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Objective: This study evaluated the effect of shortened application time on long-term bond strength with universal adhesives. Methods and Materials: Three universal adhesives were used: Clearfil Universal Bond (CU, Kuraray Noritake Dental Inc, Tokyo, Japan), Scotchbond Universal Adhesive (SB, 3M ESPE, St Paul, MN, USA) or G-Premio Bond (GP, GC Corp, Tokyo, Japan). Sixty molars were cut to expose midcoronal dentin and prepared with a regular diamond bur. Each adhesive was applied either according to the manufacturer's instruction or with shortened time. Specimens were stored in distilled water at 37°C for 24 hours and then cut into resin-dentin sticks. Microtensile bond strength (lTBS) was tested after either 24 hours or 1 year of water storage. Data were analyzed by the three-way ANOVA and Duncan tests (α=0.05). Fracture modes were analyzed under a scanning electron microscope (SEM). One dentin stick per group was selected after fracture mode analysis and further observed using transmission electron microscopy (TEM). Six additional dentin discs were prepared and conditioned with each adhesive under the different application time to observe the adhesive-smear layer interaction by SEM. Results: Shortened application time affected the μTBS (p<0.001) while storage time did not affect bond strength (p=0.187). A significant effect of shortened application time on μTBS was observed in the CU at 1 year and in the GP at both storage times. Conclusions: One-year storage time had no effect on the μTBS of universal adhesives to bur-cut dentin. The performance of universal adhesives can be compromised when applied using a shortened application time. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine whether the hardness of etch-and-rinse adhesives may be affected by the pretreatment of acid-etched dentin with potassium oxalate desensitizer. Unerupted human third molars were cut into crown segments by removing the occlusal enamel and roots. The pulp chamber of these crown segments was connected to a syringe barrel filled with phosphate-buffered saline so that the moisture of dentin was maintained during the bonding procedures. Three etch-and-rinse adhesives--two two-step systems (Adper Single Bond 2 [SB], One-Step [OS]) and one three-step system (Adper Scotchbond Multi-Purpose [MP])--were applied to acid-etched dentin that had been treated (experimental groups) or not (control groups) with potassium oxalate (BisBlock). The Knoop hardness (KHN) of adhesives was taken at different sites of the outer surface of the adhesive-bonded dentin. The KHN of the three tested adhesives applied to acid-etched dentin treated with potassium oxalate was significantly lower than that exhibited by the respective controls (not treated with oxalate; p <0.05). Regardless of the adhesive, the treatment with potassium oxalate reduced the adhesives' KHN (p<0.05), with the OS system exhibiting the lowest KHN compared with the MP and SB systems. [ABSTRACT FROM AUTHOR]

Objectives: To (1) identify the methods that dentists in The Dental Practice-Based Research Network (DPBRN) use to diagnose dental caries; (2) quantify their frequency of use and (3) test the hypothesis that certain dentist and dental practice characteristics are significantly associated with their use. Methods: A questionnaire about methods used for caries diagnosis was sent to DPBRN dentists who reported doing some restorative dentistry; 522 dentists participated. Questions included the use of dental radiographs, the dental explorer, laser fluorescence, air-drying and fiber-optic devices and magnification as used when diagnosing primary, secondary/recurrent or non-specific caries lesions. Variations on the frequency of their use were tested using multivariate analysis and Bonferroni tests. Results: Overall, the dental explorer was the instrument most commonly used to detect primary occlusal caries and caries at the margins of existing restorations. In contrast, laser fluorescence was rarely used to help diagnose occlusal primary caries. For proximal caries, radiographs were used to help diagnose 75%-100% of lesions by 96% of the DPBRN dentists. Dentists who use radiographs most often to assess proximal surfaces of posterior teeth were significantly more likely to also report providing a higher percentage of patients with individualized caries prevention (p=.040) and seeing a higher percentage of pediatric patients (p=.001). Conclusion: The use of specific diagnostic methods varied substantially. The dental explorer and radiographs are still the most commonly used diagnostic methods. [ABSTRACT FROM AUTHOR]

The current trend towards mum-intervention dentistry has introduced laser technology as an alternative technique for cavity preparation. This study assessed the null hypothesis that enamel prepared either by Er,Cr:YSGG laser or conventional diamond bur is equally receptive to adhesive procedures. The buccal and lingual surfaces of 35 sound human molars were prepared with Er,Cr:YSGG laser or a medium-grit diamond bur. One etch&rinse (OptiBond FL) and three self-etch adhesives (Adper Prompt L-Pop, Clearfil SE Bond and Clearfil S³ Bond) were applied on laser-irradiated and bur-cut enamel, followed by the application of a 5-6 mm build-up of Z100. The micro-tensile bond strength (μTBS) was determined after 24 hours of storage in water at 37°C. Prepared enamel surfaces and failure patterns were evaluated using a stereo-microscope and a field-emission-gun scanning electron microscope (Feg-SEM). The μTBS to laser-irradiated enamel was significantly lower than to bur-cut enamel (p<0.05), with the exception of Clearfil S³ Bond, which bonded equally effectively to both substrates. The latter presented the highest μTBS on laser-irradiated enamel, though it was not statistically different from the μTBS of OptiBond FL. SEM analysis revealed significant morphological alterations of the laser-irradiated enamel surface, such as areas of melted and recrystalized hydroxyapatite and deep extensive micro-cracks. In conclusion, the bonding effectiveness of adhesives to laser-irradiated enamel depends not only on the structural substrate alterations induced by the laser, but also on the characteristics of the adhesive employed. [ABSTRACT FROM AUTHOR]

This in vitro study evaluated the influence of different glass ionomer liners and curing methods on microleakage of resin composite restorations. Class V root preparations were made in 120 bovine incisors randomly divided into 12 groups according to liner and curing method. The resin composite system (Single Bond + Z100) was inserted and polymerized in one increment in all groups. Cavity preparations were either not lined (control), lined with a resin modified glass-ionomer cement (Vitrebond) or a conventional glass-ionomer cement (Ketac Bond). The restorations were light-cured using one of four curing methods. The teeth were thermocycled and immersed in 0.5% basic fuchsin, sectioned, and dye penetration was measured (Image Tool). No significant difference in leakage among conventional, ramp or pulse-delay methods was seen. High intensity light groups showed significantly greater penetration compared to other curing methods. No significant difference existed in marginal leakage between liners, but microleakage was significantly higher in groups restored using no liner. No relationship between lining technique and light curing method was observed. The use of glass ionomer liners reduced microleakage, while high intensity light curing produced the greatest dye penetration. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of peroxide bleaching regimens on the ultimate tensile strength (UTS) of human enamel. A resin composite block was built-up on the bonded occlusal surface of 14 extracted, sound, erupted third molars to enable posterior preparation for the microtermile test. The bonded teeth were serially sectioned in a buccal-lingual direction into approximately 0.7-mm thick slices. Each slice was trimmed with a fine diamond bur to reduce the area of the buccal, internal slope of the cusps to a dumb-bell shape with a cross-sectional area of less than 1 mm². The samples were randomly divided into seven groups (n=10): unbleached control group and bleached groups treated with six bleaching regimens. The specimens were tested in tension at 0.5 mm/minute and the data were analyzed by ANOVA and Tukey test. Specimens from the control group presented 51.3 ± 8.6 MPa, while the UTS of bleached enamel ranged from 22.0 ± 5.6 to 36.3 ± 9.1 MPa. All bleaching procedures significantly reduced enamel UTS (p<0.05). Differences were also observed among treatments. The results suggested that bleaching regimens can significantly reduce enamel UTS. [ABSTRACT FROM AUTHOR]

Manufacturers of mild self-tech adhesives advocate the adjunctive use of phosphoric acid etching when bonding to unground enamel. This study tested the null hypothesis that there is no difference between the recently introduced, more aggressive self-etch adhesives and a total-etch adhesive in bonding to unground enamel. The ultrastructure and microtensile bond strengths (TBS) of XENO III (Dentsply) and Simplicity (Apex Dental Materials), bonded to unground enamel, were examined after thermocycling. Clearfil SE bond (Kuraray), a mild self-tech adhesive, was used as the negative control, and One-Step (BISCO), a total-etach adhesive bonded to phosphoric acid-etched underground enamel, was used as the positive control. Differences in the thickness of enamel hybrid layers were observed and the aggressiveness of apatite dissolution in the four adhesives. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effect of different surface treatments on the shear bond strength (SBS) of lithium silicate (LS) and lithium disilicate (LD) ceramics, after thermocycling., Methods and Materials: For SBS test, 72 ceramic blocks (18×14×2 mm) were made (24 blocks from each ceramic material): VITA Suprinity (LSS), Celtra Duo (LSC), and Lithium disilicate (LD). The blocks were polished with sandpaper of increasing grit (#280, #400, #800, and #1200) and embedded in chemically activated acrylic resin. Afterwards, they were randomly divided into 12 groups (6 blocks per group) according to: "Ceramic" (LD, LSC, and LSS) and "Surface treatment" (HFS: hydrofluoric acid + silane; MEP: Monobond Etch & Prime/Ivoclar). From each treated surface ceramic block, four dual-curing resin cement cylinders (RelyX U200, 3M Oral Care) were prepared using a Tygon tube (Ø=3 mm and h=2 mm) and light cured for 40 seconds (1000 mW/cm2) (N=288/n=24). All specimens were submitted to thermocycling (10,000 cycles, 5°C and 55°C, 30 seconds) and then to SBS test at a crosshead speed of 1 mm/min using a 50-kgf load cell. Forty-five additional blocks were made for roughness and SEM analysis. Failure mode was also performed. The data (MPa) were statistically analyzed by oneway analysis of variance (ANOVA), Tukey test (5%), and Weibull analysis. The Ra was analyzed by Kruskal-Wallis and Dunn Test (5%). The other variables were analyzed qualitatively., Results: ANOVA revealed that "surface treatment" was significant for all ceramic materials (p<0.05). The LD-HFS (18.66±3.49), LSC-HFS (16.81±2.62), and LSS-HFS (16.33±3.08) groups had significantly higher SBS than the LD-MEP (7.00±4.2), LSCMEP (14.12±3.51), and LSS-MEP (13.87±2.52) groups. Complete adhesive failures at the cement-dentin interface were more frequent. Weibull modulus was superior for the LD-HFS (6.22), LSC-HFS (8.8), and LSS-HFS (7.4) groups., Conclusion: HF followed by silanization is the most suitable surface treatment for the cementation of LS and LD glass ceramics., (©Operative Dentistry, 2022.)

Clinical Relevance: The photo-initiator system based on an advanced polymerization system may be an alternative that can be used to overcome the disadvantages of radicular dentin, especially for the apical third., Summary: Objectives: The purpose of this study was to evaluate the effects of universal adhesives with different photo-initiator systems applied in etch-and-rinse (ER) and self-etch (SE) modes on dentin interaction (push-out bond strength [PBS], nanoleakage [NL], and degree of conversion [DC] within the hybrid layer) in the different root thirds after fiber post cementation.Methods and Materials: Roots of endodontically prepared human premolars were randomly divided into six groups according to one of three adhesive systems (Scotchbond Universal [SBU], Ambar Universal [AMB], and Ambar Universal APS [AMB-APS]) and two adhesive strategies (ER and SE) for each system. Posts were cemented, and PBS was tested at 0.5 mm/min. The NL was evaluated by scanning electron microscopy. DC was measured using micro-Raman spectroscopy. The data were analyzed by three-way analysis of variance and Tukey tests (α=0.05).Results: AMB-APS showed similar performance in all root thirds (p>0.05) and higher values of DC, especially in the apical third (p<0.0001). AMB and SBU showed the lowest values in the apical third (p<0.0001).Conclusions: The APS photo-initiator system contained in universal adhesives is a feasible alternative for improving radicular bonding procedure., (© Operative Dentistry, 2020.)

Objectives: To evaluate the effects of aging and temperature on working time (WT) and setting time (ST) of several dual-cured resin cements., Methods: WT and ST were determined with a thermo-controlled stage oscillating rheometer. New cement kits were used for the study. Cements were mixed according to instructions and dispensed on the oscillating stage that was preset at 22°C or 37°C. Rheologic charts were generated from the beginning of mixing until no further oscillation was detected. After initial measurements, cement kits were aged at 37°C for 12 weeks, and WT/ST was determined again at both temperatures. Five samples were read for each material and condition. Data were analyzed with repeated measures analysis of variance and a Tukey test at α=5% for each individual material., Results: The WT and ST of all cements were significantly affected by temperature and aging (p<0.05). In general, higher temperature accelerated WT/ST, but aging effects were material dependent. Some materials presented reduced WT/ST, whereas others showed increased WT/ST, regardless of the temperature., Conclusions: The WT and ST were significantly affected by temperature variation and aging condition. Although temperature changes appeared to affect all materials similarly, aging effects were material dependent.

The insertion of bonded resin composites into cavity preparations leads to a competition between polymerization contraction forces and the strength of bonds to tooth structure. The degree of stress development can be controlled, to some extent, by the cavity design (C-factor), the use of bases, the size, shape, and position of increments of composite resins placed in the cavity, and whether the resin is light- or chemically cured. Stress relief can be accomplished by maintaining the C-factor as low as possible, using chemical-curing resins, low modulus liners, and, over time, by water sorption. A thorough understanding of these principles permits clinicians to exercise more control over these variables, thereby improving the quality of their bonded restorations.

Most adhesive interface studies have involved SEM demonstration of the penetration of adhesive resins into demineralized dentin surfaces with subsequent creation of hybrid layers. Nanoleakage is a term that describes the diffusion of small ions or molecules within the hybrid layer in the absence of gap formation. The present microscopic study examined the nanoleakage of the hybrid layer using a silver nitrate staining technique. Adhesive dentin sandwiches, which were immersed in a silver nitrate solution, were prepared for both SEM and TEM examination using both the Clearfil Liner Bond and All-Bond 2 adhesive systems. Both systems demonstrated silver accumulation within the hybrid layers. Clearfil Liner Bond System showed scattered silver particles at the bottom two-thirds of the hybrid layer by both SEM and TEM observation, whereas All-Bond 2 revealed stained fiber-like structures within the full thickness of the hybrid layer. To evaluate the quality of the hybrid layer, the utilization of tracer molecules such as silver nitrate that are detectable by both SEM and TEM is proposed. It is important to determine the location and morphology of these nanometer-sized porosities that may permit the hydrolysis of collagen fibers and degradation of adhesive monomers.