Is it possible for a simultaneous biomodification during acid etching on naturally caries-affected dentin bonding?

OBJECTIVES: This study investigated the ability of modified phosphoric acids containing chlorhexidine (CHX) or grape seed extract (GSE) for promoting simultaneous biomodification during acid etching on bonding properties in caries-affected dentin (CAD). MATERIALS AND METHODS: Thirty-two human molars (8 with sound dentin [SD] and 24 naturally CAD) were selected for the study. The SD and CAD were initially exposed, then randomized and etched according to the following groups: (1) SD (SD-CT) and CAD (CAD-CT) both with 37% phosphoric acid, (2) CAD with 2% CHX containing 37% phosphoric acid (CAD-CHX), and (3) CAD with 2% GSE containing 10% phosphoric acid (CAD-GSE). The bonding procedure and composite build-ups were performed after acid etching. Subsequently, they were sectioned in resin-dentin specimens. The specimens were submitted for chemical profiling by micro-Raman, microtensile bond strength (µTBS), failure mode with chemical characterization by FEG/SEM-EDX, and in situ zymography by CLSM. The data from µTBS and CLSM were statistically analyzed (1-way ANOVA and Tukey's test; α = 0.05). RESULTS: The highest µTBS results were shown for SD-CT in comparison with all CAD groups (p < 0.001), and the lowest for CAD-CT and CAD-CHX (p < 0.001). The etching with CHX did not increase the µTBS for CAD when compared with CT (p = 0.52). However, the etching with GSE improved significantly the µTBS for CAD when compared with CT and CHX (p < 0.001). The chemical profile detected chemical and structural changes in collagen peaks for CAD-CT, which were not detected when the CAD was etched by modified acids. Also, the poorest hybridization ability was detected in CAD for CT, which was significantly improved with modified acids, especially the GSE, as evaluated by chemical profile and failure mode. A significant reduction of MMP activity on CAD was promoted by modified acids in comparison with CT (both p < 0.001). CONCLUSIONS: The GSE-containing acid was able to promote biomodification during the acid etching, increasing the bonding properties and reducing the activity of the MMPs within the hybrid layer. CLINICAL RELEVANCE: The use of GSE-containing phosphoric acid can be a promising alternative to improve the bonding performance on caries-affected dentin, since it is capable of biomodifying the dentin during the acid etching, without adding any extra step in bonding procedures.

In vitro evaluation of proximal carious lesions using digital radiographic systems.

The study aimed to compare the sensitivity and specificity of digital radiographic systems for the diagnosis of proximal carious lesions. Extracted human teeth (3 canines, 3 premolars, and 3 molars) were submitted to one of three types of proximal lesions (demineralized area, cavity affecting the enamel alone, and cavity affecting enamel and dentin). Bitewing radiographs were obtained from each system (Sirona, Kodak, and Schick) and evaluated by 12 raters (4 dental students, 4 radiology specialists, and 4 dentists). The chi-squared test was used to determine the frequency of correct diagnoses among the different systems, raters, teeth, and types of lesion. Sensitivity and specificity regarding demineralized areas were calculated for each system. The frequencies of correct diagnoses were found: Schick (70.8%), Kodak (63.9%), Sirona (59.0%), specialists (69.4%), students (62.5%), dentists (61.8%), premolars (70.1%), canines (65.3%), and molars (58.3%). No significant differences were found among the different systems, raters, or teeth (P > 0.05). Sensitivity and specificity were 0.64 and 0.47 (Schick), 0.56 and 0.50 (Sirona), and 0.48 and 0.58 (Kodak). The most correct diagnoses were achieved using the Schick digital system on premolars and evaluated by specialists in radiology. The systems demonstrated low sensitivity and specificity for the diagnosis of demineralized areas.

Influence of Relining Post on the Bond Strength of Resin Cements.

This study evaluated the influence of relining fiber posts on the bond strength (BS) of resin cements in the root canal. Forty bovine teeth were divided in four groups (n = 10): G1 (ARC)-fiber post cemented with resin cement RelyX ARC; G2 (ARC+Z350)-relined fiber post cemented with RelyX ARC; G3 (U200)-fiber post cemented with self-adhesive cement RelyX U200; G4 (U200+Z350)-relined fiber post cemented with RelyX U200. The roots were sectioned in six 1.2-mm slices and the push-out test was performed. Data were analyzed by three-way analysis of variance (ANOVA), and Tukey's test (a = 0.05). For the conventional resin cement, there was no significant difference between groups G1-ARC (15.5 ± 3.8) and G2-ARC+Z350 (16.1 ± 4.5). For the self-adhesive cement, the results revealed higher BS values for relined posts G4-U200 + Z350 (19.9 ± 7.9) as compared to non-relined posts G3-U200 (14.4 ± 4.5). For both cements, in groups of relined posts, the apical and the cervical thirds presented similar BS. Relining enhances the performance of the self-adhesive resin cement, and the interaction between relining and root third influences the BS to the conventional resin cement.

Effect of bioactive glasses and neodymium:yttrium-aluminum-garnet laser on dentin permeability.

CONTEXT: Dental hypersensitivity and loss of dental tissues are commonly observed in patients, and most of the problems are caused due to total or partial exposure of dentinal tubules. AIMS: The purpose of this study is to evaluate the performance of 45S5 bioactive glass and niobophosphate (NbG) associated with neodymium: yttrium-aluminum-garnet (Nd:YAG) laser for the reduction of dentin permeability. MATERIALS AND METHODS: Fifty bovine dentin discs were made and distributed randomly into five groups (n = 10). The Nd:YAG laser was applied with the bioactive glasses using the energy parameters (60 and 80 mJ), forming the groups; NbG_60: NbG + Nd:YAG (60 mJ); NbG_80: NbG + Nd:YAG (80 mJ), 45S5_60: 45S5 + Nd:YAG (60 mJ); 45S5_80: 45S5 + Nd:YAG (80 mJ) and C: control (untreated dentin). The permeability was measured with a split chamber device. The samples were subjected to the erosive challenge and a new permeability measurement was done. Furthermore, the dentin was analyzed by scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS). STATISTICAL ANALYSIS USED: The data were analyzed using Kruskal-Wallis and Dunn's tests (α = 0.05). RESULTS: Greater reduction in dentinal permeability was observed for 45S5 bioactive glasses (45S5_60 and 45S5_80) followed by NbG_80 and NbG_60 (P < 0.05). The SEM/EDS analysis showed the formation of a barrier after the dentin treatment. CONCLUSIONS: Bioactive glasses with Nd:YAG laser on the dentin surface may be a promising alternative for the reduction of dentin permeability.

Calcium Pre-Rinse: Effect on permeability of dentin tubules by fluoride rinse.

BACKGROUND: The aim of this study was to evaluate whether calcium (CaL) solution would enhance the capacity of sodium fluoride (NaF) solution in reducing the permeability of hypersensitive dentin. MATERIAL AND METHODS: Thirty-two Wistar rats ingested for 45 days acidic isotonic drink (Gatorade, pH 2.7) ad libitum to induce dental erosion. Then, molar teeth received a cold stimulus to confirm the presence and score the intensity of dentin hypersensitivity based on body contraction and noise. Animals were allocated to four groups (n=8), according to the solution(s) applied in the oral cavity: NaF (12 mmol/L, 1 min); CaL (150 mmol/L, 1 min); CaL followed by NaF (CaF+NaF, 1 min each); distilled water (DW, 1 min, as negative control). The animals were euthanized and the mandibles dissected into hemimandibles, which were sealed with sticky wax, except for the occlusal surface of the molar teeth. The samples were immersed in 10% copper sulphate solution and in 1% dithioxamide alcoholic solution (25 min each). The samples were sectioned longitudinally and imaged under optical microscope. Then, dentin permeability was measured as the area of copper ion penetration, using ImageJ software. Photomicrographs were obtained by scanning electron microscopy. RESULTS: 68.7% of animals had body contraction associated or not with noise. One-way ANOVA followed by Tukey´s test indicated that groups treated with NaF solution, whether or not preceded by CaL solution, presented lower permeability than the remaining groups [CaL+NaF: 3405.7 µm2 (±1796.4); NaF: 4111.7 µm2 (±2450.6); CaL: 42254.6 µm2 (±30399.2); DW: 37064.6 µm2 (±21994.4)]. Photomicrographs showed that CaL+NaF group presented an increased proportion of occluded dentin tubules in comparison to the NaF-only group. CONCLUSIONS: Although qualitatively there seems to be a benefit in using CaL pre-rinse, this solution did not quantitatively enhance the capacity of NaF in reducing permeability of hypersensitive dentin. Key words:Dentin hypersensitivity, Fluoride, Calcium lactate, Animal model.

Can the durability of one-step self-etch adhesives be improved by double application or by an extra layer of hydrophobic resin?

OBJECTIVES: This study evaluated the immediate and 6-month resin-dentin micro-bond strength (microTBS) of one-step self-etch systems (Adper Prompt L-Pop [AD] 3M ESPE; Xeno III [XE] Dentsply De Trey; iBond [iB] Heraeus Kulzer) under different application modes. MATERIALS AND METHODS: Dentin oclusal surfaces were exposed by grinding with 600-grit SiC paper. The adhesives were applied according to the manufacturer's directions [MD], or with double application of the adhesive layer [DA] or following the manufacturer's directions plus a hydrophobic resin layer coating [HL]. After applying the adhesive resins, composite crowns were built up incrementally. After 24-h water storage, the specimens were serially sectioned in "x" and "y" directions to obtain bonded sticks of about 0.8mm2 to be tested immediately [IM] or after 6 months of water storage [6M] at a crosshead speed of 0.5mm/min. The data from each adhesive was analyzed by a two-way repeated measures ANOVA (mode of application vs. storage time) and Tukey's test (alpha=0.05). RESULTS: The adhesives performed differently according to the application mode. The DA and HL either improved the immediate performance of the adhesive or did not differ from the MD. The resin-dentin bond strength values observed after 6 months were higher when a hydrophobic resin coat was used than compared to those values observed under the manufacturer's directions. CONCLUSIONS: The double application of one-step self-etch system can be safety performed however the application of an additional hydrophobic resin layer can improve the immediate resin-dentin bonds and reduce the degradation of resin bonds over time.

Effects of moisture degree and rubbing action on the immediate resin-dentin bond strength.

OBJECTIVES: To compare the effects of moisture and rubbing action on the microtensile bond strength (BS) of an ethanol/water-based (Single Bond [SB]) and an acetone-based system (One-Step [OS]) to dentin. METHODS: On 60 human molars, a flat superficial dentin surface was exposed by wet abrasion. Two coats of the adhesives were applied on either a dry (D) or rewetted surface (W), under no rubbing action (NRA), slight (SRA) or vigorous rubbing action (VRA). After light curing (600 mW/cm2/10 s), composite build-ups were constructed incrementally and specimens were stored in water (37 degrees C/24 h). They were longitudinally sectioned in the "x" and "y" directions to obtain bonded sticks (0.8 mm2) to be tested in tension at 0.5 mm/min. Resultant BS was expressed as an index that includes bond strength values of the different fracture patterns and the specimens that failed during preparation for testing. The data were analyzed by a three-way ANOVA and Tukey's multiple comparison tests (95%). RESULTS: The interactions moisture/agitation and adhesive/agitation were statistically significant (p < 0.05). In D groups, the highest BS was obtained under VRA (37.11 +/- 7.3). In W groups, the BS at SRA (41.82 +/- 8.4) and VRA (38.89 +/- 8.2) were similar. For SB system, the SRA (33.6 +/- 8.3) and VRA groups (41.26 +/- 5.9) yielded similar BS while for OS the VRA was essential to reach high BS (34.2 +/- 8.4). SIGNIFICANCE: High BS to dentin can be obtained, under dry conditions, when ethanol/water and acetone-based systems, are vigorously agitated in the surface. On wet dentin, slight agitation seems to be enough to provide high BS to dentin.

Effect of Fluoride and Simplified Adhesive Systems on the Bond Strength of Primary Molars and Incisors.

The aim of this study was evaluate in vitro the influence of simplified adhesive systems (etch-and-rinse and self-etching) and 1.23% acidulated phosphate fluoride (APF) on the microshear bond strength (µ-SBS) of composite resins on primary molars and incisors. Forty primary molars and forty incisors vestibular enamel was treated with either the self-etching Clearfil SE Bond (CSE, Kuraray) or etch-and-rinse Adper Single Bond 2 (SB2, 3M/ESPE) adhesive system. Each group was subdivided based on the prior treatment of the enamel with or without the topical application of 1.23% APF. Thereafter, matrices were positioned and filled with composite resin and light cured. After storage in distilled water at 37 ± 1°C for 24 h, the specimens were submitted to µ-SBS in a universal testing machine. Kruskal-Wallis and Mann-Whitney tests (p < 0.05) showed that the prior application of 1.23% APF led to a significant reduction in bond strength. The type of adhesive exerted no significant influence bond strength. In the inter-group analysis, however, significantly bond strength reduction was found for the incisors when CSE was employed with APF. Adhesive failure was the most common type of fracture. The bond strength was affected by the prior application of 1.23% APF and type of tooth.

Influence of crosshead speed on resin-dentin microtensile bond strength.

PURPOSE: The aim of this study was to investigate the influence of testing speed on the microtensile bond strength values of two adhesive systems to dentin. MATERIALS AND METHODS: A flat dentin surface was exposed after grinding the occlusal enamel of 10 human third molars. The adhesive systems (n = 5 each) Single Bond and Clearfil SE Bond were applied according to the manufacturers' instructions, and composite resin crowns (Z250) were constructed incrementally. After 24 h in distilled water at 37 degrees C, each tooth was longitudinally sectioned in both the x and y directions, under a cutting speed of 300 rpm, to obtain sticks with a cross-sectional area of 0.8 mm2. The sticks from each tooth were divided into 5 groups to be tested under crosshead speeds of 0.1, 0.5, 1.0, 2.0, and 4.0 mm/min. The fracture pattern was analyzed microscopically after debonding (400X). A two-way ANOVA having adhesive system (2 levels) and testing speed (5 levels) as main factors was used to compare the microtensile bond strengths. RESULTS: The two-way ANOVA did not detect statistically significant differences either for the interaction (p = 0.80) or for the crosshead speed (p = 0.69). Differences were only detected between adhesive systems (p = 0.001), with Single Bond showing higher bond strength values than Clearfil SE Bond. CONCLUSION: The crosshead speed used for microtensile bond strength tests does not influence the bond strength values, regardless of the adhesive system employed.

In vitro microleakage of packable composites in Class II restorations.

OBJECTIVES: To evaluate the microleakage in Class II resin restorations at different margins and the polymerization shrinkage of the composites used. METHOD AND MATERIALS: Four standardized Class II (3 x 5 x 2 mm) cavities were prepared in 32 teeth. The sample had the gingival margin either 1 mm below or above the cementoenamel junction. Teeth were divided and restored according to the following protocols: (1) Single Bond + P60; (2) Prime & Bond NT + Surefil; (3) Bond-1 + Alert; and (4) Prime & Bond 2.1 + TPH. After 7 days, the specimens were thermocycled (500 cycles between 5 to 55 degrees C with a 15-second dwell time), immersed in 0.5% methylene blue for 24 hours, sectioned, and evaluated (both surfaces) at the gingival margin by two examiners, using a 0 to 3 marginal infiltration score system. The polymerization shrinkage of the composites (n = 6) was evaluated by the disk deflective method. Microleakage data was evaluated by nonparametric repeated measures ANOVA. The percentage of polymerization shrinkage was evaluated by ANOVA and Tukey's test. RESULTS: Only protocol 3 showed a significant difference between enamel and cementum margin. No difference was detected among the protocols in the enamel margin. Only protocol 1 provided a good seal in the cementum margin. All packable composites showed lower polymerization shrinkage than the hybrid tested. CONCLUSION: All protocols are able to prevent dye penetration in enamel margins; however, protocol 1 is preferable to reduce the microleakage in the cementum margin. The packable composites showed lower polymerization shrinkage compared to the hybrid resin.

Microleakage of a packable composite associated with different materials.

The aim of this in vitro study was to evaluate the extent of marginal leakage with class II composite resin restorations associated with different materials. Twenty extracted sound molars were disinfected and stored in 0.9% saline solution. Four standardized class II cavities were prepared in each tooth, with the gingival margin 1 mm below the cementum-enamel junction. The teeth were then randomly divided into five groups of 16 restorations each: 1) Prime & Bond NT + Surefil; 2) Prime & Bond NT + Dyract Flow + Surefil; 3) Prime & Bond NT + Flow-it + Surefil; 4) Prime & Bond NT + Dyract AP + Surefil; and 5) Fuji II LC + Prime & Bond NT + Surefil. After a storage time of seven days, the restorations were finished and polished. Then specimens were submitted to thermocycling (500 cycles, 5 degrees-55 degrees C, 15 s-dwell time) and immersed in 0.5% methylene blue solution for 24 hours. They were washed and vertically sliced through the middle of the restoration. Both surfaces were evaluated in the gingival margin and one score (0-3) was assigned under a stereomicroscope (40x magnification) by two examiners. The frequency of the scores was evaluated by Kruskal-Wallis and Mann-Whitney tests for pairwise comparisons. None of the associations prevented dye penetration. The statistical analysis showed similar dye penetration among groups 1, 2, 3 and 4 (p > 0.05). The results of penetration in group 5 were significantly lower compared to the other groups (p < 0.05). It was concluded that the use of Fuji II LC as a base material led to the best sealing of the gingival margins based upon the lowest degree of microleakage observed.

Does the casting mode influence microstructure, fracture and properties of different metal ceramic alloys?

The aim of the present study was to evaluate the tensile strength, elongation, microhardness, microstructure and fracture pattern of various metal ceramic alloys cast under different casting conditions. Two Ni-Cr alloys, Co-Cr and Pd-Ag were used. The casting conditions were as follows: electromagnetic induction under argon atmosphere, vacuum, using blowtorch without atmosphere control. For each condition, 16 specimens, each measuring 25 mm long and 2.5 mm in diameter, were obtained. Ultimate tensile strength (UTS) and elongation (EL) tests were performed using a Kratos machine. Vickers Microhardness (VM), fracture mode and microstructure were analyzed by SEM. UTS, EL and VM data were statistically analyzed using ANOVA. For UTS, alloy composition had a direct influence on casting condition of alloys (Wiron 99 and Remanium CD), with higher values shown when cast with Flame/Air (p < 0.05). The factors 'alloy" and 'casting condition" influenced the EL and VM results, generally presenting opposite results, i.e., alloy with high elongation value had lower hardness (Wiron 99), and casting condition with the lowest EL values had the highest VM values (blowtorch). Both factors had significant influence on the properties evaluated, and prosthetic laboratories should select the appropriate casting method for each alloy composition to obtain the desired property.

Characterization of aqueous silver nitrate solutions for leakage tests.

OBJECTIVES: To determine the pH over a period of 168 h and the ionic silver content in various concentrations and post-preparation times of aqueous silver nitrate solutions. Also, the possible effects of these factors on microleakage test in adhesive/resin restorations in primary and permanent teeth were evaluated. MATERIAL AND METHODS: A digital pHmeter was used for measuring the pH of the solutions prepared with three types of water (purified, deionized or distilled) and three brands of silver nitrate salt (Merck, Synth or Cennabras) at 0, 1, 2, 24, 48, 72, 96 and 168 h after preparation, and storage in transparent or dark bottles. Ionic silver was assayed according to the post-preparation times (2, 24, 48, 72, 96, 168 h) and concentrations (1, 5, 25, 50%) of solutions by atomic emission spectrometry. For each sample of each condition, three readings were obtained for calculating the mean value. Class V cavities were prepared with enamel margins on primary and permanent teeth and restored with the adhesive systems OptiBond FL or OptiBond SOLO Plus SE and the composite resin Filtek Z-250. After nail polish coverage, the permanent teeth were immersed in 25% or 50% AgNO3 solution and the primary teeth in 5% or 50% AgNO3 solutions for microleakage evaluation. ANOVA and the Tukey's test were used for data analyses (α=5%). RESULTS: The mean pH of the solutions ranged from neutral to alkaline (7.9±2.2 to 11.8±0.9). Mean ionic silver content differed depending on the concentration of the solution (4.75±0.5 to 293±15.3 ppm). In the microleakage test, significant difference was only observed for the adhesive system factor (p=0.000). CONCLUSIONS: Under the tested experimental conditions and based on the obtained results, it may be concluded that the aqueous AgNO3 solutions: have neutral/alkaline pH and service life of up to 168 h; the level of ionic silver is proportional to the concentration of the solution; even at 5% concentration, the solutions were capable of indicating loss of marginal seal in the composite restorations; the 3-step conventional adhesive system had better performance regarding microleakage in enamel on primary and permanent teeth.

Effect of Fluoride and Simplified Adhesive Systems on the Bond Strength of Primary Molars and Incisors

The aim of this study was evaluate in vitro the influence of simplified adhesive systems (etch-and-rinse and self-etching) and 1.23% acidulated phosphate fluoride (APF) on the microshear bond strength (μ-SBS) of composite resins on primary molars and incisors. Forty primary molars and forty incisors vestibular enamel was treated with either the self-etching Clearfil SE Bond (CSE, Kuraray) or etch-and-rinse Adper Single Bond 2 (SB2, 3M/ESPE) adhesive system. Each group was subdivided based on the prior treatment of the enamel with or without the topical application of 1.23% APF. Thereafter, matrices were positioned and filled with composite resin and light cured. After storage in distilled water at 37±1°C for 24 h, the specimens were submitted to μ-SBS in a universal testing machine. Kruskal-Wallis and Mann-Whitney tests (p<0.05) showed that the prior application of 1.23% APF led to a significant reduction in bond strength. The type of adhesive exerted no significant influence bond strength. In the inter-group analysis, however, significantly bond strength reduction was found for the incisors when CSE was employed with APF. Adhesive failure was the most common type of fracture. The bond strength was affected by the prior application of 1.23% APF and type of tooth.

O objetivo deste estudo foi avaliar a influência dos sistemas adesivos simplificados (condicionamento ácido total e auto-condicionante) e fluorfosfato acidulado a 1,23% (FFA) na resistência de união ao microcisalhamento (μ-RUC) de resinas compostas em molares e incisivos decíduos. O esmalte vestibular de quarenta molares e quarenta incisivos decíduos foi tratado com Clearfil SE Bond (CSE, Kuraray) ou Adper Single Bond 2 (SB2, 3M/ESPE). Cada grupo foi subdividido com base no tratamento prévio do esmalte com ou sem aplicação tópica de FFA a 1,23%. Em seguida, matrizes foram posicionadas e preenchidas com resina composta e posterior fotopolimerização. Depois da armazenagem em água destilada a 37±1 °C por 24 h, os espécimes foram submetidos ao μ-RUC em uma máquina de ensaio universal. Teste Kruskal-Wallis e Mann-Whitney (p<0,05) mostraram que a aplicação prévia de FFA a 1,23% levou a uma redução significativa na resistência de união. O tipo de adesivo não exerceu influência significativa na resistência de união. Na análise intergrupos, entretanto, redução significativa na resistência de união foi encontrada para os incisivos quando CSE foi empregado sem FFA. Falha adesiva foi o tipo de fratura mais comum. A resistência de união foi afetada pela aplicação de FFA a 1,23% e tipo de dente.

Eighteen-month bracket survival rate: conventional versus self-etch adhesive.

The aim of this study was to evaluate, over an 18-month period, the clinical performance of a self-etch adhesive [Transbond Plus Self Etching Primer (SEP), 3M Unitek] compared with a conventional adhesive that employs the etch-and-rinse approach (Transbond XT, 3M Unitek). One operator, using the straight-wire technique, bonded 567 metallic brackets to the teeth of 30 patients (age range 12-18 years) in a way that patients acted as self-control. The brackets were bonded following the manufacturers' instructions except for the fact that the self-etch system was brushed for a longer time than recommended (10-15 seconds) since previous investigations have reported that prolonged application times can improve the bonding efficacy of self-etch systems to enamel. The failure modes were visually classified into: adhesive-enamel, adhesive-bracket, and cohesive failure. The survival rates of the brackets were estimated by Kaplan-Meier and log-rank test (P < 0.05). The failure rates of the self-etch and conventional adhesives were 15.6 and 17.6 per cent, respectively. No significant differences in the survival rate were observed between the materials (P > 0.05). Most of the failures were cohesive and at the adhesive-enamel interface. There was no difference in the fracture debonding mode. These findings indicate that Transbond Plus SEP can be safely used for orthodontic brackets since the survival rates are similar to the conventional Transbond XT.

Effect of ZOE temporary restoration on resin-dentin bond strength using different adhesive strategies.

STATEMENT OF THE PROBLEM: Eugenol is a radical scavenger that inhibits the polymerization of resin materials. Little is known about the effect of a eugenol-containing temporary restorative material on the resin-dentin bond strength of adhesive systems that partially dissolves and modifies the smear layer. PURPOSE OF THE STUDY: The aim of this study was to evaluate the effect of eugenol-containing temporary restoration (zinc oxide eugenol [ZOE]) on the resin-dentin microshear bond strength of etch-and-rinse and self-etch adhesives. MATERIAL AND METHODS: The roots of 18 human molars were removed and the crowns of the teeth were transversally sectioned into two halves. The dentin surfaces were embedded in acrylic resin. Half of the samples were stored while the remaining specimens were restored with eugenol-containing temporary restoration. After 24 hours, the ZOE restoration was mechanically removed and dentin surfaces were ultrasonically cleaned. Dentin surfaces were treated with one of the following adhesives: Single Bond, Clearfil SE, and iBond. Six cylinders of Z250 (0.5 mm high and 0.75 mm in diameter) were applied to each bonded dentin surface using a tygon tube. After storage for 24 hours, the specimens were subjected to micro-shear testing. The data was subjected to a two-way analysis of variance and Tukey's test (alpha=0.05). RESULTS: Similar bond strength values were obtained for Single Bond (p=0.48) either in the control or in the ZOE-treated group. For both self-etch systems, the bond strength in the ZOE-treated group was statistically lower than the control group (p < 0.01). CONCLUSIONS: Although the prior use of eugenol-containing temporary restoration (IRM) affects the resin-dentin bond strength of the etch-and-rinse Single Bond, a more pronounced reduction on bond strength was observed for the two self-etch systems evaluated (iBond, Clearfil SE Bond). CLINICAL SIGNIFICANCE Eugenol-containing provisional restorations (IRM) should not be used prior to the placement of resin restorations bonded with the two-step etch-and-rinse Single Bond and the self-etch adhesives systems iBond and Clearfil SE Bond.

Does the casting mode influence microstructure, fracture and properties of different metal ceramic alloys?

The aim of the present study was to evaluate the tensile strength, elongation, microhardness, microstructure and fracture pattern of various metal ceramic alloys cast under different casting conditions. Two Ni-Cr alloys, Co-Cr and Pd-Ag were used. The casting conditions were as follows: electromagnetic induction under argon atmosphere, vacuum, using blowtorch without atmosphere control. For each condition, 16 specimens, each measuring 25 mm long and 2.5 mm in diameter, were obtained. Ultimate tensile strength (UTS) and elongation (EL) tests were performed using a Kratos machine. Vickers Microhardness (VM), fracture mode and microstructure were analyzed by SEM. UTS, EL and VM data were statistically analyzed using ANOVA. For UTS, alloy composition had a direct influence on casting condition of alloys (Wiron 99 and Remanium CD), with higher values shown when cast with Flame/Air (p < 0.05). The factors 'alloy" and 'casting condition" influenced the EL and VM results, generally presenting opposite results, i.e., alloy with high elongation value had lower hardness (Wiron 99), and casting condition with the lowest EL values had the highest VM values (blowtorch). Both factors had significant influence on the properties evaluated, and prosthetic laboratories should select the appropriate casting method for each alloy composition to obtain the desired property.

Microinfiltração em restaurações classe V: análise da forma geométrica da cavidade e do tipo de adesivo / Microleakage of class V restorations: analyses of the cavity's geometric shape and type of adhesive

Introdução: o desenvolvimento de materiais e técnicas na Odontologia Restauradora tem como finalidade a obtenção de um confiável vedamento marginal, pois a microinfiltração ainda é um dos principais motivos de insucesso das restaurações. Objetivo: analisar "in vitro" o efeito da configuração cavitária e do tipo de sistema adesivo na microinfiltração em restaurações classe V, em esmalte, com resina composta. Material e método: foram selecionados 60 dentes bovinos, confeccionadas 30 cavidades na face vestibular de forma retangular e 30 de forma circular, sendo então divididos aleatoriamente em seis grupos, conforme a forma geométrica e o sistema adesivo utilizado: Magic Bond, Adper Single Bond 2 e Clearfil SE BOND. Os dentes foram restaurados com resina composta Z-350, utilizando um incremento, fotopolimerizado por 40 segundos, e feito o acabamento/polimento com disco Sof-Lex. Posteriormente, os dentes foram armazenados em água destilada à temperatura ambiente por sete dias e impermeabilizados com esmalte cosmético, deixando uma margem de 1 mm ao redor da restauração. Foram imersos, então, em solução aquosa de nitrato de prata a 50% por um período de duas horas no escuro, lavados com água corrente, colocados em solução reveladora por seis horas, lavados, seccionados no centro da restauração e as fatias foram analisadas na lupa estereoscópica de 25× de aumento. Os dados foram submetidos à análise estatística não paramétrica de Kruskal-Wallis (p < 0,05). Resultado: não houve diferença estatisticamente significante para ambos os fatores analisados (p = 0,233 e p = 0,158). Conclusão: a forma da cavidade não influenciou na microinfiltração; todos os adesivos comportaram-se de maneiras semelhantes quanto à microinfiltração.

Introduction: the development of materials and techniques in restorative dentistry aims to achieve a good marginal sealing because microleakage is still one of the main reasons for failure of restorations. Objective: To analyze "in vitro" the effect of cavity configuration and the type of adhesive system on microleakage of class V resin composite, in enamel. Material and method: 60 bovine teeth were selected, and 60 cavities were prepared on the buccal surface, 30 rectangular and 30 rounded shaped. They were randomly divided in 6 groups according to the geometric form and the bonding system used: Magic Bond, Adper Single Bond 2 and Clearfil SE BOND. The teeth were restored with Z-350 composite resin, using one increment, lightcured for 40 seconds and polished with a Sof-Lex disc. After that the teeth were stored in distilled water at room temperature for seven days and further sealed with nail varnish, leaving a 1 mm window around the restoration margin. They were then immersed in 50% aqueous silver nitrate solution for 2 hours in the dark, rinsed under tap water, placed in revealing solution for 6 hours under fluorescent light, washed, sectioned in the center of the restoration and the slices were viewed under stereoscopic glasses at 25× magnification. The data were submitted to Kruskal-Wallis non-parametric test (p < 0.05). Result: no statistically significant difference for either factor analyzed (p = 0.233 and p = 0.158) was observed. Conclusion: the cavity shape did not influence in microleakage; all the adhesives behaved in similar manners as to microleakage.

Evaluation of shear bond strength of orthodontic resin and resin modified glass ionomer cement on bonding of metal and ceramic brackets

Objective:The aim of this study was to evaluate the shear bond strength of orthodontic resin and resin-modified glass ionomer cement on bonding of metal and ceramic brackets. Material and methods: Forty bovine teeth were sectioned and embedded into PVC with chemically-cured acrylic resin. The labial surfaces were flattened and received prophylaxis with pumice and water. Then they were divided into four groups, according to the bonding material and the type of bracket. Group 1: metallic bracket + Transbond XT; Group 2: metallic bracket + Vitremer; Group 3: ceramic bracket + Transbond XT; Group 4: ceramic bracket + Vitremer. The bonding was performed according to the manufacturers’ recommendations. The shear bond strength test was conducted in a universal testing machine (TIRAtest 2420) at a crosshead speed of 0.5 mm/min. Then, the fractured surfaces were evaluated using a stereomicroscope (x15 magnification) to check the adhesive remnant index. Data was subjected to two-way ANOVA and Tukey’s test for pairwise comparisons (a = 0.05).Results: The results suggested a non-significant effect of the interaction (p > 0.97), and only main factors were significant (p = 0.0001). The bond strength of Transbond XT was statistically higher than Vitremer. Ceramic brackets obtained the highest values of resistance when compared with metal brackets. Conclusion: The ceramic brackets bonded with Transbond XT orthodontic resin have excellent bond strength results.

Microhardness of Ni-Cr alloys under different casting conditions.

This study evaluated the microhardness of Ni-Cr alloys used in fixed prosthodontics after casting under different conditions. The casting conditions were: (1-flame/air torch) flame made of a gas/oxygen mixture and centrifugal casting machine in a non-controlled casting environment; (2-induction/argon) electromagnetic induction in an environment controlled with argon; (3-induction/vacuum) electromagnetic induction in a vacuum environment; (4-induction/air) electromagnetic induction in a non-controlled casting environment. The 3 alloys used were Ni-Cr-Mo-Ti, Ni-Cr-Mo-Be, and Ni-Cr-Mo-Nb. Four castings with 5 cylindrical, 15 mm-long specimens (diameter: 1.6 mm) in each casting ring were prepared. After casting, the specimens were embedded in resin and polished for Vickers microhardness (VH) measurements in a Shimadzu HMV-2 (1,000 g for 10 s). A total of 5 indentations were done for each ring, one in each specimen. The data was subjected to two-way ANOVA and Tukey's multiple comparison tests (alpha = 0.05). The VH values of Ni-Cr-Mo-Ti (422 +/- 7.8) were statistically higher (p < 0.05) than those of Ni-Cr-Mo-Nb (415 +/- 7.6). The lowest VH values were found for Ni-Cr-Mo-Be (359 +/- 10.7). The VH values obtained in the conditions induction/argon and induction/vacuum were similar (p > 0.05) and lower than the values obtained in the conditions induction/air and flame/air torch (p < 0.05). The VH values in the conditions induction/air and flame/air were similar (p > 0.05). The microhardness of the alloys is influenced by their composition and casting method. The hardness of the Ni-Cr alloys was higher when they were cast with the induction/air and flame/air torch methods.