Article Title: Tooth anomalies associated with failure of eruption of first and second permanent molars
Author: T. Baccetti, DDS, PhD Florence, Italy
Date: American Journal of Orthodontics and Dentofacial Orthopedics, December 2000
Major Topic: Failure of eruption of first and second permanent molars
Main Purpose: To assess if there is a clinical associations between first and second molars that fail to erupt with other dental anomalies. Thus leading to possible genetic component that is phenotypic expression for arrested molars.
Introduction: 0.06% of the normal population presents with failure of eruption of first and second molars permanent molars. Mechanical obstacles are the most common reason, which includes supernumerary teeth, odontomas, and cystic formations. There has been suggestion that there is a genetic component to these anomalies. The goal of this paper is to assess the prevalence of clinical associations between failure of eruption of the permanent first and second molars with other types of dental anomalies to point to the additive genetic component.
Methods: 3600 orthodontically untreated subjects from the Department of Orthodontics at the University of Florence was in the initial group. 1080 subjects excluded due to: cleft lip and/or palate or craniofacial malformations, traumatic injuries on the dentition, familial relationships with other examined subject, crowding, nonwhite race.
Remaining 2520 subjects (1223 males, 1297 females, age range: 12-16 years; mean age 14 years 2 months) were divided into two groups:
· Experimental: 1520
· Control: 1000
Both groups were controlled for origin, age and gender distribution.
Failure to erupt was considered complete retention in alveolar bone and under the oral mucosa. Any participants with mechanical disruption were excluded.
· Experimental: 26 subjects had failure of eruption (1.7%)
o Dental anomalies found in these subjects: infraocclusion of deciduous molars, palatal displacement of maxillary permanent canines, rotation of maxillary permanent lateral incisors, aplasia of second premolars, small size of maxillary permanent lateral incisors. Only 9 subjects had no associated tooth anomaly.
· Control: 14 subjects had failure of eruption (1.4%)
Infraocclusion of deciduous molars, palatally displaced maxillary canines, and rotation of maxillary lateral incisors showed a statically significant prevalence (P < 0.001) with those who also had failure to erupt permanent molars. The gender ratio was M1:F2.25 is similar for palatally displaced canies which have been found to be M1:F1.3 to M1:F3.2. These findings suggest a possible implication of sex chromosomes in the cause of tooth eruption disturbances.
Discussion: Further studies are needed to determine if genetics or environmental factors are the contributing factors but there seems to be an additive genetic affect.