The Spider Screw for Skeletal Anchorage
Fig. 7 A. Spider Screw removal. B. Immediately after removal. C. Seven days later.
reaches its ideal position.
If the screw location is surrounded by mucosa, a small, 5mm vertical incision can be made and the flaps separated without removing tissue or denuding alveolar bone. In areas where the bone is extremely compact, initial placement can be facilitated by using a 1.8mm bur to drill deeper and reach less compact bone.
Once the screw has been inserted—espe- cially in sites with poor bone quality—it must be loaded immediately to promote mechanical sta- bility. Because miniscrews rely on mechanical retention rather than osseointegration for their anchorage, the orthodontic force should be per- pendicular to the direction of screw placement. Applied forces can range from 50g to 200g,
depending on the quality of the bone and the orthodontic movement desired.3 If any mobility is noted immediately after placement or during tooth movement, the screw should be inserted deeper into the bone, or replaced with a longer screw to engage the opposite plate of cortical bone.
Oral hygiene is simplified by the low pro- file of the screw head. For the first seven days, the patient should rinse with a .12% chlorhexa- dine solution. Normal hygiene procedures can be followed thereafter.
The Spider Screw is easily removed with a manual screwdriver, without local anesthetic in most cases (Fig. 7). Soft-tissue recovery can be expected within a few days.
Fig. 8 Case 1. 50-year-old female with overerupted maxillary posterior teeth before treatment.