Effect of Different In Vitro Aging Methods on Color Stability of a Dental Resin-Based Composite Using CIELAB and CIEDE2000 Color-Difference Formulas

Colorimetric analysis of intraoral scans: A novel approach for detecting gingival inflammation

BACKGROUND

Gingivitis, a widely prevalent oral health condition, affects up to 80% of the population. Traditional assessment methods for gingivitis rely heavily on subjective clinical evaluation. This study seeks to explore the efficacy of interpreting the color metrics from intraoral scans to objectively differentiate between healthy and inflamed gingiva.

METHODS

This study used the percentage of bleeding on probing (BOP%) as the clinical reference standard. Intraoral scans, obtained before and after gingivitis treatment using a scanner, were analyzed through a custom MATLAB script to quantify HSV (hue, saturation, value) and CIELAB (Commission Internationale de l'Eclairage L*a*b*) color coordinates. The region of interest was a 2-mm-wide gingival strip along the buccal margin of the maxillary anterior teeth. Linear regression analysis was performed to evaluate the relationship between photometric outcomes and continuous, dichotomous, and categorical BOP data. Diagnostic accuracy was assessed using the area under the receiver operating characteristic (ROC) curve (AUC), as well as sensitivity and specificity measures.

RESULTS

The analysis included clinical and digital color data from 110 scans, adhering to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines. The multilevel linear regression analysis underscored a significant correlation between the BOP% and digital color metrics, specifically the CIELAB a* (red-green chroma), CIELAB b* (yellow-blue chroma), and color saturation, with AUC performances of 70%, 79.5%, and 80.8%, respectively.

CONCLUSION

Digital color analysis of intraoral scans has demonstrated a range of performance from acceptable to excellent in distinguishing sites with BOP. This innovative approach presents a promising tool for dentists and researchers in the accurate diagnosis, screening, and management of gingivitis.

PLAIN LANGUAGE SUMMARY

Our study focuses on finding a better way to detect gingivitis, a common gum disease affecting many people. Traditional methods rely on the dentist's visual inspection, which can be subjective. We explored the use of color measurements from digital intraoral scans to objectively identify healthy versus inflamed gums. We analyzed 110 scans from 55 participants, examining the color differences in the gums before and after treatment. By measuring specific color values, we achieved up to 80.8% accuracy in distinguishing between healthy and inflamed gums. This method could offer a more reliable tool for dentists and researchers to diagnose and manage gingivitis, leading to better oral health outcomes.

Color Stability of Bulk-Fill Flowable Resin Composites After Artificial Aging

BACKGROUND

This study aimed to evaluate the color stability of bulk-fill flowable resin composites with 2 difference shades at baseline and after artificial aging.

METHODS

Disk-shaped specimens (Ø10 × 4 mm) were fabricated from three bulk-fill flowable resin resin composites (Filtek Bulk-Fill Flow, Venus Bulk-Fill Flow, and Estelite Bulk-Fill Flow). The specimens in each bulk-fill resin composite group were divided into two subgroups (n = 10 per subgroup) with two different shades, A1 (N = 30) and A3 (N = 30), and were polymerized with light curing (800 mW/cm2/Valo LED Unit, Ultradent) and polished. The color difference between bulk-fill resin composites was evaluated at baseline and after artificial aging using a spectrophotometer (CM-700d, Konica Minolta, Tokyo, Japan) under D65 illumination. Color coordinates were measured with CIEDE2000, and color differences (∆E00) and relative translucency parameter (RTP) values were calculated. Subsequently, the comparison of color changes (∆E00) before and after thermocycling was performed using the t-test for paired samples.

RESULTS

The bulk-fill flow resin composites evaluated in the present study were capable of mimicking important optical properties such as light transmission. All the resin composites provided acceptable color stability at baseline and after thermocycling when the color A1 was used. On the other hand, whenever the shade A3 was used, the Venus Bulk-Fill Flow demonstrated the best optical properties. There was no statistically significant difference when comparing baseline and after thermocycling in bulk-fill flowable resin composites (p > 0.05). After thermocycling, A1 bulk-fill flowable resin composites provided acceptable color stability, and all A3 bulk-fill flowable resin composites provided visible color change, except for the Venus Bulk-Fill Flow (∆E00 = 2.35).

CONCLUSIONS

Estelite Bulk-Fill Flow displayed the best color stability (∆E00 = 2.22) between all the combinations evaluated.

A comparative study of polishing systems on optical properties and surface roughness of additively manufactured and conventional resin based composites

This study aimed to compare polishing systems on color stability, surface roughness, and gloss of additively manufactured permanent and conventional resin composites. Totally 250 disc specimens (6 mm*2 mm) were prepared from resin-based materials [G-ænial Posterior (GP), Clearfil Majesty Esthetic (CME), SonicFill-2 (SF), Tescera (Tes), and Crowntec (CT)]. Following baseline color (ΔE00), gloss (GU), and surface roughness (Ra) measurements, the specimens were randomly divided into 5 groups (n = 10/group) according to polishing systems: Control (mylar strips); OneGloss; OneGloss + Platina Hi-Gloss; OptiDisc; and OptiDisc + Platina Hi-Gloss. Specimens were immersed in coffee for 144 h following polishing. ΔE00, GU, and Ra measurements were repeated. Atomic force microscopy images were taken in all groups. Spearman's rho correlation coefficient, Robust ANOVA, and Bonferroni correction were used for statistical analysis. Significance level was taken as p < 0.050. Significant differences in ΔE00 values were found among resin-based materials, polishing systems, and their interactions (p < 0.001,p < 0.01, and p = 0.001). Regardless of polishing system, the lowest ΔE00 values were observed in CT, while lowest gloss (GU) values were found in Tes. The lowest surface roughness (Ra) values were detected at OptiDisc group (p < 0.001). A single type of polishing system may not be sufficient to achieve optimal results in resin-based materials.

Effect of Photoaging on the Structure, Optical Properties and Roughness of One-Shade Composite Restoratives

The aim of the study was to evaluate changes in the degree of C=C conversion (DC%), chemical structure, optical properties and roughness of one-shade composites before/after photoaging. Τhe one-shade materials tested were Charisma Topaz One (CHT), Clearfil Majesty ES-2 Universal (MES), Essentia Universal (ESU) and Omnichroma (OMN), with G-aenial Anterior (CNA) serving as control. Specimens (2 mm thickness) were prepared and tested for DC% and chemical structure (ATR-FTIR spectroscopy), optical properties (L*a*b*-ΔΕ, translucency parameter-TP, opalescence parameter-OP, contrast ratio-CR and total transmittance-TT by UV-Vis spectroscopy) and roughness (Sa, Sz, Sdr, Sds and Sc by optical profilometry) before and after photoaging (Xe-arc weatherometer). Significant differences were found in DC% between top-bottom surfaces (ESU, OMN before; ESU, CNA after). Photoaging improved DC%, reduced ester peaks implying photodegradation, reduced L* (CHT, OMN, CNA), a* (CHT, CNA), b* (OMN, CNA), TP (all, except for MES), OP (only MES), CR (only MES, but an increase in CNA) and TT (CHT, OMN). OMN, CNA and MES demonstrated ΔΕ > 3.3. Photoaging significantly increased all roughness parameters in all materials, except for MES (Sz, Sdr, Sc) and OMN (Sdr). Although listed in the same group, significant differences were found in one-shade composites before and after photoaging. Several products were strongly affected by photoaging, demonstrating evidence of photodegradation, an increased roughness and color changes exceeding the clinically acceptable levels.

Color stability and translucency of newly developed composites for splinting teeth

This study aimed to investigate the colorimetric properties of newly developed composites for dental trauma splints using various staining solutions during the clinical splinting period. The clear shades of G-Fix (GF), Ortho Connect Flow (OC), Light Fix (LF), and Filtek Z350XT (FZ) were fabricated into 96 disk-shaped specimens. Specimens from each composite group were stored in distilled water, coffee, tea, and red wine solutions at 37ºC. CIE values were measured using a spectrophotometer at 24 h after specimen preparation and at 1 day, 1 week, 2 weeks, 3 weeks, and 4 weeks after storage in each solution. Color differences and translucency parameters were calculated using the initial and measured values. Within the experiment period, the color differences of GF, OC, and LF compared to the initial measurement were smaller than that for FZ for all staining solutions except distilled water. There were no significant color differences between the GF, OC, and LF groups.

The effect of various inhaled asthma medications on the color stability of paediatric dental restorative materials

BACKGROUND

The purpose of the study is to analyse the effects of different inhaled asthma medications (IAMs) on the color change of dental restorative materials (DRMs).

METHODS

In total, 192 samples were taken from six different DRMs: [Filtek Z550 (nanohybrid composite), Fusio Liquid Dentin (Self-adhering flowable composite), Filtek Ultimate (nanofilled flowable composite), Dyract XP (compomer), Fuji II LC (resin-modified glass ionomer), Fuji IX Fast (self-cured-packable glass ionomer), (n = 32)]. After the initial color values (CIELab) of DRMs were measured by using a spectrophotometer, each sample was exposed to the same IAMs via nebulizer according to the four different inhaled therapies and measurements were repeated on the 7th & 21st days.

RESULTS

In all IAM groups, DRM with the least amount of ΔE was nanohybrid composite, while the highest ΔE was found in Fuji II LC. Among all experimental groups, only Fuji II LC which was administered the combined medication, exceeded the clinically unacceptable threshold (ΔE = 3.3) on 7th & 21st days.

CONCLUSIONS

Consequently, important factors affecting the susceptibility to color stability are the type of IAMs, the administration time-dosage, and the type of DRMs.

A Comparative Study of Shade-Matching Reproducibility Using an Intraoral Scanner and a Spectrophotometer

BACKGROUND

We compared the repeatability of the shade determination of resin composite restorations and acrylic teeth in light and darker shades at baseline and after an aging process through two digital tooth color-matching methods: using a Trios 3Shape intraoral scanner and using a Vita Easyshade Compact spectrophotometer.

MATERIAL AND METHODS

Forty upper central incisor acrylic teeth in the shade A1 (n = 10) and A3 (n = 10) were randomly assigned to be restored with Filtek Bulk Fill in the shade A1 (n = 10) or A3 (n = 10). Subsequently, 20 Class V cavities were prepared in a standardized manner (mesio-distal = 3.0 mm, cervical-occlusal = 2.0 mm, depth = 1.5 mm). Cavities were restored using an universal adhesive system and resin composite in two increments and were light-cured. The shade difference between the resin composite Class V restorations in acrylic teeth of the A1 and A3 shades was evaluated at baseline and after aging. Aging was simulated using ultraviolet light for 120 h. An Easyshade device and an intraoral scanner were used under D65 illumination. Measurements were taken five times, on top of the restoration and on the acrylic teeth, in a randomized manner.

RESULTS

Data analysis was on the calculation of the arithmetic mean for the percentage of repeatability conducted by the Trios scanner and the Easyshade device. There was no statistically significant comparison between the shade measurement devices (p > 0.05). At baseline, the repeatability for both the Trios intraoral scanner and the Vita Easyshade Compact device for artificial teeth in the shades A1 and A3 was 100%. After aging, the trueness recorded by the intraoral scanner and the Easyshade device for artificial teeth in the shade A1 was 80%. For Class V restoration with shade A1, the intraoral scanner recorded 80% trueness and the Easyshade device recorded 60% trueness at baseline. For shade A3, the intraoral scanner recorded 60% trueness and the Easyshade device recorded 60% trueness.

CONCLUSIONS

The intraoral scanner and Easyshade device are reliable for baseline shade selection, but their accuracy decreases after aging, particularly for darker shades.

Effect of whitening concepts on surface roughness and optical characteristics of resin-based composites: An AFM study

The aim of this study was to evaluate the effects of various whitening agents on the surface roughness and optical characteristics of different types of resin composite restorations. Fifty specimens were prepared for each resin [G-aenial Posterior (GP), SonicFill-2 (SF), Solidex (SDX), and Nova Compo HF (NC)]. Following baseline color and surface roughness (Ra) measurements, the specimens were randomly divided into 5 groups (n = 10/group) according to whitening concepts: control (distilled water), in-office bleaching [OB-(Opalescence Boost)], at-home bleaching [HB-(Opalescence PF)], whitening toothpaste [WT-(Signal White Now)], and whitening mouthwash [WM-(Listerine Advanced White)]. ∆E00 , ∆TP00 , and ∆WID values were calculated before and after the whitening procedure with a spectrophotometer using the CIEDE2000 formula. Surface roughness measurements were repeated. The surface topography was determined using atomic force microscopy. Two- and three-way analyses of variance and Tukey's post-hoc test were performed, with p < 0.05 regarded as indicative of significance. No significant differences were detected among the resin composite materials in terms of the ΔE00 values (p > 0.05). Color change of all resin materials was above the AT threshold (>1.8) and the PT threshold (>0.8). All restorative materials presented acceptable (AT<2.62) TP00 values. Solidex specimens demonstrated the lowest WID values compared to the other composites. There were significant differences among the whitening procedures with respect to ΔE00 , ΔTP00 , and WID values (p < 0.001). SF/WT combination showed the highest and clinically unacceptable ΔE00 values. The highest roughness values were observed in the SDX specimens and the combination of SDX/OB. The effect of whitening agents on the optical characteristics and surface roughness of restorative materials depends on the type of material, agent, and time. RESEARCH HIGHLIGHTS: Clinicians should be aware that long-term use of over-the-counter products due to the abrasive effects of their ingredients and repeated bleaching session applications may affect the color stability and surface roughness of resin composites.

Effect of mouth rinses on the stainability of monolithic lithium disilicate glass-ceramics with different surface treatments: An in vitro study

STATEMENT OF PROBLEM

Mouth rinses have been reported to cause tooth surface discoloration. However, information regarding their effect on the stainability of monolithic glass-ceramics with different surface treatments is lacking.

PURPOSE

The purpose of this in vitro study was to assess the effect of mouth rinses on the color change of milled and pressed monolithic lithium disilicate glass-ceramics with different surface treatments.

MATERIAL AND METHODS

Fifty-six Ø12×1.5-mm disk specimens were fabricated using 2 different processing techniques: milling and pressing. Each group was subdivided into 2 subgroups according to surface treatments: glazed and polished. Specimens were then immersed in 2 different types of mouth rinse (n=7): chlorhexidine (CHX) and Listerine (LST). Color parameters were assessed using a digital spectrophotometer. Color difference (ΔE00) was calculated and compared with perceptibility (ΔE00=0.8) and acceptability (ΔE00=1.8) thresholds. The data were analyzed using ANOVA and Tukey post hoc tests (α=.05).

RESULTS

The color difference (ΔE00) was significantly affected by the type of processing technique, surface treatment, and mouth rinse (P<.001) and their interaction (P=.008). All ΔE00 values were below the selected clinical acceptability threshold (ΔE00=1.8). Milled groups (ΔE00=1.13) showed greater discoloration than pressed groups (ΔE00=0.86). Glazed specimens (ΔE00=0.70) were more resistant to discoloration than polished specimens (ΔE00=1.28) and immersion in CHX (ΔE00=1.09) led to more discoloration than immersion in LST (ΔE00=0.89).

CONCLUSIONS

The color of milled and pressed monolithic lithium disilicate glass-ceramics with different surface treatments was affected by using CHX and LST mouth rinses. Glazed lithium disilicate glass-ceramics showed less staining compared with those that were polished. Specimens immersed in CHX showed more discoloration than those immersed in LST.

Effect of layering strategy and prolonged water aging on masking ability of composite resins

STATEMENT OF PROBLEM

Layered composite resins may adequately mask discolored substrates. However, whether color changes that occur over time affect masking ability is unclear.

PURPOSE

The purpose of this in vitro study was to investigate the effect of layering and water aging on the masking ability of 2 composite resins.

MATERIAL AND METHODS

Disk specimens (1.5 mm-thick and shade A1) from Charisma Diamond (CD) and Filtek Z350XT (Z350) were made according to the composite resin shade combination used in the layering strategies: bilayer for CD (enamel/dentin) and for Z350 (enamel/body and enamel/dentin) and trilayer for Z350 (enamel/body/dentin) (n=5). Color measurements were obtained with a spectrophotometer over an A3.5 ceramic substrate, and the whiteness index for dentistry (WID) was calculated. The specimens were aged in water at 37 °C and evaluated at different times: 24 hours, 1 week, 1 month, 2 months, 6 months, 12 months, 18 months, and 24 months. CIEDE2000 color differences (ΔE00) and WID differences (ΔWID) were calculated and interpreted by 50:50% color and whiteness perceptibility and acceptability thresholds. Changes among strategies and aging times were analyzed using the Kruskal-Wallis test (α=.05). Contrasts were made using the Mann-Whitney U test with Bonferroni correction (α=.001).

RESULTS

ΔE00 decreased from 24 hours to 2 months of aging. From 2 months onwards, ΔE00 increased for all layering strategies and times, without significant changes in lightness for CD (P>.004). Overall, for the CD restorative system, an increase in ΔWID was observed after 1 month of aging (P<.001), while for the Z350 restorative system, ΔWID decreased after aging (P<.001), except for the Z350 bilayer strategy (enamel + dentin) at 1 week and 2 months (P>.004). For all layering strategies and aging times, color differences were higher than the 50:50% perceptibility threshold for ΔE00 and, after 6 months, higher than the 50:50% acceptability threshold for ΔE00 and the 50:50% whiteness acceptability threshold.

CONCLUSIONS

The ability of the tested composite resins to mask a discolored substrate was affected by the layering approach applied and by prolonged water aging.

"Enamel layering" using double-layered enamel-shade resin composites: The strategy to simulate the optical characteristics of human enamel

OBJECTIVE

To evaluate the optical match between enamel and resin composites fabricated using mono-layered and double-layered techniques.

MATERIALS AND METHODS

Enamel slabs were prepared from human upper incisors and canines. Mono-layered composite replicas were prepared from seven Filtek Z350XT and Estelite Sigma shades using silicone molds prepared from the respective enamel surfaces. Translucent and enamel shades (A2 or A3) of the two materials were produced from incisor molds for double-layered replicas, and the groups with the best results underwent accelerated aging. Spectrophotometric evaluation was performed using CIE color system. The differences in translucency (ΔTP) and color (ΔE00 ) between the enamel and paired composite replicas were calculated and analyzed using parametric statistics (α = 0.05).

RESULTS

For the mono-layered composites, white enamel and translucent shades of Filtek yielded the lowest ΔTP for canines (4.6) and incisors (8.9), respectively. The ΔE00 of mono-layered replicas ranged from 5.1 to 11.8. Double-layered Filtek replicas displayed a better 1-day optical match with the lowest ΔTP (3.4-4.0) and ΔE00 (4.2-4.6), irrespective of each layer's thickness.

CONCLUSIONS

For canines, the lowest ΔTP of Filtek white enamel was close to the acceptable threshold (4.43). For incisors, the thicker translucent double-layered Filtek composites demonstrated the greatest optical match before and after aging.

CLINICAL SIGNIFICANCE

Upper incisors and canines have distinct enamel optical properties. Enamel layering using specific double-layered resin composites could achieve a better optical match with upper incisor enamel.

Effects of Bio-Aging on Mechanical Properties and Microbial Behavior of Different Resin Composites

Under challenging oral environments, the overall performance of resin composites is affected by bio-aging. This study investigated the effects of saliva biofilm-induced bio-aging on the mechanical properties and microbial behavior of composites with different filler types. Microhybrid, nanohybrid, nano-filled and nano-filled flowable composites were bio-aged with saliva biofilm for 30 days. Surface morphology, roughness, mechanical and aesthetic properties were determined. A 48 h saliva biofilm model was used to evaluate the microbial behavior of different composites in vitro. Biofilm metabolic activity, lactic acid production and live/dead bacterial staining were tested. Six volunteers were selected to wear intra-oral appliances with composite slabs for 24 h and biofilms were collected and analyzed using 16S rRNA sequencing to assess the biofilm formation over those materials in situ. Although there were increasing trends, surface roughness, water resorption and material solubility had no significant changes for all groups after bio-aging (p > 0.05). There were no significant changes in elastic modulus for all groups after aging (p > 0.05). However, a decrease in flexural strength in all groups was observed (p < 0.05), except for the nanoflow composite group (p > 0.05). The Vickers hardness remained stable in all groups after aging (p > 0.05), except for the nano-filled group (p < 0.05). The nanoflow composite showed distinct color changes compared to the micro-hybrid group after aging (p < 0.05). Biofilm metabolic activity and lactic acid production in vitro increased slightly after bio-aging in all groups, but with no statistical significance (p > 0.05). The Shannon index diversity of biofilms in situ decreased after aging (p < 0.05), while no significant difference was shown in species composition at the genus level in all groups (p > 0.05). Resin composites with different sized fillers displayed a relatively stable mechanical performance and uncompromised microbial behavior both in vitro and in situ after 30 days of bio-aging. Based on the results, composites with different filler types can be selected flexibly according to clinical needs. However, a longer time for bio-aging is still needed to confirm the mechanical properties and microbial behaviors of composites in the long run.

3D Printing of Dental Prostheses: Current and Emerging Applications

Revolutionary fabrication technologies such as three-dimensional (3D) printing to develop dental structures are expected to replace traditional methods due to their ability to establish constructs with the required mechanical properties and detailed structures. Three-dimensional printing, as an additive manufacturing approach, has the potential to rapidly fabricate complex dental prostheses by employing a bottom-up strategy in a layer-by-layer fashion. This new technology allows dentists to extend their degree of freedom in selecting, creating, and performing the required treatments. Three-dimensional printing has been narrowly employed in the fabrication of various kinds of prostheses and implants. There is still an on-demand production procedure that offers a reasonable method with superior efficiency to engineer multifaceted dental constructs. This review article aims to cover the most recent applications of 3D printing techniques in the manufacturing of dental prosthetics. More specifically, after describing various 3D printing techniques and their advantages/disadvantages, the applications of 3D printing in dental prostheses are elaborated in various examples in the literature. Different 3D printing techniques have the capability to use different materials, including thermoplastic polymers, ceramics, and metals with distinctive suitability for dental applications, which are discussed in this article. The relevant limitations and challenges that currently limit the efficacy of 3D printing in this field are also reviewed. This review article has employed five major scientific databases, including Google Scholar, PubMed, ScienceDirect, Web of Science, and Scopus, with appropriate keywords to find the most relevant literature in the subject of dental prostheses 3D printing.

The effect of bleaching applications on stained bulk-fill resin composites

Background

The structure of bulk-fill resin composites differs from that of their conventional counterparts, but how this difference affects the color stability of the former after staining and bleaching is unclear. Accordingly, this study was aimed at investigating color change in nine bulk-fill resin composites and one nanohybrid resin composite treated with hydrogen peroxide and carbamide peroxide after staining with tea, coffee, and red wine.

Methods

Eighty specimens were prepared from each resins [Clearfil Majesty Posterior (CMP), SDR flow⁺ (SDR), Filtek^TMBulk-Fill Flowable Restorative (FBF), Reveal HD Bulk (RHD), Beautifil-Bulk Restorative (BBR), Tetric EvoCeram® Bulk Fill (TEC), SonicFill™2 (SF2), everX Posterior™ (eXP), X-tra base (XB), and Venus® Bulk Fill (VBF)]. Following baseline color measurements, the specimens were randomly divided into 4 groups according to immersion solutions and distilled water as the control. At the end of a 30-day test period, color measurements were repeated, and color change values (∆E₀₀) were calculated. Each resin group was then divided into 2 subgroups (with 10 specimens per group) on the basis of bleaching agent (Opalescence Boost 40%, Opalescence PF 16%). Following bleaching application, ∆E₀₀ and changes of whiteness (∆WI_D1 = WI_Dbleaching-WI_Dbaseline, ΔWI_D2 = WI_Dbleaching-WI_Dstaining) values were recorded. Two- and three-way analyses of variance and Tukey’s post hoc test were performed, with a P < 0.05 regarded as indicative of significance.

Results

After immersion in distilled water, tea, and red wine, the highest ΔE₀₀ values were observed in eXP (P < 0.05). Resin materials immersed in coffee and tea exhibited statistically higher ∆E₀₀ values than those immersed in red wine except for eXP, TEC, and FBF (P < 0.05). For eXP, the highest ∆E₀₀ values were recorded in distilled water. For TEC and FBF, there was no statistically significant difference among the immersion solutions and distilled water (P > 0.05). For all the resins and staining beverages, no statistically significant difference in ∆WI_D1 and ∆WI_D2 values were detected between bleaching agents (P > 0.05). All the ΔWI_D1 values were above the whiteness perceptibility threshold.

Conclusion

The bulk-fill materials were more resistant to discoloration and bleaching procedures than the conventional resin composites. Coffee and tea caused more staining than distilled water and red wine generally. The type of bleaching procedure had no effect on the whiteness of the tested materials.

Color change of glass ceramic restorations cemented by four types of dual-cured resin luting agents with different initiator systems

This study aimed to comprehensively evaluate the effect of dual-cured resin luting agents with different initiator systems on the color stability of glass ceramic restorations by simulating various clinical glass ceramic restorations. Three commonly used shades from each of the two dual-cured resin luting agents with an amine-initiation system or without it were studied. The individual specimens had different translucency and thickness and were artificially aged using a xenon light aging machine. The color was measured before and after aging using a digital spectrophotometer with the difference calculated and analyzed statistically. As results, the amine-free dual-cured resin luting agents were more color stable than those using amine-initiation systems for both uncovered and bonding groups. The translucency and thickness of the ceramic, and shade and type of the resin luting agent significantly affected the color stability of glass ceramic restorations.

Effect of an elastomeric urethane monomer on BisGMA-free resin composites containing different co-initiators

OBJECTIVES

The aim of this study was to investigate the mechanical, chemical, optical, and adhesive properties of BisGMA-free experimental resin composites containing Exothane-24-an elastomeric urethane monomer-and different co-initiators.

MATERIALS AND METHODS

A blend of urethane dimethacrylate (UDMA), extended dimethacrylate urethane (PEG 400), triethylene glycol dimethacrylate (TEGDMA), and camphorquinone was prepared. Two different co-initiators-dimethyl aminoethyl methacrylate (DMAEMA) or 4-N alcohol, N-dimethylamine phenylethyl (DMPOH)-were added to the blend. Exothane-24 monomer was added to the blend for each co-initiator and four groups were established as follows: DMAEMA; DMAEMA + Exothane; DMPOH; and DMPOH + Exothane. Specimens were photo-activated using a multi-wave LED light-curing unit (VALO; 954 mW/cm² of irradiance). Mechanical (ultimate tensile strength, flexural strength, flexural modulus and hardness), chemical (degree of conversion, hardness reduction, water sorption and solubility), optical (color change), and adhesive (microtensile bond strength) properties were analyzed. Data were submitted to two-way ANOVA and Tukey's test (α = 0.05).

RESULTS

The resin composite containing DMPOH and Exothane-24 showed similar or superior performance to those of the other experimental composites for mechanical and chemical properties, except for flexural strength. It also showed less color change and greater micro-tensile bond strength.

CONCLUSIONS

Among the combinations tested, the BisGMA-free resin composite containing Exothane-24 combined with the DMPOH co-initiator showed the best mechanical, chemical, optical, and adhesive properties. Clinical relevance Exothane-24 monomer and DMPOH co-initiator could be useful in the formulation of BisGMA-free resin composites in order to minimize exposure to BPA.

Effect of Staining and Aging on Translucency Parameter of CAD-CAM Materials

Objectives

To evaluate different intervals of exposure to staining solutions and artificial aging on translucency parameter (TP₀₀) of CAD-CAM materials.

Material and Methods

One millimeter thick square-shaped specimens (N = 288) were cut from Cerasmart (CS), IPS e.max (IE), Lava Ultimate (LU), Shofu HC (SH), Vita Enamic (VE), and Vita Suprinity (VS) and were divided into laboratory and chairside polishing. Reflection wavelength spectra, CIE D65 standard illuminant, 2 ° standard observer, SCI, UV included, SAV aperture, 6 mm diameter, were recorded at 10 nm sensitivity against white and black calibration tiles using a benchtop spectrophotometer. Subsequently, they were converted into CIEDE 2000 TP₀₀. After baseline measurements (T0), the specimens were divided as follows (n = 8): staining in coffee (C) and wine (W), for 60 (T1) and 120 hours (T2), and accelerated artificial aging (A). Artificial aging (ISO 4892-2 standard) was performed in two cycles of 150 KJ/m², for T1 and T2, respectively. TP measurements were repeated at T1 and T2. Data of TP₀₀ retention were submitted to analysis of variance and Fisher’s PLSD multiple comparison test (α=0.05).

Results

Fisher’s PLSD critical differences among materials, time intervals and staining/aging were 0.16, 0.11 and 0.11, respectively. SH showed the highest TP₀₀ followed by LU > CS > IE = VS > VE. For all time intervals, the lowest TP₀₀ retention was observed with C. W, and A presented similar values.

Conclusions

Translucency Parameter was a time and staining/aging-dependent material. In majority of cases, it decreased upon staining/aging.

Staining and aging-dependent changes in color of CAD-CAM materials

STATEMENT OF PROBLEM

Consumption of some beverages and aging may affect the color of dental materials used in fixed prosthodontics, but their effect on recently introduced materials is not well known.

PURPOSE

The purpose of this in vitro study was to evaluate staining, aging, and the exposure interval on color changes of computer-aided design and computer-aided manufacturing (CAD-CAM) resin nanoceramics (RNC), polymer-infiltrated ceramic-network (PICN) materials, and lithium silicate and lithium disilicate ceramics.

MATERIAL AND METHODS

A total of 288 square-shaped, 1-mm-thick specimens prepared from Cerasmart, IPS e.max, Lava Ultimate, Shofu HC, Vita Enamic, and Vita Suprinity were polished by using laboratory and chairside methods in accordance with the manufacturers' instructions. Color data were recorded with a benchtop spectrophotometer, and CIEDE2000 color differences (ΔE₀₀) were calculated. After the baseline measurements (T0), the specimens were divided into 3 groups (n=8) and exposed to staining in coffee and wine and to accelerated artificial aging. The specimens were stored in staining solutions at 37 °C for 60 (T1) and 120 hours (T2). Accelerated aging was performed by using a xenon lamp weathering test chamber for a total exposure of 150 (T1) and 300 kJ/m² (T2). The results were analyzed by using the t test, ANOVA, and the Tukey honestly significant difference test (α=.05). Color differences of ΔE₀₀ ≤0.8 and ≤1.8 corresponding to the 50:50% perceptibility threshold and 50:50% acceptability threshold were used to interpret the results.

RESULTS

As color differences (ΔE₀₀) between laboratory and chairside polishing were not statistically significant (T=-0.81, P=.418), only the results for chairside polished specimens were presented. Color differences for the T0-T1 comparisons ranged from 0.2 to 4.2, T0-T2 from 0.3 to 6.5, and T1-T2 from 0.1 to 2.3. ANOVA showed significance of factors and for interactions (P<.05). Lithium silicate-based and lithium disilicate-based ceramic materials were more color stable than RCN and PICN materials on exposure to coffee and red wine. Color changes greater than acceptability threshold after immersion in coffee were recorded for 3 (T0-T1), 4 (T0-T2), and 2 (T1-T2) materials. Corresponding findings after immersion in wine were 1, 3, and 0 and after artificial aging 0, 2, and 0. ΔE₀₀ and ΔE_ab values were highly correlated (R²=0.97).

CONCLUSIONS

No difference was found in color stability among laboratory and chairside polished specimens. Coffee caused the greatest color changes for T0-T2 interval. Staining-dependent color differences increased with increased exposure, except for IPS e.max and Vita Suprinity. For artificial aging, color change appeared to be material dependent.

Effects of different bleaching application time on tooth color and mineral alteration

BACKGROUND

The effects of HP-based products upon dental enamel are inconclusive.

PURPOSE

The purpose of this study was to evaluate the colour and mineral changes caused by the bleaching agent applications at different durations on the enamel surface.

BASIC PROCEDURES

60 caries-free lower central incisor extracted for periodontal reasons were standardized for enamel and dentin thickness after cone-beam computed tomography (CBCT) measurements in terms of mineral (n = 24) and colour change (n = 36). All teeth were divided into 3 groups according to different bleaching durations for colour (n = 12) and mineral change (n = 8) measurements. The samples for mineral change were examined with the -energy scattering X-ray (EDX, JSM-6390 LV, Jeol Inc., Japan) device before and 2 weeks after the application. For colour change, the measurement of the samples was performed with spectrophotometer device (VITA EasyShade 4.0, Germany). Opalescence Boost PF 40% (Ultradent Products, USA) was applied for 20 min (min) in Group 1, 40 min in Group 2 and 60 min in Group 3. In order to determine the efficacy of bleaching, colour measurements were repeated at 24 h, 7 and 14 days after the application. In the intragroup comparison, Friedman and Wilcoxon tests were used for non-normally distributions, while repeated variance analysis and paired t test were used for normally distributions in dependent variables. In the intergroup comparison, ANOVA and LSD tests were used for normally distributions, while Kruskal-Wallis and Dunn tests were used for non-normally distributions in independent variables. p < 0.05 was considered significant.

MAIN FINDINGS

In the study, statistically significant difference was observed between all groups in terms of colour change at different measurement times (p < 0.05). The highest ΔE₀₀ values were observed in Group 3 (ΔE₀₀₃ = 8.37 ± 2.15); the lowest value was observed in Group 1 (ΔE₀₀₁ = 4.74 ± 1.26). Ca values were similar increase among all groups (p > 0.05). The highest Ca values were observed in Group 3 (69.91 ± 5.34); the lowest value was observed in Group 2 (66.08 ± 1.50). P values were similar increase among all groups (p > 0.05). The lowest P values were observed in Group 3 (26.54 ± 5.92); the highest value was observed in Group 2 (29.86 ± 2.26).

PRINCIPAL CONCLUSIONS

Effective whitening was achieved in all study groups. When the results are evaluated as versatile in terms of bleaching effectiveness and mineral change, the most ideal bleaching duration was determined as 40 min (Group 2).

Influence of Pre-Heating Regular Resin Composites and Flowable Composites on Luting Ceramic Veneers with Different Thicknesses

The aim of this study was to evaluate of pre-heating, filler contents and ceramic thickness on film thickness, microshear bond strength, degree of conversion and color change on ceramic veneers. Two experimental composites were prepared (Bis-GMA/UDMA/BisEMA/ TEGDMA), with different amounts of filler (65% or 50%wt) simulating a conventional and a flowable composite. The flowable (F) was used at room temperature and, the conventional either at room temperature (C) or pre-heated (CPH). Disk-shaped ceramics with different thickness (0.4 mm, 0.8 mm, 1.5 mm) were prepared. The film thickness was evaluated according to the ISO 4049 (n=10). The microshear bond strength (n=10) was evaluated in enamel using tubing specimens light-cured through the ceramic veneer. The degree of conversion was evaluated using Raman spectroscopy. The color change of the ceramic restorations (n=10) was evaluated by spectrophotometry. The results were submitted to 2-way ANOVA and Tukey's post hoc test (a=5%). For the film thickness 1-way ANOVA was used (a=5%). The C presented the thicker film thickness; the CPH produced a similar film thickness in comparison to the F. All composites showed similar microshear bond strength. The degree of conversion of the F was higher than the C and CPH. The degree of conversion of the composites photo-activated through a 0.4 mm was higher than the composites photo-activated through thicker ceramics. The C showed the highest color change, while the CPH showed similar color change to the F. In conclusion, pre-heated conventional composites seem to be a potential alternative to lute ceramic veneers such as the flowable composites.

The Use of Composite Layering Technique to Mask a Discolored Background: Color Analysis of Masking Ability After Aging—Part II

The aim of this study was to evaluate the effectiveness of the layering technique to mask a discolored background (C4) after one year of water aging. The technique was used with three resin composite restorative systems (IPS Empress Direct, Charisma Diamond, and Filtek Z350XT). Ninety 1.5-mm-thick specimens were divided into groups and subgroups according to the restorative system and resin composite shade combination used in the layering technique (enamel, body, and dentin). The color measurements were made by reflection spectrophotometer (SP60, EX-Rite) over the C4 substrate at two time points: after 24-hour water immersion (T0) and after one-year water aging (T1). The masking ability was evaluated by calculating the ΔE between an inherent color background and a C4 background at T0 and T1. CIELAB and CIEDE2000 formulas were used for comparative analysis between T0 and T1 color measurements. Analysis of variance and Turkey's post hoc test (a=0.05) were performed to analyze ΔEab and ΔE00 mean values. The Z350XT restorative system presented adequate masking ability in the combinations of 0.5 mm body + 1.0 mm dentin, 0.5 mm enamel + 1.0 mm dentin, and 1.5 mm dentin after 24-hour water immersion. The masking ability was affected negatively by water aging in most of the combinations. The IPS Empress Direct was the only system that remained stable after aging in the combinations of 0.5 mm enamel + 1.0 mm dentin and + 1.5 mm dentin (p=0.05 and p=0.47 for CIELAB; p=0.15 and p=0.51 for CIEDE2000), although it did not present adequate masking ability in both time points. None of the combinations of any system presented adequate masking ability after prolonged water aging.

Recent Advances in Color and Whiteness Evaluations in Dentistry

Background:

The final goal of color measurement or shade specification in dentistry is the reproduction by prosthetic materials of all important appearance characteristics of natural oral structures. The application of color science in dentistry is an objective way to measure and evaluate such structures and dental materials in clinical practice and dental research.

Methods:

Literature on color science was reviewed to present new metrics to evaluate color differences of dental materials and dental structures. Visual acceptability and perceptibility values of color differences are reviewed and new whiteness indexes to describe whiteness in dentistry are presented.

Results:

In the last decade, the CIELAB 50:50% perceptibility and acceptability thresholds were set to 1.2 and 2.7, respectively, and the CIEDE2000 50:50% perceptibility and acceptability thresholds were set to 0.8 and 1.8. The CIEDE2000 color-difference formula became increasingly popular in dentistry. Developments in color science have led to the description of tooth whiteness and changes in tooth whiteness based on whiteness indexes, with the most relevant being the WID whiteness index, which is a customized index based in CIELAB color space.

Conclusion:

The application of color science in dentistry has allowed the precise description of tooth color and whiteness. The revised and new CIEDE2000 color-difference formula is expected to fully replace the outdated CIELAB formula in almost all dental applications. Recent psychophysical studies have reported values of visual thresholds and new whiteness indexes, which can serve as quality control tools to guide the selection of esthetic dental materials, evaluate clinical performance, and interpret visual and instrumental findings in clinical dentistry, dental research, and subsequent standardization.

Acceptability and perceptibility thresholds in dentistry: A comprehensive review of clinical and research applications

OBJECTIVE

The objective was to provide a literature review on perceptibility and acceptability thresholds in dentistry and corresponding recommendations.

OVERVIEW

A literature review on visual thresholds included findings on the judgments of the color and appearance of tooth-, gingiva- and skin-colored restorative dental materials. Discrepancies in study design contributed to inconsistencies in the research findings of some studies. These differences are related to (a) number of observers and inclusion criteria, (b) specimen number and size, (c) color measurement instrument and the setup and formulas used, (d) psychophysical experiment, (e) data processing (fitting method), and (f) % perceptibility or % acceptability values. A straightforward, consistent and practical model for the clinical and research application and interpretation of visual thresholds and recommended protocols for threshold research were provided.

CONCLUSIONS

Visual thresholds are of paramount importance as a quality control tool and guide the evaluation and selection of dental materials and their clinical performance. Although clinical shade matching conditions and method are rarely controlled, research on visual thresholds, especially when aiming to set standards for the profession, must be carefully planned and executed.

CLINICAL SIGNIFICANCE

Perceptibility and acceptability thresholds define visual match or mismatch of color, translucency, and whiteness in dentistry. Clinical and research findings cannot be fully interpreted in terms of real-life relevance without comparison with perceptibility and acceptability tolerances.

Surface Sealant Effect on the Color Stability of a Composite Resin Following Ultraviolet Light Artificial Aging

OBJECTIVE

To examine how exposure to accelerated artificial aging (AAA) stimuli (ultraviolet [UV] light) affects the color stability of a composite resin following surface sealant (SS) application.

METHODS AND MATERIALS

A total of 30 cylindrical composite resin (Esthet-X) discs were prepared using Teflon-coated rings. The treatment groups, defined by different SS (Seal-N-Sine, PermaSeal, OptiGuard, Biscover LV, and DuraFinish) use, were divided into five groups of six discs each. The discs were subjected to baseline color measurements followed by measurements after surface sealant application (specular included component [SCI] and specular excluded component [SCE]) using a spectrophotometer. Three measurements (SCI and SCE) were performed for a total of 18 readings (test surface) per specimen group. All specimens were then exposed to a UV light source for a total of 382 hours. Color readings of the specimens were again recorded for each group. Quantitative color measurements were executed using Commission Internationale de l'Eclairage L*a*b* calculations.

RESULTS

Baseline color measurements of the composite resin discs, following the AAA exposure protocol, revealed no significant differences. A comparison of the composite resin discs before and after SS application (without UV light exposure) showed statistically significant differences using both SCI and SCE measurement criteria. Although significant differences were encountered between the ΔL*, Δa*, Δb*, and ΔE parameters, all specimens (groups) were within the clinically acceptable range (1.0<ΔE≤ 3.3). Again, statistically significant differences were noted (ΔL*, Δa*, Δb*, and ΔE parameters) for all specimen groups receiving SS application, utilizing both SCI and SCE measurements, following exposure to UV light. All groups were within the clinically acceptable range (1.0<ΔE≤ 3.3), except the Durafinish group. The Durafinish SS group experienced significantly greater (p<0.001) overall color change (SCI and SCE) following UV light exposure. An intergroup comparison following UV exposure revealed that the Permaseal, OptiGuard, and Seal-n-Shine SS groups displayed the least amount of color change statistically but not necessarily always perceptibly significant, while the Durafinish group exhibited the greatest color change statistically and perceptibly.

CONCLUSIONS

The color stability of a composite resin, including the addition of most SSs, was not affected perceptibly by UV light exposure.

Shade Stability of Polymer-Infiltrated and Resin Nano Ceramics

BACKGROUND

The esthetics plays an increasingly significant role in today's dentistry.

OBJECTIVE

The objective was to investigate the shade stability of a polymer-infiltrated and a resin nano ceramic in comparison to a conventional feldspar ceramic and an acrylate polymer.

METHODS

20 specimens of each of the materials, CAD-Temp (CT), Mark II (M), VITA Enamic (VE) and Lava Ultimate (LU), were prepared using the standard method. These were divided into groups (n=5) and placed in the following stain solutions: Distilled water, coffee, Coca-Cola and red wine for 14 days. The shade of each specimen was measured before and after using a spectrophotometer (n=5). The data were analyzed using ANOVA and Tukey's test (p ≤ 0.05).

RESULTS

The largest ΔE mean values were observed in CT by Coca-Cola (4.38 ± 0.41), in M by coffee (5.95 ± 0.62), in VE (6.02 ± 0.78) and LU (8.61 ± 0.30) by red wine. LU had the largest and strongest overall shade differences (total score: SSC=16.95) and CT the least (SSC=8.74). Overall shade differences of VE (SSC=12.03) and M (SSC=12.48) were statistically indistinguishable. After 14 days, only Coca-Cola caused clinically relevant shade differences in CT (ΔE > 2.7); this was also caused by coffee, Coca-Cola and red wine in M and coffee and red wine in VE and LU.

CONCLUSION

On average, VE showed fewer shade differences than LU. After 14 days of immersion, shade differences which exceeded the clinical acceptance threshold of ΔE=2.7 were shown by CT in Coca-Cola, by M in coffee, Coca-Cola and red wine, and by VE and LU in coffee and red wine.

Properties of Experimental Dental Composites Containing Antibacterial Silver-Releasing Filler

Secondary caries is one of the important issues related to using dental composite restorations. Effective prevention of cariogenic bacteria survival may reduce this problem. The aim of this study was to evaluate the antibacterial activity and physical properties of composite materials with silver sodium hydrogen zirconium phosphate (SSHZP). The antibacterial filler was introduced at concentrations of 1%, 4%, 7%, 10%, 13%, and 16% (w/w) into model composite material consisting of methacrylate monomers and silanized glass and silica fillers. The in vitro reduction in the number of viable cariogenic bacteria Streptococcus mutans ATCC 33535 colonies, Vickers microhardness, compressive strength, diametral tensile strength, flexural strength, flexural modulus, sorption, solubility, degree of conversion, and color stability were investigated. An increase in antimicrobial filler concentration resulted in a statistically significant reduction in bacteria. There were no statistically significant differences caused by the introduction of the filler in compressive strength, diametral tensile strength, flexural modulus, and solubility. Statistically significant changes in degree of conversion, flexural strength, hardness (decrease), solubility (increase), and in color were registered. A favorable combination of antibacterial properties and other properties was achieved at SSHZP concentrations from 4% to 13%. These composites exhibited properties similar to the control material and enhanced in vitro antimicrobial efficiency.

Influence of Photoinitiator on Accelerated Artificial Aging and Bond Strength of Experimental Resin Cements

Abstract The goal of this study was to evaluate in vitro the effect of the photoinitiator phenylpropanedione (PPD), alone or combined with camphorquinone (CQ), on color stability of photoactivated resin cements and their bond strength to ceramics using a micro-shear test. Four resin cements were used: a commercial brand cement (RelyX Veneer®) and 3 experimental cements with different types and concentration of photoinitiators. For color analysis, ceramic discs were cemented on bovine dentin specimens to simulate indirect restorations (n=8) and were exposed to UV for 120 h and tested for color alteration using a reflectance spectrophotometer and the CIEL*a*b* system. Data were analyzed by Anova and Tukey’s test at 5% significance level. The color test results did not present statistically significant difference for the ∆E for all the studied cements, neither for ∆L, ∆a and ∆b. For the bond strength, all the studied cements showed statistically significant differences to each other, with the highest result for the RelyX Veneer® (29.07 MPa) cement, followed by the cement with CQ (21.74 MPa) and CQ+PPD (19.09 MPa) cement; the lowest result was obtained by the cement using only PPD as a photoinitiator (13.99 MPa). So, based on the studied parameters, PPD was not advantageous as photoinitiator of resin cements, because it showed a low value of bond strength to the ceramics and no superior color stability.