Mapping of the Micro-Mechanical Properties of Human Root Dentin by Means of Microindentation

The extensive knowledge of root dentin's mechanical properties is necessary for the prediction of microstructural alterations and the teeth's deformations as well as their fracture behavior. Standardized microindentation tests were applied to apical, medial, and cervical root sections of a mandibular human first molar to determine the spatial distribution of the hard tissue's properties (indentation modulus, indentation hardness, Martens hardness, indentation creep). Using an indentation mapping approach, the inhomogeneity of mechanical properties in longitudinal as well as in transversal directions were measured. As a result, the tooth showed strongly inhomogeneous material properties, which depended on the longitudinal and transversal positions. In the transversal cutting planes of the cervical, medial, apical sections, the properties showed a comparable distribution. A statistical evaluation revealed an indentation modulus between 12.2 GPa and 17.8 GPa, indentation hardness between 0.4 GPa and 0.64 GPa and an indentation creep between 8.6% and 10.7%. The established standardized method is a starting point for further investigations concerning the intensive description of the inhomogeneous mechanical properties of human dentin and other types of dentin.

Screening for organic mental syndromes in the medically ill

A brief mental status questionnaire adapted specifically to diagnose diffuse organic diffuse organic mental syndromes on busy medical words is developed and tested for reliability and validity. When the 30-item questionnaire was given to 17 medical patients diagnosed by consultation spychiatrists as having a diffuse organic mental syndrome, all score 20 or less. With hospitalized psychiatric patients the questionnaire was able to differentiate between the "functional psychoses" and diffuse organic brain syndromes. When administered to 69 consecutive medical admissions, fully one third showed marked cognitive limitations. A sample of normals suggested that results may be contaminated by severe cultural or educational variances. We discuss the role of cognitive dificiencies in medical patients, and suggestions are made regarding the broad usefulness of this questionniare to a medical service.