The development of the mouse molar periodontium

The normal development of the tissues of attachment of mouse molar teeth was studied using standard histological techniques. Jaws were taken from mice on the day of birth and each subsequent day, up to and including thirty days after birth, and examined. At birth, the molar teeth were in the late shell stage of development and were enclosed in the dental sac. Subsequent growth of the crown was accompanied by minor changes in the dental sac and alveolar bone. The periodontal ligament began to develop when root formation began. Fibres were laid down in a superior-oblique orientation which was maintained throughout the prefunctional and functional phases of eruption although changes which gave rise to the cervical fibre groups took place in the latter part of the prefunctional phase. Changes in the alveolar bone and cementum were observed as the tooth became functional. It was concluded that the periodontal ligament was preadapted to function and changes in other tissues of attachment, occurring as the teeth attained functional occlusion, were designed to strengthen the attachment of the fibres to bone and tooth.     

The development of the vascular bed of the marginal periodontium

The vascular bed of the periodontum of rat molars develops from the vascular network of the alveolar mucosa, from the vascular network of the enamel organ and from vessels which, with the development of roots, form the bed of the periodontal membrane. Although these vascular areas form a unity in a developed periodontium, they retain their differences in arrangement. During the formation of the enamel, the bed of the enamel organ is arranged in rat molars and in the permanently growing rat incisor according to the same principles. In both types of teeth, the principles of this arrangement correspond with the metabolic needs of amelogenesis.     

Prognosis of luxated permanent teeth — the development of pulp necrosis

Abstract A population of 400 patients, comprising 637 luxated permanent teeth was studied prospectively with respect to the development of pulp necrosis after luxation injuries. The patients were treated for traumatic dental injuries over a period of 10 years. While initial treatment was provided according to established treatment guidelines by the attending oral surgeon at the emergency room, follow-up examination and treatment was provided by one oral surgeon. It appeared that pulp necrosis occurred soon after injury, within 3 months after concussion, within the 1st yr after subluxation and extrusion, and might be diagnosed up to 2 yr after lateral- and intrusive luxation. While many factors, when considered one at a time, were found to have a significant or nearly significant died on the development of pulp necrosis (i.e. type of injury, age of patient, stage of root development, degree of dislocation, reduction/repositioning procedure, type of fixation, restorations in place at the lime of injury), a multivariate regression analysis revealed that when the type of injury (diagnosis) and stage of root development were taken into account, the effect of other factors was no longer significant. The risk of pulp necrosis increased with the extent of injury, i.e. concussion and subluxation represented the least risk, followed in ascending order by extrusive-, lateral-, and intrusive luxation. Moreover, teeth with completed root formal ion demonstrated a greater risk of pulp necrosis than teeth with incomplete root formation. No treatment effect could be demonstrated. However, as treatment was performed according to established guidelines, which might introduce bias, it would appear justified to conduct randomized clinical studies in order to determine the value of different forms of treatment (e.g. reduction and fixation of luxated teeth) to improve the prognosis with respect to the development of pulp necrosis after injury. In conclusion, the major factors influencing development of pulp necrosis after luxation injuries appear to be the extent of the initial injury to the pulp and periodontium, as reflected by the type of luxation, and the repair potential of the injured tooth, as reflected by the stage of root development.     

The mucocele — floor of the mouth

Three cases are reported to illustrate certain features related to swellings of the salivary glands. With a mucocele of the floor of the mouth difficulites may arise in the correct identification of the gland of origin, in elucidating the aetiological factors, and in obtaining adequate radiographic or sialographic views of the area. Surgical treatment follows the surgical removal of the involved gland.     

Vitamin K — its essential role in craniofacial development

The normal vitamin K status of the human embryo appears to be close to deficiency. Maternal dietary deficiency or use of a number of therapeutic drugs during pregnancy, may result in frank vitamin K deficiency in the embryo. First trimester deficiency results in maxillonasal hypoplasia in the neonate with subsequent facial and orthodontic implications.
A rat model of the vitamin K deficiency embryopathy shows that the facial dysmorphology is preceded by uncontrolled calcification in the normally uncalcified nasal septal cartilage, and decreased longitudinal growth of the cartilage, resulting in maxillonasal hypoplasia. The developing septal cartilage is normally rich in the vitamin K-dependent protein matrix gla protein (MGP). It is proposed that functional MGP is necessary to maintain growing cartilage in a non-calcified state.
Developing teeth contain both MGP and a second vitamin K-dependent protein, bone gla protein (BGP). It has been postulated that these proteins have a functional role in tooth mineralization. As yet this function has not been established and abnormalities in tooth formation have not been observed under conditions where BGP and MGP should be formed in a non-functional form.     

The adverse effects of dental restorative materials — a review

Several materials used in dentistry are described as biomaterials. Owing to the intimate contact of these materials with the oral tissues, they should possess a high degree of biocompatibility. However, some materials may exhibit adverse effects, causing both local and general pathological changes, even though the occurrence seems to be relatively low. It is, therefore, the dentist's responsibility to be aware of the potential adverse effects of these materials and to take precautions to protect the patient form such effects. The purpose of this article is to review the potential adverse effects of some commonly used restorative materials, mainly with regard to patients.