GuREx-MIH: radiographic assessment of eruption patterns of second permanent molars and premolars in 11-year-olds after early extraction of the first permanent molar - a split-mouth trial.

Background/objectives: Molar-Incisor Hypomineralisation (MIH) affects 14% of the global population, often leading to compromised first permanent molars (FPM). Early extraction of severely affected FPMs may temporarily affect proper eruption and alignment of second permanent molars (SPM) and second premolars (SP). This study aimed to evaluate the eruption patterns of SPMs and SPs, and the overeruption of opposing FPMs, after early FPM extraction using panoramic radiographs in 11-year-old patients. A secondary aim was to assess radiographic quality for these evaluations.

Subjects and methods: This split-mouth trial included patients aged 6-9 with severe MIH requiring FPM extraction. Panoramic radiographs were taken pre-extraction (T0) and at age 11 (T1) to measure eruption length and angulation of SPMs and SPs. Radiographs were analysed using Facad software, and imaging errors were recorded. Paired t-tests compared extraction and non-extraction sides.

Results: Among 47 patients, 31 had maxillary and 25 mandibular FPM extractions. At T0, eruption length and angulation of SPMs and SPs were similar between sides. At T1, maxillary SPMs erupted faster (13.5mm vs. 10.8mm, p < 0.001) and more upright (72.9° vs. 62.1°, p < 0.001) on the extraction side, while SPs showed increased mesial angulation (82.5° vs. 89.3°, p < 0.05). Mandibular SPMs and SPs showed no differences. No overeruption of opposing FPMs was observed. Measurement reliability was excellent (ICC: 0.997-0.999), despite 75 of 94 radiographic contained errors.

Limitations: The three-year follow-up limits long-term insights, and radiographic distortions may affect reliability.

Conclusions: Early FPM extraction impacts maxillary but not mandibular SPM and SP eruption patterns without causing overeruption of opposing FPMs by age 11. Radiographic techniques are essential to minimize incorrect patient positioning, as such factors may impact measurement reliability.