Dual-polymerizing Resin Research Articles

Tensile Strength and Failure Types of Direct and Indirect Resin Composite Copings for Perio-Overdentures Luted Using Different Adhesive Cementation Modalities.

Perio-overdenture design helps to reduce periodontal diseases and secondary caries on abutment teeth. Composite copings can be cemented adhesively to the abutment teeth with different techniques. In this study, direct/indirect resin composite copings for perio-overdentures, luted using different adhesive cementation modalities were compared. Human teeth (N = 40) were prepared to receive spherical attachment copings and randomly divided into four groups: (1) resin-composite copings bonded directly (DC), (2) composite copings made indirectly, luted with dual-polymerized resin cement (ICV), (3) composite copings made indirectly, bonded with resin composite (ICT), (4) composite copings made indirectly, bonded with resin composite after the immediate dentin sealing method (IDS). Specimens were tested for tensile failure and one-way ANOVA (alpha = 0.05) was performed and the two-parameter Weibull modulus, scale (m) and shape (0) were calculated. Mean tensile load (N) was significantly higher for Group IDS (238 ± 81) than for the other groups (144 ± 53–184 ± 46) (p < 0.05). Group IDS (0.54 ± 0.25 mm) showed significantly higher deformation (mm) than other groups (0.2 ± 0.1–0.32 ± 0.15) (p < 0.05). Weibull distribution presented lower shape (0) for DC (3.33) compared to other groups (3.57–4.99). Cohesive coping failures were more frequent in Group IDS (60%) and mixed failures in other groups (40–60%). In conclusion, IDS copings could be preferred over other fabrication and adhesion modalities.

Kinetics of polymerization shrinkage of self-adhesive and conventional dual-polymerized resin luting agents inside the root canal

Statement of problemInformation regarding the shrinkage kinetics and monomer conversion of dual-polymerized conventional and self-adhesive resin luting agents (RLA) in situ is lacking. PurposeThe purpose of this in vitro study was to evaluate the shrinkage strain and ratio of 1 conventional and 1 self-adhesive RLA by using fiber optic sensors based on Bragg gratings and Vickers hardness in the root canal. Material and methodsThe root canals of 34 single-rooted premolars were endodontically treated and assigned to 2 groups according to the RLA: RelyX ARC (ARC) and RelyX U200 (U200). Two Bragg grating sensors were attached to fiber posts (n=10), and both post and RLA were placed inside the root canal so that shrinkage strain and ratio values could be measured at the cervical and apical root thirds. For hardness analysis (n=7), two 1-mm-thick slices of each root-third (cervical and apical) were obtained, and 4 indentations were made on the RLA layer. The shrinkage strain and rate, as well as hardness data, were evaluated by using 2-way repeated-measures ANOVA followed by the Bonferroni post hoc test when a significant interaction between factors was detected (α=.05). ResultsThe shrinkage strain and rate values of both RLAs were higher at the cervical third than those at the apical third. ARC showed higher shrinkage strain than U200 at the cervical third. The highest hardness values were observed at the cervical third, while ARC showed the lowest hardness values at the apical third. ConclusionsThe shrinkage kinetics profile and hardness of self-adhesive RLA may differ from those of conventional RLA depending on the root third.

Bond strength of adhesive luting systems to human dentin and their durability

Statement of problemThe durability of adhesive bonding systems to dentin is of importance for restoration longevity; therefore, new adhesive systems should be tested in vitro with long-term artificial aging before clinical application. PurposeThe purpose of this in vitro study was to investigate the bonding durability of 3 dual-polymerizing resins and 1 autopolymerizing resin to human dentin with their specific self-etching primers or adhesives. Material and methodsAcrylic resin tubes filled with composite resin were bonded to human dentin disks using either an autopolymerizing resin system (Panavia 21) or dual-polymerizing resin systems (Panavia V5, RelyX Ultimate, and Variolink Esthetic DC) together with the system-specific primer or adhesive. Tensile bond strength was tested after 3 days of water storage or after 150 days of water storage with 37 500 thermocycles (5 °C to 55 °C). The failure mode was evaluated by using a light microscope. In addition, representative specimens were examined by using a scanning electron microscope. ResultsAfter 3 days, the median tensile bond strengths ranged from 18.8 to 29.1 MPa. After artificial aging for 150 days, the median tensile bond strengths ranged from 14.7 to 25.6 MPa. The dual-polymerizing resins showed significantly higher bond strength than the autopolymerizing resin (P≤.05). Artificial aging with thermocycling had no statistically significant influence on tensile bond strength for the adhesive resin systems tested (P>.05). The failure mode was mainly adhesive for the autopolymerizing resin, whereas it was mainly cohesive for the dual-polymerizing resins. ConclusionsThe 3 tested dual-polymerization resin systems provided durable bond strengths to dentin which were higher than those of the autopolymerizing resin.

Implant-supported metal-ceramic and resin-modified ceramic crowns: A 5-year prospective clinical study

Statement of problemBecause of market demand for innovation, new restoration materials have been introduced without adequate testing; clinical failure may be the consequence, and clinical studies are needed. PurposeThe purpose of this clinical study was to evaluate the biological and mechanical clinical behavior of implant-supported resin-modified ceramic crowns compared with that of metal-ceramic crowns. Material and methodsForty-two participants aged between 35 and 65 years received single implants in posterior edentulous sites. After the osseointegration period, half of the implants (selected randomly) (n=25) were restored with metal-ceramic crowns (MC group) and the other half with resin-modified ceramic crowns (RMC group) bonded with dual-polymerized resin cement onto titanium abutments. The biomechanical state of the restorations and implants was analyzed. ResultsMean peri-implant bone loss after 5 years of functional life was 0.3 ±0.6 mm. The implant clinical survival rate was 98%. RMC crowns had a survival rate of 70%, whereas MC crowns had a 100% survival rate. RMC crowns had more mechanical complications than the MC group (P<.001). Peri-implant bone loss showed no significant differences between crown type (P=.175). ConclusionsAll peri-implant bone loss values were within the range considered acceptable. Metal-ceramic crowns showed better mechanical behavior than resin-modified ceramic crowns. Biological responses of peri-implant tissue would appear to be independent of the type of cemented crown.

Effect of various polymerization protocols on the cytotoxicity of conventional and self-adhesive resin-based luting cements.

This study evaluated the cytotoxicity of resin-based luting cements on fibroblast cells using different polymerization protocols. Two conventional dual-polymerized (RelyX ARC, VariolinkN) and two self-adhesive resin cements (RelyX Unicem, Multilink Speed) specimens were polymerized using four different polymerization protocols: (a) photo-polymerization with direct light application, (b) photo-polymerization over ceramic and (c) resin nano-ceramic discs and (d) auto-polymerization. The specimens were then assigned to four groups to test cytotoxicity at 0, 1, 2 and 7 preincubation days (n = 5). MTT test was performed using NIH/3T3 fibroblast cells. Data were analysed using three- and one-way ANOVA. Multiple comparisons were made using Bonferroni post hoc test (p < 0.05). The highest cytotoxic values were recorded at day 2 for conventional resin cements and at day 0 for self-adhesive resin cements. Self-adhesive resin cements showed the most cytotoxic effect at the second day, while conventional resin cements presented immediate cytotoxicity. Auto-polymerized resin specimens and especially Multilink Speed demonstrated the most cytotoxic effect regardless of the preincubation time. Cytotoxicity of cements tested reached the lowest level at day 7. Interposition of ceramic or nano-ceramic restorative material did not significantly affect the cytotoxicity of tested luting cements (p > 0.05). Cytotoxicity of dual-polymerized resin cements was material-dependent and decreased gradually up to 7days. Photo-polymerization plays an important role in reducing the cytotoxic effects. When luting ceramic or resin nano-ceramic restorations of which thickness does not exceed 2mm, the level of cytotoxicity with the tested materials is not significant. Luting of restorative materials that do not allow for light transmission such as metal-fused porcelain, clinicians should be cautious in the use of dual-polymerized conventional resin cements as only auto-polymerization of resin cements takes place under such materials.

Effect of length of LOCATOR abutment and cement type on retention to intraradicular dentin in overdentures

Statement of problemLimited information is available on the effect of LOCATOR abutment length and luting cement type on retention to intraradicular dentin in overdentures. PurposeThe purpose of this in vitro study was to evaluate the effect of the length of a commercially available LOCATOR abutment and cement type on retention in the root canal. Material and methodsEighty LOCATOR abutments with a standard length of 6 mm were obtained. Half of them were shortened to 3 mm. Eighty recently extracted single-rooted teeth were divided into 2 groups. The post space was prepared to 6 mm in the first group and 3 mm in the second. After preparation, the LOCATOR abutments were luted with one of the following cements: dual-polymerized glass-reinforced resin cement (Parapost Paracore), dual-polymerized resin cement (Variolink II), self-adhesive resin cement (RelyX Unicem), and conventional cement (zinc phosphate). The tensile force required for the removal of the LOCATOR abutments from their corresponding roots was recorded. Data were statistically analyzed with 2-way ANOVA and the Tukey multiple comparison test. ResultsBoth the cement type (P<.001) and the length of the LOCATOR abutment (P<.001) significantly affected the mean tensile forces. Dual-polymerized glass-reinforced resin cement (Parapost Paracore) presented significantly higher mean tensile forces for the LOCATOR abutment retention among all cements (P<.05). ConclusionsRegardless of the length, LOCATOR abutments luted with Parapost Paracore resin cement presented higher mean resistance to tensile forces compared with those luted with the other cements. LOCATOR abutments of 6 mm in length were more resistant to tensile forces than those of 3 mm in length in combination with all cements.

Clinical outcomes of zirconia-reinforced lithium silicate partial coverage crowns compared to lithium disilicate partial coverage crowns. A randomized controlled split-mouth clinical study

Background: Despite the fact that preliminary clinical results of conservative partial coverage restorations (PCRs) are promising, the clinical behavior of different PCR ceramic materials is rarely investigated in clinical trials. This study aimed to evaluate the clinical outcomes of partial coverage restorations (PCR) fabricated with zirconia-reinforced lithium silicate ceramic system compared to partial coverage restorations fabricated with lithium disilicate ceramic system. Methods: 46 vital premolars and molars of 14 patients were restored with PCRs (23 Vita Suprinity and 23 IPS e.max CAD). PCRs were CAD/CAM fabricated in the lab and adhesively luted with dual-polymerizing resin cement (Duolink. BISCO, USA). Clinical evaluation of PCRs was performed according to the Modified United States Public Health Service (USPHS) at baseline, 6 and 12 months post-insertion. Absolute failure was demonstrated by Kaplan-Meier survival rate analysis. Results: After 12 months observation, all PCRs of both ceramic groups demonstrated 100% survival rate. Non-significant decrease in Alpha ratings for marginal adaptation (p = 0.1560) and marginal discoloration (p = 0.6078) in e-max group. While in the Suprinity group, PCRs demonstrated 100% Alpha ratings for marginal adaptation and only one Bravo rating (p= 0.3625) for marginal discoloration after 12 month observation. Conclusions: Both Vita-Suprinity and e.max CAD partial coverage restorations are considered reliable treatment options for restoring larger defects in posterior dentition. Trial registration: ClinicalTrials.gov NCT02861729 04/08/2016

Micro-computed tomography analysis of gap and void formation in different prefabricated fiber post cementation materials and techniques

ObjectiveThe study was built around the objective of determining the variances in the gap and void formation around cemented prefabricated fiber posts with two different cementation materials and techniques with micro-computed tomography (μCT). MethodsStandardized acrylic resin roots (N = 40) with prefabricated fiber posts (RelyX™ Fiber Post 3D) were split into four sets (n = 10) based on many types of cementation materials and techniques. In the first group, resin cement (RelyX™ Unicem) was inserted to the canals via root canal tips. In the second group, the same cement was injected, and a microbrush was used to distribute the cement inside the canal. In the third group, dual polymerizing resin cement (MultiCore® Flow) was injected into the canals by using root canal tips. In the fourth group, the same cement was injected, and a microbrush was used to distribute the cement inside the canal. The gap and void formation in the cement and the root canals was evaluated with μCT. IBM SPSS Statistics was used to perform the statistical evaluation, then the Kolmogorov-Smirnov test of normality and Kruskal-Wallis H test to compare these variables with respect to the all groups significant difference (a = 0.05). ResultsThe study outlined no difference of significance when evaluating the gap and void formation within the experimental groups (P > 0.05). ConclusionThere was a certain amount of void and gap formation inside all of the tested specimens. However, no significant variances were found.

Comparison of the Effect for Fracture Resistance of Different Coronally Extended Post Length with Two Different Post Materials.

Aims and Objectives:To compare the effect for fracture resistance of different coronally extended post length with two different post materials.Materials and Methods:One hundred and sixty endodontically treated maxillary central incisors embedded in acrylic resin with decoronated root portion were taken for the study. The postspaces were prepared according to standard protocol. The samples were divided into two groups according to the post material: glass-fiber post and Quartz fiber post. These groups were further subdivided on the basis of coronal extension of 4 and 6 mm for glass fiber and Quartz fiber posts, respectively. The posts were then luted with dual-polymerizing resin cement followed by core buildup. Samples were subjected to increasing compressive oblique load until fracture occurred in a universal testing machine. Data were analyzed with one-way ANOVA and independent Student's t-test. Analysis was done using SPSS version 15 (SPSS Inc., Chicago, IL, USA) Windows software program.Results:Glass fiber post with coronal extension of 4 mm (182.8 N) showed better results than with 6-mm length (124.1 N). Similarly, in quartz fiber posts group, 4-mm postlength (314 N) was better when compared with 6 mm (160 N). The 4-mm coronal extension of quartz fiber post displayed superior fracture resistance.Conclusions:Glass fiber posts showed better fracture resistance than Quartz fiber posts. 4-mm coronal length showed more fracture resistance than 6 mm.

Adhesion of dual-polymerized luting cement on superficial and deep dentin using different one-step self-etch mild adhesive systems

This study evaluated adhesion of dual-polymerized resin cement to superficial dentin (SD) and deep dentin (DD) using one-step self-etch adhesives at varying pH. After smear layer was created on third molars (N = 60, n = 15 per group), adhesive resins, 1- Clearfil S3 Bond Plus-CBP (Kuraray) (pH: 2.3), 2- Bisco All Bond Universal-BAU (Bisco) (pH: 3.2), 3- Single Bond Universal Adhesive-SBU (3M ESPE) (pH: 2.7), 4- Nova Compo-B Plus-NCBP (Imicryl) (pH: 2.5–3), were applied on SD and DD. Resin cement (Variolink II, Ivoclar Vivadent) was adhered incrementally on the SD surfaces using polyethylene molds and photo-polymerized for 40 s from 5 directions (output: 1200 mw/cm2). After macroshear and microshear test, in order to achieve DD specimens, SD were removed 1 mm in the pulp direction and the same bonding and test procedures were performed. The specimens were kept at 37 °C for 24 h. The adhesion tests were conducted in the Universal Testing Machine and failure types were analyzed. The data were analyzed using Univariate ANOVA, Tukey`s, Kruskal-Wallis and Mann-Whitney tests (α = .05). Test method, dentin level and the adhesive resin significantly affected the results (MPa) (p < .05). After macroshear test, more incidences of cohesive failures in DD were observed with NCBP Plus. On SD, NCBP presented the highest results followed by BAU using macroshear test. On DD, NCBP presented the highest results followed by SBU. Not only the pH but the chemical composition affected adhesion especially to SD while in DD, the difference between the adhesive resins was less significant.

Bonding of glass ceramic and indirect composite to non-aged and aged resin composite.

Since adhesion of the restorative materials to pre-polymerized or aged resin composites presents a challenge to the clinicians, existing restorations are often removed and remade prior to cementation of fixed dental prostheses (FDPs). This study evaluated bond strength of non-aged and aged resin composite to an indirect resin composite and pressed glass ceramic using two resin cements. Disk-shaped specimens (diameter: 3.5, thickness: 3 mm) (N = 160) produced from a microhybrid resin composite (Quadrant Anterior Shine) were randomly divided into eight groups. While half of the specimens were kept dry at 37°C for 24 h, the other half was aged by means of thermocycling (6000 times, 5°C to 55°C). The non-aged and aged resin composites were bonded to a highly filled indirect composite (Estenia) and a pressed glass ceramic (IPS Empress II) using either a photopolymerizing (Variolink Veneer) or a dual-polymerizing (Panavia F2.0) resin cement. While cementation surfaces of both the direct and indirect composite materials were silica coated (30 µm SiO2, CoJet-Sand) and silanized (ESPE-Sil), ceramic surfaces were conditioned with hydrofluoric acid (20 s), neutralized, and silanized prior to cementation. All specimens were cemented under a load of 750 g. Shear force was applied to the adhesive interface in a universal testing machine (1 mm/min). Failure types of the specimens were identified after debonding. Significant effects of aging (p < 0.05), restorative material (p < 0.05), and cement type (p < 0.05) were observed on the bond strength (3-way ANOVA). Interaction terms were also significant (p < 0.05) (Tukey's test). After aging, in terms of bond strength, indirect composite and pressed glass ceramic in combination with both cements showed no significant difference (p > 0.05). Both indirect composite (24.3 ± 5.1 MPa) and glass ceramic in combination with Variolink (22 ± 9 MPa) showed the highest results on non-aged composites, but were not significantly different from one another (p > 0.05). On the aged composites, indirect composite and glass ceramic showed no significant difference in bond strength within each material group (p > 0.05), with both Panavia (17.2 ± 6 and 15 ± 5.5 MPa, respectively) and Variolink (19 ± 8, 12.8 ± 5.3 MPa, respectively), but in all groups, glass ceramic-Variolink on aged composite revealed the lowest results (12.8 ± 5.3 MPa). Among all groups, predominantly cohesive failures were observed in the indirect resin composite substrate (79 out of 80) as opposed to the ceramic (18 out of 80) (p < 0.05) (Chi square). Regardless of the resin cement type, considering the bond values and the failure types, the adhesion quality of indirect composite cemented to non-aged and aged resin composite was superior with both cements compared to that of pressed glass ceramic.

Survival rate and load to failure of premolars restored with inlays: An evaluation of different inlay fabrication methods

Statement of problemStudies that evaluate the survival rate and load to fracture of premolars restored with inlays produced using different methods are lacking. PurposeThe purpose of this in vitro study was to compare the survival rate and fracture load of premolars restored with inlays fabricated using different methods. Material and methodsThirty maxillary premolars were selected, embedded, and prepared to receive inlays fabricated using different methods (n=10): LaCom-digital scanning with Lava C.O.S. scanner (3M ESPE), followed by milling of composite resin block (Lava Ultimate; 3M ESPE) in a milling unit; CeCom-digital scanning with Cerec 3D Bluecam scanner (Dentsply Sirona), followed by milling of a Lava Ultimate block in Cerec (Dentsply Sirona); PresDis-impression with polyvinyl siloxane, inlay made using the lost wax technique, and IPS e.max Press (Ivoclar Vivadent AG) pressed ceramic (lithium disilicate). A dual-polymerizing resin cement system was used to lute the inlays. Inlays were mechanically cycled (2 Hz, 106 mechanical pulses, 80 N) after 24 hours, and the specimens were stored in distilled water at 37°C for 11 months. Then, a fatigue test was conducted using a 10-Hz frequency and 400-N load on the inner inclines of the cusps. The test was complete when the specimen fractured or when the specimen reached 1.5×106 cycles. The specimens that survived fatigue testing were submitted to a single-load fracture test in a universal testing machine and analyzed using a stereoscope for failure classification. Survival rates were estimated using the Kaplan-Meier method and log-rank test (Mantel-Cox). Fracture load data were analyzed using 1-way ANOVA (α=.05). ResultsNo significant differences were detected among the groups for the survival rate (P=.87) or for the load to fracture (P=.78). Most failures were longitudinal, catastrophic fractures. ConclusionsPremolars restored with inlays fabricated using the tested methods had similar survival rates and loads to fracture.

Oval Versus Circular-Shaped Root Canals: Bond Strength Reached with Varying Post Techniques.

The aim of this study was to compare the bond strength (BS) of glass fiber posts (GFP) luted to oval and circular-shaped root canals rehabilitated using varying post techniques, at different intraradicular levels. Ninety 16-mm-long roots of human mandibular premolars, classified either as having oval or circular-shaped canals, were endodontically treated and prepared for restoration using one of three different post techniques (n=15): 1) single GFP; 2) resin-relined GFP; 3) main GFP associated with accessory posts. GFPs were luted with a dual polymerizing resin cement (RelyX ARC) after the canal had been treated with a 3-step etch-and-rinse adhesive system (Adper Scothbond Multipurpose). The samples were sectioned into three 1-mm-thick sections, which were differentiated by the root level (cervical, middle and apical) and tested for push-out BS. Assessment of failure mode was made under a stereomicroscope. Data were analyzed using repeated measures three-way ANOVA and Tukey's test. The root canal cross-section had a significant influence on BS (p<0.001), with the lowest values being observed in oval-shaped canals. The post technique also significantly affected the BS (p=0.018), with the resin-relined GFPs providing the highest BS values in both oval and circular-shaped canals. Irrespective of the cross-section of the root canal and post technique, there was no significant difference in BS in the cervical, middle and apical third of the root canal (p=0.084). In oval-shaped canals, the BS to intraradicular dentin at cervical, middle or apical level could be increased when the GFPs posts were relined.

Color change of CAD-CAM materials and composite resin cements after thermocycling

Statement of problemThe color of resin cements and computer-aided-design and computer-aided-manufacturing (CAD-CAM) restorations may change with aging. PurposeThe purpose of this in vitro study was to analyze the influence of thermocycling on the color of CAD-CAM materials with underlying resin cement. Material and methodsSeven different CAD-CAM materials, composite resins and glass-ceramics were cut into 0.7-mm and 1.2-mm thicknesses (n=10) and cemented with a dual-polymerizing resin cement, a light-polymerizing resin cement, and a preheated composite resin (N=420). Color values were measured by using spectrophotometry. Specimens were subjected to thermocycling (5°C and 55°C; 5000 cycles). The measured color difference (ΔE) data were analyzed by using descriptive statistics. Normality of data distribution was tested by using the Kolmogorov-Smirnov test. Three-way and 1-way ANOVA followed by the Scheffé post hoc test and unpaired 2-sample Student t test were computed to determine the significant differences among the tested parameters (α=.05). ResultsΔE values were significantly influenced by the CAD-CAM material (ηp2=0.85, P<.001) and the resin composite cement (ηP2=0.03, P=.003) but were not influenced by thickness (P=.179). Significant interactions were present among thickness, cement, and CAD-CAM materials (P<.001). Vita Suprinity and GC Cerasmart showed significantly the lowest ΔE values (P<.001). The highest ΔE values were observed for IPS Empress CAD. The dual-polymerizing resin cement showed significantly lower ΔE values than the preheated composite resin (P=.003). ConclusionsRestoration materials and composite resin cement types used for cementation influence the amount of color change due to aging.

Influence of immediate dentin sealing and interim cementation on the adhesion of indirect restorations with dual-polymerizing resin cement

Statement of problemDentin surface contamination before the cementation of indirect restorations may impact bonding effectiveness. PurposeThe purpose of this in vitro study was to analyze the influence of immediate dentin sealing (IDS) and interim cementation on the adhesion of indirect restorations with a dual-polymerizing resin cement. Material and methodsComposite resin inlays were placed in class V cavities prepared in the buccal and lingual surfaces of 30 extracted human molars with a dual-polymerizing resin cement in 3 different ways (n=10): CG, directly on dentin; PG, after 14 days interim cementation; SG, after IDS and 14 days interim cementation. Buccal restorations were sectioned into sticks and submitted to the microtensile bond strength (μTBS) test. Lingual restorations were submitted to micro-Raman spectroscopy (MRS). Data were analyzed with 1-way ANOVA and the Tukey-Kramer post hoc test (α=.05). ResultsSignificantly higher μTBS results were found for SG (35.7 ±8.2 MPa) when compared with CG (23.1 ±7.1 MPa) and PG (17.0 ±6.0 MPa) (P<.05), but no differences were observed between CG and PG. MRS showed that the diffusion zone in SG (3.7 ±0.5 μm) was significantly thicker than that of CG (1.8 ±1.2 μm) or PG (1.5 ±0.3 μm) (P<.05). Additionally, a new interface peak (at approximately 1330 cm-1) was found in SG, indicating a chemical interaction. ConclusionsThe use of IDS before cementation resulted in a chemical interaction at the interface and significantly higher μTBS and diffusion zone thickness values. Interim cementation did not interfere with adhesion quality when compared with the control group.

Effects of cyclic staining on the color, translucency, surface roughness, and substance loss of contemporary adhesive resin cements

Statement of problemThe staining resistance of the adhesive resin cements is critical to the long-term success of a restoration, but only limited evidence is available regarding the effects of cyclic staining on adhesive resin cements. PurposeThe purpose of this in vitro study was to investigate the effects of staining solutions on the color, translucency, substance loss, and surface roughness of contemporary adhesive resin cements. Material and methodsSix commercially available adhesive resin cements (Clearfil SA Cement, Panavia F2.0, RelyX U200, RelyX Veneer, NX-3 Light Polymerize, NX-3 Dual Polymerize) were tested. The specimens were subjected to a cyclic staining model with 4 different solutions (deionized water, cola, coffee, and red wine). All specimens were immersed in the respective solutions 12 times for 15 minutes daily over 96 days. Between staining cycles, the specimens were stored in artificial saliva. The color parameters, surface profile, and surface roughness of the specimens were measured before and after cyclic staining for 16, 32, 48, 64, 80, and 96 days. Repeated-measure ANOVA was used to evaluate the effect of the staining solutions on the color difference (ΔE), translucency change (ΔTP), substance loss, and surface roughness (Ra) of the tested adhesive resin cements (α=.05). ResultsAll the tested materials exhibited similar behaviors with longer durations of immersion in the staining solutions. Specifically, ΔE increased, TP decreased, and the surface profile and roughness remained stable. The tested adhesive resin cements exhibited variations in color and TP stability after staining. The light-polymerized adhesive resin cements were generally more color-stable than the dual-polymerized resin cements. ConclusionsThe effects of cyclic staining on the color, translucency, surface profile, and surface roughness of adhesive resin cements were not categorical but material-specific.

Effect of beverages on surface properties of resin-based sealants

Self-adhesive, dual-polymerizing resin cements require no treatment to the prepared tooth surfaces before cementation. Aim: The aim of this study was to evaluate the influence of curing mode on bond strength (BS) of three cementing systems to bovine dentin. Methods: The buccal enamel surfaces of 50 bovine incisors were removed to expose dentin and to flat the surface. The teeth were divided into five groups (n=10), which consisted of two resin cements (Multilink and Clearfil SA Cement) that were tested in dual- (halogen light for 40 s) and self-cured modes, and a control (RelyX ARC). Two cylinders of resin cements (1.0 mm X 0.75 mm) were prepared on each bonded dentin surface. After 24h at 37oC, resin cylinders were subjected to micro-shear testing in a universal testing machine (4411/Instron - 0.5 mm/min). Data were statistically analyzed by two-way ANOVA, Tukey and Dunnett`s test (5%). Results: Multilink showed higher BS than those observed on Clearfil SA. Light-curing resulted in higher BS for both Multilink and Clearfil SA. When Multilink was light-cured, no significant difference on BS was demonstrated between it and RelyX ARC. Conclusions: The highest BS values were obtained in control group and light-cured Multilink resin cement.

Influence of curing mode of resin luting cements on bond strength to dentin

Self-adhesive, dual-polymerizing resin cements require no treatment to the prepared tooth surfaces before cementation. Aim: The aim of this study was to evaluate the influence of curing mode on bond strength (BS) of three cementing systems to bovine dentin. Methods: The buccal enamel surfaces of 50 bovine incisors were removed to expose dentin and to flat the surface. The teeth were divided into five groups (n=10), which consisted of two resin cements (Multilink and Clearfil SA Cement) that were tested in dual- (halogen light for 40 s) and self-cured modes, and a control (RelyX ARC). Two cylinders of resin cements (1.0 mm X 0.75 mm) were prepared on each bonded dentin surface. After 24h at 37oC, resin cylinders were subjected to micro-shear testing in a universal testing machine (4411/Instron - 0.5 mm/min). Data were statistically analyzed by two-way ANOVA, Tukey and Dunnett`s test (5%). Results: Multilink showed higher BS than those observed on Clearfil SA. Light-curing resulted in higher BS for both Multilink and Clearfil SA. When Multilink was light-cured, no significant difference on BS was demonstrated between it and RelyX ARC. Conclusions: The highest BS values were obtained in control group and light-cured Multilink resin cement.

Survival of extensively damaged endodontically treated incisors restored with different types of posts-and-core foundation restoration material

Statement of problemWhich post-and-core combination will best improve the performance of extensively damaged endodontically treated incisors without a ferrule is still unclear. PurposeThe purpose of this in vitro study was to investigate the restoration of extensively damaged endodontically treated incisors without a ferrule using glass-ceramic crowns bonded to various composite resin foundation restorations and 2 types of posts. Material and methodsSixty decoronated endodontically treated bovine incisors without a ferrule were divided into 4 groups and restored with various post-and-core foundation restorations. NfPfB=no-ferrule (Nf) with glass-fiber post (Pf) and bulk-fill resin foundation restoration (B); NfPfP=no-ferrule (Nf) with glass-fiber post (Pf) and dual-polymerized composite resin core foundation restoration (P); NfPt=no-ferrule (Nf) with titanium post (Pt) and resin core foundation restoration; and NfPtB=no-ferrule (Nf) with titanium post (Pt) and bulk-fill resin core foundation restoration (B). Two additional groups from previously published data from the same authors (FPf=2mm of ferrule (F) and glass-fiber post (Pf) and composite resin core foundation restoration; and NfPf=no-ferrule (Nf) with glass-fiber post (Pf) and composite resin core foundation restoration), which were tested concomitantly and using the same experimental arrangement, were included for comparison. All teeth were prepared to receive bonded glass-ceramic crowns luted with dual-polymerized resin cement and were subjected to accelerated fatigue testing under submerged conditions at room temperature. Cyclic isometric loading was applied to the incisal edge at an angle of 30 degrees with a frequency of 5 Hz, beginning with a load of 100 N (5000 cycles). A 100-N load increase was applied every 15000 cycles. The specimens were loaded until failure or to a maximum of 1000 N (140000 cycles). The 6 groups (4 groups from the present study and 2 groups from the previously published study) were compared using the Kaplan-Meier survival analysis (log-rank post hoc test at α=.05 for pairwise comparisons). ResultsNone of the tested specimen withstood all 140 000 cycles. All specimens without a ferrule were affected by an initial failure phenomenon (wide gap at the lingual margin between the core foundation restoration/crown assembly and the root). NfPfP, NfPt, and NfPtB had similar survival (29649 to 30987 mean cycles until initial failure). NfPfB outperformed NfPt and NfPtB. None of the post-and-core foundation restoration materials were able to match the performance of the ferrule group FPf (72667 cycles). In all groups, 100% of failures were catastrophic. ConclusionsThe survival of extensively damaged endodontically treated incisors without a ferrule was slightly improved by the use of a fiber post with a bulk-fill composite resin core foundation restoration. However, none of the post-and-core techniques was able to compensate for the absence of a ferrule. The presence of the posts always adversely affected the failure mode.

Color stability of ceramic laminate veneers cemented with light-polymerizing and dual-polymerizing luting agent: A split-mouth randomized clinical trial

Statement of problemThe color stability of luting agents influences the esthetics of ceramic laminate veneers. Clinical studies that have evaluated the color changes of veneers cemented to enamel with light- and dual-polymerizing resin cement are lacking. PurposeThe purpose of this split-mouth randomized clinical trial was to evaluate the color change and marginal discoloration of dual- and light-polymerizing cement used for cementation of ceramic laminate veneers. Material and methodsIn 10 participants, 0.3-mm-thick ceramic laminate veneers were cemented on the buccal surface of the second premolars without tooth preparation. A randomized application of light-polymerized cement was used on one side and a dual-polymerized cement on the contralateral side. The operator and participants were blinded to the activation mode. Color was evaluated by a blinded evaluator with a spectrophotometer at 24 hours and at 2, 6, 12, and 24 months after cementation. The CIELab (ΔE*ab) and CIEDE2000 (ΔE*00) formulas were used to quantify color alteration, and Δa*, Δb*, and ΔL* were calculated between the first and subsequent measurements. US Public Health Service guidelines were used to evaluate the marginal discoloration. ResultsWilcoxon tests did not show a statistical difference in ΔE*ab and ΔE*00 between the groups (P>.05). At 24 months, the median ΔE*ab was 2.31 (interquartile ranges [IQR]: 3.34) for the light-polymerizing mode and 1.57 (IQR: 0.41) for the dual-polymerizing mode, while the median ΔE*00 was 1.65 for the light-polymerizing mode (IQR: 2.34) and 1.18 for the dual-polymerizing mode (IQR: 0.25). The thresholds for clinically acceptable color changes ΔE*ab>3.46 and ΔE*00>2.25 were found for both curing modes. Marginal discoloration was observed from the 2-year assessment. ConclusionsThe color stability of ceramic laminate veneers was similar for both of the polymerizing modes for all evaluated periods. Marginal discoloration increased over a 2-year period for both the light- and the dual-polymerizing modes.