Effects of acid-alkali treatment on bioactivity and osteoinduction of porous titanium: An in vitro study.

BACKGROUND: To elucidate the bioactivity and bone regeneration of porous titanium surfaces treated using acid-alkali combination, and to define the optimal alkali reaction time. METHODS: Ten groups of porous Ti with at least 3 per group undergoing different acid-alkali treated time were prepared. The surface was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), bicinchoninic acid method (BCA), optical contact angle measurement and Raman spectrometry. Compression testing was performed with a universal testing machine. The bioactivity and osteoinduction were evaluated by a series of biological tests using a simulated body fluid (SBF) test, cell proliferation test, vinculin, ALP and OCN expression, and cell mineralization. RESULTS: The acid-alkali treatment formed micro- and nano-scale structures on the sample surfaces. The alkali treatment for 12 h achieved the sharpest nano-scale surface relief and the most protein absorption. The treated porous surface was coated with a NaHTiO3 layer. The acid-alkali etching did not compromise the elastic modulus and compressive strength of the porous Ti samples. In addition to hydroxyapatite, a perovskite phase was also formed on the treated porous samples in SBF. Non-treated dense Ti showed more cell adhesion and proliferation (P < 0.05), while osteoinduction and mineralization were more pronounced on the treated porous sample (P < 0.05). CONCLUSION: Acid-alkali treatment is an effective means of generating nano-scale relief on porous Ti surface, and is beneficial for bioactivity and bone regeneration. The 15 min acid and 12 h alkali etching is the optimal combination. The osteoinductive efficacy may be attributable to the surface physical chemistry and the formation of hydroxyapatite and perovskite layers, rather than direct cell adhesion and proliferation.

Effect of core ceramic grinding on fracture behaviour of bilayered zirconia veneering ceramic systems under two loading schemes.

OBJECTIVE: The aim of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered zirconia under two loading schemes. METHODS: Interfacial surfaces of sandblasted zirconia disks (A) were ground with 80 (B), 120 (C) and 220 (D) grit diamond discs, respectively. Surface roughness and topographic analysis were performed using a confocal scanning laser microscope (CSLM) and a scanning electron microscopy (SEM). Relative monoclinic content was evaluated using X-ray diffraction analysis (XRD) then reevaluated after simulated veneer firing. Biaxial fracture strength (σ) and Weibull modulus (m) were calculated either with core in compression (subgroup Ac-Dc) or in tension (subgroup At-Dt). Facture surfaces were examined by SEM and energy dispersive X-ray spectroscopy (EDS). Maximum tensile stress at fracture was estimated by finite element analysis. Statistical data analysis was performed using Kruskal-Wallis and one-way ANOVA at a significance level of 0.05. RESULTS: As grit size of the diamond disc increased, zirconia surface roughness decreased (p<0.001). Thermal veneering treatment reversed the transformation of monoclinic phase observed after initial grinding. No difference in initial (p=0.519 for subgroups Ac-Dc) and final fracture strength (p=0.699 for subgroups Ac-Dc; p=0.328 for subgroups At-Dt) was found among the four groups for both loading schemes. While coarse grinding slightly increased final fracture strength reliability (m) for subgroups Ac-Dc. Two different modes of fracture were observed according to which material was on the bottom surface. Components of the liner porcelain remained on the zirconia surface after fracture for all groups. SIGNIFICANCE: Technician grinding changed surface topography of zirconia ceramic material, but was not detrimental to the bilayered system strength after veneer application. Coarse grinding slightly improved the fracture strength reliability of the bilayered system tested with core in compression. It is recommended that veneering porcelain be applied directly after routine lab grinding of zirconia ceramic, and its application on rough zirconia cores may be preferred to enhance bond strength.

Bond strength of primer/cement systems to zirconia subjected to artificial aging.

STATEMENT OF PROBLEM: Creating reliable and durable adhesion to the nonactive zirconia surface is difficult and has limited zirconia use. The introduction of functional monomers such as 10-methacryloyloxydecyl dihydrogen phosphate (MDP) appears to have enhanced bond strength to zirconia. PURPOSE: The purpose of this in vitro study was to evaluate the long-term bond strength of several MDP-containing primer/cement systems to zirconia. METHOD AND MATERIALS: Zirconia blocks were divided into 6 groups (n=24) according to the 3 primers/cements to be bonded, as follows: Scotchbond Universal/RelyX Ultimate (SU/RU; consisting of MDP-containing primer/MDP-free cement); Clearfil ceramic primer/Panavia F (CCP/PAN; consisting ofMDP-containing/MDP-containing); and Z-Prime Plus/Duo-Link (ZP/DUO; consisting ofMDP-containing/MDP-free), which were compared with 3 nonprimed groups, RU, PAN, and DUO. After bonding, each group was further divided into 3 subgroups (n=8) according to the level of aging: 24-hour storage in water at 37°C (24H); 30-day storage at 37°C (30D); and 30-day storage at 37°C followed by 3000 thermal cycles (30D/TC). After aging, a shear bond strength test and failure mode analysis were performed. The data were analyzed using 2-way ANOVA (α=.05). RESULTS: After aging, nearly all primer/cement groups presented significantly higher bond strength than the related nonprimed groups for each level of aging (P<.05), except for CCP/PAN versus PAN with 24H (P=.741). SU/RU had the highest bond strength among the groups for all treatments (P<.05), except for CCP/PAN versus SU/RU with 30D/TC (P=.171). Among the nonprimed groups, only RU went through 30D/TC without premature debonding. With 24H and 30D, the failure modes in SU/RU and CCP/PAN were purely mixed, whereas those in the other groups were mainly adhesive, except for RU. CONCLUSIONS: The superiority of the initial bond strength in SU/RU may result from some functional components other than MDP. The presence of MDP in the cement did not appear to have a positive effect on long-term bond strength to zirconia.

Clinical performance of anterior resin-bonded fixed dental prostheses with different framework designs: A systematic review and meta-analysis.

OBJECTIVES: To systematically review the failure rate and complications of different framework designs of resin-bonded fixed dental prostheses (RBFDPs) in the anterior region. METHODS: A systematic search for clinical studies on RBFDPs published prior to December 2014 in Medline/PubMed, EMBASE, and Cochrane Library databases was conducted and complemented by a manual search. Randomized controlled trials (RCTs) as well as prospective and retrospective cohort studies that compared at least two RBFDP framework designs with a minimum of 2 years follow up were included in this review. The quality of the included studies were assessed using the Newcastle-Ottawa scale for cohort studies and Cochrane Handbook for RCT. Prostheses-based data on reported failure rate/survival rate, debonding, and fractures were analyzed by meta-analysis. RESULTS: Of 1010 screened articles, one RCT and 4 cohort studies fit the inclusion criteria and were included in the meta-analysis. All included articles have a high risk of bias. Failure rates of single-retainer cantilever RBFDPs were lower than two-retainer fixed-fixed RBFDPs (OR 0.42, 95% CI 0.19-0.94, P=0.04). Metal-ceramic RBFDPs showed no difference of failure rates between cantilever RBFDPs and two-retainer fixed-fixed RBFDPs (OR 0.93, 95% CI 0.33-2.63, P=0.89). Debonding was not significantly different between cantilever RBFDPs and two-retainer fixed-fixed RBFDPs (OR 0.61, 95% CI 0.23-1.60, P=0.32). Metal-ceramic RBFDPs showed no difference of debonding between cantilever RBFDPs and two-retainer fixed-fixed RBFDPs (OR 0.81, 95% CI 0.28-2.34, P=0.70,). CONCLUSIONS: Within the limitations of the present study, cantilever RBFDPs demonstrate lower clinical failure than two-retainer RBFDPs in the anterior region. The failure of metal-ceramic RBFDPs is independent of the framework design, while the failure of all-ceramic RBFDPs with different designs has not been clear yet. CLINICAL SIGNIFICANCE: Based on the principle of minimally invasive treatment, less number of retainers is recommended for RBFDPs.

Effect of Pore Size and Porosity on the Biomechanical Properties and Cytocompatibility of Porous NiTi Alloys.

Five types of porous Nickel-Titanium (NiTi) alloy samples of different porosities and pore sizes were fabricated. According to compressive and fracture strengths, three groups of porous NiTi alloy samples underwent further cytocompatibility experiments. Porous NiTi alloys exhibited a lower Young's modulus (2.0 GPa ~ 0.8 GPa). Both compressive strength (108.8 MPa ~ 56.2 MPa) and fracture strength (64.6 MPa ~ 41.6 MPa) decreased gradually with increasing mean pore size (MPS). Cells grew and spread well on all porous NiTi alloy samples. Cells attached more strongly on control group and blank group than on all porous NiTi alloy samples (p < 0.05). Cell adhesion on porous NiTi alloys was correlated negatively to MPS (277.2 µm ~ 566.5 µm; p < 0.05). More cells proliferated on control group and blank group than on all porous NiTi alloy samples (p < 0.05). Cellular ALP activity on all porous NiTi alloy samples was higher than on control group and blank group (p < 0.05). The porous NiTi alloys with optimized pore size could be a potential orthopedic material.

Effect of core ceramic grinding on fracture behaviour of bilayered lithium disilicate glass-ceramic under two loading schemes.

OBJECTIVES: The purpose of this in vitro study was to evaluate the effect of core ceramic grinding on the fracture behaviour of bilayered lithium disilicate glass-ceramic (LDG) under two loading schemes. METHODS: Interfacial surfaces of sandblasted LDG disks (A) were ground with 220 (B), 500 (C) and 1200 (D) grit silicon carbide (SiC) sandpapers, respectively. Surface roughness and topographic analysis were performed using a profilometer and a scanning electron microscopy (SEM), and then underwent retesting after veneer firing. Biaxial fracture strength (σf) and Weibull modulus (m) were calculated either with core in tension (subgroup t) or in compression (subgroup c). Failure modes were observed by SEM, and loading induced stress distribution was simulated and analyzed by finite element analysis. Statistical data analysis was performed using Kruskal-Wallis, one-way ANOVA, and paired test at a significance level of 0.05. RESULTS: As the grits size of SiC increased, LDG surface roughness decreased from group A to D (p<0.001), which remained unchanged after veneer firing. No difference in σf (p=0.41 for subgroups At-Dt; p=0.11 for subgroups Ac-Dc), m values as well as failure modes was found among four subgroups for both loading schemes. Specimens in subgroup t showed higher σf (p<0.001) and m values than subgroup c. Stress distribution between loading schemes did not differ from each other. Cracks, as the dominant failure mode initiated from bottom tensile surface. No sign of interfacial cracking or delamination was observed for all groups. CONCLUSIONS: Technician grinding changed surface topography of LDG ceramic material, but was not detrimental to the bilayered system strength after veneer application. LDG bilayered system was more sensitive to fracture when loaded with veneer porcelain in tension. CLINICAL SIGNIFICANCE: Within the limitations of the simulated grinding applied, it is concluded that veneer porcelain can be applied directly after technician grinding of LDG ceramic as it has no detrimental effect on the strength of bilayered structures. The connector areas of LDG fixed dental prosthesis are more sensitive to fracture compared with single crowns, and should be fabricated with more caution.

Basic fibroblast growth factor enhances osteogenic and chondrogenic differentiation of human bone marrow mesenchymal stem cells in coral scaffold constructs.

Temporomandibular joint (TMJ) disorders are commonly occurring degenerative joint diseases that require surgical replacement of the mandibular condyle in severe cases. Transplantation of tissue-engineered mandibular condyle constructs may solve some of the current surgical limitations to TMJ repair. We evaluated the feasibility of mandibular condyle constructs engineered from human bone marrow-derived mesenchymal cells (BMSCs). Specifically, human BMSCs were transfected with basic FGF (bFGF) gene-encoding plasmids and induced to differentiate into osteoblasts and chondroblasts. The cells were seeded onto mandibular condyle-shaped porous coral scaffolds and evaluated for osteogenic/chondrogenic differentiation, cell proliferation, collagen deposition and tissue vascularization. Transfected human BMSCs expressed bFGF and were highly proliferative. Osteogenesis was irregular, showing neovascularization around new bone tissue. There was no evidence of bilayered osteochondral tissue present in normal articulating surfaces. Collagen deposition, characteristic of bone and cartilage, was observed. Subcutaneous transplantation of seeded coral/hydrogel hyaluran constructs into nude mice resulted in bone formation and collagen type I and type II deposition. Neovascularization was observed around newly formed bone tissue; bFGF expression was detected in implanted constructs seeded with bFGF expressing hBMSCs. This report demonstrates that engineered porous coral constructs using bFGF gene-transfected human BMSCs may be a feasible option for surgical transplantation in TMJ repair.

Differential gene expression profiles of whole lesions from patients with oral lichen planus.

BACKGROUND: The molecular biological properties of oral lichen planus (OLP) are largely unknown. The aim of this study was to identify the genes responsible for its pathogenesis at the genome scale using DNA microarray technology. METHODS: The RNA samples extracted from the specimens of nine OLP patients and nine controls were analyzed with Affymetrix GeneChip. Real-time reverse transcriptase polymerase chain reaction (RT-PCR) analysis was applied to confirm GeneChip results. RESULTS: A total of 985 differentially expressed genes (629 up-regulated and 356 down-regulated) were identified. These genes were involved in many function classifications and biochemical pathways. The results of quantitative RT-PCR analysis of FOXP3, VEGFA, ANGPT1, MMP1, and SCGB2A2 were consistent with their changes demonstrated by GeneChip. CONCLUSIONS: This study showed the gene expression profiles of OLP, which were quite distinct from that of healthy controls. These results presented a global view of physiopathologic processes in lesions, which will give important clues to understand pathogenesis and identify new therapeutic targets of OLP.

[Preparation and stability assessment of a new resin root canal filling material].

OBJECTIVE: To synthesize a new resin root canal filling material (NRCFM) and evaluate its stability in water and artificial saliva. METHODS: The new root canal filling material was made of thermoplastic elastomer (TPE), ethylene vinyl acetate (EVA) and activity fillers. The NRCFM's stability in water and artificial saliva with different pH values was assessed using gravimetric analysis, ICP and FE-SEM. RESULTS: NRCFM1 and NRCFM2 were successfully made. Gravimetric evaluation showed that the changes in mass over 30 days different solution medium for NRCFM1 and NRCFM2 were comparable to that of GP (P > 0.05) and significantly different from Resilon (P < 0.001). ICP showed slight changes in Si concentration for NRCFM1 and NRCFM2, Zn for GP, Na and Si for Resilon in the alkaline artificial saliva (pH 9.5). GP and Resilon showed release of Zn and Na respectively in distilled water whereas NRCFM1 and NRCFM2 were stable. FE-SEM micrographs showed that there were slight changes on the surface topography of NRCFM1 and NRCFM2. CONCLUSIONS: The new resin root canal filling material NRCFM1 and NRCFM2 had good stability in different experimental solutions.

[Corrosive effect of topical fluoride agents on surfaces of five composite resins].

OBJECTIVE: To evaluate the potential corrosive effect of topical fluoride agents used for professional treatments at dental prophylaxis on the polished surfaces of five composite resins. METHODS: A total of 125 specimens were fabricated from micro hybrid composite, nano-combined composite, nanocomposite, compomer and ormocer in a phi 6 mm x 3 mm cavity with 25 specimens for each composite group. The flat surfaces of the specimens were smoothed and polished, then applied respectively with four topical fluoride agents and distilled water, and stored at 37 degrees C 100% relative humidity for 30 min. The changes in morphologic features of the surfaces were assessed by scanning electron microscopy (SEM). The disintegrated surface was further analysed under a confocal laser scanning microscope (CLSM). RESULTS: All fluorides showed reaction to all composites except nanocomposite. The aggressiveness of the fluorides arranged sequentially as F (Elmex fluid) > G (Elmex gelée) > D (Duraphat) > B (Bifluorid 12). The treated surfaces were generally rough. F and G caused the overall surface corrosion, whereas etching on the surface by D and B was sporadic confined. The destructive effects demonstrated a large number of craters on the surface somewhat like an atoll owing to filler dissolution. Crack formation resulted in destruction of the filler-matrix interface was observed. Ormocer was severely affected after F and G treatment. Instead of crater glass filler protruding from the bumpy surface indicated the excessively disintegrated matrix of ormocer. Topography under CLSM exhibited the roughening of the composite surface, roughness parameters for profile (Sa, Sz, Smax) increased when the surface was treated. Surface change in nanocomposite specimens was neither visually nor numerically discerned. CONCLUSIONS: Topical application of highly concentrated fluoride prophylactic agents leaded to surface degradation and porosity of composite, nanocomposite was, however, chemically resistant. Isolation of the composite surface should be considered in clinical application of topical fluoride.