Sixty-nine male Sprague Dawley rats were divided into three groups of 23 animals each and osteotomies were performed in group 1 with a power saw, in group 2 with the Erb:Yag laser, and in group 3 with the Hol:YAG laser. Two animals of each group were sacrificed 1 week, 4, 8, and 12 weeks after operation for histologic investigation, and five animals of each group at 4, 8, and 12 weeks after osteotomy for torque testing. Anterior-posterior (AP) radiographs were taken at the same time points and investigated for callus formation and development of pseudoarthrosis. All tibiae osteotomied with the Hol:YAG laser (group 3) developed pseudoarthrosis within 12 weeks and, therefore, torque testing could not be performed for this group. Biomechanical measurements of bone treated by power saw or Erb:YAG laser osteotomies, respectively, showed no significant statistical difference in the stability of bone between the two groups. Histologic examination after 1 week exhibited fibrous tissue at the site of osteotomy in rats of all three groups and additionally carbonization in rats of group 3. Saw osteotomies resulted in more callus formation than Erb:YAG osteotomies, but both techniques provoked a certain reunion within 8 weeks. Hol:YAG laser-treated osteotomies, however, exhibited formation of dense fibrous tissue, carbonization and no callus formation within 12 weeks. Radiographic pictures showed more callus formation for saw osteotomies as compared to those performed with the Erb:YAG laser. For Hol:YAG laser osteotomies pseudoarthrosis was identified also radiologically.

Oral L-arginine expedites healing in stabilized diaphyseal defects in guinea pigs without detrimentally affecting uninjured counterparts.

All screw systems yielded acceptable results but the ICOS did produce greater compression. The essential differences were the primary deformation of the bone before reaching the sufficient compressive force for primary stability.

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Summary. Since root canal sealers and pastes can cause tissue irritation, the quantity of biologically inert gutta‐percha should constitute more than 90 per cent by volume of the root canal filling. The root canals of 40 extracted incisors with straight root canals were enlarged sequentially to size 50 and the canals were obturated, either by lateral condensation or thermomechanical condensation using standardized gutta‐percha points and Grossman's sealer. After being stored in moistened gauze for 6 hours at 37°C, transverse sections 1 mm from the apex were made, and the area of gutta‐percha in relation to the total cross section of the canal was determined planimetrically using a light microscope. Sections of teeth filled by the lateral condensation method contained 92.7 per cent gutta‐percha, while whose filled by thermomechanical condensation contained 89.1 per cent. As a result lateral condensation continues to be recommended as the filling method of choice for dental practice.