Purpose: This study aimed to investigate the bonding effectiveness of two HEMA/BPA-free universal adhesives (UAs) to flat dentin, to characterize their adhesive-dentin interfacial ultrastructure, and to measure their water sorption (Wsp), water solubility (Wsl), and hydrophobicity.Materials and Methods: The immediate and aged (50,000 thermocycles) microtensile bond strength (μTBS) to flat dentin of the HEMA/BPA-free UAs Healbond Max (HbMax; Elsodent) and Healbond MP (HbMP; Elsodent) as well as the reference adhesives OptiBond FL (Opti-FL; Kerr), Clearfil SE Bond 2 (C-SE2; Kuraray Noritake), and Scotchbond Universal (SBU; 3M Oral Care) was measured. The adhesive-dentin interfaces of HbMax and HbMP were characterized by TEM. Wsp and Wsl of all adhesive resins and of the primer/adhesive resin mixtures of HbMax, Opti-FL, and C-SE2 were measured. Hydrophobicity was determined by measuring the contact angle of water dropped on adhesive-treated dentin.Results: In terms of µTBS, HbMax and HbMP performed statistically similarly to Opti-FL and C-SE2, but outperformed SBU. Aging only significantly reduced the μTBS of SBU when applied in E&R bonding mode. TEM revealed typical E&R and SE hybrid-layer ultrastructures at dentin, while electron-lucent globules of unknown origin, differing in size and shape, were observed within the adhesive resin of HbMP and even more frequently in that of HbMax. Higher Wsp was measured for the primer/adhesive resin mixtures than for the adhesive resins. Opti-FL was more hydrophobic than all other adhesives tested.Conclusion: The HEMA/BPA-free UAs bonded durably to flat dentin with bond strengths comparable to those of the gold-standard E&R/SE adhesives and superior to that of the HEMA/BPA-containing 1-step UA. Keywords: dental bonding, bond durability, water sorption, interface, HEMA, BPA

Purpose: To measure zirconia-to-zirconia microtensile bond strength (µTBS) using composite cements with and without primer.Materials and Methods: Two Initial Zirconia UHT (GC) sticks (1.8x1.8x5.0 mm) were bonded using four cements with and without their respective manufacturer’s primer/adhesive (G-CEM ONE [GOne] and G-Multi Primer, GC; Panavia V5 [Pv5]), and Panavia SA Cement Universal [PSAu], and Clearfil Ceramic Plus, Kuraray Noritake; RelyX Universal (RXu) and Scotchbond Universal Plus [SBUp], 3M Oral Care). Specimens were trimmed to an hour-glass shaped specimen whose isthmus is circular in cross-section. After 1-week water storage, the specimens were either tested immediately (1-week μTBS) or first subjected to 50,000 thermocycles (50kTC-aged μTBS). The fracture mode was categorized as either adhesive interfacial failure, cohesive failure in composite cement, or mixed failure, followed by SEM fracture analysis of selected specimens. Data were analyzed using linear mixed-effects statistics (α = 0.05; variables: composite cement, primer/adhesive application, aging).Results: The statistical analysis revealed no significant differences with aging (p = 0.3662). No significant difference in µTBS with/without primer and aging was recorded for GOne and PSAu. A significantly higher µTBS was recorded for Pv5 and RXu when applied with their respective primer/adhesive. Comparing the four composite cements when they were applied in the manner that resulted in their best performance, a significant difference in 50kTC-aged μTBS was found for PSAu compared to Pv5 and RXu. A significant decrease in µTBS upon 50kTC aging was only recorded for RXu in combination with SBUp.Conclusion: Adequate bonding to zirconia requires the functional monomer 10-MDP either contained in the composite cement, in which case a separate 10-MDP primer is no longer needed, or in the separately applied primer/adhesive. Keywords: zirconia, bond strength, sandblasting, tribochemical silica coating, functional monomer, silane, aging.

Purpose: To investigate the bonding performance of three universal adhesives (UAs) to dentin and the effect of different curing modes and hydrofluoric-acid (HF) etching of lithium-disilicate glass-ceramic on the adhesive performance of two UA/composite cement (CC) combinations. Materials and Methods: In the first project part, the immediate and aged (25k and 50k thermocycles) microtensile bond strength (µTBS) of the two light-curing UAs G2-Bond Universal (G2B; GC) and Scotchbond Universal Plus (SBUp; 3M Oral Care), and the self-curing UA Tokuyama Universal Bond II (TUBII; Tokuyama) to flat dentin was measured, when applied in both E&R and SE bonding mode using a split-tooth design (n = 10). The resultant adhesive-dentin interfaces were characterized using TEM. In the second project part, CAD/CAM composite blocks were luted to flat dentin with either Scotchbond Universal Plus/RelyX Universal (SBUp/RxU; 3M Oral Care) or Tokuyama Universal Bond II/Estecem II Plus (TUBII/ECIIp; Tokuyama Dental) using different curing modes (AA mode: auto-curing of both adhesive and cement; AL mode: auto-curing of adhesive and light-curing of cement), upon which their immediate and aged (25k and 50k thermocycles) µTBS was measured. In the third project part, the same UA/CC combinations were luted to CAD/CAM glass-ceramic to measure their immediate and aged (6-month water storage) shear bond strength (SBS). Results: In E&R bonding mode, the performance of G2B, SBUp and TUBII was not significantly different in terms of µTBS, while G2B and SBUp significantly outperformed TUBII in SE bonding mode. No significant difference in µTBS was found between the SBUp/RxU and TUBII/ECIIp UA/CC combinations, regardless of bonding mode, aging time, or curing mode. The cement-curing mode did not significantly influence µTBS, while a significantly higher µTBS was recorded for the UA/CC combinations applied in E&R bonding mode. HF significantly improved the SBS of the UA/CC combinations to glass-ceramic. Conclusion: The self-curing adhesive performed better when applied in E&R than in SE bonding mode. The curing mode did not influence the adhesive performance of the composite cements, while an E&R bonding mode rendered more favorable adhesion in a self-curing luting protocol. When bonding to glass-ceramic, the adhesive performance of the universal adhesive/composite cement combinations benefited from HF etching. Keywords: adhesion, bonding, light curing, self-curing, bond strength, TEM

Purpose: The aim of this randomized controlled clinical trial was to evaluate the 3-year clinical performance of a universal adhesive (Clearfil Universal Bond Quick (CUBQ); Kuraray Noritake) when restoring non-carious cervical lesions (NCCLs) using two different application modes (etch-and-rinse vs self-etch with prior selective enamel etching). Materials and Methods: Fifty-one patients participated in this study. A total of 251 NCCLs (n = 251) were assigned to two groups: 1) CUBQ applied in etch-and-rinse mode (n = 122; CUBQ-ER) and 2) CUBQ applied in self-etch mode with prior selective etching of enamel with phosphoric acid (n = 129; CUPQ-SEE). The same resin composite, Clearfil Majesty ES-2 (Kuraray Noritake), was used for all restorations. The restorations were evaluated at baseline, 1 and 3 years using FDI criteria: marginal staining, fracture and retention, marginal adaptation, post-operative sensitivity and recurrence of caries. Statistical analysis was performed using a logistic regression model with generalized estimating equations (2-way GEE model). Results: The patient recall rate at 3 years was 90%. After 3 years, both groups presented an increase in the percentage of small but still clinically acceptable marginal defects (CUBQ-ER: 67%, CUBQ-SEE: 63.2%) and marginal staining (CUBQ-ER: 32.6%, CUBQ-SEE: 31.7%). The overall success rate was 82.6% and 83.8% for CUBQ-ER and CUBQ-SEE, respectively. In total, 38 restorations (19 CUBQ-ER, 19 CUBQ-SEE) failed because of loss of retention, fracture, severe marginal defect and/or marginal discoloration. A retention rate of 87.2% and 86.3% was recorded for CUBQ-ER and CUBQ-SEE, respectively. No significant difference was observed between the two bonding-mode groups for any of the evaluated parameters. Conclusion: After 3 years of clinical service, Clearfil Universal Bond Quick performed similarly in etch-and-rinse and self-etch modes with prior selective enamel etching. Keywords: randomized clinical trial, universal adhesive, application modes, non-carious cervical lesions, clinical effectiveness, bonding

Purpose: This randomized controlled trial aimed to evaluate the 14-year clinical performance of a HEMA-free 1-step self-etch adhesive (1SEa) compared with that of a 3-step etch-and-rinse adhesive (3E&Ra). Materials and Methods: 267 non-carious cervical lesions in 52 patients were restored with the microhybrid composite Gradia Direct (GC), bonded in random order either with the HEMA-free 1SEa G-Bond (GB; GC) or the 3E&Ra Optibond FL (OFL; Kerr), which is considered the gold-standard E&Ra (control). The restorations were followed over 14 years for retention, marginal adaptation and discoloration, and caries occurrence. Statistical analysis involved a logistic regression model with generalized estimating equations (2-way GEE model). Results: The patient recall rate at 14 years was 63%. In total, 79 restorations (39 GB, 40 OFL) failed because of retention loss (GB: 19.4%, OFL: 19.6%), severe marginal defects, discoloration and/or caries (GB: 21.7%; OFL: 22.5%). The overall clinical success rate was 58.9% and 57.9% for GB and OFL, respectively. The number of restorations with an unacceptable marginal defect (GB: 14.5%; OFL: 19.2%) and deep marginal discoloration (GB: 18.2%; OFL: 13.2%) increased during the last 5 years. No significant difference in overall clinical performance was recorded between the two adhesives (p > 0.05). Changes in the medical health of some patients and recurrence of abrasion/erosion/abfraction increased the failure rate and retention rate. Conclusion: After 14 years, restorations bonded with the HEMA-free 1SEa performed as well as those bonded with the 3E&Ra gold standard. Unacceptable marginal deterioration was the main reason for failure, followed by loss of retention. Keywords: randomized clinical trial, RCT, Class V, bonding, adhesion, clinical effectiveness, NCCL, non-carious cervical le-sions, composite restoration

Purpose: Mild and intermediately strong 2-step self-etch adhesives (2SEa) have been shown to bond efficiently to dentin. In general, their bonding efficiency to enamel is inferior to that of etch & rinse adhesives (E&Ra). On the other hand, their application procedure is less elaborate, and consequently leaves less room for application mistakes. The aim of this randomized controlled trial was to evaluate the clinical performance of an intermediately strong 2SEa, as compared with that of a 3-step E&Ra after 6 years of clinical functioning. Materials and Methods: 239 non-carious cervical lesions in 50 patients were restored with the nanohybrid composite Herculite XRV (Kerr), bonded in random order either with the 2SEa Optibond XTR (‘O-XTR’, Kerr) or the gold-standard control 3E&Ra Optibond FL (‘O-FL’, Kerr). The restorations were recalled after 1, 2 and 6 years of clinical service and examined for retention, marginal adaptation, marginal discoloration, caries occurrence, and postoperative sensitivity. Statistical analysis was performed using a logistic regression model with generalized estimating equations (2-way GEE model). Results: The patient recall rate at 6 years was 94%. The overall clinical success rate was 81.9% and 80.9% for O-XTR and O-FL, respectively. In total, 42 restorations (21 O-XTR, 21 O-FL) failed because of retention loss, severe abfraction/abrasion/erosion, severe marginal defects and/or discoloration, and/or caries. A retention rate of 92.9% and 88.9% was recorded for O-XTR and O-FL, respectively. Progressive marginal deterioration was observed over the 6-year period. Small clinically acceptable marginal defects were recorded in about 70% of the restorations (O-XTR: 69.9%; O-FL: 74.1%). Regarding marginal discoloration, 37% of the O-XTR and 30.2% of the O-FL restorations showed superficial clinically acceptable marginal discoloration. Six O-XTR and 4 O-FL restorations exhibited caries at the restoration margin. No significant difference was observed between the two groups for any of the evaluated parameters (p > 0.05). Conclusion: After 6 years of clinical service, Class-V restorations bonded with the 2SEa performed clinically equally well as those bonded with the 3E&Ra. Keywords: randomized clinical trial, RCT, Class V, bonding, adhesion, clinical effectiveness

The importance of the interdental anatomy of a class-2 direct composite restoration is one of the most underestimated topics in direct posterior composite restorations. The proximal emergence profile of the restoration and the contact area should be designed to maximize arch continuity and to minimize food impaction. Other restorative criteria that must be fulfilled are marginal adaptation compatible with the dental and periodontal integrity, and geometry of the marginal ridge compatible with the mechanical integrity of the restoration under load. Shortcomings will result in masticatory discomfort, caries, periodontal problems and undesired movement of teeth. In vitro and in vivo studies showed that the use a contoured sectional metal matrix band with a separation clamp results in the tightest contact point. However, this matrix system also has shortcomings and does not give the expected result in all class-2 cavities. The variation in depth, width of the box, distance between the cervical cavity margin and the adjacent tooth requires customization of the interproximal space. In order to realize this, sectional matrix bands with several profiles of curvature, variation of wedges and separation clamps, and the use of teflon tape are required. In addition, dentists should follow a protocol allowing them to build a proximal composite surface that fulfills the required restorative criteria. Pre-wedging, space evaluation, interproximal clearance, correct selection, positioning and stabilization of the matrix band are important steps in this protocol. Keywords: class-2, composite resin restoration, matrix system, proximal contact point, proximal emergence profile

Abstract: Tooth-cavity preparation contributes to a large extent to the quality of the direct posterior composite restoration, the so-called hidden quality of the restoration. Indeed, the effect of a poor cavity design is not immediately visible after placement of the restoration. To correctly prepare a cavity for a posterior composite restoration, the tooth to be restored should first be profoundly biomechanically analyzed. Here, the forces that work on the tooth during occlusion and articulation, and the amount and quality of the remaining tooth structure determine the cavity form. In addition, the dental tissues must be prepared in order to receive the best possible bond of the adhesive and subsequent restorative composite. A well-finished cavity preparation enables the restorative composite to adapt well, providing a good marginal ?seal to the direct benefit of the clinical lifetime of the posterior composite restoration. Finally, it is highly recommendable to isolate the teeth with rubber-dam before starting with the cavity preparation, as this increases the visibility of the operating field and allows the operator to work in a more precise way.

Abstract: Currently, there is a trend towards simplification of materials and clinical procedures. Simplification and quality can go together if the dentist works with materials and techniques that are well proven in vitro and in vivo. The placement of a high-quality class-1/2 direct posterior composite restoration can be time efficient following a standardized layering protocol and using composite materials that adapt well to the tooth surface and are able to mimic the natural tooth. When these materials are applied in a controlled way, finishing and polishing can also be shortened. In this article, an effective layering and finishing/polishing protocol for medium-sized class-1/2 direct posterior composite restorations is presented. Following the histo-anatomic buildup of natural teeth, dentin must be concave, as opposed to convex enamel. An isochromatic, medium-opaque, highly filled flowable composite is used to replace dentin. Enamel is replaced with a medium-translucent small-particle hybrid composite. Enamel is modelled in an anatomical way, following a successive cusp-by-cusp buildup approach. Clinical experience shows that the combination of both materials used according to this so-called bi-laminar histo-anatomical layering approach results in restorations that blend in very well within the surrounding tooth structure. Following a simplified finishing and polishing protocol, the composite restorations will have a correct contour, seamless margins, and a smooth, glossy surface. Keywords: adhesion, finishing, flowable, layering, polishing, polymerization, posterior composite, shrinkage

Purpose: Universal adhesives (UAs) are applied in 2-step etch-and-rinse (2-E&R) or 1-step self-etch (1-SE) mode. This study investigated whether three UAs could benefit from a highly filled extra bonding layer (EBL), turning them into 3-E&R and 2-SE UAs, respectively, thus also compensating for the commonly thin film thickness of UAs. Materials and Methods: Microtensile bond strength (μTBS) to bur-cut dentin of Clearfil Universal Bond Quick (C-UBq, Kuraray Noritake), G-Premio Bond (G-PrB, GC) and Prime&Bond Active (P&Ba, Dentsply Sirona), applied in E&R and SE mode without/with the adhesive resin (EBL) of OptiBond FL (Opti-FL_ar, Kerr), was compared to that of the 3-E&Ra OptiBond FL (Opti-FL; Kerr), which was also employed in 2-SE mode. As a cross reference, the SE primer of Clearfil SE Bond 2 (Kuraray Noritake) was combined with Opti-FL_ar (C-SE2/Opti-FL) and again applied in 2-SE and 3-E&R mode. μTBS was measured after 1 month of water storage (37°C) and additional 25,000 and 50,000 thermocycles (TC). All μTBS were statistically analyzed using three different linear mixed-effects models with specific contrasts (p 0.05). Results: Overall, the four parameters (adhesive, bonding mode, aging, EBL) significantly influenced μTBS. G-PrB and P&Ba benefited from EBL when applied in both E&R and SE bonding modes. In E&R mode, P&Ba generally revealed the highest µTBS; C-UBq presented an intermediate and G-PrB the lowest µTBS. No significant differences were found between different bonding modes. C-SE2/Opti-FL outperformed Opti-FL in 3-E&R and 2-SE_1 month/25k. Conclusion: The overall benefit of EBL on the 1-month and TC-aged bonding efficacy differed for the different UAs tested. Keywords: bond strength, durability, hydrophobic, linear mixed model (LME), adhesive-dentin interface