Introduction
The objectives of this study were to evaluate the prevalence of dental anomalies in patients with agenesis of maxillary lateral incisors and to compare the findings with the prevalence of these anomalies in the general population.
Methods
A sample of 126 patients, aged 7 to 35 years, with agenesis of at least 1 maxillary lateral incisor was selected. Panoramic and periapical radiographs and dental casts were used to analyze other associated dental anomalies, including agenesis of other permanent teeth, ectopia of unerupted permanent teeth, microdontia of maxillary lateral incisors, and supernumerary teeth. The occurrence of these anomalies was compared with prevalence data previously reported for the general population. Statistical testing was performed with the chi-square test ( P <0.05) and the odds ratio.
Results
Patients with maxillary lateral incisor agenesis had a significantly increased prevalence rate of permanent tooth agenesis (18.2%), excluding the third molars. The occurrence of third-molar agenesis in a subgroup aged 14 years or older (n = 76) was 35.5%. The frequencies of maxillary second premolar agenesis (10.3%), mandibular second premolar agenesis (7.9%), microdontia of maxillary lateral incisors (38.8%), and distoangulation of mandibular second premolars (3.9%) were significantly increased in our sample compared with the general population. In a subgroup of patients aged 10 years or older (n = 115), the prevalence of palatally displaced canines was elevated (5.2%). The prevalences of mesioangulation of mandibular second molars and supernumerary teeth were not higher in the sample.
Conclusions
Permanent tooth agenesis, maxillary lateral incisor microdontia, palatally displaced canines, and distoangulation of mandibular second premolars are frequently associated with maxillary lateral incisor agenesis, providing additional evidence of a genetic interrelationship in the causes of these dental anomalies.
Editor’s comment
Tooth agenesis is frequently associated with dental anomalies such as microdontia, delayed dental development, and some discrete tooth ectopia. These anomalies often appear together in a patient, perhaps because a certain genetic mutation causes a series of different phenotypic expressions. Tooth development is a complex process of reciprocal interactions with many genes involved, so the opportunity for mutations is great. Functional studies have begun to explain the precise role of genes in tooth development, and this will really help in orthodontic diagnosis and treatment planning.
As a general rule, when a deciduous tooth is missing, its permanent counterpart is also absent. Now we know that the occurrence of other anomalies in the deciduous dentition might predict similar anomalies in the corresponding permanent teeth. This close relationship between the deciduous and permanent dentitions has implications for clinical treatment and a more complete understanding of the underlying malocclusion. Tooth agenesis can be isolated, or it might be a part of approximately 49 syndromes, implying common molecular mechanisms for tooth or other organ development.
These authors analyzed the associations between a missing maxillary lateral incisor and other tooth disturbances in a large sample of subjects, compared with reference data from control population groups. Of the 126 patients with agenesis of maxillary lateral incisors, 51.6% (n = 65) had bilateral expression, and 27.7% (n = 35) had right unilateral and 20.7% (n = 26) left unilateral expression. There was a significant association between agenesis of maxillary lateral incisors and agenesis of other permanent teeth, as well as increased occurrence of microdontia of maxillary lateral incisors, palatal displacement of canines, and distal angulation of mandibular second premolars. Overall, this study highlights the importance of genetics in the field of associated dental anomalies. With advances in molecular biology, future diagnostic tools for preventing some dental anomalies might include genetic mapping.
