Resin-based luting agents and color stability of bonded ceramic veneers

Evaluation of pulp chamber temperature during cementation with the preheated composite resin technique

STATEMENT OF PROBLEM

The cementation technique using preheated composite resin requires high temperatures for optimal execution and may lead to increased and damaging intrapulpal temperatures. Whether the technique can lead to a temperature increase that might lead to necrosis of the pulp tissue is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the temperature variation in the pulp chamber of bovine teeth with veneer-type preparations during veneer cementation using the preheated composite resin technique.

MATERIAL AND METHODS

A total of 103 bovine incisors were divided into 8 groups (n=10) and prepared for indirect veneers with different preparation depths: 2.0 mm, 1.5 mm, 1.0 mm, and 0.5 mm. Veneers were cemented on these preparations using 2 cementation protocols: preheated composite resin and photopolymerizable resin cement. The teeth were attached to a device containing a temperature sensor which was inserted into the pulp chamber to quantify the intrapulpal temperature variation produced during the cementation protocols. The data were analyzed using a statistical software program. The level of statistical significance for the analyses was with a confidence interval of 95%, sampling power of 80%, and a moderate effect size (0.36).

RESULTS

The groups cemented with preheated composite resin and the groups with the greatest preparation depth had the highest mean intrapulpal temperature; the PHC2 group presented a mean ±standard deviation temperature increase of 5.70 ±2.14 °C.

CONCLUSIONS

The heat generated by heating the resin contributed to the increase in intrapulpal temperature. Temperature variations were greater in deeper preparations, especially when preheated resin technique was used.

The influence of finishing line and luting material selection on the seating accuracy of CAD/CAM indirect composite restorations

OBJECTIVES

This study aimed to assess the seating accuracy of resin composite CAD/CAM overlay restorations, employing various preparation designs and luting materials (pre-heated composite (HC) or resin cement (RC)).

METHODS

A human molar's STL file was utilized to create 100 3D-printed resin tooth replicas, randomly distributed into 5 groups (n = 20) based on finishing line preparation designs: 1) Rounded shoulder above the dental equator - DE (SA); 2) Chamfer above the DE (CA); 3) Butt joint above the DE (BJ); 4) Rounded shoulder below the DE (SB); 5) Chamfer below the DE (CB). Digital impressions were acquired for all replicas, and restorations milled using Tetric CAD (Ivoclar Vivadent). The restorations were luted with HC (Tetric Prime, Ivoclar Vivadent) or RC (RelyX Universal, 3 M). Seating accuracy was evaluated through digital scans during try-in without any luting agent and post-cementation using a 3D analysis software (Geomagic wrap, 3D Systems). Data were statistically analyzed using Two-Way ANOVA (p < 0.05).

RESULTS

The type of luting material (RC vs HC), preparation design, and their interactions significantly impacted 3D seating of the restorations (p < 0.001). HC exhibited higer volumetric increase than RC. BJ and CA designs consistently demonstrated superior seating accuracy, irrespective of the luting material used.

CONCLUSIONS

The utilization of pre-heated composite resin could negatively influence the seating of overlay restorations, probably due to its higher viscosity when compared to the resin cement. However, when HC is selected as luting agent, preparation designs lacking internal angles are recommended for enhancing the precision of overlays seating.

Application of Bulk-Fill Composite to Simplify the Cementation of Indirect Restorations: The COMBO Technique

This article proposes a technique to simplify the cementation of indirect restorations by exploiting the advantageous properties of bulk-fill composites (BFCs). The proposed technique consists of using a thin layer of a high-viscosity (HV) BFC in the interproximal margins of the preparation and applying low-viscosity (LV) resin luting agents (RLAs) to the rest of the prepared surface. The application of the HV BFC limits the extrusion of the LV RLAs in the interproximal area, deviating the excesses of LV RLAs only on the vestibular and lingual side. This deviation allows the management and control of the excess material in complicated interproximal spaces, simplifying the cementation procedure of indirect restorations and achieving a reliable final result in terms of removing excess in a safe and repeatable way. This technical report provides an alternative clinical approach for cementing indirect restorations using the consistency and viscosity of different RLAs.

Color alteration of CAD/CAM 3D-printed, milled resin-ceramic hybrid material compared to enamel

To assess color and translucency change (∆E00 and ∆TP) of 3D-printed (Varseosmile crown plus, VS) and milled resin-ceramic hybrid material (Cerasmart, CS) compared to enamel (E) when immersed in distilled water (DW) and coffee (C). Sixty VS, CS, and E specimens were immersed in DW and C for 30 days. Statistics analysis using t-test and one-way ANOVA at p≤0.05. ∆E00 of VS, CS, and E significantly increased when immersed in coffee (p<0.001, p<0.001 and p=0.01, respectively). E has more ∆E00 than VS and CS (p<0.001). The translucency of VS and CS was reduced after water and coffee immersion. The translucency of E was increased after immersion in water and coffee. ∆TP of VS, CS, and E were not different between immersion in water and coffee at p=0.08, p=0.43 and p=0.72, respectively. Therefore, DW and C have distinct effects on the ∆E00 and ∆TP among VS, CS and E.

Effects of pre-heating on physical-mechanical-chemical properties of contemporary resin composites

This research assessed the effects of pre-heating on the physical-mechanical-chemical properties of different resin composites. For this, resin composites were evaluated in 6 levels: Admira/ADM, Vitra/VIT, Filtek Supreme/FS, Filtek Supreme Flowable/FSF, Filtek One/FO, and Filtek Bulk Fill Flowable/FBF; temperature was evaluated in 4 levels using a composite heater: room temperature/22 ºC, 37 ºC, 54 ºC, and 68 ºC. Response variables were: degree of conversion/DC, flexural strength/FS and color stability/ΔE (immediately after light curing/LC, after 7 days of dark-dry-storage, and after 24 h and 3 days of artificial aging in water at 60 ºC). Data were subjected to 2-way ANOVA (DC and FR) and 3-way repeated measurements ANOVA (ΔE), all followed by Tukey's test (α = 5%). DC were similar (FBF, FS, and FSF) or increased (ADM, FO, and VIT) as the temperature increased. Results of FR were unchanged or increased for all composites except VIT and ADM. High-viscosity composites (VIT and FS) showed higher FR values than low-viscosity composite (FSF). For bulk-fill composites, FBF and FO showed similar results, but lower than high-viscosity composites. Results of color stability showed acceptable values up to 3 days aging except for ADM and FSF. ΔE was not influenced by pre-heating and, overall, ΔE: FS < VIT < FO < FSF < ADM < FBF. Only VIT and FS showed ΔE ≤ 3.3 (clinical threshold). Therefore, the effects of pre-heating depend on the material. The tested materials generally showed similar or enhanced properties after pre-heating (except ADM and VIT).

Clinical outcomes of self-glazed zirconia veneers produced by 3D gel deposition: a retrospective study

BACKGROUND

Self-glazed zirconia (SZ) restorations are made by a novel additive three-dimensional gel deposition approach, which are suitable for a straightforward completely digital workflow. SZ has recently been used as minimally invasive veneer, but its clinical outcomes have not been clarified yet. This study aimed to evaluate the preliminary clinical outcomes of SZ veneers compared with the widely used lithium disilicate glass-ceramic veneers made by either pressing (PG) or milling (MG) process.

METHODS

Fifty-six patients treated with SZ, PG, and MG veneers by 2 specialists between June 2018 and October 2022 were identified. Patients were recalled for follow-up at least 1 year after restoration. Clinical outcomes were assessed by 2 independent evaluators according to the modified United States Public Health Service (USPHS) criteria. Overall patient satisfaction was assessed using visual analogue scale (VAS), and analyzed by one-way ANOVA. Chi-square test was applied to compare the difference in the success and survival rates among the 3 groups.

RESULTS

A total of 51 patients restored with 45 SZ, 40 PG, and 41 MG veneers completed the study, with a patient dropout rate of 8.9%. Mean and standard deviation of follow-up period was 35.0 ± 14.7 months. All restorations performed well at baseline, except for 2 SZ veneers with mismatched color (rated Bravo). During follow-up, marginal discrepancy (rated Bravo) was found in 4 MG veneers and 1 PG veneer, and partially fractured (rated Charlie) was found in another 2 PG veneers. The survival rate of SZ, PG, and MG veneers was 100%, 95%, and 100%, with a success rate of 95.56%, 92.50%, and 90.24%, respectively, none of which were significantly different (p = 0.099 and 0.628, respectively). The mean VAS score of SZ, PG, and MG was 95.00 ± 1.57, 93.93 ± 2.40, and 94.89 ± 2.00 respectively, without significant difference (p > 0.05).

CONCLUSION

SZ veneers exhibited comparable preliminary clinical outcomes to PG and MG veneers, which could be considered as a feasible option for minimally invasive restorative treatment.

Color stability and marginal adaptation of ceramic veneers cemented using different composite resins

BACKGROUND

The purpose of this study was to compare the color stability and marginal adaption of lithium disilicate veneers before and after thermocycling using various resin composite materials employed as cement.

METHODS

Laminate veneer preparation was done on an acrylic tooth according to standardized procedures. The veneer preparations were duplicated into twenty-one dies. The veneers were fabricated from lithium disilicate using the CEREC in Lab system. According to the cement type, the twenty-one die specimens were randomly divided into three equal groups: group I, with light cured adhesive resin cement (N.=7), group II, with flowable light cured composite, and group III, with preheated nano filled composite. The cemented specimens underwent 5000 thermocycling cycles. Color was assessed using a reflective spectrophotometer. The vertical marginal gap, following cementation and thermocycling, was measured using a digital microscope. One-way ANOVA followed by Tukey's post-hoc test was used to statistically assess the data.

RESULTS

After thermocycling, there was no statistically significant difference in ΔE among cement type groups for color stability (P=0.369). However, the preheated composite showed the lowest ΔE mean values. Within adhesive resin cement and flowable composite groups, marginal gap means values recorded after thermocycling were significantly higher than those after cementation (P=0.013 and P<0.001, respectively).

CONCLUSIONS

Although preheated composite cement showed the highest marginal discrepancy, it would be the best choice regarding color stability.

Does the use of preheated restorative resin composite as a luting agent influence the adaptation of fixed dental prostheses? A systematic review

STATEMENT OF PROBLEM

Although studies have explored the physical and mechanical properties of different composite resins with the preheating technique, evidence that the use of preheated restorative composite resin as a luting agent influences the adaptation of fixed dental prostheses is lacking.

PURPOSE

The purpose of this systematic review was to answer the question: Does the use of preheated restorative composite resin as a luting agent influence the adaptation of fixed dental prostheses?

MATERIAL AND METHODS

Seven databases and nonpeer-reviewed literature were searched, without language or year restrictions. Studies directly comparing the adaptation of fixed dental prostheses cemented with preheated restorative composite resin or resin cement were considered eligible for inclusion. Assessment of the risk of bias was based on a 9-item checklist.

RESULTS

Of 2109 retrieved articles, 4 in vitro studies met the inclusion criteria. Three of them concluded that preheated restorative composite resin produced a greater mismatch than resin cement, and the remaining study reported that composite resin improved the adaptation of fixed dental prostheses. All included studies had a medium risk of bias. The high level of heterogeneity among the studies precluded meta-analysis.

CONCLUSIONS

The use of preheated restorative composite resin as a luting agent seems to negatively influence the adaptation of fixed dental prostheses. It was not possible to evaluate whether variables such as the formulation of the resin material or its heating time and temperature influence the adaptation of fixed dental prostheses because of the high heterogeneity of the included studies.

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.

Light Polymerization through Glass-ceramics: Influence of Light-polymerizing Unit's Emitted Power and Restoration Parameters (Shade, Translucency, and Thickness) on Transmitted Radiant Power

Background

This in vitro study assessed light transmission through ceramic discs varying in shade, translucency, and thickness using light-polymerizing units with different radiant power/flux (RP) outputs.

Methods

Disc-shaped specimens (0.5 mm, 1.0 mm, and 2.0 mm) were made from high and low-translucency glass-ceramic ingots (IPS e.max Press) in shades A1 and A4, totaling 60 discs. Two light-polymerizing units with different power outputs were used, and their emission spectra were verified. The transmitted RP values for each ceramic specimen were measured and irradiance and radiant energy influx were calculated. Differences between the light-polymerizing units and the influence of the three ceramic parameters were evaluated using an independent-samples t-test and three-way analysis of variance (ANOVA) tests (α = 0.05).

Results

A statistically significant difference was observed in the mean transmitted RP values between the two light-polymerizing units. Furthermore, the three-way ANOVA test showed a significant effect of shade, translucency, and thickness, as well as a significant interaction between each pair of variables and all three variables on the transmitted RP (P < 0.05).

Conclusions

Despite the significant attenuation in the transmitted RP, especially in ceramics with higher shade chromaticity and thickness and lower translucency, the calculated minimal irradiance values for both light-polymerizing units (their emitted power ≥ 500 mW) were greater than the minimum recommended irradiance threshold (100 mW/cm2). However, the exposure duration needs to be increased to provide the resin with sufficient radiant exposure for adequate polymerization.

Resin composite cements: Current status and a novel classification proposal

OBJECTIVES

Currently, a classification of resin cements that includes relatively recently formulated ("universal") cements is lacking. Furthermore, the terminology used to define different resin cements in the scientific reports is inconsistent. Accordingly, this work aims to: (i) propose a novel classification of resin composite cements; (ii) disambiguate the term "universal cements" and (iii) present an overview of the properties of these cements.

METHODS

An analysis of peer-reviewed literature (PubMed search), as well as market research on definitive resin composite cements were performed.

RESULTS

A tendency toward simplified and versatile luting materials was observed both in the scientific literature and on the dental market with the advent of self-adhesive/one-step resin cements. However, additional priming procedures were necessary to improve their bonding performance in certain clinical situations. Hence, several cements that can be applied both in adhesive and self-adhesive mode were introduced. These cements are associated with a universal adhesive resin, that can be used as a tooth and/or restorative material primer, without the need for other priming systems, regardless of the substrate. These systems should be considered truly universal. Therefore, we hereby suggested a new classification of resin-based cements: (1) adhesive/multi-step; (2) self-adhesive/one-step; (3) universal cements (one- or multi-step). Despite promising in vitro results, clinical trials and long-track laboratory studies are necessary to confirm the reliability of the universal cements.

CONCLUSIONS

This review presented the current advances in the field of resin-based cements, which are reflected in the proposed classification. The term "universal cement" was disambiguated, which will help standardize the terminology used in published research.

CLINICAL SIGNIFICANCE

The classification of resin-based cements and a better understanding of the proper terminology will help standardize the terminology in published research, as well as improve the understanding of the clinical practitioners of the different indications and possible modalities of use of the available cements.

Double bond conversion of preheated composite resin beneath lithium disilicate standardized occlusal veneers

The purpose of the study was the investigation of the polymerization of a preheated composite resin beneath lithium disilicate. First, lithium disilicate discs in two shades (HT A2 and HT A4) and three different thicknesses (2, 4, and 6 mm) were bonded on dentine with preheated composite resin that was photo-polymerized for 20 s. The composite resin microhardness, the double bond conversion (DC) and their correlation were estimated. Second, standardized occlusal veneers of two shades and two different thicknesses (4 and 6 mm) were bonded with preheated composite resin and photopolymerized for 60 or 270 s. A microhardness line profiling was performed on the cross-section of each specimen and the correspondence DC was calculated. Shade and thickness of lithium disilicate were found to have a significant impact on micro-hardness and DC of the composite resin. Beneath standardized occlusal veneers DC can reach clinically acceptable level if photopolymerization duration is extended properly.

Risk Factors with Porcelain Laminate Veneers Experienced during Cementation: A Review

The clinical success of porcelain laminate veneers (PLVs) depends on many clinical and technical factors, from planning to execution, among which adhesive cementation is of significant importance. This procedure carries many risk factors if not optimally executed. The objective of this study was to document the clinical parameters affecting successful cementation procedures with a focus on the adhesive strength, integrity, and esthetics of the PLVs. A literature search was conducted through MEDLINE, complemented by a hand search using predefined keywords. Articles published in English between 1995 and 2023 were selected. According to this review, the success and longevity of PLVs rely in great part on the implementation of a precise cementation technique, starting from field isolation, adequate materials selection for adhesion, proper manipulation of the materials, the seating of the veneers, polymerization, and elimination of the excess cement. Several clinical steps performed before cementation, including treatment planning, preparation, impression, and adequate choice of the restorative material, could affect the quality of cementation. Scientific evidence suggests careful implementation of this process to achieve predictable outcomes with PLVs. The short- and long-term clinical success of adhesively luted PLVs is tributary to a deep understanding of the materials used and the implementation of clinical protocols. It is also contingent upon all the previous steps from case selection, treatment planning, and execution until and after the cementation.

The mechanical properties, tribological behaviors and color stability of a feldspar nanoceramics strengthening extrinsic stain for high-translucent zirconia

The present work is aimed to explore the mechanical properties, tribological behaviors and color stability of nanoceramics and microceramics strengthened extrinsic stain coatings (NS and MS) upon high-translucent zirconia (TZ). The Na-rich feldspar ceramics component, microstructure and particle size of NS and MS were verified. The mechanical properties including elastic modulus and hardness of NS were enhanced compared to MS. Reciprocating wear tests under a ball-on-plate configuration manifested that the reduced coefficient of friction, wear depth and wear volume loss of NS was evaluated after 1 × 10 ⁴ cycles and the wear scar morphology of NS characterized by microcracks while MS featured more delamination and wear debris. Post toothbrushing simulation revealed that the color stability of extrinsic stain coatings was elevated with the addition of feldspar nanoceramics. The feldspar nanoceramics strengthening extrinsic stain exhibited enhanced elastic modulus, hardness, wear resistance and color stability, especially for TZ.

Comparison of the Color Change of Porcelain Laminate Veneers Produced by Different Materials After Luting with Three Resin Cements

OBJECTIVES

This study aimed to compare color change of porcelain laminate veneers fabricated with two lithium disilicate ceramics and a zirconia-reinforced lithium silicate ceramic material after luting with conventional dual-cure, amine-free dual-cure, or light-cure resin cements using artificial accelerated aging (AAA).

METHODS AND MATERIALS

Ninety noncarious human maxillary central incisors were embedded in autopolymerizing acrylic resin blocks to prepare conventional laminate veneers with incisal coverage. Prepared teeth were randomly divided into 3 groups (n=30) to fabricate laminate veneer restorations using: (1) lithium disilicate ceramic, (2) lithium disilicate ceramic with high-density micronization, and (3) zirconia-reinforced lithium silicate ceramic. Impressions of the preparations were taken with a laboratory scanner. Acquired 3D images were processed into a surface tessellation language file. Data were exported for 3D printing on a printer, and laminate veneers were printed in castable wax resin. Ceramic veneers were heat-pressed after investment according to the manufacturer's recommendations and further divided into three groups (n=10) according to luting cement type: (1) light-cure resin cement, (2) amine-free dual-cure resin cement, and (3) conventional dual-cure resin cement. Color measurements were performed from the middle of each specimen with a spectrophotometer before and after AAA for 300 hours with a total energy of 150 kJ/m2. Color changes were calculated with the CIEDE 2000 (ΔE00) formula. Color differences were assessed using two-way analysis of variance (ANOVA) (α=0.05), and the paired t-test was used to compare the L*, a*, and b* parameters in each group before and after aging.

RESULTS

There were no significant differences between the ceramic groups (p>0.05). The color changes of the materials ranged from 2.26 to 3.13. All materials were above the clinically acceptable limit (ΔE00>1.8). The conventional dual-cure resin cement group showed more color change (p>0.05).

CONCLUSIONS

Color changes were observed in all porcelain laminate veneers after artificial accelerated aging. The zirconia-reinforced lithium silicate veneers showed similar color changes as lithium disilicate veneers; the amine-free dual-cure resin cement showed a similar color change as light-cure resin cement after aging.

Color Stability of Resin Cements after Water Aging

The color stability of resin cements plays a key role in the achievement of esthetically-pleasant restorations. Resin luting materials can be mainly divided into two main classes: adhesive (relying on previous application of adhesive systems) or self-adhesive (also known as one-step cements). The different chemical compositions determine their physio-mechanical characteristics which, in turns, influence their color stability. To evaluate the color variations of different dual-cured resin cements after water aging, 80 disc-shaped specimens (15 mm in diameter and 1.2 mm thick) were obtained from the following resin cements (n = 10): (1) Maxcem Elite Universal, MCU (Kerr); (2) RelyX Universal, RXU (3M); (3) Calibra Ceram, CAL (Dentsply); (4) Multilink, MUL (Ivoclar-Vivadent); (5) Panavia V5, PAN (Kuraray); (6) Calibra Universal, CUN (Dentsply); (7) SpeedCEM Plus, SCP (Ivoclar); and (8) Panavia SA, PSA (Kuraray). After light-polymerization, the specimens were measured with a spectrophotometer and CIELab* values were recorded. The specimens were then placed in a digitally controlled thermostatic water bath at 60° for 30 days and afterwards the color measurements were repeated. Color differences were calculated for each specimen before and after water-aging procedures with ΔEab formula and the data were statistically analyzed (p < 0.05). The type of cement statistically influenced the ΔEab (p < 0.05), with MCU showing the lowest color variations (4.3 ± 0.7) whereas RXU and PSA the highest (16.9 ± 1.6 and 16.8 ± 1.2, respectively). No differences were observed between CAL, CUN and SCP (p = 0.05). Color stability is related to the chemical composition of the resinous luting materials, thus material dependent.

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); RelyX^TM 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 RelyX^TM 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 RelyX^TM 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.

Effect of preheating on the physicochemical properties and bond strength of composite resins utilized as dental cements: An in vitro study

STATEMENT OF PROBLEM

Little is known regarding the use of preheated composite resins to bond indirect restorations and its impact on mechanical properties when compared with resin cements.

PURPOSE

The purpose of this in vitro study was to compare the chemical and physical properties and bond strength to enamel and ceramics of preheated composite resins and resin cements.

MATERIAL AND METHODS

Two composite resins, the microhybrid Filtek Z250XT and the nanoparticulate Z350XT were tested, and 2 commercially available resin cements, the dual-polymerized Rely-X ARC and the light-polymerized Rely-X Veneer were used as controls. A device (HotSet) was used to preheat the composite resins to 69 °C before light-polymerization. The following properties were tested: flexural strength, modulus of elasticity, fracture toughness, microshear bond strength to enamel and ceramics, degree of conversion, flow, sorption and solubility, and color stability. Statistical analysis was done with ANOVA and Holm-Sidak for multiple comparisons (α=.05).

RESULTS

Preheating had no significant effect on the degree of conversion, flexural strength, fracture toughness, solubility, or microshear bond strength to the enamel of the tested composite resins (P>.05). However, preheating increased the sorption and reduced the microshear bond strength to the ceramic (P<.05). The flowability of the composite resins increased with heating but showed lower values when compared with both resin cements (P<.05). Color stability was more affected in the preheated composite resins than in the resin cements.

CONCLUSIONS

The preheating process resulted in little to no benefit in the evaluated properties for the composite resins. Resin cements appear to be the best option for cementing indirect restorations.

Effect of ceramic and resin cement type on color stability and translucency of ceramic laminate veneers for diastema closure: an in vitro study

To investigate the effect of resin cements on the color stability and translucency of ceramic laminate veneers used for diastema closure. Sixty resin abutments were prepared for ceramic laminate veneers and divided into six groups according to the ceramic type (lithium disilicate, zirconia-reinforced lithium silicate, and translucent zirconia) and the cement type (Variolink Esthetic LC and RelyX Veneer). Color coordinates and translucency were analyzed after cementation and after soaking in the coffee solution. Differences in color and translucency were estimated, and results were statistically assessed (α = 0.05). Ceramic materials showed a significant impact on color changes after soaking in coffee within Variolink Esthetic groups. Translucent zirconia showed the highest color change, followed by zirconia reinforced lithium silicate and lithium disilicate. Ceramic materials showed a significant impact among the RelyX Veneer groups. A significant interaction in color changes was found between ceramic types and cement types after cementation, and after soaking in coffee was found. All groups showed a clinically acceptable difference in translucency parameters after soaking in coffee. The resin cement affects the color and translucency of ceramic laminate veneers used for diastema closure, and ceramic laminate veneers bonded with Variolink Esthetic LC resin cement are more translucent, while ceramic laminate veneers bonded with RelyX Veneer resin are more resistant to coffee staining. The lithium disilicate laminate veneer is more resistant to coffee staining than zirconia reinforced lithium silicate and translucent zirconia laminate veneers used for diastema closure.

Influence of Novel Experimental Light-Cured Resin Cement on Microtensile Bond Strength

The purpose of this study was to evaluate the microtensile bond strength (µTBS) and Knoop hardness number (KHN) of a novel experimental light-cured resin cement (HL). Eighteen flat dentin surfaces of human molars were polished using #600 SiC paper and bonded to CAD/CAM resin blocks with the respective resin cements and composites: HL, Panavia V5 (PV), and Clearfil AP-X (AP). All specimens were stored in distilled water at 37 °C for 24 h and 7 days. Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) observations were performed to evaluate filler morphology and to detect the elements. The resin cements had a significant effect on the immediate µTBS (F = 22.59, p < 0.05) and after water storage µTBS (F = 22.83, p < 0.05). Significant differences (p < 0.05) in the KHN between the tested materials were observed, and HL indicated the highest KHN when compared with PV. HL showed a combination of the regular-shaped filler and spherical-shaped filler within the matrix. Silicon was detected in HL from the EDX evaluation. HL exhibited better bonding performance and polymerization, which may have contributed to the improvement of the adhesive strength.

The effect of amine-free initiator system and polymerization type on long-term color stability of resin cements: an in-vitro study

BACKGROUND

This in vitro study evaluated the effect of amine-free initiator system and polymerization type on long-term color change of amine-free light-cure and dual-cure resin cements.

METHODS

Sixty disk-shaped specimens (10 × 1 mm) were prepared from six different amine-free resin cements; NX3 Nexus light-cure (LC) and dual-cure (DC), Variolink Veneer (LC) and Variolink II (DC), Relyx Veneer (LC) and Rely X Ultimate (DC). A feldspathic porcelain specimen (12 × 14 × 0.8 mm) was obtained from a CAD/CAM block (Cerec Blocks; Sirona Dental Systems GmbH, Bensheim, Germany) for color testing. The feldspathic specimen was placed on the resin cement disk and all measurements were performed without cementation. A spectrophotometer was used for color measurements. Specimens were subjected to thermal aging (5 °C and 55 °C; 5000 and 20,000 cycles). Specific color coordinate differences (ΔL, Δa, and Δb) and the total color differences (ΔE₀₀) were calculated after immersion in distilled water for different periods. Normality of data distribution was tested by using the Kolmogorov-Smirnov test. Data were statistically in a model of repeated measures, using multivariate tests and Tukey's multiple comparison tests at a significance level of p < 0.05.

RESULTS

∆E₀₀ values of resin cements were influenced by cycle periods, significantly (p < 0.05). The highest ΔE00 values for long term were obtained in the NX3 (DC) (3.49 ± 0.87) and the lowest in the NX3 (LC) (1.41 ± 0.81). NX3 (LC), Variolink (DC), RELY X (LC) resin cements showed clinically acceptable color change after long-term aging (∆E₀₀ < 1.8).

CONCLUSION

Light-cure resin cements should be preferred for long-term color stability of full ceramic restorations.

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.

Intrapulpal temperature changes during the cementation of ceramic veneers

Adhesive cementation of ceramic veneers may increase pulpal temperature (PT) due to the combined effect of heat generated by the curing unit and the exothermic reaction of the luting agent (LA). PT increase may induce pulpal damage. The aim was to determine the PT rise during the luting of ceramic veneers (CV) of different thicknesses with light- or dual-curing (LC, DC) adhesive cements as well as pre-heated restorative resin-based composites (PH-RBC). For this a thermocouple sensor was positioned in the pulp chamber of a prepared maxillary central incisor. LC, DC adhesive cements and PH-RBCs heated to 55 °C were used for the luting of CVs of 0.3, 0.5, 0.7, and 1.0 mm thicknesses. The exothermic reaction of LAs added significantly to the thermal effect of the curing unit. PT change ranged between 8.12 and 14.4 °C with the investigated combinations of LAs and ceramic thicknesses (p ≤ 0.01). The increase was inversely proportional to the increasing CV thicknesses. The highest rise (p ≤ 0.01) was seen with the polymerization of PH-RBCs. Temperature changes were predominantly influenced by the composition of the LA, which was followed by CV thickness.

Luting indirect restorations with resin cements versus composite resins: Effects of preheating and ultrasound energy on film thickness

OBJECTIVE

This study aims to evaluate and compare the film thickness obtained with a resin cement and two composite resins, preheated and/or ultrasonically vibrated, as luting agents.

MATERIALS AND METHODS

One hundred and twenty-six (126) pairs of resin discs were randomly assigned to six experimental groups (n = 21) according to luting agent (Variolink Esthetic LC, IPS Empress Direct or Estelite Omega) and cementation technique (preheating at 68°C and/or ultrasonic vibration). Specimens were luted by applying a controlled force. Following sectioning and film thickness measurement through field emission gun scanning electron microscopy, statistical analysis was carried out considering a 5% significance level.

RESULTS

Statistically significant lower film thickness was observed in Variolink Esthetic LC group when compared to all composite resin groups (p < 0.001), except IPS Empress Direct preheated and ultrasonically vibrated group (p = 0.073). IPS Empress Direct with ultrasonic vibration yielded statistically lower film thickness values than Estelite Omega groups, regardless of luting technique (p < 0.05). Ultrasonically vibrated Estelite Omega groups showed statistically lower film thickness values than solely preheated groups (p < 0.05).

CONCLUSIONS

Both Variolink Esthetic LC and IPS Empress Direct preheated and ultrasonically vibrated provided the lowest film thickness. The addition of ultrasonic vibration during cementation proved to be effective in reducing film thickness of both tested composite resins.

CLINICAL SIGNIFICANCE

The cementation technique will have variable results depending on the luting material. Adhesive cementation protocols with composite resins should mainly consider ultrasonic vibration, but also preheating, as strategies for reducing film thickness. The tested resin cement, alongside with IPS Empress Direct composite resin preheated and ultrasonically vibrated, provided the lowest film thickness among the tested materials and techniques.

Effect of Optical Properties of Lithium Disilicate Glass Ceramics and Light-Curing Protocols on the Curing Performance of Resin Cement

This study aimed to investigate the effects of optical properties of lithium disilicate glass ceramics and the light-curing protocols (LCP) on the curing performance of light-cured resin cement. Lithium disilicate glass-ceramics with different optical properties were sectioned to produce ceramic specimens of 0.8 mm thickness. Irradiance through the ceramic specimens was measured by a radiometer. Light transmittance of ceramics was assessed using a UV/Vis spectrophotometer. The light-cured resin cement was injected into a Teflon mold and ceramics with different optical properties were placed on it, cured under different LCPs, and the degree of conversion (DC) and Vickers microhardness of the resin cement were separately measured by Micro-ATR/FTIR spectrometry and the microhardness tester. The shade (p < 0.001) and transparency (p < 0.001) of ceramics affect the irradiance of the light-curing unit. The transparency (p < 0.001) of the ceramic and light-curing protocols (p < 0.001) affect the DC and microhardness of resin cements. When the thickness of the ceramic is 0.8 mm, the light transmittance of the ceramic and the curing performance of the resin cement increase with the increase of the transparency of the ceramic. An appropriate increase in irradiance and exposure time can optimize the curing performance of resin cement. These factors should be taken into account by the clinician when designing the bonding solution for porcelain veneers.

Accelerated artificial aging and color stability in resin-based cements

The aim of this study was to determine color change after accelerated artificial ageing (AAA) of different composite cements that are used with veneers. Five cylindrical test specimens, 15 mm in diameter and 2 mm thick, were made from a single layer of each of the following: RelyX Veneer 3M ESPE (RX), Paracore White Coltene (PC), Solocem White Opaque Coltene (SO), Resin Duo Cement Densell (DC), Panavia V5 Paste Kuraray Noritake (PA) and Panavia F2.0 Kuraray Noritake (PF) (30 specimens altogether). The specimens were light cured following manufacturers' instructions using a Coltolux LED (Coltene) unit. Initial color was determined using an Easyshade - Vita Zahnfabrik Spectrophotometer. Then, the specimens were subjected to AAA for two weeks (336 hours) with cycles of 4 hours of UV light at 60 °C and 4 hours of vapor condensation at 50 °C, successively, after which color was recorded again. Color change was determined for each specimen according to the differenceinshadeon the Vita scale before and after AAA. Results were analyzed using Kruskal Wallis test. Mean and standard deviation for each group were: RX 8.40 (1.52); PC 8.60 (3.13); SO 6.40 (3.51); DC 10.00 (0.00); PA 7.60 (3.29); PF 2.00 (0.00). The Kruskal Wallis test showed significant difference for material (p<0.05), and comparison of means showed difference between Panavia F2.0 and the other materials. A table providing equivalence between the Vita Classic and CIELAB scales was used to transfer the recorded colors to the CIELAB scale, and the color difference ΔE was calculated for each group, where ΔL, Δa and Δb are the differences in the L, a and b values before and after the AAA. The mean and standard deviation were analyzed statistically by the ANOVA test and Tukey's test. Mean and standard deviation for each group were: RX 14.94 (2.02); PC 14.51 (4.02); SO 12.08 (4.53); DC 16.31 (0.00); PA 10.9 (3.38); PF 7.24 (0.00). The ANOVA test showed significantdifferenceformaterial (p<0.05). Tukey's test showed two groups (PF-DC, RX, PA). Under the experimental conditions of this study, it can be concluded that accelerated ageing significantly affects the color stability of the resin based cements tested.

Composite Resin Preheating Techniques for Cementation of Indirect Restorations

Purpose

Resin-based materials have been preheated by using different techniques and commercial devices. However, a consensus on the clinical protocol for cementing with preheated composite resins is lacking. The aim of this scoping review was to identify the different methods used for heating composite resins as used for cementing indirect adhesive restorations and to determine the benefits and limitations. Study Selection. A search was performed on PubMed/MEDLINE, Embase, Cochrane, Web of Science, Scopus, LIVIVO, and the nonpeer-reviewed literature database. Studies on preheating composite resins for cementing indirect restorations were included, with no restrictions on the type of study, year of publication, or language. The following data were extracted: preheating technique, the device used for preheating, preset temperature, and warming time.

Results

In total, 304 studies were identified. After removing duplicates, 270 articles were selected, and 14 articles were included in the final evaluation. Half of the included studies reported similar preheating techniques using the Calset device for composite resins. The temperatures of 54°C and 68°C were most frequently reported, with a mean warming time of 5 minutes.

Conclusions

Preheating composite resins for the cementation of indirect restorations reduces viscosity, but the material must be used promptly after removal from the device. Practical Implications. Different methodologies for preheating composite resins have been reported and used in clinical dental practice. To achieve good results and guide the clinician on use, the techniques for heating composite resins for cementation need to be standardized. Keeping the material warm until the restorative procedure, the thickness of the indirect restoration, and the composition of the composite resins can directly affect the outcome of the procedure.

The effects of provisional resin cements on the color and retentive strength of all-ceramic restorations cemented on customized zirconia abutments

This study aimed to evaluate the effects of two types of provisional resin cements on the color and retentive strength of two different all-ceramic restorations cemented onto customized zirconia abutments. Forty-two crowns were made of monolithic zirconia and lithium disilicate ceramics (n = 21 per group) and cemented on customized zirconia abutments by using two provisional resin cements of TempBond Clear and Implantlink Semi, and TempBond serving as the control (n = 7 per cement subgroup). The specimens’ color was measured before and after cementation and after thermocycling. The color difference was calculated by using CIEDE2000 formula (ΔE₀₀). The tensile force was applied to assess the retentive strength. Kruskal-Wallis, Dunn’s post-hoc, and Mann-Whitney non-parametric tests were used to compare ΔE₀₀(1) and ΔE₀₀(2) and two-way ANOVA followed by one-way ANOVA and Tukey’s HSD post hoc test and T-test were used to compare retentive strength between subgroups. In the lithium disilicate group, ΔE₀₀ of the control subgroup (TempBond) was significantly higher than that of Implantlink Semi cements subgroup (P = 0.001). But, in the monolithic zirconia group, ΔE₀₀ of the control subgroup (TempBond) was significantly higher than that of Implantlink Semi (P = 0.020) and TempBond Clear cements (P = 0.007). In the monolithic zirconia group, the control subgroup (TempBond) was significantly more retentive than TempBond Clear (P = 0.003) and Implantlink Semi cement (P = 0.001). However, in the lithium disilicate group, Implantlink Semi cement was significantly more retentive than TempBond Clear (P = 0.019) and TempBond (control) (P = 0.001). The final color of both restorations was significantly affected by the provisional resin cement type. The retentive strength was influenced by both the type of cement and ceramic.

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.

Color stability of a resin nanoceramic after surface treatments, adhesive cementation, and thermal aging

STATEMENT OF PROBLEM

Whether color changes in resin nanoceramic (RNC) restorations can occur because of material and adhesive interface degradation is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the color of RNCs submitted to surface treatments, cementation, and aging.

MATERIAL AND METHODS

RNC specimens (N=120) were produced with a thickness of 0.5 mm. The No Treatment-High/Low Translucency (NT-HT/LT) groups did not receive treatments; the Airborne-particle Abrasion-High/Low Translucency (AA-HT/LT) groups were airborne-particle abraded, and the Airborne-particle Abrasion Silane-High/Low Translucency (AASIL-HT/LT) groups received airborne-particle abrasion and a silane agent. Single specimens (n=60) were measured on a spectrophotometer before and after aging (50 000 cycles). The other half was mounted on composite resin bases and measured. The cleaned specimens were cemented (C) on the bases and measured (T0 and T1). ΔE₀₀, ΔL', ΔC', and ΔH' were obtained by using the CIEDE2000 formula and analyzed by using ANOVA and repeated-measures ANOVA. Multiple comparisons were made by using the Tukey HSD test (α=.05).

RESULTS

For single specimens, the greatest ΔE₀₀ values were observed in the AA-T1-LT resin (5.87). For mounted and cemented conditions, the greatest ΔE₀₀ values were found in the AA-C-T1-LT resin (1.74), and the ΔE₀₀ ranged from 0.75 (NT-OL) to 1.44 (AASIL-C-T1) for the HT resin (P<.001). The mounted and cemented specimens tended toward red and yellow, whereas lighter specimens were observed after cementation.

CONCLUSIONS

Aging affected the color of the RNCs evaluated. The single specimens showed greater color differences than the cemented specimens, reinforcing the importance of the adhesive cement in the optical behavior of thin restorations.

Evaluation of Color Changes of Different Resin Cements in Feldspathic Ceramic Crowns After Accelerated Aging: An In Vitro Research

Aims:

To evaluate the color changes that occur after accelerated aging in feldspathic ceramic crowns cemented with three different dual-cured resin cements.

Materials and Methods:

For each of the A2-colored RelyX U200, G-CEM LinkForce, and Panavia V5 cement groups, 45 dies from A2-colored zirconia blocks and 45 crowns from CEREC blocks were prepared. Color measurements after 24 h of cementation (T1) and after cycles of aging of 1750 (T2), 3500 (T3), and 7000 (T4) in the thermal cycle device were made using SpectroShade Micro device. The coordinates of the color were used L*, a*, and b* as base and the color change was calculated with ∆ E00 in determining the color. One-way analysis of variance test was used to compare the times in terms of ∆ L*, ∆ a*, and ∆ b* values.

Results:

It was found that ∆ L* value decreased significantly in period of the T2, T3, and T4 times compared to T1 in all groups ( P < .05), whereas the change between period of T2, T3, and T4 times was not significant ( P > .05). The ∆ a* value increased significantly in the period of T3 and T4 times compared to T1 in the only G-CEM LinkForce group, whereas the ∆ b* value increased significantly in the period of T4 time compared to T1 in the only Panavia V5 group. The changes in ∆ E00 values, which were observed in all period of times, were found to be between 0.43 and 1.04, 0.43 and 1.43, and 0.40 and 0.97 in RelyX U200, G-CEM LinkForce, and Panavia V5 groups, respectively.

Conclusion:

After accelerated aging, it was found that the color of all cements became darker and the G-CEM LinkForce group turned red and the Panavia V5 group turned yellow. However, it was found that the color changes that occurred were within clinically acceptable visible levels.

Transmission of violet and blue light and current light units through glass-reinforced ceramics with different thicknesses

Purpose To evaluate the effect of glass-reinforced ceramics (leucite and lithium disilicate) with different thicknesses (1, 2, and 3 mm) on the wavelength and irradiance spectrum of blue and violet lights. In addition, the effect of the ceramics on four current light-curing units (LCUs) was evaluated: a halogen lamp, a single peak LED, and two multi-peak LEDs.Methods Ceramic discs of different thicknesses (1, 2, and 3 mm) were obtained from computer-aided design and computer-aided manufacturing (CAD-CAM) blocks. The irradiance, radiant exposure, and emission spectrum of the four LCUs were analyzed using a spectrometer-based instrument. To evaluate the violet and blue lights, a specific device that provides a narrow emission spectrum was used.Results The ceramics reduced the irradiance of all the tested LCUs. However, the wavelength of the transmitted light was only altered slightly. The effect of leucite and lithium disilicate varied according to the type of LCU and thickness of the ceramic disc evaluated .Conclusions From the results, it could be concluded that the thickness of the leucite and lithium disilicate ceramic significantly reduced the irradiance of the light emitted by the LCUs, with minimal changes on the wavelength spectrum of the lights. The effects of the ceramic on irradiance and transmitted wavelengths of the blue and violet lights was slightly different.

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).

Impact of resin composite cement on color of computer-aided design/computer-aided manufacturing ceramics

OBJECTIVE

To analyze the impact of the color of a resin composite cement (RCC) on the optical properties of different computer-aided design and computer-aided manufacturing (CAD/CAM) ceramics.

MATERIALS AND METHODS

Specimens (N = 220, thickness: 0.9 ± 0.03 mm) were fabricated from: leucite (Initial LRF Block/IPS Empress CAD), lithium disilicate (Amber Mill/IPS e.max CAD), lithium metasilicate (Celtra Duo), and lithium alumina silicate ceramic (n!ce) in translucency levels HT and LT. All specimens were bonded with an RCC (Light+/Warm+). Color was analyzed (spectrophotometer) initially as well as after bonding of RCC with CAD/CAM ceramics using CIELab and CIEDE2000. Kolmogorov-Smirnov test, one-way ANOVA and t test served for analyzing (α = 0.05).

RESULTS

Highest impact on ΔE presented the choice of ceramic (η_p ²  = 0.155/p < 0.001), followed by translucency level (HT/LT; η_p ²  = 0.050/p = 0.001) as well as interaction between ceramic and translucency level (η_p ²  = 0.175/p < 0.001). ΔE00 was mainly influenced by the choice of ceramic (η_p ²  = 0.490/p < 0.001), the shade of resin composite (η_p ²  = 0.031/p = 0.012) as well as the interaction between ceramic and resin composite (η_p ²  = 0.258/p < 0.001).

CONCLUSIONS

RCC shades presented differential impacts on color change of CAD/CAM ceramics.

CLINICAL SIGNIFICANCE

Knowledge of the impact of available RCC shades on different CAD/CAM ceramics is crucial for an esthetic outcome and proper selection of ceramic restorations.

Minimum Radiant Exposure and Irradiance for Triggering Adequate Polymerization of a Photo-Polymerized Resin Cement

This study aimed to establish the minimum radiant exposure and irradiance to trigger an adequate polymerization of a photo-polymerized resin cement. In total, 220 disc-shaped specimens (diameter of 10 mm and thickness of 0.1 mm) were fabricated using a photo-polymerized resin cement (Variolink N-transparent, Ivoclar Vivadent). To investigate the minimum radiant exposure, the specimens were polymerized with radiant exposures of 1, 2, 3, 4, 5, 6, and 18 J/cm² (n = 20). During polymerization, the irradiance was maintained at 200 mW/cm². To investigate the minimum irradiance, the specimens were polymerized with irradiances of 50, 100, 150, and 200 mW/cm² (n = 20). During polymerization, the radiant exposure was maintained at the previously determined minimum radiant exposure. The Vickers microhardness (HV) and degree of conversion (DC) of the carbon double bond of the specimens were measured to determine the degree of polymerization of the specimens. The results were analyzed using one-way analysis of variance (ANOVA) and Tukey’s test (p < 0.05). In the investigation of the minimum radiant exposure, the HV and DC of the specimens polymerized with a radiant exposure from 1 to 5 J/cm² were significantly lower than those with 18 J/cm² (all p < 0.05). However, no significant difference in HV and DC was found between the specimens polymerized with 6 J/cm² and 18 J/cm² (p > 0.05). In the investigation of the minimum irradiance, the specimens polymerized with an irradiance of 50 mW/cm² had significantly lower HV and DC than the specimens polymerized with an irradiance of 200 mW/cm² (p < 0.05). However, no significant difference in the HV and DC was found among the specimens cured with irradiances of 100, 150, and 200 mW/cm² (p > 0.05). In conclusion, the minimum radiant exposure and irradiance to trigger an adequate polymerization of the light-cured resin cement were 6 J/cm² and 100 mW/cm², respectively.

Color stability and degree of conversion of a novel dibenzoyl germanium derivative containing photo-polymerized resin luting cement

AIM

To compare the color stability and degree of conversion (DC) of a resin cement containing a dibenzoyl germanium derivative photo-initiator (Variolink Esthetic) to resin cements containing conventional luting agents.

MATERIALS AND METHOD

Spectrophotometry and Fourier transform infrared spectroscopy (FTIR) were used to compare the color stability and DC, respectively, of Variolink Esthetic compared to Calibra, Variolink-N, and NX3 resin cements. Ten specimens (1 × 2 mm²) of each resin cement were photo-polymerized and then subjected to color stability assessments. In addition, 30 samples of each of the four resin cements were prepared and then immersed in three staining solutions (tea, coffee, and distilled water) for two weeks. Changes in color for the immersed versus non-immersed specimens (control specimens) were determined by comparing ΔL (lightness), Δa, and Δb (color components), and an overall ΔE (color difference) obtained from spectrophotometry assays. One-way analysis of variance and a multiple comparison test (Tukey's test) were used to analyze color stability and DC data. NX3 and Variolink Esthetic resin cements exhibited significantly lower values compared to the dual cured resin cements (Variolink-N and Calibra).

RESULTS

The highest DC values were observed among the photo-polymerized samples of Variolink Esthetic (87.18 ± 2.90%), while the lowest DC values were observed among the Variolink-N samples (44.55 ± 4.33%).

CONCLUSION

The resin cement, Variolink Esthetic, containing a novel dibenzoyl germanium derivative photo-initiator exhibited superior color stability (p < 0.05) and a higher DC than other resin cements containing conventional luting agents in an in vitro setting.

Long-term color stability of light-polymerized resin luting agents in different beverages

PURPOSE

The purpose of this study was to evaluate the long-term color stability of light-polymerized resin luting agents stored in different beverages.

METHODS

Eleven shades of two light-polymerized resin luting agents, Choice2 (A1, A2, B1, TRANSLUCENT, MILKY OPAQUE, and MILKY BRIGHT) and BeautiCem Veneer (H-Value, M-Value, L-Value, Ivory-D, Ivory-L) were selected in this study. Disk-shaped specimens were fabricated with 1.3 mm thickness and 15.0 mm diameter. A total of 198 specimens, 18 for each shade, were prepared and randomly divided into six storage conditions (purified water, coffee, cola, tea, red wine, and air). All shades of specimens were three times measured at three random locations (n = 9) at 24 h storage in air after specimen preparation and then measured after immersion at 1, 3, 6, 9, and 12 mos. using a colorimeter. Then, the color difference (ΔE) between the specimens at 24 h after preparation and after storage in each liquid for 12 mos. was calculated. Statistical analysis was performed using Steele-Dwass multiple comparison test of the ΔE values or one-way ANOVA and Tukey's honest significant difference test.

RESULTS

For all immersion conditions, ΔE was significantly higher than air (control). The ΔE of the shades in the various storage conditions showed no significant difference between Purified Water-Cola and Coffee-Tea. Comparisons of the color components L*, a*, and b* for each shade showed different behaviors among the shades.

CONCLUSIONS

The results suggest that the color stability of light-polymerized resin luting agents may differ between different shades and beverages.

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.

Influence of toothbrush abrasion and surface treatments on the color and translucency of resin infiltrated hybrid ceramics

PURPOSE

The study compared the color change, lightness, and translucency of hybrid resin ceramics exposed to toothbrush abrasion and surface treatment.

MATERIALS AND METHODS

Four hybrid ceramics [Lava Ultimate (LU), Vita Enamic (EN), Shofu HC (SH), and Crystal Ultra (CU)] were compared with a glass-ceramic (Vita Mark II) control. One hundred and twenty specimen blocks were prepared using a precision saw machine. Specimens in each material were divided into four subgroups based on the surface treatment (polishing or staining) and a storage medium (water or citric acid). Simulated tooth brushing with a mixture of 100 RDA (radioactive abrasives) with 0.3 ml distilled water was used for 3650 cycles (7300 strokes) for each specimen. Measurements for the color change, lightness, and translucency were measured after toothbrushing using a spectrophotometer. Statistical analysis compared outcomes using paired t-test, ANOVA, and Tukey post hoc test.

RESULTS

The maximum color change was identified in SH (stained acid) [1.44 (0.40)], whereas the lowest was identified in EN (polished water) [0.66 (0.16)] material. The maximum and minimum loss of surface translucency was observed in SH (polished water) [12.3 (0.52)] and EN (stained acid) [6.5 (0.55)] specimens, respectively. Lastly, loss of lightness was the highest in VM (polished acid) [69 (0.95)], whereas the lowest was observed in CU (stained water) [56.7 (0.86)].

CONCLUSION

The comparison presented a significant effect of toothbrush abrasion on translucency and lightness of the hybrid resin ceramics. Color change was not significantly influenced irrespective of the storage medium employed. Surface staining demonstrated the preservation and stability of color and optical properties under the influence of toothbrush abrasion and chemical trauma.

Influence of Ceramic and Substrate Types on the Microleakage of Aged Porcelain Laminate Veneers

Objective

To evaluate the effects of the type of ceramic, and the influence of the type of cervical substrate on the microleakage of aged Porcelain laminate veneers (PLVs).

Materials and Methods

A total of 48 sound human maxillary premolars were divided randomly into two groups (n=24), Group A: lithium disilicate PLVs; Group B: zirconia reinforced lithium silicate PLVs. The groups were further subdivided into four subgroups (n=12): (A1, B1): finishing line placed in Class V composite filling; (A2, B2): finishing line placed in sound enamel. In subgroups A1 and B1 standardized Class V cavities were prepared and restored with nanocomposite. Standardized PLVs tooth preparation was done for the specimens in all subgroups. Cementation of PLVs was done with a light cured resin cement and specimens were stored in distilled water for 2 weeks. Mechanical load cycling (45,000 cycle, 49 N at 2.5 Hz) and thermocycling procedure (500 cycles, 5–55°C) were done. A microleakage test was done with dye penetration (2% methylene blue) and the microleakage percentage was recorded and calculated using a stereomicroscope and ImageJ program.

Results

Means of microleakage percentage of the subgroups were: A1 (6.6075%), A2 (4.6058%), B1 (7.3158%), and B2 (6.105%), Two-way ANOVA showed a significant effect of ceramic type and cervical composite substrate. According to samples t-test, subgroup A2 was significantly lower than A1 and B2, while subgroup B2 was significantly lower than B1. A P-value≤0.05 was considered as statistically significant.

Conclusion

The type of ceramic and the type of substrate both affects PLV microleakage. Lithium disilicate PLVs had significantly lower microleakage compared to zirconia reinforced lithium silicate PLVs. Teeth with cervical composite substrate had a significantly higher microleakage compared to teeth with enamel substrate.

Influence of resin cement on color stability of ceramic veneers: in vitro study

Statement of the problem

Long-term success of ceramic veneers depends on the color stability of resin cement used for their cementation. Color change of cement may be seen through the ceramic and compromise esthetics.

Purpose

This study aimed to compare the color change of two resin cements and their visibility through the ceramic veneers after accelerated artificial aging.

Materials and methods

In this in vitro study, color change (ΔE) was measured in the following groups (n = 10) before and after accelerated artificial aging: group 1, IPS e.max press high translucent ceramic discs; groups 2, Variolink NLC resin cement discs; group 3, Choice 2 resin cement discs; groups 4, Variolink NLC discs bonded to e.max ceramic discs; group 5, Choice 2 disc bonded to e.max ceramic discs. Color change was measured using a spectrophotometer according to International Commission on Illumination Lab (CIELab). Data were analyzed using one-way ANOVA and Tukey’s post-hoc test.

Results

Group 2 showed the highest (ΔE = 10.4 ± 0.9) and group 1 the lowest (ΔE = 0.9 ± 0.4) color change. The color change of Variolink was significantly greater than Choice 2 either alone (p < .001) or through the ceramic discs (p < .004). The color change of both cements was lower through the ceramic veneer and this reduction was statistically significant (p < .001).

Conclusion

Noticeable color change may be expected in areas of cement exposure for both cements studied. Also, in case of using Variolink cement, the color change may be seen through the ceramic veneers.

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.

Evaluation of the response of esthetic restorative materials to ultraviolet aging

STATEMENT OF PROBLEM

The optical properties of esthetic computer-aided design and computer-aided manufacturing (CAD-CAM) materials can change depending on the clinical situation. Studies that compare esthetic CAD-CAM materials based on their optical properties are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the optical properties of esthetic CAD-CAM specimens after ultraviolet (UV) aging based on the type and thickness of the material.

MATERIAL AND METHODS

In total, 240 plate-shaped specimens (14×12×1 mm and 14×12×2 mm) of a nanohybrid composite resin (Tetric CAD), a fine-structure feldspathic ceramic (Vitablocs Mark II), 2 different glass-ceramics (IPS Empress CAD and IPS e.max CAD), a zirconia-reinforced lithium silicate glass-ceramic (Celtra Duo), a polymer-infiltrated ceramic network (Vita Enamic), and 2 different resin nanoceramics (Cerasmart and Lava Ultimate) were fabricated (n=15). The optical parameters were analyzed by spectrophotometry before and after UV aging. The brightness (L∗), red green (a∗), yellow-blue (b∗), chroma (Ch), and hue (h) were measured, and the color difference (ΔE₀₀) values were calculated. The translucency parameter (TP), total transmittance (Tt), and contrast ratio (CR) were also determined. Statistical analyses were performed with 1-way ANOVA, the Tukey honestly significant difference post hoc test, independent- and paired-samples t tests, and 2-way ANOVA (α=.05).

RESULTS

Significant interactions were observed for the aging process, material type, and thickness for all optical parameters (P<.05). L∗, TP, and Tt had lower values, while CR had higher values for the aging group than that of the control group (P<.05). The h, TP, and Tt values were higher, whereas the b∗ and CR values were lower for the 1-mm group than those of the 2-mm group (P<.05). The highest ΔE₀₀ value was found in the Lava Ultimate 1-mm group (ΔE₀₀=3.21) and 2-mm group (ΔE₀₀=2.42). The lowest ΔE₀₀ value was found in the Vitablocs Mark II 1-mm group (ΔE₀₀=0.31). The highest TP and Tt and the lowest CR values were observed for Tetric CAD; the lowest TP and Tt, and the highest CR values were noted in Celtra Duo (P<.05).

CONCLUSIONS

The optical properties of the CAD-CAM specimens were affected by the aging process, material type, and thickness, and the color stability was clinically applicable in all CAD-CAM materials except groups Lava Ultimate and Cerasmart(ΔE₀₀<2.25). Resin nanoceramics exhibited the greatest color changes after UV aging, and a 2-mm thickness is recommended to ensure acceptable color stability. The zirconia-reinforced lithium silicate glass-ceramic was the most opaque, with a 1-mm thickness providing increased translucency.

Viscosity and thermal kinetics of 10 preheated restorative resin composites and effect of ultrasound energy on film thickness

OBJECTIVE

This study investigated viscosity and thermal kinetics of 10 selected preheated restorative resin composites and the effect of ultrasound energy on film thickness.

METHODS

A range of different resin composites was tested: Charisma Diamond, IPS Empress Direct, Enamel Plus HRi, Essentia, Estelite Omega, Filtek Z100, Filtek Z350 XT, Gradia, TPH Spectrum and VisCalor. A flowable resin composite (Opallis Flow) and two resin cements (RelyX Veneer, Variolink Esthetic LC) also were tested. Viscosity (Pa s) was measured at 37 °C and 69 °C (preheating temperature) using a rheometer. Film thickness (μm) was measured before and after application of ultrasound energy. Temperature loss within resin composite following preheating (°C/s) was monitored. Data were statistically analyzed (α = 0.05).

RESULTS

Viscosity at 69 °C was lower than at 37 °C for all materials except the flowable resin composite. Preheating reduced viscosity between 47% and 92% for the restorative resin composites, which were generally more viscous than the flowable materials. Film thickness varied largely among materials. All preheated resin composites had films thicker than 50 μm without ultrasound energy. Application of ultrasound reduced film thickness between 21% and 49%. Linear and nonlinear regressions did not identify any relationship between filler loading, viscosity, and/or film thickness. All materials showed quick temperature reduction following preheating, showing maximum temperature loss rates after approximately 10 s.

SIGNIFICANCE

Distinct restorative resin composites react differently to preheating, affecting viscosity and film thickness. The overall performance of the preheating technique depends on proper material selection and use of ultrasound energy for reducing film thickness.

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.

Color Stability of Ceramic Veneers Luted With Resin Cements and Pre-Heated Composites: 12 Months Follow-Up

Abstract The objective was to evaluate the color stability of ceramic veneers luted with resin cements and pre-heated composite resins (60oC) for 12 months, and determine the degree of conversion (DC) of the luting agents. Two resin cements (AllCem Veneer, light-cured (LRC) and AllCem, dual-cured (DRC)] and three composite resins [Z100 (MNCR-minifilled), Herculite Classic (MHCR-micro-hybrid) and Durafill (MCCR-microfilled)] were used for cementing 0.8-mm-thick lithium-silicate glass-ceramic laminates (Suprinity, shade B2-HT, Vita) on bovine enamel (n=10). The specimens were stored at 37oC in distilled water. CIELab parameters were determined at 24h after luting (baseline), 7, 30, 90, 180 days and 12 months. Three specimens were prepared for DC evaluation, performed by micro-Raman spectroscopy. Data were analyzed by ANOVA and Tukey’s test (a=5%). For ΔEab and ΔE00, there were significant differences for luting material (p<0.001), time (p<0.001), and double interaction (p<0.001). The groups cemented with MHCR (1 year), MCCR (90 days and 1 year) and MCCR-PH (1 year) were the ones with ΔE values greater than the acceptability threshold. All other groups maintained their ΔE lower than the acceptability threshold after 1 year in distilled water. Regarding DC, there were no significant differences (p=0.127) among the materials. Non-significant negative correlations were observed between the mean ΔEab and DC (R=-0.65) and ΔE00 and DC (R=-0.64). A significant positive correlation was observed mean ΔEab and ΔE00 (R=0.99). It was concluded that the different luting agents influenced the final color of the restorations. The heating of the composite resins did not affect their DC.