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Etiology and indications for the management of impacted teeth.

Impacted teeth are a medical deformity brought about by the dietary changes of modern civilization. Ample studies exist to show that the lack of a coarse, abrasive diet--an attritive diet--is the major cause of this problem in modern civilization. Our recent ancestors did not experience this problem or the problem of the underdeveloped lower jaw and resulting Class II malocclusion to the extent present in modern society. Medical and dental scientists, practitioners, and surgeons are aware of the devastation that impacted teeth can cause to the jaws and overall health of an individual and have issued numerous warnings to the profession and to the public regarding the several clear indications for the removal of impacted teeth. The issue has been clouded by the competing economic incentives present in our society, in which fee-for-service practitioners have been and are being replaced by practitioners with a disincentive to recommend surgical care for all but acutely infected or seriously symptomatic patients presenting with impacted teeth. Oral and maxillofacial surgeons practicing in the United States at this time are aware of the many clear indications for removal of impacted teeth and make every effort to communicate this information to their patients and other dental and medical practitioners. They are also aware of the contraindications to the removal of impacted teeth and advised patients appropriately when it is safe to retain and periodically observe by radiograph certain impacted teeth.

Humans↗

Histological observations of teeth and peridental tissues in cleidocranial dysplasia imply increased activity of odontogenic epithelium and abnormal bone remodeling.

Cleidocranial dysplasia (CCD) is a heritable generalized bone dysplasia presenting with a variety of dental abnormalities. To delineate morphological features of the dental tissues, we have analyzed histologically the structure of teeth and peridental tissues obtained from four CCD patients. Dentin appeared regular, except when formed in response to caries, physiological attrition or root resorption. Both acellular and cellular cementum were present in deciduous teeth, whereas in permanent teeth, cellular cementum was virtually lacking and acellular cementum was partially hyperplastic. Enamel pearls were seen in the furcations of one deciduous and one permanent molar. The roots of most deciduous teeth were resorbed only to a slight extent. Morphologically, supernumerary teeth resembled their normal counterparts. Denticles as well as epithelial cell clusters were occasionally present in the root pulps of deciduous teeth. In the peridental tissues, epithelium was locally abundant, and the cytokeratin profile confirmed its odontogenic origin. While the organization pattern of the alveolar bone matrix related to unshed deciduous teeth and unerupted permanent teeth varied, woven bone was abundant. Both formative and resorption surfaces were seen. Also, reversal lines were prominent, suggesting that the bone had, in fact, undergone remodeling. While no direct association between the aberrant bone morphology and the multifarious histological abnormalities of dental tissues can be established, the local abundance of odontogenic epithelium in peridental tissues of developing/unerupted as well as fully developed teeth may be causally related to the formation of excess acellular cementum, enamel pearls and supernumerary teeth.

Adolescent↗

[An in vitro model for the simulation of approximal wear].

Several methods have been developed to evaluate attritional wear of restorative materials. A distinction was made between attritional wear in occlusal contact areas (OCA) and wear in contact-free occlusal areas (CFOA). Only limited data dealing with approximal wear in vitro are available. Using a new configuration of the computer-controlled masticator, approximal wear of two composites (P-50, 3M and Tetric Ceram, Ivoclar-Vivadent) was assessed in a two-body wear test after thermo-mechanical loading. Wear was quantified using a profilometer. In addition, micromorphology was assessed by SEM. Wear showed a non-linear pattern, which was comparable to occlusal abrasion. After the first loading cycle, wear increased significantly (p < or = 0.05), and subsequently decreased. After a 5-year-equivalent, the mean substance loss for composite specimens was 20.3 +/- 15.6 microns for P-50 und 17.5 +/- 3.1 microns for Tetric Ceram. Approximal wear between enamel surfaces was 3.9 +/- 4.3 microns. In another experiment, the influence of the approximal wear on an enamel bonding agent was assessed. After thermo-mechanical loading, specimens were immersed in a demineralisation gel. The protective potential of the sealant was assessed under a polarized light microscope. The results suggested that partial sealant loss could lead to caries-like demineralisation in the affected areas.

Bisphenol A-Glycidyl Methacrylate↗

The mineral composition and enamel ultrastructure of hypocalcified amelogenesis imperfecta.

Hypocalcified amelogenesis imperfecta is characterized clinically by a yellow-brown colored enamel that is prone to severe attrition, often leading to rapid destruction of the crown. While the enamel is thought to be poorly mineralized few studies have evaluated the mineral content, or the histological or microradiographic features of this specific AI type. The purpose of this investigation was to examine teeth affected with autosomal dominant hypocalcified AI histologically using light microscopy (LM), scanning electron microscopy (SEM), and to evaluate the degree of enamel mineralization chemically and with microradiography. Four AI teeth were obtained from an affected individual for comparison with age-matched teeth from normal healthy individuals. Thin sections approximately 100 microns were cut with a diamond disc for examination by LM and microradiography. Using SEM, fractured enamel samples were examined either untreated or after removal of organic material using NaOCl or urea. Normal and AI enamel particles were dissected from thin sections to evaluate the mineral per volume and carbonate content. The enamel was not uniformly affected in all areas of the teeth with the lingual surfaces of the mandibular central incisors appearing clinically and histologically normal. The affected enamel was porous and appeared opaque with LM. Both SEM and LM showed the enamel to be prismatic with relatively normal prism morphology. However, the enamel crystallites were rough and granular compared with those of normal enamel. Extraction to remove organic material did not change the appearance of the crystallites indicating their granular appearance was due to mineral and not residual organic material such as enamel protein. Microradiography showed the enamel was less radiodense and therefore poorly mineralized compared with normal enamel. This was confirmed by chemical determination of the mineral per volume, which showed some areas of the AI enamel had as much as 30% less mineral compared with normal enamel. The carbonate content was found to be similar in AI and normal enamel. Hypocalcified AI is associated with decreased mineralization as well as ultrastructural defects in the crystallite structure. The combined histological and biochemical features of hypocalcified AI seen in this investigation indicate that this AI type is distinctly different from the hypoplastic and hypomaturation AI types.

Amelogenesis Imperfecta↗