1.Mechanical properties related to the microstructure of seven different fiber reinforced composite posts.
Víctor ALONSO DE LA PEÑA ; Iria L DARRIBA ; Martín CASERÍO VALEA ; Francisco GUITIÁN RIVERA
The Journal of Advanced Prosthodontics 2016;8(6):433-438
PURPOSE: The aim of this in vitro study was to evaluate the mechanical properties (bending strength and hardness) of seven different fiber reinforced composite posts, in relation to their microstructural characteristics. MATERIALS AND METHODS: Two hundred eighty posts were divided into seven groups of 40, one group for each type of post analyzed. Within each group, 15 posts were subjected to three-point bending strength test, 15 to a microhardess meter for the Knoop hardness, and 10 to Scanning Electron Microscope in order to determine the diameter of the fibers and the percentage of fibers embedded in the matrix. To compare the flexural strength in relation to the type of fiber, matrix, and the hardness of the posts, a Kruskal-Wallis H test was used. The Jonckheere-Terpstra test was used to determine if the volume percent of fibers in the post influenced the bending strength. RESULTS: The flexural strength and the hardness depended on the type of fibers that formed the post. The lower flexural strength of a post could be due to deficient bonding between the fiber and the resin matrix. CONCLUSION: According to the results, other factors, besides the microstructural characteristics, may also influence the mechanical properties of the post. The feature that has more influence on the mechanical properties of the posts is the type of fiber.
Hardness
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In Vitro Techniques
2.Comparative evaluation of the bond strength of self-adhering and bulk-fill flowable composites to MTA Plus, Dycal, Biodentine, and TheraCal: an in vitro study
Aakrati RAINA ; Asheesh SAWHNY ; Saurav PAUL ; Sridevi NANDAMURI
Restorative Dentistry & Endodontics 2020;45(1):10-
OBJECTIVES: This study aimed to compare the shear bond strength (SBS) of a self-adhering flowable composite (Dyad Flow) and a bulk-fill flowable composite (Smart Dentin Replacement [SDR]) to several pulp-capping materials, including MTA Plus, Dycal, Biodentine, and TheraCal.MATERIALS AND METHODS: Eighty acrylic blocks with 2-mm-deep central holes that were 4 mm in diameter were prepared and divided into 2 groups (n = 40 each) according to the composite used (Dyad Flow or SDR). They were further divided into 4 sub-groups (n = 10 each) according to the pulp-capping agent used. SBS was tested using a universal testing machine at a crosshead speed of 1 mm/min. Data were analyzed using 2-way analysis of variance. A p value of < 0.05 was considered to indicate statistical significance.RESULTS: A statistically significant difference (p = 0.040) was found between Dyad Flow and SDR in terms of bond strength to MTA Plus, Dycal, Biodentine, and TheraCal.CONCLUSIONS: Among the 8 sub-groups, the combination of TheraCal and SDR exhibited the highest SBS.
Dentin
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In Vitro Techniques
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Pemetrexed
3.The effect of preheating resin composites on surface hardness: a systematic review and meta-analysis
Ali A ELKAFFAS ; Radwa I ELTOUKHY ; Salwa A ELNEGOLY ; Salah H MAHMOUD
Restorative Dentistry & Endodontics 2019;44(4):e41-
OBJECTIVES: This paper presents a systematic review and meta-analysis of the effect of preheating on the hardness of nanofilled, nanoceramic, nanohybrid, and microhybrid resin composites. MATERIALS AND METHODS: An electronic search of papers on MEDLINE/PubMed, ScienceDirect, and EBSCOhost was performed. Only in vitro studies were included. Non-English studies, case reports, clinical trials, and review articles were excluded. A meta-analysis of the reviewed studies was conducted to quantify differences in the microhardness of the Z250 microhybrid resin composite using the Comprehensive Meta-Analysis software. RESULTS: Only 13 studies met the inclusion criteria for this systematic review. The meta-analysis showed that there were significant differences between the non-preheated and preheated modes for both the top and bottom surfaces of the specimens (p < 0.05). The microhardness of the Z250 resin composite on the top surface in the preheated mode (78.1 ± 2.9) was higher than in the non-preheated mode (67.4 ± 4.0; p < 0.001). Moreover, the microhardness of the Z250 resin composite on the bottom surface in the preheated mode (71.8 ± 3.8) was higher than in the non-preheated mode (57.5 ± 5.7, p < 0.001). CONCLUSIONS: Although the results reported in the reviewed studies showed great variability, sufficient scientific evidence was found to support the hypothesis that preheating can improve the hardness of resin composites.
Hardness
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In Vitro Techniques
4.Evaluation of marginal adaptation in three-unit frameworks fabricated with conventional and powder-free digital impression techniques
Hasan KOCAAĞAOĞLU ; Haydar ALBAYRAK ; Sezgi CINEL SAHIN ; Ayşegül Güleryüz GÜRBULAK
The Journal of Advanced Prosthodontics 2019;11(5):262-270
PURPOSE: The purpose of this in vitro study was to evaluate the marginal misfits of three-unit frameworks fabricated with conventional and digital impressions techniques. MATERIALS AND METHODS: Thirty brass canine and second premolar abutment preparations were fabricated by using a computer numerical control machine and were randomly divided into 3 groups (n=10) as follows: conventional impression group (Group Ci), Cerec Omnicam (Group Cdi), and 3shape TRIOS-3 (Group Tdi) digital impression groups. The laser-sintered metal frameworks were designed and fabricated with conventional and digital impressions. The marginal adaptation was assessed with a stereomicroscope at ×30 magnification. The data were analyzed with 1-way analysis of variances (ANOVAs) and the independent simple t tests. RESULTS: A statistically significant difference was found between the frameworks fabricated by conventional methods and those fabricated by digital impression methods. Multiple comparison results revealed that the frameworks in Group Ci (average, 98.8 ± 16.43 µm; canine, 93.59 ± 16.82 µm; premolar, 104.10 ± 15.02 µm) had larger marginal misfit values than those in Group Cdi (average, 63.78 ± 14.05 µm; canine, 62.73 ± 13.71 µm; premolar, 64.84 ± 15.06 µm) and Group Tdi (average, 65.14 ± 18.05 µm; canine, 70.64 ± 19.02 µm; premolar, 59.64 ± 16.10 µm) (P=.000 for average; P=.001 for canine; P<.001 for premolar). No statistical difference was found between the marginal misfits of canine and premolar abutment teeth within the same groups (P>.05). CONCLUSION: The three-unit frameworks fabricated with digital impression techniques showed better marginal fit compared to conventional impression techniques. All marginal misfit values were clinically acceptable.
Bicuspid
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In Vitro Techniques
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Tooth
5.Assisted reproductive technology in the local setting
Philippine Journal of Reproductive Endocrinology and Infertility 2005;2(2):51-53
Assisted reproduction is generally defined as infertility treatment in which both oocytes and sperm are handled in the laboratory and is commonly called as in vitro fertilization or test tube baby.
REPRODUCTIVE TECHNIQUES
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FERTILIZATION IN VITRO
6.Comparison of the accuracy of intraoral scanner by three-dimensional analysis in single and 3-unit bridge abutment model: In vitro study
Mei Yang HUANG ; Keunbada SON ; Wan Sun LEE ; Kyu Bok LEE
The Journal of Korean Academy of Prosthodontics 2019;57(2):102-109
PURPOSE: The purpose of this study was to evaluate the accuracy of three types of intraoral scanners and the accuracy of the single abutment and bridge abutment model. MATERIALS AND METHODS: In this study, a single abutment, and a bridge abutment with missing first molar was fabricated and set as the reference model. The reference model was scanned with an industrial three-dimensional scanner and set as reference scan data. The reference model was scanned five times using the three intraoral scanners (CS3600, CS3500, and EZIS PO). This was set as the evaluation scan data. In the three-dimensional analysis (Geomagic control X), the divided abutment region was selected and analyzed to verify the scan accuracy of the abutment. Statistical analysis was performed using SPSS software (α = .05). The accuracy of intraoral scanners was compared using the Kruskal-Wallis test and post-test was performed using the Pairwise test. The accuracy difference between the single abutment model and the bridge abutment model was analyzed by the Mann-Whitney U test. RESULTS: The accuracy according to the intraoral scanner was significantly different (P < .05). The trueness of the single abutment model and the bridge abutment model showed a statistically significant difference and showed better trueness in the single abutment (P < .05). There was no significant difference in the precision (P = .616). CONCLUSION: As a result of comparing the accuracy of single and bridge abutments, the error of abutment scan increased with increasing scan area, and the accuracy of bridge abutment model was clinically acceptable in three types of intraoral scanners.
In Vitro Techniques
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Molar
7.Comparison of various estimation methods for the parameters of Michaelis-Menten equation based on in vitro elimination kinetic simulation data
Yong Soon CHO ; Hyeong Seok LIM
Translational and Clinical Pharmacology 2018;26(1):39-47
The Michaelis-Menten equation is one of the best-known models describing the enzyme kinetics of in vitro drug elimination experiments, and takes a form of equation relating reaction rate (V) to the substrate concentration ([S]) via the maximum reaction rate (Vmax) and the Michaelis constant (Km). The current study was conducted to compare the accuracy and precision of the parameter estimates in the Michaelis-Menten equation from various estimation methods using simulated data. One thousand replicates of simulated [S] over serial time data were generated using the results of a previous study, incorporating additive or combined error models as a source of random variables in the Monte-Carlo simulation using R. From each replicate of simulated data, Vmax and Km were estimated by five different methods, including traditional linearization methods and nonlinear ones without linearization using NONMEM. The relative accuracy and precision of the estimated parameters were compared by the median values and their 90% confidence intervals. Overall, Vmax and Km estimation by nonlinear methods (NM) provided the most accurate and precise results from the tested 5 estimation methods. The superiority of parameter estimation by NM was even more evident in the simulated data incorporating the combined error model. The current simulation study suggests that NMs using a program such as NONMEM provide more reliable and accurate parameter estimates of the Michaelis-Menten equation than traditional linearization methods in in vitro drug elimination kinetic experiments.
In Vitro Techniques
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Kinetics
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Methods
8.Evolving role of modeling and simulation in drug development
Translational and Clinical Pharmacology 2019;27(1):19-23
Pharmacokinetic-pharmacodynamic model is a kind of language that quantitatively describes the drug-related outcomes in the form of mathematical formula. Various outcomes can be subjected to modeling analysis if they can be expressed in numbers. Empirical models have been widely and successfully applied in drug development and research. However, a more competitive drug development environment requires more accurate and predictive models in the early stages of drug development. Accordingly, the subjects of PK-PD modeling have been extended from clinical data to preclinical and in vitro data in the discovery stage. More mechanistic and predictive models, such as physiologically based pharmacokinetic and quantitative system-based pharmacology models, are being increasingly used owing to the growing need to characterize drugs more accurately at the earliest. This tutorial briefly introduces the essential concepts of PK-PD modeling and simulation and describes the recent changing roles of PK-PD model for application in novel drug development process.
In Vitro Techniques
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Pharmacology
9.In vitro comparison of the cyclic fatigue resistance of HyFlex EDM, One G, and ProGlider nickel titanium glide path instruments in single and double curvature canals.
Koray YILMAZ ; Gülşah USLU ; Taha ÖZYÜREK
Restorative Dentistry & Endodontics 2017;42(4):282-289
OBJECTIVES: It was aimed to compare the cyclic fatigue resistances of ProGlider (PG), One G (OG), and HyFlex EDM (HEDM) nickel titanium glide path files in single- and double-curved artificial canals. MATERIALS AND METHODS: 40 PG (16/0.02), 40 OG (14/0.03), and 40 HEDM (10/0.05) single-file glide path files were used in the present study. Sixty files were subjected to cyclic fatigue test by using double-curved canals and 60 files by using single-curved canal (n = 20). The number of cycles to fracture (NCF) was calculated and the length of the fractured fragment (FL) was determined by a digital micro-caliper. Twelve pieces of fractured files were examined with scanning electron microscope to determine fracture types of the files (n = 2). The NCF and the FL data were analyzed using one-way analysis of variance and post hoc Tukey test using SPSS 21 software (p < 0.05). RESULTS: In all of the groups, NCF values were significantly lower in double-curved canals when compared to single-curved canals (p < 0.05). For both of single- and double-curved canals, NCF values of HEDM group in apical and coronal curvatures were found to be significantly higher than NCF values of PG and OG groups (p < 0.05). In both of single- and double-curved canals, NCF value of PG group was found significantly higher than OG group (p < 0.05). CONCLUSIONS: Within the limitations of this study, HEDM glide path files were found to have the highest cyclic fatigue resistance in both of single- and double-curved canals.
Fatigue*
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In Vitro Techniques*
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Nickel*
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Titanium*
10.Resistance to sliding in orthodontics: misconception or method error? A systematic review and a proposal of a test protocol.
Fabio SAVOLDI ; Aggeliki PAPOUTSI ; Simona DIANISKOVA ; Domenico DALESSANDRI ; Stefano BONETTI ; James K H TSOI ; Jukka P MATINLINNA ; Corrado PAGANELLI
The Korean Journal of Orthodontics 2018;48(4):268-280
Resistance to sliding (RS) between the bracket, wire, and ligature has been largely debated in orthodontics. Despite the extensive number of published studies, the lack of discussion of the methods used has led to little understanding of this phenomenon. The aim of this study was to discuss variables affecting RS in orthodontics and to suggest an operative protocol. The search included PubMed©, Medline©, and the Cochrane Library©. References of full-text articles were manually analyzed. English-language articles published between January 2007 and January 2017 that performed an in vitro analysis of RS between the bracket, wire, and ligature were included. Study methods were analyzed based on the study design, description of materials, and experimental setup, and a protocol to standardize the testing methods was proposed. From 404 articles identified from the database search and 242 records selected from published references, 101 were eligible for the qualitative analysis, and six for the quantitative synthesis. One or more experimental parameters were incompatible and a meta-analysis was not performed. Major factors regarding the study design, materials, and experimental setup were not clearly described by most studies. The normal force, that is the force perpendicular to the sliding of the wire and one of the most relevant variable in RS, was not considered by most studies. Different variables were introduced, often acting as confounding factors. A protocol was suggested to standardize testing procedures and enhance the understanding of in vitro findings.
In Vitro Techniques
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Ligation
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Methods*
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Orthodontics*