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Biomedical subjects

R J McConnell

Publications and source records attributed to R J McConnell.

At least 19 recordsLinked to original sources
PubMed2001

Pituitary lymphoma presenting as fever of unknown origin.

An 86-yr-old woman presented with fever of unknown origin. When laboratory evaluation revealed partial hypopituitarism, a magnetic resonance imaging scan of the head was performed and revealed a sellar mass consistent with a pituitary adenoma. Only after other possible etiologies for fever were excluded did she undergo transsphenoidal resection of the sellar mass, which proved to be a B-cell lymphoma. Primary central nervous system lymphoma of the pituitary region is a rare cause of a sellar mass, and this is the first reported case of pituitary lymphoma whose presenting manifestation was fever of unknown origin. Several disease processes can manifest themselves as fever and a sellar mass, including lymphomas. In our case, only surgical biopsy could make a diagnosis and distinguish this process from the more common pituitary adenoma.

Aged↗
PubMed1999

Changes in thyroid function tests during short-term salsalate use.

Although long-term administration of salsalate depresses blood levels of both total thyroxine (T4) and total triiodothyronine (T3) and at least transiently decreases serum thyrotropin (TSH), changes in thyroid function tests have not been fully characterized during its short-term use. It is also unclear if the observed changes are solely the result of decreased hormone binding to carrier proteins or if reduced hepatic 5'-monodeiodinase activity is important. Blood was sampled at baseline (day 0) and after 24 hours (day 1) and 72 hours (day 3) in eight subjects taking a therapeutic dose of salsalate 1,500 mg twice daily. Total T4 decreased from 90.1+/-7.7 nmol/L (mean+/-SD) on day 0 to 82.9+/-8.6 nmol/L on day 1 (P=.1 v baseline) and 68.6+/-8.7 nmol/L on day 3 (P=.0001). Total T3 decreased from 1.76+/-0.20 nmol/L to 1.61+/-0.16 nmol/L on day 1 (P<.05) and 1.31+/-0.27 nmol/L on day 3 (P=.002). The T4/T3 ratio was 51.7+/-7.7 at baseline and remained unchanged after 3 days. Levels of reverse T3 (rT3) were reduced from 0.24+/-0.05 nmol/L to 0.18+/-0.02 nmol/L on day 3 (P<.05). While the free T4 index (FTI) declined in parallel with total T4, the free T4 level by direct equilibrium dialysis (FTD) was unchanged after 3 days. Serum TSH decreased from 1.47+/-0.47 mU/L to 0.91+/-0.27 mU/L after 1 day (P<.05) and remained suppressed after 3 days (0.95+/-0.49 mU/L, P<.05). In conclusion, (1) therapeutic doses of salsalate significantly decrease serum concentrations of total T4, total T3, and rT3 to about 75% of baseline levels after 3 days without altering the T4/T3 ratio; (2) although the FTD does not change, serum TSH concentrations remain suppressed; and (3) the proportionate decrease in total thyroid hormone levels suggests that inhibition of hormone binding to serum proteins is more important in producing these changes than reduced hepatic 5'-monodeiodinase activity.

Adult↗
PubMed1997

Bond strengths of two ceramic brackets using argon laser, light, and chemically cured resin systems.

The present study compared tooth-bracket bond strengths using two types of ceramic brackets and three methods of polymerization: argon laser, conventional light, and chemical. Ninety extracted human premolars were prepared for bonding with pumice and gel etchant. Using single crystal alumina brackets with silanated bases, three groups of 15 teeth were bonded with one of the three polymerization methods. Similarly, three groups of 15 teeth were bonded with polycrystal alumina brackets with nonsilanated bases. Each bonded bracket was tested on an Instron tensile testing machine in shear mode to determine shear debonding strength. Fracture sites were recorded. Results demonstrated that (1) all combinations produced shear bond strengths greater than those considered clinically acceptable, (2) the mean shear bond strengths of the single crystal alumina brackets with silanated bases were significantly higher than those of the polycrystal alumina brackets with nonsilanated bases, and (3) no enamel fractures were found on debonding the chemically cured brackets while the light and laser groups exhibited a 10% rate of enamel fracture on debonding.

Acid Etching, Dental↗
PubMed1997

Orthodontic bonding to Adlloy-treated type IV gold.

Adlloy surface treatment of noble alloys has been shown to increase the bond strength of composite to gold alloys. The purpose of this study was to test the bond strength of Adlloy-treated type IV gold surfaces and orthodontic brackets bonded with self-curing composite resin, and compare it with sandblasted gold and etched enamel. Data were derived from a control sample of 40 human premolars and two experimental groups of Adlloy-treated and sandblasted gold surfaces. "A"-Company premolar brackets were bonded with Concise self-curing composite resin. The specimens were submerged in water for 30 days and thermocycled 1500 times before being subjected to shear bond tests. Statistically significant differences were found in the mean values of the three groups (F = 124.04; df = 2,117; P < .001). Bonds on the adlloy-treated gold were twice as strong as those found on microetched gold. Adlloy surface treatment of type IV gold will permit adequate bond strength; however, FDA approval is required for intraoral use.

Acid Etching, Dental↗
PubMed1997

External resorption presenting as an intracoronal radiolucent lesion in a pre-eruptive tooth.

A large intracoronal radiolucent lesion in an unerupted permanent molar was found during the routine assessment of a young male Caucasian prior to orthodontic treatment. The tooth was extracted. Histological examination indicated the lesion was caused by external resorption. The defect extended widely into the enamel and dentine, and was repaired in part by bone. The pulp chamber was not involved. The aetiology of these lesions is often obscure but in this case it appeared to have originated in the floor of two developmental pits on the occlusal surface of the tooth.

Child↗
PubMed1995

Bacterial adhesion to dental amalgam and three resin composites.

OBJECTIVES: The ability of three oral bacteria to adhere to hydrophobic amalgam (water contact angle 60 degrees) and hydrophobic resin composites (Prisma-AP.H 56 degrees. Herculite XRV 82 degrees and Z100 89 degrees) was compared using an in vitro assay. METHODS AND RESULTS: Following preincubation of the materials with human saliva, X-ray photoelectron spectroscopy showed the surfaces to adsorb carbon and nitrogen-containing compounds in a conditioning film that appeared to block the detection of Na and others in 2100 resin. Hg and Ag in amalgam, Si and Zn in Prisma AP.H resin and Ag and Na in Herculite resin. The precoating of the substrata by a proteinaceous conditioning film led to decreased binding of viable cells of Streptococcus sanguis CH3, Streptococcus salivarius HB and Actinomyces viscosus WG as compared with the adhesion to bare composites. With and without salivary coating, there was a correlation between increased bacterial hydrophobicity and increased retention on the substrata. However, there was no statistical difference in binding to the amalgam compared with the resin composites. In vitro studies showed that the bacteria autoaggregated in the presence of saliva. CONCLUSION: The results indicate the potential ability of normal oral flora to colonize resin composite.

Actinomyces viscosus↗
PubMed1995

The performance of conventional, fixed bridgework, retained by partial coverage crowns.

A retrospective study was carried out on 248 partial coverage retained fixed bridges, in 211 patients. All were inserted at an undergraduate dental clinic and their length of service ranged from 1 to 19 years. In 211 prostheses, on which current information was available a total of 20 (9.5%) bridges had failed. The reasons for failure were loss of retention and, to a lesser extent, caries. Using a LIFE TABLE of survival, it was calculated that the percentage of short span, partial veneer retained prostheses that would survive TEN years was 76.5% +/- 5.99% (standard error). This figure is comparable to that quoted for resin-bonded bridges, and hence would militate against the use of conventional partial coverage fixed retainers on intact teeth. Where abutment teeth are heavily restored, full coverage retainers provide a more predictable, long term result.

Adolescent↗
PubMed1994

Working time of synthetic elastomeric impression material.

This study will introduce a new method for measuring the working time of elastomeric impression materials, taking into account the perceived shortcomings of existing systems for evaluating these times. The working times of various commercially available polysulfide, addition reaction silicones and polyethers were determined at room temperature (20 degrees C), following storage in a refrigerator (6 degrees C), and at mouth temperature (35 degrees C). At room temperature, the polysulfides demonstrated the longest working times and the silicones the shortest. Both the polysulfides and the silicones had longer working times following storage at 6 degrees C for 24 hours. However, the polyethers were found to be unusable at this temperature. All the impression materials had shorter working times when placed into the testing apparatus, which had been heated to mouth temperature.

Dental Impression Materials↗
PubMed1993

Metal-resin bonding.

Achieving an effective and lasting bond of resin to dental alloys is an essential component in today's restorative dentistry. This paper reviews the history of metal/resin bonding, outlines different surface treatments of base and noble alloys and compares some of the resin luting materials used. The clinical application of metal/resin bonding to repair porcelain veneered fixed prostheses and the potential of bonded amalgams is discussed.

Acrylic Resins↗
PubMed1993

A 2-year clinical evaluation of two pit and fissure sealants placed with and without the use of a bonding agent.

The purpose of the study was to evaluate whether the clinical effectiveness of pit and fissure sealant was increased (as demonstrated by an increased retention rate) when a bonding agent was used prior to the placement of the sealant. Two pit and fissure sealants, Concise Light Cured White Sealant and Prisma Shield Light Cured Sealant, were placed in vivo with and without the use of the bonding agents, Scotchbond 2 and Prisma Universal Bond. After 2 years, 55% of the sample was available for recall. The retention rates for the sealants were 77% for Concise with Scotchbond 2, 84% for Concise with no bonding agent, 77% for Prisma Shield with Universal Bond, and 77% for Prisma Shield with no bonding agent. Results of this study indicated that the use of a bonding agent prior to the application of a pit and fissure sealant does not increase the retention rate.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1992

Abnormal thyroid function test results in patients taking salsalate.

OBJECTIVE: To evaluate how the nonsteroidal anti-inflammatory agent salsalate affects the results of routine thyroid function tests. DESIGN: In a cohort of patients taking salsalate for various rheumatic conditions, thyroid function tests were performed with patients on and off the drug. SETTING: Primary care of ambulatory patients in a university medical center. PATIENTS: A convenience sample of 14 euthyroid subjects, none of whom was taking thyroid hormone or other medication recognized to alter thyroid function. INTERVENTION: Treatment with therapeutic doses of salsalate for a mean period of 44 weeks. MAIN OUTCOME MEASURES: Serum levels of thyroxine (T4), free T4, thyroid hormone binding ratio, free T4 index (the product of T4 and the thyroid hormone binding ratio), triiodothyronine, and thyrotropin. RESULTS: Serum T4 dropped from a mean baseline level of 96.7 nmol/L off salsalate to 53.4 nmol/L on it (P less than .001), and the free T4 index showed a parallel decline from 85.9 to 50.4 (P less than .001), with both values falling into the hypothyroid range. Similarly, free T4 levels and total triiodothyronine concentrations were low in several patients treated with salsalate. Serum thyrotropin levels declined transiently, falling from a mean of 3.2 to 1.7 mU/L (P less than .02) in patients treated for less than 3 weeks. Patients treated for longer periods had levels comparable to baseline. Despite these changes in the thyroid function test results, all subjects remained clinically euthyroid. CONCLUSION: Salsalate commonly produces abnormalities in routine thyroid function test results similar to those found in central hypothyroidism.

Adult↗