Background: The objective of this study was to histologically evaluate periodontal healing following flap surgery in intrabony periodontal defects to determine the influence of the number of bone walls on periodontal regeneration. Methods: One-, 2-, and 3-wall intrabony periodontal defects were surgically produced at the proximal aspect of mandibular premolars in either right or left jaw quadrants in six beagle dogs. Mucoperiosteal flaps were positioned and sutured to their presurgery position following defect preparation. The animals were euthanized at 8 weeks post-surgery, and block sections of the defect sites were collected for histologic and histometric analysis. Results: Bone and cementum regeneration was positively correlated to the number of bone walls limiting the intrabony periodontal defects. The junctional epithelium averaged (±SD) 1.5 ± 0.2, 1.2 ± 0.3, and 0.9 ± 0.2 mm for the 1-, 2-, and 3-wall defects, respectively, with the 3-wall defects being significantly different from the 1-wall defects (P <0.05). Cementum regeneration averaged 1.2 ± 0.6, 2.0 ± 0.6, and 2.8 ± 0.5 mm for the 1-, 2-, and 3-wall defects, respectively; all groups were significantly different from each other (P <0.05). Bone regeneration averaged 1.5 ± 0.5, 1.7 ± 0.6, and 2.3 ± 0.5 mm for the 1-, 2-, and 3-wall defects, respectively, with the 3-wall defects being significantly different from the 1-wall defects (P <0.05). Conclusions: The results suggest that the number of bone walls is a critical factor determining treatment outcomes in intrabony periodontal defects. One- and 3-wall intrabony defects appear to be reproducible models to evaluate candidate technologies for periodontal regeneration.
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