Characterizing the microstructures of mammalian enamel by synchrotron phase contrast microCT.

The enamel of mammalian teeth is a highly mineralized tissue that must endure a lifetime of cyclic contact and is inspiring the development of next-generation engineering materials. Attempts to implement enamel-inspired structures in synthetic materials have had limited success, largely due to the absence of a detailed understanding of its microstructure. The present work used synchrotron phase-contrast microCT imaging to evaluate the three-dimensional microstructure of enamel from four mammals including Lion, Gray Wolf, Snow Leopard, and Black Bear. Quantitative results of image analysis revealed that the decussation pattern of enamel consists of discrete diazone (D) and parazone (P) bands of rods organized with stacking arrangement of D+/P/D-/P in all mammals evaluated; the D+ and D- refer to distinct diazone bands with juxtaposed rod orientations from the reference plane. Furthermore, the rod orientations in the bands can be described in terms of two principal angles, defined here as the pitch and yaw. While the pitch angle increases from the outer enamel to a maximum (up to ≈ 40°) near the dentin enamel junction, minimal spatial variations are observed in yaw across the enamel thickness. There are clear differences in the decussation parameters of enamel across species that are interpreted here with respect to the structural demands placed on their teeth. The rod pitch and band width of enamel are identified as important design parameters and appear to be correlated with the bite force quotient of the four mammals evaluated. STATEMENT OF SIGNIFICANCE: The multi-functionality of tooth enamel requires both hardness and resistance to fracture, properties that are generally mutually exclusive. Ubiquitous to all mammalian teeth, the enamel is expected to have undergone adaptations in microstructure to accommodate the differences in diet, body size and bite force across animals. For the first time, we compare the complex three-dimensional microstructure of enamel from teeth of multiple mammalian species using synchrotron micro-computed tomography. The findings provide new understanding of the "design" of mammalian enamel microstructures, as well as how specific parameters associated with the decussation of rods appear to be engineered to modulate its fracture resistance.

High throughput automated characterization of enamel microstructure using synchrotron tomography and optical flow imaging.

The remarkable damage-tolerance of enamel has been attributed to its hierarchical microstructure and the organized bands of decussated rods. A thorough characterization of the microscale rod evolution within the enamel is needed to elucidate this complex structure. While prior efforts in this area have made use of single particle tracking to track a single rod evolution to various degrees of success, such a process can be both computationally and labor intensive, limited to the evolution path of a single rod, and is therefore prone to error from potentially tracking outliers. Particle image velocimetry (PIV) is a well-established algorithm to derive field information from image sequences for processes that are time-dependent, such as fluid flows and structural deformation. In this work, we demonstrate the use of PIV in extracting the full-field microstructural distribution of rods within the enamel. Enamel samples from a wild African lion were analyzed using high-energy synchrotron X-ray micro-tomography. Results from the PIV analysis provide sufficient full-field information to reconstruct the growth of individual rods that can potentially enable rapid analysis of complex microstructures from high resolution synchrotron datasets. Such information can serve as a template for designing damage-tolerant bioinspired structures for advanced manufacturing. STATEMENT OF SIGNIFICANCE: Thorough characterization and analysis of biological microstructures (viz. dental enamel) allows us to understand the basis of their excellent mechanical properties. Prior efforts have successfully replicated these microstructures via single particle tracking, but the process is computationally and labor intensive. In this work, optical flow imaging algorithms were used to extract full-field microstructural distribution of enamel rods from synchrotron X-ray computed tomography datasets, and a field method was used to reconstruct the growth of individual rods. Such high throughput information allows for the rapid production/prototyping and advanced manufacturing of damage-tolerant bioinspired structures for specific engineering applications. Furthermore, the algorithms used herein are freely available and open source to broaden the availability of the proposed workflow to the general scientific community.

Psychological aspects and treatment of patients with nasal septal perforation due to cocaine inhalation.

Use of cocaine, by inhalation, is currently increasing in Western Countries and its use is superseding heroin in the rising generation. Young people of the third millennium use narcotics to avoid the negative conditions of daily life and to escape on "unreal" trips, as happened in the '60s and '70s for the heroin-addicted. Today, on the contrary, people addicted to cocaine want to be more competitive and "winners" and believe that cocaine can help them to reach this goal. A series of 104 patients (75 male, 29 female), aged between 16 and 54 yrs, all habitual inhaling cocaine users (> or = 10 times per month) have been observed for 2 years. Among them, 11 (10.5%) had nasal septal perforation, which is frequently related to cocaine use. Of these 11 patients, 8 (72.7%) had nasal septal perforation of the quadrangular cartilage, while in the other 3 (27.3%) the perforation involved also the bony tract (vomer-perpendicular ethmoidal lamina). Psychological analysis of these 104 patients is reported: 62 patients (59.6%) answered that they inhaled cocaine to improve endurance and to feel stronger and less tired; 34 patients (32.7%) in order to enjoy themselves more during parties and to communicate more effectively with other people; 5 patients (4.8%) to gain confidence and to overcome their shyness, 2 patients (1.9%) to improve their sexual performance and 1 patient (1%) to drink more alcoholic drinks for a longer time without feeling sleepy. All the patients underwent psychotherapeutic treatment, but the lack of compliance and constantly missing the scheduled follow-up visits resulted in complete therapy being performed in only 16 patients (15.3%). All the patients with nasal septal perforation underwent rhino-endoscopy, at T0, with 0 degrees, 45 degrees endoscopes, computed tomography scan of nose and paranasal sinuses and biopsy. At the time of the observational period, none of the 11 patients who presented nasal septal perforation agreed to stop cocaine abuse; therefore, a temporary solution has been offered to all the patients (accepted by 3 of them), i.e., the positioning of a silicone button to close the perforation and, thus, improve the air flow in the nose and reduce progression of local necrosis. Together with the button, the positioning is described, under local anaesthesia, of two layers per septal side of hyaluronic acid, at different levels of esterification, kept in site by the button as a "sandwich" in order to obtain better re-growth of the mucosa and fewer scabs and bleeding.

Maxillary ameloblastoma.

Maxillary ameloblastoma is a rare odontogenic neoplasm that is histologically benign and originates from epithelial cells present in bone tissue. If excised through conservative surgery, this tumour has a high relapse rate and is locally aggressive. The risk, in particularly extensive forms, that the ameloblastoma will invade extra-maxillary structures such as the orbit, the pterygomaxillary fossa, the infratemporal fossa and the base of the skull, means that surgical treatment is difficult if it is to be oncologically radical while respecting function and aesthetics. Thus, in these cases a complete and in-depth diagnostic work-up and careful planning of surgical treatment are needed: surgery entails an ablative phase with en-bloc resection of the neoformation to margins free of neoplastic infiltration, and a reconstruction phase that, within a short time-frame, will re-establish functionality and provide a good aesthetic result. Our experience in treating 2 cases of maxillary ameloblastoma is reported.