Finite element analysis of stress extent at peri-implant bone surrounding external hexagon or Morse taper implants.

PURPOSE: The purpose of the present study was to evaluate the distribution of stresses and consequent bone volume affected surrounding external hexagon or Morse taper dental implant systems by finite element analysis. MATERIAL AND METHODS: Two different dental implant-abutment designs were assessed: external hexagon or Morse taper joints. A mandibular bone model obtained from a computed tomography scan was used. The implant-abutment systems were axially or obliquely (45°) loaded on 150 N relatively to the central axis of the implant. The von Mises stresses were analysed in terms of magnitude and volume of affected surrounding bone. RESULTS: The von Mises equivalent values found on the cortical bone were higher than that recorded on the trabecular bone. Additionally, the bone volume associated with high stress values was higher in cortical and trabecular bone for oblique loading compared to axial loading. The values of von Mises equivalent stress around Morse taper implant-abutment system were lower on both axial and oblique loads than those recorded for external hexagon implant-abutment systems. CONCLUSIONS: Morse taper implant joints revealed a proper biomechanical behavior when compared to external hexagon systems concerning a significant volume of surrounding peri-implant bone subjected to lower stresses values.

Early infection with Leishmania major restrains pathogenic response to Leishmania amazonensis and parasite growth.

Experimental models of infection with Leishmania spp. have provided knowledge of several immunological events involved in the resistance mechanism used by the host to restrain parasite growth. It is well accepted that concomitant immunity exists, and there is some evidence that it would play a major role in long-lasting acquired resistance to infection. In this paper, the resistance to Leishmania amazonensis infection in C57BL/6 mice infected with Leishmania major was investigated. C57BL/6 mice, which spontaneously heal lesions caused by infection with L. major, were infected with L. amazonensis at different times before and after L. major. We demonstrated that C57BL/6 mice previously infected with L. major restrain pathogenic responses induced by L. amazonensis infection and decrease parasite burdens by one order of magnitude. Co-infected mice showed production of IFN-gamma in lesions similar to mice infected solely with L. major, but higher TNF-alpha and nitric oxide synthase (iNOS) mRNA expression was observed. Surprisingly, the restrained pathogenic response was not related to IL-10 production, as evidenced by lower levels of both mRNA, protein expression in lesions from co-infected mice and in co-infections in IL-10(-/-) mice. Examination of the inflammatory infiltrate at the site of infection showed a reduced number of monocytes and lymphocytes in L. amazonensis lesions. Additionally, differential production of the CCL3/MIP-1 alpha and CCL5/RANTES was observed. We suggest that the control of lesion progression caused by L. amazonensis in C57BL/6 mice pre-infected with L. major is related to the induction of a down-regulatory environment at the site of infection with L. amazonensis.

Influence of a lipophilic drug on the stability of emulsions: an important approach on the development of lipidic carriers.

The aim of this work was to investigate the influence of a lipophilic drug, Ibuprofen, on the stability of o/w emulsions. Five formulations were prepared by the phase inversion temperature (PIT) method, and Ibuprofen was incorporated into their oil phase. Emulsion stability was evaluated by short- and long-term studies. Concerning the former, stability under centrifugation showed an improved profile for Ibuprofen-loaded emulsions. The latter confirmed such findings. In conclusion, a rather resistant interfacial film may take place when Ibuprofen was incorporated into the emulsions. Therefore, the critical hydrophilic-lipophilic-balance (HLB) of o/w emulsions can be affected by a lipophilic drug into their oil phase. Such approach is of great importance on the development of lipid carriers for therapeutic drug targeting.