Dynamic Determinants of Incisal Display

The principal objective of this study was to use computer aided design (CAD) to better illustrate and quantify the relationship of mandibular arch depth, mandibular arch width, overbite, and overjet in the presence of mandibular dental crowding. To date, there has been no research examining how changes in the mandibular arch limit the orthodontist\u27s ability to control overbite and overjet. Understanding how to effectively manage overbite and overjet are crucial to the clinician\u27s ability to manipulate incisal display. Polyvinyl siloxane impressions of both maxillary and mandibular arches of a Caucasian patient were taken and used to pour dental stone models. Models were then potted, scanned, manipulated, and measured using Insignia™ (Ormco Corporation, Glendora, CA). Five different groups of maloccluded, diagnostic set-ups were subsequently constructed based upon location of crowding in the arch. For all groups, regression analysis revealed similar linear relationships (R2=0.963-0.999) for arch depth, arch width, and overjet changes versus dental crowding. In contrast, overbite changes displayed linear, quadratic, and cubic relationships (R2 = 0.688-0.997). Results suggest that lingual contours of maxillary incisor crowns are smile arc determinants and rate determining factors of overbite change. Guidelines for managing overbite and incisal display are offered

Enzymatic determination of plasma ammonia: evaluation of Sigma and BMC Kits.

Abstract We compared two kit methods for the enzymatic determination of plasma ammonia. The procedures involved measuring the decrease in absorbance at 340 nm resulting from the consumption of NADH in the Sigma kit, NADPH in the BMC kit. Both kits gave acceptable results for aqueous samples, but for plasma specimens values with the Sigma kit significantly exceeded those obtained with the BMC kit. In our hands, values with the BMC kit were more accurate and precise. On the basis of these results, we conclude that the BMC kit is the better choice.</jats:p