Effects of surface glazing on the mechanical and biological properties of 3D printed permanent dental resin materials

Purpose This study aimed to determine the surface glazing effect on the mechanical and biological properties of three-dimensional printed dental permanent resins.Methods Specimens were prepared using Formlabs, Graphy Tera Harz permanent, and NextDent C&B temporary crown resins. Specimens were divided into three groups: samples with untreated surfaces, glazed surfaces, and sand-glazed surfaces. The flexural strength, Vickers hardness, color stability, and surface roughness of the samples were analyzed to identify their mechanical properties. Their cell viability and protein adsorption were analyzed to identify their biological properties.Results The flexural strength and Vickers hardness of the samples with sand glazed and glazed surfaces were significantly increased. The color change was higher for surface untreated samples than that for the samples with sand-glazed and glazed surfaces. The surface roughness of the samples with sand-glazed and glazed surfaces was low. The samples with sand-glazed and glazed surfaces have low protein adsorption ability and high cell viability.Conclusions Surface glazing increased the mechanical strength, color stability, and cell compatibility, while reducing the Ra and protein adsorption of 3D-printed dental resins. Thus, a glazed surface exhibited a positive effect on the mechanical and biological properties of 3D-printed resins.

Trueness of artificial teeth for CAD-CAM complete dentures fabricated with additive manufacturing implementing different denture base-tooth offset values: An in vitro study

STATEMENT OF PROBLEM

Computer-aided design and computer-aided manufacturing (CAD-CAM) removable dentures have become popular. However, evaluations of the effect of denture base-tooth offset (DTO) values on the trueness of artificial teeth are lacking.

PURPOSE

The purpose of this in vitro study was to digitally measure the trueness of the artificial teeth of CAD-CAM dentures fabricated with additive manufacturing using different DTO values and to determine the most accurate DTO value.

MATERIAL AND METHODS

Seven study groups were formulated based on different DTO values, and 6 maxillary complete dentures were assigned to each group (n=42). A design software program was used to export the monoblock denture as control, the artificial teeth, and 7 different designs of denture bases with DTO values of 0.00, 0.01, 0.03, 0.05, 0.10, 0.15, and 0.20 mm. Denture bases were printed in denture base resin (Denture base RP; formlabs), artificial teeth were printed in tooth-shade resin (Denture teeth A2; formlabs), and both were then assembled and polymerized together. The dentures were scanned (InEos X5; Dentsply Sirona), scan data were imported in a measuring software program (GOM Inspect; GOM GmbH), and registration using local best fit was performed to align data. Color-coded maps for the surface comparison of each denture with the control denture scan were generated. Fitting center points were constructed for each artificial tooth, which were compared with their corresponding points on the data of the control scan. Multiple pairwise comparisons were performed after 1-way ANOVA to quantify and statistically evaluate the deviation values (α=.05).

RESULTS

The 0.10-mm DTO group showed the lowest values when comparing artificial tooth deviations both individually and as types. On comparing the average deviations, statistically significant differences were identified among the 7 groups (P<.001). A nonstatistically significant difference was identified when the 0.10- and 0.05-mm DTO groups were compared. Lower deviation values were found in the premolars compared with the molars, in the incisors compared with the canines, and in posterior artificial teeth compared with anterior teeth.

CONCLUSIONS

The 0.10-mm DTO value showed the highest trueness for the artificial teeth compared with the other DTO values tested in this study. The 0.05-mm DTO value is an alternative to the 0.10-mm DTO value for CAD-CAM dentures constructed by additive manufacturing. Anterior teeth of a CAD-CAM denture showed higher deviation values compared with posterior teeth.

The Impact of Oxygen Concentration on the Postcuring of 3D-Printed Dental Resin

PURPOSE

This study investigated the impact of reducing the oxygen concentration via nitrogen injection during the postcuring process of 3D-printed dental materials.

MATERIALS AND METHODS

Resin specimens for dental crown and bridge (15-mm diameter, both 1-mm and 2-mm heights) were 3D-printed and rinsed. Subsequently, the postcuring process was conducted on nine groups categorized according to atmospheric conditions within the curing device (20% [control], 10%, and 5% oxygen) and curing times (10, 15, and 20 minutes). Surface roughness was measured using a gloss meter. Surface polymerization was confirmed through Fourier-transform infrared spectroscopy (FT-IR) analysis, and the flexural strength and elastic modulus of the specimens were measured using a universal testing machine. Water absorption and solubility were determined according to Inernational Organization for Standardization (ISO) standards. All evaluation criteria were statistically analyzed using one-way ANOVA and Tukey's post hoc test based on oxygen concentration.

RESULTS

The elastic modulus did not show statistically significant differences in all groups. However, compared to the control group, the flexural strength, degree of conversion, and gloss significantly increased in the groups with decreased oxygen concentrations. Conversely, water solubility and water absorption significantly decreased in a few groups with reduced oxygen concentration.

CONCLUSIONS

Reducing oxygen concentration through nitrogen injection during the postcuring process of 3D printing enhances the suitability of the dental prosthetic materials. The significant increase in flexural strength can particularly enhance the utility of these materials in dental prosthetics.

Short-term Results of the Masking Effect of an Infiltrant Resin on Mild Molar Incisor Hypomineralization Lesions in Anterior Teeth

This non-controlled clinical study evaluated the masking effect of an infiltrant resin on mild molar incisor hypomineralization (MIH) lesions. Thirty MIH-affected anterior teeth with creamy/ white opacities from 12 children aged 6-15 years received the application of an infiltrant resin (Icon- DMG). Standard photographs were taken before (T1), immediately after (T2), and 1 week after (T3) resin infiltration. Two calibrated examiners qualitatively analyzed the color match using the Fédération Dentaire Internationale (FDI) scale. The binomial distribution test analyzed the scores of the color match at T1 with T2 and T3, and McNemar's test analyzed the scores of the color match between T2 and T3 (α=0.05). There was a significant increase in color match between T1 and T2 (p=0.0005), between T1 and T3 (p=0.0005), and between T2 and T3 (p=0.0019). It was concluded that infiltrant resin was effective in improving the esthetic appearance of creamy/white opacities on MIH-affected anterior teeth.

Surface topography and spectrophotometric assessment of white spot lesions restored with nano-hydroxyapatite-containing universal adhesive resin: an in-vitro study

BACKGROUND

White spot lesion (WSL) is a main shortcoming accompanied by orthodontic treatment. It impairs the esthetic, surface hardness, and surface texture of enamel. So, this study was conducted to analyze the surface characteristics and color change of white spot lesions treated with nano-hydroxyapatite (nHA)-enriched universal adhesive resin.

MATERIALS AND METHODS

Eighty sound human permanent molars crowns were sectioned into two halves, producing 160 specimens. 16 specimens were left untreated, and 144 specimens were artificially-demineralized to generate WSLs. The specimens were classified according to the treatment approach applied as follows: I; Sound enamel, Group II; artificially-created WSLs, Group III; ICON resin-restored WSLs, Group IV; Universal adhesive resin-restored WSLs, Group V; 0.5 wt% nHA-containing universal adhesive resin-restored WSLs, Group VI; 1 wt% nHA-containing universal adhesive resin- restored WSLs, and Group VII; 3 wt% nHA-containing universal adhesive resin-restored WSLs, Group VIII; 5 wt% nHA-containing universal adhesive resin-restored WSLs, Group IX; 7 wt% nHA-containing universal adhesive resin-restored WSLs, and Group X; 10 wt% nHA-containing universal adhesive resin-restored WSLs. Some surface characteristics and color changes were assessed. Data was collected and analyzed statistically using ANOVA and the Tukey test at p < 0.05.

RESULTS

Surface microhardness of WSLs was significantly improved with all investigated ratios of nHA-containing universal adhesive (p < 0.0001), with the highest mean belonging to 10 wt% nHA-containing universal adhesive resin treated WSLs. All ratios of nHA-containing universal adhesive resin significantly reduced the surface roughness of WSLs (p < 0.0001). The investigated ratios of 1, 3, 5, 7, and 10 wt% nHA-containing universal adhesive resin treatment approach could mask the WSLs significantly (p < 0.0001).

CONCLUSIONS

Nano-hydroxyapatite-containing universal adhesive is a promising contemporary approach for the management of WSLs, coupled both the remineralizing concept and the minimally invasive resin infiltration.

A comparison of the shear bond strength between denture teeth and denture base resins manufactured either conventionally or with a 3D printer

STATEMENT OF PROBLEM

Limited information is available on the shear bond strength (SBS) between denture teeth and denture base resins fabricated using a stereolithography (SLA) 3-dimensional (3D) printer.

PURPOSE

The purpose of this in vitro study was to evaluate the SBS between denture teeth and the denture base resins produced with the conventional method and with a 3D printer.

MATERIAL AND METHODS

Conventional or 3D printed denture teeth were included in the study. The denture base resins were manufactured either conventionally or with a 3D printer. Four subgroups were tested: conventional teeth-conventional base resin (CT-CB), conventional teeth-printed base resin (CT-PB), printed teeth-conventional base resin (PT-CB), and printed teeth-printed base resin (PT-PB). The maxillary molars were combined with Ø5×2.5-mm-cylindrical denture base resin. Shear bond testing was performed by applying a parallel force to the denture teeth-denture base resin interface by using a blade-edge chisel with a crosshead speed of 1 mm/min until failure occurred. SBS and elastic modulus (EM) were recorded. One-way ANOVA followed by the Dunnett T3 post hoc test was used for the statistical analysis (α=.05). The failure modes of the specimens were also analyzed.

RESULTS

A statistically significant difference (P<.05) was found between the evaluated groups for the SBS and EM values. PT-PB showed the highest SBS value (15.4 ±2.7 MPa), and CT-PB showed the lowest (0.9 ±0.7 MPa). The PT-CB group showed the highest EM value (62.74 ±20.80 GPa), and the CT-PB group showed the lowest (29.46 ±28.40 GPa). The CT-CB and CT-PB specimens showed mostly adhesive failure; none of the PT-PB specimens showed adhesive failure.

CONCLUSIONS

Three-dimensional printing led to a better bond between the denture teeth and the denture base resin compared with the conventional method. Although these findings need to be supported by clinical studies, the use of 3D printers is appropriate in the production of denture teeth and denture bases.

Synthesis of Pore-Size-Tunable Porous Silica Particles and Their Effects on Dental Resin Composites

The filler/resin matrix interface interaction plays a vital role in the properties of dental resin composites (DRCs). Porous particles are promising fillers due to their potential in constructing micromechanical interlocking at filler/resin matrix interfaces, therefore improving the properties of the resulting DRCs, where the pore size is significantly important. However, how to control the pore size of porous particles via a simple synthesis method is still a challenge, and how their pore sizes affect the properties of resulting DRCs has not been studied. In this study, porous silica (DPS) with a dendritic structure and an adjustable pore size was synthesized by changing the amounts of catalyst in the initial microemulsion. These synthesized DPS particles were directly used as unimodal fillers and mixed with a resin matrix to formulate DRCs. The results showed that the DPS pore size affects the properties of DRCs, especially the mechanical property. Among various DPS particles with different pore sizes, DPS6 resulted in 19.5% and 31.4% improvement in flexural strength, and 24.4% and 30.7% enhancement in compression strength, respectively, compared to DPS1 and DPS9. These DPS particles could help to design novel dental restorative materials and have promising applications in biomedicine, catalysis, and adsorption.

Comparison of coronary arteries morphometry and distribution in bovines with humans and other animal species

Background

The left coronary artery (LCA) in the bovines is more developed than the right.

Aim

The objective of the study is to describe the bovine coronary system from a morphological point of view, including the morphometry and its distribution.

Methods

Arciform suture with 2.0 silk was applied around the sinus orifice and coronary ostium and a number 14 catheter was installed, to perfuse semi-synthetic polyester resin, consisting of a mixture of 85% GP40L palatal with 15% styrene with red color mineral.

Results

The average weight of 28 bovine hearts used in our study was 1.534.1 kg. The right coronary artery had a proximal caliber of 5 +/- 0.9 mm. The LCA caliber and length were 9.4 +/- 1.2 and 18.3 +/- 4.8 mm, respectively. This artery was divided into two branches in 85.7% of the cases and trifurcated in 14.3%. The paraconal interventricular branch (PIB) ended more frequently in the apex (46.4%), and its proximal caliber was 6.4 +/- 1.4 mm. The left circumflex branch ended in 82.1% in the subsinusal interventricular sulcus, and its proximal caliber was 5.9 +/- 1.2 mm. The proximal calibers of the PIB and the left circumflex branch did not present statistically significant differences (p = 0.137). The sinoatrial branch presented a dual origin (right and LCA) in 46.4% of the cases and a single origin from the LCA in 53.6% of the samples. In the evaluated hearts, left coronary dominance was observed in most cases (96.4%). Their presence of anastomosis between the branches of the coronary arteries was observed in 57.1% of cases.

Conclusion

The presence of a myocardial bridge was found in six hearts (21.4%). In bovines, a high percentage of anastomosis was found, a protective factor in obstruction of the coronary arterial branches.

Synthesis and characterization of calcium-releasing elastomeric resin-based endodontic sealers

OBJECTIVES

To evaluate the incorporation of halloysite nanotubes (HNTs) loaded with one of two calcium sources (i.e., calcium hydroxide/CaOH2 or beta-tricalcium phosphate/β-TCP) on the physicochemical and biological properties of an experimental resin-based dual-cured endodontic sealer.

MATERIALS AND METHODS

HNTs were encapsulated with CaOH2 or β-TCP at 10 wt.%. HNTs containing CaOH2 or β-TCP were added into the experimental sealers at 50 wt.%. The control sealers were the calcium-free HNT-modified resin-based experimental sealer and AH Plus™, a commercially available endodontic sealer. Degree of conversion, setting time, flow, film thickness, radiopacity, dimensional stability, and calcium ions release were determined. Antibiofilm properties and cytocompatibility of the formulated sealers and commercial control were also evaluated. One and two-way ANOVA analysis followed by Tukey's post hoc test was conducted to evaluate the effect of the independent variable on the evaluated properties.

RESULTS

FTIR confirmed the encapsulation of calcium sources into HNTs. Regarding flow and film thickness, the values obtained from these sealers were in accordance with the specifications provided by ISO 6876. For radiopacity, AH Plus™ achieved the highest radiopacity (p<0.05). Among the experimental formulations, all experimental HNT-containing compositions exhibited values below 3 mm Al. The experimental sealers showed greater dimensional changes when compared to the commercial (AH Plus™) control. The release of calcium ions was observed for the HNT_CaOH2 and HNT_β-TCP sealers without statistical differences. Experimental sealers containing HNT_CaOH2 and HNT_β-TCP significantly reduced the CFU/mL count and showed cell compatibility.

CONCLUSIONS

The findings of this study demonstrate that the incorporation of HNT_CaOH2 or HNT_β-TCP into resin-based experimental sealers promoted antimicrobial effects and gradual calcium release without impairing cytocompatibility or physicochemical properties of the sealers. Still, an adjustment to reach the minimal radiopacity established by ISO 6876 is needed.

CLINICAL RELEVANCE

The experimental resin-based sealers seemed to be an alternative for endodontics. The incorporation of calcium sources exerts promising antimicrobial effects while displaying low cell toxicity.

Effects of washing solution temperature on the biocompatibility and mechanical properties of 3D-Printed dental resin material

The use of digital manufacturing, particularly additive manufacturing using three-dimensional (3D) printing, is expanding in the field of dentistry. 3D-printed resin appliances must undergo an essential process, post-washing, to remove residual monomers; however, the effect of the washing solution temperature on the biocompatibility and mechanical properties remains unclear. Therefore, we processed 3D-printed resin samples under different post-washing temperatures (without temperature control (N/T), 30 °C, 40 °C, and 50 °C) for different durations (5, 10, 15, 30, and 60 min) and evaluated the degree of conversion rate, cell viability, flexural strength, and Vickers hardness. Increasing the washing solution temperature significantly improved the degree of conversion rate and cell viability. Conversely, increasing the solution temperature and time decreased the flexural strength and microhardness. This study confirmed that the washing temperature and time influence the mechanical and biological properties of the 3D-printed resin. Washing 3D-printed resin at 30 °C for 30 min was most efficient to maintain optimal biocompatibility and minimize changes of mechanical properties.

Evaluation of the masking efficacy of caries infiltration in post-orthodontic initial caries lesions: 1-year follow-up

OBJECTIVES

This study aimed to qualitatively and quantitatively assess the masking efficacy and color stability of resin infiltration on post-orthodontic ICL after 1 year.

MATERIALS AND METHODS

In 17 adolescents, 112 ICL (ICDAS-1: n = 1; ICDAS-2: n = 111) in 112 teeth were treated by resin infiltration (Icon, DMG) 3 to 12 months after bracket removal. The etching procedure was performed up to 3 times. Standardized digital images were taken before treatment (T0), 7 days (T7) and 12 months (T365) after treatment. Outcomes included the evaluation of the color differences between infiltrated and healthy enamel at T0, T7, and T365 by quantitative (colorimetric analysis (ΔE), ICDAS scores) and qualitative methods (5-point Likert scale (deteriorated (1), unchanged (2), improved, but not satisfying (3), improved and no further treatment required (4), completely masked (5)).) Differences between time points were analyzed by using Friedman test (ΔΕ) and chi-square tests (ICDAS).

RESULTS

The median color difference (25th/75th percentiles) between carious and healthy enamel at baseline (ΔΕ0) was 10.2(7.7/13.6). A significant decrease was observed 7 days after treatment (ΔΕ7 = 3.1(1.8/5.0); p < 0.001; ICDAS; p < 0.001). No significant changes based on ΔΕ (p = 1.000), and ICDAS grade (p = 0.305) were observed between T7 and T365 (ΔΕ12 = 3.4 (1.8/4.9)). Furthermore, at T365 four experienced dentists classified 55% and 39% of the lesions as "improved and no further treatment required" and "completely masked," respectively (Fleiss kappa: T365 = 0.851 (almost perfect)).

CONCLUSION

Resin infiltration efficaciously masked post-orthodontic ICL 7 days and 12 months after treatment. These results for most of the teeth could not only be observed by quantitative but also by qualitative analysis.

CLINICAL RELEVANCE

Resin infiltration efficaciously masks post-orthodontic initial carious lesions. The optical improvement can be observed directly after treatment and remains stable for at least 12 months.

Application of laser on enamel surface with three types of bioactive glasses-based resin infiltrants: An in vitro study

OBJECTIVE

The study aimed to evaluate and compare the surface micro-hardness, roughness, color, and morphology of enamel after Er,Cr:YSGG laser irradiation, followed by application of three types of bioactive glasses-based resin infiltrants, and the samples groups were challenged with the pH cycle.

METHODOLOGY

Experimental photoactivated resin infiltrants were synthesized using dimethacrylate resins, whereby three different types of bioactive glasses (BGs), i.e., 45S5, fluoridated-BG (F-BG), and borosilicate-BG (B-BG), were incorporated into the resin system. Initially, white spot lesions were created artificially on the toosth enamel surface, then irradiated with Er,Cr:YSGG laser. Then, the resin-only and BG-based resins were infiltrated on the enamel surface. All samples were pH challenged for 14 days, and the micro-hardness, surface roughness, surface morphology, and color stability (ΔE) analyses were conducted before and after the 14 days pH challenge.

RESULTS

After laser irradiation, the micro-hardness was significantly high with 45S5 group compared to resin-only (p = 0.021), F-BG (p = 0.042), and B-BG (p = 0.001) groups. After the pH challenge, the micro-hardness values for all groups were reduced significantly (p ≤ 0.05). The surface roughness was least with the resin-only group and showed a non-significant difference with F-BG (p = 0.34) and significant differences with both B-BG (p = 0.005), and 45S5 (p = 0.010) groups. After the pH cycle, the roughness of all groups was increased significantly (p ≤ 0.05), except B-BG group showed a non-significant difference (p = 0.528). The B-BG group showed significantly high ΔE between day 0 and baseline compared to resin-only (p = 0.0008), F-BG (p = 0.017), and 45S5 (p = 0.029), whereas between day 14 and baseline, the lowest ΔE value was observed for B-BG (14.2 ± 2.10) and maximum for the resin-only (20.57 ± 2.47) group. The SEM images showed pitting on the surface of all resin infiltrant groups after 14 days of pH challenge.

CONCLUSION

The morphological difference was observed after the laser irradiation on the enamel surface. The differences in micro-hardness, surface roughness, and color were observed after the application of experimental resin infiltrants and significant differences were observed after the pH challenge.

Infiltrant resin and enamel infractions: two case reports of a novel and minimally invasive approach

To date, no consensus exists regarding the management of enamel infractions (cracks and craze lines), which may be associated with sensitivity. Two clinical cases are presented on the management of enamel infractions using a modified erosion-infiltration protocol for resin infiltration. Initially indicated for the treatment of early caries lesions, Icon (DMG) low-viscosity resin infiltrant has also been used to mask unesthetic developmental defects of enamel in anterior teeth. Treatment using this modified infiltration protocol immediately eliminated tooth sensitivity associated with the enamel infractions. Resin infiltration has the potential as a minimally invasive and effective treatment for the management of sensitivity associated with enamel infractions. (Quintessence Int 2023;54:180-185; doi: 10.3290/j.qi.b3631849).

Management of Hypoplastic or Hypomineralized Defects with Resin Infiltration at Pediatric Ages: Systematic Review

Hypoplastic or hypomineralized enamel defects represent a recurrent reason for consultation within the pediatric population, causing great discomfort due to their aesthetic appearance, as well as their functional limitations. Current conservative dentistry requires minimally invasive treatments in order to treat such defects and provide successful, definitive solutions. A systematic review of the literature has been carried out in accordance with the PRISMA recommendations. A search was carried out in the PubMed, Scopus, SciELO and Web of Science databases, completed with a manual search. The following variables were extracted from the selected studies: author, year, publication journal, type of study, sample, age of the participants and the materials used for its development. From the initial electronic search of the four databases, 282 articles were identified: 34 from PubMed, 240 from Scopus, 0 from SciELO and 8 from Web of Science. After eliminating duplicate articles, a total of 225 remained. After reading the title and abstract, 158 articles were eliminated, leaving 68. Upon reading the full text, the remaining studies were eliminated for not answering the research question or the inclusion criteria, leaving a total of 13 articles. Finally, 12 articles were used to carry out the systematic review. Treatments performed to date with the ICON™ system in pediatric patients have shown good results after their application. Since the variability of diagnostic methods has been observed, new diagnostic and assessment protocols should be created after treatment to objectify their effect on hypoplastic or hypomineralized enamel defects. In the same way, it has been described that treatment provides better results if combined with other opalustre-type or remineralizing materials. This review is registered in PROSPERO with the number CRD42021288738.

Aesthetic caries infiltration - Long-term masking efficacy after 6 years

OBJECTIVES

This study aimed to evaluate the masking efficacy of caries infiltration technique of initial caries lesions (ICL) six years after debonding and single treatment.

METHODS

In 10 adolescents, 74 ICL (ICDAS 2) in 74 teeth were treated by resin infiltration (Icon, DMG) at a mean (SD) of 1.2 (1.2) months after bracket removal. The etching procedure was performed up to 3 times. Standardized digital images were taken before treatment (T₀), seven days (T₇) and 6 years (T₂₁₉₀) after treatment. Outcomes included the evaluation of the color differences between carious and healthy enamel at T₀, T₇ and T₂₁₉₀ by quantitative colorimetric analysis (ΔE), ICDAS scores, quantitative light-induced fluorescence (QLF; ΔF,ΔQ,WS Area) and qualitative visual evaluation (5-point Likert-scale [deteriorated (1), unchanged (2), improved, but not satisfying (3), improved and no further treatment required (4), completely masked (5)).

RESULTS

The median color difference ΔΕ₀ (25^th/75^th percentiles) at T₀ was 10.3 (8.56/13.0). At T₇ a significant decrease was observed (ΔΕ₇=3.7 (2.0/5.8); p<0.001; Friedmann-test; ICDAS p<0.001; Chi-square test). No significant changes based on ΔΕ (p=0.972; Friedmann-test) and ICDAS grading (p=0.511, chi-square test) were observed between T₇ and T₂₁₉₀ (ΔΕ₂₁₉₀=2.9 (1.8/4.2)). Furthermore, at T₂₁₉₀ four experienced dentists classified 50% and 37% of the lesions as "improved and no further treatment required" and "completely masked", respectively (Fleiss kappa: T₂₁₉₀: 0.782 (substantial agreement)).

CONCLUSION

Aesthetic caries infiltration can effectively mask post-orthodontic initial caries lesions for at least 6 years. These results for most of the teeth could not only be observed by quantitative but also by qualitative analysis.

CLINICAL SIGNIFICANCE

Resin infiltration efficaciously masks post-orthodontic initial carious lesions. The optical improvement can be observed directly after treatment and remains stable for at six years.

Impact of type of bonding agent on adhesion of CAD-CAM denture bases and teeth manufactured using different techniques: A preliminary study

PURPOSE

To evaluate two agents for bonding denture bases and teeth manufactured either by stereolithography (SLA) or by the subtractive mixed technique.

METHODS

Two types of cylinders [small for the tooth resin and large for the base resin) were designed using CAD software according to the ANSI/ADA 15-2008 (R2013)] specification. For SLA manufacturing, 30 small cylinders were shaped with Denture Teeth resin and 30 large cylinders with Denture Base resin. For the mixed technique, 30 large cylinders were manufactured by SLA with V-print dentbase resin, and 30 small cylinders were milled with a CediTEC DT disk. Half the specimens were bonded with liquid Denture Base resin and half with CediTEC Primer and Adhesive, according to the manufacturers' protocols. Shear bond strength was measured using a universal testing machine. The failure mode was noted for all the specimens.

RESULTS

The shear bond strength values were not significantly different between the groups (P> 0.05). Specimens bonded with liquid Denture Base resin displayed cohesive failure (P> 0.05, ײ= 0). Of the specimens bonded with CediTEC Primer and Adhesive, cohesive failures were observed with five specimens manufactured with the SLA technique and one specimen manufactured with the mixed technique (P> 0.05, ײ= 3.33). The Chi-square test results were significant between groups with different bonding agents regardless of the technique used (P< 0.001). Within the limitations of the present study, even if the shear bond strength values were similar, the failure mode analysis suggests that the uncured liquid Denture Base resin may be more effective than the CediTEC Primer and Adhesive for bonding denture bases and teeth manufactured either by SLA or the mixed technique.

CLINICAL SIGNIFICANCE

The present study suggests that the uncured liquid resin (Denture Base) used as a bonding agent and the denture base and tooth materials (V-Print and CediTEC DT) manufactured by SLA and the subtractive technique are clinically compatible.

Structural Analysis of Injection-Molded Polyoxymethylene Treated Below a Melting Point Using Field-Emission Scanning Electron Microscopy and Infrared Spectroscopy

The heat treatment of an injection-molded polyoxymethylene slightly below the melting point and subsequent isothermal treatment at 130 °C were performed. The polyoxymethylene structure was examined using field-emission scanning electron microscopy and polarization infrared reflection measurements. After the heat treatment, a significant change in the surface morphology was observed, and the reflection spectrum derived from the polariton in the injection direction also changed dramatically. Since the reflection spectrum in the injection direction contains the reflection component of the perpendicular direction and vice versa, the polarization spectra of both directions can be calculated consistently. The mixing ratio of each crossed component and the pure relative permittivity both parallel and perpendicular to the main-chain direction were determined using the oscillator model. The heat treatment reduced the ratio of the perpendicular component and increased the order structure until just before melting. The structural changes characterized by the two techniques, along with Raman spectroscopy and differential scanning calorimetry, are discussed.

Preconcentrations of Zn(II) and Hg(II) in Environmental and Food Samples by SPE on B. licheniformis Loaded Amberlite XAD-4

In this work, the separations and preconcentrations of Zn(II) and Hg(II) ions on Bacillus lichenifoemis loaded onto Amberlite XAD-4 resin by solid-phase extraction has been performed. The biosorbent was characterized by using FT-IR, SEM, and EDX. pH, sample flow rate, eluent type and concentration, amount of B. licheniformis and XAD-4 resin, sample volume, and possible interfering ions effect were investigated in details as experimental variables in the SPE procedure. Limit of detection values for Zn(II) and Hg(II) were detected as 0.03 and 0.06 ng mL^-1, respectively. 0.2-15 ng mL^-1 linear range values were achieved for Zn(II) and Hg(II), respectively. Relative standard deviation values were found to be lower than 5%. For validation of the procedure, the certified standard reference materials (CWW-TM-D, EU-L-2, NCS ZC73O14, NCS ZC73350) were analyzed. The concentrations of Zn(II) and Hg(II) in water and food samples were measured by ICP-OES. Consequently, it can be inferred that the immobilized B. licheniformis microcolumn has ideal selectivity for Zn(II) and Hg(II) biosorption.

Organic compound and particle emissions of additive manufacturing with photopolymer resins and chemical outgassing of manufactured resin products

Photopolymer resins are applied at an increasing rate in additive manufacturing (AM) industry as vat photopolymerization (VP) and material jetting (MJ) methods gain more popularity. The aim of this study was to measure volatile organic compound (VOC), carbonyl compound, ultrafine particle (UFP), and particulate matter (PM₁₀) air concentrations emitted in 3D printer operations. Individual chemicals were identified when multiple photopolymer resin feedstocks were used in various VP and MJ printers. The size distributions of UFPs, and indoor air parameters were also monitored. Finally, the VOC outgassing of the cured resin materials was determined over 84 days. The data demonstrated that 3D printer operators were exposed to low concentrations of airborne exposure agents as follows: average concentrations of VOCs were between 41 and 87 µg/m³, UFP number levels ranged between 0.19 and 3.62 × 10³ number/cm³; however, no impact was detected on air parameters or PM₁₀ concentrations. A majority of the UFPs existed in the 10-45 nm size range. The identified compounds included hazardous species included sensitizing acrylates and carcinogenic formaldehyde. The outgassed products included similar compounds that were encountered during the AM processes, and post-processing solvents. Products heated to 37°C emitted 1.4‒2.9-fold more VOCs than at room temperature. Total emissions were reduced by 84‒96% after 28 days roughly from 3000-14000 to 100-1000 µg/m²/hr. In conclusion, resin printer operators are exposed to low concentrations of hazardous emissions, which might result in adverse health outcomes during prolonged exposure. Manufactured resin products are suggested to be stored for 4 weeks after their production to reduce potential consumer VOC hazards.

3D-printed swab with cover for precision diagnosis

The collection capacity of common nasopharyngeal swabs and irregularities of medical personnel limit the accuracy of PCR testing. This study describes a newly designed 3D-printed swab that is combined with a 3D-printed cover to prevent the extraction of undesired nasal secretions. This swab improved the accuracy of PCR test results. The results of a series of experiments showed that, because of the mucus extraction effect, 3D-printed swabs can replace ordinary cotton swabs. The crisis of the worldwide medical supply shortage can be ameliorated to a certain extent by applying 3D printing technology.

Rhodamine-B dye removal using aliquat-336 modified amberlite XAD-4 resin in fixed-bed columns in series

The present work reports studies on the effective removal of Rhodamine-B (RhB) using Aliquat-336 modified Amberlite XAD-4 resin in the fixed-bed columns in series. The effect of flow rate (Q = 2 to 6 mL·min^-1), bed height (h = 3.5 to 7 cm) and initial RhB dye concentration (C_in = 10 to 20 mg·L^-1) was studied. When a single column was used, 93% RhB dye was removed in 3 h at Q = 2 mL·min^-1, C_in = 10 mg·L^-1, and h = 7 cm. When three columns in series were used, almost 100% dye was removed until 80 h. The maximum breakthrough time (142 h) and saturation time (244 h) were found by keeping Q = 2 mL·min^-1, h = 7 cm of each column and C_in = 10 mg·L^-1. Mathematical modeling of the breakthrough curves was done by using Yoon-Nelson, Clark, Wolborska, and pore diffusion models. The Clark model best fitted the experimental data. The possible interaction mechanism between Aliquat-336 and RhB dye was proposed. The column was regenerated in continuous mode using 1 M HCl solution and maintaining a flow rate of 2 mL·min^-1.

Update on volatile organic compound (VOC) source profiles and ozone formation potential in synthetic resins industry in China

The synthetic resin industry plays an important role in Volatile organic compounds (VOCs) emissions from industrial sources. However, owing to various products and their different emission characteristics, it is extremely difficult to study the source profiles of synthetic resins. In this study, the product-based pollution characteristics of VOCs from eight synthetic resin enterprises were investigated in Shanghai, China. Up to 133 VOCs were identified, including 106 based on the Photochemical Assessment Monitoring Stations (PAMS) and the Toxic Organics (TO-15) methods, and the remaining 27 were identified based on the new mass spectrometry analysis method. Aromatics (39.7%) and oxygenated VOCs (29.9%) accounted for a relatively high proportion in the synthetic resin industry. The product-based source profiles of each process unit are compiled. Generally, 1,4-dioxane, methyl isobutyl ketone, toluene, benzene, styrene, propane, and dichloromethane are the most abundant species in synthetic resin. Furthermore, the product-based ozone formation potentials (OFPs) and sources reactivity (SR) were calculated, the synthetic resin industry SR range from 0.3 g g^-1 to 4.6 g g^-1. Results suggest that toluene, benzene, styrene, propylene, ethylene, and oxygenated VOCs (including 1,4-dioxane, methyl isobutyl ketone, and aldehyde) should be preferentially controlled to reduce the OFPs. A three-level classification was established to evaluate the degree of photochemical pollution in different industries. Emission factors were calculated and ranked for eight synthetic resins. A VOC emission inventory of Chinese synthetic resin from 2005 to 2018 was compiled. It is estimated that the Chinese synthetic resin emitted 23.96 Gg of VOCs in 2018. In this study, a product-based VOC source profile and emission inventory of the synthetic resin industry were established for the first time. Finally, combined with product types, processes, and processing equipment, feasible recommendations for reducing VOC emissions in the synthetic resin industry are proposed.

Resin Infiltration Therapy: A micro-invasive treatment approach for white spot lesions

Purpose: The demand for esthetic dentistry has led to the development of new treatments for white spot lesions (WSLs). Microinvasive therapies, such as resin infiltration, have been used to treat demineralized enamel. Recently, resin infiltration using the active ingredient triethylene glycol dimethacrylate (TEGDMA), has been used to restore WSLs. The purpose of this narrative review is to evaluate the evidence on TEGDMA, an innovative resin that has been introduced, as an alternative dental material for treating WSLs.Methods: A review of the literature was conducted using key words pertaining to WSLs and resin infiltration including cosmetic dentistry; dental caries; dental materials; general dentistry; sealants; technology for patient care. Evidence was incorporated from biomedical data bases including PubMed and the Cochrane Library, which formed the framework for the review.Results: Based on the synthesis of the evidence, resin infiltration using TEGDMA is an effective alternative treatment option for WSLs. Studies suggest that the outcomes for micro-invasive procedures using resin infiltration may vary depending on the depth of the lesion.Conclusion: Resin infiltration, using TEGDMA, removes minimal amounts of enamel and preserves the hard tissue surrounding the WSLs. Additionally, TEGDMA restores the natural fluorescence, hardness, and texture of intact enamel. Future studies are needed to assess the long-term clinical effects of resin infiltration using this material on both permanent and primary dentition.

A modified TEGDMA-based resin infiltrant using polyurethane acrylate oligomer and remineralising nano-fillers with improved physical properties and remineralisation potential

OBJECTIVES

This study aimed to modify an experimental triethylene glycol dimethacrylate (TEGDMA) based resin infiltrant using PUA oligomer and two remineralising fillers, including fluorohydroxyapatite (FHA) and fluoride-doped bioactive glass (FD-BG), to improve the mechanical and physical properties and induce remineralising potential.

MATERIALS AND METHODS

The polyurethane acrylate oligomer (PUA) was synthesised and characterised. Experimental resin infiltrant was prepared by mixing 10% of synthesised PUA with 88% TEGDMA. Water contact angle, penetration coefficient, and penetration depth were then measured. The FHA and FD-BG fillers were synthesised and characterised. To prepare nano-filled resin infiltrant, 5% of each powder was mixed with the prepared resin infiltrant. The prepared resin infiltrants were characterised to evaluate their degree of conversion, mechanical properties, water sorption, and solubility. The ion release of filled resin was also assessed. The non-infiltrated and infiltrated enamel specimens underwent fourteen days of pH-cycling, and a surface microhardness was done to assess the resistance to demineralisation.

RESULTS

The results showed that the addition of PUA to TEGDMA increased the mechanical properties and decreased water sorption and solubility. The addition of synthesised FD-BG fillers to resin infiltrant significantly improved the resistance to demineralisation of enamel samples compared with other groups (p ≤ 0.001). The FHA fillers also improved the resistance to demineralisation; however, the produced changes were not statistically meaningful (p > 0.05).

CONCLUSIONS

Based on the results, the PUA+TEGDMA+ FD-BG/FHA composite can be used as an alternative material for pure TEGDMA in enamel infiltration approaches owing to its better mechanical properties, lower water sorption and solubility, and also remineralisation potential.

CLINICAL SIGNIFICANCE

A resin infiltrant with remineralisation potential, lower water sorption and solubility and higher mechanical properties may enhance the management of early caries lesions.

Amberlite IRC-718 ion chelating resin extraction of hazardous metal Cr (VI) from aqueous solutions: equilibrium and theoretical modeling

Under varied conditions, the IRC 718 ion-exchange resin is used to extract chromium (VI) ions from aqueous solutions. On chromium (VI) removal effectiveness, the effects of adsorption dosage, contact time, beginning metal concentration, and pH were examined. The batch ion exchange process reached equilibrium after around 90 minutes of interaction. With an initial chromium (VI) concentration of 0.5 mg/dm³, the pH-dependent ion-exchange mechanism revealed maximal removal in the pH 2.0-10 range. The adsorption mechanism occurs between Cr (VI) determined as the electron acceptor, and IRC 718 determined as the electron donor. The equilibrium ion-exchange potential and ion transfer quantities for Amberlite IRC 718 were calculated using the Langmuir adsorption isotherm model. The overall ion exchange capacity of the resin was determined to be 187.72 mg of chromium (VI)/g of resin at an ideal pH of 6.0.

Ex vivo evaluation of a multilayered sealant patch for watertight dural closure: cranial and spinal models

Cerebrospinal fluid leakage is a frequent complication after cranial and spinal surgery. To prevent this complication and seal the dura watertight, we developed Liqoseal, a dural sealant patch comprising a watertight polyesterurethane layer and an adhesive layer consisting of poly(DL-lactide-co-ε-caprolactone) copolymer and multiarmed N-hydroxylsuccinimide functionalized polyethylene glycol. We compared acute burst pressure and resistance to physiological conditions for 72 h of Liqoseal, Adherus, Duraseal, Tachosil, and Tisseel using computer-assisted models and fresh porcine dura. The mean acute burst pressure of Liqoseal in the cranial model (145 ± 39 mmHg) was higher than that of Adherus (87 ± 47 mmHg), Duraseal (51 ± 42 mmHg) and Tachosil (71 ± 16 mmHg). Under physiological conditions, cranial model resistance test results showed that 2 of 3 Liqoseal sealants maintained dural attachment during 72 hours as opposed to 3 of 3 for Adherus and Duraseal and 0 of 3 for Tachosil. The mean burst pressure of Liqoseal in the spinal model (233 ± 81 mmHg) was higher than that of Tachosil (123 ± 63 mmHg) and Tisseel (23 ± 16 mmHg). Under physiological conditions, spinal model resistance test results showed that 2 of 3 Liqoseal sealants maintained dural attachment for 72 hours as opposed to 3 of 3 for Adherus and 0 of 3 for Duraseal and Tachosil. This novel study showed that Liqoseal is capable of achieving a strong watertight seal over a dural defect in ex vivo models.

Effects of ionizing radiation on surface properties of current restorative dental materials

To investigate the impact of radiotherapy on surface properties of restorative dental materials. A conventional resin composite-CRC (Aura Enamel), a bulk-fill resin composite-BFRC (Aura Bulk-fill), a conventional glass ionomer cement-CGIC (Riva self cure), and a resin-modified glass ionomer cement-RMGIC (Riva light cure) were tested. Forty disc-shaped samples from each material (8 mm diameter × 2 mm thickness) (n = 10) were produced according to manufacturer directions and then stored in water distilled for 24 h. Surface wettability (water contact angle), Vickers microhardness, and micromorphology through scanning electron microscopy (SEM) before and after exposition to ionizing radiation (60 Gy) were obtained. The data were statistically evaluated using the two-way ANOVA and Tukey posthoc test (p < 0.05). Baseline and post-radiation values of contact angles were statistically similar for CRC, BFRC, and RMGIC, whilst post-radiation values of contact angles were statistically lower than baseline ones for CGIC. Exposition to ionizing radiation statistically increased the microhardness of CRC, and statistically decreased the microhardness of CGIC. The surface micromorphology of all materials was changed post-radiation. Exposure to ionizing radiation negatively affected the conventional glass ionomer tested, while did not alter or improved surface properties testing of the resin composites and the resin-modified glass ionomer cement tested.

Removal of reactive orange 16 and reactive green 19 using Cyphos IL101-impregnated Amberlite XAD7HP resin in batch and recirculating stirrer vessel

Reactive dyes are highly soluble in water, and carcinogenic. Therefore, it is essential to remove these dyes from their aqueous solutions. This study focused on the simultaneous removal of reactive orange 16 (RO) and reactive green 19 (RG) dyes from their binary dye solution using Cyphos IL101-impregnated Amberlite XAD7HP resin (ILX7) in batch and recirculating stirrer vessel (RSV). In the batch study, the experimental operating conditions were designed by using central composite design of response surface methodology. Influence of important input variables (RO dye concentration, RG dye concentration, pH, and resin dosage) on the dye adsorption was studied and their values were optimized. At the optimum values of input variables, equilibrium, kinetic, and thermodynamic studies were performed for the binary dye mixture. The equilibrium and kinetic adsorption data were best fitted with extended-Freundlich and pseudo-second-order models, respectively. Now to intensify the process, continuous studies were performed in a RSV at optimum conditions and at different flow rates and stirring speeds. The impregnated resin was regenerated by using 80% v/v ethanol and successfully reused up to 3 cycles with slight decrease in the adsorption capacity.

Response of pulp cells to resin infiltration of enamel white spot-like lesions

OBJECTIVES

To investigate the trans-enamel and trans-dentinal biological effects of treating enamel white spot-like lesions (EWSLs) with resin infiltration components (RICs) on odontoblast-like cells (MDPC-23) and human dental pulp cells (HDPCs).

METHODS

EWSLs were induced in 60 enamel/dentin discs (4.0 ± 0.2 mm thick) using S. mutans. The discs were adapted into artificial pulp chambers and MDPC-23 were seeded on the dentin surface. The components of a resin infiltration system (Icon) were applied individually or in combination on the enamel surface as following (n = 10/treatment): Etch, Infiltrant, Etch+Infiltrant, or Etch+Dry+Infiltrant. The application of water or hydrogen peroxide served as negative and positive controls, respectively. After 72 h, MDPC-23 viability was evaluated. The extracts were exposed for 72 h to pre-cultured MDPC-23 and HDPCs in 96-well plates to evaluate cell viability, alkaline phosphatase activity (ALP), mineralized nodule formation (MN), and the expression of inflammatory cytokines (ICs) and mineralization-related genes (MRs). Data were analyzed by ANOVA complemented with Tukey or Games-Howell post-hocs (α = 5%).

RESULTS

Cell viability, ALP activity, and MN formation were significantly reduced in response to the RICs, presenting intermediate values compared to positive and negative controls. Likewise, ICs were upregulated, whereas MRs were downregulated. Among the RICs, the Etch component caused the most notorious detrimental effects.

SIGNIFICANCE

Resin infiltration of EWSLs negatively affected the metabolism of pulp cells in vitro. Therefore, even though resin infiltration is a micro-invasive therapy for non-cavitated caries in enamel, it should be closely followed up seen that components may diffuse and unbalance pulp homeostasis.

Application of polyoxymethylene passive air sampler to monitor hydrophobic organics in air around a confined disposal facility

Volatile losses of hydrophobic organic contaminants from a confined disposal facility (CDF) containing dredged contaminated sediments is of substantial concern to surrounding communities. A partitioning passive sampling approach using polyoxymethylene (POM) was applied to measure long-term average (weeks to months) air concentrations resulting from evaporation at a CDF. Measurements at 10 locations surrounding the CDF using the POM air samplers indicated that the highest concentrations of ΣPCBs∼13 ng/m³ and ΣPAHs ∼65 ng/m³ were measured during an active dredge material placement period when the average temperature was 23 °C. The measurements were dominated by the more volatile, lower molecular weight compounds of each type. Partitioning to the POM during the post dredge material placement period with average temperature of 5 °C was corrected for temperature and the measured ∑PCBs and ∑PAHs were ∼3 ng/m³ and 45 ng/m³ respectively. The partitioning passive sampling measurements agreed well with the available weekly 24-h high-volume air samples (HVAS) averaged over the POM equilibration time for lower congener number PCBs (15, 18, 20/28 and 31) and naphthalene but were as much as 10 times lower than HVAS for high molecular weight PAHs. The difference was likely the result of the greater association of these PAHs with particulates and sources other than evaporation from the CDF. The POM air sampler achieved the goal of providing a long-term average air concentration without having to collect, analyze and average multiple HVAS samples although the technique is largely limited to the lower molecular weight PAHs and PCBs and different equilibration times for different compounds complicate its use and analysis.

Efficient direct preparation of antifungal Alteramide B from Lysobacter enzymogenes fermentation broth by macroporous resin adsorption

Alteramide B (ATB) is an antifungal metabolite produced by Lysobacter enzymogenes. However, its separation method has not been explored. This study attempted to directly adsorb ATB from fermentation broth using macroporous adsorption resins (MARs) NKA resin exhibited better adsorption as well as desorption capacities. The static and dynamic adsorption characteristics were assessed to determine the following optimal separation conditions: initial fermentation broth with a pH of 12.0, 2 BV/h flow rate, 8 BV loading volume, and 6 BV 80% aqueous ethanol for elution. After a single treatment, ATB content in the final product was higher by 4.51-fold (i.e, from 12.72 ± 1.21% to 57.35 ± 3.46%), resulting in a recovery yield of 86.20 ± 4.47%. In addition, NKA resin showed superior reusability within eight cycles of adsorption/desorption. The developed method is thus a simple, efficient, and economical process for ATB separation.

Resin Infiltration in Dental Fluorosis Treatment-1-Year Follow-Up

Background and objective: Dental fluorosis is a disease affecting dental hard tissues featured with white or yellowish lesions. Several treatments are proposed in the literature, some even invasive. This clinical study aimed to evaluate the effectiveness of resin infiltration in terms of lesions resolution, trend of sensitive teeth and satisfaction of patients over time. Methods and material: 200 fluorosis lesions were treated using ICON infiltrating resin (DMG, Hamburg, Germany). Parameters related to patients were collected by a questionnaire and analyzed aesthetic dissatisfaction about lesions, Shiff Air Index Sensitive Scale, sensitive teeth after treatment, the satisfaction of duration of treatment. The same operator measured dimensions of lesions Tooth Surface Index of Fluorosis (TSIF) and numbers of etching cycles needed for treating lesions. Statistical analysis was performed. The follow-up was of 1-year a measurement were performed at baseline (t0), immediately after the treatment (t1) and every three months during the observation period. Results: All lesions disappeared after one treatment. Pain or sensitive teeth were reported inside the 72 h and they disappeared after. Statistical analysis showed highly statistically correlation between etching cycles and the dimension of lesions and TSIF at the time-points evaluated as well as for pain during treatment, whereas a statistical significance was not noticed where etching cycles were correlated to sensitive teeth after 72 h. Overall, the treatment was found to be statistically significantly associated with differences in answers of aesthetic dissatisfaction between t0 and t1 and those collected between t1 and t2. Between t2 and t3 and between t3 and t4 no statistical differences were found in answers of patients about dissatisfaction, indicating the stability of the results. Conclusions: The ICON resin infiltration technique was found to be effective in lesions resolution with steady results.

Evaluation of coatings for application in raffia big bags in conditioned storage of soybean cultivars in seed processing units

Different regions have different environmental conditions, which may be unfavorable for the preservation of the quality of stored soybean seeds over time. Thus, it is necessary to adopt specific technologies to control the storage environment conditions. Big raffia bags are widely used for the storage of soybean seeds, however these consist of a porous, permeable material that allows the exchange of gases between the packaging and the storage environment. In an effort to find a solution to this problem, in this study we evaluated low cost big bag coating alternatives, in order to minimize the effects of temperature and intergranular humidity on stored seeds. Thus, the aim of this work was to evaluate the quality of soybean cultivars subjected to different temperature and storage duration conditions and stored in raffia bags with or without internal coating. We used a completely randomized, three-factor (10 × 6 × 5) experimental design. We assessed 10 soybean cultivars, six storage environments, and five evaluation periods. Our results showed that seeds of the M-SOY 8866, M7110 IPRO, CD 2737 RR, and BMX DESAFIO 8473 RSF soybean cultivars preserved their physiological quality better in different storage environments. The storage duration had a cumulative effect on the negative factors that favor the deterioration of the quality of the stored seeds. The storage temperature was the main factor that affected the physiological quality of the stored seeds. The use of coated packaging was beneficial in preserving the physiological quality of stored soybean seeds; however, its effect was greater at ambient temperature than in a cold environment. The best storage environment for the preservation of the quality of the seeds was characterized by 10°C temperature conditions and the use of coated packaging, while the worst storage environment was characterized by ambient temperature conditions without the use of coated packaging. Thus, it was concluded that the use of coatings in raffia big bags can be an alternative for maintaining the quality of seeds of different soybean cultivars during storage in seed processing units.

Development of polyoxymethylene passive sampler for assessing air concentrations of PCBs at a confined disposal facility (CDF)

In this study, 76 μm polyoxymethylene (POM) strips were evaluated as a passive air sampler (PAS) for monitoring the volatile emissions from dredged material placed in confined disposal facilities (CDF). Laboratory evaluations were used to assess the uptake kinetics, average equilibrium time, and estimate the POM-air partition coefficients (K_POM-A) of 16 PCB congeners. The uptake kinetics defined the effective averaging time for air sampling and ranged from about a week for dichlorobiphenyls to 2 weeks or more for tetra- and pentachlorobiphenyls at ∼20 °C under internal mass transfer resistance control which was applicable for Log K_POM-A < 8. The measured Log K_POM-A for PCBs ranged from 5.65 to 9.34 and exhibited an average deviation of 0.19 log unit from the theoretical value of K_POM-W/K_AW. The PAS approach was then tested with a preliminary field application (n = 17) at a CDF allowing equilibration over 42 days. The field application focused on lower congener PCBs as a result of the estimated increase in K_POM-A and longer uptake times expected at the low ambient temperatures during the field study (average of 3.5 °C). Total PCB air concentrations around the CDF averaged 0.32 ng/m³ and varied according to proximity to placement of the dredged materials and predominant wind directions. Average PAS concentration of low congener number PCBs (15, 18, 20/28, 31) were compared to available high volume air sampler (HVAS) measurements. The PAS concentrations were within 20% of HVAS in the dominant north and south directions and showed similar trends as east and west HVAS samplers although PAS concentrations were as much as an order of magnitude below the west HVAS.

Adsorption Study of Lignin Removal from Recycled Alkali Black Liquor by Adsorption Resins for Improved Cellulase Hydrolysis of Corn Straw

Previous studies showed that aromatic compounds such as lignin, phenols, and furans were main inhibitors of cellulase hydrolysis in recycled alkali black liquor (RBL), which should be removed to improve alkali utilization. In this study, three polymeric resins, XAD-4, XAD-16N, and XAD-7HP, were evaluated for their abilities to remove lignin from alkali black liquor recycled at the third time. Adsorption conditions of adsorbent dose and equilibrium time, isotherms, and kinetics were investigated. Of three tested adsorbents, XAD-16N was the most efficient, which can remove 89.84% of lignin after adsorption at an adsorbent-to-solution ratio of 1:4 for 2.5 h. Pseudo-second-order model was efficient to represent XAD-16N and XAD-7HP adsorption kinetics. Adsorption behavior of XAD-4 on RBL was fitted better to Langmuir model, while XAD-16N and XAD-7HP adsorption were more consistent with Freundlich model. The cellulase hydrolysis rate of corn straw treated with RBL after XAD-16N adsorption combined with ozone was 86.89%, which was only 0.89% lower than that of sodium hydroxide combined with ozone treatment. Structure characterization proved that the damage of XAD-16N adsorbed RBL to corn straw was similar to that of sodium hydroxide. It indicated that adsorption was effective in inhibitor removal from RBL to improve alkali utilization.

Estimation on Fixed-Bed Column Parameters of Breakthrough Behaviors for Gold Recovery by Adsorption onto Modified/Functionalized Amberlite XAD7

The objective of this paper was to evaluate the potential of a new adsorbent material to recover Au (III) from real wastewater, in a column with a fixed bed in a dynamic regime. The material was obtained through functionalization, by impregnation of the commercial resin, Amberlite XAD 7 type, with L-glutamic acid, which has active groups -NH2 and -COOH. The goal of the experiments was to follow the correlation of fixed-bed column specific adsorption parameters (the effluent volume, the amounts of adsorbent, heights of the adsorbent layer in column) with the time necessary to cross the column. The experimental data obtained were modeled, using the Bohart-Adams, Yoon-Nelson Thomas and Clark models, to establish the mechanism of the Au (III) recovery process, in a dynamic regime. Also, we established the number of cycles for adsorption-desorption for which the new material can be used. We used 5% HNO3 (5%) as desorption agent in five adsorption-desorption cycles, until the process was no longer efficient. The degree of desorption varied between 84% and 34% from cycle 1 to cycle 5.

Improving oral health: a short-term split-mouth randomized clinical trial revealing the superiority of resin infiltration over remineralization of white spot lesions

OBJECTIVES

To evaluate masking effects of resin infiltration on labial white spot lesions (WSL), by comparing the latter with a remineralization approach (using hydroxyapatite and fluorides) and conventional oral care (using fluoride-free toothpaste).

METHOD AND MATERIALS

Fifteen patients with at least three WSL were enrolled for a within-person randomized controlled trial, thus allowing for intrapersonal comparisons. Each WSL per tooth in every patient was randomly assigned to one of the following groups. Group 1: lesions were resin-infiltrated with Icon (RI; DMG); Group 2: Remin Pro (RP; VOCO) was used as remineralizing agent; and Group 3 (control): affected teeth were brushed with Complete Care toothpaste (CC; Himalaya). RP and CC were applied by means of a polishing brush, using a low-speed handpiece (5 min), and these procedures were repeated chairside thrice daily for 7 consecutive days. Digital photographs were captured before and after lesion treatment under standardized conditions. The CIE L*a*b* color system was used to analyze the optical outcome, and intrapersonal color differences were statistically evaluated.

RESULTS

Compared to RP and CC, RI showed prompt and subjectively satisfactory color improvements, and this was primarily driven by L* and b* shifts. Statistical analysis of the objective color differences (ΔE*) between the three groups revealed significant differences for RI vs RP (P = .029), RI vs CC (P < .001), and RP vs CC (P = .001).

CONCLUSION

Resin infiltration is considered a time-effective treatment option for esthetically camouflaging WSL, while RP and CC failed to improve lesion appearance and oral health in the current short-term trial.

Elution of Monomers from an Infiltrant Compared with Different Resin-Based Dental Materials

PURPOSE

Low-molecular weight residuals eluting from dental materials may contribute to local and systemic adverse effects. Therefore, the aim of the present study was to compare triethylene glycol dimethacrylate (TEGDMA)-based commercial infiltrant with different conventional resin-based materials regarding their release of monomers.

MATERIALS AND METHODS

Cylindrical blocks (n = 10) of either two sealants (Helioseal, Delton FS+), a composite (EcuSphere), an adhesive (Teco) and an infiltrant (Icon) were prepared. Additionally, 20 artificial lesions (depths ≥100 µm) were created in bovine enamel and after etching with phosphoric acid infiltrated with the infiltrant. Except for 10 infiltrated lesions, all other specimens were polished. Each specimen was stored in 1 ml distilled water (elution medium) for 240 h. The medium was renewed in logarithmical divided time periods (4.5 min-76 h).

RESULTS

Total concentrations of eluted monomers within 240 h from the cylindrical specimens were 0.04-0.09 mg/ml (p >0.05; Mann-Whitney test). Unpolished infiltrated specimens showed significantly higher monomer concentrations compared to all other groups, whereas polishing of specimens resulted in significantly lower concentrations (p <0.05; Mann-Whitney test).

CONCLUSION

It can be concluded that release of monomers was low in general, but for infiltrated lesions it was considerably reduced by surface polishing reaching similar values as for commonly used monomer-containing dental materials. Thus, adverse effects by the use of an infiltrant are not expected, but polishing of the infiltrated area should be considered.

Comparative Evaluation of Antimicrobial Efficacy and Fluoride Release of Seven Different Glass-Ionomer-Based Restorative Materials

PURPOSE

The aim of this study was to evaluate one high-viscosity glass-ionomer cement (EQUIA/GC), two resin-modified glass ionomers (Fuji II LC/GC, Photac Fil Quick Aplicap/3M Oral Care), two traditional glass ionomers (Ketac Molar Easymix/3M, Fuji II/GC), and two compomers (Freedom/SDI, Dyract XP/Dentsply Sirona) through a comparison of fluoride release and antimicrobial effects.

MATERIALS AND METHODS

A total of 210 samples were prepared, as 10 for each of the 7 materials for fluoride release and 20 for each material for the antimicrobial effect tests. To measure fluoride release, 5 ml distilled water and 5 ml TISAB II were added to the samples, which were then incubated at 37˚C. The fluoride levels of the material were measured using the selective ion electrode on days 1, 3, 7, 14 and 28. To compare the antimicrobial effects, 20 samples were divided in two groups and implanted in culture media containing Streptococcus mutans and Lactobacillus acidophylus. Measurements were taken on days 2, 4 and 6. The diameter of the inhibition zone was recorded in millimetre (mm).

RESULTS

All the materials released fluoride and the difference between them was determined to be statistically significant (p < 0.01). The antimicrobial effect values of the materials against S. mutans and L. acidophylus were evaluated and statistically significant difference was determined between the materials on all the measurement days.

CONCLUSIONS

All the materials were observed to release fluoride. With the exception of the compomers, all the other materials showed an antimicrobial effect against S. mutans and L. acidophylus. Key words: fluoride, glass ionomer, antimicrobial, S. mutans, L. acidophylus.

Clinical Performance of a Glass-Hybrid System Compared with a Resin Composite in the Posterior Region: Results of a 2-year Multicenter Study

PURPOSE

To compare the clinical performance of a glass hybrid restorative system, EQUIA Forte, with that of a nanohybrid resin composite, Tetric EvoCeram, in two-surface class II cavities.

MATERIALS AND METHODS

This multicenter, randomized controlled clinical study was conducted at four different dental schools. In total, 360 restorations were placed in patients in need of two class-II, two-surface restorations in the molar region of the same jaw. Each patient received one glass hybrid restoration (EQUIA Forte, GC) and one resin composite restoration (Tetric EvoCeram, Ivoclar Vivadent). Two independent evaluators performed a clinical evaluation of each site after 1 week (baseline), 1 year, and 2 years using the criteria of the FDI World Dental Federation (FDI-2).

RESULTS

The estimated survival rates at the 2-year recall were 93.6% and 94.5% for EQUIA Forte and Tetric EvoCeram, respectively. There were no significant differences in the survival rates or in any of the evaluated esthetic, functional or biological properties between EQUIA Forte and Tetric EvoCeram restorations (p ˃ 0.05).

CONCLUSION

Both the glass-hybrid restorative system and nanohybrid resin composite showed good clinical performance in moderate to large two-surface class II restorations in a 2-year follow-up.

Near-infrared fluorescent solid material for visualizing indwelling devices implanted for medical use

BACKGROUND

In clinical practice, various devices are implanted into the body for medical reasons. As X-ray fluoroscopy is necessary to visualize medical devices implanted into the body, the development of a less-invasive visualization method is highly desired. This study aimed to investigate the clinical applicability of our novel solid material that emits near-infrared fluorescence.

METHODS

We developed a solid resin material that emits near-infrared fluorescence. This material incorporates a near-infrared fluorescent pigment, with quantum yield ≥ 20 times than that of indocyanine green. It can be sterilized for medical treatment. This resin material is designed to be molded into a catheter and inserted into the body with an endoscope clip. In this preclinical experiment using a swine model, the resin material was embedded into the body of the swine and visualized with a near-infrared fluorescence camera system.

RESULTS

Endoscopic clips were placed in the mucosa of the stomach, esophagus, and large intestine, and the indwelling ureteral catheters were successfully visualized by near-infrared fluorescence laparoscopy.

CONCLUSIONS

We confirmed the tissue permeability of the fluorescence emitted by our novel near-infrared fluorescent material and the possibility of its clinical application. This material may allow visualization of devices embedded in the body.

Conventional and contemporary approaches of splinting traumatized teeth: A review article

Trauma moves a tooth from its original position which needs to be repositioned for optimum healing and better outcomes. To stabilize the traumatically displaced teeth, splinting is specified as the gold standard. In this article we have discussed about various old and modern techniques based on the type of material to splint teeth with dentoalveolar trauma. As per recommendation of IADT, providing flexible splint is beneficial for good healing. A biologically favourable splint should not just be user friendly but also should be convenient in terms of removal. Every technique has its merits and demerits. Iatrogenic trauma to the teeth due to forceful removal of material should be avoided as it may result in post-operative sensitivity but sometimes it is inevitable. Metallic or wire based splints either secured with ligature wire or resin based material may show directly or through the cemented material and compromise aesthetics. This worsens the physiological impact which the patient is already facing after trauma. Recent advancement in splinting material with fiber reinforced material has brought a dramatic change in terms of strength and aesthetics, specifically after traumatic dental injuries. There are various other techniques discussed here which can be used for splinting teeth when the dentist has limited time in emergency or limited resources. The type and timing of the splinting span should be in accordance with the type of injury and as per IADT recommendation to follow standard of care.

Quantitative evaluation of masking effect of resin infiltration on developmental defects of enamel

OBJECTIVE

Qualitative developmental defects of enamel (DDEs) are characterized by an intact hypermineralized surface enamel layer and a porous subsurface hypomineralized layer. This structure is similar to natural early caries lesions, which are effectively arrested by resin infiltration, a micro-invasive clinical procedure. An additional reported effect in early enamel caries is recovery of enamel translucency. Due to structural similarities, a similar mechanism is expected in qualitative DDEs. The objective of the present study was to observe quantitative color masking of qualitative DDEs when subjected to resin infiltration.

METHOD AND MATERIALS

A total of 70 selected enamel defects were subjected to resin infiltration in a nonrandomized study design. Each defect was subjected to photographic imaging using a digital camera both pre- and post-intervention. Each image was assessed using ImageJ digital software (National Institutes of Health) for CIE L*a*b coordinates.

RESULTS

There were significant changes observed in L*a*b coordinates of all DDEs, when subjected to resin infiltration.

CONCLUSION

The resin infiltration intervention was successful in masking the "white" opaque discolorations of developmentally affected enamel.

Color properties of artificial white spot lesions treated by experimental resin infiltrants containing bioactive glass and nano-fluorohydroxyapatite

AIM

This study was conducted to assess the masking effects of some experimental resin infiltrants containing bioactive glass (BAG) and nano-fluorohydroxyapatite (n-FHAP) on enamel white spot lesions (WSLs).

MATERIALS AND METHODS

Fifty enamel specimens were embedded in an acrylic resin and divided into five groups (n = 10). After creating artificial enamel lesions, the specimens were infiltrated by the following resins: 1) Group 1 (T/control group): TEG-DMA; 2) Group 2 (T2H): TEG-DMA + 2 wt% n-FHAP; 3) Group 3 (T5H): TEG-DMA + 5 wt% n-FHAP; Group 4 (T2B): TEG-DMA + 2 wt% BAG; Group 5 (T5B): TEG-DMA + 5 wt% BAG. Next, the specimens were subjected to demineralization-remineralization cycles for 2 weeks. Color assessments were performed by a spectrophotometer in four distinct stages: baseline, after the production of artificial caries, after resin infiltration, and 2 weeks after resin infiltration. L*, a*, b*, and ΔE values were calculated at each stage. Color parameters were analyzed statistically using the Kruskal-Wallis and Mann-Whitney U tests. The significance level was set at 5%.

RESULTS

All treatments led to a decrease in the L3* compared with the L2* value. The resin infiltrant containing 5% fluorohydroxyapatite (FHAP) exerted the highest L* reduction effect among all the groups. The T group was the only resin infiltrant group with a lower mean of a4* than those compared at baseline. Regarding the ΔE13* and ΔE14* values, only the resin infiltrants of groups 1 (T), 2 (T2H), and 3 (T5H) were able to mask artificial caries.

CONCLUSION

Experimental resin infiltrants containing n-FHAP were able to mask WSLs after 14 days.

Clinical evaluation of the immediate masking effect of enamel white spot lesions treated with an infiltrant resin

The aim of this study was to evaluate, in vivo, the immediate masking effect of white spot lesions (WSLs) treated with an infiltrant resin (IR). The investigation was conducted on 40 young adolescent and adult patients (11 to 23 years old) who presented with at least one permanent maxillary or mandibular anterior tooth with active WSLs on the enamel (ICDAS score 2). Before resin infiltration, the color of both the WSLs and the sound adjacent enamel (SAE) was evaluated by a digital spectrophotometer (CIELab). Subsequently, a resin infiltration technique (Icon) was performed on the WSLs according to the manufacturer's instruction. At the end of the clinical session, the color of the IR was evaluated. The color difference (ΔE) was calculated between WSL × SAE, WSL × IR, and IR × SAE, and then analyzed using one-way analysis of variance (ANOVA), followed by the Tukey's test. The L*, a*, and b* values of WSL, SAE, and IR were compared using the Student's t test for related samples (α = 5%). The ΔE observed was 5.93 ± 0.41 on the WSL × IR comparison, and 5.77 ± 0.41 on the IR × S AE one, indicating that the color of the WSL changed after treatment, but that the infiltration did not fully camouflage the WSLs when compared with the SAE. The lightness was higher for the SAE than for the IR. It was concluded that the IR treatment was not able to camouflage the color of the WSLs when compared with the SAE. However, the treatment was able to attenuate the discoloration of the demineralized dental enamel.

Healing of the post extractive socket: technique for conservation of alveolar crest by a coronal seal

The first aim of the following experimental study was to assess bone changes in the horizontal and vertical dimension when using different socket preservation procedures. The second objective of our work was also to compare two clinical methods of coronal seal's management: an experimental group was treated using the natural extracted tooth; another experimental group saw the use of a provisional resin preformed as a seal technique. In twelve patients a premolar tooth was extracted without elevation of a mucoperiosteal flap and the patients were randomly distributed into four groups. The first and second group was considered as a control groups: in the first, the extraction socket was left with its blood clot and interrupted sutures were applied; In the second, the extraction socket was filled with BioOss Collagen (Geistlich Biomaterials, Wolhusen, Switzerland) and a free gingival graft was sutured to cover the socket. The third and fourth groups was considered as a test group. In the third group, after tooth extraction, for aesthetic reasons, the root of the natural dental element is cut to allow immediate temporary prosthesis. In the fourth group, as in group 3, the patient is discharged through a temporary restoration performed or by the dental technician or directly to the chair. Standardized photographs were taken eight months after tooth extraction. Five competent observers analyzed the esthetic outcome according to the PES. To assess the level of bone healing at the extraction site, the following parameters were evaluated: 1) changes in soft tissue and 2) changes in bone level. As for soft tissues, they were assessed using the PES score by two assessments, four weeks apart. The overall scores of the four treatment groups revealed PES values of 8.47 (SD 2.08, group 3), 6.62 (SD 3.24, group 4). The differences between groups 1 and 2 and were statistically significant (P=0.015 and P=0.047). The single parameter analysis displayed a certain range of fluctuation and heterogeneity. As regards hard tissue, during the 6-month period, bone remodeling occurred in all four experimental groups with different percentages. The mean vertical loss of the buccal bone plate for the Tx 1 group was -2 ± 0.2 mm. The Tx 2 group showed vertical loss of - 0.34 ± 0.2 mm. The Tx 3 group demonstrated - 0.3 mm of mean vertical loss and the 4 groups demonstrated -0.46 of mean vertical loss. The horizontal dimension of the alveolar process was 13.5 ± 0.1 mm, 7.6 ± 0.1 mm e 6.7 ± 0.1 mm at the three different levels for the Tx 1 group. The Tx 2 group depicted bone dimensions of 14.4 ± 0.2 mm, 13.7 ± 0.3 mm e 13.4 ± 0.1 mm. The horizontal dimension of the Tx 3 - Tx 4 group was 13.7 ± 0.3 mm, 13.1 ± 0.1 mm e 13 ± 0.1 mm and 13.5 ± 0.1 mm, 13.2 ± 0.1 mm e 12.9 ± 0.1 mm. The findings from the present study disclose that incorporation of coronal seals define a particular respect to the buccal bone plate.

Validating laboratory simulation with resin-based materials for temporary fixed denture prostheses - Results from clinical and laboratory trials

The aim of the current study was to relate an artificial aging protocol for the analysis of dental materials to their clinical performance. 20 fixed interim restorations (crowns and fixed denture prostheses (FDPs)) fabricated from two commercially available resin-based composites (RBCs) and a previous clinical trial served as templates for the fabrication of duplicate restorations. Duplicates were subjected to artificial aging using thermal cycling and mechanical loading. Subsequent to wear analysis, templates and duplicates were loaded to fracture and were examined using thermal gravimetric analysis (TG) and differential scanning calorimetry (DSC). For both RBCs, a relevant uptake of water was identified, which was more pronounced in the duplicates. Tribological analyses indicated relevant signs of wear in both templates and duplicates. While qualitative analyses indicated macroscopically similar wear traces in templates and duplicates, data showed that wear of FDPs was underrated in the laboratory analyses. The results of the current study suggest that chewing simulation allows a proper estimation of aging processes in materials for the fabrication of fixed interim restorations. However, simulation parameters should be continuously improved using data derived from clinical settings to enhance the quality of the simulation protocols.

Evaluation of Impact Strength of Dental Acrylic Resins by Incorporation of TiO2 Nanoparticles Using Two Different Processing Techniques

AIM

The present study aims to evaluate the impact strength of PMMA incorporated with TiO₂ nanoparticles by two different processing techniques i.e. water bath and microwave processing techniques.

MATERIALS AND METHODS

A total of 80 samples made of PMMA were divided into four groups. Each group includes 20 samples with group I and II comprising of samples made of normal acrylic resin and acrylic resin reinforced with 1 wt% TiO₂ nanoparticles processed with conventional water bath technique respectively, groups III and IV include normal acrylic resin and acrylic resin reinforced with 1 wt% TiO₂ processed using microwave technique respectively. The specimens were tested for impact strength using IZOD pendulum impact tester. The impact energy values obtained were analyzed statistically.

RESULTS

The results through one-way ANOVA showed a high mean impact strength with group IV samples (23.13) and lowest with respect to group I (19.42) with highest statistical significance (p < 0.001). A post hoc Tukey test intergroup analysis showed a statistically significant difference between group I and other groups, whereas there was no statistical significance associated with other intergroup comparisons.

CONCLUSION

PMMA with its current drawbacks in the physical and mechanical properties requires modifications to make it an ideal denture base material. The current investigation evaluates that a high mean impact strength with samples made of PMMA incorporated with TiO₂ nanoparticles processed by microwave technique was obtained when compared with normal acrylic resins processed by water bath technique.

CLINICAL SIGNIFICANCE

The methodology of current study can be used while processing of denture bases for patients to evaluate the effect of oral environment on inclusion of TiO₂ nanoparticles with microwave processing in a clinical setup. This could help in reducing the amount of fractures associated with heavy load masticatory stresses and improving the mechanical properties in denture bases. How to cite this article: Kumar CA, Kumar CR, Vamshikiran K, et al. Evaluation of Impact Strength of Dental Acrylic Resins by Incorporation of TiO₂ Nanoparticles Using Two Different Processing Techniques. J Contemp Dent Pract 2019;20(10):1184-1189.

Polymeric adsorbents for oil removal from water

In this study, the application of four synthetic resins for the removal of emulsified oil from produced water was investigated. Key experimental parameters such as adsorbent dosage, contact time, initial oil concentration and pH were evaluated for Optipore L493, Amberlite IRA 958, Amberlite XAD 7 and Lewatit AF 5. Oil removal rates upwards of 98% were achieved using AF 5, XAD 7 and L493. IRA 958 recorded very modest removal rates of less than 25%. Isotherm data were further investigated and fitted using Langmuir, Freundlich, Toth, Flory Huggins and Dubinin-Radushkevich models. The results show that the adsorption onto XAD 7 and L 493 is a multilayer adsorption process over a heterogeneous surface that is best illustrated by the Freundlich and Toth models respectively. The Dubinin-Radushkevich best described the removal using AF 5 resin that assumes that the adsorption process occurs on a heterogenous surface with a gaussian energy distribution. Kinetic studies assessing the rate of removal for each resin were conducted. Experimental results were best fitted using pseudo second order kinetics. It is concluded that XAD 7 had the highest kinetics among all tested resins. Also, AF 5 exhibited the highest adsorption capacity. Overall, the study confirmed the applicability of the resins for the removal of oil from produced water.