Histological and immunohistochemical comparison of two different allogeneic bone grafting materials for alveolar ridge reconstruction: A prospective randomized trial in humans

Abstract

Background: Preclinical studies have hypothesized a possible immunological reponse to allogeneic materials due to detection of remnants of potential immunogenic molecules. However, their impact on integration, bone remodeling and immunological reaction after the augmentation procedure is largely unknown and a direct correlation of analytical data and evaluation of human biopsies is missing.

Purpose: The present study aimed to compare two commercially available allogeneic materials regarding their content of cellular remnants as well as the bone remodeling, and integration and potential immunologic reactions on a histological and immunohistochemical level, integrating also in vitro analytical evaluation of the specific batches that were used clinically.

Materials and methods: Twenty patients were randomly assigned to treatment with Maxgraft or Puros for lateral ridge augmentation in a two-stage surgery. After a mean healing period of 5 months, implants were placed and biopsies were taken for histological, immunhistochemical, and histomorphometrical evaluation regarding bone remodeling and inflammation, protein concentrations in vitro and the presence of MHC molecules of the same batches used clinically.

Results: No differences in clinical outcome, histological, immunohistochemical, and in vitro protein analysis between the two bone grafting materials were observed. Active bone remodeling, amount of newly formed bone, and residual grafting material was independent of the materials used, but varied between subjects. MHC1 residues were not detected in any sample.

Conclusions: Within the limitations of this study, both tested materials yielded equivalent results in terms of clinical outcome, new bone formation, and lack of immunological potential on a histological and immunohistochemical level.

Keywords: guided bone regeneration; histomorphometry; human histology; lateral ridge augmentation; particulated bone allograft.

Conflict of interest statement

All authors have no conflicts of interest to report.

© 2019 The Authors. Clinical Implant Dentistry and Related Research Published by Wiley Periodicals, Inc.

Figures

Figure 1

Overview of the surgical procedure. A very thin alveolar crest appeared after reflection of a mucoperiosteal flap (A). The alveolar ridge was then prepared with cortical perforations (B). Thereafter, the bone allograft material soaked in the second phase of the PRGF solution was applied in order to build up the alveolar bone volume necessary for future implant placement (C). It was then covered with a resorbable collagen membrane (D). The surgical site was primarily closed by means of a periosteal incision (E), the use of horizontal mattress sutures and a continuous half‐hitch suture. The second surgical procedure took place after a healing period of 4 months. The significant gain in alveolar ridge volume can be appreciated (F). Four implants were placed according to the manufacturer's recommendations (Straumann Group, Basel Switzerland). Four months later, the implants were uncovered (G). Postoperative two‐dimensional radiographs demonstrate stable integration of the implants 36 months after final restauration (H)

Figure 2

Histology. Representative photomicrographs of biopsies; Maxgraft shown in (A), (C), and (E), Puros in (B), (D) and (F); osteogenesis around allogenic particles (stars, A, B, E, F); progressed osteogenesis without allogenic remnants (C) and embedded small allogenic remnant (D); small infiltrates (arrows, E, F); HE staining, original magnification ×20 except 2E (×10)

Figure 3

Histochemistry and immunohistochemistry I. Representative photomicrographs of biopsies; Maxgraft shown in (A), (C), (E), and (G), Puros in (B), (D), (F) and (H); osteoclasts on bone surfaces (arrows), TRAP staining, original magnification ×10 (A, B); alkaline phosphatase immunohistochemistry, arrows indicate immunoreactive osteoblasts; DAB, ×40; CD4 immunohistochemistry, arrows indicate very few immunoreactive cells, DAB, ×40 (E, F); CD3 immunohistochemistry, arrows indicate few immunoreactive cells, DAB ×20, ×40 (H)

Figure 4

Immunohistochemistry II. Representative photomicrographs of biopsies; Maxgraft shown in (A) and (C), Puros in (B) and (D); collagen type I immunohistochemistry; immunoreactive newly formed bone matrix and osteoblasts, focally reactive connective tissue and vessel walls (arrow, A, B, C, D), no immunostaining in allogenic remnants (stars, C, D), DAB, original magnification ×20; ED1 immunohistochemistry, immunoreactive osteoclasts on bone and allogenic surfaces (arrows, E, F), DAB, ×40

Figure 5

Immunohistochemistry III. Representative photomicrographs of biopsies; Maxgraft shown in (A), (C), (E), and (G), Puros in (B), (D), (F), and (H); osteocalcin immunohistochemistry, immunoreactive osteoid (arrows) and osteocytes, DAB, original magnification ×20 (A, B); osteopontin immunohistochemistry, immunoreactive connective tissue (stars, C, D), DAB, x20; runx2 immunohistochemistry, immunoreactive pre‐osteoblasts and osteoblasts on the surfaces of newly formed bone (arrows, E, F), DAB, ×40; vWF immunohistochemistry, immunoreactive vessels near bone and among allogenic granules (arrows, G, H), DAB, ×10