Proteoliposome-Incorporated Seawater Reverse Osmosis Polyamide Membrane: Is the Aquaporin Water Channel Effect in Improving Membrane Performance Overestimated?

The water channel feature of the aquaporin (AQP) is considered to be the key in improving the permselectivity of AQP-based thin-film composite (TFC) polyamide (PA) membranes, yet much less attention has been paid to the physicochemical property changes of the PA layer induced by AQP-reconstituted proteoliposomes. This study systematically investigated the roles of proteoliposome constituents (liposome/detergent/AQP) in affecting the physicochemical properties and performance of the membranes. For the first time, we demonstrated that the constituents in the proteoliposome could facilitate the formation of a PA layer with enlarged protuberances and thinner crumples, resulting in a 79% increase in effective surface area and lowering of hydraulic resistance for filtration. These PA structural changes of the AQP-based membrane were found to contribute over 70% to the water permeability increase via comparing the separation performance of the membranes prepared with liposome, detergent, and proteoliposome, respectively, and one proteoliposome-ruptured membrane. The contribution from the AQP water channel feature was about 27% of water permeability increase in the current study, attributed to only ∼20% vesicle coverage in the PA matrix, and this contribution may be easily lost as a result of vesicle rupture during the real seawater reverse osmosis process. This study reveals that the changed morphology dominates the performance improvement of the AQP-based PA membrane and well explains why the actual AQP-based PA membranes cannot acquire the theoretical water/salt selectivity of a biomimetic AQP membrane, deepening our understanding of the AQP-based membranes.

Hydrogen peroxide bleaching induces changes in the physical properties of dental restorative materials: Effects of study protocols.

OBJECTIVE: The purpose of this study was to evaluate the influence of study protocols on the effects of bleaching on the surface roughness, substance loss, flexural strength (FS), flexural modulus (FM), Weibull parameters, and color of 7 restorative materials. MATERIALS AND METHODS: The test materials included 4 composite resins, 1 glass-ionomer cement, 1 dental ceramic, and 1 polyacid-modified composite. The specimens were randomly divided into 4 groups (n = 20) according to different study protocols: a bleaching group at 25°C (group 25B), a bleaching group at 37°C (group 37B), a control group at 25°C (group 25C), and a control group at 37°C (group 37C). The specimens in the bleaching group were treated with 40% hydrogen peroxide for 80 min at the respective environmental temperatures. The surface roughness, substance loss, FS, FM, and color of the specimens were measured before and after treatment. FS data were also subjected to Weibull analysis, which was used to estimate of the Weibull modulus (m) and the characteristic strength (σ0 ). RESULTS: Surface roughness increased and significant color changes were observed for all tested specimens after bleaching treatment, except for the ceramic. After bleaching at 37°C, the polyacid-modified composite showed significantly reduced FS, FM, m, and σ0 values in comparison to the control specimens stored at 37°C in whole saliva. Significant differences were also found between the 37B and 25B polyacid-modified composite groups in terms of surface roughness, FS, m, σ0 , and color changes. CONCLUSIONS: Varying effects of bleaching on the physical properties of dental restorative materials were observed, and the influences of the study protocols on bleaching effects were found to be material-dependent. CLINICAL SIGNIFICANCE: The influence of study protocols on the effects of bleaching on the surface roughness, flexural properties, and color of dental restorative materials are material-dependent and should be considered when evaluating the effects of bleaching on dental restorative materials.

Analyzing the Evolution of Membrane Fouling via a Novel Method Based on 3D Optical Coherence Tomography Imaging.

The development of novel tools for studying the fouling behavior during membrane processes is critical. This work explored optical coherence tomography (OCT) to quantitatively interpret the formation of a cake layer during a membrane process; the quantitative analysis was based on a novel image processing method that was able to precisely resolve the 3D structure of the cake layer on a micrometer scale. Fouling experiments were carried out with foulants having different physicochemical characteristics (silica nanoparticles and bentonite particles). The cake layers formed at a series of times were digitalized using the OCT-based characterization. The specific deposit (cake volume/membrane surface area) and surface coverage were evaluated as a function of time, which for the first time provided direct experimental evidence for the transition of various fouling mechanisms. Axial stripes were observed in the grayscale plots showing the deposit distribution in the scanned area; this interesting observation was in agreement with the instability analysis that correlated the polarized particle groups with the small disturbances in the boundary layer. This work confirms that the OCT-based characterization is able to provide deep insights into membrane fouling processes and offers a powerful tool for exploring membrane processes with enhanced performance.

Microscopic characterization of FO/PRO membranes--a comparative study of CLSM, TEM and SEM.

Osmotically driven membrane processes (including forward osmosis (FO) and pressure retarded osmosis (PRO)) have received increasing attention in recent decades. The performance of an FO/PRO membrane is significantly limited by internal concentration polarization, which is a strong function of the membrane support layer pore structure. The objective of the current study was to develop microscopic characterization methods for quantitative/semiquantitative analysis of membrane pore structure (both pore diameter and porosity distribution across membrane thickness). The use of confocal laser scanning microscopy (CLSM) for noninvasive characterization of the internal pore structure of FO/PRO membranes is reported for the first time. By performing optical sectioning, information on pore diameter, porosity depth profile and pore connectivity can be obtained. The CLSM porosity results are further compared to those obtained using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and reasonably good agreement was observed. A comparison of these characterization methods reveals their complementary nature, and a combination of these techniques may allow a more comprehensive understanding of membrane structure. The current study also provided a comprehensive insight into the pore structure of commercially available FO/PRO membranes.

Thermo-responsive nonionic amphiphilic copolymers as draw solutes in forward osmosis process for high-salinity water reclamation.

Recently, thermo-responsive nonionic amphiphilic copolymers have shown a great potential as forward osmosis (FO) draw solutes for high-salinity water desalination and zero-liquid discharge (ZLD). However, the relationship between the copolymer structural properties and key characteristics as draw solutes, as well as copolymer's chemical stability after regeneration have not been much studied. In this work, we systematically investigated poly (ethylene oxide)-block-poly (propylene oxide)-block-poly (ethylene oxide) (PEO-PPO-PEO) copolymers as draw solute. The results showed that the PEO segments significantly influenced the viscosity, osmotic pressure and lowest phase separation temperature of the copolymer aqueous solutions. Among four commercial copolymers studied, Pluronic® L35 with moderate molecular weight (Mn 1,900 Da), 50% PEO, and relatively high hydrophilic-lipophilic balance (HLB) showed the best draw solution (DS) performance. It also showed great stability in physiochemical properties and draw capacity after more than ten cycles of regeneration. On the other hand, despite the fact that membrane fouling was observed due to the use of copolymer DS, the FO flux (∼1.2 L m‒2 h‒1, as similar with the virgin membrane) was not affected when high-salinity feedwater such as seawater RO brine was applied. Overall, our study has provided a more comprehensive understanding on the characteristics of nonionic amphiphilic copolymer DS and showcased the promise of copolymer-driven FO process in high-salinity water desalination and ZLD.

Fouling of nanofiltration, reverse osmosis, and ultrafiltration membranes by protein mixtures: the role of inter-foulant-species interaction.

Protein fouling of nanofiltration (NF), reverse osmosis (RO), and ultrafiltration (UF) membranes by bovine serum albumin (BSA), lysozyme (LYS), and their mixture was investigated under cross-flow conditions. The effect of solution chemistry, membrane properties, and permeate flux level was systematically studied. When the solution pH was within the isoelectric points (IEPs) of the two proteins (i.e., pH 4.7-10.4), the mixed protein system experienced more severe flux decline compared to the respective single protein systems, which may be attributed to the electrostatic attraction between the negatively charged BSA and positively charged LYS molecules. Unlike a typical single protein system, membrane fouling by BSA-LYS mixture was only weakly dependent on solution pH within this pH range, and increased ionic strength was found to enhance the membrane flux as a result of the suppressed BSA-LYS electrostatic attraction. Membrane fouling was likely controlled by foulant-fouled-membrane interaction under severe fouling conditions (elevated flux level and unfavorable solution chemistry that promotes fouling), whereas it was likely dominated by foulant-clean-membrane interaction under mild fouling conditions. Compared to nonporous NF and RO membranes, the porous UF membrane was more susceptible to dramatic flux decline due to the increased risk of membrane pore plugging. This study reveals that membrane fouling by mixed macromolecules may behave very differently from that by typical single foulant system, especially when the inter-foulant-species interaction dominates over the intra-species interaction in the mixed foulant system.

Nanofiltration membrane fouling by oppositely charged macromolecules: investigation on flux behavior, foulant mass deposition, and solute rejection.

Nanofiltration membrane fouling by oppositely charged polysaccharide (alginate) and protein (lysozyme) was systematically studied. It was found that membrane flux decline in the presence of both lysozyme and alginate was much more severe compared to that when there was only lysozyme or alginate in the feed solution. The flux performance for the mixed foulants was only weakly affected by solution pH and calcium concentration. These effects were likely due to the strong electrostatic attraction between the two oppositely charged foulants. Higher initial flux caused increased foulant deposition, more compact foulant layer, and more severe flux decline. The deposited foulant cake layer had a strong tendency to maintain a constant foulant composition that was independent of the membrane initial flux and only weakly dependent on the relative foulant concentration in feed solution. In contrast, solution chemistry (pH and [Ca²âº]) had marked effect on the foulant layer composition, likely due to the resulting changes in the foulant-foulant interaction. The mixed alginate-lysozyme fouling could result in an initial enhancement in salt rejection. However, such initial enhancement was not observed when there was 1 mM calcium present in the feedwater, which may be attributed to the charge neutralization of the foulant layer.

Changes in bone density and cyst volume after marsupialization of mandibular odontogenic keratocysts (keratocystic odontogenic tumors).

PURPOSE: To evaluate bone formation after marsupialization of odontogenic keratocysts (keratocystic odontogenic tumors) of the mandible. PATIENTS AND METHODS: A total of 53 patients with mandibular odontogenic keratocysts underwent marsupialization. Clinical and radiographic examinations were done at 1, 3, and 6 months postoperatively. The bone density of the cyst site was measured on the panoramic radiographs using the Digora. The volume of the cyst was measured by injection of saline solution into the cyst cavity. Student t test and Spearman's rank correlation were used for statistical analysis. RESULTS: Healing was uneventful in all patients. The diameter of the cysts was 4.1 to 11.0 cm (average 5.4). The panoramic radiographs showed a continuous increase in bone density of the cystic area, with a 22.42% increase at 1 month, 46.07% at 3 months, and 64.69% at 6 months postoperatively compared with the preoperative values. The decrease in cyst volume was 19.05% at 1 month, 55.62% at 3 months, and 79.67% at 6 months postoperatively. The increase in bone density and decrease in cyst volume were more significant in the first 3 months than in second 3 months (P < .01). The increase in bone density correlated inversely with the decrease in the cyst volume (P < .01). CONCLUSION: Bone regeneration can occur more rapidly in large mandibular odontogenic keratocysts after marsupialization with drainage by a cyst plug. After 3 months, secondary enucleation of the cyst can be performed.

Alveolar ridge preservation prior to implant placement with surgical-grade calcium sulfate and platelet-rich plasma: a pilot study in a canine model.

PURPOSE: To evaluate the combination of surgical-grade calcium sulfate (SGCS) and platelet-rich plasma (PRP) for alveolar ridge preservation prior to implant placement. MATERIALS AND METHODS: Five mongrel dogs were used as subjects. Four enlarged mandibular extraction sockets, 2 on each side, were created in each dog. According to a split-mouth design, the 2 anterior sockets received either SGCS/PRP (SGCS/PRPant) or were left unfilled, while the 2 posterior sockets received either SGCS/PRP (SGCS/PRPpost) or SGCS. Computerized tomographic (CT) scans were conducted at 1 day and 8 weeks postextraction to detect the change in ridge height. Bone scintigraphy was performed at 2, 4, and 6 weeks to investigate new bone formation activity. At 8 weeks, 1 dog was sacrificed for histologic and histomorphometric study. Meanwhile, implants were placed in the remaining 4 dogs. These 4 dogs were sacrificed after 3 months. RESULTS: Less ridge resorption was observed in the anterior SGCS/PRP-filled sites compared to unfilled sites (P = .001), while no significant difference was found between the SGCS/PRPpost and SGCS groups (P = .544). Bone scintigraphy showed that sites filled with SGCS/PRP showed significantly higher count/pixel at 2 (P = .028), 4 (P = .009), and 6 weeks (P = .037) than the unfilled sites. Nevertheless, the SGCS/PRPpost group achieved significantly higher values than the SGSC group only at 2 weeks (P = .036). Histomorphometrically, the SGCS/PRPant group showed a significantly higher percentage of bone-implant contact than the unfilled group (P = .024), but no significant difference was detected between the SGCS/PRPpost and SGCS groups (P = .979). CONCLUSION: Grafting SGCS/PRP in fresh extraction sockets reduced alveolar ridge resorption and promoted the bone formation in this canine model. The addition of PRP to SGCS resulted in the enhancement of bone regeneration in the early phase of healing.

Enhancing boron rejection in FO using alkaline draw solutions.

This study provides a novel method to enhance boron removal in a forward osmosis (FO) process. It utilizes the reverse solute diffusion (RSD) of ions from alkaline draw solutions (DSs) and the concentration polarization of the hydroxyl ions to create a highly alkaline environment near the membrane active surface. The results show that boron rejection can be significantly enhanced by increasing the pH of NaCl DS to 12.5 in the active-layer-facing-feed-solution (AL-FS) orientation. The effect of RSD enhanced boron rejection was further promoted in the presence of concentration polarization (e.g., in the active-layer-facing-draw-solution (AL-DS) orientation). The current study opens a new dimension for controlling contaminant removal by FO using tailored DS chemistry, where the RSD-induced localized water chemistry change is taken advantage in contrast to the conventional method of chemical dosing to the bulk feed water.

Evaluation of the osseointegration of dental implants coated with calcium carbonate: an animal study.

In an attempt to overcome the limitations of titanium in dental and orthopaedic clinical applications, a new method has been developed to prepare calcium carbonate coatings on sandblasted and acid-etched (SA) titanium implants. The purpose of this study was to investigate the effect of calcium carbonate-SA (CC-SA) implants on osseointegration in vivo. The surfaces of SA and CC-SA implants were characterised for surface morphology and surface chemistry. Subsequently, these two kinds of implants were implanted in the femoral condyles of rabbits. The implants were retrieved and prepared for histological and histomorphometric evaluation 1, 2, 4, 8 and 12 weeks after implantation. Significantly higher values of bone-to-implant contact of the entire implant except the gap area (BIC_ALL) and the bone-to-implant contact of the gap area (BIC_GAP) were found in animals with the CC-SA implants than in those with the SA implants at 4 weeks. Higher values of total gap bone were found in those with the CC-SA implants than in those with the SA implants at 1, 2 and 4 weeks. In conclusion, the current findings demonstrate that the calcium carbonate coating can improve and accelerate the early ingrowth of bone and osseointegration at the early healing phase. This may reduce clinical healing times and thus improve implant success rates.

Effects of different concentrations and exposure time of sodium hypochlorite on the structural, compositional and mechanical properties of human dentin.

This study evaluated the effects of sodium hypochlorite (NaOCl) with different concentrations and exposure time on the structural, compositional and mechanical properties of human dentin in vitro. Sixty dentin slabs were obtained from freshly extracted premolars, randomly distributed into four groups (n=15), and treated with 1%, 5%, 10% NaOCl and distilled water (control group), respectively, for a total of 60 min. Attenuated total reflection infrared (ATR-IR) spectroscopy, Raman spectroscopy and X-ray diffraction (XRD) were carried out before, 10 min and 60 min after the treatment. Scanning electron microscopy (SEM) and flexural strength test were conducted as well. The results showed that dentins experienced morphological alterations in the NaOCl groups, but not in the control group. Two-way repeated-measures analysis of variance revealed that the carbonate:mineral ratio (C:M), Raman relative intensity (RRI), a-axis, c-axis length and full width at half maximum (FWHM) with the increase of time and concentration in the NaOCl groups were not significantly different from those in the control group (P>0.05). Nevertheless, the mineral:matrix ratio (M:M) increased and the flexural strength declined with the increase of concentration and the extension of time in the NaOCl groups (P<0.05). Additionally, it was found that the M:M and the flexural strength remained unchanged after 1% NaOCl treatment (P>0.05), and the morphology changes were unnoticeable within 10 min in 1% NaOCl group. These results indicated that NaOCl has no significant effects on the inorganic mineral of human dentin; but it undermines and eliminates the organic content concentration- and time-dependently, which in turn influences the flexural strength and toughness of dentins. In addition, an irrigation of 1% NaOCl within 10 min can minimize the effects of NaOCl on the structural and mechanical properties of dentin during root canal treatment.

The influence of resin cements on the final color of ceramic veneers.

PURPOSE: To evaluate the effect of three brands of resin cement on the final color of ceramic veneers. METHODS: 50 disk-shaped ceramic specimens (IPS e.Max, 0.6mm×8.0mm diameter) and disk-shaped composite resin background specimens (4.0mm×8.0mm diameter) were prepared and divided into 10 groups (n=5). These paired specimens were bonded using ten shades of resin cement (Variolink Veneer, shades LV-3, LV-2, MV, HV+2, HV+3; Panavia F, shades light and brown; and RelyX™ Veneer, shades WO, TR, A3). A spectrophotometer (VITA Easyshade) was used to measure the color parameters (CIE L*a*b* values) of the paired disks before and after cementation. The color differences (ΔE values) after cementation were calculated and statistically analyzed by the One-way ANOVA (at the significant level p<0.05). RESULTS: The color parameters of the ceramic disks were measured in terms of the increase in L* value, and the decrease in Cab(*) value after bonding with the resin cement. The ΔE values of ceramic disks after cementation ranged from 1.38 to 7.16. The ΔE values were more than 3.3 when the ceramic disks were cemented with resin cements in shade HV+3 (4.90) and shade WO (7.16). One-way ANOVA of ΔE values revealed significant differences in the resin cement shades. CONCLUSIONS: Resin cements can affect the final color of ceramic veneer restorations, and the extent of this effect varies according to the resin cement shades.

Organic fouling of thin-film composite polyamide and cellulose triacetate forward osmosis membranes by oppositely charged macromolecules.

Fouling of cellulose triacetate (CTA) and thin-film composite (TFC) forward osmosis (FO) membranes by organic macromolecules were studied using oppositely charged lysozyme (LYS) and alginate (ALG) as model foulants. Flux performance and foulant deposition on membranes were systematically investigated for a submerged membrane system. When an initial flux of 25 L/m(2)h was applied, both flux reduction and foulant mass deposition were severe for feed water containing the mixture of LYS and ALG (e.g., 50% LYS and 50% ALG at a total foulant concentration of 100 mg/L). In comparison, fouling was much milder for feed water containing either LYS or ALG alone. Compared to the CTA FO membrane, the TFC FO membrane showed greater fouling propensity under mild FO fouling conditions due to its much rougher surface. Nevertheless, under severe FO fouling conditions, fouling was dominated by foulant-deposited-foulant interaction and membrane surface properties played a less important role. Furthermore, when the feed water contained both LYS and ALG in sufficient amount, the deposited cake layer foulant composition (i.e., the LYS/ALG mass ratio) was not strongly affected by membrane types (CTA versus TFC) nor testing modes (pressure-driven NF mode versus osmosis-driven FO mode). In contrast, solution chemistry such as pH and calcium concentration had remarkable effect on the cake layer composition due to their effects on foulant-foulant interaction.

Effects of temperature and in-office bleaching agents on surface and subsurface properties of aesthetic restorative materials.

OBJECTIVES: To investigate the effects of in-office bleaching agents on surface and subsurface properties of dental materials at different environmental temperatures. METHODS: Four composite resins, a compomer, a conventional glass-ionomer cement (CGIC), and an industrially sintered ceramic material were evaluated in the present study. Four groups of each material (n=10) were treated: bleaching with 40% hydrogen peroxide at 25°C and 37°C, stored in artificial saliva at 25°C and 37°C. The specimens from bleaching groups were bleached for two sessions, each of two 20 min application, at respective temperatures. After bleaching, the surface and subsurface (0.1-0.5mm) microhardness were evaluated using a Vickers microhardness tester. The substance loss was determined by surface profilometry. The data were statistically analyzed with ANOVA and the Tukey's post hoc test. RESULTS: All materials were found to have surface softening after bleaching, and bleaching effects on surface micorhardness increased at 37°C compared with 25°C, except for the ceramic. After being bleached at 37°C, the microhardness values of flowable composite resin significantly reduced at a depth of 0.1mm compared with control specimen stored at 37°C. No significant difference was found between the control and bleached specimens with respect to substance loss for any of the materials. CONCLUSION: The influence of environmental temperature on the in-office bleaching effects on surface and subsurface microhardness of dental materials was material-dependent. However, no substance loss was detected due to the tested bleaching regimen. CLINICAL SIGNIFICANCE: Environmental temperature should be considered when evaluating the possible bleaching effects on restorative materials. Moreover, dentists should be aware that there might be a need for polishing of restorative materials in clinical situations in which restorations are accidentally exposed to bleaching gels.

[Effect of hydrogen peroxide with different pH values on the color, translucency and laser-induced fluorescence of human dentin].

OBJECTIVE: To investigate the effect of 30% hydrogen peroxide(HP) with different pH values on color, translucency and laser-induced fluorescence of human dentin. METHODS: Sixty dentin specimens from crown of mandibular third molars were randomly assigned into four groups (n = 15) and treated with acidic 30% HP, neutral 30% HP, alkaline 30% HP and deionized water (control group), respectively. The bleaching process was 0.5 h×4 times, and time points for measuring were baseline (0), 0.5, 1 and 2 h. A colorimeter was employed to measure the L(*), a(*), b(*) coordinates of dentin against white, black and yellow background. Then the parameters of translucency, masking effects, chroma and whiteness were calculated. The dentinal laser-induced Raman/fluorescence spectra was recorded by a Raman spectrometer and the fluorescence intensity(FI) and FI% were calculated. RESULTS: ΔFI of acidic, neutral, alkaline 30% HP at 2 h were 9960.03 ± 2037.74, 8502.09 ± 1413.86, 8554.29 ± 1986.19. And ΔFI% were 84.60 ± 3.43, 84.89 ± 5.19, 86.72 ± 2.65, respectively. Repeated measure of ANOVA revealed that all parameters in the bleaching groups were significantly influenced by time (P < 0.001). Compared with control group, bleaching resulted significant change of ΔTP, Δchroma, Δwhiteness, ΔL(*), Δa(*), Δb(*), ΔE, ΔFI and ΔFI% (P < 0.001). There was no significant difference between three bleaching groups on ΔTP, Δmasking effects, Δchroma, Δwhiteness, ΔL(*), Δb(*), ΔE, ΔFI and ΔFI%. Correlation analysis demonstrated that FI was associated with chroma, a(*), b(*) and whiteness, respectively, and ΔFI was associated with ΔTP, Δmasking effects, Δwhiteness, Δchroma, Δb(*) and ΔE. CONCLUSIONS: 30% HP with different pH values could result in the same change of the color, translucency and laser-induced fluorescence of human dentin.Laser-induced fluorescence was associated with dentinal color and translucency, which might be a novel way to investigate the bleaching mechanism of dentin.

[Three-dimensional finite element analysis of removable partial denture with periodontally compromised abutments].

OBJECTIVE: To evaluate three-dimensional (3D) finite element (FE) modeling of different periodontally compromised unilateral distal extension removable partial denture (RPD) abutments using the data of a 3D non-contact digitizing scanner. METHODS: FE models were established, and the following structures were simulated in the models: alveolar bone, mucosa, abutments, periodontal ligaments, framework and artificial teeth. The alveolar bone and periodontal ligaments around the distal abutment in the three models were designed as normal, with bone defect and with periodontal ligaments defect respectively.Vertical or buccally inclined forces of 50, 100, 100 N were applied on the artificial teeth of the RPD and the stress distributions on the supporting tissues were calculated. RESULTS: Under vertical loading, the maximal stress on the alveolar bone of the abutment were as follows: periodontal ligaments defect model (3.57 MPa) > bone defect model (3.21 MPa) > normal model (2.63 MPa). Under buccally inclined loading, the maximal stress on the alveolar bone of the abutment were as follows: periodontal ligaments defect model (2.50 MPa) > bone defect model (2.41 MPa) > normal model (1.79 MPa). Under buccally inclined loading, the stresses on distal aspects of the residual alveolar ridge were higher than that of the vertical loading model. CONCLUSIONS: 3D non-contact digitalizing scanner was useful for the finite element modeling process of removable partial denture.

[Effects of three at-home bleaching agents on enamel structure and structure-related mechanical properties].

OBJECTIVE: To investigate the effects of three differently concentrated at-home bleaching agents on the structure and the structure-related mechanical properties of human enamel. METHODS: Sixty enamel specimens were randomly divided into four groups and treated with 10% carbamide peroxide (CP), 15% CP, 20% CP and distilled water, respectively. The bleaching process was 8 h/day for 14 consecutive days. Baseline and final atomic force microscopy (AFM) surface detection, Raman spectroscopy, attenuated total reflectance-infrared spectroscopy (ATR-IR), microhardness and fracture toughness (FT) measurements were carried out before and after bleaching experiments. RESULTS: CP didn't change the morphology of enamel. Meanwhile, the three bleached groups and the control group had no significant difference in root mean square detection (P = 0.774), ν(2)CO(3)(2-) : ν(1)ν(3)PO(4)(3-) (P = 0.263) and microhardness (P = 0.829). The percentage of relative Raman intensity in the three bleached groups and the control group were (105.74 ± 11.34)%, (104.46 ± 8.83)%, (99.52 ± 9.32)% and (97.62 ± 7.46)%, respectively. There was no significant difference among them (P = 0.062). However, the percentage of laser-induced fluorescence in the three bleached groups and the control group were (20.86 ± 7.23)%, (22.14 ± 7.34)%, (21.10 ± 7.59)% and (100.78 ± 3.70)%, respectively. There was significant difference between either of the bleached groups and the control group (P < 0.001). Moreover, FT declined significantly in the three groups (P = 0.024, P = 0.005, P = 0.013) when compared with the control group. CONCLUSIONS: Under in vitro condition, three differently concentrated at-home bleaching agents wouldn't induce the demineralization and the decline of microhardness on enamel. However, the decrease of FT on enamel seemed to be inevitable after bleaching.

[Effects of try-in paste and luting agent on the resultant color of all-ceramic veneers].

OBJECTIVE: The purposes of this study was to investigate the effects of luting agents on the resultant color of IPS e.max all-ceramic veneer restorations, and to evaluate the similarity of try-in pastes and the corresponding luting agents on the final color. METHODS: Disc-shaped ceramic specimens were fabricated and seated on four shades of resin specimens to mimic the complex of ceramic veneer laying on tooth substrates. Try-in pastes and luting agents (Shades of TR, B0.5, A1, A3, W0) were applied into the inter-layer of ceramic and resin specimens, respectively. The color of the combinations was measured using a spectrophotometer and subsequently converted to CIE L*a*b* values. Color changes after luting agent applied, and between try-in paste and corresponding luting agent were calculated and registered as DeltaEresin and DeltaEpaste-resin. RESULTS: DeltaEresin value of A2, A3 backgrounds was more than 1.0. DeltaEresin value of A4, A5 backgrounds was less than 1.0. The DeltaEpaste-resin value of A3 backgrounds was more than 1.0, whereas, A2 was less than 1.0 (except for shade W0). The DeltaEpaste-resin value of shade W0 was significantly different from other shades of luting agents. CONCLUSION: The color of ceramic veneer restorations were affected by luting agents with A2, and A3 background colors. The agreement of the try-in paste and the corresponding luting agent was excellent for A2 background (except for W0).

Influence of galvano-ceramic and metal-ceramic crowns on magnetic resonance imaging.

BACKGROUND: Magnetic resonance imaging (MRI) is prone to be deformed by artifacts caused by the presence of metallic materials. The aim of this study was to evaluate the artifacts from galvano-ceramic and metal-ceramic crowns in MRI, in order to analyze their influences on diagnostic interpretation of MRI. METHODS: Galvano-ceramic and metal-ceramic crowns (Bio98, Wiron99, SP-78, BioKC97) were fabricated with the same model. All materials were imaged by means of 1.5T MRI apparatus with three different sequences, T1-weighted spin-echo (T1-weighted SE), T2-weighted spin-echo (T2-weighted SE) and Gradient echo (GE). Mean and standard deviation of distilled water signal intensity (SI) around the sample in the region of interest (500 mm2) enclosing the whole artifacts were determined, and compared for evaluation of the homogeneity of signal intensity. Images around the sample were acquired and evaluated. RESULTS: There were statistically significant differences in the values of signal intensity between acrylic resin control and BioKC97, Wiron99 in the three sequences (P<0.001). The mean values of signal intensity for Bio98, SP-78 were significantly different from that of acrylic resin control (RE) in GE sequence (P<0.001). No difference was showed between acrylic resin control and galvano-ceramic crown (P>0.05). Images showed that the greatest artifact was a 25 mm ring with distortion in Wiron99 in GE sequence. CONCLUSIONS: This in vitro study suggested that galvano-ceramic crown had no influence on the MRI, while metal-ceramic crowns caused moderate artifacts in the MRI. Therefore, galvano-ceramic restoration is a valuable alternative in dentistry.