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Eruption disturbances of teeth should not be considered as a curiosity. Acquaintance with these phenomena should form a substantial component of the dentist's, orthodontist's and oral and maxillofacial surgeon's basic expertise. Early detection of these disturbances followed by treatment in due time, can minimise progressive negative effects, such as the development of severe malocclusion. Treatment modalities are described.
This cross-sectional study investigated normal positional changes of the upper permanent canine and posterior teeth, hard palate, and sinus floor in normal Taiwanese children from the deciduous to early permanent dentition. In total, 261 panoramic radiographs were used. During the observation period, almost all structures changed their positions toward the distal and occlusal direction. The vertical positional changes of crowns of all teeth were greater than those of the root apices through all developmental stages. There were small positional changes in the mesial surfaces of the crowns of the upper buccal teeth until their roots had formed. There were continuous positional changes in the crowns and root apices of the permanent molars during tooth development and eruption. There were no significant changes in tooth inclination for any of the buccal teeth, whereas there were conspicuous changes in tooth inclination for the permanent molars. The floor of the maxillary sinus remarkably changed its position in an occlusal direction during the active eruption period of the first molar and buccal teeth.
Retention, that is, a permanent tooth which is unerupted more than a year after the normal age of eruption, is a relatively rare event, except in the case of the third molars and the upper canines. Transmigration is defined as the phenomenon of more than half an unerupted impacted tooth crossing the midline. We report the clinical case of a twenty-year-old patient presenting transmigration of the lower left canine, with a type 4 transmigration pattern (Mupparapu). Likewise, we carried out a review of the literature of the cases that have been published on transmigration, updating the main aspects of this pathology.
Impacted canines are not uncommon in clinical practice, but intraosseous movement of impacted canines crossing the midline (transmigration) is a rare phenomenon. We report 4 cases of mandibular canine transmigration to emphasize the need to supplement periapical radiographs with a panoramic radiographic examination in patients with over-retained deciduous canines or missing permanent canines.
A lot of attention has been paid to the questions of how and why teeth erupt. In the past many theories were developed, all of which showed mechanistic characteristics and suggested that a certain structure exerts force on the tooth germ to initiate its eruption. The dominant theory considered the collagenous fibres or the fibroblasts within the periodontal ligament to be the primary moving force in the eruption process. However, most research was done on continuously erupting incisors of rodents or lagomorphs, an experimental model with serious drawbacks. Because dogs, like humans, have teeth with limited eruption, 25 years ago research was carried out on tooth eruption in beagles. One of the most important conclusions of this study was that the periodontal ligament is not the primary moving force in tooth eruption, as its development only begins at the end of the eruption process. In subsequent years several others have focused their research on tooth eruption in beagles. The current state of knowledge in this field can be summarized as follows: the reduced enamel epithelium and the dental follicle control bone deposition and resorption around an erupting tooth germ, enabling its occlusal movement; the periodontal ligament develops only after its emergence in the oral cavity, and is thus not important in the eruption process; the tooth itself does not play a role in the regulation of its eruption.
Space maintainers are very important in the prevention of malocclusions. Their indications and limits are described.
Fifty-five asymptomatic mandibular third molars (M3) in 34 dental students (mean age 20.6 years at the start of the study) were followed radiographically for 4 years. Based on clinical evaluation the 55 teeth included 20 almost erupted, 13 partly erupted and 22 non-erupted M3. The following were assessed on the radiographs: root development, level of eruption, sagittal angulation, resorption, pericoronitis/bony pockets/paradental cysts and widening of the periodontal space/dentigerous cysts. The state of 21 teeth (38 per cent) was radiographically changed at the end of the observation period. The most remarkable finding was that 15 teeth changed their sagittal angulation, all in a distal direction; five mesioangular to vertical, five vertical to distoangular, five mesioangular to distoangular. Radiographically, 13 M3 moved to a more advanced level of eruption. No real pathological osseous lesions and no root resorption were observed at initial or follow-up examinations. It is concluded that there are frequent essentially unpredictable changes in the position of M3 after the age of 19 years which may influence decisions on their removal or preservation.
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30 mesially tipped lower molars in 18 patients have been uprighted previous to prosthetic treatment. The uprighting was performed using arch wires, box loops and uprighting springs. The plaque and gingival conditions as well as the pocket depths and levels of periodontal attachment were assessed at the start of the treatment, after a successfully completed hygienic phase and after the uprighting of the tipped molars. Following the successful completion of the hygienic phase a significant pocket reduction was seen on all surfaces of the teeth besides a highly significant reduction of plaque and gingival index scores. As a result of the orthodontic uprighting, a further significant reduction in pocket depth, associated with a gain of periodontal attachment, was found on the mesial and lingual aspects of the molars. The results indicate that the uprighting of lower tipped molars prior to prosthetic treatment is a simple and predictable procedure to positively influence the prognosis of the teeth involved.
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This article has focused on developmental changes in molar occlusion. Its purpose is to alert the reader to changes in these relationships, which can occur naturally from birth to the period of developed dentition. The practitioner should be cognizant of these changes and the importance of preserving and promoting good molar relationships, which are the foundation of occlusions.