Influence of the thyroid upon the glycosaminoglycans in the salivary glands in the rat

The glycosaminoglycans of the salivary glands were studied in male rats 2 months after radiothyroidectomy, and after the daily administration of 0.1 and 1.0 μg of sodium-1-triiodothyronine to radiothyroidectomized rats for 1 month. Total uronic acid concentration was determined in the salivary glands. Chromatographie separation of the uronic acid fractions was performed on cellulose microcolumns. Radiothyroidectomy increased and the administration of triiodothyronine decreased the uronic acid concentration in the submandibular glands. These changes occurred only in the hyaluronic acid and glycoprotein fractions. No changes in uronic acid concentration were detected in the retrolingual and parotid glands.     

Location of implants in the interforaminal region of the mandible and the consequences for the design of the superstructure

The location and the number of implants to support an overdenture is of major importance for the superstructure design. Sometimes, jaw bone anatomy or posteriorly placed implants enforce the use of an angular bar to achieve a position above the alveolar ridge. Loads on such a bar may introduce a moment on the implants which can result in high bone stresses and eventually the loss of the implants.
This study on stress distribution in the bone around the implants in an edentulous mandible was performed using a three-dimensional finite element model. One model with two implants placed just anteriorly of the mental foramen and connected with an anteriorly placed bar, following the curvature of the alveolar ridge, was compared with two other designs. First with a similar model but now without a bar and secondly with a model with four implants connected with straight bars.
It is concluded that loading a bar, which is placed anteriorly of the interconnecting line between two implants, causes extremely large compressive and tensile stress concentrations in the bone around the implants. Therefore, in those cases, it is advised not to connect the implants or, in case a bar-clip attachment is preferred, to place additional implants in the frontal region.