Light-cured Resin Research Articles

Bacterial Adhesion and In Situ Biodegradation of Preheated Resin Composite Used as a Luting Agent for Indirect Restorations.

To evaluate surface roughness and bacterial adhesion after in situ biodegradation of the cementation interface of indirect restorations cemented with preheated resin composite. Resin composite blocks (Z250XT/3M ESPE) were cemented to bovine enamel (7 × 2.5 × 2 mm) using preheated microhybrid resin composites: (1) Filtek Z100 (3M ESPE) (Z100); (2) Gradia Direct X (GC America) (GDX); and (3) Light-cured resin cement RelyX Veneer (3M ESPE) (RXV) (n = 21). The resin composites were preheated on a heating device (HotSet, Technolife) at 69°C for 30 minutes. Disk-shaped specimens (7 x 1.5 mm) were made for biodegradation analysis with the luting agents (n = 25). The in situ phase consisted of 20 volunteers' using an intraoral palatal device for 7 days. Each device had six cylindrical wells for the blocks and the disk-shaped specimens. Biodegradation was evaluated through surface roughness (Ra), scanning electron microscopy (SEM) micromorphological analysis, and colony-forming unit (CFU) count. The film thickness of the luting agents was also measured under stereomicroscopy. Increased surface roughness was observed after the cariogenic challenge without differences between the luting agents. Higher variation and surface flaws suggestive of particulate detachment were observed for Z100. No differences were observed in CFU counts. All materials underwent surface biodegradation, and the surface roughness of the resin cements was similar to or lower than that of the preheated resin composites. The resin composites' film thickness was thicker than that of the resin cement. Clinicians should be aware of these factors when choosing the use of preheated resin composite since it can lead to reduced longevity of the cementation interface and, therefore, restorations.

Impact of Battery Levels of a Cordless LED Curing Unit on Resin Cement under Varied Lithium Disilicate Thicknesses and Translucencies.

This study aimed to evaluate the impact of battery levels on the emission of a multi-peak cordless LED light-curing unit (LCU) and the effect on the degree of conversion (DC) and Knoop hardness (KH) of a light-cure resin luting agent activated through varying lithium disilicate (LiS2) ceramic thicknesses and translucencies. High and low translucency LiS2 discs (IPS e.max Press HT and LT, respectively; shade A1) with thickness of 0.5, 1.0, 1.5, and 2.0 mm were fabricated. Resin luting agent specimens (Variolink Esthetic LC) were prepared and cured using a Bluephase G2 LCU at different battery levels (100%, 50%, and 10%) through the LiS2 ceramics. The transmitted irradiance was evaluated using USB4000 MARC, while FTIR and a microhardness tester assessed DC and KH, respectively. After ensuring homoscedasticity, the data wee analyzed using analysis of variance and Tukey HSD test (α=0.05). The study found strong positive correlations between battery levels and irradiance, particularly with no ceramic interposition and through HT ceramics (R2=0.9471), although this correlation diminished with thicker HT (R2=0.7907) and LT ceramics (R2<0.2980). Both battery levels and ceramic thickness significantly influenced transmitted irradiance (p<0.0001), resulting in lower values with decreased battery levels and increased ceramic thicknesses (p<0.0001). LT ceramics showed lower transmittance than HT. DC was significantly affected by both battery levels and ceramic thicknesses, with generally lower DC values except for LT ceramics at a 10% battery level (p<0.0001). No significant differences in DC were observed between HT and LT translucencies (p=0.548). KH was higher in HT than LT ceramics at 100% and 50% battery levels, with thicker ceramics showing lower KH values at 10% battery level (p<0.0001). Conclusion: Reduced battery levels in cordless LED curing units significantly affect the irradiance, degree of conversion, and hardness of light-curable resin luting agents. Maintaining battery levels above 50% is recommended for optimal performance. Thicker and more opaque ceramics significantly impacted incident irradiance. However, preserving radiant energy could potentially mitigate these limitations.

Clinical study of pit and fissure sealant combined with light-cured flowable resin in prevention of dental caries in children.

Clinical study of pit and fissure sealant combined with light-cured flowable resin in prevention of dental caries in children.

Influence of Polymerization Protocol on Adhesion and Proliferation of Streptococcus mutans on Three Dental Composite Resins.

Background/Objectives: The aim of this in vitro study was to analyze and compare the Streptococcus mutans ability to adhere and form biofilm on the surface of light-cured VS heat-cured dental composite resins; Methods: Three composite resins with different chemical formulations were selected: GrandioSO (GR), Venus Diamond (VD) and Enamel Plus Hri Biofunction (BF). Disk-shaped specimens were manufactured by light-curing the composite resins (light-cured subgroups) and subjecting them to a further heat-curing cycle at 80° for 10 min (heat-cured subgroups). Specimens were analyzed for planktonic CFU count (CFU/mL), sessile CFU count (CFU/mL) and for biomass quantification (OD570nm); Results: The planktonic CFU count was higher in all the light-cured subgroups than in the heat-cured subgroups (light-cured: GR = 7.23 × 106, VD = 2.14 × 107, BF = 4.40 × 107; heat-cured: GR = 4.89 × 106, VD = 4.95 × 106, BF = 2.80 × 107), with a statistically significant increase for BF and VD. Focusing on the sessile CFUs, both GR (light-cured = 7.49 × 106; heat-cured = 3.97 × 106) and VD (light-cured = 2.93 × 107; heat-cured = 6.07 × 106) showed a significantly increased number of colonies in the light-cured subgroups. The OD570nm values recorded for the light-cured BF subgroup (0.4280) were significantly increased compared to the heat-cured BF subgroup (0.1931); Conclusions: A more complete polymerization protocol seems to lead to a potential reduction in the risk of secondary caries.

Effect of preparation design on fracture resistance of molars restored with occlusal veneers of different CAD-CAM materials: an in vitro study

BackgroundOcclusal veneer had been evaluated for mechanical properties using lithium disillicate. However, studies evaluating the mechanical properties of occlusal veneer with different preparation designs and ceramic materials are lacking. So, this in vitro study aimed to evaluate the fracture resistance of occlusal veneers with two designs fabricated from two different ceramic materials.Material and methodsFourty mandibular third molars were distributed to 2 groups (n = 20) according to preparation design: group (O) anatomical occlusal reduction and group (OA) anatomical occlusal and 1 mm axial reduction. Each group was additionally subdivided into two subgroups (n = 10) according to ceramic materials; in subgroup X, lithium disilicate (e.max CAD, Ivoclar AG, Schaan, Liechtenstein) was used, and in subgroup S, zirconia-reinforced lithium silicate (ZLS) (Vita Suprinity, VitaZahnfabrik, Bad Säckingen, Germany) was used. All specimens were cemented with a light-cure resin cement (Choice 2, Bisco, Schaumburg, USA). 5000 thermocycles were applied to all specimens with both temperatures of 5 °C and 55 °C in two water baths; the dwell time was 30s at each bath, and the transfer time was 10s. Then all specimens were subjected to a fatigue simulation under dynamic loading of 200 N for 250,000 cycles. A universal testing machine (5500R/1123, Instron, Norwood, USA) was used to evaluate the fracture strength with a crosshead speed of 1 mm/min. All data were analyzed statistically by using a two-way ANOVA, and for some violations of assumptions, these results were compared with those obtained by the nonparametric test (Scheirer Ray Hare) (α = 0.05).ResultsA statistically significantly higher fracture resistance in the ‘OA’ (3389 N) compared to the ‘O’ (2787 N) group regardless of the ceramic material (P < .001) and a statistically significantly higher fracture resistance in the ‘X’ (3295 N) compared to the ‘S’ (2881 N) regardless of the preparation design (P = .015).ConclusionsFor occlusal veneers, all preparation designs and materials (such as Vita Suprinity and e.max CAD) had clinically acceptable fracture resistance values that were greater than the maximal biting forces. On the other hand, the e.max CAD with occlusal veneer, including axial reduction design, demonstrated the maximum fracture resistance value. Finally, no relationship between fracture strength and mode of failure was found.

An Advanced Surface Treatment Technique for Coating Three-Dimensional-Printed Polyamide 12 by Hydroxyapatite

Polymer 3D printing has is used in a wide range of applications in the medical field. Polyamide 12 (PA12) is a versatile synthetic polymer that has been used to reconstruct bony defects. Coating its surface with calcium phosphate compounds, such as hydroxyapatite (HA), could enhance its bonding with bone. The aim of this study was to coat 3D-printed polyamide 12 specimens with hydroxyapatite by a simple innovative surface treatment using light-cured resin cement. Polyamide 12 powder was printed by selective laser sintering to produce 80 disc-shaped specimens (15 mm diameter × 1.5 mm thickness). The specimens were divided randomly into two main groups: (1) control group (untreated), where the surface of the specimens was left without any modifications; (2) treated group, where the surface of the specimens was coated with hydroxyapatite by a new method using a light-cured dental cement. The coated specimens were characterised by both Fourier transform infrared spectroscopy (FTIR) and Transmission Electron Microscopy (TEM), (n = 10/test). The control and treated groups were further randomly subdivided into two subgroups according to the immersion in phosphate-buffered saline (PBS). The first subgroup was not immersed in PBS and was left as 3D-printed, while the second subgroup was immersed in PBS for 15 days (n = 10/subgroup). The surfaces of the control and treated specimens were examined using an environmental scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDXA) before and after immersion in PBS. Following the standard American Society for Testing and Materials (ASTM D3359), a cross-cut adhesion test was performed. The results of the FTIR spectroscopy of the coated specimens were confirmed the HA bands. The TEM micrograph revealed agglomerated particles in the coat. The SEM micrographs of the control 3D-printed polyamide 12 specimens illustrated the sintered 3D-printed particles with minimal porosity. Their EDXA revealed the presence of carbon, nitrogen, and oxygen as atomic%: 52.1, 23.8, 24.1 respectively. After immersion in PBS, there were no major changes in the control specimens as detected by SEM and EDXA. The microstructure of the coated specimens showed deposited clusters of calcium and phosphorus on the surface, in addition to carbon, nitrogen, and oxygen, with atomic%: 9.5, 5.9, 7.2, 30.9, and 46.5, respectively. This coat was stable after immersion, as observed by SEM and EDXA. The coat adhesion test demonstrated a stable coat with just a few loose coating flakes (area removed &lt;5%) on the surface of the HA-coated specimens. It could be concluded that the 3D-printed polyamide 12 could be coated with hydroxyapatite using light-cured resin cement.

In vitro evaluation of the effect of two pediatric syrups on the microhardness and surface roughness of restoration materials.

The prolonged use of pediatric syrups without adequate control of oral hygiene can cause effects on the physical characteristics of the restoration materials, which in turn can cause deterioration of the material and subsequent carious recurrence. Aim: To evaluate the effect of two long-term use syrups in children on the microhardness and surface roughness of three restorative materials. Three study groups were formed, consisting of a conventional self-curing ionomer cement, a light-curing ionomer cement, and a light-curing composite resin. Each group had 40 specimens made with the respective restorative material; in addition, these were distributed in 2 subgroups with 20 specimens each, which were immersed in Paracetamol and Ferrous Sulfate in syrup following a protocol that consisted of 2 minutes each day for 28 days. Over time (0, 7, 14, 21, and 28 days), when evaluating microhardness, the composite resin subgroup exposed to ferrous sulfate (p = 0.027) and the Ketac Molar ionomeric cement subgroup (p = 0.002) exposed to Paracetamol showed statistically significant differences; while, when evaluating surface roughness, the composite resin subgroups (p = 0.032) and Ketac Molar ionomeric cement (p = 0.01) exposed to ferrous sulfate showed a statistically significant difference. The more days of exposure to ferrous sulphate syrup, the less the microhardness of the composite resin decreases; something similar occurs with the microhardness of Ketac Molar ionomeric cement when exposed to Paracetamol syrup. Meanwhile, the surface roughness of the composite resin and Ketac Molar ionomeric cement increases considerably when exposed to ferrous sulphate. Key words:Ionomeric cement, Microhardness, Composite resins, Surface roughness.

Flowable composite as an alternative to adhesive resin cement in bonding hybrid CAD/CAM materials: in-vitro study of micro-shear bond strength

ObjectiveTo assess the micro-shear bond strength of light-cured adhesive resin cement compared to flowable composite to hybrid CAD/CAM ceramics.Materials and methodsRectangular discs were obtained from polymer-infiltrated (Vita Enamic; VE) and nano-hybrid resin-matrix (Voco Grandio; GR) ceramic blocks and randomly divided according to the luting agent; light-cured resin cement (Calibra Veneer; C) and flowable composite (Neo Spectra ST flow; F), resulting in four subgroups; VE-C, VE-F, GR-C and GR-F. Substrates received micro-cylinders of the tested luting agents (n = 16). After water storage, specimens were tested for micro-shear bond strength (µSBS) using a universal testing machine at 0.5 mm/min cross-head speed until failure and failure modes were determined. After testing for normality, quantitative data were expressed as mean and standard deviation, whereas, qualitative data were expressed as percentages. Quantitative data were statistically analysed using Student t test at a level of significance (P ≤ 0.05).ResultsGroup GR-F showed the highest µSBS, followed by VE-C, VE-F and GR-C respectively, although statistically insignificant. All groups showed mixed and adhesive failure modes, where VE-F and GR-C showed the highest mixed failures followed by GR-C and VE-C respectively.ConclusionsAfter short-term aging, flowable composite and light-cured resin cement showed high comparable bond strength when cementing VE and GR.

5-Year clinical performance of ceramic onlay and overlay restorations luted with light-cured composite resin

ObjectivesThis prospective clinical trial evaluated the clinical performance of ceramic partial coverage indirect adhesive restorations (PCIARs) in posterior teeth luted with a light-cured composite resin. MethodsFrom April 2016 to January 2017, a total of 60 patients (27 males, 33 females; mean age: 42.2 ± 10.86 years old) received 83 glass-ceramic PCIARs (26 onlay, 57 overlay) made of IPS Emax CAD (Ivoclar Vivadent). All restorations were luted with a light-cured composite resin (Filtek Z250, 3 M ESPE) by two operators. Two independent calibrated examiners blinded to the operators performing the treatment evaluated the restorations at baseline, 1-year, and 5-year following FDI World Dental Federation criteria including esthetic, functional, and biological properties. Data were analyzed with the Friedman test and the Wilcoxon sign test (p < 0.05). ResultsNone of the restorations failed due to fracture or retention loss. One restoration was clinically unsatisfactory because of secondary caries. Marginal staining (p:0.000), marginal adaptation (p:0.018) showed significant differences between 1-year and 5-year recall. ConclusionsThe PCIARs demonstrated excellent clinical performance at 1-year period. The degradation parameters appeared as minor staining and minor irregularities after 5-year, without any affect on the clinical performance. Clinical SignificanceOur findings provide evidence that the clinical performance of PCIARs luted with a light-cured composite resin was clinically acceptable after a five-year evaluation period. Due to secondary caries, only one restoration was considered clinically unsatisfactory. ClinicalTrials registration number: NCT04838483

Physical properties of experimental light-curing pattern resins based on poly (n-butyl methacrylate) or poly(iso-butyl methacrylate).

Experimental light-curing pattern resins were fabricated to produce pattern resin materials with adequate dimensional stability. The light-curing pattern resins consisted of poly(n-butyl methacrylate) or poly(iso-butyl methacrylate) (PiBMA) polymers and methacrylate monomers. The physical properties, amount of residual ash after burning, Vickers hardness, flexural strength, and volumetric polymerization shrinkage of each material were determined. The data obtained for the prepared resins were compared with those of a commercially available pattern resin, Palavit G (PG). A lower amount of residual ash was observed for some of the prepared resins than for PG. The Vickers hardness and flexural strength values of all experimental resins were lower than those of PG. The volumetric polymerization shrinkage of all the experimental resins based on PiBMA was lower than that of PG. These results suggest that acrylic light-curing resin materials based on PiBMA may be useful for patterning and indexing during soldering.

Full Digital Workflow for Aesthetic Rehabilitation of the Upper Teeth: A Case Report

The present case report presents a digital workflow for designing an aesthetic rehabilitation of the upper anterior teeth in an adult male. The patient suffered from a gummy smile resulting from an unfavorable ratio between upper lip length and gingiva/tooth display. In addition, the tooth shapes, color, and position were not accepted by the patient. The treatment planning included gingivectomy based on a digitally designed PMMA guide performed using a soft tissue SOGA laser (Shenzhen Soga Technology Co., Ltd., Shenzhen, China). The preparation was guided by the plastic guides for preparation control created digitally in Exocad software (Rijeka 3.1. Darmstadt, Germany) and printed in three-dimensional plastic. Next, both arches and maximum intercuspation were scanned. The milled lithium disilicate veneers were manufactured using CAD-computer-aided manufacturing (CAM) equipment. The restorations were cemented using a translucent light-cure resin cement (RelyX Universal, 3M ESPE, St. Paul, MN, USA). Next, occlusion adjustment and polishing were executed. Based on the present case report, it can be assumed that the application of digital techniques allows us to achieve an aesthetic and functional result with reduced work time and errors. Emphasizing the clinical impact, these methods enhance patient satisfaction and treatment accuracy in intricate aesthetic rehabilitations.

The effect of photoinitiator type and filler load on physicochemical and mechanical properties of experimental light-cured resin cements through lithium disilicate ceramics of different shades and thicknesses

ObjectiveThis study investigated the influence of photoinitiator types on degree of conversion (DC), rate of polymerization (RP), flexural strength (FS), flexural modulus (FM), and light transmittance (LT) of filled and unfilled light-curable resin cements through different thicknesses and shades of lithium disilicate ceramics. MethodsLithium disilicate ceramic discs (IPS Emax Press, background [0.0], 0.5, 1.0, 2.0, 3.0, and 4.0 mm, shades A1 and BL3) were prepared. Experimental resin-based cements [TEGDMA/BisGMA (50/50 mass%)] were prepared using either camphorquinone (CQ)/amine (0.44/1.85 mol%) or TPO (0.44 mol%)], and a micro and nanofiller loads of nil (unfilled); 40/10 mass%; and 50/10 mass%). Resin cements (0.2 mm thick) were placed on the lower surface of the ceramic specimens and light-activated for 30 s from the upper surface using a Bluephase Style curing light (exitance at tip: 1236 mW/cm2 ± 1.20). LT and distribution of irradiance through the ceramics were measured using a UV–vis spectrometer and a beam profile camera, respectively (n = 3). The DC and RP were measured in real-time using mid infrared spectroscopy in attenuated total reflectance (ATR) mode (n = 3). FS and FM were measured using a universal testing machine (n = 5). Statistical analyses were performed on LT, DC, RP, FS, and FM data using a general linear model, and supplementary ANOVA and post hoc Tukey multiple comparison test were also performed (α = .05). ResultsThicknesses, shades, photoinitiator type, and fillers load significantly influenced the optical and mechanical characteristics of the resin-based materials (p < 0.05). The BL3 shade ceramic provided higher values of DC, RP, FS, FM, and LT compared with the A1 shade (p < 0.05). Increasing ceramic thickness decreased the properties of the resin-based materials (p < 0.05). Generally, TPO improved mechanical properties of the resin cement compared with CQ (p < 0.05). SignificanceThe luting process of indirect restorations may be improved by using high molar absorptivity, more reactive, and more efficient photoinitiators such as TPO, as opposed to conventional CQ. The use of such initiator may allow the placement of thicker and more opaque indirect restorations.

A tricalcium phosphate (TCP) and hydroxyapatite (HA) based light-cured biomaterial for vital pulp therapy

Evaluate a new light-cured material with better properties for vital pulp therapy. Light-cured resin materials consisted of polyethylene glycol (600) diacrylate mixed with different ratios of TCP to HA. In addition to the temperature change (n=5 for each subgroup) were tested, cell viability and Alizarin Red Staining (ARS) assay were also tested in vitro on human dental pulp cells (n=6 for each subgroup). Lastly, the material was then compared with Biodentine and control groups in the molars of Wistar rats in vivo for histology assessment. The temperature change for the new materials were under 5 degrees Celsius. For the in vitro assessments, there was no significant difference on day 3 and day 7 for cell viability test. ARS assay showed significantly higher mineralized nodule formation when treated without induction medium for Group D and Biodentine on day 10 compared to Group C and control. On the contrary, Biodentine and control groups treated with induction medium showed significant higher mineralization than the new materials. Histology assessments demonstrated higher mineralized content in Group D and Biodentine on week 3 and week 6. The inflammatory cells in the dental pulp complex of the Biodentine group resolved on week 6 while the inflammation resolved in Group D on week 3. The new material exhibits low heat production, low cytotoxicity, and good calcium ion release capability. Compared to traditional materials, it has shorter setting time and better aesthetic outcomes, making it highly suitable for use in vital pulp therapy.

A Questionnaire-based Study on Impression Materials and Techniques for Complete Denture Construction among Dentists Practicing in Central/Western Regions of Libya

Background: The success of complete dentures mainly depends on impression-making accuracy; thus, dentists need to select the proper impression materials and techniques to achieve optimal outcomes. Objective: To determine the favoured impression materials and techniques used for complete denture construction among dentists practicing in the Central/Western regions of Libya. Materials and Methods: This study was conducted between July 2023 and September 2023. The questionnaire was comprised of 30 questions, which were divided into two parts including; 11 questions for demographic and professional attitude and 19 questions focused on professional steps of complete denture fabrication for edentulous patients. Results: The response rate for this questionnaire was (66%). It was revealed that (96.1%) of respondents used only irreversible hydrocolloid (alginate) as an ideal option for primary impressions. In response to the same question for final impressions, (45.8%) of participants exhibited that polyvinylsiloxane was the favourite choice. Regarding custom trays, (41.7%) of practitioners preferred using light-cured acrylic resin as a custom tray to take definitive impressions. (87.4%) of prosthodontists border molded the custom tray in sections by (81.9%), using modelling plastic impression compound by (92.1%). The most used philosophy for final impression making was the mucostatic impression technique by (50.4%), while (37.0%) used selective pressure and (12.6%) selected muco-compressive. Implant-supported overdenture was discussed as an alternative treatment by (65.4%). The obtained data was statistically analyzed using SPSS 28. Conclusion: This study reflects a diversity of opinion among Libyan dentists during the construction of complete dentures. The most commonly used material for primary impression was irreversible hydrocolloid (alginate) and for final impression was polyvinylsiloxane, which coincides with professional practices worldwide. Modelling plastic impression compound was the most preferred material for border molding. The mucostatic technique was the predominantly used impression philosophy for final impression making.

Performance of two laser motion modes versus conventional orthodontic ceramic brackets debonding technique on enamel surface topography.

The risk of enamel deterioration that frequently coexists with debonding of orthodontic teeth brackets elevates the mandate for finding an optimum approach for debonding them without harmful effects. This in-vitro study is intended to compare the effects of two different laser modes (scanning and circular) and a conventional method on the enamel surface after debonding orthodontic brackets. 66 extracted premolars were assigned into 3 groups. After that, light-cure composite resin was used to attach the ceramic brackets to the teeth. Amongst the test groups, Group I: specimens that were debonded using conventional debonding using pliers; Group 2: specimens that were debonded using Er, Cr: YSGG laser applications using the circular motion method; and Group 3: specimens that were debonded using Er, Cr: YSGG laser applications using the scanning motion method. Adhesive Remnant Index (ARI) assessment, intra-pulpal temperature increase, enamel surface roughness after polishing, and assessment of the microstructure of enamel were carried out with scanning electron microscopy. The gathered information was examined statistically. The conventional debonding method had a significantly higher proportion of adhesive remnant index (ARI) scores of 2 and 3 in comparison to the circular (p < .004) and scanning laser groups (p < .001). There was no significant difference in ARI scores between the circular and scanning laser groups (p > .05). Moreover, the circular and scanning laser debonding methods resulted in a significantly higher proportion of Enamel Surface Roughness (ESR) scores of 0 and a lower proportion of ESR scores of 3 compared to the conventional technique group (p < .001). However, there was no significant difference in ESR scores between the circular and scanning laser methods (p = .945). Lastly, the average intra-pulpal temperature was significantly higher in the circular laser group (1.9 ± 0.5 ) compared to the scanning laser group (0.9 ± 0.2) with p < .001. Er, Cr: YSGG laser irradiation is a tool that shows promise for debonding ceramic brackets with minimal harm to the enamel surface. The scanning laser technique is more desirable due to the lower intra-pulpal temperature increase.

Characterization of dental light-curing resin composites incorporating multiple modified low-shrink monomers

ObjectivePolymerization shrinkage poses a significant challenge in dental resin composites. The objective of this study is to introduce spiroorthocarbonate monomer 3,9-dimethylene-1,3,5,7-tetraoxa-spiro[5,5]undecane (BMSOC) and epoxy resin monomer 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (ECHM-ECHC) into bisphenol-S-bis(3-methacrylato-2-hydroxy propyl)ether (BisS-GMA) based resin composites to develop composites with reduced shrinkage properties. MethodsBMSOC and BisS-GMA were synthesized and thoroughly mixed with ECHM-ECHC, followed by inorganic fillers and photoinitiators. Based on the composition of the resin matrix, five groups of experimental composites were prepared, with traditional bisphenol A-dimethacrylate glycidyl ester (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) based composite serving as the control. The polymerization properties, including degree of conversion (DC) and polymerization shrinkage (PS), as well as marginal microleakage, wettability, flexural strength (FS), flexural modulus (FM), and biocompatibility were evaluated. ResultsThe results demonstrated that compared with the control group, the PS of BisS-GMA based composites containing BMSOC and ECHM-ECHC were significantly reduced (P < 0.05), and the lowest PS (0.96 ± 0.08 %) was observed when the ratio of BisS-GMA: (Epoxy + BMSOC) was 4:6. Additionally, the experimental composites also exhibited improved DC, minimal microleakage, low hydrophilicity, enhanced mechanical properties, qualified in vivo biocompatibility, and slight/moderate in vitro biocompatibility. SignificanceThe resin composites incorporating multiple modified low-shrink monomers are promising for dental applications to prevent various clinical problems caused by PS and extend restoration longevity.

A study of mechanical properties of photosensitive resins used in vat photopolymerization process

In recent years, the rapid advancement of Additive Manufacturing (AM) technology has led to resource-efficient processes and reduced gaps between design and product/prototypes. Particularly, sectors like medicine and dentistry stand to gain from these advancements if materials with suitable mechanical characteristics for clinical use are available. One such evolving AM process is VAT photopolymerization through LCD 3D Printer technology, characterized by the curing of photosensitive polymeric resins. This study aims to assess the impact of the angle of layer photopolymerization of UV resin in three positions (horizontal, vertical, and inclined at 45°) using a cost-effective LCD 3D Printer. Additionally, specimens, distributed across five positions on the printing platform, underwent testing with three types of UV light-curing resin. Mechanical properties, including tensile stress, elasticity modulus, and hardness, were evaluated and analyzed statistically. Results indicate that both the chosen manufacturing platform position and the inclined layer angle significantly influence the final characteristics of the workpiece.

Hydrated Calcium Silicate in Resin Composites for Prevention of Secondary Caries

Introduction and aimsThe gaps at the margins of restorative composite resin can increase as the carious process occurs underneath the materials, causing further demineralization along the tooth cavity wall. The aim of this study was to evaluate the effects of restorative resin composite containing hydrated calcium silicate (hCS) filler on enamel protection against demineralization by simulating microleakage between the test material and teeth in a cariogenic environment. MethodsThe experimental resin composites were composed of 70 wt.% filler, which was mixed with a glass filler and hCS in a weight ratio of 70.0% glass (hCS 0), 17.5% hCS + 52.5% glass (hCS 17.5), 35.0% hCS + 35.0% glass (hCS 35.0), and 52.5% hCS + 17.5% glass (hCS 52.5). A light-cured experimental resin composite disk was positioned over a polished bovine enamel disk, separated by a 30-µm gap, and immersed in artificial saliva with pH 4.0 for 15, 30, and 60 days. After the immersion period, the enamel disk was separated from the resin composite disk and evaluated using a microhardness tester, atomic force microscopy, and polarized light microscopy. The opposing sides of the enamel and resin composite disks were observed using scanning electron microscopy/energy dispersive X-ray spectrometry. ResultsThe enamel surface showed a significant increase in microhardness, decreased roughness, and remineralization layer as the proportion of hCS increased (P < .05). In the scanning electron microscopy image, the enamel surface with hCS 35.0 and 52.5 after all experimental immersion periods, showed a pattern similar to that of a sound tooth. ConclusionsThe results demonstrated that increasing the hCS filler level of restorative resin composites significantly decreased enamel demineralization. Clinical relevanceHydrated calcium silicate laced restorative resin composites may be a promising dental biomaterial for protecting teeth against demineralization and preventing secondary caries around restorations.

Effect of computer-aided design/computer-aided manufacturing bleach shade ceramic thickness on its light transmittance and microhardness of light-cured resin cement

Effect of computer-aided design/computer-aided manufacturing bleach shade ceramic thickness on its light transmittance and microhardness of light-cured resin cement

An assessment of Brazilian dentists' knowledge about tooth fragment reattachment: A cross-sectional study.

Crown fractures are common traumatic dental injuries and tooth fragment reattachment is a viable option for restoring a fractured tooth. The aim of this study was to assess the knowledge and experience of dentists in the Federal District regarding the tooth fragment reattachment technique for enamel and dentin fractures. For the cross-sectional observational study, an electronic form was designed with objective and self-report questions for dentists. The data were analyzed using descriptive statistics, with their absolute and relative frequencies. For the analysis of categorical variables, the nonparametric chi-squared or Fisher exact association tests were used in the statistical software R (version 4.2.1). A total of 416 dentists participated in the study (58.9% female and 41.1% male). Of these, 70% declared they knew about fragment reattachment, but only 42.3% reported previous experience with this procedure. The most common storage medium used for the fractured fragment was milk (78.1%), and the bonding material used for reattachment was light-cured composite resin (86.3%). A majority (66.3%) reported that for a patient with enamel and dentin fracture, with the crown fragment in good condition, they would choose to do the reattachment. Dentists demonstrated that they had adequate knowledge about the tooth fragment technique, although many did not have previous experience with this procedure.