The use of photo-curable resin composite restorations is an essential treatment modality in modern dental practice. The success and longevity of these restorations depend on achieving predictable and effective polymerization. Understanding the dynamics of the polymerization and the effect of light cure units (LCUs) on this process is paramount. The goal of this concise narrative review is to provide a simplified presentation of basic principles of composite chemistry, polymerization reactions, and photo-curing with relevant terminologies. Clinical guidelines for choosing and maintaining LCUs, as well as safety precautions and factors under the control of the clinician are listed. Finally, clinical recommendations of LCUs’ usage and monitoring are included to aid practitioners in achieving predictable polymerization during the placement of direct resin composite restorations.

Bulk-fill (BF) dental resin composites are made to be polymerized in increments of up to 5 mm rather than the 2 mm increment recommended for conventional composites. This project aimed to determine microhardness (MH) profiles of BF resin composites at different depths and varying light cure (LC) distances from the light source in an attempt to mimic varying clinical situations. Forty-eight cylindrical specimens (4 mm diameter and 6 mm height) were prepared from 3 BF composites: Tetric N-Ceram Bulk-Fill (TBF), Filtek One Bulk-Fill (FBF), and Sonic-Fill 2 (SF2). Four different distances (0, 2, 4, and 6 mm) from the LC unit were investigated. Vickers MH was measured at the top and bottom of the samples and at every 1 mm, by creating 3 indentations at each depth. The bottom-top microhardness ratio (MHR) and percentage reduction in MHR were also measured. Data was analyzed using mixed-model repeated-measure ANOVA at 0.05 significance level. The main variables effects “material, LC distance, and depth” were significant (p < 0.001). Increasing LC distance and the depth of the tested BF significantly affected Vickers MH and MHR. None of the tested BF materials had sufficient MHR at the depths of 4–6 mm. SF2 showed the least MHR reduction.

Aims: This work aims to assess the flexural strength and depth of cure of Optishade, Omnichroma and Z350 dental resin composites. Study Design: Experimental Laboratory Study. Methods: To assess flexural strength as per ISO standards, 15 samples of each of the three materials were made (n=5) with the dimensions 25x2x2 mm. They were then subjected to 3 point bending testing on a universal testing machine. To assess depth of cure as per ISO standard, 15 cylindrical samples 4 mm in diameter and 6 mm in height were created (n=5) and scraping test was performed. Results: There was a significant difference between the 3 materials in both flexural strength and depth of cure. Z350 had the lowest depth of cure and the highest flexural strength. Conclusion: Within the limitations of this study, all three tested materials fell within the ISO requirementsfor dental resin compositesfor both flexural strength and depth of cure.

Introduction: With the increase in aesthetic requirements, more people are requesting tooth coloured fillings. An anterior restoration is deemed unacceptable if its color changes significantly. Aim: To assess the colour stability of a single shade, a group shade and a nano fill dental resin composite which comes in multiple shades. Materials and Methods: This in-vitro study was conducted in the month of August 2021 at the Advanced Technology Dental Research Laboratory at the King Abdul Aziz University, Jeddah,Western region, Saudi Arabia. Three composites were tested; a single shade (Omnichroma), a group shade (Optishade light (OL) and Optishade Medium (OM)) and a conventional nano fill (Z350) 40 cylindrical discs (10 mm in diameter and 2 mm in depth) were fabricated in total. Each material and shade to be tested had 10 samples per group (n=10). The materials were aged in a thermocycler for 5000 cycles then stained with either green tea or coffee for six days. Upon completion of the staining protocol, they were then polished with soflex diamond polishing system. Colour measurements were taken at each stage, calculated and compared. Mixed model repeated Analysis Of Variance (ANOVA) was performed to determine significance of the color change (ΔE00) between materials and treatments and Bonferroni test was used for multiple comparison between groups. Results: The effect of ageing varied according to individual material; Z350 had lower ΔE00 when compared to other materials. After staining with tea, it was found that Z350 and Omnichroma exhibited a significant change (p<0.05) in ΔE00 when compared to OL. Polishing improved the ΔE00 in all the materials. All green tea-stained materials with the exception of omnichroma returned to a clinically acceptable E00 after polishing. After polishing coffee stained samples, OL and OM remained above the clinically acceptable threshold while Z350 and omnichroma were returned to a clinically acceptable level. Conclusion: All the materials showed a change in ΔE00 after ageing, with OM and Z350 being the only materials to exhibit a clinically acceptable change. While polishing decreased ΔE00 in all the materials, it did not return them all to a clinically acceptable level. Thus, polishing helps improve the appearance of stained restorations but may not be enough to completely remove stains, even in newly introduced direct aesthetic dental materials.

The field of dentistry is consistently innovating with the introduction of novel hybrid and polymer materials for computer-aided design and manufacturing (CAD/CAM). It is noteworthy that the temperature within the oral cavity has a significant impact on the strength of new biomaterials utilized for CAD/CAM fabrication of fixed partial dentures (FPDs). Studies have demonstrated that alterations in intraoral temperature may significantly affect the longevity and durability of dental restorative materials. This study aimed to evaluate the flexural strength, flexural modulus, and effect of thermal aging on CAD/CAM restorative materials. Five CAD/CAM materials were investigated: nano-ceramic-hybrid (GR), polymer-infiltrated-ceramic-network (VE), polyether-ether-ketone (PK), fiberglass-reinforced epoxy-resin (CT), and Feldspar Ceramic (VB). A total of 100 bar-shaped specimens were prepared (N = 20). Each group was subdivided into thermocycling (TC) and no-thermocycling (NTC) subgroups (n = 10). All the specimens underwent a 3-point bending test. The mean flexural strengths and moduli were statistically analyzed using paired t-test, analysis of variance (ANOVA), and Bonferroni pair-wise comparison (p < 0.05). Significant differences were observed in the flexural strength (FS) and modulus (E) between the materials (p < 0.001). GR had the highest FS among tested hybrid materials. NTC CT had the highest FS (924.88 ± 120.1 MPa), followed by GR (385.13 ± 90.73 MPa), then PK (309.56 ± 46.84 MPa). The FS of brittle ceramic VB was the lowest (p < 0.001), but similar to that of PICN VE. Only resin-containing VE and CT significantly decreased in E after thermocycling (p < 0.01, p = 0.013), showing the softening effect of thermocycling on their resin matrix. It can be concluded that new hybrid materials (GR) had higher flexural strength than feldspar ceramic and other resin/polymeric CAD/CAM materials. Polymeric PEEK and GR hybrid materials were resistant to significant deleterious effects of TC. Therefore, they would be appropriate for situations with a higher stress load.

Background: This study aims to compare the compressive strength and microhardness of four tooth-colored restorative materials: bulk fill glass hybrid (GH), resin-modified glass ionomer (RMGIC), conventional glass ionomer (CGIC), and resin-based composite (RBC). Methods: Stainless steel molds were used to prepare 20 specimens for each material. Half of the specimens were subjected to 10,000 thermal cycles; the materials were subjected to compressive strength and microhardness tests. Mean values were statistically compared using a one-way ANOVA Test and Bonferroni pairwise comparisons. Results: GH (147.03 ± 20.19 MPa) had lower compressive strength than RBC (264.82 ± 30.95 MPa) but showed no significant difference with CGIC (130.19 ± 30.38 MPa) and RMGIC (183.52 ± 18.45 MPa). RMGIC’s compressive strength also significantly fell short of RBC (p < 0.05), but it significantly increased after thermocycling (160.14 to 183.52 MPa). As for microhardness, no significant difference was found between the groups. Thermocycling significantly increased the microhardness of CGIC (from 24.27 to 31.8 ± 2.66). Conclusion: Resin-based materials outperformed the other materials. Glass hybrid restorative material performed as well as resin-modified glass ionomer regarding compressive strength; however, further studies are necessary before considering glass hybrids for use as a permanent restoration.