Regeneration of periodontal tissue after a loss of attachment due to disease or trauma repesents an important issue in dentistry, and various bone graft materials have been used to regenerated lost periodontal tissue and restore proper fuctions. Among those, allografts have been extensively researched and widely used clinically, since they are known to possess an excellent osteoinduction capability and result in proper topography of alveolar bone. Regeneration of periodontal tissue in supraalveolar defects may be technically difficult. However, a large amount of regeneration has been observed by complete tissue coverage of involved teeth. In this study, supraalveolar defects in adult dogs were treated with periodontal surgery, decalcified freez-dried bone allograft, complete tissue coverage was attained, and effects on repair and regeneration of alveolar bone, cementum and periodontal ligament were studied. Exposure of premolar furcation of adult dogs was attained by removing marginal alveolar bone down to 5mm from CEJ, and root surfaces were planed with curettes. On the left side, defects were treated without any allograft(Control Group). On the right side, a DFDB was used(Experimental Group). In all groups, flaps were coronally positioned and sutured, completely submerging the treated defects. At two weeks, the crown were exposed 2-3mm. Healing progresses were histologically observed after eight weeks and the results were as follows : 1. Distance from CEJ to AJE was : $2.82{pm}0.66mm$ in the control group, $1.71{pm}0.51mm$ in experimental group, with significant differences between groups.(P<0.01) 2. Periodontal repair was : $2.18{pm}0.66mm$ in the control group, $3.29{pm}0.51mm$ in experimental group, with significant differences between groups.(P<0.01) 3. Connective tissue repair was : $1.43{pm}0.52mm$ in the control group, $0.76{pm}0.47mm$ in experimental group, with significant differences between groups.(P<0.01) Orientation of connective tissue fibers in relation to root surfaces was : mostly parallel in the control group, vertical or parallel or irregular in experimental group. 4. The amount of cementum formation was : $1.66{pm}0.58mm$ in the control group, $2.86{pm}0.66mm$ in experimental group, with significant differences between groups. 5. The amount of alveolar bone formation was : $0.76{pm}0.72mm$ in the control group, $2.53{pm}0.56mm$ in experimental group, with significant differences between groups.(P<0.01)