Influence of light-cured luting agents and associated factors on the color of ceramic laminate veneers: A systematic review of in vitro studies

Using digital photographs as a tool to assess the clinical color stability of lithium disilicate veneers: A clinical trial

STATEMENT OF PROBLEM

Clinical information regarding the color stability of lithium disilicate veneers by using different methods of evaluation is scarce.

PURPOSE

This clinical trial aimed to evaluate whether digital photographs are a reliable method of clinically assessing the color stability of lithium disilicate veneers. Standardized digital photographs (ELAB) were compared with the VITA Easyshade spectrophotometer (ES) at baseline and at a 6-month follow-up.

MATERIAL AND METHODS

A split-mouth model was used in this randomized clinical trial to assess the performance of ceramic veneers (N=162), which were produced by either the CAD (IPS e.max CAD; n=81) or PRESS technique by heat pressing (IPS e.max PRESS; n=81), including the color dimension assessment. The ELAB evaluation was performed by making digital photographs with polarized light and a white balance (WhiBal) card. These data were transferred to the Adobe Lightroom CC2015 software program in RAW extension. The Digital Color Meter App (Apple) was used to measure L∗, a∗, and b∗ coordinates in this method. The ES color evaluation was performed with a spectrophotometer (Easy Shade) (control group) in the CIELab system. Measurements were performed 1 week after cementation (baseline) and at a 6-month follow-up. Data collected by the ELAB and ES methods were analyzed by a blinded calibrated operator to calculate ΔE by using the Mann-Whitney-Wilcoxon test (α=.05).

RESULTS

For all periods, the comparison among ELAB and ES methods (P=.331), CAD×PRESS by ELAB (P=.658), and CAD×PRESS by ES (P=.833) showed no statistically significant differences.

CONCLUSIONS

Standardized digital photographs (ELAB) were shown to be a straightforward and available resource for evaluating the color stability of lithium disilicate veneers, manufactured by CAD or PRESS.

The capacity of conservative preparations for lithium disilicate glass-ceramic laminates luted with different resin cements to mask different substrate shades: A minimally invasive esthetic approach

OBJECTIVE

Demonstrate the ability of 0.5 mm thickness lithium disilicate laminates associated with resin cement to mask different substrate saturations.

METHODS

60 specimens (n = 5) were prepared with CAD/CAM lithium disilicate glass-ceramic IPS e.max CAD, 0.5 mm thick, in three degrees of translucency (HT, MT and LT); cemented by Variolink Esthetic LC Light+ (L) and Neutral (N) on composite resin substrates A1 and A4 shades. Color measurements were performed by a spectrophotometer (CM-3700d -Konica Minolta). The L*, a*, b* parameters of the tri-layer structure (laminate/ resin cement/ substrate) were used to calculate color difference ( ∆ E 00 ) by CIEDE2000 formula and Translucency Parameter (TP 00 ). This study adopted ∆ E 00 = 0.8, as perceptibility threshold (PT), and ∆ E 00 = 1.8, as acceptability threshold (AT). Statistical analyses were performed by one-way ANOVA and Tukey tests (a = 0.05).

RESULTS

Color difference between resin cement shades showed statistical differences (p < 0.0001) and ∆ E 00 > 1.8 for all groups. Color difference between substrates saturations showed a significant statistical difference (p < 0.0001) and ∆ E 00 values above AT for all groups. TheTP 00 demonstrated significant statistical differences (p < 0.0001). The LTL combination, the opaquest set, showed the smallest ∆ E 00 values between substrate shades differences, however, above AT.

CONCLUSION

The translucency of the lithium disilicate, the substrate saturation and the resin cement opacity influenced final color of restoration. The ceramic translucency impact on final color was reduced by opaque resin cement. Furthermore, the LT lithium disilicate and the Light+ resin cement reduced the translucency of the restoration, contributing to mask saturated substrate.

CLINICAL RELEVANCE

This study shows the influence of conservative lithium disilicate laminates with different degrees of translucency associated with resin cement on final color of saturated substrate restorations. A minimally invasive esthetic protocol for masking substrates is demonstrated by associating low translucency ceramic laminates and opaque resin cement.

Effect of shade and opacity on color differences and translucency of resin composite veneers over lighter and darker substrates

To evaluate color differences (ΔE00) and translucency parameters (TP) from mono, bi, and trilayer resin composite veneers using different opacities and shades of resin composite over lighter and darker simulated tooth-colored substrates. Mono, bi, and trilayer veneers (1.5 mm) (n = 12) were made using two shades (A1 and A2) and three opacities (enamel, body, and dentin) of resin composite over simulated lighter (A1) and darker (C4, and C4+) tooth-colored substrates. CIEDE2000 formula was used to calculate ΔE00 considering simulated tooth-colored substrate versus opacities in distinct mono, bi, and trilayer combinations of resin composite over the simulated tooth-colored substrate. The TP was calculated using color coordinates measured over standard white and black backgrounds. Differences in ΔE00 and TP values were calculated with a Three-way Analysis of Variance followed by Tukey's post-hoc test. A1E and A1B monolayer veneers showed similar TP values. Significantly higher ΔE00 values were observed over darker (C4 and C4+), and lower over lighter (A1) simulated tooth-colored substrate. Bilayer and trilayer veneers using dentin opacity provided similar ΔE00 values over the darker tooth-colored substrate. Distinct shades and opacities of resin composite layer combinations over lighter and darker tooth-colored substrates significantly affected TP and ΔE00 values. A1 shade and dentin opacity of monolayer resin composite veneers yielded higher ΔE00 values over darker tooth-colored substrates.

Color stability of dual-cured and light-cured resin cements: A systematic review and meta-analysis of in vitro studies

PURPOSE

This systematic review and meta-analysis aimed to evaluate the difference in the color stability of light-cured and dual-cured resin cements.

MATERIALS AND METHODS

Two separate reviewers used the PubMed, Scopus, Web of Science, Embase, and Scielo databases to execute the systematic review. For the analysis, studies that evaluated the color stability of dual-cured and light-cured resin cements over time were used. The random effects model was used in the meta-analysis. Analyses of subgroups were carried out based on the aging technique. The methodological quality of each in vitro study was evaluated in accordance with the parameters of a prior systematic review.

RESULTS

From all databases, a total of 2223 articles were retrieved. Following the screening of titles and abstracts, 44 studies were selected for full text review, and a total of 27 articles were used for the qualitative analysis. Finally, 23 articles remained for the qualitative analysis. The majority of studies were labeled as having a medium risk of bias. The global analysis showed that the dual-cure resin cements had considerably greater differences in the color change (p = 0.006). A high heterogeneity index (86%) was found in the analysis.

CONCLUSIONS

The best available in vitro evidence suggests that dual-polymerizing cement has higher color variation than light-polymerized materials. To reduce the likelihood of color change after the luting of thin ceramic restorations, clinicians should employ light-polymerizable resin cements.

Overviews on the Progress of Flowable Dental Polymeric Composites: Their Composition, Polymerization Process, Flowability and Radiopacity Aspects

A review article has been conducted including the main research results and comments referring to flowable dental polymeric materials. To begin with, the synthesis and composition of this category of composites is discussed, revealing the major components of the commercial products in terms of chemistry and proportion. Later, the polymerization characteristics are unfolded regarding the reaction time and rate, volumetric shrinkage and depth of cure for both photocurable and self-curable composites. To continue, some perspectives of the pre-treatment or accompanying processes that a clinician may follow to enhance the materials' performance are described. Fluidity is certainly associated with the progress of polymerization and the in-depth conversion of monomers to a polymeric network. Last, the aspects of radiopacity and translucency are commented on, showing that all flowable polymeric composites satisfy the radiography rule, while the masking ability depends on the fillers' properties and specimen thickness. The reviewing article is addressed to all field scientists and practitioners dealing with flowable dental composites studies or applications.

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.

A systematic review and meta-analysis on using preheated resin composites as luting agents for indirect restorations

OBJECTIVES

This systematic review investigated the hypothesis that preheated resin composites (RCs) used as luting agents improve the mechanical properties, physicochemical performance, and color of indirect ceramic restorations.

MATERIALS AND METHODS

Literature search was performed in three databases (Medline/PubMed, Scopus, and Web of Science) and in the grey literature (OpenGrey, ProQuest, and Catalog of Theses & Dissertations from CAPES). Eligibility criteria included only studies comparing at least one preheated RC used as a luting agent with resin cements.

RESULTS

Data regarding the mechanical properties, physicochemical characteristics, and color were analyzed qualitatively, and the microtensile bond strength and film thickness were also evaluated by meta-analysis. The search strategy identified 3894 papers, and 28 were full-text screened. Seven studies were included in the review, and 5 were included in the meta-analysis. No significant difference was found for microtensile bond strength (P = 0.14). Preheated RCs showed significantly higher film thickness than resin cements (P = 0.001).

CONCLUSION

Overall, the use of preheated RCs as luting agents offers similar to poorer performance than using resin cements for bonding indirect restorations.

CLINICAL RELEVANCE

Despite the claim that preheated RC could be used as a luting agent, further studies should investigate the effect of clinically unacceptable film thickness.

Effect of aging on color stability of amine-free resin cement through the ceramic laminate veneer

Background

This study aimed to assess the color change of two amine-free dual-cure resin cements following aging in comparison with a light-cure resin cement.

Materials and Methods

This in vitro, experimental study evaluated 6 groups (n = 10), including three groups of cements bonded to feldspathic porcelain and three groups of resin cements alone. Panavia V5 (Kuraray) and G-CEM LinkForce (GC) dual-cure resin cements and Choice 2 (Bisco) light-cure resin cements were bonded to porcelain according to the manufacturers' instructions. The color parameters of the groups were measured before and after 5000 thermal cycles by spectrophotometry. Data were analyzed using two-way ANOVA and Tukey's post hoc test (α =0.05).

Results

The color change (ΔE) of the cement groups alone was significantly greater than that of porcelain-bonded cements. The ΔE of G-CEM LinkForce cement group was significantly higher than that of Panavia V5 group (P = 0.020), and the ΔE of the latter group was significantly higher than that of Choice 2 cement group (P = 0.021).

Conclusion

Considering the color change of cements evaluated in this study, Choice 2 and Panavia V5 cements bonded to porcelain showed acceptable color change, which indicates that they are suitable for cementation of esthetic dental restorations. Ceramic laminates have become an ideal esthetic treatment for anterior restorations. The resin cement discoloration can affect final appearance of these restorations. Besides that, exposed resin cement line can lead to the esthetic problem over time.

Effect of aging on color stability and bond strength of dual-cured resin cement with amine or amine-free self-initiators

This study aimed to evaluate the effect of aging on the color stability and bond strengths of dual-cured resin cements containing amine or amine-free self-initiators. Three dual-cured and one light-cured resin cements were used. The covered (by lithium disilicate ceramic disks) and uncovered groups (n=10) were included. Color measurements were tested after 24 h, 10,000 and 20,000 thermal cycles (TCs). Micro-shear bond strengths (µSBS) were tested after 24 h, 10,000 and 20,000 TCs, and failure modes were analyzed (n=14). Two-way ANOVA and Tukey's test were implemented for color difference (ΔE*_ab) and µSBS (α=0.05). The mean ΔE*_ab difference was significant among groups (p<0.001). The lowest ΔE*_ab values were obtained for dual-cured resin cement with amine-free self-initiators dual-cured cement after aging in all dual-cured resin cements, and the µSBS of the dual-cured resin cements on ceramic was significantly higher than that of the light-cured ones after aging (p<0.001).

Colour stability of sectional laminate veneers: A laboratory study

BACKGROUND

This study aimed to evaluate the colour stability of sectional laminate veneers (SLVs) fabricated with four and cemented with two different materials.

METHODS

Eighty SLVs were prepared with a thickness of 0.2-0.4 mm from IPS e.max CAD, Lava Ultimate, CEREC Blocs and IPS InLine and were cemented with Variolink Veneer and Variolink N to form eight groups (n:10). After cementation, specimens underwent 5000 thermocyles prior to immersion in a coffee solution.

RESULTS

Colour change before and after thermal cycling did not reveal significant differences (P > 0.05). After coffee immersion, significant colour change was observed in all groups (P > 0.05). Only IPS InLine cemented with Variolink Veneer was considered clinically acceptable (∆E < 3.3). According to observer scorings, marginal discolouration was higher in Lava Ultimate, while no discolouration was observed in IPS InLine. Dual or light-curing resin cements showed insignificant differences.

CONCLUSIONS

SLVs fabricated with different aesthetic materials underwent perceptible (∆E > 3.3) discolouration except for the IPS InLine cemented with light-curing resin cement. Cementation with either dual-curing or light-curing resin cements does not by itself affect colour stability. The highest marginal discolouration was in the Lava Ultimate group while no discolouration was detected in the IPS InLine group.

3D printing restorative materials using a stereolithographic technique: a systematic review

OBJECTIVE

To present through a systematic review a qualitative analysis of studies published on stereolithography-based 3D printing of restorative materials and their clinical applicability.

METHODS

The literature search was conducted based on the question: "What is the state-of-the-art of available restorative materials for 3D printing based on stereolithography?" Online search was conducted in three databases (MEDLINE/PubMed, Scopus and Web of Science) with no restriction for year of publication. Data are reported based on PRISMA, including publication details such as authors and their countries, year and journal of publication, and study design. The synthesis is focused on describing the dental restorative materials and properties evaluated, applied methods, 3D printers used and clinical applicability.

RESULTS

Studies that fit the inclusion criteria were performed in Asia (21), Europe (16) and USA (10), mostly using polymer-based restorative materials (38) for 3D printing constructs. Stereolithographic-printed ceramic-based restorative structures were evaluated by 9 studies. Many studies reported on dimensional accuracy (14), strength (11) and surface morphology (9) of the printed structures. Antibacterial response, cytotoxicity, internal and marginal fit, fracture and wear resistance, density, viscosity, elastic modulus, hardness, structural shrinkage and reliability, degree of conversion, layer cure depth, fatigue, and color were also evaluated by the included studies. Many of them (11) published a proof of concept as an attempt to demonstrate the clinical feasibility and applicability of the technology to print restorative materials, but only 5 studies actually applied the 3D printed restorative structures in patients, which highlights an increasing interest but limited early-stage translation.

SIGNIFICANCE

The fast expansion of stereolithographic-based 3D printing has been impressive and represents a great technological progress with significant disruptive potential. Dentistry has demonstrated an incredible willingness to adapt materials, methods and workflows to this promising digital technology. However, esthetic appearance, wear resistance, wet strength and dimensional accuracy are the main current clinical limitations restricting the progression to functional part production with 3D printing, which may explain the absence of clinical trials and reports on permanent/definitive dental restorative materials and structures.

Influence of feldspar ceramic thickness on the properties of resin cements and restorative set

This in vitro study evaluated the influence of feldspathic ceramic thickness on the properties of light- and dual-cured resin cements. For each cement (RelyX Veneer, Allcem Veneer, RelyX Ultimate, and Allcem Dual), three ceramic specimens were prepared, with seven thicknesses for each (0.5, 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 mm). The degree of conversion, Vickers microhardness, irradiance power, color variation (ΔE₀₀ ), and translucency parameters were assessed. Microhardness and irradiance power were analyzed using analysis of variance (ANOVA) with post hoc Tukey's test, while ΔE₀₀ , translucency parameters, and degree of conversion were analyzed using ANOVA of ranks with post hoc Duncan's Multiple Range Test. The relationship between each of the dependent variables (degree of conversion, ΔE₀₀ , and translucency parameter tests) and the specimen thickness was described using linear regression for each of the four resin cements. The significance level for all analyses was set at 5%. RelyX Ultimate yielded the lowest degree of conversion values among all resin cements. Allcem Veneer produced the lowest microhardness values, without statistical differences between thicknesses, of up to 1 mm. Allcem Dual produced the highest ΔE₀₀ and translucency parameter values. Feldspathic ceramic thickness influenced the mechanical properties of resin cements and optical aspects of the restorative set.

Curing potential and color stability of different resin-based luting materials

PURPOSE

To determine the curing potential and color stability of resin-based luting materials for aesthetic restorations.

MATERIAL AND METHODS

Four resin-based luting agents were tested: traditional dual-activated resin cement (RelyX ARC, ARC), amine-free dual-activated resin cement (RelyX Ultimate, ULT), light-activated resin cement (RelyX Veneer, VEN), and pre-heated restorative resin composite (Filtek Supreme, PHC). Degree of C=C conversion was determined by infrared spectroscopy (n=3) with direct light exposure or with interposition of 1.5-mm-thick ceramic (e.max Press HT) between the luting material and light. The curing potential considered the ratio between these two scenarios. Color difference (n=6) was determined by CIELAB (ΔE_ab) and CIEDE2000 (ΔE₀₀) methods, by spectrophotometer measurements made 24h after photoactivation and 90 days after storage in water. Data was submitted to ANOVA and Tukey's test (α=0.05).

RESULTS

The luting agents affected both conversion and color stability. With ceramic, ARC produced the highest conversion among the tested groups (75±1%) and the pre-heated composite (PHC) the lowest one (51±3%), but the curing potential was similar for all materials. ULT produced lower ΔE_ab than ARC. PHC presented the lowest color difference when considered both CIELAB and CIE2000 methods (ΔE_ab 2.1±0.4; ΔE₀₀ 1.6±0.2).

SIGNIFICANCE

All luting strategies presented high curing potential. Amine-free dual-activated material was able to reduce color difference than that formulated with the amine component. Pre-heated composite produced the least color variation after storage.

Annual review of selected scientific literature: A report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

This comprehensive review of the 2018 dental literature is provided to inform busy dentists about progress in the profession. Developed by the Committee on Scientific Investigation of the American Academy of Restorative Dentistry, each author brings discipline-specific expertise to one of the 8 sections of the report including (1) prosthodontics; (2) periodontics, alveolar bone, and peri-implant tissues; (3) implant dentistry; (4) dental materials and therapeutics; (5) occlusion and temporomandibular disorders; (6) sleep-related breathing disorders; (7) oral medicine and oral and maxillofacial surgery; and (8) dental caries and cariology. The report targets important information that will likely influence day-to-day treatment decisions. Each review is not intended to stand alone but to update interested readers so that they may visit source materials if greater detail is desired. As the profession continues its march toward evidence-based clinical decision-making, an already voluminous library of potentially valuable dental literature continues to grow. It is the intention of this review and its authors to provide assistance in navigating the extensive dental literature published in 2018. It is our hope that readers find this work useful in the clinical management of patients moving forward.

Color stability of ceramic veneers as a function of resin cement curing mode and shade: 3-year follow-up

The influence of curing mode and shade of resin cements on the color stability of minimum-thickness ceramic veneers after a three-year storage time in distilled water was evaluated in this study. Ninety-six 0.5-mm-thick feldspathic ceramic veneers (Mark II) were luted onto resin composite substrates (Filtek Z350 XT, shade A2E) with two light-cured (NX3 Light-cure and AllCem Veneer) and dual-cured resin cements (NX3 dual-cure and AllCem) in various shades. The specimens were stored in distilled water at 37°C. Color measurements were performed with a spectrophotometer at the following times: 1h and 24h; 7, 30, and 180 days; and 1, 2, and 3 years. Data for color difference (ΔE_ab) light-cured and dual-cured resin cements were analyzed by two-way ANOVA with repeated measures and Tukey’s test (α = 0.05). For the light-cured cements, the ΔE_ab values were as follows: NX3-Yellow (2.37±1.35) = ACV-A1 (2.40±1.21) = ACV-Trans (2.52±1.46) = ACV-E-Bleach M (2.56±1.42) = NX3-White (2.69±1.49) = NX3-Clear (2.98±1.68). The lowest ΔE values were found for 1 h (0.61±0.36)^a, followed by 24 h (1.15±0.55)^b and 30 days (2.48±1.11)^c. One year, 180 days, and 2 and 3 years presented higher ΔE_ab values (3.34±0.94, 3.52±1.04, 3.52±0.95 and 3.55±1.14, respectively)^d. For the dual-cured cements, the ΔE_ab values varied as follows: NX3-Clear (2.32±1.24)^a = NX3-Yellow (2.37±1.32)^a = NX3-White (2.76±1.43)^a < AC-Trans (3.77±1.91)^b = AC-A3 (4.13±2.11)^b < AC-A1 (5.38±2.92)^c. Considering time, the lowest ΔE_ab values were found for 1 h (0.48±0.25)^a, followed by 24 h (2.13 ±0.83)^b, 30 days (3.54±1.31)^c, and 180 days (3,70±1.73)^c. The follow-up times of 1 (4.43±2.15)^d, 2 (5.02±1.74)^e, and 3 years (4.90±2.12)^e presented higher ΔE_ab values. This study demonstrated that light-cured resin cements were less susceptible to color change than dual-cured cements. After 2 years of follow-up, all cements presented ΔE_ab values above the acceptability threshold.

The influence of different shades and brands of resin-based luting agents on the final color of leucite-reinforced veneering ceramic

Objectives

This study aimed to evaluate the influence of different shades and brands of resin-based luting agents on the final color of a leucite-reinforced veneering ceramic.

Methods

This in-vitro study was done on 36 ceramic discs (IPS Empress I, 11 × 0.5 mm, A2 shade) and 36 cement disks (11 × 0.2 mm) made of Panavia SA Cement Plus (Kuraray Medical Inc.) and Choice2 (Bisco Inc., Schumburg) brands in translucent, universal A2, and opaque shades (n = 6 per each color in each resin cement brand). Color parameters (CIEL^*a^*b^*) of ceramic specimens were calculated without and with each brand/shade of resin-based luting agents by using a spectrophotometer, and put into CIELab formula. The color differences (ΔE) between the two sets of measurements were calculated and analyzed with two-way ANOVA and Tukey’s post hoc test (α = 0.05).

Results

Both the resin-based luting agent shade (P < 0.001) and brand (P = 0.023) significantly affected the color differences. ΔE values were significantly different between Panavia-opaque and Choice2-opaque (P < 0.001). No significant difference existed between ΔE of the two brands in A2 (P = 0.178) and translucent shades (P = 0.079). The ΔE values of Panavia-A2 was significantly different from the translucent and opaque shades of the same brand. Moreover, the ΔE of Choice2-translucent shade was significantly lower than that of A2 and opaque shades. The ΔE values were higher than the clinically-acceptable threshold in all groups (ΔE > 3.7) except for Choice2-translucent (ΔE = 3.37).

Conclusions

The final color of leucite-reinforced veneering ceramic can be affected by the same shades of resin-based luting agents from different brands and different shades of resin-based luting agents from the same brand.