Periodontal tissue reaction to customized nano-hydroxyapatite block scaffold in one-wall intrabony defect: a histologic study in dogs

Abstract

Purpose: This study evaluated histologically the tissue responses to and the effects of a customized nano-hydroxyapatite (n-HA) block bone graft on periodontal regeneration in a one-wall periodontal-defect model.

Methods: A customized block bone for filling in the standardized periodontal defect was fabricated from prefabricated n-HA powders and a polymeric sponge. Bilateral 4×4×5 mm (buccolingual width×mesiodistal width×depth), one-wall, critical-size intrabony periodontal defects were surgically created at the mandibular second and fourth premolars of five Beagle dogs. In each dog, one defect was filled with block-type HA and the other served as a sham-surgery control. The animals were sacrificed following an 8-week healing interval for clinical and histological evaluations.

Results: Although the sites that received an n-HA block showed minimal bone formation, the n-HA block was maintained within the defect with its original hexahedral shape. In addition, only a limited inflammatory reaction was observed at sites that received an n-HA block, which might have been due to the high stability of the customized block bone.

Conclusions: In the limitation of this study, customized n-HA block could provide a space for periodontal tissue engineering, with minimal inflammation.

Keywords: Bone substitutes; Guided tissue regeneration; Periodontal disease; Tissue engineering; Tissue scaffolds.

Figure 1

Representative photomicrographs of surgical procedures. (A) Preoperative view, (B) flap elevation, (C) defect creation at the mesial side of the mandibular fourth premolar teeth, (D) application of customized nano-hydroxyapatite block within the defect, and (E) suture with coronally positioned flap.

Figure 2

Representative micro computed tomography images of control and experimental site at 8 weeks after surgery. Three-dimensional reconstruction of (A) the control and (B) the experimental site. The part highlighted in blue is the residual nano-hydroxyapatite (n-HA) block (left). (C) Transverse and (D) sagittal cross-sections of the experimental site reveals a well-maintained n-HA block within the defect.

Figure 3

Representative photomicrographs (Hematoxylin and eosin staining) from control (B, E, and F) and experimental sites (A, C, and D). A low-magnification view of the experimental site (A, ×40) shows well-maintained biomaterial (white asterisk) within the defect with connective-tissue ingrowth and minimal bone formation, whereas control site (B, ×40) shows slight linear bone growth and the collapse of soft tissues into the defect site. In the high magnification photomicrographs (C to F, ×100), thick cellular cementum (black asterisk) is observed at the notch area, and thin acellular cementum formation in the area remote from the base of the defect (arrow).

Figure 4

High magnification photomicrographs (Hematoxylin and eosin staining, ×200) from the sites received nano-hydroxyapatite (n-HA) block. (A) Surface resorption with subsiding of n-HA biomaterials into the native bone is observed at the base of the defect, in which n-HA block contacting to the native bone. (B, C) Space within the n-HA block is filled with connective tissues comprised of collagen fibers, fibroblasts, newly formed blood vessels (arrowhead), and osteoclast-like multinuclear cells onto the residual biomaterials (arrow). In some area (C), dense collagen fibers and extensive fibroblasts arranged in a same direction are observed between the residual n-HA biomaterials.