with the accelerated wax-elimination method as a vital alternative to the time-consuming conventional technique of casting restorations in fixed prosthodontics.

Axial Loads on Implant-Supported Partial Fixed Prostheses for External and Internal Hex Connections and Machined and Plastic Copings: Strain Gauge Analysis

The aim of this in vitro study was to use strain gauge (SG) analysis to compare the effects of the implant-abutment joint, the coping, and the location of load on strain distribution in the bone around implants supporting 3-unit fixed partial prostheses. Three external hexagon (EH) implants and 3 internal hexagon (IH) implants were inserted into 2 polyurethane blocks. Microunit abutments were screwed onto their respective implant groups. Machined cobalt-chromium copings and plastic copings were screwed onto the abutments, which received standard wax patterns. The wax patterns were cast in a cobalt-chromium alloy (n = 5): group 1 = EH/machined. group 2 = EH/plastic, group 3 = IH/machined, and group 4 = IH/plastic. Four SGs were bonded onto the surface of the block tangentially to the implants. Each metallic structure was screwed onto the abutments and an axial load of 30 kg was applied at 5 predetermined points. The magnitude of microstrain on each SG was recorded in units of microstrain (με). The data were analyzed using 3-factor repeated measures analysis of variance and a Tukey test (α = 0.05). The results showed statistically significant differences for the type of implant-abutment joint, loading point, and interaction at the implant-abutment joint/loading point. The IH connection showed higher microstrain values than the EH connection. It was concluded that the type of coping did not interfere in the magnitude of microstrain, but the implant/abutment joint and axial loading location influenced this magnitude.

Straight and Offset Implant Placement under Axial and Nonaxial Loads in Implant‐Supported Prostheses: Strain Gauge Analysis

The aim of this in vitro study was to quantify strain development during axial and nonaxial loading using strain gauge analysis for three-element implant-supported FPDs, varying the arrangement of implants: straight line (L) and offset (O). Three Morse taper implants arranged in a straight line and three implants arranged in an offset configuration were inserted into two polyurethane blocks. Microunit abutments were screwed onto the implants, applying a 20 Ncm torque. Plastic copings were screwed onto the abutments, which received standard wax patterns cast in Co-Cr alloy (n = 10). Four strain gauges were bonded onto the surface of each block tangential to the implants. The occlusal screws of the superstructure were tightened onto microunit abutments using 10 Ncm and then axial and nonaxial loading of 30 Kg was applied for 10 seconds on the center of each implant and at 1 and 2 mm from the implants, totaling nine load application points. The microdeformations determined at the nine points were recorded by four strain gauges, and the same procedure was performed for all of the frameworks. Three loadings were made per load application point. The magnitude of microstrain on each strain gauge was recorded in units of microstrain (με). The data were analyzed statistically by two-way ANOVA and Tukey's test (p < 0.05). The configuration factor was statistically significant (p= 0.0004), but the load factor (p= 0.2420) and the interaction between the two factors were not significant (p= 0.5494). Tukey's test revealed differences between axial offset (με) (183.2 ± 93.64) and axial straight line (285.3 ± 61.04) and differences between nonaxial 1 mm offset (201.0 ± 50.24) and nonaxial 1 mm straight line (315.8 ± 59.28). There was evidence that offset placement is capable of reducing the strain around an implant. In addition, the type of loading, axial force or nonaxial, did not have an influence until 2 mm.

Machined and plastic copings in three-element prostheses with different types of implantabutment joints: a strain gauge comparative analysis

ObjectiveUsing strain gauge (SG) analysis, the aim of this in vitro study was quantify the strain development during the fixation of three-unit screw implant-supported fixed partial dentures, varying the types of implant-abutment joints and the type of prosthetic coping. The hypotheses were that the type of hexagonal connection would generate different microstrains and the type of copings would produce similar microstrains after prosthetic screws had been tightened onto microunit abutments.Materials and methodsThree dental implants with external (EH) and internal (IH) hexagonal configurations were inserted into two polyurethane blocks. Microunit abutments were screwed onto their respective implant groups, applying a torque of 20 Ncm. Machined Co-Cr copings (M) and plastic prosthetic copings (P) were screwed onto the abutments, which received standard wax patterns. The wax patterns were cast in Co-Cr alloy (n=5), forming four groups: G1) EH/M; G2) EH/P; G3) IH/M and G4) IH/P. Four SGs were bonded onto the surface of the block tangentially to the implants, SG 1 mesially to implant 1, SG 2 and SG 3 mesially and distally to implant 2, respectively, and SG 4 distally to implant 3. The superstructure’s occlusal screws were tightened onto microunit abutments with 10 Ncm torque using a manual torque driver. The magnitude of microstrain on each SG was recorded in units of microstrain (µε). The data were analyzed statistically by ANOVA and Tukey’s test (p<0.05).ResultsMicrostrain values of each group were: G1= 338.1±223.0 µε; G2= 363.9±190.9 µε; G3= 415.1±53.5 µε; G4= 363.9±190.9 µε. No statistically significant difference was found between EH and IH, regardless of the type of copings (p>0.05). The hypotheses were partially accepted.ConclusionsIt was concluded that the type of hexagonal connection and coping presented similar mechanical behavior under tightening conditions.

Chewing fails to induce oral bacteraemia in patients with periodontal disease

To investigate whether chewing in patients with untreated chronic periodontitis or plaque-induced gingivitis causes bacteraemia of oral origin. Twenty-one patients with untreated chronic periodontitis (32-75 years old) and 20 with plaque-induced gingivitis (26-54 years old) chewed a standard wax medium for 4 min. Blood samples were drawn before, during and 5 min. post-chewing. Aerobic and anaerobic Bactec system culturing was performed for 21 days and positive bottles were subcultured and isolates were identified to genus level. A full periodontal analysis was performed on all teeth and included probing depths, recession, attachment levels, bleeding on probing, mobility plaque index and gingival index. Radiographs were assessed for the severity of alveolar bone loss. No bacteraemia of oral origin was detected in any patient. Skin contaminants (Staphylococcus epidermidis, Propionibacterium spp.) were detected in blood samples from three patients (two periodontitis; one gingivitis). Chewing did not cause bacteraemia in chronic periodontitis or plaque-induced gingivitis patients and may not be a risk factor for infective endocarditis in at-risk individuals with periodontal disease.

Influence of food platform width of mandibular removable partial denture on food mixing ability

The aim of this study was to clarify the influence of food platform width on food mixing ability in patients with mandibular removable partial dentures (RPDs). Twelve subjects (six males and six females, mean age 56.8 years) with intact dentition except for unilaterally missing mandibular first and second molars participated in the study. The food platforms of their RPDs were made of light polymerized composite and three platform conditions were evaluated. A food platform (Control condition) had 7 mm width with a central focus on the top of the residual ridge. Narrowed platforms (5 mm) were created by trimming a lingual portion (Buccally oriented occlusion, Buccal condition) or a buccal portion (Lingually oriented occlusion, Lingual condition) from the control. Subjects chewed a standardized wax cube which provided an estimate of food mixing ability [Mixing Ability Index (MAI)] for each of the three platforms. A significant effect (P < 0.001) on the MAI was found for food platform type (repeated measures one-way analysis of variance). Tukey multiple comparisons found significant differences of MAI between Control condition (1.05 +/- 0.26) and Buccal condition (0.86 +/- 0.23) (P = 0.032), and between Control and Lingual condition (0.54 +/- 0.37) (P < 0.001). Furthermore, MAI with Lingual condition was significantly smaller than that with Buccal condition (P < 0.001). These results suggest that reduction in the width of the food platform may impair masticatory function and the buccal portion of mandibular food platform of RPD is more critical for food mixing than the lingual portion of the platform.

Porosity and mould filling of titanium castings

A vacuum/Ar pressure casting machine was used to study porosity and mould filling of cast bridges of Ti. Two series of experiments were carried out: (1) The melting and the mould chamber were separated by a thin Ti foil until penetrated by the Ti melt. The mould chamber including the mould cavity was evacuated. (2) No separating Ti foil was applied. The pressure in the mould chamber was then controlled by diffusion of Ar through the investment. The moulds were made of two investments with different gas permeability. A standardized wax pattern for a five-unit bridge was used. Mould filling was evaluated by visual inspection and by measuring the missing lengths of the margins of the crowns. The porosity was studied by x-ray radiography and density measurements. In the first series mould filling was satisfactory in all cases, while the porosity was substantial for high Ar pressures. Without a Ti foil (second series) all castings contained little porosity, but the mould filling was adequate only for the high permeability investment. The experiments show that porosity can be avoided by maintaining small pressure differences between the melting chamber and the mould cavity. Adequate mould filling is promoted by minimal back pressures from trapped Ar gas in the mould.