Evaluation of a technique for color correction in restoring anterior teeth.

OBJECTIVE: This study aimed to evaluate the ability of the proposed technique in producing restorations that exhibit mimesis with tooth structure and to define a restorative clinical protocol. MATERIALS AND METHODS: For this study a typodont was used. The right upper central incisor with Class IV lesion was restored with the layering technique (reference tooth, RT). For the left upper central incisor with Class IV lesion, six teeth were restored monochromatically (test teeth, TT), using DA3.5 (n = 3) and DA4 (n = 3) composite resins-resulting in six unsatisfactory color restorations. TT were divided into six groups depending on the color of unsatisfactory restoration and preparation depth. First, a preparation was realized on the labial surface with 0.5 mm, 0.7 mm or 1.0 mm of depth. A second preparation was then performed to reproduce the dentinal mamelons. Next, adhesive procedures were performed and the teeth restored. Opaque halo, opalescent halo and vestibular enamel were then reproduced by the addition of different composite resins. The RT and TT were photographed side by side in typodont to obtain six photographic prints. The photographs of the groups were subjected to visual evaluation by 120 volunteers via a questionnaire. Data were analyzed by the prevalence of answers, and Chi-square test was used to investigate the association between variables at .05 significance. Furthermore, ΔE of groups was evaluated in comparison RT. RESULTS: The results demonstrated that the moderate intensity restorations (DA3.5) with depths of 0.5 mm and 0.7 mm had the highest prevalence of acceptance. For severe intensity restorations (DA4), the preparation depth of 1.0 mm obtained better acceptance. CONCLUSIONS: The technique was able to modify the final color of Class IV restorations, producing satisfactory color restorations. CLINICAL SIGNIFICANCE: This technique can be used for color correction in cases of Class IV restorations, in situations where there is no time for immediate layered restoration, and as a restorative technique.

Marginal and internal fit of four-unit zirconia fixed dental prostheses based on digital and conventional impression techniques.

OBJECTIVES: The aim of this in vitro study was to evaluate the marginal and internal fit of CAD/CAM-generated four-unit zirconia fixed dental prostheses made with digital and conventional impressions. MATERIALS AND METHOD: A titanium master model was used. For group conventional impression (CI), 12 polyether impressions of the master model with Impregum(TM) were made. For group digital impression (DI), 12 digital impressions of the master model using Lava(TM) C.O.S. system were made. The replica technique was applied. The Mann-Whitney U statistical test was applied to detect statistical differences between the groups, in terms of marginal and internal fit. Face-by-face comparisons between groups were also carried out. RESULTS: Groups DI and CI presented mean marginal fit of 63.96 and 65.33 µm, respectively, and showed no statistically significant difference. Groups DI and CI presented significantly different internal fit with mean values of 58.46 and 65.94 µm, respectively. Group DI showed statistically significantly lower values for marginal and internal fit on premolar mesial face, and on molar distal and palatal faces. CONCLUSIONS: Frameworks fabricated from digital and conventional impressions showed clinically acceptable marginal fit. Frameworks fabricated from digital impression demonstrated better internal fit than ones fabricated from conventional impression. Reviewing each retainer face, digital impression showed better marginal and internal fit at the premolar mesial and molar distal faces. CLINICAL RELEVANCE: The results of this in vitro study show that digital impressions made with the Lava(TM) C.O.S. system and its digital workflow are suitable for fabricating four-unit zirconia frameworks, with regard to marginal and internal fit requirements.

Does operatory field isolation influence the performance of direct adhesive restorations?

PURPOSE: To evaluate the influence of different adhesive strategies (etch-and-rinse and self-etching adhesives) and type of field isolation (absolute or relative) on the clinical performance of restorations of noncervical carious lesions (NCCLs). MATERIALS AND METHODS: One hundred forty NCCLs were selected from 38 patients, according to previously established inclusion/exclusion criteria, and assigned to one of four groups (n = 35): etch-and-rinse/rubber-dam (ERR), etch-and-rinse/cotton roll (ERC), self-etching/rubber-dam (SER) and self-etching/cotton roll (SEC). The adhesive systems used were: Adper Single Bond 2 (3M ESPE) and Adper SE Plus (3M ESPE), with restorations made using a composite resin (Z350, 3M ESPE). Using the USPHS modified criteria, 140 restorations were evaluated by two calibrated examiners at 5 different times: immediately after placement, at 7 days, and 2, 6, and 12 months. In order to evaluate the presence of gingival recession after the use of the #212 rubber-dam clamp, the clinical crowns of the teeth from groups ERR and SER were measured at six different periods (baseline, immediately, and at 7 days, 2, 6, and 12 months). Data were subjected to McNemar's, chi-square, and Student's t-tests. RESULTS: Both adhesive strategies reduced tooth sensitivity beyond the second period of evaluation (7 days); tooth sensitivity disappeared after the third period of evaluation (2 months). There were no statistically significant differences between the adhesive techniques or isolation techniques, except for a Bravo score for marginal discoloration in group SEC at 6 months, which was significantly different from the other groups. The rubber-dam isolation technique was more uncomfortable for the patient and resulted in short-term gingival recession. CONCLUSION: No significant differences were found between the types of isolation or adhesive strategy in this clinical evaluation, with the exception of 2 restorations in group SEC that showed marginal discoloration, possibly due to inadequate enamel etching by the self-etching adhesive. Class V restorations perform equally well placed with or without rubber-dam.

Clinical performance of cervical restorations with desensitizing agents: 18-month clinical trial.

PURPOSE: To evaluate the clinical performance and postoperative sensitivity of noncarious Class V restorations with and without the use of a potassium oxalate-based desensitizing agent over a period of 18 months. MATERIALS AND METHODS: One hundred forty cervical lesions (40 patients) were selected and randomly divided into four groups: group 1 (G1) - teeth restored with the application of a potassium oxalate-based desensitizing agent (BisBlock) after acid etching and before the application of the adhesive Adper Single Bond 2; group 2 (G2) - teeth restored using the same adhesive system used in G1, without the use of any desensitizing agent; group 3 (G3) - similar to G1, but using the adhesive One-Step; group 4 (G4) - similar to G3, but without the application of BisBlock. All restorations were evaluated (double blind) after 1 week and 2, 6, 12, and 18 months according to the modified USPHS criteria. The McNemar and chi-square tests were used to analyze the results (p ≤ 0.05). RESULTS: There were no statistical differences between groups restored with or without the use of a desensitizing agent for postoperative sensitvity. After 18 months, retention rates proved to be statistically significantly lower for One-Step than Adper Single Bond 2. CONCLUSION: The use of potassium oxalate-based desensitizing agent did not decrease postoperative sensitivity when it was used under composite resin restorations.

Effect of multiple coats of ultra-mild all-in-one adhesives on bond strength to dentin covered with two different smear layer thicknesses.

PURPOSE: To evaluate the effect on bond strength of 1, 2, or 3 coats of two one-step self-etching adhesives on dentin covered with two different smear layer thicknesses. MATERIALS AND METHODS: Flat dentin surfaces from recently extracted third molars were wet ground with 60- or 600-grit SiC paper to produce smear layers of different thicknesses. Adper Easy Bond (3M ESPE) and Clearfil S3 Bond (Kuraray) were applied in 1, 2, or 3 consecutive coats after air drying each coat. ScotchBond Multi Purpose (3M) and Clearfil SE Bond (Kuraray) were used as controls. Composite resin crowns (Filtek Z250, 3M ESPE) were built up, stored for 24 h, and cut in x and y directions. Eight to twelve sticks (0.65 ± 0.05 mm2 of area) from the central area of each tooth were fractured in tension (0.5 mm/min). Sticks from each group were processed for interfacial micromorphological evaluation with SEM. RESULTS: Three-way ANOVA revealed a significant interaction between factors (p < 0.05). Tukey's post-hoc test showed that only when Adper Easy Bond was applied on dentin prepared with 600-grit SiC paper, microtensile bond strength was not significantly affected by the number of coatings. However, the effect of smear layer thickness was only statistically significant when the adhesives were applied in one coat, for both adhesives. When they were applied in two or three coats, smear layer thickness did not significantly affect bond strength (p > 0.05). CONCLUSIONS: The thickness of the smear layer affected the bond strength of both all-in-one adhesives. Additional coats can be beneficial to bond strength, especially with Clearfil S3 Bond.

Post-etching cleaning and resin/ceramic bonding: microtensile bond strength and EDX analysis.

PURPOSE: The aim of this study was to evaluate the microtensile bond strength of a resin composite bonded to two heat-pressed ceramics after performing different post-etching cleaning techniques. MATERIALS AND METHODS: Resin composite specimens were bonded to IPS Empress Esthetic (EE) and IPS Empress 2 (E2) heat-pressed ceramic disks after etching with 10% HF, surface cleaning, silanization and application of an unfilled hydrophobic resin. Resin composite specimens were fabricated using 4-mm (height) Tygon tubes of 0.8 mm diameter and bonded according to the post-etching cleaning technique employed (n = 30): no cleaning (NC); air-water spray for 30 s (AWS); 37% phosphoric acid etching for 30 s (PA); ultrasonic bath in distilled water for 5 min (UB); PA + UB (PAUB); application of a self-etching silane/bonding system Clearfil Silane Kit (CSK). The resin composite specimens were subjected to tensile tension at a crosshead speed of 0.5 mm/min. SEM observation and EDX analysis were performed for each group to determine elemental distribution in the samples. RESULTS: Two-way ANOVA with random effect showed statistically differences between subgroups for E2, in which E2NC only showed bond strength significantly lower than E2AWS and E2BU, as indicated by Student's t-test and a contrast method. For EE, subgroups EENC and EECSK groups showed statistically significant differences between each other and among the other post-etching cleaning technique groups (p < 0.05). CONCLUSION: Air-water spray may be used as a post-etching cleaning technique for both ceramics. The presence of residues did not significantly reduce the bond strength of resin composite to IPS Empress 2 ceramic.

Influence of Preparation Reconstruction on the Compressive Strength of CAD/CAM Ceramic Inlays.

The aim of this study was to evaluate whether the compressive strength of lithium dissilicate ceramic inlays is influenced by the substrate (dentin or composite resin build-up) and to compare it to nonrestored teeth. Thirty freshly extracted human maxillary third molars were selected and randomly ascribed to three groups (n=10). Standardized Class II MOD preparations were made (bucco-palatal width = 2/3 of the intercuspal width and 2/3 of the width at the tooth equator for the proximal boxes), varying the extension of the preparations (Group 2: preparation limited to tooth structure; Group 3: pulpal floor of the preparation rebuilt with composite resin, IPS Empress Direct, restored with lithium dissilicate CAD/CAM ceramic inlays (e.max CAD) and cemented with a resin cement (Variolink II)). All groups were subjected to compressive strength test (1mm/min crosshead speed). The results showed that the fracture strength of G1 (control group) was significantly higher than G2 and G3, while within these groups there were no statistically significant differences. Both groups restored with lithium dissilicate restorations did not reach the fracture strength of the sound teeth but were statistically equivalent and sufficient to withstand physiologic masticatory forces.

Effect of prolonged application times on the durability of resin-dentin bonds.

OBJECTIVES: To examine the effect of prolonged application time on the early and 3-year resin-dentin microtensile bond strength. METHODS: Water/ethanol (Single Bond [SB]) and acetone-based systems (One Step [OS]) were employed. A flat superficial dentin surface was exposed in third human molars by wet abrasion. The adhesives were applied to a delimited area of 52 mm2 on wet surfaces, for 40, 90, 150 and 300 s. Four teeth were assigned for each experimental condition. Composite build-ups were constructed incrementally. After water storage at 37 degrees C for 24 h, teeth were sectioned to obtain sticks with cross-sectional areas of 0.8 mm2 to be tested in tension (0.5 mm/min) either immediately (IM) or after 3 years (3Y) of water storage. The microtensile bond strength (microTBS) values were analyzed by two way repeated measures ANOVA and Tukey's test (alpha=0.05). RESULTS: The 90- and 150-s groups achieved the highest IM microTBS for OS (p<0.01). For SB, the highest IM microTBS values were observed after 300-s application (p<0.01). Significant decreases in microTBS were observed for OS in the 40- and 90-s groups after 3Y, except for the 150-s group. With regard to SB, after 3Y significant drops in microTBS values were observed for the 40- and 150-s groups, except for the 300-s group. SIGNIFICANCE: Prolonged application times can increase the immediate microTBS of two-step etch-and-rinse adhesive systems and make the adhesive layer more stable over time.

The influence of two home-applied bleaching agents on enamel microhardness: an in situ study.

OBJECTIVE: This in situ study evaluated the influence of two home-applied bleaching agents (10% carbamide peroxide and 7.5% hydrogen peroxide) on enamel microhardness. METHODS: Ninety enamel slabs were obtained from human third molars and baseline Knoop hardness measurements were recorded under a 50 g load for 5s. The specimens were attached to intra-oral devices delivered to 10 volunteers (donor of the teeth) who used the devices 24h/day throughout the experiment. The specimens were divided in three groups, two experimental and one control; in the last group, enamel slabs were not submitted to bleaching agents, but exposed only to the action of saliva. Two custom-made trays were made for each volunteer to recover the teeth and the appliances containing the enamel slabs. The bleaching regimen was 1h/day for 21 consecutive days. Subsequently, additional hardness measurements were recorded. RESULTS: The mean values of the baseline and final microhardness were: 348 and 352.2; 346.6 and 354.5; 342 and 340.8, for control, 10% carbamide peroxide and 7.5% hydrogen peroxide groups, respectively. One-way ANOVA of the microhardness mean values revealed no statistically significant differences among groups, the specimens treated with 7.5% hydrogen peroxide has shown a tendency (p=0.056) to microhardness decrease. CONCLUSIONS: Data suggested that the tested home bleaching agents did not change the superficial enamel microhardness.

Evaluation of the fracture resistance of premolars with extensive and medium cavity preparations restored with direct restoring systems.

CONTEXT: Studies have been conducted to measure the fracture resistance of restored teeth with the current restorative materials. However, most of those studies disregard the cavity size as an influencing variable. AIMS: To evaluate the fracture resistance of prepared and restored maxillary premolars with medium and large preparations. MATERIALS AND METHODS: Seventy superior and sound premolars were randomly divided: G1 (control) - sound tooth; G2, G3, and G4 received a Class II mesial-occlusal-distal (MOD) preparation with an occlusal box width 1/3 of the intercuspal distance, and were restored with Filtek Z350 XT, IPS Empress Direct, and Charisma Diamond, respectively; G5, G6, and G7 received a Class II MOD preparation with an occlusal box width 2/3 of the intercuspal distance, and were restored with Filtek Z350 XT, IPS Empress Direct, and Charisma Diamond, respectively. After storage in water, at 37°C, the specimens were subjected to a fracture test under compression in a universal testing machine where the loads were applied vertically and at a speed of 0.5 mm/min. STATISTICAL ANALYSIS USED: Data were analyzed with two-way ANOVA and Tukey's multiple comparison post hoc test (P < 0.05). RESULTS: G1 presented a fracture resistance significantly higher (P = 0.005) than any other experimental groups. Among the experimental groups, only G5 showed a significantly low fracture resistance (P = 0.019) when compared to the other groups. For the other resins, the change in intercuspal distance from 1/3 to 2/3 the intercuspal distance did not significantly reduce the fracture resistance (P > 0.05). CONCLUSIONS: The cavity preparation weakens the remaining tooth structure; however, its resistance could be partially restored using direct adhesive restorations.

Light irradiance through novel CAD-CAM block materials and degree of conversion of composite cements.

OBJECTIVE: To assess light irradiance (LI) delivered by two light-curing units (LCU's) and to measure the degree of conversion (DC) of three composite cements, when cured through different thicknesses of two novel CAD-CAM block materials. METHODS: 100-µm-thick films of a dual-curable composite cement (G-CEM LinkAce, GC), a light-curable flowable resin-based composite (RBC) (G-ænial Universal Flo, GC) and a micro-hybrid RBC (G-ænial Posterior, GC) were investigated as luting agents. Two 'polymer-ceramic' CAD-CAM blocks (Cerasmart, GC; Enamic, Vita Zahnfabrik) were sectioned in slabs with different thicknesses (1, 3 and 5mm). LI at the bottom of the specimens was measured using a calibrated spectrometer, while being light-cured through the CAD-CAM block slabs for 40s with a low- (±500mW/cm2) or high- (±1,600mW/cm2) irradiance LCU (n=5). After light-curing, micro-Raman spectra of the composite films were acquired to determine DC at 5min, 10min, 1h and 24h. LI data were statistically analyzed by Kruskal-Wallis followed by post-hoc comparisons, while a linear mixed-effect model was applied for the DC analysis. In addition, the CAD-CAM blocks ultrastructure was characterized upon argon-ion slicing using scanning transmission electron microscopy (STEM). Finally, light transmission (LT) through each CAD-CAM block material was assessed using a spectrophotometer. RESULTS: Curing-light attenuation and DC were significantly influenced by thickness and type of the overlying material. LCU only had a significant effect on DC of the micro-hybrid RBC. DC significantly increased over time for all composite cements. CAD-CAM block structural analysis revealed a relatively small and homogenous filler configuration (mean filler size of 0.2-0.5µm) for Cerasmart, while Enamic contained ceramic grains varying in shape and size (1-10µm), which were interconnected by the polymer-based network. LT was much higher at a wavelength range of 300-800nm for Cerasmart than for Enamic. SIGNIFICANCE: Light-curable composite cements can be cured through a restoration up to 2.7-mm thickness, depending on the kind of CAD-CAM material. A high-irradiance LCU only has a limited effect on the maximum thickness of the polymer-ceramic CAD-CAM material that can be cured through.

Biomechanical behavior of endodontically treated premolars using different preparation designs and CAD/CAM materials.

OBJECTIVES: To evaluate the effect of restoration design ('2.5-mm deep endocrown', '5-mm deep endocrown' or '5-mm deep post&crown') and CAD/CAM material type (composite or lithium disilicate glass-ceramic) on the load-to-failure of endodontically treated premolars in absence of any ferrule. METHODS: The crowns of 48 single-rooted premolars were cut and the roots were endodontically treated. Teeth were randomly divided into six groups (n=8); teeth in each group were restored using one of the two tested materials with standardized CAD/CAM fabricated endocrowns (with either 2.5-mm or 5-mm deep intra-radicular extension) or conventional crowns (5-mm deep post&crown). After cementation using luting composite, the specimens were immersed in distilled water and subjected to 1,200,000 chewing cycles with a load of 50N applied parallel to the long axis of the tooth (0°). After cyclic loading, a compressive load was applied at 45° to the tooth's long axis using a universal testing machine until failure. Load-to-failure was recorded (N) and the specimens were examined under a stereomicroscope with 3.5x magnification to determine the mode of failure. RESULTS: All specimens survived the 1,200,000 chewing cycles. A significant interaction between restoration design and CAD/CAM material was found using two-way ANOVA. In the '2.5-mm deep endocrown' groups, the composite achieved a significantly higher load-to-failure than the lithium disilicate glass-ceramic, while no differences between materials were found in the '5-mm deep endocrown' and '5-mm deep post&crown' groups. More unfavorable failures (root fractures) were observed for higher load-to-failure values. CONCLUSIONS: Only following a '2.5-mm deep endocrown' design, composite appeared more favorable than lithium disilicate glass-ceramic as crown material; this may be explained by their difference in elastic modulus. CLINICAL SIGNIFICANCE: Shallow endocrown preparations on premolars present less surface for adhesive luting and a difference in crown material becomes apparent in terms of load-to-failure. The use of a more flexible composite crown material appeared then a better option.

Influence of resin composite shade and location of the gingival margin on the microleakage of posterior restorations.

OBJECTIVE: The objective of this in vitro study was to evaluate the influence of resin composite shade and location of the gingival margin (enamel or dentin) on the microleakage of proximal restorations on posterior teeth. METHODS AND MATERIALS: Sixty freshly extracted human third molars were prepared with standardized Class II box-shaped cavities with proportional size and shape, with distal gingival margins located on the enamel and mesial gingival margins on dentin. The teeth were randomly divided into 6 groups according to resin shade (n=10): G1-Incisal; G2-A1; G3-A2; G4-A3; G5-A3.5; G6-A4. The cavities were restored with a total-etch 1-bottle adhesive system and microhybrid resin composites inserted in 4 increments, light cured for 20 seconds through the occlusal surface, then an additional 60 seconds for each surface. After 1 week of immersion in distilled water, the specimens were thermocycled (500 cycles, 5 degrees -55 degrees C, 30 seconds dwell time), sealed with nail polish and immersed in 0.5% basic fuschin solution for 24 hours. The restorations were sectioned longitudinally, and microleakage was evaluated using a 0-3 score scale. RESULTS: Data were subjected to Kruskal-Wallis and Wilcoxon tests at p<0.05. No statistically significant differences between groups were observed regarding the shade of resin composite (p=0.8570). When margins (enamel or dentin) were considered separately, statistically significant differences were observed between groups (p<0.0001), with enamel margins exhibiting lower degrees of microleakage. CONCLUSION: The variation of resin composite shades utilized in this study did not influence the microleakage of Class II restorations. However, the location of the gingival margin influenced the microleakage.

Dentin bond strengths of simplified adhesives: effect of dentin depth.

The objective of this study was to compare the shear bond strength of 3 simplified adhesive systems applied on shallow vs deep dentin. For superficial dentin, 30 human molars were sectioned with a diamond saw to expose dentin immediately below the dentoenamel junction. For deep dentin, 30 molars were sectioned 3 mm below the dentoenamel junction. The teeth were mounted, polished to 600-grit, and randomly assigned to 3 groups (n=10): Single Bonda and OptiBond Solo, total-etch adhesives, and Clearfil Liner Bond 2V, a self-etching primer adhesive. Adhesives were applied, the restorative material Filtek Z250 inserted in a No. 5 gelatin capsule, and light-cured. After 24 hours in water at 37 degrees C, shear bond strength was measured with an Instron at 5 mm/min. The data were analyzed with 2-way ANOVA and Duncan's post-hoc test. The results showed the following shear bond strengths (mean +/- SD in MPa): Single Bond/superficial dentin = 22.1 +/- 2.8; Single Bond/deep dentin = 14.2 +/- 7.0; OptiBond Solo/superficial dentin = 18.9 +/- 4.1; OptiBond Solo/deep dentin = 18.4 +/- 4.8; Clearfil Liner Bond 2V/superficial dentin = 21.0 +/- 7.4; Clearfil Liner Bond 2V/deep dentin = 17.6 +/- 5.9. There were no significant differences between mean shear bond strength for the factor "adhesive system" (P>.822). The Duncan's test showed that Single Bond resulted in higher shear bond strength on superficial dentin than on deep dentin. The mean shear bond strength for Clearfil Liner Bond 2V and OptiBond Solo were not influenced by dentin depth. When data were pooled for dentin depth, deep dentin resulted in statistically lower bond strengths than superficial dentin (P<.01). The influence of dentin depth on shear bond strength depends on the specific composition of the dentin adhesive.

Shear bond strength of acetone-based one-bottle adhesive systems.

The aim of this study was to assess the shear bond strength of four acetone-based one-bottle adhesive systems to enamel and dentin, and compare to that of an ethanol-based system used as control. Fifty human molars were bisected mesiodistally and the buccal and lingual surfaces were embedded in acrylic resin using PVC cylinders. The buccal surfaces were ground to obtain flat dentin surfaces, while the lingual surfaces were ground to obtain flat enamel surfaces. All specimens were polished up to 600-grit sandpapers and randomly assigned to 5 groups (n=20; 10 dentin specimens and 10 enamel specimens), according to the adhesive system used: One-Step (Bisco); Gluma One Bond (Heraeus Kulzer); Solobond M (Voco); TenureQuik w/F (Den-Mat) and OptiBond Solo Plus (Kerr) (control). Each adhesive system was applied according to the manufacturers' instructions. The respective proprietary hybrid composite was applied in a gelatin capsule (d=4.3 mm) and light-cured for 40 s. The specimens were tested in shear strength with an Instron machine at a crosshead speed of 5 mm/min. Bond strengths means were analyzed statistically by one-way ANOVA and Duncan's post-hoc (p< or =0.05). Shear bond strength means (MPa) (+/-SD) to enamel and dentin were: Enamel: One-Step=11.3(+/-4.9); Gluma One Bond=16.3(+/-10.1); Solobond M=18.9(+/-4.5); TenureQuik w/F=18.7(+/-4.5) and OptiBond Solo Plus=16.4(+/-3.9); Dentin: One-Step=6.4(+/-2.8); Gluma One Bond=3.0(+/-3.4); Solobond M=10.6(+/-4.9); TenureQuik w/F=7.8(+/-3.9) and OptiBond Solo Plus=15.1(+/-8.9). In enamel, the adhesive systems had statistically similar bond strengths to each other (p>0.05). However, the ethanol-based system (OptiBond Solo Plus) showed significantly higher bond strength to dentin than the acetone-based systems (p< or =0.0001). In conclusion, the solvent type (acetone or ethanol) had no influence on enamel bond strength, but had great influence on dentin bonding, which should be taken into account when choosing the adhesive system.

Evaluation of microtensile bond strength of self-etching adhesives on normal and caries-affected dentin.

The purpose of this study was to evaluate the µTBS (microtensile bond strength) of currently available self-etching adhesives with an experimental self-etch adhesive in normal and caries-affected dentin, using a portable hardness measuring device, in order to standardize dentin Knoop hardness. Normal (ND) and caries-affected dentin (CAD) were obtained from twenty human molars with class II natural caries. The following adhesive systems were tested: Mega Bond (MB), a 2-step self-etching adhesive; MTB-200 (MTB), an experimental 1-step self-etching adhesive (1-SEA), and two commercially available one-step self-etching systems, G-Bond Plus (GB) and Adper Easy Bond (EB). MB-ND achieved the highest µTBS (p<0.05). The mean µTBS was statistically lower in CAD than in ND for all adhesives tested (p<0.05), and the 2-step self-etch adhesive achieved better overall performance than the 1-step self-etch adhesives.

In Vitro Fatigue Resistance of Teeth Restored With Bulk Fill versus Conventional Composite Resin.

The aim of this study was to compare the fatigue resistance of restored teeth with bulk fill composite resin, conventional composite resin with incremental insertion and unprepared sound teeth. Twenty-eight extracted maxillary premolars were selected and divided into 4 groups based on composite resin and insertion technique: control (C), conventional composite resin with incremental insertion (I) and bulk fill composite resin with three (BF3) or single increment (BF1). The restored specimens were submitted to fatigue resistance test with a 5 Hz frequency. An initial application of 5,000 sinusoidal load cycles with a minimum force of 50 N and a maximum force of 200 N was used. Next, were applied stages of 30,000 load cycles with the maximum force increasing gradually: 400, 600, 800, 1000, 1200 and 1400 N. The test was concluded when 185,000 load cycles were achieved or the specimen failed. The fatigue resistance data were recorded for comparison, using the Kaplan-Meier survival curve and analyzed by log-rank test at 0.05 significance. Fractures were classified based on the position of the failure - above or below the cementoenamel junction (CEJ). Statistical analysis of the Kaplan-Meier survival curve and log-rank test showed a significant difference between groups (p=0.001). The fracture analysis demonstrated that only 28.58% of failures were below the CEJ in group C, while for groups I, BF1 and BF3 they were 42.85%, 85.71% and 85.71%, respectively. Teeth restored with composite bulk fill in both techniques present similar fatigue resistance values compared with those restored with a conventional incremental insertion of composite, while the fatigue strength values of unprepared sound teeth were higher. Furthermore, unprepared sound teeth showed a lower percentage of fractures below the CEJ.

Effect of prolonged application times on resin-dentin bond strengths.

PURPOSE: To evaluate the cumulative loss of mass of two-step solvent-based adhesives, examine the effect of prolonged application time on the resin-dentin microtensile bond strength (microTBS), and correlate the microTBS with the evaporation rate of adhesive systems. MATERIALS AND METHODS: An ethanol/water based (Single Bond: SB) and an acetone-based system (One Step: OS) were employed. Approximately 16 microl of each product was transferred to a small glass container and placed in an analytical balance. The cumulative loss of mass (CLM) was determined in every minute for 5 min to the nearest 0.0001 mg and again after 20 min (n = 4). For the microTBS test, a flat superficial dentin surface was exposed in 24 human third molars by wet abrasion. The adhesives were applied to a delimited area of 52 mm2 on wet surfaces, for 40, 90, and 150 s. Four teeth were assigned to each experimental group. Composite crowns were constructed incrementally. After storage in water at 37 degrees C for 24 h, teeth were sectioned to obtain sticks with cross-sectional areas of 0.8 mm2 to be tested in tension (0.5 mm/min). The CLM (%) for both adhesives was compared using a Student-t test at each minute (alpha = 0.05). The microTBS values were analyzed by two-way ANOVA and Tukey's test (alpha = 0.05). RESULTS: The CLM for OS was higher than for SB during the first 5 min, but these values were only statistically different at minutes 3, 4, and 5 (p < 0.05). A CLM of approximately 50% was observed for both adhesive systems after 20 min. The factor application duration and the interaction between application duration and adhesive were significant (p < 0.05). The increase in the application duration led to an increase in microTBS for both systems; however, the differences were only statistically significant for OS over the 150 s period (p < 0.05). A strong correlation was found between the microTBS and the cumulative loss of mass of adhesives. CONCLUSION: Prolonged application times can increase the resin-dentin microTBS of two-step adhesive systems, but the application duration is dependent on the solvent present in the bonding system.

Effect of solvent type on microtensile bond strength of a total-etch one-bottle adhesive system to moist or dry dentin.

This study evaluated the effect of organic solvent (acetone or ethanol) on the microtensile bond strengths (MTBS) of an adhesive system applied to dry and moist dentin. Sixteen extracted human third molars were ground to expose a flat occlusal dentin surface and acid etched for 20 seconds (20% phosphoric acid gel, Gluma Etch 20 Gel, Heraeus/Kulzer). After rinsing the acid etchant, an ethanol-based one-bottle adhesive system was applied to the mesial half of the occlusal dentin surface. An acetone-based, one-bottle adhesive system was applied to the distal half of the ground dentin surface. The teeth were randomly assigned to groups. In Group 1, the etched dentin was thoroughly air dried and an ethanol-based one-bottle adhesive system was applied (Gluma Comfort Bond, Heraeus/Kulzer) (GCB). In Group 2, the etched dentin was thoroughly air dried and an acetone-based one-bottle adhesive system was applied (Gluma One Bond, Heraeus/Kulzer)(GOB). In Group 3, excess moisture was removed after acid etching, leaving a moist dentin surface and a one-bottle ethanol-based adhesive was applied (Gluma Comfort Bond). In Group 4, excess moisture was removed after acid etching, leaving a moist dentin surface and an acetone-based adhesive was applied (Gluma One Bond). A hybrid resin composite (Venus, Heraeus/Kulzer) was applied to the bonded surface in four 1-mm increments and light cured according to manufacturer's directions. The specimens were then sectioned with a slow-speed diamond saw in two perpendicular directions to obtain sticks with a cross-section of 0.5 +/- 0.05 mm2. The microtensile bond strength (MTBS) test was performed with a Bencor device in an Instron machine at a crosshead speed of 0.5 mm/minute. The data were subjected to a two-way ANOVA and Scheffé Post hoc test (p < 0.05). The experimental MTBS measured for dry dentin were Group 1 = 37.0 +/- 10.6 and Group 2 = 34.7 +/- 9.0 in MPa (mean +/- SD); and on moist dentin, Group 3 = 50.7 +/- 11.0 and Group 4 = 38.5 +/- 10.5 in MPa (mean +/- SD). The ethanol based adhesives resulted in higher MTBS than acetone-based adhesive (p < 0.008) and bonding to moist dentin resulted in higher MTBS (p < 0.001). GCB applied on moist dentin resulted in statistically higher bond strengths than the other groups. The highest MTBS were achieved with the use of an ethanol-based adhesive to moist dentin.

Dentin bond strength of self-etching primers/adhesives.

This study compared the shear bond strengths (SBS) to dentin achieved with six self-etching systems and one total-etch one-bottle adhesive system. Seventy freshly extracted bovine incisors were mounted in acrylic molds and the facial surfaces ground to expose middle dentin, which was polished by 600-grit sand paper. The incisors were randomly assigned to groups (n=10): Adper Prompt Self-Etch Adhesive, 3M-ESPE (ADP) and One-Up Bond F, Tokuyama (OU) as self-etching adhesives; AdheSE, Ivoclar-Vivadent (ADH), Clearfil SE Bond, Kuraray (SE), Optibond Solo Plus-Self-Etch, Kerr (OP) as self-etching primers, Tyrian SPE, BISCO (TY) as a self-priming etchant and Single Bond, 3M-ESPE (SB), a total-etch one-bottle adhesive served as a control. All adhesives were applied according to the manufacturers' instructions with the respective hybrid composites. The specimens were thermocycled for 500 cycles (5 degrees C to 55 degrees C), then loaded to failure in an Instron Universal Testing Machine at a crosshead speed of 0.5 mm/minute. Mean bond strengths were analyzed with one-way ANOVA, followed by a Duncan's post hoc test. SBS (mean +/- SD) were: ADH = 13.2 (+/- 5.3)b;ADP = 6.8 (+/- 4.4)c; OP = 18.2 (+/- 3.8)a; OU = 3.5 (+/- 1.5)c; SB = 12.2 (+/- 4.2)b; SE = 12.4 ( +/- 4.0)b; TY = 5.5 (+/- 1.4)c. Superscript letters indicate Duncan's homogeneous subsets. The self-etching adhesives OU and ADP and the self-priming etchant TY resulted in lower dentin SBS. OP resulted in the highest mean dentin SBS, while the other materials tested in this study (SE and ADH) presented similar dentin SBS to a total-etch one-bottle bonding system (SB).