Histologic Evaluation of Early Papilla Healing after Augmentation with Injectable Hyaluronic Acid-A Proof of Concept

Abstract

Objectives: This human histological study's purpose was to histologically evaluate papillae's healing after hyaluronic acid (HA) gel augmentation at three healing time points after one injection with hyaDENT BG^®. Methods: Fifteen papillae from two patients with stage III, grade B periodontitis have been selected for this study. Every week for three weeks, five papillae were injected once with HA gel, and during the fourth week, the papillae were surgically removed as part of step 3 of the periodontal treatment. The histological analysis was performed on fifteen papillae, with five papillae corresponding to every timepoint of healing (weeks 1, 2, and 3). The primary outcome was considered to be the newly formed collagen fibers. The presence of residual HA, the integrity of epithelium or the presence of erosions/ulcerations, the presence and characteristics of inflammatory infiltrate, the presence of granulomatous reactions, and interstitial edema were considered to be secondary outcomes. Results: From the first to the third week, newly formed connective tissue begins to appear, while the observed HA pools (vesicles) content decreases. The density of inflammatory infiltrate was higher in the first week after injection, decreasing considerably by week 3; however, it was still visible throughout the healing time points. A granulomatous reaction was present in only three samples, while no signs of ulceration or necrosis could be observed; however, epithelial erosions could be observed on some samples after the first week. Conclusions: Papila augmentation with hyaluronic acid promotes new collagen formation from the second week of healing despite some foreign body granulomatous reactions.

Keywords: early wound healing; histologic analysis; hyaluronic acid; papilla augmentation.

Figure 1

Time diagram.

Figure 2

Clinical view of papilla injection with hyaluronic acid gel (hyaDENT BG^®).

Figure 3

Illustration of intraoperative steps: papilla measurements (a–c); papilla incisions (d–f); sutured scalloped flaps (g); excised papillae with green staining on the base (h).

Figure 4

Histologic images of papillae from the three healing timepoints: (A) Overall view of a 4 µ thickness section of a sample harvested after the first week of healing: note the general rounded shape due to the lack of the papilla tip, and the epithelial erosion (a), green tint used to mark the papilla base that spread on the epithelium (b), higher magnification of section represented in (B) (arrow), sample T3.1, magnification 1×; (B) light microscopy of 4 µm section: cell-rich granulation tissue with dense inflammatory infiltrate and tissue edema (a), sample T3.1, scale bar = 30 µm, first week of healing; (C) light microscopy of 4 µm section: cell-rich granulation tissue with dense inflammatory infiltrate (a), hyaluronic acid pools (b), scale bar = 50 µm, first week of healing; (D) overall view of 4 µm section harvested after the second week of healing: green tint used to mark the papilla base that spread on the epithelium (b), higher magnification of section represented in (E) (arrow), sample T2.3, magnification 900×; (E) light microscopy of 4 µm section: subepithelial, maturing granulation tissue (a), decrease in the density of inflammatory infiltrate (b), hyaluronic acid pools (c), newly formed collagen fibers, thin and loosely packed (d), sample T2.3, scale bar = 50 µm, second week of healing; (F) light microscopy of 4 µm section: less interstitial edema (a), granulomatous reaction on hyaluronic acid pools surrounded by macrophages and multinucleated giant foreign body cells (b), scale bar = 100 µm, second week of healing; (G) overall view of 4 µm section of sample harvested after the third week of healing: green tint used to mark the papilla base that smeared on the epithelium (b), higher magnification of section represented in (H) (arrow), sample T1.3, magnification 2×; (H) light microscopy of 4 µm section: maturation of granulation tissue (a), hyaluronic acid lakes without granulomatous reactions (b), sample T1.3, scale bar = 50 µm, third week of healing; (I) overall view of a 4 µ thickness section of a non-injected sample: note the general aspect of an unaltered papilla used for comparison, sample T0, magnification 2×.

Figure 5

The mean, median, and mode of all parameters.