[The transmandibular implant. From bone loss to bone growth--an investigation of 116 patients]

In a prospective study 116 consecutive patients were treated according to a revised protocol to induce and control bone growth. Revisions included: 1. lengthening of the transosseous posts and cortical screws between the mental foramina so that two threads extended beyond the alveolar crest of the mandible without protruding through the mucosa; and 2. fabricating an implant borne prosthesis with a gap of 2 mm between the denture base and the mucosal tissues in the saddle areas and loading only the retromolar pads. The gap was re-opened every 8 weeks until further bone growth would prevent proper oral hygiene. Measurements of the height of the mandible were made using a digital millimeter caliper and standardized radiographs. The radiographic enlargement was calculated per radiograph for the sites to be measured. The follow-up varied from 15 up to 39 months. Bone growth had occurred in 104 of the 116 patients, while the resorption of bone had ceased in the remaining patients. The increase of bone height varied from 9 mm in patients with severe mandibular atrophy down to 2 mm for patients with mild atrophy. The revised protocol for TMI insertion and rehabilitation is advocated to promote bone growth and to cease further resorption in the atrophic mandible.