Effect of S53P4 bioactive glass and low-level laser therapy on calvarial bone repair in rats submitted to zoledronic acid therapy

Abstract

Purpose: To evaluate the influence of bioactive glass and photobiomodulation therapy (PBMT) in calvarial bone repair process in rats submitted to zoledronic acid therapy.

Methods: Twenty-four rats were selected and treated with the dose of 0.035 mg/kg of zoledronic acid every two weeks, totalizing eight weeks, to induce osteonecrosis. After the drug therapy, surgical procedure was performed to create 5-mm diameter parietal bone defects in the calvarial region. The rats were then randomly assigned to groups according to the following treatments: AZC: control group, treated with blood clot; AZBIO: bone defect filled with bioactive glass; AZL: treated with blood clot and submitted to PBMT; and AZBIOL: treated with bioactive glass S53P4 and submitted to PBMT. Tissue samples were collected and submitted to histomorphometric analysis after 14 and 28 days.

Results: At 14 days, bone neoformation in the AZBIO (52.15 ± 9.77) and AZBIOL (49.77 ± 13.58) groups presented higher values (p ≤ 0.001) compared to the AZC (23.35 ± 10.15) and AZL groups (23.32 ± 8.75). At 28 days, AZBIO (80.24 ± 5.41)still presented significant higher bone recovery values when compared to AZC (59.59 ± 16.92)and AZL (45.25 ± 5.41) groups (p = 0.048). In the 28-day period, the AZBIOL group didn't show statistically significant difference with the other groups (71.79 ± 29.38).

Conclusions: The bioactive glass is an effective protocol to stimulate bone neoformation in critical defects surgically created in rats with drug induced osteonecrosis, in the studied periods of 14 and 28 days.

Figure 1. Flowchart exemplifying intravenous zoledronic acid therapy and group division.

Figure 2. Photomicrographs of sections stained with hematoxylin and eosin in post-operative periods of 14 days: (a) Central region of bone defect filled with granulation tissue (gt), collagen fibers, non-viable fragments of bone tissue (*) and bone neoformation at the margins of the defect (#); (b) Bone neoformation in the margins of the defect (*). In the central region, there is the presence of granulation tissue (gt) and of fragments of non-viable bone tissue (#), surrounded by giant cells (arrows); (c) Central area of the defect with intense inflammatory infiltrate (ii), formed by predominantly mononuclear cells (§) bordering biomaterial particles (*) and fragments of non-viable bone tissue (#). Presence of large amount of giant cells around the non-viable bone tissue (arrows); (d) Presence of biomaterial in the central area of the defect (arrows), permeated by connective tissue (CT) and fragments of necrotic bone tissue (*). Original magnification of x10 and x20.

Figure 3. Photomicrographs of sections stained with hematoxylin and eosin in post-operative periods of 28 days: (a) Bone neoformation in the marginal region of the defect (*), bordered by osteoblastic cells (arrow), in connective tissue and nonviable bone particles (#); (b) Central region of the defect filled with connective tissue (CT), few areas of bone neoformation (*) and fragments of nonviable bone tissue (#); (c) Central region of bone defect filled with fibrous connective tissue (#). Presence of neoformed bone tissue (*) in the margin of the bone defect and adjacent areas and presence of necrotic bone (§). More centralized regions containing biomaterial (arrows); (d) Bone neoformation in areas near the margin of the defect (*). Central region containing fragments of biomaterial (arrows) and non-viable bone tissue (#). Original magnification of x10 and x20.

Figure 4. Graphic representation of means of histometric analysis related to bone neoformation area in percentage. Statistically significant difference within the group: a-A (p = 0.003); b-B (p = 0.005) and c-C (p ≤ 0.001). In the intergroup evaluation, a statistically significant difference: 14 days: C-A; C-B; D-A; D-B (p ≤ 0.001).28 days: c-a; c-b (P = 0.048).