Optical, polarized, metallographic and electron scanning microscopies from osteoformation by polylactic-polyglycolic acid

Abstract

Tooth extraction is one of the most common dental procedures. This situation is followed by irreversible alveolar bone resorption during the first three months of healing, although dimensional changes can be observed up to a year later. The clinical consequences limit the availability of bone for implant placement. Among the existing therapeutics, bone graft materials (BGM) are the choice, since in addition to providing structural support, they promote osteopromotion. In the present study, Polylactic-Polyglycolic Acid (PLA-PGA) particles were characterized and biological behavior as BGM in dental alveoli was evaluated. The in vivo model used was the post extraction alveolus in Wistar rats. Animals were divided into 2 groups: 1) Control Group (CG): without MRO; 2), Experimental Group (EG): with PLA-PGA. Bone samples were evaluated with soft X-rays (SXR), histological with light microscopy (LM) and polarized light (PL), histometric (H) and statistics studies at weeks 1, 2, and 3 after surgery. The characterization was carried out with a metallographic optical microscope (MOM) and a Scanning Electron (SEM). Results: MOM: particle conglomerates composed of small grains. Average size: 18 ± 6 µm. SEM: particle conglomerates with an ampfractuous and irregular surface, with wide interconnected channels limited by discontinuous and porous walls. In vivo model: SXR: CG: varied radiopacity areas, random, without reaching the apex of the alveolar ridges. EG: low radiopacity images (PLA-PGA particles) surrounded by more radiopaque areas (newly formed bone). LM: GC: alveolus covered by lamellar bone EG: alveolus covered by fibrous connective tissue, PLA-PGA particles surrounded by lamellar bone and primitive bone marrow. PL: in two thirds dense fibrous connective tissue birefringent reddish orange and in the apical third areas of reddish newly formed bone (type I collagen), with some yellowish green areas (type III collagen). GE: superficial third, birefringent dense fibrous connective tissue of intense reddish and orange colors (type I collagen), middle and apical third trabeculae of laminar neoformed bone, red orange and yellow birefringent (type III collagen), with persistence of PLA- particles PGA surrounded by a loose, reddish-orange fibrous area. EH: Bone volume in the GC was 75.12% and GE 78.26% at 3 weeks without statistically significant differences (P = 0.35). PLA-PGA was biocompatible and behaved as an osteoconductor and osseostimulator since it promoted the formation of type I and III collagen and bone neoformation around its particles. The alveolar space was preserved.