Mesiodistal inclination of the unerupted second premolar in the mandible of Japanese orthodontic patients with incisor agenesis

OBJECTIVE

To elucidate the mesiodistal inclination of the unerupted mandibular second premolar (MnP2) in cases of mandibular incisor (MnIc) agenesis and unilateral MnP2 agenesis.

MATERIALS AND METHODS

Twenty-two cases of unilateral MnP2 agenesis (MnP2 agenesis group) and a control group (control group A) of 22 cases without permanent tooth agenesis excluding third molars were selected. Thirty-six cases of MnIc agenesis (MnIc agenesis group) and another control group (control group B) of 36 subjects were also selected. Mesiodistal inclination of the unerupted MnP2 on the panoramic X-rays was measured according to the distal angle and premolar-molar angle using the methods of Shalish et al. and Baccetti et al., respectively. Differences in mean values of the angular measurements between agenesis groups and corresponding controls were investigated (unpaired t-test).

RESULTS

In the MnP2 agenesis group, the mean distal angle decreased 12.3° and the mean premolar-molar angle increased 13.3° for the MnP2 compared with control group A (both P < .001). In the MnIc agenesis group, no significant differences in the means of those angles for the MnP2 were found when compared with control group B.

CONCLUSION

In Japanese orthodontic patients, there is a relationship between unilateral MnP2 agenesis and the mesiodistal angulation of the unerupted MnP2. However, no significant relationship was observed between MnIc agenesis (which relationship is often seen in Asian populations) and the position of the unerupted MnP2. These results suggest that different genetic factors are involved in MnP2 agenesis and MnIc agenesis.

Deep submersion: severe phenotype of deciduous-molar infraocclusion with biological associations

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.

Orthodontic treatment of a bilateral cleft lip and palate patient with bilateral tooth transpositions and congenitally missing teeth

Treatment of patients with a cleft lip and palate can be challenging. A boy, 15 years 11 months old, with a bilateral cleft lip and palate and a convex profile, transposed teeth and congenitally missing teeth was treated by orthodontic treatment. 3 year posttreatment records showed excellent results with good occlusion, facial balance and harmony, and long-term stability.

Increased occurrence of dental anomalies associated with infraocclusion of deciduous molars

OBJECTIVE

To test the null hypothesis that there is no relationship between infraocclusion and the occurrence of other dental anomalies in subjects selected for clear-cut infraocclusion of one or more deciduous molars.

MATERIALS AND METHODS

The experimental sample consisted of 99 orthodontic patients (43 from Boston, Mass, United States; 56 from Jerusalem, Israel) with at least one deciduous molar in infraocclusion greater than 1 mm vertical discrepancy, measured from the mesial marginal ridge of the first permanent molar. Panoramic radiographs and dental casts were used to determine the presence of other dental anomalies, including agenesis of permanent teeth, microdontia of maxillary lateral incisors, palatally displaced canines (PDC), and distal angulation of the mandibular second premolars (MnP2-DA). Comparative prevalence reference values were utilized and statistical testing was performed using the chi-square test (P < .05) and odds ratio.

RESULTS

The studied dental anomalies showed two to seven times greater prevalence in the infraocclusion samples, compared with reported prevalence in reference samples. In most cases, the infraoccluded deciduous molar exfoliated eventually and the underlying premolar erupted spontaneously. In some severe phenotypes (10%), the infraoccluded deciduous molar was extracted and space was regained to allow uncomplicated eruption of the associated premolar.

CONCLUSION

Statistically significant associations were observed between the presence of infraocclusion and the occurrence of tooth agenesis, microdontia of maxillary lateral incisors, PDC, and MnP2-DA. These associations support a hypothesis favoring shared causal genetic factors. Clinically, infraocclusion may be considered an early marker for the development of later appearing dental anomalies, such as tooth agenesis and PDC.

Malposition of Unerupted Mandibular Second Premolar in Children with Palatally Displaced Canines

Objective: To test the hypotheses that (1) the distal angulation of unerupted mandibular premolar (MnP2) is significantly greater in children with palatally displaced canines (PDC) than in those in a control sample; and (2) delayed tooth formation is significantly more frequent in children with both malposed MnP2 and PDC than in children with PDC only.

Materials and Methods: We examined retrospectively panoramic radiographs from 43 patients with PDC who had no previous orthodontics. A control sample consisted of age- and sex-matched patients. The distal angle formed between the long axis of MnP2 and the tangent to the inferior border was measured. Dental age was evaluated using the Koch classification.

Results: A significant difference was observed between the mean inclination of the right side MnP2 in the PDC group (75.4 degrees) and that of the control group (85.8 degrees). This difference was highly statistically significant (P &lt; .0001). The same evaluation was carried out for the left side, with similar results. The average dental age was found to be delayed in patients who showed both abnormalities (malposed MnP2 and PDC) compared with patients who showed the PDC anomaly only.

Conclusion: Both hypotheses are retained. Statistically, PDC and MnP2 malposition are significantly associated suggesting a common genetic etiology, despite taking place on opposite jaws. While the presence of PDC or MnP2 anomaly has been associated with a delay in tooth formation, we find the presence of both anomalies to show a more profound delay. Our findings suggest a delay in tooth formation as a possible common genetic mechanism for these 2 malposition anomalies.