Early healing after ridge preservation with a new collagen matrix in dog extraction sockets: preliminary observations.

The aim of the present animal study was to investigate the early healing processes developing in the post-extraction sockets preserved with a new-marketed collagen matrix as, to our knowledge, such investigations have not been reported so far. In both quadrants of the mandible of a mongrel dog, the distal sockets of the second premolars served as experimental sites for ridge preservation. The experimental site 1 was protected with a resorbable membrane and then with the collagen matrix. The experimental site 2 was filled with a xenograft and then covered with the collagen matrix. The samples were harvested after one month of healing. In both experimental sites, the bundle bone lining the inner surface of the alveolus was replaced with trabecular bone containing areas of woven bone. A continuous layer of osteoblasts could be observed on the surface of woven bone areas. Osteoclasts encased within resorptive lacunae lined the outer portions of bone walls for the experimental site 1. The trabecular bone occupied only the apical third of the socket in experimental site 1, but it was obviously more abundant in the experimental site 2, occupying also the central compartment of the socket. Moreover, the trabeculae of the bone occupying the inner area of the alveolus were thicker for the experiment site 2 than for experiment site 1, suggesting an increased osseous deposition in the latter situation. Our preliminary results suggest that the association collagen matrix plus xenograft may be a valuable method for ridge preservation.

The effect of distraction rate on bone histological and histomorphometrical properties in an ovine mandible model.

UNLABELLED: Lengthening the mandible by distraction osteogenesis (DO) is nowadays a well-recognized technique in maxillofacial surgery. This study compared two different distraction rates and evaluated histological and histomorphometrical properties of the distracted bone in an experimental ovine mandible model with the goal of elaborating a universally accepted distraction protocol. STUDY DESIGN: Tissue blocks of regenerated bone were harvested from twelve young adult sheep. DO was performed on the mandibular midline after five days of latency period. The sheep were divided into two groups. The first group underwent activation of 0.8 mm÷day during 12 days resulting in 9.6 mm of new bone while the second group followed a geometric rate pattern of 0.2 mm - three days, 0.4 mm - three days, 0.8 mm - three days and 1.6 mm - three days resulting in 9 mm of new bone. The regenerated bone was histologically and histomorphometrically analyzed after 30, 45 and 60 days of consolidation. The relative osteoid volume (OV÷TTV) was significantly increased in the geometric rate distraction group (p=0.015) comparing with linear distraction group while the relative bone volume (BV÷TTV) was significantly increased in the linear distraction group (p=0.019) compared to the geometric distraction group.

The influence of expansion on intraoperative bone blood flow in multisegmental maxillary osteotomies: an experimental study.

The aim of the presented study was to investigate the effect of maxillary expansion in multisegmental Le Fort I osteotomies on bone blood flow. Five sheep underwent a three-piece total maxillary osteotomy. Bone blood flow was measured intraoperatively by laser Doppler flowmetry in the premaxilla, the lateral segments and the mandible before osteotomy, after osteotomy and segmentation as well as after 4mm, 8mm and 12mm expansion with a Hyrax screw. A significant reduction in blood flow was seen after osteotomy and segmentation with a factor of 3.10 and between 4mm and 8mm expansion with a factor of 1.81. No significant differences could be found between 0mm and 4mm widening or between 8mm and 12mm widening. These results suggest that expansion of more than 4mm in multisegmental osteotomies enhances the risk of avascular sequelae. As greater maxillary widening has been carried out in many cases without avascular complications, further research on additional factors, influencing the recovery of perfusion, is needed.