Purpose: To investigate the changes in the enamel bond performance of a two-step adhesive containing a primer derived from a universal adhesive in the early phase before 24 h and compare them to those of other adhesives. The Knoop hardness number (KHN) of the cured adhesive layers and resin composite was measured. Materials and Methods: A new two-step adhesive using universal adhesive technology, G2-Bond Universal, was tested. Two conventional two-step adhesives, Clearfil SE Bond 2 and OptiBond eXTRa, and an established universal adhesive, Scotchbond Universal Plus Adhesive, were used as comparison materials. Twelve specimens per group were used to measure the shear bond strength (SBS) to bovine enamel in different etching modes. The bonded specimens were stored in distilled water at 37°C for 5 min or 1, 6, 12, or 24 h before SBS testing. The KHN of the adhesive layer and resin composite was determined after the same storage periods as for SBS testing. Results: All adhesives exhibited increased SBS with prolonged storage periods, irrespective of the etching mode. The KHN of the adhesive layer and resin composite increased over time. Conclusions: There were strong positive correlations between the SBS and KHN of the adhesive layer and resin composite. Phosphoric acid pre-etching of enamel effectively increases enamel bond performance. The two-step adhesive G2-Bond Universal demonstrated significantly higher bond strength in the early phase than the other adhesives in self-etch mode. Keywords: enamel bond strength, universal-adhesive-derived primer, two-step adhesive, early bonding performance

Purpose: To investigate the changes in the dentin bond strengths of universal adhesives during the early phase and evaluate the effect of a double-layer adhesive application on the performance of the dentin bond. Materials and Methods: Three universal adhesives and a two-step self-etch adhesive were employed to ascertain the shear bond strengths (SBS) of specimens to bovine dentin with the use of the etch-and-rinse or self-etch mode. The specimens were further divided into two groups based on adhesive application in a single or a double layer. The bonded specimens were stored in distilled water at 37°C for 5 min or 1, 6, 12, or 24 h prior to SBS measurement and the adhesives’ Knoop hardness number (KHN). Results: All the adhesives showed increased SBS with prolonged storage periods regardless of the adhesive layer (single or double) or etching mode. Most universal adhesives in the double adhesive layer groups showed significantly higher SBS than single adhesive layer groups for the same storage period. All the adhesives also showed increased KHN with increased storage period. Conclusion: The SBS and KHN values of the adhesives increased with increasing storage duration over a 24-h period. Double adhesive layer application mediated increased dentin bond strength in the early phase. Keywords: dentin bond strength, double-layer application, universal adhesive, early bond effectiveness, SEM analysis

Purpose: To investigate the effect of application of a primer resembling a universal adhesive with or without light irradiation followed by a hydrophobic bonding agent on bonding effectiveness, based on shear bond strength (SBS) and shear fatigue strength (SFS) tests. Materials and Methods: An experimental two-step self-etch adhesive (BZF) that comprises a primer resembling a universal adhesive (BZP) and a hydrophobic bonding agent (BZB) were used. The two-step self-etch adhesive, Clearfil SE Bond 2 (SE), served as a comparison. Three experiments were conducted. Experiment 1: (1) BZP alone without light irradiation (BZP w/o); (2) BZP alone with light irradiation (BZP w/); (3) BZP without light irradiation followed by BZB (BZPB w/o); (4) BZP with light irradiation followed by BZB (BZPB w/). Experiment 2: (1) BZPB w/o, (2) SE primer + BZ bonding agent (SEP + BZB), and (3) SE primer + SE bonding agent (SEPB). The bonded specimens of experiment 1 and 2 were subjected to SBS tests. Experiment 3: Bonded specimens following the same experimental protocol as experiment 2 were subjected to SFS tests. Results: BZPB showed significantly higher mean enamel and dentin SBS than did BZP. BZPB showed significantly higher SBS without light irradiation than with light irradiation to both substrates. The group of BZPB without light irradiation showed significantly higher SBS than the group of BZPB with light irradiation to both substrates. For experiments 2 and 3, although no significant differences were found in SBS among groups for enamel, SEP + BZB showed a significantly lower SBS and SFS than other groups for dentin. Conclusions: BZF showed bonding performance equivalent to that of the gold standard Clearfil SE Bond 2. Keywords: HEMA free primer, hydrophobic bonding agent, shear bond strength, shear fatigue strength

Purpose: To use shear bond strength (SBS) and shear fatigue strength (SFS) testing to determine the durability of adhesion of self-adhesive restorative materials compared to composite resin bonded with a universal adhesive. Materials and Methods: A universal adhesive, Prime & Bond Active, was used in self-etch mode to bond Z-100 composite resin to enamel and dentin. Three commercially available restorative materials and one experimental material with self-adhesive properties, Activa (A), Fuji II LC(F), and Equia Forte (E) and ASAR-MP4 (S) were also bonded to enamel and dentin. The SBS and SFS were determined for all materials. A staircase method was used to determine the SFS with 10 Hz frequency for 50,000 cycles or until failure occurred. Results: On enamel, S generated similar values to the adhesive/composite materials and higher values than F, E, and A. On dentin, the composite/universal adhesive showed significantly higher SBS and SFS than the self-adhesive materials. S, F, and E generated higher values than A on dentin. Conclusion: SBS and SFS values to enamel were similar for all materials tested except Activa which generated lower enamel values. On dentin surfaces, the self-adhesive materials generated similar SBS and SFS, with the exception of Activa. Those values were lower than that generated with composite resin and a universal adhesive. Keywords: adhesion to dental hard tissues, fatigue testing, glass ionomers, bond durability, self-adhesive restoratives

Purpose: To investigate simulated localized and generalized wear of self-adhesive restorative materials. Materials and Methods: Three commercially available restorative materials and one experimental material with self-adhesive properties were evaluated. The experimental material was tested in both light-cured and self-cured conditions. Activa (A), Fuji II LC (F), and Equia Forte (E) and the experimental material ASAR-MP4 (S) were investigated. Two kinds of wear were simulated in an Alabama wear machine. Localized wear was simulated with a stainless-steel ball bearing antagonist and generalized with a flat-ended stainless-steel cylinder antagonist. The wear challenge was carried out in an aqueous slurry of polymethyl methacrylate beads. Material volume loss was measured on polyvinyl siloxane replicates of each worn surface using a Proscan 2100 noncontact profilometer in conjunction with Proscan and AnSur 3D software. Results: There were significant differences (p 0.05) among the materials for both generalized and localized wear. The experimental material in both curing modes exhibited significantly less localized wear than F and A and significantly less generalized wear than F and E. Conclusion: Self-adhesive materials offer unique handling properties for direct placement of posterior restorations in permanent teeth. The experimental material ASAR-MP4 generated similar wear values to the other self-adhesive materials tested. Keywords: localized wear, generalized wear, self-adhesive, bulk fill, glass ionomer

Purpose: To use shear bond strength (SBS) testing to determine the effect of surface moisture and smear layer thickness on the adhesion of self-adhesive restorative materials and a universal adhesive. Materials and Methods: One single-step self-etch universal adhesive, Prime & Bond Active (PA), was used to bond Ceram.x Spectra ST HV composite resin to dentin and enamel using the self-etching technique. Three commercially available restorative materials and one newly developed material with self-adhesive properties, Activa (A), Fuji II LC(F), Equia Forte (E), and ASAR-MP4 (S), respectively, were also bonded to enamel and dentin prepared moist and dry and to dentin prepared with a thick smear layer. Shear bond testing was performed using an Ultradent bonding apparatus. Results: The universal adhesive generated the highest SBS to dentin and enamel, followed by the newly developed material. None of the materials tested were significantly affected by the moisture conditions on enamel or dentin. The thickness of smear layer significantly affected SBS to dentin for S, F, and E. However, S and F still exhibited higher shear bond strength to dentin with the thicker smear layer compared to the other self-adhesive materials. Only the universal adhesive in self-etch mode was not affected by the thicker smear layer and maintained significantly higher SBS. Conclusion: None of the materials tested were affected by bonding to overdried dentin or enamel. All of the self-adhesive materials exhibited lower SBS to specimens with a thicker smear layer. The newly developed material ASAR-MP4 compared favorably to the other self-adhesive materials tested under all test conditions. Keywords: adhesion to dental hard tissues, shear bond testing, glass ionomers, self-adhesive restoratives

The clinical report describes a three-dimensional (3D) printed coping for intraoral evaluation before milling final anterior restorations. The use of printed copings allows restorations for complex and esthetically important restorations to be thoroughly tested at relatively low cost without introducing large delays into the fabrication process. Keywords: abutment design, computer modeling, prosthetic procedure, prosthodontics, restorative dentistry

Purpose: To investigate the influence of application time and etching mode of universal adhesives on enamel adhesion. Materials and Methods: Five universal adhesives, Adhese Universal, Bondmer Lightless, Clearfil Universal Bond Quick, G-Premio Bond, and Scotchbond Universal, were used. Bovine incisors were prepared and divided into four groups of ten teeth each. SBS, Ra, and SFE were determined after the following procedures: 1. self-etch mode with immediate air blowing after application (IA); 2. self-etch mode with prolonged application time (PA); 3. etch-and-rinse mode with IA; 4. etch-and-rinse mode with PA. After 24-h water storage, the bonded assemblies were subjected to shear bond strength (SBS) tests. For surface roughness (Ra) and surface free energy (SFE) measurements, the adhesives were simply applied to the enamel and rinsed with acetone and water before the measurements were carried out. Results: Significantly higher SBS and Ra values were obtained with etch-and-rinse mode than with self-etch mode regardless of the application time or type of adhesive. Although most adhesives showed decreased SFE values with increased application time in self-etch mode, SFE values in etch-and-rinse mode were dependent on the adhesive type and application time. Conclusions: Etching mode, application time, and type of adhesive significantly influenced the SBS, Ra, and SFE values. Keywords: universal adhesive, etching mode, application time, enamel bond efficacy

Purpose: To use shear bond strength (SBS) and shear fatigue strength (SFS) testing to determine the influence of phosphoric acid pre-etching times prior to application of self-etch adhesives on enamel bonding. Materials and Methods: Two single-step self-etch universal adhesives (Prime&Bond Elect and Scotchbond Universal), a conventional single-step self-etch adhesive (G-ӕnial Bond), and a conventional two-step self-etch adhesive (OptiBond XTR) were used. The SBS and SFS were obtained with phosphoric acid pre-etching for 3, 10, or 15 s prior to application of the adhesives, and without pre-etching (0 s) as a control. A staircase method was used to determine the SFS with 10 Hz frequency for 50,000 cycles or until failure occurred. The mean demineralization depth for each treated enamel surface was also measured using a profilometer. Results: For all the adhesives, the groups with pre-etching showed significantly higher SBS and SFS than groups without pre-etching. However, there was no significant difference in SBS and SFS among groups with > 3 s of preetching. In addition, although the groups with pre-etching showed significantly deeper demineralization depths than groups without pre-etching, there was no significant difference in depth among groups with > 3 s of pre-etching. Conclusion: Three seconds of phosphoric acid pre-etching prior to application of self-etch adhesive can enhance enamel bonding effectiveness. Keywords: phosphoric acid pre-etching time, shear fatigue strength, self-etch adhesive, universal adhesive, demineralization depth

Purpose: To examine the influence of the oxygen inhibited layer (OIL) on shear bond strength (SBS) to dentin and surface free energy (SFE) characteristics of different adhesive systems. Materials and Methods: Three adhesive systems were used: Scotchbond Multipurpose (SM), Clearfil SE Bond (CS), and Scotchbond Universal (SU). Resin composite was bonded to dentin surfaces to determine SBS with and without OIL of adhesives. The SFE, dispersion force (γSd), polarity force (γSp), and hydrogen bonding force (γSh) of cured adhesives with and without an OIL were measured. Two-way ANOVA and Tukey's honestly significant difference (HSD) test were used for analysis of SBS data, and one-way ANOVA and Tukey's HSD test were used for the SFE and contact angle data. Results: The SBS of SM and CS showed no significant differences between specimens with and without the OIL. However, the SBS of SU with the OIL was significantly higher than without the OIL. The SFE, γSp, and γSh of cured adhesives with an OIL were significantly higher than those of cured adhesives without an OIL. The SFE, γSp, and γSh of SM and CS with an OIL were significantly higher than those of SU with an OIL. Conclusion: The results of this study indicate that the presence of an OIL with a single-step self-etching adhesive promotes higher SBS to dentin, unlike in the other types of adhesive systems. The SFE characteristics of the OIL of dental adhesives differed depending on the type of adhesive system. Keywords: oxygen inhibited layer, bond strength, surface free energy, adhesive system