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ExperimentaL Oral Medicine
Published in Samuel Dreizen, Barnet M. Levy, Handbook of Experimental Stomatology, 2020
Samuel Dreizen, Barnet M. Levy
At doses of 1000 to 2000 R, the changes were localized to the labial part of the odontogenic zone consisting of transient edema and permanent injury to the zonal odontoblasts that caused dentinal hypoplasia and produced dentinal niches. After degeneration of the odontoblasts, osteodentin was formed in the adjacent area of the pulp. Slight inhibition of pulpal growth led to waviness of the dentinoenamel junction. Slight injury to the ameloblasts caused shallow enamel hypoplasia. At doses of 3000 to 4000 R, destructive changes were followed by regeneration. Destruction was manifested by severe pulpal and periodontal edema, which led to formation of cystic cavities that destroyed the odontoblasts and prevented formation of new ameloblasts. Great masses of osteodentin formed in the pulp. With stoppage of pulpal growth and eruption, there was progressive maturation of the entire enamel matrix and reversion of the enamel organ into reduced epithelium. Regeneration was dependent on the amount of enamel destruction caused by the expanding cyst cavities. Only if viable remnants of odontogenic epithelium persisted to the time of organization of the cysts did epithelial proliferation initiate formation of a new incisor.
Dental Caries: Resistance Factors — Enamel Chemistry and Saliva
Published in Lars Granath, William D. McHugh, Systematized Prevention of Oral Disease: Theory and Practice, 2019
Stephen H. Y. Wei, James J. Crall, James S. Wefel
In a more extensive lesion as shown in the lower half of Figure 4, the bitewing radiograph used clinically shows only a slight etch of the enamel. Using microradiography, it shows a lesion that is present in the entire depth of the enamel and extends almost to the dentine. In polarized light microscopy, an extensive involvement of the dentino-enamel junction is clearly visible.
Micromorphology, microstructure and micro-Raman spectroscopy of a case of amelogenesis imperfecta
Published in J. Belinha, R.M. Natal Jorge, J.C. Reis Campos, Mário A.P. Vaz, João Manuel, R.S. Tavares, Biodental Engineering V, 2019
Sebastiana Arroyo Bote, Alfonso Villa-Vigil, M.C. Manzanares Céspedes, Esteban Brau-Aguadé
Regarding the ultrastructure of the enamel prisms in occlusal surface of the molar samples, the control sample showed both a regular disposition of the enamel prisms and a regular level of calcification of the enamel layer (Fig. 3: C, black arrow). On the contrary, the enamel layer from the AI teeth showed both an irregular disposition, size and shape of the prisms and a heterogeneous level of calcification (Fig. 3: D, black arrow), evidenced in the different whiteness of the material at the BSSEM, despite of the presence of the same elements in the EDX analysis in both sample series. However, such alterations were not observed in the dentin-enamel junction of the dental organs studied.
Interaction of rod decussation and crack growth in enamel
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Siyong Liu, Yuanzhi Xu, Bingbing An, Dongsheng Zhang
Enamel is a biological composite with ingenious hierarchical structure. At the nanoscale, enamel is composed of stiff mineral crystals embedded in soft protein matrix (Zhou and Hsiung 2006; Bar-On and Wagner 2012). The nanoscale mineral crystals are further assembled into enamel rods at the microscale, where non-uniform arrangement of mineral crystals is observed (Xie et al. 2009; An et al. 2012). The rods are wrapped by thin organic layers and exhibit unique arrangement in enamel (He and Swain 2008; Chai 2014). In the outer enamel that is close to occlusal plane, the rods are organized in a parallel manner whereas rod decussation, which is associated with the crossing of rod bundles, emerges in the inner enamel near the dentin–enamel junction (Cox 2013; Weng et al. 2016). Such rod decussation leads to formation of the parazone and diazone (Bajaj and Arola 2009a; Thompson 2020).
A comparison of perceived diagnostic image quality in direct digital panoramic images between standard and advanced external GOP image processing
Published in Acta Odontologica Scandinavica, 2019
Björn Svenson, Magnus Båth, Reet Karlsson, Bo Persson
However, one can discuss the choice of structures and their observability with regard to the three structures that were positively affected by GOP technology. DEJ, FMS and CRA contain high-contrast details. FMS and CRA consist of a distinctly radiopaque structure, which can be easily identified, while DEJ is the dentino-enamel junction, which appears radiopaque on radiographs and is generally regarded as a high-contrast anatomical structure [19,34]. The perception of the dentino-enamel junction can be significantly affected by the density of the surrounding shadows, and the contrast between adjacent structures can change the perceived density [35]. It has been suggested that the contrast between enamel and dentin DEJ is lower than the contrast between the root canal and dentin RCS, which has been previously considered to be harder than the former. For this reason, DEJ was considered neither a low- nor a high-contrast object, as proposed by Baksi et al. [2]. The GOP technology handles many different parts, such as edge enhancement, contrast equalization, noise and so forth.
Three-dimensional finite element analysis of the composite and compomer onlays in primary molars
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
Zuhal Kirzioglu, Derya Ceyhan, Fatih Sengul, Ayse Ceren Altun
According to a previous study, the adhesive cement layer transmits the stress coming from the restoration to the dental tissues with minimum resistance (Dejak et al. 2003). In analyzing the stress distribution formed in the cement layer in our restored tooth models, we observed that the cement had a similar stress distribution and that the stress on the surfaces facing the restoration was more intense than that on the surfaces adjacent to the tooth for both restoration materials. The cement could have transmitted the stress coming from the restoration to the tooth by absorbing some of it, and thus the stress was more intense on the surface of the cement adjacent to the restoration. In evaluating the stress that was transmitted from the cement to the enamel and dentine tissues, we noted that the stress became intense at the dentinoenamel junction, especially in the enamel tissue. Other researchers have suggested that the main components determining the form of stress distribution on the cement are the physical properties of the enamel and dentine layers located under the cement, elasticity modulus, and the direction of the force application (Liu et al. 2011). When the von Mises values of the restorations and cement ranged between themselves, the lower second primary molar had the highest value for both compomer and composite restored tooth models. This finding may be due to the occlusal contacts of the lower second primary molar with both of the upper primary molars. Thus, the properties of the enamel and dentine layers located under the cement are important as the main component determining the form of stress distribution on the cement.