Self-adhering implantable device of titanium: Enhanced soft-tissue adhesion by sandblast pretreatment.

Self-adhering implantable devices, which can be immobilized inside the bodies without suturing nor organic glues, made of metallic biomaterials would be optimal devices for preventing device-related complications such as device migration after implantation. We reported previously that acid-treated commercially-pure titanium (CpTi) adhered directly and immediately on hydrous non-keratinized soft tissues. Herein, we investigated the influence of sandblasting as pretreatment for acid-treated CpTi to increase its soft tissue adhesiveness. First, the effects of sandblasting conditions (i.e., pressure, distance and time) were investigated in terms of the sandblasted surface area and the degree of deformation (i.e., internal stress formation) of CpTi films. The effect of the sandblasting on the immediate soft tissue adhesion of acid-treated CpTi was investigated using an ex vivo shear adhesion test with mouse dermal tissues. The optimal sandblasting pretreatment remarkably improved the soft tissue adhesion strength of acid-treated CpTi (102 ± 19 kPa) compared with the non-sandblasted counterparts (41 ± 2 kPa). Finally, the CpTi adhesive was applied for immobilizing a near field communication (NFC) device in vivo, and was shown to have strong immediate adhesion to muscle fascia.

What impact does postgraduate clinical training have on empathy among Japanese trainee dentists?

BACKGROUND: Enhancing empathy in healthcare education is a critical component in the development of a relationship between healthcare professionals and patients that would ensure better patient care; improved patient satisfaction, adherence to treatment, patients' medication self-efficacy, improved treatment outcomes, and reduced patient anxiety. Unfortunately, however, the decline of empathy among students has been frequently reported. It is especially common when the curriculum transitions to a clinical setting. However, some studies have questioned the significance and frequency of this decline. Thus, the purpose of this study was to determine the impact of postgraduate clinical training on dental trainees' empathy from cognitive, behavioral, and patients' perspective. METHODS: This study included 64 trainee dentists at Okayama University Hospital and 13 simulated patients (SPs). The trainee dentists carried out initial medical interviews with SPs twice, at the beginning and the end of their clinical training. The trainees completed the Japanese version of the Jefferson Scale of Empathy for health professionals just before each medical interview. The SPs evaluated the trainees' communication using an assessment questionnaire immediately after the medical interviews. The videotaped dialogue from the medical interviews was analyzed using the Roter Interaction Analysis System. RESULTS: No significant difference was found in the self-reported empathy score of trainees at the beginning and the end of the clinical training (107.73 [range, 85-134] vs. 108.34 [range, 69-138]; p = 0.643). Considering the results according to gender, male scored 104.06 (range, 88-118) vs. 101.06 (range, 71-122; p = 0.283) and female 109.17 (range, 85-134) vs. 111.20 (range, 69-138; p = 0.170). Similarly, there was no difference in the SPs' evaluation of trainees' communication (10.73 vs. 10.38, p = 0.434). Communication behavior in the emotional responsiveness category for trainees in the beginning was significantly higher than that at the end (2.47 vs. 1.14, p = 0.000). CONCLUSIONS: Overall, a one-year postgraduate dental training program neither reduced nor increased trainee dentists' empathy levels. Providing regular education support in this area may help trainees foster their empathy.

Outer membrane vesicles derived from Porphyromonas gingivalis induced cell death with disruption of tight junctions in human lung epithelial cells.

OBJECTIVE: Porphyromonas gingivalis (P. gingivalis) is a major bacterium responsible for the progression of periodontitis. P. gingivalis produces small vesicles called outer membrane vesicles (OMVs) containing virulence factors. Increasing evidence suggests a close relationship between periodontitis and respiratory system diseases, such as aspiration pneumonia. However, little is known about whether P. gingivalis OMVs give rise to the impediment of lung epithelial cells. We investigated the effect of the OMVs on cell viability and tight junctions of lung epithelial cells. DESIGN: Human lung epithelial A549 cells were treated with P. gingivalis OMVs. Cell viability was evaluated, and cell morphology was examined using scanning electron and phase contrast microscopies. To detect apoptosis induced by P. gingivalis OMVs, activation of caspase-3 and poly ADP-ribose polymerase (PARP) cleavage was examined by using Western blotting. Immunocytochemistry was performed to stain tight junction proteins. RESULTS: P. gingivalis OMVs decreased cell viability in A549 cells in a dose- and time-dependent manner. Microscopic analysis revealed that the OMVs induced morphological changes leading to irregular cell membrane structures. The OMVs caused cell shrinkage, membrane blebbing, and cytoplasmic expulsion in a dose-dependent manner. Western blot analysis showed the OMVs induced caspase-3 activation and PARP cleavage. Treatment with the OMVs disrupted the intact distributions of tight junction proteins. CONCLUSIONS: These results indicate that P. gingivalis OMVs induced cell death by destroying the barrier system in lung epithelial cells. Our present study raises the possibility that P. gingivalis OMVs is an important factor in the engagement of periodontitis with respiratory system diseases.

Toughening of highly translucent zirconia by monoclinic ZrO2 and SiO2 particle coating.

The mechanical properties of highly translucent partially stabilized zirconia (PSZ) need to be improved; however, improvement of mechanical properties often decreases translucency. To overcome this problem, a monoclinic ZrO2 (mZrO2)/SiO2 dispersion was prepared and applied as a coating material for PSZ. The influence of surface treatment by the mZrO2/SiO2 dispersion on the surface topography, crystallography, and mechanical properties of highly translucent PSZ was investigated in this study. Following the treatment, the mechanical strength of highly translucent PSZ improved by 170% compared with control, for the best mZrO2/SiO2 dispersion ratio and heating temperature condition, while maintaining its translucency. The proposed coating is promising for improving the mechanical properties of highly translucent PSZ.

Improvement of mechanical properties of Y-TZP by thermal annealing with monoclinic zirconia nanoparticle coating.

OBJECTIVE: To assess whether a thermal annealing with a monoclinic zirconia (mZrO2) nanoparticle coating can improve the reliability of sandblasted yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and maintain its mechanical strength. METHODS: Commercially available Y-TZP (Lava Frame, 3M Dental Products) disks were sintered and surface-treated as follows: AS (as sintered, with no treatment); SB (sandblasting); SB-TA (sandblasting followed by thermal annealing at 1000 °C); and SB-mZr-TA (sandblasting followed by thermal annealing at 1000 °C with the mZrO2 nanoparticle coating). The mZrO2 nanoparticles of 21 nm in size were prepared by a hydrothermal method, and coated onto Y-TZP sintered disks as a 5 g/L ethanol dispersion. Biaxial flexural strength (S) was measured using the piston-on-three-ball test, and reliability was evaluated by the Weibull modulus (m). RESULTS: Biaxial flexural tests showed a significant increase in the strength of Group SB (SSB = 1445 ± 191 MPa) compared with Group AS (SAS = 1071 ± 112 MPa). The thermal annealing improved the reliabilities of the sandblasted Y-TZP (mSB-TA = 20.14 and mSB-mZr-TA = 21.33), as compared with Group SB (mSB = 7.77). However, the conventional thermal annealing without the mZrO2 coating caused a significant decrease in the strength of sandblasted Y-TZP (SSB-TA = 1273 ± 65 MPa). Importantly, the mZrO2 coating prevented the decrease in the strength caused by conventional thermal annealing (SSB-mZr-TA = 1379 ± 65 MPa). SIGNIFICANCE: The thermal annealing with the mZrO2 nanoparticle coating can improve the reliability of sandblasted Y-TZP and maintain its mechanical strength, which would otherwise be decreased by the conventional annealing process.

Optimal sandblasting conditions for conventional-type yttria-stabilized tetragonal zirconia polycrystals.

OBJECTIVE: To assess the influence of sandblasting conditions applied to conventional-type yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) on surface roughness, phase transformation, and biaxial flexural strength. METHODS: Commercially available Y-TZP (Lava Frame, 3M Dental Products) disks were used after sintering (specimen dimensions: 14mm in diameter and 1.2mm in thickness). The surfaces of specimens were ground, and then sandblast treatments were conducted at different pressures (0.20, 0.25, 0.30, 0.35 and 0.40MPa) and distances (1, 5, 10 and 20mm) with 50µm alumina particles. Surface roughness measurements were performed and scanning electron microscopy (SEM) images were taken for surface characterizations. Phase transformation of Y-TZP was identified by X-ray diffraction (XRD). Biaxial flexural strength was measured using the piston-on-three-ball test. RESULTS: The surface roughness increased significantly by increasing the sandblasting pressure, and microcracks were observed at high sandblasting pressure at 0.40MPa. The shortest sandblasting distance (1mm) was not effective to increase the surface roughness compared with other sandblasting distances. A tetragonal to monoclinic phase transformation was observed after grinding. The degree of the phase transformation tended to increase with sandblasting pressure, and significant effect was independent of the sandblasting distance. The biaxial flexural test showed improved mechanical strengths for the samples after sandblasting at 0.20-0.35MPa, with the maximum strength at 0.25MPa. Sandblasting at 0.40MPa decreased the strength as compared with 0.25MPa. SIGNIFICANCE: The surface roughness increased with increasing the sandblasting pressure, whereas there was an optimal sandblasting pressure range to increase biaxial flexural strength of Y-TZP.

Relationship of trainee dentists' self-reported empathy and communication behaviors with simulated patients' assessment in medical interviews.

OBJECTIVES: We aimed to clarify the communication behaviors between trainee dentists and simulated patients (SPs), to examine how the level of trainee dentists' self-reported empathy influences assessment by SPs in medical interviews. MATERIALS AND METHODS: The study involved 100 trainee dentists at Okayama University Hospital and eight SPs. The trainee dentists conducted initial interviews with the SPs after completing the Japanese version of the Jefferson Scale of Empathy (JSE). All interviews were recorded and analyzed using the Roter Interaction Analysis System (RIAS). The SPs assessed the trainees' communication immediately after each interview. The trainee dentists were classified into two groups (more positive and less positive) according to SP assessment scores. RESULTS: Compared with less-positive trainees, the more-positive trainees scored higher in the RIAS category of emotional expression and lower in the medical data gathering category. There was no difference in dental data gathering between the two groups. SP ratings for more-positive trainees were higher for use of positive talk and emotional expression and lower for giving medical information and dental information. Trainees with more positive ratings from SPs had significantly higher JSE total scores. CONCLUSION: The results of this study suggest that responding to the emotions of patients is an important behavior in dentist-patient communication, according to SPs' positive assessment in medical interviews. Further, SPs' assessment of trainees' communication was related to trainees' self-reported empathy, which indicates that an empathic attitude among dentists is a significant determinant of patient satisfaction.

Morphological and Functional Analyses of the Tight Junction in the Palatal Epithelium of Mouse.

Tight junction (TJ) is one of the cell-cell junctions and known to have the barrier and fence functions between adjacent cells in both simple and stratified epithelia. We examined the distribution pattern, constitutive proteins, and permeability of TJ in the stratified squamous epithelium of the palatal mucosa of mice. Ultrastructural observations based on the ultrathin section and freeze-fracture methods revealed that poorly developed TJs are located at the upper layer of the stratum granulosum. The positive immunofluorescence of occludin (OCD), claudin (CLD)-1 and -4 were localized among the upper layer of the stratum granulosum showing a dot-like distribution pattern. And CLD-1 and -4 were localized among the stratum spinosum and the lower part of stratum granulosum additionally showed a positive reaction along the cell profiles. Western blotting of TJ constitutive proteins showed OCD, CLD-1, -2, -4, and -5 bands. The permeability test using biotin as a tracer revealed both the areas where biotin passed through beyond OCD positive points and the areas where biotin stopped at OCD positive points. These results show that poor TJs localize at the upper layer of the stratum granulosum of the palatal epithelium, and the TJs are leaky and include at least CLD-1 and -4.

Resin adhesion strengths to zirconia ceramics after primer treatment with silane coupling monomer or oligomer.

Resin bonding to zirconia ceramics is difficult to achieve using the standard methods for conventional silica-based dental ceramics, which employ silane coupling monomers as primers. The hypothesis in this study was that a silane coupling oligomer -a condensed product of silane coupling monomers- would be a more suitable primer for zirconia. To prove this hypothesis, the shear bond strengths between a composite resin and zirconia were compared after applying either a silane coupling monomer or oligomer. The shear bond strength increased after applying a non-activated ethanol solution of the silane coupling oligomer compared with that achieved when applying the monomer. Thermal treatment of the zirconia at 110°C after application of the silane coupling agents was essential to improve the shear bond strength between the composite resin cement and zirconia.

Peptide-modified Substrate for Modulating Gland Tissue Growth and Morphology In Vitro.

In vitro fabricated biological tissue would be a valuable tool to screen newly synthesized drugs or understand the tissue development process. Several studies have attempted to fabricate biological tissue in vitro. However, controlling the growth and morphology of the fabricated tissue remains a challenge. Therefore, new techniques are required to modulate tissue growth. RGD (arginine-glycine-aspartic acid), which is an integrin-binding domain of fibronectin, has been found to enhance cell adhesion and survival; it has been used to modify substrates for in vitro cell culture studies or used as tissue engineering scaffolds. In addition, this study shows novel functions of the RGD peptide, which enhances tissue growth and modulates tissue morphology in vitro. When an isolated submandibular gland (SMG) was cultured on an RGD-modified alginate hydrogel sheet, SMG growth including bud expansion and cleft formation was dramatically enhanced. Furthermore, we prepared small RGD-modified alginate beads and placed them on the growing SMG tissue. These RGD-modified beads successfully induced cleft formation at the bead position, guiding the desired SMG morphology. Thus, this RGD-modified material might be a promising tool to modulate tissue growth and morphology in vitro for biological tissue fabrication.

Effect of fluoride-releasing liner on demineralized dentin.

OBJECTIVE: The aim of this study was to evaluate the remineralization of residual demineralized dentin underneath restorations by fluoride-releasing liners in vitro. METHOD AND MATERIALS: Two glass-ionomer cement liners, Lining Cement (GC) and RK-141A (GC), and two light-cured resin liners with and without 5 wt% NaF were used in this study. The resin liners were made by mixing TEGDMA and bis-GMA. Class 5 cavities were prepared on extracted human premolars. Demineralized dentin was promoted by using a bacterial caries induction system at the cavity floor. Cavities were restored with a resin composite following application of each liner. Specimens were then stored for 4 weeks at 37 degrees C and 100% humidity. After storage, the specimens were cut through the restorations, and axial sections of about 80-microm thickness were prepared. Contact microradiographs were taken, and the radiopacity of the demineralized dentin layer underneath the liner was analyzed. RESULTS: The ratios of radiopacity of demineralized dentin under the fluoride-releasing liners were significantly higher than those under the resin liner without fluoride release. Although the amounts of fluoride release from the glass-ionomer cement liners were lower than that from the resin liner with fluoride release, there were no significant differences in the ratios of radiopacity in demineralized dentin layers among the 3 liners with fluoride release. CONCLUSION: Although the fluoride released from liners can enhance remineralization of demineralized dentin, the amount of fluoride release does not affect the ratio of radiopacity in the remineralized dentin.

Effect of two-step adhesive systems on inhibition of secondary caries around fluoride-releasing resin composite restorations in root dentine.

OBJECTIVE: The purpose of this study was to investigate the effect of two-step adhesive systems on secondary caries inhibition around fluoride-releasing materials in vitro. METHODS: Two self-etching primer systems, Clearfil SE Bond (SE) and UniFil Bond (UB), and two one-bottle systems with a total-etch wet-bonding technique, Single Bond (SB) and One-Step (OS), were used prior to placement of resin composites either with (Reactmer) or without (Z100) fluoride release. Class V cavities prepared in extracted human premolars were restored with various combinations of materials: Reactmer/SE, Reactmer/UB, Reactmer/SB, Reactmer/OS, Z100/SE, Z100/UB, Z100/SB and Z100/OS. After storage for 14 days, the restored teeth were incubated in bacterial medium containing sucrose with Streptoccus mutans for 2 weeks. Water sorption and desorption of the adhesives and fluoride release from the resins either coated with adhesive or uncoated were also determined. RESULTS: The one-bottle groups showed higher water sorption and desorption than the self-etching primer groups. Although fluoride release from the Reactmer specimens was suppressed by the adhesive coating, the one-bottle groups allowed significantly higher fluoride release than the self-etching primer groups. On microradiographs, the radio-opaque layers adjacent to the Reactmer restorations were thick and clear, while the layers adjacent to the Z100 restorations were thin and unclear. For the Reactmer restorations, the radio-opaque layers associated with the one-bottle groups were significantly thicker than for the self-etching primer groups. CONCLUSIONS: These results indicated that the use of one-bottle wet-bonding systems for bonding of fluoride-releasing resin composites to dentine may contribute to inhibit secondary caries compared to self-etching primer systems.

Calbindin D-28k distribution in odontoblasts underneath tertiary dentine in human carious teeth.

OBJECTIVE: The aim of this study was to examine the calbindin D-28k immunoreactivity in carious teeth to know whether this protein may have a function in tertiary dentine formation. METHODS: Human extracted teeth with or without carious lesions were immersion-fixed with Zamboni fixative, demineralized in 4.13% EDTA solution (pH 7.4), frozen-sectioned, and processed for calbindin immunoreactivity and hematoxylin-eosin stain. The intensity of the immunostaining was evaluated by quantitative densitometry. RESULTS: In intact teeth, numerous odontoblasts were aligned underneath the secondary dentine and their cell bodies showed the immunoreactivity. In carious teeth, tertiary dentine had poor- or rich tubular patterns under the carious lesion. Underneath the tubule-poor tertiary dentine, distinct odontoblasts could not be seen at the central site. However, some cells with a flat appearance were located at this site and were immunonegative for calbindin D-28k. On the other hand, columnar odontoblasts were seen at the peripheral site, and their cell bodies and processes showed strong immunoreactivity. Underneath the tubule-rich tertiary dentine, columnar odontoblasts were abundantly distributed, and the strong immunoreactivity was observed in their cell bodies and processes. The immunoreactivity in odontoblasts underneath the tertiary dentine with poor or rich tubular pattern was more intense than that for the secondary dentine in intact teeth (P<0.05). On the other hand, the intensity of the immunoreactivity in odontoblasts was similar underneath the secondary dentine in intact and carious teeth. CONCLUSIONS: The present study demonstrated that calbidin D-28k was actively synthesised by odontoblasts under the carious lesion. These findings may suggest that this protein plays an important role in the tertiary dentine formation.

Effect of drying methods on hybrid layer thickness.

PURPOSE: To evaluate the effect of drying methods used in scanning electron microscopy on the thickness of the hybrid layers created by several different adhesive systems. METHODS: A total etch dry bonding system, (Photobond), a three-step bonding adhesive system, (Scotchbond Multi-Purpose), a wet-bonding adhesive system (All-Bond 2) and a self-etching primer system (Mac Bond II) were used in this study. To permit measurement of the thickness of the hybrid layer, the resin-dentin interfaces were polished and etched briefly to remove polishing debris followed by immersion in 10% NaOCl for 4 hours. Half of the specimens in each group were subjected to fixation and critical-point drying followed by gold sputter-coating. The remaining specimens were allowed to air dry prior to gold sputter-coating. SEM observations were carried out to determine the structure and thickness of the hybrid layers. RESULTS: The thickness of hybrid layers were affected by the drying methods with the critical-point drying methods producing the thickest hybrid layers (P < 0.05). The thickest hybrid layers were created by Photobond, with Scotchbond Multi-Purpose and All-Bond 2 producing intermediate thickness hybrid layers, among the total etch systems. The thinnest hybrid layer among all of the adhesive systems was produced by the self-etching primer, Mac Bond II.

Resin adhesion to carious dentin.

PURPOSE: To investigate the microtensile bond strength (microTBS) of a self-etching priming adhesive system to normal, caries-affected and caries-infected dentin, and to observe the ultrastructure of the resin-dentin interface by transmission electron microscopy (TEM). MATERIALS AND METHODS: Twelve extracted human molar teeth with deep occlusal caries were stained with caries detector solution and ground flat occlusally. The red-stained soft dentin was classified as caries-infected. The surrounding discolored dentin was classified as caries-affected dentin. The surrounding normal dentin served as a control. The entire flat surface was bonded with Clearfil Liner Bond 2V (CV) and covered with resin composite to form a composite crown 5 mm high. One day later the specimens were serially sectioned vertically into multiple slabs 0.8 mm thick. Under microscopic observation, the specimens were divided into normal or caries-infected or caries-affected dentin. These regions were isolated by cutting away the remaining dentin to form hour-glass shapes with the smallest surface area at the test site. After measuring the areas, the specimens were fixed to a microtensile tester and pulled under tension to failure. Additional slabs that were not used for bond strength tests were processed for TEM. Bond strength data were analyzed by Kruskal-Wallis one-way ANOVA and Student-Newman-Keuls multiple comparisons. RESULTS: The microTBS of CV to normal, caries-affected and caries-infected dentin were 45 +/- 10 MPa, 30 +/- 10 MPa, 10 +/- 5 MPa, respectively. TEM images showed that CV formed thin hybrid layers that were less than 1 microm thick in normal dentin, but that were between 6-8 microm thick in caries-affected dentin. Bacteria were only sparsely observed in the dentin tubules of bonded caries-affected dentin. However, in caries-infected dentin, an unusual interface was seen in which carious bacteria within disorganized non-banded collagen fibrils could be seen embedded by the adhesive. The hybrid layer in caries-infected dentin was found to be 30-60 microm thick.

Effect of self-etching primer containing N-acryloyl aspartic acid on enamel adhesion.

OBJECTIVES: A previous study demonstrated that N-acryloyl aspartic acid (N-AAsp) aqueous solution is useful as a self-etching primer for dentin adhesion. The purpose of this study was to evaluate whether N-AAsp solution can be used for enamel etching, when compared with phosphoric acid. METHODS: N-AAsp was synthesized by the reaction of DL-aspartic acid and acryloyl chloride. The experimental self-etching primers were prepared by dissolving N-AAsp in water at various concentrations up to 20 wt%. The tensile bond strength of resin to bovine enamel was measured after the enamel was treated with the N-AAsp primers. The 40 wt% H(3)PO(4) was used for comparison. The treated enamel surfaces and the resin-enamel interfaces were also observed with a scanning electron microscope. RESULTS: The tensile bond strength to enamel increased linearly with the increasing N-AAsp concentration and reached the same value as that to enamel etched with 40 wt% H(3)PO(4) when N-AAsp concentration was 20 wt%, even though the etching ability of 20 wt% N-AAsp was inferior to 40 wt% H(3)PO(4). Regardless of the concentration of N-AAsp, the bond strength to enamel was the same as that to dentin reported in our previous study. SIGNIFICANCE: The 20 wt% N-AAsp aqueous solution showed enamel bonding equivalent to 40 wt% H(3)PO(4) in addition to the advantage of eliminating the rinse step with water. Based on the results obtained in this study along with those obtained in a previous study, it was concluded that 20 wt% N-AAsp aqueous solution is a promising self-etching primer to simultaneously treat enamel and dentin.

Effect of EDTA conditioning on bond strength to bovine dentin promoted by four current adhesives.

PURPOSE: To investigate the effect of disodium dihydrogen ethylenediamine tetraacetate dihydrate (EDTA) conditioning prior to the application of adhesive systems on the bond strength of resin composite to dentin. METHODS: 80 bovine teeth were ground with 600-grit SiC paper to obtain flat dentin surfaces. Half of the specimens were conditioned with 0.5 mol EDTA aqueous solution (pH 7.4) for 60 seconds, water-rinsed and air-dried, and the other half were used without any treatment. The specimens were randomly divided in four groups of 10 each. The dentin surfaces were treated with each of two "all-in-one" adhesive systems (One-up Bond F, OB; Reactmer Bond, RB), a self-etching priming system (Clearfil SE Bond, SE), and a total-etch one-bottle bonding system (Single Bond, SB). For SB, the adhesive was applied on EDTA-conditioned dentin without H3PO4 etching. Then a layer of resin composite was placed and light-cured for 40 seconds. The tensile bond strength was measured and the resin-dentin interface was observed using a scanning electron microscope. RESULTS: The mean and standard deviation of tensile bond strength in MPa to ground dentin were 9.3+/-3.5/OB, 11.6+/-2.0/RB, 23.2+/-4.9/SE and 19.7+/-4.1/SB. Bond strengths to EDTA-conditioned dentin were 15.0+/-3.0/OB, 16.8+/-3.6/RB, 22.8+/-5.2/SE and 19.4+/-5.1/SB. Duncan's Multiple Range test revealed that the EDTA-conditioned dentin showed significantly higher tensile bond strength than the non-conditioned one for "all-in-one" adhesive systems (P < 0.05) but no significant difference was found for the self-etching priming and total-etch one-bottle bonding systems. At the resin-dentin interface, EDTA-conditioned specimens formed thicker hybrid layers than non-conditioned ones for all systems except for SB.

Effect of fluoride application on tensile bond strength of self-etching adhesive systems to demineralized dentin.

STATEMENT OF PROBLEM: It has been reported that the bond strength of composite to demineralized dentin is lower than that to sound dentin. This can be a problem in the success of so-called sealed restorations. PURPOSE: The aim of this study was to evaluate the effect of fluoride application on the tensile bond strength of self-etching adhesive systems to demineralized dentin. MATERIAL AND METHODS: One hundred twenty extracted bovine incisors were ground flat with 600-grit silicone carbide paper. Ninety teeth were then immersed in acetate buffer (pH 4.0) to form demineralized dentin. These teeth were randomly divided into 3 groups of 30 each: surfaces treated with fluoride solution (Group NF), surfaces treated with fluoride solution followed by a water rinse (Group RF), and control surfaces with no pretreatment (Group C). The remaining 30 teeth comprised a group with normal dentin surfaces (Group S). Each group was further divided into 3 subgroups of 10 each to test the bond strength test of Clearfil SE Bond, Unifil Bond, and Mac-Bond II. Tensile bond strengths (in MPa) were measured with a universal testing machine at a crosshead speed of 0.5 mm/min. Mean bond strengths were analyzed by 2-way analysis of variance and Fisher's PLSD (P =.05). SEM observations of the surfaces before and after priming and at resin-dentin interfaces in each group were performed. Elemental analysis of the dentin surfaces before priming was also carried out. RESULTS: The bond strengths of the adhesives to demineralized dentin in Groups NF, RF, and C were significantly lower than that of the normal dentin in Group S (P <.05). The mean bond strengths of the 3 adhesives in Group NF were higher than those in Groups RF and C, but a significant difference was observed only when Clearfil SE Bond was used (P <.05). In SEM images the open dentinal tubules on the surface and the resin tag formation at the resin-dentin interface were apparent in Group NF but were not observed in Groups RF and C. On elemental analysis, considerable amounts of fluoride and calcium were detected in the surfaces of Group NF. CONCLUSION: Within the limitations of this study, the surface treatment with fluoride solution supported the resin tag formation at the resin-dentin interface and slightly improved the bond strength of the self-etching adhesive systems tested to demineralized dentin. This result indicated that the fluoride treatment to demineralized dentin might contribute to the success of the sealed restoration.

Effects of fluoride release from bis-GMA/TEGDMA resin regulated by gamma-methacryloxypropyltrimethoxysilane on demineralization of bovine enamel.

We previously demonstrated that fluoride release from resins could be regulated by the polysiloxane coating of the fluoride additives. The present study investigated the effects of regulated fluoride release from resin on enamel demineralization in vitro. Bovine enamel cavities were restored with bis-GMA/TEGDMA resins containing 50 wt% NaF powders treated with or without gamma-methacryloxypropyltrimethoxysilane. Specimens were immersed in distilled water that was changed daily to measure the amount of fluoride released over 40 days, and thereafter subjected to pH-cycling. Microradiographic observations were performed to determine total mineral loss (AZ) and lesion depth (Ld) on the enamel. In addition, fluorine distribution was analyzed using EPMA. The resin containing untreated NaF exhibited high-rate and short-term fluoride release, whereas the resin containing treated NaF released low concentrations of fluoride over a longer period. The former showed high fluorine uptake in the adjacent enamel. In contrast, the latter showed high fluorine uptake not only in the adjacent enamel, but also in a wider area of enamel surface. The latter also showed lower AZ and Ld values in the surrounding enamel, indicating a high inhibitory effect on caries formation. Therefore, it is suggested that regulated fluoride release from the resin based on polysiloxane coating is effective in preventing caries formation.

Regulation of NaF release from bis-GMA/TEGDMA resin using gamma-methacryloxypropyltrimethoxysilane.

OBJECTIVES: The aim of this study was to evaluate the feasibility of regulation of NaF release from bis-GMA/TEGDMA resin using gamma-methacryloxypropyltrimethoxysilane (gamma-MPTS). METHODS: NaF powder was treated with gamma-MPTS to form a polysiloxane layer on its surface. The morphology and the composition of the NaF powder treated with gamma-MPTS were evaluated using scanning electron microscopy, infrared spectroscopy, contact angle measurement and X-ray photoelectron spectroscopy. Bis-GMA/TEGDMA resin containing 50 wt% NaF powder was prepared as a model resin and immersed in distilled water at 37 degrees C, and the amount of fluoride released from the resin was measured using a fluoride electrode. The mechanical strength in terms of diametral tensile strength before and after fluoride release was also measured, and statistically analyzed using one-way factorial ANOVA and Fisher's PLSD method. RESULTS: NaF powder was covered with hydrophobic gamma-MPTS delivered polysiloxane. A larger amount of fluoride was released at the initial stage from the resin containing NaF treated with no gamma-MPTS. However, fluoride release terminated in a relatively shorter period. In contrast, we observed a smaller amount of fluoride released for a longer period from the resin containing NaF treated with gamma-MPTS. SIGNIFICANCE: We found that gamma-MPTS treatment is useful for the regulation of NaF release from bis-GMA/TEGDMA resin. The mechanism of slow NaF release may be the formation of a hydrophobic polysiloxane layer on the surface of NaF powder and resulting slow water diffusion to NaF powder.