Effect of surface topography and wettability on shear bond strength of Y-TZP ceramic.

Zirconia ceramics have been widely used as dental restorations due to their esthetic appearance and high flexural strength. The bonding of zirconia with resin cement should rely on both mechanical and chemical bonds. This study was performed to investigate the effect of zirconia surface topography and its wettability after surface pretreatments on the microshear bond strength (µSBS) of a resin cement. Zirconia slabs were prepared and randomly divided into 5 groups based on the surface treatment as follows: no treatment (control), air abrasion (AB), etching with hydrofluoric acid (F), the mixture of hydrofluoric acid and nitric acid (FN), or the mixture of hydrochloric acid and nitric acid (CN) for 10 min. The specimens were subjected to investigation of surface roughness characteristics [average roughness (Ra), peak-to-valley average distance (Rpv), skewness (Rsk), and kurtosis (Rku)] using atomic force microscopy (AFM) and measurements of surface contact angle (θc) and µSBS of a resin cement. In addition, the area % of the nanoscale surface irregularity (nSI%) was calculated from the AFM images. The effects of nSI%, Ra and θc on the µSBS were analyzed by multiple linear regression analysis (p < 0.05). Multiple regression analysis revealed that the nSI% was the most predominant factor for the µSBS (p < 0.001). A surface with larger nSI%, higher Ra and relatively lower θc was essential for establishing a reliable resin-zirconia bond.

Influence of a Novel Lithium Disilicate Coating on Composite-Zirconia Bonding and Bond Characterization.

PURPOSE: To investigate microtensile bond strength and characterization with the novel lithium disilicate coating technique compared to conventional air abrasion. MATERIALS AND METHODS: Eight zirconia blocks were fabricated and assigned to two groups (n = 4 each): (1) Lithium disilicate coating followed by hydrofluoric acid etching and Monobond N Primer (LiDi group); and (2) alumina air abrasion (MUL group). For each group, two identically pretreated zirconia blocks were bonded together with Multilink Speed Cement and cut into 30 stick-shaped specimens (1 × 1 × 9 mm3). The 120 specimens were stored in water for 24 hours and assigned to one of three groups (n = 20/group): (1) short-term storage for 24 hours; (2) thermocycling for 5,000 cycles; and (3) thermocycling for 10,000 cycles. A microtensile bond strength test was performed and evaluated. The bond strength results were analyzed using two-way ANOVA followed by one-way ANOVA and Tukey HSD (α = .05). Energy-dispersive x-ray spectroscopy (EDS), Fourier-transform infrared (FTIR), x-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), and scanning electron microscopy (SEM) were used for chemical, crystalline phase, and failure mode analyses. RESULTS: The MUL groups recorded higher bond strength than the LiDi groups. Thermocycling significantly decreased the bond strength in both groups. Chemical analyses suggested that the lithium disilicate layer underwent hydrolysis, which compromised long-term bond strength. CONCLUSION: The bond between composite cement and alumina-abraded zirconia performed better than that with the lithium disilicate coating technique. Int J Prosthodont 2023;36:172-180. doi: 10.11607/ijp.6744.

Polymerization shrinkage of light-cured conventional and bulk-fill composites -The effect of cavity depth and post-curing.

Volumetric shrinkage (VS) of conventional, bulk-fill, and core build-up resin-based composites (RBCs) of various thickness (1-5 mm) was measured using the modified bonded-disk method with confocal laser scanning microscopy. Additionally, the bottom-to-top ratio of Vickers hardness (%VH) was measured. Conventional RBCs exhibited significantly higher VS than bulk-fill and core build-up RBCs (p<0.05). As specimen thickness increased, VS relative to volume (%VS) and difference in VS at each depth (VSdepth) decreased. For conventional RBCs, there was a significant drop in VSdepth between 1 mm and 2 mm (p<0.05), and another drop was observed between 3 mm and 4 mm (p<0.05) where %VH decreased below 90%. For bulk-fill and core build-up RBCs, VSdepth decreased significantly between 2 mm and 3 mm (p<0.05), but %VH exceeded 90% even in 5 mm deep cavities. These results indicated that post-curing contributed to lower shrinkage in deeper layers, and that conventional RBCs were not adequately polymerized at the depth of over 3 mm.

Addition of metal chlorides to a HOCl conditioner can enhance bond strength to smear layer deproteinized dentin.

OBJECTIVES: To evaluate the effect of smear layer deproteinization using hypochlorous acid (HOCl) with/without metal chlorides (SrCl2 and ZnCl2) on the microtensile bond strength (µTBS) of two simplified adhesives to dentin. METHODS: Human dentin surfaces with a standardized smear layer were pretreated using a 105 ppm HOCl solution with/without SrCl2 (0.05 M, 0.1 M, 0.2 M, 0.4 M) or ZnCl2 (0.05 M, 0.1 M, 0.2 M) for 5 s, 15 s, or 30 s. After the deproteinizing solution was washed out with water for 5 s, 15 s, or 30 s, pretreated surfaces were bonded with one-step self-etch adhesive Bond Force II or universal adhesive Clearfil Universal Bond Quick, and µTBS was measured after 24 h. Additionally, the deproteinizing effects of HOCl solutions with/without the metal chlorides were compared by measuring changes in the amide:phosphate ratio using attenuated total reflection Fourier transform infrared spectroscopy. Statistical analysis was performed using multifactor ANOVA, Tukey's post hoc tests and t-tests (p < 0.05). RESULTS: Pretreatment with pure HOCl for 15 s and 30 s significantly decreased the amide:phosphate ratio (p < 0.05), indicating effective deproteinization, but the µTBS of both adhesives increased significantly only if HOCl was washed out for 30 s (p < 0.05). Increasing the concentrations of metal chlorides enabled shortening of the wash-out time down to 5 s while maintaining the improved µTBS (p < 0.05). The deproteinizing effect of HOCl was not significantly altered by the addition of metal chlorides (p > 0.05). SIGNIFICANCE: The effectiveness of smear layer deproteinization using HOCl can be improved by the addition of metal chlorides, as their increasing concentration allowed to shorten the wash-out time from 30 s down to 5 s.

Application of Sulfinate Agent in Conjunction with HOCl Smear-Layer Deproteinization Improves Dentin Bonding Durability of One-step Self-etch Adhesives.

PURPOSE: To evaluate the effect of a sulfinate agent on the bonding durability of one-step self-etch adhesives (1-SEAs) to smear-layer-covered dentin deproteinized with hypochlorous acid (HOCl). MATERIALS AND METHODS: Human coronal dentin disks with a standardized smear layer were deproteinized with 100 ppm HOCl solution for 0 s (control), 15 s or 30 s. After rinsing with water for 30 s and air drying, half of the specimens were treated with a sulfinate agent (Scotchbond Universal Dual Cure Activator; SDA) prior to the application of a 1-SEA (Bond Force II [Tokuyama Dental] or Clearfil Universal Bond Quick [Kuraray Noritake]). Microtensile bond strength (µTBS) was measured after 24 h or 10,000 thermal cycles (TC). The data were analyzed by three-way ANOVA with Tukey's post-hoc tests and t-tests at the 0.05 significance level. RESULTS: The 24-h µTBS of both adhesives increased statistically significantly with the HOCl pretreatment for 15 s or 30 s (p < 0.05), but it was not statistically significantly affected by the application of SDA (p > 0.05). However, after TC, the groups treated with the combination of HOCl and SDA maintained their µTBS (p > 0.05), as opposed to untreated dentin and dentin treated with either HOCl or SDA, whose µTBS decreased significantly (p < 0.05). CONCLUSION: The application of the sulfinate agent did not statistically significantly affect the immediate bond strength of 1-SEAs, and it could not prevent a significant decrease in the bond strength to untreated dentin after thermocycling. However, the sulfinate agent significantly improved the bonding durability of 1-SEAs to HOCl smear-layer deproteinized dentin.

Smear layer deproteinization with NaOCl and HOCl: Do application/wash-out times affect dentin bonding of one-step self-etch adhesives?

This study investigated the influence of application/wash-out times of sodium hypochlorite (NaOCl) and hypochlorous acid (HOCl) on dentin bond strength of one-step self-etch adhesives (1-SEAs). Human coronal dentin discs with a standardized smear layer were pretreated with 6% NaOCl or 100 ppm HOCl for 5 s, 15 s, or 30 s, and washed out with water for 5 s, 15 s or 30 s with or without the application of Clearfil DC Activator (CDA). No pretreatment was used as a control. The discs were bonded with a 1-SEA (Bond Force II or Clearfil Universal Bond Quick) and microtensile bond strength (µTBS) was measured after 24 h. Pretreatment with NaOCl for 15 s and 30 s significantly decreased µTBS (p<0.05), irrespective of wash-out time. The application of CDA recovered µTBS but did not outperform the control group. Conversely, pretreatment with HOCl for 15 s and 30 s followed by 30 s wash-out time significantly increased µTBS of 1-SEAs (p<0.05), regardless of CDA application.

UV-Mediated Photofunctionalization of Indirect Restorative Materials Enhances Bonding to a Resin-Based Luting Agent.

PURPOSE: The potential of UV-mediated photofunctionalization to enhance the resin-based luting agent bonding performance to aged materials was investigated. METHODS: Sixty samples of each material were prepared. Yttria-stabilized zirconia (YZr) and Pd-Au alloy (Pd-Au) plates were fabricated and sandblasted. Lithium disilicate glass-ceramic (LDS) was CAD-CAM prepared and ground with #800 SiC paper. Half of the specimens were immersed in machine oil for 24 h to simulate the carbon adsorption. Then, all of the specimens (noncarbon- and carbon-adsorbed) were submitted to UV-mediated photofunctionalization with a 15 W UV-LED (265 nm, 300 mA, 7692 µW/cm2) for 0 (control groups), 5, and 15 min and subjected to contact angle (Ɵ) measurement and bonded using a resin cement (Panavia™ V5, Kuraray Noritake, Japan). The tensile bond strength (TBS) test was performed after 24 h. The Ɵ (°) and TBS (MPa) data were statistically analyzed using two-way ANOVA and Bonferroni correction tests (α = 0.05). RESULTS: In the carbon-adsorbed groups, UV-mediated photofunctionalization for 5 min significantly decreased Ɵ of all materials and increased TBS of YZr, and UV for 15 min significantly increased the TBS of LDS and Pd-Au. In noncarbon-adsorbed groups, UV-photofunctionalization did not significantly change the Ɵ or TBS except YZr specimens UV-photofunctionalized for 15 min. CONCLUSION: UV-mediated photofunctionalization might have removed the adsorbed hydrocarbon molecules from the materials' surfaces and enhanced bond strengths of Panavia™ V5 to YZr, LDS, and Pd-Au. Additionally, UV-mediated photofunctionalization improved the overall TBS of YZr. Further investigation on the optimum conditions of UV photofunctionalization on indirect restorative materials should be conducted.

Bond strengths of three-step etch-and-rinse adhesives to silane contaminated dentin.

This study aimed to evaluate the effect of silane coupling agent contamination on the microtensile bond strength (µTBS) of 3-step etch-and-rinse adhesives on dentin. Flat occlusal dentin surfaces were prepared and randomly divided into 8 groups (n=20) based on the tested adhesives; Scotchbond Multi-purpose or Optibond FL, with contamination of an experimental silane (2 vol% of 3-m ethacryloxypropyltrimethoxysilane at pH 4.5) before acid-etching, after-etching or after-priming; while the groups without silane contamination served as controls. µTBS data were analyzed by two-way ANOVA and Tukey's HSD tests at a significance level of 0.05. Additional specimens of contaminated dentin were used to analyze changes in the organic molecules by Fourier transform infrared spectroscopy (FTIR). Silane contamination before acid-etching did not significantly change µTBS (p>0.05), but contamination after-etching and after-priming significantly decreased µTBS of both adhesives (p<0.05). Silane contamination had an adverse effect on the dentin bond strength of 3-step etch-and-rinse adhesives especially after-priming.

Air-blowing strategies for improving the microtensile bond strength of one-step self-etch adhesives to root canal dentin.

The effect of different air-blowing strategies using a prototype of a newly developed clinically applicable warm air-blowing device on the microtensile bond strength (µTBS) of one-step self-etch adhesives (1-SEAs) to human root-canal dentin was evaluated. Post cavities (8 mm depth, 1.5 mm diameter) were prepared and bonded with four 1-SEAs. Air-blowing was performed using normal air (23±1°C) for 10 or 20 s; warm air (60±1°C) for 10 or 20 s; or their combination for 10 s (5 s normal, 5 s warm) or 20 s (10 s normal, 10 s warm). After filling with corresponding core materials and 24-h water storage, µTBS test was performed. For three of the 1-SEAs, combined air-blowing for 20 s significantly increased µTBS compared to other air-blowing strategies (p<0.05). This suggests that the combination of normal and warm air-blowing for 20 s can enhance solvent evaporation from 1-SEAs, thus resulting in their improved bonding performance to root-canal dentin.

The repair bond strength to resin matrix in cured resin composites after water aging.

The repair microshear bond strengths (µSBSs) to resin matrices in 4 different cured-composites after water storage (0, 60 s, 1 week, 1 month) were evaluated. Three different adhesive application methods to the cured-composites were performed; (1) none, (2) onestep self-etch adhesive application, and (3) one-step self-etch adhesive application with a silane coupling agent. Degree of conversion (DC) of the composite discs was determined using ATR/FT-IR with a time-based spectrum analysis. Initially, the amount of un-reacted resin monomers in the repaired cured-composite contributed to the bonding performance of newly-filled uncured-composite to resin matrix of the cured-composite. Adhesive application could not improve their repair µSBS. After 1-month of water-storage, the repair µSBS was dependent on material, which either reduced or did not and was not influenced by their amount of un-reacted resin monomers. When repairing aged composite resin, the appropriate adhesive application procedures were different among resin composites.

Effect of Polymerization Accelerator on Bond Strength to Eugenol-Contaminated Dentin.

PURPOSE: To evaluate the effect of a polymerization accelerator on the microtensile bond strength (µTBS) of etch-and-rinse and self-etch adhesives to eugenol-contaminated dentin. MATERIALS AND METHODS: Sixty flat dentin surfaces were prepared from human molars. Half of the specimens were restored with zinc oxide eugenol temporary cement (IRM) (eugenol-contaminated group) and the other half remained without restoration (control group). After 24-h storage, the cement was mechanically removed. Then the specimens in each group were further divided into three subgroups based on the application procedure of a polymerization accelerator (p-toluenesulfinic acid sodium salt; Accel): no application, 10-s application, or 30-s application. After air drying, the dentin surfaces were bonded with either a three-step etch-and-rinse adhesive (OptiBond FL) or a two-step self-etch adhesive (Clearfil SE Bond) and restored with composite. After 24-h water storage, the bonded specimens were subjected to the µTBS test. Data were analyzed by three-way ANOVA and Dunnett's T3 test (p < 0.05). RESULTS: The eugenol-contaminated groups had significantly lower µTBS than the control groups with both types of adhesives (p < 0.05), and the application of Accel significantly increased the compromised µTBS to eugenol-contaminated dentin. Optibond FL presented significantly higher µTBS to eugenol-contaminated dentin than did Clearfil SE Bond (p < 0.05). CONCLUSION: The application of a polymerization accelerator on eugenol-contaminated dentin prior to adhesive resin application increased the µTBS of both the three-step etch-and-rinse and two-step self-etch adhesive.

Effect of Water Aging of Adherend Composite on Repair Bond Strength of Nanofilled Composites.

PURPOSE: To evaluate the effect of water aging of adherend composite on repair bond strength to nanofilled composites with specific fillers using different bonding agents. MATERIALS AND METHODS: Three nanofilled composites - Beautifil II with S-PRG filler (BE) / Filtek Supreme ultra with nanocluster filler (SP) / Estelite Σ Quick (ES) - and one microhybrid composite, Clearfil APX (AP), were used in this study. The composite disks were immersed in water for different durations (immediate, 1 week, 2 weeks or 1 month), and then the polished surfaces were treated with one of three bonding agents - no treatment (control), application of Clearfil SE One (SE), application of Clearfil SE One plus Clearfil Porcelain Bond Activator (PB) - then filled with a repair composite. The bonded composite disks were subjected to the microshear bond strength (µSBS) test. Additionally, water sorption (Wsp) and solubility (Wsl) of the resin composite were measured. The µSBS data were was statistically analyzed using a three-way ANOVA and t-test with Bonferroni correction for multiple comparisons. RESULTS: Water aging of adherend composite affected the repair bond strength (p < 0.05). For BE, SP, and ES, application of an adhesive agent improved repair bond strengths to water-aged composites (p < 0.05), but adding a silane coupling agent could not (p > 0.05). For AP, the µSBS significantly increased, with control group < SE group < PB group (p < 0.05). CONCLUSION: Microhybrid composite was a more suitable material for composite repair than nanofilled composite, due to adhesion to exposed, larger silica fillers. S-PRG filler and nanocluster filler in the nanofilled composites played a slight role in improving their repair bonding performances with the bonding agents tested.

The strategies used for curing universal adhesives affect the micro-bond strength of resin cement used to lute indirect resin composites to human dentin.

We evaluated the effect of different curing strategies for universal adhesives on micro-tensile bond strength (µTBS) between resin cement and dentin and/or between resin cement and indirect resin composite. Flat coronal dentin surfaces and composite resin disks were pretreated with silane-containing universal adhesives, with or without light-curing on the dentin-side and/or composite resin disk-side. Resin disks were luted onto the pretreated dentin surfaces with the corresponding dual-cure adhesive resin cements and light-cured, and cut into beams after 24-h water storage. After 0 or 10,000 thermocycles (5ºC/55ºC) in a water bath, the µTBS of the composite resin disk-dentin beam was tested. The µTBS was highest when universal adhesives were applied to both the dentin- and the indirect composite resin disk-side, followed by light-curing. Thermocycling decreased µTBS in all but the Scotchbond Universaltreated group, with light-curing on both sides. The effect of curing strategies is dependent upon the materials.

Smear layer-deproteinizing improves bonding of one-step self-etch adhesives to dentin.

OBJECTIVES: Smear layer deproteinizing was proved to reduce the organic phase of smear layer covered on dentin surface. It was shown to eliminate hybridized smear layer and nanoleakage expression in resin-dentin bonding interface of two-step self-etch adhesive. This study aimed to investigate those effects on various one-step self-etch adhesives. METHODS: Four different one-step self-etch adhesives were used in this study; SE One (SE), Scotchbond™ Universal (SU), BeautiBond Multi (BB), and Bond Force (BF). Flat human dentin surfaces with standardized smear layer were prepared. Smear layer deproteinizing was carried out by the application of 50ppm hypochlorous acid (HOCl) on dentin surface for 15s followed by Accel® (p-toluenesulfinic acid salt) for 5s prior to adhesive application. No surface pretreatment was used as control. Microtensile bond strength (µTBS) and nanoleakage under TEM observation were investigated. The data were analyzed by two-way ANOVA and Tukey's post-hoc test and t-test at the significant level of 0.05. RESULTS: Smear layer deproteinizing significantly improved µTBS of SE, SU, and BB (p<0.001). Hybridized smear layer observed in control groups of SE, BB, and BF, and reticular nanoleakage presented throughout the hybridized complex in control groups of BB and BF were eliminated upon the smear layer deproteinizing. SIGNIFICANCE: Smear layer deproteinizing by HOCl and Accel® application could enhance the quality of dentin for bonding to one-step self-etch adhesives, resulting in the improving µTBS, eliminating hybridized smear layer and preventing reticular nanoleakage formation in resin-dentin bonding interface.

Bonding Durability of a Self-etch Adhesive to Normal Versus Smear-layer Deproteinized Dentin: Effect of a Reducing Agent and Plant-extract Antioxidant.

PURPOSE: To evaluate the effect of a reducing agent and plant-extract antioxidant on the bonding durability of a self-etch adhesive to normal and NaOCl-treated, smear-layer-deproteinized dentin. MATERIALS AND METHODS: Flat smear-layer-covered dentin surfaces from 60 extracted human molars were prepared by removing the occlusal enamel. The teeth were divided into two groups with or without NaOCl-deproteinizing treatment for 30 s, and further divided into three subgroups as follows: no application of antioxidant, application of Accel (p-toluenesulfinic acid sodium salt solution) for 5 s, or application of rosmarinic acid solution for 5 s. All treated dentin surfaces were bonded with a two-step self-etch adhesive (Clearfil SE Bond) and restored with composite (Clearfil AP-X). The bonded teeth were sectioned into a hourglass-shaped sticks with a composite-dentin bonded interface area of 1.0 mm2. After storage in artificial saliva for 24 h or 1 year, the specimens were subjected to the microtensile bond strength test (n = 15). Data were statistically analyzed with three-way ANOVA, Tukey's post-hoc test, and the t-test (p < 0.05). RESULTS: Without an antioxidant, 1-year storage significantly reduced the bond strengths of the self-etch adhesive to normal and smear-layer-deproteinized dentin compared with those after 24-h storage (p < 0.05). Application of Accel and rosmarinic acid restored the compromised initial bond strengths to smear-layer-deproteinized dentin (p < 0.05), and prevented long-term deterioration of bond strengths to both normal and smear-layer-deproteinized dentin (p > 0.05). CONCLUSION: Application of Accel and rosmarinic acid improved bonding durability of the self-etch adhesive to both normal and smear-layer-deproteinized dentin.

Effect of Scrubbing Technique with Mild Self-etching Adhesives on Dentin Bond Strengths and Nanoleakage Expression.

PURPOSE: To evaluate the effect of a scrubbing technique with one-step self-etching adhesives on bond strengths and nanoleakage expression at the resin/dentin interface. MATERIALS AND METHODS: Flat human dentin surfaces bonded with one of two mild self-etching adhesives, SE One (SE) or Scotchbond Universal (SU) applied either with scrubbing or without scrubbing technique, were prepared (n = 5). The microtensile bond strengths (µTBS), SE micrographs of morphological changes on treated dentin surfaces, and expression of nanoleakage along the bonded dentin interfaces as shown with TEM were evaluated. µTBS data were analyzed using two-way ANOVA and the post-hoc t-test at the significance level of 0.05. RESULTS: The scrubbing technique had a significant positive effect on the µTBS of SU (p < 0.05), while it produced no significant difference for SE (p > 0.05). Morphological evaluation of the treated dentin surfaces demonstrated that SU with scrubbing showed the highest etching ability, followed by scrubbing SE > nonscrubbing SE > nonscrubbing SU. In the nonscrubbing groups, nanoleakage formation using SU exhibited a reticular pattern throughout the hybridized complex, whereas with SE, water-tree nanoleakage was only found in the adhesive layer at dentinal tubule orifices. The scrubbing groups of both adhesives did not exhibit any nanoleakage expression. CONCLUSION: Using a scrubbing technique when applying mild self-etching adhesives could improve resin monomer infiltration into dentin, chase water on adhesive surfaces, and facilitate smear layer removal.

Effect of smear layer deproteinizing on resin-dentine interface with self-etch adhesive.

OBJECTIVES: This study aimed to investigate deproteinizing effect of sodium-hypochlorite (NaOCl) and mild acidic hypochlorous-acid (HOCl) pretreatment on smear layer-covered dentine and to evaluate their effects on morphological characteristics of resin-dentine interface with self-etch adhesive. METHODS: Human coronal-dentine discs with standardized smear layer were pretreated with 6% NaOCl or 50ppm HOCl for 15s or 30s. Their deproteinizing effects at the treated smear layer-covered dentine surfaces were determined by the measurement of amide:phosphate ratio using ATR-FTIR analysis. In addition, using TEM, micromorphological alterations of hybridized complex and nanoleakage expression were evaluated at the interface of a self-etch adhesive (Clearfil SE Bond) to the pretreated dentine surface with or without subsequent application of a reducing agent (p-Toluenesulfinic acid salt; Accel(®)). RESULTS: Both pretreatments of NaOCl and HOCl significantly reduced the amide:phosphate ratio as compared with the no-pretreated group (p<0.05), coincident with the elimination of the hybridized smear layer on their bonded interfaces. Nanoleakage within the hybrid layer was found in the no-pretreated and NaOCl-pretreated groups, whereas the subsequent reducing agent application changed the reticular nanoleakage to spotted type. HOCl-pretreated groups showed less nanoleakage expression in a spotted pattern, regardless of reducing agent application. CONCLUSIONS: NaOCl and HOCl solutions could remove the organic component on the smear layer-covered dentine, which could eliminate the hybridized smear layer created by self-etch adhesive, leading to the reduction of nanoleakage expression within hybrid layer. CLINICAL SIGNIFICANCE: Smear layer deproteinizing could modify dentine surface, giving an appropriate substrate for bonding to self-etch adhesive system.

Polymerization behavior within adhesive layer of one- and two-step self-etch adhesives: a micro-Raman spectroscopic study.

This study investigated the polymerization behavior within the adhesive layer of one- and two-step self-etch adhesives at the dentincomposite interface. Dentin surfaces were applied with Clearfil S(3) Bond (TS), Clearfil S(3) Bond Plus (TSP) and Clearfil SE Bond (SE), and then placed with a light-curing resin composite. After water storage for 24 h, the bonded teeth were sectioned and polished perpendicular to the adhesive interface, and the degree of conversion (DC) of the adhesive layer between the dentin and composite were determined using micro-Raman analysis. For all the adhesives, the DCs of the adhesive layers significantly decreased near the adhesive-composite join (p<0.05). For the maximum DC value (Pmax) and the DC value at the adhesive-composite join (Pitf), TS was significantly lower than TSP and SE (p<0.05). The polymerization of oxygen-inhibited layer at the top of the adhesive could not reach maximum DC even after polymerization of the overlying resin composite.

Effect of a calcium-phosphate based desensitizer on dentin surface characteristics.

This study aimed to evaluate the ability of a newly developed calcium-phosphate desensitizer in dentin permeability reduction and its integration with dentin surface before and after immersion in artificial saliva (AS) under two different dentin surface characteristics; with or without the collagen exposure.Humandentin discs treated by EDTA to expose collagen fibrils or EDTA/NaOCl to expose plain dentin surface were subjected to a calcium-phosphate desensitizer (Teethmate Desensitizer; TMD), while non-desensitizer treatment served as control. TMD application showed the occlusion in dentinal tubules and reduction in dentin permeability up to 92%, regardless of dentin surface characteristics. After AS immersion, permeability reduction percent (PR%) significantly increased in EDTA/NaOCl pretreatment (p<0.05). Newly-formed crystallites were observed on desensitizer treated dentin and EDTA/NaOCl pretreatment control group, whereas the crystallites did not exist on EDTA pretreatment control group. Ultrasonication revealed the integration of the calcium-phosphate rich layer of desensitizer on dentin surface after AS immersion.

In vitro evaluation of dentinal hydraulic conductance and tubule sealing by a novel calcium-phosphate desensitizer.

In the current trend of materials used for dentin hypersensitivity treatment, calcium-phosphate-containing desensitizers are expected to have advantages in oral environment. A newly formulated desensitizer containing tetracalcium phosphate and dicalcium phosphate anhydrous (CPD-100) was evaluated in comparison to oxalate containing desensitizer (SS) regarding permeability reduction (PR%) by measuring hydraulic conductance on the etched dentin discs in vitro. CPD-100 exhibited mean PR% of 91%, which significantly increased to 98% after immersion in artificial saliva (AS) for 4 weeks (p < 0.001), while SS showed a significant decrease from 99% to 93% (p < 0.01). SEM observation showed newly formed crystallites on CPD-100 treated dentin, which did not exist in SS treated dentin after AS immersion, suggesting that calcium oxalate inhibited formation of new calcium-phosphate minerals. Five-minute acid challenge did not significantly affect PR% of dentin treated by any of the desensitizers. The energy dispersive X-ray spectroscopy (EDS) analysis indicated that the formed layer of CPD-100 were minerals with similar Ca/P ratio to hydroxyapatite. In conclusion, the newly developed calcium-phosphate desensitizer has the potential to exhibit long-term stability in the oral environment, owing to its chemical properties that promote the crystal growth in salivary fluid.