Anterior intrusion mechanics for adult deep bite correction: a systematic review of randomised controlled trials

Deep bite, defined as excessive vertical overlap of the lower incisors, remains a challenging malocclusion in adults. The existing literature largely focuses on growing patients, with limited high-quality evidence on treatment outcomes in skeletally mature individuals.

To systematically evaluate randomised controlled trials (RCTs) assessing anterior intrusion mechanics for deep-bite correction in adults (≥ 18 years), focusing on measurable dentoalveolar outcomes, specifically the magnitude of overbite reduction, the extent of incisor intrusion, and treatment duration.

This systematic review was conducted in accordance with the PRISMA 2020 guidelines. Comprehensive searches of six electronic databases and grey literature sources were conducted up to 10 March 2025, with no language restrictions. Only RCTs involving adults were included. Two reviewers independently conducted study selection, data extraction, and risk of bias assessment using the Cochrane RoB 2.0 tool. Certainty of evidence for each outcome was assessed using the GRADE framework. Due to substantial clinical and methodological heterogeneity, a quantitative synthesis was not undertaken, and findings were narratively synthesised.

Six randomised controlled trials (RCTs) met the inclusion criteria. The included studies were few in number, generally small in sample size, and clinically heterogeneous with respect to treatment indication, imaging modality, reference planes, and follow-up duration. Across individual studies, miniscrew-assisted intrusion mechanics were associated with slightly greater overbite reduction and greater incisor intrusion than conventional approaches; however, the observed differences were modest and inconsistent across studies. Dual miniscrew configurations generally resulted in greater incisor intrusion (up to 3.81 ± 0.55 mm) than single miniscrew systems (up to 2.62 ± 0.40 mm). Treatment duration ranged from approximately 4.8 to 5.9 months, with minimal differences between intervention groups. None of the included trials evaluated post-treatment stability, patient-reported outcomes, anchorage loss, or temporomandibular joint outcomes. The overall certainty of the evidence varied from low to very low across the assessed outcomes, primarily due to high risk of bias and imprecision.

Current adult RCT evidence suggests that miniscrew-supported approaches may provide slight benefits in anterior intrusion for deep bite correction. However, the magnitude and consistency of these benefits are limited. Changes in overbite reduction are typically small, and any decrease in treatment time is minimal and probably not clinically significant. Secondary outcomes, such as root resorption and periodontal health, are reported inconsistently but tend to be mild. No trials have assessed long-term stability or patient-reported outcomes. The reliability of these findings is further reduced by the limited number of studies, brief follow-up periods, varied outcome measures, and significant clinical differences. Consequently, the current evidence does not allow for definitive clinical recommendations.

Registration: Registration number: PROSPERO CRD420250654373.