Morphometric study of the mylohyoid bridging in dry mandibles.

ABSTRACT: The mylohyoid bridging is a hyperostotic variation representing formation of bony bridges over the mylohyoid groove. The goals of this study were to establish the frequency of mylohyoid bridging in contemporary and medieval series from Bulgaria and to examine the changes in the prevalence through time, to assess and compare the different types of mylohyoid bridging, to establish the patterns of distribution with respect to laterality, sex and age and to accomplish a morphometric analysis. Materials and methods: The study was performed on a total of 448 intact dry mandibles of adult individuals from both sexes, grouped into contemporary male, medieval male and medieval female series from Bulgaria. The individuals in the series were distributed into two age cohorts: between 20-40 years old and above 40 years. Мacroscopic, metric and statistical analyses were performed. Results and Conclusions: The frequency of the mylohyoid bridging was 10.99% (21 out of 191 mandibles) for the contemporary male series, 9.45% (12 out of 127) for the male series and 7.69% (10 out of 130) for the medieval female series. The comparison between both male series indicated slightly increasing of the mylohyoid bridging with time. No significant bilateral and sex differences in the frequency and pattern of distribution of the mylohyoid bridging were established. The most common type of bridging was the distal one. The dependence of the mylohyoid bridging on the aging is controversial since in the female series its frequency was significantly higher in the individuals over 40 years, while in both male series it did not differ considerably between the age groups. The metric analysis did not show significant differences between the male series. However, the sexual differences were noteworthy with respect to the whole length of the mylohyoid groove and the distance between the bridge and the distal point of the mylohyoid groove. Furthermore, the considerable differences between the metric characteristics of lingular and distal type showed that this approach is useful and could be applied for precise differentiation of the mylohyoid bridging types. During the investigation, we also observed several cases of an accessory groove in the region of the mylohyoid groove. This additional groove most probably reflects variations in the branching patterns of the inferior alveolar nerve and/or mylohyoid nerve and could be of importance in oral surgery and dental practice.

Multiple Wormian bones and their relation with definite pathological conditions in a case of an adult cranium.

Wormian bones, also known as intrasutural bones, are present as an anatomical variation in healthy individuals. However, a higher than the usual incidence can be an important feature of some congenital pathological conditions. In this study we describe a case of an adult cranium with multiple Wormian bones. The cranium was a single sample obtained from an archaeological excavation in Vinitsa, Northeastern Bulgaria, and probably dated in the Chalcolithic. The Chalcolithic is a period of human history connected with discovering and using of copper. Actually, it is a transitional phase between the Neolithic and the Bronze Age. In this case the Wormian bones are mostly large in size and arranged in a mosaic pattern in several cranial regions. The cranium also shows features such as dolichocrany, a moderate platybasia, a notch in the posterior margin of the foramen magnum, hypoplastic and asymmetrical frontal sinuses, underdeveloped mastoid air cells, hyperostosis cranii interna, moderate frontal bossing, a complete metopic suture, a delayed sutural closure, relatively small facial bones, an early loss of teeth, dental caries and hypoplastic enamel defects on two preserved molars. Differential diagnosis indicates that the combination of all these features shows a link with pathological conditions involving dysplasias with prominent membranous bone involvement and an increased bone density such as cleidocranial dysplasia and pyknodysostosis.

Absence of foramen spinosum and abnormal middle meningeal artery in cranial series.

In comparative and evolutionary aspects in humans, the middle meningeal artery enters the cranium through the foramen spinosum, whereas in great apes the middle meningeal artery can enter the cranium through foramen spinosum, through foramen ovale or through petrosphenoid fissure. Generally, in nonhuman primates the anterior meningeal system is associated with the ophthalmic branch of the internal carotid artery. The vessels joining the two systems pass through the additional channels: the superior orbital fissure or through the cranio-orbital foramen. In anatomically modern humans, the absence of foramen spinosum involves abnormal development and course of the middle meningeal artery and it is usually accompanied with replacement of the conventional middle meningeal artery with such, arising from the ophthalmic artery system. In these cases the middle meningeal artery most often enters the middle cranial fossa through the superior orbital fissure and rarely through the meningo-orbital foramen. All skulls, investigated in the present study, belonged to adult individuals of both sexes, conditionally grouped into three cranial series--contemporary male, medieval male, and medieval female series. The absence of foramen spinosum was established only among the medieval male and female series--in 1 (0.70%) male and in 1 (0.72%) female skull on the right side and in 3 (2.13%) female skulls on the left side. In 1 (0.72%) female skull, a small atypically located foramen spinosum was established on the right side. In all of the described cases, the intracranial meningeal grooves started from the lateral edge of the superior orbital fissure and probably reflect the ophthalmic origin of the middle meningeal artery.