Repair bond strength and nanoleakage of artificially aged CAD-CAM composite resin

Effect of brushing simulation on the wear behavior of repaired CAD-CAM restorations

OBJECTIVE

The aim of the present study was to evaluate the influence of multidirectional brushing on the surface roughness, morphology, and bonding interface of resin-repaired CAD-CAM ceramic and composite restorations.

MATERIALS AND METHODS

Twelve (N = 12) blocks (4 mm × 4 mm × 2 mm for parallel axis; 5 mm × 4 mm × 2 mm for perpendicular axis) of lithium disilicate glass-ceramic (IPS e.max CAD, Ivoclar AG) and CAD-CAM resin composite (Tetric CAD, Ivoclar AG) were obtained and repaired with direct resin composite (Clearfil AP-X, Kuraray). An abrasive slurry was prepared and the brushing was performed according to each restorative material and axis of brushing (n = 6; perpendicular to repair interface and parallel to repair interface) during 3,650 cycles (240 strokes per minute) to simulate 3 years of brushing. The surface roughness (Ra) and the profile variation for each material (restoration and direct repair resin composite) were measured at the baseline condition and after brushing, and the mean roughness and presence of steps at the repair interface were evaluated through factorial analysis of Variance (ANOVA). Scanning Electron Microscopy (SEM) images were taken to evaluate the surface topography of the repaired materials after brushing.

RESULTS

The mean roughness of the repaired CAD-CAM restorations was affected by the brushing (P < .05), mainly when evaluating the repair material and the interface (P < .05), while the restorative CAD-CAM materials presented more stable values. The profile evaluation showed higher steps at the interface when repairing lithium disilicate than for CAD-CAM resin composite.

CONCLUSION

Repaired CAD-CAM restorations were susceptible to wear after brushing simulation. The surface roughness of the direct resin composite was the most affected leading to step development at the interface, particularly in the repaired lithium disilicate samples. Cinical maintenance recalls and polishing protocols must be considered to enhance the longevity of such restorations.

Repair protocols for indirect monolithic restorations: a literature review

Despite the advancements in indirect monolithic restorations, technical complications may occur during function. To overcome this issues, intraoral repair using resin composite is a practical and low-cost procedure, being able to increase the restoration's longevity. This review aimed to evaluate the need for repair and suggest a standardized repair protocol to the main indirect restorative materials. For this, studies were surveyed from PubMed with no language or date restriction, to investigate the scientific evidence of indirect monolithic restoration repair with direct resin composite. A classification to guide clinical decisions was made based on the FDI World Dental Federation criteria about defective indirect restorations considering esthetic and functional standards, along with the patient's view, to decide when polishing, repairing or replacing a defective restoration. Based on 38 surveyed studies, different resin composite intraoral repair protocols, that included mechanical and chemical aspects, were defined depending on the substrate considering resin-based, glass-ceramic or zirconia restorations. The presented criteria and protocols were developed to guide the clinician's decision-making process regarding defective indirect monolithic restorations, prolonging longevity and increasing clinical success.

The effect of repair protocols and chewing simulation on the microtensile bond strength of two resin matrix ceramics to composite resin

BACKGROUND

To assess the micro tensile bond strength (µTBS) of two resin matrix ceramic (RMC) blocks bonded to composite resin by using different repair protocols with and without chewing simulation (CS).

MATERIALS AND METHODS

Two resin matrix ceramic blocks (Vita Enamic and Lava Ultimate) were divided into 4 groups according to the surface treatments: Bur grinding (control), Bur grinding + silane, 9.5% HF acid etching, and 9.5% HF acid etching + silane. The single bond universal adhesive was applied on all specimens after the surface treatments according to the manufacturer's instructions, it was administered actively on the treated surface for 20 s and then light cured for 10 s, followed by incremental packing of composite resin to the treated surface. Each group was further divided into 2 subgroups (with/without chewing simulation for 500,000 cycles). A micro tensile bond strength test was performed for each group (n = 15). The effect of surface treatments on the materials was examined by using a scanning electron microscope (SEM). The micro tensile bond strength (MPa) data were analyzed with a three-way ANOVA, the independent t-test, and one-way ANOVA followed by the Tukey post-hoc test.

RESULTS

µTBS results were significantly higher for Lava Ultimate than Vita Enamic for all the surface treatment protocols with (p < 0.01). The chewing simulation significantly negatively affected the micro-tensile bond strength (p < 0.001). Bur grinding + saline exhibited the highest bond strength values for Lava Ultimate, both with and without chewing simulation. For Vita Enamic, bur grinding + saline and HF acid + saline showed significantly higher bond strength values compared to other surface treatments, both with and without chewing simulation (p ≤ 0.05).

CONCLUSION

Bur grinding + silane could be recommended as a durable repair protocol for indirect resin matrix ceramics blocks with composite resin material.

Mechanical Behavior of Repaired Monolithic Crowns: A 3D Finite Element Analysis

This study evaluated the mechanical behavior and risk of failure of three CAD-CAM crowns repaired with different resin composites through a three-dimensional (3D) finite element analysis. Three-dimensional models of different cusp-repaired (conventional nanohybrid, bulk-fill, and flowable resin composites) crowns made of zirconia, lithium disilicate, and CAD-CAM resin composite were designed, fixed at the cervical level, and loaded in 100 N at the working cusps, including the repaired one. The models were analyzed to determine the Maximum Principal and Maximum Shear stresses (MPa). Complementary, an in vitro shear bond strength test (n = 10) was performed to calculate the risk of failure for each experimental group. The stress distribution among the models was similar when considering the same restorative material. The crown material affected the stress concentration, which was higher for the ceramic models (±9 MPa for shear stress; ±3 MPa for tensile stress) than for the CAD-CAM composite (±7 MPa for shear stress; ±2 MPa for tensile stress). The shear bond strength was higher for the repaired CAD-CAM resin composite (±17 MPa) when compared to the ceramics (below 12 MPa for all groups), while the repair materials showed similar behavior for each substrate. The stress distribution is more homogenous for repaired resin composite crowns, and a flowable direct resin composite seems suitable to repair ceramic crowns with less risk of failure.

Effect of different surface treatments on the retention force of additively manufactured interim implant-supported crowns

PURPOSE

To compare the effect of different pre-cementation surface treatments and bonding protocols on the retention force of additively manufactured (AM) implant-supported interim crowns.

MATERIAL AND METHODS

A total of 50 AM interim crowns (Temporary CB resin) were cemented on implant abutments. Five groups (n = 10) were established based on the different surface pre-treatments performed in the intaglio surface of the specimens: no surface pre-treatment (Group C or control), air-abraded with 50-μm aluminium oxide particles (Group AP), air-abraded with 50-μm aluminium oxide particles followed by the application of silane (Group AMP), silane (Group MP), and air-abraded with 30 μm silica-coated aluminum oxide particles followed by the application of silane (Group CMP). Each specimen was cemented into an implant abutment using a composite resin cement (Rely X Unicem2). Afterward, the specimens underwent retention testing with a Universal Instron machine. Pull-off forces (N) and modes of failure were registered. Statistical analysis was performed using Mann-Whitney U tests with Bonferroni corrections for multiple tests (α = 0.05).

RESULTS

The median retention force values were 233.27 ±79.28 N for Group Control, 398.59 ±68.59 N for Group MP, 303.21 ±116.80 N for Group AMP, 349.31 ±167.73 N for Group CMP, and 219.85 ± 55.88 N for Group AP. The pull-off forces were significantly greater for Group MP, while the differences between the remaining groups were not statistically significant (P > 0.05). Group AP showed the lowest retention force values among all the groups. Failure modes after the pull-off testing were predominantly adhesive and substrate failure of the AM interim material.

CONCLUSIONS

The surface treatment of the intaglio AM crown tested significantly influenced the retention force values measured. Pre-treatment with an MDP-containing silane improved the retentive force values computed, whereas pre-treatment with 50-μm Al2 O3 air-particle abrasion alone is not recommended prior to cementation on a titanium-based implant abutment.

Wear behavior at margins of direct composite with CAD/CAM composite and enamel

OBJECTIVES

The aim was to investigate the two-body wear at the marginal area between direct filling composites and substrate of CAD/CAM composites or enamel.

MATERIALS AND METHODS

Flat specimens were prepared from CAD/CAM composites (CERASMART 270 and SFRC CAD) and bovine enamel. A box-shaped cavity cut into CAD/CAM composites and enamel surfaces was made. The prepared cavity in CAD/CAM composites was treated with a primer, while in enamel, the cavity was treated with an adhesive. Three conventional composites (Universal Injectable, G-aenial A'Chord, and Filtek Bulk Fill) and one short fiber composite (everX Flow) were placed and cured in the prepared cavities. A two-body wear test was conducted with 15,000 chewing cycles using a dual-axis chewing simulator. The specimens (n = 5/per group) were positioned to produce wear (load = 20 N) across the marginal area between filling composites and substrates. The wear depth was analyzed using a 3D optical profilometer. SEM was used to evaluate the wear behavior and margins between the filling and substrate materials.

RESULTS

All composites used displayed different wear behavior (20-39 µm) (p < 0.05). The highest wear values were recorded for A'Chord and Filtek, while the lowest values were for Injectable and CERASMART 270. The data analysis showed that the wear behavior of substrate materials depends on the filling materials used at margins (p < 0.05). The marginal breakdown was seen only between bovine enamel and filling composites.

CONCLUSIONS

The use of the two-body wear simulation method revealed important information about the behavior of the filling composites at the marginal area with CAD/CAM composites or bovine enamel substrates.

CLINICAL RELEVANCE

The marginal breakdown related to the material combination at the bonding region.

Effect of Different Surface Treatments on Repair Bond Strength of CAD/CAM Resin-Matrix Ceramics

The purpose of this study was to investigate the influence of different surface treatment methods on the micro-tensile bond strength (μTBS) of resin-matrix ceramic (RMC) blocks repaired with resin composite. Three different prefabricated RMC blocks including Lava Ultimate (LU), Grandio Blocs (GB), and Shofu Block HC (HC) were thermo-cycled and divided into five surface treatment groups: Control (C), bur grinding (G), airborne particle abrasion (APA), Er,Cr:YSGG laser irritation (LI), and APA combined with LI (APA+LI). After surface treatments, topographic alterations were examined by scanning electron microscopy. Then, Universal Adhesive (Single Bond Universal) was applied and repair was simulated with nanohybrid composite (Grandio SO). Bonded specimens were cut into 1 mm2 sized beams (n = 16) and a μTBS test was conducted by using a universal test machine. Fracture types were evaluated by using a stereomicroscope. The bond- strength data was evaluated by two-way ANOVA and Tukey post-hoc test (α = 0.05). The μTBS values were significantly affected by the surface treatment variable and the interaction terms of the variables (p ≤ 0.001). However, no significant effect of RMC type was detected (p > 0.05). Among all materials, GBAPA+LI indicated the highest µTBS value. Except for the GBC, all surface treatments showed clinically acceptable bond-strength values. However, the surface treatments applied to GB and LU before the repair processes increased the repair bond-strength values while causing a negative effect for HC. In addition, LI and APA+LI can be applied as an alternative route compared to other procedures recommended by the manufacturer for surface preparation in intraoral RMC repair.

Influence of mechanical and chemical pre-treatments on the repair of a hybrid ceramic

OBJECTIVES

This study aimed to investigate the influence of the respective mechanical and chemical pre-treatments on the composite repair of a CAD/CAM hybrid ceramic using a microtensile bond strength test (μTBS).

METHODS

15 CAD/CAM Blocks of Vita Enamic (VE) were randomly sectioned into three mechanical pre-treatments: (1.) Diamond bur (D), (2.) Airborne abrasion (A), (3.) Tribochemical silica coating (T) and subsequently five chemical pre-treatments: (1.) Clearfil SE Bond Bond (B; negative control), (2.) ESPE Sil (S), (3.) Clearfil Ceramic Primer Plus (CPP), (4.) Clearfil Repair (CR) and (5.) Scotchbond Universal (SCB). Per block, n = 20 specimens were sawn. Half of the specimens were randomly selected and subjected to an immediate bond strength test, while the other half was subjected to artificial aging for 6 months 180 days at 37 °C and subsequent thermocycling of 5000 cycles. A μTBS was performed and data (MPa) were compared in one-way and two-way ANOVA and Tukey's HSD. Paired-t-test was used for artificial aging (α = 0.05). Debonded specimens were analyzed of for failure modes with a stereomicroscope (SEM).

RESULTS

The results of one-way ANOVA for the fifteen fastening procedures after aging indicated significant differences according to SCB-A and CPP-T. Two-way ANOVA after aging observed inferior bond strength for SCB. No differences were observed for mechanical pre-treatments. Artificial aging showed a significant reduction in bond strength on most of the fastening procedures.

SIGNIFICANCE

SCB showed the lowest bond strength values besides B, S, CPP, and CR. MDP and silane are both suitable for the repair of VE.

Effects of different universal adhesives and surface treatments on repair bond strength between resin composites

OBJECTIVE

This study aimed to evaluate the effects of different universal adhesives and surface treatments on the repair bond strength between resin composites.

MATERIALS AND METHODS

A total of 220 composite samples were divided into three groups according to the adhesive resin to be applied: 1) Scotchbond Universal, 2) G-Premio Bond, and 3) Peak Universal Bond. They were then divided into seven subgroups according to surface treatments (n = 10): A) air abrasion, B) air abrasion+silane, C) hydrofluoric acid, D) hydrofluoric acid+silane, E) air abrasion+hydrofluoric acid+silane, F) silane, and G) no surface treatment (negative control). After surface treatment, a repair composite was applied. Samples aged in the thermocycle were subjected to micro-tensile bond strength testing. Cohesive strength values of 10 non-aged composite blocks were used as a positive control. Kruskal-Wallis and one-way ANOVA tests were used for statistical evaluation. Fractured surfaces were evaluated using a scanning electron microscope.

RESULTS

In Scotchbond Universal and G-Premio Bond, the mean micro-tensile bond strength value of the no surface treatment subgroup was significantly lower than that of the positive control. All subgroups of Peak Universal Bond showed similar values to the positive control.

CONCLUSION

While Scotchbond Universal and G-Premio Bond required mechanical roughening before adhesive application, Peak Universal Bond did not require any surface treatment.

CLINICAL SIGNIFICANCE

Different universal adhesives may show different repair bonding strengths with different surface treatments. Since achieving a standard in this regard can be associated with many independent factors, clinicians should determine how to apply the adhesive they use most effectively with the most appropriate surface treatment based on their own clinical experience.

Composite repair: On the fatigue strength of universal adhesives

OBJECTIVES

To determine whether the composition of universal adhesives and the use of silane coupling agents could affect the fatigue strength of composite repair.

METHODS

Composite samples were aged in water at 37 °C for 90 days and bonded to fresh composite to produce twin-bonded bar-shaped composite specimens (2 × 2 × 12 mm). Five universal adhesives, a multistep composite repair system and a hydrophobic solvent-free resin associated to a separate silane coupling agent application were used for bonding. Composite samples were tested under 4-pointflexure initially at quasi-static loading (n = 12) followed by cyclic loading (n = 25). The stress-life fatigue behavior was evaluated following the staircase method at 4 Hz. The unfractured side of cyclic loaded beams were evaluated under SEM to determine crack initiation sites. Fatigue data was analyzed by ANOVA and Tukey test and Wilcoxon Rank Sum Test (α = 0.05).

RESULTS

Bonding protocols were unable to restore the cohesive strength of the nanofilled composite (p < 0.05). Fatigue testing was more discriminative to reveal discrepancies in composite repair than conventional quasi-static loading. While the composition of universal adhesives affected composite repair potential, the highest endurance limits occurred for the separate silane coupling agent application. Crack propagation sites were mostly located on the aged composite surface.

SIGNIFICANCE

Although a trend for simplification invariably overruns current adhesive dentistry, composite repair using solely universal adhesives may result in inferior repair potential. The additonal use of silane coupling agents remains as an important procedure in composite repairs.

Surface Characterisation of Dental Resin Composites Related to Conditioning and Finishing

Due to the little information related to surface processing and conditioning of resin matrix ceramic materials previous glazing, the main purpose of this in vitro study was to investigate the effect of different surface treatments on the surface morphology of different resin composite materials. Five types of resin composite CAD-CAM materials: a resin composite ceramic Vita Enamic (E) and four types of nanoparticle-filled resins, like Lava Ultimate (L), Cerasmart (C), Shofu HC (S), Hyramic (H) were taken into consideration. Specimens received the following surface treatment protocols: conventional polishing [p], polishing and glazing [pg], conditioning with CoJet [c], conditioning with CoJet and glazing [cg], sandblasting [s], sandblasting and glazing [sg], etching [e], etching and glazing [eg]. Surface roughness was analyzed for all samples and nanosurface topographic characterization was made by Atomic Force Microscopy. The highest roughness was registered for sandblasted surfaces [s], followed by tribochemical silica airborne particle abrasion [c], and etching [e]. A very strong correlated conditioning behavior of resin nanoceramic materials, like L, C and S samples was found. The microroughness decreased thus [s] > [c] > [e]. These are moderate correlated with H, and are moderate negative correlated to E, where e is more efficient. Three-dimensional images indicated visible grain boundaries after conditioning, for all materials. After polishing and glazing, surfaces became smoother. For all tested conditioning and finishing methods, surface roughness values were within clinically acceptable limits. Finishing by polishing was proved to be a good choice for all materials taken into consideration, polishing and glazing likewise, excepting Hyramic. For Enamic and Shofu HC sandblasting or tribochemical conditioning and glazing and for Hyramic polishing and glazing are not the best options, related to nanoroughness values. Referring to the nanosurface topography, for Enamic, Cerasmart and Hyramic, glazing would be the method of choice, associated with the adequate conditioning method for each material.

Shear-bond strength and optical properties of short fiber-reinforced CAD/CAM composite blocks

The aim of this study was to assess the shear-bond strength (SBS) of resin-luting cement to experimental short fiber-reinforced CAD/CAM composite (SFRC) compared to conventional CAD/CAM (Cerasmart 270), 3D printed (GC TEMP PRINT, Pro3dure GR-17), and laboratory (Gradia Plus) composites. Moreover, translucency parameter values and light transmission were evaluated. For each of the five types of composites, discs were prepared (n = 16/group) and divided into subgroups (n = 8/group) according to surface treatment protocol (hydrofluoric acid or air-particle abrasion). SBS test was performed using universal testing machine until failure, and failure modes were visually analyzed. Translucency parameter and curing-light transmission values through 1, 2, and 3 mm thickness were quantified using spectrophotometry and the MARC resin calibrator, respectively. Scanning electron microscopy (SEM) was used to examine the CAD/CAM composites after surface treatment. Composite type and surface treatment had a significant effect on SBS. Laboratory composite showed the highest SBS value (22.4 MPa). Cerasmart 270 exhibited higher translucency parameter values (19.8, 11.0, 5.0) than SFRC (14.5, 5.2, 1.6) at the three composite thicknesses tested. Air-particle abrasion was more effective in enhancing SBS than acid etching. Experimental SFRC CAD/CAM composite showed higher SBS values than Cerasmart 270. For all composites, translucency parameter values and light transmission decreased as thickness increased.

Adhesion of Denture Characterizing Composites to Heat-Cured, CAD/CAM and 3D Printed Denture Base Resins

PURPOSE

To measure the adhesion of the denture characterizing composite to heat-cured, CAD/CAM and 3D printed denture base resins.

METHODS AND MATERIALS

Two different denture characterizing composites with different viscosities (SR Nexco; high viscosity (SR) and Kulzer Cre-active; low viscosity (K)) and three denture base resins (Heat cure, CAD-milled and 3D printed) were investigated. 60 beams (25 × 4 × 3 mm) were fabricated for each denture base resin; 30 were bonded to SR and 30 to K to form a beam 50 × 4 × 3 mm. These were further divided (n = 10/group) to simulate the effects of 0, 6, and 12 months intraorally via thermocycling. The beams were subjected to a 4-point bend test using the chevron-notched beam method. Fracture toughness K_1C (MPa ·m^1/2 ) and flexural bond strength (MPa) were calculated. All specimens were analyzed for the mode of failure under the light microscope and selected specimens under scanning electron microscope. Results were statistically analyzed using ANOVA (SPSS Ver 25).

RESULTS

The mean K_1C was highest for the SR composite bonded to the heat-cured denture resin group (0.28 ± 0.11), followed by CAD/CAM (0.18 ± 0.04) and 3D printed groups (0.23 ± 0.16). Differences were not statistically significant (p = 0.268). Within each group, aging showed no statistical significance between the mean K_1C and flexural bond strength (p = 0.209). The mean K_1C for the K composites bonded to the three different denture bases were significantly lower compared to the SR group (p < 0.001). The mean K_1C for the heat-cured denture resin group was (0.21 ± 0.1), followed by CAD/CAM (0.13 ± 0.04) and 3D printed groups (0.03 ± 0.02). Within each of the K group, aging showed a statistical significance for both the mean K_1C and flexural bond strength (p = 0.002).

CONCLUSION

The high viscosity SR showed significantly higher K1C and flexural bond strength to the lower viscosity K when bonded to heat-cured, CAD-milled and 3D printed denture base resins. Heat-cured denture base resins produced the highest K_1C and flexural bond strength when bonded to two different types of characterizing composites.

Bonding performance of dispersed filler resin composite CAD/CAM blocks with different surface treatment protocols

The effect of various pretreatments on the bonding of a resin cement to resin-composite CAD/CAM blocks (RCBs) was examined. The surface of dispersed-filler RCBs (DF-RCBs) and a polymer infiltrated ceramic network RCB (PICN-RCB) was roughened using hydrofluoric acid etching (HF) or sandblasting, and followed by silanization and/or universal adhesive (UA) application. Microtensile bond strength (µTBS), surface roughness parameters (arithmetical mean height (Sa); developed interfacial area ratio (Sdr)), and critical surface energy (γ_c) were determined. For most DF-RCBs, the highest µTBS was obtained using HF+UA. UA application to DF-RCBs resulted in similar or higher µTBS compared to silanization, which indicates that silane treatment is not crucial for DF-RCBs, especially after HF. In contrast, the highest µTBS to PICN-RCB was obtained with silanization. Both roughening pretreatments significantly increased the surface roughness parameters and the γ_c of all RCBs. The γ_c was positively correlated with Sa (r=0.756, p<0.001) and Sdr (r=0.837, p<0.001).

Influence of different surface treatments and universal adhesives on the repair of CAD-CAM composite resins: An in vitro study

STATEMENT OF PROBLEM

The repairability of computer-aided design and computer-aided manufacturing (CAD-CAM) composite resins might be adversely affected by the high degree of matrix polymerization that occurs during their manufacturing process. However, information on their repairability is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the microtensile bond strength of CAD-CAM composite resins subjected to simulated repair procedures by using varying surface treatments and universal adhesives.

MATERIAL AND METHODS

Four different CAD-CAM blocks (Brilliant Crios, Lava Ultimate, Shofu Block HC, and Vita Enamic) were thermocycled (5000 times, 5/55 °C) and divided into 4 groups according to the surface treatment: control, 9% hydrofluoric acid etching, aluminum oxide airborne-particle abrasion, and tribochemical silica airborne-particle abrasion. After surface treatments, the surface roughness was measured with a nanoindenter and further examined with scanning electron microscopy. After the application of 3 different universal adhesives (Clearfil Universal Bond, Prime&Bond Universal, and Single Bond Universal), the specimens were subjected to a simulated repair process with composite resin. Bonded specimens were cut into 1 mm² beams, and microtensile bond strength values were determined until failure at a crosshead speed of 0.5 mm/min. The bond strength data were analyzed with 3-way analysis of variance, and surface roughness data were analyzed with 2-way analysis of variance tests. Pairwise analyses were performed with the Tukey test (α=.05).

RESULTS

All surface treatments effectively improved repair microtensile bond strength values compared with the control (P<.05). Aluminum oxide airborne-particle abrasion had similar mean bond strength values compared with tribochemical silica airborne-particle abrasion (P>.05). Among the CAD-CAM blocks treated with hydrofluoric acid etching, Vita Enamic had the highest mean bond strength values. The highest mean microtensile bond strength repair values with the highest cohesive failure rates were found with the silane-containing universal adhesive (Single Bond Universal).

CONCLUSIONS

Surface treatment with aluminum oxide airborne-particle abrasion and tribochemical silica airborne-particle abrasion produced successful repair results for aged resin nanoceramics, whereas hydrofluoric acid etching can be used for aged hybrid ceramic repair. Silane-containing universal adhesive reported increased bond strength. Application of universal adhesive after surface treatment is recommended to increase repair strength.

Silane Effect of Universal Adhesive on the Composite-Composite Repair Bond Strength after Different Surface Pretreatments

This study investigated the impact of a separate silanization step on the repair bond strength of composite substrates using a universal adhesive after various mechanical surface treatments. Composite specimens were aged and exposed to the following mechanical roughening treatments: diamond bur abrasion, aluminum oxide sandblasting, or silica coating. The specimens were then either left untreated or conditioned with universal adhesive (Scotchbond Universal), or a silane coupling agent was applied before the use of the universal adhesive or a conventional adhesive (Optibond FL). The conditioned surfaces and fresh substrate (positive control group) were covered with repair composite, and microtensile bond strength testing was performed. The significantly highest bond strength was obtained in the positive control group. Repair bond strength of the universal adhesive applied after a separate silanization step was similar to that without prior silanization, independent of the mechanical surface treatment. Moreover, after silica coating, no significant differences in the repair bond strength were detected among the different adhesive treatments. In conclusion, a separate silanization step before surface conditioning with the universal adhesive does not enhance the repair bond strength. On silica-coated composite substrates, repair bond strength values of the universal adhesive were similar to those of the conventional adhesive.

Effect of surface treatments and universal adhesive application on the microshear bond strength of CAD/CAM materials

PURPOSE

The aim of this study was to evaluate the microshear bond strength (µSBS) of four computer-aided design/computer-aided manufacturing (CAD/CAM) blocks repaired with composite resin using three different surface treatment protocols.

MATERIALS AND METHODS

Four different CAD/CAM blocks were used in this study: (1) flexible hybrid ceramic (FHC), (2) resin nanoceramic (RNC), (c) polymer infiltrated ceramic network (PICN) and (4) feldspar ceramic (FC). All groups were further divided into four subgroups according to surface treatment: control, hydrofluoric acid etching (HF), air-borne particle abrasion with aluminum oxide (AlO), and tribochemical silica coating (TSC). After surface treatments, silane was applied to half of the specimens. Then, a silane-containing universal adhesive was applied, and specimens were repaired with a composite, Next, μSBS test was performed. Additional specimens were examined with a contact profilometer and scanning electron microscopy. The data were analyzed with ANOVA and Tukey tests.

RESULTS

The findings revealed that silane application yielded higher µSBS values (P<.05). All surface treatments were showed a significant increase in µSBS values compared to the control (P<.05). For FHC and RNC, the most influential treatments were AlO and TSC (P<.05).

CONCLUSION

Surface treatment is mandatory when the silane is not preferred, but the best bond strength values were obtained with the combination of surface treatment and silane application. HF provides improved bond strength when the ceramic content of material increases, whereas AlO and TSC gives improved bond strength when the composite content of material increases.

Universal dental adhesives: Current status, laboratory testing, and clinical performance

Increasing demand for simplified and user-friendly adhesive systems has led to the development of a new class of adhesives termed as Universal Adhesives (UAs). The term "Universal" reflects manufacturers' claims that these adhesives can be applied with any adhesion strategy and offer the versatility of use with a variety of direct and indirect restorative materials. The aim of this review was to synthesize the literature regarding the current status of UAs, their adhesion potential to various substrates and their performance in different restorative situations. In vitro studies, clinical trials and systematic reviews were identified utilizing controlled vocabulary and keyword searches in Medline and EMBASE databases. About 282 studies (272 in vitro studies; 11 clinical studies) were included. Available laboratory and clinical evidence does not support the claim that UAs can be used with any adhesive strategy. Although, they can chemically bond to various tooth and direct/indirect restorative substrates, the stability of this bond is material-dependent and subject to hydrolytic degradation. Hence, additional measures are still needed to ensure long-term durability. which undermines the versatility of UAs. The lack of long-term data regarding the clinical performance of UAs further complicates clinical decision-making. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 2121-2131, 2019.