The Effect of TBB, as an Initiator, on the Biological Compatibility of PMMA/MMA Bone Cement.

Acrylic bone cement is widely used in orthopedic surgery for treating various conditions of the bone and joints. Bone cement consists of methyl methacrylate (MMA), polymethyl methacrylate (PMMA), and benzoyl peroxide (BPO), functioning as a liquid monomer, solid phase, and polymerization initiator, respectively. However, cell and tissue toxicity caused by bone cement has been a concern. This study aimed to determine the effect of tri-n-butyl borane (TBB) as an initiator on the biocompatibility of bone cement. Rat spine bone marrow-derived osteoblasts were cultured on two commercially available PMMA-BPO bone cements and a PMMA-TBB experimental material. After a 24-h incubation, more cells survived on PMMA-TBB than on PMMA-BPO. Cytomorphometry showed that the area of cell spread was greater on PMMA-TBB than on PMMA-BPO. Analysis of alkaline phosphatase activity, gene expression, and matrix mineralization showed that the osteoblastic differentiation was substantially advanced on the PMMA-TBB. Electron spin resonance (ESR) spectroscopy revealed that polymerization radical production within the PMMA-TBB was 1/15-1/20 of that within the PMMA-BPO. Thus, the use of TBB as an initiator, improved the biocompatibility and physicochemical properties of the PMMA-based material.

Effects of adding silver nanoparticles on the toughening of dental porcelain.

STATEMENT OF PROBLEM: Dental porcelains currently used for ceramic restorations are brittle, and it is sometimes necessary to replace fractured or chipped restorations. Porcelain is fragile and exhibits elastic deformation rather than plastic deformation, leading to fracture or chipping of restorations. PURPOSE: The purpose of this study was to investigate the toughening of porcelain through the addition of silver nanoparticles. MATERIAL AND METHODS: Noritake Super (NS) Porcelain AAA modified with the addition of silver nanoparticles was used. The concentration of silver in the solution was adjusted to 100, 200, 500, and 1000 ppm (Ag100, Ag200, Ag500, and Ag1000). The Vickers hardness (Hv) and median crack length extending from the corner of each indent were measured. The fracture toughness (KIC) was calculated by the indentation method. Optical reflectance spectra were recorded by using a spectrometer in the wavelength range of 200 to 700 nm. X-ray diffraction spectroscopy, color measurement, Fourier transform infrared spectroscopy, and electron probe microanalysis were also performed. The observed values of Hv, 2a, E, and KIC were compared and evaluated with a 1-way ANOVA, followed by the Bonferroni method (α=.05). RESULTS: The addition of silver nanoparticles significantly increased the Hv of all specimens with the exception of Ag100. The median crack length was significantly smaller in Ag500 (104.5 µm, SD: 11.9) and Ag1000 (100.0 µm, SD: 5.5). Significantly higher toughness values were observed for Ag500 (1.54 MPa·m(1/2), SD: 0.05) and Ag1000 (1.51 MPa·m(1/2), SD: 0.08) than for the control (1.36 MPa·m(1/2), SD: 0.03). In terms of color difference, Ag500 (5.08, SD:1.32) and Ag1000 (5.47, SD:1.05) had values significantly greater than ΔE*=2.69. CONCLUSIONS: The addition of silver nanoparticles significantly increased the fracture toughness and Vickers hardness of the NS porcelain. A residual compressive stress was generated due to the ion exchange reaction and differential thermal expansion of the silver metal nanoparticles. However, the addition of Ag500 and Ag1000 nanoparticles led to a color change.

The enhanced shear bond strength of resin cement to zirconia with ordered conical spots through the CO2 laser process.

In this study, a new shear bonding system was created that uses a CO2 laser to form a pattern of conical spots on a zirconia prosthesis surface to improve mechanical interlocking. Four types of zirconia substrates were employed, which underwent particle abrasion after being polished, machined, spotted, and spot-particle abraded. The surface roughness of each substrate was measured via scanning electron microscopy and X-ray diffraction (XRD). A shear bond strength test was performed with the zirconia-based material and a composite resin assuming abutment construction. XRD did not indicate that forming spots caused a phase transformation in zirconia with respect to machined zirconia. The shear bond strength was approximately twice that of the machined samples and approximately 2.3 times that of the samples that underwent particle and spot-particle abrasion. Surface modification by spotting improved the mechanical fitting force. However, no significant difference was observed between particle abrasion and spot-particle abrasion.

Clinical assessment of resin-coating technique applied to exposed dentin after crown preparation.

The resin-coating technique, in which exposed dentin surfaces are covered using a thin-film coating material, was approved in the Japanese public health insurance system in December 2019. The purpose of this study was to evaluate clinical cases treated using the resin-coating technique with Hybrid Coat II (HC II) after tooth preparation on vital teeth. A total of 134 cases from patients who visited nine dental clinics were examined from the clinical records. Clinical signs and symptoms of cases before, during, and after treatment and at the time of recall were evaluated. The resin-coating was applied as either a single application with HC II (86.6%) or a combined application of HC II and a flowable resin composite (13.4%). The success rate without any symptoms of sensivity to cold water was 92.5% (124 cases). The current results indicated that the resin-coating with HC II is a reliable treatment for the tooth preparation of vital teeth.

Effects of silica sputtering on adhesion between zirconia and composite resin cores.

Radiofrequency magnetron sputtering of silicon was applied onto zirconia surfaces by use of a non-doped Si wafer at 2%, 5%, 8%, and 10% oxygen volumes. Immediately after sputtering, the contact angle was practically 0 for all oxygen volume specimens. In terms of sustainability of the hydrophilicity, however, 5% oxygen volume was found to be optimal. Scanning electron microscopy and energy dispersive X-ray spectroscopy clearly suggested the presence of silica layer on zirconia surfaces. The shear bond strength of the pre-treated zirconia and resin was 35.03±4.97 MPa, which was approximately 3.5 times higher than that of zirconia without any sputtering treatment (9.26±1.21 MPa). The failure mode of the pre-treated zirconia specimen was cohesive failure, whereas that of the control specimen was observed to be interface failure.

[A case report of esthetic and functional rehabilitation by a combination of periodontal and orthodontic treatments for advanced periodontal disease].

PATIENT: The patient was a 44-year-old woman who presented with masticatory and esthetic problems. She had discoloration of CR filling of a maxillary anterior tooth, marginal discoloration, anterior protrusion, median diastema, and closed bite where the mandibular anterior tooth region occluded with the maxillary alveolar region, tooth 8 elongation and tooth 4 defect. Periodontal and orthodontic treatments were therefore performed for esthetic and functional recovery. DISCUSSION: After prosthodontic therapy, postoperative management techniques are crucial, including thorough plaque control, use of a retainer to prevent teeth from moving back towards the original positions (Begg technique), muscle function therapy (improving tongue movement patterns and strengthening the lingual and oral sphincter muscles) and occlusal adjustment. CONCLUSION: In the present patient, the effectiveness of orthodontic therapy before prosthodontic therapy was reaffirmed: dentine can be preserved, prosthodontic therapy is easier to perform, and therapeutic outcomes are highly predictable.

[Manufacture of a titanium full crown by CAD/CAM--tolerance of the cutting tool].

PURPOSE: We investigated the durability of the cutting tool(bar)that is used when creating a dental crown by using the CAD/CAM system of a computer-assisted NC machine tool. METHODS: We used the chamfer type as the shape of the dental cervical margin of the support tooth model. We also used a mold model whose shaft surfaces on both sides had an 8-degree taper. We used the CAD/CAM system of DENTAL Cadim (Advance Inc.). First, we manufactured a nonocclusion dental crown of the resin-pattern on top of the support dental model, and measured its 3-dimensional shape. Upon measuring the 3-dimensional shape, we created a pure-titanium block by using cutting bars continuously for rough processing and for finishing processing separately. Upon completion of the pure-titanium block, we measured the time required for each processing and measured the surface roughness after each processing. RESULTS: The surface roughness Ra of the rough processing became significantly worse after the fifth processing (p<0.01). Rmax became significantly worse after the sixth processing(p<0.05)and after the seventh processing (p<0.01). The surface roughness of both Ra and Rmax of the finishing processing became significantly worse after the fifth processing (p<0.05) and after the seventh processing (p<0.01). CONCLUSIONS: From the viewpoint of quality of the crown's finished surface and compatibility fitness, the number of cuttings, the number of rough processing and the number of finishing processing using the same cutting tool for making a full crown of a molar tooth should be limited to four times.

Effects of dental porcelain containing silver nanoparticles on static fatigue.

The purpose of this study was to clarify the effect of silver nanoparticles on the behavior of subcritical crack growth (SCG) in dental porcelains. Prior to occurrence of fast fracture in dental porcelains, SCG occurs and leads to strength degradation over time. SCG in dental porcelains can be characterized by the stress corrosion susceptibility coefficient, n. A higher n value means a higher resistance to SCG. In this study, porcelain disks were prepared by mixing a commercial dental porcelain powder with different concentrations of silver nanoparticles, and then air-dried and fired according to manufacturer's instructions. Stress corrosion susceptibility coefficients of powder compacts were determined using a post-indentation method. A Vickers indenter was applied to the porcelain surface, and lengths of median cracks were measured at fixed time intervals over a 24-h period to calculate n. Addition of silver nanoparticles significantly increased the stress corrosion susceptibility coefficient of dental porcelain.

Addition of platinum and silver nanoparticles to toughen dental porcelain.

Several studies have investigated toughening porcelain that is layered over a frame or a core. The introduction of residual compressive stress to the surface of porcelain has been shown to be effective to strengthen it. In the present study, nanoparticles of precious metals of silver and platinum (rather than non-precious metals) were used to evaluate if they could increase the fracture resistance of porcelain. The addition of silver and platinum nanoparticles was found to improve the mechanical properties of porcelain since it increased both the Young's modulus and the fracture toughness of commercial porcelain.

Toughening of CAD/CAM all-ceramic crowns by staining slurry.

The ability of staining slurries containing silver and/or potassium compounds to enhance the mechanical properties of a leucite-reinforced glass ceramic (IPS Empress CAD) was investigated by measuring the Vickers hardness, median crack length, toughness, and compressive residual stress of specimens. A staining slurry containing potassium ions was found to increase the toughness of IPS specimens more than a staining slurry containing only silver ions when applied prior to sintering. None of the staining slurries produced any color changes. Thus, the results obtained in this study demonstrate that staining slurries increase the Vickers hardness and the fracture toughness of the surface and subsurface regions of all-ceramic IPS blocks fabricated by a CAD/CAM system without sacrificing their aesthetics.