Browsing by Subject "Analysis of Variance"

Now showing 1 - 5 of 5
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    The effect of polymerization methods and fiber types on the mechanical behavior of fiber-reinforced composite resin
    (2015) Huang, Nan-Chieh; Chu, Tien-Min Gabriel; Hara, Anderson T.; Brown, David T.; Bottino, Marco C.; Levon, John A.
    Background: Interim restoration for a lost anterior tooth is often needed for temporary esthetic and functional purposes. Materials for interim restorations usually have less strength than ceramic or gold and can suffer from fracture. Several approaches have been proposed to reinforce interim restorations, among which fiber reinforcement has been regarded as one of the most effective methods. However, some studies have found that the limitation of this method is the poor polymerization between the fibers and the composite resin, which can cause debonding and failure. 64 Purpose: The purpose of this study was to investigate the effects of different polymerization methods as well as fiber types on the mechanical behavior of fiberreinforced composite resin. Material and Methods: A 0.2-mm thick fiber layer from strip fibers or mesh fibers embedded in uncured monomers w as fabricated with polymerization (two-step method) or without polymerization (one-step method), on top of which a 1.8-mm composite layer was added to make a bar-shape sample, followed by a final polymerization. Seventy-five specimens were fabricated and divided into one control group and four experimental groups (n=15), according to the type of glass fiber (strip or mesh) and polymerization methods (one-step or two-step). Specimens were tested for flexural strength, flexural modulus, and microhardness. The failure modes of specimens were observed by scanning electron microscopy (SEM). Results: The fiber types showed significant effect on the flexural strength of test specimens (F = 469.48; p < 0.05), but the polymerization methods had no significant effect (F = 0.05; p = 0.82). The interaction between these two variables was not significant (F = 1.73; p = 0.19). In addition, both fiber types and polymerization steps affected the flexural modulus of test specimens (F = 9.71; p < 0.05 for fiber type, and F = 12.17; p < 0.05 for polymerization method). However, the interaction between these two variables was not significant (F = 0.40; p = 0.53). Both fiber types and polymerization steps affected the Knoop hardness number of test specimens (F = 5.73; p < 0.05 for polymerization method. and F = 349.99; p < 0.05 for fiber type) and the interaction between these two variables was also significant (F = 5.73; p < 0.05). SEM images revealed the failure mode tended to become repairable while fiber reinforcement was 65 existed. However, different polymerization methods did not change the failure mode. Conclusion: The strip fibers showed better mechanical behavior than mesh fibers and were suggested for use in composite resin reinforcement. However, different polymerization methods did not have significant effect on the strength and the failure mode of fiber-reinforced composite
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    Effects of Age of Pups and Removal of Existing Litter on Pup Survival during Cross-Fostering between Multiparous Outbred Mice
    (American Association for Laboratory Animal Science, 2011-09) Hickman, Debra L.; Swan, Melissa P.; Laboratory Animal Resource Center, IU School of Medicine
    Periparturient manipulation of mice is a valuable tool for modern research facilities. Although fostering and Caesarian section frequently are used to eradicate pathogens, an often overlooked use is to rescue poorly breeding strains of mice. Here we characterized the weaning success rates after fostering outbred pups of variable ages (younger than 24 h; 5 to 7 d; 10 to 12 d) with full or partial replacement of litters and multiparous dams. There were no significant differences between most groups when analyzed by full or partial replacement or age of donor pups as compared with control groups, in which pups were manipulated but returned to the birth dam or the birth dam was not disturbed. However, significant differences were associated with fostering of 10- to 12-d-old pups in combination with younger pups. Overall, these findings suggest that limiting fostering to pups that are within 48 h of age and age-matching litters when fostering are unnecessary.
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    Evaluation of the Aesthetics of Physical Methods of Euthanasia of Anesthetized Rats
    (American Association for Laboratory Animal Science, 2011-09) Hickman, Debra L.; Johnson, Steven W.; Laboratory Animal Resource Center, IU School of Medicine
    Dissection of living brain tissue for in vitro experiments requires the use of a rapid euthanasia method. However, the method must not subject animals to unnecessary pain and must be aesthetically acceptable to experimenters. The purposes of the current study were to assess the aesthetics of 6 euthanasia methods, measure the procedure duration, and evaluate brain for pathology after each procedure. We digitally recorded euthanasia of isoflurane-anesthetized rats by 6 physical methods: anesthetic overdose, cardiac exsanguination, decapitation, closed intrathoracic transection of the great vessels and heart, thoracic percussion, and thoracotomy with rupture of great vessels. Volunteer researchers and animal caretakers watched the video and completed an associated questionnaire. Anesthetic overdose and cardiac exsanguinations were rated most aesthetically pleasing, although these procedures took the longest to complete. In contrast, decapitation and thoracic percussion were the least aesthetically pleasing, but these methods were the quickest. No demographic factor was identified that could predict whether a given euthanasia procedure would be favored for aesthetic reasons, and participants provided a wide variety of rationales for the aesthetic ratings they assigned. Although all of these euthanasia methods meet the criteria of approved methods of euthanasia of anesthetized rats as defined by the AVMA, aesthetic features and the scientific need for rapid euthanasia are both considerations in selecting a method.
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    Induction of chronic migraine phenotypes in a rat model after environmental irritant exposure
    (Lippincott, Williams & Wilkins, 2018-03) Kunkler, Phillip Edward; Zhang, LuJuan; Johnson, Philip Lee; Oxford, Gerry Stephen; Hurley, Joyce Harts; Biochemistry and Molecular Biology, School of Medicine
    Air pollution is linked to increased emergency department visits for headache and migraine patients frequently cite chemicals or odors as headache triggers, but the association between air pollutants and headache is not well understood. We previously reported that chronic environmental irritant exposure sensitizes the trigeminovascular system response to nasal administration of environmental irritants. Here, we examine whether chronic environmental irritant exposure induces migraine behavioral phenotypes. Male rats were exposed to acrolein, a transient receptor potential channel ankyrin-1 (TRPA1) agonist, or room air by inhalation for 4 days before meningeal blood flow measurements, periorbital cutaneous sensory testing, or other behavioral testing. Touch-induced c-Fos expression in trigeminal nucleus caudalis was compared in animals exposed to room air or acrolein. Spontaneous behavior and olfactory discrimination was examined in open-field testing. Acrolein inhalation exposure produced long-lasting potentiation of blood flow responses to a subsequent TRPA1 agonist and sensitized cutaneous responses to mechanical stimulation. C-Fos expression in response to touch was increased in trigeminal nucleus caudalis in animals exposed to acrolein compared with room air. Spontaneous activity in an open-field and scent preference behavior was different in acrolein-exposed compared with room air-exposed animals. Sumatriptan, an acute migraine treatment blocked acute blood flow changes in response to TRPA1 or transient receptor potential vanilloid receptor-1 agonists. Pretreatment with valproic acid, a prophylactic migraine treatment, attenuated the enhanced blood flow responses observed after acrolein inhalation exposures. Environmental irritant exposure yields an animal model of chronic migraine in which to study mechanisms for enhanced headache susceptibility after chemical exposure.
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    The Validity of Articulare for Measurement of Mandibular Length
    (2001) Martinez, Fernando Luis; Roberts, W. Eugene; Baldwin, James J.; Haas, Dennis W.; Miller, James R.; Shanks, James C.
    Mandibular length is commonly defined as the linear distance between condylion and pogonion. The use of condylion in mandibular length and growth measurements, however, is technically difficult because condylion is often obscured in the standard closed-mouth lateral cephalogram. As a result, many studies have utilized articulare as a substitute for condylion because it is readily identifiable in most lateral cephalometric films and is reasonably close in proximity to condylion. To date, very few studies have examined the validity of articulare and the literature provides conflicting reports. The present study examines the validity of articulare in mandibular length measurements by taking three cephalograms on each of 60 consecutive patients: 1) closed-mouth with the patient in habitual occlusion, 2) closed-mouth lateral with the patient in centric relation, and 3) an open-mouth lateral cephalogram. The linear distances (mm) of Ar-Pog, Ar-Go, and Go-Pog were measured on the two closed-mouth cephalograms and compared with each other as well as the linear distances of Co-Pog, Co-Go, and Go-Pog measured from the open mouth cephalogram on each individual. Product-moment correlation coefficients were used to measure the linear associations between the mandibular measurements from the three techniques. Repeated measures analysis of variance were also fit to estimate the correlations between the three measurements adjusted for age and gender. The results of this study show that measurements taken from both closed-mouthed techniques agreed extremely well (ICC=.99). In addition, measurements from both closed-mouth techniques correlated very highly with corresponding measurements taken with the open-mouth technique (ICC=.94). This data suggests that measurements taken from Ar correlate very well with measurements taken from Co and that this correlation is not dependent on whether the patient is positioned in habitual occlusion or centric relation.