Resin-based materials to control human dentin permeability under erosive conditions in vitro: A hydraulic conductance, confocal microscopy and FTIR study.

OBJECTIVES: To characterize the behavior of three different polymeric agents before and after an erosive challenge on dentin permeability, to analyze their degradation in both conditions, and to analyze their degree of conversion (DC). METHODS: The permeability of human dentin disks (1.0 ± 0.2 mm) was measured with smear layer, after its removal, after treatment (LpTreat) with Gluma Desensitizer, PRG Barrier Coat (PBC) or Icon infiltrant (n = 11/group) and after exposure to citric acid (LpEro) (6%, pH 2.1, 1 min). The specimens were analyzed under a Laser Scanning Confocal Microscope (n = 2/group) and the products' DC were calculated. Data were subjected to 2-way repeated measures ANOVA and post-hoc Bonferroni (permeability analysis), to paired t-test (for specimens treated with Icon) and to t-test (DC analysis) (α < 0.05). RESULTS: Icon showed the lowest LpTreat and LpEro values, while PBC and Gluma did not differ from each other under these conditions. Icon and PBC showed LpEro similar to a dentin with smear layer. Under the Laser Scanning Confocal Microscope, more deposits were noticeable on dentin after treating with PBC. Gluma presented the deepest penetration in dentin. The DC of PBC was the highest. SIGNIFICANCE: Icon caused the highest reduction on permeability values, followed by PBC and Gluma. PBC generated more deposits covering dentin and seemed to be more efficient after an erosive challenge. The association of a polymeric resin with inorganic ion-releasing fillers seem to be a great strategy to manage dentin hypersensitivity under erosive conditions.

Effect of bioactive glasses containing strontium and potassium on dentin permeability.

Dentin hypersensitivity (DH) is characterized by pain caused by an external stimulus on exposed dentin. Different therapeutic approaches have been proposed to mitigate this problem; however, none of them provide permanent pain relief. In this study, we synthesized and characterized experimental bioactive glasses containing 3.07 mol% SrO or 3.36 mol% K2 O (both equivalent to 5 wt% in the glass), and evaluated their effect on dentin permeability to verify their potential to treat DH. The experimental materials were characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, micro-Raman spectroscopy, and X-ray diffraction to confirm the respective structures and chemical compositions. The reduction in the hydraulic conductance of dentin was evaluated at the three stages: minimum permeability; maximum permeability (24% ethylenediaminetetraacetic acid [EDTA] treatment); and final dentin permeability after treatment with the bioactive glasses. They all promoted a reduction in dentin permeability, with a significant difference for each sample and posttreatment group. Also, a significant reduction in dentin permeability was observed even after a simulated toothbrushing test, demonstrating effective action of these materials against DH. Besides, incorporating 3.07 mol% SrO was a positive factor. Therefore, strontium's desensitizing and re-mineralizing properties can be further exploited in bioactive glasses to promote a synergistic effect to treat DH.

Comparing the Effectiveness of Different Dentinal Desensitizing Agents: In Vitro Study.

OBJECTIVES: To evaluate the in vitro effectiveness of desensitizing agents in reducing dentine permeability. METHODS: The efficacy of desensitizing agents in reducing dentine permeability by occluding dentine tubules was evaluated using a fluid filtration device that conducts at 100 cmH2O (1.4 psi) pressure, and SEM/EDX analyses were evaluated and compared. Forty-two dentine discs (n = 42) of 1 ± 0.2 mm width were obtained from caries-free permanent human molars. Thirty dentine discs (n = 30) were randomly divided into 3 groups (n = 10): Group 1: 2.7% wt. monopotassium-monohydrogen oxalate (Mp-Mh oxalate), Group 2: RMGI XT VAR, and Group 3: LIQ SiO2. Dentine permeability was measured following treatment application after 10 minutes, storage in artificial saliva after 10 minutes and 7 days, and citric acid challenge for 3 minutes. Data were analysed with a repeated measures ANOVA test. Dentine discs (n = 12) were used for SEM/EDX analyses to acquire data on morphological changes on dentine surface and its mineral content after different stages of treatment. RESULTS: Desensitizing agents' application on the demineralized dentine discs exhibited significant reduction of permeability compared to its maximum acid permeability values. Mp-Mh oxalate showed a significant reduction in dentine permeability (p < 0.05) when compared to RMGI XT VAR and LIQ SiO2. On SEM/EDX analysis, all the agents formed mineral precipitates that occluded the dentine tubules. CONCLUSIONS: 2.7% wt. monopotassium-monohydrogen oxalate was significantly effective in reducing dentine permeability compared to RMGI XT VAR and LIQ SiO2.

Effects of microsurface structure of bioactive nanoparticles on dentinal tubules as a dentin desensitizer.

In this in vitro study, spherical mesoporous bioactive glass nanoparticle (MBGN) and non-porous bioactive glass nanoparticle (BGN) were fabricated. The impact of mesopores on dentinal tubule occlusion and bioactivity was compared to examine the potential of these materials in alleviating dentine hypersensitivity (DH). MBGN, dense BGN were synthesized by sol-gel methods and characterized. Bioactivity and ion dissolution ability were analyzed. Twenty-four simulated sensitive dentin discs were prepared and randomly divided into three groups (n = 8 each); Group 1, no treatment; Group 2, Dense BGN; Group 3, MBGN. Then, four discs per group were treated with 6wt.% citric acid challenge to determine the acidic resistance. The effects on dentinal tubule occlusion were observed by FESEM. The microtensile bond strength (MTBS) was also measured. Cytotoxicity was examined using the MTT assay. According to the results, dense BGN without mesopore and MBGN with mesopore were successfully fabricated. Dense BGN and MBGN occluded the dentinal tubule before and after acid challenge. However, only MBGN formed a membrane-like layer and showed hydroxyapatite formation after soaking SBF solution. There were no significant differences in MTBS among dense BGN, MBGN (P>0.05). The cell viability was above 72% of both materials. The higher bioactivity of MBGN compared with that of dense BGN arises from the structural difference and it is anticipated to facilitate dentin remineralization by inducing hydroxyapatite deposition within the dentinal tubule.

Dentin sealing and antibacterial effects of silver-doped bioactive glass/mesoporous silica nanocomposite: an in vitro study.

OBJECTIVES: To synthesize a silver-doped bioactive glass/mesoporous silica nanoparticle (Ag-BGN@MSN), as well as to investigate its effects on dentinal tubule occlusion, microtensile bond strength (MTBS), and antibacterial activity. MATERIALS AND METHODS: Ag-BGN@MSN was synthesized using a modified "quick alkali-mediated sol-gel" method. Demineralized tooth disc models were made and divided into four groups; the following treatments were then applied: group 1-no treatment, group 2-bioglass, group 3-MSN, group 4-Ag-BGN@MSN. Next, four discs were selected from each group and soaked into 6 wt% citric acid to test acid-resistant stability. Dentinal tubule occlusion, as well as the occlusion ratio, was observed using field-emission scanning electron microscopy. The MTBS was also measured to evaluate the desensitizing effect of the treatments. Cytotoxicity was examined using the MTT assay. Antibacterial activity was detected against Lactobacillus casei, and ion dissolution was evaluated using inductively coupled plasma optical emission spectrometry. RESULTS: Ag-BGN@MSN effectively occluded the dentinal tubule and formed a membrane-like layer. After the acid challenge, Ag-BGN@MSN had the highest rate of dentinal tubule occlusion. There were no significant differences in MTBS among the four groups (P > 0.05). All concentrations of Ag-BGN@MSN used had a relative cell viability above 72%. CONCLUSIONS: Ag-BGN@MSN was successfully fabricated using a modified sol-gel method. The Ag-BGN@MSN biocomposite effectively occluded dentinal with acid-resistant stability, did not decrease bond strength in self-etch adhesive system, had low cytotoxicity, and antibacterial effect. CLININAL RELEVANCE: Dentinal tubule sealing induced by Ag-BGN@MSN biocomposite with antibacterial effect is likely to increase long-term stability in DH.

Effect of different sizes of bioactive glass-coated mesoporous silica nanoparticles on dentinal tubule occlusion and mineralization.

OBJECTIVES: To synthesize two different sizes of bioactive glass-coated mesoporous silica nanoparticles (BGN@MSNs) and to investigate their effects on dentinal tubule occlusion and remineralization. MATERIALS AND METHODS: Two different sizes of mesoporous silica nanoparticles (MSNs) were synthesized using the Stöber method (368A, 1840A) and coated with bioactive glass nanoparticles (BGNs) using a modified quick alkali-mediated sol-gel method (368B, 1840B). Sensitive tooth disc models were prepared and divided into six groups and the following treatments were applied: group 1-no treatment, group 2-bioglass, group 3-368A, group 4-368B, group 5-1840A, and group 6-1840B. Then, five discs were selected from each group and soaked in 6 wt% citric acid to test acid resistance. Dentinal tubule occlusion and occlusion ratio were observed using field-emission scanning electron microscopy. In vitro mineralization tests using simulated body fluid solution were performed to evaluate the remineralization effect of the treatment. RESULTS: All samples effectively occluded the dentinal tubule and formed a membrane-like layer. After acid treatment, 1840B (group 6) exhibited the highest rate of dentinal tubule occlusion. Remineralization was observed in 368B and 1840B, and 1840B exhibited the fastest remineralization. CONCLUSIONS: Dentinal tubule remineralization induced by the BGN@MSN biocomposite can be used to stabilize long-term prognosis in dentin hypersensitivity. The 1840B induced the most efficient remineralization, and its smaller size and larger surface area were effective for remineralization. CLINICAL RELEVANCE: The BGN@MSN biocomposite with its smaller size and larger surface area was more effective for remineralization and dentinal tubule sealing.

Effects of in-office bleaching agent combined with different desensitizing agents on enamel

Abstract Objective: To analyze color change, microhardness and chemical composition of enamel bleached with in-office bleaching agent with different desensitizing application protocols. Materials and Methods: One hundred and seventeen polished anterior human enamel surfaces were obtained and randomly divided into nine groups (n = 13). After recording initial color, microhardness and chemical composition, the bleaching treatments were performed as G1: Signal Professional White Now POWDER&LIQUID FAST 38% Hydrogen peroxide(S); G2: S+Flor Opal/0.5% fluoride ion(F); G3: S+GC Tooth Mousse/Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) paste(TM); G4: S+UltraEZ/3% potassium nitrate&0.11% fluoride(U); G5: S+Signal Professional SENSITIVE PHASE 1/30% Nano-Hydroxyapatite (n-HAP) suspension(SP); G6: S-F mixture; G7: S-TM mixture; G8: S-U mixture; G9: S-SP mixture. Color, microhardness and chemical composition measurements were repeated after 1 and 14 days. The percentage of microhardness loss (PML) was calculated 1 and 14 days after bleaching. Data were analyzed with ANOVA, Welch ANOVA, Tukey and Dunnett T3 tests (p<0.05). Results: Color change was observed in all groups. The highest ΔE was observed at G7 after 1 day, and ΔE at G8 was the highest after 14 days (p<0.05). A decrease in microhardness was observed in all groups except G6 and G7 after 1 day. The microhardness of all groups increased after 14 days in comparison with 1 day after bleaching (p>0.05). PML was observed in all groups except G6 and G7 after bleaching and none of the groups showed PML after 14 days. No significant changes were observed after bleaching at Ca and P levels and Ca/P ratios at 1 or 14 days after bleaching (p>0.05). F mass increased only in G2 and G6, 1 day after bleaching (p<0.05). Conclusions: The use of desensitizing agents containing fluoride, CPP-ACP, potassium nitrate or n-HAP after in-office bleaching or mixed in bleaching agent did not inhibit the bleaching effect. However, they all recovered microhardness of enamel 14 days after in-office bleaching.

Effects of in-office bleaching agent combined with different desensitizing agents on enamel.

OBJECTIVE: To analyze color change, microhardness and chemical composition of enamel bleached with in-office bleaching agent with different desensitizing application protocols. MATERIALS AND METHODS: One hundred and seventeen polished anterior human enamel surfaces were obtained and randomly divided into nine groups (n = 13). After recording initial color, microhardness and chemical composition, the bleaching treatments were performed as G1: Signal Professional White Now POWDER&LIQUID FAST 38% Hydrogen peroxide(S); G2: S+Flor Opal/0.5% fluoride ion(F); G3: S+GC Tooth Mousse/Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) paste(TM); G4: S+UltraEZ/3% potassium nitrate&0.11% fluoride(U); G5: S+Signal Professional SENSITIVE PHASE 1/30% Nano-Hydroxyapatite (n-HAP) suspension(SP); G6: S-F mixture; G7: S-TM mixture; G8: S-U mixture; G9: S-SP mixture. Color, microhardness and chemical composition measurements were repeated after 1 and 14 days. The percentage of microhardness loss (PML) was calculated 1 and 14 days after bleaching. Data were analyzed with ANOVA, Welch ANOVA, Tukey and Dunnett T3 tests (p<0.05). RESULTS: Color change was observed in all groups. The highest ΔE was observed at G7 after 1 day, and ΔE at G8 was the highest after 14 days (p<0.05). A decrease in microhardness was observed in all groups except G6 and G7 after 1 day. The microhardness of all groups increased after 14 days in comparison with 1 day after bleaching (p>0.05). PML was observed in all groups except G6 and G7 after bleaching and none of the groups showed PML after 14 days. No significant changes were observed after bleaching at Ca and P levels and Ca/P ratios at 1 or 14 days after bleaching (p>0.05). F mass increased only in G2 and G6, 1 day after bleaching (p<0.05). CONCLUSIONS: The use of desensitizing agents containing fluoride, CPP-ACP, potassium nitrate or n-HAP after in-office bleaching or mixed in bleaching agent did not inhibit the bleaching effect. However, they all recovered microhardness of enamel 14 days after in-office bleaching.

Application of electrophoretic deposition to occlude dentinal tubules in vitro.

OBJECTIVES: This study aims to apply electrophoretic deposition (EPD) for occlusion of dentinal tubules in vitro and investigate its effect on tubule occlusion and shear bond strength (SBS). METHODS: Charged mesoporous silica nanoparticles (MSNs) were synthesized and characterized through field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), and Fourier transform infrared (FT-IR) spectroscopy analyses. Thirty-nine sensitive dentin specimens were modeled and assigned randomly to three groups with different treatments (n = 13 each): group 1, immersion in the MSN suspension; and groups 2 and 3, anodic EPD with the specimen on the negative and positive electrode respectively. The effect of dentinal tubule occlusion was evaluated by dentin permeability test (n = 10 each) and FESEM examination (n = 3 each). Moreover, 18 specimens were grouped (n = 6 each) and treated in the same method. A resin stick was bonded onto each of the specimen using a self-etch adhesive (single bond universal) for SBS testing. RESULTS: Negatively-charged MSNs were synthesized and characterized as small and well-dispersed particles. After the EPD treatment (group 3), the dentinal tubules were effectively occluded by MSNs, which infiltrated into the tubules at a depth of approximately 7-8 µm and tightly associated with the tubular inwalls. SBS was not significantly different among the three groups (P > 0.05). CONCLUSIONS: Synthesized MSNs were deposited into dentinal tubules by EPD treatment without compromising dentin bond strength. CLINICAL SIGNIFICANCE: Application of EPD is a new approach for occlusion of dentinal tubules and exhibits potential in the study of dentin hypersensitivity.

Reducing dentine hypersensitivity with nano-hydroxyapatite toothpaste: a double-blind randomized controlled trial.

OBJECTIVES: The present randomized double-blind clinical trial aimed to compare the efficacy in reducing dentin hypersensitivity of a dentifrice formulation containing nano-hydroxyapatite with a fluoride dentifrice and a placebo. METHODS AND MATERIALS: One hundred and five subjects were recruited to participate in the study. A computer-generated random table with blocking to one of the three study treatments was used in order to have 35 subjects per group: (1) nano-hydroxyapatite 2% gel toothpaste fluoride free; (2) fluoride gel toothpaste; (3) placebo. Groups 1, 2, and 3 were instructed to treat their teeth for 10 min twice a day with the provided toothpaste gel. The participant's dentin hypersensitivity was evaluated at baseline and after 2 and 4 weeks using airblast and tactile tests. In addition, a subjective evaluation using a visual analogue scale was used. RESULTS: Significant lower values of cold air sensitivity and tactile sensitivity (p < 0.05) were found for the test group at 2 weeks and 4 weeks. In addition, statistically significant (p < 0.05) lower values of sensitivity were reported for group 1 compared to those for groups 2 and 3 at 2 and 4 weeks, respectively. The VAS scores were significantly lower (p < 0.05) in the test group at 2 and 4 weeks compared to those at baseline and in the control groups. CONCLUSION: The application of nano-hydroxyapatite in gel toothpaste fluoride free is an effective desensitizing agent providing relief from symptoms after 2 and 4 weeks.

Comparison of nanofluoridated hydroxyapatite of varying fluoride content for dentin tubule occlusion.

PURPOSE: To evaluate the viability of a series of nano-fluoridated hydroxyapatite (nano-FHA) formulations of varying fluoride content for the occlusion of exposed dentin tubules, in comparison to nano-hydroxyapatite (nano-HA). METHODS: Nano-FHA powders with varying levels of fluoride ion were synthesized to substitute hydroxyl ions (⁻OH) present in hydroxyapatite (HA). Nano-FHA were defined as 2nFHA,4nFHA,6nFHA, 8nFHA and 10nFHA, with the molar ratio of F(⁻ to Ca243; of 0.002,0.004,0.006,0.008 and 0.01, respectively. The powders were synthesized using a wet chemistry route, and characterized by transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The methylthiazol tetrazolium (MTT) assay was used to assess cell viability toward nano-FHA. According to the content of F⁻, the nano-nFHA and nano-HA powders were divided into six groups, with the artificial saliva as control. They were spread over the dentin surface for 1 minute and repeated three times per day for 7 consecutive days. After washing and brushing with distilled water for an additional 7 days, scanning electron microscopy was used to evaluate the in vitro plugging rate of the tubules and penetrating depth. RESULTS: The 2nFHA, 4nFHA, 6nFHA, 8nFHA and 10nFHA powders were prepared and characterized. The 8nFHA had less crystallinity compared to 2nFHA,4nFHA, and 6nFHA.The MTT assay (from 12 to 120 hours) showed that the cell viability of the L-929 fibroblasts in the 2nFHA, 4nFHA, 6nFHA, 8nFHA, 10nFHA, and nano-HA groups ranged from 80.54± 3.35% to 112.9± 4.8%. Most of the nano-FHA powders successfully occluded dentin tubules. The plugging rate of 8nFHA was significantly higher than that of the 2nFHA, 4nFHA, 6nFHA and nano-HA groups. The penetrating depth of the 8nFHA group into the tubules was also significantly higher than that of the other nano-FHA and nano-HA group. CLINICAL SIGNIFICANCE: The nano-FHA formulation 8nFHA showed higher plugging rate and penetrating depth into the tubules. It has the potential to be used as a desensitizing agent in treating dentin hypersensitivity with better long-term durability and efficacy of dentin tubule occlusion.

Study of three types of desensitizers in dentin bonding strength.

One hundred and twenty human molars without decay (premolars and complete third molars) freshly extracted for orthodontic purposes were used in the study to explore the impact of application of three kinds of desensitizers on self-etching/all-etching bond strength of dentin. The roots were ground along the cementoenamel junction (CEJ), the residual crowns were divided into two parts along mesial and distal direction, and the enamel layer was removed. The dentin was ground into standard pieces of 3x3x3 mm and then polished using alumina waterproof abrasive paper. Two hundred and forty specimens were divided into two groups according to self-etching bond (OptiBond, iBond, XenoIV) and all-etching bond (OptiBond, iBond, Probond). Each of the two groups were subdivided into three groups with different brands, and then further subdivided into three experimental groups and a control group (10 samples in each final group). The surface of dentin coated with desensitizer was examined using scanning electron microscope. Results showed that only the shear strength of iBond + Ddes + Z100 resin group was lower compared to the control group (P < 0.05). The comparison of the resin shear strength in other experimental groups with the control groups demonstrated no statistically significant difference (P > 0.05). The shear strength of Optibond + Gluma, Optibond + Ddes, iBond + Ddes + Z100 resin group in all-etching bond group and the experimental groups in Probond group was lower than in the control group (P < 0.05). The resin shear strength in other groups did not differ from the controls (P > 0.05).

The effect of calcium phosphate-containing desensitizing agent on the microtensile bond strength of multimode adhesive agent.

OBJECTIVE: The aim of this study was to investigate the effect of calcium phosphate containing desensitizing pretreatments on the microtensile bond strength (MTBS) and microleakage of the multimode adhesive agent to dentin. MATERIALS AND METHODS: In this study, twelve noncarious, freshly extracted human third molar teeth for MTBS and 20 premolar teeth for the microleakage test were used. The teeth were restored using Clearfil Universal Bond + Clearfil APX and Teeth mate Desensitizer (TMD). For MTBS test, Group 1: Self-etch, Group 2: Etch and rinse (G1 and 2, nondesensitizer treatment served as a control), Group 3: TMD/self-etch, Group 4: Acid-etch/TMD/etch and rinse. For microleakage test, Class V adhesive cavities (3 mm × 2 mm × 2 mm) were prepared and restored as mentioned before. The restored teeth were subjected to thermal cycling. The MTBS test was performed in all procedures. The MTBS data were submitted to a one-way ANOVA and post hoc Tukey test (P P Results: Control groups exhibited a higher mean MTBS value than TMD groups, and there were statistical differences between the groups. TMD groups also demonstrated significantly less microleakage than control groups (P Conclusions: This study proves that the application of TMD with a multimode adhesive bonding system produced significantly lower MTBS and microleakage.

Comparison of in vitro dentinal tubule occluding efficacy of two different methods using a nano-scaled bioactive glass-containing desensitising agent.

OBJECTIVE: This study aimed to compare the in vitro dentinal tubule occluding efficacy of two different methods using a nano-scaled bioactive glass (BG)-containing desensitising agent. METHODS: Citric acid treated dentine discs were randomly divided into 7 groups (n=8). Group A1, A2 and A3: dentine discs coated with BG desensitising paste; Group B1, B2 and B3: dentine discs coated with BG desensitising paste and covered with matched transparent trays; and control group (GroupC): dentine discs treated with deionised water. Field Emission Scanning Electron Microscopy (FE-SEM) was used to capture topographical images of each dentine discs after they were immersed in artificial saliva for corresponding treatment time and dentinal tubules exposure rates were thus measured. Elemental compositions of dentine discs were identified using Energy-Dispersive X-ray Spectroscopy (EDX). RESULTS: FE-SEM revealed better tubule occluding effects in Group B. Dentinal tubules in Group B3 were totally occluded with continuous homogeneous minerals to a depth of 20.6-24.7µm. Dentinal tubule exposure rates in Group B1, Group B2 and Group B3 were lower than that in Group A1, Group A2 and Group A3. EDX indicated that occluding deposits observed in each group were calcium-deficient hydroxyapatite. CONCLUSIONS: The application of transparent trays in combination with nano-scaled BG-containing desensitising paste could increase the dentinal tubule occluding effectiveness of the latter one and shorten the treatment time. CLINICAL RELEVANCE: Transparent trays could be used in combination with BGs-containing desensitising paste as the containers of the latter one in order to increase the dentinal tubule occluding effectiveness. This could lead to the development of a new therapeutic technique for treating dentine hypersensitivity.

Effect of two desensitizing agents on dentin permeability in vitro.

OBJECTIVE: The aim of this in vitro study was to investigate the effect of two desensitizing agents and water on hydraulic conductance in human dentin. MATERIAL AND METHODS: GLUMA Desensitizer PowerGel (GLU) contains glutaraldehyde (GA) and 2-hydroxyethyl methacrylate (HEMA), and Teethmate Desensitizer (TD) is a powder comprising tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) that is mixed with water. Deionized water was used as a negative control (CTR). Thirty discs with a thickness of 1.2 mm were cut from the coronal dentin of the third molars and cleaned with 0.5 M EDTA (pH 7.4). After being mounted in a split-chamber device, the discs were pressurized with water at 1 kPa and 3 kPa in order to measure flow rates with a highly sensitive micro-flow sensor and to calculate hydraulic conductance as a baseline value (BL). Following the application of GLU, TD, and CTR (n=10), hydraulic conductance was remeasured with intermittent storage in water after 15 min, 1 d, 1 w, and 1 m. Reduction in permeability (PR%) was calculated from hydraulic conductance. Data were statistically analyzed using nonparametric methods (α<0.05). Representative discs were inspected by SEM. RESULTS: PR% for GLU and TD were 30-50% 15 min and 1 m after their application. Post hoc tests indicated that PR% of CTR was significantly greater than those of GLU and TD at all time points tested. The PR% of GLU and TD were not significantly different. SEM examinations showed noncollapsed collagen meshes at the tubular entrances after GLU, and crystalline precipitates occluding the tubular orifices after TD, whereas CTR specimens showed typical patterns of etched dentin. CONCLUSIONS: The present study on hydraulic conductance in dentin discs treated with two chemically different desensitizing agents and water as a control demonstrated that both products may be characterized as effective.

Effect of two desensitizing agents on dentin permeability in vitro

Abstract Objective The aim of this in vitro study was to investigate the effect of two desensitizing agents and water on hydraulic conductance in human dentin. Material and Methods GLUMA Desensitizer PowerGel (GLU) contains glutaraldehyde (GA) and 2-hydroxyethyl methacrylate (HEMA), and Teethmate Desensitizer (TD) is a powder comprising tetracalcium phosphate (TTCP) and dicalcium phosphate anhydrous (DCPA) that is mixed with water. Deionized water was used as a negative control (CTR). Thirty discs with a thickness of 1.2 mm were cut from the coronal dentin of the third molars and cleaned with 0.5 M EDTA (pH 7.4). After being mounted in a split-chamber device, the discs were pressurized with water at 1 kPa and 3 kPa in order to measure flow rates with a highly sensitive micro-flow sensor and to calculate hydraulic conductance as a baseline value (BL). Following the application of GLU, TD, and CTR (n=10), hydraulic conductance was remeasured with intermittent storage in water after 15 min, 1 d, 1 w, and 1 m. Reduction in permeability (PR%) was calculated from hydraulic conductance. Data were statistically analyzed using nonparametric methods (α<0.05). Representative discs were inspected by SEM. Results PR% for GLU and TD were 30-50% 15 min and 1 m after their application. Post hoc tests indicated that PR% of CTR was significantly greater than those of GLU and TD at all time points tested. The PR% of GLU and TD were not significantly different. SEM examinations showed noncollapsed collagen meshes at the tubular entrances after GLU, and crystalline precipitates occluding the tubular orifices after TD, whereas CTR specimens showed typical patterns of etched dentin. Conclusions The present study on hydraulic conductance in dentin discs treated with two chemically different desensitizing agents and water as a control demonstrated that both products may be characterized as effective.

An exploratory clinical trial to evaluate the efficacy of an experimental dentifrice formulation in the relief of dentine hypersensitivity.

OBJECTIVES: This study aimed to investigate whether addition of an octadecene/maleic anhydride copolymer (O/MA) to a potassium nitrate (KNO3) dentifrice could facilitate delivery of potassium to dentine and enhance its efficacy in dentine hypersensitivity relief. METHODS: This was a randomised, examiner-blind, controlled, parallel group study in 139 healthy subjects with at ≥2 sensitive teeth. Assessment of dentine hypersensitivity to tactile (Yeaple probe) and evaporative (air) stimuli (Schiff Sensitivity Scale, visual analogue scale [VAS]) was carried out at baseline and after 1, 2, 4 and 8 weeks twice daily treatment with an experimental 5% KNO3/3% O/MA dentifrice, a comparator 5% KNO3 dentifrice (active comparator), a 0% KNO3/3% O/MA dentifrice (placebo) and a regular fluoride dentifrice (negative control). This study was not powered to detect statistically significant differences between treatments. RESULTS: Across the treatment period an improvement in sensitivity to evaporative air stimulus was observed for all products and to a tactile stimulus for the potassium-containing treatments, with the greatest reductions for the experimental dentifrice (5% KNO3/3% O/MA). Reductions in sensitivity observed for the potassium-containing dentifrices compared to the placebo and negative control dentifrices were statistically significantly for Schiff sensitivity score and tactile threshold at all time-points and for VAS at Weeks 4 and 8. Trends in the study data also favoured the experimental dentifrice, compared to the active comparator dentifrice, for all clinical measures. Study treatments were generally well tolerated. CONCLUSION: This study provides initial clinical evidence to suggest that addition of a polymer excipient may enhance the anti-sensitivity efficacy of potassium-containing dentifrices. CLINICAL SIGNIFICANCE: Daily use potassium-containing dentifrices are established as efficacious for the relief of dentine hypersensitivity. Inclusion of a polymer excipient in such formulations may facilitate delivery of potassium to the dentine surface and so enhance clinical efficacy. Further clinical studies are required to confirm this hypothesis.

Efficacy of desensitizing products containing 8% arginine and calcium carbonate for hypersensitivity relief in MIH-affected molars: an 8-week clinical study.

OBJECTIVES: The objective of this study was to compare the efficacy in reducing hypersensitivity in molar incisor hypomineralization (MIH)-affected molars immediately and over 8 weeks combining a single in-office application and a homed-based program with desensitizing products containing 8% arginine and calcium carbonate. MATERIALS AND METHODS: Nineteen children with at least one MIH-affected molar with hypersensitivity were included. Hypersensitivity was assessed with an evaporative (air) stimulus and a tactile stimulus. Each child received a single in-office treatment with a desensitizing paste containing 8% arginine and calcium carbonate (elmex Sensitive Professional desensitizing paste), followed by 8 weeks of brushing twice daily with a desensitizing toothpaste containing 8% arginine, calcium carbonate with 1450 ppm fluoride (elmex Sensitive Professional toothpaste), using the elmex Sensitive Professional toothbrush. Additionally, the corresponding mouthwash (elmex Sensitive Professional mouthwash) was used. Clinical assessments were made at baseline, immediately after the in-office treatment and after 1, 2, 4 and 8 weeks of brushing twice daily. RESULTS: Fifty-six molars with an air blast hypersensitivity score of 2 or 3 (Schiff Cold Air Sensitivity Scale) were included. Application of the desensitizing paste decreased hypersensitivity significantly immediately and throughout the 8 weeks recalls (p < 0.001). CONCLUSIONS: In conclusion, 8% arginine and calcium carbonate were able to reduce hypersensitivity successfully during this 8-week trial. CLINICAL RELEVANCE: Hypersensitivity is a major complaint in patients with MIH. This is the first study evaluating the desensitizing effect of a desensitizing paste containing 8% arginine and calcium carbonate in patients with MIH.

Effects of different desensitizing treatments on root dentin permeability.

The objective of this study was to evaluate the effects of diode laser and a desensitizing dentifrice on dentin permeability. Fifty-two root dentin fragments were obtained (5 × 5mm) and treated with 24% EDTA gel. The samples were divided into 4 groups (n = 13): G1, control (no treatment); G2, diode laser (λ = 908 nm, 1.5 W, continuous mode, 20s); G3, application of abrasive dentifrice for 1 minute (Elmex Sensitive Professional (International Gaba); and G4, application of abrasive dentifrice for 1 minute followed by irradiation with diode laser. Ten samples per group were immersed in 2% methylene blue solution for 4h. The specimens were washed, longitudinally sectioned, observed under optical microscopy, photographed and assessed based on the degree of dye leakage. The remaining samples were observed under scanning electron microscopy (SEM). The leakage data were subjected to ANOVA test, followed by Tukey's t-test (α = 5%). Groups 2, 3 and 4 showed less dye penetration than the control group (p < 0.05), but were similar among each other. SEM images showed that dentinal tubules were open in G1, and fused and occluded in G2. Group 3 showed dentinal tubules that were occluded by the metal ions from the toothpaste. G4 presented similar characteristics to G3, and the presence of fused dentin. The diode laser and the dentifrice were effective in reducing dentinal permeability, and the combination of the two treatments did not show better results than either one used alone.

Strontium effects on root dentin tubule occlusion and nanomechanical properties.

OBJECTIVES: Dentin hypersensitivity often is treated by promotion of dentin tubule occlusion. In this in vitro study we evaluated nanomechanical properties and degree of tubule occlusion conferred to sound and demineralized human root dentin following treatment with a 10% (w/w) strontium acetate solution and its relation to the treatment duration and delivery method. METHODS: 24 human cervical root dentin disks (8 groups of 3) were polished through 0.25 µm. 12 disks were subjected to an acid challenge (1% citric acid, pH 3.8) for 2 min. The specimens were incubated in artificial saliva, treated by soaking or brushing with deionized (DI) water or a solution of 10% strontium acetate for 2 min twice a day for 28 days. The occlusion percent and nanomechanical properties were determined at the baseline, 5, 14 and 28 days. Cross-sectioned specimens were prepared to evaluate the depth affected by strontium acetate / dentin interaction by SEM. Statistical analysis was performed using linear mixed effects models. RESULTS: A 10% strontium acetate treatment over 5-28 days significantly increased tubule occlusion for normal root dentin and to a lesser extent for demineralized dentin and increased the AFM based nanomechanical properties of demineralized dentin. Brushing was more effective than soaking in recovery of properties of demineralized dentin when treated with strontium. No difference in tubuleocclusion was found between the two delivery methods. SIGNIFICANCE: Strontium acetate itself proved to have the ability to occlude dentin tubules and result in small changes in the mechanical properties of dentin.