ẢNH HƯỞNG CỦA KHOẢNG E ĐẾN TƯƠNG QUAN RĂNG CỐI LỚN THỨ NHẤT: NGHIÊN CỨU DỌC TỪ BỘ RĂNG HỖN HỢP ĐẾN VĨNH VIỄN

Abstract

Introduction: The mesiodistal relationship of the permanent first molar is a critical parameter in occlusal assessment. During the mixed‑dentition stage, two principal factors have been identified in the literature as influencing this relationship: the first molar relationship: late mesial drift into the leeway space and differential growth between the maxilla and mandible. Leeway space—the difference between the combined mesiodistal widths of the deciduous canine and first and second molars and those of their permanent successors—has been widely associated with first molar occlusion. In contrast, E‑space—the width differential between the deciduous second molar and its corresponding permanent second premolar—is a novel, simpler, and more rapidly measurable index proposed as a predictive indicator. However, evidence in Vietnamese populations remains limited. Methods: A retrospective longitudinal study was conducted on 112 pairs of dental casts from mixed to permanent dentition. Mesiodistal tooth widths were measured with a digital caliper (precision ± 0.01 mm) to calculate leeway space and E‑space in both arches. Final molar relationships were classified according to Angle’s criteria. Comparison was made between the cohort transitioning from a flush terminal‐plane R6 relationship in the mixed dentition to a Class I R6 relationship (n = 84) and the cohort transitioning to a Class II R6 relationship (n = 28) were analyzed using the t‑test and the Mann–Whitney test (SPSS 22.0). Results: The study found no statistically significant differences in leeway space in either arch or in maxillary E space between the Class I and Class II R6 relationship groups in the permanent dentition (p > 0.05). However, mandibular E‑space was significantly greater in the Class I group (2.6 ± 0.5 mm) than in the Class II group (2.4 ± 0.5 mm; p < 0.05). Discussion: Mandibular E‑space, being simpler to measure than leeway space, demonstrated statistical value as a predictor of favorable versus unfavorable molar relationship development from mixed to permanent dentition. Further in‑depth research is warranted to clarify the role of E‑space in occlusal maturation and to evaluate its application in preventive and interceptive orthodontic practice. Conclusion: Mandibular E‑space significantly influences the development of an Angle Class I molar relationship, underscoring its advantage over leeway space in predicting future occlusal outcomes.Top of Form

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