Influence of plasma cleaning procedure on the interaction between soft tissue and abutments: a randomized controlled histologic study

Introduction: Plasma application can lead to an improved adhesion between soft tissue and abutments and promotes cell spreading. Objective: A triple-blinded randomized controlled clinical trial was performed to in vivo test the effect of cleaning abutment titanium surfaces with plasma of argon on cell adhesion and collagen fiber orientation at an early healing time. Material and methods: Thirty healthy patients with 30 submerged implants, at the second surgery, randomly received either a specially designed abutment with no additional treatment (as they come from industry; control group, G1) or cleaned by plasma of argon (test group, G2). Two weeks thereafter, a small biopsy including abutment and soft tissues around the abutment was performed. Abutments were analyzed using scanning electron microscopy to assess cell adhesion to the abutment surface. Outcome measures were the following: percentage of area occupied by cells, the presence or absence of cells, aspect of adhered cells, and the presence of contaminants. At the same time, the soft tissue histological analysis evaluated density and orientation of collagen fibers. Statistical analysis was performed using the Kolmogorov–Smirnov normality test and Levene variance homogeneity test. Data were analyzed using a nonparametric ranking test. The associations between the different qualitative variables were studied using Pearson's chi-squared test. The Mann–Whitney U-test (for two independent samples) was applied for quantitative variables. Results: Mean percentages of area occupied by cells were 15.14% (range 2.91–44.27) and 33.75% (range 2.37–68.4) for G1 and G2, respectively. Differences were close to significance (P = 0.089). The proportion of samples presenting adhered cells was homogeneous between the two groups (P = 0.142). In all cases, cells presented a flattened aspect, but not in three cases in the G2; in 17 cases, cells were efficiently adhered, and in 11 cases, cells presented filopodia with no statistical differences between groups (P > 0.05). No case from G2 showed contamination with cocobacteria with statistical differences between groups (P = 0.006). Collagen fiber density was higher in the basal, medial, and coronal area of G2 compared to G1 with a statistical difference in the internal area (P < 0.05). The orientation of the fibers varied according to the coordinate area with oblique fibers predominant in G2 than in G1. Conclusion: Plasma of argon may promote cell adhesion and positively influence collagen fiber orientation. A greater sample is necessary to confirm these preliminary results.