Zn-Containing Membranes for Guided Bone Regeneration in Dentistry

Abstract

Barrier membranes are employed in guided bone regeneration (GBR) to facilitate bone in-growth. A bioactive and biomimetic Zn-doped membrane with the ability to participate in bone healing and regeneration is necessary. The aim of the present study is to state the effect of doping the membranes for GBR with zinc compounds in the improvement of bone regeneration. A literature search was conducted using electronic databases, such as PubMed, MEDLINE, DIMDI, Embase, Scopus and Web of Science. A narrative exploratory review was undertaken, focusing on the antibacterial effects, physicochemical and biological properties of Zn-loaded membranes. Bioactivity, bone formation and cytotoxicity were analyzed. Microstructure and mechanical properties of these membranes were also determined. Zn-doped membranes have inhibited in vivo and in vitro bacterial colonization. Zn-alloy and Zn-doped membranes attained good biocompatibility and were found to be non-toxic to cells. The Zn-doped matrices showed feasible mechanical properties, such as flexibility, strength, complex modulus and tan delta. Zn incorporation in polymeric membranes provided the highest regenerative efficiency for bone healing in experimental animals, potentiating osteogenesis, angiogenesis, biological activity and a balanced remodeling. Zn-loaded membranes doped with SiO₂ nanoparticles have performed as bioactive modulators provoking an M2 macrophage increase and are a potential biomaterial for promoting bone repair. Zn-doped membranes have promoted pro-healing phenotypes.

Keywords: antibacterial; bioactivity; cytotoxicity; guided bone regeneration; mechanical; membranes; microscopy; zinc.

Figure 1

Illustration representing the surgical protocol for alveolar ridge preservation with membranes after tooth extraction (a). Use of membrane in regenerative procedures for periodontal defects (b). Membranes for peri-implantitis regeneration (c). In all cases, membranes are stabilized with mini-screws and pins to the surrounding bone.

Figure 2

The carboxyl-terminal on polymeric Zinc-doped membranes surfaces, after their immersion on ZnCl₂.

Figure 3

AFM image of the surface’s Zn-matrix. Overlapped and randomly distributed nanofibers may be observed. Spotty nanodeposits, at high magnification, are distributed onto the Zn-fiber surfaces.

Figure 4

FESEM micrographs of a Zn-doped membrane after immersion in SBFS. Nanofiber diameter is about 500 nm, and fibers lost the smooth appearance of their surface. Nanodeposits of mineral (100 nm) are randomly distributed onto the nanofiber surfaces. Numerous agglomerations of other spherical nanocrystals (bigger than 200 nm) are identified onto the Zn-matrix surface.

Figure 5

Bone histology image obtained by dye with toluidine blue after using Zn-NMs, in experimental animals after their healing time. Few isles of newly formed trabecular bone (NB) were observed at both side of Zn-NMs. Single arrows point the presence of osteoblasts; double arrows mean osteocytes and pointers indicate osteoclast. Face arrows mean blood vessels. Bony bridging (BB), mononuclear cells (Mnc) and osteoid (Os) may be observed.

Figure 6

Bone histology image obtained after using Zn-NMs dye with toluidine blue in experimental animals to visualize mineral bone after their healing time. Single arrows point the presence of osteoblast with typical cuboid shape. Double arrows indicate osteocytes, pointers mean osteoclast and faced arrows point blood vessels. Asterisk are located close by canaliculi. Arrow heads signal the presence of osteoid.

Figure 7

Bone histology image obtained in samples treated with Zn-loaded membranes by coloration with toluidine blue in experimental animals. At high magnification, vessels are clearly visualized (faced arrows) promoting and maintaining bone maturation.

Figure 8

Bone histology images obtained by dye with toluidine blue after using Zn-loaded membranes in experimental animals. Blood vessels (faced arrows) that connect bone marrow directly with the blood supply can be easily observed (a,b).

Figure 9

Nano-DMA analysis, on scanning mode, of the surface’s Zn-matrix. The property map corresponds to the tan delta values.

Figure 10

Bone histomorphometry obtained by dye with Von Kossa silver nitrate stain to visualize formed mineralized bone in experimental animals at six weeks of follow-up, around Zn-loaded membranes. Trabecular bone formations were formed along the margin of calvarial defect and within the defect (arrow head). Bony bridging (BB), Fibrous tissue (FT), Membrane (Mbr), Osteoid (OS), Old bone (OB).

Figure 11

Bone histology obtained by fluorescence with calcein at the region of interest to see mineralized bone, at six weeks of healing time after using Zn-loaded membranes. Pointers indicate bone perimeter and arrows signal osteoid perimeter. Bone area (BA), Osteoid area (OA).