Evaluation of thermal cycling and mechanical loading on bond strength of a self-etching primer system to dentin

Real-time imaging and quantitative analysis of internal gap formation in bulk-fill and conventional resin composites: An OCT evaluation

BACKGROUND

This study used optical coherence tomography (OCT) to observe real-time internal gap formation in both bulk-fill and conventional resin composites. It aimed to provide a quantitative analysis of variations, addressing the inconclusive nature of microleakage assessment caused by differences in testing methods.

METHODS

Fifty extracted third molars prepared with Class I cavities, were divided into five groups (n = 10). Conventional resin Filtek Z350 XT (FZX) was applied with a double-layer filling of 2 mm per layer. Bulk-fill resins X-tra fil (XTF), Filtek Bulk Fill Posterior Restorative (FBP), Surefil SDR Flow + (SDR), and Filtek Flowable Restorative (FFR) were applied with a single-layer filling of 4 mm. Real-time OCT imaging was conducted during light curing. Post-curing, the entire sample was OCT-scanned. Following this, ImageJ software was used to measure the gap (G1 %). Subsequently, thermal cycling (TC) (5000 times, 5 °C-55 °C) was applied, followed by OCT scanning to calculate the gap (G2 %) and ΔG%. Data were analyzed using two-way repeated measures ANOVA, Kruskal-Wallis test, and Duncan's test (α=0.05).

RESULTS

There was no significant difference in G1 % among the groups (p > 0.05). Following TC, FZX exhibited the highest G2 %, succeeded by FFR, FBP, XTF, and SDR, with SDR demonstrating the lowest G2 % (p < 0.05). FZX showed the highest ΔG% (p < 0.05), while SDR exhibited the lowest ΔG% (p < 0.05).

CONCLUSION

OCT proves to be a promising tool for detecting microleakage. TC exerted a more significant negative impact on conventional resin. Surefil SDR Flow + displayed the least microleakage, both before and after TC.

Clinical evaluation of Giomer and self-etch adhesive compared with nanofilled resin composite and etch-and-rinse adhesive - Results at 8 years

OBJECTIVE

This study aimed to evaluate the long-term clinical performance of Giomer and a self-etch adhesive system compared with a nanofilled resin composite and etch-and-rinse adhesive system in Class I and Class II restorations.

METHOD

The study was designed to be double-blinded with intra-individual control. 48 patients with 54 pairs of cavities (class I or class II) were recruited. Each pair of restorations was placed with either BEAUTIFIL II (BF) and FL-BOND II (FL) or Filtek Z350 (Z350) and Scotchbond Multi-Purpose (SMP). Clinical evaluation was performed at baseline, 6-month, 18-month, 4-year and 8-year after placement according to modified USPHS criteria. Kaplan-Meier survival analysis and log rank tests were performed (SPSS 20.0, IBM Corporation, US) to compare the survival probability of different restorations.A generalized linear mixed model (GLMM) was adopted to assess the performance of the materials. The McNemar test was used to show significant changes for all the evaluation criteria and difference between them.

RESULTS

At the eight-year recall, 32 patients with 67 restorations were present. There were twelve restorations in total recorded as failure due to loss of retention, restoration fracture, secondary caries, tooth fracture or endodontic treatment due to pulp necrosis. The survival probabilities and calculated annual failure rate(AFR) of BF and Z350 restorations at 8-year were 87.2 % vs 87.8 % and 1.6 % vs 1.5 % respectively with no significant difference (p > 0.05)between the two materials. Over the recall time range of eight years, decreased possibility of alpha rating was observed for retention, marginal adaptation, marginal staining and surface roughness for both materials (p < 0.05). Decreased possibility of alpha rating was observed for surface staining and secondary caries for Z350 (p < 0.05) and restoration fracture for BF (p < 0.05), respectively. Comparing the two restorative systems over eight years, no significant difference was seen for linear decline of the possibility of alpha rating for any of the criteria evaluated (p > 0.05).

CONCLUSION

Giomer material and the self-etch adhesive system had comparable clinical performance with nanofilled resin composite and etch-and-rinse adhesive system over the observation period of eight years.

Assessment of Intra-Oral Repair Systems for Veneered Zirconia and Zirconia Only

The aim of this study was to compare bond strength resin composites to porcelain laminate veneers in the indirect repair method to composite resins used in the direct repair method for cases of porcelain veneer fracture of zirconia-based fixed dental prostheses. In the study, the groups were formed with different percentages of areas to be repaired to mimic porcelain fractures in the mouth. The experimental group of veneered zirconia were as follows: Group A = 100% Zr surface; Group B = 70% Zr, 30% porcelain surface; Group C = 50% Zr, 50% porcelain surface; Group D = 30% Zr, 70% porcelain surface; Group E = 100% porcelain surface. The repairs of the specimens were made using composite resin systems in half of the groups and using porcelain laminate veneers in the other half. Specimens were embedded in acrylic blocks before surface treatments and repairs were applied. After surface conditioning, laminate veneers were applied to the first half of the groups, and composite repair systems were applied to the second half of the groups. After all specimens were aged by thermal cycling, their bond strength values were measured using a Universal Testing Machine, and the obtained data were recorded. The specimens were examined with a stereomicroscope and classified according to failure types (adhesive/cohesive/mixed). Bond strength values were evaluated based on independent-samples t-test statistics. According to the comparisons among the groups, the bond strength of the indirect repairs made with the laminate material was higher than the bond strength of the repairs made with the composite. There was a statistically significant difference in favor of the indirect repair groups among all groups except for Group C. The highest bond strength was found in Group A in the indirect repair method, while the lowest bond was found in the direct repair method in Group E. Adhesive failure was mostly seen in the groups that were repaired with the composite.

Evaluation of the Combination of CO2 Laser and Bifunctional Bonding Agents for Composite Resin Repairs After 1 Year of Aging

Objective: to evaluate the bond strength of repairs to composite resin restorations treated with CO₂ laser and bifunctional monomers after 1 year of aging. Background: Adequate bond strength between a composite restoration and resin repair agent can be achieved through mechanical and/or chemical treatment. However, the longevity of such repairs is unknown. Methods: Resin blocks (volume: 125 mm³) were created. Failure surfaces were either not treated or were treated before the repair with a universal adhesive, a silane bonding agent and/or CO₂ laser. The blocks were distributed into six groups (n = 6 per group): resin+resin group (RRG), universal adhesive+resin group (ARG), silane+universal adhesive group (SAG), laser+silane+universal adhesive group (LSAG), laser+universal adhesive group (LAG), and laser+silane group (LSG). After treatment, repairs were made with another resin composite. "Sticks" (1.0 mm² in area and 1.0 cm in length) were cut from the specimens in each group and immersed in distilled water at 37°C. Microtensile bond strength was evaluated after 1 year of aging. Bond strength values were compared using the Kruskal-Wallis test and Dunn's test. Results: Bond strength was significantly higher in the LSAG compared with the RRG, adhesive system, LSG, whereas statistically similar results were found for the SAG, LSAG, and LAG. Bond strength was lowest in the RRG. The LSAG and LAG presented predominantly cohesive fractures. Conclusions: The bond strength of composite resin repairs was satisfactory over time. Treatment with CO₂ laser contributed to the maintenance of bond strength during the 1-year storage period and bifunctional monomers present in the universal adhesive on the irradiated repair surface were of fundamental importance to the maintenance of bond strength values, as demonstrated by microtensile bond test and fracture pattern analysis.

The efficacy of different sealer removal protocols on the microtensile bond strength of adhesives to a bioceramic sealer-contaminated dentin

Background

The optimal bonding of adhesives to dentin requires the sealer to be completely removed from the dentinal walls.

Aim

This study compared the efficacy of different sealer removal protocols on the microtensile bond strengths (MTBS) of single-step adhesives to a calcium silicate-based bioceramic root canal sealer-contaminated dentin.

Materials and Methods

Standardized box-shaped Class I cavities were prepared in human lower third molars (N = 50). All cavities were contaminated with a bioceramic root canal sealer (Endosequence BC Sealer, Brasseler, Savannah, USA), except the control group (G1) cavities. For the experimental groups, contaminated dentin surfaces were wiped with a dry cotton pellet (G2), wiped with a cotton pellet saturated with water (G3), rinsed with the air/water spray (G4), and passively applied aqueous ultrasonic energy with an ultrasonic scaler (G5) before the restoration procedure. All the cavity surface was restored with a one-bottle universal adhesive and composite resin. All the specimens were subjected to both thermocycling (2,500 thermal cycles from 5 to 55°C, with a 30-s dwelling time and a 10-s transfer time) and mechanical loading (50 N load for 100,000 cycles). The restored specimens were sectioned into resin-dentin beams for MTBS evaluation. Additional specimens were prepared for the scanning electron microscopy (SEM) to examine the dentin-adhesive interface (n = 10).

Results

No significant difference was found between the mean bond strengths of the groups. In SEM examination, no residual sealer was found in any group.

Conclusion

Calcium silicate-based bioceramic sealer was removed from the dentin surface with all removal protocols when evaluated with MTBS after the thermal and mechanical cycle tests.

Tensile Bond Strength and Marginal Integrity of a Self-adhering and a Self-etch Adhesive Flowable Composite after Artificial Thermomechanical Aging

Aim

This study aims to compare the self-etch adhesive (SEA) and self-adhesive flowable composite (SAF) concerning tensile bond strength (TBS) and marginal integrity by microleakage (µ LK) test in deciduous molars after artificial thermomechanical aging.

Materials and methods

120 extracted primary molars were collected. Sixty teeth were mounted for testing TBS. Teeth were restored using SAF (n = 30) and SEA-conventional flowable (CF) composite (n = 30) and subjected to artificial thermal aging. Half the teeth (n = 15) from each material were subjected to mechanical loading (SEA-TBS-L and SAF-TBS-L). The specimens with no-load (NL) served as control (SEA-TBS-NL and SAF-TBS-NL). Class V cavity prepared and restored with SAF (n = 30) and SEA-CF (n = 30) to test µ LK after thermal aging. The subgroups were as same as the TBS based on with or without mechanical loading (SEA-µ LK-L, SEA-µ LK-NL, SAF-µ LK-L, SAF-µ LK-L; n = 15 each). µ LK was determined by employing the dye immersion technique.

Results

Concerning TBS, there is a significant difference between SEA and SAF with load or no load. Concerning µ LK, there is a significant difference between the materials under loading and no difference was found when not mechanically loaded. Also, concerning both TBS and µ LK, a significant difference was observed between the load and no-load subgroups within each material.

Conclusion

SAF exhibited higher TBS than the SEA. Mechanical loading not only adversely affected the TBS but also increased the µLK of the compared materials.

Clinical Significance

Restoring the primary teeth with SAF not only shortens the laborious operatory time but also yields good clinical serviceability with the good bond strength and minimal µ LK, thus preventing premature loss of teeth and consequential malocclusion.

How to cite this article

Kamatchi M, Ajay R, Gawthaman M, et al. Tensile Bond Strength and Marginal Integrity of a Self-adhering and a Self-etch Adhesive Flowable Composite after Artificial Thermomechanical Aging. Int J Clin Pediatr Dent 2022;15(2):204-209.

Impact of Resin Composite Viscosity and Fill-technique on Internal Gap in Class I Restorations: An OCT Evaluation

The aim of this in vitro study was to quantitatively evaluate the internal gap of resin composites of high-and low-viscosity used in single- and incremental-fill techniques in Class I cavities exposed to thermal cycling (TC) using optical coherence tomography (OCT). Cavities of 4-mm depth and 3-mm diameter were prepared in 36 third molars randomly distributed into four groups, according to viscosity of restorative resin-based composite (high or low viscosity, all from 3M Oral Care) and technique application (bulk or incremental fill) used (n=9): RC, high-viscosity, incremental-fill, resin-based composite (Filtek Z350 XT Universal Restorative); BF, high-viscosity, bulk-fill, resin-based composite (Filtek One Bulk Fill); LRC, low-viscosity, incremental-fill, resin-based composite (Filtek Z350 XT Flowable Universal Restorative); and LBF, low-viscosity, bulk-fill, resin-based composite (Filtek Flowable Restorative). Single Bond Universal Adhesive system (3M Oral Care) was used in all the experimental groups. The incremental-fill technique was used for RC and LRC groups (2-mm increments), and a single-layer technique was used for BF and LBF groups, as recommended by the manufacturer. The internal adaptation of the resin at all dentin walls was evaluated before and after TC (5000 cycles between 5°C and 55°C) using OCT images. Five images of each restored tooth were obtained. Images were analyzed using ImageJ software that measured the entire length of the gaps at the dentin-restoration interface. The length of gaps (μm) was analyzed using two-way repeated measures ANOVA and the Tukey tests (α=0.05). There was a significant interaction between material types and TC (p=0.006), and a significant difference among all material types (p<0.0001), before and after TC (p<0.0001). Increased internal gaps at the dentin-restoration interface were noticed after TC for all groups. RC presented the lowest value of internal gap before and after TC, while LBF showed the highest values of internal gap after TC. In conclusion, TC negatively affected the integrity of internal gap, whereas high-viscosity, incremental-fill, resin-based composite presented better performance in terms of internal adaptation than low-viscosity, bulk-fill materials in Class I cavities.

Effect of mastication simulation on the phase transformation of posterior 3-unit monolithic zirconia fixed dental prostheses

STATEMENT OF PROBLEM

Monolithic zirconia restorations are directly exposed to cyclic loads and temperature changes in the oral cavity after cementation. These stresses may reduce the long-term success of the material by causing uncontrolled phase transformations within the zirconia.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of mastication simulation and different measurement points on the phase transformation of posterior 3-unit monolithic zirconia partial fixed dental prostheses (FDPs) in the posterior region.

MATERIAL AND METHODS

Posterior 3-unit FDPs of monolithic yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP), including BruxZir Shaded (group B), FireZr (group F), and Upcera (group U) (n=10), were machined from presintered blocks. All specimens were exposed to mastication simulation (240 000 cycles/1.7 Hz/50 N). The monoclinic phase content was evaluated by X-ray diffraction (XRD). Phase transformation was measured at the mesial connector (group M), distal connector (group D), and pontic regions (group P) before and after mastication simulation. The relative monoclinic phase amount (Xm) was calculated for all specimens. The data were analyzed by ANOVA and post hoc tests (α=.05).

RESULTS

According to XRD analysis, Xm for all groups and regions showed higher results after aging than before aging (P<.05). Group B has the lowest Xm among the groups. Group B showed a statistically significant difference compared with both group F and group U (P<.05). There was no significant difference between group F and group U (P>.05). When the regions were evaluated regardless of brand and the groups were evaluated in terms of regions, no statistically significant difference was observed between connectors and the pontic region (P>.05).

CONCLUSIONS

Mastication simulation causes an increase in the Xm. However, this increase was unlikely to be clinically significant. There may be differences in phase transformation depending on the contents of the brands and sintering procedures. Variations in the phase quantity were independent of the connector regions and pontic for FDPs.

Tooth Mobility Reproduction in Dental Material Research: A Scoping Review

Background:

Introducing tooth mobility simulation in laboratory studies can provide results with high accuracy and predictability.

Objectives:

This study aims to review in vitro methodologies replicating tooth mobility and provide a recommended approach for future laboratory models.

Methods:

Databases, such as PubMed, Cochrane Database of Systematic Review, BioMed Central and Chinese databases are searched, and twelve articles are included in the final review.

Results:

Simulation methods of tooth mobility involving socket enlargement, screw loosening, alveolar bone loss simulation and a combination approach are identified from the extracted data. The materials used in preparing artificial teeth, artificial sockets and periodontal ligament simulator are discussed with a focus on their limitations. The achieved degrees of mobility and the presence of the centre of rotation are also evaluated. A timeline of the review articles is constructed to understand the trend of the preferred methods in tooth mobility simulation.

Conclusion:

Future in vitro investigations can achieve clinical reliability, particularly for materials tested in the field of dental traumatology and periodontology, by recognising the importance of incorporating tooth mobility in laboratory studies. Improvised methods are proposed to ensure that potential laboratory models can resemble the actual oral environment.

Comparison of Internal Adaptation of Bulk-fill and Increment-fill Resin Composite Materials

Objectives:

To evaluate 1) the internal adaptation of a light-activated incremental-fill and bulk-fill resin-based composite (RBC) materials by measuring the gap between the restorative material and the tooth structure and 2) the aging effect on internal adaptation.

Methods and Materials:

Seventy teeth with class I cavity preparations were randomly distributed into five groups; four groups were restored with bulk-fill RBCs: Tetric EvoCeram Bulk Fill (TEC), SonicFill (SF), QuiXX Posterior Restorative (QX), and X-tra fil (XF); the fifth group was restored with incremental-fill Filtek Supreme Ultra Universal Restorative (FSU). One-half of the specimens of each group were thermocycled. Each tooth was sectioned, digital images were recorded, and the dimensions of any existing gaps were measured. Data were analyzed using analysis of variance (α=0.05).

Results:

FSU had the smallest gap measurement values compared with the bulk-fill materials except QX and TEC (p≤0.008). FSU had the smallest sum of all gap category values compared with the bulk-fill materials, except QX (p≤0.021). The highest gap incidence and size values were found at the composite/adhesive interface. All aged groups had greater gap values in regard to the gap measurement and the sum of all gap categories compared with non-aged groups.

Significance:

The incrementally placed material FSU had the highest internal adaptation to the cavity surface, while the four bulk-fill materials showed varied results. Thermocycling influenced the existing gap area magnitudes. The findings suggest that the incremental-fill technique produces better internal adaptation than the bulk-fill technique.

Evaluation of the effect of different post materials and adhesive systems on the bonding strength of short-post technique for primary teeth

BACKGROUND

The most important process in treating grossly decayed teeth, including decay in the pulp, is the ability to hold a retainer in for a short time.

AIM

The aim of this study was to investigate the bond strengths of different adhesive systems and post materials on primary teeth.

DESIGN

One hundred and twenty extracted maxillar primary central incisor teeth were randomly divided into two main groups (total-etch and self-etch adhesive systems) and five subgroups (1: control-nanohybrid composite resin, 2: pre-impregnated glass fiber, 3: unsaturated glass fiber, 4: polyethylene fiber, 5: short-fiber reinforced composite resin). The push-out test was performed using a universal testing machine with a crosshead speed of 0.5 mm/min.

RESULTS

No statistically significant difference was detected between the two different adhesive systems and five different materials in terms of the maximum values measured for fractures in the specimens when both the adhesive materials and the short-post materials were evaluated separately (P > 0.05). However, as a result of multiple comparisons made, it was found that statistical differences between the groups applying the total-etch adhesive system occurred in Groups 3 and 5. The highest push-out test values were measured in Group 5 and Group 1, and the lowest value in Group 3. Although the fracture type distribution in the total-etch adhesive system groups was not statistically different based on the material used (χ²  = 11,865; P = 0.309), the self-etch adhesive systems did show differences (χ²  = 28,463; P < 0.001). Both the total-etch and the self-etch adhesive system groups showed mostly adhesive failures.

CONCLUSION

The fiber-reinforced and nanohybrid composite resin had higher values in the short-post technique, and there was no significant difference between the different fiber posts.

A zinc chloride-doped adhesive facilitates sealing at the dentin interface: A confocal laser microscopy study

The aim of this study was to ascertain the effect of Zn-doping of dental adhesives and mechanical load cycling on the micromorphology of the resin-dentin interdiffusion zone (of sound and caries affected dentin). The investigation considered two different Zn-doped adhesive approaches and evaluated the interface using a doubled dye fluorescent technique and a calcium chelator fluorophore under a confocal laser scanning microscopy. Sound and carious dentin-resin interfaces of unloaded specimens were deficiently resin-hybridized, in general. These samples showed a rhodamine B-labeled hybrid layer and adhesive layer completely affected by fluorescein penetration (nanoleakage) through the porous resin-dentin interface. It was thicker after phosphoric acid-etching and more extended in carious dentin. Zn-doping promoted an improved sealing of the resin-dentin interface, a decrease of the hybrid layer porosity, and an increment of dentin mineralization. Load cycling augmented the sealing of the Zn-doped resin-dentin interfaces, as porosity and nanoleakage diminished, and even disappeared in caries-affected dentin substrata conditioned with EDTA. Sound and carious dentin specimens analyzed with the xylenol orange technique produced a clearly outlined fluorescence when resins were Zn-doped, due to a consistent Ca-mineral deposition within the bonding interface and inside the dentinal tubules. It was more evident when load cycling was applied on specimens treated with self-etching adhesives that were Zn-doped. Micropermeability at the resin-dentin interface diminished after combining EDTA pretreatment, ZnCl₂-doping and mechanical loading stimuli on restorations. It is clearly preferable to include the zinc compounds into the bonding constituents of the self-etching adhesives, instead of into the primer ingredients. The promoted new mineral segments contributed to reduce or avoid both porosity and nanoleakage from the load cycled Zn-doped resin dentin interfaces. EDTA+SB-ZnCl₂ or SEB·Bd-Zn doping are preferred to treat caries-affected dentin surfaces. ZnO-doping encouraged for etch-and-rinse adhesives.

Mechanical loading influences the viscoelastic performance of the resin-carious dentin complex

The aim of this study was to evaluate the changes in the mechanical behavior and bonding capability of Zn-doped resin-infiltrated caries-affected dentin interfaces. Dentin surfaces were treated with 37% phosphoric acid (PA) followed by application of a dentin adhesive, single bond (SB) (PA+SB) or by 0.5 M ethylenediaminetetraacetic acid (EDTA) followed by SB (EDTA+SB). ZnO microparticles of 10 wt. % or 2 wt. % ZnCl₂ was added into SB, resulting in the following groups: PA+SB, PA+SB-ZnO, PA+SB-ZnCl₂, EDTA+SB, EDTA+SB-ZnO, EDTA+SB-ZnCl₂. Bonded interfaces were stored for 24 h, and tested or submitted to mechanical loading. Microtensile bond strength was assessed. Debonded surfaces were evaluated by scanning electron microscopy and elemental analysis. The hybrid layer, bottom of the hybrid layer, and peritubular and intertubular dentin were evaluated using a nanoindenter. The load/displacement responses were used for the nanodynamic mechanical analysis III to estimate complex modulus, tan delta, loss modulus, and storage modulus. The modulus mapping was obtained by imposing a quasistatic force setpoint to which a sinusoidal force was superimposed. Atomic force microscopy imaging was performed. Load cycling decreased the tan delta at the PA+SB-ZnCl₂ and EDTA+SB-ZnO interfaces. Tan delta was also diminished at peritubular dentin when PA+SB-ZnO was used, hindering the dissipation of energy throughout these structures. Tan delta increased at the interface after using EDTA+SB-ZnCl₂, lowering the energy for recoil or failure. After load cycling, loss moduli at the interface decreased when using ZnCl₂ as doping agent, increasing the risk of fracture; but when using ZnO, loss moduli was dissimilarly affected if dentin was EDTA-treated. The border between intertubular and peritubular dentin attained the highest discrepancy in values of viscoelastic properties, meaning a risk for cracking and breakdown of the resin-dentin interface. PA used on dentin provoked differences in complex and storage modulus values at the intertubular and peritubular structures, and these differences were higher than when EDTA was employed. In these cases, the long-term performance of the restorative interface will be impaired.

Repair Strength in Simulated Restorations of Methacrylate- or Silorane-Based Composite Resins

The study verified the bond strength in simulated dental restorations of silorane- or methacrylate-based composites repaired with methacrylate-based composite. Methacrylate- (P60) or silorane-based (P90) composites were used associated with adhesive (Adper Single Bond 2). Twenty-four hemi-hourglass-shaped samples were repaired with each composite (n=12). Samples were divided according to groups: G1= P60 + Adper Single Bond 2+ P60; G2= P60 + Adper Single Bond 2 + P60 + thermocycling; G3= P90 + Adper Single Bond 2 + P60; and G4= P90 + Adper Single Bond 2 + P60 + thermocycling. G1 and G3 were submitted to tensile test 24 h after repair procedure, and G2 and G4 after submitted to 5,000 thermocycles at 5 and 55 ?#61616;C for 30 s in each bath. Tensile bond strength test was accomplished in an universal testing machine at crosshead speed of 0.5 mm/min. Data (MPa) were analyzed by two-way ANOVA and Tukey's test (5%). Sample failure pattern (adhesive, cohesive in resin or mixed) was evaluated by stereomicroscope at 30?#61655; and images were obtained in SEM. Bond strength values of methacrylate-based composite samples repaired with methacrylate-based composite (G1 and G2) were greater than for silorane-based samples (G3 and G4). Thermocycling decreased the bond strength values for both composites. All groups showed predominance of adhesive failures and no cohesive failure in composite resin was observed. In conclusion, higher bond strength values were observed in methacrylate-based resin samples and greater percentage of adhesive failures in silorane-based resin samples, both composites repaired with methacrylate-based resin.

Oral Function Improves Interfacial Integrity and Sealing Ability Between Conventional Glass Ionomer Cements and Dentin

The aim of this study was to investigate if load cycling affects interfacial integrity of glass ionomer cements bonded to sound- or caries-affected dentin. A conventional glass ionomer, Ketac Bond, and a resin-modified glass ionomer (Vitrebond Plus), were applied to dentin. Half of the specimens were load cycled. The interfaces were submitted to dye-assisted confocal microscopy evaluation. The unloaded specimens of sound and carious dentin were deficiently hybridized when Ketac Bond was used. Ketac Bond samples showed an absorption layer and an adhesive layer that were scarcely affected by fluorescein penetration (nanoleakage), in sound dentin. Nevertheless, a higher degree of micropermeability was found in carious dentin. In Ketac Bond specimens, load cycling improves the sealing capability and remineralization at the cement-dentin interface as porosity and nanoleakage was reduced. In contrast, samples treated with Vitrebond Plus exhibited a Rhodamine B-labeled absorption layer with scarce nanoleakage in both sound and carious unloaded dentin. The adhesive layer was affected by dye sorption throughout the porous cement-dentin interface. Samples treated with Vitrebond Plus had significant increases in nanoleakage and cement-dye sorption after load cycling. Within the limitations of an in vitro study, it is expected that conventional glass ionomers will provide major clinical efficacy when applied to carious-affected or sound dentin.

A Critical Review of the Durability of Adhesion to Tooth Tissue: Methods and Results

The immediate bonding effectiveness of contemporary adhesives is quite favorable, regardless of the approach used. In the long term, the bonding effectiveness of some adhesives drops dramatically, whereas the bond strengths of other adhesives are more stable. This review examines the fundamental processes that cause the adhesion of biomaterials to enamel and dentin to degrade with time. Non-carious class V clinical trials remain the ultimate test method for the assessment of bonding effectiveness, but in addition to being high-cost, they are time- and labor-consuming, and they provide little information on the true cause of clinical failure. Therefore, several laboratory protocols were developed to predict bond durability. This paper critically appraises methodologies that focus on chemical degradation patterns of hydrolysis and elution of interface components, as well as mechanically oriented test set-ups, such as fatigue and fracture toughness measurements. A correlation of in vitro and in vivo data revealed that, currently, the most validated method to assess adhesion durability involves aging of micro-specimens of biomaterials bonded to either enamel or dentin. After about 3 months, all classes of adhesives exhibited mechanical and morphological evidence of degradation that resembles in vivo aging effects. A comparison of contemporary adhesives revealed that the three-step etch-and-rinse adhesives remain the ‘gold standard’ in terms of durability. Any kind of simplification in the clinical application procedure results in loss of bonding effectiveness. Only the two-step self-etch adhesives approach the gold standard and do have some additional clinical benefits.

Bonding effectiveness of composite-dentin interfaces after mechanical loading with a new device (Rub&Roll)

This study evaluated the effect of mechanical loading with a new device on the microtensile bond strength (µTBS) of adhesive systems to dentin. Forty molars were divided according to adhesive systems: self-etch (Clearfil^TM SE Bond -CSE) and etch-and-rinse (Adper Scotchbond^TM 1XT -ASB); and to aging (n=5): control; MC1-250,000; MC2-500,000; and MC3-750,000 mechanical cycles. Microtensile bond strength was measured and fracture modes were analyzed. Data for µTBS were subjected to Kruskal-Wallis and post hoc tests (p<0.05). Mechanical loading (p<0.001) and adhesive systems (p=0.024) affected µTBS values. The adhesive systems showed a similar behavior, except in the MC3 group, which the self-etch CSE showed the highest µTBS. The new device promotes a decreasing of µTBS as the number of cycles increased. Difference between materials was observed only after 750,000 mechanical cycles.

Dentin bonding performance using Weibull statistics and evaluation of acid-base resistant zone formation of recently introduced adhesives

Dentin bonding durability of recently introduced dental adhesives: Clearfil SE Bond 2 (SE2), Optibond XTR (XTR), and Scotchbond Universal (SBU) was investigated using Weibull analysis as well as analysis of the micromorphological features of the acid-base resistant zone (ABRZ) created for the adhesives. The bonding procedures of SBU were divided into three subgroups: self-etch (SBS), phosphoric acid (PA) etching on moist (SBM) or dry dentin (SBD). All groups were thermocycled for 0, 5,000 and 10,000 cycles followed by microtensile bond strength testing. Acid-base challenge was undertaken before SEM and TEM observations of the adhesive interface. The etch-and-rinse method with SBU (SBM and SBD) created inferior interfaces on the dentin surface which resulted in reduced bond durability. ABRZ formation was detected with the self-etch adhesive systems; SE2, XTR and SBS. In the PA etching protocols of SBM and SBD, a thick hybrid layer but no ABRZ was detected, which might affect dentin bond durability.

Effect of different surface treatments and thermocycling on shear bond strength to polyetheretherketone

This study was designed to evaluate the shear bond strength of an adhesive/composite system subjected to different pretreated polyetheretherketone (PEEK) surfaces using different thermocycling conditioning methods. A total of 128 specimens were equally divided into four main groups ( n = 32/group): control (no pretreatment), air abrasion, argon plasma pretreatment, and femtosecond laser groups. The surface topographies and surface roughness were observed by atomic force microscopy after different pretreatments. The specimens were bonded with SE Bond/Clearfil AP-X™. All bonded specimens were stored in distilled water at 37°C for 24 h. Afterward, each group was divided into three subgroups ( n = 8/group) as follows: (a) stored in water for 56 h (37°C); (b) thermal aging for 5000 cycles (5°C/55°C); and (c) thermal aging for 10,000 cycles (5°C/55°C). The shear bond strengths were measured. Air abrasion, argon plasma pretreatment, and femtosecond laser significantly strengthened the bond of SE Bond/Clearfil AP-X™ to PEEK composite compared with that without additional pretreatment. In the same surface pretreatment, the shear bond strengths of specimens conditioned using water storage were higher than that using thermocycles (TCs). Additionally, the specimens with 5000 TC showed significantly higher shear bond strength than that with 10000 TC.

Analysis and simulation of heat transfer in human tooth during the curing of orthodontic appliance and food ingestion

The aim of this study was to analyze and simulate the heat transfer in the human tooth undergoing fixed orthodontic appliances and food intake. An in vivo representative mathematic model of a layered thermographic profile was developed during the LED curing of Gemini bracket 0.022 in slot (conventional ligating system) and Transbond XT adhesive. The characterization of the layered thermic response allowed to identify if during the LED curing process, according to manufacturer’s specification (light curing unit, adhesive) can induce pulpar necrosis. The profile’s thermographic model was the simulation basis of many conditions such as food intake, due to in vivo metrology is affected by the impossibility of a correct apparatus position and the physiologic function of the oral cavity which is exposed to uncontrollable temperature changes. The metrology was carried out with a T-440 thermographic camera during LED curing bracket, using a LED curing light (Elipar S10) placed at 3 ± 1 mm for 5 s at each mesial and distal surface. The thermography outcomes were analyzed in the FLIR Tools Software, Microsoft Excel 2013 and SPSS 22. To adjust the mathematic model error, in vitro studies were performed on third molars for the purpose of realizing extreme exposition temperature condition tests caused by the LED curing unit without jeopardizing the human tooth vitality as would it be on in vivo experimentation. The bracket curing results according to manufacturer’s conditions reached 39°C in vivo temperatures and 47°C on in vitro tests, which does not jeopardize human tooth vitality as said by previous researches, although, an LED curing precise protocol established by the manufacturer’s LED curing light is sustained.

Tensile Bond Strengths of Two Adhesives on Irradiated and Nonirradiated Human Dentin

The aim of this study was to assess the effect of radiotherapy on bond efficiency of two different adhesive systems using tensile bond strength test. Twenty extracted teeth after radiotherapy and twenty nonirradiated extracted teeth were used. The irradiation was applied in vivo to a minimal dose of 50 Gy. The specimens of each group were randomly assigned to two subgroups to test two different adhesive systems. A three-step/etch-and-rinse adhesive system (Optibond FL) and a two-steps/self-etch adhesive system (Optibond XTR) were used. Composite buildups were performed with a nanohybrid composite (Herculite XTR). All specimens were submitted to thermocycling ageing (10000 cycles). The specimens were sectioned in 1 mm(2) sticks. Microtensile bond strength tests were measured. Nonparametric statistical analyses were performed due to nonnormality of data. Optibond XTR on irradiated and nonirradiated teeth did not show any significant differences. However, Optibond FL bond strength was more effective on nonirradiated teeth than on irradiated teeth. Within the limitations of an in vitro study, it can be concluded that radiotherapy had a significant detrimental effect on bond strength to human dentin. However, it seems that adhesive choice could be adapted to the substrata. According to the present study, the two-steps/self-etch (Optibond XTR) adhesive system tested could be more effective on irradiated dentin compared to three-steps/etch-and-rinse adhesive system (Optibond FL).

Nanoscopic dynamic mechanical analysis of resin-infiltrated dentine, under in vitro chewing and bruxism events

The aim of this study was to evaluate the induced changes in mechanical behavior and bonding capability of resin-infiltrated dentine interfaces, after application of mechanical stimuli. Dentine surfaces were subjected to partial demineralization through 37% phosphoric acid etching followed by the application of an etch-and-rinse dentine adhesive, Single Bond (3M/ESPE). Bonded interfaces were stored in simulated body fluid during 24h, and then tested or submitted to the mechanical loading challenge. Different loading waveforms were applied: No cycling (I), 24h cycled in sine (II) or square (III) waves, sustained loading held for 24h (IV) or sustained loading held for 72h (V). Microtensile bond strength (MTBS) was assessed for the different groups. Debonded dentine surfaces were studied by field emission scanning electron microscopy (FESEM). At the resin-dentine interface, both the hybrid layer (HL) and the bottom of the hybrid layer (BHL), and both peritubular and intertubular were evaluated using a nanoindenter in scanning mode. The load and displacement responses were used to perform the nano-Dynamic Mechanical analysis and to estimate the complex and storage modulus. Dye assisted Confocal Microscopy Evaluation was used to assess sealing ability. Load cycling increased the percentage of adhesive failures in all groups. Specimens load cycled in held 24h attained the highest complex and storage moduli at HL and BHL. The storage modulus was maximum in specimens load cycled in held 24h at peritubular dentine, and the lowest values were attained at intertubular dentine. The storage modulus increased in all mechanical tests, at peritubular dentine. An absence of micropermeability and nanoleakage after loading in sine and square waveforms were encountered. Porosity of the resin-dentine interface was observed when specimens were load cycled in held 72h. Areas of combined sealing and permeability were discovered at the interface of specimens load cycled in held 24h. Crack-bridging images appeared in samples load cycled with sine waveform, after FESEM examination.

Bond strength and bioactivity of Zn-doped dental adhesives promoted by load cycling

The purpose of this study was to evaluate if mechanical loading influences bioactivity and bond strength at the resin-dentin interface after bonding with Zn-doped etch-and-rinse adhesives. Dentin surfaces were subjected to demineralization by 37% phosphoric acid (PA) or 0.5 M ethylenediaminetetraacetic acid (EDTA). Single bond (SB) adhesive—3M ESPE—SB+ZnO particles 20 wt% and SB+ZnCl2 2 wt% were applied on treated dentin to create the groups PA+SB, SB+ZnO, SB+ZnCl2, EDTA+SB, EDTA+ZnO, and EDTA+ZnCl2. Bonded interfaces were stored in simulated body fluid for 24 h and tested or submitted to mechanical loading. Microtensile bond strength (MTBS) was assessed. Debonded dentin surfaces were studied by high-resolution scanning electron microscopy. Remineralization of the bonded interfaces was assessed by atomic force microscope imaging/nanoindentation, Raman spectroscopy/cluster analysis, and Masson's trichrome staining. Load cycling (LC) produced reduction in MTBS in all PA+SB, and no change was encountered in EDTA+SB specimens, regardless of zinc doping. LC increased the mineralization and crystallographic maturity at the interface; a higher effect was noticed when using ZnO. Trichrome staining reflected a narrow demineralized dentin matrix after loading of dentin surfaces that were treated with SB-doped adhesives. This correlates with an increase in mineral platforms or plate-like multilayered crystals in PA or EDTA-treated dentin surfaces, respectively.

A castor oil-containing dental luting agent: effects of cyclic loading and storage time on flexural strength

Favorable results in the use of castor oil polyurethane (COP) as pulp capping, membrane material, sealer, mouthwash and in bone repair, associated with the fact that Ricinus communis is not derived from petroleum and it is abundant in Brazil, encourage researches in the development of luting agents.

Validity of bond strength tests: A critical review-Part II

Background:

Macro-bond strength tests resulted in cohesive failures and overestimation of bond strengths. To reduce the flaws, micro-bond strength tests were introduced. They are the most commonly used bond-strength tests.

Objective:

Thus the objective of this review is to critically review the reliability of micro-bond strength tests used to evaluate resin-tooth interface.

Data Collection:

Relevant articles published between January 1994 and July 2013 were collected from Pubmed database, Google scholar and hand searched journals of Conservative Dentistry, Endodontics and Dental materials.

Data Synthesis:

Variables that influence the test outcome are categorized into substrate related factors, factors related to specimen properties, specimen preparation and test methodology. Impact of these variables on the test outcome is critically analyzed.

Conclusion:

Micro-bond tests are more reliable than macro-bond tests. However, no standard format exists for reporting the bond strength tests which could lead to misinterpretation of the data and bonding abilities of adhesives.

Polymerization Shrinkage Stress Kinetics and Related Properties of Bulk-fill Resin Composites

The present study assessed the polymerization shrinkage stress kinetics of five low-shrinkage light-cured bulk-fill resin composites: Surefil SDR flow (SF, Dentsply), Tetric EvoCeram Bulkfil (TE, Ivoclar Vivadent), Venus Bulk Fill (VB, Heraeus Kulzer), x-tra fil (XF, Voco), and experimental bulk fill (FB, 3M ESPE). Filtek Z250 (FZ, 3M ESPE) was used as a control. Real-time shrinkage stress of investigated composites was measured using a tensometer; maximum shrinkage stress, stress rate (Rmax), and time to reach maximum stress rate (tmax) were recorded. Flexural strength and modulus were measured using a standard procedure, and curing efficiency of 4-mm long specimens was determined using bottom/top percentage Knoop microhardness. Data were analyzed using one-way analysis of variance and Bonferroni multiple range tests at a significance level of α=0.05. Results of shrinkage stress, Rmax, and tmax of all bulk-fill materials were significantly lower (p&lt;0.05) than those of the control except for XF. All tested bulk-fill materials were able to achieve acceptable curing efficiency (≥80% bottom/top percentage) at 4-mm depth. In conclusion, this study reports a significant reduction in polymerization shrinkage stress while maintaining comparable curing efficiency at 4 mm for some bulk-fill composites and supports their potential use in posterior clinical situations.

Micro-CT evaluation of internal adaptation in resin fillings with different dentin adhesives

Objectives

The purpose of present study was to evaluate the internal adaptation of composite restorations using different adhesive systems.

Materials and Methods

Typical class I cavities were prepared in 32 human third molars. The teeth were divided into the following four groups: 3-step etch-and-rinse, 2-step etch-and-rinse, 2-step self-etch and 1-step self-etch system were used. After the dentin adhesives were applied, composite resins were filled and light-cured in two layers. Then, silver nitrate solution was infiltrated, and all of the samples were scanned by micro-CT before and after thermo-mechanical load cycling. For each image, the length to which silver nitrate infiltrated, as a percentage of the whole pulpal floor length, was calculated (%SP). To evaluate the internal adaptation using conventional method, the samples were cut into 3 pieces by two sectioning at an interval of 1 mm in the middle of the cavity and they were dyed with Rhodamine-B. The cross sections of the specimens were examined by stereomicroscope. The lengths of the parts where actual leakage was shown were measured and calculated as a percentage of real leakage (%RP). The values for %SP and %RP were compared.

Results

After thermo-mechanical loading, all specimens showed significantly increased %SP compared to before thermo-mechanical loading and 1-step self-etch system had the highest %SP (p < 0.05). There was a tendency for %SP and %RP to show similar microleakage percentage depending on its sectioning.

Conclusions

After thermo-mechanical load cycling, there were differences in internal adaptation among the groups using different adhesive systems.

Marginal adaptation of indirect restorations using different resin coating protocols

This study evaluated the influence of material combinations used in the resin coating technique (RCT) on the marginal adaptation of indirect restorations with gingival margins in enamel (EM) and cement (CM). Eighty third-molars were used. Two cavities were prepared in each tooth. The cavities were distributed into 16 groups. Cavities with EM were filled with the following material combinations: G1: Single-Bond 2 (Sb2), G2: Sb2 + Bond/Scotchbond-Multipurpose (Sb2B), G3: Sb2 + Filtek-Flow Z350 (Sb2Fl), G4: Scotchbond-Multipurpose (SBMP), G5: Clearfil-S3 (CS3), G6: CS3 + Bond/Clearfil-SE Bond (CSE3B), G7: CS3 + Protect Liner F (CS3PL) and G8: Clearfil SE Bond + Protect Liner F (CSEBPL). The same combinations were applied to the cavities in CM: G9, G10, G11, G12, G13, G14, G15, G16, respectively. The fillings were performed with the Sinfony-System (3M/ESPE). After 24 h, the teeth were submitted to thermocycling (2,000 cycles, 5° to 55°C) and load-cycling (50,000 cycles, 50 N). Next, the Caries-Detector (Kuraray) was applied to the restoration margins. Images from the proximal margin were evaluated using the Image-Tool 3.0 software. The results were submitted to ANOVA and Tukey's test (α=0.05). The mean values (%) for the groups were: EM: G1=46.68, G2=15.53, G3=19.83, G4=27.53; G5=59.49, G6=25.13, G7=34.37, G8=15.20; CM: G9=38.38, G10=23.25, G11=26.97, G12=25.85, G13=37.81, G14=30.62, G15=29.17, G16=20.31. The highest percentages of marginal gap on EM or CM were found in the groups that did not use a liner. It can be concluded that the most appropriate RCT combinations were the groups that used a liner.

Thermo-mechanical degradation of composite restoration photoactivated by modulated methods-a SEM study of marginal and internal gap formation

OBJECTIVE

To evaluate the influence of thermal-mechanical degradation on superficial and internal gap formation of composite restorations photoactivated using modulated methods.

MATERIALS AND METHODS

An experimental composite was prepared using a resin matrix containing 65wt% Bis-GMA and 35wt% TEGDMA. Camphorquinone (0.5wt%) and dimethylaminoethyl-methacrylate (0.5wt%) were dissolved in the resin as a photo-initiator system and 65wt.% silanized glass fillers were added to the matrix. Ground buccal surfaces of bovine lower incisors were used to make 160 preparations (3 mm × 3 mm × 2 mm in depth). An adhesive system (Adper Single Bond 2) was applied and the specimens were assigned into 16 groups (n = 10), according to the photoactivation method [high intensity (HI), low intensity (LI), soft-start (SS) and pulse-delay (PD)] and the degradation protocol [(control/no degradation; thermal cycling (TC); mechanical loading (ML); thermo-mechanical loading (TC+ML)]. Marginal and internal interfaces of bonded restorations were replicated in epoxy resin and analyzed by SEM. Gaps were expressed as a percentage of the total length of the margins. Data were submitted to 2-way ANOVA and Tukey's test (α = 0.05).

RESULTS

For the control group no significance was noted among the photoactivation methods. TC had no effect in gap formation. ML and TC+ML increased the incidence of superficial gaps for both HI and SS groups as well as increased the internal gaps for all groups.

CONCLUSION

Although photoactivation methods do not influence gap formation at first, composite restoration photoactivated by low intensity or modulated methods showed improved resistance to thermo-mechanical degradation. Mechanical loading is determinant for interfacial degradation of composite restorations, while thermal cycling has no effect on gap formation.

Alternatives in polymerization contraction stress management

Polymerization contraction stress of dental composites is often associated with marginal and interfacial failure of bonded restorations. The magnitude of the stress depends on the composite's composition (filler content and matrix composition) and its ability to flow before gelation, which is related to the cavity configuration and curing characteristics of the composite. This article reviews the variations found among studies regarding the contraction stress testing method, contraction stress values of current composites, and discusses the validity of contraction stress studies in relation to results from microleakage tests. The effect of lower curing rates and alternative curing routines on contraction stress values is also discussed, as well as the use of low elastic modulus liners. Moreover, studies with experimental Bis-GMA-based composites and recent developments in low-shrinkage monomers are described.

Immediate and delayed micro-tensile bond strength of different luting resin cements to different regional dentin

We sought to evaluate immediate and delayed micro-tensile bond strength of Panavia F2.0 and Multilink Sprint resin cement to superficial, deep and cervical dentin. Thirty-six freshly extracted non-carious human molars were sectioned in the mesiodistal direction to expose three different dentin regions including superficial dentin (1 mm below the dentine-enamel junction), deep dentin (1 mm above the highest pulp horn) and cervical dentin (0.5 mm above the cemento-enamel junction and 0.5 mm below the dentine-enamel junction). Resin cements were applied on dentin surfaces and composite blocks were luted under constant seating pressure. Each group was divided into three subgroups according to time intervals. Specimens were sectioned to obtain sticks of 1 mm² in diameter and subjected to microtensile bond strength testing at a cross head speed of 1 mm/min. Both resin cements showed higher micro-tensile bond strength to superficial dentin than that to deep or cervical dentin (P < 0.001). Micro-tensile bond strengths of Panavia F2.0 were higher than those of Multilink Sprint at different dentin regions (P < 0.001). Immediate micro-tensile bond strengths were higher than those of delayed micro-tensile bond strengths for both resin cements (P < 0.001). It was concluded that resin cements with different chemical formulations and applications yield significantly different micro-tensile bond strengths to different dentin regions.

Clinical evaluation of self-etch and total-etch adhesive systems in noncarious cervical lesions: a two-year report

OBJECTIVE

The purpose of this study was to compare the clinical performance of two self-etch dental adhesives with Single Bond Plus, a traditional one-bottle total-etch dental adhesive, for the restoration of noncarious cervical lesions.

MATERIALS AND METHODS

A total of 156 restorations were placed in noncarious cervical lesions with a minimum depth of 1.5 mm. Patients had no chronic periodontal disease and had normal salivary function. Each patient received restorations on three teeth, each bonded with either Adper Single Bond Plus, Adper Easy Bond, or Adper Scotchbond SE dental adhesive. All lesions were restored with Filtek Supreme Plus composite resin. All teeth were isolated with a rubber dam, received a short enamel bevel, and were cleaned with flour of pumice. The adhesives and resin composite were applied following the manufacturers' instructions. Restorations were clinically evaluated at baseline, six months, one year, and two years using modified US Public Health Service criteria.

RESULTS

Two-year retention was recorded as 97.3%, 90.5%, and 95.2%, for Single Bond Plus, Scotchbond SE, and Easy Bond, respectively. Statistical analysis did not show a significant difference (p>0.05) in clinical performance between any of the three adhesives after a period of two years.

Effect of loading on the microtensile bond strength and microleakage of a self-etching and etch-and-rinse adhesive in direct Class II MOD composite restorations in vitro

The effect of loading on microleakage and microtensile bond strength of MOD composite restorations bonded with either self-etching or etch-and-rinse adhesive was investigated. MOD cavities were prepared in 28 extracted molar teeth. 14 teeth were bonded with a one-step self-etching adhesive (G-Bond) and 14 with an etch-and-rinse adhesive (Optibond Solo Plus) then restored with resin composite. For each adhesive, 7 teeth were loaded and 7 unloaded (controls). Loading was achieved with an axial force of 80 N at 2.5 cycles/s for 250,000 cycles. All the teeth were stored in 0.25% rhodamine solution for 24 h and sectioned in a bucco-lingual direction at the proximal boxes to examine microleakage then further sliced mesiodistally into beams for the μTBS test. Failure modes were determined using confocal and scanning electron microscopy. ANOVA assessed the effect of loading on microleakage and bond strength. After loading, restorations bonded with G-Bond exhibited significantly greater dye penetration compared to Optibond Solo Plus at both the axial walls and cavity floor. On the other hand, loading significantly reduced the μTBS of Optibond Solo Plus, whereas it had no significant effect on the μTBS of G-Bond.

Adhesion of Indirect MOD Resin Composite Inlays Luted With Self-adhesive and Self-etching Resin Cements

This study investigated the effect of loading on the bond strength to dentin and microleakage of MOD indirect composite restorations bonded with self-adhesive and self-etching resin cements with or without acid etching of the proximal enamel margins. Class II MOD cavities were prepared in 48 molar teeth into dentin and divided into three groups of 16 teeth. Impressions were taken and indirect composite inlays fabricated (Estenia C & B). The enamel margins of the proximal boxes of half the specimens were phosphoric acid etched, and the inlays were cemented with one of three cements (Panavia F 2.0, SA Cement, or Rely X Unicem). After luting, eight teeth in each cement group were mechanically loaded at 2.5 cycles/s for 250,000 cycles. Unloaded teeth acted as controls. Teeth were stored in Rhodamine B solution for 24 hours, sectioned buccolingually at the proximal boxes to examine microleakage using confocal microscopy, and further sectioned for μTBS testing of the resin-dentin interface. Analysis of variance was performed to assess the effect of loading and acid etching on microleakage and bond strength. Acid etching had no effect on microleakage. No significant difference in the dentin bond strengths between the three cements existed after loading. Panavia F 2.0 exhibited a significant reduction in bond strength. With regard to microleakage at the proximal boxes, loading had no effect on dye penetration at the cavity floor. However, at the axial walls, loading had a significant deleterious effect on Panavia F 2.0. No difference in microleakage existed between the three cements at both sites before and after loading. In conclusion, the two tested self-adhesive cements exhibited similar bond strengths before and after loading to the self-etching resin cement. Loading reduced dentin bond strengths and increased microleakage at the resin-dentin interface. However, acid etching of the enamel margins had no significant effect on microleakage in the approximal regions of the bonded inlays.

Selective Enamel Etching: Effect on Marginal Adaptation of Self-Etch LED-Cured Bond Systems in Aged Class I Composite Restorations

The aim of this study was to evaluate the influence of previous enamel etch and light emitting diode (LED) curing on gap formation of self-etch adhesive systems in Class I composite restorations after thermomechanical aging (TMA). Thus, on 192 human molars, a box-shaped Class I cavity was prepared maintaining enamel margins. Self-etch adhesives (Clearfil SE and Clearfil S3) were used to restore the preparation with a microhybrid composite. Before application of the adhesives, half of the teeth were enamel etched for 15 seconds with 37% phosphoric acid; the other half were not etched. For the photoactivation of the adhesives and composite, three light-curing units (LCUs) were used: one polywave (Ultra-Lume LED 5, UL) and two single-peak (FlashLite 1401, FL and Radii-cal, RD) LEDs. After this, epoxy resin replicas of the occlusal surface were made, and the specimens were submitted to TMA. New replicas were made from the aged specimens for marginal adaptation analysis by scanning electron microscopy. Data were submitted to Kruskal-Wallis and Wilcoxon tests (α=0.05). Before TMA, when enamel was etched before the application of S3, no gap formation was observed; however, there were gaps at the interface for the other tested conditions, with a statistical difference (p≤0.05). After TMA, the selective enamel etching previous to the S3 application, regardless of the LCU, promoted higher marginal adaptation compared to the other tested groups (p≤0.05). Prior to TMA, higher marginal integrity was observed, in comparison with specimens after TMA (p≤0.05). With regard to Clearfil SE and Clearfil Tri-S cured with FL, no differences of gap formation were found between before and after aging (5.3 ± 3.8 and 7.4 ± 7.5, respectively), especially when the Clearfil Tri-S was used in the conventional protocol. When cured with RD or UL and not etched, Clearfil Tri-S presented the higher gap formation. In conclusion, additional enamel etching promoted better marginal integrity for Clearfil Tri-S, showing it to be an efficient technique for Class I composite restorations. The two-step self-etch adhesive was not influenced by selective enamel etching or by the LED-curing unit.