Digital dental radiographic identification in the pediatric, mixed and permanent dentitions.

The purpose of this paper is to investigate the utility of digital dental radiographic superimposition in the various stages of development of the human dentition. Digital, computer assisted dental identification is a means of identification which allows the spatial relationships of the root and support structures of the teeth to be compared one to the other. The technique has not been tested in patients with developing dentitions. Dental radiographs from patients in the pediatric, mixed and permanent dentition stages of development, simulating "antemortem" and "postmortem" radiographs, were digitized using a flat field radiograph scanner. Anatomic features were used as points of comparison utilizing image editing software whereby anatomic sections were digitally cut from the antemortem image and compared to the same anatomic locations on the postmortem image to assess for points of concordance. The technique was applied to 25 cases within the primary dentition, 25 cases within the mixed dentition and 25 cases within the permanent dentition. Results showed that this was a viable technique within both the pediatric and permanent dentition although it was of little value within the mixed dentition.

The in vitro photolysis of whole rat lenses using focused 290 nm laser radiation.

Whole rat lenses have been irradiated with a UV laser at 290 or 298 nm focused to a 0.08 mm diameter spot. The irradiated spot was analyzed using fluorescence spectroscopy and it was observed that the intensity of fluorescence (290 nm excitation, 335 nm emission) fell as the irradiation proceeded. These observations were interpreted in terms of a model which postulates photolysis of tryptophan, primarily present as residues in lens proteins, and formation of photoproducts which absorb the UV laser radiation to an ever-increasing extent as the irradiation proceeds. The effect is to produce a linear dependence of log If on log t, where If is the observed tryptophan fluorescence intensity after time, t, of exposure to the laser radiation. Evidence is also presented which indicates that an observed fast component of the tryptophan fluorescence decay results from local heating of the lens tissues due to energy dissipation by the laser. The most important conclusion from the present series of experiments is that tryptophan residues can be photolyzed by UV light in the whole lens, in vitro, in a fashion entirely analogous to that reported previously only for lens protein solutions. Hence the present work demonstrates that the photochemical behavior of lens protein solutions is indeed relevant to whole lens photolysis and that no special protective mechanism appears to be operative in the intact organ.