scholarly journals Enamel Microcracks Induced by Simulated Occlusal Wear in Mature, Immature, and Deciduous Teeth

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Manhal Ijbara ◽  
Kanae Wada ◽  
Makoto J. Tabata ◽  
Junichiro Wada ◽  
Go Inoue ◽  
...  
Keyword(s):  
Sliding Wear ◽  
Age Groups ◽  
Study Groups ◽  
Wear Testing ◽  
Deciduous Teeth ◽  
Hard Particles ◽  
Occlusal Wear ◽  
Enamel Wear ◽  
Sliding Wear Testing ◽  
Deciduous Molars

Enamel wear, which is inevitable due to the process of mastication, is a process in which the microcracking of enamel occurs due to the surface contacting very small hard particles. When these particles slide on enamel, a combined process of microcutting and microcracking in the surface and subsurface of the enamel takes place. The aim of this study was to detect microscopic differences in the microcrack behavior by subjecting enamel specimens derived from different age groups (immature open-apex premolars, mature closed-apex premolars, and deciduous molars) to cycles of simulated impact and sliding wear testing under controlled conditions. Our findings indicated that the characteristics of the microcracks, including the length, depth, count, orientation, and relation to microstructures differed among the study groups. The differences between the surface and subsurface microcrack characteristics were most notable in the enamel of deciduous molars followed by immature premolars and mature premolars whereby deciduous enamel suffered numerous, extensive, and branched microcracks. Within the limitations of this study, it was concluded that enamel surface and subsurface microcracks characteristics are dependent on the posteruptive age with deciduous enamel being the least resistant to wear based on the microcrack behavior as compared to permanent enamel.

Wear-Resistant Properties of TiC/Fe Ceramic Composite Coating on Steel Plate via Combustion Synthesis

2010 ◽  
Vol 105-106 ◽  
pp. 435-437
Author(s):  
Hong Zhao ◽  
Shi Wei Yang ◽  
Ying Jie Qiao ◽  
Xing Hong Zhang
Keyword(s):  
Sliding Wear ◽  
Ceramic Composite ◽  
Wear Test ◽  
Wear Testing ◽  
Dry Sliding Wear ◽  
Wear Resistant ◽  
Contact Wear ◽  
High Temperature Synthesis ◽  
Sliding Wear Testing ◽  
Static Pressing

The highly dense TiC/Fe ceramic coating was fabricated on Q235 steel surface by self- propagating high-temperature synthesis combined with pseudo hot iso-static pressing. The wear-resistant properties were examined by means of ball-on-disk contact wear test. The microstructure of TiC/Fe cermets coating was investigated. The results show that TiC/Fe cermets coating has an excellent wear-resistant property. There is little mass loss after 1200s under 30N loading under the condition of dry sliding wear testing. The major wear mechanisms are described by the following stages: sticking friction, grain abrasion and stripping of hard phase.

Wear Resistance of Super Alloys at Elevated Temperatures

1998 ◽  
Vol 120 (2) ◽  
pp. 339-344 ◽  
Author(s):  
J. L. Lawen ◽  
S. J. Calabrese ◽  
O. S. Dinc
Keyword(s):  
Wear Resistance ◽  
Gas Turbines ◽  
Sliding Wear ◽  
Elevated Temperatures ◽  
Operating Temperature ◽  
Wear Testing ◽  
Aircraft Engines ◽  
Wear Rates ◽  
Sliding Wear Testing ◽  
Cobalt Base

This paper provides the results of an extensive sliding wear testing program to evaluate wear resistance of several material couples currently used for high temperature applications such as ground based gas turbines and aircraft engines. Nickel and cobalt base superalloys and iron base stainless steels were tested in different combinations, and their wear rates compared to determine optimal wear resistance. The results show that an alloy’s wear resistance is highly dependent on operating temperature and its coupling with another material. The influences of friction, hardness, and oxide formation on the alloy’s wear resistance are also presented and discussed.

Avaliação da prevalência da perda precoce de molares decíduos na dentição mista

2020 ◽  
Vol 13 (52) ◽  
pp. 102-106
Author(s):  
Ana de Lourdes Sá de Lira ◽  
Cassius Wander Coelho Martins ◽  
Luis Paulo da Silva Dias ◽  
Tito Cacau Sousa Santos
Keyword(s):  
Mixed Dentition ◽  
Deciduous Teeth ◽  
Chi Square ◽  
Space Maintainer ◽  
Chi Square Test ◽  
Fixed Space ◽  
Deciduous Molar ◽  
One Year ◽  
Deciduous Molars ◽  
Lower Arch

Objective: To assess primary molars early loss in mixed dentition prevalence. Method: A study was carried out in children aged 6 to 12 years. Deciduous molar loss was considered early when it occurred before Nolla stage 6 (full formed crown) of the permanent successor or one year before its physiological exfoliation. Periapical radiographs were obtained to verify the presence of the permanent successor and the level of root formation, as well as the need for placement of fixed space maintainer lingual arch or Nance button. For the study of frequency distribution of early dental loss in relation to gender and dentition, we used the Chi-square test of 5% probability level and the non-parametric Mann-Whitney test for adequate statistical analysis. Results: Of the 315 children examined, 159 (50.47%) were male and 156 (49.52%) were female. Only 25 (7.9%) presented multiple dental losses in the posterior region, 19 in the lower arch and 6 in the upper arch. In the inferior one there was predominance of first and second deciduous molars loss. There was no difference in the association between genders and the occurrence of multiple dental losses (χ² (1) = 0.03, p>0.05). Conclusion: The prevalence of deciduous teeth premature loss was of 7.9% and the most affected teeth were the first and second molars in the lower arch. Lingual arch space holders were installed in 6 children, who will remain with it until the permanent successors erupt into the oral cavity.

Employing Gamma Ray Irradiated Giardia lamblia as Trialed Vaccine in Experimental Animal

2019 ◽  
Vol 9 (02) ◽  
Author(s):  
Amal Kamil Abdul Sada ◽  
Amany Mohamed Al-Kaysi
Keyword(s):  
Giardia Lamblia ◽  
Gamma Ray ◽  
Age Groups ◽  
Active Phase ◽  
Study Groups ◽  
Negative Control ◽  
Control Group ◽  
High Dose ◽  
Histopathological Changes ◽  
Gamma Irradiated

This is an experimental trial to prepare a vaccine from gamma-irradiated Giardia lamblia which is evaluated in experimental animals. The study was conducted from December 2015 to April 2016. The field survey of the parasite was conducted from those patients attending the laboratories of the Alawi Children's Hospital in Rusafa and the Al-Yarmouk Teaching Hospital in Karkh, through which 1250 stool samples of different age groups were examined. Five groups of mice were used in the study; the first was injected with normal saline and considered as a negative control group, the second was injected with cystic form of non-irradiated Giardia lamblia and considered as a positive control group, whereas the other three groups were injected with gamma irradiated Giardia lamblia at three different doses 10, 15 and 25 rad respectively. Giardia lamblia was primarily cultivated in liver infusion agar for ten days to obtain the active phase. On the sixth day, the cystic phase was purified and standardized to be used in the infection of mice with or without the exposure of gamma rays. Mice showed high sensitivity to parasitic infestation, in the gamma non-irradiated and the irradiated with gamma 10 rad, and 15 rad irradiated groups which was 100%. The results expressed an excystation process of the depleted phases and the release of the feeder phases. The results of the three irradiated groups consisted of histopathological changes of the small, and the rectum by dissection after two weeks of infection, with intestine amputation lesions, as well as ulceration and inflammation of the inflammatory cells represented in small numbers of neutrophil, lymphocytes, and eosinophils. The presence of ulceration and fall of epithelial cells in the intestinal cavity has been shown, and different forms of the parasite have been observed. Mice which was injected with irradiated G lamblia at high dose (25 rad), not show and sensitivity to the challenge infection and no excystation of thy parasite had been done. After 2 wreaks, a comparison was achieved between all study groups in which no histopathological changes were noticed in the mice irradiated with dose of25 rad. After another two weeks, a challenge dose was given (un-attenuated G lamblia) and mice were dissected after another two weeks, no changes on the level of histopathology of intestinal tissue were noticed the results suggested that mice acquire an immunity against the parasite infection.

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