introduction: this study investigated the influence of erbium-doped yttrium aluminum garnet (er:yag) laser on microhardness, chemical composition and subsurface morphology of dentin cavity walls. methods: forty sound human premolars were selected and randomly assigned into four groups. class v cavities were prepared either with an er:yag laser (groups 1 and 2; 15 hz, 250 mj for enamel, 10 hz, 2...

current ruminant feeding systems depend on knowledge of the composition of feeds and the rate and extent of degradation of feed organic matter (om) and crude protein (cp) in the rumen. the effect of storage and preparation of samples on in vitro gas production and fermentation characteristics of two common forage species, namely alfalfa and ryegrass werestudied. samples were prepared as fresh (...

objectives: different chelators may be used during root canal treatment, offering various advantages including lubricant effect inside the canal and smear layer removal. however, chelator residues in narrow root canals can lead to apical microleakage. the aim of this in-vitro study was to compare apical microleakage following the use of three root canal chelators via fluid filtration method in ...

introduction: disinfection and subsequent obturation of the root canal space require adequate mechanical enlargement of the canals. the purpose of this in vitro study was to compare the shaping ability of mtwo, race and medin rotary instruments during the preparation of curved root canals. materials and methods: sixty mesiobuccal root canals of mandibular molars with severe curvatures between 2...

introduction: root fracture is not an instant phenomenon but a result of gradual development of tiny craze lines in tooth structure. recent studies have shown that canal instrumentation has the potential to cause dentinal cracks. the purpose of this study was to evaluate and compare the formation of dentinal cracks caused by protaper rotary system to hand instrumentation. materials and methods:...

introduction: the aim of the present study was to compare hand stainless steel k-files and nickel-titanium profile 0.04 taper 29 series rotary instruments for their efficiency, procedural errors and time consumed in preparation of root canal system. materials and methods: a total of 46 maxillary and mandibular first premolars extracted for orthodontic purposes were collected (two contralateral ...

introduction: in this experimental study, the amount of smear layer (sl) remnants in curved root canals after chemomechanical instrumentation with two engine-driven systems or hand instrumentation was evaluated. methods and materials: forty-eight mesiobuccal roots of mandibular first molars with curvatures ranging between 25 and 35 degrees (according to schneider’s method) were divided into thr...

the background of consideration to local and national characteristics of land preparation management in development plans is recently and also of old. it is of old because it is traced back to human presence in land area and definition of the land and curiosity about life. it is recent because it has been begun in the last 100 years and it started mainly in the half of the past century and afte...

in this investigation the thickness of enamel in the gingival, middle, and incisal thirds of the labial surface of the anterior teeth were measured regarding preparation of the teeth for porcelain laminate veneers.part one, 20 extracted intact human maxillary central and lateral incisors ten of each were selected. the teeth were imbedded in autopolimerize acrylic resin. cross section was prefor...

Partially stabilized zirconia (PSZ) agglomerate toughened alumina has been prepared by the "deflocculation-flocculation" technique, using 2 and 3 mol. % Y2O3-doped zirconia powders. Samples containing up to about 30 vol.% zirconia were obtained. The resulting microstructure seems to be mainly influenced by the physical properties of the starting powders, e.g. agglomerate size and the specific s...