scholarly journals Enamel cracks evaluation —A method to predict tooth surface damage during the debonding

2015 ◽  
Vol 34 (6) ◽  
pp. 828-834 ◽  
Author(s):  
Irma DUMBRYTE ◽  
Tomas JONAVICIUS ◽  
Laura LINKEVICIENE ◽  
Tomas LINKEVICIUS ◽  
Vytaute PECIULIENE ◽  
...  
Keyword(s):  
Author(s):  
Eiichirou TANAKA ◽  
Keyaki NAKAJIMA ◽  
Kazunari OKABE ◽  
Hitoshi TAKEBE ◽  
Kazuteru NAGAMURA ◽  
...  

2015 ◽  
Vol 78 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Frank L’Engle Williams

Abstract Pleistocene Paranthropus robustus fossils from Swartkrans have yielded stable isotope values suggesting some foraging on C4 plants possibly including underground storage organs. Dental microwear texture analysis on P. robustus (SK 6, SK 34 and SK 47) from Swartkrans Member 1 is performed to examine whether tooth surface damage from mastication agrees with prior dietary inferences from carbon isotopes. There is considerable variation in textural characteristics among the P. robustus specimens. Specifically, adult SK 34 stands apart from the two subadult specimens, SK 6 and SK 47, suggesting life history could be reflected in patterns of dental microwear texture characteristics, although seasonality and availability of fallback foods may also explain the variation observed in P. robustus. The fossils all exhibit elevated surface texture complexity, resembling the values for Lophocebus albigena and Cebus apella, and to a lesser extent, Pan troglodytes. Paranthropus robustus is dissimilar to primary folivores, such as Trachypithecus cristatus or folivore- frugivores such as Alouatta palliata suggesting leaves comprised very little of its diet. The textural fill volume of P. robustus differs from that observed in extant primates from tropical forests indicating extreme durophagy, perhaps a function of differences in habitat. Ingestion of extraneous grit on the underground parts of plants and from terrestrial resources, perhaps as fallback foods or as dietary staples, may account for these enamel textural properties and may help explain the mixed C3/C4 isotopic signal in P. robustus.


2014 ◽  
Vol 8 (3) ◽  
pp. JAMDSM0039-JAMDSM0039 ◽  
Author(s):  
Qingrong FAN ◽  
Kiyotaka IKEJO ◽  
Kazuteru NAGAMURA ◽  
Masato KAWADA ◽  
Mitsuo HASHIMOTO

1996 ◽  
Vol 23 (2) ◽  
pp. 121-124 ◽  
Author(s):  
Muhamad Subra Bin Abdullah ◽  
W. P. Rock

Groups of orthodontic brackets were attached to enamel after etching for 15, 30 or 60 seconds, they were debonded by shear forces after 5 or 15 minutes, or 24 hours. The 15 seconds etch/5 minutes debond time specimens had much lower shear strengths than other groups. Sixty-second specimens showed evidence of tooth surface damage after tie bonding. Fifteen seconds of etching is therefore recommended routinely for bonding brackets. If a bracket is to be ligated within 5 minutes of placement, 30 seconds etching is recommended. A 60-second etch is considered too severe and should not be used.


Author(s):  
Keyaki Nakajima ◽  
Eiichirou Tanaka ◽  
Kazunari Okabe ◽  
Hitoshi Takebe ◽  
Kazuteru Nagamura ◽  
...  

We developed a method which can diagnose damage on a gear tooth surface by using laser beam without a rotary encoder. This method is as follows: 1) The tooth bottom, the tooth tip and their two medians are detected by the differentials of the laser reflection data. 2) The gear rotation speed is calculated with these four positions, and interpolated according to the rotation fluctuation. 3) By using the calculated gear rotation speed, the measured data can be converted corresponding to the gear rotation angle. Thus we diagnose gear tooth surface damage without being influenced by rotational fluctuation. We did diagnosis experiments and we made contour maps show diagnosis accuracy. From these maps, we got the following conclusions: 1) The accuracy of damage diagnosis is the same level regardless of the presence or absence of a rotary encoder. 2) The cycle of rotational fluctuation hardly affects the accuracy. 3) Bigger fluctuation amplitude makes the range accuracy worse, however the position accuracy improves.


1977 ◽  
Vol 99 (4) ◽  
pp. 189-194 ◽  
Author(s):  
R. Boehm ◽  
J. Rich ◽  
J. Webster ◽  
S. Janke

A detailed study is reported of the potential thermal stress effects and surface cracking of human teeth after absorption of laser energy. This study was motivated by the desire to define damage thresholds if lasers are used for preventive dentistry techniques. A large group of extracted teeth was exposed to manually pulsed bursts of energy of varying durations from a CW CO2 laser. The teeth were examined photographically under magnification before and after irradiation, using fluorescent dye to facilitate observation of cracks in the tooth surface. In an attempt to understand the cracking phenomena, predictions of the temperatures and thermal stresses were made. The tooth surface in the vicinity of the focused beam impingement was assumed to behave as a semi-infinite solid for the short periods of time considered. Estimated stresses where cracking occurred are compared in the paper to measured values of the ultimate strength of tooth enamel. Results are shown to be in reasonable agreement with predictions. Based on this work, a criterion is given for minimizing surface damage to the tooth.


2011 ◽  
Vol 86 ◽  
pp. 443-447
Author(s):  
Bin Wu ◽  
Wan Kai Shi ◽  
Long Zhao ◽  
Ping Fu

A complete numerical solution for the micro thermal elastohydrodynamic lubrication (EHL) of planetary gearing in wind turbine gearbox is obtained with taking roughness effects and characteristics of non-Newtonian fluids into account. The oil film pressure profile, film shape and the trend of equivalent temperature rise in planetary gearing in special meshing points are drawn. Through comparing with lubrication performance in different surface morphology between Ra=0.8μm and 0.2μm, the results show that the film thickness ratio of ring gear and planetary gears with Ra=0.8μm is greatly smaller than 1.5. From the relationship between tooth surface damage and film thickness ratio, these gears are in abnormal lubrication state, surface damage, when Ra=0.8μm, can theoretically reach more than 15%. However, the surface damage ratio with Ra=0.2μm has been greatly deceased, so as to that it provides a theoretical basis of reliable lubrication analysis for wind turbine gearbox.


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