This prospective split-mouth clinical study aims to evaluate space changes in the mandibular dental arch following premature extraction of the lower first primary molar in children aged 3 to 5.5 years. Using digital 3D models, changes in the D space and mandibular arch perimeter will be measured at baseline and 6 months post-extraction. The goal is to determine whether space maintainers are necessary in the primary dentition stage.

Premature loss of primary molars in children is a common result of caries or trauma, potentially affecting future occlusion and alignment. This study investigates the space changes that occur after unilateral premature extraction of the mandibular first primary molar before the eruption of the permanent first molar. Using a split-mouth design, the contralateral non-extracted side serves as the control. Digital impressions will be taken at baseline (day of extraction) and after 6 months. The primary outcome is the change in the D space, and the secondary outcome is the change in the mandibular arch perimeter, both measured using 3D digital software. The study aims to provide evidence for or against the routine use of space maintainers in similar clinical scenarios, potentially reducing unnecessary treatment and improving patient comfort.

Inclusion Criteria:

• Children aged 3 to 5.5 years
• Mandibular first primary molar indicated for extraction due to extensive decay or hopeless prognosis
• Contralateral mandibular first primary molar must be intact and free of proximal caries
• No eruption of mandibular permanent first molar at the time of enrollment
• Presence of primary canines and second primary molars
• No space maintainers placed
• Parents/caregivers unable or unwilling to fabricate a space maintainer

Exclusion Criteria:

• Bilateral premature loss of mandibular first primary molars
• Contralateral mandibular molar has proximal caries or poor prognosis
• Children with good prognosis first primary molars (i.e., not needing extraction)
• Eruption of the mandibular permanent first molar
• Children who already have space maintainers
• Uncooperative behavior preventing study participation

Children aged 3 to 5.5 years attending the Pediatric Dentistry and Dental Public Health outpatient clinics at the Faculty of Dentistry, Cairo University, who require unilateral extraction of the mandibular first primary molar due to poor prognosis and meet the study's inclusion criteria.

This study does not plan to share individual participant data (IPD). All data collected will remain confidential and used solely for the purposes of this research. Any results presented will be in aggregate form, without disclosing participant-level data.