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 andabutments and promotes cell spreading.Objective: A triple-blinded randomized controlled clinical trial was performed to in vivo test theeffect of cleaning abutment titanium surfaces with plasma of argon on cell adhesion and collagenfiber 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 theycome from industry; control group, G1) or cleaned by plasma of argon (test group, G2). Two weeksthereafter, a small biopsy including abutment and soft tissues around the abutment wasperformed. Abutments were analyzed using scanning electron microscopy to assess cell adhesion tothe abutment surface. Outcome measures were the following: percentage of area occupied bycells, 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 collagenfibers. Statistical analysis was performed using the Kolmogorov–Smirnov normality test and Levenevariance homogeneity test. Data were analyzed using a nonparametric ranking test. Theassociations between the different qualitative variables were studied using Pearson’s chi-squaredtest. The Mann–Whitney U-test (for two independent samples) was applied for quantitativevariables.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 17cases, cells were efficiently adhered, and in 11 cases, cells presented filopodia with no statisticaldifferences between groups (P > 0.05). No case from G2 showed contamination with cocobacteriawith statistical differences between groups (P = 0.006). Collagen fiber density was higher in thebasal, medial, and coronal area of G2 compared to G1 with a statistical difference in the internalarea (P < 0.05). The orientation of the fibers varied according to the coordinate area with obliquefibers predominant in G2 than in G1.Conclusion: Plasma of argon may promote cell adhesion and positively influence collagen fiberorientation. A greater sample is necessary to confirm these preliminary results.