A 24-month randomized clinical trial of a two- and three-step etch-and-rinse technique

Purpose This 24-month randomized paired tooth clinical study evaluated the performance of All Bond 3 used in the simplified (2-step) and full (3-step) versions Methods 33 patients, with at least two similar sized non-carious cervical lesions participated in this study A total of 66 restorations were placed, half using the 2-step All Bond 3 (AB3-2) and the other half using 3-step All Bond 3 (AB3-3) The restorations were placed incrementally using the composite resin Aelite The restorations were evaluated at baseline and after 6, 12 and 24 months following the modified USPHS criteria Statistical differences between the adhesive were tested using with McNemar`s test and clinical performance over time for each material with the Fisher`s exact test (alpha= 0 05) Results After 24 months, six AB3-2 and four AB3-3 were rated as bravo for marginal discoloration but did not differ from each other significantly (P> 0 05) The retention rates at 24 months of AB3-2 and AB3-3 were 90 9% and 97 0%, respectively (P> 0 05) (Am J Dent 2010,23 231-236)

Fatigue life and failure modes of crowns systems with a modified framework design

Objectives: To evaluate the effect of framework design on the fatigue life and failure modes of metal ceramic (MC, Ni-Cr alloy core, VMK 95 porcelain veneer), glass-infiltrated alumina (ICA, In-Ceram Alumina/VM7), and veneered yttria-stabilized tetragonal zirconia polycrystals (Y-TZP, IPSe.max ZirCAD/IPS e.max,) crowns. Methods: Sixty composite resin tooth replicas of a prepared maxillary first molar were produced to receive crowns systems of a standard (MCs, ICAs, and Y-TZPs, n = 10 each) or a modified framework design (MCm, ICAm, and Y-TZPm, n = 10 each). Fatigue loading was delivered with a spherical steel indenter (3.18 mm radius) on the center of the occlusal surface using r-ratio fatigue (30-300 N) until completion of 10(6) cycles or failure. Fatigue was interrupted every 125,000 cycles for damage evaluation. Weibull distribution fits and contour plots were used for examining differences between groups. Failure mode was evaluated by light polarized and SEM microscopy. Results: Weibull analysis showed the highest fatigue life for MC crowns regardless of framework design. No significant difference (confidence bound overlaps) was observed between ICA and Y-TZP with or without framework design modification. Y-TZPm crowns presented fatigue life in the range of MC crowns. No porcelain veneer fracture was observed in the MC groups, whereas ICAs presented bulk fracture and ICAm failed mainly through the veneer. Y-TZP crowns failed through chipping within the veneer, without core fractures. Conclusions: Framework design modification did not improve the fatigue life of the crown systems investigated. Y-TZPm crowns showed comparable fatigue life to MC groups. Failure mode varied according to crown system. (C) 2010 Elsevier Ltd. All rights reserved.

Substantivity of chlorhexidine to human dentin

Objectives. To better comprehend the role of CHX in the preservation of resin-dentin bonds, this study investigated the substantivity of CHX to human dentin. Material and methods. Dentin disks (n = 45) were obtained from the mid-coronal portion of human third molars. One-third of dentin disks were kept mineralized (MD), while the other two-thirds had one of the surfaces partially demineralized with 37% phosphoric acid for 15 s (PDD) or they were totally demineralized with 10% phosphoric acid (TDD). Disks of hydroxyapatite (HA) were also prepared. Specimens were treated with: (1) 10 mu L of distilled water (controls), (2) 10 mu L of 0.2% chlorhexidine diacetate (0.2% CHX) or (3) 10 mu L of 2% chlorhexidine diacetate (2% CHX). Then, they were incubated in 1 mL of PBS (pH 7.4, 37 degrees C). Substantivity was evaluated as a function of the CHX-applied dose after: 0.5 h, 1 h, 3 h, 6 h, 24 h, 168 h (1 week), 672 h (4 weeks) and 1344 h (8 weeks) of incubation. CHX concentration in eluates was spectrophotometrically analyzed at 260 nm. Results. Significant amounts of CHX remained retained in dentin substrates (MD, PPD or TDD), independent on the CHX-applied dose or time of incubation (p < 0.05). High amounts of retained CHX onto HA were observed only for specimens treated with the highest concentration of CHX (2%) (p < 0.05). Conclusion. The outstanding substantivity of CHX to dentin and its reported effect on the inhibition of dentinal proteases may explain why CHX can prolong the durability of resin-dentin bonds. (C) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Mechanical Testing of Indirect Composite Materials Directly Applied on Implant Abutments

Purpose: To test the strength to failure and fracture mode of three indirect composite materials directly applied onto Ti-6Al-4V implant abutments vs cemented standard porcelain-fused-to-metal (PFM) crowns. Materials and Methods: Sixty-four locking taper abutments were randomly allocated to four groups and were cleaned in ethanol in an ultrasonic bath for 5 min. After drying under ambient conditions, the abutments were grit blasted and a custom 4-cusp molar crown mold was utilized to produce identical crowns (n = 16 per group) of Tescera (Bisco), Ceramage (Shofu), and Diamond Crown (DRM) according to the manufacturer`s instructions. The porcelain-fused-to-metal crowns were fabricated by conventional means involving the construction and a wax pattern and casting of a metallic coping followed by sintering of increasing layers of porcelain. All crowns were loaded to failure by an indenter placed at one of the cusp tips at a 1 mm/min rate. Subsequently, fracture analysis was performed by means of stereomicroscopy and scanning electron microscopy. One-way ANOVA at 95% level of significance was utilized for statistical analysis. Results: The single load to failure (+/- SD) results were: Tescera (1130 +/- 239 N), Ceramage (1099 +/- 257 N), Diamond Crown (1155 +/- 284 N), and PFM (1081 +/- 243 N). Stereomicroscopy analysis showed two distinct failure modes, where the loaded cusp failed either with or without abutment/metallic coping exposure. SEM analysis of the fractures showed multiple crack propagation towards the cervical region of the crown below a region of plastic deformation at the indenter contact region. Conclusion: The three indirect composites and PFM systems fractured at loads higher than those typically associated with normal occlusal function. Although each material had a different composition and handling technique, no significant differences were found concerning their single load to fracture resistance among composite systems and PFM.

Monolithic CAD/CAM Lithium Disilicate Versus Veneered Y-TZP Crowns: Comparison of Failure Modes and Reliability After Fatigue

Purpose: The aim of this research was to evaluate the fatigue behavior and reliability of monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) lithium disilicate and hand-layer-veneered zirconia all-ceramic crowns. Materials and Methods: A CAD-based mandibular molar crown preparation, fabricated using rapid prototyping, served as the master die. Fully anatomically shaped monolithic lithium disilicate crowns (IPS e.max CAD, n = 19) and hand-layer-veneered zirconia-based crowns (IPS e.max ZirCAD/Ceram, n = 21) were designed and milled using a CAD/CAM system. Crowns were cemented on aged dentinlike composite dies with resin cement. Crowns were exposed to mouth-motion fatigue by sliding a WC-indenter (r = 3.18 mm) 0.7 mm lingually down the distobuccal cusp using three different step-stress profiles until failure occurred. Failure was designated as a large chip or fracture through the crown. If no failures occurred at high loads (> 900 N), the test method was changed to staircase r ratio fatigue. Stress level probability curves and reliability were calculated. Results: Hand-layer-veneered zirconia crowns revealed veneer chipping and had a reliability of < 0.01 (0.03 to 0.00, two-sided 90% confidence bounds) for a mission of 100,000 cycles and a 200-N load. None of the fully anatomically shaped CAD/CAM-fabricated monolithic lithium disilicate crowns failed during step-stress mouth-motion fatigue (180,000 cycles, 900 N). CAD/CAM lithium disilicate crowns also survived r ratio fatigue (1,000,000 cycles, 100 to 1,000 N). There appears to be a threshold for damage/bulk fracture for the lithium disilicate ceramic in the range of 1,100 to 1,200 N. Conclusion: Based on present fatigue findings, the application of CAD/CAM lithium disilicate ceramic in a monolithic/fully anatomical configuration resulted in fatigue-resistant crowns, whereas hand-layer-veneered zirconia crowns revealed a high susceptibility to mouth-motion cyclic loading with early veneer failures. Int J Prosthodont 2010; 23: 434-442.

Effect of repeated cycles of chemical disinfection on the roughness and hardness of hard reline acrylic resins

Objective: The aim of this study was to assess the effect of repeated cycles of five chemical disinfectant solutions on the roughness and hardness of three hard chairside reliners. Methods: A total of 180 circular specimens (30 mm x 6 mm) were fabricated using three hard chairside reliners (Jet; n = 60, Kooliner; n = 60, Tokuyama Rebase II Fast; n = 60), which were immersed in deionised water (control), and five disinfectant solutions (1%, 2%, 5.25% sodium hypochlorite; 2% glutaraldehyde; 4% chlorhexidine gluconate). They were tested for Knoop hardness (KHN) and surface roughness (mu m), before and after 30 simulated disinfecting cycles. Data was analysed by the factorial scheme (6 x 2), two-way analysis of variance (anova), followed by Tukey`s test. Results: For Jet (from 18.74 to 13.86 KHN), Kooliner (from 14.09 to 8.72 KHN), Tokuyama (from 12.57 to 8.28 KHN) a significant decrease in hardness was observed irrespective of the solution used on all materials. For Jet (from 0.09 to 0.11 mu m) there was a statistically significant increase in roughness. Kooliner (from 0.36 to 0.26 mu m) presented a statistically significant decrease in roughness and Tokuyama (from 0.15 to 0.11 mu m) presented no statistically significant difference after 30 days. Conclusions: This study showed that all disinfectant solutions promoted a statistically significant decrease in hardness, whereas with roughness, the materials tested showed a statistically significant increase, except for Tokuyama. Although statistically significant values were registered, these results could not be considered clinically significant.

Fatigue and damage accumulation of veneer porcelain pressed on Y-TZP

Objectives: This study compared the reliability and fracture patterns of zirconia cores veneered with pressable porcelain submitted to either axial or off-axis sliding contact fatigue. Methods: Forty-two Y-TZP plates (12 mm x 12 mm x 0.5 mm) veneered with pressable porcelain (12 mm x 12 mm x 1.2 mm) and adhesively luted to water aged composite resin blocks (12 mm x 12 mm x 4 mm) were stored in water at least 7 days prior to testing. Profiles for step-stress fatigue (ratio 3:2:1) were determined from single load to fracture tests (n = 3). Fatigue loading was delivered on specimen either on axial (n = 18) or off-axis 30 degrees angulation (n = 18) to simulate posterior tooth cusp inclination creating a 0.7 mm slide. Single load and fatigue tests utilized a 6.25 mm diameter WC indenter. Specimens were inspected by means of polarized-light microscope and SEM. Use level probability Weibull curves were plotted with 2-sided 90% confidence bounds (CB) and reliability for missions of 50,000 cycles at 200 N (90% CB) were calculated. Results: The calculated Weibull Beta was 3.34 and 2.47 for axial and off-axis groups, respectively, indicating that fatigue accelerated failure in both loading modes. The reliability data for a mission of 50,000 cycles at 200 N load with 90% CB indicates no difference between loading groups. Deep penetrating cone cracks reaching the core-veneer interface were observed in both groups. Partial cones due to the sliding component were observed along with the cone cracking for the off-axis group. No Y-TZP core fractures were observed. Conclusions: Reliability was not significantly different between axial and off-axis mouth-motion fatigued pressed over Y-TZP cores, but incorporation of sliding resulted in more aggressive damage on the veneer. (C) 2009 Elsevier Ltd. All rights reserved.

Transdentinal protective role of sodium ascorbate against the cytopathic effects of H(2)O(2) released from bleaching agents

Objectives. The objectives of this study were to evaluate the transdentinal cytotoxicity of 10% and 16% carbamide peroxide gel (CP), as well as the ability of the antioxidant, 10% sodium ascorbate (SA), to protect the odontoblasts in culture. Study design. Human dentin discs of 0.5-mm thickness were obtained and were placed into artificial pulp chambers. MDPC-23 odontoblastlike cells were seeded on pulp surface of the discs and the following groups were established: G1-No Treatment (control), G2-10% SA/6hs, G3-10%/CP6hs, G4-10%SA/6hs+10%CP/6hs, G5-16%CP/6hs, and G6-10%SA/6hs+16%CP/6hs. The cell viability was measured by the MTT assay. Results. In groups where 16% CP was used, decreased cell viability was observed. Conversely, the application of 10% SA on the dentin discs, before the use of the CP, reduced the cytotoxic effects of these products on cells. Conclusions. The 16% CP cause a significant decrease in MDPC-23 cell viability and 10% SA was able to partially prevent the toxic effects of CP. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 109: e70-e76)

Influence of curing protocol on selected properties of light-curing polymers: Degree of conversion, volume contraction, elastic modulus, and glass transition temperature

Objectives. The purpose of this study was to investigate the effect of light-curing protocol on degree of conversion (DC), volume contraction (C), elastic modulus (E), and glass transition temperature (T(g)) as measured on a model polymer. It was a further aim to correlate the measured values with each other. Methods. Different light-curing protocols were used in order to investigate the influence of energy density (ED), power density (PD), and mode of cure on the properties. The modes of cure were continuous, pulse-delay, and stepped irradiation. DC was measured by Raman micro-spectroscopy. C was determined by pycnometry and a density column. E was measured by a dynamic mechanical analyzer (DMA), and T(g) was measured by differential scanning calorimetry (DSC). Data were submitted to two-and three-way ANOVA, and linear regression analyses. Results. ED, PD, and mode of cure influenced DC, C, E, and T(g) of the polymer. A significant positive correlation was found between ED and DC (r = 0.58), ED and E (r = 0.51), and ED and T(g) (r = 0.44). Taken together, ED and PD were significantly related to DC and E. The regression coefficient was positive for ED and negative for PD. Significant positive correlations were detected between DC and C (r = 0.54), DC and E (r = 0.61), and DC and T(g) (r = 0.53). Comparisons between continuous and pulse-delay modes of cure showed significant influence of mode of cure: pulse-delay curing resulted in decreased DC, decreased C, and decreased T(g). Influence of mode of cure, when comparing continuous and step modes of cure, was more ambiguous. A complex relationship exists between curing protocol, microstructure of the resin and the investigated properties. The overall performance of a composite is thus indirectly affected by the curing protocol adopted, and the desired reduction of C may be in fact a consequence of the decrease in DC. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The influence of storage condition and duration on the resistance to fracture of different fiber post systems

Purpose: To evaluate the effects of storage condition and duration on the resistance to fracture of different fiber post systems (and to morphologically assess the post structure before and after storage. Methods: Three types of fiber posts (DT Light Post, GC Post, FRC Postect Plus) were divided in different groups (n=12) according to the storage condition (dry at 37 degrees C; saline water at 37 degrees C; mineral oil at 37 degrees C and storage inside the roots of extracted human teeth immersed in saline water at 37 degrees C and duration (6, 12 months). A universal testing machine loading at a 90 degrees angle was employed for the three-point bending test. The test was carried out until fracture of the post. A 3-way ANOVA and Tukey`s test (alpha= 0.05) were used to compare the effect of the experimental factors on the fracture strength. Two posts of each group were observed before and after the storage using a scanning electron microscope. Results: Storage condition and post type had a significant effect on post fracture strength (P< 0.05). The interaction between these factors was significant (P< 0.05). Water storage significantly decreased the fracture strength, regardless of the post type and the storage duration. Storage inside roots, in oil, and at dry conditions did not significantly affect post fracture strength. SEM micrographs revealed voids between fibers and resin matrix for posts stored in water. Posts stored under the other conditions showed a compact matrix without porosities. (Am J Dent 2009;22:366-370).

Cytotoxic Effects of Different Concentrations of a Carbamide Peroxide Bleaching Gel on Odontoblast-Like Cells MDPC-23

This study evaluated the cytotoxic effects of a carbamide peroxide (CP) bleaching gel at different concentrations on odontoblast-like cells. Immortalized cells of the MDPC-23 cell line (30,000 cells/cm(2)) were incubated for 48 h. The bleaching gel was diluted in DMEM culture medium originating extracts with different CP concentrations. The amount (mu g/mL) of hydrogen peroxide (H(2)O(2)) released from each extract was measured by the leukocrystal violet/horseradish peroxidase enzyme assay. Five groups (n = 10) were formed according to the CP concentration in the extracts: G1-DMEM (control); G2-0.0001 % CP (0.025 mu g/mL H(2)O(2)); G3-0.001% CP (0.43 mu g/mL H(2)O(2)); G4-0.01% CP (2.21 mu g/mL H(2)O(2)); and G5-0.1 % CP (29.74 mu g/mL H(2)O(2)). MDPC-23 cells were exposed to the bleaching gel extracts for 60 min and cell metabolism was evaluated by the NITT assay. Data were analyzed statistically by one-way ANOVA and Tukey`s test (alpha = 0.05). Cell morphology was examined by scanning electron microscopy. The percentages of viable cells were as follows: G1, 100%; G2, 89.41%; G3, 82.4%; G4, 61.5%; and G5, 23.0%. G2 and G3 did not differ significantly (p > 0.05) from G1. The most severe cytotoxic effects were observed in G3 and G4. In conclusion, even at low concentrations, the CP gel extracts presented cytotoxic effects. This cytotoxicity was dose-dependent, and the 0.1% CP concentration caused the most intense cytopathic effects to the MDPC-23 cells. (C) 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 9013: 907-912, 2009

Clinical evaluation of two packable posterior composites A five-year follow-up

Background. Research has suggested that packable resin-based composites inserted with a placement technique similar to amalgam condensation can reduce the sensitivity associated with posterior restorations. The authors evaluated the clinical performance, including associated sensitivity, of two packable composites in a randomized five-year clinical trial. Methods. A single operator randomly placed two restorations in each of 33 patients: one restoration consisting of Alert (Jeneric/Pentron, Wallingford, Conn.) and the other consisting of SureFil (Dentsply/Caulk, Milford, Del.). There were 30 Class I and 36 Class II restorations. Two independent evaluators evaluated the restorations by using modified U.S.; Public Health Service criteria. The authors analyzed data by means of the Fisher, chi(2) and McNemar tests at P < .05. Results. Of 60 restorations evaluated at five years, two Class II restorations (one SureFil, one Alert) failed. All other restorations received the highest score possible for sensitivity and vitality. The only difference between the composites at the five-year recall was the significantly better surface texture of SureFil. The authors observed significantly different scores between the baseline and at five years for marginal discoloration (Alert and SureFil), surface texture (Alert and SureFil) and color (SureFil). Conclusions. Both packable resin-based composites showed excellent durability during the five-year follow-up. Clinical Implications. The investigated resin-based composites are suitable for posterior restorations.

Effect of 2% Chlorhexidine Digluconate on the Bond Strength to Normal Versus Caries-affected Dentin

This study evaluated the effect of 2% chlorhexidine digluconate (CHX) used as a therapeutic primer on the long-term bond strengths of two etch-and-rinse adhesives to normal (ND) and caries-affected (CAD) dentin. Forty extracted human molars with coronal carious lesions, surrounded by normal dentin, were selected for this study. The flat surfaces of two types of dentin (ND and CAD) were prepared with a water-cooled high-speed diamond disc, then acidetched, rinsed and air-dried. In the control groups, the dentin was re-hydrated with distilled water, blot-dried and bonded with a three-step (Scotchbond Multi-Purpose-MP) or two-step (Single Bond 2-SB) etch-and-rinse adhesive. In the experimental groups, the dentin was rehydrated with 2% CHX (60 seconds), blot-dried and bonded with the same adhesives. Resin composite build-ups were made. The specimens were prepared for microtensile bond testing in accordance with the non-trimming technique, then tested either immediately or after six-months storage in artificial saliva. The data were analyzed by ANOVA/Bonferroni tests (alpha=0.05). CHX did not affect the immediate bond strength to ND or CAD (p>0.05). CHX treatment significantly lowered the loss of bond strength after six months as seen in the control bonds for ND (p<0.05), but it did not alter the bond strength of CAD (p>0.05). The application of NIP on CHX-treated ND or CAD produced bonds that did not change over six months of storage.

Microtensile vs Microshear Bond Strength of All-in-One Adhesives to Unground Enamel

Purpose To determine the bond strength to unground enamel of all in one adhesives in comparison with an etch and rinse system and to compare the reliability of microtensile and microshear methods in providing such measurements Materials and Methods The bonding procedure was performed on enamel of 64 extracted molars The tested all in one adhesives were Bond Force (Tokuyama), AdheSE One (Ivoclar Vivadent) and Xeno V (Dentsply) Prime&Bond NT (Dentsply) served as control Microtensile specimens were obtained from 4 teeth per group Twelve teeth per group were used for microshear testing Microtensile specimens that failed prior to testing were included in statistical calculations, they were assigned the lowest value measured in the respective group Failure modes were observed under light microscope and classified (cohesive within substrates, adhesive mixed) Statistically significant differences in bond strength were assessed among the adhesives within each testing method and between microshear and microtensile data for each adhesive Failure mode distributions were compared using the chi square test Results All in-one adhesives had similar microshear and microtensile bond strengths In both testing methods, the etch and rinse system achieved the strongest bond For all adhesives significantly higher bond strengths were measured with the microshear test In microtensile testing specimens bonded with the etch and rinse adhesive exhibited a significantly different distribution of failure modes The coefficients of variation were extremely high for microtensile bond strength data, particularly of all in one adhesives Conclusion The adhesive potential to intact enamel of recently introduced all in-one adhesives was inferior to that of an etch and rinse system When testing bond strength to enamel of all in one adhesives, microshear testing may be a more accurate method than microtensile

Evaluation of physicochemical properties of four root canal sealers

P>Aim To assess the physicochemical properties and the surface morphology of AH Plus, GuttaFlow, RoekoSeal and Activ GP root canal sealers. Methodology Five samples of each material were evaluated for setting time, dimensional alteration, solubility and radiopacity tests, according to ANSI/ADA Specification 57. A total of 50 mL of deionized distilled water from the solubility tests were used to measure the metal solubility by atomic absorption spectrometry. The morphologies of the external surface and the cross-section of the samples were analysed by means of a scanning electron microscope (SEM). Statistical analysis was performed by using one-way anova and post hoc Tukey-Kramer tests with the null hypothesis set as 5%. Results AH Plus had the longest setting time (580.6 +/- 3.05 min) (P < 0.05). Activ GP did not have a mean value on the radiopacity and solubility tests (1.31 +/- 0.35 mm and 11.8 +/- 0.43%, respectively) in accordance with ANSI/ADA, being significantly different from the other materials (P < 0.05), which had mean values for these tests in accordance with the ADA`s requirements. GuttaFlow was the only sealer that conformed to the Specification 57 concerning the dimensional alteration test (0.44 +/- 0.16%) (P < 0.05). The spectrometry test revealed significant Ca2+, K+, Zn2+ ion release from Activ GP sealer (32.57 +/- 5.0, 1.57 +/- 0.22 and 8.20 +/- 1.74 mu g mL-1, respectively). In SEM analysis, the loss of matrix was evident and the filler particles were more distinguishable in all groups. Conclusions The setting time of all sealers was in accordance with ANSI/ADA`s requirements. Activ GP did not fulfill ANSI/ADA`s protocols regarding radiopacity, dimensional alteration and solubility. GuttaFlow was the only sealer that conformed to the Specification 57 in all tests. SEM analysis revealed that the surfaces of all sealers had micromorphological changes after the solubility test.