This paper reviews the developments of self-etching primers and adhesives, with a special focus on the effect of acidic adhesive monomers and polymerization initiators on bonding to ground, smear layer-covered teeth. Ionized acidic adhesive monomers chemically interact with tooth substrates and facilitate good bonding to ground dentin. Polymerization initiators in self-etching primers further promote effective bonding to ground dentin. To promote bonding to both dentin and enamel, phosphonic acid monomers such as 6-methacryloyloxyhexyl phosphonoacetate (6-MHPA) were developed. These novel adhesive monomers also have a water-soluble nature and are hence endowed with sufficient demineralization capability. A new single-bottle, self-etching, 2-hydroxyethyl methacrylate (HEMA)-free adhesive comprising 6-MHPA and 4-acryloyloxyethoxycarbonylphthalic acid (4-AET) was developed. This novel adhesive enabled strong adhesion to both ground enamel and dentin, but its formulation stability was influenced by pH value of the adhesive. To develop hydrolytically stable, single-bottle, self-etching adhesives, hydrolytically stable, radical-polymerizable acidic monomers with amide or ether linkages have been developed.

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The aim of this study was to investigate the antibacterial effect and cytocompatibility of a nano-structured TiO₂ film that contained Cl and had been coated onto commercially pure titanium. First, we prepared nano-structured TiO₂ by anodization with hydrofluoric acid. Then, to confer an antibacterial effect, we performed a second anodization with NaCl solutions of different concentrations (0.5 M, 1 M, 2 M). The morphology, composition, and wettability of the surface were investigated by SEM, EDS, and a video contact angle measuring system. The antibacterial effect was evaluated by film adhesion method. And cytotoxicity was determined by the viability of MG-63 cells in a MTT assay. The SEM and EDS results showed that the TiO₂ nano-structure containing Cl had successfully formed after the second anodization. The contact angle analysis showed that the anodized titanium had a hydrophilic character. The results of this in vitro investigation demonstrated that the TiO₂ nano-structure film anodized in 1 M NaCl had an antibacterial effect and good cell compatibility.

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This study evaluated the cytotoxicity of self-etching primers/adhesives by direct contact and dentin barrier tests. The three two-step self-etching systems Clearfil SE Bond (CSE), Clearfil Protect Bond (CPB), Prime&Bond NT/NRC (PB) and one-step self-etching systems Reactmer Bond (RB), Clearfil Tri-S Bond (CTS), and Adper Prompt L-Pop (AP) were examined. In direct contact tests, L929 cells were cultured in the presence of diluted solutions (50, 20, 10, and 1%) of primer/conditioner of adhesive systems. For dentin barrier tests, each system was applied onto 0.5 or 1.5 mm thick human dentin assembled in a simple pulp chamber device and incubated for 24 h at 37°C to make the diffusive components contact the L929 cells placed at the bottom of the chamber. The cytotoxic effects were assessed by MTT assay. Cell culture without application of any primers/adhesives served as the control for both tests. One-way ANOVA and Tukey HSD tests were used for statistical analyses. The direct contact tests demonstrated that CSE and CPB were less toxic than the other materials at all dilutions. In the dentin barrier tests, toxic effects of materials were reduced with an increase in thickness of intervening dentin. CSE and CPB showed less cytotoxicity than the other adhesives (p<0.05) when applied to 0.5 mm-thick dentin, and CSE was the least toxic in the 1.5 mm-dentin group (p<0.05). Dentin thickness positively affected biocompatibility of the tested bonding systems. Two-step self-etching systems with HEMA-based primers were more biocompatible than other self-etching adhesives.

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The present study examined the influence of different post materials and their lengths on the mechanical stress of endodontically treated incisor roots in two alveolar bone conditions. Two-dimensional photoelastic models were fabricated to simulate the endodontically treated maxillary central incisors restored with three kinds of posts materials (low Young’s modulus glass fiber post, high Young’s modulus glass fiber post, and prefabricated stainless steel post) and two post lengths (8 and 4 mm). Completed models were placed in a transmission polariscope and loaded with a static force of 150 N at 45° to the tooth axis. Photoelastic photographs and the magnitudes of fringe order revealed stress distribution in the root, and suggest that the glass fiber post with a low Young’s modulus and long length can reduce the stress concentration both in normal and alveolar bone resorption conditions.

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This study evaluated the effects of two exogenous enzymes on the resin-dentin interface. Collagenase (Col) and acetylcholinesterase (Ach) were used to simulate salivary enzymes and accelerate the aging process of the bonding interfaces. Four adhesives, Adper Single Bond 2 (SB), Clearfil SE Bond (SE), Clearfil tri-S Bond (S3) and G-Bond (G), were bonded to the dentin surfaces. After storage in water with collagenase or acetylcholinesterase, the specimens were examined using a microtensile bond strength test (MTBS). Nanoleakage patterns were observed with a scanning electron microscope (SEM). The MTBS results demonstrated significantly lower bond strengths in the groups stored with either enzyme than in water. SB exhibited severe degradation after exposure to collagenase, while G showed severe degradation after exposure to acetylcholinesterase. All of the self-etch systems (SE, S3 and G) exhibited water-tree patterns within the adhesive layer when immersed in water for three months. The etch-and-rinse system (SB) showed nanoleakage within the hybrid layer and the adhesive.

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This study investigated the bonding effectiveness of novel acryloyloxyalkyl and methacryloyloxyalkyl 6,8-dithiooctanoates (dithiooctanoate monomers) to precious metals and alloys. Eight kinds of dithiooctanoate monomers were synthesized in 16.09–39.34% yields. They were characterized and confirmed as new compounds using ¹H- and ¹³C-NMR spectroscopy and mass spectral analysis. Eight experimental primers each containing 5.0 wt% of a novel dithiooctanoate monomer in acetone were prepared. After primer treatment and 2,000 thermal cycles, tensile bond strengths of MMA-PMMA/TBBO resin to seven metal adherends were measured. Results were as follows: 17.2–29.3 MPa (Au), 41.9–49.6 MPa (Ag), 36.8–47.6 MPa (Pt), 36.7–47.5 MPa (Pd), 34.0–48.9 MPa (Au alloy), 24.3–49.6 MPa (Ag alloy), 35.0–48.8 MPa (Au-Ag-Pd alloy). 10-Methacryloyloxydecyl 6,8-dithiooctanoate exhibited the highest mean bond strength to gold (29.3 MPa) and 12-methacryloyloxydodecyl 6,8-dithiooctanoate to Au alloy (48.9 MPa). Therefore, it was found that the novel dithiooctanoate monomers synthesized in this study exhibited excellent bonding to precious metals and alloys.

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The purpose of this in vitro study was to evaluate the bonding durability of three self-adhesive resin cements to titanium using the Highly Accelerated Life Test (HALT). The following self-adhesive resin cements were used to bond pairs of titanium blocks together according to manufacturers’ instructions: RelyX Unicem, Breeze, and Clearfil SA Luting. After storage in water at 37°C for 24 h, bonded specimens (n=15) immersed in 37°C water were subjected to cyclic shear load testing regimes of 20, 30, or 40 kg using a fatigue testing machine. Cyclic loading continued until failure occurred, and the number of cycles taken to reach failure was recorded. The bonding durability of a self-adhesive resin cement to titanium was largely influenced by the weight of impact load. HALT showed that Clearfil SA Luting, which contained MDP monomer, yielded the highest median bonding lifetime to titanium.

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The aim of this study was to evaluate wear effects on overdenture resilient attachments. Six commercially available attachments were investigated: ERA orange and white (EO and EW), Locator pink, white and blue (LRP, LRW and LRB) and OP anchor (OP). Five specimens were used for wear simulation while other two specimens served as controls. Fifteen thousands insertion-removal cycles were simulated. Dimensional changes and surface characteristics were evaluated using light microscopy and SEM, respectively. Sudden decrease of retentive force was characteristic for EO and EW attachments. Retentive force of Locator attachments fluctuated throughout the wear simulation period. Dimensional changes and surface wear was more expressed on plastic cores than on plastic rings of attachment males. Based on SEM analysis, some of the specimens obtained smoother surface after wear simulation. Mechanism of retention loss of resilient overdenture attachments can be only partially explained by dimensional changes and surface alterations.

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The purpose of the present study was to evaluate the effects of silane primers with and without heat treatment on bonding between a resin and a leucite-reinforced ceramic (GN-Ceram). Six dental primers (GC Ceramic Primer, GP; Clearfil Ceramic Primer, CP; RelyX Ceramic Primer, RP; Tokuso Ceramic Primer, TP; Shofu Porcelain Primer, SP; and Porcelain Liner M, PM) and five experimental primers (MDS, MTS, MDES, MTES, and ATS) were evaluated. GN-Ceram specimen was primed, heated at 100°C for 60 min (Heat), and then bonded to a resin composite using a self-curing resin. Shear bond testing revealed that GP, GP/Heat, CP, CP/Heat, RP, RP/Heat, TP, TP/Heat, SP, SP/Heat, PM, PM/Heat, MDS/Heat, MTS, MTS/Heat, and ATS/Heat exhibited superior bond strengths. No-primer, No-primer/Heat, MDS, MDES, MTES, and ATS exhibited low bond strengths, while there were no significant differences in bond strength among SP, MDS, MDES/Heat, and MTES/Heat. It seemed that heat treatment improved the bonding performance for MDS, MTES, and ATS only.

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The purpose of present investigation was to compare the cyto-genotoxicity induced by five dental alloys in vitro. The cyto-genotoxicity induced by five dental alloy extracts on human B lymphoblast cells was assessed with neutral red uptake (NRU) , CCK-8, comet and micronucleus (CBMN) assays in vitro, respectively. The results of in vitro comet and CBMN assays indicated that DNA damage (% tail DNA) and micronucleus frequencies (MNFs) in all exposure groups did not significantly increase, as compared with the control group. However, the results of NRU and CCK-8 assays demonstrated that there were to some extent differences in the cytotoxicity among 5 dental alloy extracts in vitro. The cytotoxicity may be relevant to the Ni and Be ions released in the alloy extract.

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This study aimed to compare the biomechanical behaviour of functionally graded structured posts (FGSPs) and homogenous-type posts in simulated models of a maxillary central incisor. Two models of FGSPs consisting of a multilayer xTi-yHA composite design, where zirconia and alumina was added as the first layer for models A and B respectively were compared to homogenous zirconia post (model C) and a titanium post (model D). The amount of Ti and HA in the FGSP models was varied in gradations. 3D-FEA was performed on all models and stress distributions were investigated along the dental post. In addition, interface stresses between the posts and their surrounding structures were investigated under vertical, oblique, and horizontal loadings. Strain distribution along the post-dentine interface was also investigated. The results showed that FGSPs models, A and B demonstrated better stress distribution than models C and D, indicating that dental posts with multilayered structure dissipate localized and interfacial stress and strain more efficiently than homogenous-type posts.

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Previous works studied the effect of the material and the dimensions of the post on the biomechanical performance (fracture strength and stress distribution) of restored teeth, under static loads. The aim of this work was to study the effect of the post material (glass fibre and stainless steel) on restored teeth, which have the final crown, under dynamic conditions. The use of a biomechanical model, including a fatigue analysis from FEA, is presented as a powerful method to study the effect of the material of the intraradicular post. The inclusion of the fatigue analysis allows for a more realistic study that takes into account the dynamic nature of masticatory forces. At the same time, the results obtained are easier to interpret by both dentists and mechanical engineers. No differences were found, with the load and number of cycles considered, between glass fibre and stainless steel as material for the intraradicular post used in premolars restorations.

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This study evaluated fatigue strength of CP-Ti laser-welded joints. Sixty (20/diameter) CP-Ti casted dumbbell rods with diameters of 1.5, 2.0, and 3.5 mm were sectioned and welded using two joint openings (0.0 (00) and 0.6 mm (06)). Six groups were formed, amounting to a total of 9 (n=10) with inclusion of intact groups. Welding was executed using 360 V/8 ms (1.5 and 2.0 mm) and 380 V/9 ms (3.5 mm). Joints were finished, polished, and submitted to radiographic examination to visually analyze presence of porosity (PP). Specimens were submitted to cyclic tests, and the number of cycles until failure (NC) was recorded. Fractured surfaces were examined by SEM. Kruskal-Wallis and Dunn (α=0.05) tests demonstrated that NC was lower for all diameters with 06, and for 3.5 mm/00. NC and PP were found to have a negative correlation (Spearman Coefficient). For CP-Ti frameworks with thin diameters, laser welding is better when structures are juxtaposed.

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Six kinds of experimental magnetic resin composites containing SUS447J1 stainless steel particles as filler were prepared. UDMA/MAA resin with an MAA mole fraction of 0.67 was used as the matrix resin. The effects of six levels of 4-META content (2, 4, 6, 8, 10, and 12 mass%) on the setting and flexural properties were studied. The metal filler content in each paste was 90 mass%. Although working time and setting time significantly diminished with the increase of the BPO and DMPT contents, both working time and setting time satisfied the ISO 4049 requirements for all experimental levels. Flexural strength and elastic modules significantly improved with the increase of 4-META content up to 10%. The optimum 4-META content necessary to develop better composite resins for magnetic attachment has been clarified.

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Objective: This study aimed to evaluate a prototype surface reaction-type pre-reacted glass-ionomer (S-PRG) filler-containing endodontic sealer (S-PRG sealer) in terms of its ion-releasing ability and the incorporation of the released ions by root canal dentin. Materials and Methods: The concentration of ions in the set S-PRG sealer was measured by ICPS and with a fluoride ion electrode. Element mapping and chemical component bulk analysis of the outermost dentin of the S-PRG sealer-dentin interface were performed by SEM-EPMA. The incorporation depth of the elements in dentin was measured by element line scanning. Results and Discussion: Ions released from the S-PRG sealer (Al, B, F, Na, Si, Sr, and Zn) were detected over time. The incorporation of fluoride (F), strontium (Sr), silicon (Si), and boron (B) was observed along the outermost dentin of the S-PRG sealer-dentin interface by EPMA analysis, and the incorporation depth increased with prolonged immersion. Conclusion: The continuous release of ions from the S-PRG sealer and their subsequent incorporation by root canal dentin were confirmed.

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This study evaluated the cytotoxicity of various polybasic acids, poly(alkenoic acid)s, and the monomers with various acidic functional groups such as carboxyl, phosphoryl, and sulfo group. The cell growth of fibroblasts cultivated in medium containing polybasic acids and polymers up to the concentration to 5 mmol/L was not significantly different compared with that of control without their acids. On the other hand, the cell growth fibroblasts cultivated in medium containing 1 mmol/L of the monomers with acryloyloxy and phosphoryl or carboxyl group decreased remarkably compared with that of the control and the cells were probably lifeless. Those exposed to the monomers with a ether bond and a carboxyl group or a amide bond and a sulfo group was not significantly different compared with that of control.

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We evaluated the effects on bone formation of combining synthesized collagen model polypeptides consisting of a Pro-Hyp-Gly [poly(PHG)] sequence and alpha-tricalcium phosphate (α-TCP) particles with various median sizes (large: 580.8 μm; small: 136.2 μm; or large and small mixed: 499.3 μm) in a skull defect model in mini-pigs. Quantitative image analyses for the volume density (VD) of new bone revealed that the VD in each α-TCP group was significantly higher than that in the poly(PHG) control group, with the mixed group showing the highest VD among all the groups at 4 weeks after implantation. Histological assessments revealed that the small α-TCP particles were almost completely degraded at 8 weeks. At 12 weeks, all sizes of α-TCP particles were completely degraded and remodeling of the lamellar bone was observed. The present findings suggest that particle size may influence the success of bone formation in defects.

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We evaluated the concentration of fluoride release at the initial stage and after recharging the fluoride from a resin-based sealant containing surface reaction-type pre-reacted glass-ionomer (S-PRG) filler and conventional resin-based sealants. The concentration of other ions released from the sealants in the surrounding distilled water was also examined. At the initial stage, fluoride was released from all sealants. For the sealant containing S-PRG filler, a significantly higher amount of Sr and B ions was detected relative to those from other sealants. After sealant samples were soaked in a sodium fluoride solution, a significant amount of fluoride and other ions was released from the sealant containing S-PRG filler. These findings suggest that sealants containing S-PRG filler enhance the enamel demineralization-inhibiting effect and the remineralization-promoting effect for long-term dental care.

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This study aimed to investigate the influence of different overdenture attachment systems on the stress generated in peri-implant bone during overdenture dislodgement and loading. Two implants were placed in the canine regions on an acrylic edentulous mandibular model. Four strain gauges were attached to the resin surface adjacent to the left implant. Bar, ball, and magnetic attachments were examined. Three experimental overdentures were fabricated, and the denture parts of the attachment systems were incorporated into the mucosal surface. Retentive forces and strains generated in peri-implant bone during three types of dislodgement (vertical, anterior and posterior) and loading (left first molar region, right first molar region and mid-anterior region) were measured. The bar attachment showed the highest retentive force and reduced strain on posterior dislodgement. The ball attachment demonstrated the largest strain on loading at molar regions. The magnetic attachment showed the smallest retentive force and little strain.

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A zirconia-binding peptide motif was identified using a peptide phage display system. Yttria stabilized zirconia beads and discs were used as the target. Quartz crystal microbalance was used to monitor the binding of phages to zirconia. Starting from a library of phages displaying random sequences of 12-mer peptides, we repeated cycles of biopanning against zirconia beads. After four cycles of biopanning, we isolated a phage clone Φ#17. DNA sequencing of the corresponding portion of Φ#17 unexpectedly revealed that it displayed a 58-mer peptide (amino acid sequence: WMPSDVDINDPQGGGSRPNLHQPKPAAEAASKKKSENRKVPFYSHSWY-SSMSEDKRGW). We found that Φ#17 had a 300-fold, significantly higher binding affinity for zirconia discs than phages displaying no peptide. In quartz crystal microbalance assay, a rapid increase in energy dissipation was observed from Φ#17 but not from the control phages, indicating that Φ#17 binds to the surface of zirconia via its displayed peptide. We successfully identified a peptide motif that binds zirconia.

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The purpose of this study was to evaluate influence of etching ability of one-step self-etch adhesives on bonding to non-carious cervical sclerotic lesion. Forty-eight human maxillary premolars with and without natural non-carious cervical sclerotic lesions at buccal surfaces were used in this study. Artificial wedge-shaped lesions were prepared in sound premolars. All lesions were bonded with Bond Force (BF; pH=2.3) or G-Bond Plus (GBA; pH=1.5) according to the manufacturers’ instructions. After water storage for 24 hours at 37°C, bonded specimens were subjected to microtensile bond test to measure bond strength to the gingival wall in each lesion. The μTBS of BF to the natural lesion was significantly lower than that of artificial lesion (p<0.05), while for GBA, there is no significant difference (p>0.05). There was no difference in μTBS to artificial lesion between these two adhesives, however in case of non-carious cervical sclerotic lesion, the μTBS of GBA was statistically higher than that of BF.

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The aim of this study was to compare the efficacy of Mtwo, ProTaper retreatment files and Hedström files for the retreatment of root canals filled with BeeFill 2 in1 and cold lateral compaction techniques. 63 single-rooted human teeth were prepared with Mtwo rotary files to size 35/.04 and assigned into three groups (n=21/group). (1) BeeFill 2 in1/2Seal, (2) BeeFill 2 in1/AH26 and (3) laterally-compacted gutta-percha/AH26. The specimens were subgrouped according to the file system used to remove root fillings (n=7/subgroup): 1. Mtwo retreatment file, 2. ProTaper retreatment file, 3. Hedström file. Roots were split longitudinally and photographed. The time required for removal of root canal fillings and the areas of residual root filling materials were compared statistically (p<0.05). The maximum amount of remnant was observed in the Mtwo group for removal of BeeFill 2 in1/AH26. ProTaper retreatment files required less time to remove root filling material than Mtwo retreatment files and Hedström files (p<0.05). Among the tested removal systems, ProTaper retreatment files may offer the best efficiency-speed combination.

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PETG/PC/TPU polymer blend was prepared by mechanical blending. The mechanical properties of modified PETG/PC/TPU blend were characterized using a universal testing machine, and results were compared against two commercial thermoplastic products —Erkodur and Biolon. Blending modification improved the properties of PETG/PC/TPU. When blending ratio (wt%) was 70/10/20, PETG/PC/TPU exhibited optimal mechanical properties which exceeded those of Erkodur and Biolon. Tear strength was 50.23 MPa and elongation at break was 155.99%. Stress relaxation rate was 0.0136 N/s after 1 hour, which was significantly slower than Erkodur and Biolon (p<0.05). Water absorption rate was 0.57% after 2 weeks, which was significantly lower than Erkodur and Biolon (p<0.05).

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The antibacterial properties of a polymeric phosphonium salt were studied to determine its suitability as an additive to develop an antibacterial dental resin. The phosphonium salt monomer studied was tri-n-butyl(4-vinylbenzyl)phosphonium chloride (VP), and acrylic acid (AC) and methacryloyloxyethyl trimethyl ammonium chloride (MA) were used as controls. The antibacterial activity of these monomers and their corresponding polymers (PVP, PAC, and PMA) against Streptococcus mutans (S. mutans) was examined. When incubating S. mutans in a medium containing 10 μmol/mL for 24 hours, the antibacterial activity of PVP against S. mutans was high, while the antibacterial activity of PMA and VP was lower. AC, PAC and PMA exhibited the lowest antibacterial activity. The mechanical properties of the copolymers of methyl methacrylate, 2-hydroxyethyl methacrylate, and VP decreased as VP content increased, and were lower than those of poly(methyl methacrylate).

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