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Material and Methods: The corrosion resistance of ten different round orthodontic wires as plastic-encased extensions was evaluated in vitro. Following the production of defined test samples with free as well as with acrylic-embedded wire segments, ten samples of each product were subjected to gap provocation by deflecting the free-running wire ends with an electric drive, while 10 samples remained provocation-free. The tests were run under standardized conditions (7 days, 37°C, pH 2.3, 0.1 mol NaCl/CH3CHOHCOOH), and the findings were analyzed by stereo light microscopy and scanning electron microscopy. Results: The following alterations were observed on the wire surfaces: a) crevice corrosion with substantial linear surface erosion and opaque discolorations, b) localized pitting corrosion, and c) mild surface erosion with translucent discolorations. The reactions of the test samples were similar in both those that were subjected to addition mechanical loading in the electrolyte and those that were not. Cr-Ni steels were susceptible to corrosion, whereas Co-Cr alloys as well as low-nickel manganese steels had only slight visible alterations, if any, in the embedded wire sections. Conclusions: Clinically occurring discolorations in the acrylic can be attributed to corrosion processes on the embedded wire extensions. These processes can be simulated and observed in vitro. During the processing of acrylic materials now customary in the orthodontic laboratory, crevices are inevitably formed between the wire and the acrylic, furthering the corrosion process. Our results suggest that, being more resistant to crevice corrosion, Co-Cr alloys or low-nickel steels can be considered as alternatives.

Zur Behandlung funktioneller Storungen der Kaumuskulatur wird in den letzten Jahren vermehrt die transkutane Elektroneurostimulation (TENS) eingesetzt, wobei dem Klimiker heute verschiedene TENS-Gerate zur Verfugung stehen. In einer elektromyographischen Untersuchung an 17 erwachsenen Probanden mit Bruxismus und einem Kontrollkollektiv (n=18) wurde der Effekt dieser Art der Neurostimulation auf den Musculus temporalis pars anterior und den Musculus masseter pars superficialis untersucht. Die myoelektrischen Signale wurden vor und nach dei TENS Behandlung bei verschiedenen Unterkieferfunktionen registriert. Die Neurostimulation erfolgte uber mehrere Tage mit dem Myo-Monitor® (Myotronics, Seattle) und dem TNS SM2 MF®-Gerat (schwa-medico, Giesen), Gleichzeitig wurde der unterschiedliche Effekt einer dauernden niederfrequenten bzw diskontinuierlichen hochfrequenten Reizsetzung analysiert. Die Bestirmmung der Muskelaktivitat erfolgte durch eine Integration der gemessenen Rohsignale. Eine Fourieranalyse des Powerspektrums gab Aufschlus uber das Frequenzverhalten der untersuchten Muskeln. Die statistische Ausweitung der Daten belegt: 1. Durch die TENS-Behandlung wurden bei allen Probanden die Integralwerte verkleinert, Die Mittel- und Medianfrequenzwerte des myoelektrischen Powerspektrums stiegen an. Diese EMG-Befunde zeigen, das das subjektive Empfinden eines verbesserten Entspannungszustands der Kaumuskulatur nach TENS-Behandlung objektiv nachweisbar ist. 2. Die Relaxation der Kaumuskeln war bei Anwendung des Myo-Monitors® und bei elektrischer Reizsetzung in Form einer Dauerstimulation mit dem TNS SM2 MF®-Gerat nicht signifikant anders als bei der Burststimulation. 3. Die Aktivitat der untersuchten Muskeln war bei Probanden mit Bruxismus im Vergleich zum Kontrollkollektiv nicht signifikant erhoht. Die EMG-Veranderungen nach TENS-Applikation waren in beiden Gruppen gleich. Nach den vorliegenden Untersuchungsergebnissen erscheint die TENS-Behandlung eine adaquate unterstutzende Therapiemasnahme bei Probanden mit Bruxismus.

With the aid of bipolar surface electrodes, the electromyographic activity of the anterior temporal and the superficial masseter muscles were recorded bilaterally and evaluated by counting the integrated potentials and mean power frequency using Fourier's analysis. A comparison between 17 patients with myofacial pain dysfunction (average age 21.3 years) and a group of 20 controls (average age 20.5 years) revealed a significantly greater activity in patients with pain syndrome, while no significant inter-group difference in mean power frequency was seen. The differences in the level of activity between the right and left sides in the control group were significantly smaller than in patients with pain dysfunction. An investigation of measures aimed at reducing the right/left asymmetry in a further 14 patients with pain dysfunction revealed the practice of "maximum occlusion with feedback" to be the most effective measure.

The acrylic materials used in orthodontics for the fabrication of removable appliances are subjected in the oral cavity to processes of change which influence their physical, mechanical and biological properties. It is therefore essential that every newly developed material must be judged in terms of its clinical value. In the present study, 2 orthodontic cold-cure acrylics, Orthocryl and Forestacryl, and 4 orthodontic photocure acrylics, Triad, Wil-O-Dont, Odontolux and Lux-A-Tech, were investigated and compared with 2 prosthetic acrylic materials: the cold-cure acrylic Palapress and the hot-cure acrylic Paladon. The quantity of residual monomers from methyl methacrylate (MAA) or urethane dimethacrylate (UDMA) eluted from the sample in a given time after the processing was estimated by high pressure liquid chromatography (HPLC). The cytotoxic properties of the materials were examined by Mosmann's proliferation-inhibition test with an established culture of fibroblasts (= MTT test). The hot-cure acrylic Paladon produced by far the smallest amount of eluted residual monomer and the least growth inhibition in the MTT test. The prosthetic cold-cure acrylic Palapress achieved significantly better results than the orthodontic cold-cure materials Orthocryl and Forestacryl. The photocure acrylics released less UDMA than did the cold-cure acrylics MMA. In the cell culture test, all the orthodontic materials examined were assessed as "slightly cytotoxic"; the prosthetic acrylics were graded under ISO-standard 10993-5 as "noncytotoxic". After soaking the plastic material in water for 3 days its cytotoxic properties, as exemplified by the cold-cure acrylic Forestacryl and the photocure acrylic Triad, were reduced, and during the following investigation no more inhibition of growth was observed. It was possible to confirm with the tests used that, for Triad, it is necessary to carefully remove the oxygen-inhibition layer of the photocure acrylic in order to improve the biological properties. The influence of the plastic material on fibroblast cultures was assessed, among other methods, by the quantity of residual monomers liberated. These were significantly reduced after soaking the manufactured substance in water for 3 days. Careful laboratory treatment of the photocure acrylics is necessary in order to improve their biological properties.

In an electromyographic study on subjects with no functional disturbances of the masticatory muscles, the duration of the post-therapeutic effects of transcutaneous electrical nerve stimulation (= TENS) on the superficial masseter and anterior temporal muscle was analyzed. The myoelectric signals were registered from 20 healthy volunteers in 3 different mandibular positions. The recordings were performed before a 20-minute TENS application with the J-4 Myomonitor and continued with a sequence of follow-up registrations with increasing interval to the initial stimulation. The EMG signals underwent computer-aided analysis and were evaluated by determining the integrated values as a parameter of muscle activity, and after Fourier transformation by 7 describing parameters of the power spectrum (e.g. mean power frequency = MPF). A detailed analysis of variance of all data was used to investigate significant changes of the parameters during the observation period. Muscular response to TENS includes a decrease in muscular activity (= reduction in integrated EMG signals) and a shift in the power spectrum to higher frequencies (increase in MPF). These changes were statistically highly significant for both analyzed muscles and for all different mandibular exercises. As these reactions to TENS are contrary to muscle fatigue, the results can be interpreted as indicating that this type of therapy stimulates a change in the biochemical and physiological muscular conditions, which leads to muscle relaxation. Electromyographically, the post-therapeutic effect lasted for 2 hours in case of normal masticatory muscle activity but for more than 7 hours in case of low muscular loading. The alterations of the integrated EMG values were more persistent than those of the parameters of the power spectrum.

The alloys used in orthodontics are subject in the moist environment of the oral cavity to various corrosion processes. If the products of the corrosion are introduced into a biological system they may cause changes. In the present investigation the corrosion rate of 23 different orthodontic wires (preformed arch wires and straight wires) made from 5 different alloys were examined in a nutrient medium by ICP-AES analysis, and the influence of the corrosion products on the cytotoxicity of a fibroblast culture was investigated using Mosmann's MTT test. The nickel-titanium wires Nitinol, Sentalloy and Original Chinese Wire and the beta-titanium alloy TMA had no effect on the rate of cell proliferation. Nor did stainless steel wires inhibit growth significantly, with the exception of Australian Wire and Wildcat Wire. The manganese-steel alloys Noninium h and Mezanium caused significant reductions in growth rate, which were attributed to the manganese ions released by the corrosion. The most severe growth inhibition was caused by the Co-Cr-Ni alloy Elgiloy, and this reaction is independent of the 4 levels of resilience. The degree of growth inhibition depended upon the concentration of corrosive cobalt and nickel ions in the eluate. In spite of the differences observed, all the orthodontic wires examined are graded under ISO-standard 10993-5 as "non-cytotoxic". The degree of toxicity was found to be determined essentially by the corrosion rate of the alloy and the cytotoxic characteristics of the resulting trace elements.

In recent years transcutaneous electrical neuromuscular stimulation (TENS) has become increasingly more common in the treatment of functional diseases of the masticatory muscles and currently the practitioner can choose among a variety of stimulators. In an electromyographic study of 17 adults suffering from nocturnal bruxism and of a control group consisting of 18 adults without any functional disturbances of the masticatory muscles, the effect of this kind of neuromuscular stimulation on the temporal and masseter muscle was examined. The myoelectric signals were registered before and after TENS treatment in 3 different positions of the mandible. Each person was treated 3 times with both the Myo-Monitor (Myo-Tronics, Seattle) and the TNS SM2 MF stimulator (schwa-medico, Giessen). The different effects of continuous low frequency and intermittent high frequency muscular stimulation were studied simultaneously. Muscular activity was determined by computer aided integration of the electromyographically measured raw signals. A fourier analysis of the power spectrum yielded information on the frequency behavior of the studied muscles resulting from the TENS treatment. A statistical analysis of the results led to the following significant conclusions: 1. TENS treatment decreased the values of the registered integrated signals on all test persons, however, the treatment increased the median frequency and the mean power frequency (MPF). Since this effect is contrary to muscle fatigue, these electromyographic results can be interpreted as providing objective proof of a relaxation in the treated muscles. 2. The electromyographic changes after TENS treatment were similar when using either the Myo-Monitor or the TNS SM2 MF stimulator. In addition, the 2 different types of stimulation (high or low frequency) showed the same effects. 3. Compared to the persons in the control group, there was no significant increased muscular activity in patients with nocturnal bruxism. Following TENS treatment both groups showed the same alterations in the electromyograms. The results of the study provide further evidence that TENS treatment is an adequate supportive procedure in the treatment of nocturnal bruxism.

The strength and mode of failure of three different designs of custom-made all-ceramic implant abutments fabricated by milling of In-Ceram sintered ceramic blocks were compared with the conventional CeraOne system under static load. Four test groups were formed with different locations of abutment screws. In three test groups, In-Ceram crowns were fabricated for placement on the all-ceramic abutments, and in one test group, a veneer porcelain was fired directly on the abutment; crowns in the control group were fabricated using the CeraOne system. Ten-mm-long Brånemark implants were placed into a brass block that allowed loading at a 30-degree angle to the long axis. The test group in which the veneer porcelain was fired directly on the all-ceramic abutments was the weakest, and it showed fractures at a mean value of 236 N. The fracture strength of the three other test groups was dependent on the extension of the crown margin relative to the location of the screw head. The test group that had the screw on the top compressing the entire ceramic abutment showed a mean value of 422 N that was similar to the results that were achieved with the CeraOne system (427 N). The weakest link in the all-ceramic single implant restorations was the abutment screw in which the bending began at approximately 190 N.

With the aid of bipolar surface electrodes, the electromyographic activity of the anterior temporal and the superficial masseter muscles were recorded bilaterally and evaluated by counting the integrated potentials and mean power frequency using Fourier's analysis. A comparison between 17 patients with myofacial pain dysfunction (average age 21.3 years) and a group of 20 controls (average age 20.5 years) revealed a significantly greater activity in patients with pain syndrome, while no significant inter-group difference in mean power frequency was seen. The differences in the level of activity between the right and left sides in the control group were significantly smaller than in patients with pain dysfunction. An investigation of measures aimed at reducing the right/left asymmetry in a further 14 patients with pain dysfunction revealed the practice of "maximum occlusion with feedback" to be the most effective measure.

Electron microscopic investigations of the core material In-Ceram show how its texture is formed. While these are processed the Al2O3 crystallites turn idiomorphic. Etching the material with sulphuric acid selectively dissolves the glassy phase and reveals the crystallites. The chemical composition of the two components of the core material is determined by microprobe analysis. While the crystallites are pure Al2O3, the glass consists of La2O3, SiO2, Al2O3 and CaO. Measurements of the thermal expansions of the glass and the Al2O3 frame show the value for the glass to be 5.1% lower than that of the Al2O3 frame. This results in internal pressure and contributes to the high strength of the material.

It was the objective of this in-vitro field study to evaluate the marginal fit of the In-Ceram system (Vita). All the materials applied in this system were compared with each other under the aspect of their dimensional behavior to determine the influence of this factor on die adaptation. The mean value of the marginal fit of the In-Ceram restorations on the master models was 12 (+/- 10) microns. The PFM bridges showed marginal openings of 9 (+/- 10) microns. The values on the patient models were 38 (+/- 12) microns for In-Ceram, and 44 (+/- 19) microns for PFM. This increase had been anticipated because of the grain size of the Harvard Cement. The dimensional changes of the materials involved were in great harmony. At least one coat of die spacer is necessary to compensate for the contraction of the ceramic and the expansion of the special plaster. Two paints are recommended for crowns and three for bridges. Careful shoulder or chamber preparation is required to create smooth surfaces.

The mechanical strength of the new oxide ceramic system In-Ceram introduced by Vita (Bad Säckingen, Germany) was investigated by an in-vitro study for its mechanical strength and suitabilities for use as posterior three-unit bridges. The transverse strength value measured by a three-point bending test (DIN 13,927) is 320 MPa and the maximum vertical load on three-unit bridges until brittle failure occurs is in the range of 1000 to 1350 N. This is up to four times higher than corresponding values of other ceramics, e.g. Dicor (Dentsply) or Optec (Jeneric). The dental bridges were luted to metallic pontics, and a layer of silicon rubber simulating the periodontal membrane, separated the pontic from a resin base in the testing machine. Life value tests were performed before and after 10 days of thermocycling at temperatures alternating between 5 and 55 degrees C in artificial saliva. Although the pontics had a much higher mobility than normal teeth, the fatigue limit was found to be above 600 N which is much higher than the average biting forces acting on the first and second molars.

The acrylic materials used in orthodontics for the fabrication of removeable appliances are subjected in the oral cavity to processes of change which influence their physical, mechanical and biological properties. It is therefore essential that every newly developed material must be judged in terms of its clinical value.

The influence of oxygen on the minority carrier lifetime of silicon is reported. Bulk annealed, oxygen-rich crystals subsequently sliced into wafers show lifetime degradation with annealing time. Silicon oxide precipitates and punched out dislocation loops induced during annealing are identified as electrically active defects responsible for the observed lifetime degradation. Increase in device yields (diodes) and improved lifetime in epitaxial films obtained with oxygen-rich wafers as substrates are a result of “intrinsic gettering” of oxygen-rich wafers. It is shown that “external gettering” cannot improve minority carrier lifetime in silicon wafers if during processing “intrinsic gettering” is activated. It is also shown that “external gettering” such as impact sound stressing (ISS) is very effective in improving lifetime for wafers not containing “intrinsic gettering” sources. Der Einflus von Sauerstoff auf die Minoritatslebensdauer von Silizium wird untersucht. Volumengetemperte, sauerstoffreiche Kristalle, die anschliesend in Wafer geteilt wurden, zeigen Lebensdauerverringerung mit der Temperungsdauer. Siliziumdioxidprazipitate und austretende Versetzungsschleifen, die wahrend der Temperung induziert werden, werden als elektrisch aktive Defekte identifiziert, die fur die beobachtete Lebensdauerverringerung verantwortlich sind. Der Anstieg in der Bauelementeausbeute (Dioden) und die verbesserte Lebensdauer in Epitaxieschichten, die mit sauerstoffreichem Wafer als Substrat erhalten werden, sind das Ergebnis eines “inneren Getterungsmechanismus” der sauerstoffreichen Wafer. Es wird gezeigt, das eine “ausere Getterung” die Minoritatslebensdauer in Siliziumwafer nicht verbessern kann, wenn wahrend der Herstellung “innere Getterung” aktiviert worden ist. Es wird auch gezeigt, das eine “ausere Getterung”, wie Schallstosbeanspruchung (ISS) sehr effektiv fur die Verbesserung der Lebensdauer von Wafern ist, die keine “inneren” Getterungsquellen enthalten.

Das Korrosionsverhalten von neun verschiedenen orthodontischen Drahten wurde im Labor durch potentiodynamische Polarisation und durch Licht- und Rasterelektronenmikroskopie untersucht. Es zeigt sich, das Legierungen auf Eisen- oder Nickelbasis zu Lochfras und Spaltkorrosion neigen. Bei der potentiodynamischen Polarisation weisen diese Legierungstypen niedrige Durchbruchspotentiale von weniger als 600 mV sowie ein sehr ungunstiges Repassivierungsverhalten auf. Kobaltbasislegierungen zeigen eine ausreichend gute Korrosionsbestandigkeit, falls die Gefugestruktur des Drahtes einheitlich und die Oberflache unverletzt ist. Die besten Korrosionseigenschaften besitzen Titanbasislegierungen mit hohen Durchbruchspotentialen von uber 1000 mV, mit einem ausgezeichneten Repassivierungsverhalten und keiner mesbaren Neigung zu Lochfras oder Spaltkorrosion.

Primary and secondary defect profiles in silicon crystals have been investigated after 2 MeV and 80 keV Si+ irradiation by electronmicroscopy and optical reflectivity measurements. The primary irradiation damage leads to a more or less amorphous layer in the sample depending on target temperature and dose. The distance from the surface and the thickness of the amorphous layer determine the residual damage structure after annealing. In general two defect layers exist: one consisting of interstitial loops and misfit dislocations is formed approximately in the center of the region which was amorphous and where the two recrystallization fronts meet each other during annealing in the temperature range from 450 to 600°C. The other layer consisting of extrinsic stacking faults due to precipitation of implanted excess interstitials develops below the amorphous region. The appearance of this general defect profile after different implantation and annealing treatments is discussed.

An 25 jugendlichen Lippen-Kiefer-Gaumen-Spaltpatienten wurden die Auswirkungen der Cheiloplastik auf die dentofaziale Morphologie untersucht. Dazu wurden folgende Messungen durchgefuhrt: a) Oberlippenkraftmessung, b) elektromyographische Aktivitatsbestimmung der Lippenmuskulatur, c) rontgenkephalometrische und Weichteilanalyse im Fernrontgenseitenbild, d) Modellanalyse. Die Befunde wurden denen von 15 Nichtspalttragern mit normaler Okklusion und Funktion gegenubergestellt. Nur zwischen der Ruhekraft der operierten Oberlippe und dem sagittalen und vertikalen Gesichtsschadelaufbau bestand bei den Lippen-Kiefer-Gaumen-Spaltpatienten ein positiver Zusammenhang, der auf die veranderte funktionnell-mechanische Wirkung der perioralen Muskulatur bei diesen Patienten zuruckgefuhrt wird. Die Kraftwirkung der operierten Oberlippe auf ihre knocherne Unterlage wurde durch verschiedene Faktoren beeinflust: a) durch die Ruheaktivitat der Oberlippenmuskulatur und b) durch die Belastungsrichtung der Kraft, die durch die Lange und Dicke der Weichteile bestimmt ist. Diese Befunde waren spezifisch fur Patienten mit Lippen-Kiefer-Gaumen-Spalten und zeigten keine Alters- und Geschlechtsabhangigkeit. Im Gegensatz zu den dentalen Fehlstellungen konnten durch die kieferorthopadische Behandlung die skelettalen Veranderungen als Folge der muskularen Storung nicht ausgeglichen werden. Die Ergebnisse belegen, das die richtige Wahl der Lippenplastik sowohl fur die Gesichtsschadelentwicklung bei Lippen-Kiefer-Gaumen-Spalttragern als auch fur die Moglichkeit ihrer kieferorthopadischen Behandlung sehr wichtig ist. Aus theoretischen Uberlegungen wird unter funktionell-mechanischen Gesichtspunkten der Lippenplastik nachDelaire der Vorzug gegeben.

It is shown that the minority carrier lifetime τ in silicon can be reduced effectively by doping with cesium. A lifetime value of 2.2 × 10−10 s can be achieved by implantation of 1013 Cs+/cm2 at 200 keV and subsequent anneal in nitrogen followed by an oxidation of 47 min at 1000 °C. The reduction of τ in silicon is caused by the cesium distribution which is stable at this temperature. In comparison to gold the efficiency of the cesium recombination center is about 6%. Due to its low diffusion rate at high temperature cesium is proposed as a useful alternative for device applications which require gold as a dopant. Es wird gezeigt, das die Lebensdauer τ der Minoritatsladungstrager in Silizium durch Casiumdotierung effektiv reduziert werden kann. Ein Lebensdauerwert von 2.2 × 10−10 s last sich durch Implantation von 1013 Cs+/cm2 bei 200 keV und nachfolgender Temperung in Stickstoff gefolgt von einer Oxidation von 47 min bei 1000 °C erreichen. Die Reduktion von τ in Silizium wird durch die Casiumverteilung verursacht, die bei dieser Temperatur stabil ist. Im Vergleich zu Gold ist die Effizienz der Casiumrekombinationszentren etwa 6%. Aufgrund seiner niedrigen Diffusionsgeschwindigkeit bei hohen Temperaturen wird Casium als nutzliche Alternative fur Bauelementeanwendungen vorgeschlagen, die Gold als Dotierungssubstanz erfordern.

In einer kombinierten In-vitro- und In-vivo-Studie werden die Ursachen fur Korrosionserscheinungen bei der Anwendung der Bracket-Adhasiv-Technik analysiert. Analas der Untersuchung waren persistierende Schmelzverfarbungen an den beklebten Zahnoberflachen und die zunehmende Anzahl kieferorthopadischer Patienten mit erworbenen Metallallergien. Die untersuchten Brackets vier verschiedener Hersteller zeigten nach 14tagiger Lagerung in kunstlichem Speichel unter dem Lichtmikroskop rauhe korrodierte Oberflachen mit einem braunlichen Belag. Im Rastermikroskop konnte nachgewiesen werden, das Plaquebildung die Korrosion erheblich verstarkt. Mehrjahrig getragene Brackets aus nichtrostendem Chrom-Nickel-Stahl mit Kleberresten zeigten unter dem Lichtmikroskop ebensolche braunlichen Verfarbungen. Mit Hilfe der energiedispersiven Rontgenfluoreszenzanalyse wird nachgewiesen, das diese Verfarbungen mit dem Vorhandensein von Cr- und Fe-Spuren in der Klebermatrix korrelieren. Als Korrosionsprodukte kommen Oxide und Salze der metallischen Spurenelemente in Frage. Daneben fanden sich im Rasterelektronenmikroskop Mikrorisse und Spalten bis zu 10 μm Dicke in den Kleberresten. Durch diese Materialinhomogenitat gelangen die Korrosionsprodukte direkt an den Zahnschmelz, der durch das Anatzen mit Phosphorsaure entmineralisiert wurde. Es wird vermutet, das ahnlich wie in der Klebermatrix auch metallische Spurenelemente in die Zahnschmelzoberflache eindiffundieren und diese verfarben.

Si crystals are implanted with 2 MeV O+ and Si+ ions. The ion and damage profiles are revealed by beveling. The implanted oxygen concentration is measured at the beveled surface with a microprobe. The radiation damage profile is investigated by high resolution electron microscopy. The micrographs are analysed quantitatively as far as the size and depth distribution of radiation induced clusters is concerned with a Leitz Texture-Analysis-System. The damage profile matches the ion profile in case of O+ implantation, yet both ranges are about 20% shallower than the LSS estimate. In case of Si+ implantation, however, the damage profile agrees with the LSS theory. Si-Kristalle werden mit 2 MeV O+- and Si+-Ionen implantiert. Durch einem Schragschliff wird das Ionen- und das Strahlenschadigungsprofil freigelegt. Mit einer Mikrosonde wird das Sauer-stoffprofil auf dem Schragschliff gemessen. Das Strahlenschadigungsprofil wird durch hochauflosende Elektronenmikroskopie untersucht. Die Aufnahmen werden mit einem Leitz-Textur-Analyse-Gerat quantitativ bezuglich der Grosen- und Tiefenverteilung von Strahlenschadigungsclustern vermessen. Beide Profile ergeben im Fall der O+-Implantation ein zusammenpassendes Bild, die Reichweiten sind allerdings um etwa 20% kleiner als nach LSS berechnete Werte. Dagegen wird fur das Strahlenschadigungsprofil nach Si+-Beschus eine gute Ubereinstimmung mit der LSS-Theorie erhalten.

Undoped LPCVD silicon films have been deposited at five temperatures between 560° and 620°C. The films were characterized as grown and after thermal annealing at 900°, 950°, and 1000°C. We used x‐ray diffraction, TEM, SEM, Raman and elastic light scattering, optical absorption and reflection, and other techniques in order to obtain information on the grain size, structure, structural perfection, and surface roughness. We found that polysilicon films of good structural perfection, low strain, and small surface roughness are obtained when the films are deposited in the amorphous phase and subsequently crystallized at 900°–1000°C. Such films are superior in all investigated material aspects to films grown in the crystalline phase.

Oxygen profiles in silicon implanted with energies between 2 and 20 MeV by means of a Tandem accelerator have been investigated with a microprobe after bevelling the sample surface. It is shown that the measured profiles correspond to the implantation profiles when the microprobe is operated with a well focussed 2 keV electron beam. The projected ion ranges and the profiles thus obtained are compared with theoretical profiles which have been calculated by a Monte Carlo simulation of the stopping procedure. Takingk=1.30k LSS for the electronic stopping coefficient in the LSS region up to 2.55 MeV and a constant value of 162 eV/A for the electronic stopping at higher energies the calculation yields satisfactory range estimates, whereas the range straggling is systematically too small up to 13% in comparison with the experimental results.

Minority carrier lifetime changes in MOS diodes implanted with 200 keV Ar+ or 80 keV Si+ in the dose range 1011 to 1016 ions/cm2 are investigated and related to the implanted ions and the damage in the substrate. Lifetime degradation observed after Ar+ implantation varies with the dose. A factor of 105 is achieved by implanting a dose of 1015 Ar+/cm−2. Contrarily Si+ implantation does not affect the lifetime up to 1014 Si+/cm2. For a higher Si+ dose the lifetime is reduced by four orders of magnitude. Transmission electron microscopy studies reveal no defects for implants up to 1012 Ar+/cm2 and 1014 Si+/cm2. At higher argon dose bubble like defects are identified. For Ar+ and Si+ ion doses close to the amorphization dose stacking faults and dislocation loops are observed additionally.

Undoped and in situ phosphorus‐doped low pressure chemical vapor deposited polysilicon films have been studied by various structural analysis and optical techniques as a function of deposition temperature. Polysilicon films of high quality can only be obtained by deposition in the amorphous phase and subsequent crystallization.

The effects of thermocycling and water penetration on the bond strength of resin-metal-systems and improvements using bonding agents have been tested by shear, bending and tensile tests. After 10,000 cycles within 10 days in different water-baths with 5-37-55 degrees C, there is a decrease in bond strength by 40 to 60%. The use of bonding agents increases the adhesion of the resin to the metal by more than 100%. No significant differences were found between the three bonding agents Silicoater, Sebond MKV and OVS.

The presence of different alloys in the oral cavity may produce potential differences of up to 900 mV. In the majority of the patients this phenomenon presents no problems. Occasionally, however, disturbing sensations, such as "metallic taste", "twinging or stabbing" and "minute electric shock" are reported. In finding out on the threshold level for discomforting sensations due to galvanic potentials in different probands, a special battery operated device was developed. Using a pair of electrodes connected to metallic restorations in the mouth, this device enabled the application and adjustment of direct current voltage and a superimposed pulse spectrum to evoke sensible reactions. The trials were conducted with 102 probands. The mean value for the threshold of sensation was above 1000 mV. In solitary cases, however, the threshold level was as low as 250 mV. This method may be used as a diagnostic aid to the objective assessment of complaints due to galvanic effects in the oral cavity and for the selection of a suitable metal in sensitive patients.

The critical compressive strength of cast glass-ceramic samples with a standardised shape was evaluated as a function of the ceramization temperature. The maximum critical compressive stress was obtained under conditions prescribed by the manufacturer. After under- and overceramization by only 6 degrees C, as well as after repeated ceramization, the critical compressive strength was decreased significantly (p less than or equal to 0.05) by about 13-24%.

In 15 children and 15 adults the influence of muscle length on the EMG-recordings of the anterior temporal and superficial masseter muscles was investigated. Myoelectric activity was measured by surface electromyography during maximal clenching in habitual occlusion. The quantitative EMG analysis was performed by means of a computer program which allowed calculation of a) the integrated value and b) the mean frequency of the power spectrum (MPF) from the raw signal after Fourier transformation. Muscle length was determined with the aid of lateral cephalometric films. Using a correlation analysis this investigation revealed the following results: Under standardized functional conditions short muscles work with a higher activity and a higher MPF than long muscles. In children as well as in adults muscle activity and MPF show close negative correlations with the parameter "muscle length". These relations are directly proportional.

The crystallization of enstatite at the surface of Dicor glass during 'ceramization' is proved by electron microscopy and x-ray diffraction. Microprobe measurements demonstrate a loss of potassium and an uptake of calcium in the outer region of the glass-ceramic after ceramization due to an ion exchange between glass and ceramization investment. This investment consists of gypsum and leucite. A thermal analysis reveals the decomposition of gypsum in the range of the ceramization temperature. Calcium diffuses into the surface of the glass while simultaneously potassium leaves the glass. The altered composition allows the crystallization of enstatite.

Prolonged heat treatment of Czochralski-grown silicon crystals containing oxygen concentrations on the order of 1018 atoms/cm3 usually causes formation of precipitates (1-3). These precipitates are assumed to be a form of silicon oxide. This assumption is based on the fact that the oxygen concentration, as measured by IR spectroscopy, is reduced after annealing. The precipitates growth kinetics are diffusion-controlled and their size can be calculated with reasonable accuracy from the supersaturation and diffusion coefficient of oxygen in silicon at the annealing temperature (3). However, no direct evidence of the precipitates as a form of silicon oxide has been reported. The main difficulty arises from the fact that microanalysis of the precipitates requires an instrument with both a capability of detecting oxygen plus high spatial resolution and detection sensitivity. Techniques such as electron diffraction fail to reveal extra dots or rings from the precipitates (1-3).The Czochralski crystals used contained 1018 atoms/cm3 oxygen, were oriented and doped with boron to 2 Ω-cm, annealed at 1100°C for 40 hours and then prepared for TEM analysis by chemical etching.