root fracture injuries affect up to 7% of permanent teeth. this type of injury is rarely seen in teeth with open apices and depending on the fracture site, the prognosis is good. this case report describes a horizontal intra-alveolar root fracture in the middle third of a maxillary central incisor associated with an extrusive luxation of the coronal segment and its treatment in a 6-year-old gir...

although esthetic is a relative issue, depending upon the country and culture, almost all around the world, there is a consensus that a beautiful set of teeth is the one which is white and bright and is aligned regularly. in iran also the main feature of a beautiful tooth is its whiteness. during the past decades and centuries, tooth discoloration was considered as an esthetic issue and differe...

In this paper, quantitative evaluation of ultrasonic Cscan images through estimation of their Fractal Dimension (FD) is discussed. Necessary algorithm for evaluation of FD of any 2-D digitized image is implemented by developing a computer code. For the evaluation purpose several C-scan images of the Kevlar composite impacted by high speed bullet and glass fibre composite having flaw in the form...

let r be an associative ring with identity, c(r) be the category of com-plexes of r-modules and flat(c(r)) be the class of all at complexes of r-modules. we show that the at cotorsion theory (flat(c(r)); flat(c(r))−)have enough injectives in c(r). as an application, we prove that for each atcomplex f and each complex y of r-modules, exti (f,x)= 0, whenever ris n-perfect and i > n.

Abstract Purpose Considering the time-varying pressure angle and dynamic clearance, effects of rotational speed, tooth surface friction, morphology on system’s response are studied. Method An improved gear nonlinear model is proposed, which considered factors such as angle, position morphology, friction. The backlash deduced, equation established. system obtained based Runge–Kutta method. Resul...

o bjectives: correct determination of working length is an important step for suc- cess of endodontic therapy. conventional radiography has limitations in providing the accurate location of apical foramen. for this reason, electronic apex locators (eals) were developed to shorten the treatment time and decrease the radiation dose. the aim of this study was to evaluate the accuracy of root zx ea...

As the most important working area of gear, teeth play the role of transmitting load and power. Tooth line and tooth profile are the two main characteristics of the tooth surface, which affect the shape of the tooth surface, tooth meshing characteristics and contact characteristics. Taking the elliptical cylinder gear pair in the reversing device of a new type of drum pumping unit as the resear...

background and aims. hypodontia is a common developmental abnormality of dentition. this study aimed to determine tooth width in patients affected with mild hypodontia and compare the results with a control group without tooth agenesis. materials and methods. the orthodontic records of 25 patients with congenital missing of one or two teeth (hypodontia group), and 25 subjects with full dentitio...