Erosive assessment of dry mouth lozenges and tablets on enamel and dentin.

OBJECTIVES: To assess the erosive potential of dry mouth lozenges and tablets on enamel and dentin. MATERIALS AND METHODS: The following lozenges and tablets were tested: Salese, Oracoat Xylimelts, Cotton Mouth, TheraBreath, DenTek OraMoist, SmartMouth, ACT, CVS Health, Rite Aid, Med Active, and Hager Pharma. pH Analysis: Each lozenge or tablet was crushed with a pestle and mortar and 5 g of the resultant powder was dissolved in 10 ml of distilled water (pH 7.02) The pH of each lozenge solution was assessed by using a calibrated pH meter. Titratable Acidity (TA) was determined by adding 0.1 M of NaOH to each homogenous tablet solution until the pH reached 7.0. Gravimetric Analysis was measured with freshly extracted molars crown/roots were sectioned at the CEJ and enamel and dentin specimens were fabricated. The specimens were then submerged in 5 ml of solution containing 2.5 gm of crushed tablets for 24 h, 48 h, 96 h and 14 days with measurements performed at each interval after drying. The solutions were renewed at each interval. RESULTS: Significant correlation between pH and TA was observed for lozenges and tablets evaluated (p < 0.0001). Both variables were strongly correlated with enamel and dentin loss (p < 0.0001). For enamel, DenTek resulted in significantly more substance loss (p < 0.05) than with the other tested products, while Xylimelts presented the lowest percentage of substance loss. For dentin, Cotton Mouth resulted in the highest substance loss, and Xylimelts presented the lowest percentage of substance loss. CONCLUSIONS: There is a strong correlation between the pH, tritatable aciditiy, and erosive potential of these products. DenTek and Cotton Mouth reported erosive effect to the enamel and dentin, respectively. Xylimelts performed better than the rest of the products in relationship to enamel and dentin.

Direct and transdentinal biostimulatory effects of grape seed extract rich in proanthocyanidin on pulp cells.

AIM: To evaluate the potential biostimulatory effects of grape seed extract (GSE) on a primary culture of human pulp cells. METHODOLOGY: Human molars were used to obtain the primary pulp cell culture and 0.5-mm dentine discs. For GSE direct exposure, dose-response (0.0065-6.5%) and time response (1-60 min of contact) were examined. For transdentinal exposure, 0.65% of GSE was tested for 24 h. Cellular metabolism, nitric oxide and collagen production, and cell morphology alterations were assessed at periods of 24 and 72 h. After cell differentiation and direct exposure to GSE, the total protein production (TP), alkaline phosphatase activity (ALP) and formation of mineralization nodules (MN) were assessed. The results were analysed by parametric tests or non-parametric tests (α = 0.05). RESULTS: The lower concentration of GSE tested (0.0065%) was associated with an increase in cellular metabolism, a reduction in the production of nitric oxide and an increase in extracellular matrix synthesis (collagen). Distinct behaviours were observed for the different concentrations, without a reduction of cellular metabolism >10% compared with the control, either when applied directly or transdentinally. SEM revealed no significant change in cell morphology, except for the positive control (H2 O2 ). There was no difference in TP, ALP or MN between the control group and the group exposed to GSE. CONCLUSIONS: Treatment with grape seed extract, even at the highest concentration and longest period, caused neither direct nor transdentinal cytotoxic effects on human pulp cells. Grape seed extract components may play a biostimulatory role and protect dental pulp cells when in direct contact.

Performance of the IOTA ADNEX model in preoperative discrimination of adnexal masses in a gynecological oncology center.

OBJECTIVE: To evaluate the performance of the International Ovarian Tumor Analysis (IOTA) ADNEX model in the preoperative discrimination between benign ovarian (including tubal and para-ovarian) tumors, borderline ovarian tumors (BOT), Stage I ovarian cancer (OC), Stage II-IV OC and ovarian metastasis in a gynecological oncology center in Brazil. METHODS: This was a diagnostic accuracy study including 131 women with an adnexal mass invited to participate between February 2014 and November 2015. Before surgery, pelvic ultrasound examination was performed and serum levels of tumor marker CA 125 were measured in all women. Adnexal masses were classified according to the IOTA ADNEX model. Histopathological diagnosis was the gold standard. Receiver-operating characteristics (ROC) curve analysis was used to determine the diagnostic accuracy of the model to classify tumors into different histological types. RESULTS: Of 131 women, 63 (48.1%) had a benign ovarian tumor, 16 (12.2%) had a BOT, 17 (13.0%) had Stage I OC, 24 (18.3%) had Stage II-IV OC and 11 (8.4%) had ovarian metastasis. The area under the ROC curve (AUC) was 0.92 (95% CI, 0.88-0.97) for the basic discrimination between benign vs malignant tumors using the IOTA ADNEX model. Performance was high for the discrimination between benign vs Stage II-IV OC, BOT vs Stage II-IV OC and Stage I OC vs Stage II-IV OC, with AUCs of 0.99, 0.97 and 0.94, respectively. Performance was poor for the differentiation between BOT vs Stage I OC and between Stage I OC vs ovarian metastasis with AUCs of 0.64. CONCLUSION: The majority of adnexal masses in our study were classified correctly using the IOTA ADNEX model. On the basis of our findings, we would expect the model to aid in the management of women with an adnexal mass presenting to a gynecological oncology center. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Effect of gamma irradiation on ultimate tensile strength of enamel and dentin.

The effect of gamma irradiation therapy on the ultimate tensile strength (UTS) of enamel and dentin in relation to prism orientation, dentin tubule orientation, and location is unknown. It was hypothesized that tubule and prism orientation, location, and irradiation have an effect on the UTS of dental structures. Forty human third molars were used, half of which were subjected to 60 Gy of gamma irradiation, in daily increments of 2 Gy. The specimens were evaluated by microtensile testing. Results showed that irradiation treatment significantly decreased the UTS of coronal and radicular dentin and of enamel, regardless of tubule or prism orientation. With or without irradiation, enamel was significantly stronger when tested parallel to its prismatic orientation. Coronal and radicular dentin of non-irradiated specimens presented significantly higher UTS when tested perpendicularly to tubule orientation. However, when the teeth were irradiated, the influence of tubule orientation disappeared, demonstrating that irradiation is more harmful to organic components.

Influence of intracoronal bleaching agents on the ultimate strength and ultrastructure morphology of dentine.

OBJECTIVE: To evaluate the effects of intracoronal bleaching on ultimate tensile strength (UTS) of sound and etched dentine and its ultrastructure morphology. METHODOLOGY: Bovine dentine specimens with (e) or without previous etching with 37% phosphoric acid for 15 s were used for the intracoronal bleaching experiments. Teeth were randomly assigned to five treatments (n = 10): (C) control--no bleaching, (SP) sodium perborate, (CP) 35% carbamide peroxide, (25% HP) 25% hydrogen peroxide and (35% HP) 35% hydrogen peroxide. Bleaching was performed four times within a 72 h interval and afterwards, dentine pulp chamber blocks were obtained. The blocks were sectioned in 0.7 mm-thick slices and these were trimmed to reduce the inner dentine to a dumbbell shape with a cross-sectional area of 0.8 mm(2). Specimens were tested with the microtensile method (0.5 mm min(-1)) and data were analysed (two-way ANOVA-Tukey test, P < 0.05). Additional teeth were prepared for transmission electron microscopy (TEM) to evaluate dentine ultramorphology. RESULTS: The mean values of the UTS (SD) in MPa for sound dentine were: C = 48.3(8.5)a, SP = 34.6 (8.2)b, CP = 32.9 (8.9)b, 25% HP = 28.0(4.6)b, 35% HP = 26.4(6.6)b, and pre-etched dentine: Ce = 38.9(13.8)a, SPe = 31.3 (9.3)ab, CPe = 28.4 (6.2)ab, 25% HPe = 30.0 (7.9)ab, 35% HPe = 19.9(4.6)b. Significant differences between the means are indicated by the letters. TEM observations exhibited demineralization areas for all bleaching treatments. CONCLUSION: Bleaching decreased dentine UTS after treatment. Pre-etched not-bleached dentine (Ce) presented UTS similar to pre-etched bleached dentine, except for 35% HPe. The decrease of UTS of bleached dentine could be attributed to ultrastructural alterations such as loss of inorganic components.

Effects of natural cross-linkers on the stability of dentin collagen and the inhibition of root caries in vitro.

PURPOSE: To evaluate the effects of dentin collagen modifications induced by various cross-linkers on the stability of collagen matrix and the inhibition of root caries. MATERIALS AND METHODS: The following cross-linkers were tested: 5% glutaraldehyde (GA), 0.5% proanthocyanidin (PA), 0.625% genipin (GE). In the first experiment, cross-linker-treated demineralized human root dentin was digested with bacterial collagenase, centrifuged, and the supernatants were subjected to amino acid analysis to determine collagen content. The residues were analyzed by SDS-PAGE and hydroxyproline analysis. In the second experiment, bovine root surfaces were conditioned with phosphoric acid, treated with the cross-linkers, incubated with Streptococcus mutans and Lactobacillus acidophilus for 1 week and the root caries inhibition was evaluated with confocal microscopy. Lastly, the ability of the bacteria to colonize the root surface was evaluated. In this experiment slabs of bovine root were treated with the cross-linkers and incubated in a suspension of S. mutans and L. acidophilus. The slabs were washed, resuspended in water, glucose was added, and the pH measured. RESULTS: While all collagen was digested with collagenase in the control groups, only a small proportion was solubilized in the GA-, PA-, and GE-treated groups. The root caries was significantly inhibited by treatment with PA or GA. Drops in pH in the cross-linker-treated groups were essentially the same as in the untreated group. CONCLUSION: Naturally occurring cross-linkers, especially PA, could be used to modify root dentin collagen to efficiently stabilize collagen and to increase its resistance against caries.

Interfacial ultramorphology of single-step adhesives: nanoleakage as a function of time.

The aim of this study was to examine the effectiveness of single-step self-etching adhesives in preventing nanoleakage over a 90-day water-storage period, and analyse the ultramorphological characteristics of resin-dentin interfaces. Three single-step self-etching adhesives were evaluated: Adper Prompt L-Pop - LP (3M ESPE), iBond - iB (Heraeus Kulzer), and Clearfil Tri-S Bond - S3 (Kuraray). Bonded specimens were sectioned into 0.9-mm thick slabs and stored in water for 1, 60 or 90 days. After the storage periods, a silver tracer solution was used to reveal nanometer-sized spaces and evidence of degradation within resin-dentin interfaces. Epoxy resin-embedded sections were prepared, and the interfaces observed with the TEM. Nanoleakage patterns were compared among adhesives and storage periods using image analysis software. Data were statistically analysed by two-way anova and Tukey test. Nanoleakage was observed in all resin-dentin interfaces produced by the single-step self-etching adhesives. Results showed that LP presented the lowest silver deposition means at 1 day. However, after 60 and 90 days, the area of silver deposition significantly increased for LP. iB presented intense silver deposition after 1 day and a small increase after 90 days. S3 presented the lowest silver deposition means after 60 and 90 days of water-storage.

Removal of noncollagenous components affects dentin bonding.

The structural integrity of fibrillar type I collagen is critical for effective dentin bonding. Since most noncollagenous matrix components in dentin are closely associated with collagen, we hypothesized that they may also contribute to dentin bonding. To test this hypothesis, bovine dentin was acid-etched, treated with chondroitinase ABC (C-ABC), endo-beta-galactosidase (Endo-beta), or trypsin. Controls were prepared in the same manner but without the enzymes. All control and experimental specimens were then bonded with One-Step. Bond strength data were analyzed by one-way ANOVA and Fisher's PLSD test (p < 0.05). When dentin was treated with C-ABC or trypsin, bond strengths significantly decreased for the rewetted groups (p < 0.05). The treatment with Endo-beta showed no effects on bond strengths (p > 0.05). When the treated dentin surfaces were observed under SEM, the C-ABC and trypsin treated groups revealed significant loss of collagen fibril architecture. The results indicate that chondroitin sulfate glycosaminoglycans and trypsin-digestible noncollagenous proteins play roles in maintaining the open dimensions of the collagen fibril scaffold, which is essential for optimal dentin bonding.

Effect of blood contamination with 1-step self-etching adhesives on microtensile bond strength to dentin.

This study evaluated the effect of blood contamination and decontamination methods on the microtensile bond strength of 1-step self-etching adhesive systems to dentin contaminated after adhesive application and light curing. Three commercially available "all-in-one" adhesives (One Up Bond F, Xeno III and Adper Prompt L-Pop) and 1 resin composite (Clearfil AP-X) were used. Third molars that had been stored in distilled water with 0.5% thymol at 4 degrees C were ground with #600 SiC paper under running water to produce a standardized smear layer. The specimens were randomly divided into groups according to the 3 adhesive systems. The adhesive systems were used under 3 conditions: no contamination, which was the control (C); contamination of the light-cured adhesive surface with blood and reapplication of adhesive (Contamination 1) and contamination of the light-cured adhesive surface with blood, then washing, drying and reapplication of the adhesive (Contamination 2). Following light curing of the adhesive, the resin composite was placed in 3 increments up to a 5-mm-thick layer on the bonded surface. All specimens were stored in distilled water at 37 degrees C for 24 hours. The microtensile bond strength was measured using a universal testing machine (EZ test), and data were analyzed by 1-way ANOVA followed by the Duncan test to make comparisons among the groups (p=0.05). After debonding, 5 specimens were selected from each group and examined in a scanning electron microscope to evaluate the modes of fracture. For all adhesives, contamination groups showed lower bond strength than the control (p<0.05). There was no statistically significant difference among the control groups (p>0.05). For Xeno III and Adper Prompt L-Pop, contamination group #2 showed the lowest bond strength among the groups (p<0.05). For One Up Bond F, contamination group #2 showed higher bond strength than contamination group #1 but showed no statistical significance between them (p>0.05).

Effect of saliva contamination on the microshear bond strength of one-step self-etching adhesive systems to dentin.

This study evaluated the effect of saliva contamination and decontamination methods on the dentin bond strength of one-step self-etching adhesive systems. Three commercially available "all-in-one" adhesives (One Up Bond F, Xeno III and Adper Prompt) and one resin composite (Filtek Z-250) were used. Third molars stored in distilled water with 0.5% thymol at 4 degrees C were ground with #600 SiC paper under running water to produce a standardized smear layer. The specimens were randomly divided into groups according to contamination methods: no contamination, which was the control (C); contamination of the adhesive surface with fresh saliva before light curing (A) and contamination of the adhesive surface with fresh saliva after light curing (B). Each contamination group was further subdivided into three subgroups according to the decontamination method: A1-Saliva was removed by a gentle air blast and the adhesive was light-cured; A2-Saliva was rinsed for 10 seconds, gently air-dried and the was adhesive light-cured; A3-Saliva was rinsed and dried as in A2, then the adhesive was re-applied to the dentin surface and light-cured; B1-Saliva was removed with a gentle air blast; B2-Saliva was rinsed and dried; B3-Saliva was rinsed, dried and the adhesive was re-applied and light cured. Tygon tubes filled with resin composite were placed on each surface and light cured. All specimens were stored in distilled water at 37 degrees C for 24 hours. Microshear bond strength was measured using a universal testing machine (EZ test), and data were analyzed by one-way ANOVA followed by the Duncan test to make comparisons among the groups (p<0.05). After debonding, five specimens were selected and examined in a scanning electron microscope to evaluate the modes of fracture. The A2 subgroup resulted in the lowest bond strength. For One Up Bond F and Adper Prompt, there was no significant difference between subgroup A1 and the control, and subgroup A3 and the control (p>0.05). Bond strengths of all B groups were significantly lower compared to the controls (p<0.05). For Xeno III, A1 subgroup showed the greatest decrease in bond strength as compared to the control (p<0.05). On the other hand, it showed more resistance to salivary contamination after adhesive curing. There was no statistically significant difference among the control groups (p>0.05).

Collagen cross-linking and ultimate tensile strength in dentin.

Several studies have indicated differences in bond strength of dental materials to crown and root dentin. To investigate the potential differences in matrix properties between these locations, we analyzed upper root and crown dentin in human third molars for ultimate tensile strength and collagen biochemistry. In both locations, tensile strength tested perpendicular to the direction of dentinal tubules (undemineralized crown = 140.4 +/- 48.6/root = 95.9 +/- 26.1; demineralized crown = 16.6 +/- 6.3/root = 29.0 +/- 12.4) was greater than that tested parallel to the tubular direction (undemineralized crown = 73.1 +/- 21.2/root = 63.2 +/- 22.6; demineralized crown = 9.0 +/- 3.9/root = 16.2 +/- 8.0). The demineralized specimens showed significantly greater tensile strength in root than in crown. Although the collagen content was comparable in both locations, two major collagen cross-links, dehydrodihydroxylysinonorleucine/its ketoamine and pyridinoline, were significantly higher in the root (by ~ 30 and ~ 55%, respectively) when compared with those in the crown. These results indicate that the profile of collagen cross-linking varies as a function of anatomical location in dentin and that the difference may partly explain the site-specific tensile strength.

Effect of thermal and mechanical load cycling on microtensile bond strength of a total-etch adhesive system.

To evaluate the effect of thermal and mechanical cycles on dentin bond strength to cervical margins of Class II restorations, 80 box-type Class II cavities were prepared on the surfaces of bovine incisors. The cavities were restored with Single Bond (3M-ESPE) and Z-250 composite (3M-ESPE) according to manufacturer's instructions. The incisors were divided into four groups: G1-Control, G2- Thermal cycling (2,000 cycles, 5 degrees C-55 degrees C), G3- Mechanical cycling (100,000 cycles; 50N) and G4- Thermal and mechanical cycling (2,000 cycles 5 degrees C-55 degrees C/100,000 cycles; 50N). The restorations were sectioned perpendicular to the cervical bonded interface into 0.7 +/- 0.2 mm-thick slabs. The slabs were further trimmed at the interface to 1.4 +/- 0.2 mm with a fine diamond bur to produce a cross-sectional surface area of 1 mm2. All specimens were then subjected to microtensile bond testing. Means and standard deviations were expressed in MPa. The bond strength data were analyzed by one-way ANOVA and Fisher's PLSD test (p<0.05). Fracture mode analysis was performed using SEM. Bond strengths were significantly lower when thermal and mechanical cycling were performed [G4-2.41 (8.57)] when compared to the other groups [G1-28.15 (14.03); G2-27.60 (10.14); G3-27.59 (8.67)]. No differences were observed among Groups 1, 2 and 3. Interfacial fracture of the control (G1) and thermocycling (G2) groups mainly occurred between the deepest portion of the adhesive resin and the top layer of the demineralized dentin (Interphase). Mixed failure was predominant and increased when mechanical cycling was applied (G3 and G4).

Dimensional changes and ultimate tensile strengths of wet decalcified dentin applied with one-bottle adhesives.

OBJECTIVES: The objectives of this study were to test the null hypothesis that no dimensional changes in wet decalcified dentin matrices will occur during the application of one-bottle adhesives, and to evaluate the ultimate tensile strengths (UTS) of resin-infiltrated dentin matrices using the microtensile test. METHODS: Dentin disks 0.2 mm thick were prepared from mid-coronal dentin of human unerupted third molars. They were completely decalcified in 0.5 M EDTA (pH 7.4) for 5 days at 25 degrees C and then placed in the bottom of an aluminum well to permit use of the LVDT portion of a thermal mechanical analyzer. Changes in matrix height in response to the application of Single Bond, One-Step or Prime & Bond NT were measured along with the UTS of resin-infiltrated specimens that were compared using a one-way ANOVA and Fisher's PLSD test. RESULTS: All one-bottle adhesives produced a gradual, progressive shrinkage of the decalcified matrix of 26-33%. The shrinkage produced by Single Bond was significantly greater (p<0.05) than that produced by the other adhesives. The UTS of One-Step was significantly higher (<0.05) than that of Prime & Bond NT (42.0+/-13.6 vs 29.7+/-1.9 MPa, respectively), with Single Bond producing intermediate UTS (34.3+/-7.4 MPa). SIGNIFICANCE: If the durability of resin-dentin bonds depends upon the size of interfibrillar spaces for both diffusion channels and resin uptake, then adhesive formulations should be designed to minimize matrix shrinkage during resin infiltration.

Effects of mechanical properties of adhesive resins on bond strength to dentin.

OBJECTIVES: The purpose of this study was to evaluate the relationship between the micro-tensile bond strength to dentin and mechanical properties of the cured adhesive resins. METHODS: Coronal dentin surfaces of extracted human teeth were treated with four commercial self-etching priming systems (Clearfil SE Bond; UniFil Bond; Tokuso Mac-Bond II; and Imperva Fluoro Bond) and bonded with a resin composite. After 24h storage in water at 37 degrees C, the bonded specimens were trimmed and subjected to micro-tensile bond strength testing at a cross-head speed of 1mm/min. Debonded surfaces were observed under a FE-SEM. For testing mechanical properties, 0.7-mm thick slabs of each adhesive resin were prepared, light-cured, and stored dry at the room temperature for 24h. After trimming, ultimate micro-tensile strength was measured. The nano-hardness and Young's modulus were also evaluated using cured adhesives that were prepared in the same manner as described above. RESULTS: The micro-tensile bond strengths to dentin and ultimate micro-tensile strengths of the resins were not significantly different among all systems (P>0.05). However, the nano-hardness and Young's modulus of Clearfil SE Bond and Imperva Fluoro Bond adhesive resins were significantly higher than those of UniFil Bond and Tokuso Mac-Bond II resins (P<0.05). The micro-tensile bond strength significantly correlated with the ultimate micro-tensile strength of the resins (r(2)=0.77; P<0.05), but was not correlated with the nano-hardness or Young's modulus (P>0.05). SEM observation of the debonded surfaces revealed a mixed type of fracture with a combination of interfacial and cohesive failure within the adhesive resin. SIGNIFICANCE: The four self-etching priming systems exhibited similar dentin bond strengths, which also correlates with the ultimate strength of the adhesive resins.

Maximizing esthetic results in posterior restorations using composite opaquers.

UNLABELLED: After removal of caries or a faulty existing restoration in a posterior tooth, frequently the pulpal floor is a dark substrate. Composites are translucent by nature, and even the more opaque shades transmit nearly 60% of visible light, meaning that composites require a certain thickness to maintain their intended shade, especially if the underlying substrate is particularly dark. Depending on the intensity of the dark substrate, even relatively thick composite restorations may not be capable of disguising the discolored dentin underneath. The substrate absorbs a significant part of the light that would otherwise reflect toward the occlusal surface, and the restoration has a nonvital monochromatic grayish color. Opaquers and tints (color modifiers) may be extremely useful to overcome this situation. In this study, composite restorations were placed in extracted teeth to demonstrate that the final esthetic results rely upon the optical properties of the background as well as those of the composite material itself. Preparations with simulated dark pulpal floors were restored without the use of opaquers and tint modifiers. After tooth hydration, the final shade was recorded with photographs. The restoration was removed and a new restoration was placed, but this time with a technique involving opaquer and tints. This article compares and discusses the outcomes of these two procedures. CLINICAL SIGNIFICANCE: This demonstration shows a simple technique that can help dentists obtain predictable esthetic results in their daily practice with posterior composite restorations.

Relationship between nanoleakage and long-term durability of dentin bonds.

This study tested the hypothesis that long-term durability of resin bonds to dentin would directly relate to the nanoleakage of dentin bonding systems. Twenty extracted third molars were ground flat with #600 grit SIC paper under running water to expose middle dentin. One-Step or Single Bond was applied to the dentin surface according to the manufacturer's instruction. A crown was built-up with Clearfil AP-X resin composite and the specimens were stored in water for 24 hours at 37 degrees C. The bonded assemblies were cut mesio-distally perpendicular to the interface in approximately 0.7 mm thick slabs and trimmed for microtensile bond strength testing. All slabs were immersed in individual bottles containing 37 degrees C water that was changed daily. Specimens were randomly assigned to four groups (one day, three, six and nine months), and at the specified time period, the specimens to be tested were randomly divided into two subgroups for testing: 50% AgNO3 and the control. In the 50% AgNO3 subgroup, the slabs were coated with fingernail varnish except for approximately 0.5 mm around the bonded interface and immersed for one hour in 50% AgNO3, followed by exposure in a photo developing solution for 12 hours just prior to debonding. The specimens in the control subgroup were soaked in water until they were debonded. Then, all specimens were subjected to microtensile bond testing. Micrographs of the fractured surfaces of the debonded specimens in the AgNO3 subgroup were taken using light microscopy. They were then subjected to image analysis by NIH Image PC (Scion, Fredrick, MD, USA), and the area of silver penetration was quantitated. The fractured surface was further analyzed under the SEM. Bond strength data and the silver penetration areas were subjected to two and three-way ANOVA and Fisher's PLSD test at the 95% level of confidence. Regression analysis was used to test the relationship between bond strengths and the silver penetra tion area at each time period. The tensile bond strength of both materials gradually decreased over time. Specimens bonded with One-Step showed less silver nanoleakage at one day compared to three, six and nine months (p<0.05), but there were no significant differences between the nanoleakage measured at three, six and nine months. In contrast, for specimens bonded with Single Bond, there were no statistically significant differences in the silver nanoleakage among the four time periods tested (p>0.05). No correlation was observed between bond strength and nanoleakage for either bonding system. Nanoleakage occurred in both adhesive systems, and bond strengths gradually decreased over time. However, there was no correlation between bond strength and nanoleakage for either adhesive system in this study.

Relationship between bond strengths and nanoleakage: evaluation of a new assessment method.

PURPOSE: To test if there was a correlation between resin-dentin bond strengths and nanoleakage of total etch and self-etching primer bonding systems. MATERIALS AND METHODS: Ten extracted third molars were ground flat with 600 grit SIC paper under running water to expose middle dentin. Clearfil Liner Bond 2V or Single Bond was applied to the dentin surface according to the manufacturers' instructions. A crown was built-up with Clearfil AP-X resin-based composite, and the specimens stored in water for 24 hrs at 37 degrees C. The bonded assemblies were cut mesiodistally perpendicular to the interface into approximately 0.7 mm thick slabs, and trimmed for microtensile bond strength testing. Alternate slices from each tooth were either entirely double-coated with nail varnish leaving a 0.5 mm window around the interface, or left uncoated to be immersed in water for 13 hrs as the control. The varnished (experimental) slabs were immersed in 50% AgNO3 for 1 hr, and then immersed in a photo developing solution for 12 hrs. All specimens were subjected to microtensile bond test at a crosshead speed of 1 mm/min. After debonding, the specimens were embedded in epoxy resin and observed under a confocal laser scanning microscope for determination of lateral silver penetration within the interface. Silver penetration was further analyzed under the SEM. Data were analyzed with one- and two-way ANOVA, Fisher's PLSD test (P < 0.05), and regression analysis. RESULTS: The bond strengths of Clearfil Liner Bond 2V and Single Bond were not significantly different (P > 0.05); however the bond strengths of the specimens that were soaked in 50% AgNO3 for 1 hr significantly increased (P < 0.01). No correlation was observed between bond strengths and nanoleakage.

Adhesive sealing of the pulp chamber.

The purpose of this in vitro study was to evaluate quantitatively the ability of four different filling materials to seal the orifices of root canals as a secondary seal after root canal therapy. Forty extracted human molar teeth were used. The top of pulp chambers and distal halves of the roots were removed using an Isomet saw. The canal orifices were temporarily sealed with a gutta-percha master cone without sealer. The pulp chambers were then treated with a self-etching primer adhesive system (Clearfil SE Bond), a wet bonding system (One-Step), a 4-methacryloyloxyethyl trimellitate anhydride adhesive system (C&B Metabond), or a reinforced zinc oxide-eugenol (IRM). The specimens were randomly divided into four groups of 10 each. A fluid filtration method was used for quantitative evaluation of leakage. Measurements of fluid movement were made at 2-min intervals for 8 min. The quality of the seal of each specimen was measured by fluid filtration immediately and after 1 day, 1 wk, and 1 month. Even after 1 month the resins showed an excellent seal. Zinc oxide-eugenol had significantly more leakage when compared with the resin systems (p < 0.05). Adhesive resins should be considered as a secondary seal to prevent intraorifice microleakage.

Regional bond strengths of adhesive resins to pulp chamber dentin.

Microleakage of oral microorganisms, which can occur due to the lack of sealing ability of permanent restorative materials, may cause failure of root canal treatments. Although a great deal of research has been done on sealing enamel and coronal dentin with resins, little research has been done on the adhesion of resins to the walls of pulp chambers. The purpose of this study was to evaluate regional bond strengths of two adhesive systems to the walls of pulp chambers. A section was made horizontally through the middle of the pulp chamber of extracted human third molars to divide the chamber into upper and lower halves. The pulp tissue was removed and the tooth segments were then divided into treatment subgroups. The pulp chambers were bonded with C&B Metabond (Parkell) or One-Step (Bisco), with or without 5% NaOCI pretreatment. The microtensile bond strengths of these resins to four different pulp chamber regions (bottom, wall, roof, and pulp horn areas) were then measured using an Instron machine. The data were expressed in MPa and were analyzed by a three-way ANOVA. Statistically significant differences were found among the test groups (p < 0.001). One-Step produced higher bond strengths to all pulp chamber regions except the floor, compared with C&B Metabond. The results indicated that high bond strengths can be achieved between adhesive resins and the various regions of the pulp chamber. This should permit the use of a thick layer of unfilled resin along the floor of the pulp chamber and over the canal orifices as a secondary protective seal after finishing root canal therapy.

Effects of different burs on dentin bond strengths of self-etching primer bonding systems.

This study evaluated the effects of cutting dentin with different types of burs on tensile bond strength using three self-etching primer bonding systems (Clearfil Liner Bond 2 [LB2], Clearfil Liner Bond 2V [2V] and Clearfil SE BOND [SE], Kuraray, Co, Ltd, Osaka, Japan). Thirty-six intact extracted human third molars were ground flat to expose occlusal dentin, followed by polishing the dentin surfaces with #600 SiC paper. The teeth were divided into four groups according to bur type and grit: fine cut fissure steel bur (SB600), cross cut fissure steel bur (SB703), regular grit diamond bur (DB). Controls were abraded with #600 grit SiC paper (AP#600). The dentin surfaces of the SB600, SB703 and DB groups were cut under copious air-water spray with the respective burs mounted in a dental handpiece. The teeth were treated with one of three adhesive systems, then composite buildups were created with Clearfil AP-X (Kuraray Co, Ltd, Osaka, Japan). After soaking in water at 37 degrees C for 24 hours, serial vertical sections (0.7 mm thick, 7-8 slices per one tooth) were made, trimmed to form an hour-glass shape with a 1.0 mm2 cross-section and tensile bond strengths were determined at a cross-head speed of 1 mm/min. Statistical analysis was made using one and two-way ANOVA and Fisher's PLSD test (p<0.05). Eight additional molars were prepared. Burs or abrasive paper were used for SEM observations of the dentin surfaces of each group before and after treatment with the self-etching primers. All adhesive systems yielded the same ranking of bond strengths to the surfaces prepared with different abrasives: from highest to lowest, AP#600 > SB600 > SB703 > DB. This ranking reached statistical significance using Clearfil Liner Bond 2V (p<0.05). Therefore, when cutting dentin, selecting the adequate bur type is important for improved bonding of adhesive systems using self-etching primer to dentin.