Anatomical analysis of preangular mandibular notch in humans

The authors have analysed in detail the mandibular preangular notch on the basis of 273 human cadaver mandibles. They have revealed that the pregonial notch is present in almost 90% of cases and that it is generally asymmetric and elliptical in shape. The depth and length of the anterior part of the notch is greater in males. Moreover, the preangular notch depth is greater on the right side (regardless of sex). Knowledge of the preangular notch anatomy can be useful for surgeons during reconstructive and plastic procedures on the mandibular shaft

Typology of the antegonial notch in the human mandible

Background: Surgical treatment for serious malocclusions and fractures of the organ of mastication is a golden standard in medicine. Procedures performed on the mandible require detailed knowledge of the anatomy of the organ. Antegonial notching constitutes a serious technical challenge for surgeons. Therefore, a detailed anatomical description of this structure, which is the subject of this paper, is essential. Materials and methods: We analysed 251 human Caucasian mandibles of identified sex and took measurements of all sections describing the mandibular antegonial notch. Depending on the proportion between sections we classified the shape of the antegonial notch into three types. The surface area of the notch was calculated. We analysed the dimorphic and bilateral differences for each of the three types of notch. We used variance analysis for the assessment of statistical difference. Results: The analysis revealed that in both men and women, regardless of body side, the type 3 antegonial notch was the most frequent. Type 3 occurred with a frequency of between 38% in men on the right side and 55.9% in women on the left side of the body. Type 1 was the least frequent. Dimorphic differences in the presence of individual types of antegonial notch were statistically significant only for the left side of the body. The symmetrical type (type 2) occurred more frequently in men (by 11%) than in women. Type 3 was found more frequently in women (by 10%) than in men. Bilateral differences in men were revealed for the frequencies of types 1 and 3. On the right side type 1 was more frequent (by 8%), and on the left side type 3 was also more frequent (by 8%). The greatest surface area was found for the asymmetrical posterior type (type 1). The smallest surface area was found for the asymmetrical anterior type 3. This difference was statistically significant with respect to the surface area of types 1 and type 2 and found for both sexes for both sides of the body. However, no statistically significant differences were found between the surface areas of types 1 or 2. Conclusions: Knowledge of the preangular notch anatomy can be useful for surgeons during reconstructive and plastic procedures on the body of the mandible

Anomalous NMR behavior of meso compounds with remote stereogenic centers on addition of chiral shift reagent or chiral solvating agent

A problem has arisen in using chiral shift reagents (CSR) and chiral solvating agents (CSA) to determine meso and racemic forms of diastereoisomers in which the stereogenic centers of the molecules are separated by achiral spacers. It is found that NMR signals of both meso and racemic forms of diastereoisomers may exhibit doubling on addition of CSR/CSA, which means that unequivocal assignments cannot be made without characterizing the effects for separate meso and racemic forms; this is particularly important for additions of CSR/CSA at relatively low concentrations, which always result in the splitting of some NMR signals of diastereoisomers. The phenomenon is demonstrated in the 31P NMR spectra of meso and racemic forms of three spermine-bridged gem-disubstituted cyclotriphosphazatrienes, 1a-c, and compared with analogous achiral molecules, the per-substituted spermine-bridged cyclotriphosphazatrienes 2a-d. As expected, only one set of 31P NMR signals was observed for the achiral compounds 2a-d, even on addition of CSA. Two sets of 31P NMR ABX multiplets corresponding to meso and racemic diastereoisomers were observed for compounds 1a-c; on addition of CSA, the signals of at least one of the multiplets for each compound separated into more than the expected groups of three lines with an intensity distribution of 2:1:1. To understand this phenomenon, the meso and racemic forms of 1a and 1b and the meso form of 1c have been separated and characterized by X-ray crystallography. On addition of CSA to the racemic forms of 1a and 1b, the 31P NMR spectrum shows the expected doubling of signals, but, unexpectedly, the same is observed for each of the meso forms of 1a-c. Analogous results using both CSA and CSR have been obtained for the meso and racemic forms of the diastereoisomeric piperazine-bridged macrocyclic-phosphazene compound, 3, whereas no effect was observed for the two meso forms of the doubly bridged macrocyclic-phosphazene compound 4. The phenomenon of doubling of the 31P NMR signals of the meso form of singly bridged cyclotriphosphazatrienes, 1a-c and 3, is explained by consideration of the equilibrium in solution of independent complexation of a chiral ligand with molecules that have two chiral cyclophosphazene moieties separated by an achiral spacer group. The results show that the stereogenicity of such diastereoisomeric molecules in solution cannot be characterized unequivocally by NMR measurements on addition of either CSR or CSA