Bond Strength and Interfacial Micromorphology of Etch-and-Rinse and Self-Adhesive Resin Cements to Dentin

Shape optimization of a 2-unit cantilevered posterior resin-bonded fixed dental prosthesis

STATEMENT OF PROBLEM

The cantilevered resin-bonded fixed dental prosthesis (RBFDP) is a feasible and minimally invasive treatment option to restore a single missing tooth, especially when the missing tooth space is small (<7 mm) and cost-effectiveness is essential. However, its long-term survival needs to be improved by increasing its structural strength and interfacial adhesion.

PURPOSE

The purpose of this study was to improve the interfacial bonding and to enhance the structural strength of a 2-unit inlay-retained cantilevered RBFDP with a 2-step numerical shape optimization.

MATERIAL AND METHODS

A finite element model of a mandibular first molar with a second premolar pontic was constructed. A load of 200 N simulating the average occlusal force was applied on the mesial fossa of the pontic. In the first step, an in-house user-defined material subroutine was used to generate the cavity preparation. The subroutine iteratively changed the tooth tissues next to the pontic to composite resin according to the local stresses until convergence was achieved. In the second step, the subroutine was used to optimize the placement of fibers in the pontic by placing fibers in high-stress regions. To assess the debonding resistance and load capacity of the optimized and conventional designs, further analyses were conducted to compare their stresses at the tooth-restoration interface and those within the restoration.

RESULTS

Shape optimization resulted in a shovel-shaped cavity preparation and a pontic with fibers placed near the occlusal surface of the connector region. With the optimized cavity preparation only, the maximum principal stress within the restoration and the tooth structure was reduced from 639.4 MPa to 525.4 MPa and from 381.7 MPa to 352.8 MPa, respectively. With the embedded fibers, the shovel-shaped cavity preparation reduced the maximum interfacial tensile stress by approximately 70% (conventional: 189.6 MPa versus optimized: 57.0 MPa) and the peak maximum principal stress of the veneering composite resin by 45% (conventional: 638.8 MPa versus optimized: 356.5 MPa). The peak maximum principal stress was also reduced for the remaining tooth structure by approximately 30% (conventional: 372.2 MPa versus optimized: 253.1 MPa).

CONCLUSIONS

Shape optimization determined that a shovel-shaped retainer with fibers placed near the occlusal surface of the connector area can collectively reduce the interfacial and structural stresses of the 2-unit cantilevered fiber-reinforced RBFDP. This may offer a more conservative treatment option for replacing a single missing tooth.

Shear bond strength of resin bonded zirconia and lithium disilicate - effect of surface treatment of ceramics and dentin

Objectives:The purpose of the study was to investigate the effect of ceramic surface pretreatment, effect of resin cement and dentin surface roughness on shear bond strength.

Methodology: Zirconia rods (n = 140) were randomly assigned to air born particle abrasion with aluminum oxide (Al₂O₃) or hot etching with potassium hydrogen difluoride (KHF₂). Lithium disilicate rods (LDS; n = 50) etched with hydrofluoric acid served as reference material. In Part 1 of the study, ceramic rods were cemented to bovine dentin using 5 dual-polymerizing resin cements (Variolink Esthetic, Multilink Automix (Ivoclar Vivadent), Duo-Link (BISCO Dental), Panavia F2.0 (Kuraray Dental), RelyX Unicem (3 M)). Shear bond strength was tested and fracture morphology determined. In Part 2 of the study, test groups with the highest frequency of adhesive fractures between cement and dentin were selected for further bond strength testing with different surface roughness of dentin; ground with P1200 or P80 silicon carbide paper. Dentin samples were fractured vertically to the cemented surface and the adherence between cement and dentin was studied.

Results: The results of Part 1 showed that hot etching of zirconia significantly improved bond strength to Duo-Link cement. In Part 2, RelyX Unicem showed significantly higher bond strength to P1200 compared to P80 ground dentin. For Variolink Esthetic, bond strengths to P1200 and P80 ground dentin were similar. Adhesive fracture between cement and dentin dominated.

Conclusions: A smooth dentin surface (P1200) improved bond strength to RelyX Unicem. Surface roughness was not important for Variolink Esthetic.

Physicochemical Properties of Dentine Subjected to Microabrasive Blasting and Its Influence on Bonding to Self-Adhesive Prosthetic Cement in Shear Bond Strength Test: An In Vitro Study

The aim of this in vitro study was to assess the influence of microabrasive blasting on the physicochemical properties of dentine and shear bond strength (SBS) of self-adhesive resin cement (Maxcem Elite, Kerr, Orange, CA, USA) bonded to the dentine surface. Ninety cylindrical specimens with exposed dentine of human teeth were prepared and divided into three randomized, parallel sample sets A, B, and C. Groups B and C were subjected to abrasive blasting using a micro-sandblasting device (Microetcher IIa, Danville Materials, Carlsbad, CA, USA) with two gradations of Al₂O₃ abrasives (Group B, abrasion with a gradation of 50 μm; group C, abrasion with a gradation of 27 μm). SEM imaging, profilometry, chemical composition analysis, contact angle measurements, surface free energy, and SBS tests were performed. The resulting data were statistically analyzed using the Statistica software (ver. 13.3, Tibco Software Inc., Palo Alto, CA, USA). Microabrasive blasting caused changes in surface topography, structural features, and the connection strength between the dentin surface and self-adhesive prosthetic cement. Air microabrasion through the multifactorial positive reorganization of the treated surface of dentine is recommended as a pretreatment method in fixed prosthodontics adhesive cementation protocols.

Bonding Reactions of Dental Self-Adhesive Cements with Synthetic Hydroxyapatite as a Function of the Polymerization Protocol

Objectives

This study evaluated the influence of the cement composition and different polymerization protocols on the bonding chemical interaction of self-adhesive cements with synthetic hydroxyapatite.

Materials and Methods

Two commercial self-adhesive resin cements (RelyX U200 and Maxcem Elite) were selected, manipulated, mixed with hydroxyapatite dry powder (HAp), dispensed into molds, and distributed into three groups according to polymerization protocols: immediate photoactivation (IP); delayed photoactivation, 10 min self-curing and light-curing (DP); and chemical activation (CA, no light exposure). The detailed chemical information, at atomic scale, on the surface and deeper into the bulk of self-adhesive cement/hydroxyapatite mixtures was evaluated with X-ray photoelectron spectroscopy (XPS).

Results

Chemical elements were detected in both cements, such as Na, O, Ca, C, P, and Si. Other elements were detected in minor concentrations. RelyX U200 exhibited the most intense formation of calcium salts products when the cement/HAp mixtures were photoactivated (immediate or delayed). RelyX U200/HAp mixture under delayed photoactivation (DP) also exhibited higher binding energy between calcium moieties of the HAp and methacrylates in the cement. A higher energy difference in the interaction of HAp with the cement comparing the bulk and surface areas was observed when RelyX U200 underwent the delayed photoactivation protocol. Maxcem Elite exhibited an increased chemical reactivity when either chemically activated or immediately photoactivated and a higher binding energy of the carboxyl groups bonded to the calcium of HAp when chemically activated.

Conclusions

The interaction of cements with hydroxyapatite is chemical in nature and leads to the formation of calcium salts, which may favor better integrity and longevity of adhesive restorations. The polymerization protocol affects the chemical interaction in mixtures of self-adhesive cements and hydroxyapatite, influencing the formation of these salts and the establishment of intermolecular interactions between the HAp and the cements.

Is Conventional Resin Cement Adhesive Performance to Dentin Better Than Self-adhesive? A Systematic Review and Meta-Analysis of Laboratory Studies

CLINICAL RELEVANCE

Conventional multistep resin cements presented higher adhesive performance to dentin than simplified self-adhesive cements, which is an important criterion for indirect restoration prognosis.

SUMMARY

This study aimed to conduct a systematic review of the literature on laboratory studies assessing bonding performance to dentin of conventional and self-adhesive resin cements, in cementing indirect restorations. This review was reported according to the PRISMA Statement. Of a total of 518 studies, 36 were screened full text and reviewed according to exclusion criteria. Nineteen papers were included in the systematic review and meta-analyses, according to the following inclusion criteria: studies that evaluated the bond strength to dentin of indirect restorations cemented with dual conventional or self-adhesive resin cements and those that presented bond strength data in MPa as an outcome. Statistical analyses were conducted using Rev-Man 5.1. Comparisons were performed with random effects models at 5% significance level. A global analysis comparing conventional and self-adhesive cements and three subgroup analyses comparing immediate and long-term results were performed. Global analysis showed a difference between groups, with conventional resin cements presenting higher bond strength results than self-adhesive resin cements, in immediate and long-term time periods (both p=0.03). Immediate and longterm bond strength results were different for self-adhesive cements, favoring immediate bond strength (p=0.03), but immediate and long-term bond strength results for conventional resin cements were not different (p=0.06). Medium or high risk of bias was found in all studies. Conventional multistep resin cements showed superior overall adhesive performance compared with simplified self-adhesive resin cements when used to cement indirect restorations to dentin.

Scanning electron microscopy comparison of the resin-dentin interface using different specimen preparation methods

Microscopy has been widely used to complement the data of studies related to dentin bonding; however, different specimen preparation methods may influence the analysis. Aiming to contribute to the reported scenario, this study evaluated the effect of two specimen-sectioning methods (cleavage and diamond disk cut) on the quality of the scanning electron microscopy (SEM) images. Four crowns of human molars were selected and had an area of approximately 6 mm² of dentin exposed. They were then divided into two groups according to the universal adhesive application: total and self-etching modes. Then, composite blocks were built up and the specimens were stored in deionized water to allow the postcuring. The specimens were further divided according to the sectioning method: cleavage or diamond disk cut. Four specimens were obtained from each tooth. They were desiccated, placed on aluminum stubs, sputter-coated with gold, and observed in a scanning electron microscope, with ×2000 of magnification. The quality of the SEM images were evaluated by two calibrated examiners and classified into four scores (1-4). Mann-Whitney test (p < .05) showed that the diamond disk provided significantly higher scores than cleavage, whereas no significant difference was observed when comparing the total-etching and self-etching modes of application. The diamond disk cut method is preferable to the cleavage method to ensure the quality of the SEM analysis in studies involving the resin-dentin interface.

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.

Effects of Polymerization Mode and Interaction with Hydroxyapatite on the Rate of pH Neutralization, Mechanical Properties, and Depth of Cure in Self-Adhesive Cements

Objective The aim of the study was to evaluate the physicochemical properties of self-adhesive resin cements associated with hydroxyapatite (HAp) according to the polymerization activation.

Materials and Methods Specimens of cements (PermaCem 2.0 [DMG]; MaxCem Elite [Kerr], and RelyX U200 [3M ESPE]) were distributed into three groups: activation mode; self-cured and dual-cured modes; and association or not with HAp powder mode. The pH neutralization was evaluated as a function of time. Flexural strength and elastic modulus were also tested (0.5 mm/min.). The depth of cure was also analyzed using the scraping test (ISO 4049). Infrared spectroscopy was also used to collect the spectra of specimens to evaluate the chemical bonds. Statistical comparisons were conducted at 5% of significance.

Results The aggressiveness of the self-adhesive resin cements evaluated varied among the materials with a tendency for neutralization. Self-cure groups exhibited lower pH throughout the entire evaluation when compared with that of the dual-cure ones, irrespective of the addition of HAp. MaxCem Elite when photoactivated was the only cement influenced by the addition of the HAp in terms of mechanical properties. The self-adhesive cements tested presented equivalent depth of cure based on the ISO 4049 requirements, regardless of the evaluated factors.

Conclusions Based on the parameters evaluated, the results demonstrated that most of the self-adhesive cements remained unaltered or improved when mixed with HAp, regardless of the activation mode.

Effect of a filled adhesive as the desensitizer on bond strength of "Self-Adhesive Cements To" differently severity of fluorosed dentin

The objectives were to evaluate the efficacy of a filled adhesive named Prime & Bond NT (P&B NT) as the dentin desensitizer in occluding fluorosis dentinal tubules and compare the shear bond strength (SBS) of RelyX U200 self-adhesive resin cement (RXU) and RelyX Luting self-adhesive resin-modified glass ionomer cement (RMGIC) before and after P&B NT pretreatment. 176 non-carious fluorosis were classified into four subgroups by the Thylstrup and Fejerskov index (TFI): normal group (TFI = 0), mild group (TFI = 1-3), moderate group (TFI = 4-5), severe group (TFI = 6-9). 160 composite cylinders (4 × 5 mm) were fabricated, then every severity of fluorosed dentin was subjected to four treatments: P&B NT + RXU (n = 40), RXU (n = 40), P&B NT + RMGIC (n = 40), RMGIC (n = 40). The specimens were immersed in water at 37°C for 24 hr first and half of them underwent 5,000 thermocycling before shear bond strength test. A factorial design (factorial 4 × 2 × 2 × 2) was developed to make statistical analysis. Scanning electron microscope (SEM) analysis (n = 16) in cross section and longitudinal section view characterized the occlusion situation of dentinal tubules. P&B NT might occlude dentinal tubules as the dentin desensitizer for normal teeth and mild-moderate fluorosis. P&B NT significantly increased the SBS of RXU (p < .05) but had no statistical significance on the SBS of RMGIC (p > .05). RXU could benefit from P&B NT desensitization to achieve a better quality of adhesion.

Evaluation of long-term bond strength and selected properties of self-adhesive resin cements

This study evaluated the shear bond strength (SBS) of self-adhesive resin cements (SARCs) to dentin and their physical-chemical properties. Five commercial SARCs were evaluated [SmartCem®2 - DENTSPLY (SC2); BisCem® - Bisco (BC); SeT PP® - SDI (SeT); Relyx U100® - 3M ESPE (U100) and YCEM® SA - Yller (YCEM)]. The SARCs were evaluated for SBS to dentin (n = 10) after 24 h, 6 months, and 12 months. The dentin demineralization caused by acidic monomers was observed by SEM, and pH-neutralization of eluate was observed for 24 h. Degree of conversion (DC), rate of polymerization (Rp), flexural strength (FS), and elastic modulus (E) were evaluated. Immediate SBS of SC2, SET, U100, and YCEM were statistically higher than that of BC (p < 0.001). After 12 months, all SARCs showed reduced SBS values and U100 showed values similar to those of SET and YCEM, and higher than those of BC and SC2 (p = 0.001). Demineralization pattern of SARCs was similar. At 24h, all SARCs showed no differences in the pH-value, except BC and U100 (p < 0.001). YCEM showed the highest Rp. U100, YCEM, and SC2 showed statistically higher FS (p<0.001) and E (p < 0.001) when compared with SET and BC. U100 and YCEM showed the best long-term bonding irrespective of the storage period. A significant reduction in SBS was found for all groups after 12 months. SBS was not shown to be correlated with physical-chemical properties, and appeared to be material-dependent. The polymerization profile suggested that an increased time of light activation, longer than that recommended by manufacturers, would be necessary to optimize DC of SARCs.

Comparison of the shear bond strength of self-adhesive resin cements to enamel and dentin with different protocol of application

AIM

The aim of the present study was to determine the shear bond strength of self-adhesive resin cements to enamel and dentin with and without surface treatments, and compare them with conventional resin cement as the control group.

METHODS

In this experimental study, buccal and lingual surface of the thirty sound human premolars were polished in order to obtain a flat surface of enamel (E) in buccal, and dentin (D) in lingual. Sixty feldspathic ceramic blocks (2×3×3 mm) were prepared and randomly divided into six groups (n=10). Each block was cemented to the prepared surface (30 enamel and 30 dentin surface) according to different protocol: E1 and D1; RelyX ARC as control group, E2, D2; RelyX Unicem, E3, D3; acid etching +RelyX Unicem. The specimens were termocycled and subjected to shear forces by a universal testing machine at a cross head speed of 0.5 mm/min. The mode of fracture were evaluated by stereomicroscope. Data were analyzed with descriptive statistical methods using SPSS version 15. One-way ANOVA, and post hoc Tukey tests were used to compare bond strengths between the groups with different adhesives at α=0.05.

RESULTS

Statistical analysis showed no significant differences within the enamel subgroups, but there were significant differences within the dentinal subgroups, and statistically significant differences were found between the groups D1and D3 (p=0.02). Comparison between similar enamel and dentinal subgroups showed that there was a significant difference just between the subgroups E3 and D3 (p=0.01).

CONCLUSION

Elective etching of enamel did not lead to significant increase in the shear bond strength of RelyX Unicem in comparison to RelyX ARC. On the other hand, elective etching of dentin reduces the bond strength of RelyX Unicem with the dentin.

The effect of repeated bonding on the shear bond strength of different resin cements to enamel and dentin

PURPOSE

Cementation failures of restorations are frequently observed in clinical practice. The purpose of this study is to compare the effect of initial and repeated bonding on the bond strengths of different resin cements to enamel and dentin.

MATERIALS AND METHODS

Ninety human maxillary central incisors were bisected longitudinally. The 180 tooth halves were divided into 2 groups (n = 90) for enamel and dentin bonding. The enamel and dentin groups were further divided into 3 groups (n = 30) for different resin cement types. Composite resin (Filtek Ultimate) cylinders (3 × 3 mm) were prepared and luted to enamel and dentin using Variolink II (Group V), RelyX ARC (Group R), or Panavia F 2.0 (Group P) resin cement. After 24 hours, initial shear bond strengths of the resin cements to enamel and dentin were measured. Using new cylinders, the specimens were de-bonded and re-bonded twice to measure the first and the second bond strengths to enamel and dentin. Failure modes and bonding interfaces were examined. Data were statistically analyzed.

RESULTS

Initial and repeated bond strengths to enamel were similar for all the groups. The first (15.3 ± 2.2 MPa) and second (10.4 ± 2.2 MPa) bond strengths to dentin were significantly higher in Group V (P<.0001). Second bond strengths of dentin groups were significantly lower than initial and first bond strengths to dentin (P<.0001).

CONCLUSION

All resin cements have similar initial and repeated bond strengths to enamel. Variolink II has the highest first and second bond strength to dentin. Bond strength to dentin decreases after the first re-bonding for all resin cements.

Effects of the application techniques of self-adhesive resin cements on the interfacial integrity and bond strength of fiber posts to dentin

Objective:

To evaluate the influence of an application technique of a glass-fiber post using self-adhesive resin cements on the push-out bond strength and the presence of bubbles in the root thirds. The cements were either applied according to the manufacturer's instruction or using a commercial delivering system (Centrix), at which the cement pastes were collected and applied after manipulation.

Material and Methods:

Self-adhesive resin cements (RelyX U200/3M ESPE-U200; Maxcem Elite/Kerr-MAX; Clearfil SA Cement/Kuraray-CSA) and a conventional cement (RelyX ARC/3M ESPE-ARC) were used to cement a post and applied either based on the manufacturer's instructions or using a Centrix syringe to deliver the cements directly onto the post of choice, or directly into canal. The roots were scanned with a micro-computed tomography (μCT) and then sectioned into nine 1-mm thick slices for a push-out bond strength test. The μCT images showed the percentage of bubbles in the root thirds (cervical, medium, and apical). Data were analyzed with three-way ANOVA/Tukey (α=0.05).

Results:

Triple interaction was not significant (p>0.05). The interaction “material” vs “root third” was not significant. A significant interaction was observed between “material” vs “application technique” (p<0.05). For ARC, U200, and MAX, significantly lower percentages of bubbles were observed when the Centrix syringe delivered the cements. Equivalent percentages of voids were observed for CSA, irrespective of the application technique (p>0.05). Significantly higher bond strength was observed when the self-adhesive resin cements were applied using the Centrix delivery system, in comparison with the manufacturer's instructions (p<0.05). Bond strength varied with the root third: cervical>medium>apical (p<0.05). No correlations were found between the bond strength and voids.

Conclusions:

Bond strength and voids are negatively influenced by the conventional application technique for luting fiber posts. The delivery system (Centrix) seems to produce better results when cementing fiber posts.

The Retentive Strength of Cemented Zirconium Oxide Crowns after Dentin Pretreatment with Desensitizing Paste Containing 8% Arginine and Calcium Carbonate

The effect of dentin pretreatment with Desensitizing Paste containing 8% arginine and calcium carbonate on the retention of zirconium oxide (Y-TZP) crowns was tested. Forty molar teeth were mounted and prepared using a standardized protocol. Y-TZP crowns were produced using computer-aided design and computer-aided manufacturing (CAD-CAM) technology. The 40 prepared teeth were either pretreated with Desensitizing Paste or not pretreated. After two weeks, each group was subdivided into two groups, cemented with either Resin Modified Glass Ionomer Cement (RMGIC) or Self Adhesive Resin Cement (SARC)). Prior to cementation, the surface areas of the prepared teeth were measured. After aging, the cemented crown-tooth assemblies were tested for retentive strength using a universal testing machine. The debonded surfaces of the teeth and crowns were examined microscopically at 10× magnification. Pretreating the dentin surfaces with Desensitizing Paste prior to cementation did not affect the retention of the Y-TZP crowns. The retentive values for RMGIC (3.04 ± 0.77 MPa) were significantly higher than those for SARC (2.28 ± 0.58 MPa). The predominant failure modes for the RMGIC and SARC were adhesive cement-dentin and adhesive cement-crown, respectively. An 8.0% arginine and calcium carbonate in-office desensitizing paste can be safely used to reduce post-cementation sensitivity without reducing the retentive strength of Y-TZP crowns.

Tensile Bond Strength of Self Adhesive Resin Cement After Various Surface Treatment of Enamel

INTRODUCTION

In self adhesive resin cements adhesion is achieved to dental surface without surface pre-treatment, and requires only single step application. This makes the luting procedure less technique-sensitive and decreases postoperative sensitivity.

AIM

The purpose of this study was to evaluate bond strength of self adhesive resin after surface treatment of enamel for bonding base metal alloy.

MATERIALS AND METHODS

On the labial surface of 64 central incisor rectangular base metal block of dimension 6 mm length, 5mm width and 1 mm height was cemented with RelyX U200 and Maxcem Elite self adhesive cements with and without surface treatment of enamel. Surface treatment of enamel was application of etchant, one step bonding agent and both. Tensile bond strength of specimen was measured with universal testing machine at a cross head speed of 1mm/min.

RESULTS

Least tensile bond strength (MPa) was in control group i.e. 1.33 (0.32) & 1.59 (0.299), Highest bond strength observed when enamel treated with both etchant and bonding agent i.e. 2.72 (0.43) & 2.97 (0.19) for Relyx U200 and Elite cement. When alone etchant and bonding agent were applied alone bond strength is 2.19 (0.18) & 2.24 (0.47) for Relyx U200, and 2.38 (0.27) 2.49 (0.16) for Max-cem elite. Mean bond strength was higher in case of Max-cem Elite as compared to RelyX U200 resin cement, although differences were non-significant (p > 0.05).

CONCLUSION

Surface treatment of enamel increases the bond strength of self adhesive resin cement.

Important compositional characteristics in the clinical use of adhesive systems

Improvements in dentin bonding systems have influenced modern restorative dentistry. The desire for minimal invasiveness has resulted in more-conservative cavity design, which basically relies on the effectiveness of current dentin bonding systems. Interaction of adhesives with enamel and dentin is based on two systems, commonly described as etch-and-rinse and self-etch. Priming and bonding agents can be separate or combined, resulting in two- or three-step systems for etch-and-rinse adhesives and one- or two-step systems for self-etch adhesives. Self-etch systems use acidic functional monomers that simultaneously demineralize and impregnate tooth structures. Etch-and-rinse and self-etch systems have advantages and disadvantages, which are primarily related to the simplified bonding procedures required under clinical conditions. Knowledge of the composition, characteristics, and mechanisms of adhesion for each adhesive system is critical in selecting the ideal adhesive materials for clinical use.

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.

Qualitative evaluation of scanning electron microscopy methods in a study of the resin cement/dentine adhesive interface

Sample preparation and imaging techniques for scanning electron microscopy (SEM) of dehydrated dental samples can hinder the structural analyses. This study qualitatively evaluated images obtained with two different protocols of SEM preparation and analysis to assess the dentine adhesive interface. The crown and root dentine of 12 bovine incisors were subjected to cementation with the resin cement RelyX U100 or RelyX ARC/SBMP (n = 6). After storage for 7 days in a moist environment at 37 ± 1°C, the dentine samples were dehydrated in an ascending alcohol series, and three specimens from each group were coated with gold or carbon and examined in a high-vacuum (JEOL JSM-6360LV, 10 kV) or low-vacuum (FEI Quanta 200F, 15-30 kV) microscope. Images were obtained at magnifications between 50 and 2,000×, but with different working distances. The use of high vacuum for carbon and gold coating and SEM visualization led to cracks in the samples. A small number of cracks can be described in the specimens subjected to the low-vacuum technique. The protocol for SEM imaging in low vacuum was considered more appropriate for preservation of the integrity of the evaluated structures.

Effect of Replacing a Component of a Self-Etch Adhesive by Chlorhexidine on Bonding to Dentin

The purpose of this study was to evaluate the effect of replacing a component of the self-etch adhesive Adper Scotchbond SE (liquid A + liquid B) by 2% chlorhexidine (CHX) on bond strength to dentin after 1 day, 3 months or 6 months of water storage. Eight human teeth were sectioned to expose a flat dentin surface and were then randomly assigned to 2 groups. In the control group, the dentin surfaces were treated with the adhesive according to the manufacturer's instructions. In the experimental group, liquid A was replaced by 2% CHX. Next, a 6-mm-high resin composite block was incrementally built on the bonded surfaces. The restored teeth were then sectioned to produce stick-shaped specimens (cross-sectional area - 0.8 mm2). The microtensile bond strength (µTBS) was recorded, and the failure modes were assessed. Data were analyzed by two-way repeated measures ANOVA (α=0.05). Four additional teeth were processed in order to conduct a micromorphological analysis of the resin-dentin interface. The µTBS values did not significantly decrease after water storage in either the control or the experimental group, whose values did not differ significantly irrespective of storage time. The morphological aspect of the bonding interface appears not to have been affected by CHX. A higher incidence of cohesive failures within the adhesive and mixed failures (cohesive within adhesive and resin composite) was observed for both groups. It may be concluded that dentin pre-treatment with 2% CHX did not influence significantly the bonding performance of the evaluated adhesive.

Micro-shear bond strength of adhesive resins to enamel at different relative humidity conditions

This study tested whether exhaled humid conditions would affect the adhesion of etch-and-rinse, two-step and one-step self-etch adhesive resins to enamel. Enamel surfaces of human maxillary anterior teeth (N=240, n=20) were exposed to four humid conditions (H1: 63-68%, H2: 73-78%, H3: 93-98%, H4: 36-45% RH) during bonding with Adper Single Bond 2 (SB2), Clearfil SE Bond (CSE) and Adper Easy Bond (AEB). Specimens were stored in distilled water at 37 ºC for 24 h and tested to failure using micro-shear bond strength (μSBS) test. Data were analyzed using two-way ANOVA and Tukey's test (p<0.05). The μSBS to enamel with SB2, CSE and AEB was not significantly affected by humidity parameters. AEB resulted in significantly lower μSBS in all conditions. The frequency of adhesive failures was the highest at H2, H3 for SB2, H3 for CSE and H1-4 for AEB indicating that humidity conditions may decrease adhesion quality to enamel.