Palatal bone support for orthodontic implant anchorage--a clinical and radiological study.

When maximal anchorage is required during orthodontic treatment, additional aids are often needed to support the anchoring teeth. While intra-oral aids may be limited in their anchorage potential, extra-oral anchoring aids are often rejected by the patients. Endosseous implants may therefore be a valuable alternative for stable intra-oral anchorage. However, the possibility of using conventional implants is insufficient, e.g. for treating purely orthodontic patients with full dentition or where extraction sites are to be closed. Therefore, the mid-sagittal area of the palate is an alternative insertion site for the placement of implants for orthodontic anchorage. The limited bone height in this area inspired this comparison between bone thickness in the implantation site as verified by probing during the implantation of Straumann Ortho-system implants, and thickness as measured on the lateral cephalogram. The results suggest that vertical bone support is at least 2 mm higher than apparent on the cephalogram. In none of 12 patients was a perforation to the nasal cavity found. However, in five subjects the implant projected into the nasal cavity on the post-operative cephalogram. These results were supported by the study of the projections of palate and wires in wire-marked skulls where the wires were placed bilaterally on the nasal floor and on the nasal crest. It is therefore concluded that the mid-sagittal area of the palate lends sufficient bony support for the implantation of small implants (4-6 mm endosseous length, diameter 3.3 mm).