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Biomedical subjects

E Lynch

Publications and source records attributed to E Lynch.

At least 55 records · Page 3Linked to original sources
PubMed1994

A new laboratory method to fabricate lower porcelain veneers.

The fabrication of porcelain veneers in the laboratory presents many problems for the technician in the production of accurate margins and contacts, good aesthetics and, in some cases, function with the opposing dentition. Therefore, a simple, accurate and previously unpublished method of producing multiple contiguous veneers is described in this paper, involving the fabrication of six lower anterior porcelain veneers in a difficult case of tooth surface loss.

Cuspid↗
PubMed1993

Prenatal diagnosis of Charcot-Marie-Tooth disease type 1A by multicolor in situ hybridization.

Genetic heterogeneity within the most common genetic neuropathy, Charcot-Marie-Tooth disease (CMT) results in about 70% slow nerve conduction CMT1 and 30% normal nerve conduction CMT2. Autosomal dominant CMT1A on chromosome 17p11.2 represents about 70% of CMT1 cases and about 50% of all CMT cases. Three different size CMT1A duplications with variable flanking breakpoints were characterized by multicolor in situ hybridization and confirmed by pulsed field gel electrophoresis and quantitative polymerase chain reaction (PCR) amplification. These different size duplications result in the same CMT1A phenotype confirming that trisomy of a normal gene region results in CMT1A. The smallest duplication does not include the 409 locus used previously to screen for CMT1A duplications. Direct analysis of interphase nuclei from fetuses and at-risk patients by multicolor in situ hybridization to a commonly duplicated CMT1A probe is informative more often than polymorphic PCR analysis, faster than pulsed field gel electrophoresis (PFGE), and faster, more informative, and more reliable than restriction enzyme analysis. CMT1B restriction enzyme analysis of CMT pedigrees without CMT1A is expected to diagnose another 8% of at-risk CMT1 patients (total: 78%).

Amniocentesis↗
PubMed1993

Pharmacokinetics of newer cephalosporins after subconjunctival and intravitreal injection in rabbits.

Pharmacologic considerations suggest that third-generation cephalosporins might penetrate the vitreous humor better after periocular injection and might be eliminated less readily after intravitreous injection than older agents. We studied the sodium salts of ceftizoxime, ceftriaxone, and ceftazidime, and of an investigational cephalosporin, cefepime, in rabbits. After a single subconjunctival injection in animals with normal eyes, vitreous levels ranged from 3 to 13 mg/L. After five subconjunctival injections in rabbits with infected eyes, vitreous concentrations ranged from 12 to 34 mg/L. These concentrations are not appreciably greater than those found with older beta-lactams. The vitreous half-life of the four drugs after intravitreous injection varied from 5.7 to 20 hours in rabbits with uninflamed eyes and from 9.4 to 21.5 hours in rabbits with infected eyes. Except for ceftizoxime, the half-lives were substantially longer than those for older beta-lactams and suggest predominantly anterior route elimination. Vitreous penetration of these new agents after subconjunctival injection does not appear to be sufficient to overcome the need for intravitreous injections in the treatment of endophthalmitis. However, the longer vitreous half-lives of some of the newer agents may be useful if the drugs are to be given intravitreally.

Animals↗
PubMed1993

Ocular penetration of ceftriaxone, ceftazidime, and vancomycin after subconjunctival injection in humans.

Vancomycin (25 mg), ceftriaxone (125 mg), and ceftazidime (100 mg) were given by subconjunctival injection before vitrectomy to patients with uninfected eyes. Most of the patients had diabetic vitreous hemorrhage with or without traction retinal detachments, and some had rhegmatogenous retinal detachments with proliferative vitreoretinopathy. Samples of vitreous were obtained by pars plana vitrectomy at intervals from 46 minutes to 4 hours 13 minutes after the subconjunctival injection. The median vitreous concentrations of all three drugs were below the limit of detection. Vitreous concentrations of these drugs after a single subconjunctival injection are exceedingly low.

Adult↗
PubMed1993

Elaboration of interleukin 1-receptor antagonist is not attenuated by glucocorticoids after endotoxemia.

The body's response to infection/inflammation is initiated by the elaboration of cytokines, such as tumor necrosis factor, interleukin 1-beta (IL-1-beta), IL-6, and IL-8. Cytokines, in turn, stimulate the pituitary-adrenal axis, and it has been suggested that the corticosteroids elaborated serve as negative feedback signals to diminish inflammatory events. To test this hypothesis, we administered hydrocortisone shortly before endotoxin administration to normal volunteers. Steroids greatly reduced the clinical response to endotoxin and attenuated the appearance of tumor necrosis factor, IL-6, and IL-8 in the circulation. In contrast, IL-1-receptor antagonist, a competitive antagonist of the IL-1 receptor, was unaffected by steroid administration. These data suggest that IL-1-receptor antagonist may act in synergism with corticosteroids to reduce inflammation. Elevation of concentrations of these two factors, corticosteroids and IL-1-receptor antagonist, in plasma appears to be the mechanism used by the body to overcome the effects of inflammatory cytokines.

Adult↗
PubMed1993

High-density genetic map of the BRCA1 region of chromosome 17q12-q21.

To facilitate the positional cloning of the breast-ovarian cancer gene BRCA1, we constructed a high-density genetic map of the 8.3-cM interval between D17S250 and GIP on chromosome 17q12-q21. Markers were mapped by linkage in the CEPH and in extended kindreds in our breast cancer series. The map comprises 33 ordered polymorphisms, including 12 genes and 21 anonymous markers, yielding an average of one polymorphism every 250 kb. Twenty-five of the markers are PCR-based systems. The order of polymorphic genes and markers is cen-D17S250-D17S518-HER2-THRA1-RARA-D17S80 -KRT10-[D17S800-D17S857]-GAS- D17S856-EDH17B-D17S855-D17S859-D17S858-[++ +PPY-D17S78]-D17S183-EPB3-D17S579- D17S509-[D17S508-D17S190 = D17S810]-D17S791-[D17S181 = D17S806]-D17S797- HOX2B-GP3A-[D17S507 = GIP]-qter. BRCA1 lies in the middle of the interval, between THRA1 and D17S183. Markers from this map can be used to determine whether cancer is linked to BRCA1 in families, to evaluate whether tumors have lost heterozygosity at loci in the region, and to identify probes for characterizing chromosomal rearrangements from patients and from tumors.

Alleles↗
PubMed1993

Marginal adaptation.

A critical review of studies assessing the marginal adaptation of direct placement, plastic restorations is presented. The effects upon adaptation of cavity design and location of cavity margins are examined, together with the effects of differing placement and finishing techniques. Both the choice of restorative material and the use of liners/bases are shown to influence the quality of restoration margins. Techniques used in both in vivo and in vitro assessment are reviewed, however it appears that a wide variety of methodologies exist and the establishment of standard, published criteria for the qualitative assessment of marginal adaptation is recommended.

Composite Resins↗
PubMed1993

Epidemiology of root caries.

Many epidemiological studies have been conducted on a variety of populations. Unfortunately, comparison of the prevalence data, and to a lesser degree of the incidence data, between the various studies is of little use due to the lack of standardised diagnostic criteria, reporting methods and population diversity. In the few incidence studies which have been conducted around 30-40% of people developed root caries, although many adults in the population appear to have been affected by root caries. Many risk factors associated with the occurrence of root caries have been identified and these include oral, medical, mental, behavioural and psychosocial conditions.

Adolescent↗
PubMed1993

Relationships between mutans streptococci and perceived treatment need of primary root-caries lesions.

A total of 447 primary root-caries lesions from 169 dental patients was studied to determine the relationships between mutans streptococci and the perceived treatment need of primary root-caries lesions. Samples of this altered dentine for microbiological culture were obtained. Lesions were classified into 5 treatment categories: soft and restore, leathery and restore, leathery and debride of caries, leathery and treat chemotherapeutically, and hard, to receive no treatment. The total numbers of mutans streptococci decreased significantly with decreased treatment need. The percentage of mutans streptococci from lesions requiring no treatment was significantly less than from lesions requiring treatment. The frequency of isolation of mutans streptococci was significantly greater from lesions requiring more treatment. Significantly more lesions containing > 10(2) mutans streptococci were distributed in the groups with a greater perceived treatment need or with larger dimensions occluso-gingivally and/or mesio-distally or bucco-lingually or with a closer proximity to the gingival margin.

Adult↗
PubMed1993

Relationships between yeasts and primary root-caries lesions.

A total of 447 primary root-caries lesions from 169 dental patients was studied to determine the relationships between their clinical severity and the number and frequency of isolation of yeasts. Yeasts were isolated more frequently from soft lesions, from lesions at the gingival margin and from lesions deemed to require restoration. These associations may be due to the aciduricity and acido- genicity of yeasts but the relatively low numbers found do not support a pathogenic role for yeasts in the aetiology of root caries: at best they may be marker organisms of the most severe disease.

Analysis of Variance↗
PubMed1993

Assessment of the clinical status of primary root carious lesions using an enzymic assay.

The microflora of root carious lesions (n = 151) and sound root surfaces (n = 30) in 22 institutionalized, older patients was investigated using a standardized method of sampling. Material was removed using a sterile excavator and the numbers of bacteria in each sample were determined using conventional culturing techniques and by rapid (2 h) fluorogenic enzyme assay. Correlation between bacterial counts and enzyme assay result was 0.873 (p < 0.001). The numbers of bacteria and fluorogenic enzyme assay values were significantly (p < 0.001) greater from soft lesions than from leathery lesions while hard lesions and sound root surfaces had significantly (p < 0.001) lower values than the other lesion types and were not different from each other. A similar trend was apparent when these values were correlated with treatment needs. The fluorogenic enzyme assay may provide a rapid, objective measure of root caries severity which might be used in the monitoring and comparison of treatment protocols.

Aged↗
PubMed1993

A microbiological study of primary root-caries lesions with different treatment needs.

Samples of altered or carious dentin for microbiological culture were obtained from 301 primary root-caries lesions in 59 patients by means of a standardized sampling procedure. This involved the cleansing of each root surface of extraneous supragingival plaque by means of a hand-held toothbrush and distilled water and the collection of the sample with a sterile dental excavator passed through the entire vertical dimension of each lesion. The total number of colony-forming units (cfu) in each sample and the numbers of mutans streptococci (primarily Streptococcus mutans), lactobacilli, yeasts, and Gram-positive pleomorphic rods (GPPR) were determined. Individual bacterial counts were expressed as log10 (cfu per sample), as a percentage of the total number of bacteria per sample, and as a frequency of isolation from lesions with different clinical diagnostic criteria. Clinical measurements of each lesion were made for color, texture, position relative to the gingival margin, and treatment need. Lesions classified as soft yielded significantly more bacteria, mutans streptococci, lactobacilli, and GPPR than leathery lesions, which yielded more bacteria than hard lesions. Lesions were classified into 5 treatment categories: soft and restore, leathery and restore, leathery and debride of caries; leathery and treat therapeutically; and hard no treatment. The total numbers of bacteria, mutans streptococci, lactobacilli, GPPR, and yeasts decreased significantly with decreasing treatment need. The frequency of isolation of mutans streptococci, lactobacilli, and yeasts was significantly greater from lesions requiring restoration and from lesions situated within 1 mm of the gingival margin. We suggest that the majority of root caries is initiated adjacent to the gingival margin.

Actinomyces↗
PubMed1993

Principles of enamel etching.

Amongst the innovations that have changed the practice of dentistry over the past three decades, the acid-etch technique and the use of composite resins may be regarded as two of the most influential. In 1955, Michael Buonocore, a researcher at the Eastmen Dental Centre in Rochester, New York, made the astute observation that the application of weak inorganic acid could alter the surface enamel so that bonding of a resin to the surface could take place. Buonocore experimented with acrylic resins but found these were much too weak to withstand the stresses exerted upon them in the mouth. It was not until Rafael Bowen developed a unique system containing 25 percent by weight of polymerisable monomer and 75 percent by weight of a vitreous filler--the composite resin--that the acid-etch technique became an effect procedure. This article reviews historical and current research, in the search to optimise the resin to enamel bond.

Acid Etching, Dental↗
PubMed1992

The gene for an inherited form of deafness maps to chromosome 5q31.

Primary--i.e., nonsyndromal-postlingual deafness is inherited as an autosomal dominant phenotype in a large kindred in Costa Rica. Genetically susceptible individuals begin to lose hearing at low frequencies at about age 10 years, after language and speaking are learned. Deafness inevitably progresses by age 30 years to bilateral hearing loss of all frequencies. Intelligence, fertility, and life expectancy are normal. The family traces its ancestry to an affected founder born in Costa Rica in 1754. We have mapped the gene for deafness in this kindred to chromosome 5q31, between the markers IL9 and GRL, by linkage analysis involving 99 informative relatives.

Base Sequence↗
PubMed1992

Varying intensity of postremission therapy in acute myeloid leukemia.

The Eastern Cooperative Oncology Group (ECOG) conducted a randomized trial in patients less than or equal to 65 years old (median, 44 years) to determine whether increasing the intensity of postremission therapy in acute myeloid leukemia (AML) would improve the outcome. After uniform induction therapy, patients in complete remission (CR) who were less than 41 years old and who had a histocompatible sibling underwent allogeneic bone marrow transplantation (alloBMT) (54 patients). The remainder of patients in CR were randomized to receive either 2 years of continuous outpatient maintenance therapy with cytarabine and 6-thioguanine (83 patients) or a single course of inpatient consolidation therapy consisting of 6 days of high-dose cytarabine plus 3 days of amsacrine (87 patients). The median duration of follow-up is now 4 years, and patients are included in the analyses of outcome regardless of whether they relapsed before starting the intended treatment. Four-year event-free survival (EFS) was 27% +/- 10% for consolidation therapy versus 16% +/- 8% for maintenance therapy (P = .068) and 28% +/- 11% versus 15% +/- 9% (P = .047) in patients less than 60 years old. The outcome for patients receiving alloBMT was compared with the subset of patients less than 41 years old who received consolidation therapy (N = 29) or maintenance therapy (N = 21). Four-year EFS was 42% +/- 13% for alloBMT, 30% +/- 17% for consolidation therapy, and 14% +/- 15% for maintenance therapy. AlloBMT had a significantly better EFS (P = .013) than maintenance therapy, but was not different from consolidation therapy. In patients less than 41 years old, 4-year survival after alloBMT (42% +/- 14%) did not differ from consolidation therapy (43% +/- 18%), but both were significantly better than maintenance therapy (19% +/- 17%), P = .047 and .043, respectively. The mortality rate for maintenance therapy was 0%, consolidation therapy, 21%; and alloBMT, 36%. Consolidation therapy caused an especially high mortality rate in the patients greater than or equal to 60 years old (8 of 14 or 57%). The toxicity of combined high-dose cytarabine and amsacrine is unacceptable, especially in older patients, and alternative approaches to consolidation therapy such as high-dose cytarabine alone need to be tested. In AML, a single course of consolidation therapy or alloBMT after initial CR produces better results than lengthy maintenance therapy. Although EFS and survival of alloBMT and consolidation therapy do not differ significantly, a larger number of patients need to be studied before concluding that they are equivalent.

Acute Disease↗
PubMed1992

Microleakage.

A critical review of techniques used in the assessment of microleakage in dental restorations is presented. These techniques include the use of air pressure, bacteria, radioisotopes, electrochemistry, chemical tracers and dye penetration. Wide variations in methodologies are revealed.

Dental Leakage↗