Evaluation of the use of PEEK material in implant-supported fixed restorations by finite element analysis.

AIMS: The purpose of this study is to compare the stresses occurring in the peri-implant bones, implants, crowns, abutments, and screws after loading through finite element analysis by using the poly-ether-ether-ketone (PEEK) materials, which are alternative to titanium abutment and metal supported restorations and to try to reduce the level of neck resorption. MATERIALS AND METHODS: In our study, three-dimensional modeling of 2 PEEK and titanium abutments, metal-ceramic, and monolithic PEEK upper central dental restorations were made on four titanium implants (Biohorizons® Implant Systems Ins., Birmingham, AL, USA) with diameters of 3.8 mm and 10.5 mm and four groups were obtained. Then, a stress analysis of the finite element was performed by applying a 178 N oblique force of 45° to the long axis of the tooth 2 mm below the incisal edge of the model's palatal surface. RESULTS: It has been observed that the PEEK material reduces the stresses caused by the force applied on itself during all tests. In all groups, PEEK abutments and PEEK crowns have reduced stress on the abutment. The most significant difference is observed in the stresses on the crowns and screws. When the stresses on the crown are examined, the use of PEEK crown reduces the stresses on itself and the use of PEEK abutment increases the stresses on the crown. CONCLUSIONS: The stress on the implant system can be changed through the usage of different prosthetic materials.

Prevalence of traumatic dental injuries and associated factors among 8 to 12-years-old schoolchildren in Diyarbakir, Turkey.

BACKGROUND AND OBJECTIVES: This study aimed to assess the prevalence of traumatic injuries of the permanent incisors in public primary schoolchildren from 8 to 12 years old in South-Eastern Anatolia, Turkey. Additionally, the relationship between traumatic dental injuries, parents' education level, family income, size of incisal overjet and the presence of anterior open bite were examined. MATERIALS AND METHODS: Data were collected through oral examinations and structured interviews, and included socio-economic indicators. A total of 2907 children of both genders (1498 boys, 1409 girls) were included in the study. The response rate was 97%. RESULTS: The prevalence of dental injuries was 4.6% (n = 135). The highest frequency of trauma in permanent teeth was observed at the age of 12 (8%). Boys experienced more dental injuries than girls, 5.9% and 3.3% (p = 0.001), respectively. The most commonly reported cause of injuries to the permanent incisors was falls (71.8%), followed by collision with objects or people (17.8%). Maxillary central incisors were the most affected by dental injuries (154, 84.6%). The most common crown fracture was in enamel only (67.58%) followed by crown fracture of enamel and dentin (22.52%). CONCLUSION: Socio-economic indicators and parents' level of education were not statistically significantly associated with the occurrence of traumatic dental injuries. Factors associated with increased risk of dental injuries in permanent teeth were age, gender, having an incisal overjet greater than 5mm and anterior open bite.

Effects of X-ray radiation on lipid peroxidation and antioxidant systems in rabbits treated with antioxidant compounds.

The aim of this study was to investigate the effects of supplemental antioxidant vitamins and minerals on lipid peroxidation and on the antioxidant systems in rabbits exposed to X-rays. The rabbits were divided into two experimental groups and one control group, each group containing seven rabbits. The first group (VG) received daily oral doses of vitamin E (460 mg/kg live weight) and vitamin C (100 mg/kg live weight). The second group (MG) was fed a mineral-enriched diet that contained 60 mg manganese chloride, 40 mg zinc sulfate, and 5 mg copper sulfate per kilogram of feed. The third group served as controls and received only a standard diet. Blood samples were obtained before and after the supplementation with vitamins or minerals, as well as before and after irradiation with a total dose of 550-rad X-rays. The blood samples were analyzed for their content of malondialdehyde (MDA), plasma vitamins C and E, retinol, reduced glutathione (GSH), and glutathione peroxidase activity (GPx). After irradiation, the control group showed increased levels of MDA and activity of GPx (p<0.05), whereas the levels of GSH, vitamin C, and vitamin E were decreased. In the VG, the concentration of MDA was lower (p<0.05), and the concentration of GSH and vitamins C and E were higher (p<0.05) when compared to controls. In the MG, the concentrations of MDA, GSH, vitamin C, and retinol were not affected by the mineral administration and radiation. The level of vitamin E in the MG increased with mineral administration (p<0.05), but decreased after irradiation (p<0.05). For the control group, the level of GSH was higher than in the two experimental groups. After irradiation, the VG animals had vitamin E and C levels that were higher than in MG and control groups (p<0.05). The activity of GPx was not affected by vitamin or mineral supplementation or by irradiation. We conclude that the supplementation with antioxidant vitamins and minerals may serve to reinforce the antioxidant systems, thus having a protective effect against cell damage by X-rays.

Studies on the effects of x-ray on erythrocyte zinc and copper concentrations in rabbits after treatment with antioxidants.

The aim of this study was to investigate the effect of supplemental antioxidant vitamins and minerals on the erythrocyte concentrations of zinc and copper in rabbits after exposure to X-rays. The animals were divided into two experimental and one control group (CG). The first group (VG) was given daily oral doses of vitamins E and C; supplemental amounts of manganese, zinc, and copper were mixed with the feed and given to the second group of experimental animals (MG). Blood samples were taken from all groups before and after 4 wk of vitamin and mineral administration and after irradiation with a total dose of 550-rad X-rays. The administration of minerals caused the most significant increases of Zn and Cu. Even after irradiation, the zinc levels in the irradiated animals were higher than in the nonirradiated vitamin-supplemented animals (p<0.05). The results suggest that supplementation with antioxidant vitamins and minerals may have a protective effect against X-ray-induced damage.

Effect of short-term hypothermia on lipid peroxidation and antioxidant enzyme activity in rats.

This experiment was carried out to determine the effect of short-term hypothermia on blood malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glucose-6-phosphate dehydrogenase (G-6-PD) concentrations in rats. Twenty Sprague-Dawley rats were used weighing 180-200 g and on average 3.5 months old. They were randomly divided into two experimental groups: control (without cooling) and hypothermic (with cooling). The rats of the hypothermic group were cooled by immersion into cold water (10-12 degrees C), and the control rats were immersed into water of body temperature (37 degrees C) up to the neck without using any anaesthetic or tranquilizer for 3 min Rectal body temperatures of both groups were measured and blood samples to analyse MDA, GSH, SOD, GSH, GSH-Px and G-6-PD were collected immediately after the treatment. It was found that the MDA level was higher and the GSH and G-6-PD levels were lower in the hypothermic group than those in the controls. There was no difference between the control or hypothermic group regarding SOD or GSH-Px levels. It is concluded that acute hypothermia increased the lipid peroxidation and decreased the GSH and G-6-PD levels in rats.

Short communication serum copper, zinc, and calcium concentrations in lice-infested sheep.

The purpose of this study was to investigate changes in serum concentration of copper, zinc, and calcium in sheep naturally infested with lice (Bovicola caprae, Linognathus africanus, Linognatus ovillus, and Linognattus pedalis). Twenty sheep naturally infested with lice and 20 healthy sheep were used as subjects. Blood samples were collected from the sheep before and 8 and 15 d after treatment with Avermectin, a veterinary antiparasitic drug. The samples were analyzed for their serum copper, zinc, and calcium concentrations by atomic absorption spectrometry. The concentrations of these elements in the infested animals were lower than in the healthy controls, mainly because the general condition of the affected sheep was poor. When the infested animals were treated with an ectoparasitic drug, the serum levels of the studied elements rose to normal ranges while the health of the animals improved.