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Biomedical subjects

G R Holt

Publications and source records attributed to G R Holt.

At least 37 records · Page 2Linked to original sources
PubMed1994

Osseointegrated implants in oro-dental and facial prosthetic rehabilitation.

A basic prerequisite for establishing true and lasting tissue integration of a nonbiologic prosthesis is the minimal risk of adverse local or general tissue reactions. It consists of a detailed understanding of the response behavior of highly differentiated hard and soft tissues to the surgical preparation of a recipient site and the installation of the prosthesis, as well as long-term tissue adaptation and the functional demands on the anchorage unit. The complex arrangement of titanium implant material, surface physics, and biocompatibility with the host tissues will be reviewed in this article.

Humans↗
PubMed1994

Soft-tissue response to synthetic biomaterials.

The soft-tissue response to an implanted synthetic material is an inflammatory reaction to foreign body; factors that minimize this inflammation will maximize biocompatibility. The ideal implant is selected from a material that is non-toxic, nonantigenic and in chemical proximity to calcium or carbon on the periodic table. If it is porous, the pores should be large enough to admit immune and phagocytic cells and ideally, to allow native tissue ingrowth. The implant should be of appropriate size and shape and should be implanted in the correct location. The material should be nonparticulate, should resist fragmentation, and should be secured in the selected location after gentle insertion. All these factors help decrease the body's natural response to an implanted foreign body, but inflammation and foreign body reaction are the common threads in all responses to all implanted synthetic materials. Optimum soft-tissue biocompatibility, characterized either by thin fibrous encapsulation or by mesenchymal ingrowth into pores and interstices, is achieved by avoiding or containing this response.

Biocompatible Materials↗
PubMed1992

Toxicology of upper aerodigestive tract pollutants.

The field of environmental toxicology has become quite important to the study of environmental health in human beings. The stability of the ecosystem in which we live is threatened by the nearly 5 million chemical compounds that have been synthesized worldwide, many of which have real or potentially toxic effects on the environment and on life forms. Four major groups of chemicals--metallic elements, nonmetallic elements, organic compounds and inorganic compounds--have certain agents within them that are known toxins to human beings. Some of these agents have an as yet unknown effect, whereas others have been well characterized. They can be found in the workplace, home, and outdoors, and many are unseen and odorless. In the past, most agents have been described in terms of their carcinogenic potential or major toxic effects on organ systems. It is now likely that the important characterization of some of these agents referrable to the upper aerodigestive tract should be at their receptor sites and identify the very discrete and small effects on these sites and their cumulative effects. The concept of threshold is probably an arbitrary one because to date these discrete effects have not been studied. Susceptibility on an individual basis probably varies from low to high, depending on the patient's immunologic and defense mechanisms and the existence of congenital or acquired risk factors. New attention must be given to more subtle effects on the upper aerodigestive tract (i.e., sinusitis and laryngitis) in view of the potential effects of certain toxic agents on these tissues.

Environmental Exposure↗
PubMed1992

An intraosseous device for studies of bone-healing. The effect of transforming growth-factor beta.

A novel implantable device, the analytic bone implant, was used in order to establish a model for studies of bone-healing and the evaluation of factors that augment the process, such as transforming growth-factor beta (TGF-beta). This device was implanted into the tibiae of four baboons. After healing, bone was removed from the center chamber. Recombinant human TGF beta-1 was then delivered to the core of the device. After twenty-two days of healing, the device was disassembled and the newly formed bone was removed from the core of the implant for histomorphometric analysis. An analysis of the bone revealed a substantial effect of TGF-beta on osteoblastic activity and proliferation compared with that seen in control and placebo groups. However, despite increased osteoblastic activity, trabecular bone volumes at twenty-two days were equivalent among the groups. The number of osteoclasts and the erosion of the surface were also increased, although not significantly so. Substantial endochondral formation of bone was seen in the supraperiosteal tissues directly over the implants that contained TGF-beta but not over the implants in the control and placebo groups. These data demonstrate the utility of this bone-implant model for studies of bone-healing with minimally invasive methods. In addition, use of the device provided the first in vivo data on the effects of TGF-beta at an intermediate (twenty-two-day) time-point in the healing process in a non-human primate.

Animals↗
PubMed1991

Chondrosarcoma of the jaws: clinical findings, histopathology, and treatment.

Three cases of chondrosarcoma involving the jaws are presented, one in the maxilla and two in the mandible. The salient points of clinical presentation elucidated by this series of cases are that a widened periodontal ligament space is present in chondrosarcomas as well as in osteosarcomas, and that a slowly increasing diastema may be the earliest clinical sign. The most important lesson to be learned from the histopathology is that one should not accept a diagnosis of a benign cartilaginous tumor of the jaws. Treatment of these lesions should consist of wide surgical excision and consideration of adjunctive or palliative radiotherapy, especially in the maxilla. It should also be noted that recurrences may develop 10 to 20 years later, and follow-up should be lifelong.

Adult↗
PubMed1990

Concepts of soft-tissue trauma repair.

The proper evaluation and treatment of soft-tissue trauma to the face is extremely important because of the psychologic, cosmetic, and functional sequelae that can occur from these injuries. The facial trauma surgeon should have a wide armamentarium of techniques to manage soft-tissue facial trauma and should approach the repair in a meticulous and scientific fashion. Although the best possible repair of the acute trauma is the goal, it is usually necessary to perform later some camouflage or revision procedures on the scar because of the high likelihood of hypertrophic scarring or inappropriate healing in the trauma scar.

Esthetics↗
PubMed1988

Delayed onset post-tympanotomy otorrhea.

Otorrhea is the most frequent complication of the use of tympanostomy tubes. When it occurs after the immediate postoperative period, otorrhea is probably the result of external contamination of the middle ear or acute otitis media. We analyzed data from 627 operations upon 1248 ears of 491 children with chronic secretory otitis media and found that delayed onset (longer than 7 weeks) postoperative otorrhea occurred after 26.4 percent of the 382 operations in which tympanostomy tubes were used. The average number of episodes of otorrhea per case was 1.46 and ranged from 1 to 9. The rate of otorrhea occurrence in patients with tubes in place was significantly higher in the summer months. Otorrhea also occurred after 9.0 percent of 245 myringotomy procedures. The average number of episodes was 1.32 and ranged from 1 to 3. Treatment of postoperative otorrhea increases the health care costs of surgical treatment of chronic otitis media with effusion; this problem should be included in the calculation of cost-effectiveness.

Child↗
PubMed1988

Nasolacrimal evaluation and surgery.

The lacrimal drainage system is a very important functional and anatomic assembly in the orbit and midface. For surgeons who intend to become involved in its repair or reconstruction, it is mandatory to understand the full range of anatomic, physiologic, and diagnostic considerations prior to embarking upon a surgical course. Proper eyelid function depends upon the integrity of its constituent parts, including the margin, tarsus, muscle, and globe apposition. The lacrimal pump mechanism is produced by proper eyelid function and structure, and must be adequately assessed. The puncta and canaliculi are delicate structures and must be manipulated with care and gentleness. The lacrimal sac is a static structure that serves as a collecting sphere but also may be forced to evacuate its contents into the nasolacrimal duct by the "squeezing" action of the investing tendons. Proper tendon position must be maintained after surgery or trauma to facilitate this action. The nasolacrimal sac may be damaged after facial fractures or blocked from intranasal conditions. If the blockage cannot be relieved, it must be bypassed by performing a dacryocystorhinostomy. The use of long-term, indwelling silicone intubation catheters greatly facilitates the successful reconstruction of the lacrimal drainage system. Proper attention to all of these points will be appreciated by the patient.

Dacryocystitis↗
PubMed1988

Management of orbital trauma and foreign bodies.

Blunt and penetrating trauma to the orbital region can have a devastating effect both functionally and cosmetically for the orbit. Penetrating injuries to the orbit should be suspected whenever there is a history of trauma to the regions of the eyelids. Meticulous inspection of the eyelids and globe should be undertaken, and if there is any suspicion of a foreign body retained within the orbital soft tissues, then a CT scan should be obtained. It is possible that the foreign body is not opaque, and exploration of the soft tissues may be indicated. Blow-out fractures of the orbit should be explored and repaired when the evidence clearly indicates that a blow-out is present. This includes the clinical presence of diplopia, evidence of muscle entrapment with forced duction testing, and CT scan showing orbital wall fracture with explosion of the orbital contents into the paranasal sinuses. If these signs or symptoms are equivocable, then a waiting period of 10 to 14 days is indicated to rule out the presence of a nerve palsy, which should improve. However, a CT scan showing a large blow-out defect of the orbit should be repaired regardless of the clinical signs at the time because of the late sequelae of enophthalmos and hypophthalmos. It is very difficult to secondarily repair an orbit that is contracted owing to loss of volume from an orbital blow-out fracture. Procedures of this sort involve the reintroduction of autogenous fat into the orbital contents and are very difficult technically. Although orbital fractures should not be routinely explored, each should be viewed with its own merit and an aggressive approach developed if there is clinical evidence of a blow-out fracture.

Eye Foreign Bodies↗
PubMed1987

Sexual dimorphism in the distribution of estrogen receptors in the temporomandibular joint complex of the baboon.

The localization of radiolabeled estradiol was examined in the temporomandibular complex of male baboons by means of an autoradiographic technique. Five baboons were studied. Four animals received only the tritiated estrogen (1 microgram/kgm) and one animal, which served as the control, received both the tritiated estrogen and the unlabeled estrogen (100 micrograms/kgm). The study failed to demonstrate nuclear uptake and retention of tritiated estrogen in any of the tissues of the temporomandibular joint complex, including the articular surface of the condyle, articular disk, capsule, and muscles of mastication. However, estrogen receptors were identified in other tissues, including the pituitary. All tissues examined in the control animal were negative for estrogen receptors. It was concluded that there were no estrogen receptors in the temporomandibular joint complex of aged male baboons. As in previous studies, these findings provide additional evidence of a sexual dimorphism with respect to estrogen receptor distribution in the temporomandibular joint complex of the baboon. Furthermore, it is reasonable to speculate that estrogens may modulate a variety of metabolic functions in these tissues that could be important in the maintenance, repair, and/or pathogenesis of the temporomandibular joint.

Animals↗
PubMed1987

Human Curvularia infections. Report of five cases and review of the literature.

Curvularia lunata is a saprobic dematiaceous mould that resides primarily in soil (Ellis, 1966). Reports of human disease caused by this organism are rare but include: endocarditis, brain abscess, skin infections, onychomycosis, keratitis, pneumonia, disseminated disease, mycetoma, allergic bronchopulmonary disease, and one case of sinusitis. Since 1983, we have encountered five cases of paranasal sinusitis due to C. lunata. None of the patients suffered from known immunologic disorders or underlying debilitating diseases. These five cases are presented and the literature of human phaeohyphomycosis caused by Curvularia spp. is reviewed.

Adult↗