Search results for " surface"
showing 10 items of 2838 documents
Algebraic Curves and Riemann Surfaces in Matlab
2010
In the previous chapter, a detailed description of the algorithms for the ‘algcurves’ package in Maple was presented. As discussed there, the package is able to handle general algebraic curves with coefficients given as exact arithmetic expressions, a restriction due to the use of exact integer arithmetic. Coefficients in terms of floating point numbers, i.e., the representation of decimal numbers of finite length on a computer, can in principle be handled, but the floating point numbers have to be converted to rational numbers. This can lead to technical difficulties in practice. One also faces limitations if one wants to study families of Riemann surfaces, where the coefficients in the al…
Thermodynamic Studies of Sodium Dodecyl Sulfate–Sodium Dodecanoate Mixtures in Water
1996
Abstract Conductivity, density, heat capacity, enthalpy of dilution, and osmotic coefficient measurements of water–sodium dodecyl sulfate (NaDS)–sodium dodecanoate systems were carried out as functions of the surfactants total molality ( m t ) at different mole fractions ( X NaDS ). From conductivity data, the critical micelle concentration (cmc) and the degree of ionization of the micelles (β) were calculated. The cmc vs X NaDS profile deviates negatively from that predicted on the basis of the Clint approach, while the β vs X NaDS profile deviates positively from the line correlating the values for pure surfactants. At a given mole fraction, the profiles of all the investigated properties…
Untersuchungen zur Reaktionsfähigkeit statistisch verteilter Estergruppierungen in Copolymeren aus Styrol und Acrylsäureestern
1974
Die Aminolyse der ortho- und para-Nitrophenylester von Propionsaure, Isobuttersaure, 4-Phenylbuttersaure und 4-Phenylvaleriansaure sowie von Copolymeren aus Styrol und geringen Mengen Acrylsaure wurde mit Butylamin in Dioxan untersucht. Bei grosem Aminuberschus reagieren die niedermolekularen Ester streng nach erster Ordnung, wobei die Reaktionsgeschwindigkeit durch Zugabe von Polystyrol nicht beeinflust wird. Fur Copolymere, deren Reaktionsgeschwindigkeit deutlich geringer ist, erhalt man dagegen keine Beziehung erster Ordnung, obwohl die Anfangsgeschwindigkeit der Gesamtkonzentration der Estergruppen direkt proportional ist. Bei den Copolymeren erhalt man annahernd die gleichen Aktivierun…
Impact of different rectangular wires on torsional expression of different sizes of buccal tube.
2017
Background Torsions in rectangular wires are the essential part of corrections in the finishing stage of treatment. Moreover the greatest amounts of torques are applied in the molar areas. a clinically effective moment is between 5 and 20 Nmm. In this study we have decided to evaluate the impact of different tube sizes and different dimensions of wires with different modulus of elasticities on the amount torsional bond strength of molar tubes. Material and Methods 60 human impacted molar teeth were collected. A buccal tube was bonded on the buccal surface of all the samples by using light cured adhesive resin. After that, the teeth were mounted in a hard acrylic block. According to the size…
Effect of rotary cutting instruments on the resin-tooth interfacial ultra structure: An in vivo study
2013
Objectives: To evaluate the effect of cutting teeth with different types of burs at various speeds on surface topogra - phy of tooth surface and interfacial gap formation at resin-tooth interface. Material and Methods: The human molars were divided into seven groups: Diamond bur in airrotor (DA) & mi - cromotor (DM), crosscut carbide bur in airrotor (CCA) & micromotor (CCM), plain carbide bur in airrotor (CA) & micromotor (CM) and #600-grit silicon carbide paper (SiC). In five samples from each group Class II box-only cavities were restored. The occlusal surface of four teeth per group was flattened. Two out of four teeth were acid etched. Teeth were subjected for scanning electron microsco…
Periodontal disease affecting tooth furcations. A review of the treatments available
2007
The molars are the teeth that suffer the greatest periodontal destruction in untreated patients. When periodontal disease affects the furcation of a tooth, the chance that it will be lost increases considerably. An increase in the exposed root surface, anatomical peculiarities and irregularities of the furcation surface all favor the growth of bacteria. These problems make it harder for the patient to maintain hygiene, and impede adequate treatment. The treatment of furcations affected by periodontal disease is one of the most difficult problems for the general dentist and periodontist. The motivation of both the attending professional and of the patient are therefore of great importance. N…
Assessment of non-carious root surface defects in areas of gingival recession: A descriptive study.
2015
BACKGROUND The purpose of this descriptive study was to observe the distribution of four different classes of non-carious cervical root surface discrepancies in teeth with gingival recession. Additionally to explore the different treatment modalities in the literature for each of these defects. MATERIAL AND METHODS A total of 150 subjects with at least one labial gingival recession were included in the study. 1400 teeth were evaluated using 2.5 X magnification loupes and UNC -15 probe for the presence of the cemento-enamel junction and step like defects according to Pini-Prato's classification: A-, identifiable CEJ without defect; A+, identifiable CEJ with defect; B-, unidentifiable CEJ wit…
Effects of elevated hydrogen peroxide 'strip' bleaching on surface and subsurface enamel including subsurface histomorphology, micro-chemical composi…
2007
Abstract Objectives This study examined the effects of elevated concentration hydrogen peroxide tooth whitening treatments on tooth surface and subsurface integrity. Methods Sound human molars were ground and polished to prepare an uniform substrate for bleaching treatments. A cycling treatment included alternating ex vivo human salivary exposures with bleaching treatments under conditions of controlled temperature and durations of treatment. Bleaching was carried out with prototype bleaching strips containing hydrogen peroxide gel at 13% and 16% concentrations. A non-bleached group was used as a control. Treatments included 28 h of total bleaching exposure in vitro . Surface color was meas…
Influence of two different surgical techniques on the difficulty of impacted lower third molar extraction and their post-operative complications
2015
Background : Post-operative complications of various degrees of severity are commonly observed in third molar impaction surgery. For this reason, a surgical procedure that decreases the trauma of bone and soft tissues should be a priority for surgeons. In the present study, we compare the efficacy and the post-operative complications of patients to whom two different surgical techniques were applied for impacted lower third molar extraction. Material and Methods : Patients of the first group underwent the classical bur technique, while patients of the second group underwent another technique, in which an elevator was placed on the buccal surface of the impacted molar in order to luxate the …
One-stage laser-microtextured implants immediately placed in the inter-radicular septum of molar fresh extraction sockets associated with GBR techniq…
2018
Background The outcome of one-stage trans-mucosal immediate implants with simultaneous guided bone regeneration (GBR) technique has become highly predictable. Furthermore, when this approach is performed to place one-stage implants into the inter-radicular septum of fresh extraction sockets in the molar region, the risk of incorrect emergence profile and off-angle loading is reduced. The aim of the present study was to clinically evaluate the horizontal hard and soft tissue changes, and radiographically the vertical socket walls remodeling, and the early peri-implant marginal bone loss (EMBL) following the placement of immediate one-stage implants in the inter-radicular septum of molar fres…