Vertical marginal discrepancy of ceramic copings with different ceramic materials finish lines and luting agents: An in vitro evaluation

Statement of problem. Prosthetic restorations that fit poorly may affect periodontal health and occlusion. Studies that have evaluated the accuracy of fit of ceramic restorations before and after cementation assessed primarily intracoronal restorations.Purpose. This in vitro study evaluated the effect of different finish lines, ceramic manufacturing techniques, and luting agents on the vertical discrepancy of ceramic copings.Material and methods. Two stainless steel molars were prepared for complete crowns with 2 different finish lines (heavy chamfer and rounded shoulder); each molar was duplicated to fabricate 90 copings. A total of 180 copings generated 18 groups (n=10 for each finish line-coping material-luting agent combination). Luting agents tested included zinc phosphate, resin-modified glass ionomer (Fuji Plus), and resin composite cements (Panavia F). A metal frame was developed on which to screw the stainless steel model and a ceramic coping; the distance (mum) between 2 predetermined points was measured before and after cementation by a profile projector under a torquing force. A 4-way ANOVA with repeated measurements was performed to assess the influence of each factor in the vertical marginal discrepancy: 3 between-coping factors (finish line-coping material-luting agent) and 1 within-coping factor (before and after cementation) (alpha=.05).Results. Procera copings presented the lowest mean values (P<.05) of vertical marginal discrepancy before and after cementation (25/44 mum) when compared to Empress 2 (68/110 mum) and InCeram Alumina copings (57/117 mum), regardless of any combinations among all finish lines and luting agents tested.Conclusion. Considering each factor separately, the ceramic manufacturing technique appeared to be the most important factor tested for the definitive vertical discrepancy of all-ceramic copings, with lower mean values for Procera copings.

Ability of bacteriophages isolated from different sources to reduce Salmonella enterica serovar enteritidis in vitro and in vivo

Salmonella enterica serovar Enteritidis-lysing bacteriophages isolated from poultry or human sewage sources were used to reduce Salmonella Enteritidis in vitro and in experimentally infected chicks. Cocktails of 4 different bacteriophages obtained from commercial broiler houses (CB4O) and 45 bacteriophages from a municipal wastewater treatment plant (WT45O) were evaluated. In experiment 1, an in vitro crop assay was conducted with selected bacteriophage concentrations (105 to 101 pfu/mL) to determine ability to reduce Salmonella Enteritidis in the simulated crop environment. Following 2 h at 37 degrees C, CB40 or WT45O reduced Salmonella Enteritidis recovery by 1.5 or 5 log, respectively, as compared with control. However, CB40 did not affect total SE recovery after 6 h, whereas WT45O resulted in up to a 6-log reduction of Salmonella Enteritidis. In experiment 2, day-of-hatch chicks were challenged orally with 3 x 103 cfu /chick Salmonella Enteritidis and treated cloacally with 1 X 109 WT45O pfu/chick I h postchallenge. One hour later, chicks were treated or not with a commercially available probiotic (Floramax-B11). Both treatments significantly reduced Salmonella Enteritidis recovery from cecal tonsils at 24 h following vent lip application as compared with controls, but no additive effect was observed with the combination of bacteriophages and probiotic. In experiment 3, day-of-hatch chicks were challenged orally with 9 x 103 cfu/chick Salmonella Enteritidis and treated via oral gavage with I X 108 CB40 pfu/chick, 1.2 x 108 WT45O pfu/chick, or a combination of both, I h postchallenge. All treatments significantly reduced Salmonella Enteritidis recovered from cecal tonsils at 24 h as compared with untreated controls, but no significant differences were observed at 48 h following treatment. These data suggest that some bacteriophages can be efficacious in reducing SE colonization in poultry during a short period, but with the bacteriophages and methods presently tested, persistent reductions were not observed.

In vitro study of antiviral activity of mycophenolic acid on Brazilian orthobunyaviruses

Objective: Oropouche, Caraparu, Guama, Guaroa and Tacaiuma are ssRNA viruses that belong to the genus Orthobunyavirus and have been associated with human febrile illnesses and/or encephalitis. In this study, we evaluated the antiviral action of mycophenolic acid (MPA) on these orthobunyaviruses to achieve a therapeutic agent to treat the diseases caused by these viruses. Methods: the in vitro antiviral evaluation to MPA was done by using plaque assay at different periods of treatment. Results: Results showed that MPA at a concentration of 10 mu g/ml has significant antiviral activity on Tacaiuma virus when treatment was initiated either 24 h before or 2 h after viral infection. Moreover, MPA has an inhibitory effect on Guama virus replication, but only when treatment was initiated before cell infection. Addition of guanosine in the culture reverted the inhibitory effect of MPA on Tacaiuma and Guama viruses, suggesting that the antiviral activity of this substance was via depletion of the intracellular guanosine pool. Conclusion: Our results suggest that MPA would not be a good therapeutic agent to treat the diseases caused by Oropouche, Caraparu, Guama, Guaroa, and Tacaiuma viruses.

An In Vitro Comparison of Different Cementation Strategies on the Pull-out Strength of a Glass Fiber Post

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Comparative Study of the Mechanical Resistance of 2 Separate Plates and 2 Overlaid Plates Used in the Fixation of the Mandibular Condyle: An In Vitro Study

Purpose: The objective of this study was to carry out a comparative evaluation of the mechanical resistance of 2 rigid internal fixation techniques for fractures of the mandibular condyle using miniplates.Materials and Methods: Fort), polyurethane resin replicas of human hemimandibles were used. The hemimandibles were sectioned to simulate a high subcondylar fracture and then stabilized with 2 fixing techniques using 2.0-mm system plates and screws. The fixation techniques were 2 separate 4-hole plates with 8 screws, and 2 overlaid 4-hole plates with 4 screws. Each system was submitted to load tests, with the application of the load in mediolateral and anteroposterior directions in an Instron 4411 universal assay machine (Instron, Norwood, MA).Results: Load values and peak displacement were measured. Means and standard deviations were evaluated by analysis of variance (P < .05) and Tukey tests, in which it was verified that the anteroposterior peak load value was affected by the arrangement of the plates on the models, although no differences were observed between the groups for the mediolateral peak load. The arrangement of the plates did not have any influence on peak displacement. Similarly, the final value of the mediolateral load was not affected by the arrangement of the plates on the model.Conclusion: The experimental model with 2 separate plates was statistically superior to the model with 2 overlaid plates only in relation to anteroposterior peak load. Despite showing superiority in mediolateral peak load and peak displacement, there was no statistical difference between the groups for these parameters. (C) 2009 American Association of Oral and Maxillofacial Surgeons

The slippery slope - Critical perspectives on in vitro research methodologies

Objectives. This paper attempts to provide critical perspectives on common in vitro research methodologies, including shear bond testing, wear testing, and load-to-failure tests. Origins of interest in high-quality laboratory data is reviewed, in vitro data is categorized into property and simulation protocols, and two approaches are suggested for establishing clinical validity. It is hoped that these insights will encourage further progress toward development of in vitro tests that are validated against clinical performance and/or by producing clinically validated failure or damage mechanisms.Materials and methods. Published shear and tensile bond data (macro and micro) is examined in light of published finite element analyses (FEA). This data is subjected to a Weibull scaling analysis to ascertain whether scaling is consistent with failure from the bonded interface or not. Wear tests results are presented in light of the damage mechanism(s) operating. Quantitative wear data is re-examined as being dependent upon contact pressure. Load-to-failure test results are re-analyzed by calculating contact stresses at failure for 119 tests from 54 publications over more than 25 years.Results. FEA analyses and reported failure modes (adhesive, mixed, cohesive) are consistent with failure not involving interfacial "shear stresses" as calculated in published work. Weibull scaling clearly suggests failure involving external surfaces of specimens, not interfacial origins. Contact stresses (pressures) are clearly an important variable in wear testing and are not well-controlled in published work. Load-to-failure tests create damage not seen clinically due to excessively high contact stresses. Most contact stresses in the 119 tests examined were calculated to be between 1000 MPa and 5000 MPa, whereas clinical contact stresses at wear facets have been measured not to exceed 40 MPa.Conclusions. Our community can do a much better job of designing in vitro tests that more closely simulate clinical conditions, especially when contact is involved. Journals are encouraged to thoughtfully consider a ban on publishing papers using bond tests and load-to-failure methods that are seriously flawed and have no clinical relevance. (C) 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

In Vitro Evaluation of ICDAS and Radiographic Examination of Occlusal Surfaces and Their Association With Treatment Decisions

This in vitro study evaluated the performance of visual (International Caries Detection and Assessment System [ICDAS]) and radiographic (bitewing [BW]) examinations for occlusal caries detection and their associations with treatment decision (TD). Permanent teeth (n=104) with occlusal surfaces varying from sound to cavitated were selected. Sites were identified from 10x occlusal surface photographs. Standardized bitewing (BW) radiographs were taken. Four dentists with at least five years of experience scored all teeth twice (one-week interval) for ICDAS (0-6), BW (0=sound, 1=caries restricted to enamel, 2=caries in outer third dentin, 3=caries in inner third dentin), and TD (0=no treatment, 1=sealant, 2=microabrasion and sealant, 3=round bur sealant, 4a=resin, 4b=amalgam). Histological validation was performed by observation under a light microscope, with lesions classified on a five-point scale. Intraexaminer and inter-examiner repeatability were assessed using two-way tables and intraclass correlation coefficients (ICCs). Comparisons between percentage correct, specificity, sensitivity, and area under the receiver-operating characteristic (ROC) curve were performed using bootstrap analyses. ICCs for intraexaminer and interexaminer repeatability indicated good repeatability for each examiner, ranging from 0.78 to 0.88, and among examiners, ranging from 0.74 to 0.81. Correlation between ICDAS and TD was 0.85 and between BW and TD was 0.78. Correlation between the methods and histological scores was moderate (0.63 for ICDAS and 0.61 for BW). The area under the ROC curve was significantly greater for ICDAS than for BW (p<0.0001). ICDAS had significantly lower specificity than BW did (p=0.0269, 79% vs 94%); however, sensitivity was much higher for ICDAS than for BW (p<0.0001, 83% vs 44%). Data from this investigation suggested that the visual examination (ICDAS) showed better performance than radiographic examination for occlusal caries detection. The ICDAS was strongly associated with TD. Although the correlation between the ICDAS and BW was lower, it is still valuable in the clinical decision-making process.

Evaluation of developmental changes in bovine in vitro produced embryos following exposure to bovine Herpesvirus type 5

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Intrapulpar temperature during continuous CO2 laser irradiation in human molars: An in vitro study

To establish safety parameters, we in vitro studied the increase in intrapulpal temperature caused by the use of a cw CO2 laser. A thermistor was implanted in the inner part of the pulpal chamber of 25 human lower third molars to measure the intrapulpal temperature produced by laser powers between 2-10 W and exposure times of 0.5-25.0 s. The Pearson linear correlation factor applied to the measured values showed there is a direct relationship between the independent variable and the applied power. A variance analysis produced the linear regression equation: T=1.10+(0.127)E where T is the temperature and E the energy. The results showed that, with a power of 4 W and maximum exposure time of 2.5 s (10 J) and a power density of 12738.85 W cm-2, there will be no damaging reactions affecting the pulpal tissues.

Influence of natural fruit juices in removing the smear layer from root surfaces - An in vitro study

Certain elements of a patient's diet may be associated with dentin hypersensitivity. The intent of this study was to evaluate the degree of removal of the smear layer from dentin surfaces by various fruit juices. A smear layer was created on extracted human teeth by manual scaling. The roots were reduced and distributed into 8 experimental groups. Distilled water was the negative control. The juices were applied by 2 methods: topical application and topical application with friction. Specimens were photomicrographed and graded according to an index of smear layer removal. With topical application, all but 2 of the tested substances resulted in significantly greater removal of the smear layer and opening of dentinal tubules than was the case with the negative control (p = 0.05); the exceptions were Gala apple and Italian grape juices, which were no different from the control. For the active application (with friction), most substances removed more smear layer than the control (p < 0.05); Gala apple, Italian grape and orange juices were similar to the control. For each of the tested substances, removal of the smear layer did not differ with the method of application (topical vs. friction; p > 0.05). It is concluded that natural fruit juices can remove the smear layer from dentin surfaces, and the efficacy of this removal varies with the type of juice. © J Can Dent Assoc 2004.

Effects of acetylsalicylic acid and acetic acid solutions in VX2 carcinoma cells. In vitro analysis

Purpose: To analyze, in vitro, the effects of acetylsalicylic acid (aspirin) and acetic acid solutions on VX2 carcinoma cells in suspension and to examine the correlation between these effects and neoplastic cell death. Methods: The VX2 tumor cells (107 cells/ml) were incubated in solutions containing differing concentrations (2.5% and 5%) of either acetylsalicylic acid or acetic acid, or in saline solution (controls). Every five minutes, cell viability was tested (using the trypan blue test) and analyzed under light microscopy. Results: Tumor cell viability (in %) decreased progressively and, by 30 minutes, neoplastic cell death had occurred in all solutions. Conclusion: Based on this experimental model and the methodology employed, we conclude that these solutions cause neoplastic cell death in vitro.

Influence of cavity preparation and curing method on the marginal seal of resin composite restorations: an in vitro evaluation.

OBJECTIVE: To evaluate the influence of cavity design and photocuring method on the marginal seal of resin composite restorations. METHOD AND MATERIALS: Seventy-two bovine teeth were divided into 2 groups: group 1 received box-type cavity preparations, and group 2 received plate-type preparations. Each group was divided into 3 subgroups. After etching and bonding, Z250 resin composite (3M Espe) was applied in 2 equal increments and cured with 1 of 3 techniques: (1) conventional curing for 30 seconds at 650 mW/cm2; (2) 2-step photocuring, in which the first step was performed 14 mm from the restoration for 10 seconds at 180 mW/cm2 and the second step was performed in direct contact for 20 seconds at 650 mW/cm2; or (3) progressive curing using Jetlite 4000 (J. Morita) for 8 seconds at 125 mW/cm2 and then 22 seconds at 125 mW/cm2 up to 500 mW/cm2. The specimens were thermocycled for 500 cycles and then submitted to dye penetration with a 50% silver nitrate solution. Microleakage was assessed using a stereomicroscope. Data were analyzed using analysis of variance and Tukey test (5% level of significance). RESULTS: A statistically significant difference was found between groups when a double interaction between photocuring and cavity preparation was considered (P = .029). CONCLUSIONS: No one type of cavity preparation or photocuring method prevented micro-leakage. The plate-type preparation showed the worst dye penetration when conventional and progressive photocuring methods were used. The best results were found using the 2-step photocuring with the plate-type preparation.

In vitro evaluation of the precision of working casts for implant-supported restoration with multiple abutments

Objective: The purpose of this study was to compare the accuracy of two working cast fabrication techniques using strain-gauge analysis. Methods: Two working cast fabrication methods were evaluated. Based on a master model, 20 working casts were fabricated by means of an indirect impression technique using polyether after splinting the square transfer copings with acrylic resin. Specimens were assigned to 2 groups (n=10): Group A (GA): type IV dental stone was poured around the abutment analogs in the conventional way; Group B (GB), the dental stone was poured in two stages. Spacers were used over the abutment analogs (rubber tubes) and type IV dental stone was poured around the abutment analogs in the conventional way. After the stone had hardened completely, the spacers were removed and more stone was inserted in the spaces created. Six strain-gauges (Excel Ltd.), positioned in a cast bar, which was dimensionally accurate (perfect fit) to the master model, recorded the microstrains generated by each specimen. Data were analyzed statistically by the variance analysis (ANOVA) and Tukey's test (α= 5%). Results: The microstrain values (με) were (mean±SD): GA: 263.7±109.07με, and GB: 193.73±78.83με. Conclusion: There was no statistical difference between the two methods studied.

The influence of zero-value subtraction on the performance of two laser fluorescence devices for detecting occlusal caries in vitro

Background. The aim of this study was to evaluate the influence of zero-value subtraction on the performance of two laser fluorescence (LF) devices developed to detect occlusal caries. Methods. The authors selected 119 permanent molars. Two examiners assessed three areas (cuspal, middle and cervical) of both mesial and distal portions of the buccal surface and one occlusal site using an LF device and an LF pen. For each tooth, the authors subtracted the value measured in the cuspal, middle and cervical areas in the buccal surface from the value measured in the respective occlusal site. Results. The authors observed differences among the readings for both devices in the cuspal, middle and cervical areas in the buccal surface as well as differences for both devices with and without the zero-value subtraction in the occlusal surface. When the authors did not perform the zero-value subtraction, they found statistically significant differences for sensitivity and accuracy for the LF device. When this was done with the LF pen, specificity increased and sensitivity decreased significantly. Conclusions. For the LF device, the zero-value subtraction decreased the sensitivity. For this reason, the authors concluded that clinicians can obtain measures with the LF device effectively without using zero-value subtraction. For the LF pen, however, the absence of the zero-value subtraction changed both the sensitivity and specificity, and so the authors concluded that clinicians should not eliminate this step from the procedure. Clinical Implications. When using the LF device, clinicians might not need to perform the zero-value subtraction; however, for the LF pen, clinicians should do so.

In vitro evaluation of the effect of natural orange juices on dentin morphology

The patient's diet has been considered an important etiological factor of dentin hypersensitivity. The frequent ingestion of acidic substances can promote the loss of dental structure or remove the smear layer. The purpose of this study was to evaluate the degree of smear layer removal and dentinal tubules exposure by different natural orange juices. Extracted human teeth were submitted to manual scaling in order to develop the smear layer. Seventy dentin samples were obtained and distributed into the following groups: Control, lime orange, lime, valência orange, navel orange, mandarin, and tangerine. Each group included 2 methods of application: Topical and topical + friction. After preparation for SEM analysis, photomicrographs were assessed by a blind calibrated examiner using an index system. The Kruskal-Wallis test indicated a significant influence of the orange juices on smear layer removal. Significant difference was observed between navel orange, valência orange, mandarin and the control group (p < 0.05). These orange juices resulted in greater removal of the smear layer and greater opening of dentinal tubules. The comparison between the application methods for each group using the Mann-Whitney test showed that friction increased smear layer removal significantly only for lime orange and lime. The data suggest that certain natural orange juices are more effective in terms of smear layer removal and dentinal tubules exposure than others.