Dr. Maino is a Visiting Professor at Parma University and in the pri- vate practice of orthodontics at Viale Milano 53, 36100 Vicenza, Italy; e-mail: vicenza@mainog. com. Dr. Bednar is an Assistant Professor, Department of Ortho- dontics, Boston University School of Dental Medicine, and in the pri- vate practice of orthodontics in Nashua, NH. Dr. Pagin is in the private practice of orthodontics in Bologna, Italy, and Dr. Mura in Vicenza, Italy.
smooth, self-tapping surface permits easy removal at the completion of treatment.
The placement site should have enough bone depth to accommodate the screw length and at least 2.5-3mm of bone width to protect adja- cent dental roots and anatomic structures such as the maxillary sinus or the inferior alveolar nerve. Typical insertion areas include the maxillary tuberosity, the retromolar areas, edentulous ridges, interradicular septi, the palate, and the
Fig. 4 Radiographic evaluation of screw place- ment site using surgical index.
Fig. 5 Osseous site preparation with 1.5mm pilot drill.
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anterior alveolar processes above the apices.
If the screw is to be placed in an area where there is a possibility of damaging adjacent struc- tures, a surgical index should be fabricated from orthodontic wire and thermoplastic or acrylic (Fig. 3). The acrylic fits over the occlusal sur- faces of the teeth near the surgical site, and the wire is inserted in the acrylic and bent so that its tip corresponds to the point of screw placement, which is marked with a pressure point or a meth- ylene blue dot on the soft tissue. The distance from the index point to the adjacent anatomic structures can be determined radiographically using the long-cone parallel technique (Fig. 4).
A water-cooled 1.5mm pilot drill with a stop corresponding to the length of the Spider Screw is used to perforate the soft tissue and cor- tical bone (Fig. 5). A low-speed handpiece should be used—straight for anterior locations or contra-angular for buccal or posterior locations. No separate incision is required if the area has sufficient attached gingiva.
The Spider Screw is removed from its ster- ile package and mounted on the pick-up device of a low-speed contra-angle for insertion at about 30rpm (Fig. 6). A manual screwdriver is then used for final turning until the screw collar
Fig. 6 Spider Screw insertion with low-speed con- tra-angle.