Abstract Background Both fixed and removable functional appliances are commonly used to stimulate mandibular growth and enhance the facial profile of retrognathic patients. This forward posturing of the mandible may affect condylar morphology and position. Objective This study systematically evaluated the effects of functional appliance treatment on condylar morphological and positional changes in growing skeletal Class II patients. Search methods A comprehensive literature search involved five databases: PubMed, Cochrane Library, ScienceDirect, Web of Science, and Scopus, from 2000 to 2025. Selection criteria The study included randomized controlled trials (RCTs) and nonrandomized longitudinal studies which employed cone-beam computed tomography and magnetic resonance imaging. The study selection adhered to the PICO (Population, Intervention, Comparison, and Outcome) criteria, and data extraction was performed using the open-source systematic review software, Rayyan. Data collection and analysis The risk of bias was assessed using the Cochrane Risk-of-Bias tool for randomized trials (RoB2) and the Risk of Bias in Nonrandomized Studies of Interventions (ROBINS-I) tool for nonrandomized studies of interventions. To assess the certainty of evidence, the Grading of Recommendations Assessment, Development, and Evaluation tool was employed. Results Thirty-four studies were included, comprising 6 RCTs, 23 prospective longitudinal studies, and 5 retrospective longitudinal studies. The overall risk-of-bias assessment indicated that 47.06% of studies were of low risk, and 52.94% of studies had moderate risk of bias. Functional appliances treatment was associated with anterior condylar shifts, altered condylar shape, retracted articular discs, increased joint spaces, and glenoid fossa remodeling. Few studies reported nonsignificant changes in condylar morphology and position following functional appliance treatment. The overall level of scientific evidence was low. Conclusion A relatively low level of scientific evidence suggests that treatment with functional appliances may be associated with alterations in condylar position and morphology. Registration The protocol for this systematic review was registered in PROSPERO with the ID CRD42024507040.
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