This study aimed to evaluate the effect of pre-etching for two-step self-etch adhesive bonding to bur-cut and uncut enamel. Bur-cut and uncut enamel surfaces were assigned to surface treatments of no etchant (CT), Enamel Conditioner (EC; Shofu, Kyoto, Japan), or K-etchant syringe (KE; Kuraray Noritake Dental, Tokyo, Japan). The bonded samples were thermal cycled and evaluated by microshear bond strength (μSBS). The adhesive interface after acid-base challenge and the conditioned enamel surfaces were morphologically analyzed using scanning electron microscopy (SEM). For bur-cut enamel, EC and KE pre-etching significantly improved μSBS. For uncut enamel, KE showed higher μSBS than EC. SEM observation revealed that only KE removed the prismless layer of the uncut enamel surface. EC could improve enamel bonding and appears to be a substitute for phosphoric acid, especially for bur-cut enamel. However, uncut enamel could not be effectively conditioned by EC with a lower bond strength than KE.

Bone regeneration requires cells, growth factors, and scaffolds that should have biocompatibility, porosity, and physical strength. Therefore, coral granules (CG) with diameters of 600–1,000 µm were prepared as a potential graft material from cultured edaphic thermostable corals. X-ray and electron microscopy characterization revealed that CGs were porous and permeable with lumen diameters of approximately 200 µm. Human periodontal ligament fibroblasts showed significantly increased mitochondrial activity in culture seven days after adding CG. After CG filling into an experimentally created one-wall infrabony defect in a beagle dog jawbone, the defect almost completely disappeared within approximately 8 weeks, and bone tissue growth was observed in the replacement area. This could indicate extremely rapid healing of a bone defect previously considered incapable of self-healing. Based on stable supply of cultured coral (Montipora digitata), CG is potentially an ideal replacement material for alveolar and jawbone defects.

Phosphoric acid (PA) etchants are widely used for the bonding pretreatment of teeth; however, their influences on the bonding between glass-ceramics and resin cement have not been clarified yet. This study investigated the effect of a thickening agent on the bonding strength between feldspar porcelain treated with a PA etchant and resin cement with a silane coupling agent. The experiments were performed using two PA etchants: commercial one and prepared one consisting a PA aqueous solution and poly(ethylene glycol) thickening agent. The samples were evaluated by shear bond strength testing, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The obtained results revealed that the thickening agent adhered to the porcelain surface and inhibited cement bonding. Meanwhile, PA remained on the surface due to the presence of the thickening agent and activated the silane coupling agent. Overall, the PA etchant did not improve the bond durability.

This study aimed to evaluate the retentive force of polyetheretherketone (PEEK) and zirconia secondary crowns on ready-made titanium implant abutments (with height, diameter, and taper as 5.5 mm, 4.5 mm, and 6°, respectively) as the primary crown. PEEK, zirconia, and titanium secondary crowns were fabricated using a CAD/CAM system. Insertion and removal tests of secondary crowns on the primary crown were conducted for 2,000 cycles. The initial retentive forces recorded at the 100th cycle for PEEK, zirconia, and titanium were 13.0±7.9, 2.9±2.6, and 27.6±1.7 N, respectively. The retentive forces of PEEK and zirconia showed no significant difference among all cycles. However, the retentive force of the titanium used as a control decreased (20.3±2.8 N) significantly at the 2,000th cycle. Although the retentive force of PEEK was lower than that of titanium, it was within the range that can provide a suitable retentive force of 5 N for removable dental prostheses.

The color-matching ability of single-shade composites Omnichroma (OMN) and Omnichroma Flow (OCF) is ensured by structural color, which arises from monodisperse 260 nm spherical fillers. This study evaluated how filler load influences the color adjustment potential of composite restorations to human teeth of various shades. The performance of composites containing the 260 nm spherical fillers —OMN (79 wt%), OCF (71 wt%), and experimental composites R1 (65 wt%), and R2 (60 wt%)— was compared to two conventional A2-shade composites and a transparent composite. Additionally, the translucency parameter, spectral reflectance, and light transmission properties were assessed. Composites with a lower load of the 260 nm spherical fillers exhibited lower light diffusion and lower reflectance in the yellow-to-red range (580–650 nm), which is characteristic for the structural color of OMN and OCF. The best color adjustment was achieved with OCF, presumably due to its high translucency and uniform spectral reflectance.

Senescence-associated secretory phenotype (SASPs) secreted from senescent cells often cause the deleterious damages to the surrounding tissues. Although dedifferentiated fat (DFAT) cells prepared are considered a promising cell source for regenerative therapies, SASPs from DFAT cells undergoing long-term cell culture, which latently induce replicative senescence, have barely been explored. The present study was designed to investigate senescent behaviors in rat-derived DFAT cells at high passage numbers and to analyze the possible types of SASPs. Our data show that DFAT cells undergo senescence during replicative passaging, as determined by multiple senescent hallmarks including morphological changes in cell shape and nucleus. Moreover, RT² PCR array analysis indicated that senescent DFAT cells expressed higher levels of 16 inflammatory cytokines (Ccl11, Ccl12, Ccl21, Ccl5, Csf2, Cxcl1, Cxcl12, Ifna2, IL11, IL12a, IL13, IL1a, IL1rn, IL6, Mif, and Tnf) associated with SASPs than non-senescent cells. This study implicates that rat DFAT cells undergo cellular senescence after long-term cell culture; cautious consideration should be paid to treat SASP secretion when senescent DFAT cells are used in regenerative medicine.

Reparative dentin formed by dental cavity preparation (DCP) is frequently used in clinical operations and plays a pivotal role in pulp protection. Recent reports have shown that senescent cells induced by various stressors aggravate many diseases. They can be treated using senolytics, which are drugs that selectively eliminate senescent cells. However, the association between DCP, senescent cells, and senolytics remains unclear. In this study, we established a rat model of DCP and analyzed the spatiotemporal localization of senescent cells in the pulp. The results showed that p21- and p16-positive senescent cells appeared mostly around the pulp horn (PH) under DCP. Furthermore, administration of senolytics (dasatinib and quercetin) successfully eliminated these senescent cells, thereby restoring the volume of reparative dentin formation. These data indicate that senescent cells induced by DCP may hamper the formation of reparative dentin. Senescent cells may be targets for the development of new restorative dentistry therapies.

The aim of this in vitro study was to compare the fracture resistance of immature anterior teeth restored with different biomaterials. After preparation of bovine incisors to simulate immature permanent teeth, 98 specimens were assigned into seven groups as follows: G1 —negative control group; G2 —apexification with hydraulic calcium silicate cement in the whole root; G3 —apexification and gutta percha; G4 —apexification and fiber post; G5 —apexification with micro-posts; G6 —apexification with composite; and G7 —revascularization. Both the fracture resistance and the location where the fracture occurred were recorded. Group 4 with a fiber post increased fracture resistance value compared to control (p<0.05). The different tested biomaterials did not influence the location where the fractures occurred among the seven groups (χ²₁=1.760, p=0.1846).

The present study investigated the effects of a co-stimulation with surface reaction-type pre-reacted glass-ionomer (S-PRG) filler eluate and muramyl dipeptide (MDP) on matrix metalloproteinase (MMP)-1 production by human dental pulp fibroblast-like cells (hDPFs). S-PRG filler eluate contains 6 ions (F, Na, Al, B, Sr, and Si) released from S-PRG filler. Each S-PRG filler eluate and MDP stimulation enhanced MMP-1 production by hDPFs. The co-stimulation with S-PRG filler eluate and MDP enhanced MMP-1 production more than the MDP stimulation alone. A similar stimulation induced the phosphorylation of ERK 1/2. The increased secretion of MMP-1 and enhanced phosphorylation of ERK 1/2 by the co-stimulation with S-PRG filler eluate and MDP were suppressed by the selective and potent CaSR antagonist NPS 2143. Since strontium binds to CaSR, these results suggest that the enhanced production of MMP-1 by the co-stimulation with S-PRG filler eluate and MDP was due to the effects of strontium.

This study examined the crystal orientation of four kinds of pressable lithium disilicate glass-ceramics and evaluated the effect of crystal orientation on flexural strength. Bar-shaped (24 mm in length, 1.2 mm in thickness, 4.0 mm in width), disk-shaped (12 mm in diameter, 0.5 mm in thickness), and crown-shaped (maxillary first molar) specimens were prepared according to the manufacturer’s instructions. Three-point and biaxial flexural strengths were measured for bar- and disk-shaped specimens. Microstructure analysis was performed using X-ray diffractometry and scanning electron microscopy. Three-point flexural strength was improved by parallel crystal orientation along the longitudinal direction of the bar-shaped specimen. There was no relationship between two-dimensional crystal orientation and biaxial flexural strength. The results of this study assumed that biaxial flexural strength was improved by the crystal orientation in the cross-sectional direction. Pressed restorations are expected to possess higher strength than milled restorations due to their crystal orientation.

Ti-50Zr alloy is 2.5 times as strong as pure Ti and has a lower Young’s modulus, making it a useful material for repairing bone and teeth. However, Ti-50Zr alloy has a limited ability to bond with bone in vivo. Under biological conditions, apatite formation at the surface of a Ti or alloy implant is necessary for its bonding with bone. Various approaches to surface modification have been proposed to impart bone-bonding ability to Ti-50Zr alloy; however, there remains a need for further improvements to the alloy’s apatite-forming ability. Hence, in this study, we compared apatite formation at the surface of alloy substrates in simulated body fluid, after various surface treatments. Treatment with 5 M NaOH followed by 1 M CaCl₂ was the most effective procedure, whereas a sample subjected to a hot water post-treatment formed less apatite. Notably, no apatite formed on samples treated with 10 M NaOH.

There is a high risk of external apical root resorption (EARR) following the application of intrusive orthodontic forces to the apical root. However, there is a lack of suitable animal models to study this phenomenon in depth. This study compared the usability of three different types of loops, namely, vertical helical loop, box loop, and L loop, for preparing a rat model of orthodontic tooth movement with invasive forces. Results showed a significant downward movement in the first molar of the rat after L loop placement for 14 days. Three-dimensional reconstructed images showed root resorption and length shortening on the apical root and decreased bone volume and trabecular thickness in the alveolar bone under compression. Histological staining revealed odontoclasts on the root resorption fossa. This study showed that orthodontic tooth movement using the L loop provides an effective experimental animal model of EARR.

This study aimed to identify the optimal technological parameters for rebonding zirconia brackets treated using an erbium-doped yttrium aluminum garnet (Er:YAG) laser. Er:YAG lasers with varying energies were compared with the flaming and sandblasting treatment methods. Detached zirconia brackets were treated and evaluated for shear rebond strength, bracket bottom-plate morphology, position, and depth of microleakage. They were then treated for rebonding using flaming, sandblasting, or an Er:YAG laser set at 250-mJ, 300-mJ, 350-mJ energy. Their shear rebond strength were measured using microforce tester. The topography of the treated bottom plates were observed using scanning electron microscopy. A confocal laser scanning microscope was used to measure the depth of the joint and gingival-side microleakage at the bracket-adhesive (B-A) and enamel-adhesive interfaces. With 300 mJ Er:YAG laser treatment, the detached zirconia brackets can obtain good rebonding strength and minimize the shape change of bracket bottom plates; the adhesion of the B-A interface is better than other methods.

The recently developed biphasic calcium phosphate cement (BCPC) consists of α-tricalcium phosphate-tetracalcium phosphate as the solid phase and calcium phosphate solution as the liquid phase. BCPC powder is composed of a single solid solution with a monomodal size distribution. Here, we used a bacterial leakage model to examine the utility of BCPC as a seal for root-end filling. We prepared large (median particle size=9.96 µm; BCPC-L) and small (median particle size=4.84 µm; BCPC-S) BCPC powders. In total, 45 single-rooted teeth were instrumented, resected at the root-end, and retrofilled with experimental materials. Mineral trioxide aggregate (MTA) was used as the control. After visual confirmation of BCPC powder size and retrofilling quality by microscopy, bacterial leakage tests were conducted using Enterococcus faecalis. The bacterial leakage tests did not reveal any significant differences between BCPC-S and MTA. Our findings suggest that BCPC-S is useful for root-end filling.

This study evaluated the effect of luting system with acidic primers on the durability of bonds with Ti-15Mo-5Zr-3Al titanium alloy (Ti-15Mo-5Zr-3Al) and its component metals. Adherend metals were Ti-15Mo-5Zr-3Al, Ti, Mo, Zr, and Al. Four primers were evaluated as adhesion promoters: Alloy Primer (ALP), Estenia Opaque Primer (EOP), M. L. Primer (MLP), and Super Bond liquid (SBL). An acrylic resin was used as the luting material. Pre- and post-thermocycling shear bond strength was determined to evaluate the bonding durability, and the results were compared using non-parametric statistical analyses (n=11/group). The post-thermocycling bond strength in MPa (median) associated with ALP, EOP, MLP, and SBL were 18.8, 19.8, 4.1, and 0.8, respectively, for Ti-15Mo-5Zr-3Al. The results showed that two primers containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) were effective for the durability of bonding of Ti-15Mo-5Zr-3Al to the resin. MDP enhanced the bonding durability of the resin bonded to either Ti, Zr, or Al.

Volumetric shrinkage (VS) of conventional, bulk-fill, and core build-up resin-based composites (RBCs) of various thickness (1–5 mm) was measured using the modified bonded-disk method with confocal laser scanning microscopy. Additionally, the bottom-to-top ratio of Vickers hardness (%VH) was measured. Conventional RBCs exhibited significantly higher VS than bulk-fill and core build-up RBCs (p<0.05). As specimen thickness increased, VS relative to volume (%VS) and difference in VS at each depth (VS_depth) decreased. For conventional RBCs, there was a significant drop in VS_depth between 1 mm and 2 mm (p<0.05), and another drop was observed between 3 mm and 4 mm (p<0.05) where %VH decreased below 90%. For bulk-fill and core build-up RBCs, VS_depth decreased significantly between 2 mm and 3 mm (p<0.05), but %VH exceeded 90% even in 5 mm deep cavities. These results indicated that post-curing contributed to lower shrinkage in deeper layers, and that conventional RBCs were not adequately polymerized at the depth of over 3 mm.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) is one of the growth factors that may induce the formation of new bone. The aim was to determine the efficacy of low doses of rhBMP-2 for bone regeneration using a collagen sponge as a carrier. Three doses of rhBMP-2 (1.167, 0.117, and 0.039 mg/mL) were combined with an absorbable collagen sponge (ACS) as a delivery vehicle. The rhBMP-2/ACS implants were placed in the subcutaneous tissues of rat backs. X-ray microcomputed tomography (micro-CT) and histological analysis were used to evaluate bone formation. The samples treated with 1.167 mg/mL of rhBMP-2 showed greater bone formation than the samples treated with 0.117 mg/mL of rhBMP-2 four weeks after surgery. However, there was no evidence of bone formation in the samples that were treated with 0.039 mg/mL of rhBMP-2. It was found that rhBMP-2 was osteogenic even at one-tenth of its manufacturer’s recommended concentration (1.167 mg/mL), indicating its potential for clinical use at lower concentrations.

The aim of this study was to evaluate the accuracy and adaptation of all-ceramic zirconia crowns fabricated by stereolithography (SLA) compared with computer-aided design/computer-aided manufacturing (CAD/CAM) milling technology. Ten all-ceramic zirconia crowns each were fabricated with SLA (experimental group) and CAD/CAM numerical control milling technology (control group). The accuracy (including trueness and precision), and the internal and marginal adaptation of the crowns were measured with the optical impression and silicone rubber film method and the three-dimensional deviation analysis software Geomagic studio, and the results were statistically analyzed. The results indicated no statistical difference in trueness and the occlusal, axial and marginal adaptation between groups (p>0.05), and the precision in the SLA group was better than that in the milling group (p<0.05). Thus, crowns fabricated with SLA meet clinical application requirements.

The aim of this study was to assess the shear bond strength and durability between plasma-pretreated and polydopamine (PDA)-coated zirconia and titanium. Four groups were prepared according to the different surface treatments (untreated ZrO₂, plasma-pretreated ZrO₂, PDA-coated ZrO₂, and plasma-pretreated and PDA-coated ZrO₂ (PP+PDA-ZrO₂). The surface topography and roughness, contact angle, and elemental analysis of the coatings of the four groups were investigated, and the bond strength and durability of the specimens were evaluated based on shear bond strength and thermocycle tests. Physical and chemical characterization results confirmed that PDA coatings can be successfully formed on zirconia substrates. The roughness and hydrophilicity were significantly higher in the PP+PDA-ZrO₂ group_, which demonstrated better shear bond strength and durability between zirconia and titanium. The plasma pretreatment of zirconia substrates can enhance the stability of the PDA coating layer, and hybrid surface modifications can provide several bonding advantages for clinical use.