556 – Interceptive treatment of congenitally missing agenesis of mandibular second premolars: A prospective, randomized longitudinal split-mouth study

Agenesis prevalence ranges from 6.1-8.2%, with mandibular second premolars most often missing. Early extraction of the deciduous second molar promotes spontaneous space closure during eruption. An alternative is hemisection, where the deciduous molar is sliced and extracted in two stages. A recent systematic review on interceptive treatment for mandibular premolar agenesis identified a knowledge gap, as no prospective longitudinal studies compare extraction with hemisection. The aim was to therefore to compare conventional tooth extraction and hemisection in terms of space closure and inclination of adjacent teeth in patients with bilateral congenital agenesis of permanent second premolars. This prospective, randomized, longitudinal split-mouth study included patients with bilateral agenesis of mandibular second premolars and unerupted second molars. Participants were randomly assigned to receive either conventional extraction or hemisection. Randomization determined which side would undergo hemisection or extraction. Clinical and radiographic evaluations were conducted at baseline (T1) and at a three-year follow-up (T2). Measurements of residual spaces and inclination of the teeth after extraction were obtained from panoramic radiographs and dental casts. Statistical analysis was performed using paired t-tests. A total of 40 patients (25 males,15 females) with a mean age of 10.03 ± 1.07 years at T1 participated. None were lost to follow-up. The mean residual space between the first permanent molar and premolar was significantly smaller at the hemisection side than the conventional extraction side (2.04 ± 1.67mm and 2.39 ± 1.86mm, respectively, p=0.0525). However, the mean residual space between the first permanent premolar and the canine was significantly larger at the hemisection side than the conventional extraction side (1.80±1.01mm and 1.55± 0.92mm, respectively, p= 0.0455). On the other hand, when the total residual space (molar-premolar distance and premolar-canine distance) was compared between the sides, no significant difference was seen (p = 0.6446). Hemisection is not recommended as an interceptive treatment for patients with congenital agenesis of the mandibular second premolars, as only minimal, non-clinically relevant differences were observed between hemisection and conventional extraction.