Estimation of tooth agenesis risks between tooth types in orthodontic patients with non-syndromic oligodontia

Mesiodistal angulation and developmental stages of unerupted mandibular second premolars in nonsyndromic oligodontia

INTRODUCTION

Oligodontia is a serious developmental dental anomaly that requires long-term multidisciplinary treatment, but its clinical characteristics are not well understood because it is rare. This study evaluated the mesiodistal angulation and developmental stages of unerupted mandibular second premolars (MnP2s) in orthodontic patients with nonsyndromic oligodontia.

METHODS

Thirty-seven patients with oligodontia with at least 1 unerupted MnP2 in Demirjian's developmental stages between D and G were selected. Age- and sex-matched patients without tooth agenesis, excluding third molars, were selected as the control group. Mesiodistal angulation between the long axis of the available MnP2 and the mandibular plane was measured on panoramic radiographs.

RESULTS

The MnP2 was significantly more distally angulated in the oligodontia group than in the control group. The developmental stage of the MnP2 in the oligodontia group was significantly delayed (1.04 ± 0.26 years; 95% confidence interval, 0.53-1.55 years). No correlation between the mesiodistal angulation and the developmental stage of the MnP2 was found in both groups.

CONCLUSIONS

Significant distal angulation and delayed developmental stages of MnP2s were found in patients with nonsyndromic oligodontia compared with age- and sex-matched patients without agenesis of permanent teeth, excluding third molars. However, no significant correlation was found between them. Regardless of the severity of the distal angulation of MnP2, observing delayed dental development in each patient is important.

Association between Hypodontia and Angle’s Malocclusions among Orthodontic Patients in Kathmandu, Nepal

Background. Disturbances during the early tooth development stages may result in the congenital absence of teeth. The purpose of this study was to assess the relationship between hypodontia and Angle’s malocclusions. Materials and Methods. The sample comprised 601 orthodontic patients’ pretreatment records (242 men and 259 women), selected from the achieved orthodontic records. Developmental anomalies of teeth affecting the number were examined on dental panoramic radiographs. Based on Angle’s classification, pretreatment dental casts were assessed and classified into different classes of malocclusion. The relationship between hypodontia and different classes of malocclusion was evaluated using the chi-square test. Results. The prevalence of tooth agenesis was 7.48%, that is, 45 out of 601 samples. There were a total of 72 (0.42%) missing teeth, excluding the third molars. The most frequent missing tooth was the maxillary lateral incisor (35, 48.61%), followed by the mandibular lateral incisor (14, 19.44%), the mandibular central incisor (6, 8.33%), the mandibular second premolar (5, 6.294%), and the maxillary second premolar (4, 5.55%). Hypodontia was more common in the upper jaw. Although hypodontia was mostly seen in Class I malocclusion patients (7.87%), followed by Class II malocclusion patients (6.99%) and least in Class III malocclusion patients. However, there was no significant difference in hypodontia among different classes of malocclusions (p = 0.352). Conclusion. The most frequently missing tooth was the maxillary lateral incisor, followed by lateral and central mandibular incisors and mandibular second premolars, while excluding the third molars. The present study did not find any association between various types of malocclusions and hypodontia.

Consecutive tooth agenesis patterns in non-syndromic oligodontia

Agenesis of two or more consecutive adjacent permanent teeth (consecutive tooth agenesis, CTA) is a serious manifestation of oligodontia requiring long-term, multi-disciplinary treatment. Therefore, the present study investigated the characteristics of the CTA pattern in orthodontic patients with non-syndromic oligodontia. Using panoramic radiographs, the number of agenetic permanent teeth excluding third molars in non-syndromic orthodontic patients was evaluated, and patients with six or more agenetic teeth (oligodontia group, n = 97) and with one to five agenetic teeth (hypodontia group, n = 107) were selected. The numbers of CTA including third molars in each quadrant and in each patient were compared between the groups. Each quadrant with CTA of patients was categorized into one of the following four types: (I) involves anterior teeth only; (II) involves posterior teeth only; (IIIA) includes anterior and posterior teeth; and (IIIB) separate in the anterior and posterior teeth. CTA in at least one quadrant was found in 91.8 and 4.7% of patients in the oligodontia and hypodontia groups, respectively. The highest frequency CTA patterns included agenesis of the first and second premolars and of the second and third molars in the oligodontia and hypodontia groups, respectively. In the oligodontia group, type IIIA was significantly more frequent in the maxillary than in the mandibular quadrant. Most oligodontia patients who visit orthodontic clinics have CTA. A rare but severe CTA pattern that continues from the anterior to posterior segments is more frequent in the maxillary than in the mandibular quadrant.

Sexual dimorphism of tooth agenesis patterns in non-syndromic oligodontia in Japanese patients

OBJECTIVE

Wide individual variation observed in tooth agenesis patterns in patients with non-syndromic oligodontia could be affected by sexual dimorphism. Therefore, the present study investigated sex-associated differences in tooth agenesis patterns in patients with non-syndromic oligodontia.

DESIGN

Subjects were 108 male (ages 7-46 years) and 184 female (ages 7-43 years) orthodontic patients missing ≥6 permanent teeth, excluding third molars. The number of agenetic teeth per patient, excluding third molars, and the prevalence of agenesis of each tooth type were evaluated using panoramic radiographic images. Rankings of the most common tooth agenesis patterns in the maxillary and mandibular arches were calculated. The number of agenetic teeth per patient was compared between sexes using the Mann-Whitney test. The prevalence of tooth agenesis for each tooth type was compared between sexes using the χ² and Fisher's exact tests with Bonferroni correction.

RESULTS

No significant sex difference in the distribution of the number of agenetic teeth was observed. The prevalence of agenesis of the maxillary second premolars was significantly higher in females (P < 0.007) and the prevalence of agenesis of the mandibular central incisors was significantly higher in males (P < 0.007). Sexual dimorphism was observed in the highly ranked tooth agenesis patterns.

CONCLUSIONS

No significant difference in the severity of tooth agenesis was observed between sexes; however, sexual dimorphism was observed in the tooth agenesis patterns of patients with non-syndromic oligodontia. Although various tooth agenesis patterns were identified, sex-specific tendencies suggest that categories can be utilized in future epidemiologic research and planning.