Cortical gyrification induced by fibroblast growth factor 2 in the mouse brain

Gyrification allows an expanded cortex with greater functionality to fit into a smaller cranium. However, the mechanisms of gyrus formation have been elusive. We show that ventricular injection of FGF2 protein at embryonic day 11.5-before neurogenesis and before the formation of intrahemispheric axonal connections-altered the overall size and shape of the cortex and induced the formation of prominent, bilateral gyri and sulci in the rostrolateral neocortex. We show increased tangential growth of the rostral ventricular zone (VZ) but decreased Wnt3a and Lef1 expression in the cortical hem and adjacent hippocampal promordium and consequent impaired growth of the caudal cortical primordium, including the hippocampus. At the same time, we observed ectopic Er81 expression, increased proliferation of Tbr2-expressing (Tbr2(+)) intermediate neuronal progenitors (INPs), and elevated Tbr1(+) neurogenesis in the regions that undergo gyrification, indicating region-specific actions of FGF2 on the VZ and subventricular zone (SVZ). However, the relative number of basal radial glia-recently proposed to be important in gyrification-appeared to be unchanged. These findings are consistent with the hypothesis that increased radial unit production together with rapid SVZ growth and heightened localized neurogenesis can cause cortical gyrification in lissencephalic species. These data also suggest that the position of cortical gyri can be molecularly specified in mice. In contrast, a different ligand, FGF8b, elicited surface area expansion throughout the cortical primordium but no gyrification. Our findings demonstrate that individual members of the diverse Fgf gene family differentially regulate global as well as regional cortical growth rates while maintaining cortical layer structure.

[Determination of vertical dimension of dental occlusion]

Principles and concepts in determining the vertical dimension of occlusion in mutilated dentitions are summarized. Historically, most concepts have been developed for full dentures. However, in the rehabilitation of a mutilated dentition it is often necessary to increase or change the vertical dimension of occlusion. If the vertical dimension of occlusion has to be altered the patient's adaptability to the new position should be tested during a trial period. Determination of the vertical dimension of occlusion is apparently a combination of art, science and experience.

Making an alternative occlusal splint

An occlusal splint is commonly used in the diagnosis and management of temporomandibular disorders. In a partially edentulous patient a poorly adapted removable partial denture can prevent the use of a conventional occlusal splint. This article describes the fabrication of an occlusal splint that also incorporates a provisional removable partial denture.