Basal Implants Research Articles

The use of finite element analysis to model bone-implant contact with basal implants

The purpose of this study was to develop a model that accurately represents the interface between bone and basal implants throughout the healing process. The model was applied to the biological scenario of changing load distribution in a basal implant system over time. We did this through finite element analysis (FEA, or finite element method [FEM]), using multiple models with changing bone-implant contact definitions, which reflected the dynamic nature of the interface throughout the bony healing process. In the simple models, peak von Mises stresses decreased as the bone-implant-contact definition was changed from extremely soft contact (i.e., immature bone during early loading) to hard contact (i.e., mature bone). In upgraded models, which more closely approximate the biological scenario with basal dental implant, peak von Mises stresses decreased at the implant interface; however, they increased at the bone interface as a harder contact definition was modeled. Further, we found a shift in peak stress location within the implants during different contact definitions (i.e., different stages of bony healing). In the case of hard contact, the peak stress occurs above the contact surface, whereas in soft contact, the stress peak occurs in the upper part of the contact area between bone and the vertical shaft of the implant. Only in the extreme soft contact definitions were the peak stresses found near the base plate of the implant. Future FEM studies evaluating the functional role of dental implants should consider a similar model that takes into account bone tissue adaptations over time.

Muscle basal lamina as a grafting material for elongation of axons from rat brain

Autografts of peripheral nerve or allografts of muscle basal lamina were inserted into the putamen-caudate complex of rats, with the outer end of the implant being sutured to the temporalis muscle. Elongation of central axons within the grafts, as revealed by the horseradish peroxidase retrograde labelling technique, did occur in the presence of basal lamina implants. With both types of grafting materials stained neurones exhibited a comparable distribution, being mainly found in the proximity of the central tip of the grafts. However, labelled cells in the presence of basal lamina were limited in number, compared with peripheral nerve autografts. Therefore, the usefulness of implants of muscle basal lamina into the central nervous system, in order to direct regenerating central axons toward distant target regions, is limited. This material might be suitable, as an alternative grafting material, in experimental models where avoidance of neurological impairment or size and length of the graft are crucial factors.

The adenohypophysis of female rats after hypothalamic oestradiol implants: an electron microscopic study.

SUMMARY The ultrastructural effect of oestradiol implants into the hypothalamus on the adenohypophysis of adult female rats was studied. The main results are the demonstration that mammotrophs or prolactin cells, and to a lesser extent somatotrophs, increased their secretory activity after bilateral implants into the median eminence and arcuate nuclei; in the periventricular area the reaction was weaker and in the anterior hypothalamus the response was negative. In animals with implants in the basal tuberal region, mammotrophs showed an asynchronous secretory activity. Mitosis has been found to occur in fully differentiated mammotrophs, a finding which can be correlated with the increased number of such cells after basal tuberal implants. The gonadotrophs appeared to be atrophied.