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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of oral rehabilitation 27 (2000), S. 0 
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The purpose of this study was to compare the mandibular movements of anterior openbite patients using those of normal bite (angle class I) patients, to ascertain which components of mandibular movement are different in the two groups, and to use this information for occlusal treatment. The Saphon Visi-trainer Model 3 and the Denar Pantronic were used to record mandibular movement and a Pantronic survey was performed using an arbitrary hinge axis, according to manufacturer's instructions. The subjects were 43 adults and included 28 subjects presenting with acceptable normal occlusion (angle class I) with no sign of TM dysfunction syndrome (TMD) and 15 subjects with anterior openbite with no anterior guidance. In the anterior openbite group, the average anterior and lateral condylar inclination, maximum opening and the distance between the intercuspal position with retruded contact position distance (anterior–posterior) were significantly lower than normal. The results suggest that in openbite patients the condyle inclination is flatter and the function of the TMJ is more restricted than in the mandibular movements of the normal group. It is hoped that these results will be useful for the correction of the anterior openbite condition.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: summary  The aim of this study was to quantify the extent of abutment screw loosening and thus understand the role of frictional and wear factors in abutment screw loosening by using a cyclic loading device to compare Diamond Like Carbon (DLC)-coated and non-coated implants. The properties of DLC films, including hardness, wear resistance, chemical stability, and biocompatibility, are similar to those of real diamond materials. In this study, a 1-μm thick DLC film served to protect and lubricate a layer of commercially-pure titanium affixed to the top of a dental implant (external hexagon-shaped implant). A cyclic loading force was then applied to the top of the prosthetic portion of the implants in order to determine the difference in looseness of the titanium abutment screw between ten DLC-coated implants and ten non-coated implants. The abutment screw loosening tests were performed with 100 N of force at a frequency of 20 Hz. Data indicate that implants with a DLC coating are more resistant to an applied force (P = 0·002) than are those without the coating. We hope these results will be useful for preventing implant abutment screw loosening.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Finite element analyses were performed for various shapes of dental implant to study effects on stress distribution generated in the surrounding jaw bone and to determine an optimal thread shape for even stress distribution. It was found that the square thread shape filleted with a small radius was more effective on stress distribution than other dental implants used in the analyses. Additional analyses were performed on the implant with the thread shape obtained from previous analyses for varying other design parameters, such as the width of thread end and height of thread for various load directions, to determine the optimal dimensions of the implant. Stress distribution was more effective in the case when the width of thread end and the height of thread were 0·5p and 0·46p, respectively, where p is the screw pitch. Then, using the optimal implant thread dimensions determined previously, stress analyses were performed with various screw pitches and implant lengths, to investigate effects on stress distribution and to find the way to reduce the maximum effective stress generated in the jaw bone. Results show that the maximum effective stress decreased not only as screw pitch decreased gradually but also as implant length increased.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary This in vitro study evaluated the effect of tooth brushing and thermal cycling on the surface lustre and surface roughness of three ceromer systems treated with different surface finishing methods. The ceromers studied were: (1) Artglass, (2) Targis, (3) Sculpture and (4) the control group, Z100. Half of the Targis and Sculpture groups were polished and the rest were coated with staining and glazing solution, respectively. All specimens were subjected to thermocycling 10 000 times. Tooth brushing abrasion tests were performed in a customized tooth-brushing machine with 500 g weight applied on a back-and-forth cycle for 20 000 repetitions. The lustre determined by measuring the light reflection area and the average roughness was compared between groups and between pre- and post-test values. All materials showed a lower lustre and rougher surface after thermocycling and tooth brushing (P 〈 0·05). All ceromer specimens, except glazed Sculpture, showed a higher lustre and similar roughness to the control group. The post-brushing results revealed that glazed Sculpture presented discretely fallen out glaze coatings and had maximum change. However, stained Targis showed minimum change (P 〈 0·05) and polished Targis presented more changes than that of the staining treatment. It is therefore concluded that the glaze coatings for Sculpture don't exhibit long-term durability, while stain coatings for Targis acted like a protective layer.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford UK : Blackwell Science Ltd
    Journal of oral rehabilitation 28 (2001), S. 0 
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The chewing cycle is a functional movement, closely related to occlusion, the neuromuscular system and the central nervous system. Although actual chewing paths are complicated and vary from individual to individual, there are two typical patterns. One is more vertical in nature and is similar to a chopping movement. The other is a more lateral type that is similar to a grinding movement. The purpose of this study was to evaluate the effects of chewing patterns on occlusal wear. Fifteen subjects exhibiting a chopping–chewing pattern and 15 subjects exhibiting a grinding–chewing pattern were selected using a jaw tracking device. The occlusal wear values, obtained by both ordinal and Woda’s arbitrary scales, and frequencies of non-working facets were calculated for each group. The occlusal wear values in all teeth and in each segment, obtained by the use of the ordinal scale did not vary significantly between the chopping and the grinding type group. However, the occlusal wear values of the grinding type group in all teeth and in posterior teeth segments, obtained by the use of Woda’s arbitrary scale, were significantly greater than those of the chopping type group. Frequencies of non-working facets in posterior teeth showed no significant differences between the groups.
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  • 6
    ISSN: 1365-2842
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: summary  In this study, effects of different overdenture attachments on the stress distributions in the maxillary bone surrounding the overdenture implants are studied. Four different types of attachment are considered. They are rigid Dalbo Stud, movable Dalbo Stress Broken, movable Dalro, and movable O-ring attachments. Three-dimensional finite element analysis was conducted with commercial package to obtain the stress distributions in the maxillary bone. Varying the attachment types and angle of inclination of load, the stress distributions in the portions of compact bone and trabecular bone were monitored separately. The analysis was conducted by assuming two different boundary conditions at the interface between cap and overdenture abutment in order to evaluate influence of interface boundary condition on stress distribution in the maxillary bone. They were perfect bonding condition and contact with friction at the interfaces. However, it is preferable to assume perfect bond condition at the interface for rigid type attachment systems and contact with friction at the interface for movable type attachment systems. From the numerical results, it was found that the load transfer mechanism of the implant system is altered significantly by the types of the overdenture attachment and also special care must be taken to assign proper boundary conditions at the interface for the analysis. The movable type Dalro attachment generated the highest maximum effective stress in the maxillary bone among the models under the same inclined loading condition for contact with friction. The rigid type Dalbo Stud attachment generated the smallest maximum effective stress in the maxillary bone among the models under the same inclined loading condition for perfect bonding condition.
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  • 7
    ISSN: 1617-4623
    Keywords: Key words Chromosome segregation ; Nocodazole ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Saccharomyces cerevisiae gene RHC21 is a homologue of the fission yeast rad21 +gene, which affects the sensitivity of cells to γ-irradiation and is essential for cell growth in S. pombe. Disruption of the RHC21 gene showed that it is also essential in S. cerevisiae. To examine its function in cell growth further, we have isolated temperature-sensitive mutants for the RHC21 gene and characterized one of them, termed rhc21-sk16. When this mutant was incubated at 36° C, the percentage of large-budded cells was increased. Most of the large-budded cells had aberrant nuclear structures, such as unequally extended nuclear DNA with incompletely elongated spindles across the mother-daughter neck or only in a mother cell. Furthermore, a circular minichromosome is more unstable in the mutant than in the wild-type, even at 25° C. Flow cytometry showed that the bulk of DNA replication takes place normally at the restrictive temperature in the mutant. These results indicated that the RHC21 gene is required for proper segregation of the chromosomes. In addition, we found that the mutant is sensitive not only to UV radiation and γ-rays but also to the antimicrotubule agent nocodazole at 25° C. This suggests that the RHC21 gene is involved in the microtubule function. We discuss how the RHC21 gene product may be involved in chromosome segregation and microtubule function.
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