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Objectives: To assess the null hypothesis that there is no difference in the rate of dental development and the occurrence of selected developmental anomalies related to shape, number, structure, and position of teeth between subjects with impacted mandibular canines and those with normally erupted canines., Materials and Methods: Pretreatment records of 42 subjects diagnosed with mandibular canines impaction (impaction group: IG) were compared with those of 84 subjects serving as a control reference sample (control group: CG). Independent t-tests were used to compare mean dental ages between the groups. Intergroup differences in distribution of subjects based on the rate of dental development and occurrence of selected dental anomalies were assessed using χ(2) tests. Odds of late, normal, and early developers and various categories of developmental anomalies between the IG and the CG were evaluated in terms of odds ratios., Results: Mean dental age for the IG was lower than that for the CG in general. Specifically, this was true for girls (P < .05). Differences in the distribution of the subjects based on the rate of dental development and occurrence of positional anomalies also reached statistical significance (P < .05). The IG showed a higher frequency of late developers and positional anomalies compared with controls (odds ratios 3.00 and 2.82, respectively; P < .05)., Conclusions: The null hypothesis was rejected. We identified close association of female subjects in the IG with retarded dental development compared with the female orthodontic patients. Increased frequency of positional developmental anomalies was also remarkable in the IG.

Objective: To evaluate the clinical manifestation of and treatment modalities for this severe phenotype of infraocclusion and to examine relationships between deep submersion and the occurrence of other dental anomalies., Materials and Methods: The experimental sample consisted of 25 orthodontic patients with at least one deciduous molar in infraocclusion greater than 5 mm. Dental records were used to assess severity of infraocclusion, treatment modality, and presence of other dental anomalies (tooth agenesis, small maxillary lateral incisors, palatally displaced canines, and distal angulation of mandibular second premolars)., Results: The sample included 14 females and 11 males, age 7 to 14 years (mean age 10.1 years). The mean infraocclusion depth was 9 mm, with a range of 5-18 mm. The crowns of the adjacent teeth were severely tilted toward the infraoccluded tooth, space was lost in the dental arch, and the successor premolars were impacted in all cases. Treatment consisted of space regaining, surgical extraction of the deciduous molar, and space maintenance. The impacted premolar erupted spontaneously in 95% of the cases. There was a significant increase in prevalence of dental anomalies in the deep-submersion sample compared with that of reference values (P < .001)., Conclusions: The treatment modality used in this sample resulted in spontaneous eruption of the impacted premolar in most cases. Markers for early diagnosis of deep submersion include other dental anomalies, severe tilt of adjacent teeth, and local space loss. The increased prevalence of other dental anomalies supports a shared genetic etiology.

Objective: To compare the root development and the growth rate of the mandibular third molar (M3 inf) in individuals where the M3 inf erupted vs individuals exhibiting M3 inf impaction., Materials and Methods: Serial standardized intraoral radiographs (Eggen technique) were taken annually of the mandibular third molar region from 132 subjects (71 male and 61 female) from 15 to 20 years of age. Based on the films, 264 lower third molars were classified into an eruption and an impaction group. Root development was recorded according to a quantitative method described by Haavikko (1970), and the eruption status was analyzed using logistic regression., Results: In total, 155 (59%) of the M3 inf erupted, and 109 (41%) were impacted at age 20. In 44 (33%) patients both M3 inf were impacted, in 21 (16%) patients one tooth was erupted and the contralateral tooth impacted, and in 67 (51%) patients both M3 inf were erupted. The more mature a tooth was at age 15, the higher was the probability of eruption (odds ratio: 3.89, P < .001). The growth rate of the root development stage was statistically significantly associated with the probability of eruption (odds ratio: 10.50, P  =  .041)., Conclusions: Delayed mandibular third molar root development is associated with impaction. Radiographs taken at age 15 may predict the risk of impaction and thereby guide decision making for the orthodontist or the oral and maxillofacial surgeon.

Intrabony migration of impacted teeth is a rare dental anomaly, which occurs only in the permanent dentition of the lower jaw. The teeth involved in this phenomenon are the mandibular lateral incisor, canine, and second premolar. Migration of the lateral incisor is usually in a distal direction, resulting in transposition with the canine. Migration of the canine is most frequently in a mesial direction, resulting in transmigration across the mandibular symphysis to the opposite side of the dental arch. The second premolar most often migrates distally, sometimes past the gonial angle and as far as the coronoid process. Surgical and orthodontic treatment options are presented for the three intrabony migrating teeth.

Upper cuspid impaction is a serious problem that occurs with sufficient frequency to justify diagnosis and intervention as early as a dental age of 8 years. Screening consists of identifying patients who lack a normal cuspid bulge on palpation, with follow-up radiographic evaluation where indicated. Selective removal of deciduous cuspids is a suggested interceptive measure in Class I uncrowded malocclusions.

The present study supports previous findings that root resorption takes place simultaneously with and after the elimination of hyalinized tissue. The cementoid layer and the more mature periodontal collagen fibers adjacent to cementum are possible barriers preventing root resorption. The microenvironment around hyalinized tissue is favorable for the introduction of hard-tissue resorbing cells. The findings show that the elimination of hyalinized tissue leads to the removal of the cementoid and the mature collagen thus leaving a raw cemental surface without a barrier. It is therefore hypothesized that such an area is readily attacked by odontoclasts. Once resorption lacunae are established, the cementum is resorbed from the rear as an undermining process. By continued orthodontic force application the resorption process will proceed even after all hyalinized tissue is eliminated. If the orthodontic force is discontinued or falls under a certain level, the resorption lacunae are repaired.