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PubMedDate not supplied

Part one: The restoration of non-vital teeth: structural, biological, and micromechanical issues in maintaining tooth longevity.

This manuscript will review research from 1967 to the present to find the best evidence for the reconstruction of non-vital teeth. The paper will review the contention that non-vital teeth are "more brittle" by analyzing the relevant physical properties of vital versus non-vital teeth; describe the structures of the tooth used to manage stress and strain; describe the formation of dentinal cracks and propagation of fracture planes through dentin; and analyze forces placed on human teeth and their effects on the tooth in Part One. In Part Two, the paper will describe the strength of various dowel and core designs relative to strength, retention, and durability and describe the results of testing various dentin bonding materials in strength and retention of dowels in non-vital teeth. The review will conclude with recommendations as to the materials and techniques in specific clinical situations best capable of single tooth reconstruction to ensure tooth longevity together with the scientific basis for their adoption.

Biomechanical Phenomena↗
PubMed1990

An investigation of factors influencing the longevity of restorations in primary molars.

The treatment records of three dentists working in south-east England were screened and 361 chosen for the investigation of the longevity of restorations placed in primary molars. The analysis was carried out using an independent sampling technique, i.e., one restoration per patient. The median survival time for all the restorations was 70.6 months (standard error +/- 3.7 months). The survival pattern of the restorations for the three dentists was different and therefore the influence of six factors on the life-span of restorations was investigated using the Cox regression model. There was no evidence that the life-span of the restorations depended on the sex of the patients (p = 0.506), or the type of primary molars being treated (p = 0.776); there was weak evidence that the life-span depended on the caries susceptibility of the patient (p = 0.151) and preformed metal crown restorations (p = 0.106); there was good evidence that the life-span depended on the age of the patients at the time of treatment (p = 0.016), whether pretreatment radiographs had been taken (p = 0.023) and type of amalgam restoration (p = 0.003).

Child↗
PubMed1990

Clinical longevities of ramus frame implants.

A variety of ramus frame dental implant designs is indicated for endosseous restoration to retain lower dentures, and the different designs utilize various alloys. The objective of this study was to present an analysis of the clinical applications for ramus frame dental implants with emphasis on the statistics of clinical longevities. The investigation involved an extensive statistical evaluation and, when possible, metallographic, scanning electron microscopic, histological, mechanical, and stereomicroscopic surface evaluations. The statistical analysis presents averages and percentages of devices in place vs. devices removed. Analyses of survival probability were also determined by means of the Kaplan-Meier statistical methods. A comparison of these results with the general criteria listed in the Harvard Conference shows that more than 75% of the implant devices were in place after five years.

Dental Alloys↗
PubMed1989

[Longevity of amalgam fillings in permanent teeth of minors].

The longevity of 3,300 amalgam fillings was tested with 1,165 juvenile minors at the age of 16 to 17, born in 1967-69. Up to the closing of peadontic care it was necessary to renew 25 percent of all amalgam fillings once or several times. After a manual trituration the renewing rate was more than the double of hight. Fillings applied between 6 and 9 years of life must be renewed to 37 percent during 5 years; fillings applied between 9 and 11 years of life were renewed to 25 percent. Differences between fillings applied at the High School and in the territory, respectively, have not been registered.

Adolescent↗
PubMed1987

A novel family of mitochondrial plasmids associated with longevity mutants of Podospora anserina.

We have identified a novel family of plasmids, each containing very short monomeric units, in Podospora anserina longevity mutants. These plasmids, termed small mitochondrial DNAs (sMt-DNAs), are derived from a highly ordered 368-base pair region of the mitochondrial genome. A total of five direct repeat sequences and seven significant regions of dyad symmetry (i.e. palindromes) were found within a 434-base pair mitochondrial sequence, which includes this 368-base pair region. Mitochondrial DNA rearrangements accompany the formation of these small plasmids indicating their derivation from a plastic region of the mitochondrial genome. A possible relationship between the direct repeat sequences, the palindromic regions, and the excision process is discussed.

Ascomycota↗
PubMed1987

Longevity of microorganisms in natural environments.

Bacterial endospores are exceptional among living systems in respect to their resistance to adverse environmental conditions, notably to heat and dessication, and consequently might be expected to show crytobiosis of very long duration. This report considers recent observations indicating that the maximal longevity of bacterial spores is probably much greater than previously believed.

Environment↗
PubMed1988

Basic studies on the laboratory assessment of macrofilaricides using Brugia malayi in the jird, Meriones unguiculatus. 1. Longevity and periodicity of microfilaremia.

The longevity and periodicity of microfilaremia were examined in the jird infected with Brugia malayi to be used for assessing the filaricides. Jirds 4 to 6 weeks old were inoculated subcutaneously with 100 to 200 infective larvae of B. malayi. Microfilariae were present in 75 out of 94 jirds observed over 3 years and high microfilaremia, with 10 mf/microliters or higher, developed in 43 out of 75 jirds. Such a high level of microfilaremia was necessary for narrowing the variation of microfilaria counts among the blood samples. The microfilaria negative jirds, 4 months after inoculation, were abandoned, because in those cases where they became patent later the microfilaria density did not reach an appropriate level. The selected jirds were used for experiment from 6 to 15 months after inoculation when most of them revealed the maximal count of microfilariae. The jirds that failed to develop microfilaremia to the level of 10 mf/microliters by 9 months after inoculation were also abandoned because they did not continue the appropriate level of microfilaremia even when they reached this level later. Although a significant periodicity was observed only in of 10 jirds examined by the Aikat and Das method, the peak hour of microfilaria density was observed in most animals in the afternoon and the time was nearly the same in each animal. Therefore, the blood sampling would be performed preferably in the afternoon.

Animals↗
PubMed1988

The effects of modern cementing techniques on the longevity of total hip arthroplasty.

Modern prosthetic design and cementing techniques have dramatically improved femoral component fixation. Compared to studies reported in the 1970s, the incidence of radiographic loosening for periods up to 5 years postoperatively has been reduced by at least a factor of 10. These results are the benchmark by which alternative forms of femoral component fixation must be measured. With the likelihood of increased longevity of total hip arthroplasty resulting from improved fixation, the problems of wear debris from the bearing surfaces and loss of bone stock with time will become preeminent.

Bone Cements↗
PubMed1986

Longevity of microfilariae following removal of the adult worms.

The present study was undertaken to determine the longevity of a population of microfilariae in a natural host following the removal of the adult worms without drug intervention. Four squirrel monkeys previously infected with Dipetalonema gracile were allowed to develop stable microfilaremias. All adult worms were then removed surgically from the peritoneal cavity. Weekly microfilaria counts were made on each animal and the decline in microfilariae recorded. At the time of adult worm removal, microfilaremias ranged from 750 to 12,500 mf/ml. The observed decline in microfilaria densities was gradual, but steady, in all animals. Microfilariae persisted in 1-ml blood samples for 60, 62, 91, and 101 weeks following removal of adult worms. The results indicate clearly that in a naturally produced population, in a natural definitive host, microfilariae survive for 60 to 100 weeks. The gradual decrease in microfilarial densities would appear to be the result of the death of specific batches or broods of microfilariae. The microfilariae which persisted in the blood the longest undoubtedly represent those which were produced just prior to the removal of the adult worms. It is postulated that because of the long life-span of microfilariae, female worms are not called upon to produce a continual supply of microfilariae, nor is the need for mating as frequent as might be expected. Equally important, the number of microfilariae which the host is called upon to phagocytize is considerably smaller than previously suggested.

Animals↗
PubMed1980

Tumour incidence and longevity in neutron and gammairradiated rabbits, with an assessment of r.b.e.

Rabbits were kept for the whole of their natural life-span (6--9 years) after exposures of 440--1410 rad of gamma-rays or 180--550 rad fission neutrons. Irradiated rabbits did not live as long as unirradiated controls but the difference was statistically significant only after the higher doses of neutrons. Earlier deaths were explained by increased incidences of a wide variety of tumours. The increases were statistically significant for basal-cell tumours of the skin, fibroasarcomas, osteosarcomas and Sertoli-cell tumours of the testis. Other phenomena assoicated with natural ageing were unchanged or decreased in irradiated rabbits. The r.b.e. of the neutrons was assessed as 3--3.5 for tumour induction and 3x5--4x0 for longevity. Comparisons with previous data on acute and subacute effects suggest that the r.b.e. increased linearly with the logarithm of time for 5--2000 days after irradiation.

Age Factors↗
PubMed1982

Longevity of osteoclasts in radiation chimaeras of beige and osteopetrotic microphthalmic mice.

Beige (bg/bg) mice lethally X-irradiated (900 or 1000 rad) and rescued with spleen cells from osteopetrotic (mi/mi) mice were examined periodically up to 6 months thereafter for signs of osteopetrosis, radiographic and histological. Their metaphyses were also examined electromicrographically for general characteristics of osteoclasts and for giant lysosomal granules. Measurements of lysosomal area indicated no change in the first weeks, then an exponential decline to near base line after 3 months with a half-period of or approximately 10 days. In this combination osteopetrosis was of slower progression than hitherto reported in C57BL mice. We suggest that osteoclasts have no fixed life span and that their longevity is a function of genetic background and perhaps operational needs.

Animals↗
PubMed1982

Longevity of osteoclasts in radiation chimaeras of osteopetrotic beige and normal mice.

Beige mice, osteopetrotic from incorporated mi/mi genes, and their skeletally normal siblings were X-irradiated and converted to radiation chimaeras by rescue with normal CBA bone marrow. The procedure produced rapid cure of the osteopetrosis. Electron micrographic measurement of the decline in giant lysosomes of the host mice indicated that the longevity of the host's osteoclasts was up to 30 days in the osteopetrotic and 40 days in the skeletally normal mice. In each case the decline was roughly exponential with half-times of about 6 and 8 days respectively. Monogenetic and perhaps polygenetic and teleological factors are invoked. Absence of a latent period before decline in the score seen in the companion paper is attributed to the presence of partially mature osteoclast precursors in bone marrow, not present in spleen.

Animals↗
PubMed1994

Cloning and characterization of LAG1, a longevity-assurance gene in yeast.

The yeast Saccharomyces cerevisiae has a finite life span that is measured by the number of times the individual cell divides. The gene coding for one of several transcripts that are differentially expressed during the replicative life span has been cloned. The nucleotide sequence revealed an open reading frame capable of encoding a transmembrane protein of 411 amino acids that displays no significant similarities to any known proteins. Nevertheless, sequences similar to this gene were found in several mammals, including humans. The transcript levels decreased with replicative age of yeast cells. A gene deletion in haploid cells resulted in a pronounced increase (approximately 50%) in mean and in maximum life span. These results indicate that this gene, which we call LAG1, plays a role in determining yeast longevity.

Amino Acid Sequence↗
PubMed1995

[Clinical and laboratory studies of effect of longevity-antihypertensive-mixture on elderly hypertension with kidney deficiency].

UNLABELLED: Longevity-Antihypertensive-Mixture (LAM) is a Chinese herbal drug, which could tonify Kidney in treating the hypertension with Kidney Deficiency in aged patients. RESULTS: 302 patients were randomly divided into three group: The treated group was subdivided into group I (107 Kidney Yin Deficiency patients) and group II (96 non-Kidney Yin Deficiency cases) and group III (99, control group). After treatment of LAM for 8 weeks, the rate of normalizing the blood pressure was 92.52% in group I while in group II, it was 84.43%, the symptoms were also significantly alleviated, and in group III, the rate was 70.71% only. The aorta compliance in group I significantly improved after LAM treatment (P < 0.025), the quality index of left ventricle reduced in treated group, and there was significant difference between treated and control groups. After treatment, LAM could shorten the length of extracorporal thrombus in group. The study showed that LAM could treat hypertension through LAM, administration with good effect.

Aged↗
PubMedDate not supplied

[Unequal conditions for longevity--determinants of mortality from the longitudinal perspective].

Longitudinal data of the German Socioeconomic Panel (GSOEP) offer new possibilities to identify the determinants for longevity respective the mortality risk. A panel probit model shows that beyond the cohort effects a low income position and a low educational level are determinants which increase the mortality risk dramatically. Widowhood and small family size also have increasing effect on mortality for men while marital status of single (unmarried, separated, divorced) has shortening effect on a woman's life expectancy. Reduced societal participation creates conditions which increase the mortality risk.

Aged↗
PubMedDate not supplied

Hickman lines inserted and managed by a general surgical team: longevity and complications.

Long-term venous access lines are commonplace in the management of patients requiring continuous intravenous chemotherapy, intravenous nutrition or simply as a means of avoiding repeated peripheral access lines in patients with difficult venous access. The insertion and maintenance of these lines is not without major complication. Four years' experience with the Hickman catheter in a general surgical oncology setting are reviewed. Thirty-seven lines were inserted in 37 patients with a mean longevity of 107 days (range 2-322) and an overall complication rate of 1.25 per 1000 catheter days. Four catheters were removed prematurely due to late complications. These figures compare favourably with results for long-term venous access from larger specialist units.

Adult↗
PubMed1997

Enhanced lymphocyte longevity and absence of proliferation and lymphocyte apoptosis in Quilty effects of human heart allografts.

"Quilty effect" (QE) is a common and problematic observation in endomyocardial biopsy specimens from patients after cardiac transplantation. The origin, fate, and significance of QE cellular elements are unknown. Twenty-six paraffin-embedded endomyocardial biopsy specimens with QE (five QE As and twenty-one QE Bs) from twenty-two cardiac allografts were studied by immunohistochemistry for expression of Bcl-2, Fas antigen, proliferating cell nuclear antigen (PCNA), perforin, T cells (UCHL-1), macrophages (CD68), and apoptosis by in situ terminal deoxyribonucleotide transferase (TdT)-mediated dUTP nick end labeling (TUNEL). Approximately 50% of the lymphocytes present, mainly in the deeper region of 20 of 21 QE Bs and all 5 QE As, expressed Bcl-2 in a pseudo-nodular pattern surrounding high endothelial venules. Fas expression was detected in lymphocytes in 20 of 21 QE Bs and 5 QE As in a similar pattern to Bcl-2. However, endothelial cells and macrophages were Bcl-2 negative, whereas both cell types were Fas positive. Perforin was negative in nearly all lymphocytes. TUNEL staining revealed that lymphocytes in QEs did not undergo apoptosis; however, TUNEL positivity was observed in approximately 70% of endothelial cells and macrophages and certain adjacent cardiac myocytes in 20 of 21 QE Bs and 5 QE As. One large QE B with a germinal center was noted. Germinal center cells expressed PCNA intensely but were negative for Bcl-2, Fas, and TUNEL. Cells surrounding the germinal center expressed abundant Bcl-2. The following conclusions were drawn. 1) Apoptosis does not occur in lymphocytes in QE where enhanced Bcl-2 (apoptosis inhibitor) and Fas antigen (apoptosis inducer) are expressed. 2) PCNA negativity indicates that QE lymphocytes may not proliferate, and perforin negativity indicates that they may not exhibit perforin-based cytotoxicity. We propose that there may be a relationship between the longevity of lymphocytes in QE and the absence of apoptosis.

Adult↗