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Biomedical subjects

T C May

Publications and source records attributed to T C May.

5 recordsLinked to original sources
PubMed1992

Finite element analysis of interface geometry effects on the crestal bone surrounding a dental implant.

Using a two-dimensional axisymmetric finite element analysis technique, different geometrical configurations of implants, abutments, and interfaces have been investigated to alter the stress distribution in the crestal bone region. The crestal bone region is of particular interest due to observations of progressive bone resorption (saucerization). The ability of a prosthetic restoration-implant construct to transfer an appropriate stress at this region will, by definition of Wolff's law (bone's response to strain) and principles of bone remodeling, help to maintain the integrity of the surrounding bone via force transfer. The two geometries investigated involved a traditional flat mating surface and a slanted (oblique) mating surface. In both models a vertical load of 400 N (63 N/rad across 2 pi radians) was applied to the abutment apex. In the crestal bone region the oblique mating surface increased the transfer of horizontal stress 67 percent over the traditional flat mating surface design. The magnitude of stress transferred and the area which it was transferred across was increased in this region. Results indicate potentially more favorable mechanical conditions for bone maintenance surrounding an endosseous dental implant may be achieved if force is transferred preferentially via circumferential grooves and an oblique (dished) implant-abutment mating surface. These theoretical results are consistent with basic principles of stress transfer, stress shielding, and remodeling as well as clinical observations of bone maintenance and resorption.

Alveolar Bone Loss↗
PubMed1991

The tri-spade drill for endosseous dental implant installation.

Many aspects of endosseous dental implant practice have been addressed over the past several decades. While most of this attention has centered on the dental implant body itself and, most recently, on various aspects of prosthetic restoration, the installation armamentarium for site preparation and implant placement has been neglected. Drills, in particular, have received minimal attention, with most drills currently used for implant placement being identical, or nearly identical, to century-old wood or metal cutting instruments. The tri-spade drill design represents an innovation that has evolved from analysis of currently used implant drills, drill mechanics, and the mechanical and physical properties of bone, in consideration of the clinical realities of contemporary endosseous implant placement. The tri-spade drill design, which features three cutting edges, is much more stable in the hands of the practicing clinician. It reduces crestal chatter upon entry into the bone site (a stable drilling situation), resulting in a more perfectly prepared final hole for placement of a cylindrical root-form dental implant. The drill tip angle is designed specifically for use with bone; the reaming action associated with the sharpened cutting edges adjacent to the large side flutes also allows for efficient debris removal. The tri-spade drill design represents an incremental increase in the dental implant armamentarium and efficacy for the installation of endosseous cylindrical dental implants.

Dental Implantation, Endosseous↗
PubMed1990

Use of high-energy shock waves for bone cement removal.

The revision rate of total hip arthroplasty has increased dramatically over recent years, leading to different methods of extraction of the femoral cement mantle to reduce operative time and surgical risks. The use of high-energy shock waves produced by the Dornier HM.3 Lithotripter to interrupt the cement-bone interface and to reduce the material properties of the cement is investigated. Tests were conducted to measure the pull-out strength of cemented treated rods versus untreated rods, from the medullary canal of canine femurs. The treated femurs showed an average reduction in pull-out strength of 43%. An investigation involving the material properties of acrylic bone cement was also conducted. The properties tested were the compressive modulus of elasticity, the ultimate compressive strength, the ultimate tensile strength, and fracture toughness. The scanning electron microscope aided in determining whether microfractures in the cement resulted from the shock wave treatment. A theoretical study utilizing the finite element method was used to investigate areas of select shock wave treatment about the femoral prosthesis. Analysis of the results showed that the lithotripter treatment had no significant effect on the compressive properties but reduced the tensile properties and fracture toughness significantly. Scanning electron microscopy uncovered definite areas of induced microfractures not present in the control specimens. This study supports the concept of clinically noninvasive, preoperative shock wave treatment prior to total hip revision.

Animals↗
PubMed1987

Electron microscopy of CO2-laser-induced effects in human fibrocartilage.

Previous reports of effects of CO2 laser energy on human fibrocartilage suggest thermal injury extends to a depth of approximately 70 microns from the target surface with power settings of 35 W and exposure times of 0.5 seconds. The present study was undertaken to look for more subtle evidence of thermal alteration of human fibrocartilage treated with CO2 laser irradiation. Fifteen human menisci were irradiated at power settings of 10, 20, and 30 W with exposure times of 0.1 and 0.5 seconds. The specimens were immediately fixed and sectioned for electron microscopic examination. Loss of a normal cross banding, and marginal clarity of individual collagen fibers were observed in the extracellular matrix and were observed at distances up to 300 microns from the exposed tissue surface. In addition, cellular changes at similar tissue depth consisted of cell membrane invaginations, clumping of nuclear chromatin, breakdown of endoplasmic reticulum architecture, and loss of mitochondria and Golgi complexes from the cytoplasm were observed. This study demonstrates deeper penetration of a radiation that was previously appreciated by light microscopy in irradiated human fibrocartilage, although the implications with respect to contraside viability and healing potential of the tissue in vivo is not known.

Cartilage, Articular↗