Showing 4 results for Displacement
F. Heravi , H. Ziaee ,
Volume 12, Issue 3 (10-1999)
Abstract
Lateral and anterior displacements of mandible may cause malocclusion. The aim of this study was to determine the prevalence of these displacements in a population of 597 childrens age 12 in Mashhad secondary schools. Displacment of mandible was shown to be in 11.8 percent of the population (6.2 percent anterior and 5.6 percent lateral displacement).Anterior displacement of mandible was diagnosed in all mandibie lateral displacements. Premature contacts were observed in upper lateral incisors, second premolars and first molar in anterior and lateral displacements, respectively.
T. Jafarzadeh , M. erfan , Dc. Watts , A. Cash ,
Volume 15, Issue 2 (5-2002)
Abstract
Dentine bonding systems are usually unfilled, and so their shrinkage may be significant. High shrinkage may cause internal stress at the interface between resin-composite restoration and the dentine substrate. Failure of the adhesive interface may be observed due to the interna! stress. The aims of this study were:A) To obtain a suitable method for measuring the kinetics of polymerisation shrinkage in unfilled resm at different thicknesses, particularly for thin films.B) Consideraing the effect of thickness on shrinkage.Scotchbond Multipurpose (3M) adhesive bond resin was used. To overcome the particular challenges presented by thin films, a filled-ring measurement procedure was used. Also, a non-contact laser analogue displacement sensor system was developed and applied to measure polymerisation shrinkage. Regression analysis was performed on a complete data set. Non-linear regression analysis established a logarithmic relationship between polymerisation shrinkage and layer thickness. The method applied in this study was found to be sensitive and accurate procedure for determining photo-polymerisation shrinkage of thin films. Polymerisation shrinkage increased with logarithmic of the adhesive thickness.
Gh. Shirani , D. Kazemi ,
Volume 16, Issue 4 (1-2004)
Abstract
Statement of Problem:The choung osteotomy (Intraoral Vertico- Sagittal Ramus Osteotomy) has developed since 1992 in the treatment of mandibular prognathism. In IVSRO, osteotomy plane is theoretically parallel to the original sagittal plane and thereby attempting to decrease the incidence of condylar dispacement. This osteotomy designed additionally to decrease neurosensory disturbances.
Purpose: The aim of this study was to evaluate the incidence of neurosensory deficit and condylar displacement with IVSRO and Sagittal Split Ramus Osteotomy (SSRO).
Materials and Methods: In this study, mandibular set back surgery was accomplished upon 7 patients by choung osteotomy. In addition to choung osteotomy, in 2 patients Lefort 1 osteomy was performed for maxillary protrusion and for 2 other patients, chain surgery was performed. Variables such as the neurosensory disturbances of inferior alveolar nerve and condylar displacement following choung osteotomy were investigated. All the patients were followed up one year after osteotomy. OPG, Lateral Cephalogram and Submentovertex radiographies were take pre and postoperatively for all patients.
Results: No statistically significant differences were found in condylar displacement (P>0.5). However, Mc Nemar analysis showed significant difference of neurosensory deficit between IVSRO and SSRO (P=0.001).
Conclusion: It is suggested that choung osteotomy is a safe procedure for mandibular surgery.
Marzieh Alikhasi, Mahnaz Arshad, Hakime Siadat, Susan Rahimian,
Volume 25, Issue 3 (7-2012)
Abstract
Background and Aims: Passive fit of prosthetic frameworks is a major concern in implant dentistry. Impression technique is one of the several variables that may affect the outcome of dental implants. The purpose of this study was to compare the three dimensional accuracy of direct and indirect abutment level implant impressions of ALL-ON-4 treatment plan.
Materials and Methods: A reference acrylic resin model with four Branemark fixtures was made according to All-On-4 treatment plan. Multiunit abutments were screwed into the fixtures and two special trays were made for direct and indirect impression techniques. Ten direct and ten indirect impression techniques with respective impression transfers were made. Impressions were poured with stone and the positional accuracy of the abutment analogues in each dimension of x, y, and z axes and also angular displacement (Δθ) were evaluated using a Coordinate Measuring Machine (CMM). Data were analyzed using T- test.
Results: The results showed that direct impression technique was significantly more accurate than indirect technique (P<0.001).
Conclusion: The results showed that the accuracy of direct impression technique was significantly more than that of indirect technique in Δθ and Δr coordinate and also Δx, Δy, Δz.
