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Biomedical subjects

M Frentzen

Publications and source records attributed to M Frentzen.

At least 19 recordsLinked to original sources
PubMed2004

Effect of diode laser and fluoride varnish on initial surface demineralization of primary dentition enamel: an in vitro study.

INTRODUCTION: Previous investigations have demonstrated improved enamel caries resistance after laser irradiation. The purpose of this in vitro study was to assess the caries-preventive potential of 809 nm diode laser treatment of the enamel of primary teeth compared to topical fluoride application. METHODS: Eighty samples of sound primary teeth were embedded in plastic and stored in saline solution. The enamel surface of 80 samples was polished in an area of 2 x 2 mm. These tooth specimens were randomly assigned to one control and three test groups: (1) no treatment/control; (2) application of 0.1 mg of fluoride varnish (Duraphat) for 6 h; (3) diode laser application (809 nm, 140 mJ, 50 Hz, Ø 600 micro m fibre, contact mode, absorber, 1 min; ORA-LASER01 I.S.T.); and (4) combined application - laser/fluoride varnish. Caries-like lesions were created by pH-cycling. After lesion formation, longitudinal sections were taken and examined by polarized light microscopy. RESULTS: In the control group, all samples showed lesions up to 30 micro m in depth. After laser application, lesions could be identified in 15 out of 20 samples. Topical fluoride treatment in groups 2 (varnish) and 4 (laser/varnish) completely inhibited the development of caries-like lesions in all samples. CONCLUSION: In this in vitro investigation, topical fluoride treatment enhances the resistance of sound enamel of primary teeth more effectively than diode laser application.

Chi-Square Distribution↗
PubMed2004

Clinical and microbiological effects of topical subgingival application of hyaluronic acid gel adjunctive to scaling and root planing in the treatment of chronic periodontitis.

BACKGROUND: Hyaluronic acid (HA) has shown anti-inflammatory effects in gingivitis therapy. The potential benefits of local subgingival application of HA adjunctive to scaling and root planing (SRP) were evaluated in this study. METHODS: Twenty patients with chronic periodontitis were included in this split-mouth study. Sulcus fluid flow rate (SFFR) and sulcus bleeding index were monitored at baseline and after 1, 2, 3, 4, 5, 6, and 12 weeks; probing depth and clinical attachment level were monitored at baseline and 6 and 12 weeks. Subgingival plaque samples were also taken at these same three appointments to determine the presence of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythensis, and Treponema denticola. All patients were treated with full-mouth scaling and root planing (SRP); in addition, an HA gel was administered subgingivally in the test sites every week for 6 weeks. RESULTS: An improvement of all clinical variables was observed (P < 0.05) in both groups. Clinically, no difference between test and control sites could be found. No difference between test and control sites was seen in the tested microorganisms. CONCLUSIONS: No clinical or microbiological improvement was achieved by the adjunctive use of HA gel compared to SRP alone. Only SFFR was affected by the use of HA in terms of a more rapid reduction of SFFR in the test sites.

Administration, Topical↗
PubMed2004

[Clinical study of hyaluronic acid in the treatment of chronic periodontitis].

OBJECTIVE: Clinical effects in local application of hyaluronic acid (HA) adjunctive to scaling and root planing (SRP) were evaluated. METHODS: In this cross over design study 20 patients with chronic periodontitis were included. Plaque index, sulcus-fluid-flow-rate (SFFR), sulcus bleeding index, probing pocket depth and attachment level were monitored. All patients were treated with full mouth SRP, in addition a HA gel was administered subgingivally in the test site every week for 6 weeks. RESULTS: A statistically significant improvement of all clinical test parameters was observed in both groups (P < 0.05). Clinically, no significant difference between test and control group could be found. However, the SFFR decreased significantly faster in the test group. CONCLUSION: No post-inflammatory tissue regeneration could be achieved by the adjunctive use of HA gel to SRP in the patients with chronic periodontitis. Due to SFFR a control of local inflammation can be achieved quickly.

Adult↗
PubMed2003

The possibility of detecting subgingival calculus by laser-fluorescence in vitro.

The aim of the present study was to investigate laser-fluorescence effects on the root surface. The possibility of detecting subgingival calculus should be evaluated to control complete calculus removal after scaling and root planing. Twenty freshly extracted human teeth, partially covered with calculus on the root surface, were fixed on a translation stage. The specimens were irradiated by light from a laser source (diode laser, <1 mW) with a wavelength of 655 nm using the Diagnodent trade mark -system. To simulate the conditions in a periodontal pocket during the measurement procedure, the teeth were covered by a layer of physiological saline solution or blood in order to determine the influence of different inflammatory fluids. The root surface was scanned on a line of about 1 cm in steps of 0.5 mm. The start and end was marked by a notch. The results of the laser-fluorescence detection were compared to clinical and histological findings. Clinically apparent calculus on the root surface was always accompanied with a statistically significant increase of laser-fluorescence values ( p < 0.05). These values were not influenced by the different fluids ( p < 0.05). The laser-fluorescence values were reproducible ( p > 0.05). After scaling, when no debris remained at the root surface, laser-fluorescence values decreased significantly ( p < 0.05). The histological findings supported the clinical results. In conclusion, the present study indicates that laser-fluorescence values on the root surface are strongly correlated to the presence of calculus. This fluorescence effect can basically be used to develop a new detecting system for subgingival calculus in periodontal pockets.

Bacteria↗
PubMed2003

Osteotomy with 80-micros CO2 laser pulses--histological results.

Haemostatic and aseptic effects and intricate cut geometry are beneficial aspects of non-contact laser osteotomy. Collateral thermal damage, however, has severely limited the use of conventional lasers. The purpose of this study was to test the side effects on bone after cutting it with short CO2 laser pulses and simultaneous application of a fine air-water spray. The 10.6 microm CO2 laser emitted 80 micros pulses of 46 mJ energy, f=100 Hz, focused to a spot diameter of 130 ìm. Scan rate amounted to 40 mm/s. To approximate live conditions 10 samples of cortical bone and 10 rib segments were prepared immediately after sacrificing of pigs. A reference cut with a bandsaw and three laser cuts with an increasing number of beam passes (4, 16, 64) were performed on each sample. Half of the samples were decalcified in EDTA. The others were embedded in plastic to cut non-decalcified sections. The laser incisions were not accompanied by carbonisation. The incisions with slightly convergent walls were 150 ìm wide. The depths of the cavities increased with the number of the beam passes from approximately 0.5 mm (4 passes) to 3 mm (64 passes). At the border of the incisions two narrow zones of damage were noted: an amorphous intensively stained zone of 1-3 microm width and a wider, also sharply demarcated but faintly stained zone of 7-10 microm. A broader zone of about 50 microm was characterised by empty lacunae and osteocyte damage. These effects were not predictable; intact osteocytes were also observed near to the cut surface. Polarised light microscopy showed no alterations in the inorganic structure of the bone at the cut borders. The histological results indicated only minimal damage to bone ablated at the specified parameters. The described laser procedure might have advantages over mechanical instruments.

Animals↗
PubMed2003

Endodontic and surgical treatment of a geminated maxillary incisor.

AIM: A geminated maxillary incisor required complex multidisciplinary treatment to preserve health and restore aesthetics. This report describes the coordination of coronal division, root extraction, bone grafting, endodontic treatment and orthodontics in achieving treatment goals. It is the intention of this report to show how a difficult case could be managed by properly coordinated multidisciplinary care. SUMMARY: Pulp testing of the geminated central right maxillary incisor gave a normal response. Radiographic investigation indicated a connection of the pulp chambers. Both the mesial and distal root were filled with gutta-percha. The connection between the two root canals was sealed with a flowable dentine-bonded resin. After dividing the crown with a diamond bur, the mesial part of the tooth was removed and the extraction socket was filled with beta-tricalcium phosphate ceramic (Cerasorb). Radiographs taken immediately after surgery and after 6 months showed no periodontal or periapical lesions. No signs of external resorption were identified. The diastema between the central incisors was closed by orthodontic treatment. KEY LEARNING POINTS: Geminated teeth may present aesthetic and functional problems which require multidisciplinary care. Careful clinical and radiographic examination is essential to decide on the fate of the coronal and root halves involved. A proper coordination between endodontic and surgical treatment may result in maintaining one tooth half, even if a midroot connection between the pulp chambers becomes evident. Orthograde endodontic treatment, hemisection and orthodontics may solve the aesthetic problem of a geminated tooth.

Bone Substitutes↗
PubMed2002

Clinical and microbiological effects of local chlorhexidine applications.

AIM: To study the effects of an application of chlorhexidine varnish (40%) on dental plaque. DESIGN: Randomised controlled clinical trial. SUBJECTS: 40 patients (50% females), aged 25-34 years after undergoing any necessary restorative treatment. Exactly one half of these individuals practiced good oral hygiene, the efforts of the others were poor. METHOD: Test groups received a chlorhexidine varnish application, the control group received a placebo varnish. Initially and after 2 and 6 weeks, a modified Dentocult SM-test, bleeding on probing, and a plaque index (Quigley-Hein) were recorded. RESULTS: In contrast to the control group, improvements in plaque index and bleeding on probing scores were found in patients with poor oral hygiene. The results of the Dentocult SM-tests showed a considerable reduction of streptococcus colonisation. The test group with good oral hygiene showed only slight improvement of the examined indices after chlorhexidine application. The index parameters of all patients of the placebo groups remained unchanged over the examination time period. CONCLUSION: The application of a chlorhexidine varnish reduced the quantity of the Streptococcus mutans colonies significantly and improved clinical parameters in patients with elevated plaque accumulation.

Adult↗
PubMed2002

Cavity preparation using a superpulsed 9.6-microm CO2 laser--a histological investigation.

BACKGROUND AND OBJECTIVES: The superpulsed 9.6-microm CO(2) laser is an effective laser for ablating dental tissues and decay. This histological study compares laser class V preparations with conventional treatment to evaluate the resulting formation at the cavity walls. STUDY DESIGN/MATERIALS AND METHODS: Four class V preparations (one made with a diamond drill and three with the CO(2) laser (9.6 microm, 60 microseconds pulse width, 40 mJ pulse energy, 100 Hz, integrated scanner system, water cooling) were performed on ten extracted teeth. The cavities were filled with a composite resin partly including enamel and dentine conditioning. RESULTS: After laser preparation, no cracks or signs of carbonisation were detected. The results were comparable to those attained with conventional treatment. Following cavity filling without prior conditioning, gaps were noted at the cavosurface indicating a lack of adhesion. Dentinal bonding decreased gap formation significantly. CONCLUSION: The 9.6-microm CO(2) laser is an effective tool for cavity preparation.

Acrylic Resins↗
PubMed2002

Er:YAG laser scaling of diseased root surfaces.

BACKGROUND: The removal of calculus and plaque is an essential component of a therapeutic approach to control periodontal disease. Er:YAG laser scaling was recently introduced as an alternative to conventional scaling procedures. In this histological study, the effects of laser instrumentation of diseased root surfaces are compared to mechanical removal of plaque and calculus with ultrasonic instruments and scalers. METHODS: Areas of subgingival calculus were identified on 40 freshly extracted human teeth. Each of these areas was randomly divided into 2 equal parts. The control site was treated either with scaling and root planing or with an ultrasonic instrument. The test site was cleaned using an Er:YAG laser according to the manufacturer's instructions. The end point of debridement was the inability to mechanically or visibly detect any remaining calculus. After pre- and postsurgical photographs and impressions for scanning electronic microscopic investigation, a plastic embedding technique was used to cut the undecalcified roots into 15 microm thick sections. RESULTS: Clinically and histologically, scaling resulted in complete debridement at all samples, producing a smooth root surface. At the test sites, laser scaling was accompanied by an increased removal of tissue and roughened surfaces. CONCLUSIONS: Laser scaling results in an increased loss of cementum and dentin, which should be taken into account in clinical situations.

Aluminum Silicates↗
PubMed2001

Phosphatidylglycerophosphate synthases from Arabidopsis thaliana.

Two Arabidopsis thaliana genes were shown to encode phosphatidylglycerophosphate synthases (PGPS) of 25.4 and 32.2 kDa, respectively. Apart from their N-terminal regions, the two proteins exhibit high sequence similarity. Functional expression studies in yeast provided evidence that the 25.4 kDa protein is a microsomal PGPS while the 32.2 kDa protein represents a preprotein which can be imported into yeast mitochondria and processed to a mature PGPS. The two isozymes were solubilized and purified as fusion proteins carrying a His tag at their C-terminus. Enzyme assays with both membrane fractions and purified enzyme fractions revealed that the two A. thaliana isozymes have similar properties but differ in their CDP-diacylglycerol species specificity.

Arabidopsis↗
PubMed2001

In vitro analysis of the effects of acid or laser etching on microleakage around composite resin restorations.

OBJECTIVES: The aim of the present study was to determine the effect of two conditioning methods, phosphoric acid and XeCl laser application on microleakage at composite resin restorations. METHODS: Class II MOD (mesio-occluso-distal) cavities were prepared on 90 extracted human wisdom teeth with one proximogingival margin on enamel and the other on dentin. Phosphoric acid (37%) and a XeCl excimer laser system were used for the etching procedure. The prepared teeth were randomly assigned to six groups: In group 1, acid-etching of the enamel margins was followed by application of enamel bonding, in group 2 additionally a dentin bonding system was used. In group 3, acid-etching of the enamel and dentin (total etch) was followed by the application of dentin bonding. In group 4, laser-etching of enamel margins was followed by the application of enamel bonding, in group 5 dentin bonding was used additionally. In group 6, laser-etching of enamel and dentin margins was followed by the application of dentin bonding. All restorations were placed incrementally and polymerized with a halogen light source. After restoration, all samples were thermocycled and stained in 0.5% basic fuchsin and sectioned longitudinally in a mesio-distal plane. Microleakage was scored by means of a stereomicroscope. The margins of the restorations at tooth-resin interface were examined with a scanning electron microscope. RESULTS: In all groups, marginal leakage was more extensive at the gingival margin that was in dentin than at the gingival margin in enamel. Microleakage scores and the gap at the tooth-resin interface were significantly lower in all acid-etched groups than in laser-etched groups. CONCLUSION: Acid-etch technique is more effective than the investigated laser-etch technique at 308nm concerning the reduction of marginal leakage in composite restorations.

Acid Etching, Dental↗
PubMed2001

Functional characterization of beta-ketoacyl-CoA synthase genes from Brassica napus L.

Seed-specifically expressed beta-ketoacyl-CoA synthase genes of Brassica napus (Bn-FAE1.1 genes) were cloned from two cultivars, namely Askari, a high-erucic-acid type, and Drakkar, a low-erucic-acid type. The genes from the two cultivars were found to be nearly identical. They encode proteins of 507 amino acids, the sequences of which differ only at position 282. The Bn-FAE1.1 gene of Askari, unlike that of Drakkar, was functionally expressed in yeast cells suggesting that the single amino acid exchange effects the low erucic acid phenotype at the E1 gene locus. In yeast cells the beta-ketoacyl-CoA synthase of Askari elongated not only oleoyl but also palmitoleoyl groups as well as saturated acyl groups in such a way that monounsaturated acyl groups of 22 carbons and saturated ones of 26 carbons were formed as main products. A reporter gene fused to the promoter region of the Bn-FAE1.1 gene from Askari showed seed-specific expression in transgenic rapeseed plants. Over-expression of the coding region of the Askari gene in developing seeds of transgenic Drakkar plants resulted in a significant increase in the levels of eicosenoic acid and erucic acid esterified in the seed oil. On the other hand, in transgenic high-erucic-acid rapeseed plants the increase in erucic acid level was at most 60% although the chimeric Bn-FAE1.1 gene was co-expressed with an erucoyl-CoA-specific lysophosphatidate acyltransferase gene enabling trierucoyl glycerol to accumulate in the seed oil.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗
PubMed1996

The effects of pulsed ultraviolet and infra-red lasers on dental enamel.

To evaluate micromorphological changes seen in enamel following irradiation with pulsed lasers, extracted human teeth were treated with a TEA-CO2, an Er:YAG and an ArF laser systems. Light and scanning electron microscopic studies demonstrate that the Er:YAG laser produces a zone of microcracks in the subsurface area. While TEA-CO2 laser irradiation results mostly in surface melting, the Er:YAG laser produces a roughened enamel surface. After ArF laser irradiation a retentive surface appears, accompanied by some melting effects and an increased porosity. The observed results of all the employed laboratory type lasers varied over a wide range due to the widespread biologic differences in tooth structures.

Argon↗
PubMed1995

A plant acyltransferase involved in triacylglycerol biosynthesis complements an Escherichia coli sn-1-acylglycerol-3-phosphate acyltransferase mutant.

The second acylation reaction in glycerolipid biosynthesis is catalyzed by an sn-1-acylglycerol-3-phosphate acyltransferase. The enzyme of Limnanthes douglasii involved in triacylglycerol synthesis has an unusual specificity for very long chain acyl groups in both of its substrates, namely acyl-CoA and sn-1-acylglycerol-3-phosphate, and causes the enrichment of erucoyl groups in the sn-2 position of the seed oil of this plant species. We have isolated a cDNA clone encoding this embryo-specific, microsomal acyltransferase via heterologous complementation of an Escherichia coli mutant deficient in sn-1-acylglycerol-3-phosphate acyltransferase activity. The open reading frame of the cDNA insert encodes a protein with a length of 281 amino acids, with three predicted membrane-spanning domains and of about 31.7 kDa. The sequence exhibits substantial sequence similarity to the sn-1-acylglycerol-3-phosphate acyltransferase of E. coli. The corresponding transcript was detectable in developing embryos but not in leaves of L. douglasii, and expression of the open reading frame in E. coli caused sn-1-acylglycerol-3-phosphate acyltransferase activity which showed properties different from those of the bacterial acyltransferase but typical of the L. douglasii enzyme involved in triacylglycerol biosynthesis.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗
PubMed1993

[The value of high resolution computed tomography (HRCT) in the diagnosis of deep forms of parodontitis].

It is difficult to demonstrate the extent of parodontal bone erosions with conventional radiographic techniques. HRCT makes it possible to demonstrate the alveolar structures without superimposition. 10 patients with parodontitis marginalis profunda were examined by conventional methods and HRCT. Comparison showed considerable superiority of HRCT in respect of demonstrating bone destruction. The absence of superimposition produces excellent demonstration of the roots and shows the bifurcation and trifurcation of teeth; consequently, mapping the position and shape of the root canals is possible and this is an important aid in the planning of parodontal surgical treatment.

Adult↗
PubMed1992

[Laser-induced photoacoustic effects in the dentin].

To study photoacoustic effects in dentin caused by UV-laser ablation, laser-induced shockwaves were measured using piezoelectric PVDF films. Above the tissue-specific energy threshold for photoablation the amplitude of the acoustic shock waves is proportional to the applied laser energy density. Laser energy densities of 2 J/cm2 cause pressure amplitudes of 50 bar, densities of 20 J/cm2 cause pressure amplitudes of 1000 bar. To avoid microcracks in dentine the maximum laser energy density to prepare dentin should be limited to approximately 20 J/cm2.

Biophysical Phenomena↗
PubMed1992

Excimer lasers in dentistry: future possibilities with advanced technology.

The thermal side effects of carbon dioxide and neodymium:yttrium-aluminum-garnet lasers limit their clinical applications. These high-powered, infrared lasers result in zones of charring and carbonization even in soft tissues and the bone. In contrast, the pulsed, ultraviolet radiation emitted by excimer lasers causes limited thermal, denaturative damage to surrounding tissues. Therefore, treatment of dental tissues with the nonthermal process of photoablation with excimer lasers may present alternatives to traditional dental practice. Possible future applications of the excimer laser include selective caries removal, the conditioning of tooth surfaces, and cleaning of root surfaces; the zones of necrosis are small, so that there is no residual debris.

Dental Caries↗