Lower first permanent molars: developing better predictors of spontaneous space closure

Area of Science:

• Dentistry
• Orthodontics
• Oral Surgery

Background:

• First permanent molars (FPMs) with poor prognosis are often extracted at an 'ideal time' to facilitate favorable second permanent molar (SPM) eruption.
• However, extraction timing alone is an unreliable predictor for successful space closure following lower FPM removal.

Purpose of the Study:

• To identify additional radiographic factors that can more accurately predict the degree of spontaneous space closure of the lower SPM after FPM extraction.

Main Methods:

• Re-analysis of data from 127 lower SPMs in 66 patients.
• Incorporation of radiographic factors: SPM bifurcation calcification stage, second premolar position, SPM mesial angulation relative to FPM, and third permanent molar presence.
• Analysis using ordered logistic regression.

Main Results:

• Only 58% of FPMs extracted at the 'ideal time' (SPM Demirjian stage E) achieved complete space closure.
• Optimal outcomes (85% complete space closure) were achieved when SPMs were not at Demirjian stage G, and the third permanent molar was present with SPM mesial angulation.

Conclusions:

• Extraction timing of the FPM is insufficient for predicting reliable spontaneous space closure of the lower SPM.
• The presence of the third permanent molar and the angulation of the SPM are crucial additional factors to consider for predictable space closure.