[Geometric analysis of three-dimensional position blocking in implant surgery: clinical decision making of instrument length and implant guidance methods].

The current design of ideal implant sites often fails to include the assessment of the restrictions imposed by the limited geometric space of the surgical area on instrument manipulation. This limitation may cause three-dimensional position blocking during actual surgery, resulting in the inability to complete implantation at the predesigned geometric position. On the basis of the previously proposed new concept and classification system of surgical area mouth opening (SO), this work divides the surgical procedure into two stages: instrument placement and instrument working. The minimum instrument length required to avoid blocking are precisely calculated and different SO requirements are matched by establishing a complete geometric analysis model and defining key geometric parameters. Consequently, a complete pathway from anatomical space assessment, to instrument length selection, and then to guidance method decision is constructed, realizing a comprehensive and accurate assessment of the virtual designed implant site and the evaluation of the accessibility of the implantation operation. This study further improves the clinical decision-making system of SO and provides a complete arithmetic scheme for the clinical implementation of digital preoperative implant designs.