A dental drill guide system, including a handpiece guide which interfaces with a custom surgical guide. The custom surgical guide may be designed based on patient-specific data, such as medical images, for example, and fits conformingly over at least a portion of the patient's dentition at the implant site. The handpiece guide is attachable to an existing dental handpiece, and includes a guide protrusion that interfaces with a guide receptacle of the surgical guide to position and guide the movement of the drill along a desired trajectory. The guide receptacle may have a curved shape to allow for varying the position of the handpiece to aid surgeon access in the drilling procedure.