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Biomedical subjects

M D Bagby

Publications and source records attributed to M D Bagby.

9 recordsLinked to original sources
PubMed2000

The effectiveness of prophylactic etodolac on postendodontic pain.

To determine if prophylactic etodolac would significantly reduce postendodontic pain, when compared with ibuprofen or placebo, 36 patients consented to single blind oral administration of either 400 mg of etodolac, 600 mg of ibuprofen, or a placebo, before conventional one-appointment root canal therapy. Patient-reported visual analog scale ratings of pain intensity were conducted upon initial clinical presentation, immediately postoperative, 4, 8, 12, 24, 48, and 72 h after initiation of root canal therapy. Results showed that prophylactic ibuprofen administration significantly reduced postendodontic pain at 4 and 8 h after initiation of root canal therapy, when compared with etodolac and a placebo. Patients with a periapical diagnosis of acute apical periodontitis or with a Phoenix abscess showed a significant increased need for additional medication after completion of root canal therapy, compared with all other periapical diagnoses.

Acute Disease↗
PubMed1998

Working times and dimensional accuracy of the one-step putty/wash impression technique.

PURPOSE: Using the one-step polyvinyl siloxane impression technique, this study compared the effect of putty material working time on the dimensional accuracy of recovered improved stone casts. MATERIALS AND METHODS: An acrylic resin master cast was fabricated with embedded reference points to enable both horizontal and vertical measurements. Four commercially available polyvinyl siloxane impression putties with light body washes were evaluated: 1) Extrude (Kerr), 2) Cutter (Coltere), 3) Express (3M), and 4) Reprosil (Caulk). Each putty was mixed by hand for 30 seconds, placed in a plastic stock tray, and seated on the master cast at 0, 30, 60, 90, and 120 seconds after mixing (N = 100, n = 5). The impressions were poured in improved stone, and vertical and horizontal measurements were made to 0.001 mm between reference points on recovered casts using an optical traveling microscope. ANOVA (p < or = .05) was used to compare vertical and horizontal measurements to master cast dimensions. RESULTS: No statistically significant difference was found among casts for all materials and time periods tested. When horizontal measurement ranges were evaluated, Extrude casts exhibited the widest range of measurement, especially when the trays were seated at 90 and 120 seconds. When vertical measurement ranges were evaluated, Express casts at 120 seconds exhibited the widest range. CONCLUSIONS: A high range of variability in vertical and horizontal dimensions occurred at the later time periods, especially for Extrude and Express casts. As a result of rapid polymerization and poor flow properties of putty materials, the impression tray should be seated within 60 seconds after putty mixing to reduce dimensional variability of recovered casts.

Analysis of Variance↗
PubMed1997

Torsional creep of polycarbonate orthodontic brackets.

OBJECTIVE: Polycarbonate materials are known to exhibit creep. The purpose of this study was to investigate torsional creep of polycarbonate orthodontic brackets. METHODS: Four polycarbonate, one metal, and one ceramic brackets were tested. An in vitro torque apparatus was constructed which applied 2000 g-mm of torque to the bracket slot via a cantilever beam perpendicular to the bracket face. The apparatus was placed in a 37 degrees C water bath. Measurements of the angle of the cantilever beam were made at various times from 1 to 28 d. The initial angular change on loading and subsequent changes with time were compared with ANOVA and Tukey tests at p < 0.5. RESULTS: All but one bracket showed the majority of creep by 2 d. Creep was not judged to be clinically significant for the metal, ceramic and the metal slot-reinforced brackets. The polycarbonate bracket without metal slots demonstrated significantly more creep (p < 0.05) than the polycarbonate reinforced with a metal slot, metal and ceramic brackets. SIGNIFICANCE: Clinically significant bracket slot angle (torque) change due to creep can occur when using polycarbonate brackets without metal slot reinforcement.

Analysis of Variance↗
PubMed1996

Mechanical behavior of thermo-responsive orthodontic archwires.

OBJECTIVES: This investigation was conducted to describe the mechanical behavior of thermo-responsive nitinol archwires in flexure at 5 degrees and 37 degrees C. METHODS: Four same-sized (but different force level) rectangular archwires were examined using a three-point bend test. Samples were tested at 5 degrees and 37 degrees C. Linear regressions were fit to different segments of the load-deflection plots. Regression parameters of the segments and other properties were statistically analyzed. RESULTS: Superelastic behavior was exhibited by all wires tested at 37 degrees but not at 5 degrees C. Permanent deformation was greater at 5 degrees than 37 degrees. The initial slope of the load-deflection data averaged 1230 g/mm at 37 degrees, which was significantly different from the average at 5 degrees (500 g/mm). Loads at the apparent yield point and the loads at 1, 2, and 3 mm of deflection were greater at 37 degrees C than at 5 degrees. While the slope and length of the superelastic region were not judged to be clinically significantly different, the average load of the superelastic region was significantly different: F300 (340 g) > F200 (250 g) > F100 (180 g) and Bioforce (180 g). When loaded at 5 degrees and then unloaded at 37 degrees, the mechanical hysteresis of the wires tested at 37 degrees and the permanent deformation of the wires tested at 5 degrees were reduced for all wires. SIGNIFICANCE: Nitinol wires are available with a variety of mechanical properties. The different mechanical properties of thermo-responsive wires at 5 degrees and 37 degrees C result in clinically useful shape-memory behavior. Utilizing the superelastic and shape-memory features of thermo-responsive wires has clinical advantages.

Alloys↗
PubMed1995

X-ray diffraction of nitinol orthodontic arch wires.

Superelastic mechanical behavior of nitinol alloy orthodontic wires is thought to be the result of a stress induced crystallographic transformation from austenite to martensite. The purpose of the study was to compare the SE mechanical behavior of nitinol wires to stress-induced phase changes. Eight nitinol arch wires having rectangular cross-sections were strained from 0% to 10% in tension with a mechanical testing machine. Load/extension plots were subjectively ranked for SE behavior. X-ray diffraction patterns were collected with and without 6% strain. Without strain, nitinol wires were found to be predominantly austenite with some wires containing a small amount of martensite. When strained 6%, superelastic wires demonstrated a phase transformation from austenite to martensite. XRD patterns were ranked for percent transformation and 110 peak width. Product rankings of the degree of superelasticity were positively correlated with the rank of martensitic transformation (p < 0.05). Superelasticity ranks were negatively correlated with XRD peak width ranks (p < 0.01). Increased peak width indicates greater cold work. A range of superelastic mechanical behavior and martensitic transformation is exhibited by wires currently on the market. Cold work and heat treatments are important variables to be controlled during the manufacture of nitinol products.

Alloys↗
PubMed1994

Comparative evaluation of ceramic bracket base designs.

Since the initial introduction of ceramic brackets, base designs have been modified to reduce tooth damage during debonding. The purpose of this study was to compare shear and tensile bond strengths and fracture sites of four second-generation ceramic brackets: Allure IV (A) (GAC International, Inc., Central Islip, N.Y.), Ceramaflex (C) (TP Orthodontics, Inc., LaPorte, Ind.), Intrigue (I) (Lancer Orthodontics, Carlsbad, Calif.), Transcend 2000 (T) (Unitek Corp., Monrovia, Calif.), and a foil-mesh base stainless steel bracket, DynaBond II (D) (Unitek Corp., Monrovia, Calif.). Twenty brackets of each type were bonded to 100 mandibular bovine incisor teeth with Concise bonding adhesive. The samples were thermocycled for 24 hours and the brackets were debonded with an Instron universal testing machine (Instron Corp., Canton, Mass.). A modified Transcend debonding instrument was used for tensile debonding, whereas a chisel was used for shear debonding. An analysis of variance was performed with a 0.05 level of confidence. Mean shear strengths (kg/cm2) necessary to debond were 174.0 (A), 71.0 (C), 189.0 (I), 228.0 (T), and 160.0 (D). Mean tensile strengths (kg/cm2) were 27.0 (A), 26.7 (C), 51.3 (I), 56.5 (T), and 48.6 (D). Fracture sites examined with a light microscope showed no enamel damage with any of the ceramic brackets. Intrigue was the only bracket to fracture and had 30% bracket fracture in the tensile mode and 20% bracket fracture in the shear mode. The percentage of fractures at the adhesive-bracket base interface for shear and tensile modes, respectively, were 80, 100 (A); 100, 90 (C); 10, 60 (I); 60, 90 (T); and 90, 80 (D).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Static frictional force and surface roughness of nickel-titanium arch wires.

Surface roughness and static frictional force resistance of orthodontic arch wires were measured. Nine nickel-titanium alloy arch wires were studied. One beta-titanium alloy wire, one stainless steel alloy wire, and one cobalt-chromium alloy wire were included for comparison. Arithmetic average roughness in micrometers was measured with a profilometer. Frictional force resistance was quantified by pushing wire segments through the stainless steel self-ligating brackets of a four-tooth clinical model. The cobalt-chromium alloy and the nickel-titanium alloy wires, with the exception of Sentalloy and Orthonol, exhibited the lowest frictional resistance. The stainless steel alloy and the beta-titanium alloy wires showed the highest frictional resistance. The stainless steel alloy wire was the smoothest wire tested, whereas NiTi, Marsenol, and Orthonol were the roughest. No significant correlation was found between arithmetic average roughness and frictional force values.

Chromium Alloys↗
PubMed1990

The effect of long-term deflection on permanent deformation of nickel-titanium archwires.

The clinician must now consider the alloy along with cross-sectional shape and size when selecting archwires. The purpose of this study is to quantify permanent deformation after long-term deflection of available nickel-titanium archwires. Nine nickel-titanium, one beta-titanium and one stainless steel archwires, .016 inch round, were deflected into orthodontic brackets of simulated archform. One lateral incisor was positioned to yield a deflection of 5 mm in a lingual direction. After wire deactivation, deformation was measured at 1, 14, and 28 days. Two-way ANOVA and Tukey's critical difference tests were used to determine statistical differences. The nickel-titanium wires exhibited better springback characteristics and less permanent deformation than the stainless steel and TMA wires. Several wires increased deformation as deflection time increased. No clinically significant difference was found between presently available nickel-titanium wires in terms of permanent deformation, long- or short-term.

Analysis of Variance↗