The Journal of Adhesive Dentistry

Purpose: To evaluate the effects of C-factor on the bond strength of universal adhesives to floor and wall dentin in class-I composite restorations using a bulk-fill composite. Materials and Methods: 108 non-carious humans third molars were randomly divided into four groups as follows: flat wall, flat floor, cavity wall, and cavity floor (n = 36). Then, each group was subdivided into three subgroups according to the type of adhesive used: Single Bond Universal, G-premio Bond (both universal adhesives), or Adper Single Bond 2 (an etch-and-rinse adhesive). After the bonding procedure, X-tra fill resin composite was applied in bulk to build up the flat surfaces or fill the cavities.Then the teeth were sectioned into 1-mm2 sticks and microtensile bond strength (µTBS) was measured using a universal testing machine. µTBS (MPa) was analyzed by one-way, two-way, and three-way ANOVA using SPSS Version 23 (α = 0.05). Results: Interactions between adhesives and bonding surfaces, as well as C-factor and bonding surfaces showed statistically significant differences, but the interaction between the C-factor and type of adhesive was not statistically significant. The comparison of bonded surfaces including the flat wall and the flat floor in Adper Single Bond 2 was statistically significant (p < 0.05), except for the cavity wall and cavity floor. Conclusion: Regardless of the type of adhesives, the C-factor reduced the µTBS of the composite resin to dentin. Adper Single Bond 2 mediated higher µTBS than did the universal adhesives G-premio Bond and Single Bond Universal. Keywords: C-factor, microtensile bond strength, universal adhesive

Purpose: To compare the effect of active pre-conditioning with 17% ethylenediaminetetraacetic acid (EDTA) vs 37% phosphoric acid (PA) on the resin-enamel microshear bond strength (μSBS), enamel-etching pattern, and in situ degree of conversion (in situ DC) of four universal adhesives on sound and fluorotic enamel. Material and Methods: In this study, 448 extracted human molars (224 without fluorosis and 224 with fluorosis) were sectioned into four parts and divided into 16 experimental groups based on the enamel surface (sound or fluorotic enamel), adhesive (Clearfil Universal Bond [CUB], Futurabond U [FBU], iBond Universal [IBU], or Scotchbond Universal [SBU]), and enamel conditioning agent (PA or EDTA). The specimens were stored for 24 h and tested under shear stress at 1.0 mm/min to determine the μSBS. The adhesive-enamel interfaces were evaluated for in situ DC using micro-Raman spectroscopy. The enamel-etching pattern was evaluated using a scanning electron microscope. The µSBS and in situ DC data were analyzed separately using three-way ANOVA and Tukey’s post-hoc test (α = 0.05). Results: Sound enamel showed higher μSBS and in situ DC compared to fluorotic enamel (p < 0.05). However, no significant difference was observed for μSBS, in situ DC (p > 0.05), or etching patterns when PA and EDTA etching were compared in sound and fluorotic enamel. Moreover, CUB and SBU showed higher mean μSBS than did FBU and IBU in both sound and fluorotic enamel (p < 0.05). Conclusions: Compared to PA, active pre-conditioning with EDTA showed similar μSBS and enamel etching patterns for all the adhesives in fluorotic enamel, without compromising the in situ DC. Keywords: universal adhesives, ethylenediaminetetraacetic acid, fluorosis, dental bonding

Purpose: This study investigated the ability of two chewing simulation devices to emulate in vitro the clinical deterioration observed in anterior composite restorations in severe tooth-wear patients. Materials and Methods: Advanced tooth wear was simulated in bovine incisors, which were restored with palatal and buccal direct composite veneer restorations. The incisal edges of restorations were subjected to 960K cycles of either compressive loading (Biocycle-V2; 125 N at 2 Hz) or wear and mechanical loading (Rub&Roll, 30 N at 20 rpm). Surface degradation was rated using FDI scores to compare the chewing devices (Fisher’s test, α = 0.05). Topography and deterioration of restorations was analyzed using SEM. The ability to emulate the deterioration was investigated by comparing the surface degradation observed in vitro with the clinical degradation observed in restorations placed in severe tooth-wear patients after 3.5 years. Results: Distinct degradation patterns were observed between the simulation devices: Biocycle-V2 generated deterioration that was not comparable to the clinical situation, including contact damage, minor wear, and localized roughening. The degradation caused by Rub&Roll was more similar to the in vivo situation, including wear facets, chipping, delamination, staining, and marginal ditching. The FDI scores were different between the chewing devices for surface/marginal staining, material/retention, and marginal adaptation (p ≤ 0.003). SEM analysis showed microcracking at the interface between composite layers at the incisal edges. Conclusions: The Rub&Roll chewing device was able to emulate the clinical deterioration observed in anterior restorations in severe tooth-wear patients and thus may be used as an oral-cavity simulation method, contributing to translational research. Keywords: dental restoration, degradation, tooth wear, chewing simulation methods, FDI scores

Purpose: To evaluate through a systematic review and meta-analysis the bonding performance of adhesive materials to silver diamine fluoride (SDF)-treated dentin. Materials and Methods: Studies located in PubMed, Web of Science, LILACS, and Scopus up to September 2020, which compared the bond strength of adhesives (AD) or glass-ionomer cement (GIC) to SDF-treated and untreated (control) dentin were included. Mean differences were estimated separately by material and dentin condition (sound or caries-affected), with a random-effects model, at a 5% significance level. Results: Twenty-two studies, including 11 new studies not included in our previous systematic review, met the eligibility criteria, and 21 studies were considered in the meta-analyses. SDF dentin pretreatment did not influence the bonding of GIC (Z = 0.53; p = 0.60), independent of dentin condition. SDF treatment significantly impaired the bonding of AD (Z = 2.43; p = 0.01). A rinsing step after SDF eliminated this effect in sound dentin (Z = 1.82; p = 0.07) and increased the bond strength to caries-affected dentin (Z = 2.14; p = 0.03). Conclusion: SDF pretreatment does not influence the bond strength of GIC. A rinsing step after SDF application can improve the bond strength of AD to caries-affected dentin. Keywords: bond strength, adhesion, glass-ionomer cement, adhesive, silver diamine fluoride

Purpose: To experimentally assess the effect of regenerative heat treatment (HT) on yttria-stabilized tetragonal zirconia polycrystalline ceramic (Y-TZP) to guarantee veneer adhesion strength. Materials and Methods: One surface of bar-shaped Y-TZP specimens was ground (G) with a diamond stone, while the control samples (C) were not. Groups C900 and G900 were submitted to HT at 900°C for 60 min, whereas groups C1000 and G1000 were submitted to HT at 1000°C for 30 min. The treated surfaces were characterized by x-ray diffractometry (XRD), scanning electron microscopy (SEM), and optical and mechanical profilometry. The energy release rate through interface fracture was determined by a four-point bending test on notched Y-TZP veneered specimens. XRD was refined by the Rietveld method, mean roughness (Ra) and energy release rate were submitted to two-way ANOVA (α = 0.05), and the images were analyzed descriptively. Results: The monoclinic phase (vol%), means of Ra (µm), and the energy release rate (J/m2) were, respectively: C = 1.2/0.17/6.8, C900 = 0.0/0.18/6.6, C1000 = 0.0/0.18/7.6, G = 2.6/1.16/8.3, G900 = 0.0/1.07/8.0, and G1000 = 0.0/1.01/5.7. The surface fraction of monoclinic zirconia increased by grinding and decreased by HT. Ra also increased after grinding (p < 0.005) but remained unaltered after HT (p = 0.22). Increased irregularity was observed in the G groups and a subtle smoothing of the surface after HT. After the fracture of the bilayers, a residual amount of porcelain could be seen on the zirconia surface in all groups. The energy release rate was statistically equal among all groups (p > 0.05). Conclusion: Heat treatment after grinding completely restored the tetragonal phase of zirconia without altering the energy release rate during interfacial fracture. Keywords: zirconia, dental prosthesis, x-ray diffraction, surface properties, heat treatment

Purpose: To evaluate the influence of dimethyl sulfoxide (DMSO) solutions used as dentin pretreatments on microtensile bond strength (µTBS), as well as the dentin/restoration interface micromorphology of a universal adhesive in etch-and-rinse or self-etch mode. Materials and Methods: Eighty blocks of dentin were submitted to acid conditioning with 35% phosphoric acid (etch-and-rinse), or not (self-etch), and distributed among the treatments (n = 10): CON: Scotchbond Universal/3M Oral Care; DMSO: pretreatment with DMSO; DMSO/water: pretreatment with DMSO in water (1:1); DMSO/ethanol: pretreatment with DMSO in ethanol (1:1). Microtensile bond strength and failure tests were performed after 24-h and 6-month storage. The tooth-restoration interface was evaluated using scanning electron microscopy to assess the hybrid layer formed. Results: The interaction between treatments, storage time, and etching modes was not significant for µTBS (p = 0.2469). The DMSO, DMSO/water and DMSO/ethanol pretreatments did not affect µTBS values at either time point (p = 0.8732). Aging decreased µTBS over time only for the etch-and-rinse strategy, although the groups presented higher microtensile bond strengths in etch-and-rinse mode than in self-etch mode at both time points (p < 0.0001). The micromorphological images of the interface showed that different DMSO pretreatment solutions did not impair hybrid layer formation. Conclusion: The use of dentin pretreatments containing DMSO did not improve the bonding or the micromorphology of a universal adhesive in etch-and-rinse or self-etch modes. Keywords: aging, ethanol, hybrid layer, micromorphology, microtensile bond strength

Purpose: The present study investigated the influence of simulated intraoral conditions (increased temperature and humidity) on two different surface pretreatment methods to repair a lithium-disilicate glass-ceramic (LDS). Materials and Methods: A total of 540 rectangular lithium-disilicate glass-ceramic bars were manufactured (3 x 7 x 9 mm; IPS e.max CAD, Ivoclar Vivadent). Further specimen preparation was performed in an incubator with controlled relative humidity (RH) and temperature to simulate three different environmental settings: laboratory conditions (LC, n = 180, 23°C, 50% RH), rubber-dam conditions (RC, n = 180, 30°C, 50% RH) or oral conditions (OC, n = 180, 32°C, 95 ± 5% RH). One-third of the bars under each condition (n = 60) were grit blasted (GBL) with alumina (35 µm at 1 bar pressure for 10 s and a working distance of 4 ± 1 cm) and primed (60 s, Monobond Plus, Ivoclar Vivadent). Another third (n = 60) were pretreated with a self-etching glass-ceramic primer (MEP, Monobond Etch & Prime, Ivoclar Vivadent). One group without surface pretreatment (n = 60, NoPT) served as a control. All pretreated surfaces were coated with Heliobond (Ivoclar Vivadent). Two bars from the same pretreatment method were luted perpendicular to each other with a resin composite to form a square adhesion area of 9 mm2 (TetricEvo Ceram, Ivoclar Vivadent), and light cured for 20 s on each side (1200 mW/cm2, Bluephase 20i, Ivoclar Vivadent). All specimens were stored for 24 h in distilled water at 37°C. Half of the specimens from each environmental setting and pretreatment method (n = 15) were thermocycled (TC, 5000 cycles, 5/55°C, 30-s dwell time), and tensile bond strength (TBS) testing was performed for all groups using an x-bar rope-assisted set-up. Data were statistically analyzed using two-way ANOVA (α = 0.05) with Bonferroni adjustment. Results: Regardless of the environmental and storage conditions (24 h or TC), MEP showed a significantly higher mean TBS than GBL. A decrease in TBS was recorded in specimens under OC compared to RC and LC for both pretreatment methods independent of the storage condition. No significant difference in mean TBS was found between RC and LC within the MEP pretreatment group for the 24 h stored and thermocycled specimens. For all MEPs and GBLs, TC reduced the mean TBS in all environmental conditions. The NoPT groups showed no adhesion regardless of environmental or storage conditions. Conclusions: Increased temperature and high humidity significantly reduced TBS. However, MEP was less sensitive to environmental influences than GBL, which makes it a promising candidate for intraoral ceramic repair. These findings suggest that clinical intraoral repair of lithium-disilicate glass-ceramics should be performed using a rubber-dam, primarily when using GBL. Keywords: self-etching glass-ceramic primer, grit blasting, silanization, lithium-disilicate ceramic, tensile bond strength, thermocycling

Purpose: To evaluate the long-term effect of different surface treatments on the repair microtensile bond strength (µTBS) of resin composite using a universal adhesive. Materials and Methods: Thirty-six resin composite blocks were fabricated and aged in 37°C distilled water for 1 month. The blocks were randomly assigned to different surface treatments: no treatment (control); diamond bur grinding (D); diamond bur + phosphoric acid cleaning (DP); diamond bur + silane application (DSi); diamond bur + phosphoric acid + silane (DPSi); and grit blasting with 50 µm H3PO4 particles + phosphoric acid + silane (APSi). Thereafter, Single Bond Universal adhesive was applied and repaired with the same composite. Composite-composite stick-shaped specimens were fabricated and subjected to the µTBS test either after 37°C water storage for 24 h or thermocycling for 10,000 cycles. Roughness of different surface-prepared specimens was measured by profilometer. Data were analysed using ANOVA and Duncan’s post-hoc test (α = 0.05). Failure mode and micromorphology of different surface-prepared specimens were observed with SEM and EDS analysis. Results: The highest µTBS was found in DPSi group at 24 h, and was significantly higher than others. The bond strengths in all thermocycled groups were significantly lower than those measured at 24 h. The highest µTBS was also found in the DPSi group, but this did not significantly differ from the DSi group. Conclusion: Thermocycling significantly reduced the repair bond strength. Diamond bur roughening with application of silane and universal adhesive yielded the highest repair bond strength for the aged resin composite. Keywords: bond durability, resin composite repair, surface treatments, universal adhesive

Purpose: To evaluate the clinical performance of direct composite restorations using nanohybrid and nanofill composite materials in anterior teeth in patients with amelogenesis imperfecta (AI). Materials and Methods: The study included 15 patients with AI aged 14–30 years. During the study, the patients received anterior direct composite laminate veneer restorations using either a nanohybrid (Clearfil Majesty ES-2 and Clearfil Universal Bond, Kuraray Noritake) or a nanofill resin composite (Filtek Ultimate Universal Restorative and Single Bond Universal Adhesive, 3M Oral Care). The restorations were evaluated according to the modified USPHS criteria at baseline and at 1-, 2-, 3- and 4-year follow-up periods. Results: The cumulative success rate of anterior restorations was 80.5% for nanohybrid and 92.5% for nanofill composite after 4 years. Eight restorations with nanohybrid and three restorations with nanofill resin composites failed. Ten restorations failed due to fracture; the fracture rate was 12.3%. Statistically significant differences were found between nanohybrid and nanofill composites regarding marginal discoloration and surface texture after 3 years. Furthermore, statistically significant differences were observed with respect to color match after 4 years. Conclusion: The use of a nanohybrid or nanofill composite for anterior direct restorations in patients with AI was observed to be satisfactory, based on the rate of ideal and clinically acceptable restorations. The primary reason for restoration failure was fracture. The failure rate of nanohybrid composite restorations was higher than with nanofill composite restorations with respect to survival and marginal adaptation criteria. Keywords: amelogenesis imperfecta, dental enamel, composite resin, dental restoration, prospective study

Purpose: To evaluate the effects of different smear layers on the microtensile bond strength (µTBS) of a reference two-step self-etch adhesive and two universal adhesives. Materials and Methods: Mid-coronal dentin of 90 teeth was exposed and divided into three bur groups (coarse diamond, fine diamond, or tungsten carbide). Each bur-prepared group was further divided into three adhesive groups: Clearfil SE Bond (SE, Kuraray Noritake), Single Bond Universal (SB; 3M Oral Care), and G-Premio Bond (GP, GC). After adhesive application, 4-mm-thick resin composites were built up. Half of the teeth in each bur-adhesive group were used in immediate µTBS testing, and the others were tested after thermal aging (n = 5). Rectangular sticks were prepared using a low-speed diamond saw. For each tooth, 6 central sticks were used in the µTBS test. Statistical analysis was performed using three-way ANOVA and Bonferroni tests (α = 0.05). Results: SE presented higher µTBS than universal adhesives and SB presented higher µTBS than GP regardless of dentin surface preparation and thermal aging (p ˂ 0.05). For SE and SB, the tungsten carbide bur demonstrated higher immediate and aged µTBS than did the extra-fine diamond bur (p ˂ 0.05). The immediate µTBS was similar for GP with all bur types (p ˃ 0.05); the tungsten carbide and extra-fine diamond burs presented higher µTBS than did the coarse-diamond bur after thermal aging (p ˂ 0.05). Conclusion: Dentin surface preparation and adhesive type had significant effects on µTBS. The smear layer created with an extra-fine diamond or tungsten carbide bur is favorable when mild and ultra-mild self-etch adhesives are used. Keywords: smear layer, universal adhesive, self-etch adhesives, bond strength, microtensile bond strength

Purpose: To evaluate push-out bond strength (PBS) and interfacial nanoleakage (NL) of adhesively luted fiber posts using different composite cements and polymerization protocols. Material and Methods: 100 premolars were endodontically treated and assigned to the following groups (n=10): RelyX Universal light-cure (3M Oral Care); RelyX Universal self-cure (3M Oral Care); Maxcem Elite Chroma light-cure (Kerr); Maxcem Elite Chroma self-cure (Kerr); Calibra Universal light-cure (Dentsply Sirona); Calibra Universal self-cure (Dentsply Sirona); Multilink Automix light cure (Ivoclar Vivadent); Multilink Automix self-cure (Ivoclar Vivadent); Luxacore Z Dual light-cure (DMG); Luxacore Z Dual self-cure (DMG). Half of the teeth from each group were subjected to the PBS test after 24 h (T0), while the other half was tested after 12 months (T12) of artificial saliva aging. An additional 4 teeth per group were prepared for NL expression. PBS values were analyzed using multivariate ANOVA and Tukey’s post-hoc test. NL scores were analyzed using chi-squared tests (α = 0.05). Results: Statistical analysis revealed that the variables “cement” and “aging” significantly influenced PBS (p < 0.05), but not “polymerization” and “root region” (p > 0.05). Significantly lower PBS values (p < 0.05) were detected for the Calibra Universal groups compared to other cements, while the RelyX Universal groups performed equally well (p > 0.05) or better than other cements (p < 0.05). At T12, PBS values increased in the majority of groups, irrespective of root region (p < 0.05). Differences in NL expression were present at T0, and in general, the aging process increased marginal infiltration. Conclusion: Aging and choice of composite cement influenced PBS, while root region and polymerization protocol seemed to have no influence on posts’ resistance to dislodgment. Keywords: aging, bonding, fiber post, polymerization, composite cement

Purpose: The aim of this prospective study was to evaluate the clinical performance of minimally invasive, CAD/CAM nano-ceramic (composite) restorations in patients with severe tooth wear, the effect of the restorative treatment on the oral health-related quality of life (OHRQoL), and the etiology of tooth wear as a risk factor for restoration failure. Materials and Methods: Patients with generalized severe tooth wear were included. Restorations (LAVA Ultimate, 3M Oral Care) were cemented (RelyX Ultimate, 3M Oral Care) on all teeth and were evaluated after 1 month and 1 year. OHRQoL was assessed via questionnaires at baseline and after 1 year. Differences were evaluated (paired t-test). Two mechanical tooth-wear lesions resulting from tooth-tooth contact, and 3 chemical tooth wear lesions resulting from intrinsic or extrinsic acids dissolving natural hard tooth substance, were evaluated to assess the etiology of tooth wear in association with restoration failure using multilevel logistic regression analyses (p < 0.05). Results: Twenty-one patients (age: 41.7 ± 10.4 years) were evaluated after 1 year (13.5 ± 1.2 months). 568 indirect CAD/CAM restorations were placed. None were replaced or lost. Twelve were repaired and 10 were refurbished. Success rates were 100% to 97.2%. Questionnaires showed a significant positive impact of the treatment on OHRQoL (p < 0.001). The presence of mechanical lesions did not pose a higher risk for restoration failure (p = 0.78). The presence of chemical lesions showed a lower risk of restoration failure (p = 0.002). Conclusion: The use of minimally invasive, CAD/CAM nano-ceramic (composite) restorations in the restorative treatment of severely worn dentitions showed satisfactory results in the short term. Keywords: tooth wear, composite resins, occlusal vertical dimension, dental restoration, oral health-related quality of life, CAD/CAM, oral rehabilitation, restorative materials, minimally invasive

Purpose: To investigate the effects of plasma surface treatments and methyl methacrylate-based adhesives on polyetheretherketone. Materials and Methods: One hundred ten polyetheretherketone specimens were fabricated and divided into five pretreatment groups: group ArP, 100% argon plasma; group ArOP, 50% argon + 50% oxygen plasma; group ArNP, 50% argon + 50% nitrogen plasma; group ArONP, 75% argon + 12.5% oxygen + 12.5% nitrogen plasma; group C, control. Atomic force microscopy and scanning electron microscopy were performed after surface treatments. After topographical surface examinations, Visio.link primer (Bredent) (n = 10) was applied to the surface of half of the samples in each group (n = 20) and the veneering resin was polymerized onto the polyetheretherketone. The shear bond strengths were measured using a universal test machine. Results: The mean bond strengths of the Visio.link primer applied to group ArP and group ArONP (13.9 and 13.6 MPa, respectively) were statistically significantly higher than that of group C (9.0 MPa). The average shear bond strength of the Visio.link subgroups was higher than that of the Visio.link subgroups (p > 0.05). Conclusions: The use of a methyl methacrylate-based adhesive (Visiolink) provides bonding between polyetheretherketone-veneering composites. Different plasma treatments without primer application had no significant effect on bonding. Keywords: polyetheretherketone, surface treatment, shear bond strength, surface roughness, veneering procedure, adhesion in dentistry

Purpose: To evaluate the effects of different hydrofluoric acid (HF) concentrations and etching times on the surface topography, roughness, and resin bond strength to ceramic-coated zirconia (CC), and to compare them with the effects of alumina air-abrasion combined with 10-MDP (AA). Materials and Methods: AA and CC specimens were divided into 12 groups (N = 10). The CC groups were etched with HF at different concentrations (5% or 9.5%) for various durations (0 min, 1 min, 2 min, 3 min, 5 min or 10 min). The surface morphology was analyzed using SEM. Energy-dispersive x-ray spectroscopy (EDS) and x-ray diffraction (XRD) were performed for chemical and crystalline-phase analyses. Surface roughness (Ra) and shear bond strength (SBS) were recorded and statistically analyzed. Results: The SBS of CC groups initially increased, but then decreased with etching time for both HF acid concentrations. The 9.5% HF group displayed more marked topographical changes and higher Ra compared with the 5% HF group for the same etching period. Mean SBS was lower in the AA group compared with the CC groups etched with 5% HF for 2–10 min and 9.5% HF for 1–3 min (p < 0.05). Conclusions: Different HF concentrations and etching times influenced the surface topography, roughness, and resin bond strength of/to ceramic-coated zirconia. Etching with 5% HF for 5 min and with 9.5% HF for 2 min, respectively, provided the highest SBS. Keywords: ceramic-coated zirconia, etching, shear bond strength, surface roughness

Purpose: To investigate the effect of roughness and drying time of dentin as well as the number of coats of a self-adhesive composite-cement primer on the bond strength of self-adhesive composite cement. Material and Methods: Sixty human teeth were prepared and assigned to 12 groups (n = 5), according to three experimental factors: 1) dentin surface roughness, rough or fine, as achieved by 250- and 600-grit silicon carbide papers, respectively; 2) dentin wetness based on air-drying time (5 or 10 s); and 3) the self-adhesive composite-cement primer applications (no-coat, 1-coat, and 2-coat). Composite resin blocks were made with hybrid composite resin (M1 GraceFil) and cemented with G-CEM ONE (both GC). Cement-dentin sticks (12) were prepared, and the microtensile bond strength (μTBS) test was performed. Failure modes were observed with a stereomicroscope (40X), and bonding interfaces were evaluated with confocal laser scanning microscopy (CLSM). Statistical analysis was performed using three-way ANOVA and Tukey’s post-hoc comparisons test (α = 0.05). Results: Dentin roughness (250-grit > 600-grit, p = 0.000), drying time (5-s drying > 10-s drying, p = 0.000), and primer application (no-coat < 1-coat = 2-coat, p = 0.000) had significant effects on bond strength. These factors also showed significant interactions with each other (p = 0.003). The highest μTBS (31.8 ± 3.1 MPa) was observed in the 1-coat/fine roughness/10-s drying group and the lowest μTBS (13.4 ± 2.7 MPa) in the no-coat/coarse roughness/5-s drying group. CLSM showed higher penetration of cement in the primer-coated groups compared to that in the no-coat groups. Conclusion: Bond strength between the self-adhesive composite cement and dentin was higher in the fine-roughness dentin group than in the coarse-roughness dentin group, and in the 5-s drying group compared to the 10-s drying group. Applying a primer to dentin improved bond strength of the self-adhesive composite cement. Keywords: self-adhesive composite cement, self-adhesive composite-cement primer, smear layer, dentin drying time, microtensile bond strength, confocal laser scanning microscopy

Purpose: To determine the interfacial fracture energy (IFE) and stress distribution of Brazil-nut–shaped specimens made of translucent zirconia and resin cement. Materials and Methods: Three types of translucent zirconia were used: 3Y-TZP (high, Vita YZ HT), 4Y-TZP (super, Vita YZ ST), and 5Y-TZP (extra, Vita YZ XT). The adhesive surfaces were air abraded and 10-MDP-based resin cement was used. The cemented Brazil-nut–shaped specimens, with an elliptical defect in the center (as in real Brazil nuts), were thermally aged (5°C–55°C; 40,000 cycles). The IFE test was conducted with a piston to apply compression on the specimen, while the adhesive interface was positioned at four different angles (0, 10, 20, and 30 degrees) to measure the IFE during tensile, shear, and mixed failure modes. All adhesive interfaces were observed to determine failure patterns. The finite element analysis (FEA) was used to calculate tensile and shear stress distributions according to inclinations. Statistical analysis was conducted using the Kruskal-Wallis and Dunn’s post-hoc tests (95%), as well as the Mann-Whitney test (95%) was applied to compare each group regarding the aging factor. Results: According to Kruskal-Wallis and Dunn’s post-hoc tests, there were no statistically significant differences between non-aged (p > 0.05) and aged materials (p > 0.05). However, there was a significant difference between aged and non-aged materials for all inclinations (p < 0.05) (Mann-Whitney test). According to the FEA, the compressive loading of Brazil-nut–shaped specimens at different angles showed a predominance of tensile stress at 0 degrees and shear stress at 30 degrees. Conclusion: The IFE under predominantly shear stresses is higher than when specimens are subjected only to tensile stresses, which allows the interpretation that failures in the oral environmental will probably occur preferentially under tensile stresses, because less energy is needed. All translucent zirconia bonded to resin cement has similar IFE, and thermal aging negatively affects these bonding interfaces. Keywords: zirconia, finite element analysis, fracture, dental materials

Purpose: This in vitro study aimed to investigate the effect of incorporating the semiconductor nanostructured silver vanadate decorated with silver nanoparticles (β-AgVO3) in a dual-cure resin cement on the degree of conversion (DC), microhardness, roughness, color, adhesion properties before and after artificial aging, and antimicrobial efficacy. Material and Methods: Three test groups were established: control (without β-AgVO3), with the incorporation of 2.5% and 5% (by weight) of β-AgVO3 in dual-cure resin cement (Allcem, FGM). The degree of conversion was measured using Fourier transform infrared spectroscopy (FTIR). To evaluate roughness (n = 10), microhardness (n = 10), color (n = 10), and to perform agar disk diffusion (n = 8), disks of 6-mm diameter and 2-mm height were manufactured using the same concentrations. For the color and shear bond strength test (n = 6), orthodontic brackets (Morelli) were used, which were cemented to natural human enamel and evaluated before and after artificial aging via thermocycling at 5°C and 55°C for 1000 cycles. For color measurements, a portable spectrocolorimeter and the CIE-Lab method were used. Data were analyzed using Student’s t-test, ANOVA, and Tukey’s multiple comparisons with significance set at α = 0.05. Results: Semiconductor incorporation did not influence the cements’s DC. The incorporation of 2.5% and 5% of β-AgVO3 resulted in a significant increase in Knoop microhardness and surface roughness. Significant changes were observed in the color of the specimens when the semiconductor was incorporated. Adhesion after aging remained within the clinically recommended values in all groups, and antimicrobial activity was observed against Staphylococcus aureus, Streptococcus mutans, and Enterococcus faecalis at both concentrations tested. Conclusion: It is suggested to incorporate the semiconductor β-AgVO3 in the dual-cure resin cement at both concentrations. Moreover, the physical-mechanical properties remained satisfactory for the proposed application. Keywords: mechanical properties, surface roughness, resin cements, silver vanadate, nanomaterials

Purpose: To compare a self-etch and a two-step etch-and-rinse adhesive in terms of internal and marginal composite-tooth bond failure separately on enamel and dentin/cement at 36–48 months after restoration placement using optical coherence tomography (OCT). Materials and Methods: Twenty-seven patients with two or three class V composite restorations of noncarious cervical lesions 36–48 months after placement were included. The one-step self-etch adhesive Futurabond M ([Voco] group SE, n = 25) and the two-step etch-and-rinse adhesive Solobond M ([Voco] group ER, n = 20) combined with the nanohybrid composite Amaris (Voco) were evaluated. The four-step etch-and-rinse adhesive Syntac classic combined with Tetric EvoCeram (Ivoclar Vivadent) served as the control (n = 18). Spectral-domain OCT (SD-OCT, 1310-nm center wavelength) was applied. Marginal gaps and internal interfacial adhesive defects were quantified in cross-sectional OCT images. Groups were statistically compared using the Friedman/Wilcoxon test (α = 0.05). Results: In enamel, nonsignificantly different percentages of marginal gap formation and internal interfacial adhesive defects were found between the groups (pi ≥ 0.258). In dentin/cement, SE showed significantly less marginal gap formation compared to ER (p < 0.001) and control (p = 0.001), and at the internal dentin-composite interface less adhesive defects were found compared to ER (p < 0.001) and control (p = 0.003). Conclusion: The self-etch adhesive used in the current study appears recommendable for restoration of noncarious cervical lesions with composite. Keywords: class V composite restoration, self-etching adhesive, etch-and-rinse adhesive, OCT, internal interfacial gap formation, quantitative margin analysis. Keywords: class V composite restoration, self-etching adhesive, etch-and-rinse adhesive, OCT, internal interfacial gap formation, quantitative margin analysis

Purpose: To identify the most effective cleaning method for saliva-contaminated zirconia surface before adhesive cementation through a systematic review and meta-analysis. Materials and Methods: PubMed, Scopus, and Web of Science databases were searched to select in vitro studies published through October 2021. Studies that did not perform aging methods, had a sample size less than 5 per group, or did not present a group with zirconia contaminated only with saliva were excluded. Data were extracted and risk of bias was assessed. Statistical analysis comparing the cleaning methods was conducted, and the standardized mean difference was assessed using the R software program. Results: Among 804 potentially eligible studies, 36 were selected for full-text reading, of which 13 were included in qualitative analysis, and 11 of these were subsequently included in the quantitative analysis. A meta-analysis revealed a significant difference in the bond strength between the cleaning methods. Sandblasting with Al2O3  showed a higher bond strength than cleaning solution (Ivoclean, Ivoclar Vivadent) (p < 0.01, I2 = 65%), and both methods promoted higher resin-bond strength to zirconia than water cleaning. In addition, there was no significant difference in the bond strength between alcohol (p = 0.35, I2 = 79%), phosphoric acid (p < 0.23, I2 = 90%), and water cleaning. Conclusion: Sandblasting with Al2O3 seems to be the best method for zirconia surface cleaning before adhesive luting, promoting better resin-bond strength to zirconia. Keywords: adhesion, bond strength, decontamination, dental materials, saliva contamination, surface cleaning, zirconia

Purpose: To describe the digital workflow applied for restoring a severely worn dentition with minimally invasive CAD/CAM resin nano-composite restorations. Materials and Methods: A 40-year-old male in good general health and with full-arch dentition suffered from dentin hypersensitivity and wanted to improve the esthetics of his worn anterior teeth. The dental wear can be described as general, grade 3, according to the Tooth Wear Index,27 with more wear in maxillary than in mandibular teeth. Signs and symptoms were typical for a chemical type of wear, with some mechanical wear also apparent. No functional problems, eg, impaired chewing, were present. On the OHIP-49 questionnaire, the patient expressed a reduced quality of life. The goal of the treatment was to reconstruct the anatomical form of the teeth as far as possible, thereby also improving quality of life. Due to the rather large volume of lost tooth tissue per tooth, indirect treatment using CAD/CAM resin nano-composite restorations (LAVA Ultimate, 3M Oral Care) was applied. Results: The seating of the CAD/CAM resin nano-composite restorations (LAVA Ultimate, 3M Oral Care) restorations was considered precise. Conclusion: In the treatment of severe tooth wear, the described digital workflow using CAD/CAM restorations for occluding restorations and direct composite materials in the esthetic zone is a potential treatment modality that is workable and minimally invasive. Keywords: CAD-CAM, case report, digital workflow, indirect composite materials, minimally invasive, oral rehabilitation, restorative dentistry, tooth wear

Purpose: This study evaluated the effect of incorporating different concentrations of biosilicate in an experimental self-etch adhesive (SE). Materials and Methods: Biosilicate microparticles (0, 2, 5, and 10 wt%) were incorporated into the primer, and degree of conversion (DC) and wettability were tested (one-way ANOVA, Tukey’s test, p < 0.05). The two best concentrations were selected (2% and 5%) for µTBS evaluation. Sound human molars (n=20) were sectioned into quarters and randomly assigned to 4 experimental groups: 1. experimental SE + 0% biosilicate (Exp0%; negative control); 2. experimental SE + 2% biosilicate (Exp2%); 3. experimental SE + 5% biosilicate (Exp5%); 4. AdheSE (Ivoclar Vivadent, positive control). After adhesive application, Filtek Z350 (3M Oral Care) composite was built up incrementally to 5 mm. Each quarter tooth was sectioned into sticks (0.9 mm2) and stored in distilled water (37°C) for 24 h, 6 months, or 1 year. After storage, sticks were submitted to µTBS (0.75 mm/min). The Ca:P ratio was analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Data were analyzed using two-way ANOVA with Bonferroni’s correction, with statistical siginificance set at p < 0.05. Fracture patterns were observed under a digital microscope and adhesive interfaces with transmission electron microscopy (TEM). Results: Exp2% presented the highest DC (p < 0.05), Exp5% exhibited the lowest µTBS (p < 0.05), and adhesive failures were predominant in all groups. TEM suggested remineralized areas in Exp2% and to a lesser degree in Exp5%. Exp2% and Exp5% showed a higher Ca:P ratio after aging (p < 0.05). Conclusion: The incorporation of biosilicate microparticles can improve the properties of self-etch adhesives. It increased the DC of the experimental adhesive as well as mineral deposition. However, the adhesive properties are concentration dependent, as a higher concentration of microparticles can adversely affect the mechanical properties of an adhesive. Keywords: degree of conversion, wettability, bond strength, bioactive glass-ceramic, self-etch adhesive

Purpose: To morphologically evaluate the interface between a conventional glass-ionomer cement (GIC) and dentin one day after placement, as well as the changes at the interface after one year of aging/functioning in monkey teeth. Materials and Methods: On the buccal surfaces of seven intact teeth in each of two monkeys, shallow class V cavities were prepared, which were then filled with Fuji IX GP (GC) to provide 1-year in vivo data. A year later, two more teeth in each monkey were similarly prepared and restored for the 1-day in vivo group. The following day, the restored teeth were extracted and the restoration interfaces observed using transmission electron microscopy (TEM). In addition, restorations were similarly placed in two extracted human teeth (control, 1-day in vitro group) and observed a day after placement using TEM. Results: The 1-day in vivo and in vitro results showed that the GIC appeared to bond to dentin through a demineralized zone similar to the hybrid layer produced by resinous adhesives. However, the interface between GIC and dentin after 1 year in vivo appeared to change over time: many needle-like crystals were detected within the remineralized layer and along the collagen fibrils. Slow diffusion of ions resulted in pores, which filled with mineral crystals and made the pores smaller. Conclusion: The interface between GIC and dentin morphologically changes over time, and recrystallization or remineralization at the interface may occur (1 year in vivo). Keywords: adhesion to dentin, adhesive dentistry, adhesive interface, glass-ionomer cements, TEM

Purpose: This systematic review aims to explore and compile the effect of adhesive luting on the mechanical properties of dental ceramics used as restorative materials. Materials and Methods: The PubMed/MEDLINE, Web of Science and Scopus databases were searched on January 31st, 2021 to select laboratory studies written in English, without publishing-date restrictions, which compared the mechanical properties of commercially available dental ceramics as restorative materials luted using adhesive vs non-adhesive strategies. A total of 20 (out of 2039) studies were eligible and included in the analysis. Two authors independently selected the studies, extracted the data and assessed the risk of bias. Mean differences (RevMan5.1, random effects model, α = 0.05) were obtained by comparing resistance values of adhesive and non-adhesive conditions (global analysis). Subgroup analyses were performed considering ceramic composition and aging. Results: In the global analysis, adhesive luting induced higher mechanical resistance values compared to non-adhesive luting (p ≤ 0.01). The same effect was observed for glass and alumina ceramics (p ≤ 0.01), but not for zirconia polycrystals (p = 0.83). Adhesive luting was favorable in both the aged and non-aged subgroup analysis (p ≤ 0.01). High heterogeneity was found in all meta-analyses. All analyzed studies in the systematic review scored negatively for risk of bias in most of the factors considered. Conclusions: Adhesive luting reinforces the mechanical properties of dental ceramics used as restorative materials, with the exception of zirconia polycrystals. Keywords: adhesion, cementation technique, dental ceramic, luting, mechanical property

Purpose: To evaluate the effect of a sulfinate agent on the bonding durability of one-step self-etch adhesives (1-SEAs) to smear-layer-covered dentin deproteinized with hypochlorous acid (HOCl). Materials and Methods: Human coronal dentin disks with a standardized smear layer were deproteinized with 100 ppm HOCl solution for 0 s (control), 15 s or 30 s. After rinsing with water for 30 s and air drying, half of the specimens were treated with a sulfinate agent (Scotchbond Universal Dual Cure Activator; SDA) prior to the application of a 1-SEA (Bond Force II [Tokuyama Dental] or Clearfil Universal Bond Quick [Kuraray Noritake]). Microtensile bond strength (µTBS) was measured after 24 h or 10,000 thermal cycles (TC). The data were analyzed by three-way ANOVA with Tukey’s post-hoc tests and t-tests at the 0.05 significance level. Results: The 24-h µTBS of both adhesives increased statistically significantly with the HOCl pretreatment for 15 s or 30 s (p < 0.05), but it was not statistically significantly affected by the application of SDA (p > 0.05). However, after TC, the groups treated with the combination of HOCl and SDA maintained their µTBS (p > 0.05), as opposed to untreated dentin and dentin treated with either HOCl or SDA, whose µTBS decreased significantly (p < 0.05). Conclusion: The application of the sulfinate agent did not statistically significantly affect the immediate bond strength of 1-SEAs, and it could not prevent a significant decrease in the bond strength to untreated dentin after thermocycling. However, the sulfinate agent significantly improved the bonding durability of 1-SEAs to HOCl smear-layer deproteinized dentin. Keywords: adhesion to dentin, all-in-one adhesive, hypochlorous acid, longevity, microtensile bond strength, resin-dentin bond strength, touch-cure activator

Purpose: To identify and discuss the available surface treatments and adhesives for polyetheretherketone (PEEK) to increase its bond strength to resin-based materials used in dentistry. Materials and Methods: The reporting of this scoping review was based on PRISMA. The study protocol was made available at: https://osf.io/4nur9/. Studies which evaluated PEEK surface treatments and its bond strength to resin-based materials were selected. The search was performed in PubMed, Scopus, Web of Sciences and Cochrane databases. The screening was undertaken by 3 independent researchers using the Rayyan program. A descriptive analysis was performed considering study characteristics and main findings (title, data of publication, authors, PEEK characteristics, surface treatments, control group, bonded set, luting agent, specimen geometry, storage, thermocycling, pre-test failures, test geometry, failure analysis, main findings, and compliance with normative guidelines). Results: The initial search yielded 1965 articles, of which 32 were included for descriptive analysis. The review showed that the use of surface treatments and adhesives are important to promote bond strength to PEEK. Up until now, various surface treatments have been explored for bond improvement to PEEK. Sulfuric acid etching is commonly reported as promoting the highest bond strength, followed by alumina-particle air abrasion. Regarding adhesives, the use of a specific adhesive containing MMA, PETIA (pentaerythritol triacrylate), and dimethacrylates yields the best adhesive performance. Conclusion: Sulfuric acid etching and alumina particle air abrasion followed by application of bonding agents containing MMA, PETIA and dimethacrylates are the most effective choices to increase resin-based materials’ adhesion to PEEK. Keywords: adhesion, PEEK, surface modification, resin cement, resin composite

Purpose: To investigate marginal integrity of restorations applied with preheated and non-preheated composite, flowable composite, sonically activated composite, and a new thermo-viscous bulk-fill composite using near-infrared technology for preheating, in class V cavities of human molars. Materials and Methods: Standardized cavities were prepared on the buccal surfaces of 60 human mandibular molars and restored with one of the following resin composite materials after application of an etch-and-rinse adhesive (OptiBond FL, Kerr): non-preheated or preheated conventional composite (Filtek Supreme XTE, 3M Oral Care), preheated thermo-viscous composite (VisCalor bulk, Voco), soncially activated composite (SonicFill 3, Kerr), or flowable composite (Filtek Supreme XTE Flowable, 3M Oral Care) applied in bulk or as a lining material using the snow-plow technique. After light curing and polishing, the percentage of continuous margins (PCM) of the restorations in enamel and dentin was assessed using SEM both before and after thermomechanical loading (TML). TML was carried out with 3000 thermal cycles (5°C–50°C) and a simultaneous mechanical stress application with 1.2 million load-cycles (1.7 Hz, 49 N) in a computer-controlled masticator. Non-parametric statistical analysis was performed using Wilcoxon, Kruskal-Wallis, and Mann-Whitney U-tests (α = 0.05). Results: All groups revealed a significant decline in marginal integrity after TML in both enamel and dentin. Although the flowable group in enamel and the snow-plow group in dentin showed the highest PCM before TML, the differences between the groups were compensated after TML. Conclusion: All of the tested composites and application methods showed similar marginal integrities after thermomechanical loading and can be recommended for clinical implementation. Keywords: preheating, sonic activation, flowable composite, resin composite, marginal adaptation

Purpose: To investigate the influence of primers on polymerization kinetics of resin-based luting and its effect on the microhardness and bond strength to zirconia. Materials and Methods: Panavia V5 (PV; Kuraray Noritake) with Tooth Primer (TPprimer; Kuraray Noritake) or Clearfil Ceramic Primer (CPprimer; Kuraray Noritake), and RelyX Ultimate (RU; 3M Oral Care) with Scotchbond Universal (SUadhesive; 3M Oral Care) were evaluated. Polymerization kinetics of luting materials with or without primers (TPprimer or SUadhesive) were evaluated using Fourier transform near-infrared (FT-NIR) spectroscopy in self- and dual-curing modes (n = 5). Microhardness of luting materials was evaluated after 1, 12, and 24 h (n = 5). Shear bond strengths to zirconia ceramics (Katana Zirconia, Kuraray Noritake; and Lava Esthetic, 3M Oral Care) after 24 h and 1 year (n = 8) were assessed to determine the effect of the following surface treatments: no treatment, non-thermal atmospheric plasma, primer (CPprimer or SUadhesive), and the combination of plasma + primers. Statistical analyses were performed at a 5% significance level. Results: PV achieved a significantly higher degree of conversion (DC) when TPprimer was used, while there was no increase in conversion for RU combined with SUadhesive. Light activation significantly improved polymerization, which also produced greater microhardness. CPprimer and SUadhesive significantly improved immediate bond strength to zirconia ceramics. However, after 1 year, only SUadhesive with RU was able to maintain the bond strength. Plasma surface treatment did not improve bonding to zirconia. Conclusion: The use of primers improved the DC for PV only. Light curing produced higher conversion and microhardness for both resin-based luting materials. Bond strength to zirconia was improved when primers were used. However, only RU demonstrated reliable long-term adhesion to zirconia. Keywords: adhesion, ceramics, indirect restoration, primer, composite cement, surface treatments, zirconia

Purpose: To present a new restorative technique for the restoration of teeth with deep subgingival hard tissue defects extending down to the osseous crest without additional surgical or orthodontic interventions by combining mineral trioxide aggregate (MTA) and composite material. Materials and Methods: The MTA matrix technique starts by deeply inserting a metal matrix as far down to the bone level as possible. The matrix should then be fixated with a matrix holder in its end position. If the matrix band does not seal tightly in the deepest area of the cavity, small portions of MTA are carefully applied to the lower end of the inner side of the matrix band. The MTA acts as a barrier for fluid control. Additional haemostasis is not necessary. Subsequently, the tooth is restored with an etch-and-rinse adhesive and composite resin. The clinical effects were observed in a case series of three patients over a period of 3 to 4.5 years. Results: Excellent outcomes were observed clinically and radiologically. Teeth restored with the MTA matrix technique showed no failures due to the materials used or due to secondary caries or periodontal inflammation after an observation period of 3 to 4.5 years. Probing depths ranged from 2 to 4 mm without bleeding on probing, including the subgingivally restored areas. Conclusion: Although only a few casuistic observations are available to date, by using the MTA matrix technique, successful restoration of teeth with subgingival defects down to the alveolar bone crest seems possible without the need of additional surgical or orthodontic measures. Further clinical studies are necessary to confirm the feasibility of this technique. Keywords: MTA matrix technique, restoration of deep cavities, treatment technique, supracrestal tissue attachment, biological width, deep subgingival hard tissue defects, mineral trioxide aggregate