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Biomedical subjects

P Hahn

Publications and source records attributed to P Hahn.

At least 19 recordsLinked to original sources
PubMed2006

Two-year evaluation of a new nano-ceramic restorative material.

The purpose of this prospective study was to evaluate the clinical performance of a new restorative material (Ceram.X) in combination with a new primer-adhesive (K-0127). One operator placed two Class I or II restorations in molars of 43 patients. One molar was restored with Ceram.X/K-0127, the other one with Tetric Ceram/Syntac Classic. At baseline, after 1 and 2 years, the restorations were evaluated by one evaluator using modified Ryge's criteria. After 2 years, 31 patients were examined. One Ceram.X-restoration had to be removed for root canal treatment due to pulpitis. Thus, failure rate of Ceram.X was 3.2% and of Tetric Ceram, 0%. In both groups, no sensitivity, no recurrent caries, and no changes in surface texture were recorded after 2 years. One restoration in each group showed slight changes in color stability (score B). Marginal discoloration (score B) was found concerning three Ceram.X-restorations (10.0%) and two Tetric Ceram-restoration (6.5%). Marginal integrity was score B for four Ceram.X-restorations (13.3%) and for four Tetric Ceram-restorations (12.9%). No statistically significant differences were found (p>0.05). After 2 years of clinical service, 96.8% of Ceram.X/K-0127 and 100% of Tetric Ceram/Syntac Classic restorations were in place and performed clinically well.

Ceramics↗
PubMed2006

Two-staged reconstruction of the flexor pollicis longus tendon.

The purpose of this study was to evaluate the results of two-stage reconstruction of the flexor pollicis longus (FPL) tendon. Sixteen patients who underwent reconstructive surgery of the FPL tendon were assessed retrospectively. Eight weeks after implantation of a silastic spacer, a tendon graft was used for reconstruction (thirteen palmaris longus tendons, two plantaris tendons, one half of the flexor carpi radialis tendon). Power grip, active range of motion, passive range of motion, the Buck-Gramcko assessment, the ASSH assessment and the DASH score were used to evaluate the results. Adequate function in 75% of the cases and a median of 11 on the DASH score was achieved. The results showed that two-stage reconstruction of the FPL tendon can produce satisfactory results, even if primary repair is the ideal.

Adult↗
PubMed2006

Outcome analysis, including patient and parental satisfaction, regarding nonvascularized free toe phalanx transfer in congenital hand deformities.

The therapy for congenital hand malformations, especially in symbrachydactyly and constriction ring syndromes, is challenging. Between 1975 and 1995, 20 children with congenital hand deformities underwent reconstruction by 56 nonvascularized free toe phalanx transfers. The average age at initial surgery was 4.8 (range, 0.5 to 22) years. Retrospectively, the children were examined after an average of 3.5 (range, 1.5 to 17.6) years for function of the hand, transplanted phalanx growth, assessment for the epiphyseal plate, and assessment for psychologic performance with their parents. Donor-site morbidity was determined according to measured growth deficit, observing the child's gait, and toe function. In the younger patients (up to 1.5 years), the grafts were well tolerated and showed good growth and only few resorptions. In the age group from 1.5 to 4 years, the grafts showed no growth. In the age group older than 4 years, the grafts were mostly resorbed. The clinical reexamination revealed in most cases only passive motion in the joints, but the function of the hand was improved, with only few problems of the donor site. Most patients and their parents reported a positive effect of the phalanx transfer.

Adolescent↗
PubMed2005

[Conservative treatment results of the acute and chronic mallet finger].

BACKGROUND: In the treatment of the acute ligamentous mallet finger, conservative therapy with a Stack or Winterstein splint is an established approach, though there are many different conservative therapy regimes. There are even more therapy options for the chronic mallet finger (more than 4 weeks old) including different operation techniques. MATERIAL AND METHODS: In a retrospective study, 44 patients with an acute and 33 patients with a chronic ligamentous mallet finger treated with a Stack or Winterstein splint were investigated. RESULTS: The results in both groups are satisfactory (SD <10 degrees : 70.5% in the acute, 87.9% in the chronic lesions). The subjective satisfaction (scale 1-6) was high in both groups. It was even significantly higher in the group with the chronic lesions (acute: 2.55+/-1.63, chronic: 1.82+/-1.38). In both groups there was no correlation between an initially high extension deficit and a bad therapy outcome. CONCLUSIONS: Also in chronic ligamentous mallet finger, conservative therapy should be attempted before an operation, irrespective of the initial extension deficit, especially because the stress and the therapy risk for the patient with this therapy is small.

Acute Disease↗
PubMed2005

[Reoperation in carpal tunnel syndrome. Retrospective analysis].

BACKGROUND: The goal of this study was the reexamination, description, and analysis of postoperative results after carpal tunnel release reoperation. PATIENTS AND METHODS: Thirty-eight patients were examined retrospectively 2 years after reoperation of carpal tunnel release. All of them had had complaints after the first operation. On the basis of DASH and Amadio questionnaires after the reoperation, the patients were divided into two groups: good results and inadequate results. RESULTS: The reasons for reoperation included incomplete division of the retinaculum, early fibrosis, reoccurrence, late fibrosis, intraoperative complication, and one unclear situation. A quarter of the patients were free of complaints; three quarters had symptoms in which sensation improved but strength and function did not. CONCLUSION: The clinical findings showed satisfying results for the patients. Reoperation is indicated after early postoperative deterioriation or if there is no improvement.

Carpal Tunnel Syndrome↗
PubMed2004

Deficiency of Bax and Bak protects photoreceptors from light damage in vivo.

Photoreceptors of bax(-/-)bak(-/-) but neither bax(-/-) mice nor bak(-/-) mice are protected from developmental apoptosis, suggesting that bax(-/-)bak(-/-) photoreceptors may also be protected from pathologic apoptosis. To test this possibility, we exposed bax(-/-)bak(-/-) and bax(-/-) mice to bright light, which normally induces photoreceptor death. Photoreceptors in bax(-/-)bak(-/-) mice were protected from death compared to bax(-/-) mice as indicated by a reduction in the number of TUNEL-positive photoreceptor nuclei 24 h following light damage and almost complete preservation of photoreceptors 7 days following light damage. These results provide the first in vivo evidence that combined deficiency of Bax and Bak can rescue cells from a pathologic stimulus more effectively than Bax deficiency and suggest that combined deficiency of Bax and Bak may also protect cells from other insults.

Animals↗
PubMed2004

[Chemotherapy for colorectal carcinoma in the elderly].

With nearly 50 % of all colorectal cancers being diagnosed in patients at the age of 70 or above colorectal cancer is a disease of the elderly. In an adjuvant setting, fit elderly patients can receive the same benefit from cytotoxic therapy as younger patients with an only slightly increased toxicity. In a palliative setting, the treatment of elderly patients with respect to clinical endpoints such as response, time to progression or overall survival is as effective as in their younger counterparts. In clinical studies, older patients are generally underrepresented and among the elderly patients involved in clinical studies there is a bias towards particularly fit patients. Therefore it is not possible to extrapolate the results of many randomized trials to all elderly patients. A Comprehensive Geriatric Assessment (CGA) should be applied to detect the diversities in the geriatric population. Based on this assessment elderly patients classified as suitable for chemotherapy should be enrolled into clinical trials for colorectal cancer.

Aged↗
PubMed2004

Adenovirus-mediated delivery of catalase to retinal pigment epithelial cells protects neighboring photoreceptors from photo-oxidative stress.

Oxidative stress is involved in the pathogenesis of many diseases. Overexpression of antioxidant enzymes by gene therapy may protect tissues from oxidative damage. Because the reactive oxygen species hydrogen peroxide can diffuse across cell membranes, we hypothesized that overexpression of the antioxidant catalase within certain cells might protect neighboring cells. To test this hypothesis, we transduced retinal pigment epithelial (RPE) cells in vitro and in vivo with adenovirus carrying the catalase gene (Ad.CMV.catalase). After transduction of only a subset of RPE cells in vitro, all cells in the culture were protected from exogenous hydrogen peroxide. Similarly, in vivo, eyes injected with Ad. CMV. catalase had high catalase levels in the RPE, which protected the adjacent photoreceptors from light damage and reduced photoreceptor oxidative stress as measured by the markers 4-hydroxynonenal and nitrotyrosine. Both in vitro and in vivo, gene therapy with Ad. CMV. catalase protected neighboring cells from oxidative stress-induced terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) positivity. The data provide a paradigm for antioxidant gene therapy with catalase, designed to protect not only transduced cells, but also neighboring cells.

Adenoviridae↗
PubMed2004

An in vitro investigation of penetration depth of dentine bonding agents into carious dentine.

The aim of the present in vitro study was to determine the penetration depth of dentine bonding agents into carious dentine as a possible strategy in caries treatment of deep lesions. Forty-eight extracted carious teeth were used for the experiments and divided in four groups. In a split-tooth design, one half of each tooth was treated without caries excavation, and the second half after caries excavation. In group 1 the teeth were treated with Prime & Bond 2.0 without phosphoric acid etching, and in group 2 with phosphoric acid etching. In group 3, the teeth were treated with All-Bond 2 without phosphoric acid etching, and in group 4 with phosphoric acid etching. Bonding agents were marked with an orange dye prior to application. The composition of the bonding agents had no significant influence on penetration depths. The mean thickness of the outer, necrotic caries zone in unexcavated specimens was 117 microm (+/-126). Bonding agents penetrated significantly deeper into unexcavated carious dentine (mean 124 +/- 76 microm) compared with excavated dentine (11 +/- 14 microm) and sound dentine (3 +/- 4 microm). Acid etching significantly reduced the thickness of the outer caries zone, and the penetration depth of the bonding agents into unexcavated carious specimens by approximately 50%, and increased it into sound dentine. The results indicate that dentine bonding agents could completely penetrate the unexcavated outer carious dentine in 90% of specimens. Further studies are required to determine whether further caries activity is arrested after treatment with dentine bonding procedures.

Dental Caries↗
PubMed2003

[Rehabilitation of extensor tendon injuries].

The extensor mechanism of the hand consists of different tendons, originating from extrinsic and intrinsic muscles of the hand and forearm. Because of their course near to skin and bone separated only by a thin layer of paratenon, they are very sensitive to injuries and adhesions. Treatment protocols have to be adapted according to the different zones. This paper explains the basic principles of rehabilitation in extensor tendon injuries.

Aftercare↗
PubMed2003

[Rehabilitation after flexor tendon surgery].

During the last 20 years there have been significant innovations in injury repair and aftercare for patients who sustain zone 2 flexor injuries. Based on improvements in our understanding of the mechanism of repair, new differentiated concepts could be developed. Active extension, passive flexion as introduced by Kleinert is still the standard in flexor tendon surgery. New stronger suture techniques allow immediate active flexion. The purpose of this article is to review the current concepts of flexor tendon and pulley repair as well as reconstruction of these structures and the rehabilitation programs for tenolysis.

Aftercare↗
PubMed2003

[Results after staged reconstruction of the flexor pollicis longus tendon].

The objective of this study was to evaluate results after staged reconstruction of the flexor pollicis longus tendon (FPL) and to compare the results with literature. The advantages and disadvantages of staged reconstruction with a total duration of therapy of four months are discussed and theoretically compared with the simple and fast alternative, the arthrodesis of the interphalangeal joint (IP) of the thumb. The results of 22 patients from 1993 until 2000, 16 of which could be re-examined, are presented. Clinical parameters (grip strength and motion) were evaluated as well as the DASH score. In all cases a long graft to the forearm was used. The second operation usually followed eight weeks after the first operation. The results show a sufficient function in 75 % of the cases (scoring system of Buck-Gramcko et al.), which is paralleled by a median of 11 in the DASH score. The study shows that staged reconstruction can produce satisfactory results even in thumbs. The results are influenced negatively by persistent flexion contractures, insufficiency of annular pulleys and ailments after algodystrophy, which can be seen as indicator of the severity of the initial injury.

Adolescent↗
PubMed2002

[Structural and functional features of Epstein-Barr virus LMP-1 gene in patients with anaplastic carcinoma of the nasopharynx in Russia].

Epstein-Barr virus (EBV) is known to be closely associated with the development of anaplastic nasopharyngeal carcinoma (NPC) in some malignancy endemic regions in South-East Asia. LMP1 gene is one of the EBV latent genes, which encodes a latent membrane protein. LMP1 gene is thought to be a classical oncogene since it morphologically transforms cells in vitro and induces tumors in experimental animals in vivo. LMP1 is one of a few genes which is expressed in NPC tissues. It was first shown that C-terminus of LMP1 gene obtained from NPC patients in South-East Asia contained a deletion of 30 base pairs (bp). However, this deleted LMP1 gene was then found in the EBV isolates persisting among healthy virus carriers and patients with other EBV-associated abnormalities from both NPC endemic and non-endemic regions. The aim of this investigation was to accomplish a molecular biological analysis of EBV LMP1 genes obtained from Russian NPC patients. To this end, the authors isolated and sequenced the LMP1 clones amplified from the tumor tissues from 7 NPC patients at the N. N. Blokhin Russian Cancer Research Center and primary blood lymphocytes (PBL) from 6 healthy donors. As a result, the authors could not find the deletion of the above-mentioned 30 bp in NPC LMP1 clones, but could in one healthy donor (PBL-2). A functional analysis revealed no significant differences between LMP1 variants with or without 30 bp deletion in their capacity to activate NF kappa B and jun/AP-1 transcription factors. Nevertheless, Russian NPC-derived LMP1 variants as compared with those from PBLs featured some specific amino acid exchanges. These data indicate that the 30 bp deletion of LMP1 gene is not a factor that predisposes to NPC in Russia.

Adaptor Proteins, Signal Transducing↗
PubMed2001

The LMP1 gene isolated from Russian nasopharyngeal carcinoma has no 30-bp deletion.

The Epstein-Barr virus (EBV) is tightly linked to the induction of undifferentiated nasopharyngeal carcinoma (NPC), a tumour endemic in certain areas of southeast Asia. The LMP1 gene encoded by EBV is a classical oncogene due to its ability to transform rodent fibroblasts. LMP1 is absolutely essential for transformation of B cells by the virus and is one of the few EBV genes found to be expressed in NPC. It was originally shown that the LMP1 gene from NPC harbours a deletion of 30 bp in the 3' part of the gene. However, this deletion is also present in the virus spread in healthy people of the areas endemic for NPC and also in other EBV-positive tumours as well as in healthy carriers. We isolated and sequenced the LMP1 gene obtained from tissue of 7 Russian patients with NPC and 1 German patient with an NPC-like tumour of the parotid gland (PG) and compared them with the LMP1 gene isolated from peripheral blood lymphocytes (PBLs) of 6 Russian and 4 German healthy EBV-positive carriers. Neither the Russian NPC cases nor the German NPC-like tumour harboured an LMP1 gene with the 30-bp deletion, while 1 Russian and 2 German carriers contained the LMP1 gene with the 30-bp deletion. In addition, the LMP1 gene isolated from PBLs of the German patient was virtually identical to the gene isolated from the primary tumour. Functional analysis showed no correlation between the presence or absence of the 30-bp deletion and the level of induction of the transcription factors NFkappaB and jun/AP-1 caused by LMP1. These data indicate that the 30-bp deletion is not a factor predisposing for NPC. Comparison of the DNA sequences revealed that the LMP1 genes present in the NPCs most likely represent the "strain" persisting in the general population.

Adolescent↗
PubMed2001

Nonlinear dynamic properties of low calcium-induced epileptiform activity.

The analysis of the dynamic properties of epileptiform activity in vitro has led to a better understanding of the time course of neural synchronization and seizure states. Nonlinear analysis is thus potentially useful for the prediction of seizure onset. We have used nonlinear analysis methods to investigate the development of activity in the low calcium model of epilepsy in brain slices. This model is particularly interesting since neurons synchronize in the absence of synaptic transmission. The dynamic properties calculated from extracellular recordings of activity were used to analyze the transition to synchronous firing and their relation to neuronal excitability. The global embedding dimension, local dimension and the Lyapunov exponent were calculated from time segments corresponding to the onset, transition and fully developed stages of activity. The analysis was repeated for recordings made in the presence of various levels of DC electric fields to modulate neuronal excitability. The global and local dimensions did not change once activity was first initiated, even in the presence of the electric field. The maximum Lyapunov exponents increased during the onset of activity but decreased when the applied hyperpolarizing electric field was large enough to partially suppress the activity. These findings establish a relationship between neuronal excitability and the maximum Lyapunov exponent, and suggest that the Lyapunov exponent may be used to distinguish between various states of the neural network and might be important in seizure prediction and control.

Action Potentials↗
PubMed2001

Phenotypic characteristics of human monocytes undergoing transendothelial migration.

In our study we characterised the immunophenotype of monocytes that migrated through an endothelial cell (EC) monolayer in vitro. We found that monocyte migration led to an enhanced expression of CD11a, CD33, CD45RO, CD54 [intercellular cell-adhesion molecule (ICAM)-1] and human leucocyte antigen-DR. The most striking increase was observed for ICAM-1 when ECs were activated with tumour necrosis factor-alpha and interleukin-1alpha. The results of our study indicate the following: (1) there is a characteristic immunophenotype on the surface of monocytes after transendothelial migration; (2) this phenotype seems to be induced by interactions between monocytes and ECs; and (3) this change is enhanced by the pretreatment of ECs with cytokines. Taken together, the results suggest that local cytokine production activating ECs is sufficient to enhance monocyte migration and that this, in turn, can induce changes consistent with an activated phenotype known to be interactive between antigen-presenting cells and T cells. These results have implications for our pathogenetic insights into rheumatoid arthritis.

Cell Movement↗
PubMed2001

Chemomechanical caries removal: a comprehensive review of the literature.

Compared to the past, caries removal has become more efficient, however inherent fundamental drawbacks of the drilling approach have remained: unpleasantness to patients, need for local anesthesia, and potential adverse effects to the pulp due to heat and pressure. Chemomechanical caries removal, introduced almost three decades ago, was claimed to be a non-invasive alternative for the removal of carious dentine. In essence, the technique involved applying a solution onto the decayed dentinal tissue, allowing it to soften it, and, finally, scraping it off with blunt hand instruments. The partially degraded collagen in carious dentine was chlorinated by chemomechanical caries removal solutions. This chlorination affected the secondary and/or quaternary structure of collagen, by disrupting hydrogen bonding. Carious material removal was thus facilitated. The purpose of this paper is to perform a comprehensive review of the literature regarding chemomechanical caries removal, including the most recently available product, the initial reports on which warrant renewed interest in the approach.

Aminobutyrates↗