Effect of upper second molar eruption status on the efficiency of upper first molar distalization: a systematic review and meta-analysis
Bibliographic record
Abstract
OBJECTIVES: To assess the distalization, tipping, and vertical movement of the maxillary first permanent molar in patients with and without erupted maxillary second molar (MSM). METHODS: Eligibility criteria: Randomized/non-randomized clinical studies comparing distalization, tipping, and vertical movement of the maxillary first permanent molar in patients with and without erupted MSM. Information sources: Unrestricted literature search of six databases was conducted up to May, 2024. Risk of bias: The quality assessment of the studies was conducted using the Cochrane Risk of Bias Tool (ROBINS-I). Synthesis of results: Random effects meta- analyses using standardized mean differences (SMDs) and their 95% confidence intervals (CIs) were performed, followed by meta-regressions, sensitivity analyses, and assessment of the quality of evidence using GRADE. RESULTS: Included studies: Eleven studies (8 retrospective and 3 prospective non-randomized trials) involving 562 participants (43.97% male) were included. Synthesis of results: Distalization was significantly more effective when the maxillary second molar was unerupted (9 studies; SMD = -0.41; 95% CI: -0.81--0.004; P = .04; I² = 68.6%). The eruption status of MSM has no significant effect on tipping (8 studies; SMD = -0.27; 95% CI: -0.68-0.15; P = .17), and vertical movement (4 studies; SMD = 0.08; 95% CI: -0.32-0.48; P = .57) of upper first molars during distalization. Sensitivity analyses showed no significant differences based on study design, appliance type, or anchorage type, confirming the robustness of the findings. The certainty in the estimates was very low due to high risk of bias, methodological weaknesses, and small sample sizes. DISCUSSION: Limitations of evidence: The inclusion of non-randomized, mostly retrospective studies, unmatched baseline, Class II severity, and insufficient reporting of treatment duration are key limitations. Interpretation: Very low level of evidence indicates that it may be preferable to perform distalization before the eruption of the upper second molar. REGISTRATION: PROSPERO (CRD42024591126).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.015 | 0.033 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.019 | 0.040 |
| Bibliometrics | 0.007 | 0.006 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.004 | 0.002 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".