A2 Shade Research Articles

The Effect of Different Immersion Media, Polymerization Modes, and Brushing on the Color Stability of Different Composite Resins.

This in vitro study investigated color stability of two photo-polymerized nano-filled and nano-hybrid composite resins in different polymerization modes immersed in different staining solutions before and after brushing. Disc-shaped specimens (n = 120) were prepared from two composite resins based on filler particle size: nano-filled (Filtek Z350, shade A1, 3M ESPE) and nano-hybrid (Spectra ST-HV, shade A1, Dentsply Sirona) composite resins (n = 60 per composite type). Specimens of each resin type were photopolymerized using the following polymerization modes: LED conventional, ramp, and pulse (n = 20 specimens per resin type and LED mode). After preparation, baseline color of the specimens was evaluated using a spectrophotometer (Easyshade V, VITA), and color change was evaluated using the CIE L*a*b* formula. Specimens were soaked in distilled water for 4 weeks in separate containers. The specimens from each polymerization-mode group were separated into two groups of 10 specimens; one group was stored in tea and the other group was stored in cola, each 1 hour daily for 4 weeks. After 4 weeks, the color was measured again. The specimens were brushed for 2 minutes under 200-g weight using an electronically powered toothbrush on the polymerized side of the specimen. The color was reevaluated immediately after brushing. Color-difference data (ΔE) between groups were analyzed by one-way analysis of variance for main comparison and by independent t test for color change after brushing. Nano-filled composite resin was more color-stable than nano-hybrid composite resin (P < .001), regardless of the staining media. For both composite resin types, the conventional polymerization method produced a more color-stable result (P < .0001). ΔE after brushing was reduced significantly (P < .0001). Both staining solutions have significant effects on color change, with tea staining more than cola (P < .0001). Nanofilled composite resin had greater color stability than nano-hybrid composite resin after immersion in staining solutions. Polymerization mode influences the color stability of both composite resin types. Int J Periodontics Restorative Dent 2023;43:247-255. doi: 10.11607/prd.6427.

Histocompatibility of Light-Curing Composites Used in Pediatric Dentistry in Human Oral Fibroblast Cells.

Tooth-colored composites are used to repair caries lesions and other dental defects, particularly in anterior regions in children. Although a wide range of composites is using, little attention has been paid to the important indicators such as biological profiles or products released from these materials. The current study aimed to compare the histocompatibility and cytotoxicity of light-curing resin used to repair children's teeth with different brands (3M, DenFil, and Opallis) in curing times of 20 and 40 seconds in human oral fibroblast cells (HGF1). In this in vitro study, Three types of flow composites (3M, Opallis, and DenFil), all at A2 shade, were used. The composites were at 4×2mm with separate exposure times of 20 and 40 seconds. MTT test was used to determine the cytotoxicity of composites on oral fibroblast cells. This test is based on the conversion of tetrazolium bromide to a purple compound known as formazan that its color intensity can be evaluated using the ELISA. The higher intensity of the color reveals the higher survival rate of the mitochondria, which indicates less toxicity. One-way variance analysis and unpaired t-test were used to compare the cytotoxicity of each brand in two conditions of 20 and 40 seconds of curing. Statistical significance was considered when p< 0.05. 3M and Opallis composites were significantly reduced vitality of cells compared to control group in both 20s and 40s curing status. While DenFil brand did not show marked cytotoxicity. In each brand, there are no significant deference between 20s and 40s curing times. Histocompatibility depends on the type of composite resin. In the current study, DenFil brand showed the highest histocompatibility, followed by 3M and Opallis.

Can we use the translucency parameter to predict the CAD/CAM ceramic restoration aesthetic?

To evaluate the effects of background color, ceramic type and coping thickness on masking ability (ΔE) and translucency parameter (TP) of CAD/CAM lithium disilicate glass-ceramic/monolithic zirconia and, to determine the correlations between coping thickness, TP and ΔE. A total of 120 ceramic specimens (2mm, 1mm and 0.5mm thickness; n=10) of four CAD/CAM ceramics: IPS e.max, IPS ZirCAD, Upcera Li CAD and Upcera TT CAD, were studied. Specimens were tested over nine fabricated backgrounds: A1, A2, A3.5, ND2 and ND7 shade resin-based composites, cobalt-chromium alloy (CC), medium precious alloy (MPA), black (B) and white (W). CIELab values (L*, a* and b*), color difference (ΔE) and translucency parameter (TP) were measured and calculated using a digital spectrophotometer (color i7, X-Rite, Pantone®). Data were analyzed using the Shapiro-Wilk test, one-way ANOVA, three-way ANOVA, independent t-tests and Tukey post-hoc tests (p<0.05). 2mm CAD/CAM ceramics showed ideal color matching (ΔE<2.6) over different backgrounds, except for CC, B and W backgrounds. Monolithic zirconia had lower ΔE values than lithium disilicate glass-ceramics. ΔE and TP values significantly reduced with the increased coping thickness (p<0.05). Regardless of ceramic type and thickness, a strong TP-SD of ΔE correlation was observed. CAD/CAM ceramic restoration color was significantly affected by background color, ceramic type and coping thickness. TP is a promising predictor for appropriate ceramic selection to receive an acceptable CAD/CAM ceramic restoration aesthetic.

Bleaching Effect of Ozonized Substances on Resin Composite: A New Potentiality for Ozone Therapy in Dentistry

Composite resins are commonly used in dentistry for direct restorations. The color stability of these materials still represents a major concern for both the clinician and the patient. In recent years, ozone therapy has been extensively used in dentistry to manage wounds healing, dental caries, oral lichen planus, gingivitis and periodontitis, halitosis, osteonecrosis of the jaw, post-surgical pain, plaque and biofilms, root canal treatment, dentin hypersensitivity, temporomandibular joint disorders, and teeth whitening. To date, several studies have evaluated the bleaching effect exerted by ozone on natural teeth, but no studies have been conducted to determine the effect on the color of composite resins. The aim of the present study is to determine whether ozonized oils/gels could determine a color change on composite resin. A total of 40 discs of an A3 shade restorative composite were divided into two groups, respectively exposed to a pigmentation treatment consisting of 10 applications of 10 min each of a 1% chlorhexidine-based gel (trial group) and to storage into physiological solution (control group). The samples of both groups were respectively subdivided into four subgroups which underwent four different protocols, three of which were based on the exposure to different ozonized products and the latter representing the control. A colorimetric analysis with the CIELAB method was conducted with the following timing: after 24 h of storage in physiological solution (before the experimental procedures) (T0), after the subdivision into groups A and B (corresponding to the pigmentation for samples of group A and storage in physiological solution for samples of group B) (T1), and after subdivision into subgroups 1–4 (corresponding to the application of the ozonized products vs. control) (T2). No statistically significant difference was found between the samples at T0. The 20 samples of group A, exposed to the colorant agent, underwent a color change from T0 to T1, whereas the 20 samples exposed to the physiologic solution did not undergo any significant color change. A positive but moderate influence was assessed for E and L values, whereas no significant change occurred for A and B values. Therefore, dental ozonized oils/gels could be valuable in restorative dentistry as bleaching agents of resin composites exposed to discoloration, an alternative to the traditional hydrogen peroxide and carbamide peroxide, but further studies are required to confirm these findings.

Effect of White Light-Emitting Diode Illuminants Recommended by the CIE on Colors of Dental Ceramic Materials

The aim of this study was to evaluate color inconstancy of dental ceramics under the white light-emitting diode illuminants recently proposed by the CIE. From spectral reflectance factors of 18 dental ceramics (VST, NSP, and IEC; shades A1, A2, A3, A3.5, B2, and C2), the corresponding colors under illuminant D65 and CIE 1931 Standard Colorimetric Observer were computed for all samples, using the chromatic adaptation transform CIECAT16. CIEDE2000 color differences between dental ceramics illuminated by CIE D65 standard illuminant and different white LED illuminants were calculated. Perceptibility and acceptability thresholds (PT00 and AP00) in dental ceramics were used to analyze color changes. Color gamut size was within the same range for all illuminants and for all ceramics, since MCDM computed values were 4.1–4.4 for VST, 4.0–4.2 for NSP, and 4.3–4.6 for IEC. For all ceramics and shades, the color inconstancies were higher than 50:50% PT00 and, in general, lower than 50:50% AT00. The effect of CIE-proposed LED illuminants on dental ceramic is perceptible and slightly lower than on natural teeth. Dental clinicians should consider these lighting effects on the visual appearance of dental ceramics.

Color Assessment of Feldspathic Ceramic with Two Different Thicknesses, Using Multiple Polymeric Cements.

The purpose of this study was to evaluate the color changes of feldspathic ceramics CEREC Blocs (Dentsply Sirona, Milford, DE, USA) when cemented with different luting agents, while varying the ceramic thickness. Seventy ceramic discs of feldspathic ceramic (A2 shade) were obtained with 0.5 and 0.8 mm thicknesses. Seventy composite discs (A3 shade) 1 mm in thickness were used as substrates. After being polished and conditioned, the ceramic and composite discs were cemented with different resin cements and a flowable composite: Variolink® Esthetic Light, Neutral and Warm (Ivoclar Vivadent, Schaan, Liechtenstein); RelyXTM Veneer B0.5, Translucent and A3 Opaque/yellow shades (3M Oral Care, St. Paul, MN, USA); G-aenial® Universal Flow A2 (GC Europe, Leuven, Belgium). Color difference (ΔE) was determined using a spectrophotometer. A two-way ANOVA and multiple comparisons were performed using the Bonferroni method with a 95% confidence interval. Variolink® Neutral showed the highest ΔE (15.12 ± 0.71) and RelyXTM Veneer A3 the lowest value (1.59 ± 0.33). There are no statistically significant differences between the two ceramic thicknesses for Variolink® Light (p = 0.230) and RelyXTM Veneer B0.5 (p = 0.318) cements. The feldspathic ceramic final color is influenced by the cement used and the ceramic thickness. The use of different cements in a thin ceramic has a clinically significant impact on the final esthetic result.

Background and surrounding colors affect the color blending of a single-shade composite.

This study evaluated the background and effect of surrounding colors on the color blending of a single-shade composite used in a thin layer. Disc-shaped specimens (1.0 mm thickness) were built with the Vittra APS Unique composite surrounded (dual specimens) or not surrounded (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens were also built with only control composites. The specimen color was measured against white and black backgrounds with a spectrophotometer (CIELAB system). The whiteness index for dentistry (WID) was calculated for simple specimens. Differences (ΔE00) in color and translucency parameters (ΔTP00) between the simple/dual specimens and the controls were calculated. The translucency adjustment potential (TAP) and color adjustment potential (CAP) were estimated based on the ratios between data from simple and dual specimens. The Vittra APS Unique composite showed higher WID values than the controls. No differences between ΔTP00_SIMPLE and ΔTP00_DUAL were observed for any of the shades. The composite shade did not affect TAP values. The lowest values of ΔE00_SIMPLE and ΔE00_DUAL were observed for shade A1 regardless of the background color. For the white background, ΔE00_SIMPLE values did not differ from those of ΔE00_DUAL for all shades. Only A1 showed ΔE00_DUAL values lower than ΔE00_SIMPLE when the black background was used. The highest modulus of CAP (negative values for the white background) was observed when shade A1 surrounded the Vittra APS Unique composite. The color blending ability of the single-shade resin composite used in a thin layer was affected by both the surrounding shade and background color.

Effect of Repeated Heat-Pressing on Marginal and Internal Fit of Lithium Disilicate Glass Ceramic Crowns after Thermo-Mechanical Fatigue

Purpose: To evaluate the effect of repeated heat-pressing on marginal and internal fit of lithium disilicate glass ceramic crowns. Materials and Methods: A freshly extracted caries free human maxillary 1st premolar was prepared according to standardized preparation for all-ceramic crown restoration. The preparation was duplicated to produce thirty epoxy resin dies. The resin dies were divided into three groups (n=10) according to the number of heat-pressings of IPS e.max Press (Shade A2, LT) used for crowns construction. Group 1: Crowns constructed from freshly pressed ingots, Group 2: Crowns constructed from leftover repressed buttons for 1st time, and Group 3: Crowns constructed from leftover repressed buttons for 2nd time. The constructed crowns were cemented to their corresponding resin dies using adhesive resin cement, then samples were subjected to the thermo-mechanical fatigue with a ROBOTA chewing simulator. Each cemented ceramic crown was vertically sectioned bucco-lingually into 2 sections. Marginal, axial, and occlusal gaps were measured at seven defined points on each section using digital microscope. Data were tabulated and statistically analyzed using One-way ANOVA and Pearson’s correlation tests. The significance level was set at P<0.05. Results: The largest marginal and internal gap values were recorded in Group 1, while the lowest marginal and internal gap values were recorded in Group 3. Statistical analysis revealed that there were no significant differences in marginal and internal gaps between the tested groups (P<0.05). Conclusions: Repressing and thermomechanical fatigue have no significant effect on marginal and internal fit of IPS e.max Press crowns.

Effects of different toothpastes on the color and whiteness of stained anterior composite resin.

To evaluate changes in the color of an anterior nanohybrid composite resin and differences in its whitening index after 30 days of brushing with six brands of whitening toothpaste in vitro to simulate the situation in individuals with high coffee consumption. Eighty-four disk-shaped resin specimens were prepared (shade A2). For initial staining, the samples were immersed in coffee solution for 14 days and then divided into eight groups for treatment with various toothpastes. Color was assessed at the baseline, after initial staining, and on days 7, 14, and 30 of the staining-and-brushing cycle. Color stability was evaluated based on the CIEDE2000 color difference (ΔE00), and differences in whiteness were determined using the whitening index for dentistry (WID). The highest ΔE00 and ΔWID values were obtained with Colgate Herbal, followed by Opalescence Whitening and Crest Baking Soda and Peroxide, whereas the lowest values were obtained with distilled water, followed by Yotuel Pharma B5, on day 30 of the staining-and-brushing cycle. In terms of improving the color and whiteness of coffee-stained anterior nanohybrid composite resin, Colgate Herbal, Opalescence Whitening, and Crest Baking Soda and Peroxide yielded promising results after 30 days of continuous use.

Effects of surrounding and underlying shades on the color adjustment potential of a single-shade composite used in a thin layer.

This study aimed to evaluate the surrounding and underlying shades' effect on the color adjustment potential (CAP) of a single-shade composite used in a thin layer. Cylinder specimens (1.0 mm thick) were built with the Vittra APS Unique composite, surrounded (dual specimens) or not (simple specimens) by a control composite (shade A1, A2, or A3). Simple specimens were also built only with the control composites. Each specimen's color was measured against white and black backgrounds or the simple control specimens with a spectrophotometer (CIELAB system). The whiteness index for dentistry (WID) and translucency parameters (TP00) were calculated for simple specimens. Differences (ΔE00) in color between the simple/dual specimens and the controls were calculated. The CAP was calculated based on the ratios between data from simple and dual specimens. The Vittra APS Unique composite showed higher WID and TP00 values than the controls. The highest values of ΔE00 were observed among simple specimens. The color measurements of Vittra APS Unique (simple or dual) against the control specimens presented the lowest color differences. Only surrounding the single-shade composite with a shaded composite barely impacted the ΔE00. The highest CAP values were obtained using a shaded composite under simple or dual specimens. The CAP of Vittra APS Unique was strongly affected by the underlying shade, while surrounding this composite with a shaded one barely affected its color adjustment.

Effect of Ozonated Water on the Color Stability of Denture Teeth and Heat Polymerized Acrylic Base Resin

Objective: To determine the effect of ozonated water on the color stability of denture tooth and denture bases. Material and Methods: Thirty denture base discs consisting of 15 Acropars and 15 ProBase Hot specimens with the dimensions of 40 × 5 mm were prepared. Fifteen denture teeth in shade A1 (Ivoclar Vivadent, Schaan, Liechtenstein) were mounted in a specific acrylic jig. All specimens were immersed in three solutions (1% sodium hypochlorite, ozonated water, and distilled water) for four months (one year of clinical use). Color measurements were done with a spectrophotometer and assessed using the CIE L*a*b* colorimetric system (0, 4, 8, 12, and 16 weeks). Data were analyzed using the three-way ANOVA and Tukey test (α=0.05). Results: Tukey's post hoc test revealed a significant change in color in the Acropars denture base for the distilled water group compared to the ozonated water and 1% hypochlorite (p<0.05). Regarding the ProBase Hot denture base, significantly less color change was observed in the 1% hypochlorite group compared to the ozonated water and distilled water (p≤0.001). For the denture teeth, significantly less color change was seen in the distilled water group than in the ozonated water (p=0.015) and 1% hypochlorite (p<0.05) groups. Conclusion: The color change of denture bases and denture tooth in ozonated water are acceptable. Ozonated water can be considered a good disinfectant for cleaning dentures.

Evaluation and Comparison of Color Change in Two Commercially Shade Guides after Disinfection

Background: Due to the close proximity to the oral cavity, shade guides are prone to contamination with saliva. Hence, disinfection of shade guides is important to prevent cross infection in clinics. This study has compared and evaluated the color change in VITA shade guide and the WALDENT shade guide after disinfecting with 70% isopropyl alcohol. Objectives: The objective of this study was to compare and evaluate the amount of color change in the VITA shade guide and WALDENT shade guide after disinfecting them with 70% isopropyl alcohol for the simulated time of 6 months and 1 year. Materials and Methods: Four commonly used shade tabs, namely A2, A3.5, B2, and C1 of two shade guides – VITA Classical Shade Guide and Waldent shade guides – were chosen for this study. VITA Easyshade spectrophotometer measured the shade, and the values were recorded in the International Commission on Illumination L*a*b* Scale. Baseline values of 8 shade tabs were obtained followed by surface disinfection using 70% isopropyl alcohol using gauze. The testing process was done to simulate a 6-month period and 1-year period. Results: Unpaired t-test was used for statistical analysis. It was found that shade tabs underwent significant changes in short period of time. Conclusion: Within the limitations of this study, it was found that shade guides undergo significant changes in color when disinfected with 70% isopropyl alcohol during a simulated period of 6 months. Clinical Significance: If shade guides are not periodically evaluated using a control (preferably unused) shade guide, they may have a profound impact on resulting restoration.

Influence of ceramic thickness, background and cement shade on the translucency of zirconia reinforced lithium silicate and lithium disilicate ceramics.

Although, the influence of cement and background shade on the final color and translucency of zirconia reinforced lithium silicate (ZLS) and lithium disilicate (LDS) ceramics has been previously investigated, there is still little data on the translucency of LDS and ZLS ceramics in decreased thickness (0.4 and 0.6 mm). The aim of this study was to investigate ceramic thickness', background and cement shades' effects on the zirconia reinforced lithium silicate (ZLS) and lithium disilicate (LDS) ceramics' translucency. Totally 160 square-shaped A1 shade LDS and ZLS samples produced in 0.4 and 0.6 mm thicknesses were cemented with light and neutral shade resin cement on A2 and A3 shade composite resin backgrounds. The color notations of specimen were measured and translucency parameter (TP) values were calculated. Factorial ANOVA and Tamhane's T2 multiple comparison statistical analyzes were used. Highest TP values (11.82±0.97) were obtained in ZLS specimens that were 0.4 mm in thickness, cemented on A2 background with light shade resin cement. While, the lowest TP values (9.60±0.55) were calculated in LDS samples that had 0.6 mm thickness, cemented on A3 background with neutral shade resin cement. Material type, thickness, and background shade affected TP values of specimens. The cement and background shade used might change the final translucency of ZLS and LDS ceramics that had 0.4 and 0.6 mm thickness. Key words:Ceramics, lithium disilicate, spectrophotometry, zirconia, dental materials.

The effect of thickness and cement shade on the color match of different CAD-CAM glass-ceramic materials

Aim: This study aimed to assess the impact of the type and thickness of the ceramic and cement color on the targeted shade of glass-ceramics with various chemical compositions. Methodology: Thirty ceramic specimens were prepared from leucite-reinforced (GC Initial LRF, GC Group) and lithium-disilicate (IPS e.max CAD, EM Group) materials in three different thicknesses (0.5 mm, 0.7 mm, and 1 mm). Four 4-mm-thick substrates were then made from A3-shaded composite resin material to mimic tooth structure and be utilized for cement application. Four shades (Variolink II: transparent, white, yellow, and bleach) of 0.2-mm-thick resin cement were polymerized over these substrates. Next, the specimens were placed over these substrates, and color measurements were applied with a spectrophotometer (VITA Easyshade V) leading to 24 group combinations (n=5). The color difference (∆E) readings were obtained in the spectrophotometer's reference shade verification mode by selecting the A2 shade standard. Three-way mixed ANOVA, Tukey HSD, and Bonferroni tests were used for statistical analysis (α=0.05). Results: The main effects of material, cement, and thickness were found to be statistically significant (p &lt; 0.05), as were the interactions of cement×material, cement×thickness, and material×thickness (p &lt; 0.05). However, the material×cement×thickness interaction was not found to be statistically significant (p = 0.568). Regardless of thickness or cement shade, the GC group had a lower mean ∆E value than that of the EM group (p &lt; 0.05). Lower ∆E values were achieved in both materials with a thickness of 1 mm and bleach-shaded cement (p &lt; 0.05). The materials with the greatest mean ∆E values were those with the thickness of 0.5 mm and the transparent shade cement combination (p &lt; 0.05). Conclusion: The thickness and shade of the cement used influenced the final color of the glass-ceramic materials with the same shade and translucency but diverse chemical compositions. When compared to the lithium disilicate glass-ceramic material, the leucite-reinforced feldspathic glass-ceramic material displayed lower color difference values and a better color match with the targeted shade. How to cite this article: Yılmaz Savaş T. The effect of thickness and cement shade on the color match of different CAD-CAM glass-ceramic materials. Int Dent Res 2022;12(Suppl.1):108-13. https://doi.org/10.5577/intdentres.457 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Comparison of Color Accuracy between Natural Dentin Substrate and Three Dentin Porcelain Brands of Glass-Matrix Ceramic System (Digital Image Analysis)

Purpose: The purpose of this laboratory study was to differentiate the color of natural dentin (ND) and dentin porcelain (DP) by using three brands of Glass-Matrix Ceramic System (GMCS) by parametric CIE L*, a*, b* system. Materials and methods: An extracted human upper central incisor was prepared as a control group. Uniformly thick dentin specimen was taken from the middle coronal third of the labial half longitudinally. Twelve disks of GMCS dentin porcelain were fabricated according to manufactures' instructions by using conventional powder/slurry technique, 4 disks for each group; Feldspathic ceramic VITA VMK 95 (VMK), Leucite-based ceramic VITA VM9 (VM9), and Fluorapatite-based ceramic IPS e.max Ceram IVOCLAR (IEC). ND and DP specimens' thickness were (8×1 mm, shade A3) and (n=4). A digital camera was used to take samples' photos while the color readings were obtained by graphic software. The specimens' colors were measured, and the data were statistically evaluated using Levene's test, One-way ANOVA, and Post Hoc Multiple Comparisons. Results: Parametric CIE L*, a*, b*, and ΔE values of all ceramic disks compared to ND were significantly different even within ceramic brands (P&lt;.05), ΔE were ND &gt; IEC &gt; VMK &gt; VM9. Conclusions: To reproduce ND color by DP needs proper color shade guide selection due to color differences from one brand to another even in the same shade guide tab. Clinical Significance: There is a lack of information on how identical natural dentin color to dentin porcelain is at the same shade guide.

How the Duration and Mode of Photopolymerization Affect the Mechanical Properties of a Dental Composite Resin.

Composite materials are the most common materials in use in modern dentistry. Over the years, the methods of photopolymerization of composite materials have been improved with the use of various devices, such as quartz tungsten halogen lamps (QTHs), light-emitting diode units (LEDs), plasma-arc lamps and argon-ion lasers. This study aimed to compare the mechanical properties of a composite material, depending on the time and mode of photopolymerization. One hundred and forty rectangular specimens (25 × 2 × 2 mm) and forty-two disc-shaped samples (5 mm diameter and 2 mm thickness) were prepared from shade A2 Boston composite resin. Samples were cured using the following seven photopolymerization protocols: four fast-cure modes (full power for 3, 5, 10, and 20 s), two pulse-cure modes (5 and 10 shots of 1 s exposures at full power), and one step-cure mode (soft start with a progressive cycle lasting 9 s). Specimens were subjected to a flexural strength test, Vickers microhardness test, and FTIR spectroscopy test. A 2-factor ANOVA and post-hoc tests were carried out to assess the differences in the flexural strength parameter between the tested groups of samples before and after aging. A mixed-model ANOVA was carried out to assess the differences in the Vickers microhardness parameter between the tested groups of samples before and after aging. The lowest values of flexural strength (p < 0.001) and Vickers microhardness (p < 0.001) were obtained for the 3 s mode for the pre- and post-aging groups. The FTIR mapping tests showed a much more homogeneous chemical structure of the composite after 20 s of continuous irradiation, compared to the sample irradiated for 5 s in the continuous mode. The mode and cure time affects the mechanical properties of the composite resin. Appropriate selection of the cure mode and time ensures better mechanical properties of composite resin. This suggests that the survival of dental restorations within the oral cavity could be extended by using longer photopolymerization durations.

Effect of Water Storage and Bleaching on Light Transmission Properties and Translucency of Nanofilled Flowable Composite.

This study investigated the effect of water sorption and bleaching on light transmission properties (Straight-light transmission (G0), Light diffusion (DF) and Amount of transmitted light (AV)) and translucency parameters (TP) of nano-filled flowable composites. A total of 35 composite disks (0.5 mm thickness) were prepared using A2 shade of 5 nanofiller composites (n = 7/each); Beautifil Flow Plus X F03 (SHOFU INC), Clearfil Majesty ES Flow (Kuraray Noritake Dental), Estelite Universal Flow (EUF, Tokuyama Dental), Estelite Flow Quick (Tokuyama Dental) and Filtek Supreme Ultra Flowable Restorative (FSU, 3M ESPE). Then, they were cured by LEDs (VALO, Ultradent) on standard mood (1000 mW/cm2) for 20 s. Samples were tested for straight-line transmission (G0), diffusion (DF), the amount of transmitted light (AV) and (TP) immediately after 24 h (dry storage), after 1-week water storage and after each of the three cycles of in-office bleaching (HiLite, SHOFU INC). Result: G0, DF, AV and TP were significantly affected by different materials (p < 0.001). The AV of FSU increased significantly after the 1-week water storage, then after the second bleaching cycle (p < 0.001). The TP for EUF slightly decreased (p = 0.019) after 1-week water storage, then increased throughout bleaching. Conclusion: Ageing/bleaching conditions do not affect G0, DF, AV and TP. The compositional variation between nano-filler composites resulted in a significant difference between materials.

The Effect of Varying Dentin Chroma and Enamel Thickness on the Color of A2 Double-layered Resin Composite.

To evaluate chroma (C*) and overall color of double-layered (DL) resin composite (RC) restorations with various dentin shades and enamel thicknesses. Enamel specimens were fabricated using custom-made molds to replicate VITA shade tabs with variant enamel thicknesses (0.5, 0.7, and 1.0 mm) (n=7) from two RC: Clearfil-Majesty (CM) shade (A2), and Vit-l-escence (VL), shade (pearl-neutral). Dentin specimens (shades A1, A2, and A3) were fabricated using custom molds corresponding to the enamel molds. Each enamel specimen was paired with three different dentin specimens. L*a*b* parameters were measured with VITA Easyshade-V. Color difference between DL specimens and the A2 VITA shade tab were calculated with the CIEDE2000 formula. Relationships among enamel thickness, ΔE00, C* of dentin layer, C* of DL, and change in chroma were assessed by Spearman rank correlations. ΔE00 was compared among groups using one-way analysis of variance with Tukey post-hoc adjustment for all possible pairwise group comparisons (experiment-wise α=0.05). There was no statistical difference among C* of DL specimens (p=0.65, 0.53) for CM and VL, respectively. Combinations of enamel thickness/ dentin shade had a significant difference in ΔE00 (p>0.05). No significant correlation was observed among enamel thickness and C* of dentin, and C* of the DL (p>0.05). Significant correlations were observed between ΔE00 of the VL DL and C* DL (r=-0.8, p<0.001); and ΔE00 of CM DL and enamel thickness (r=0.5, p<0.001). Enamel thickness did not affect C* of the dentin layer. Unlike VL RC, variations in dentin shades with CM produced a closer match to the A2 shade tab. Enamel is recommended to be 0.7 mm or less.

Does age determine the lightness and darkness of tooth shades? A retrospective study.

The study aimed to analyze whether age determines the lightness and darkness of tooth shades. The demand for esthetics has soared to a next level progressively in many developing countries including India; the importance provided to match the tooth shade creates a great difference in the satisfactory outcome of the patient in the field of dentistry. Therefore, this particular study analyzed the differences in tooth shade values based on age factor among the Indian population. 238 individual's case sheets with the age between 18 and 65 years. 18-30 years of age were considered as group 1 (young adults), 31-45 years in group 2 (middle age), and above 45 years in group 3 (older age). The clinical intraoral pictures of the patients which were taken prior to the treatment were obtained and the shade of any one of the upper permanent central incisors was assessed using the Vitapan 3D-Master shade guide, especially the middle portion of the facial surface of the incisors. The collected data were imported to Statistical Package for the Social Sciences, version 17 (IBM Corporation). Chi-square test was used to assess the significance. From the data, 17.2% showed A1 shade, 35.2% A2 shade, 7.5% A3 shade, 5% A4 shade, 7.1% B1 shade, 15.9% B2 shade, 7.1% B3 shade, 3.3% B4 shade, and 1.1% C1 shade. The individuals under the category of above 45 years showed darker tooth shade compared to young adults and middle age population (Chi-square test, P < 0.001). Significant association was established with darker tooth shades by increasing age and vice versa. The older age population showed a higher correlation for dark shade between teeth. The aging process significantly affects the teeth color. Hence, as a dentist, it is important to know about the distribution of tooth shade and its association with age to get an outcome with adequate patient satisfaction.

Effect of External Bleaching on Color Change of Single Shade Resin Composite Versus Nano-Filled Resin Composite in Class V: In Vitro Study

Aim: This study investigated the effect of bleaching on color change of the single shade universal composite (Omnichroma) versus nano-filled resin composite (Z350 XT). Materials and Methods: Twenty premolars of shade A3 were used for the study. Standardized class V cavities were prepared on the cervical third of the buccal surface of all teeth. After that, teeth were randomly divided into two groups of 10 teeth each according to the type of resin composite used. After composite application, all teeth were stored individually in distilled water for 24 hours. Evaluation of the restoration color was done using VITA Easyshade. The teeth were bleached and stored again for another 24 hours. Re-evaluation of the restoration color was done at 24 hours, one week and one month after bleaching. Results: There was no statistically significant difference between the two restorative materials at 24 hours and after one week. While there was a statistically significant difference between the two restorative materials after one month. Conclusion: Omnichroma single shade universal restorative material demonstrates structural color change post-bleaching procedure