Accuracy of transfer of bite recording to simulated prosthetic reconstructions.

OBJECTIVES: A key aspect of complex restorative therapy is reconstruction of a new three-dimensional jaw relation. The objective of this study was to test the hypotheses that the initially recorded jaw relation would deviate substantially from the jaw position of the prosthetic reconstruction and that activity ratios of the jaw muscles would be significantly different for each of these jaw positions. MATERIALS AND METHODS: In 41 healthy subjects, 41 examiners incorporated intraoral occlusal devices fabricated with all the technical details and procedures commonly used during prosthetic reconstructions. The jaw positions in centric relation with the incorporated occlusal devices were telemetrically measured in the condylar, first molar and incisal regions, relative to intercuspation. Electromyographic (EMG) activity of the temporalis and masseter muscles was recorded, and activity ratios were calculated for homonymous and heteronymous muscles. RESULTS: The recorded jaw relation differed significantly (p < 0.001) from the jaw position reconstructed with the intraoral occlusal devices. The initially recorded jaw relation was reproduced with the intraoral occlusal device with spatial accuracy of approximately 0.3 mm in the condylar, molar and incisal regions. The EMG ratios between centric relations and the reconstructed positions were significantly different (p < 0.05) for the temporal muscle and the temporalis/masseter ratio. CONCLUSIONS: The findings revealed that three-dimensional jaw-relation recording may be reproduced in a simulated prosthetic reconstruction within the accuracy reported for replicate intraoral bite recordings. CLINICAL RELEVANCE: Centric relation recordings may be reproduced in a prosthetic reconstruction with the spatial accuracy of 0.3 mm.

Nature and properties of cardiovascular deposits.

Mineral deposits from human aortas and bioprosthetic devices implanted in experimental animals show close similarities in chemical composition, solubility and structural characteristics. Chemical analyses show compositions corresponding to a Na, Mg, CO3 substituted apatitic calcium phosphate. Synergistic XRD, FT-IR and Raman microprobe spectroscopic data provided coherent indication of Type-B CO3(2-) incorporation. Microscopic and electron microprobe microanalyses, however, indicate substantial morphological and spatial heterogeneity in the deposits. Solubility and kinetic dissolution data of the mineral fraction of deposits can be compared with the corresponding data of octacalcium phosphate (OCP). This may indicate that OCP is a possible precursor phase which initiates formation of the mineral deposit. Our data indicate that the deposits can be represented by a series of carbonate-substituted products, arising from OCP that has hydrolyzed to varying degrees. Dissolution of deposits can be described kinetically as a surface controlled rate process. The similarities in the two types of deposits suggest that they form by a common mechanism (e.g., OCP could be the precursor for both deposits).

Molecular microanalysis of pathological specimens in situ with a laser-Raman microprobe.

A laser-Raman microprobe has been used to identify microscopic inclusions of silicone polymer in standard paraffin sections of lymph node. This example of organic chemical microanalysis in situ in pathological tissue represents an extension of microanalytical capabilities from elemental analysis, performed with electron and ion microprobes, to compound-specific molecular microanalysis.

Raman microprobe studies of two mineralizing tissues: enamel of the rat incisor and the embryonic chick tibia.

The laser-Raman microprobe developed at the National Bureau of Standards has been applied to the study of the mineralization process in rat incisor enamel and embryonic chick tibia. Cryostat sections were prepared from fresh frozen tissues and allowed to air dry. In these mineralizing tissues two forms of phosphorus compounds have been observed: (1) an inorganic phase identified as apatitic phosphate and (2) an organic phosphate. The distribution of these components from the mineralizing front to regions of higher mineralization has been determined with a spatial resolution of approximately 15 micrometer. The studies suggest the existence of a carbonate, with a Raman band corresponding to that of the mineral huntite, Mg3Ca(CO3)4, and found in regions of low phosphate mineral content.