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Biomedical subjects

W R Ledoux

Publications and source records attributed to W R Ledoux.

11 recordsLinked to original sources
PubMed2001

Pennation angles of the intrinsic muscles of the foot.

As mathematical models of the musculoskeletal system become increasingly detailed and precise, they require more accurate information about the architectural parameters of the individual muscles. These muscles are typically represented as Hill-type models, which require data on fiber length, physiological cross-sectional area (PCSA) and pennation angle. Most of this information for lower limb muscles has been published, except for data on the pennation angle of the intrinsic muscles of the foot. Each (n=20) intrinsic muscle of three human feet was dissected free. The dorsal and plantar surfaces were photographed and a digitized color image was imported into Abobe Photoshop. The muscles were divided into "anatomical units". For each anatomical unit (n=26), a line was drawn along the tendon axis and a number of other lines were drawn along individual muscle fibers. The angle between the tendon line and each fiber line was defined as the pennation angle of that fiber. By visual inspection, an effort was made to take measurements such that they represented the distribution of fibers in various parts of the muscle. Although some individual muscles had higher or lower pennation angles, when averaged for all specimens, the second dorsal interosseous had the smallest pennation angle (6.7+/-6.81 degrees) while the abductor digiti minimi had the largest (19.1+/-11.19 degrees). Since the cosines of the angles range from 0.9932 to 0.9449, the effect of the pennation angle on the force generated by the muscle was not great.

Aged↗
PubMed2001

Acceleration of the calcaneus at heel strike in neutrally aligned and pes planus feet.

OBJECTIVE: The purpose of this research was twofold: (1) to study the impulsive acceleration of the calcaneus at heel strike in subjects with neutrally aligned (i.e., normal) feet and (2) to explore how the acceleration may differ in subjects with pes planus (i.e., flat) feet. The component of the acceleration vector aligned with the long axis of the tibia was quantified. DESIGN: Subjects with either foot type were instrumented and calcaneal acceleration was quantified during comfortable cadence locomotion. BACKGROUND: Aberrant peak acceleration has been associated with osteoarthritis. While tibial acceleration has been quantified, calcaneal acceleration has not. Additionally, foot morphology, or foot type, has demonstrated an effect on foot function and thus there may be differences in calcaneal acceleration between foot types. METHODS: Six subjects with neutrally aligned feet and six with pes planus feet were selected via a clinical exam. Accelerometers were attached to the posterior aspect of the medial surface of the calcanei bilaterally and 10 walking trials were collected.Results. The average baseline-to-peak acceleration for the neutrally aligned and pes planus feet was 4.79 g (SD, 2.14 g) and 5.24 g (SD, 3.28 g), respectively; the peak-to-peak acceleration was 5.03 g (SD, 2.74 g) and 6.75 g (SD, 3.89 g). There were no significant differences (P>0.05) between foot types. CONCLUSIONS: The calcaneal acceleration at heel strike for neutrally aligned and pes planus feet was not sensitive to foot type. RELEVANCE: Aberrant acceleration has been associated with the development of osteoarthritis [J. Biomech. 5 (3) (1972) 267; J. Biomech. 6 (1) (1973) 51; J. Biomech. 15 (7) (1982) 487]. Osteoarthritis at the subtalar joint, as well as the ankle and midtarsal joints, may be initiated and/or perpetuated by excessive calcaneal acceleration at heel strike.

Acceleration↗
PubMed1997

Iliac apophyseal cartilage augmentation of the deficient piriform rim and maxilla in alveolar cleft grafting.

This article presents a new approach to cleft lip and cleft palate repair, where the retained bulk of alveolar cleft grafts is augmented by simultaneous cartilage augmentation of the deficient maxilla. Nine patients who provided 10 cleft sites underwent secondary bone grafting of the clefted alveolus by this technique. This study evaluates the following: (1) the postoperative esthetic results, (2) the quantity of bone in the grafted area, and (3) the provision of bone support for unerupted teeth, for teeth adjacent to the cleft, and for orthodontic tooth movement when the secondary bone grafting of the cleft is integrated with the onlay augmentation of the deficient maxilla. Photographic and radiographic investigations were undertaken. The photographic evaluation showed that all patients exhibited improved facial esthetics in the area of the cleft, particularly in the paranasal area of the maxilla; improved alar base support, symmetry of the columella, and less deviation of the tip of the nose were seen. The radiographic evaluation indicated the following: (1) the average percentage of the alveolar bone height of the grafted area was equal to 76% of the normal side; (2) nine canines erupted or were erupting through the grafted area; there were no adequate records to evaluate the fate of the remaining canine; (3) no teeth involved in the cleft area were ankylosed, because of inadequate records, so evaluators could not determine the status of one tooth; (4) all patients had adequate quantity of bone for orthodontic tooth movement through the grafted area; and (5) the periodontal support of the teeth involved in the cleft was adequate.

Alveolar Process↗
PubMed1990

Shear bond strength of four orthodontic bonding systems.

Recently new orthodontic bonding systems have been developed for attachment of brackets to the etched facial surfaces of teeth. Two of these new systems use bonding agents that contain solvents. It is claimed that this improves the polymerization of the unfilled resin primer and may increase bond strength. A new light-cured restorative enamel/dentin-bonding agent has also recently been introduced. Its value in orthodontic bonding has not been determined. The aim of this investigation was to evaluate the shear bond strengths of the three new bonding systems and to compare these with a conventional orthodontic bonding system. Forty-eight enamel specimens were prepared with 600-grit silicone carbide paper, acid etched with 37% phosphoric acid, and assigned to four enamel-bonding treatment groups: (A) Saga sealant; (B) Maximum Cure; (C) Scotchbond-2; and (D) Concise enamel bond. After enamel priming, the specimens were bonded to Concise orthodontic bonding resin. The bonded specimens were thermocycled (15 degrees C to 45 degrees C) and then stored in distilled water at 37 degrees C for 7 days. Shear bond strength was tested with an Instron testing machine at a strain rate of 0.02 in/min. The mean shear bond strengths and standard deviations reported in MN/m2 were (A) 20.34 (5.37); (B) 25.33 (5.96); (C) 14.59 (5.25); and (D) 20.13 (4.98). The mean shear bond strengths for groups A, B, and D were significantly greater (p less than 0.05) than that for group C. The addition of solvents to the new orthodontic bonding systems does not appear to have a clinically significant effect. The new restorative bonding resin does not provide comparable enamel bond strengths.

Composite Resins↗
PubMed1990

Shear bond strength of ceramic orthodontic brackets to enamel.

The recent introduction of ceramic orthodontic brackets has generated interest among orthodontists. The aim of this investigation was to evaluate the in vitro shear bond strengths to enamel of four ceramic orthodontic brackets and one stainless steel bracket in trials with two separate acid-etching times for enamel. Eighty extracted human central incisors were prepared for bonding to Starfire, Allure, Transcend, Quasar, and stainless steel (in the control group) orthodontic bracket systems. Enamel etching times of 15 seconds and 60 seconds were used. There was a total of 10 groups. After acid etching, one coat of low-viscosity bonding agent was applied and the brackets were bonded to etched enamel with Concise orthodontic bonding resin. The bonded test specimens were stored in distilled water at 37 degrees C for 14 days, after which they were thermocycled for 500 cycles (5 degrees C to 60 degrees C). The bonds were stressed to failure in an Instron machine at a crosshead speed of 0.02 inch per minute. The shear bond strengths were calculated and Weibull analysis was used to obtain a shape factor (the slope of the straight line and a measure of predictability) and the characteristic level (the 63.2% bond strength value of median rank on the strength line) for each group. Predictability and high bond strength, along with other factors, are important in the clinical selection of a bracket system. When either predictability or bond strength was considered independently, several bracket systems, coupled with a particular etch time, had either high predictability or high bond strength. The highest predictability and the highest bond strength were both found with the Allure bracket system.

Acid Etching, Dental↗
PubMed1989

A bond strength study of luted castable ceramic restorations.

Accurate intracoronal castings can be produced using a castable ceramic--DICOR--for which there is a need to identify a suitable luting cement. The aim of this investigation was to evaluate the bond strength of three glass-ionomer luting cements and one resin cement to treated and untreated DICOR, enamel, and dentin surfaces. Forty "cerammed" DICOR specimens were assigned to four groups: (1-3) grit-blasting and bonding to each of the three glass-ionomer cements; and (4) acid-etching, silane coating, and bonding to the resin cement. Seventy enamel specimens were assigned to seven groups: (1-3) no etching and bonding to each of the glass-ionomer cements; (4-7) acid-etching and bonding to the glass-ionomer cements and the resin cement. Seventy dentin specimens were assigned to seven groups: (1-4) bonding to each of the three glass-ionomer cements and the resin cement; (5-7) polyacrylic acid preconditioning and bonding to each of the three glass-ionomer cements. The mean resin cement bond strengths (MN/m2) to DICOR (9.4) and to etched enamel (10.7) were significantly greater (p less than 0.01) than those of the glass-ionomer cements (DICOR, 0.8-1.2; enamel, 0.4-0.9). Preconditioning of enamel and dentin significantly increased (p less than 0.05) the bond strengths to the glass-ionomer cements. The mean bond strength of the resin cement to untreated dentin (4.3) was significantly higher (p less than 0.05) than the glass-ionomer bond strengths to untreated dentin (1.0-1.7) and to preconditioned dentin (2.1-3.3). The high bond strengths achieved with the resin cement are encouraging. Selected surface treatment of DICOR, enamel, and dentin prior to luting should be clinically useful.

Acrylic Resins↗
PubMed1988

Orthodontic bonding to porcelain--bond strength and refinishing.

Glazed porcelain surfaces are not amenable to resin penetration for orthodontic bonding. The aims of this study were to evaluate (1) the bond strengths of two orthodontic composite materials to treated porcelain surfaces, (2) the effect of thermocycling, and (3) the porcelain surfaces after refinishing. Sixty glazed porcelain disks were assigned to three surface treatment groups: Silane (S), roughening and silane (RS), and roughening (R). The acid-etched enamel surfaces of 20 extracted teeth served as a control group. Ten specimens in each group were bonded with either Concise or System 1. They were stored in water at 37 degrees C or thermocycled 8 degrees to 45 degrees C. Shear bond strength was tested with an Instron testing machine (0.05 cm/min). Analysis of variance showed that the four surface treatment groups and the two composite materials produced significantly different bond strengths (P less than 0.01 and P less than 0.05, respectively). The effect of thermocycling was not significant (P greater than 0.05). Acid-etched enamel/Concise produced the highest mean bond strength (17.4 MN/m2). This was significantly greater (P less than 0.05) than the mean bond strengths of S/Concise (11.1), RS/System 1 (8.6), RS/Concise (8.1), and enamel/System 1 (7.8). The latter four mean bond strengths in turn were significantly greater (P less than 0.05) than S/System 1 (2.5), R/Concise (2.1), and R/System 1 (1.8). Of the four refinishing systems evaluated, all produced smooth surfaces but were unable to reproduce a glazed appearance. Roughening of porcelain and the silane treatment achieve bond strengths that should be clinically successful.(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesives↗
PubMed1987

Managing orthodontic data on a small computer.

A literature survey of file management, relational database management, and network/hierarchical database management systems led to selection of dBASE III to manage patient records on an IBM PC in the Department of Orthodontics at the Louisiana State University School of Dentistry. The versatility of this system's internal language enables ad hoc analysis of clinical and personal data to meet both anticipated and unanticipated management and scientific needs.

Computers↗
PubMedDate not supplied

Can the presence of equinus contracture be established by physical exam alone?

The condition in which ankle dorsiflexion is restricted is known as equinus contracture (EC). Equinus contracture is purported to be associated with a number of clinical conditions. However, there are no data to support or refute a clinician's ability to diagnose EC by clinical exam. We prospectively evaluated the maximum ankle dorsiflexion with the knee fully extended in 68 people (34 patients with isolated fore- or midfoot pain and 34 asymptomatic subjects) both by clinical exam and by a custom-designed ankle goniometer. We compared the likelihood of agreement of the clinical impression (equinus, no equinus) to the maximum ankle dorsiflexion measured with the instrument at two different numerical definitions of EC (< or =5 degrees and < or =10 degrees of maximum dorsiflexion). When all subjects were included and equinus defined as < or =5 degrees of ankle dorsiflexion, a clinician's ability to detect the equinus when it is truly present is 77.8%. If equinus is defined as < or =10 degrees, this ability increases to 97.2%. Alternatively, if equinus is not present, as defined by < or =5 degrees, then a clinician's ability to correctly diagnose no equinus is 93.8%. If equinus is defined to < or =10 degrees, this ability decreases to 68.8%.

Adult↗