DNA damage response in a 2D-culture model by diffusing alpha-emitters radiation therapy (Alpha-DaRT)

Diffusing alpha-emitters radiation therapy (Alpha-DaRT) is a unique method, in which interstitial sources carrying 224Ra release a chain of short-lived daughter atoms from their surface. Although DNA damage response (DDR) is crucial to inducing cell death after irradiation, how the DDR occurs during Alpha-DaRT treatment has not yet been explored. In this study, we temporo-spatially characterized DDR such as kinetics of DNA double-strand breaks (DSBs) and cell cycle, in two-dimensional (2D) culture conditions qualitatively mimicking Alpha-DaRT treatments, by employing HeLa cells expressing the Fucci cell cycle-visualizing system. The distribution of the alpha-particle pits detected by a plastic nuclear track detector, CR-39, strongly correlated with γH2AX staining, a marker of DSBs, around the 224Ra source, but the area of G2 arrested cells was more widely spread 24 h from the start of the exposure. Thereafter, close time-lapse observation revealed varying cell cycle kinetics, depending on the distance from the source. A medium containing daughter nuclides prepared from 224Ra sources allowed us to estimate the radiation dose after 24 h of exposure, and determine surviving fractions. The present experimental model revealed for the first time temporo-spatial information of DDR occurring around the source in its early stages.

Improvement of the setting properties of mineral trioxide aggregate cements using cellulose nanofibrils

Cellulose nanofibrils (CNFs) exhibit excellent mechanical properties and are used to reinforce various composites. The effects of incorporating CNFs into commercial mineral trioxide aggregate (MTA) cements (NEX MTA (NEX) and ProRoot® MTA (PR)) on the underwater setting properties, compressive strength, and flowability were estimated in this study. NEX mixed without CNFs disintegrated after water immersion. NEX mixed with CNF-suspended solutions showed good setting properties under water immersion and a similar compressive strength, which was kept in air (100% relative humidity). PR did not degrade after water immersion, regardless of the presence of CNFs, and no significant difference in the compressive strength caused by CNFs incorporation was detected. The relative flowability of the NEX mixture decreased with increasing CNFs content up to 1.0 w/v%. The application of CNF-incorporated MTA in various dental cases is promising because CNFs prevent the water-immersion-dependent collapse of some MTA cements immediately after mixing.

Preparation and properties of the fine ground strontium-based endodontic cements

In this study, fine powders of tristrontium aluminate (S3A) and distrontium cerate (S2Ce) cement were prepared using a dry grinding process, and their mechanical and ion dissolution properties were estimated. Fine cements showed the particles about 10 μm in diameter or smaller with sharp particle size distribution curves. The setting reaction of the fine cements was rapid; therefore, a 0.1% w/v of citric acid solution was used as the retarder. The compressive strengths of the fine cements were improved compared to those of the coarse cements at both 1 and 28 days after mixing at a water/powder ratio (W/P) of 0.4. The dissolution of Sr and Al ions from fine S3A cement was enhanced. However, the relative flowability decreases with fine grinding. Further studies on flowability, handling property are required. Additionally, the biological effects of endodontic cement should be studied both in vitro and in vivo.

Effects of build orientation and bar addition on accuracy of complete denture base fabricated with digital light projection: An in vitro study

PURPOSE

We evaluated the effects of build orientation and bar addition between lingual flanges on the accuracy of mandibular denture bases fabricated using a digital light processing (DLP) device.

METHODS

Mandibular denture bases with and without a bar at the lingual flanges were virtually designed and assigned to eight build orientations. Six dentures per condition were fabricated using a DLP device with a methacrylate-based photopolymerizable monomer (Dima Print denture base) (n=96). The fabricated denture surfaces were digitized, and intaglio surfaces were obtained. These digitized surfaces were compared via superimposition using graphical software (Artec studio12 profession) to their original designed files, and root mean square estimates were obtained. The trueness of the entire and intaglio data was statistically analyzed non-parametrically.

RESULTS

The range of trueness of the entire and intaglio denture bases was 0.15-0.31 mm and 0.11-0.38 mm, respectively. The trueness at 135° and 270° for the entire denture base and that at 270° for the intaglio data without the bar were significantly lower than those for the other build orientations. The trueness at 270° was <0.15 mm irrespective of the conditions. The trueness with the bar of all build orientations, except that of 0° for intaglio data, was significantly smaller than or equal to the trueness without the bar of the corresponding build orientations.

CONCLUSIONS

Build orientation and bar addition influenced the accuracy of the complete dentures fabricated using DLP. A build orientation of 270° is recommended for fabricating a mandibular complete denture, irrespective of the bar addition.

Mechanical analysis of the improved superelastic Ni-Ti alloy wire using the orthodontic simulator with high-precision sensors

PURPOSE

The authors have been using improved superelastic Nickel-Titanium alloy wire (ISW) to close and align extraction spaces simultaneously, instead of separately using rigid wires for closing extraction spaces and Ni-Ti alloy wires for leveling and aligning. ISW has a low stiffness, which makes it challenging to generate sufficient moments. This study aimed to demonstrate the forces and moments exerted on adjacent brackets using an orthodontic simulator (OSIM) attached to a high-precision 6-axis sensor.

MATERIALS AND METHODS

In experiment 1, a 0.016 × 0.022-inch ISW, stainless steel (SS) wire, and β-titanium wires were ligatured into the two brackets. The 0.018 × 0.025-inch slot self-ligating brackets were bonded to two simulated teeth at the same height, and the experiment was conducted using the high-precision OSIM. The distance between the brackets was 10 mm, the V-bend angles of the installed wires were 10°, 20°, 30°, and 40°, and the apex position was set at the center of the bracket. In experiment 2, 6.0- and 9.0-mm long elastomeric chains were placed on the same brackets as in Experiment 1 to measure forces and moments. The distance between the brackets was increased by 1.0 mm from 6.0 to 15.0 mm. Both experiments were conducted in a 37 °C thermostatic chamber similar to the oral environment.

RESULTS AND DISCUSSION

In experiment 1, we measured moments on both sides for all the wires. As the V-bend angle increased, the absolute values of the moments also increased. With a V-bend angle of 10°, there was a significant (p < 0.05) difference in the moment generated in the left and right brackets among the three wire types. In the ISW, -1.67 ± 0.38 N・mm was generated in the left bracket, while 0.38 ± 0.26 N・mm was generated in the right bracket at 10°. At 20°, -1.77 ± 0.69 N・mm was generated in the left bracket, while 2.37 ± 0.94 N・mm was generated in the right bracket. At 30°, -2.98 ± 0.49 N・mm was generated in the left bracket, while 3.25 ± 0.32 N・mm was generated in the right bracket. Moreover, at 40°, -3.96 ± 0.58 N・mm was generated in the left bracket, while 3.55 ± 0.53 N・mm was generated in the right bracket. Furthermore, in experiment 2, the moments increased in proportion to the increase in distance between the centers of the two brackets. Absolute values of the moments were approximately equal for the left and right brackets. The 6.0-mm elastomeric chain generated a minimum force of -0.09 ± 0.05 N in the left direction when the distance between brackets was 6.0 mm, while a maximum of 1.24 ± 0.3 N when the distance between brackets was 12 mm in the right bracket. In the left bracket, minimum and maximum forces of -0.09 ± 0.07 and 1.3 ± 0.4 N were generated in the right direction, respectively. The 9.0-mm elastomeric chain generated a minimum force of 0.03 ± 0.07 N in the left direction when the distance between brackets was 9.0 mm, while a maximum of 1.3 ± 0.1 N when the distance between brackets was 15 mm in the right bracket. In the left bracket, minimum and maximum forces of 0.05 ± 0.06 and 0.98 ± 0.2 N were generated in the right direction, respectively.

CONCLUSION

Mechanical data of the ISW have been collected in the study, which was previously difficult to perform owing to the low stiffness of the wire. It is suggested that the ISW can provide sufficient moments with the addition of V-bends to close the space by bodily movement.

Structure of Atomically Dispersed Pt in a SnO2 Thin Film under Reaction Conditions: Origin of Its High Performance in Micro Electromechanical System Gas Sensor Catalysis

A battery-driven micro electromechanical system (MEMS) gas sensor has been developed for household safety when using natural gas. The heart of the MEMS gas sensor is a 7.5 at % Pt-SnO₂ thin film catalyst deposited on the SnO₂ sensor layer. The catalyst enhances the sensitivity to methane, though its structure under working conditions is unclear. In this study, in situ XAFS was applied to a 7.5 at % Pt-SnO₂ catalyst layer deposited on a Si substrate, and we demonstrated that atomically dispersed Pt maintains its lattice position in SnO₂ with a small loss of surrounding lattice oxygen in the presence of 1% CH₄ and a more reducing gas of 1% H₂ at the reaction temperature (703 K), i.e., no Pt aggregation is observed. The lost oxygen is easily recovered by re-oxidation by air. This work has revealed that the atomically dispersed Pt in the SnO₂ lattice is the active structure and it is stable even under reaction conditions, which guarantees a long lifetime for the gas sensor.

Influence of different ligation methods on force and moment generation in a simulated condition of the maxillary crowded anterior dentition with linguo-version and rotation

BACKGROUND: Most orthodontic cases consist of varying degrees of crowding. To manage crowded dentitions, nickel-titanium archwires with various ligation methods are often used. OBJECTIVE: We aimed to investigate the effect of different ligation methods with respect to force and moment and suggest the efficient ligation method for treating rotation and displacement simultaneously. METHODS: We built a model that simulated the three anterior teeth of the maxilla. The teeth on the two ends were fixed, and the middle tooth was set in several different positions by manipulating the amount of displacement in bucco-lingual direction and rotation angle. The measurements were taken with three different ligation methods of self-ligation (SL), elastomeric o-ring ligation on both side wings (EB), and on one side wings (EO). RESULTS: The magnitude of linguo-buccal force exceeded the standard optimal force in each condition examined and was significantly larger in EB than in other ligation methods. Moreover, the magnitude of moment generation with SL was suitable in the 0.0 mm linguo-version, whereas it was suitable with EO in the linguo-version ranging 1.0–3.0 mm. CONCLUSIONS: The ligation method significantly affected the force and moment. SL and EO are recommended in dentitions with light and deep lingual displacements, respectively.

Chemical Diagnosis of Calcium Pyrophosphate Deposition Disease of the Temporomandibular Joint: A Case Report

Calcium pyrophosphate dihydrate (CPPD) deposition disease is a benign disorder characterized by acute gouty arthritis-like attacks and first reported by McCarty. CPPD deposition disease rarely occurs in the temporomandibular joint (TMJ), and although confirmation of positive birefringence by polarized light microscopy is important for diagnosis, it is not reliable because other crystals also show birefringence. We reported a case of CPPD deposition disease of the TMJ that was diagnosed by chemical analysis. A 47-year-old man with a chief complaint of persistent pain in the right TMJ and trismus was referred to our department in 2020. Radiographic examination revealed destruction of the head of the mandibular condyle and cranial base with a neoplastic lesion involving calcification tissue. We suspected CPPD deposition disease and performed enucleation of the white, chalky masses. Histopathologically, we confirmed crystal deposition with weak birefringence. SEM/EDS revealed that the light emitting parts of Ca and P corresponded with the bright part of the SEM image. Through X-ray diffraction, almost all peaks were confirmed to be CPPD-derived. Inductively coupled plasma atomic emission spectroscopy revealed a Ca/P ratio of nearly 1. These chemical analyses further support the histological diagnosis of CPPD deposition disease.

Nickel particles are present in Crohn's disease tissue and exacerbate intestinal inflammation in IBD susceptible mice

Crohn's disease is an inflammatory disease of the gut caused by a complex interplay among genetic, microbial, and environmental factors. The intestinal tract is constantly exposed to metals and other trace elements ingested as food. Synchrotron radiation-induced X-ray fluorescence spectroscopy and X-ray absorption fine structure analysis revealed the deposition of nickel particles within Crohn's disease tissue specimens. After nickel particle stimulation, THP-1 cells showed filopodia formation and autophagic vacuoles containing lipid bodies. Nickel particles precipitated colitis in mice bearing mutations of the IBD susceptibility protein A20/TNFAIP3. Nickel particles also exacerbated dextran sulfate sodium-induced colitis in mice harboring myeloid cell-specific Atg5 deficiency. These findings illustrate that nickel particle ingestion may worsen Crohn's disease by perturbing autophagic processes in the intestine, providing new insights into environmental factors in Crohn's disease pathogenesis.

Useful design of custom-made mouthguard for athletes undergoing orthodontic treatment with brackets and wires

Background/purpose

Custom-made mouthguards (MGs) are strongly recommended for athletes during sports activities to prevent dental injuries. Athletes undergoing orthodontic treatment and wearing brackets require specially designed MGs for better protection and to create more space that will not hinder the planned orthodontic tooth movement. The purpose of this study was to fabricate effective, specially designed, custom-made MGs for patients or athletes with ongoing orthodontic treatment and to evaluate the shock absorption abilities of these MGs by an in vitro comparison of three different designs.

Materials and methods

Three different types of specially designed, double-layered MGs, (i) creating inter bracket space inside the MG, (ii) embedding silicon wax inside the MG, and (iii) creating a buffer space with additional hard insertion, were fabricated from a simulated bracket attached model. Impact test was performed using a free-falling object on a vertical rod, and the strain-gauge system was used to assess the strain on the dentition with the MGs for the comparison of the shock absorption abilities of the three types. Analysis of variance at a significance level of 5% and multiple comparisons were performed for statistical analysis.

Results

The strains on the dentition with the MG creating buffer space with hard insertion were significantly lower than those with the other two types of MG (P < 0.001).

Conclusion

Insertion of a hard material and ensuring buffer space between the MG and the teeth and/or appliance was more effective than other methods of fabricating custom-made MGs to prevent sports-related traumatic dental injuries in athletes undergoing orthodontic treatment.

Distrontium Cerate as a Radiopaque Component of Hydraulic Endodontic Cement

This study aimed to synthesize distrontium cerate (2SrO·CeO2: S2Ce) and evaluate its properties as an alternative component of the endodontic cement. S2Ce cement was prepared through calcination of strontium hydroxide and cerium carbonate. Subsequently, the crystal phase was confirmed using X-ray diffraction. S2Ce cement exhibited a rapid setting time (121 min) and achieved a high compressive strength (72.1 MPa) at 1 d after mixing, comparable to the compressive strength of a commercial mineral trioxide aggregate (MTA) cement (ProRoot MTA) after 28 d post mixing. However, the compressive strength decreased after 28 d of storage when the W/P ratio was 0.30-0.40 (p < 0.05). Ion dissolution test of the S2Ce cement showed that strontium ions were released after immersion in water (5.27 mg/mL after 1 d), whereas cerium dissolution was not detected. S2Ce exhibited approximately three times higher radiopacity (9.0 mm aluminum thickness equivalent) compared to the commercial MTA (p < 0.05). These findings suggest that S2Ce is a possible component for hydraulic endodontic cement that demonstrates a rapid setting and high radiopacity.

Tissue Conditioner Incorporating a Nano-Sized Surface Pre-Reacted Glass-Ionomer (S-PRG) Filler

We aimed to evaluate the properties of a novel tissue conditioner containing a surface pre-reacted glass-ionomer (S-PRG) nanofiller. Tissue conditioners containing 0 (control), 2.5, 5, 10, 20, or 30 wt% S-PRG nanofiller or 10 or 20 wt% S-PRG microfiller were prepared. The S-PRG nanofillers and microfillers were observed using scanning electron microscopy. The ion release, acid buffering capacity, detail reproduction, consistency, Shore A0 hardness, surface roughness, and Candida albicans adhesion of the tissue conditioners were examined. The results indicated that the nanofiller particles were smaller and more homogeneous in size than the microfiller particles. In addition, Al, B, F, and Sr ions eluted from S-PRG were generally found to decrease after 1 day. Acid neutralization was confirmed in a concentration-dependent manner. The mechanical properties of tissue conditioners containing S-PRG nanofiller were clinically acceptable according to ISO standard 10139-1:2018, although the surface roughness increased with increasing filler content. Conditioners with 5-30 wt% nanofiller had a sublethal effect on C. albicans and reduced fungal adhesion in vitro. In summary, tissue conditioner containing at least 5 wt% S-PRG nanofiller can reduce C. albicans adhesion and has potential as an alternative soft lining material.

Novel antimicrobial denture adhesive containing S-PRG filler

The antimicrobial effects of denture adhesives containing novel surface pre-reacted glass-ionomer (S-PRG) fillers were assessed. We prepared denture adhesives containing S-PRG (particle sizes: 1 and 3 µm; quantities: 5, 7.5, and 10 wt%). We evaluated acid buffering capacity, ion release, and antimicrobial effects of denture adhesives with and without S-PRG. Significantly higher pH changes were observed in 1 µm S-PRG adhesives than in 3 µm S-PRG adhesives. Adhesives containing 7.5 and 10 wt% S-PRG exhibited significantly higher ion release than adhesives with 5 wt% S-PRG. The 1µm-10wt% S-PRG denture adhesive exhibited significantly lower colony-forming units on the denture adhesive contact surface than in the control group; additionally, it exhibited excellent acid buffering capacity, ion release properties, and antimicrobial effect against C. albicans, C. glabrata, S. mutans, and A. naeslundii. Longer contact periods resulted in significantly lower adhesion of Candida albicans to the denture base resin treated with denture adhesive.

Use of the fiberglass reinforcement method in thermoplastic mouthguard materials to improve flexural properties for enhancement of functionality

The purpose of this study was to evaluate the application of fiberglass reinforcement method in thermoplastic mouthguard materials to improve flexural properties and adhesive strength. Commonly used two types of commercial mouth guard materials (ethylene-vinyl acetate copolymer-based and polyolefin-based) were reinforced with glass fiber clothes by two-step hot press. Flexural strength and adhesive strength with each base material were examine via three-point bending test and delamination test, respectively. Ethylene-vinyl acetate copolymer-based fiberglass-reinforced material has significantly greater adhesive strength with base material and improvement of flexural properties compared with polyolefin-based material. These results suggest that flexural properties of both conventional commercial mouthguard materials were improved when the glass-fiber-reinforced method was applied to reinforce mouthguard materials, and more, ethylene-vinyl acetate copolymer was more desirable for the base material.

Nickel ions attenuate autophagy flux and induce transglutaminase 2 (TG2) mediated post-translational modification of SQSTM1/p62

Nickel, the most frequent contact allergy cause, is widely used for various metallic materials and medical devices. Autophagy is an intracellular protein degradation system and contributes to metal recycling. However, it is unclear the functions of nickel in autophagy. We here demonstrated that NiCl2 induced microtubule-associated protein 1 light chain 3 (LC3)-II and LC3 puncta, markers of autophagosomes. Bafilomycin A1 (BafA1) treatment did not enhance LC3 puncta under NiCl2 stimulation, suggesting that NiCl2 did not induce autophagic flux. In addition, NiCl2 promotes the accumulation of SQSTM1/p62 and increased SQSTM1/p62 colocalization with lysosomal-associated membrane protein 1 (LAMP1). These data indicated that NiCl2 attenuates autophagic flux. Interestingly, NiCl2 induced the expression of the high-molecular-weight (MW) form of SQSTM1/p62. Inhibition of NiCl2-induced reactive oxygen species (ROS) reduced the high-MW SQSTM1/p62. We also showed that NiCl2-induced ROS activate transglutaminase (TG) activity. We found that transglutaminase 2 (TG2) inhibition reduced high-MW SQSTM1/p62 and SQSTM1/p62 puncta under NiCl2 stimulation, indicating that TG2 regulates SQSTM1/p62 protein homeostasis under NiCl2 stimulation. Our study demonstrated that nickel ion regulates autophagy flux and TG2 restricted nickel-dependent proteostasis.

Application of Glass Fiber and Carbon Fiber-Reinforced Thermoplastics in Face Guards

Face guards (FGs) are protectors that allow for the rapid and safe return of athletes who are to play after sustaining traumatic facial injuries and orbital fractures. Current FGs require significant thickness to achieve sufficient shock absorption abilities. However, their weight and thickness render the FGs uncomfortable and reduce the field of vision of the athlete, thus hindering their performance. Therefore, thin and lightweight FGs are required. We fabricated FGs using commercial glass fiber-reinforced thermoplastic (GFRTP) and carbon fiber-reinforced thermoplastic (CFRTP) resins to achieve these requirements and investigated their shock absorption abilities through impact testing. The results showed that an FG composed of CFRTP is thinner and lighter than a conventional FG and has sufficient shock absorption ability. The fabrication method of an FG comprising CFRTP is similar to the conventional method. FGs composed of commercial FRTPs exhibit adequate shock absorption abilities and are thinner and lower in weight as compared to conventional FGs.

Preparation and properties of tristrontium aluminate as an alternative component of mineral trioxide aggregate (MTA) cement

This study evaluated tristrontium aluminate (S₃A) and its viability as a component for tricalcium silicate (C₃S) cements. The properties of S₃A, C₃S, and S₃A/C₃S mixtures were evaluated in terms of setting time, compressive strength, flowability, and radiopacity. X-ray diffraction (XRD) pattern verified the powder synthesized in the laboratory as S₃A, consequently, confirming the preparation method. S₃A exhibited the lowest setting time, followed by C₃S and S₃A/C₃S mixtures. Compressive strength of C₃S was significantly higher than S₃A. The S₃A/C₃S mixture showed comparable compressive strength to C₃S for 1-day post initial mixing. There was no significant difference in flowability between S₃A/C₃S and mineral trioxide aggregate (MTA). S₃A showed comparable radiopacity to MTA, whereas that of the S₃A/C₃S mixture was significantly lower comparatively; however, it achieved sufficient radiopacity (3 mm aluminum thickness equivalent). Further studies are needed to improve the manufacturing process of S₃A and evaluate the bioactive effect of strontium.

Comparative evaluation of square and rectangular slot three-point play behavior

The play between bracket slots and archwires affects tooth movement and the transmission of orthodontic force by multi-bracket appliances. We assessed play by quantifying the play behavior of three-point brackets and comparing the amount of play that occurred with square and rectangular slots, respectively, by using archwires of various sizes. Horizontal play with the square slot was significantly smaller than that with the rectangular slot. These data demonstrate that brackets with square slots can more effectively bring about tooth movement in the labio-lingual direction and control rotational movement with round and square archwires. Since the horizontal and vertical play ratios for the round and square wires within the square slot were approximately 1.0, three-dimensional tooth movement may also be achieved with uniform play in the vertical and horizontal directions.

Basic properties of novel S-PRG filler-containing cement

This study was aimed to evaluate the effect of a novel surface pre-reacted glass-ionomer (S-PRG) filler-containing cement for root caries. We prepared the cements using five different S-PRG filler amounts (0, 10, 20, 30, and 40 wt%). Compressive strength, ion release, acid buffering capacity, and microstructure of the as-prepared cements were evaluated. The compressive strength was statistically significant; it was highest for 0 wt% S-PRG cement. Ion release in 0 wt% S-PRG was highest for F^- and Al, whereas in 40 wt% S-PRG it was highest for B. For 20, 30, and 40 wt% S-PRG cements, Na and Sr release was higher compared to the other ions. The acid buffering capacity was significantly higher in the 40 wt% S-PRG cement than in the others. In the microstructural analysis, no difference of surface structure was observed among each of the S-PRG filler contents (0-40 wt% S-PRG).

The influence of temperature on sheet lamination process when fabricating mouthguard on dental thermoforming machine

Laminated custom-made mouthguards tend to delaminate with use; this is a problem in clinical use. Insufficient bonding strength causes delamination, and bonding strength is strongly affected by heating temperature during lamination. The present study aimed to evaluate the influence of heating temperature on the sheet lamination process. Seven mouthguard sheet products were laminated together at different heating temperatures. To evaluate the bonding strength, a delamination test (n = 6) was performed, and the fracture patterns were inspected visually. To evaluate the shock absorption capability, a falling impact test (n = 5) was performed, and the specimen thicknesses were measured. All recorded values were analyzed using two-way analysis of variance and Tukey's Honest Significant Difference Test (P < 0.05). The present study confirmed that bonding strength was dependent on heating temperature: In ethylene-vinyl acetate copolymer products, the bonding strength was almost constant at 130°C and above, and it was constant at 110°C and above in polyolefin products. The thickness of every specimen decreased and, in some specimens, the shock absorption capability decreased with increasing heating temperature. The present study concludes that the heating temperature during the sheet lamination process when laminated custom-made mouthguards are fabricated may not be less than 120°C in ethylene-vinyl acetate copolymer products and 110°C in polyolefin products.

Efficacy of Various Surface Treatments on the Bonding Performance of Saliva-contaminated Lithium-Disilicate Ceramics

PURPOSE

To investigate the efficacy of different ceramic surface cleaning methods after saliva contamination on the resin bond strength to lithium disilicate ceramics.

MATERIALS AND METHODS

300 e.max CAD blocks (Ivoclar Vivadent) were polished with 600-grit silicon carbide paper and divided into five groups with or without human saliva contamination and according to the surface treatment performed (n = 10); control: no pretreatment; MP: Monobond Plus; PA+MP: 37% phosphoric acid (PA) followed by MP; HF+MP: 5% hydrofluoric acid (HF) followed by MP; MEP: Monobond Etch & Prime. The specimens were bonded with one of three resin cements: Variolink Esthetic DC (VE), Multilink Automix (MA) and Speed CEM (SC). After 24-h water storage, tensile bond strength (TBS) was measured. The ceramic surfaces after pretreatment were analyzed using x-ray photoelectron spectroscopy (XPS).

RESULTS

XPS analysis showed similar elemental distributions between saliva contamination vs no saliva in PA, HF, and MEP. The TBSs were significantly influenced by surface treatments (p < 0.05). HF+MP and MEP showed statistically non-significantly different bond strengths to saliva-contaminated HF+MP and MEP, but were different from MP and saliva-contaminated MP. The TBSs after 24 h were significantly higher in HF+MP and MEP groups with VE. HF+MP and MEP did not show statistically significant differences among any groups with or without saliva contamination.

CONCLUSION

Surface treatments with PA or HF followed by silane or by MEP alone were effective in removing saliva contamination and enhancing the resin bond strength.

Morphological and elemental analysis of silver penetration into sound/demineralized dentin after SDF application

OBJECTIVE

The aim of this study was to evaluate the penetration depth of silver into sound and demineralized dentin after application of silver diamine fluoride (SDF).

METHODS

Two hundred and eighty-eight dentin specimens were used. The specimens were divided into 3 groups: (1) sound dentin (control), (2) 30min EDTA-treated dentin; and (3) 13h EDTA-treated dentin. SDF was applied to all specimens. Each group was divided into 3 subgroups according to storage time into: 24h, 2 weeks and 1-year storage time. Each subgroup was further divided into four subgroups (n=8) according to different examinations as optical microscope (OM) observation, scanning electron microscopic (SEM) observation, elemental analysis with energy dispersive spectroscopy (EDS) and Micro-PIXE test.

RESULTS

The OM showed discoloration in the superficial layer after 24h and keep extending deeper after 2 weeks and 1-year. SEM showed silver crystals within dentinal tubules after 2 weeks and 1-year. EDS analysis can detect silver penetration only in the 1-year group reaching around 1200μm inside dentin. Micro-PIXE test detected silver at all time intervals, confirming the EDS depth results.

SIGNIFICANCE

It can be concluded that silver ions can completely infiltrate the demineralized dentin lesion with further penetration into the underlying mineralized dentin.

Effectiveness of low binding frictional materials: Evaluation of the binding frictional resistance of improved superelastic nickel-titanium alloy wires with different bracket combinations

Introduction:

This study aimed to evaluate the binding frictional resistance of improved superelastic nickel- titanium alloy wires (ISW) with different bracket combinations and to verify the effectiveness of low binding frictional materials by applying them in orthodontic treatment.

Materials and Methods:

Straight stainless steel wire (SSW; 0.016 × 0.022-inch) and straight ISW (0.016 × 0.022- inch) were set to each displaced bracket, and the tensile resistance load was measured. The maximum tensile resistance load was statistically compared using the Tukey test. For exemplification, we treated a typical extraction case of Angle Class I crowding malocclusion with lip protrusion using lower binding frictional materials, which were selected based on tensile test results.

Results:

The SSW and metal bracket combination had the largest maximum tensile resistance load, and the ISW and metal slot-equipped plastic bracket combination had the smallest load (P < 0.01). In a patient treated using lower binding frictional materials, the active treatment period was 9 months. Satisfactory patient results were obtained without using reinforced anchorage.

Conclusions:

Binding frictional resistance varies, depending on the archwire and bracket combination. In a multibracket appliance, selecting materials with as low a binding frictional resistance as possible may make a more effective treatment.

Bonding Efficacy of 4-META/MMA-TBB Resin to Surface-treated Highly Translucent Dental Zirconia

PURPOSE

To evaluate the bonding efficacy of 4-META/MMA-TBB resin to highly translucent zirconia subjected to various surface treatments.

MATERIALS AND METHODS

Highly translucent zirconia specimens (Zpex Smile, Tosoh; 11.5 mm diameter, 5.0 mm thick) were mechanically pre-treated to improve micromechanical interlocking either by sandblasting with 50-µm Al2O3 particles (Kulzer Japan) or subjecting the specimens to a low-pressure plasma treatment (PM100, Yamato), or evaluated using the as-sintered surfaces as controls. Next, specimens from each condition were primed with an MDP-containing primer (PZ Primer, Sun Medical), while some remained unprimed. All specimens were bonded to stainless rods using 4-META/MMA-TBB resin (Super-Bond, Sun Medical). The specimens were stored in ultrapure water at 37°C for 24 h, after which a portion were subjected to 10,000 thermocycles. For all specimens (n=10/group) the tensile bond strength (TBS) was determined with a universal testing machine. The measured values were statistically analyzed using Weibull analysis. Fractographic analysis was performed using a light microscope and an SEM.

RESULTS

After aging, Weibull analysis revealed significantly lower bond strengths for both as-sintered and plasma-treated zirconia without a primer treatment. The fractographic analysis showed that these two conditions resulted in a higher frequency of adhesive failure.

CONCLUSION

Chemical pre-treatment with an MDP-containing primer improved bonding efficacy of 4-META/MMA-TBB resin to highly translucent zirconia. In addition, Al2O3 sandblasting resulted in durable bonding of 4-META/MMA-TBB resin to highly translucent zirconia, regardless of chemical pre-treatment.

Quantitation and distribution of metallic elements in sequestra of medication-related osteonecrosis of jaw (MRONJ) using inductively coupled plasma atomic emission spectroscopy and synchrotron radiation X-ray fluorescence analysis

Medication-related osteonecrosis of the jaw (MRONJ) is a serious adverse effect of antiresorptive agents like bisphosphonates. Abnormal concentrations of various trace metallic elements contained in bone minerals have been associated with MRONJ. In this study, we focused on trace metallic elements contained in the MRONJ sequestrum; their content and distribution were compared to those in osteomyelitis and non-inflammatory bones using inductively coupled plasma atomic emission spectroscopy (ICP-AES) and synchrotron radiation X-ray fluorescence analysis (SR-XRF). On ICP-AES analyses, various trace elements (Co, Cr, Cu, Fe, K, Mg, Ni, Sb, Ti, V, Pb) were significantly more in MRONJ sequestra than non-inflammatory bones. The Cu content was significantly higher in MRONJ sequestra than osteomyelitis and non-inflammatory bones. The Cu content in MRONJ sequestra was high even after decalcification. Additionally, Cu was distributed along the trabecular structures in decalcified MRONJ specimens, as observed using SR-XRF analysis. Therefore, this study was indicative of the characteristic behavior of Cu in MRONJ.

Time dependence of multi-ion absorption into human enamel from surface prereacted glass-ionomer (S-PRG) filler eluate

Ion incorporation into the tooth is expected to be effective for caries prevention. Time-dependent ion incorporation released from surface pre-reacted glass-ionomer (S-PRG) filler eluate into tooth enamel was estimated by using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Al, B, and Sr contents in enamel were increased in a time-dependent manner with immersion in S-PRG eluate. Clear ion incorporation was observed after 1 h of immersion in S-PRG filler eluate. Sr showed remarkable incorporation in enamel -up to 7,900 ppm- after 28 days of immersion. Sr and B incorporation rapidly occurred in S-PRG filler eluate, compared with their single component solutions. Simultaneous incorporation of cations and anions from S-PRG eluate occurred under balanced charge and may assist in rapid ion incorporation. Thus, various useful ions could be effectively incorporated into tooth enamel by applying S-PRG filler or its eluate; a bioactive effect can be expected.

Effect of Different Surface Treatments on the Tensile Bond Strength to Lithium Disilicate Glass Ceramics

PURPOSE

To evaluate the influence of different surface treatments of lithium disilicate glass ceramics on the bonding efficacy of three luting composites.

MATERIALS AND METHODS

A total of 450 blocks of e.max CAD (Ivoclar Vivadent) ground with 600-grit silicon carbide paper were prepared and divided into three groups (n = 150) according to the composite cements used: Variolink Esthetic DC (VE), Multilink Automix (MA), and SpeedCEM (SC). Each group was further divided into five subgroups (n = 10) according to the surface treatment performed: no treatment (control), Monobond Plus (MP), 37% phosphoric acid and Monobond Plus (PA), < 5% hydrofluoric acid and Monobond Plus (HF), and Monobond Etch & Prime (ME). All treated ceramic specimens were bonded with three composite cements and light cured. After 24-h water storage and 5000 or 10,000 thermocycles, tensile bond strength (TBS) was measured. The specimens underwent failure mode analysis. The results were statistically analyzed using two-way ANOVA and t-tests with Bonferroni correction.

RESULTS

The TBSs were significantly influenced by surface treatments (p < 0.05). There were no significant differences in HF and ME among most of the groups. Furthermore, ME showed the highest bond strength with MA after 10,000 thermocycling. Most specimens of the ME groups exhibited cohesive failures, whereas a combination of adhesive failures and mixed failures were observed in control, MP, PA, and HF groups.

CONCLUSION

In the surface treatment of lithium disilicate glass ceramics, Monobond Etch & Prime was found to be a possible substitution for the combination of hydrofluoric acid and Monobond Plus.

Influence of FCP-COMPLEX on bond strength and the adhesive-artificial caries-affected dentin interface

FCP-COMPLEX is a newly developed solution containing fluoride, calcium, and phosphoric acid that has the potential to reinforce caries-affected dentin. This study evaluated the effect of FCP-COMPLEX on micro-tensile bond strength (µTBS) and acid-challenge at the dentin-adhesive interface. FCP-COMPLEX, 2% NaF, and distilled water were applied to artificial caries-affected dentin (ACAD) and the effect on acid-induced damage after resin composite restoration was observed. Scanning electron microscopy and X-ray absorption fine structure (XAFS) were used to evaluate tooth morphology. The µTBS test revealed no effect of FCP-COMPLEX either immediately or after 3 months' storage. The area of acid damage in caries-affected dentin was reduced by FCP-COMPLEX. XAFS analysis revealed that absorbed fluorine on the surface would form CaF₂. In conclusion, FCP-COMPLEX significantly reduced the damage of acidic attack at the ACAD-adhesive interface, while the µTBS value was maintained after storage.

Development of Surface Fluorescence X-Ray Absorption Fine Structure Spectroscopy Using a Laue-Type Monochromator

Surface fluorescence X-ray absorption fine structure (XAFS) spectroscopy using a Laue-type monochromator has been developed to acquire structural information about metals with a very low concentrate on a flat highly oriented pyrolytic graphite (HOPG) surface in the presence of electrolytes. Generally, surface fluorescence XAFS spectroscopy is hindered by strong scattering from the bulk, which often chokes the pulse counting detector. In this work, we show that a bent crystal Laue analyzer (BCLA) can efficiently remove the scattered X-rays from the bulk even in the presence of solution. We applied the technique to submonolayer (∼10¹⁴  atoms cm^-2 ) Pt on HOPG and successfully obtained high signal/noise in situ XAFS data in combination with back-illuminated fluorescence XAFS (BI-FXAFS) spectroscopy. This technique allows in situ XAFS measurements of flat electrode surfaces to be performed in the presence of electrolytes.

The effect of different cleaning agents on saliva contamination for bonding performance of zirconia ceramics

The effects of contamination and cleaning methods on bonding of self-adhesive resin cement to zirconia ceramics were examined. Airborne particle-abraded zirconia (Zpex Smile) specimens were divided into the following four groups: control (con), contaminated with saliva and cleaned with tap water (HS), cleaned with Ivoclean (IC), and cleaned with Multi Etchant (ME). The pretreated specimens were bonded using three self-adhesive resin cements, and tensile bond strengths were measured using a universal testing machine at a crosshead speed of 2 mm/min. Con and IC groups showed significantly higher bond strength than those of HS and ME groups. Separately, the surface chemical composition of the groups was determined using X-ray photoelectron spectroscopy (XPS). XPS revealed that the N/Zr ratio increased in the HS group but decreased in the IC and ME groups. Cleaning agents can improve the adverse effect of saliva contamination on zirconia, but this effect varies depending on the product.

Effect of fluoride mouthrinse on adhesion to bovine root dentin

The purpose of this study was to evaluate the effect of fluoride mouthrinses on dentin bonding performance of a two-step selfetch adhesive; Clearfil SE Bond. Bovine root dentin surface was treated with either 450, 900, or 9,000 ppm F solutions for 30 s (immediate), and continually treated for one month (one month) before the bonding procedures. Microtensile bond strength (µTBS) test and scanning electron microscopic (SEM) observation of the acid-base resistance zone (ABRZ) were performed. Chemical state of fluorine on dentin surface was analyzed by X-ray absorption fine structure (XAFS). The 450 and 900 ppm F fluoride mouthrinses did not influence the µTBS to dentin, while the 9,000 ppm F fluoride solution adversely affected the µTBSs. The fluoride application to dentin significantly enhanced acid resistance at the adhesive/dentin interface including the ABRZ. The XAFS analysis indicated different concentrations of fluoride might create different chemical compounds on the dentin surface, influencing the µTBS results.

Development of 6-Axis Orthodontic Force and Moment Sensing Device for Decreasing Accident of Orthodontic Treatment. Annu Int Conf IEEE Eng Med Biol Soc 2018;2018:1797-1800. [PMID: 30440743 DOI: 10.1109/embc.2018.8512648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The purpose of this study is to develop the sensing device which measures three-axis force and three-axis moment for reducing the number of accident in orthodontic treatment. The device is necessary for adequate quantitative evaluation of orthodontic forces during orthodontics. The developed sensing device is composed of six-axis force sensors, tooth models, and arms for connecting sensors and tooth models. The developed device simulates rows of teeth in orthodontic operation and measures $14 \times 6$ axes force and moment from tooth models simultaneously. The averages of the difference of force and moment to theoretical values in each direction are 1.78 % (0.043 N) and 2.72 % (0.60 Nmm) respectively. The average moment applying couple forces is 17.1 % (0.81 Nmm). Then the device is able to measure more accurately as the value of the moment was larger. Therefore using our proposed device, we can conduct the orthodontic treatment which dentition moves large for attaching the rail of wire to the teeth.

Establishment of experimental models to evaluate the effectiveness of dental trauma splints

The purpose was to describe a novel simple experimental model of injured teeth for developing dental trauma splints (DTS), and to test various splints by combining use of this model and the Periotest^® device. Rubber O-rings and spring washers were used to simulate and modify injured tooth mobility. Splinting effects were assessed among three kinds of DTS, including a composite splint and two wire-composite splints (1: rectangular orthodontic wire 0.533×0.635 mm, 2: cobalt-chromium alloy wire Φ0.9 mm). The Periotest values were measured three times for each tooth before and after splint insertion. The splinting effect was defined as the change in tooth mobility. Splinting effects significantly increased in the order wire-composite splint 1<wire-composite splint 2<composite splint (p<0.05). This model system could evaluate the effects of DTS including the differences among various splint methods, which showed reasonable reproducibility of dental trauma situations depending on severity in clinical usage.

Six-axis orthodontic force and moment sensing system for dentist technique training

The purpose of this study is to develop a sensing system device that measures three-axis orthodontic forces and three-axis orthodontic moments for dentist training. The developed sensing system is composed of six-axis force sensors, action sticks, sliders, and tooth models. The developed system also simulates various types of tooth row shape patterns in orthodontic operations, and measures a 14 × 6 axis orthodontic force and moment from tooth models simultaneously. The average force and moment error per loaded axis were 2.06 % and 2.00 %, respectively.

Structural analysis of strontium in human teeth treated with surface pre-reacted glass-ionomer filler eluate by using extended X-ray absorption fine structure analysis

The bioactive effects of strontium released from surface pre-reacted glass-ionomer (S-PRG) fillers may aid in caries prevention. In this study, the local structure of strontium taken up by teeth was estimated by extended X-ray absorption fine structure analysis. Immersing teeth into S-PRG filler eluate increased the strontium content in enamel and dentin by more than 100 times. The local structure of strontium in enamel and dentin stored in distilled water was the same as that in synthetic strontium-containing hydroxyapatite (SrHAP). Moreover, the local structure of strontium in enamel and dentin after immersion in the S-PRG filler eluate was also similar to that of SrHAP. After immersion in the S-PRG filler eluate, strontium was suggested to be incorporated into the hydroxyapatite (HAP) of enamel and dentin at the calcium site in HAP.

Erratum to: Application of addition-cured silicone denture relining materials to adjust mouthguards

The purposes of this study were to examine the shock absorption capability of addition-cured silicone denture relining materials and the bonding strength of addition-cured silicone denture relining materials and a commercial mouthguard material to determine its applicability to mouthguard adjustment. Two addition-cured silicone denture relining materials were selected as test materials. The impact test was applied by a free-falling steel ball. On the other hand, bonding strength was determined by a delamination test. After prepared surface treatments using acrylic resin on MG sheet surface, 2 types of addition-cured silicone denture relining materials were glued to MG surface. The peak intensity, the time to peak intensity from the onset of the transmitted force and bonding strength were statistically analyzed using ANOVA and Tukey's honest significant difference post hoc test (p<0.05). These results suggest that the silicone denture relining materials could be clinically applicable as a mouthguard adjustment material.

Use of a gelatin hydrogel membrane containing β-tricalcium phosphate for guided bone regeneration enhances rapid bone formation

The purpose of this study was to evaluate a thin gelatin hydrogel membrane containing β-tricalcium phosphate (G-TCP) for use in guided bone regeneration, a technique that we developed. G-TCP membranes were fabricated from gelatin and β-TCP powder, freezedried, and cross-linked by heating. The resulting G-TCP membranes were as thin as collagen membranes, with high mechanical integrity. Proliferation and differentiation of rat bone marrow stromal cells (BMSCs) on G-TCP and collagen membranes were examined. On both membranes, BMSCs proliferated well and expressed alkaline phosphatase. However, more bone-like mineralized tissue formed on G-TCP membranes than on collagen membranes at 4 weeks. The effects of G-TCP and collagen membranes on bone regeneration in rat parietal bone defects were histologically examined. Bone bridges with mature uniform bone were observed under G-TCP membranes as early as 2 weeks. These results indicate that G-TCP is a GBR membrane that is comparable or superior to collagen membrane.

Degradation mechanism of a high-performance real micro gas sensor, as determined by spatially resolved XAFS

Of late, battery-driven high-performance gas sensors have gained acceptability in practical usage, whose atomic-scale structure has been revealed by μ-fluorescence X-ray absorption fine structure analysis. We studied the chemical distribution of Pd species in the Pd/Al2O3 catalyst overlayer in the real gas sensor at various degrees of deterioration. In a freshly prepared sensor, all Pd species were in the PdO form; in a heavily deteriorated sensor, Pd/Al2O3 in the external region changed to metallic Pd particles, while the PdO structure in the inner region near the heater remained unchanged. The Pd species distribution was in agreement with the simulated thermal distribution. Temperature control was crucial to maintain the high performance of the gas sensor. The improved sensor allows homogeneous heating and has a lifetime of more than 5 years.

A method to visualize transdermal nickel permeation in mouse skin using a nickel allergy patch

Metal patch test is often used in clinical settings when metal-induced contact dermatitis is suspected. However, the transdermal permeation behavior of metal ions from the patch test remains unclear. Current patch tests using high concentrations of metal salt solutions have some side effects, e.g. acute skin reactions to high concentrations of metal salt. To resolve these, estimating metal ion transdermal permeation is wished. In this study, synchrotron radiation X-ray fluorescence (SR-XRF) and micro-focused particle-induced X-ray emission (micro-PIXE) were used to visualize the time-dependent Ni permeation in mouse skin. The cross-sectional diffusion of Ni was visualized in a time-dependent manner. Our results indicate that maximum Ni permeation occurs after 24 h of patch treatment, and the permeated Ni content was high in the epidermis and spread into the dermis beyond the basal layer. This method may be useful to determine the appropriate solution concentration and duration of administration for the patch test.

Copper accumulation in the sequestrum of medication-related osteonecrosis of the jaw

Bisphosphonates (BPs) have been widely, efficiently, and safely used for the treatment of various bone-related diseases such as osteoporosis. However, concerns about jaw osteonecrosis associated with oral treatment (medication-related osteonecrosis of the jaw [MRONJ]) have been increasing. Although many risk factors for MRONJ have been elucidated, its precise etiology and methods of prevention remain unknown. In this study, we have applied various elemental analysis methods for MRONJ specimens (e.g., X-ray fluorescence with synchrotron radiation [SR-XRF], particle-induced X-ray emission [PIXE], X-ray absorption fine structure [XAFS]) in order to reveal the accumulation and chemical state of trace bone minerals. In four MRONJ sequestra, the characteristic localization of copper (Cu) was observed by SR-XRF. Using micro-PIXE analysis, Cu looked to be localized near the edge of the trabecular bone. The chemical state of the accumulated Cu was estimated using XAFS and the possibility of a Cu–BP complex formation was assumed. Thus, in this study we argue for the feasibility of the trace element analysis to evaluate the potential pathophysiological mechanism of MRONJ.

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Characteristic localization of Cu was observed by SR-XRF in the four MRONJ sequestra.

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The accumulated Cu was suspected as Cu–bisphosphonate complex by XAFS analysis.

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The feasibility of the trace element analysis for the pathophysiological mechanism of MRONJ was suggested.

Two cases of hard metal lung disease showing gradual improvement in pulmonary function after avoiding dust exposure

We present herein two cases of hard metal lung disease (HMLD) with distinct pathological findings. Both cases showed gradual improvements in pulmonary function over a period of a few years (Case 1: 30 months; Case 2: 12 months) after the avoidance of dust exposure, while improvements on high-resolution computed tomography were modest. The increased lymphocytes and decreased CD4/CD8 ratio in BALF observed at initial diagnosis normalized after the avoidance of dust exposure in one case. To the best of our knowledge, this is the first report demonstrating continual follow-up of pulmonary function and radiographic findings, and a comparison of BALF findings before and after avoidance of hard metal dust exposure.

Improvement of a Real Gas-Sensor for the Origin of Methane Selectivity Degradation by µ-XAFS Investigation

We have directly investigated the chemical state of the Pd species in a real μ-gas sensor device by examining the μ-fluorescence X-ray absorption fine structure. The μ-gas sensor device was heavily damaged by a heating process in which the temperature was ill-controlled, resulting in decrease of methane selectivity. We found that the PdO in the fresh μ-gas sensor was reduced to Pd metal particles as the methane selectivity decreased. Based on the investigation results, we modified the device structure so as to heat up homogeneously. The lifetime of the sensor was then successfully increased by more than 5 years.

Mechanical properties of orthodontic wires made of super engineering plastic

Most orthodontic equipment is fabricated from alloys such as stainless steel, Co-Cr and Ni-Ti because of their excellent elastic properties. In recent years, increasing esthetic demands, metal allergy and interference of metals with magnetic resonance imaging have driven the development of non-metallic orthodontic materials. In this study, we assessed the feasibility of using three super engineering plastics (PEEK, PES and PVDF) as orthodontic wires. PES and PVDF demonstrated excellent esthetics, although PEEK showed the highest bending strength and creep resistance. PEEK and PVDF showed quite low water absorption. Because of recent developments in coloration of PEEK, we conclude that PEEK has many advantageous properties that make it a suitable candidate for use as an esthetic metal-free orthodontic wire.

Estimation of trace metal elements in oral mucosa specimens by using SR-XRF, PIXE, and XAFS

The effects of dissolved elements from metal dental restorations are a major concern in lesions of the oral mucosa, and the evaluation of accumulated metal elements, especially their distribution and chemical state, is essential for determining the precise effects of trace metals. In this study, X-ray fluorescence with synchrotron radiation (SR-XRF) and particle-induced X-ray emission (PIXE) were applied for distribution analysis of the trace metal elements contained in the oral mucosa, and the chemical states of the elements were estimated using X-ray absorption fine structure (XAFS) analysis. Appropriate combination of these analysis techniques, particularly SR-XRF and PIXE, to visualize the distributions of the elements in the oral mucosa allowed for the observation and evaluation of accumulated metal ions and debris. Importantly, the analyses in this study could be carried out using conventional histopathological specimens without damaging the specimens. Therefore, this method would be applicable for the detection of accumulated trace metal elements in biopsy specimens from the oral mucosa.

Effect of immersion time of restorative glass ionomer cements and immersion duration in calcium chloride solution on surface hardness

OBJECTIVES

The objective of this study was to evaluate the effect of immersion time of restorative glass ionomer cements (GICs) and immersion duration in calcium chloride (CaCl2) solution on the surface hardness.

METHODS

Two high-viscosity GICs, Fuji IX GP and GlasIonomer FX-II, were selected. Forty-eight specimens were randomly divided into two groups. Sixty minutes after being mixed, half of them were immersed in a 42.7wt% CaCl2 solution for 10, 30, or 60min (Group 1); the remaining specimens were immersed after an additional 1-week of storage (Group 2). The surface hardness of the specimens was measured and analyzed with two-way ANOVA and the Tukey HSD test (α=0.05). The surface compositions were examined using energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy.

RESULTS

The surface hardness of Group 1 significantly increased as the immersion duration in CaCl2 increased; that of Group 2 significantly increased only after 60-minute CaCl2 immersion. After CaCl2 immersion, the amounts of Ca increased as the immersion duration increased. The surface hardness after CaCl2 immersion significantly correlated with the amount of Ca in Group 1, but not in Group 2. The binding energy of the Ca2p peak was similar to that of calcium polyalkenoate. These findings indicated that the Ca ions from the CaCl2 solution created chemical bonds with the carboxylic acid groups in the cement matrix.

SIGNIFICANCE

Immersion of GICs in CaCl2 solution at the early stage of setting was considered to enhance the formation of the polyacid salt matrix; as a result, the surface hardness increased.