AGING LIVE ANTARCTIC FUR SEALS AND SOUTHERN ELEPHANT SEALS

This study describes a method for extracting post-canine or incisor teeth from live antarctic fur seals ( Arctocephalus gazella ) and southern elephant seals ( Mirounga leonina ) respectively and their use to determine age in a field situation. Dental elevators were used to loosen the teeth from the alveolus and periodental ligament. Most teeth were removed within l-2 min and a total of 214 and 81 teeth were collected by this method from antarctic fur seals and southern elephant seals respectively. No seal recaptured at intervals up to a year after a tooth was extracted showed signs of infection or distress related to removal of the tooth. Teeth were thin-sectioned for the purpose of aging. In both species cementum growth layer groups were a more satisfactory indicator of age than dentinal growth layer groups. Estimates of age from cementum growth layers were confirmed for Antarctic fur seals using seals which had been tagged as pups up to 16 yr before sampling.     

Effect of round curvature of anterior implant-supported zirconia frameworks: finite element analysis and in vitro study using digital image correlation

Two groups of 4-unit zirconia frameworks were produced by CAD/CAM to simulate the restoration of an anterior edentulous gap supported by 2 implant-abutment assemblies. Group 1 comprised straight configuration frameworks and group 2 consisted of arched frameworks. Specimens were made with the same connector cross-section area and were cemented and submitted to static loads. Displacements were captured with two high-speed photographic cameras and analysed with video correlation system. Frameworks and the implant-abutment assembly were scanned and converted to 3DCAD objects by reverse engineering process. A specimen of each group was veneered and the corresponding 3D geometry was similarly obtained after scanning. Numerical models were created from the CAD objects and the FE analysis was performed on the zirconia frameworks and on the FPDs bi-layered with porcelain (veneered frameworks). Displacements were higher for the curved frameworks group, under any load. The predicted displacements correlated well with the experimental values of the two framework groups, but on the straight framework the experimental vertical displacements were superior to those predicted by the FEA. The results showed that the round curvature of zirconia anterior implant-supported FPDs plays a significant role on the deformation/stress of FPDs that cannot be neglected neither in testing nor in simulation and should be considered in the clinical setting.     

Hominid molars from a Middle Stone Age level at the Mumba Rock Shelter, Tanzania

Three hominid molars were recovered from a depth of 7.0-7.1 meters in the Mumba Shelter at Lake Eyasi, northern Tanzania. Geological context of the finds and archaeological data indicate that people with a Middle Stone Age technology were using the Mumba locality intermittently whenever retreat of lake waters allowed access to the site. Uranium series dates suggest an age on the order of 130,000 years bp for the teeth and stone tools. Based on morphological analyses, the dental remains probably belonged to one individual and appear to be the crowns of two upper permanent M2s and one lower permanent M2. Crown areas are very small, even in comparison to the variation exhibited by recent African populations. Crown patterns have no archaic features. These teeth are smaller than any verifiable archaic Homo sapiens examples; thus, they may represent early anatomically modern Homo sapiens.     

Wound healing--a study on circaseptan reactive periodicity

The course of swelling after maxillo-facial surgery was investigated by measuring the distance from the tragus to the pogonium. The post-surgical swelling does not diminish continuously, but decreases in a circaseptan periodic mode. The reactive periodicity is preferentially induced not by the injury, but by the surgical treatment. Identical surgical treatment induces a lower level of swelling under local anaesthesia. In contrast to 'biologicaľ remedies, 'chemicaľ antiphlogistic agents, derived from antirheumatic drugs, reduce the extension of swelling, but they also flatten out the increase of swelling around day 7 after surgery.     

Modeling the effects of cingula structure on strain patterns and potential fracture in tooth enamel

The mammalian cingulum is a shelf of enamel, which rings the base of the molar crown (fully or partially). Certain nonmammalian cynodonts show precursors of this structure, indicating that it may be an important dental character in the origins of mammals. However, there is little consensus as to what drove the initial evolution of the cingulum. Recent work on physical modeling of fracture mechanics has shown that structures which approximate mammalian dentition (hard enamel shell surrounding a softer/tougher dentine interior) undergo specific fracture patterns dependent on the material properties of the food items. Soft materials result in fractures occurring at the base of the stiff shell away from the contact point due to heightened tensile strains. These tensile strains occur around the margin in the region where cingula develop. In this article, we test whether the presence of a cingulum structure will reduce the tensile strains seen in enamel using basic finite element models of bilayered cones. Finite element models of generic cone shaped “teeth” were created both with and without cingula of various shapes and sizes. Various forces were applied to the models to examine the relative magnitudes and directions of average maximum principal strain in the enamel. The addition of a cingulum greatly reduces tensile strains in the enamel caused by “soft‐food” forces. The relative shape and size of the cingulum has a strong effect on strain magnitudes as well. Scaling issues between shapes are explored and show that the effectiveness of a given cingulum to reducing tensile strains is dependent on how the cingulum is created. Partial cingula, which only surround a portion of the tooth, are shown to be especially effective at reducing strain caused by asymmetrical loads, and shed new light on the potential early function and evolution of mammalian dentitions. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.     

Correlation between the size,shape and position of the teeth on the jaws and the bite force in Theropoda

Theropods have fascinated both paleontologists and the general public due to their large diversity of sizes and morphologies. They also present a large variation in tooth morphologies. Previous studies have estimated the bite force of several specimens. The goal of this study is to determine if there is a correlation between the tooth size, shape and position on the skull and mandible and the bite force of these dinosaurs. Measurements were made on several theropods, including the bending strength of the teeth on the anterior-posterior and the mediolateral axes of the jaws, as well as the bending strength of the mandible, and were compared to fossil and modern Crocodylia. We observed that several bending strength maxima of the teeth trends were aligned with key areas of the mandible, and that the size, shape as well as the position of the teeth on the jaws were correlated with the bite force of both Crocodylia and theropods, which can be related to their diet and feeding habits.     

Evaluation of corneal structures in myopic eyes more than twenty‐two years after photorefractive keratectomy

The aim of this study is to evaluate corneal epithelial thickness (CET), corneal densitometry (CD) in 84 myopic eyes (57 patients) more than 22 years after photorefractive keratectomy, using anterior segment‐optical coherence tomography (AS‐OCT) and Scheimpflug imaging system. The CET was significantly higher in all operated eyes than in unoperated eyes in central sector. A statistically significant increase in CD in corneal anterior layer of central sector was shown in groups of operated eyes with greater ablation depth respect to unoperated eyes. While there was no significant difference in CD between the operated eyes groups with lower ablation depth and unoperated eyes. A significant trend toward higher values in anterior CD with deeper ablations in central sector was found. These noninvasive imaging techniques allow to better understand the corneal remodeling process after photoablation and to monitor the patients over time.     

Morphological aspects of the third instar larva of Haematobia irritans

The main morphological features of the cephalic region of the larva of Haematobia irritans (L.) are the oral grooves, tripartite labium and the antennomaxillary protuberances that have the dorsal, terminal and ventral sensory organs. The total number of sensilla that are found on the terminal organ differs from other cyclorrhaphous-fly larvae. The fan-shaped anterior spiracles usually consist of seven bulbous digits that are unequal in length. The creeping welts consist of notched, convex plates that split into two separate plates as they approach the midline of the venter. This characteristic has not been described previously for this species or other, higher, dipterous larvae. There are two posterior spiracles with an ecdysial scar, four fan-shaped and branching spiracular hairs and irregularly-shaped spiracular openings. The longitudinal anal opening is situated in the cuticular band that is known as the anal organ.     

Spatial distribution of lead in the roots of human primary teeth

Lead remains one of the most hazardous metals in our environment. The concentrations of lead in coronal dentine and enamel have previously been reported but limited information is available regarding lead levels in radicular dentine and cementum. This study reports the distribution of lead in 26 roots of 16 human maxillary primary teeth from seven individuals. In addition, calcium and phosphorous concentrations were also measured to detect any variations in the degree of mineralization in different regions of the roots. The mean lead concentration in these roots was 1.67 +/- 1.43 microg/g, which is comparable to other studies. In all cases there were higher lead concentrations in the apices of non-resorbed roots of primary maxillary teeth relative to middle and cervical regions. The findings reported here are of potential significance during the process of physiological root resorption whence periapical tissue may be exposed to higher levels of lead.