Search results for "STRESS"
showing 10 items of 6278 documents
Primary loading of palatal implants for orthodontic anchorage--a pilot animal study.
2006
Summary Objectives This study aimed at evaluating the clinical performance and osseointegration of short orthodontic implants immediately loaded with orthodontic forces. Material and methods The investigation was designed as an experimental animal study. Eight palatal implants of the Ortho-system® were immediately loaded with 100 cN after palatal insertion in 4 female german shepherd dogs. Xylene orange and calcein green were used for polychrome sequential labelling. Histological preparation utilized the cutting and grinding technique. Outcome variables were clinical implant success, histological osseointegration and bone-to-implant contact rates. Results All (8/8) implants were clinically …
Luting of ceramic crowns with a self-adhesive cement: Effect of contamination on marginal adaptation and fracture strength
2012
Objectives: This study evaluated the percentages of continuous margins (%CM) and fracture strength (FS) of crowns made out from blocs of leucite-reinforced ceramic (IPS Empress CAD) and luted with a representative self-adhesive cement (RelyX Unicem) under four contaminating agents: saliva, water, blood, a haemostatic solution containing aluminium chloride (pH= 0.8) and a control group with no contamination. Study Design: %CM at both tooth-cement (TC) and cement-crown (CC) interfaces were determined before and after a fatigue test consisting of 600’000 chewing loads and 1’500 temperature cycles changing from 5º C to 50º C. Load to fracture was recorded on fatigued specimens. Kruskal-Wallis t…
Fracture resistance after implantoplasty in three implant-abutment connection designs
2020
Background To assess the effect of implantoplasty and implant-abutment design on the fracture resistance and macroscopic morphology of narrow-diameter (3.5 mm) dental implants. Material and Methods Screw-shaped titanium dental implants (n = 48) were studied in vitro. Three groups (n = 16) were established, based on implant-abutment connection type: external hexagon, internal hexagon and conical. Eight implants from each group were subjected to an implantoplasty procedure; the remaining 8 implants served as controls. Implant wall thickness was recorded. All samples were subjected to a static strength test. Results The mean wall thickness reductions varied between 106.46 and 153.75 µm. The me…
Load-deflection characteristics of superelastic and thermal nickel-titanium wires
2011
SUMMARY The aim of this study was to investigate the mechanical properties of superelastic and thermal nickel–titanium (NiTi) archwires for correct selection of orthodontic wires. Seven different NiTi wires of two different sizes (0.014 and 0.016 inches), commonly used during the alignment phase, were tested. A three-point bending test was carried out to evaluate the load–deflection characteristics. The archwires were subjected to bending at a constant temperature of 37°C and deflections of 2 and 4 mm. Analysis of variance showed that thermal NiTi wires exerted significantly lower working forces than superelastic wires of the same size in all experimental tests (P < 0.05). Wire size had a s…
The influence of platform switching on the biomechanical aspects of the implant-abutment system. A three dimensional finite element study
2011
Objective: To evaluate the biomechanical scenario of platform switching geometric implant-abutment configuration relative to standard configurations by means of finite element analysis.Study Design: A 3D Finite Element Analysis (FEA) was performed on 3 different implant-abutment configurations: a 3.8 mm implant with a matching diameter abutment (Standard Control Design, SCD), a 5.5 mm implant with matching diameter abutment (Wider Control Design, WCD), and a 5.5mm implant with a 3.8 mm abutment (Experimental Design, ED). All the different experimental groups were discretized to over 60000 elements and 100000 nodes, and 130N vertical (axial) and 90N horizontal loads were applied on the coron…
Measurement of gap between abutment and fixture in dental conical connection implants. A focused ion beam SEM observation
2020
Background The aim of the authors was to examine the abutment-fixture interface in Morse-type conical implants in order to verify gaps at this level using a new microscopical approach. Material and Methods In this in vitro study, 20 abutment-fixture complexes were prepared by sectioning (longitudinal and cross-sectional to the long axis) with a microtome and then with a focused ion beam (FIB). This is a micrometric machine tool that uses gallium ions to abrade circumscribed areas to dig deeper into the cuts obtained with the microtome in order to eliminate cut-induced artifacts. This is because the FIB abrasion is practically free from artifacts, which are normally generated by the action o…
Influence of material and diameter of pre-fabricated posts on maxillary central incisors restored with crown.
2009
Summary Numerous research works have studied the effect of post-design parameters on the mechanical behaviour of restored teeth without reaching any clear conclusions. Previous works by the authors ascertained the effect of material and post-dimensions for non-crowned restored teeth. The aim of this work was to study the effect of post-material and diameter for crowned teeth. First, an experimental fracture strength test was performed on eighteen extracted human maxillary central incisors. Teeth were decoronated, treated endodontically and restored (nine with glass fibre posts and nine with stainless steel posts). Several post-diameters were used. The final crown restoration was carried ou…
Familia, profesorado e iguales: claves para el apoyo a las víctimas de acoso escolar
2011
ResumenEl objetivo del presente estudio fue analizar las diferencias en ajuste psicológico en víctimas de acoso escolar en función de la calidad de sus relaciones con padres, profesores e iguales. En concreto, se compararon cuatro indicadores de ajuste psicológico (autoestima, ánimo depresivo, soledad y percepción de estrés) en víctimas con buena o mala comunicación con la madre, buena o mala comunicación con el padre, alta o baja percepción de ayuda del profesor, y alta o baja identificación con su grupo de iguales. La muestra inicial estuvo compuesta por 1795 adolescentes, entre 11 y 18 años (M=14.2, DT=1.68). Los resultados indicaron que las víctimas que mantenían mejores relaciones soci…
The Influence of Guilt on the Relationship Between Burnout and Depression
2012
Burnout is a serious problem that can be expressed as psychological symptoms, such as depressive mood. Earlier studies have shown that feelings of guilt appear to be involved in the burnout process. However, the exact nature of the relationships among burnout, guilt, and depression is unclear. The purpose of this study was to test the mediator role of guilt in the relationship between burnout and depression. The sample of this cross-sectional study consisted of 700 employees working with intellectually disabled persons. Hypotheses were tested together in a path model. Two models were constructed to test the relationships among the variables. The difference between the models was the order …
Photogrammetric UAV technologies aimed at monitoring of infrastructures
2022
The research has three key concept: the first one is the application of data analysis using limited data sets to understand historical and future road maintenance interventions; the second one is the application of image based 3D modelling and analysis of pavement distresses; the third one is the application of deep learning to detect and pinpoint pavement distresses