Micro-tensile bond testing of resin cements to dentin and an indirect resin composite

Effect of crown retention systems and loading direction on the stress magnitude of posterior implant-supported restorations: A 3D-FEA

This study aimed to investigate the effect of four retention systems for implant-supported posterior crowns under compressive loading using three-dimensional finite element analysis. A morse-taper dental implant (4.1 × 10 mm) was designed with Computer Aided Design software based on non-uniform rational B-spline surfaces. According to International Organization for Standardization 14,801:2016, the implant was positioned at 3 mm above the crestal level. Then four models were designed with different crown retention systems: screw-retained (A), cement-retained (B), lateral-screw-retained (C), and modified lateral-screw-retained (D). The models were imported to the analysis software and mesh was generated based on the coincident nodes between the juxtaposed lines. For the boundary conditions, two loads (600 N) were applied (axial to the implant fixture and oblique at 30°) totaling 8 conditions according to retention design and loading. The von-Mises stress analysis showed that different retention systems modify the stress magnitude in the implant-supported posterior crown. There is a similar stress pattern in the implant threads. However, models C and D presented higher stress concentrations in the crown margin in comparison with A and B. The oblique loading highly increased the stress magnitude for all models. In the simulated conditions, part of the stress was concentrated at the lateral screw under axial loading for model C and oblique loading for model D. The results indicate a possible new failure origin for crown retained using lateral screws in comparison to conventional cement-retained or screw-retained systems.

Durability of Resin Bonding to Dental 3Y-TZP Zirconia Using Different Adhesive Systems

This laboratory study was conducted to evaluate and compare the resin bond strength of different adhesive resin systems in different combinations and the durability of their bonds with zirconia ceramic.

MATERIALS AND METHODS

One hundred and twenty-eight specimens were milled from 3Y-TZP zirconia ceramic. The bonding surfaces of all disks were wet polished, steam cleaned, airborne-particle abraded and ultrasonically cleaned in 99% isopropanol. The specimens were randomly divided into four main groups according to the applied resin system; two conventional and two self-adhesive systems were used. Each group was further subdivided into two subgroups; the first was conditioned with the specified primer for conventional luting resins or not conditioned for the self-adhesive systems, whereas the second subgroup of each was conditioned with the same phosphate monomer-containing primer (Alloy Primer). The zirconia specimens were adhesively bonded, using the allocated luting resin, to plexiglass tubes filled with self-curing composite resin (Clearfil FII). Half of the specimens of each subgroup were stored in distilled water at 37 °C for 3 days, whereas the other half were subjected to artificial aging, 150 days of storage and additional thermal cycling. Thereafter, all specimens were subjected to TBS testing using a universal testing machine. Statistical analysis was conducted using two-way ANOVA followed by separate one-way ANOVAs. The Games-Howell post-hoc test was applied for pairwise comparisons.

RESULTS

All specimens survived storage with thermal cycling. The mean TBS values ranged from a minimum of 43.4 ± 5.0 MPa to a maximum of 66.4 ± 3.5 after 3 days and from a minimum of 13.6 ± 2.5 MPa to a maximum of 50.1 ± 9.4 MPa after 150 days.

CONCLUSIONS

Artificial aging had a significantly negative effect on all test groups. The chosen adhesive-resin system had a significant effect on the resulting TBS values. The highest TBS values were achieved for the self-adhesive luting resin G-Cem One but were statistically comparable to the results obtained for the dual-cure luting resin G-Cem LinkForce.

Clinical survival and performance of premolars restored with direct or indirect cusp-replacing resin composite restorations with a mean follow-up of 14 years

OBJECTIVES

The objective is to evaluate the long-term clinical survival and performance of direct and indirect resin composite restorations replacing cusps in vital upper premolars.

METHODS

Between 2001 and 2007, 176 upper premolars in 157 patients were restored with 92 direct and 84 indirect resin composite restorations as part of an RCT. Inclusion criteria were fracture of the buccal or palatal cusp of vital upper premolars along with a class II cavity or restoration in the same tooth.

RESULTS

Forty patients having 23 direct and 22 indirect composite restorations respectively, were lost to follow-up (25.6%). The cumulative Kaplan-Meier survival rates were 63.6% (mean observation time: 15.3 years, SE 5.6%) with an AFR of 2.4% for direct restorations and 54.5% (mean observation time: 13.9 years, SE: 6.4%) with an AFR of 3.3% for indirect restorations. The Cox regression analysis revealed a statistically significant influence of the patient's age at placement on the survival of the restoration (HR 1.036, p = 0.024), the variables gender, type of upper premolar, type of restoration, and which cusp involved in the restoration had no statistically significant influence. Direct composite restorations failed predominantly due to tooth fracture, indirect restorations primarily by adhesive failure (p < 0.05).

SIGNIFICANCE

There was no statistically significant difference in survival rates between direct and indirect composite cusp-replacing restorations. Both direct and indirect resin composite cusp-replacing restorations are suitable options to restore compromised premolars. The longer treatment time and higher costs for the indirect restoration argue in favor of the direct technique.

Influence of pulse duration and water/air cooling ratio on the efficiency of Er:YAG 2940 nm laser in debonding of porcelain laminate veneers: An in vitro study

Objective

To determine the effectiveness of different pulse durations (PD) and the water/air (W/A) cooling ratio of the Er:YAG 2940 nm laser that are required for debonding porcelain laminate veneers (PLV), by investigation of the needed time for PLV debonding (DT) and the changes in dental pulp temperature.

Materials and Methods

Thirty‐six extracted noncarious human maxillary premolars were prepared for receiving PLV. Samples were randomly assigned to six different groups, based on PD and the W/A ratio: Groups A (50 µs, 1:1), B (50 µs, 3:3), C (100 µs, 1:1), D (100 µs, 3:3), E (300 µs, 1:1), and F (300 µs, 3:3). Veneers were debonded using laser irradiation by the same parameters (270 mJ, 15 Hz) with noncontact application mode.

Results

All 36 veneers were debonded. Samples of the 50 and 100 µs PDs showed significantly shorter DT (7.4−17 s) than that of the 300 µs which showed significantly the longest DT (104 s) among all other groups (p < .001). However, the highest elevation of pulp temperature was observed in Group E (300 µs, 1:1) which reached (3.4°C).

Conclusion

Using the 50 or 100 µs PD of the Er:YAG laser was more efficient than 300 µs in reducing DT of PLVs with minimal change in pulp temperature. W/A cooling ratio had minimal influence on the DT of PLV.

Effect of differences in the type of restoration and adhesive resin cement system on the bonding of CAD/CAM ceramic restorations

The effect of differences in the type of restoration and adhesive resin cement system on the bonding of CAD/CAM ceramic restoration after cyclic loading was examined quantitatively and qualitatively. Seventy-two human maxillary first molars were divided into three restoration groups: MOD-inlay, MODP-onlay, and crown. Immediate dentin sealing was applied to the exposed dentin of all prepared specimens. The 24 specimens of each restoration group were further divided into another three groups, and a different adhesive resin cement system was applied to each group for cementation. All restoratives were fabricated from feldspathic-ceramic-blocks and cemented with each adhesive resin cement system according to the manufacturer's instructions. The microtensile bond-strength was measured after cyclic loading and was not significantly affected by differences in the type of restoration or adhesive resin cement system. However, the type of restorations and adhesive resin cement systems did show significant differences in terms of the bonding reliability.

Interfacial Evaluation of CAD/CAM Resin Inlays on the Cavity Floor Using Swept-source Optical Coherence Tomography

CLINICAL RELEVANCE

When a resin nanoceramic inlay is cemented using self-adhesive cement, a universal dentin adhesive can be applied to the prepared cavity. The application of the adhesive before self-adhesive cement placement provides similar or better interfacial adaptation than without the adhesive.

SUMMARY

Purpose: The first objective of this study was to determine whether the luting material used for computer-aided design and computer-aided manufacture resin nanoceramic inlays affected interfacial adaptation. The second objective was to investigate whether application of a universal dentin adhesive before cementation affected interfacial adaptation. The final objective was to compare the inlay-side and dentin-side interfaces in the cement space.Methods and Materials: Seventy-four class I cavities were prepared on extracted human third molars. Cavities were optically scanned, and resin nanoceramic inlays were milled using Lava Ultimate blocks (3M ESPE). For the control groups, the fabricated inlays were cemented using Panavia V5 (Kuraray Noritake) or FujiCem 2 (GC). For the experimental groups, the teeth were randomly divided into groups I and II. Group I contained four subgroups using different luting materials; in all subgroups, the inlays were cemented and dual cured without pretreatment. Group II contained six subgroups in which inlays were cemented and dual cured after application of a universal dentin adhesive. After thermocycling, interfacial adaptation was measured using swept-source optical coherence tomography (SS-OCT) imaging and statistically compared among groups.Results: Interfacial adaptation was different depending on the luting material used (p<0.05). After application of a universal adhesive, some subgroups showed improved interfacial adaptation (p<0.05). In the comparison of inlay-side and dentin-side interfaces, no difference was found in interfacial adaptation (p>0.05).Conclusions: Interfacial adaptation for resin nanoceramic inlays differed with luting material. For some self-adhesive cements, application of a universal adhesive before cementation improved interfacial adaptation.

Effect of Pretreatment and Activation Mode on the Interfacial Adaptation of Nanoceramic Resin Inlay and Self-adhesive Resin Cement

OBJECTIVES

The first objective of this study was to determine if the luting material used for resin nanoceramic inlay affects interfacial adaptation. The second was to investigate whether pretreatment and the adhesive curing method before cementation affects interfacial adaptation. The final objective was to compare activation modes of luting material.

METHODS

Class I cavities were prepared on extracted human third molars. Resin nanoceramic inlays were fabricated using Lava Ultimate CAD/CAM block (3 M). For the control groups, inlays were cemented using Panavia V5 (Kuraray Noritake). For the experimental groups, teeth were randomly divided into five experimental groups with four subgroups using different self-adhesive cements (SACs). Cement in Group I was dual-cured without pretreatment. In Group II, the cement was dual-cured after polyacrylic acid treatment of the tooth cavity. In Groups III and IV, the cement was dual-cured after universal dentin adhesive treatment with pre-cure and co-cure methods. In Group V, the inlay was cemented in self-cure mode. After thermocycling, interfacial adaptation at the inlay-tooth interface was measured using swept-source optical coherence tomography (SS-OCT) imaging. Finally, polymerization shrinkage strain of the luting material was measured and compared.

RESULTS

Interfacial adaptation differed depending on the luting material. After application of a universal adhesive, some subgroups showed improved interfacial adaptation. Interfacial adaptation and polymerization shrinkage strain differed significantly depending on activation mode.

SIGNIFICANCE

Interfacial adaptation for a resin nanoceramic inlay can differ according to the type of SAC and activation mode. For some SACs, application of a universal adhesive before cementation improves interfacial adaptation.

Bond strength and adhesive interfacial micromorphology of self-adhesive resin cements: Effect of reduced times of pre-etching

Background

Although acid-etching could increase enamel bond strength of self-adhesive (SA) cements, it may lead to negative effect on dentin. The aim of this study was to assess the effect of shortening of phosphoric acid pre-etching duration on enamel/ dentin shear bond strength (SBS) and interfacial microstructure of Panavia SA Luting Plus (PASA) and Bifix SE (BXSE).

Material and Methods

For both enamel and dentin, effect of pre-etching time was significant (p<0.001); however, effect of cement brand and the interaction of two factors was significant only for dentin (p≤0.008). Three pre-etching times increased SBS of both cements to enamel and BXSE to dentin. In case of dentin SBS of PASA, this improvement was significant only for 5 and 10 seconds (p<0.001). Adding acid-etching in the three times to both cements similarly improved interfacial adaptation, particularly for enamel.

Results

The evaluations of the biofilm elimination showed results that indicate that the 4% sodium hypochlorite group with positive pressure irrigation presented significant differences with the group that had irrigation with sodium hypochlorite activated with XP-endo Finisher and the chlorhexidine groups to 2% (P<0.05).

Conclusions

Interfacial bond strength and adaptation of SA cements used in this study were improved following addition of enamel/dentin etching step for a short time. This was not exceeded for longer times than 5-second.

Key words:Dentin bond strength, enamel bond strength, pre-etching time, self-adhesive cement.

Evaluation of rebonding strengths of leucite and lithium disilicate veneers debonded with an Er:YAG laser

Resin cements create a high bond between the tooth and ceramic surfaces, thus making it impossible to remove the restoration in one piece. The aims of this study were to evaluate (i) the efficiency of an Er:YAG laser for debonding, and (ii) the changes in the rebonding strength values of all-ceramic veneers, which were removed after laser application. A tooth reduction of 120 extracted human maxillary central incisors was made to provide two different bonding surfaces (60 enamel and 60 dentin). Sixty leucite and 60 lithium disilicate discs (1-mm thickness, 5-mm diameter) were cemented to prepared surfaces with a dual-cure resin cement. Each group was divided into two subgroups (n = 15): control and laser-irradiated. Er:YAG laser (2940 nm) was applied for 9 s at 3 W power (10 Hz, 300 mJ) with 100 μs pulse duration. Shear bond strength (SBS) test was made with a universal testing machine. After the tested laser-irradiated specimens had been rebonded, the SBS test was performed again and rebonding strengths were measured. The statistical evaluations were performed by using repeated measures one-way ANOVA and post hoc Bonferroni tests (p < 0.05). Significant differences were found between the control and laser-irradiated groups (p < 0.001). While the required SBS values for control groups were between 30.04 and 24.66 MPa, the values for laser-irradiated groups were between 6.60 and 4.09 MPa. There was no significant difference between the control and rebonded groups. Er:YAG laser-irradiation is an effective method for removing all-ceramic restorations without affecting the rebonding strength.

In Vitro Cytotoxicity of Self-Adhesive Dual-Cured Resin Cement Polymerized Beneath Three Different Cusp Inclinations of Zirconia

The aim of the present study was to evaluate the in vitro cytotoxicity of self-adhesive dual-cured resin cement (SADRC) polymerized beneath three different cusp inclinations of zirconia with different light curing time. A commercial SADRC (Multilink Speed) was polymerized beneath zirconia (ZrO₂) with three different cusp inclinations (0°, 20°, and 30°) for 20 s or 40 s. After being stored in light-proof box for 24 h, the ZrO₂-SADRC specimens were immersed in DMEM for 72 h and then we got the extract solution, cultured the human gingival fibroblasts (HGF, 8 × 10³ per well) with 100% or 50% concentrations of the extract solution for 24 h, 72 h, and 120 h, respectively, and evaluated cytotoxicity of the polymerized SADRC with CCK-8 assay in optical density (OD) values, relative growth rates (RGR), and cytotoxicity grades. Statistical analysis was conducted using a two-way ANOVA followed by post hoc Student–Newman–Keuls test. The OD values varied from 0.8930 to 3.2920, the RGR varied from 33.93% to 98.68%, and the cytotoxicity grades varied from 0 to 2. There was significant difference in the OD values among the different cusp inclinations of zirconia (P < 0.001), and there was significant difference in the OD values between the different light curing times in some situations (P < 0.05). The cusp inclination of zirconia affects the in vitro cytotoxicity of SADRC. Prolonging the light curing time from 20 s to 40 s can reduce the in vitro cytotoxicity of SADRC when the cusp inclination of zirconia is smaller than 20°.

Longevity of indirect restorations cemented with self-adhesive resin luting with and without selective enamel etching. A Systematic review and meta-analysis

OBJECTIVE

To investigate the influence of the selective etching in the survival rates of indirect restorations cemented with self-adhesive resin luting.

MATERIALS AND METHODS

The eligibility criteria were formulated based on PICOS strategy. The search without restrictions was performed in PubMed/Medline, the Cochrane Library, Web of Science, Scopus, LILACS databases and gray literature until May 2018. Cochrane Collaboration's tool was performed for assessing the risk of bias. According to the bias risk analysis, the studies were classified as low risk of bias and high quality of evidence. The systematic review was conducted according to PRISMA and registered in PROSPERO (CRD42018091202). The meta-analysis was performed using RevMan 5.3 software (RevMan, Copenhagen, Denmark) and the risk ration and confidence interval was obtained (p < 0.05).

RESULTS

After database screening, removal of duplicates and eligibility criteria application, two studies were selected for this systematic review, with 65 participants (34 in one and 31 in the other). The pooled meta-analysis demonstrated no statistically significant difference in clinical longevity for selective etching in indirect restorations (P > .05; I² = 0%) and risk ratio of 0.46 [0.19-1.09].

CONCLUSIONS

Based on the findings, the results of this systematic review suggest that the selective enamel etching prior to application of self-adhesive luting cements systems for indirect restoration do not influence the clinical longevity of indirect restorations.

CLINICAL SIGNIFICANCE

The knowledge of the clinical steps of adhesive procedures is fundamental to the success of adhesive restorations and their longevity. Self-adhesive resin cements simplify the luting procedure of indirect restorations. However, adding a step that could significantly improve long-term survival would be of great value. Thus, the results of this systematic review will provide data so that the decision making regarding materials used for adhesive cementation is conducted based on scientific evidence.

Effect of Different Adhesive Systems Used for Immediate Dentin Sealing on Bond Strength of a Self-Adhesive Resin Cement to Dentin

OBJECTIVE

The purpose of this study was to investigate the immediate and three-month water storage behavior of adhesives when used for immediate dentin sealing (IDS).

METHODS AND MATERIALS

Four adhesive systems were used to perform IDS: a one-step self-etch (Xeno V), a two-step self-etch (Clearfil SE Bond), a two-step etch-and-rinse (XP Bond), and a three-step etch-and-rinse (Optibond FL). For the control group, IDS was not performed. The self-adhesive resin cement RelyX Unicem was used for the luting procedures. After seven days of water storage, specimens (n=6) were sectioned into beams (n=5) with an approximately 1-mm² cross-sectional area. Half of the specimens were tested in tension after seven days of water storage at 37°C, while the other half was stored for three months prior to testing in tension using a universal testing machine (1 mm/min). The failure pattern was determined using a stereomicroscope and scanning electron microscopy. Microtensile bond strength (μTBS) data were statistically analyzed by two-way analysis of variance and Tukey post hoc test (α=0.05).

RESULTS

After seven days, the control group presented the lowest μTBS but did not differ from XP Bond and Clearfil SE Bond. After three months, there was no μTBS difference between the IDS groups and the control.

CONCLUSIONS

After seven days of water storage, the groups with IDS presented higher μTBS values than the control group, although XP Bond and Clearfil SE Bond did not present significant differences. However, after three months of storage in water, IDS groups did not differ significantly from control group, which did not receive IDS.

Efficiency of Er:YAG laser in debonding of porcelain laminate veneers by contact and non-contact laser application modes (in vitro study)

OBJECTIVE

To determine the efficiency of debonding porcelain laminate veneers (PLV) by using several laser parameters and two different application modes of Er:YAG laser [contact (CM) and non-contact (NCM)], by verification of the consumed PLV debonding time and the changes in dental pulp temperature.

MATERIALS AND METHODS

Forty extracted non-carious human maxillary premolars were prepared for receiving PLV. Sixteen of them were divided into two groups, each of them comprised eight samples based on the application mode; group A with NCM, and group B with CM. Veneers of both groups were debonded by the same laser parameters (360 mJ, 15 Hz) during loading of a 15 N force on specially fabricated veneer cervical margins. The primary results showed that the NCM was more efficient, thus, additional groups (C, D, and E) of the same mode and number of samples were tested with different laser parameters of energy and frequency; group C (400 mJ, 10 Hz), group D (270 mJ, 15 Hz), group E (300 mJ, 10 Hz). The failure mode was determined and classified for the debonded samples of all groups.

RESULTS

All veneers were debonded and samples of the NCM group had considerably lower debonding time (12.6 seconds) than the CM samples (96.3 seconds), however, higher changes of temperature in NCM (4.2°C) than in CM were observed (2.9°C). The failure mode of samples was either type 1 or 3.

CONCLUSION

Er:YAG laser is an effective tool in debonding PLVs. The NCM application mode was more efficient in reducing debonding time than CM application mode but with a higher change in pulp temperature.

CLINICAL SIGNIFICANCE

Investigating the efficacy of Er:YAG laser as a non-invasive particle technique for debonding of failed or malpositioned of porcelain laminated veneers.

Effect of adhesive luting on the fracture resistance of zirconia compared to that of composite resin and lithium disilicate glass ceramic

OBJECTIVES

The purpose of this study was to evaluate the effect of adhesive luting on the fracture resistance of zirconia compared to that of a composite resin and a lithium disilicate glass ceramic.

MATERIALS AND METHODS

The specimens (dimension: 2 mm × 2 mm × 25 mm) of the composite resin, lithium disilicate glass ceramic, and yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) were prepared. These were then divided into nine groups: three non-luting groups, three non-adhesive luting groups, and three adhesive luting groups, for each restorative material. In the non-luting groups, specimens were placed on the bovine tooth without any luting agents. In the non-adhesive luting groups, only zinc phosphate cement was used for luting the specimen to the bovine tooth. In the adhesive luting groups, specimens were pretreated, and the adhesive luting procedure was performed using a self-adhesive resin cement. For all the groups, a flexural test was performed using universal testing machine, in which the fracture resistance was measured by recording the force at which the specimen was fractured.

RESULTS

The fracture resistance after adhesive luting increased by approximately 29% in the case of the composite resin, 26% in the case of the lithium disilicate glass ceramic, and only 2% in the case of Y-TZP as compared to non-adhesive luting.

CONCLUSIONS

The fracture resistance of Y-TZP did not increased significantly after adhesive luting as compared to that of the composite resin and the lithium disilicate glass ceramic.

In vivo and in vitro Permeability of One-step Self-etch Adhesives

Adhesive dentistry should effectively restore the peripheral seal of dentin after enamel removal. We hypothesize that non-rinsing, simplified, one-step self-etch adhesives are effective for minimizing dentin permeability after tooth preparation procedures. Crown preparations in vital human teeth were sealed with Adper Prompt, Xeno III, iBond, or One-Up Bond F. Epoxy resin replicas were produced from polyvinyl siloxane impressions for SEM examination. Dentin surfaces from extracted human teeth were bonded with these adhesives and connected to a fluid-transport model for permeability measurements and TEM examination. Dentinal fluid droplets were observed from adhesive surfaces in resin replicas of in vivo specimens. In vitro fluid conductance of dentin bonded with one-step self-etch adhesives was either similar to or greater than that of smear-layer-covered dentin. TEM revealed water trees within the adhesives that facilitate water movement across the polymerized, highly permeable adhesives. Both in vitro and in vivo results did not support the proposed hypothesis.

Effect of Storage Time on Bond Strength Performance of Multimode Adhesives to Indirect Resin Composite and Lithium Disilicate Glass Ceramic

Purpose: To investigate the bond strength performance of multimode adhesives (MMAs) to indirect resin composite and lithium disilicate glass ceramic after 24 hours or one year of water storage.

Methods and Materials: Thirty flat and polished plates of indirect resin composite (Epricord) and thirty lithium disilicate glass ceramic plates (IPS e.max Press) were prepared. Surfaces were pretreated using sandblasting (indirect resin composite) or hydrofluoric acid (glass-based ceramic). Specimens were bonded with one of two MMAs (Scotchbond Universal [SBU] or All-Bond Universal [ABU]) or ceramic primer and hydrophobic bonding (RelyX Ceramic Primer and Adper Scotchbond Multi-Purpose Bond) as a control (n=10). Resin cement cylinders (0.75 mm in diameter × 0.5 mm in height) were bonded to both substrate surfaces using the respective adhesives. After 24 hours or one year of water storage, bonding performance was measured by microshear bond strength (MSBS) testing. Results were analyzed using three-way ANOVA with Bonferroni post hoc tests (α=0.05).

Results: For indirect resin composite, significantly higher MSBS values were found for ABU after 24 hours (ABU &gt; SBU = control); however, no significant difference among the adhesives was observed after one year (p&gt;0.05). For glass-based ceramic, significantly different bond strengths were observed among the adhesives after 24 hours (control = ABU &gt; SBU) and one year (control &gt; SBU = ABU; p&lt;0.05).

Conclusions: Both MMAs tested can be considered effective alternatives for bonding to sandblasted indirect resin composite after aging, as they showed similar bond performance to that of the control group. However, separate bottles of silane bonding resin showed higher MSBS values and more durable bonding for etched glass–based ceramic.

The influence of elastic modulus of inlay materials on stress distribution and fracture of premolars

SUMMARY The purpose of this study was to evaluate the influence the width of the occlusal isthmus and inlay material had on the stress distribution, displacement, and fracture resistance of upper human premolars. For this in vitro test, 35 intact upper premolars (UPM) were selected and five were kept intact for the control group (group I). The remaining 30 were divided into two experimental groups (n=15) according to the width of isthmus: conservative (CP) and extensive preparation (EP), one third and more than two thirds of cuspal distance, respectively. Five teeth from each experimental group were left without restoration for negative controls (CPnc and EPnc), and the remaining 10 in each group were subdivided according to the inlay material (resin or ceramic): group CPr, CP + indirect resin; group CPc, CP + ceramic; group EPr, EP + indirect resin; and group EPc, EP + ceramic. The cemented inlays were loaded in a universal testing machine at a crosshead speed of 0.5 mm/min until fracture. The fractured specimens were analyzed with stereomicroscopy, and the values of the fracture resistance evaluated by analysis of variance and Tukey test. For the finite element analyses, an average UPM for each group was modeled in Rhinoceros CAD software and imported to Ansys 13.0. An average of 320,000 tetrahedral elements and 540,000 nodes for the seven models were performed using the same experimental simulation setup for each. The models were constrained on the base, and a displacement of 0.02 mm was applied to keep a linear behavior for the analysis. A von Mises stress and total displacement fields were used for the coherence test and the maximum principal stress fields were used for mechanical behavior comparisons. Group I (161.73 ± 22.94) showed a significantly higher mean value than the other experimental groups (EPc: 103.55 ± 15.84; CPc: 94.38 ± 12.35; CPr: 90.31 ± 6.10; EPr: 65.42 ± 10.15; CPnc: 65.46 ± 5.37; EPnc: 58.08 ± 9.62). The stress distribution was different in all of the groups. EPnc showed a higher concentration of tensile stress on the cervical region of the proximal box. CPc and EPc provided a lower tensile stress and a smaller cuspal displacement. Within the limits of this study, the configuration of the inlay preparation is a significant factor in the fracture resistance of premolars: the smaller the amount of remaining tooth, the lower the fracture resistance. In addition, the teeth restored with ceramic materials showed a higher fracture resistance than those restored with composite resin.

Effects of Immediate Dentin Sealing and Pulpal Pressure on Resin Cement Bond Strength and Nanoleakage

Objective: The object of this study was to evaluate the simulated pulpal pressure (SPP) and immediate dentin sealing technique (IDS) effects on the microtensile bond strength (μTBS) and nanoleakage of interfaces produced by different luting agents.

Methods and Materials: Two self-adhesive luting agents (RelyX Unicem [UC] and Clearfil SA Luting [SA]) and two conventional luting agents (Rely X ARC [RX] and Panavia F [PF]) were evaluated. Eighty human molars were divided in four groups according to luting agents. Each group was subdivided according to SPP (with or without) and dentin sealing (immediate or delayed) using Clearfil SE Bond (n=5). After IDS was performed, specimens were stored in water for seven days before luting procedures. Composite blocks were luted according to the manufacturers' instructions. One half of the specimens were subjected to 15 cm H2O of hydrostatic pressure for 24 hours before cementation procedures and continued for 24 hours afterward. Then, restored teeth were sectioned into beams and tested in tension. Two additional teeth per group were prepared for nanoleakage evaluation with scanning electron microscopy. Bond strength data were statistically analyzed by three-way analysis of variance and Tukey test.

Results: μTBS of RX decreased when it was subjected to SPP without IDS. However, in the same conditions, μTBS of UC increased. The IDS prevented negative influence of SPP on μTBS of RX and PF; however, a decrease in μTBS of SA and UC was observed. Except for RX, IDS increased μTBS for all resin cements.

Conclusion: Independent of SPP, the IDS technique obtained higher μTBS for PF, SA, and UC and did not influence RX μTBS.

Microtensile strength of resin cement bond to indirect composite treated by different output powers of Er:YAG laser

The study aimed to evaluate the effect of different output powers of Er:YAG laser on microtensile bonding strength of indirect composite to resin cements.36 indirect composite blocks (GC Gradia DA2, Japan) size 15 × 10 × 10 mm(3) were constructed, and divided into 12 groups, as follows:G1: control group (no treatment); Groups G2 to G6: treated with Er:YAG laser (2,940 nm) in noncontact mode, frequency 20 Hz, pulse duration 470 µs, with output power ranging from 2W to 6W; Groups G7 sandblasting, Groups 8 to G12: as Groups G2 to G 6 with preparatory sandblasting. One specimen from each group was analyzed by SEM; each specimen was fixed to a specialized metal jig using cyanoacrylate (Mitreapel, Beta Kimya San. Ve TIC, Iran) and debonded under tension with a universal testing machine (Zwick, Germany) at a crosshead speed of 0.5 mm min(-1). Sandblasting and laser can improve bond strength above an energy level of 150 mJ. SEM evaluation of laser-treated specimens showed irregularities and deep undercuts. T test analysis showed no significant difference between sandblasted and non-sandblasted group, with laser output power of 0, 100, or 150 mJ (P = 0.666, P = 0.875, and P =  .069); in the specimens irradiated with energy output of 200, 250, or 300 mJ, sandblasted specimens showed higher bond strength than non-sandblasted ones. The results demonstrate that, in composite resin irradiated with laser at energy output of 200-300 mJ, sandblasting might be a suitable procedure to enhance bond strength of resin cement.

Influence of Temporary Cements on the Bond Strength of Self-Adhesive Cement to the Metal Coronal Substrate

This research evaluated the influence of temporary cements (eugenol-containing [EC] or eugenol-free [EF]) on the tensile strength of Ni-Cr copings fixed with self-adhesive resin cement to the metal coronal substrate. Thirty-six temporary crowns were divided into 4 groups (n=9) according to the temporary cements: Provy, Dentsply (eugenol-containing), Temp Cem, Vigodent (eugenol-containing), RelyX Temp NE, 3M ESPE (eugenol-free) and Temp Bond NE, Kerr Corp (eugenol-free). After 24 h of temporary cementation, tensile strength tests were performed in a universal testing machine at a crosshead speed of 0.5 mm/min and 1 kN (100 kgf) load cell. Afterwards, the cast metal cores were cleaned by scraping with curettes and air jet. Thirty-six Ni-Cr copings were cemented to the cast metal cores with self-adhesive resin cement (RelyX U200, 3M ESPE). Tensile strength tests were performed again. In the temporary cementation, Temp Bond NE (12.91±2.54) and Temp Cem (12.22±2.96) presented the highest values of tensile strength and were statistically similar to each other (p>0.05). Statistically significant difference (p<0.05) was observed only between Provy (164.44±31.23) and Temp Bond NE (88.48±21.83) after cementation of Ni-Cr copings with self-adhesive resin cement. In addition, Temp Cem (120.68±48.27) and RelyX Temp NE (103.04±26.09) showed intermediate tensile strength values. In conclusion, the Provy eugenol-containing temporary cement was associated with the highest bond strength among the resin cements when Ni-Cr copings were cemented to cast metal cores. However, the eugenol cannot be considered a determining factor in increased bond strength, since the other tested cements (1 eugenol-containing and 2 eugenol-free) were similar.

Haemostatic agents on the shear bond strength of self-adhesive resin

Background

Dentin surface contaminated with haemostatic agents can interfere with the bonding of self-adhesive resin cement. Therefore the purpose of this study was to evaluate the effect of various haemostatic agents such as Aluminium chloride, Ferric sulphate and Tannic acid on the shear bond strength of self-adhesive resin luting agent.

Material and Methods

The buccal surfaces of extracted premolars were flattened to expose the dentine. The teeth were then randomly divided into four groups. In Group I Aluminium Chloride was applied on the flattened dentinal surface, in Group II Ferric Sulphate was applied to exposed dentin surface, in Group III tannic acid was applied on to the dentinal surface, and the control group, i.e. Group IV was rinsed with saline. After the surface treatment, all the teeth were air dried. Then a predetermined dimension of RelyX™ U200 self-adhesive resin cement was bonded to the pretreated dentin surfaces. The samples were then stored under 370C in distilled water for 24 hours under 100 % humidity. Following this each sample was tested for shear bond strength with an Instron testing machine at a crosshead speed of 1mm/min.

Results

There was significant difference in the shear bond strength of control and tannic acid contaminated group (p<0.05), whereas there was no significant differences between the shear bond strength between control and aluminium chloride and ferric sulphate groups (p>0.05).

Conclusions

The usage of haemostatic agent can negatively affect the bond strength of self-adhesive resin cement (Rely X) on to the dentin surface. As per the study Tannic acid significantly weakened the bond between the self-adhesive resin and dentin.

Key words:Aluminium chloride, Ferric sulphate, haemostatic agent, self-adhesive resin cement, shear bond strength, Tannic acid.

Comparative Shear-Bond Strength of Six Dental Self-Adhesive Resin Cements to Zirconia

This study compared shear bond strength (SBS) of six self-adhesive resin cements (SARC) and one resin-modified glass ionomer cement (RMGIC) to zirconia before and after thermocycling. The cylinder shape (Φ 2.35 mm × 3 mm) of six SARCs (G-CEM LinkAce (GLA), Maxcem Elite (MAX), Clearfil SA Luting (CSL), PermaCem 2.0 (PM2), Rely-X U200 (RXU), Smartcem 2 (SC2)) were bonded to the top surface of the zirconia specimens with light-curing. RMGIC (Fujicem (FJC)) was bonded to the specimens with self-curing. The shear bond strength of all cemented specimens was measured with universal testing machine. Half of the specimens were thermocycled 5000 times before shear bonding strength testing. Fractured surfaces were examined with a field-emission SEM (10,000×) and analyzed by energy dispersive x-ray analysis. MAX, PM2, SC2 group without thermocycling and GLA, MAX, PM2 group with thermocycling showed adhesive failure, but GLA, CSL, RXU, FJC group without thermocycling and SLC, RXU, SC2, FJC group with thermocycling indicated cohesive failure. Within the limitation of this study, All of SARCs except MAX demonstrated higher bond strength than that of RMGIC regardless of thermocycling. Also, SARC containing MDP monomers (CSL) retained better bonds than other cements.

Effect of a zirconia primer on the push-out bond strength of zirconia ceramic posts to root canal dentin

STATEMENT OF PROBLEM

The retention of zirconia ceramic posts to root canal dentin with resin-based luting cements is relatively poor.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of a new zirconia primer, a mixture of organophosphate and carboxylic acid monomers, on the push-out bond strength of zirconia posts to root canal dentin.

MATERIAL AND METHODS

The root canals of 40 extracted human maxillary central incisors were endodontically treated and the post spaces were prepared. Zirconia posts were luted with 2 different resin luting agents (Panavia F and Clearfil SA luting cements) with and without the zirconia primer (Z-Prime Plus; Bisco). Three segments, each 2 mm high, were cut perpendicular to the post from each root. Bond strength was determined by pushing out the post with a universal testing machine. Three-way ANOVA and the Tukey HSD test was used to assess the effects of the zirconia primer, the 2 different resin luting cements, and different thirds of the root canal (α=.05).

RESULTS

The zirconia primer significantly increased the push-out bond strength of zirconia posts to root canal dentin. Clearfil SA luting cement provided significantly higher bond strength than did Panavia F. For all experimental groups combined, bond strength decreased from the coronal to the apical section.

CONCLUSIONS

A zirconia primer based on organophosphate/carboxylic acid monomers increased the bond strength of zirconia posts to root canal dentin bonded with both resin luting cements.

Bond Durability of Different Resin Cements to Caries-Affected Dentin Under Simulated Intrapulpal Pressure

Objective:

To evaluate the durability of the bond of different resin cement systems to normal dentin (ND) and caries-affected dentin (CAD) with and without simulated intrapulpal pressure (IPP).

Methods and Materials

Molars with midcoronal caries were used. Occlusal enamel was cut to expose both dentin substrates (ND and CAD). Dentin substrates were differentiated using visual, tactile, caries-detecting dye, and dye-permeability methods. Prepared crown segments were equally divided according to the tested resin cement systems: etch-and-rinse resin cement, self-etch resin cement containing methacryloyloxydecyl dihydrogen phosphate (MDP), and self-adhesive resin cement. In addition to the dentin substrates and the resin cement types, the effect of application/storage conditions (with or without simulated IPP and with or without thermocycling) were tested. A microtensile bond strength test was done using a universal testing machine. Failure modes were determined using a scanning electron microscope.

Results

Etch-and-rinse resin cement strength values were significantly affected by the difference in the dentin substrates as well as the different application/storage conditions. Self-etch adhesive containing MDP bonded equally to ND and CAD and remained stable under all tested conditions. Self-adhesive resin cement revealed a similar bond to ND and CAD; however, its values were the lowest, especially when IPP and thermocycling were combined. Mixed failure was the predominant failure mode.

Conclusions

Etch-and-rinse resin cement was sensitive to dentin substrate and application/storage conditions. Resin cement with self-etch adhesive containing MDP revealed more reliable bonding to ND/CAD even when IPP and thermocycling were combined. The bonding of the self-adhesive resin cement could not compete with other resin cements.

Resin bond to indirect composite and new ceramic/polymer materials: a review of the literature

STATEMENT OF THE PROBLEM

Resin bonding is essential for clinical longevity of indirect restorations. Especially in light of the increasing popularity of computer-aided design/computer-aided manufacturing-fabricated indirect restorations, there is a need to assess optimal bonding protocols for new ceramic/polymer materials and indirect composites.

PURPOSE OF THE STUDY

The aim of this article was to review and assess the current scientific evidence on the resin bond to indirect composite and new ceramic/polymer materials.

MATERIALS AND METHODS

An electronic PubMed database search was conducted from 1966 to September 2013 for in vitro studies pertaining the resin bond to indirect composite and new ceramic/polymer materials.

RESULTS

The search revealed 198 titles. Full-text screening was carried out for 43 studies, yielding 18 relevant articles that complied with inclusion criteria. No relevant studies could be identified regarding new ceramic/polymer materials. Most common surface treatments are aluminum-oxide air-abrasion, silane treatment, and hydrofluoric acid-etching for indirect composite restoration. Self-adhesive cements achieve lower bond strengths in comparison with etch-and-rinse systems. Thermocycling has a greater impact on bonding behavior than water storage.

CONCLUSIONS

Air-particle abrasion and additional silane treatment should be applied to enhance the resin bond to laboratory-processed composites. However, there is an urgent need for in vitro studies that evaluate the bond strength to new ceramic/polymer materials.

CLINICAL SIGNIFICANCE

This article reviews the available dental literature on resin bond of laboratory composites and gives scientifically based guidance for their successful placement. Furthermore, this review demonstrated that future research for new ceramic/polymer materials is required.

Effect of water storage on the flexural strength of four self-etching adhesive resin cements and on the dentin-titanium shear bond strength mediated by them

AIM

The aim of this study was to evaluate the effect of water storage on the flexural strength (σf) of four self-etching adhesive resin cements (SEARC) and on the dentin-titanium shear bond strength (SBS) mediated by them.

MATERIALS AND METHODS

The selected SEARC were Rely X Unicem, G-Cem, Maxcem, and SmartCem2. For each material, 50 bars (2×2×25 mm) were made and stored in water at 37°C for 1 hour, 1 day, 7 days, 30 days, and 60 days before σf was determined via a three-point bend test. Titanium cylinders were bonded to freshly exposed human dentin surfaces using the selected cements. Fifty samples were obtained for each SEARC and were stored in water at 37°C for 1 hour, 1 day, 7 days, 30 days, and 60 days before SBS was determined. The results were statistically analyzed using two-way analysis of variance followed by Scheffé multiple means comparisons (α=0.05). Pearson's correlation coefficient between σf and SBS was determined.

RESULTS

Significantly different σf and SBS values were obtained for the four cements. With regards to the effect of water storage, the σf of all materials increased during the first 7 days, was not significantly different between materials by 30 days, and then remained relatively constant or decreased for SmartCem2; SBS was not affected by water storage, with the exception of Maxcem, where a significant drop in SBS was detected after 1 day and no deterioration thereafter. No correlation was found between σf and SBS.

CONCLUSIONS

Under the experimental conditions of this study, 60 days of water storage negatively affected the σf of SmartCem2 but did not negatively affect the SEARC-mediated dentin-titanium SBS (Maxcem showed a significant drop in SBS after 1 day but no deterioration thereafter). The dentin-titanium adherence afforded by Rely X and G-Cem was significantly higher than that of Maxcem and SmartCem2.

Effect of long-term simulated pulpal pressure on the bond strength and nanoleakage of resin-luting agents with different bonding strategies

This study evaluated the effects of simulated hydrostatic pulpal pressure (SPP) on the microtensile bond strength (μTBS) to dentin and nanoleakage patterns produced by self-adhesive luting agents after 12 months. Three self-adhesive luting agents (RelyX Unicem [UN], RelyX U100 [UC], and Clearfil SA Luting [SA]) and three conventional luting agents (Rely X ARC [RX], Panavia F [PF], and a two-step self-etching adhesive system [Clearfil SE Bond] associated with Panavia F [PS]) were evaluated. One hundred twenty-three human molars were abraded to expose occlusal surfaces. Resin cements were used to lute cylindrical composite blocks to the teeth either subjected or not to SPP. Sixty specimens were subjected to 15 cm H2O of SPP for 24 hours before and 24 hours or 12 months after cementation procedures. Afterward, restored teeth were serially sectioned into beams with a cross-sectional area of 1 mm(2) at the bonded interface and were tested in tension (cross-head speed of 1 mm/min). Failure mode was determined using scanning electron microscopy (SEM). Data were statistically analyzed by three-way analysis of variance and post hoc Tukey test (p=0.05). Two additional teeth in each group were serially sectioned into 0.9-mm-thick slabs, which were submitted to a nanoleakage protocol with AgNO3 and analyzed with scanning and transmission electron microscopes. The μTBS values of the etch-and-rinse group (RX) were negatively influenced by SPP and long-term water storage with SPP. After 12 months, UC and SA presented premature failures in all specimens when submitted to SPP. SPP increased silver deposition in most groups in both evaluation times. The hydrostatic pulpal pressure effect was material dependent. The storage time without SPP did not affect bond strength. However, long-term SPP influenced the performance of the etch-and-rinse and self-adhesive cements regarding μTBS and nanoleakage pattern, except to UN.

The effect of different adhesive system applications on push-out bond strengths of glass fiber posts

PURPOSE

Over the past years, the adhesion of fiber posts luted with simplified adhesive systems has been a matter of great interest. The aim of this study was to assess the post retentive potential of a self-adhesive resin cement using different adhesive systems to compare the push-out bond strengths of fiber posts.

MATERIALS AND METHODS

The post spaces of 56 mandibular premolar roots were prepared and divided into 4 experimental groups and further divided into 2 subgroups according to testing time (n=7). The fiber posts (Rely X Fiber Post) were luted with a self-adhesive resin cement (RelyX Unicem) and one of the following adhesive systems: no adhesive, a total-etch adhesive resin (Single Bond), a two-step self-etch adhesive resin (Clearfil SE Bond) and a one-step self-etch adhesive resin (Clearfil S3 Bond). Each root was cut horizontally, and 1.5 mm thick six root segments were prepared. Push-out tests were performed after one week or three months (0.5 mm/min). Statistical analysis were performed with three-way ANOVA (α=.05).

RESULTS

Cervical root segments showed higher bond strength values than middle segments. Adhesive application increased the bond strength. For one week group, the total-etch adhesive resin Single Bond showed higher bond strength than the self-adhesive resin cement RelyX Unicem applied without adhesive resin at middle region. For 3 months group, the two-step self-etch adhesive resin Clearfil SE Bond showed the highest bond strength for both regions. Regarding the time considered, Clearfil SE Bond 3 months group showed higher bond strength values than one week group.

CONCLUSION

Using the adhesive resins in combination with the self-adhesive resin cement improves the bond strengths. The bond strength values of two-step self-etch adhesive resin Clearfil SE Bond improved as time passes.

Microleakage of endodontically treated teeth restored with 3 different adhesive systems and 4 different fiber-reinforced posts

STATEMENT OF PROBLEM

Despite recent advances in adhesive dentistry, fiber-reinforced post/resin cement/dentin adhesive combinations are not able to prevent microleakage. While studies have examined microleakage in endodontically treated teeth restored with posts and cores, microleakage among post and adhesive systems remains a concern.

PURPOSE

This study compared the sealing properties of 4 adhesively luted post systems: glass fiber, quartz-glass fiber, zirconia-glass fiber and polyethylene fiber posts.

MATERIAL AND METHODS

Forty-eight permanent maxillary central incisors were divided into 4 groups (n=12). Post space was prepared and each post was adhesively luted with 1 of 3 systems: a 1-stage self-etch, a 2-stage total-etch, and a 3-stage total-etch adhesive. The specimens were separately immersed in freshly prepared 2% methylene blue solution for 1 week. The cleaned specimens were then embedded in autopolymerizing acrylic resin. The teeth were horizontally sectioned into apical, middle, and coronal portions. An occlusal view of each section was digitally photographed with a stereomicroscope. The methylene blue-infiltrated surface for each specimen was measured and data were collected with software. Dye penetration was estimated as the ratio of the methylene blue-infiltrated surface to the total dentin surface. Nonparametric data were analyzed with the Kruskal-Wallis test (α=.05). The Mann-Whitney U-test was used to compute multiple pairwise comparisons that identified differences among groups. Dentin-luting agent and post interfaces were evaluated with a scanning electron microscope.

RESULTS

Significant differences in adhesive and post systems were observed in all sectioned regions (P<.05). There were significant differences between the apical and coronal sections of each post type, and between the following pairs: middle versus coronal sections of zirconia-glass fiber and glass fiber posts and apical versus middle sections of quartz-glass fiber and polyethylene fiber posts (P<.05). No significant differences were found among post types. The variables of middle section and 3-stage adhesive produced significant differences in microleakage between the following post pairs: zirconia-glass fiber versus quartz-glass fiber, zirconia-glass fiber versus polyethylene fiber, and quartz-glass fiber versus polyethylene fiber (P<.05).

CONCLUSIONS

The 3-stage adhesive and zirconia-glass fiber posts demonstrated the least microleakage.

Effect of Dentin-cleaning Techniques on the Shear Bond Strength of Self-adhesive Resin Luting Cement to Dentin

Objective

This in vitro study evaluated the influence of different cleansing techniques on the bond strength of self-adhesive cement to dentin.

Methods and Materials

A total of 33 noncarious human molars were sectioned mesiodistally and embedded in chemically cured resin with the buccal or lingual surfaces facing upward. Superficial dentin was exposed and resin disk provisional restorations were cemented to the dentin surfaces with noneugenol provisional cement and were stored in distilled water at 37°C. After seven days, the provisional restorations were removed and 13 specimens were randomly assigned to each of the five groups (n=13), according to the following cleansing treatments: G1—excavator (control); G2—0.12% chlorhexidine digluconate; G3—40% polyacrylic acid; G4—mixture of flour pumice and water; and G5—sandblasting with 50 μm aluminum oxide particles at a pressure of 87 psi. Resin composite disks (Filtek Supreme Plus, 3M ESPE Dental Products, St Paul, MN, USA) 4.7 (±0.1) mm in diameter and 3.0 (±0.5) mm in height were cemented with self-adhesive cement (RelyX Unicem, 3M ESPE), photocured, and stored in distilled water at 37°C for 24 hours. Shear bond strength testing was conducted using a universal test machine at a crosshead speed of 0.5 mm/min until failure.

Results

Data were analyzed using analysis of variance (ANOVA) and the Tukey-B rank order test. Sandblasting with aluminum oxide (11.32 ± 1.70 MPa) produced significantly higher shear bond strength values compared with any other treatment groups (p&lt;0.05). No significant differences were found between G1-control (7.74 ± 1.72 MPa), G2-chlorhexidine (6.37 ± 1.47 MPa), and G4-pumice (7.33 ± 2.85 MPa) (p&lt;0.05).