PDF: Associated Dental Anomalies: case report

Tooth agenesis is the most common developmental anomaly of the human dentition, occurring in 25% of the population.

The third molar (M3) represents the tooth most affected with agenesis, having a prevalence rate of 20.7%. In contrast, permanent second molar (M2) agenesis is a rare occurrence, found in only 2 of 6,000 consecutive orthodontic patients (0.03%).

Excluding the third molars, the prevalence rate of tooth agenesis is reported as 4.3 to 7.8%. The mandibular second premolar (MnP2) is the tooth most often absent, with a relative frequency of 2.2 to 4.1%. 

In fact, the MnP2 is highly variable developmentally. Besides the high prevalence of agenesis, the MnP2 often shows significantly retarded development, especially when there is agenesis of other permanent teeth.

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Despite the fact that the mean initial calcification age for MnP2 is 3 years (varying from 2y3m to 3y7m), its development can be suppressed until 6 years, and some published reports show radiographic appearance of the MnP2 after the age of  9 and even at 13 years old. 

In addition, the MnP2 accounts for approximately 24% of all impacted teeth, excluding the third molars. 

The most frequent malposition reported for the unerupted MnP2 is distoangular development, with a prevalence rate of 0.2% in dental clinic patients. This malposition was found to be associated with agenesis of the contralateral MnP2.

The present study reports a rare and interesting case of a 12-year-old girl with an association of multiple dental abnormalities, including agenesis, tooth malposition and delayed development.