Light Curing Research Articles

THE EFFECT OF GLYCERIN APPLICATION ON ROUGHNESS OF NANOHYBRID COMPOSITE RESIN IMMERSED IN ISOTONIC DRINK

ABSTRACTBackground: Composite resin is the most commonly used restorative material. One type of composite resin based on the filler material is a nanohybrid composite resin which has the advantage of good strength and smooth surface to produce good improvements in terms of durability and aesthetics. The roughness of the resin can be affected by drinks with low pHs, such as isotonic drink. Glycerin can reduce the roughness of the composite resin by acting as a barrier so that an oxygen inhibition layer (OIL) is not formed. Purpose: This study is to determine the effect of glycerin application on the roughness of nanohybrid composite resin immersed in an isotonic drink. Method: A total of 32 samples of nanohybrid composite resin used in this study were made with a diameter of 5 mm and a thickness of 2 mm. The nanohybrid composite resin samples were divided into group I without glycerin application and group II with glycerin application before the light curing process. Both groups were then immersed in an isotonic drink for 18 hours in an incubator. The research continued with roughness testing using a surface roughness tester. Result: There was a significant difference in the roughness of the nanohybrid composite resin immersed in an isotonic drink with and without glycerin application. This is indicated by the p-value < 0.05 in the unpaired bivariate t-test, which means that there is a significant difference in the two sample groups. Conclusion: The application of glycerin can reduce the roughness of the nanohybrid composite resin immersed in isotonic drink. Keywords: Glycerin application, Nanohybrid composite resin, Roughness.

Toward Optimum Light Curing of Resin Composite Restorations: A survey on Current Awareness and Practice among General Dentists in Saudi Arabia

Introduction: This study aimed to assess the current awareness and practices of resin composite light curing of general dental practitioners (GDPs) in Saudi Arabia and to set several evidence-based recommendations to improve the quality of the outcome of concern. Methods: An online questionnaire was created. Two hundred and fifty email invitations were sent to GDPs appointed in general governmental hospitals in five main cities in Saudi Arabia to join the survey voluntarily and anonymously. The survey consisted of 24 questions classified into the following domains: 1-Demographic criteria 2- frequency and technical aspects of resin composites application 3- criteria of the currently used light curing units and curing light. Descriptive statistics and chi-square test were used to analyse the obtained responses. Results: One hundred and fifty-six responses were received. A significant number of GDPs are significantly satisfied with the quality of their light curing, not aware of the thermal hazards of light curing, and do not check power output of their LCUs (light curing units) (P<0.05). An insignificant number of respondents use eye shields for eye protection during light curing. Conclusion: There was no uniform light curing protocol followed by respondent GDPs. GDPs in Saudi Arabia should improve their knowledge and clinical skills of light-curing resin composite.

Skill Retention of Light-Curing Technique Using Only Verbal Instructions versus Using an Instructional Video: A 2-Year Follow-Up Study of Dental Students.

To evaluate the retention of light-curing skills among dental students after two years of clinical experience and determine if there are any differences in the skills retention between students who received verbal instructions or those who had received an instructional video. The students' satisfaction with past learning, self-confidence, and general knowledge about light-curing were also evaluated. This study is a 2-year evaluation of previous work. Students had previously been divided into two groups: those who received only verbal instructions, and those who received only an instructional video about the correct light curing technique to use clinically. Each student had light-cured simulated restorations (anterior and posterior) for 10 sec using the Managing Accurate Resin Curing-Patient Simulator (MARC-PS) (BlueLight Analytics, Halifax, Nova Scotia, Canada) and a multiple-emission peak light-emitting-diode (Bluephase N, Ivoclar Vivadent, Schaan, Liechtenstein) curing light. Students then received instructions according to their assigned group and light-cured the simulated cavities again. Two years later, students from both groups light-cured the same simulated cavities. Then, they completed a modified version of the National League of Nursing (NLN) satisfaction and self-confidence questionnaire and answered light-curing knowledge questions. Statistical analysis: The mean radiant exposure values delivered before receiving specific instructions on light curing, immediately after, and two years after instruction for both teaching methods (Friedman test followed by Wilcoxon signed-rank post hoc test), and the difference between both teaching methods was assessed (two-sample Wilcoxon rank-sum test). The satisfaction and self-confidence scores were compared between teaching method groups (Wilcoxon rank-sum test) (p<0.05). The mean and median irradiance values ranged between 194-1777 and 1223-1302 mW/cm2 before instructions, 320-1689 and 1254-1394 mW/cm2 immediately after instructions, and 95-1945 and 1260-1331 mW/cm2 two years later regardless of the simulated restoration or the teaching method. The mean and median radiant exposure values ranged between 2-23 and 12.5-13.6.4 J/cm2 before instructions, 3-28 and 12.8-14.3 mW/cm2 immediately after instructions, and 0.7-20 and 12.8-13.6 mW/cm2 two years later regardless of the simulated tooth being light cured and the teaching method. Students retained their light-curing skills after two years of clinical experience, with no significant differences between both groups. The instructional video group delivered significantly higher radiant exposure values (p=0.021) when light-curing the anterior tooth than the posterior. Students were satisfied with their past learning and confident in their light-curing skills (p=0.020). There were statistical differences in how well the two groups remembered what they had been taught about light-curing. Only 5.7% of students answered all knowledge questions correctly. Students retained their light-curing skills after two years of clinical experience, with no significant difference between verbal instructions or instructional video teaching methods. However, their knowledge about light curing remained very poor. Nevertheless, the students were satisfied with how they had been taught and had confidence in both teaching methods.

Remineralization Potential of Three Restorative Glass Ionomer Cements: An In Vitro Study.

The aim of this in vitro study was to evaluate the remineralizing ability of three glass ionomers on demineralized dentin with different thicknesses and time periods. Fifty third molars were obtained and were sectioned into 1-, 2-, and 3-mm thick slices (n = 36 for each thickness). The specimens were demineralized with 18% EDTA for 2 h. From the glass ionomer cements (GICs) under study (Ketac Molar Aplicap, Equia Forte, or Riva Light Cure), 1 mm was placed over each slice, set, and preserved in PBS until observation after 1, 7, 14, and 28 days after placement. For each material, thickness, and time, three samples were prepared. Using Fourier Transform Infrared Spectrometry (FTIR), apatite formation was determined on the side opposite to that on which the material had been placed. By means of Energy Dispersive Spectroscopy (EDX), the changes in the Calcium/Phosphate (Ca/P) ratio were evaluated. These changes were compared between the different materials by means of a two-way ANOVA test, considering time and dentin thickness, for a significance level of p < 0.05. Results: FTIR showed a peak at 1420 cm-1, evidencing the presence of carbonated hydroxyapatite in all the materials after 14 days, which indicates that a remineralization process occurred. Riva Light Cure showed the most homogeneous results at all depths at 28 days. The Ca/P ratio was maximum at 7 days in 2 mm of dentin for Riva Light Cure and Equia Forte HT (3.16 and 3.07; respectively) and for Ketac Molar at 14 days in 1 mm (3.67). All materials induced remineralization. Equia Forte achieved the greatest effect at 2 mm and Ketac Molar at 1 mm, whereas Riva Light Cure showed similar results at all depths. In terms of Ca/P ratio, Equia Forte and Riva Light Cure remineralized best at 2 mm, whereas for Ketac Molar, it was 1 mm. Carbonate apatite formation was higher at 24 h and 7 days for Ketac Molar, whereas it decreased at 14 days for Ketac Molar and peaked in Riva Light Cure and Equia Forte.

A Comparative Evaluation of Shear Bond Strength of Embrace WetbondTM Pit and Fissure Sealant with or without the Use of a Universal Dental Adhesive System [ScotchbondTM Universal Adhesive] Using Different Bonding Protocols: A Multiparametric In Vitro Study.

To evaluate and compare the shear bond strength (SBS) of Embrace WetBondTM (EWS) Pit and Fissure Sealant (PF sealants) with or without the use of a universal dental adhesive system ScotchbondTM Universal Adhesive (SBU) using different bonding and curing protocols and to assess and compare the mode of failure as determined by visualization of the fractured surfaces of the test specimens after shear testing under an optical microscope at a magnification of 20×. A total of 85 samples were prepared for testing SBS on enamel on caries-free, extracted permanent human molars. The specimens were randomly divided into five groups based on different bonding and curing protocols. A knife-edge blade in a universal testing machine was used to perform the SBS test with a crosshead speed of 1 mm/minute. Then the mode of failure was assessed. Results were analyzed using a one-way analysis of variance with Tukey's post hoc test and Chi-squared test. A probability value 0.05 (p ≤ 0.01) was regarded as significant. ScotchbondTM Universal Adhesive (SBU) in total-etch (TE) mode/etch-and-rinse (ER) mode with individual light curing of the sealant and adhesive showed the highest SBS to enamel (5.40 ± 2.51 MPa). A predominance of cohesive mode of failure was observed for all the test groups. Embrace WetBondTM (EWS) PF sealants with SBU in the ER mode of application, with either curing mode, can be used as an alternative to a conventional technique for sealant placement for improving interfacial bond strength to enhance sealant retention and efficacy. Embrace WetBondTM (EWS) PF sealants with SBU in the ER mode of application can be used as an alternative to a conventional technique for sealant placement for improving interfacial bond strength. Swathy SR, Naidu J. A Comparative Evaluation of Shear Bond Strength of Embrace WetbondTM Pit and Fissure Sealant with or without the Use of a Universal Dental Adhesive System [ScotchbondTM Universal Adhesive] Using Different Bonding Protocols: A Multiparametric In Vitro Study. Int J Clin Pediatr Dent 2023;16(1):48-53.

Evaluation of a novel caries detecting oral rinse

AimLumiCare™ Caries Detection Rinse (LC Rinse), a starch-based rinse, illuminates active initial caries (positive response) using dental curing light, thus augmenting the dentist’s visual examination. This clinical study investigated if active caries as assessed by the International Caries Detection and Assessment System (ICDAS) were more likely to have positive LC Rinse response than sound surfaces and inactive caries.Methods25 subjects participated in the study. Caries was assessed on selected teeth and the entire dentition, firstly using ICDAS and then by fluorescence evaluation after LC Rinse application. Data were statistically analyzed using Diagnostic Odds Ratio (OR) and Chi-square test X2 (α = 0.05). Sensitivity (Se), specificity (Sp), and Diagnostic accuracy (DA) were calculated.ResultsWith selected teeth, active caries were 638.6 times (60.05 with full dentition) more likely to have positive LC Rinse response than sound surfaces and inactive caries combined (X2, p < 0.01) and 191.67 times (18.35 with full dentition) than inactive lesions only (X2, p < 0.01). With combined sound surfaces and inactive caries, Se, Sp, and DA of LC Rinse assessment were 0.94, 0.98, and 0.96 respectively.ConclusionsLC Rinse can distinguish between active caries, inactive caries and hypomineralization, and can augment caries detection with high sensitivity, specificity, and diagnostic accuracy.

Development of a ZIF-91-Porous-Liquid-Based Composite Hydrogel Dressing System for Diabetic Wound Healing.

Porous metal-organic framework (MOF) liquids with permanent porosity, good fluidity, and fine dispersion attract broad attention in catalysis, transportation, gas storage, and chemical separations. Yet, the design and synthesis of porous MOF liquids for drug delivery remain less explored. Herein, a simple and general strategy is reported to prepare ZIF-91 porous liquid (ZIF-91-PL) via surface modification and ion exchange. The cationic nature of ZIF-91-PL not only renders it antibacterial but also with high curcumin loading capacity and sustained release. More importantly, the acrylate group on the grafted side chain of ZIF-91-PL makes it feasible to crosslink with modified gelatin through light curing, and the obtained hydrogel shows a significantly improved healing effect on the wound of diabetes. This work demonstrates for the first time, a MOF-based porous liquid for drug delivery, and the further fabrication of composite hydrogel may have potential applications in biomedical science.

Influence of lithium disilicate pretreatment using photodynamic therapy, non-thermal plasma, and laser treatment on surface roughness and bond strength

AimsTo assess the shear bond strength (SBS) and surface roughness (Ra) of lithium disilicate ceramic (LDC) after using different pretreatment methods i.e., Non-Thermal Plasma (NTP), self-etching ceramic primer (SECP), curcumin photosensitizer (CP), Er and Cr: YSGG lasers (ECL) in comparison to hydrofluoric acid + Silane (HF + S). Materials and methodsA total of fifty LDC discs were prepared. All the discs were arbitrarily divided into five groups based on the surface conditioning used (n = 10). Group 1: PDT+S, group 2: HF+ S, group 3: NTP + S, group 4: SECP, and group 5: ECL+ S. A confocal optical microscope was used to calculate Ra for each sample. A self-adhesive resin cement was applied followed by LED light curing. A universal testing machine was used to assess SBS and a stereomicroscope was used to determine the failure mode. Two-way analysis of variance (ANOVA), and a Tukey post hoc test was used to analyze data (p = 0.05). ResultsThe highest bond integrity of resin luting bonded to conditioned LDS ceramics were presented by group 2 (HF+ S) (21.48±1.39 MPa) and lowest by group 1 (CP+S) (13.01±1.19 MPa) respectively. Intergroup comparison analysis revealed that group 1(13.01±1.19 MPa) and group 3 (14.28±0.62 MPa) displayed comparable outcomes of bond integrity(p>0.05). Similarly, it was observed that group 2 (21.48±1.39 MPa) and group 5 (21.31±1.85 MPa) exhibited comparable values of bond strength(p>0.05). Specimens conditioned with HF+ S showed the highest Ra (1445.86±0.019 µm). However, discs treated with SECP exhibited the lowest Ra (0139.76±0.081 µm). ConclusionEr, Cr: YSGG laser retains the ability to be used as an LDC surface conditioner as an alternative to HF+ S.Both the methods of pretreatment results in high surface roughness of LDC.

Effect of Ceramic and Dentin Thicknesses and Type of Resin-Based Luting Agents on Intrapulpal Temperature Changes during Luting of Ceramic Inlays.

The adhesive cementation of ceramic inlays may increase pulpal temperature (PT) and induce pulpal damage due to heat generated by the curing unit and the exothermic reaction of the luting agent (LA). The aim was to measure the PT rise during ceramic inlay cementation by testing different combinations of dentin and ceramic thicknesses and LAs. The PT changes were detected using a thermocouple sensor positioned in the pulp chamber of a mandibular molar. Gradual occlusal reduction obtained dentin thicknesses of 2.5, 2.0, 1.5, and 1.0 mm. Light-cured (LC) and dual-cured (DC) adhesive cements and preheated restorative resin-based composite (RBC) were applied to luting of 2.0, 2.5, 3.0, and 3.5 mm lithium disilicate ceramic blocks. Differential scanning calorimetry was used to compare the thermal conductivity of dentin and ceramic slices. Although ceramic reduced heat delivered by the curing unit, the exothermic reaction of the LAs significantly increased it in each investigated combination (5.4-7.9 °C). Temperature changes were predominantly influenced by dentin thickness followed by LA and ceramic thickness. Thermal conductivity of dentin was 24% lower than that of ceramic, and its thermal capacity was 86% higher. Regardless of the ceramic thickness, adhesive inlay cementation can significantly increase the PT, especially when the remaining dentin thickness is <2 mm.

Effect of polymerization mode on shrinkage kinetics and degree of conversion of dual-curing bulk-fill resin composites

ObjectivesTo assess the behavior of dual-cure and conventional bulk-fill composite materials on real-time linear shrinkage, shrinkage stress, and degree of conversion.Materials and methodsTwo dual-cure bulk-fill materials (Cention, Ivoclar Vivadent (with ion-releasing properties) and Fill-Up!, Coltene) and two conventional bulk-fill composites (Tetric PowerFill, Ivoclar Vivadent; SDR flow + , Dentsply Sirona) were compared to conventional reference materials (Ceram.x Spectra ST (HV), Dentsply Sirona; X-flow; Dentsply Sirona). Light curing was performed for 20 s, or specimens were left to self-cure only. Linear shrinkage, shrinkage stress, and degree of conversion were measured in real time for 4 h (n = 8 per group), and kinetic parameters were determined for shrinkage stress and degree of conversion. Data were statistically analyzed by ANOVA followed by post hoc tests (α = 0.05). Pearson’s analysis was used for correlating linear shrinkage and shrinkage force.ResultsSignificantly higher linear shrinkage and shrinkage stress were found for the low-viscosity materials compared to the high-viscosity materials. No significant difference in degree of conversion was revealed between the polymerization modes of the dual-cure bulk-fill composite Fill-Up!, but the time to achieve maximum polymerization rate was significantly longer for the self-cure mode. Significant differences in degree of conversion were however found between the polymerization modes of the ion-releasing bulk-fill material Cention, which also exhibited the significantly slowest polymerization rate of all materials when chemically cured.ConclusionsWhile some of the parameters tested were found to be consistent across all materials studied, heterogeneity increased for others.Clinical relevanceWith the introduction of new classes of composite materials, predicting the effects of individual parameters on final clinically relevant properties becomes more difficult.

Can We Use Our Dental Curing Lights to Polymerize Objects Produced with 3D Resin Printer?

BACKGROUND&#x0D; Dental treatment objects produced with 3D resin printers barely polymerize after fabrication. They need post-curing and an extra polymerization oven is required. Present study is aimed to determine the effectiveness of dental curing lights for post-curing of objects produced with a 3D resin printer.&#x0D; METHODS&#x0D; Samples were produced with Alias ​​Sharp &amp; Rigid Model 3D Printing Resin in Photon Mono X 3D resin printer. The control set samples were cured with UV light for 2 min in Wash &amp; Cure Plus device. T-20, T-40 and T-60 set samples were exposed to VALO Cordless curing light for 20, 40 and 60 seconds respectively. The hardness was measured with the Shore D Durometer. Then, the samples were subjected to compression. For statistical analysis, one way analysis of variance (ANOVA) and Tukey test was used.&#x0D; RESULTS&#x0D; The set cured with VALO Cordless for 20 seconds showed the highest strength. Compressive strength decreased with prolongation of the curing time. All experimental sets showed significantly higher hardness than the control set. Hardness increased gradually in the 20 and 40 second sets, but the difference between the 40 and 60 second sets was not significant. Also, color change was observed in the experimental sets samples.&#x0D; CONCLUSIONS&#x0D; Dental curing lights are effective in post-curing 3D printer resins.

Effect of Different Cross-Infection Control Barriers on Intensity of Curing Light: An In-Vitro Study

Aim: To evaluate the effect of different cross infection control barriers on the intensity of the curing light. Study Design: In-vitro experimental study. Place and duration: Department of Operative and Pediatric Dentistry, The University of Lahore from January to March 2022. Methodology: The intensity of the light-curing unit was measured using a radiometer. The intensity of light without using any barrier was taken as control. Four barriers were used; polythene glove, latex glove, cling film wrap and standard barrier tape. Ten measurements for each group were performed after placing each type of protection barrier and the average was taken. The data was analyzed using SPSS v 22. Results: The mean value for light intensity without using any barrier was found to be 737.6 mW/cm2. The light intensity was maximum for cling film, polythene glove, barrier tape and latex glove with mean values of 720.6 mW/cm2, 581.2 mW/cm2, 541.7 mW/cm2 and 255.06 mW/cm2 respectively. A comparison of the output values without barrier and with different barriers showed a statistically significant difference with all barriers except cling film. Conclusion: It was found that cling film, polythene glove and barrier tape could serve as a barrier to cover the tip of the light curing unit. Keywords: Dental curing light, cross-infection, composite resin

A three-dimensional actively spreading bone repair material based on cell spheroids can facilitate the preservation of tooth extraction sockets.

Introduction: Achieving a successful reconstruction of alveolar bone morphology still remains a challenge because of the irregularity and complex microenvironment of tooth sockets. Biological materials including hydroxyapatite and collagen, are used for alveolar ridge preservation. However, the healing effect is often unsatisfactory. Methods: Inspired by superwetting biomimetic materials, we constructed a 3D actively-spreading bone repair material. It consisted of photocurable polyether F127 diacrylate hydrogel loaded with mixed spheroids of mesenchymal stem cells (MSCs) and vascular endothelial cells (ECs). Results: Biologically, cells in the spheroids were able to spread and migrate outwards, and possessed both osteogenic and angiogenic potential. Meanwhile, ECs also enhanced osteogenic differentiation of MSCs. Mechanically, the excellent physical properties of F127DA hydrogel ensured that it was able to be injected directly into the tooth socket and stabilized after light curing. In vivo experiments showed that MSC-EC-F127DA system promoted bone repair and preserved the shape of alveolar ridge within a short time duration. Discussion: In conclusion, the novel photocurable injectable MSC-EC-F127DA hydrogel system was able to achieve three-dimensional tissue infiltration, and exhibited much therapeutic potential for complex oral bone defects in the future.

A Scoping Review on the Polymerization of Resin-Matrix Cements Used in Restorative Dentistry.

In dentistry, clinicians mainly use dual-cured or light-cured resin-matrix cements to achieve a proper polymerization of the organic matrix leading to enhanced physical properties of the cement. However, several parameters can affect the polymerization of resin-matrix cements. The main aim of the present study was to perform a scoping review on the degree of conversion (DC) of the organic matrix, the polymerization, and the light transmittance of different resin-matrix cements used in dentistry. A search was performed on PubMed using a combination of the following key terms: degree of conversion, resin cements, light transmittance, polymerization, light curing, and thickness. Articles in the English language published up to November 2022 were selected. The selected studies' results demonstrated that restorative structures with a thickness higher than 1.5 mm decrease the light irradiance towards the resin-matrix cement. A decrease in light transmission provides a low energy absorption through the resin cement leading to a low DC percentage. On the other hand, the highest DC percentages, ranging between 55 and 75%, have been reported for dual-cured resin-matrix cements, although the polymerization mode and exposure time also influence the DC of monomers. Thus, the polymerization of resin-matrix cements can be optimized taking into account different parameters of light-curing, such as adequate light distance, irradiance, exposure time, equipment, and wavelength. Then, optimum physical properties are achieved that provide a long-term clinical performance of the cemented restorative materials.

Analysis and prospect of 3D printing technology research status

The earliest idea of 3D printing can be traced back to the late nineteenth century, and now after nearly two hundred years of development, 3D printing has played an irreplaceable role in various fields. This article introduces several common printing methods, such as Fused Deposition Modeling, light curing, and powder molding, and demonstrates the application of 3D printing in some fields.

Load-bearing composite fracture-fixation devices with tailored fibre placement for toy-breed dogs

Fibre reinforced composites are attractive materials for hard tissue reconstructions, due to the high strength and low flexural modulus. However, lack of contourability in the operation theatre inhibits their clinical applications.The study presents a novel in situ contourable composite implant system for load-bearing conditions. The implant system consists of a thin bioresorbable shell with several cavities, much like bubble-wrap. The central cavity contains a semi-flexible glass fibre preform prepared using Tailored Fibre Placement method. The preform is either pre-impregnated with a light curable resin, or the resin is injected into the cavity during the surgical procedure, followed by light curing. The semi-flexible glass fibre preforms were also examined as separate devices, “miniplates”. Two types of miniplates were scrutinized, a simplified pilot design and a spatially refined, “optimized” design. The optimized miniplates were implemented as biostable and bioresorbable versions.The feasibility of the in situ contourable composite implant system was demonstrated. The potential of Tailored Fibre Placement for the semi-flexible glass fibre preforms and miniplates was confirmed in a series of biomechanical tests. However, structural optimization is required. Antebrachial fractures in toy-breeds of dogs are exemplar veterinary applications of the devices; further applications in veterinary and human patients are foreseen.

Do Different Types of Adhesive Agents Effect Enamel Demineralization for Orthodontic Bonding? An In Vitro Study

(1) Objective: The aim of this study was to compare the demineralization around brackets bonded with different types of adhesive agents in a cariogenic suspension environment. (2) Methods: In the study, 60 extracted upper first premolar teeth were divided into three groups with 20 teeth in each group. In Group 1, Transbond XT Primer + Transbond XT Light Cure Adhesive (3M Unitek, Monrovia, CA, USA), in Group 2, GC Ortho Connect Light Cure Adhesive (GC Crop, Tokyo, Japan) and in Group 3, Transbond™ Plus Self Etching Primer + Transbond XT Light Cure Adhesive (3M Unitek, Monrovia, CA, USA) adhesive agents were used. In Group 1 and 2, buccal enamel surfaces were etched for 30 s, washed for 15 s and dried for 15 s. All groups were bonded with Gemini metal (3M Unitek, Monrovia, CA, USA) brackets. Gingival, occlusal and proximal enamel surfaces of the brackets were measured with a DIAGNOdent pen (KaVo, Biberach, Germany), and demineralization values were recorded. Measurements were performed after bracketing (T0) and after 28 days in a cariogenic environment (T1), which was renewed every 48 h. The Kolmogorov–Smirnov test was used to determine whether or not the data were homogeneously distributed, the Wilcoxon test was used for comparisons within groups, and the Mann–Whitney U and Kruskal–Wallis tests were used for comparisons between groups. (3) Results: In all groups, demineralization values on all enamel surfaces of the brackets were found to be statistically significantly higher in the T1 period than in the T0 period (p &lt; 0.05). In the T1 period, demineralization values of occlusal enamel surfaces in Groups 1 and 2 were found to be significantly higher than in Group 3 (p &lt; 0.05). The amount of increase in occlusal enamel surface demineralization value between T0 and T1 periods in Groups 1 and 2 was significantly higher than in Group 3 (p &lt; 0.05). There was no statistically significant difference in demineralization values of proximal and gingival enamel surfaces between the groups in the T1 period (p &gt; 0.05). (4) Conclusion: Significantly less occlusal enamel surface demineralization was observed in teeth in which the Transbond™ Plus Self Etching Primer adhesive agent was not applied with acid etching.

Printing depth modeling, printing process quantification and quick-decision of printing parameters in micro-vat polymerization

Vat photopolymerization is a widely employed additive manufacturing (AM) technique that commonly applying a digital light processing (DLP) light engine to provide a patterned light source. Notably, printing extreme-size structures is challenging, and the selection of printing parameters was currently highly reliant on repeatable trial-and-error experiments. In this work, a theoretical model for curing depth prediction was established by observing the effect of light intensity. A correction factor n was introduced to optimize the relationship among the critical curing energy, exposure time, and light intensity. Forming experiments verified the accuracy of the proposed theoretical curing depth prediction model, and a correction factor n equal to 0.75 was obtained. Optical rheological characterization experiments and Fourier transform infrared spectroscopy (FTIR) supported the quantitative characterization of the DLP printing process while revealing a stepwise transition during photocuring. Finally, a guidance for quick selection of the optimal curing time for 3D structure was obtained and applied to the high-precision microstructure printing process. High-fidelity microneedle arrays with 12 μm details were printed. This method of rapid selection of printing parameters and printing microstructures with high-precision details can potentially be used in the field of 3D bioprinting.

Comparison of the temperature changes in pulp using monophasic light-emitting diode curing unit at different exposure times: An in vivo study

This invivo study evaluated the temperature changes in the pulp chamber at different exposure times using a monophasic light-emitting diode curing unit. Forty-five patients (aged 13-25 years) requiring extraction of maxillary first premolars for orthodontic reasons were included in the study. After access opening, the temperature rise was recorded when exposed to monophasic light-emitting diode curing light (Elipar 3M ESPE; Pymble, New South Wales, Australia) at 5, 10, 15, and 20 seconds with K-type thermocouple probe. Teeth were atraumatically extracted on the same day. The results were analyzed with an analysis of variance and the Bonferroni test. There was a significant increase of 2.1°C ± 0.5°C of pulpal temperature in the maxillary first premolar tooth during exposure to a light curing unit from baseline to 20 seconds. The mean baseline temperature was 35.7°C ± 0.52°C. The highest mean temperature was recorded at 20 seconds (37.8°C ± 0.57°C), and the lowest mean temperature was recorded at 5 seconds (36.1°C ± 0.61°C). There were significant differences among each group (P<0.001) with a mean increase in pulpal temperature from baseline to exposure mode of 5, 10, 15, and 20 seconds. The study results reveal a statistically significant increase in pulpal temperature with a monophasic curing light, which can be used for up to 20 seconds without causing any detrimental effects on the pulp.

An evaluation of elution of leachable components from composite resins after light curing by light emitting diode and halogen light: An in vitro study.

The purpose of our study was to determine the amount of eluted triethyleneglycol dimethacrylate (TEGDMA) and to compare the eluted TEGDMA in different composite resins after light curing with conventional halogen light curing unit and light emitting diode (LED). The present study was conducted on the two types of composite resins, which were divided equally into four groups - Group I: Denoted as Hybrid-LED, Group II: Denoted as Microhybrid-LED, Group III: Denoted as Hybrid-Halogen Group IV: Denoted as Microhybrid-Halogen. Polymerized specimens of hybrid and microhybrid composite resins were stored in air tight centrifuge tubes at 37°C for 24 h, then extract the monomers in high-performance liquid chromatography (HPLC) grade acetonitrile and water and incubated at 37°C for 24 h. All extracts were analyzed by HPLC. Eluted TEGDMA was detected by ultraviolet detector. The results obtained for TEGDMA were computed and analyzed using the one-way ANOVA and independent samples F-test at significance level 0.05. Elution of TEGDMA from all the samples of Group III (Hybrid-Halogen) was greatest and from Group II (Microhybrid-LED) was lowest. The sequence of TEGDMA elution was Group III > Group I > Group IV > Group II. From our results, we can conclude that the LED light curing unit may be more efficient than standard halogen light curing unit. The extractable quantities of composite resin components should be minimized. Furthermore, all ingredients of a dental composite should be declared by the manufacturers, in order to identify those substances in a product which may cause adverse side effects in patients and dental personnel.