Germectomy: Two-stage orthodontic treatment of dental crowding (A clinical case)

Abstract

Correction of dental crowding remains one of the main objectives of orthodontics. The prevalence of this anomaly varies from 34% in mixed dentition to 68% in permanent dentition. One of the methods for correcting this anomaly is orthodontic treatment with premolar extraction. At the same time, retention and distopia of the mandibular third molars often accompany dental crowding and are observed in 35—50% of the population. This problem is associated with insufficient growth of the mandible and should be considered a complicating factor of the aforementioned pathology. Eruption anomalies of the third molars can cause various complications (caries of the second molars, pericoronitis) and theoretically provoke the development of temporomandibular joint (TMJ) dysfunction. Extraction of third molars in adulthood is traumatic and associated with a high risk of serious complications (alveolitis, injury to the inferior alveolar nerve). Germectomy (removal of a tooth germ at the stage of root development less than one-third) is a theoretically possible way to prevent these complications. However, this approach has not yet become widespread due to the lack of strict indications for its use. The aim is to analyze the potential benefits of two-stage orthodontic treatment of dental crowding using germectomy, illustrated by a pilot clinical case.
Materials and methods.
A 14-year dynamic follow-up was conducted for a female patient with dental crowding. At the first stage of treatment (age 8—14 years), germectomy of the mandibular third molars and extraction of the first premolars on both jaws were performed. The initial incisor crowding was 8 mm in the maxilla and 5 mm in the mandible. To justify the germectomy, growth prediction methods according to Ricketts and Turley were used. Diagnostics included assessment of dental arch and facial photographs, panoramic radiograph (OPTG), lateral cephalogram (TRG), and cone-beam computed tomography (CBCT), as well as analysis of diagnostic models.
Results.
Based on Ricketts’ calculations, considering the average molar size (10 mm) and predicted annual growth (1.5 mm/year), a space deficit of approximately 8.5 mm for third molar eruption was predicted. Comparison of panoramic radiographs at ages 9 and 11 confirmed 100% space availability for the second molars and its absence for the thirds. CBCT analysis at age 20 showed an actual lack of retromolar space, despite subsequent treatment involving extraction of four premolars and mesialization of the lateral teeth. This confirmed the validity of the theoretical calculations. Germectomy successfully prevented the development of posterior crowding.
Conclusion.
Germectomy of the mandibular third molars, performed at the first stage, successfully prevented the development of posterior crowding. However, the removal of the mandibular third molar germs did not affect the space deficiency in the anterior segment of the mandibular arch, which necessitated sequential premolar extraction and subsequent comprehensive orthodontic treatment. The methodology of early tooth extraction for orthodontic indications, including germectomy, requires further detailed study to improve the algorithms for its application.