Spontaneous Second Molar Migration After MIH-Affected First Molars Extraction: A Radiographic-Based Method Evaluation

Background: Molar–incisor hypomineralization (MIH) represents a challenging dental condition, often requiring complex and invasive interventions. In severe cases, extraction of the first permanent molars (FPM) is frequently indicated. However, methods to assess the effectiveness of this approach in promoting spontaneous mesialization of the second permanent molars (SPM) through Orthopantomography (OPT), as well as the factors influencing this process, remain unexplored. Aim: This perspective study aimed to assess the effectiveness of novel radiograph-based methods for assessing spontaneous SPM mesialization after FPM extraction and to identify clinical and developmental factors associated with complete space closure. Methods: OPTs of 19 patients (12 males, 7 females; age range 6.2–13.8 years) who underwent extraction of 36 FPM due to severe MIH were analyzed by 2 operators. Pre- and post-extraction OPTs were evaluated using specifically developed geometric measurements of distances and angles to quantify SPM movement. Variables considered included patient age at extraction, dental developmental stage (Demirjian index), observation period, and presence or absence of the third permanent molar (TPM). The reliability of the proposed measurements evaluated through ICC (Intraclass Correlation Coefficient) resulted in values above 0.9, confirming excellent intra- and inter-operator reliability. Results: Complete or quite-complete mesialization (target scores 0–1 and ≤33% residual space) occurred in 78.6% of maxillary and 73.7% of mandibular sites. Maxillary SPMs showed more favorable spontaneous movement, exhibiting substantial uprighting (e.g., from −32◦ to 2◦ ) and a higher frequency of complete or near-complete space closure (78.6% vs. 73.7% in the mandible). Developmental stages D–E of SPM were associated with successful outcomes. Conclusions: Early extraction of severely compromised first permanent molars (FPMs) can represent an effective treatment option to promote spontaneous mesialization of SPMs, particularly in the maxilla. The proposed radiograph-based measurement method demonstrated high consistency and reproducibility. Overall, this novel measurement approach may serve as a reliable and valuable tool for future clinical and research applications.