Bone–Screw–Force Interactions in Palatal Orthodontic Mini-Implants: A Scoping Review and Decision Framework for Primary Stability and Biomechanically Driven Site Selection

Background: Palatal orthodontic mini-implants are increasingly used for sagittal, vertical, and transverse mechanics, including molar distalization, mesialization, posterior intrusion, impacted tooth traction, and miniscrew-assisted rapid palatal expansion. Yet site selection is often discussed as if anatomical bone availability were the dominant determinant of performance. Objective: This scoping review maps direct palatal evidence and supporting mechanistic evidence on how palatal substrate, miniscrew design, insertion protocol, digital planning, biomaterial surface, and biomechanical loading interact to determine primary stability, loaded stability, survival, and failure risk. Methods: Records were searched in PubMed/MEDLINE, Scopus and Web of Science Core Collection and organized into two evidence streams, as follows: P1 direct palatal evidence and P2 supporting mechanistic/biomaterials evidence. Data were charted using a Bone–Screw–Force framework. Results: The evidence indicates that anterior palatal and anterior paramedian sites are usually favorable for routine anchorage, but posterior sites, PPSAIS, and MARPE locations may warrant patient-specific three-dimensional assessment when clinical and conventional radiographic evaluation is insufficient. Primary stability emerges from cortical thickness, trabecular quality, effective intraosseous length, miniscrew diameter, thread design, insertion angle, pilot-hole protocol, torque, force magnitude, and biological response. Digital workflows are best interpreted as trajectory-control technologies rather than as convenience tools. Biomaterial and surface evidence remains promising but insufficiently connected to palatal-specific outcomes. Conclusions: Palatal miniscrew performance should be reframed as an interface problem rather than a site-only problem. A Bone–Screw–Force framework can support biomechanically driven site selection while identifying where quantitative evidence remains insufficient.