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Biomedical subjects

W M Davidson

Publications and source records attributed to W M Davidson.

At least 19 recordsLinked to original sources
PubMed2001

A useful insight into 2 occlusal indexes: HLD(Md) and HLD(CalMod).

Maryland and California are among the states that have adopted the Handicapping Labiolingual Deviation (HLD) Index to determine eligibility for public funding of orthodontic treatment. As a result of several lawsuits against the state, California has developed and employed a modification of that index, called the HLD(CalMod) index. This study compared and contrasted the effects of analyzing prospective patients with the HLD(Md)-the HLD index as used in Maryland-and the HLD(CalMod) indexes. The specific aims of this study were to observe (1) the correlation between the 2 occlusal indexes in determining patients' eligibility for treatment with public funding, (2) the characteristics of patients eligible according to each index, and (3) the major contributing factors in assigning patients as eligible under each index. Initial study models of 313 patients from the orthodontic clinic at the University of Maryland were scored by both HLD(Md) and HLD(CalMod) indexes. According to the scores, the patients were divided into 2 groups-those with handicapping malocclusions and those without handicapping malocclusions. Scores from each index were analyzed by the Pearson product moment correlation. The Angle classification for each patient was also recorded with the HLD variables. The mean and the percentage of the total score for each variable were calculated. The following conclusions were obtained: (1) Of the 313 patients, 127 (41%) were approved for treatment by the HLD(Md) index, and 110 (35%) were approved for treatment by the HLD (CalMod) index.(2) The correlation between the 2 indexes (R = 0.78) was not very strong, indicating the power of the additional variables introduced in the HLD(CalMod) index. (3) The use of the HLD(CalMod) index directs more public funding toward patients with severe Class II malocclusions than does the HLD(Md) index.

Adolescent↗
PubMed2000

Orthodontic dental visits during 1987 and 1996.

Americans underwent approximately 355 million dental procedures during 1987, approximately 8% for orthodontic treatment. Individual rates of utilization vary and are not uniform across the population. This article provides estimates of orthodontic utilization for each of several socioeconomic and demographic categories, using household data from the 1987 National Medical Expenditure Survey (NMES) and the 1996 Medical Expenditure Panel Survey (MEPS). These data show that slightly more than 3% of the population, or approximately 39 million Americans, visited a dentist to receive orthodontic care nationwide during 1987 and 1996. For those with an orthodontic visit, the mean number of visits per patient decreased in number from 1987 to 1996.

Adolescent↗
PubMed1998

A case of supernumerary teeth in the premaxilla, maxillary cuspid, and mandibular premolar regions.

A case of several developing supernumerary teeth is reported. A seven-year-old African-American boy presented with retained primary maxillary central incisors, two impacted mesiodens, and unerupted permanent maxillary central incisors. A dentigerous cyst was removed at the time of surgical removal of the mesiodens. Approximately fourteen months post-extraction, a new panoramic radiograph showed the presence of six previously unidentified developing and unerupted supernumerary teeth, one on each of the maxillary cuspid areas and two on the mandibular premolar regions bilaterally. Practitioners should be aware that supernumerary teeth may develop late. Thus, periodic reevaluation with appropriate radiographs is indicated, especially in patients who have presented with supernumerary teeth.

Child, Preschool↗
PubMed1993

Permeability of latex gloves after contact with dental materials.

The use of latex examination gloves in the dental office has become the standard of care. However, the effectiveness of gloves as a barrier after coming into contact with specific dental materials is still uncertain. To examine the effects of dental materials is still uncertain. To examine the effects of dental materials on latex, 100 latex examination glove finger tips were divided into 10 groups. Each group was manipulated in a different dental material for 15 minutes. Permeability was detected by the passage of herpes virus across the latex membrane, rinsed from the inner glove surface and titrated onto Vero cells. Significant virus leakage was discovered in gloves treated with acrylic monomer, chloroform, and orange solvent. Little virus leakage was noted in bleach, soap, and 30% phosphoric acid etchant treated gloves, and no virus leakage was found with composite resin, ethanol, formocresol, and water treated gloves. These data were supported with scanning electron micrographs taken of the treated glove samples and comparing with the controls. When certain dental materials are manipulated while wearing gloves, irreversible damage to the material occurs and may increase the practitioner's exposure to pathogens.

Animals↗
PubMed1988

Long-term cytotoxicity of orthodontic direct-bonding adhesives.

The purpose of this study was to examine the potential toxic effects of several orthodontic adhesives immediately after polymerization and at various time intervals up to 2 years postopolymerization by means of an in vitro overlay assay. Adhesive samples were incubated on tissue cultures containing an agar overlay with a vital dye (neutral red). Viable cells were stained red; nonviable cells were unstained. The circular pattern of nonviable cells demonstrated a zone of inhibition that was measured and compared. All materials tested showed cytotoxic effects immediately after polymerization and the toxic effect decreased with time postpolymerization. However, 2 years after initial polymerization, significant zones of inhibition indicating continued in vitro toxicity were still evident in all but one of the adhesives.

Adhesives↗
PubMed1988

Protection by latex or vinyl gloves against cytotoxicity of direct bonding adhesives.

The cytotoxicity of orthodontic bonding agents (OBAs) has been demonstrated in both animal and in vitro studies. Many practitioners and their assistants have experienced contact dermatitis of the fingers following contact with OBA. Latex gloves have also been reported to cause similar symptoms in several reports. The purpose of this study was to evaluate and quantify the toxic effects of latex and vinyl gloves, several OBAs, and combinations of these in vitro to determine the kind of glove that should by worn by practitioners when manipulating an OBA. It was determined that when OBAs are applied to washed latex, the combined toxic effect on cultured cells exceeded that of the washed gloves alone. However, when vinyl glove material instead of latex was tested, the toxic effects decreased more than 50%. Therefore, we suggest that practitioners who experience contact dermatitis in orthodontic practices wear vinyl gloves instead of latex, especially when manipulating OBAs. We also acknowledge the need for further research on the subject.

Adhesives↗
PubMed1988

Experimental acetabular dysplasia associated with a lesion of iliopubic limb of the triradiate cartilage.

An experimental lesion was created in the iliopubic limb of the triradiate cartilage in young Wistar rats with the object of studying the role of this structure in the development of hip joint disorders. Roentgenographic, functional, morphologic, and morphometric results were evaluated during the following 12 weeks. Acetabular dysplasia, dislocation, or subluxation of the hip, deformities of the acetabulum and the femoral head, and bending and hypoplasia of the innominate bone were the most significant findings. It is concluded that a lesion of the iliopubic limb of the triradiate cartilage may be a cause of severe hip joint disorders such as acetabular dysplasia, subluxation, and dislocation.

Acetabulum↗
PubMed1983

In vitro cytotoxicity of orthodontic bonding materials.

Previous studies have shown that toxic reactions to direct-bonding adhesives can be demonstrated both in animals and in cell culture tests. These effects have also been shown with other related dental materials. The purpose of this study was to compare the relative toxicity of a number of common orthodontic adhesives and to determine, by means of a rapid, sensitive in vitro cell culture agar overlay test, how their toxicity changed with time subsequent to polymerization. Various othordontic bonding materials were tested either immediately or at various times up to 30 days after polymerization. The cells were stained with a vital dye (neutral red), the diameter of the area of unstained, nonviable cells was measured, and the results of three tests per sample were averaged and analyzed by means of Duncan's Multiple Range Tests. All materials were found to have some cytotoxic effect immediately after mixing, with the activator components of two "no-mix" materials exhibiting significantly higher toxicity (p less than 0.05) than other materials tested. The sealant materials showed a significantly greater toxicity than paste resins, both initially after mixing and after 30 days postpolymerization. If applicable to the clinical situation, these data indicate that care is needed particularly in handling liquid activators. Excess "polymerized" sealant, which may contain many nonreacted groups, should be carefully removed by scaling peripheral to the bracket bases, particularly in subgingival and interproximal areas.

Adhesives↗
PubMed1982

Incisor shape and incisor crowding: a re-evaluation of the Peck and Peck ratio.

Although lower incisor tooth shapes, defined as mesiodistal length divided by labiolingual width, have bee proposed as important factors in lower incisor crowding, the question of whether or not these ratios are more useful than simple measurements of incisor mesiodistal length has not been addressed. In order to test this question, we measured mesiodistal and labiolingual incisor dimensions and lower incisor crowding (defined as the crowding index proposed by Little) on dental casts from two groups: 100 pretreatment orthodontic patients and 100 Hutterites from a religious isolate in Canada. The orthodontic patients are our primary interest. The Hutterites serve mainly to test whether or not results are consistent in another population of different ethnicity, age distribution, and occlusal status. In each population, incisor crowding is correlated with the tooth shape ratios, confirming the general observations of Peck and Peck. However, mesiodistal incisor lengths have slightly higher correlations with crowding than the shape ratios. In multiple regression equations to predict crowding in each population, incisor mesiodistal lengths are the most important variable, and neither the tooth shape ratios nor labiolingual widths significantly improve the equations. Although statistically significant, none of the correlations is higher than 0.30, and they are thus of little clinical value. The use of tooth size measurements or ratios as a guide to clinical procedures is an oversimplification of a complex problem.

Canada↗
PubMed1982

Tissue reaction to orthodontic adhesives.

The widespread introduction of materials for direct bonding into practices and the numerous reports of a variety of toxic reactions to similar materials prompted a study of the toxicity of six adhesives in an animal model. Thirty-nine hamsters were employed to evaluate responses of skin, oral mucosa, and gingiva, sites of possible contamination by adhesives in clinical use. Animals were treated topically with separate components of adhesives. Adhesives were also allowed to polymerize on and remain in contact with tissues. Test sites were examined grossly and histologically and evaluated for toxic response. The monomer component of one adhesive consistently caused gross irritation and histologic inflammation in twelve animals (p less than 0.001) in which it was used. Other adhesives and components did not have this effect. This adhesive was withdrawn from the market and modified at about the same time these experiments were performed. Similar results have not been observed with the modified product. Clinicans should recognize the potential for reaction to adhesives and realize that products with a toxic potential can reach the market. They should be prepared to change adhesives should reactions to one be observed. They should further recognize that absence of reaction in any test system does not preclude reaction in clinical use.

Adhesives↗
PubMed1975

Reduced lymphocyte transformation in early cancer of the breast.

The cell mediated immune response has been measured in vitro by lymphocyte transformation in 53 patients with malignant tumours of the breast and an equal number of patients in the same age group operated upon for benign tumours. The response to phytohaemagglutinin (PHA) was reduced in the patients with malignant tumours when the lymphocytes were grown either in the patient's plasma or in autologous plasma. This was observed when the response was measured both by the uptake of radioactive DNA precursor and by autoradiography. Reduced lymphocyte transformation was present even very early in the disease and certainly preoperatively. The reduction appeared to be even more marked in the advanced cases. An interesting finding was that the plasma from cancer patients contained a factor which reduced the PHA transformation of lymphocytes from a healthy donor.

Autoradiography↗
PubMed1973

Acquired trisomy 9.

Explore the source record for details and available documents.

Bone Marrow Diseases↗
PubMed1972

Bone marrow lipofuscin.

Lipofuscins are commonly present in the macrophages of the marrow. In unstained preparations they may be confused with haemosiderin, but they are readily distinguished by fluorescence microscopy. In contrast to the belief that lipofuscins are a manifestation of senility, no age dependence has been demonstrated. Exceptionally large amounts have been found in illnesses accompanied by fever and leucocytosis, in keeping with the concept of their formation from insoluble remains of ingested cell fragments. It is probable that the ;sea-blue histiocytes', described in the literature, are macrophages laden with strikingly uniform granules of lipofuscin.

Adolescent↗