ExperimentaL Oral Medicine
Samuel Dreizen, Barnet M. Levy in Handbook of Experimental Stomatology, 2020
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.
The Science of Tooth Whitening
Linda Greenwall in Tooth Whitening Techniques, 2017
Gingival areas on cervical dentin do not whiten to the same effect. This is because at the gingival level there is reduced enamel thickness, and where there is gingival recession present the root appears more yellow. It is important to warn the patient that this area may not whiten to the full extent. There is debate as to whether extending the whitening tray over the gingival area to the extent of the gingival recession and onto the full extent of the exposed root will help to whiten this area fully. The root dentin will never whiten fully. The root dentin will lighten, but it will not be completely white. It is unrealistic to expect this, and this should be carefully explained to the patient. There are many different tray designs to address this issue, and although many manufacturers have trademarks and patents on the whitening tray design and where to finish the scalloped margin—whether to the edge of the tooth, beyond the tooth onto the gingivae, or 1 mm above the gingivae—the root has not shown a perfect white shade. Some studies have shown that the last 1 mm can be cut off the whitening tray to reduce sensitivity, and this has made no difference to the final whitening effect. Some gingival margins can become irritated from too much gel in this area. Whitening treatments were observed to reduce background luminescence of enamel, dentinoenamel junction (DEJ), and dentin in a study using confocal laser scanning microscopy (Götz et al. 2007).
Bacterial Infections of the Oral Cavity
K. Balamurugan, U. Prithika in Pocket Guide to Bacterial Infections, 2019
Diagnosis is made possible by drying the tooth surface and examination under good light source. Caries can also be diagnosed by radiographs like intraoral periapical or bitewing radiographs. They present as radiolucent lesion extending from the deepest part of the fissure in a triangular fashion with their base at the dentinoenamel junction. Smooth surface caries break down is also triangular, but their base is at the surface and apex toward the pulp at the dentinoenamel junction. Diagnosis of caries is important for planning the treatment.
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.
Related Knowledge Centers
- Dentin
- Tooth Enamel
- Tooth